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Comparative study of the kinetics and equilibrium of phenol biosorption on immobilized white-rot fungus Phanerochaete chrysosporium from aqueous solution

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ColloidsandSurfacesB:Biointerfacesxx(2012)xxx–xxx

ContentslistsavailableatSciVerseScienceDirect

Colloids and Surfaces B: Biointerfaces

j our na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / c o l s u r f b

Graphical Abstract

ColloidsandSurfacesB:Biointerfacesxx (2012)xxx–xxx Comparativestudyofthekineticsandequilibriumofphenolbiosorption

onimmobilizedwhite-rotfungusPhanerochaetechrysosporiumfromaqueoussolution ViktorFarkas,AttilaFelinger,AlˇzbetaHeged ˝usova,ImreDékány,TímeaPernyeszi

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COLSUB53561

ARTICLE IN PRESS

G Model

ColloidsandSurfacesB:Biointerfacesxx(2012)xxx–xxx

ContentslistsavailableatSciVerseScienceDirect

Colloids and Surfaces B: Biointerfaces

j our na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / c o l s u r f b

Highlights

ColloidsandSurfacesB:Biointerfacesxx (2012)xxx–xxx Comparativestudyofthekineticsandequilibriumofphenolbiosorption

onimmobilizedwhite-rotfungusPhanerochaetechrysosporiumfromaqueoussolution ViktorFarkas,AttilaFelinger,AlˇzbetaHeged ˝usova,ImreDékány,TímeaPernyeszi

Thebiosorptionprocessofphenolontofree,immobilizedwhite-rotfungiandalginatebeadswasexamined.Thebiosorptionprocess followspseudosecond-orderkineticsbyallbioadsorbents.Phenolbioadsorptionprocessfollowsananti-Langmuirbehaviorforfreefungal biomassandimmobilizedfungalbiomass.Thenonlinearestimationcanbesuggestedforbioadsorption-equilibriumevaluation.

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Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx

ContentslistsavailableatSciVerseScienceDirect

Colloids and Surfaces B: Biointerfaces

j o ur na l ho me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / c o l s u r f b

Comparative study of the kinetics and equilibrium of phenol biosorption on immobilized white-rot fungus Phanerochaete chrysosporium

from aqueous solution

1

2

3

Viktor Farkas

a,b

, Attila Felinger

a,b

, Alˇzbeta Heged ˝usova

c

, Imre Dékány

d,e

, Tímea Pernyeszi

a,b,∗

4 Q1

aAnalyticalChemistryandGeoanalyticalResearchGroup,SzentágothaiResearchCenter,UniversityofPécs,H-7624Pécs,Ifjúságútja34.,Hungary 5

bDepartmentofAnalyticalandEnvironmentalChemistry,FacultyofScience,UniversityofPécs,H-7624Pécs,Ifjúságútja6.,Hungary 6

cDepartmentofVegetablesProduction,SlovakUniversityofAgricultureinNitra,SK-7624Nitra,Slovakia 7

dSupramolecularNanostructuredMaterialsResearchGroupoftheHungarianAcademyofSciences,UniversityofSzeged,AradiVértanúktere1.,H-6720Szeged,Hungary 8

eDepartmentofMedicalChemistry,FacultyofMedicine,UniversityofSzeged,AradiVértanúktere1.,H-6720Szeged,Hungary 9

10

a r t i c l e i n f o

11 12

Articlehistory:

13

Received4June2012 14

Receivedinrevisedform1September2012 15

Accepted6September2012 16

Available online xxx 17

Keywords:

18

Biosorption 19

Phenol 20

Ph.chrysosporium 21

Kinetics 22

Equilibrium 23

Nonlinearleast-squaresestimation 24

a b s t r a c t

Inthisstudythekineticsandequilibriumofphenolbiosorptionwerestudiedfromaqueoussolutionusing batchtechniqueataninitialpHof5.5.ThebiosorptionwasstudiedonCa–alginatebeads,onnon-living mycelialpelletsofPhanerochaetechrysosporiumimmobilizedonCa–alginate,andonfreefungalbiomass.

