research article treatment of wastewater from a dairy ... · industry, like many others, challenged...

Research ArticleTreatment of Wastewater from a Dairy Industry UsingRice Husk as Adsorbent Treatment Efficiency IsothermThermodynamics and Kinetics Modelling

Uttarini Pathak Papita Das Prasanta Banerjee and Siddhartha Datta

Department of Chemical Engineering Jadavpur University Kolkata 700032 India

Correspondence should be addressed to Uttarini Pathak uttarini1212gmailcom

Received 24 September 2015 Revised 16 December 2015 Accepted 24 December 2015

Academic Editor Perla B Balbuena

Copyright copy 2016 Uttarini Pathak et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Effluent from milk processing unit contains soluble organics suspended solids and trace organics releasing gases causing tasteand odor and imparting colour and turbidity produced as a result of high consumption of water from the manufacturing processutilities and service section chemicals and residues of technological additives used in individual operations which makes it crucialmatter to be treated for preserving the aesthetics of the environment In this experimental study after determination of the initialparameters of the raw wastewater it was subjected to batch adsorption study using rice husk The effects of contact time initialwastewater concentration pH adsorbent dosage solution temperature and the adsorption kinetics isotherm and thermodynamicparameters were investigated The phenomenon of adsorption was favoured at a lower temperature and lower pH in this caseMaximum removal as high as 925 could be achieved using an adsorbent dosage of 5 gL pH of 2 and temperature of 30∘C Theadsorption kinetics and the isotherm studies showed that the pseudo-second-order model and the Langmuir isotherm were thebest choices to describe the adsorption behavior The thermodynamic parameters suggested that not only was the adsorption byrice husk spontaneous and exothermic in nature but also the negative entropy change indicated enthalpy driven process

1 Introduction

Dairy industry one of the largest types of food industrycontributes to a great extent to pollution with pollutantsbeing organic in nature normally consisting of 13 dissolved13 colloidal and 13 suspended substances while inorganicmaterials are usually present mainly in solution [1] Consid-ering the ever increasing demand for milk the dairy industryin India arises as the largest industry to have the maximumwaste generation and related environmental problems are ofincreasing importance Thus the rapid growth of industrieshas not only enhanced the productivity but also resulted inthe release of toxic substances into the environment creatinghealth hazards andhampering the normal activity of flora andfauna The dairy industry converts the raw milk into variousproducts like butter cheese yogurt and processed milk ascondensedmilk and driedmilk (milk powder) involving pro-cesses such as chilling pasteurization and homogenizationWater is used in all processes in the dairy industry in the ratio

of 1 10 (water milk) per liter of milk [2] containing highconcentration of organic materials and all these componentscontribute largely towards their high values of biologicaloxygen demand (BOD) inflated rates of chemical oxygendemand (COD) high concentration of suspended solidsand oil greases liquid effluents and slurries containing aspectrum of large quantities of casein lactose and fats inaddition to inorganic salts besides detergents sanitizers andso forth used for washing [3] The volume of the wastewaterproduced depends largely on the quantity of milk processedand type of product manufactured It appears white in colourwith heavy black sludge and strong butyric acid odors due tothe decomposition of casein [4] It is slightly alkaline in natureand becomes acidic quite rapidly because of the fermentationof milk sugar to lactic acid The COD of dairy wastewater ismainly due to milk cream or whey Casein and whey are themain components of dairy wastewater which are relativelyhydrophobic making it poorly soluble in water and have anegative charge in milk The casein micelles exist in milk as a

Hindawi Publishing CorporationJournal of ermodynamicsVolume 2016 Article ID 3746316 7 pageshttpdxdoiorg10115520163746316

2 Journal of Thermodynamics

very stable colloidal dispersion and held together by calciumions inorganic phosphate citrate ions

H2N-R-COOminus +H+ 997888rarr +H

3N-R-COOminus

Casein Micelle Acid CaseinColloidal dispersion Insoluble Particles

(1)

Therefore all the above-mentioned phenomena make dairyindustry like many others challenged with rising costs forwastewater treatment and disposal Moreover industries haveto meet the discharge standards mentioned by CPCB whichbecomes a great problem for the industrialists

Technologies such as coagulationflocculation processand oxidation process have been developed over the yearsto remove organic matter (expressed as chemical oxygendemand COD) from industrial wastewater These methodsare effective in fields of reduction and time but are expensiveand require skilled personnel They also become disadvanta-geous in terms of pH adjustment and generation of chemicalsludge that must be treated before disposal [5] In additionto these various treatments which are already present inthe dairy industry there are biological treatments includingtrickling filters and activated sludge process Though theyare effective for complete treatment of the wastewater butare noneconomical large power demand more chemicalconsumption and large area availability Thus it is verymuch necessary for characterization of wastewater treatabil-ity studies and planning of proper units and processes foreffluent treatment

Adsorption technique emerges as promising techniquein the removal efficiency (COD) economy and operation[6] Physical adsorption using activated carbon is effective inremoval but has a high initial cost low adsorption capacitiesand separation inconvenience andneeds a costly regenerationsystem [7] All these have simulated the search of cheaperalternatives and application of biosorption in environmentaltreatment has become a significant research area in thepast years It is widely recognized that biosorption providesa feasible technique for the removal of pollutants fromwastewater Biosorption may be defined as a process whereina solute molecule is removed from the liquid phase in contactwith a solid usually an inexpensive adsorbent which has aspecial affinity for the solute particles [8] To explore thesenovel adsorbents the use of biosorbents from numerousagroindustry wastes has received much attention and led toa constructive approach

