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Hindawi Publishing CorporationChinese Journal of EngineeringVolume 2013 Article ID 362682 14 pageshttpdxdoiorg1011552013362682
Research ArticleNumerical Simulation and Investigation of System Parametersof Sonochemical Process
Sankar Chakma and Vijayanand S Moholkar
Department of Chemical Engineering Indian Institute of Technology Guwahati Guwahati 781 039 Assam India
Correspondence should be addressed to Sankar Chakma sankariitgernetin
Received 25 July 2013 Accepted 19 August 2013
Academic Editors B-Y Cao S Tang and G Xiao
Copyright copy 2013 S Chakma and V S Moholkar This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited
This paper presents the effects of various parameters that significantly affect the cavitation In this study three types of liquidmediums with different physicochemical properties were considered as the cavitation medium The effects of various operatingparameters such as temperature pressure initial bubble radius dissolved gas content and so forth were investigated in detail Thesimulation results of cavitation bubble dynamics model showed a very interesting link among these parameters for production ofoxidizing species The formation of ∙OH radical and H
2
O2
is considered as the results of main effects of sonochemical processSimulation results of radial motion of cavitation bubble dynamics revealed that bubble with small initial radius gives highersonochemical effects This is due to the bubble with small radius can undergo many acoustic cycles before reaching its criticalradius when it collapses and produces higher temperature and pressure inside the bubble On the other hand due to the low surfacetension and high vapor pressure organic solvents are not suitable for sonochemical reactions
1 Introduction
The sonochemistry concept is a well-established techniqueand now it is considered as one of the most popular advancedoxidation processes In the last few decades sonochemicalprocess became one of the most popular techniques forsynthesis of catalysts as well as different types of materials[4ndash7] degradation of pollutants [8ndash12] synthesis of biodiesel[13 14] and so forth Numerous literatures on sonochemistryhave already been published [15ndash18] which reported thevarious beneficial effects of sonochemistry The principalphenomenon behind all of these effects is the cavitationCavitation is nothing but nucleation growth and implosivecollapse of a bubble Cavitation occurs through the forma-tion of bubbles or cavities present in liquid medium Eachcavitating bubble contains gas or vapor or a mixture ofgas-vapor When bubble contains only gas the expansionof bubble is mainly by diffusion pressure reduction or byrise in temperature However there are several parameterswhich are directly involved in transient cavitation Transientcavitation is nothing but the growth of bubbles extensivelyover time scales of the order of the acoustic cycle and then
undergoes an implosiveenergetic collapse resulting in eitherfragmentation decaying oscillation or a repeat performance[19] Cavitation can also be the result of the enlargement ofcavities that are already present in bulk liquid Sometimescavitation bubbles are suspendedtrapped in tinny cracks inthe interface of solid and liquid These cavitation bubblesgrow and collapse in the medium based on the pressurevariation inside the bubble On the basis of pressure variationcavitation can be categorized into four subsections (1)hydrodynamic cavitation (2) acoustic cavitation (3) opticcavitation and (4) particle cavitation [20] Hydrodynamiccavitation is the result of pressure variation in the liquidmedium due to the flow variation of liquid through themedium while acoustic cavitation is due to the passing ofacoustic waves in the liquid medium Generally acousticcavitation occurs in the frequency range of 20 kHz to 1MHzthat is high power low frequency [20] In acoustic cavitationvery high temperature and pressure (sim 5000K and sim 500 bar)are produced inside the bubbles due to transient collapse ofcavitation bubblesThe bubble collapse occurs within as smalltime as 50 ns and it is almost adiabatic During the collapseof the bubble many species are formed such as H
2
O2
H2
O2
2 Chinese Journal of Engineering
O3
∙OH ∙H ∙O andHO2
∙ Among these species ∙OH radicalis the most predominant radical species [21 22] having anoxidizing potential of 233V [9 23] For greater details incavitation concepts we would like to refer the readers to seethe state of art reviews by Xu et al [4] Apfel [24] Gong andHart [25] Suslick et al [26] and Gogate and Pandit [27]
2 Cavitation Bubble Dynamics Model
In order to investigate the various effects of cavitation wehave considered a model for a single cavitation bubble tosimulate the radial motion of cavitation bubble Although thesingle bubble analysis for radial motion of cavitation bubbledoes not give the entire phenomenon of the sonochemicalprocess but it can give a qualitative physical insight into themechanism The resultant effect of sonochemical reaction isthe collective oscillations and collapse of cavitation bubbleswith strong interaction between them For simulation ofradial motion the single bubble model is the most popularmodel to present the effects of cavitation namely physi-cal and chemical effect The physical and chemical effectsinduced by ultrasound and cavitation bubbles in the systemcan be determined using diffusion limited ordinary differen-tial equation (ODE) model This model is basically based onthe boundary layer approximation proposed by Toegel et al[28]This radial motion of cavitation bubble model is derivedfrom the partial differential equation (PDE) model of Storeyand Szeri [29] which showed that water vapor entrapment inthe cavitation bubble ismainly a diffusion limited process andnot the condensation limited process The main componentsof the radial motion of cavitation bubble dynamics are (1)Keller-Miksis equation for the radial motion of the bubble[30] (2) equation for the diffusive flux of water vapor andheat conduction through bubble wall The overall diffusioncoefficient in ternary mixture (eg N
2
ndashO2
ndashH2
O in case ofair bubbles) or binary mixture (eg N
2
ndashH2
O or O2
ndashH2
Oor ArndashH
2
O) has been determined using Blancrsquos law [31] (3)equation for heat conduction through cavitation bubble walland (4) overall energy balance treating the cavitation bubbleas an open system The set of 4 ODEs are also given below
(1) Radial motion of the cavitation bubble
(1 minus119889119877119889119905
119888L)119877
1198892119877
1198891199052+3
2(1 minus
119889119877119889119905
3119888L)(
119889119877
119889119905)
2
=1
120588L(1 +
119889119877119889119905
119888L) (119875119894
minus 119875119905
)
+119877
120588L119888L
119889119875119894
119889119905minus 4]
119889119877119889119905
119877minus2120590
120588L119877
(1)
Internal pressure in the bubble 119875119894
= 119873tot(119905)119896119879[4120587(119877
3
(119905) minus ℎ3
)3]
Pressure in bulk liquid medium 119875119905
= 1198750
minus 119875Asin(2120587119891119905)
(2) Diffusive flux of water molecules 119889119873W119889119905 = 41205871198772
119863W(120597119862W120597119903)|119903=119877 asymp 41205871198772119863W((119862W119877 minus 119862W)119897diff)
Instantaneous diffusive penetration depth119897diff = min(radic(119877119863w)|119889119877119889119905| 119877120587)
(3) Heat conduction across bubble wall 119889119876119889119905 = 41205871198772120582(120597119879120597119903)|
119903=119877
asymp 41205871198772120582((1198790
minus 119879)119897th)
Thermal diffusion length 119897th = min(radic119877120581|119889119877119889119905| 119877120587)
(4) Overall energy balance119862119881mix119889119879119889119905 = 119889119876119889119905minus119875119894119889119881
119889119905 + (ℎW minus 119880W)119889119873W119889119905
Mixture heat capacity 119862119881mix = sum119862
119881119894
119873119894
(where 119894 = N2
O2
H2
O)Molecular properties of water Enthalpy ℎw =4119896119879119900
Internal energy 119880W = 119873W119896119879(3 + sum
3
119894=1
((120579119894
119879)
(exp(120579119894
119879) minus 1)))Heat capacity of various species (119894 = N
2
O2
H2
O)
119862119881119894
= 119873119894
119896(119891119894
2+sum(
(120579119894
119879)2 exp (120579
119894
119879)
(exp (120579119894
119879) minus 1)2
)) (2)
The initial conditions of the ordinary differential equa-tions are taken as at 119905 = 0 119877 = 119877
119900
119889119877119889119905 = 0 119873w =
0 119876 = 0 and 119879 = 119879119900
