8/6/2019 Physical Chemistry Lina 2009
1/36
PHYSICAL CHEMISTRY
8/6/2019 Physical Chemistry Lina 2009
2/36
Applied physical chemistry
procedures is used to solve commonenvironmental engineering problems.
8/6/2019 Physical Chemistry Lina 2009
3/36
Physical Chemistry - is a combined scienceof physics, chemistry, thermodynamics,electrochemistry and quantum mechanics.It functions to provide molecular levelinterpretation of observed macroscopicphenomena; typically, changes intemperature, pressure, volume and heat
in the liquid solid and gas phase andcorrelates to microscopic atomic andmolecular interactions.
8/6/2019 Physical Chemistry Lina 2009
4/36
G asses.Indefinite volume.Indefinite shape.Take the shape and volumeof container.Particles are far apart.Particles move fast
.high Kinetic Energy -particles can separate andmove throughout container..
8/6/2019 Physical Chemistry Lina 2009
5/36
Henrys Law
It states that theamount of gas thatdissolves in a liquidis proportional tothe partial pressurethat the gas exertson the surface of the liquid
8/6/2019 Physical Chemistry Lina 2009
6/36
Henrys LawCA = K HPA
WhereCA = concentration of A [mol/L] or
[mg/L]KH = Henrys Law constant
[mol/L.atm] or [mg/L.atm]PA = partial pressure of A [atm]
8/6/2019 Physical Chemistry Lina 2009
7/36
Air StrippingAir stripping is a common method of removing dissolved gasses from waterand wastewater.G asses commonly removed includeammonia, carbon dioxide and hydrogensulfide.The only gasses with appreciable partialpressure in air are nitrogen andoxygen.
8/6/2019 Physical Chemistry Lina 2009
8/36
Air StrippingOther gasses represent only 1% of thetotal pressure.Thus , since the equilibriumconcentration of a dissolved gas isproportional to the partial pressure of thegas on the liquid surface, any gas exceptnitrogen and oxygen can be air strippedto relatively low concentration by bringingit into intimate contact with air.
8/6/2019 Physical Chemistry Lina 2009
9/36
8/6/2019 Physical Chemistry Lina 2009
10/36
Air stripping
8/6/2019 Physical Chemistry Lina 2009
11/36
Sample problemAn air-stripping tower is used to removedissolved carbon dioxide from agroundwater supply. If the tower lowersthe level to twice the equilibriumconcentration, what amount of dissolvegas will remain in the water aftertreatment? The partial pressure of carbon
dioxide in the atmosphere is 1 x 10 -3.5 atm.
8/6/2019 Physical Chemistry Lina 2009
12/36
IdealG
as Law
Where
PV = nRTWhere:
P = absolute pressure [atm]V = volume [L]n = number of moles [mol]
T = absolute temperature [KR = gas constant [0.0821L.atm/mol.K]
8/6/2019 Physical Chemistry Lina 2009
13/36
Sample ProblemAnaerobic microorganisms metabolize
organic matter to carbon dioxide andmethane gases. Estimate the volume of gas produced (at atmospheric pressureand 25 oC) from the anaerobicdecomposition of 1 mol of glucose. Thereaction is
C6H12 0 6 p 3CH 4 + 3CO 2
8/6/2019 Physical Chemistry Lina 2009
14/36
D altons Law of Partial Pressure
Dalton's Law
The total pressure of a mixture of gasesis equal to the sum of the partialpressures of the gases in a mixture
Ptotal = PA + PB + PC + ..Pi
8/6/2019 Physical Chemistry Lina 2009
15/36
Sample ProblemAnaerobic digester are commonly used inwastewater treatment. The biologicalprocess produces both carbon dioxide
and methane gas. A laboratory workerplans to make a sysnthetic digester gas.There are cu rrently 2L methane gas at1.5 atm and 1 L of carbon dioxide gas at1 atm in the laboratory. If these twosamples are mixed in a 4-L tank, what willbe the partial pressure of individualgasses? What is total pressure?
8/6/2019 Physical Chemistry Lina 2009
16/36
It deals with numerical relationshipsbetween reactants and products in
chemical reactions.Stoichiometric analysis can be usedto determine the product yield for agiven amount of reactant converted.
Stoichiometry
8/6/2019 Physical Chemistry Lina 2009
17/36
Example of Stochiometric Analysis
Nuetralization of hydrochloric acid withlime
2HCl + Ca(OH)2 CaCl2 + 2H2O
Oxidation of acetic acid to carbon dioxideand water.