Rice husk which is the protective outer shell of the ricegrain is abundantly obtainable as a by-product of the ricemilling industries It has been estimated that the annualproduction of rice husk is estimated to be around 120 milliontonnes [9] constituting about one-fifth part of the totalannual rice production throughout the world [10] Thusthe disposal becomes a crucial factor The composition ofrice husks is found to consist of about 32 cellulose 21hemicelluloses 21 lignin 20 silica and 3 crude protein[11] Moreover their granular structure containing abundantfloristic fiber insolubility in water chemical stability andhigh mechanical strength make them potential adsorbentThey also consist of functional group such as carboxyl

hydroxyl and amidogen representing a favourable charac-teristic of rice husk [12]

However the application of plant wastes as adsorbents canalso bring several problems such as high chemical oxygendemand (COD) and biological chemical demand (BOD) aswell as total organic carbon (TOC) due to release of solubleorganic compounds contained in the plant materials Silicapresent on the external surface of rice husks in the formof silicon-cellulose membrane is responsible for insufficientbinding between functional groups existing on rice husksurfaces and adsorbate ions or molecules present in solutionPresence of wax and natural fats on the internal surface ofrice husk as impurities has also got impact on the adsorptionproperties of rice husk chemically and physically [12]

In this study the potential ability of rice husk withoutany modification as biosorbent for the adsorption of organicpollutants fromdairywastewater was investigatedThe effectsof initial concentration pH adsorbent dosage solutiontemperature on adsorption and the adsorption kineticsisotherms and thermodynamic parameters were studied

2 Materials and Methods

Wastewater sample was collected from outfall of a dairyindustry at Dankuni near Durgapur Express HighwayWastewater sample collected from the plant was placed incontainers to be transported to the laboratory and storedat 4∘C in a refrigerator All the initial parameters of thewastewater were analysed in the laboratory as per the givenstandard methods in the handbook [13] All the chemicalswere of analytical reagent grades and used as receivedwithout further purifications

21 Adsorbent Preparation The rice husk used was obtainedfrom a nearby rice mill in Dankuni West Bengal India Itwas washed repeatedly with double-distilled water to removedust and soluble impurities and this was followed by dryingat 343K for 24 h It was sieved usingmeshes to get the desiredadsorbent size of 30 micrometers and stored in an air tightcontainer

22 Experimental Batch Study The biosorption studies werecarried out in 250mL glass-stoppered Erlenmeyer flaskscontaining a fixed amount of adsorbent Solution pH wasadjusted with HCl or NaOH (01 N) pH had been measuredby following electrometric method using a digital pH meterA known amount of adsorbent was added to samples andwas agitated at 150 rpm agitation speed allowing sufficienttime for adsorption Then the mixtures were centrifugedand filtered through filter paper and the final concentrationwas determined in the filtrate using UVVIS spectropho-tometer The effects of various parameters on the percentageremoval were observed by varying adsorbent dosage (4 68 and 10 gL) initial pH of wastewater (2 4 6 8 and 10)temperature (293K 298K 308K and 313 K) and concen-tration (183mgL 1954mgL 2074mgL 2196mgL and

Journal of Thermodynamics 3

Table 1 Characteristics of dairy wastewater

Initial parameters of wastewaterCOD 468mgLBOD 210mgLOil and grease 240mgLChloride 136mgL (less than 250 ppm)Alkalinity 4625mgL CaCo

3

equivalentpH 734ndash738TSS 942mgLTDS 680mgLConductivity 1200mScm

2318mgL) The adsorption capacity was measured by thefollowing equation

119902119890=

(119862119900minus 119862119905) 119881

119898

(2)

where 119862119900is initial concentration (mgL) 119862

119905is concentration

at time 119905 (mgL) 119881 is the volume (L) of wastewater and119898 ismass of biosorbent (g)

3 Results and Discussions

31 Characterization of Wastewater The dairy wastewatercollected from the local industry had the following char-acteristics presented in Table 1 Various physicochemicalparameters with whitish effluents along with unpleasantodor were observed The results showed that though thewastewater did not have a very high COD value it was abovethe permissible limit The COD value was found to be largerthan the BOD value suggesting that the organic compoundsinwastewater are slowly biodegradable [2]ThepHwas foundto be slightly alkaline in the range of 734ndash738 The chloridesmay be present due to the use of detergents and sanitizers inthe cleaning of equipment but the value was not above thepermissible value Oil and grease were high due to presenceof fats lactose and proteins with a value of 240mgL Theamounts of total suspended solids and total dissolved solidswere quite high with values of 942mgL and 680mgL Thepresence of calcium ions as a prime constituent of casein wasindicated by the high value of alkalinity of 4625mgL CaCO

3

equivalent Electrical conductivity of the wastewater was alsorecorded to be quite high

