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Bruguiera gymnorhiza (Mangrove leaf powder) for removal of Pb (II): Characterization,
Kinetics, Isotherms and Thermodynamic Studies
M. Krishna Prasada, K. Jyothi b
a
Department of Chemical Engineering, GMR Institute of Technology, Rajam, Andhra Pradesh.
b
Department of Microbiology, Andhra University, Visakhapatnam, Andhra Pradesh. Corresponding Author: jyothikaparapu@gmail.com
Article History: Received: 11 January 2021; Revised: 12 February 2021; Accepted: 27 March 2021; Published online: 4 June 2021
Abstract: In this study green plant material Bruguiera gymnorhiza (Mangrove leaf powder) was used for the biosorption of
lead (II) ions by Atomic absorption spectrometry. In a batch process, Bruguiera gymnorhiza was exposed to several aspects, pH (2-6) and temperature (25-55°C) in the presence of different lead concentrations (25-125 mg/L) for 2h. This paper studies the Equilibrium isotherms, kinetic and thermodynamic parameters calculations. The highest occupied lead concentration was found at pH 5 which was 97.6% at an initial concentration is 25 mg/L. The maximum lead accumulation was obtained at 25◦C as 10.044 mg/g in 125 mg/L at pH 5.0, and the minimum was at 55◦C as 1.821 mg/g at a dosage of 10 g/L and initial concentration of 25 mg/L. Lead adsorption increased up to 75 mg/L but did not change significantly in the 75–100mg/L range. Equilibrium data fit well to the Freundlich isotherm. The kinetic data follows the pseudo-first-order model. Finally, the adsorbent was characterized by FT-IR and XRD. The biomass of Bruguiera gymnorhiza is an optimistic and cost-effective, biosorbent for lead (II) removal from aqueous environment and adsorption capacity it‟s good, easy of sampling analysis, as well as availability
Keywords: Biosorption; Bruguiera gymnorhiza; kinetics; Isotherms; Thermodynamics.
1. Introduction
In irecent iyears iLead ihas ibeen iintroduced iinto inatural iwater ifrom ia ivariety iof isources isuch ias
istorage ibatteries, ilead ismelting, ielectro iplating iand ifinishing, iprinting, iphotographic imaterials, ipigment
iand idye iindustries, iexplosive imanufacturing, itetraethyl ilead imanufacturing, iceramic iand iglass iindustries,
ietc. i(Majumdar iet ial., i2010; iYurtsever iand iSengil, i2008; iGercel iand iGercel, i2007). iThe ipermissible
ilimit iof ilead iin idrinking iwater iis i0.05 img/l ias iper iUnited iStates ienvironmental iprotection iagency.
iExcess iLead iin idrinking iwater ican ialso icause ia ivariety iof iadverse ihealth ieffects. iIn iindividuals iof iall
iages, ilead ican icause ianaemia, ikidney imalfunction, iimpaired ifunction iof iperipheral inervous isystem, ihigh
iblood ipressure, ireproduction iabnormality, idevelopmental idefects, iabnormal ivitamin iD imetabolism,
icoliclike iabnormal ipains, idementia, imadness iand, iin isome isituations, ideath i(Ferreira iet ial., i2011; iHurd
iet ial., i2008, iKazi iet ial., i2008; iOkoro iand iEjike, i2007, iAfridi iet ial., i2006). iDue ito itoxic ieffects iof
ilead iand iother itoxic imetal iions, ithe iremoval iof ithem ifrom iwater iand iwastewater iis iimportant iin iterms
iof iprotection iof ipublic ihealth iand ienvironment i(Unlu iand iErsoz, i2006). iThere iare iseveral itechniques
ifor iremoval iof ilead isuch ias iprecipitation, ievaporation, ireverse iosmosis, ielectroplating, iion-exchange,
imembrane iseparation, ietc. ifrom ithe iaqueous isolution. iWhen iheavy imetals iare ipresent iin ilow
iconcentrations ialmost iall iof ithese imethods iwere ifound ito ibe ieither iprohibitively icostly ior iunacceptably
iinefficient i(Sulaymon iet ial., i2013).The imost icommon itechnique iis iadsorption iand iit iis ia iwellestablished
iand ipowerful itechnique ifor itreating iboth idomestic iand iindustrial ieffluents i( iOzcan iet ial., i2009 iand i iSulaymon iet ial., i2012). i
Bioadsorbents ihave iemerged ias ione iof ithe ipotential ialternatives ifor iremoval iof iheavy imetals iand
imetalloids. iPlants, ialgae, ifungi iare isome iof ithe ibiomass iderived iadsorbents iwhich iare icapable iof
iremoving iheavy imetals iand imetalloids ifrom iaqueous isolution iby iadsorption i(Mohan iet ial, i2007).
iCinnamomum icamphora ileave‟s ipowder iwas iinvestigated ias ia ibiosorbent ifor ithe iremoval iof iCu i(II) iand
iPb i(II) iions ifrom iaqueous isolutions i(Chen iet ial., i2010). iFurthermore, iit iwas ireported ithat iMoringa
ioleifera ileaves iextract iis ia igood isorbent ifor iPb i(II) ifrom iaqueous isolution i(Reddy iet ial., i2010). iA
ibatch iadsorption istudy iof iCd i(II) iions ifrom iaqueous isolution iby iHevea ibrasiliensis i(HB) ileaf ipowder
ihas ialso ibeen ireported i(Hanafiah iet ial., i2006). iSharma iand iBhattacharyya, i(2005) ihave istudied ithe
iadsorption iof iCd i(II) iusing ineem ileaf ipowder. iIn iaddition, ithe ileaves iof ithe iolive itree i(Olea ieuropaea)
iwere iproposed ias ia inovel iadsorbent ifor ithe iremoval iof iCd i(II) ifrom isolutions i(Hamdaoui, i2009).