Ph.chrysosporiumwasgrowninaliquidmediumcontainingmineralandvitaminmaterialswithcomplex composition.Thebiosorptionprocessfollowedpseudosecond-orderkineticsonallbioadsorbents.The bioadsorption-equilibriumonblankCa–alginate,freeandimmobilizedfungalbiomasscanbedescribed byLangmuir,anti-LangmuirandFreundlichisothermmodelsusingnonlinearleast-squaresestimation.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

25

Phenoliswidelypresentinwastewatersdischargedfromindus-

26

triesanditisconsideredasprioritypollutantbecauseofitshigh

27

toxicityatlowconcentrationsaswell.Industrialsourcesofcontam-

28

inantssuchasoilrefineries,coalgasificationsites,petrochemical

29

units,and so on, generate largequantitiesof phenols. In addi-

30

tion,phenolderivativesarewidelyusedasintermediatesinthe

31

synthesis of plastics, colors, pesticides, insecticides, etc. [1]. In

32

ordertokeepwatersfreefromphenolcompounds,differentpurifi-

33

cation methodssuchas adsorption,chemical oxidation,solvent

34

extraction,orreverseosmosisareusedforremovingphenolsfrom

35

wastewaters[2].

36

Biosorption, as an efficient, cost-effective and environmen-

37

tallyfriendly technique– forheavy metals andvarious organic

38

pollutants– hasemerged asa potentialalternativetothe con-

39

ventional techniques [3–6]. Biomass of somenatural microbial

40

species,includingbacteria,fungiandalgae,iscapableofremoving

41

Correspondingauthorat:H-7624Pécs,Ifjúságútja6.,Hungary.

Tel.:+3672503600;fax:+3672501518.

E-mailaddress:ptimea@gamma.ttk.pte.hu(T.Pernyeszi).

thedifferentorganicpollutantsbybiosorption,biodegradationor 42

mineralization[7,8]. 43

Growingattentionisbeinggiventothepotentialhealthhaz- 44

ardpresentedbyheavymetalstotheenvironment.Uluozluetal. 45

used lichen biomass for theremoval of different heavy metals 46

fromaqueoussolution.Theystudiedtheeffectofdifferentparam- 47

eters,suchaspH,biomassdosage,contacttime,andtemperature. 48

[9].Biosorption ofCd(II) andCr(III)fromaqueoussolutionon 49

Hylocomium splendens biomass wereinvestigated by Sari et al. 50

Theyuseddifferentkineticandisothermmodelstoevaluatethe 51

experimentaldata.TheyfoundthattheLangmuirmodelfittedthe 52

equilibrium databetterthantheFreundlichone.Theuseofthe 53

Dubinin–Rhadushkevichmodeldemonstratedthattheprocessis 54

ion-exchange[10].Lactofungusscrobiculatusbiomasswasusedfor 55

heavymetalremovalbyAnayurtetal.Thekineticstudiesindicated 56

thattheprocessfollowedwellpseudosecond-ordermodel.The 57

recoveryofthemetalionwasfoundashigherthan95%[11]. 58

Phanerochaetechrysosporiumisawell-knownwhite-rotfungus 59

andithasastrongabilitytodegradexenobiotics[12,13].Relatively 60

fewstudieshavebeencarriedoutwithPh.chrysosporiumindetox- 61

ifyingmetaleffluentsandeffluentscontainingphenolderivatives 62

[6,7,14–19].Moststudiesonbioadsorptionwerecarriedoutwith 63

powderedbiomassandbatchsystems.Thepowderedbiomassis 64 0927-7765/$seefrontmatter© 2012 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.colsurfb.2012.09.029

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Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption on immobilized white-rot fungus Phanerochaete chrysosporium from aqueous solution, Colloids Surf. B: Biointerfaces (2012), http://dx.doi.org/10.1016/j.colsurfb.2012.09.029

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2 V.Farkasetal./ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx difficulttouseinapplicationsduetoitsdisadvantages,thesmall

65

particlesizeandlowmechanicalstrength,whichmaycausediffi-

66

cultyintheseparationofbiomassafterbiosorptionandsignificant

67

masslossafterregeneration.