32 Batch Adsorption Study

321 Effect of Adsorbent Dosage The experiments weredone under the conditions of constant temperature (30∘C)agitation speed (150 rpm) constant pH of 738 and variableadsorbent dosage (4 6 8 and 10 gL) The adsorbent dosagewas varied and the percentage removal as a function of adsor-bent dosage was calibrated in Figure 1(a) It was observedthat the percentage removal was found to be decreasing withincrease in dosage This increase in COD value may be dueto the release of soluble organic compounds contained in theplantmaterialsThe reductionwas quite steep up to 8 gL after

which there was no further reduction up to 10 gL It is to benoted that experiments were done for dosage beyond 10 gLbut there was no further change for adsorption or desorptionThese biosorbent materials are highly pervious in nature butthe porous volume is associated with numerousminute porescausing additional diffusional resistance that causes decreasein removal [7 14 15]

322 Effect of pH In biosorption studies pH of the solutionis the most important factor influencing the process depictedin Figure 1(b) It influences not only the surface charge of thebiosorbent but also the degree of ionization of the organicsubstances present in the solution and the dissociation offunctional groups on the active sites of the sorbent In thisstudy the pH was varied between 2 and 10 from highly acidicrange to high alkaline range keeping other parameters likeadsorbent dosage at 5 gL temperature of 30∘C and rotationalspeed of 150 rpm The removal was favoured at a lower pHand there is a sharp decrease in the percentage removal withincrease of pHThis shows that organic removal is favoured atlower pH Due to dissociation of functional groups at higherpH the adsorbent surface carries a net negative charge whileat lower pH it carries a net positive charge [16] At low pHvalues the rice husk surface would be protonated and becamepositive and the surface will be surrounded by the hydrogenions which enhances the interactions between the organicsubstances and binding sites through attractive forces Onthe other hand the casein has a negative charge in milk andwater resulting in electrostatic repulsion due to the reductionof electrostatic force of attraction between the oppositelycharged adsorbate molecules and the binding adsorbent sitesin alkali medium

323 Effect of Temperature Figure 1(c) displays the effect ofvariation of temperature on the adsorption process keepingother parameters same as before (like adsorbent dosage at5 gL pH of 738 and rotational speed of 150 rpm) andthe temperature was varied between 20∘C and 40∘C Thepercentage removal decreased with increasing temperatureDue to weakening of the bonds between the adsorbatemolecules and the active binding sites of the biosorbentthe binding capacity decreases with increasing temperature[17] Since the sorption potential of the adsorbent wasgreater at lower temperature it can also be said that thesorption might be an exothermic process With regard tothe effect of temperature on the adsorption an increasinguptake of organic molecules is expected when the adsorptiontemperature decreases because adsorption is a spontaneousprocess

324 Effect of Concentration The concentration of thewastewater was varied by the method of dilution keepingthe other parameters same as above (adsorbent dosageat 5 gL pH of 738 temperature of 30∘C and rotationalspeed of 150 rpm) It was observed that on increasingthe dilution or reducing the concentration the percentageremoval increased It is evident from Figure 1(d) that removalefficiency decreases slightly with the increase in initial


Effect of adsorbent dosageRe

mov

al (

)

80

82

84

86

88

90

92

2 4 6 8 10 120Adsorbent dosage (gL)

(a)

Effect of solution pH

Rem

oval

()

2 4 6 8 10 120pH

65707580859095

100

(b)

Effect of temperature

Rem

oval

()

80

82

84

86

88

90

92

295 300 305 310 315290Temperature (K)

R2 = 09987

(c)

180 190 200 210 220 230 240

Effect of initial concentration

Rem

oval

()

88

89

90

91

92

93

(d)

Figure 1 (a) Effect of adsorbent dosage on percentage removal by rice husk (b) Effect of solution pH on percentage removal by rice husk(c) Effect of temperature on percentage removal by rice husk (d) Effect of initial concentration on percentage removal by rice husk

concentration between 1952 and 2074mgL after which itremains almost constant indicating saturation of the sitesThephenomenon may be traced back to the reason due to theinterference between binding sites at higher concentrationsor inadequacy of solutes on solution with respect to availablebinding sites Also in case of lower concentrations the ratioof the initial number of moles of ions to the available surfacearea of adsorbent is large and subsequently the fractionaladsorption becomes independent of initial concentrationHowever at higher concentrations the available sites ofadsorption become fewer and hence the percentage removaldecreases [18]

33 Adsorption Isotherm In the present study the adsorptionbehavior was investigated since isotherms like Langmuir andFreundlich provide the most important piece of informationin understanding the adsorption process They give someidea about the underlying sorption mechanism as well asthe surface affinity and properties of the sorbent [19] Theequation is stated as follows

119862119890

119902119890

=

1

119870119871119876119900

+

119862119890

119876119900

(3)

where 119862119890is the equilibrium concentration 119902

119890is the amount

of ions or molecules adsorbed (mgg) 119876119900is 119902119890for a complete

monolayer (mgg) and 119870119871is sorption equilibrium constant

A plot of 119862119890119902119890versus 119862

119890should indicate a straight line of

slope 1119876119900and an intercept of 1119870

119871

Data for Langmuir Freundlich isotherm were plotted foradsorption of molecules into the nanoadsorbent in Figures2(a) and 2(b) The parameters obtained from the Langmuir(119862119890119902119890versus 119862