Thermodynamic data for variousspecies and physicochemical properties of various solventsthat is cavitation medium are given in Tables 1 and 2The thermal conductivity and diffusion coefficient (transportparameters for the heat and mass transfer) are estimatedusing Chapman-Enskog theory using Lennard-Jones 12-6potential at the bulk temperature of the liquid medium [1ndash3 31] This model ignores the diffusion of gas across bubbleinterface because the time scale for the diffusion of gasesis much higher than the time scale of cavitation bubblemodel The ODEs in the bubble dynamics model have beensolved simultaneously using Runge-Kutta 4th- and 5th-orderadaptive step size method [32] Various parameters used inthe numerical solution of radial motion of cavitation bubbledynamics and their numerical values are given in Tables 1 and2 The other parameters are as follows ultrasound frequency(119891) = 20 kHz ultrasound pressure amplitude (119875A) = 150 kPainitial bubble radius (119877
119900
) = 5 120583m sound velocity in water(119888W) = 1481ms sound velocity in toluene (119888T) = 1275msand sound velocity in n-hexane (119888H) = 1203ms All theseparameters remain unchanged unless otherwise stated
Physical Effect of UltrasoundUltrasound propagates throughthe medium in the form of longitudinal wave with seriesof compression and rarefaction and causes rapid oscillatorymotion of fluid elements called microstreamingThis motiongives rise to intense micromixing in the medium Themagnitude of the microstreaming velocity is given by 119906 =119875A120588119888 Substituting values of 119875A as 15 times 105 Pa (or 15 bar)120588w = 1000 kgm
3 and 119888w = 1481ms gives 119906w = 0101ms
Sonochemical Effect of Cavitation Bubbles The numericalsolution of bubble dynamics model predicts the temperature
Chinese Journal of Engineering 3
Table 1 Thermodynamic data for various species (data taken from [1ndash3])
Species Degrees of freedom(translational + rotational) (119891
119894
)
Lennard-Jones force constants Characteristic vibrational temperatures 120579 (K)120590 (10minus10 m) 120576119896 (K)
N2 5 368 92 3350O2 5 343 113 2273Ar 3 342 124 mdashH2O 6 265 380 2295 5255 5400C6H12 6 575 3864 1036 1932 1987 2104 4193C6H5ndashCH3 6 582 451 1004 1056 2112 2153 2326 4224 4375
Table 2 Physicochemical properties of various solvents as cavitation medium
Solvent Boiling point (K) Density (kgm3) Viscosity (Pa-s) Surface tension (Nm) Vapor pressure (kPa)Water 373 1000 10 times 10
minus6 0072 25Toluene 384 867 68 times 10minus7 0029 40n-Hexane 341 658 50 times 10minus7 0018 162 calculated using Antoine type correlations
pressure and the number of gas and solvent moleculesin the bubble at transient collapse At transient collapsetemperature and pressure reach extreme conditions whichresult in dissociation of molecules to form various chemicalspecies To calculate the composition of the bubble at thetime of collapse we assume that thermodynamic equilibriumis attained [9] The equilibrium mole fraction of differentchemical species in the bubble at the peak conditions reachedat transient collapse is estimated using Gibbs free-energyminimization technique [33]The radial motion of cavitationbubbles generates intense convection in the medium throughtwo phenomena
(i) Microconvection [20] 119881turb(119903 119905) = (11987721199032)(119889119877119889119905)
(ii) Shock (or acoustic) waves [34 35] 119875AW(119903 119905) = (120588L4120587119903)(1198892119881
119887
1198891199052
) = 120588L(119877119903)[2(119889119877119889119905)2
+ 119877(1198892119877 1198891199052
)]
where 119881119887
is the volume of the bubble A representative valueof 119903 is taken as 1mm In bubble dynamic model directestimation of initial bubble radius is very difficult Severalphenomena such as rectified diffusion and fragmentation ofthe bubble cause continuous change in this parameter Ina multibubble system a large variation in this parametermay be expected In order to investigate the influence of thisparameter two numerical values for this parameter namely 5and 10 120583m are selected for this present studyThe equilibriumcomposition of the bubble contents was determined usingthe FactSage online software [36] which is based on thefree-energy minimization algorithm same as proposed byEriksson [33]
3 Numerical Solution of Mathematical Model
The simulation results of radial motion of cavitation bubbledynamics are depicted in Figures 1 2 3 4 and 5 and Tables3 4 5 6 and 7 Tables 3ndash7 present the temperature (119879max)and pressure (119875max) peaks reached at themoment of transientcollapse of cavitation bubble the number of water moleculesin the bubble at collapse and the equilibrium composition of
the various species resulting from dissociation of entrappedmolecules in the bubble when the temperature and pressurereached to its extreme conditions during transient collapse ofcavitation bubbles
31 Initial Bubble Size in the Liquid Medium Bubbles withdifferent initial radius present in the liquid medium play animportant role in cavitation Kumar and Moholkar [37] havereported that the smaller bubble has higher Laplace pressurewhich results in higher expansion and more intense collapseduring the transient collapse In this present study a singlebubble model with different initial radius has been chosen topresent the effects of bubble radius in sonochemical processFrom Table 3 it could be seen that the ∙OH radical formationduring transient collapse of cavitation bubble is higher withthe initial bubble radius of 5 120583m followed by 25120583m Thisis due to the bubble with small bubble radius can undergomany acoustic cycles before reaching its critical radius whenit collapses and as a result the highest temperature peak isreached at the moment of transient collapse of the cavitationbubble with 5120583m radius bubble as shown in Figure 1 andTable 3
32 Static Pressure of the System As stated earlier in theprevious section the cavitation is nothing but the nucle-ation growth and implosive collapse of bubbles but thegrowthexpansion of the bubble depends on the systemrsquosstatic pressure So when the bubble contains vapor cavitationmay occur due to reduced static pressure sufficiently atconstant temperature To investigate the effects of pressurefive different static pressures ranging from 100ndash300 kPa havebeen chosen The results showed that as the static pressureincreases the radical formation decreases drastically even itbecomes zero at higher ambient static pressure This is dueto at elevated static pressure the sonochemical effects geteliminated which directly affects the generation of radicalformation provided the applied pressure must be greaterthan or equal to the acoustic pressure amplitude (119875
119900
ge 119875AW)[9 38]Thehighest ∙OHradical productionwas seen at nearly
4 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50N
o o
f wat
er v
apor
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
5 middot 1010
1 middot 1011
3 middot 1012
6 middot 1012
(c)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
10
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus100 1 2 3 4 5
05
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus1
minus025
(e)
0 1 2 3 4 5
148
300
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
5120583m bubble
0 1 2 3 4 50
50
100
No of acoustic cycles
25120583m bubble
Acou
stic w
ave
ampl
itude
(bar
)
minus4
(f)
Figure 1 Simulations of radial motion of 5 and 25 micron air bubble in water 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPa Time historyof (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside the bubble (e)microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 5
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
15
3
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
2000
4000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
4 middot 1010
2 middot 1010
1 middot 1010
5 middot 109
(c)
0 1 2 3 4 50
2000
4000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
30
60
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5No of acoustic cyclesO
scill
ator
y ve
loci
ty (m
s)
minus04
minus01
0 1 2 3 4 5
0
01
Osc
illat
ory
velo
city
(ms
)
minus01
No of acoustic cycles
(e)
0 1 2 3 4 50
30
60
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
120 kPa
0 1 2 3 4 50
075
15
No of acoustic cycles
150kPa
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 2 Simulations of radial motion of 5 micron air bubble in water at 120 kPa and 150 kPa 119891 = 20 kHz 119875A = 150 kPa and 119877119900 = 5 120583mTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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2 Chinese Journal of Engineering
O3
∙OH ∙H ∙O andHO2