iRecently, iextensive istudies ion iCd i(II) iadsorption itaking ipowdered ileaves iof ia ivariety iof itrees ihave
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Several ibiomaterials ihad ibeen iexploited ifor ithe iremoval iof iPb i(II) ifrom iaqueous isolution, isuch ias
iusing ifungal ibiomass iof iAspergillus iniger i(Jianlong iet ial., i2001), ibiomass iof imarine ialgae i(Jalali iet ial.,
i2002), ibacterial idead iStreptomyces irimosus ibiomass i(Selatnia iet ial., i2004), iactivated icarbon iprepared
ifrom ibiomass iplant imaterial iof iEuphorbia irigida i(Gercel iand iGercel iet ial., i2007), iChrysophyllum
ialbidum iSeed iShell i i(Amuda iet ial., i2007), iwheat iStems ibiomass i(Tan iand ixiao i2008), ibiomass iof
ihazelnut iand ialmond ishell i(Pehlivan iet ial., i2009), ibiomass iof iPhaseolus ivulgaris i(Ozcan iet ial., i2009),
iMucor irouxii ibiomass i(Majumdar iet ial., i2010), ibiomass iof iBrevundimonas ivesicularis i(Resmi iet ial.,
i2010), ifilamentous ifungal ibiomass-loaded iTiO2 inanoparticles i(Bakircioglu iet ial., i2010), i ipine icone
iactivated icarbon i(Milan iet ial., i2011), i ia inonliving imoss ibiomass i(Bamidele iet ial., i2012), iFicus iHispida
ileaves ipowder i(Namdeti iand iPulipati i2013) iand i ibiomass iof iMaize istover i(Guyo iet ial., i2015).
Andaman iand iNicobar iarchipelago iis ione iof ithe imega-biodiversity ihotspots iof iIndia. iThe iarchipelago
ilocated iin ithe iBay iof iBengal, ilying ibetween i6450 i–13450 iN iand i92120 i–93570 iE iin ithe iIndo
iBurmese imicroplate ijunction. iThe iislands iare ispread iover ia idistance iof i1,120 ikm iwith ia icoast iline iof
i1,962 ikm. iThe iclose iproximity iof ithese igroups iof iislands ito ithe iequator iand ithe iirregular iand ideeply
iindented icoast iline, icreeks, ibays iand iestuaries ifacilitate ithe irich iand idiverse imangrove iforests. iRozaini
iet ial. i(2010) iidentified ithat imangrove ibark ihas ia ipotent iadsorbent ifor iNi(II) iand iCu(II) iions ifrom
iaqueous isolutions. iThe icurrent istudy iwas iaimed ito idetermine ithe icapability iof imangrove ileaves ifrom
iAndaman iand iNicobar iislands ias ia ipotent iadsorbent ito iremove ithe iLead i(II) ifrom iaqueous isolutions. The iaim iof ithis iwork iis iremoval iof iPb i(II) ion iBruguiera igymnorhiza, ithere ihas ibeen ino ireported
iwork ion ilead iions ifrom iaqueous isolution. iIn ithis istudy, ithe ibiosorption ibehavior iof iPb i(II) ifrom
iaqueous isolution iusing iBruguiera igymnorhiza iwas istudied iunder ivarious iconditions, isuch ias icontact
itime, isolution ipH, itemperature iand idifferent iconcentrations, iwith ithe iaim iof idetermining ithe imechanism
ifor ithe iremoval iof iPb i(II) ifrom iaqueous isolution iby ibiomass iof iBruguiera igymnorhiza. iIn iaddition,
iequilibrium iand ikinetic istudies iwere icarried iout. iLangmuir iand iFreundlich iisotherm imodels iwere iapplied
ito ifit ithe iexperimental idata. iFTIR, iSEM, iand iXRD iwere ialso iused ito iilluminate ithe ibiosorption
iprocess.
2.Materials iand imethods 2.1Preparation iof ibiosorbent iBruguiera igymnorhiza
The iMangrove ileaves i(Bruguiera igymnorhiza) iunder istudy iwere icollected ifrom ifrom imangrove iplants
ilocated iin ithe iMinnie iBay iarea, iPort iBlair, iAndaman iand iNicobar iislands, iIndia. iThe icollected
iMangrove ileaves iwere iwashed iwith ideionized iwater iseveral itimes ito iremove idirt ion ithe isurface iof ithe
ileaves. i iThe iwashed ileaves iwere idried iin isunlight ifor i15 idays iand iwere ipowdered iusing idomestic
imixer. iThe ipowdered ibiomass iwas isieved ithrough i200 imesh isieves iand ibiomass ipowder iwas ipreserved
iin ia ihumidity icontrol ioven ito imaintain ia istandard ihumidity ithroughout ifor iequilibrium istudies iduring
ithe ientire iperiod iof istudy. i 2.2.Preparation iof istock isolution
All ithe ichemicals iused iwere iof ianalytical ireagent igrade. iStock iPb i(II) isolution i(1000 img/L) iwas
iprepared iby idissolving irequired iamount iof iPb(NO3)2 iin idouble idistilled iwater. iAll ithe iexperimental
isolutions iwere iprepared iby idiluting ithe istock isolution. iThe itest isolutions iof ithe ipH iwere iadjusted iby
ireagent igrade i0.05N iof iHcl iand i0.05N iof iH2SO4. i 2.3.Equilibrium iStudies
The iexperiments iwere icarried iout iin i250 iml iErlenmeyer iconical iflasks, iat ia iconstant iagitation ispeed
i(200 irpm) iwith i50ml isolution iwith ivarious i imetal iconcentrations i(19.21, i36.12, i68.056, i73.85 iand
i109.44mg/L) iand irequired iamount iof iadsorbent i(5, iand i10, ig/L) iusing iorbital ishaker. iInitially ithe ieffect
iof icontact itime i(0-120 imin) ion ithe isorption icapacity iof iBruguiera igymnorhiza iwas ievaluated. i
2.4.Analytical iprocedure
An iatomic iabsorption ispectrophotometer i(Perkin iElmer iAA400) iwith ian iair iacetylene iflame iwas
idetermining ithe iconcentrations iof iun-adsorbed iPb i(II) iions iin ithe isample isupernatant iliquid. iCo iand iC*
iwere idetermined iand itabulated ifor isubsequent ianalysis iof ithe iexperimental idata. iThe imetal iuptake i(Cs)
iwas icalculated iusing ithe igeneral idefinition:
C
s=V(C
o−C
*)
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i i i i i i i i i i i i i i i i i i i i i i i i i i i(1)
WhereCs iis ithe imetal iuptake img/g ibiomass, iV iis ithe ivolume iof imetal icontaining isolution iin icontact
iwith ithe ibiosorbent iin iL, iCo iand iC *
iare ithe iinitial iand iequilibrium i(residual) iconcentration iof imetal iin
ithe isolution img/L, irespectively, iand iM iis ithe iamount iof iadded ibiosorbent iin ig. iMetal i% iof iremoval
iby iBruguiera igymnorhiza iwas idetermined iby iequation i2 ias ifollows:
R(%) =C
o−
C
*100
i i i i i i i i i i i i i i i i i i(2)
C
oWhere iR iis ithe ipercentage iof iPb i(II) iadsorbed iby ibiomass, iCo iis ithe iinitial iconcentration iof imetal
iions iin img/L iand iC* iis ithe iconcentration iof imetal iions iat itime it iin img/L. 2.5.Biomass icharacterization
2.5.1.FTIR istudies i
The ipowdered ibiomass, iprior iand iafter iadsorption iwas iair idried, iand idemoisturized iat i60 i_C iin
ihumidity icontrol ioven. iThe ipowder iwas ianalysed iby iFourier itransform iinfra ired ispectrophotometer.