119890) Freundlich (log 119902

119890versus log119862

119890) isotherm

were evaluated Further plots for adsorption equilibriums atdifferent temperature for 119902

119890= 119891(119862

119890) have been demon-

strated in Figures 2(c) and 2(d) To compare the accuracyof the models quantitatively the correlation coefficients (1198772)were calculated as 0984 (Langmuir) and 0941 (Freundlich)whose analysis suggested that the Langmuir isotherm modelfurnishes a better fit to the adsorption data as compared toFreundlich model This indicated monolayer coverage of themolecules onto the adsorbent with achmolecule having equalactivation energy and that sorbate-sorbate interaction isnegligible [20]The essential features of Langmuir adsorptionisotherm can be expressed in terms of a separation factoror equilibrium parameter (119877

119871) which is a dimensionless

constant The 119877119871value indicates the shape of the isotherm to

be irreversible (119877119871= 0) favourable (0 lt 119877

119871lt 1) linear (119877

119871=

0) or unfavourable (119877119871gt 1) [21] The maximum uptake of

pollutants by rice husk was calculated as 714285mggOn the other hand the Freundlich isotherm [22] states

that uptake occurs on a heterogeneous surface by monolayeradsorption [23] and is expressed as

log 119902119890= log119870

119891+ (

1

119899

) log119862119890 (4)


119890is the amount

of ions or molecules adsorbed (mgg) and 119870119891and 119899 are


Langmuir

R2 = 09849

y = 00149x + 02417

Ceq

e

04

045

05

055

06

065

20 25 3015Ce

(a)

Freundlich

R2 = 09418

y = 04649x + 22075log q

e

34

35

36

37

28 29 3 31 32 3327log Ce

(b)

qe versus Ce plot

qe

(mg

g)

20 25 3015Ce (mgL)

05

1015202530354045

(c)

R2 = 09697

Linear (y = qe)z = temperaturey = qe

qe

(mg

g)290

295

300

305

310

315

Tem

pera

ture

(K)

10 20 30 40 500Ce (mgL)

39

40

41

42

43

44

45

(d)

Pseudo second order

R2 = 09946

y = 00217x + 0004

tqt

05 1 15 20t (h)

00005

0010015

0020025

0030035

004

(e)

minus025

minus02

minus015

minus01

minus005

0

Thermodynamics

R2 = 09923

y = 55417x minus 19976

000315 00032 000325 00033 000335 00034 0003451T

(f)

Figure 2 (a) Langmuir isotherm plot for adsorption onto rice husk (b) Freundlich isotherm plot for adsorption onto rice husk (c) Plot of 119902119890

versus 119862119890

for adsorption isotherms onto rice husk (d) Plot of 119902119890

versus 119862119890

at different temperature for adsorption isotherms onto rice husk(e) Pseudo-second-order kinetic model for adsorption onto rice husk (f) Vanrsquot Hoff plot for estimation of thermodynamic parameters foradsorption onto rice husk

Freundlich constants related to the adsorption capacity andadsorption intensity respectively

The Freundlich isotherm showed that the situation 119899 gt1 (119899 = 2155) is often prevalent and may be due to thedistribution of surface sites or any other significant factor thatcauses a reduction in adsorbent-adsorbate interaction withexpanding surface density [24]

34 Adsorption Kinetics Several kinetic models are in use toexplain the mechanism of the adsorption processes in order

to be able to design industrial scale separation processes Asimple pseudo-second-order equation was used

119905

119902119905

=

1

1198702119902119890

2

+

119905

119902119890

(5)

where 119902119905and 119902

119890are the amount of adsorption at time 119905 and

equilibrium respectively and1198702denotes the rate constant of

the pseudo-second-order adsorption process


The experimental data for the adsorption kinetics showedthat it was found to be well suited with the pseudo-second-order model It is presented in Figure 2(e) The pseudo-second-order model constants 119870

2and 119902

119890 were evaluated

from the slope and intercept of the plots of 119905119902119905versus 119905

The model parameters along with the correlation coefficientvalues (1198772) as 0994 are calculated with 119902

119890= 476190mgg

and 1198702= 0110 gmgminus1minminus1 It can be also concluded that

the rate limiting step may be a chemisorption process

35 AdsorptionThermodynamics Thethermodynamics of anadsorption process is obtained from a study of the influenceof temperature on the process Standard Gibbs energy was asfollows

Δ119866∘

= minus119877119879 ln119870119888 (6)

The equilibrium constant 119870119888was evaluated at each tempera-

ture using the following relationship

119870119888=

119862119886

119862119890

(7)

119870119888is distribution coefficient for adsorption119862

119886is equilibrium

concentration on the adsorbent119862119890is equilibrium concentra-

tion in solutionOther thermodynamic parameters such as change in

standard enthalpy Δ119867∘ and standard entropy Δ119878∘ weredetermined using the following equations

Both the values of energy and entropy are the actualindicators for practical application of a process factorsin any adsorption process and engineering practice thesethermodynamic parameters should be considered in orderto determine what processes will occur spontaneously Thethermodynamic parameters such as Gibbs energy (Δ119866)enthalpy (Δ119867) and entropy changes (Δ119878) for the adsorptionprocess can be determined using Vanrsquot Hoff equation

Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)