∙ Among these species ∙OH radicalis the most predominant radical species [21 22] having anoxidizing potential of 233V [9 23] For greater details incavitation concepts we would like to refer the readers to seethe state of art reviews by Xu et al [4] Apfel [24] Gong andHart [25] Suslick et al [26] and Gogate and Pandit [27]
2 Cavitation Bubble Dynamics Model
In order to investigate the various effects of cavitation wehave considered a model for a single cavitation bubble tosimulate the radial motion of cavitation bubble Although thesingle bubble analysis for radial motion of cavitation bubbledoes not give the entire phenomenon of the sonochemicalprocess but it can give a qualitative physical insight into themechanism The resultant effect of sonochemical reaction isthe collective oscillations and collapse of cavitation bubbleswith strong interaction between them For simulation ofradial motion the single bubble model is the most popularmodel to present the effects of cavitation namely physi-cal and chemical effect The physical and chemical effectsinduced by ultrasound and cavitation bubbles in the systemcan be determined using diffusion limited ordinary differen-tial equation (ODE) model This model is basically based onthe boundary layer approximation proposed by Toegel et al[28]This radial motion of cavitation bubble model is derivedfrom the partial differential equation (PDE) model of Storeyand Szeri [29] which showed that water vapor entrapment inthe cavitation bubble ismainly a diffusion limited process andnot the condensation limited process The main componentsof the radial motion of cavitation bubble dynamics are (1)Keller-Miksis equation for the radial motion of the bubble[30] (2) equation for the diffusive flux of water vapor andheat conduction through bubble wall The overall diffusioncoefficient in ternary mixture (eg N
2
ndashO2
ndashH2
O in case ofair bubbles) or binary mixture (eg N
2
ndashH2
O or O2
ndashH2
Oor ArndashH
2
O) has been determined using Blancrsquos law [31] (3)equation for heat conduction through cavitation bubble walland (4) overall energy balance treating the cavitation bubbleas an open system The set of 4 ODEs are also given below
(1) Radial motion of the cavitation bubble
(1 minus119889119877119889119905
119888L)119877
1198892119877
1198891199052+3
2(1 minus
119889119877119889119905
3119888L)(
119889119877
119889119905)
2
=1
120588L(1 +
119889119877119889119905
119888L) (119875119894
minus 119875119905
)
+119877
120588L119888L
119889119875119894
119889119905minus 4]
119889119877119889119905
119877minus2120590
120588L119877
(1)
Internal pressure in the bubble 119875119894
= 119873tot(119905)119896119879[4120587(119877
3
(119905) minus ℎ3
)3]
Pressure in bulk liquid medium 119875119905
= 1198750
minus 119875Asin(2120587119891119905)
(2) Diffusive flux of water molecules 119889119873W119889119905 = 41205871198772
119863W(120597119862W120597119903)|119903=119877 asymp 41205871198772119863W((119862W119877 minus 119862W)119897diff)
Instantaneous diffusive penetration depth119897diff = min(radic(119877119863w)|119889119877119889119905| 119877120587)
(3) Heat conduction across bubble wall 119889119876119889119905 = 41205871198772120582(120597119879120597119903)|
119903=119877
asymp 41205871198772120582((1198790
minus 119879)119897th)
Thermal diffusion length 119897th = min(radic119877120581|119889119877119889119905| 119877120587)
(4) Overall energy balance119862119881mix119889119879119889119905 = 119889119876119889119905minus119875119894119889119881
119889119905 + (ℎW minus 119880W)119889119873W119889119905
Mixture heat capacity 119862119881mix = sum119862
119881119894
119873119894
(where 119894 = N2
O2
H2
O)Molecular properties of water Enthalpy ℎw =4119896119879119900
Internal energy 119880W = 119873W119896119879(3 + sum
3
119894=1
((120579119894
119879)
(exp(120579119894
119879) minus 1)))Heat capacity of various species (119894 = N
2
O2
H2
O)
119862119881119894
= 119873119894
119896(119891119894
2+sum(
(120579119894
119879)2 exp (120579
119894
119879)
(exp (120579119894
119879) minus 1)2
)) (2)
The initial conditions of the ordinary differential equa-tions are taken as at 119905 = 0 119877 = 119877
119900
119889119877119889119905 = 0 119873w =
0 119876 = 0 and 119879 = 119879119900
Thermodynamic data for variousspecies and physicochemical properties of various solventsthat is cavitation medium are given in Tables 1 and 2The thermal conductivity and diffusion coefficient (transportparameters for the heat and mass transfer) are estimatedusing Chapman-Enskog theory using Lennard-Jones 12-6potential at the bulk temperature of the liquid medium [1ndash3 31] This model ignores the diffusion of gas across bubbleinterface because the time scale for the diffusion of gasesis much higher than the time scale of cavitation bubblemodel The ODEs in the bubble dynamics model have beensolved simultaneously using Runge-Kutta 4th- and 5th-orderadaptive step size method [32] Various parameters used inthe numerical solution of radial motion of cavitation bubbledynamics and their numerical values are given in Tables 1 and2 The other parameters are as follows ultrasound frequency(119891) = 20 kHz ultrasound pressure amplitude (119875A) = 150 kPainitial bubble radius (119877
119900
) = 5 120583m sound velocity in water(119888W) = 1481ms sound velocity in toluene (119888T) = 1275msand sound velocity in n-hexane (119888H) = 1203ms All theseparameters remain unchanged unless otherwise stated
Physical Effect of UltrasoundUltrasound propagates throughthe medium in the form of longitudinal wave with seriesof compression and rarefaction and causes rapid oscillatorymotion of fluid elements called microstreamingThis motiongives rise to intense micromixing in the medium Themagnitude of the microstreaming velocity is given by 119906 =119875A120588119888 Substituting values of 119875A as 15 times 105 Pa (or 15 bar)120588w = 1000 kgm
3 and 119888w = 1481ms gives 119906w = 0101ms
Sonochemical Effect of Cavitation Bubbles The numericalsolution of bubble dynamics model predicts the temperature
Chinese Journal of Engineering 3
Table 1 Thermodynamic data for various species (data taken from [1ndash3])
Species Degrees of freedom(translational + rotational) (119891
119894
)
Lennard-Jones force constants Characteristic vibrational temperatures 120579 (K)120590 (10minus10 m) 120576119896 (K)
N2 5 368 92 3350O2 5 343 113 2273Ar 3 342 124 mdashH2O 6 265 380 2295 5255 5400C6H12 6 575 3864 1036 1932 1987 2104 4193C6H5ndashCH3 6 582 451 1004 1056 2112 2153 2326 4224 4375
Table 2 Physicochemical properties of various solvents as cavitation medium
Solvent Boiling point (K) Density (kgm3) Viscosity (Pa-s) Surface tension (Nm) Vapor pressure (kPa)Water 373 1000 10 times 10
minus6 0072 25Toluene 384 867 68 times 10minus7 0029 40n-Hexane 341 658 50 times 10minus7 0018 162 calculated using Antoine type correlations
pressure and the number of gas and solvent moleculesin the bubble at transient collapse At transient collapsetemperature and pressure reach extreme conditions whichresult in dissociation of molecules to form various chemicalspecies To calculate the composition of the bubble at thetime of collapse we assume that thermodynamic equilibriumis attained [9] The equilibrium mole fraction of differentchemical species in the bubble at the peak conditions reachedat transient collapse is estimated using Gibbs free-energyminimization technique [33]The radial motion of cavitationbubbles generates intense convection in the medium throughtwo phenomena
(i) Microconvection [20] 119881turb(119903 119905) = (11987721199032)(119889119877119889119905)
(ii) Shock (or acoustic) waves [34 35] 119875AW(119903 119905) = (120588L4120587119903)(1198892119881
119887
1198891199052
) = 120588L(119877119903)[2(119889119877119889119905)2
+ 119877(1198892119877 1198891199052
)]
where 119881119887
is the volume of the bubble A representative valueof 119903 is taken as 1mm In bubble dynamic model directestimation of initial bubble radius is very difficult Severalphenomena such as rectified diffusion and fragmentation ofthe bubble cause continuous change in this parameter Ina multibubble system a large variation in this parametermay be expected In order to investigate the influence of thisparameter two numerical values for this parameter namely 5and 10 120583m are selected for this present studyThe equilibriumcomposition of the bubble contents was determined usingthe FactSage online software [36] which is based on thefree-energy minimization algorithm same as proposed byEriksson [33]
3 Numerical Solution of Mathematical Model