iFTIR istudies iwere iconducted iby iPotassium iBromide i(KBr) ipellet imethod i(Jasco i5300) iin ithe iwave
inumber irange iof i400.00–4000.00 icm_1. 2.5.2.Scanning ielectron imicroscopy i
The idried ibio imass ipowders iand ithe icorresponding imetal iion iloaded ipowders iwere icoated iwith i ultra-thin ifilm iof igold iby ian iion isputter i(JFC-1100), iexposed iunder ielectron imicroscope i(JEOL, iJX8100) iat
iworking iheight iof i15 imm iwith ivoltage iranging ibetween i10 iand i25 ikV. 3.Results iand idiscussion
The iexperimental idata ion ibiosorption iwere iobtained ibatch iwise ito istudy ithe ieffect iof ivarious
iparameters ion ithe iremoval iof ilead iions ifrom ithe iaqueous isolutions iprepared iin ithe ilaboratory iby iusing
iBruguiera igymnorhiza i(mangrove ileaf ipowder). i iEffect iof icontact itime
Experiments iwere iconducted ito iestimate ithe itime irequired ito ireach ithe isorption iequilibrium iby itaking
ian iinitial icharge iof i50 iml iof iaqueous isolution icontaining iPb i(II) iions iand ithe irequired iquantities iof
ibiomass. iThe imixture iwas ishaken iin ian iorbital ishaker, ithe isamples iwere idrawn iat iregular itime
iintervals iand ithe imetal iconcentration iwas iestimated iusing iAAS. iThe idata iof iconcentration iof imetal iion
iCt, iin isolution iwith itime iare ishown ifor idifferent iquantities iof ibiomass iin iFig i.1.
Figure i1: iVariation iof iPb i(II) iconcentration iin isolution iwith itime iat ivarious iquantities iof ibiomass iat
i25°C, i50 img/L iand ipH i5.
The ieffect iof icontact itime iwas istudied ion i% iadsorption iof iPb i(II) iover ia itime iperiod iof i1-120
imin, iusing i0.25 ig iof iBruguiera igymnorhiza ibiomass ipowder i(diameter iof iparticle; idp i= i0.074mm),
iinitial iPb i(II) iconcentration iis i50 0.324 img iL-1 iat ipH i5 iand itemperature i25 C. iPercentage iadsorption 0 10 20 30 40 50 60 70 80 0 50 100 150
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n
0.25 g 0.5 gResearch Article
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iincreased ifrom i35.3 ito i71.24% iduring ia icontact itime iperiod ifrom i1 imin ito i120 imin. iThe irapid iinitial
isorption iwas ilikely idue ito iextra-cellular ipolymeric isites i(ionizable) ibinding iand ithe islower isorption
iresulted ifrom iintracellular ibinding i(Areco iand iAfonso, i2010, iMaria iand iMaria idos, i2010, isarada iet ial.,
i2013) ion iadsorbent. iSimilar istudies iwas iperformed iwith i10 ig/L iof ibiomass iconcentrations iin iaqueous
isolutions iand ithe iresults iindicated ithat ithe i2h iis ithe ioptimum itime iof icontact ifor ithe irange iof
iconcentrations iused. iEffect iof ipH iThe ipH ieffect iof isolution ion ithe iadsorption iof iPb i(II) iions ionto
iBruguiera igymnorhiza iwas istudied
iby ichanging ithe isolution ipH ivalues iwith iin ithe ipH irange iof i2.0–6.0 iand ithe iresults iare ishown iin iFig.
Figure i2: iEffect iof ipH ion ithe ilead iremoval ipercentage iat ivarious iinitial iPb i(II) iconcentrations i
Figure i3: iMetal iuptake iat ivarious ipH isolutions.
