Photo Catalytic Treatment of Paper and Pulp Industry Effluents Using TiO2 Deposited Calcium Alumino Silicate Beads

8/3/2019 Photo Catalytic Treatment of Paper and Pulp Industry Effluents Using TiO2 Deposited Calcium Alumino Silicate Beads

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Photo catalytic Treatment

of Paper and Pulp IndustrialEffluents using TiO2Deposited Calcium

Alumino-Silicate Beads

Research Paper ByS. Ananda, H.P. Shivaraju, Dr. K. ByrappaDepartment of Studies in Chemistry, Department ofStudies in Environmental Science,Department of Studies in Geology,University of Mysore, Manasagangothri, Mysore- 570006, India


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IntroductionThe initial interest in thephotocatalysis was started whenFujishima and Honda discovered thephotochemicalsplitting of water into hydrogen andoxygen with TiO2.The catalyst absorbs a photon of lightmore energetic than band gap of thecatalyst.Main Advantage:Because the process gradually breaksdown the contaminant organicpollutants, no residue of the original


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TiO2+ hv e- CB (TiO2) + h+CB (TiO2)

h+ + OH- OHOOO2 + e- O-2 OO-2O + H+ HOO2HOO2 + HOO2 H2O2 + O2H2O2 + O-2 O OHO + OH-H2O2 + hv 2OHOH2O2 + e- OH- + OHO


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Paper and pulp industryeffluentsIn India, pulp and paper mills are now

considered as the

nations third largest polluter and it has been

estimated that this industry is

responsible for 50% of all the waste dumped into

the nations waters.

The main

component groups of wood are cellulose and

lignin.

The ul in and bleachin ste s enerate most


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Pulping -the raw material is treated mechanically or

chemically to remove lignin in order to facilitate cellulose

fibre separation and to improve the papermaking properties

of fibres.Bleaching -process to whiten and brighten the pulp through

removal of residual lignin.

The effluents generated by the mills are associated withthe following major problems:

1. Dark brown coloration of the receiving water bodies

result in reduced penetration of light, thereby affecting

benthic growth and habitat.

2. High content of organic matter, which contributes to

the biological oxygen demand (BOD) and depletion of

dissolved oxygen in the receiving ecosystems.


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3. Significant solid wastes from pulp and paper mills

include bark; reject fibres, wastewater treatment plant

sludge, scrubber sludge and boiler and furnace ash.

4. Sludge disposal is a serious environmental problem due

to the partitioning of chlorinated organic from effluents

to solids-Harmful to the fish population.

5. The major air emissions are fine and coarse

particulates from recovery furnaces and burners, sulphur

oxides (SOx) from sulphite mills, volatile organic

compounds (VOC) from wood chip digestion, spent liquor

evaporation and bleaching, Volatile organics include carbon

disulfide, methanol, methyl ethyl ketone, phenols, terpenes,

acetone, alcohols, chloroform, chloromethane, and

trichloroethane.


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In order to increase the photocatalyticefficiency of photocatalyst, attemptsmade based on the immobilization of thephotocatalysts on various supportingmaterials.In the present work, CASB of 0.5 to 1 mmdiameter as the supporting material fordeposition of TiO2 by hydrothermaltechnique has been used.Photoreactor setupcarried out batch scale photoreactor.

photoreactor :100 ml standard borosilicatereaction vessel ke t on heatin late with

Use of caSB balls


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The effluent and suspended catalysts

continuously mixed by magnetic stirrerReactor vessel was exposed to the light

sources in a closed chamber provided

with UV light source (Sankyo Denki,

Japan, 8W) and visible light sourcePhili s 220V 15W India .


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The experimental runs were carried out for 5 h

duration.

COD was estimated for the effluent before and afterthe photochemical treatments to observe reduction

of carbon contents in the effluent.Based on the COD results the photocatalytic

degradation efficiency was calculated by usingEquation

Photocatalytic degradation efficiency() =

((initial COD final COD)/ initial COD) * 100


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Results and discussion

The photocatalytic degradation rate of organics

depends on various experimental parameters:

Photocatalyst load

Temperature

pH

concentration of organic substrate

Light sources


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Lightsource: UV

lightPaper &pulpindustrialeffluent

Irradiationtime: 5 hInitial pH: 10

100

80

60

40

20

0

0 10 20 30 40 50 60 7080 90 100

Effect of photocatalysts load on the photocatalytic

degradation efficiency.