The simulation results of radial motion of cavitation bubbledynamics are depicted in Figures 1 2 3 4 and 5 and Tables3 4 5 6 and 7 Tables 3ndash7 present the temperature (119879max)and pressure (119875max) peaks reached at themoment of transientcollapse of cavitation bubble the number of water moleculesin the bubble at collapse and the equilibrium composition of
the various species resulting from dissociation of entrappedmolecules in the bubble when the temperature and pressurereached to its extreme conditions during transient collapse ofcavitation bubbles
31 Initial Bubble Size in the Liquid Medium Bubbles withdifferent initial radius present in the liquid medium play animportant role in cavitation Kumar and Moholkar [37] havereported that the smaller bubble has higher Laplace pressurewhich results in higher expansion and more intense collapseduring the transient collapse In this present study a singlebubble model with different initial radius has been chosen topresent the effects of bubble radius in sonochemical processFrom Table 3 it could be seen that the ∙OH radical formationduring transient collapse of cavitation bubble is higher withthe initial bubble radius of 5 120583m followed by 25120583m Thisis due to the bubble with small bubble radius can undergomany acoustic cycles before reaching its critical radius whenit collapses and as a result the highest temperature peak isreached at the moment of transient collapse of the cavitationbubble with 5120583m radius bubble as shown in Figure 1 andTable 3
32 Static Pressure of the System As stated earlier in theprevious section the cavitation is nothing but the nucle-ation growth and implosive collapse of bubbles but thegrowthexpansion of the bubble depends on the systemrsquosstatic pressure So when the bubble contains vapor cavitationmay occur due to reduced static pressure sufficiently atconstant temperature To investigate the effects of pressurefive different static pressures ranging from 100ndash300 kPa havebeen chosen The results showed that as the static pressureincreases the radical formation decreases drastically even itbecomes zero at higher ambient static pressure This is dueto at elevated static pressure the sonochemical effects geteliminated which directly affects the generation of radicalformation provided the applied pressure must be greaterthan or equal to the acoustic pressure amplitude (119875
119900
ge 119875AW)[9 38]Thehighest ∙OHradical productionwas seen at nearly
4 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50N
o o
f wat
er v
apor
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
5 middot 1010
1 middot 1011
3 middot 1012
6 middot 1012
(c)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
10
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus100 1 2 3 4 5
05
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus1
minus025
(e)
0 1 2 3 4 5
148
300
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
5120583m bubble
0 1 2 3 4 50
50
100
No of acoustic cycles
25120583m bubble
Acou
stic w
ave
ampl
itude
(bar
)
minus4
(f)
Figure 1 Simulations of radial motion of 5 and 25 micron air bubble in water 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPa Time historyof (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside the bubble (e)microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 5
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
15
3
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
2000
4000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
4 middot 1010
2 middot 1010
1 middot 1010
5 middot 109
(c)
0 1 2 3 4 50
2000
4000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
30
60
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5No of acoustic cyclesO
scill
ator
y ve
loci
ty (m
s)
minus04
minus01
0 1 2 3 4 5
0
01
Osc
illat
ory
velo
city
(ms
)
minus01
No of acoustic cycles
(e)
0 1 2 3 4 50
30
60
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
120 kPa
0 1 2 3 4 50
075
15
No of acoustic cycles
150kPa
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 2 Simulations of radial motion of 5 micron air bubble in water at 120 kPa and 150 kPa 119891 = 20 kHz 119875A = 150 kPa and 119877119900 = 5 120583mTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
Chinese Journal of Engineering 3
Table 1 Thermodynamic data for various species (data taken from [1ndash3])
Species Degrees of freedom(translational + rotational) (119891
119894
)
Lennard-Jones force constants Characteristic vibrational temperatures 120579 (K)120590 (10minus10 m) 120576119896 (K)
N2 5 368 92 3350O2 5 343 113 2273Ar 3 342 124 mdashH2O 6 265 380 2295 5255 5400C6H12 6 575 3864 1036 1932 1987 2104 4193C6H5ndashCH3 6 582 451 1004 1056 2112 2153 2326 4224 4375
Table 2 Physicochemical properties of various solvents as cavitation medium
Solvent Boiling point (K) Density (kgm3) Viscosity (Pa-s) Surface tension (Nm) Vapor pressure (kPa)Water 373 1000 10 times 10
minus6 0072 25Toluene 384 867 68 times 10minus7 0029 40n-Hexane 341 658 50 times 10minus7 0018 162 calculated using Antoine type correlations
pressure and the number of gas and solvent moleculesin the bubble at transient collapse At transient collapsetemperature and pressure reach extreme conditions whichresult in dissociation of molecules to form various chemicalspecies To calculate the composition of the bubble at thetime of collapse we assume that thermodynamic equilibriumis attained [9] The equilibrium mole fraction of differentchemical species in the bubble at the peak conditions reachedat transient collapse is estimated using Gibbs free-energyminimization technique [33]The radial motion of cavitationbubbles generates intense convection in the medium throughtwo phenomena
(i) Microconvection [20] 119881turb(119903 119905) = (11987721199032)(119889119877119889119905)
(ii) Shock (or acoustic) waves [34 35] 119875AW(119903 119905) = (120588L4120587119903)(1198892119881
119887
1198891199052
) = 120588L(119877119903)[2(119889119877119889119905)2
+ 119877(1198892119877 1198891199052
)]
where 119881119887
is the volume of the bubble A representative valueof 119903 is taken as 1mm In bubble dynamic model directestimation of initial bubble radius is very difficult Severalphenomena such as rectified diffusion and fragmentation ofthe bubble cause continuous change in this parameter Ina multibubble system a large variation in this parametermay be expected In order to investigate the influence of thisparameter two numerical values for this parameter namely 5and 10 120583m are selected for this present studyThe equilibriumcomposition of the bubble contents was determined usingthe FactSage online software [36] which is based on thefree-energy minimization algorithm same as proposed byEriksson [33]
3 Numerical Solution of Mathematical Model
The simulation results of radial motion of cavitation bubbledynamics are depicted in Figures 1 2 3 4 and 5 and Tables3 4 5 6 and 7 Tables 3ndash7 present the temperature (119879max)and pressure (119875max) peaks reached at themoment of transientcollapse of cavitation bubble the number of water moleculesin the bubble at collapse and the equilibrium composition of
the various species resulting from dissociation of entrappedmolecules in the bubble when the temperature and pressurereached to its extreme conditions during transient collapse ofcavitation bubbles
31 Initial Bubble Size in the Liquid Medium Bubbles withdifferent initial radius present in the liquid medium play animportant role in cavitation Kumar and Moholkar [37] havereported that the smaller bubble has higher Laplace pressurewhich results in higher expansion and more intense collapseduring the transient collapse In this present study a singlebubble model with different initial radius has been chosen topresent the effects of bubble radius in sonochemical processFrom Table 3 it could be seen that the ∙OH radical formationduring transient collapse of cavitation bubble is higher withthe initial bubble radius of 5 120583m followed by 25120583m Thisis due to the bubble with small bubble radius can undergomany acoustic cycles before reaching its critical radius whenit collapses and as a result the highest temperature peak isreached at the moment of transient collapse of the cavitationbubble with 5120583m radius bubble as shown in Figure 1 andTable 3
32 Static Pressure of the System As stated earlier in theprevious section the cavitation is nothing but the nucle-ation growth and implosive collapse of bubbles but thegrowthexpansion of the bubble depends on the systemrsquosstatic pressure So when the bubble contains vapor cavitationmay occur due to reduced static pressure sufficiently atconstant temperature To investigate the effects of pressurefive different static pressures ranging from 100ndash300 kPa havebeen chosen The results showed that as the static pressureincreases the radical formation decreases drastically even itbecomes zero at higher ambient static pressure This is dueto at elevated static pressure the sonochemical effects geteliminated which directly affects the generation of radicalformation provided the applied pressure must be greaterthan or equal to the acoustic pressure amplitude (119875