Δ119866∘ is Gibbs free energy change and Δ119867∘ is enthalpy of

reactionThe enthalpy change is determined graphically by plotting

ln(119870eq) versus 1119879which gives a straight line and the values ofΔ119866 and Δ119878 computed numerically from the slope and inter-cept shown in Figure 2(f) and Table 2 Gibbs energy valuesat 293K 298K 308K are 313 K are negative and large andincrease with increase of temperature Furthermore decreasein the negative value of Δ119866 with increasing temperaturesuggests that the adsorption process was more favourableat lower temperatures and thermodynamically favourableNegative value ofΔ119867 indicates that the process is exothermicThe value of Δ119878 shows the feasibility of the adsorption andthe increased randomness at the sorbentsolution interfaceduring the adsorption of molecules onto rice husk Thenegative value of Δ119878 also suggests that the process is enthalpydominated [25]

Table 2Thermodynamic parameters for adsorption onto rice husk

Temperature(K) Δ119866

∘ (Jmole) Δ119867∘ (Jmole) Δ119878∘ (Jmole K)

293 minus253100 Slope = minus5541 Intercept = minus1997Δ119867 = minus460678 Δ119878 = minus16603

298 minus3547883308 minus524177313 minus585253

4 Conclusion

The present study shows that rice husk can be effectivelyused as adsorbent for treatment of dairy wastewater as itcould bring about a removal up to 925 which couldbe achieved using an adsorbent dosage of 5 gL pH of 2and temperature of 30∘C Moreover it is a cost-effectiveprocess since it is cheaply available raw material The entireprocess was favoured at lower temperature and lower pHwith a little adsorbent dosage The solution pH controls theadsorptive-adsorbent and adsorptive-adsorptive electrostaticinteractions which can have a profound effect on the adsorp-tion process The organic removal was favoured at lowertemperature which concluded that the process is exothermicThermodynamic parameters stated that the process wasspontaneous and enthalpy driven The maximum uptake ofpollutants by rice husk was calculated to be 714285mggLangmuir isotherm and pseudo-second-order models fittedbest But using of rice husk without any modification canbring several problems of COD loading when used inhigh dosages in industrial applications because the silicaon the outer and impurities (fats and waxes) on the innersurfaces cause improper binding between the active sites andmolecules Thus future studies can be done by undergoingmodification of rice husk

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] Dairy Processing Handbookchapter 22 Dairy Effluents httpwwwdairyprocessinghandbookcomchapterdairy-effluent

[2] W Qasim and A V Mane ldquoCharacterization and treatment ofselected food industrial effluents by coagulation and adsorptiontechniquesrdquoWater Resources and Industry vol 4 pp 1ndash12 2013

[3] N B Singh R Singh and M M Imam ldquoWaste water man-agement in dairy industry pollution abatement and preventiveattitudesrdquo International Journal of Science Environment andTechnology vol 3 no 2 pp 672ndash683 2014

[4] B S Shete and N P Shinkar ldquoDairy industry waswater sourcescharacteristics and its effects on environmentrdquo InternationalJournal of Current Engineering and Technology vol 3 pp 1611ndash1615 2013

[5] V Mehta and A Chavan ldquoPhysico-chemical treatment of tar-containing wastewater generated from biomass gasification


plantsrdquoWorld Academy of Science Engineering and Technologyvol 3 no 9 pp 9ndash29 2009

[6] G Crini ldquoRecent developments in polysaccharide-based mate-rials used as adsorbents in wastewater treatmentrdquo Progress inPolymer Science vol 30 no 1 pp 38ndash70 2005

[7] G Crini ldquoNon-conventional low-cost adsorbents for dyeremoval a reviewrdquo Bioresource Technology vol 97 no 9 pp1061ndash1085 2006

[8] M X Loukidou A I Zouboulis T D Karapantsios and KA Matis ldquoEquilibrium and kinetic modeling of chromium(VI)biosorption by Aeromonas caviaerdquo Colloids and Surfaces A vol242 no 1ndash3 pp 93ndash104 2004

[9] H Jaman D Chakraborty and P Saha ldquoA study of the thermo-dynamics and kinetics of copper adsorption using chemicallymodified rice huskrdquo CleanmdashSoil Air Water vol 37 no 9 pp704ndash711 2009

[10] K Y Foo and B H Hameed ldquoInsights into the modeling ofadsorption isotherm systemsrdquo Chemical Engineering Journalvol 156 no 1 pp 2ndash10 2010

[11] T G Chuah A Jumasiah I Azni S Katayon and S Y TChoong ldquoRice husk as a potentially low-cost biosorbent forheavy metal and dye removal an overviewrdquo Desalination vol175 no 3 pp 305ndash316 2005

[12] B S Ndazi S Karlsson J V Tesha and C W NyahumwaldquoChemical and physical modifications of rice husks for useas composite panelsrdquo Composites Part A Applied Science andManufacturing vol 38 no 3 pp 925ndash935 2007

[13] APHA AWWA and WEF Standard Methods for the Exam-ination of Water and Wastewater American Public HealthAssociation Washington DC USA 21st edition 2005

[14] R Gong Y DingM Li C YangH Liu andY Sun ldquoUtilizationof powdered peanut hull as biosorbent for removal of anionicdyes from aqueous solutionrdquo Dyes and Pigments vol 64 no 3pp 187ndash192 2005