The iuptake iof ibiomass iwas ifound ito iincrease iwith ithe iincrease iin ipH ias ishown iin ifig.3. iIt iwas
ifound ito ihave ia ihigh icontent iof icarboxyl igroups ithat irender iit isusceptible ito ipH ichanges. iSimilar
iobservations iwere ireported iearlier iby iseveral iinvestigators i(Wang iand iChen, i2009; iYi-Chao iand
iShuiPing i2011). i iFig.2 ishows ithat ian iincrease iin iinitial ipH ifrom i2.0 ito i5.0 iresulted iincreased i%
ibiosorption iof iPb i(II) ifrom i84.3% ito i97.6% iat ian iinitial imetal iconcentration iof i19.21 img/L. iA idrastic
ifall iin i% ibiosorption i ias ilow ias i95.44% iwas iobserved iat ipH ivalue iof i6.0, iIt imay ibe ibecause iof ithe
itendency iof i iprecipitation iof ilead ias iPb(OH)2 i(Yi-Chao iand iShui-Ping i2011). iConsequently, ia ipH ivalue
iof i5.0 iwas iused ias ithe ioptimum iof ipH ithroughout ithe iexperimental iconditions ito iavoid ithe iformation
iof imetal ihydroxides. iSimilarly, ifor iall iother iconcentrated isolutions, isimilar itrend iwas iobserved. iAs ithe
ipH iincreased ithe iligands isuch ias icarboxylate igroups iin iBruguiera igymnorhiza. iwould ibe iexposed, 0 20 40 60 80 100 120 0 1 2 3
pH
4 5 6 7 mg/L 19.21 36.12 mg/L 68.056 mg/L 73.85 mg/L 0 2 4 6 8 10 12 0 1 2 3pH
4 5 6 7 19.21 mg/L 36.12 mg/L 68.065 mg/L 73.85 mg/L 109.44 mg/L2197
iincreasing ithe inegative icharge idensity ion ithe ibiomass isurface, iincreasing ithe iattraction iof imetallic iions
iwith ipositive icharge iand iallowing ithe ibiosorption ionto ithe icell isurface i(Namdeti iand iPulipati, i2014).
iEffect iof itemperature
All ithe iexperiments iwith iPb i(II) iwere iconducted iin ithe itemperature irange iof i25-55 C, ithe i%
iremoval iof ilead iby iBruguiera igymnorhiza ibiomass idecreases ifrom i97.6 ito i94.1% iwith iincrease iin
itemperature iin ithe irange i25-55 C iat iinitial iconcentration iof i19.21 img/L i(Fig.4). iThe isimilar itrend iwas
iobserved iat iall iinitial iPb i(II) iconcentrations. iIn imost iof ithe ichemical ireactions ithe itemperature iis
iexpected ito iactivate ithe iprocess iincreasing ithe iheat ior imass itransport iprocesses. iSorption icapacity iof
ithe ibiomass ihas idecreased iwith iincrease iin itemperature, irise iin itemperature ihas ia itendency ito idesorb
ithe iadsorbed imetal iions ifrom ithe isurface ito ithe isolution. iThe isame itrend iwas iobserved ifor iother iinitial
imetal iconcentrations iand iwas isupported iby ithe iearlier ireport i(Aksu, i2001). i
Figure i4: iVariation iof i% iremoval iof iPb i(II) iwith ivarious itemperatures iat idifferent iinitial
iconcentration iof iPb i(II) iat ibiomass i10 ig/L iand ipH i5. 4.Effect iof imetal iion iconcentration
The ieffect iof iinitial iPb i(II) iconcentration ion ithe imetal iuptake iwas ishown iin iFig.5. iThe iadsorption
icapacity i(qe) iof ithe ibiomass iincreased ifrom i2.879 ito i10.536 img ig-1 iwith iincreasing iPb i(II)
iconcentration ifrom i48.31 img iL-1 ito i186.71 img iL-1 iat isorbent idose iof i10g iL-1 iwith ithe itemperature
iof i25 C iand ipH i5. iAn iincrease iin ithe iinitial iion iconcentration iprovides ia ilarger idriving iforce ito
iovercome iall imass itransfer iresistances ibetween ithe isolid iand ithe iaqueous iphase, iwhich iresults iin ihigher
imetal iion iadsorption. iSimilar iobservations ialso iwere imade iby iearlier iinvestigators i(Mohammad iet ial,
i2011) iin itheir istudies ion ithe iadsorption iof iLead.
y = - 0.066 x + 98.992 R² = 0.9954 y = - 0.1054x + 97.918 R² = 0.9993 y = - 0.1255x + 97.059 R² = 0.9972 82 84 86 88 90 92 94 96 98 100 0 20 40 60 80 100 120
Initial ilead i(II) iconcentration, img/L
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pH 3 pH 4 pH 5 pH 6
Fig. i5. iVariation iof i% iremoval iof iPb i(II) iwith ivarious iInitial iconcentrations iat itemperature iof
i25 C, ipH i5 iand ibiomass i10 ig iL-1. 5. Effect iof iadsorbent idosage
Biosorbent idosage idetermines ithe ipotential iof ibiosorbent ithrough ithe inumber iof ibinding isites
iavailable ito iremove imetal iions iat ia ispecified iinitial imetal iion iconcentration. iThe ieffect iof iamount iof
ibiomass iwas istudied ion ithe ibiosorption iof iPb i(II) iusing iBruguiera igymnorhiza. iThe i% iremoval iof iPb
i(II) ion iBruguiera igymnorhiza iranged ifrom i54.98 ito i80.02 i(Fig.4) iat ia ipH ivalue iof i5 iat i24.8 img/L
iand ithe iuptaking icapacity i ideclined ifrom i12.39 ito i1.93 img ig-1 iwhen iincreasing ithe ibiomass idosage
ifrom i5 ig iL-1 ito i20 ig iL-1. iThe isimilar itrend iwas iobserved ifor iall iinitial imetal iion iconcentrations.
iThis idecrease icould ibe idue ito ithe iconcentration igradient ibetween ithe isorbent iand ithe isorbate; ian
iincrease iin ibiomass icaused ia idecrease iin ithe iamount iof imetal isorbed ionto ia iunit iweight iof ithe ialgae.