119900
ge 119875AW)[9 38]Thehighest ∙OHradical productionwas seen at nearly
4 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50N
o o
f wat
er v
apor
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
5 middot 1010
1 middot 1011
3 middot 1012
6 middot 1012
(c)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
10
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus100 1 2 3 4 5
05
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus1
minus025
(e)
0 1 2 3 4 5
148
300
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
5120583m bubble
0 1 2 3 4 50
50
100
No of acoustic cycles
25120583m bubble
Acou
stic w
ave
ampl
itude
(bar
)
minus4
(f)
Figure 1 Simulations of radial motion of 5 and 25 micron air bubble in water 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPa Time historyof (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside the bubble (e)microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 5
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
15
3
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
2000
4000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
4 middot 1010
2 middot 1010
1 middot 1010
5 middot 109
(c)
0 1 2 3 4 50
2000
4000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
30
60
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5No of acoustic cyclesO
scill
ator
y ve
loci
ty (m
s)
minus04
minus01
0 1 2 3 4 5
0
01
Osc
illat
ory
velo
city
(ms
)
minus01
No of acoustic cycles
(e)
0 1 2 3 4 50
30
60
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
120 kPa
0 1 2 3 4 50
075
15
No of acoustic cycles
150kPa
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 2 Simulations of radial motion of 5 micron air bubble in water at 120 kPa and 150 kPa 119891 = 20 kHz 119875A = 150 kPa and 119877119900 = 5 120583mTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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DistributedSensor Networks
International Journal of
4 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50N
o o
f wat
er v
apor
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
5 middot 1010
1 middot 1011
3 middot 1012
6 middot 1012
(c)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
10
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus100 1 2 3 4 5
05
Osc
illat
ory
velo
city
(ms
)
No of acoustic cycles
minus1
minus025
(e)
0 1 2 3 4 5
148
300
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
5120583m bubble
0 1 2 3 4 50
50
100
No of acoustic cycles
25120583m bubble
Acou
stic w
ave
ampl
itude
(bar
)
minus4
(f)
Figure 1 Simulations of radial motion of 5 and 25 micron air bubble in water 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPa Time historyof (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside the bubble (e)microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 5
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
15
3
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
2000
4000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
4 middot 1010
2 middot 1010
1 middot 1010
5 middot 109
(c)
0 1 2 3 4 50
2000
4000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
30
60
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5No of acoustic cyclesO
scill
ator
y ve
loci
ty (m
s)
minus04
minus01
0 1 2 3 4 5
0
01
Osc
illat
ory
velo
city
(ms
)
minus01
No of acoustic cycles
(e)
0 1 2 3 4 50
30
60
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
120 kPa
0 1 2 3 4 50
075
15
No of acoustic cycles
150kPa
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 2 Simulations of radial motion of 5 micron air bubble in water at 120 kPa and 150 kPa 119891 = 20 kHz 119875A = 150 kPa and 119877119900 = 5 120583mTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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DistributedSensor Networks
International Journal of
Chinese Journal of Engineering 5
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
15
3
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
2000
4000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
4 middot 1010
2 middot 1010
1 middot 1010
5 middot 109
(c)
0 1 2 3 4 50
2000
4000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
30
60
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5No of acoustic cyclesO
scill
ator
y ve
loci
ty (m
s)
minus04
minus01
0 1 2 3 4 5
0
01
Osc
illat
ory
velo
city
(ms
)
minus01
No of acoustic cycles
(e)
0 1 2 3 4 50
30
60
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
120 kPa
0 1 2 3 4 50
075
15
No of acoustic cycles
150kPa
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 2 Simulations of radial motion of 5 micron air bubble in water at 120 kPa and 150 kPa 119891 = 20 kHz 119875A = 150 kPa and 119877119900 = 5 120583mTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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6 Chinese Journal of Engineering
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
5
10
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
1500
3000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or
mol
ecul
es
3 middot 1010
15 middot 1010 1 middot 1012
2 middot 1012
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
1000
2000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104
(d)
0 1 2 3 4 5
0
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus050 1 2 3 4 5
1
minus05
minus2
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
150
300
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
283K
0 1 2 3 4 50
30
60
343K
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 3 Simulations of radial motion of 5 micron air bubble in water at 283K and 343K 119891 = 20 kHz 119875A = 150 kPa and 119875119900 = 100 kPaTime history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d) pressure inside thebubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
Chinese Journal of Engineering 7
0 1 2 3 4 50
3
6
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
0 1 2 3 4 50
No of acoustic cycles
No
of w
ater
vap
or m
olec
ules
1 middot 1011
5 middot 1010
1 middot 1011
5 middot 1010
(c)
0 1 2 3 4 50
5000
No of acoustic cycles
Pres
sure
(bar
)
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles
1 middot 104 1 middot 104
(d)
0 1 2 3 4 5
05
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
minus1
minus025
0 1 2 3 4 5
05
minus1
minus025
No of acoustic cyclesOsc
illat
ory
velo
city
(ms
)
(e)
0 1 2 3 4 50
200
400
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
Oxygen bubble
0 1 2 3 4 50
150
300
Nitrogen bubble
No of acoustic cycles
Acou
stic w
ave
ampl
itude
(bar
)
(f)
Figure 4 Simulations of radial motion of 5 micron air bubble in water with O2
bubble and N2
bubble 119891 = 20 kHz 119875A = 150 kPa and119875119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
8 Chinese Journal of Engineering
0 1 2 3 4 50
2
4
No of acoustic cycles0 1 2 3 4 5
0
3
6
No of acoustic cycles
Radi
us (R
Ro)
Radi
us (R
Ro)
(a)
0 1 2 3 4 50
3000
6000
Tem
pera
ture
(K)
No of acoustic cycles0 1 2 3 4 5
0
750
1500
Tem
pera
ture
(K)
No of acoustic cycles
(b)
0 1 2 3 4 50
No
of t
olue
ne
vap
mol
ecul
es
No of acoustic cycles0 1 2 3 4 5
0
No of acoustic cycles
No
of h
exan
eva
pm
olec
ules
1 middot 105
2 middot 105 3 middot 1011
15 middot 1011
(c)
1 middot 104
0 1 2 3 4 50
5000
Pres
sure
(bar
)
No of acoustic cycles0 1 2 3 4 5
0
500
1000
Pres
sure
(bar
)
No of acoustic cycles
(d)
0 1 2 3 4 5
Osc
illat
ory
velo
city
(ms
)
minus03
minus01
No of acoustic cycles0 1 2 3 4 5
0005
Osc
illat
ory
velo
city
(ms
)
minus001
minus00025
No of acoustic cycles
(e)
0 1 2 3 4 50
200
400
Acou
stic w
ave
ampl
itude
(bar
)
Toluene
No of acoustic cycles0 1 2 3 4 5
0
1
2
Acou
stic w
ave
ampl
itude
(bar
)
No of acoustic cycles
n-hexane
(f)
Figure 5 Simulations of radial motion of 5 micron air bubble in toluene and n-hexane as cavitation medium 119891 = 35 kHz 119875A = 150 kPaand 119875
119900
= 100 kPa Time history of (a) radius of the bubble (b) temperature inside the bubble (c) water vapor evaporation in the bubble (d)pressure inside the bubble (e) microturbulence generated by the bubble and (f) acoustic waves emitted by the bubble
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
Chinese Journal of Engineering 9
Table 3 Simulation summary of initial bubble size (119877119900
) dependent sonochemical process
Conditions at the first collapse of the bubble119877119900
= 5 120583m 119877119900