[15] K H Chu and M A Hashim ldquoRemoval of Copper(II) fromaqueous solutions by prawn shell particlesrdquo in Proceedings ofthe 5th World Congress of Chemical Engineering MelbourneAustralia September 2001

[16] C Moreno-Castilla ldquoAdsorption of organic molecules fromaqueous solutions on carbon materialsrdquo Carbon vol 42 no 1pp 83ndash94 2004

[17] S Chakraborty S Chowdhury and P Das Saha ldquoAdsorption ofCrystal Violet from aqueous solution ontoNaOH-modified ricehuskrdquoCarbohydrate Polymers vol 86 no 4 pp 1533ndash1541 2011

[18] L J Yu S S Shukla K L Dorris A Shukla and J L MargraveldquoAdsorption of chromium from aqueous solutions by maplesawdustrdquo Journal of Hazardous Materials vol 100 no 1ndash3 pp53ndash63 2003

[19] S Chowdhury R Mishra P Kushwaha and P Das ldquoOptimumsorption isotherm by linear and nonlinearmethods for safraninonto alkali-treated rice huskrdquo Bioremediation Journal vol 15no 2 pp 77ndash89 2011

[20] I Langmuir ldquoThe adsorption of gases in plane surface of glassmica and platinumrdquo Journal of the American Chemical Societyvol 40 no 9 pp 1361ndash1368 1916

[21] K R Hall L C Eagleton A Acrivos and T VermeulenldquoPore- and solid-diffusion kinetics in fixed-bed adsorptionunder constant-pattern conditionsrdquo Industrial amp EngineeringChemistry Fundamentals vol 5 no 2 pp 212ndash223 1966

[22] H M F Freundlich ldquoUber die adsorption in losungenrdquoZeitschrift fur Physikalische Chemie vol 57 pp 385ndash470 1906

[23] Y Bulut and Z Baysal ldquoRemoval of Pb(II) from wastewaterusing wheat branrdquo Journal of Environmental Management vol78 no 2 pp 107ndash113 2006

[24] I Vazquez J Rodrıguez-Iglesias EMaranon L Castrillon andM Alvarez ldquoRemoval of residual phenols from coke wastewaterby adsorptionrdquo Journal of Hazardous Materials vol 147 no 1-2pp 395ndash400 2007

[25] P D Saha S Chakraborty and S Chowdhury ldquoBatch andcontinuous (fixed-bed column) biosorption of crystal violet byArtocarpus heterophyllus (jackfruit) leaf powderrdquo Colloids andSurfaces B Biointerfaces vol 92 pp 262ndash270 2012

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very stable colloidal dispersion and held together by calciumions inorganic phosphate citrate ions

H2N-R-COOminus +H+ 997888rarr +H

3N-R-COOminus

Casein Micelle Acid CaseinColloidal dispersion Insoluble Particles

(1)

Therefore all the above-mentioned phenomena make dairyindustry like many others challenged with rising costs forwastewater treatment and disposal Moreover industries haveto meet the discharge standards mentioned by CPCB whichbecomes a great problem for the industrialists

Technologies such as coagulationflocculation processand oxidation process have been developed over the yearsto remove organic matter (expressed as chemical oxygendemand COD) from industrial wastewater These methodsare effective in fields of reduction and time but are expensiveand require skilled personnel They also become disadvanta-geous in terms of pH adjustment and generation of chemicalsludge that must be treated before disposal [5] In additionto these various treatments which are already present inthe dairy industry there are biological treatments includingtrickling filters and activated sludge process Though theyare effective for complete treatment of the wastewater butare noneconomical large power demand more chemicalconsumption and large area availability Thus it is verymuch necessary for characterization of wastewater treatabil-ity studies and planning of proper units and processes foreffluent treatment

Adsorption technique emerges as promising techniquein the removal efficiency (COD) economy and operation[6] Physical adsorption using activated carbon is effective inremoval but has a high initial cost low adsorption capacitiesand separation inconvenience andneeds a costly regenerationsystem [7] All these have simulated the search of cheaperalternatives and application of biosorption in environmentaltreatment has become a significant research area in thepast years It is widely recognized that biosorption providesa feasible technique for the removal of pollutants fromwastewater Biosorption may be defined as a process whereina solute molecule is removed from the liquid phase in contactwith a solid usually an inexpensive adsorbent which has aspecial affinity for the solute particles [8] To explore thesenovel adsorbents the use of biosorbents from numerousagroindustry wastes has received much attention and led toa constructive approach

Rice husk which is the protective outer shell of the ricegrain is abundantly obtainable as a by-product of the ricemilling industries It has been estimated that the annualproduction of rice husk is estimated to be around 120 milliontonnes [9] constituting about one-fifth part of the totalannual rice production throughout the world [10] Thusthe disposal becomes a crucial factor The composition ofrice husks is found to consist of about 32 cellulose 21hemicelluloses 21 lignin 20 silica and 3 crude protein[11] Moreover their granular structure containing abundantfloristic fiber insolubility in water chemical stability andhigh mechanical strength make them potential adsorbentThey also consist of functional group such as carboxyl

hydroxyl and amidogen representing a favourable charac-teristic of rice husk [12]