68

Theimmobilizationofnativemicroorganismsonnaturalorsyn-

69

theticpolymersimprovestheirmechanicalstrength,rigidity,size,

70

porositycharacteristics,andresistancetoenvironmentalrestrains.

71

Theselectionofimmobilizationmatrix iscrucialintheapplica-

72

tionofimmobilizationbiomass.Thepolymermatrixdetermines

73

themechanical strength,rigidity,and porositycharacteristicsof

74

theimmobilizedbeadsandtheiradsorptioncapacity.Thephysi-

75

calentrapmentofmicroorganismsinsideapolymermatrixisone

76

ofthemostwidelyused techniquesorimmobilization[20–27].

77

Sodium alginate, chitin, chitosan, and cellulose derivatives as

78

naturalpolymershavebeenusedasthematricesforimmobiliza-

79

tion[20–27].Immobilizedbiomassexhibitsagreaterpotentialin

80

fixed/fluidizedbed reactors becauseof minimal clogging under

81

continuousflowingconditions,convenienceforregeneration,reuse

82

ofbiomassandeasysolid–liquidseparation[3,26,27].

83

For the immobilization of Ph. chrysosporium, little informa-

84

tionexistsintheliterature.YuandWu[25]usedalginate,pectin

85

and polyvinyl alcohol (PVA) to immobilize Ph. chrysosporium

86

cellsfor2,4-dichlorophenolbioadsorption.Theimmobilizationof

87

Ph.chrysosporiumonto pectin wasless efficient than that onto

88

othermatrices becauseofitspoormechanicalstrengthand low

89

adsorptionefficiency.Ca-alginateimmobilizedfungalbeadswith

90

biocompatibilityexhibitedgoodmechanicalstrengthandadsorp-

91

tionefficiencyover60%.Amongthedifferentbiomassdosagein

92

Ca–alginateimmobilizedfungalbeads1.25%(w/v)wastheopti-

93

mum[20,25].

94

The continuous-flow adsorption of 2,4-dichlorophenol (2,4-

95

DCP) from aqueous solutionon immobilized Ph.chrysosporium

96

biomass in a fixed-bed column was also studied [26]. They

97

foundthatthebreakthroughtimedecreasedwithincreasingflow

98

rate,increasinginfluentconcentration,anddecreasingbeddepth.

99

Thedata alsoindicated thatthe equilibrium uptakeof 2,4-DCP

100

increasedwithdecreasingflowrateandincreasinginfluentcon-

101

centrationof2,4-DCP.

102

MathialaganandViraraghavanstudiedthebiosorptionofpen-

103

tachlorophenol(PCP) ontreatedAspergillus niger biomass.They

104

foundthatthebiosorptionwaspHdependent.TheremovalofPCP

105

decreasedwiththeincreaseofpHforalltypesofbiomass.Theyalso

106

evaluatedtheresultswithdifferentkineticandisothermmodels

107

[8,28].

108

Ca–alginateandloofaspongeasasupportforlead(II),copper

109

(II),andzinc(II)biosorptiononimmobilizedPh.chrysosporiumwas

110

alsostudied[20,21,23].IqbalandSaeedreportedthepossibilityof

111

immobilizingPh.chrysosporiumonabiostructuralmatrixofloofa

112

spongeasadyebiosorbentsystemfortheremovalofRBBR(Rema-

113

zolBrilliantBlueR), areactivedye,fromaqueoussolution.The

114

reactivedyeuptakefromaqueoussolutionwasfoundtobeinflu-

115

encedbysolutionpH,temperatureandinitialdyeconcentration

116

[23].

117

ThefibrousnetworkofPapayawoodasaspecialimmobiliza-

118

tionmatrixwasusedtoimmobilizePh.chrysosporiumbyIqbaland

119

Saeed[22].Theyusedthismatrixforremovalofzinc(II)fromaque-

120

oussolution.Theyobtainedthattheimmobilizedfungalbiosorbent

121

removedzinc(II)rapidlyandefficientlywithamaximummetal

122

removalcapacity of 66.17mgg1 at equilibrium, 41.93% higher

123

thantheamountofzinc(II)removedbyfreebiomass.Thesorp-

124

tiondataagreedwellwiththesecond-order kineticmodel,the

125

equilibriumdatafittedverywelltotheLangmuirmodel.