= 25 120583m 119877119900
= 50 120583m 119877119900
= 100 120583m 119877119900
= 200 120583m119879max = 3999K 119879max = 1688K 119879max = 7785K 119879max = 409K 119879max = 3299K119875max = 6967MPa 119875max = 3057MPa 119875max = 256MPa 119875max = 288 kPa 119875max = 136 kPa119881turb = 036ms 119881turb = 611ms 119881turb = 62ms 119881turb = 795ms 119881turb = 112ms119875AW = 2404MPa 119875AW = 880MPa 119875AW = 063MPa 119875AW = 027MPa 119875AW = 035 kPa
119873N2 = 128 times 1010 119873N2 = 132 times 10
12 119873N2 = 103 times 1013 119873N2 = 811 times 10
13 119873N2 = 644 times 1014
119873O2 = 341 times 109 119873O2 = 351 times 10
11 119873O2 = 273 times 1012 119873O2 = 216 times 10
13 119873O2 = 171 times 1014
119873W = 291 times 109
119873W = 25 times 1011
119873W = 908 times 1011
119873W = 298 times 1012
119873W = 115 times 1013
Species Equilibrium composition of species in the bubble at collapse5120583m 25 120583m 50 120583m 100120583m 200120583m
N2 626 times 10minus1 686 times 10minus1 738 times 10minus1 768 times 10minus1 779 times 10minus1
O2 128 times 10minus1 182 times 10minus1 196 times 10minus1 204 times 10minus1 207 times 10minus1
H2O 141 times 10minus2 130 times 10minus1 650 times 10minus2 280 times 10minus2 140 times 10minus2
N 156 times 10minus5 mdash mdash mdash mdash
O 595 times 10minus3 mdash mdash mdash mdashH 283 times 10minus4 mdash mdash mdash mdashO3 170 times 10
minus5 mdash mdash mdash mdashH2 253 times 10minus4 mdash mdash mdash mdashOH 951 times 10minus3 903 times 10minus5 mdash mdash mdashHO2 559 times 10
minus4
581 times 10minus6 mdash mdash mdash
H2O2 200 times 10minus5 mdash mdash mdash mdashNO 847 times 10minus2 258 times 10minus3 149 times 10minus6 mdash mdashNO2 170 times 10minus3 127 times 10minus4 284 times 10minus6 mdash mdashN2O 361 times 10
minus4
218 times 10minus6 mdash mdash mdash
NH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10minus5 mdash mdash mdash mdashHNO2 175 times 10
minus4
706 times 10minus6 mdash mdash mdash
Note solvent = water temperature (119879) = 303K static pressure (1198750) = 100 kPa dissolved gas = air and frequency (119891) = 20 kHz
ambient static pressure (ie 100 kPa) and the productionof ∙OH radical decreases as the static pressure approachesto the magnitude of acoustic pressure that is 150 kPa Theproduction of ∙OH radical at 100 kPa is typically 15 foldhigher than the ∙OH radical production at 120 kPa while at150 kPa or higher static pressure no ∙OH radical formationwas seenThis result can be attributed to the temperature peakreached at the moment of collapse of the bubble At the timeof transient collapse the highest temperature peak (3999K)was seen when the pressure was 100 kPa while the lowesttemperature peak (sim313 K) was observed with elevated staticpressure of 300 kPa
33 System Operating Temperature Another important fac-tor that affects the transient cavitation is system temperatureTo study the temperature effect on sonochemical processthe numerical simulations were run in the temperature rangefrom 283 to 373K (viz 283 303 323 343 and 373 K)The sim-ulation results are depicted in Figure 3 As the temperaturein the system increases the formation of oxidizing speciesdue to transient cavitation of bubbles reduces drasticallyThiscould be attributed to the effects of bubble radius as discussedin the earlier section In this case vapor bubbles grow
with increasing the temperature through the phenomenonof boiling [20] So the lower the temperature means thehigher the cavitation effects in the system Table 5 shows thatthe production of ∙OH radical is highest with the lowesttemperature that is at 283K while at the boiling point ofwater no ∙OH radical formation has been observed Theoverall trend of the ∙OH radical production under variousoperating temperature is 283K gt 303K gt 323K gt 343K
34 Type of Dissolved Gas Content The type of dissolvedgas has an impact on bubble nucleation rate as described inthe literatures [15 37] The simulation results for four gasesare shown in Table 6 and Figure 4 The production of ∙OHradical as well as H
2
O2
is highest for O2
bubble followed byair Ar and N
2
bubble Also the generation of O3
per bubblefor oxygen bubble is one order of magnitude higher thanthe O
3
generation by air bubble The radicals by air bubbleare formed through the reactions (3)ndash(22) while (24) and(25) represent the radical formation by O
2
bubble [39] Theproduction of radicals is least with N
2
bubble as compared toother gas bubbles This is due to the scavenging of radicals byN2
molecules through the reactions (3)ndash(16) Moreover thereis no regeneration of ∙OH and O∙ radicals by O
2
when the
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
10 Chinese Journal of Engineering
Table 4 Simulation summary of sonochemical process under various static pressures (119875119900
)
Conditions at the first collapse of the bubble119875119900
= 100 kPa 119875119900
= 120 kPa 119875119900
= 150 kPa 119875119900
= 200 kPa 119875119900
= 300 kPa119879max = 3999K 119879max = 3024K 119879max = 9773K 119879max = 3534K 119879max = 3127K119875max = 6967MPa 119875max = 2863MPa 119875max = 462MPa 119875max = 416 kPa 119875max = 477 kPa119881turb = 036ms 119881turb = 021ms 119881turb = 007ms 119881turb = 0008ms 119881turb = 0002ms119875AW = 2404MPa 119875AW = 543MPa 119875AW = 120 kPa 119875AW = 2 kPa 119875AW = 06 kPa
119873N2 = 128 times 1010 119873N2 = 148 times 10
10 119873N2 = 178 times 1010 119873N2 = 228 times 10
10 119873N2 = 328 times 1010
119873O2 = 341 times 109
119873O2 = 395 times 109
119873O2 = 474 times 109
119873O2 = 607 times 109
119873O2 = 873 times 109
119873W = 291 times 109
119873W = 181 times 109
119873W = 886 times 108
119873W = 819 times 1010
119873W = 381 times 108
Species Equilibrium composition of species in the bubble at collapse1 bar 12 bar 15 bar 2 bar 3 bar
N2 626 times 10minus1 699 times 10minus1 760 times 10minus1 768 times 10minus1 783 times 10minus1
O2 128 times 10minus1 167 times 10minus1 202 times 10minus1 204 times 10minus1 208 times 10minus1
H2O 141 times 10minus2
745 times 10minus2
380 times 10minus2
280 times 10minus2
900 times 10minus3
N 156 times 10minus5 mdash mdash mdash mdashO 595 times 10minus3 935 times 10minus4 mdash mdash mdashH 283 times 10minus4 409 times 10minus5 mdash mdash mdashO3 170 times 10
minus5
371 times 10minus6 mdash mdash mdash
H2 253 times 10minus4 167 times 10minus4 mdash mdash mdashOH 951 times 10minus3 633 times 10minus3 mdash mdash mdashHO2 559 times 10
minus4
360 times 10minus4 mdash mdash mdash
H2O2 200 times 10minus5 274 times 10minus5 mdash mdash mdashNO 847 times 10minus2 430 times 10minus2 264 times 10minus5 mdash mdashNO2 170 times 10
minus3
103 times 10minus3
109 times 10minus5 mdash mdash
N2O 361 times 10minus4 110 times 10minus4 mdash mdash mdashNH 170 times 10minus6 mdash mdash mdash mdashHNO 595 times 10
minus5
138 times 10minus5 mdash mdash mdash
HNO2 175 times 10minus4
140 times 10minus4 mdash mdash mdash
Note solvent = water dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) = 303K and frequency (119891) = 20 kHz
bubble contents are N2
gas So the total number of radicalsper bubble in N
2
bubbling is always lower than the other gasbubbles The trend of production of ∙OH radical per bubblewith various gases bubbling is as follows O
2
gt Air gt Ar gtN2
N2
+O∙ 999448999471 N∙ +NO (3)
N2
+∙OH 999448999471 N
2
H +O∙ (4)
N2
+∙OH 999448999471 N
2
O +H∙ (5)
N2
+∙OH 999448999471 NH +NO (6)
N2
+H∙ 999448999471 N2
H (7)
N2
+H∙ 999448999471 NH + N∙ (8)
N + ∙OH 999448999471 NO +H∙ (9)
N2
O +O∙ 999448999471 2NO (10)
NO + ∙OH 999448999471 NO2
(11)
NH + ∙OH 999448999471 NH2
+O∙ (12)
NH2
+O∙ 999448999471 H∙ +HNO (13)
HNO +O∙ 999448999471 NH +O2
(14)
HNO +O∙ 999448999471 NO + ∙OH (15)
HNO + ∙OH 999448999471 NO +H2
O (16)
N +O2
999448999471 NO +O∙ (17)
NO +O2
999448999471 NO2
+O∙ (18)
NH +O2
999448999471 HNO +O∙ (19)
NH +O2
999448999471 NO + ∙OH (20)
N2
+O2
999448999471 N2
O +O∙ (21)
H∙ +O2
999448999471 HO2
∙ (22)∙OH+O
2
999448999471 HO2
∙
+O∙ (23)
O∙ +O2
rarr O3
(24)
2HO2
∙
999448999471 H2
O2
+O2
(25)
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
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International Journal of
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DistributedSensor Networks
International Journal of
Chinese Journal of Engineering 11
Table 5 Simulation summary of system temperature (119879119900
) dependent sonochemical process
System temperature119879 = 283K 119879 = 303K 119879 = 323K 119879 = 343K 119879 = 373K