However the application of plant wastes as adsorbents canalso bring several problems such as high chemical oxygendemand (COD) and biological chemical demand (BOD) aswell as total organic carbon (TOC) due to release of solubleorganic compounds contained in the plant materials Silicapresent on the external surface of rice husks in the formof silicon-cellulose membrane is responsible for insufficientbinding between functional groups existing on rice husksurfaces and adsorbate ions or molecules present in solutionPresence of wax and natural fats on the internal surface ofrice husk as impurities has also got impact on the adsorptionproperties of rice husk chemically and physically [12]

In this study the potential ability of rice husk withoutany modification as biosorbent for the adsorption of organicpollutants fromdairywastewater was investigatedThe effectsof initial concentration pH adsorbent dosage solutiontemperature on adsorption and the adsorption kineticsisotherms and thermodynamic parameters were studied

2 Materials and Methods

Wastewater sample was collected from outfall of a dairyindustry at Dankuni near Durgapur Express HighwayWastewater sample collected from the plant was placed incontainers to be transported to the laboratory and storedat 4∘C in a refrigerator All the initial parameters of thewastewater were analysed in the laboratory as per the givenstandard methods in the handbook [13] All the chemicalswere of analytical reagent grades and used as receivedwithout further purifications

21 Adsorbent Preparation The rice husk used was obtainedfrom a nearby rice mill in Dankuni West Bengal India Itwas washed repeatedly with double-distilled water to removedust and soluble impurities and this was followed by dryingat 343K for 24 h It was sieved usingmeshes to get the desiredadsorbent size of 30 micrometers and stored in an air tightcontainer

22 Experimental Batch Study The biosorption studies werecarried out in 250mL glass-stoppered Erlenmeyer flaskscontaining a fixed amount of adsorbent Solution pH wasadjusted with HCl or NaOH (01 N) pH had been measuredby following electrometric method using a digital pH meterA known amount of adsorbent was added to samples andwas agitated at 150 rpm agitation speed allowing sufficienttime for adsorption Then the mixtures were centrifugedand filtered through filter paper and the final concentrationwas determined in the filtrate using UVVIS spectropho-tometer The effects of various parameters on the percentageremoval were observed by varying adsorbent dosage (4 68 and 10 gL) initial pH of wastewater (2 4 6 8 and 10)temperature (293K 298K 308K and 313 K) and concen-tration (183mgL 1954mgL 2074mgL 2196mgL and




3



119902119890=

(119862119900minus 119862119905) 119881

119898

(2)






3










mov

al (

)

80

82

84

86

88

90

92


(a)


Rem

oval

()

2 4 6 8 10 120pH

65707580859095

100

(b)


Rem

oval

()

80

82

84

86

88

90

92

295 300 305 310 315290Temperature (K)

R2 = 09987

(c)

180 190 200 210 220 230 240


Rem

oval

()

88

89

90

91

92

93

(d)




119862119890

119902119890

=

1

119870119871119876119900

+

119862119890

119876119900

(3)


119890is the amount



A plot of 119862119890119902119890versus 119862



119871




119890) isotherm


119890= 119891(119862






119871lt 1) linear (119877

119871=




log 119902119890= log119870

119891+ (

1

119899

) log119862119890 (4)


119890is the amount



Langmuir

R2 = 09849

y = 00149x + 02417

Ceq

e

04

045

05

055

06

065

20 25 3015Ce

(a)

Freundlich

R2 = 09418

y = 04649x + 22075log q

e

34

35

36

37

28 29 3 31 32 3327log Ce

(b)

qe versus Ce plot

qe

(mg

g)

20 25 3015Ce (mgL)

05

1015202530354045

(c)

R2 = 09697


qe

(mg

g)290

295

300

305

310

315

Tem

pera

ture

(K)

10 20 30 40 500Ce (mgL)

39

40

41

42

43

44

45

(d)

Pseudo second order

R2 = 09946

y = 00217x + 0004

tqt

05 1 15 20t (h)

00005

0010015

0020025

0030035

004

(e)

minus025

minus02

minus015

minus01

minus005

0

Thermodynamics

R2 = 09923

y = 55417x minus 19976

000315 00032 000325 00033 000335 00034 0003451T

(f)


versus 119862119890


versus 119862119890






119905

119902119905

=

1

1198702119902119890

2

+

119905

119902119890

(5)

where 119902119905and 119902






2and 119902




119890= 476190mgg




Δ119866∘

= minus119877119879 ln119870119888 (6)



119870119888=

119862119886

119862119890

(7)







Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)









4 Conclusion




References

































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics






3



119902119890=

(119862119900minus 119862119905) 119881

119898

(2)






3










mov

al (

)

80

82

84

86

88

90

92


(a)


Rem

oval

()

2 4 6 8 10 120pH

65707580859095

100

(b)


Rem

oval

()

80

82

84

86

88

90

92

295 300 305 310 315290Temperature (K)

R2 = 09987

(c)

180 190 200 210 220 230 240


Rem

oval

()

88

89

90

91

92

93

(d)




119862119890

119902119890

=

1

119870119871119876119900

+

119862119890

119876119900

(3)


119890is the amount



A plot of 119862119890119902119890versus 119862



119871




119890) isotherm


119890= 119891(119862






119871lt 1) linear (119877

119871=




log 119902119890= log119870

119891+ (

1

119899

) log119862119890 (4)