iMoreover, ithe iincrease iin ipercentage ibiosorption iof imetals iby iincreasing ithe ibiomass idosage iis idue ito
ian iincrease iin ithe inumber iof iactive isites iand isurface iarea iavailable ifor ibiosorption. iSimilar itrends ihave
ibeen ireported iin ithe iliterature i(Taqvi iet ial, i2006; iGupta iand iRastogi, i2008; iYi-Chao iand iShui-Ping
i2011). iFrom iFig.6 iwe ican iconclude ithat ipercentage iadsorption iincreased iwith idecrease iin ibiomass
idosage. 60 65 70 75 80 85 0 50 100 150 200
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Fig. i6. iEffect iof iBiomass iwieght i(a) iVariation iof i% iPb i(II) isorption i(b) imetal iuptake iwith ibiomass
iweight iat itemp i25 C, ipH i5 iand iat ivarious iinitial imetal iconcentrations. 6.Equilibrium iisotherms
iLangmuir iIsotherm
The iequation iproposed iby iLangmuir iis iuniversally iapplicable ito ichemisorption iwith isome ilimitations
iinvolving iphysical iadsorption i(Dąbrowski, i2001). iThis iequation iis iapplicable ito ithe iphysical ior ichemical
iadsorption ion isolid isurface iwith ione itype iof iadsorption iactive icenter. i i iLinear iform iof ithe iLangmuir
iequation iis igiven iby
C
*1
C
*=
+
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i iC
sC
mb
C
m i i i i i i i i i i i (3)Where i„Cm’(mg/g) iis ithe imaximum iamount iof ithe imetal iion iper iunit iweight iof iadsorbent ito iform ia
icomplete imonolayer ion ithe isurface. i„Cs‟ iis iequilibrium iadsorption icapacity i(mg/g), i„C*‟ iis ithe
iequilibrium iconcentration iof ithe iadsorbate iin isolution i(mg/L), iand ib iis ia iconstant iwhich iaccounts ifor
ithe iaffinity iof ithe ibinding isites i(L/mg). iCm irepresents ithe ilimiting iadsorption icapacity iwhen ithe isurface
iis ifully icovered iwith imetal iions iand ihelps iin ithe ievaluation iof iadsorption iperformance, iparticularly iin
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isimple itwo iparameter iequation i(Langmuir, i1918). iFrom ithe iplots ibetween i(C*/Cs) iand iC *
the islope
i(1/Cm) iand ithe iintercept i(1/ iCmb) ican ibe icalculated.
The iLangmuir iconstant iused ito idetermine ithe isuitability iof ithe iadsorbent ito iadsorbate iby iusing
idimensionless ifactor iRL i(Hall iseparation ifactor) icalculated iby: i
1 R
L=
1+bC
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i (4)
0 i<RL i<1 i i iindicates ifavorable ifor iadsorption, iRL> i1indicates iun-favorable ifor iadsorption iRL i= i1
iindicates ilinear iadsorption, iRL i= i0 iindicates iirreversible iadsorption.
Figure i7: iLangmuir iplot iof iBruguiera igymnorhiza iat ivarious itemperatures iat ipH i5
The ilinearized iLangmuir iadsorption iisotherms iof iPb i(II) ionto iBruguiera igymnorhiza iwere iobtained iat
idifferent itemperatures. iAdsorption iconstants iand icorrelation icoefficients iare ishown iin iTable.1
iC*/CsvsC*plot iyielded ia istraight iline iwith iR2 i(0.970) iindicating ithe isorption idata icould ibe irepresented
iby ithe iLangmuir imodel i(Fig. i7). iThe ihigher iadsorption icapacity, iqm(»1) iindicated ithe istrong
ielectrostatic iforce iof iattraction iand ib iis ia iconstant iwhich iaccounts ifor ithe iaffinity iof ithe ibinding isites
i(L/mg) iMoreover, ithe ib ivalues iare i1.030928, i1.02145, i1.029866L/mg iindicating ithat ibiosorption icapacity
iof iBruguiera igymnorhiza ibiomass ifor iPb i(II) iis ihigher. iThe iadsorption iof iPb i(II) ion ipowder isurface iis
ithus ia ihighly ifavourable iprocess. iFurther, iit iis iobserved ithat ithe isorption iof ilead iis imore ifavourable iat
ihigher iPb i(II) iinitial iconcentration i(109.44 img/L) ithan ifor ithe ilower iones i(19.21 img/L).
i i i i iTable i.1. iLangmuir iand iFreundlich iisotherm imodel iparameters ifor iPb i(II) ionto iBruguiera igymnorhiza
Langmuir iconstants Freundlich iconstants
Temp.( K) Cm(mg ig -1) b i(L immol -1) R2 KF nf R2 298 13.333 0.295276 1 0.970 0.32961 1.79211 5 0.9 97 318 12.658 0.311024 0.979 5 0.46451 1.78253 1 0.9 96 328 12.3456 0.318898 0.971 7 0.53579 1.79211 5 0.9 98 7.Freundlich iIsotherm
An iadsorption iisotherm iwas iproposed iby iBoedecker i(Dąbrowski, i2001) iwhich iwas ilater imodified iby
iFreundlich i(Freundlich, i1926). iThe iFreundlich iadsorption iequation ican ibe iwritten ias: y = 0.0755x + 0.2542 R² = 0.9707 y = 0.0794x + 0.4505 R² = 0.9793 y = 0.0819x + 0.5763 R² = 0.9712 0 0.5 1 1.5 2 2.5 0 5
c* i
10 15 20 K 298 318 K 328 K2201 1
C
=
K C
*n f i i i i i i i i i i i i i i i i i i i i i i i i(6) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i iWhere i„Cs‟ iis iequilibrium iadsorption icapacity i(mg/g), i„C*‟ iis ithe iequilibrium iconcentration iof ithe
iadsorbate iin isolution, i„Kf‟ iand inf iare iconstants irelated ito ithe iadsorption iprocess isuch ias iadsorption
icapacity iand iintensity irespectively. iThis iempirical imodel ihas ishown ibest ifit ifor inon-ideal isorption ion
iheterogeneous isurfaces ias iwell ias imultilayer isorption. iThe iFreundlich iisotherm iis ialso imore iwidely iused
ibut iprovides ino iinformation ion ithe imonolayer iadsorption icapacity, iin icontrast ito ithe iLangmuir imodel.
iFreundlich iisotherm ihas ibeen iderived iby iassuming ian iexponentially idecaying isorption isite ienergy
idistribution. iThe icoefficient iof idetermination ifor ithis icase iis i0.997 iand ithe ivalues iof inf iand iKf i(table
i1) iare ifound ito ibe i1.79 i(g/L) iand i0.329 i{(mg/g)(mg/L)n}at i25 C. iFreundlich iconstant inf ibetween i1 iand
i10 iindicates ia itrend imore ifavorable i(Fig.8) ifor ibiosorption iby imacro ialgae iBruguiera igymnorhiza. iThis
iis ialso isuggestive ithat ithe imetal iion iunder istudy icould iwell ibe iseparated ifrom iits iaqueous isolution
iwith ihigh iadsorption icapacity.