Amount of photocatalyst load in mg


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Photocatalytic degradation efficiency was gradually

increased up to 87 % when the photocatalyst load was

increased up to the range of 60 mg/50ml and beyond 60

mg/50 ml the photocatalytic degradation efficiency slightly

decreased.It is due to the increased number of active sites available on

the surface of deposited photocatalyst for the photoreaction.

The large number of active sites in turn increases the rate ofradical formation in the aqueous solution.The photochemical reaction rate was slightly reduced

beyond the 60 mg of photocatalyst load due to the large

amount of photocatalyst load in the effluent leads to light

scattering and reduction in light penetration through the

effluent.


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Photocatalytic experiments were carried out at differentlevels of initial pH ranging from 2 to 12.

The minimum rate of photodegradation (43%) was

recorded at pH 5.5

Photocatalytic efficiency of COD removal

from the effluent increased under alkaline conditions due

to increase of hydroxyl ions, which induces more

hydroxyl radicals that can form hydrogen peroxide.

Under acidic conditions, the per-hydroxyl (HO2) radical

can form hydrogen

peroxide, which in turn gives rise to the hydroxyl

radicals.

Effect of pH


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Effect of temperatureThe photocatalytic treatment of effluent has been studied

at different temperatures in the range 293-323 K.Constant temperature (> 303 K) of the effluent was

maintained by keeping the reaction vessel on the heating

plate provided with magnetic stirrer and the low

temperature ( 293 K) was maintained by keeping thereaction vessel in the cold water bath with continuous

stirring.Photocatalytic treatment efficiency was reached up to

100 % in the temperature range of 323 K within 3 h and the

same rate of photocatalytic degradation (96%) was

achieved in the range of 313 to

318 K for 4 h irradiation time.Results obtained show the rate of photochemical reaction

increases with an increased experimental temperature, itenhanced the photocatalytic treatment efficiency of the


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Photocatalytictreatmentundersunlight, 5

hirradiationtime

PhotocatalytictreatmentunderUV light, 5 h

irradiationtime

Initial

COD inmg/l

Final

CODinmg/l

COD

removal%

Initial

COD inmg/l

Final

CODinmg/l

COD

removal%

Untreatedraweffluent

2700 459 83 2700 351 87

Conventio1040 52 95 1040 20.8 98


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Under uv lightUnder visible light

Under sunlight100

80

60

40

20 0

0 1 2 34 5

PhotocatalyticDegradation

%Irradiation timein hrs

CODin

mg/l

2500

2000

1500

1000

500 0 1 2 3

4 5Irradiation timein hrs

a) b) Under uv light

Under visible lUnder sunligh


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Scope of photocatalytictreatement

The future of this technology will depend on demand due

to current and emerging pollution issues and innovative

reactor designs that maximize the effectiveness of

photocatalysis so it can compete economically withestablished technologies like activated carbon

adsorption and biological treatment.

It offers great potential as an industrial technology for

detoxification of wastewater due to several factors:

1. The process occurs under ambient conditions very

slowly; direct UV light exposure increases the rate of

reaction.


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2. The formation of photocyclized intermediate products,

unlike direct photolysis techniques, is avoided.

3. Oxidation of the substrates to CO2 is complete.

4. The photocatalyst is inexpensive.

Although photocatalytic reactors have the potential to

oxidize compounds to carbon dioxide and water, the

reactor design must provide sufficient conditions

(residence time, mass transfer and UV flux) to ensure that

complete oxidation takes place.


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references

International Journal of Chemical EngineeringResearch ISSN 0975 - 6442 Volume 2, Number 2(2010), Research India Publicationshttp://www.ripublication.com/ijcher.htm (slides-2,3,7-16)

Treatment of Pulp and Paper Mill Wastes bySuresh Sumathi, Indian Institute of Technology,Bombay, India

Yung-Tse Hung, Cleveland State University,Cleveland, Ohio, U.S.A. (slide- 4, 5, 6)

Fujishima A., and Honda, K., 1972,Electrochemical photolysis of water at asemiconductor electrode, Nature., 238. ( slide-
http://www.ripublication.com/ijcher.htmhttp://www.ripublication.com/ijcher.htm


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Photo Catalytic Treatment of Paper and Pulp Industry Effluents Using TiO2 Deposited Calcium Alumino Silicate Beads