119890is the amount



Langmuir

R2 = 09849

y = 00149x + 02417

Ceq

e

04

045

05

055

06

065

20 25 3015Ce

(a)

Freundlich

R2 = 09418

y = 04649x + 22075log q

e

34

35

36

37

28 29 3 31 32 3327log Ce

(b)

qe versus Ce plot

qe

(mg

g)

20 25 3015Ce (mgL)

05

1015202530354045

(c)

R2 = 09697


qe

(mg

g)290

295

300

305

310

315

Tem

pera

ture

(K)

10 20 30 40 500Ce (mgL)

39

40

41

42

43

44

45

(d)

Pseudo second order

R2 = 09946

y = 00217x + 0004

tqt

05 1 15 20t (h)

00005

0010015

0020025

0030035

004

(e)

minus025

minus02

minus015

minus01

minus005

0

Thermodynamics

R2 = 09923

y = 55417x minus 19976

000315 00032 000325 00033 000335 00034 0003451T

(f)


versus 119862119890


versus 119862119890






119905

119902119905

=

1

1198702119902119890

2

+

119905

119902119890

(5)

where 119902119905and 119902






2and 119902




119890= 476190mgg




Δ119866∘

= minus119877119879 ln119870119888 (6)



119870119888=

119862119886

119862119890

(7)







Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)









4 Conclusion




References

































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics





mov

al (

)

80

82

84

86

88

90

92


(a)


Rem

oval

()

2 4 6 8 10 120pH

65707580859095

100

(b)


Rem

oval

()

80

82

84

86

88

90

92

295 300 305 310 315290Temperature (K)

R2 = 09987

(c)

180 190 200 210 220 230 240


Rem

oval

()

88

89

90

91

92

93

(d)




119862119890

119902119890

=

1

119870119871119876119900

+

119862119890

119876119900

(3)


119890is the amount



A plot of 119862119890119902119890versus 119862



119871




119890) isotherm


119890= 119891(119862






119871lt 1) linear (119877

119871=




log 119902119890= log119870

119891+ (

1

119899

) log119862119890 (4)


119890is the amount



Langmuir

R2 = 09849

y = 00149x + 02417

Ceq

e

04

045

05

055

06

065

20 25 3015Ce

(a)

Freundlich

R2 = 09418

y = 04649x + 22075log q

e

34

35

36

37

28 29 3 31 32 3327log Ce

(b)

qe versus Ce plot

qe

(mg

g)

20 25 3015Ce (mgL)

05

1015202530354045

(c)

R2 = 09697


qe

(mg

g)290

295

300

305

310

315

Tem

pera

ture

(K)

10 20 30 40 500Ce (mgL)

39

40

41

42

43

44

45

(d)

Pseudo second order

R2 = 09946

y = 00217x + 0004

tqt

05 1 15 20t (h)

00005

0010015

0020025

0030035

004

(e)

minus025

minus02

minus015

minus01

minus005

0

Thermodynamics

R2 = 09923

y = 55417x minus 19976

000315 00032 000325 00033 000335 00034 0003451T

(f)


versus 119862119890


versus 119862119890






119905

119902119905

=

1

1198702119902119890

2

+

119905

119902119890

(5)

where 119902119905and 119902






2and 119902




119890= 476190mgg




Δ119866∘

= minus119877119879 ln119870119888 (6)



119870119888=

119862119886

119862119890

(7)







Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)









4 Conclusion




References

































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




Langmuir

R2 = 09849

y = 00149x + 02417

Ceq

e

04

045

05

055

06

065

20 25 3015Ce

(a)

Freundlich

R2 = 09418

y = 04649x + 22075log q

e

34

35

36

37

28 29 3 31 32 3327log Ce

(b)

qe versus Ce plot

qe

(mg

g)

20 25 3015Ce (mgL)

05

1015202530354045

(c)

R2 = 09697


qe

(mg

g)290

295

300

305

310

315

Tem

pera

ture

(K)

10 20 30 40 500Ce (mgL)

39

40

41

42

43

44

45

(d)

Pseudo second order

R2 = 09946

y = 00217x + 0004

tqt

05 1 15 20t (h)

00005

0010015

0020025

0030035

004

(e)

minus025

minus02

minus015

minus01

minus005

0

Thermodynamics

R2 = 09923

y = 55417x minus 19976

000315 00032 000325 00033 000335 00034 0003451T

(f)


versus 119862119890


versus 119862119890






119905

119902119905

=

1

1198702119902119890

2

+

119905

119902119890

(5)

where 119902119905and 119902






2and 119902




119890= 476190mgg




Δ119866∘

= minus119877119879 ln119870119888 (6)



119870119888=

119862119886

119862119890

(7)







Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)









4 Conclusion




References

































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics





2and 119902




119890= 476190mgg




Δ119866∘

= minus119877119879 ln119870119888 (6)



119870119888=

119862119886

119862119890

(7)







Δ119866∘

= Δ119867∘

minus 119879Δ119878∘

ln119870eq = minusΔ119867∘

119877119879

+

Δ119878∘

119877

(8)









4 Conclusion




References

































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics






























FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



research article treatment of wastewater from a dairy ... · industry, like many others, challenged...

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