Conditions at the first collapse of the bubble119879max = 3989K 119879max = 3999K 119879max = 3733K 119879max = 2683K 119879max = 8117K119875max = 6815MPa 119875max = 6967MPa 119875max = 6239MPa 119875max = 1753MPa 119875max = 179MPa119881turb = 035ms 119881turb = 036ms 119881turb = 045ms 119881turb = 108ms 119881turb = 463ms119875AW = 2475MPa 119875AW = 2404MPa 119875AW = 2156MPa 119875AW = 443MPa 119875AW = 220 kPa
119873N2 = 138 times 1010
119873N2 = 128 times 1010
119873N2 = 121 times 1010
119873N2 = 113 times 1010
119873N2 = 104 times 1010
119873O2 = 366 times 109 119873O2 = 341 times 10
9 119873O2 = 320 times 109 119873O2 = 302 times 10
9 119873O2 = 277 times 109
119873W = 794 times 108 119873W = 291 times 10
9 119873W = 123 times 1010 119873W = 815 times 10
10 119873W = 179 times 1012
Species Equilibrium composition of species in the bubble at collapse283K 303K 323K 343K 373K
N2 707 times 10minus1 626 times 10minus1 413 times 10minus1 116 times 10minus1 600 times 10minus3
O2 145 times 10minus1
128 times 10minus1
884 times 10minus2
283 times 10minus2
200 times 10minus3
H2O 163 times 10minus2 141 times 10minus2 121 times 10minus2 280 times 10minus2 993 times 10minus1
N 172 times 10minus5 156 times 10minus5 384 times 10minus6 mdash mdashO 667 times 10
minus3
595 times 10minus3
244 times 10minus3
569 times 10minus5 mdash
H 321 times 10minus4 283 times 10minus4 106 times 10minus4 257 times 10minus6 mdashO3 189 times 10minus5 170 times 10minus5 838 times 10minus6 228 times 10minus7 mdashH2 291 times 10minus4 253 times 10minus4 130 times 10minus4 229 times 10minus5 mdashOH 108 times 10
minus2
951 times 10minus3
527 times 10minus3
808 times 10minus4 mdash
HO2 631 times 10minus4 559 times 10minus4 325 times 10minus4 422 times 10minus5 mdashH2O2 228 times 10minus5 200 times 10minus5 136 times 10minus5 460 times 10minus6 mdashNO 951 times 10
minus2
847 times 10minus2
472 times 10minus2
457 times 10minus3 mdash
NO2 190 times 10minus3 170 times 10minus3 104 times 10minus3 111 times 10minus4 mdashN2O 401 times 10minus4 361 times 10minus4 188 times 10minus4 869 times 10minus6 mdashNH 189 times 10
minus6
170 times 10minus6 mdash mdash mdash
HNO 667 times 10minus5 595 times 10minus5 274 times 10minus5 969 times 10minus7 mdashHNO2 196 times 10minus4 175 times 10minus4 112 times 10minus4 176 times 10minus5 mdashNote solvent = water dissolved gas = air initial bubble size (119877
0) = 5 120583m static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz
35 Type of Solvent or Cavitation Medium The solvent orcavitation medium is another important factor that affectsdirectly on the sonochemical process In order to assess thesuitability of solvent for cavitation we have chosen threesolvents with different physicochemical properties namelywater toluene and n-hexane as shown in Table 2 To addressthis issue we have presented the numerical solution withvarious solvent as cavitation medium in Figure 5 and Table 7which lists the temperature and pressure peak reached at themoment of collapse with various equilibrium compositionsof species The number of ∙OH radical production is highestwhen water is used as cavitation medium This can beattributed to the lower surface tension and higher vaporpressure of the organic solvent The production of ∙OHradical in water is typically two orders of magnitude higherthan that in toluene So due to the low intensity of bubblecollapse organic solvents are not able to generate sufficientnumbers of radical in-situ for sonochemical reactions
4 Conclusions
The lower is the system temperature the higher is thecavitation effects that is when the system temperature is
moderately low the effect of cavitation is more In this presentstudy the radical formation due to cavitation is highest whenthe system temperature is 283K So the system with lowoperating temperature and cavitation medium contents withsmall initial bubble radius is always preferable for sono-chemical reactions since this type of sonochemical reactionsystems are able to generate large amount of highly oxidizingspecies Due to the high vapor pressure and low surfacetension organic solvents cannot produce large amount ofradicals in the reaction medium thus they are not suitablefor sonochemical reactions However they could be goodsolvents for extraction or other processes using ultrasoundMoreover depending on the process requirement one canchoose the system with different gas bubbling and aqueousor organic solvents for conducting experiments
Nomenclature
119862119881119894
Heat capacity at constant volume Jkgminus1 Kminus1
119888L Velocity of sound in liquid medium m sminus1119888W Velocity of sound in water m sminus1
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
12 Chinese Journal of Engineering
Table 6 Effect of dissolved gas content on sonochemical process
Conditions at the first collapse of the bubbleAir bubble Nitrogen bubble Oxygen bubble Argon bubble119879max = 3999K 119879max = 4379K 119879max = 4155K 119879max = 4551K119875max = 6967MPa 119875max = 7723MPa 119875max = 7582MPa 119875max = 7866MPa119881turb = 036ms 119881turb = 037ms 119881turb = 037ms 119881turb = 037ms119875AW = 2404MPa 119875AW = 2825MPa 119875AW = 3078MPa 119875AW = 2728MPa
119873N2 = 128 times 1010 119873N2 = 163 times 10
10 119873O2 = 163 times 1010 119873Ar = 163 times 10
10
119873O2 = 341 times 109
119873W = 388 times 109
119873W = 388 times 109
119873W = 254 times 109
119873W = 291 times 109
Species Equilibrium composition of species in the bubble at collapseAir bubble Nitrogen bubble Oxygen bubble Argon bubble
N2 626 times 10minus1 805 times 10minus1 mdash mdashO2 128 times 10minus1 280 times 10minus4 793 times 10minus1 109 times 10minus3
Ar mdash mdash mdash 865 times 10minus1
H2O 141 times 10minus2 969 times 10minus3 113 times 10minus2 921 times 10minus3
N 156 times 10minus5 585 times 10minus5 mdash mdashO 595 times 10minus3 506 times 10minus4 187 times 10minus2 134 times 10minus3
H 283 times 10minus4
248 times 10minus3
221 times 10minus4
259 times 10minus3
N3 mdash 145 times 10minus6 mdash mdashO3 170 times 10minus5 mdash 328 times 10minus4 mdashH2 253 times 10
minus4
673 times 10minus3
103 times 10minus4
431 times 10minus3
OH 951 times 10minus3 250 times 10minus3 157 times 10minus2 409 times 10minus3
HO2 559 times 10minus4 677 times 10minus6 234 times 10minus3 207 times 10minus5
H2O2 200 times 10minus5
886 times 10minus7
475 times 10minus5
179 times 10minus6
NO 847 times 10minus2 565 times 10minus3 mdash mdashNO2 170 times 10minus3 493 times 10minus6 mdash mdashN2O 361 times 10
minus4
302 times 10minus5 mdash mdash
NH 170 times 10minus6
268 times 10minus5 mdash mdash
NH2 mdash 242 times 10minus5 mdash mdashNH3 mdash 178 times 10minus5 mdash mdashHNO 595 times 10
minus5
225 times 10minus5 mdash mdash
HNO2 175 times 10minus4 216 times 10minus6 mdash mdashNote solvent = water initial bubble size (119877
0) = 5 120583m temperature (119879) = 303K static pressure (119875
0) = 100 kPa and frequency (119891) = 20 kHz O2 gt air gt Ar gt
N2
119888T Velocity of sound in toluene m sminus1119888H Velocity of sound in n-hexane m sminus1119863w Diffusion coefficient of solvent vapor m2
sminus1119891 Frequency of ultrasound wave Hz119891119894
Translational and rotational degrees offreedom
ℎ Van der Waalrsquos hard core radius m119868diffw Instantaneous diffusive penetration depth
for water molecules119896 Boltzmann constant J Kminus1119873W Number of water molecules trapped in the
bubble119873N2
Number of N2
molecules in the bubble119873O2
Number of oxygenmolecules in the bubble119873T Number of toluenemolecules in the bubble119873H Number of n-hexane molecules in the
bubble
119873Ar Number of Ar molecules in the bubble119873tot Total number of molecules (gas + vapor) in
the bubble119875119900
Static pressure in the liquid medium Pa119875max Pressure peak reached in the bubble at the
time of first collapse Pa119875AW Pressure amplitude of the acoustic wave
generated by the cavitation bubble Pa119876 Heat conducted across bubble wall J sminus1119877 Radius of the bubble m119877119900
Initial radius of the cavitation bubble m119889119877119889119905 Bubble wall velocity m sminus1119905 Time s119879 Temperature of the bubble contents K119879119900
Ambient (or bulk liquid medium) temper-ature K
119879max Temperature peak reached in the bubble atthe time of first collapse K
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Chinese Journal of Engineering 13
Table 7 Simulation summary of sonochemical process with differ-ent solvent as cavitation medium
Conditions at the first collapse of the bubbleH2O2 C6H5ndashCH3 C6H12
119879max = 3179K 119879max = 4835K 119879max = 1151K119875max = 355MPa 119875max = 9617MPa 119875max = 4455MPa119881turb = 025ms 119881turb = 015ms 119881turb = 0005ms119875AW = 1261MPa 119875AW = 3016MPa 119875AW = 188 kPa