CH3COOH + 2O2 2CO2 + 2H2O
8/6/2019 Physical Chemistry Lina 2009
18/36
Sample ProblemA trailer truck with a full load of
hydrochloric acid HCl (40,000lbs)crashes into a bridge, spilling the acidinto the stream. How mu ch limeCa(OH) 2 is trequired to neutralize theacid.
The neutralization reaction is2HCl + Ca(OH)2 CaCl2 + 2H2O
8/6/2019 Physical Chemistry Lina 2009
19/36
An environmental engineeringapplication of stoichiometry is the
estimation of the amount of oxygen,a known organic chemical willconsume as it is converted to C0 2 andH20.
This is frequently termed asTheoretical Oxygen D emand or ThO D .
Theoretical Oxygen D emand
(ThOD
)
8/6/2019 Physical Chemistry Lina 2009
20/36
Theoretical Oxygen D emandIt is simply the amount of oxygen
required to convert the material tocarbon dioxide and water.In situations where the organic
matter contains amine compounds(-NH 2 ), the end produuct of the nitrogen
is ammonia (NH 3 )
8/6/2019 Physical Chemistry Lina 2009
21/36
Sample ProblemEthanol or ethyl alcohol is used inbeverages as gasoline additive, andin other industrial applications.Because small amounts of ethanoland sugar are used in the biologicalprocess to produce methanol, both of these compounds end up in thewastewater of methanol plants.
8/6/2019 Physical Chemistry Lina 2009
22/36
Sample ProblemCalculate the theoretical oxygen demand for
a wastewater containing:
a) 25 mg/L ethanol CH 3CH 2OHb) 45 mg/L glucose C 6H12 O6c) A mixture of 25 mg/L ethanol and 45
mg/L glucose
8/6/2019 Physical Chemistry Lina 2009
23/36
Equilibrium Chemistry
It can be used to analyze avariety of differentaqueous reactions of interest to theenvironmental engineer
or the environmentalengineering student.
8/6/2019 Physical Chemistry Lina 2009
24/36
Reactions of environmental significanceincludedetermining the amount of a base to addan acid spill,the amount of acid to neutralize a basicprocess wastewater,the solubility of a metal in a chemical
waste streamand estimating the removal of phosphorusin wastewater treated with lime.
8/6/2019 Physical Chemistry Lina 2009
25/36
Mass balance
A mass balance is written statementor equation that describes thedifferent species in which acomponent may exists.
8/6/2019 Physical Chemistry Lina 2009
26/36
U NIT OF EXPRESSIONMolarity
Normality
8/6/2019 Physical Chemistry Lina 2009
27/36
Adsorption
It is a surface phenomenon in which asolute (soluble material) concentrates orcollects at a surface.
This contrasts with ABSORPTION, whicha substance penetrates the material.
8/6/2019 Physical Chemistry Lina 2009
28/36
Ad sorption is a process that occurswhen a gas or liquid solute
accumulates on the surface of a solidor a liquid (adsorbent), forming a filmof molecules or atoms (theadsorbate ).
8/6/2019 Physical Chemistry Lina 2009
29/36
Adsorbents Characteristics and G eneralRequirements
They must have high abrasionresistance, high thermal stability andsmall pore diameters, which results in
higher exposed surface area andhence high surface capacity foradsorption.
8/6/2019 Physical Chemistry Lina 2009
30/36
The adsorbents must also have adistinct pore structure which enables
fast transport of the gaseous vapors.
8/6/2019 Physical Chemistry Lina 2009
31/36
Adsorbents are used usually in theform of spherical pellets, rods,
moldings, or monoliths withhydrodynamic diameters between 0.5and 10 mm.
8/6/2019 Physical Chemistry Lina 2009
32/36
Silica gel is a chemically inert,nontoxic, polar and dimensionally
stable (< 400 C) amorphous form of SiO 2 .Zeolites are natural or syntheticcrystalline aluminosilicates whichhave a repeating pore network andrelease water at high temperature.
8/6/2019 Physical Chemistry Lina 2009
33/36
Activated carbon is a highly porous,amorphous solid consisting of
microcrystallites with a graphitelattice, usually prepared in smallpellets or a powder. It is non-polarand cheap.
8/6/2019 Physical Chemistry Lina 2009
34/36
Activated carbon can be used toremove toxic organics from both
water and air.It is commonly used in aquariumfilters.
8/6/2019 Physical Chemistry Lina 2009
35/36
It is used in some potable waterplants to remove organics before or
after chlorination, in industrialwastewater treatment to remove avariety of organics, and occasionallyto remove residual organics following
conventional wastewater treatment.
8/6/2019 Physical Chemistry Lina 2009
36/36
It is used in air pollution control toremove organic contaminants from
contaminated air before discharge.