The ivalues iof ihigh icorrelation icoefficients iindicated ithat ithe iPb(II) isorption idata iwas ivery iwell
irepresented iby iFreundlich imodel. iThe iFreundlich iconstant inf iwas igreater ithan i1, iat iall itemperatures ias
iwell ias iinitial imetal iconcentrations irepresenting ithat iadsorption iintensity iof ithe isorbate ion ithe isorbent
isurface iwas ihigh, ireflecting ithe ifavorable isorption ieven iat ihigh imetal iconcentration.
i i i i i i i i i i i i i i i i i i i iFigure i8: iFreundlich iplot iof iBruguiera igymnorhiza iat ivarious itemperatures iat
ipH i5.
s f i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
(5) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
Taking ilogarithm ion iboth isides,
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
1
In
Cs = lnK f+ InC
*n
f i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i y = 0.5583x + 0.482 R² = 0.997 y = 0.5618x + 0.333 R² = 0.9965 0 0.5 1 1.5 -0.5 0log ic
0.5 * 1 1.5 298 K 318 KResearch Article
2202
8.Adsorption iKinetic iModels
The ikinetic idata ihelps iin itracing ithe irate idetermining istep iof itransport imechanism iand iis irequired
ifor iselecting ioptimum ioperating iconditions ifor ifull-scale ibatch ior icontinuous iprocess. i iIn ithe ipresent
istudy iPseudo ifirst iorder iand iPseudo isecond iorder ikinetic imodels ihave ibeen iattempting ito ifit ithe
ipresent ibiosorption idata i(Table. i2).
9 Pseudo-first-order/Lagergren ikinetic imodel
The iPseudo-first-order ior iLagergren ikinetic irate iequation ifor ithe iadsorption iof iliquid-solid isystem iwas
iderived ibased ion isolid iadsorption icapacity. iIt iis ione iof ithe imost iwidely iused iadsorption irate iequations
ifor ithe iadsorption iof ia isolute ifrom ia iliquid isolution i(Taqvi iet ial, i2006; iSuddhodan iand iMishra, i2006).
i
The ipseudo ifirst iorder ikinetic iequation ican ibe iexpressed ias:
dcdt = k
1(
C
S−C
t)
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i ii i i i i i i i i i i i i i i i i i i i i(7) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
Where i„Cs‟ iis ithe iamount iof isolute iadsorbed iat iequilibrium iper iunit imass iof iadsorbent i(mg/g), i„Ct‟ iis ithe iamount iof isolute iadsorbed iat iany igiven itime i„t‟ iand i„k1‟ iis ithe irate iconstant. iBy iusing ithe
iboundary iconditions iand isimplifying, ithe iequation i7 iyields.
ln(Cs −Ct) = lnCs −k
1t
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i ii i i i i i i i i i i i i i i i i i i i(8) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
„k1‟ ican ibe icomputed ifrom ithe islope iof ithe ilinear iplot ibetween iln(Cs-Ct) ivs. i„t‟ ifor idifferent
iadsorption iparameters isuch ias ipH, itemperature. iThe ipseudo ifirst iorder irate iconstant ik1could ibe iobtained
ifrom ithe islope iof ithe iplot ibetween ilog i(Cs i–Ct) iand itime it‟. iFig. i9 ishows ithat ithe iLagergren
ipseudofirst iorder ikinetic iplot idoes inot ifit iwell ifor ithe iadsorption iof i i iPb i(II) ionto iBruguiera igymnorhiza, ias iit idoes inot ifollow ia istraight iline.
Figure i.9: iPseudo ifirst iorder ikinetic iplot ifor ibiosorption iof iPb i(II) iat i25°C, i50 img/L iand ipH i5. 10.Pseudo- isecond- iorder ikinetic imodel
In iview iof ithe iabove ithe ifitness iof ithe isorption idata iwas itested iusing ipseudo- isecond- iorder ireaction
imodel i.The ipseudo-second-order ireaction imodel icould ibe iexpressed iby ithe irate iexpression ias i(Ho iand
iMckay, i1999; i2000).
dcdt
= k
2(C
s −Ct)2
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i y = - 0.0095x + 1.0169 R² = 0.9352 y = - 0.015 + 0.8392 x R² = 0.9854 -1 -0.5 0 0.5 1 1.5 0 20 40 60 80 100 120 140Time,min
0.25 g 0.5 g2203
i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i(9) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
On iintegration ifor iboundary iconditions iwhen it=0 ito it>0 iand iqt=0 ito iqt>0 iand ifurther isimplifications,
iequation i9 ibecomes,
t
= 1 + 1 t
Ct
k
2C
s2 C
s i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i(10) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i iThe iplot i(Fig.8) iof it/qt iversus it iof iEq. i(10) igave ia ilinear irelationship ifrom iwhich ithe iqe iand ik2
ivalues iwere idetermined. i
Figure. i10: iPseudo isecond iorder ikinetic ifor ibiosorption iof iPb i(II) iat i25°C, i50 img/L iand ipH i5.