119873N2 = 131 times 1010
119873N2 = 113 times 109
119873N2 = 107 times 1010
119873O2 = 347 times 109
119873O2 = 299 times 108
119873O2 = 285 times 109
119873W = 121 times 109 119873T = 402 times 10
3 119873H = 605 times 1010
SpeciesEquilibrium composition of species in the bubble at
collapseH2O2 C6H5ndashCH3 C6H12
N2 709 times 10minus1 717 times 10minus1 140 times 10minus1
O2 166 times 10minus1 126 times 10minus1 mdashH2O 537 times 10
minus2 mdash 628 times 10minus2
N mdash 192 times 10minus4 mdash
O 138 times 10minus3 206 times 10minus2 mdashH 590 times 10minus5 151 times 10minus6 mdashN3 mdash 386 times 10
minus6 mdashO3 544 times 10minus6 384 times 10minus5 mdashH2 177 times 10minus4 mdash 898 times 10minus1
OH 696 times 10minus3
195 times 10minus5 mdash
HO2 410 times 10minus4 104 times 10minus6 mdashH2O2 268 times 10minus5 mdash mdashNO 514 times 10
minus2
142 times 10minus1 mdash
NO2 123 times 10minus3
229 times 10minus3 mdash
NO3 mdash 166 times 10minus6 mdashN2O 149 times 10minus4 748 times 10minus4 mdashN2O3 mdash 115 times 10
minus6 mdashHNO 191 times 10minus5 mdash mdashHNO2 157 times 10minus4 mdash mdashCO mdash 710 times 10
minus6
118 times 10minus2
CO2 mdash 126 times 10minus5 702 times 10minus4
NH3 mdash mdash 990 times 10minus3
HCN mdash mdash 148 times 10minus5
CH4 mdash mdash 237C2H4 mdash mdash 111 times 10minus4
C2H6 mdash mdash 409 times 10minus3
Note dissolved gas = air initial bubble size (1198770) = 5 120583m temperature (119879) =
303K static pressure (1198750) = 100 kPa and frequency (119891) = 35 kHz
119881turb Average velocity of the microturbulencein the medium generated by ultrasoundand cavitation in the medium (estimated at1mm distance from bubble center) m sminus1
120588L Density of the liquid kg mminus3120592 Kinematic viscosity of liquid m2 sminus1120590 Surface tension of liquid N mminus1120581 Thermal conductivity of bubble contents
W mminus1 Kminus1120582 Thermal diffusivity of bubble contents m2
sminus1
120579 Characteristic vibrational temperature(s) ofthe species K
Conflict of Interests
The authors of the paper do not have any direct financialrelation that might lead to a conflict of interest for any of theauthors
References
[1] J O Hirschfelder C F Curtiss and R B BirdMolecularTheoryof Gases and Liquids John Wiley amp Sons New York NY USA1954
[2] E U Condon and H Odishaw Handbook of Physics McGraw-Hill New York NY USA 1958
[3] R C Reid J M Prausnitz and B E Poling Properties of Gasesand Liquids McGraw-Hill New York NY USA 1987
[4] H Xu B W Zeiger and K S Suslick ldquoSonochemical synthesisof nanomaterialsrdquo Chemical Society Reviews vol 42 pp 2555ndash2567 2013
[5] J H Bang and K S Suslick ldquoApplications of ultrasound to thesynthesis of nanostructuredmaterialsrdquoAdvancedMaterials vol22 no 10 pp 1039ndash1059 2010
[6] S Kanmuri and V S Moholkar ldquoMechanistic aspects ofsonochemical copolymerization of butyl acrylate and methylmethacrylaterdquo Polymer vol 51 no 14 pp 3249ndash3261 2010
[7] M Sivakumar A Gedanken W Zhong et al ldquoNanophaseformation of strontium hexaferrite fine powder by the sono-chemical method using Fe(CO)
5
rdquo Journal of Magnetism andMagnetic Materials vol 268 no 1-2 pp 95ndash104 2004
[8] P R Gogate and G S Bhosale ldquoComparison of effectiveness ofacoustic and hydrodynamic cavitation in combined treatmentschemes for degradation of dye wastewatersrdquo Chemical Engi-neering and Processing Process Intensificationdoi 2013
[9] S Chakma and V S Moholkar ldquoPhysical mechanism of sono-fenton processrdquo AIChE Journal 2013
[10] J B Bhasarkar S Chakma and V S Moholkar ldquoMechanis-tic features of oxidative desulfurization using sono-fenton-peracetic acid (UltrasoundFe2+-CH
3
COOH-H2
O2
) systemrdquoIndustrial amp Engineering Chemistry Research vol 52 no 26 pp9038ndash9047 2013
[11] P Braeutigam M Franke R J Schneider A Lehmann AStolle and B Ondruschka ldquoDegradation of carbamazepine inenvironmentally relevant concentrations in water by Hydrody-nam ic-Acoustic-Cavitation (HAC)rdquo Water Research vol 46no 7 pp 2469ndash2477 2012
[12] J Madhavan P S S Kumar S Anandan M Zhou FGrieser and M Ashokkumar ldquoUltrasound assisted photocat-alytic degradation of diclofenac in an aqueous environmentrdquoChemosphere vol 80 no 7 pp 747ndash752 2010
[13] P A Parkar H A Choudhary andV SMoholkar ldquoMechanisticand kinetic investigations in ultrasound assisted acid catalyzedbiodiesel synthesisrdquo Chemical Engineering Journal vol 187 pp248ndash260 2012
[14] H A Choudhury S Chakma andV SMoholkar ldquoMechanisticinsight into sonochemical biodiesel synthesis using heteroge-neous base catalystrdquo Ultrasonics Sonochemistry 2013
[15] J Rooze E V Rebrov J C Schouten and J T F KeurentjesldquoDissolved gas and ultrasonic cavitationmdasha reviewrdquoUltrasonicsSonochemistry vol 20 pp 1ndash11 2013
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
14 Chinese Journal of Engineering
[16] K D Bhatte S-I Fujita M Arai A B Pandit and BM Bhanage ldquoUltrasound assisted additive free synthesis ofnanocrystalline zinc oxiderdquo Ultrasonics Sonochemistry vol 18no 1 pp 54ndash58 2011
[17] K S SuslickMMMdleleni and J T Ries ldquoChemistry inducedby hydrodynamic cavitationrdquo Journal of the American ChemicalSociety vol 119 no 39 pp 9303ndash9304 1997
[18] J S Krishnan P Dwivedi and V S Moholkar ldquoNumericalinvestigation into the chemistry induced by hydrodynamiccavitationrdquo Industrial and Engineering Chemistry Research vol45 no 4 pp 1493ndash1504 2006
[19] T G LeightTheAcoustic Bubble Academic Press London UK1995
[20] Y T Shah A B Pandit and V S MoholkarCavitation ReactionEngineering Kluwer AcademicPlenum New York NY USA1999
[21] K S Suslick ldquoSonochemistryrdquo Science vol 247 no 4949 pp1439ndash1445 1990
[22] T Sivasankar and V S Moholkar ldquoMechanistic approach tointensification of sonochemical degradation of phenolrdquo Chem-ical Engineering Journal vol 149 no 1ndash3 pp 57ndash69 2009
[23] R Andreozzi V Caprio A Insola and R Marotta ldquoAdvancedoxidation processes (AOP) for water purification and recoveryrdquoCatalysis Today vol 53 no 1 pp 51ndash59 1999
[24] R E Apfel ldquoAcoustic cavitation inceptionrdquo Ultrasonics vol 22no 4 pp 167ndash173 1984
[25] C Gong and D P Hart ldquoUltrasound induced cavitationand sonochemical yieldsrdquo Journal of the Acoustical Society ofAmerica vol 104 no 5 pp 2675ndash2682 1998
[26] K S Suslick Y Didenko M M Fang et al ldquoAcoustic cavitationand its chemical consequencesrdquo Philosophical Transactions ofthe Royal Society A vol 357 no 1751 pp 335ndash353 1999
[27] P R Gogate and A B Pandit ldquoA review of imperative technolo-gies for wastewater treatment II hybrid methodsrdquo Advances inEnvironmental Research vol 8 no 3-4 pp 553ndash597 2004
[28] R Toegel B Gompf R Pecha and D Lohse ldquoDoes water vaporprevent upscaling sonoluminescencerdquo Physical Review Lettersvol 85 no 15 pp 3165ndash3168 2000
[29] B D Storey and A J Szeri ldquoWater vapour sonoluminescenceand sono chemistryrdquo Proceedings of the Royal Society A vol 456no 1999 pp 1685ndash1709 2000
[30] J B Keller and M Miksis ldquoBubble oscillations of large ampli-tuderdquo Journal of the Acoustical Society of America vol 68 no 2pp 628ndash633 1980
[31] R B Bird W E Stewart and E N Lightfoot LightfootTransport Phenomena JohnWiley amp Sons New York NY USA2nd edition 2001
[32] WH Press S A Teukolsky B P Flannery andW T VetterlingNumerical Recipes Cambridge University Press New York NYUSA 2nd edition 1992
[33] G Eriksson ldquoThermodynamic studies of high temperatureequilibriamdashXII SOLGAMIX a computer program for cal-culation of equilibrium composition in multiphase systemsrdquoChemica scripta vol 8 pp 100ndash103 1975
[34] SGrossmann SHilgenfeldtM Zomack andD Lohse ldquoSoundradiation of 3-MHzdriven gas bubblesrdquo Journal of theAcousticalSociety of America vol 102 no 2 pp 1223ndash1230 1997
[35] V S Moholkar and M M C G Warmoeskerken ldquoIntegratedapproach to optimization of an ultrasonic processorrdquo AIChEJournal vol 49 no 11 pp 2918ndash2932 2003
[36] FACTSAGE httpwwwfactsagecom[37] P Kumar and V S Moholkar ldquoNumerical assessment of hydro-
dynamic cavitation reactors using organic solventsrdquo Industrialand Engineering Chemistry Research vol 50 no 8 pp 4769ndash4775 2011
[38] S Chakma and V S Moholkar ldquoMechanistic features of ultra-sonic desorption of aromatic pollutantsrdquo Chemical EngineeringJournal vol 175 no 1 pp 356ndash367 2011
[39] A Prosperetti and A Lezzi ldquoBubble Dynamics in a compress-ible liquid part 1 first order theoryrdquo Journal of Fluid Mechanicsvol 168 pp 457ndash478 1986
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of