W i(g/L) Ce(exp) i(mg/g) K1(g/mg-min) R i2
5 3.66 -0.009 0.939
10 4.57 -0.015 0.986
i i i i i i i i i i i i i i i i i iTable i.2: i iKinetic iparameters ifor iPb i(II) ibiosorption ion iBruguiera igymnorhiza
The irate iconstants iand ithe icorrelation icoefficients ifor iPseudo-First-order ikinetic imodel iwere icalculated
iand isummarized iin iTable. i2. iThese ivalues ishowed ithat ithe ipseudo-first iorder ikinetic iplot ifits iwell ithe
iadsorption idata. iThe ivalue iof icorrelation icoefficient iR2 ifor ithe ipseudo-first-order iadsorption imodel iis
irelatively ihigh i(>0.9909), iand ithe iadsorption icapacities icalculated iby ithe imodel iare ialso iclose ito ithose
idetermined iby iexperiments. iHowever, ithe ivalues iof iR2 ifor ithe ipseudo-second-order iare inot isatisfactory.
iTherefore, iit ihas ibeen iconcluded ithat ithe ipseudo-first-order iadsorption imodel iis imore isuitable ito
idescribe ithe iadsorption ikinetics iof ilead iover ithis iBruguiera igymnorhiza ibiomass. 11.Thermodynamic iparameters
Gibbs iFree iEnergy iΔG iis ithe iThermodynamic icriterion iat iconstant iP iand iT ifor ideciding iwhether ithe
ichemical iprocess idoes iproceed ior inot. iThe ispontaneity iof ithe ireaction ican ialso ibe ijudged iby ithe isign
iand imagnitude iof iΔG0. iA inegative isign ifor iΔG0 iis ian iindicative iof ithe ispontaneity iof iany ichemical
iprocess. iTo idesign iany ichemical iprocess isystem ione ishould ihave ithe iknowledge iof ithe ichanges ithat
iare iexpected ito ioccur iduring ia ichemical ireaction. i
0 5 10 15 20 0 50
Time,min
100 150 0.25 g 0.5 gResearch Article
2204
In iview iof ithe iabove, ianalysis ihas ibeen icarried iout ion ithe ivalues iof ithermodynamic iparameters ion
ithe ibiosorption iof iPb i(II) iby iBruguiera igymnorhiza. iThe ithermodynamic iparameters isuch ias ichanges iin
istandard ifree ienergy ichange iΔG , iEnthalpy iΔH , iEntropy iΔS ifor iany igiven iadsorption iprocess icould
ibe idetermined ifrom ithe iEquations:
G
0=−
RTInK
c i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i ii i i i i i i i i i i i i i i i i i i i i i i i i i i i i(11) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
Where iΔG iis ithe ifree ienergy ichange, iexpressed ias iJ/mol. iKc iis ithe iapparent iequilibrium iconstant
ifor ithe iprocess. iKc ican ibe iderived ifrom:
C
SK
C=C
* i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i (12) i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i ilog
C
*S=−
2.303 HRT
0+
RS
0 i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i iC
i i i i i i i i i i(13) i i i i i i i i i i i i i i i i i i i i i i i i iC
SC
* Can ibe idefined ias iadsorption iaffinity.Cs iis ithe iconcentration iof imetal iion i(mg) iin isolidiadsorbent.C* iis iequilibrium imetal iConcentration img/L i.The ienthalpy ichanges i(ΔH ) iand ientropy ichanges
i(ΔS ) ifor ithe iadsorption iprocess ifor iall ithe iinitial imetal iconcentrations iin ithe iaqueous isolutions iwere
iobtained ifrom ithe iplots iof ilog CS* drawn iagainst i1/T i(Fig.11). iThe icalculated ithermodynamic
idata iare
C
Fig.11. iVant iHoff iplot ifor iadsorption iof iPb i(II) ionto iBruguiera igymnorhiza iat ivarious itemperatures
ifor ibiomass i10 ig/Land iat ipH i5.
i compiled i in i Table i .4. y = - 250 x + 11.859 R² = 0.9998 11 11.02 11.04 11.06 11.08 11.1 11.12 0.003 0.00305 0.0031 0.00315 0.0032 0.00325 0.0033 0.00335 0.0034
1
/T
2205
A iLarge inegative ivalue ifor iΔG iindicates ithe ispontaneity iof ibiosorption iprocess iat ia igiven
itemperature. iThe ifree ienergy ivalues iincreased ipositively iwith iincrease iin itemperature ifor ithe iadsorption iof
iPb i(II), ishows ithat ithe ispontaneity iof ithe ibiosorption iprocess ireduces iwith iincrease iin itemperature. iThe
inegative iΔH ivalues iindicated ithe iexothermic inature iof ithe iadsorption. iThe inegative ivalues iof
iΔS suggested ia idecrease i(Ahmet iet ial., i2008) iin ithe irandomness iat isolid/solution iinterface iduring ithe
iadsorption iof iPb i(II) iions ionto iBruguiera igymnorhiza i i i i i i i iTable. i4: iThermodynamic iparameters ifor
iPb i(II) ibiosorption ion iBruguiera igymnorhiza
Temp. i(0K)
12.Characterization iof iBiomass 12.1.Fourier iTransform iInfrared iSpectroscopy i(FTIR)
The iFTIR idifferences iof ispectra iin ipure iBruguiera igymnorhiza ibiomass iadsorbent iwere icompared ito
ithe ispectra iobtained iin iPb(II) iloaded iBruguiera igymnorhiza ito idetermine iwhether ithe iobserved
idifferences iare idue ito iinteraction iof ithe imetal iions iwith ifunctional igroups i(Fig. i12 iand i13). iThe
iabsorption ipeaks iwere itabulated iin itable i4 ifor ipure ibiomass iand iPb2+ iloaded ialgal ibiomass. i i i i i i i i i i i i i i i i i i i i Figu re i12: iFTIR iSpectrum iof iBruguiera igymnorhiza ibefore itreatment
H ( KJ/mol ) S J/mol ( 0 K) G ( KJ/mol ) 298 2078.5 98.5209 - 27.2807 318 2078.5 98.5209 - 29.2511 328 2078.5 98.5207 - 30.2364
Research Article
2206
Figure i13: iFTIR iSpectrum iof iBruguiera igymnorhiza iafter itreatment iwith iPb i(II)
The ibroad ibands iat i3607.22 iand i3392.13 icm-1 iwere idue ito i–OH iand i–NH2 istretching ivibrations idue
ito ilignins i(Lalhruaitluanga iet ial., i2010) iand i–OH istretching ivibrations irespectively iinvolved iin ithe
ibiosorption iby ishifting ithe iband ito i3351.93 iand i3340.37 icm-1. iThe ibands iat i3051.31 icm-1 iindicate ithe
ipresence iof iCH2 istretching ivibrations iof iaromatic iaryl irings iand ishifted ito i3021.30 icm-1. iThe iband iat
i2376.67 icm-1 ican ibe iattributed ito i–C≡N iin ithe ipolyacrylonitrile i(Sarada iet ial., i2014) iand iis iinvolved
iintensely iby ishifting ito i2366.27 icm-1. iThe iband ipeak iat i1705.14 icm-1 iis iassigned ito iCarbonyl
ifunctional igroup iof, iafter iadsorption iof iPb2+ ithe iband islightly ishifted ito i1716.30 icm-1. iFurther ithe
isharp ipeak iat i1376.07 icm-1 irepresenting ithe ipresence iof i–CH2 ibending ivibrations iin ithe ibiomass iand iis
ialso ishifted ito i1316.48 icm-1 iindicating ithe iinvolvement iin ibiosorption iprocess. i
The ipresence iof isiliceous ifrom idiatomaceous iearth, iin imangrove iplant iwaste iand icomposite imaterial,
ican ijustify ifor ithe iabsorbance ipeak iat i757.44 icm−1 i(Si–C) iand iN icontaining ibioligands iis ishifted ito ithe
i746.93 icm−1. i iThe ibands ipresent ibelow i800cm−1 iare ifinger iprint izone iof iphosphate iand isulphur
ifunctional igroups iand iN icontaining ibioligands. iThe isignificant ichanges iin ithe iwave inumbers iof ithe
ispecific ipeaks isuggested ithat i–OH iand i–NH2, ibounded i–CH2, iamide iN-H ibending ivibrations iand iC=O
iof icarboxylic iacid igroups icould ibe ipredominantly iinvolved iin ithe ibiosorption iof iPb+2 ionto iBruguiera igymnorhiza. iSimilar iresults iwere ireported ifor ithe ibiosorption iof idifferent iheavy imetals ion ivarious iplant
ispecies i(Sibel iet ial, i2009; iSuleman iet ial, i2009; iLalhruaitluanga iet ial, i2010; iMunagapati i iet ial, i2010;
iSarada iet ial, i2014) 13 conclusion
Experimental idata iwere iobtained ifor iremoval iof iPb i(II) iions iusing iBruguiera igymnorhiza ias
ibiosorbent. iBased ion ithe ianalysis ithe ifollowing iconclusions iwere imade.
The ibiosorption iperformances iare istrongly iaffected iby iparameters isuch ias iinitial iconcentration, ipH,
iand itemperature.The ipercentage ibiosorption iPb i(II) iions iof iincreases iwith iincreasing icontact itime.The
iequilibrium iuptake iwas iincreased iand ipercentage ibiosorption iwas idecreased iwith iincreasing ithe iinitial
iconcentration. iThe iplot iof ipH iversus ipercentage ibiosorption ishows ithe isignificant ibiosorption itakes
iplace iat i5.The ipercentage ibiosorption iPb i(II) iof iincreases iwith iincrease iin ithe ibiosorbent idosage.The
ipercentage ibiosorption iPb i(II) iof idecreases iwith iincrease iin ithe itemperature.The iremoval idata iof ilead
iions ifollows ithe iFreundlich imodel iwith ithe ibest ifit.The ikinetics iof ithe ibiosorption iof ilead iions ion
iBruguiera igymnorhiza ican ibe ibetter idescribed iwith iFirst-order ikinetics. iIntra-particle idiffusion imight
ialso ihave ia isignificant irole iin ithe ibiosorption iprocess islowing idown ithe iapproach itowards
iequilibrium.The ithermodynamic iparameters isuch ias ifree ienergy ichange, ienthalpy ichange iand ientropy
ichanges iwere icalculated iand ithe ibiosorption iprocess iwas iexothermic. References
1. Ademoroti, iC. iM. iA., i(1996). iEnvironmental ichemistry iand itoxicology. iPollution iby iheavy imetals. iFoludex ipress, i171- i172 i
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2. Afridi iH. iI., iKazi iT. iG., iKazi iG. iH., iJamali iM. iK., iShar iG. iQ., i2006. iEssential itrace iand itoxic ielement idistribution iin ithe iscalp ihair iof iPakistani imyocardial iinfarction ipatients iand icontrols. iBiol. iTrace iElem. iRes. i113, i19-34.
3. Ahmet, iS., iDurali, iM., iMustafa, iT., iMustafa, iS., i“Biosorption iof iCd i(II) iand iCr i(III) ifrom iaqueous isolution iby imoss i(Hylocomiumsplendens) ibiomass: iEquilibrium, ikinetic iand ithermodynamic istudies,” iChem. iEngg. iJ, ivol. i144, ipp. i1–9, i2008
4. Ahmet, iS., iMustafa, iT., i“Biosorption iof iPb(II) iand iCd(II) ifrom iaqueous isolution iusing igreen ialga i(Ulva ilactuca) ibiomass,” iJ. iHazard. iMater, ivol. i i152, ipp. i302–308, i2008.
5. Aksu, iZ.,” iEquilibrium iand ikinetic imodeling iof icadmium i(II) ibiosorption iby iC. iVulgaris iin ia ibatch isystem: ieffect iof itemperature,” iSepn.Purifi. iTechno, ivol. i21, ipp. i285–294, i2001.
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