126

Themain objective of thepresent study wasto immobilize

127

inactive Ph. chrysosporium fungal biomass in Ca–alginate poly-

128

mermatrix andevaluatethephenolbioadsorptionkineticsand

129

equilibriumonblankCa–alginate,immobilizedPh.chrysosporium

130

fungalbiomasswithcomparisonoftheadsorptiondataonfreePh. 131 chrysosporiumbiomass,TheeffectofpH,adsorptiontime,initial 132

phenolconcentrationonbioadsorptioncapacitywasstudiedina 133

batchsystem. 134

2. Experimental 135

2.1. Chemicals 136

Allchemicalsusedwereofanalyticalgrade.Na–alginatewas 137

purchasedfromSigmaAldrichLtd.,Germany.Phenol(>99%purity) 138

waspurchasedfromSigma–AldrichLtd.,Germanyandwasused 139

withoutfurtherpurification.Stocksolutionswerepreparedbydis- 140

solving0.2gofphenolin1.0Lofdistilledwater.Thetestsolutions 141

containingphenolwerepreparedbydiluting200mgL1ofstock 142

solutionofphenoltothedesiredconcentrations.ThepHvalueofthe 143

biosorptionsystems(2.0–7.0)wasadjustedtotherequiredvalue 144

using0.1MNaOHor0.1MHCl(MerckAG.,Germany)solutions.All 145

solutionswerestoredinthedarkat4Cpriortouse. 146

2.2. Cultivationoffungalbiomass 147

Ph.chrysosporium(strainSzMC1726)obtainedfromtheDepart- 148

mentofEnvironmentalMicrobiology,FacultyofScience,University 149

ofPécs(Hungary)wasusedinthisstudy.Itwascultivatedasprevi- 150

ouslydescribedbyKirketal.[29].After5daysincubationat35C 151

onashaker(app.180rpm),themycelialpelletswereremovedfrom 152

themediumthroughfiltrationandinactivatedinapressurecooker 153

athightemperature(120C)for20min.Thenthemyceliapellets 154

werewashedseveraltimeswithdeionizedwater.Thesemycelial 155

pelletswereimmobilizedinthenextstep. 156

2.3. ImmobilizationofPhanerochaetechrysosporiumin 157

Ca–alginatebeads 158

Forimmobilizationoffungalbiomass,theoptimumconcentra- 159

tionofPh.chrysosporiumbiomassandNa–alginatesolutionwas 160

determinedbyWu andYu[25].Theoptimized concentrationof 161

biomassinCa–alginatewas1.25%andtheoptimizedconcentra- 162

tion ofNa–alginate solutionwas2%. For the immobilizationof 163

biomass,these concentrationvalues wereused.Fungal suspen- 164

sionwasdroppedinto a0.2MCaCl2 solution,andthedropsof 165

alginate–biomassmixturewerelatergelledintobeadswithamean 166

diameterof3–4mm.TheCa-alginateimmobilizedPh.chrysospo- 167 riumbeadswerestoredintheCaCl2solutionatfridgetemperature 168

around5C for4htocure.Thenthebeads wererinsedseveral 169

timeswithdeionizedwaterandstoredinfridgepriortouse.For 170

blankCa–alginatebeads,similarprocedureswereusedbutwithout 171

fungalbiomass. 172

2.4. Biosorptionstudy 173

ThebiosorptionofphenolontotheblankCa–alginatebeads,free 174

andimmobilizedfungalbeadswasinvestigatedinbatchbiosorp- 175

tionsystems. 176

Forcomparison,0.075goffreebiomass(dryweight),immo- 177

bilizedfungalbeadscontaining0.075gbiomass(dryweight)and 178

blankbeads(dryweight) wererespectively mixedwith250mL 179

phenolsolutionat theconcentrations of25 and 50mgL−1.The 180

sampleholderwasagitatedonashakerat400rpmatroomtem- 181

perature.Samplesweretaken atgiven timeintervals,and then 182

centrifugedat10,000rpmfor5min.Thesupernatantwasusedfor 183

analysis. 184

Forequilibriumstudies,theblankbeads,thefreeandimmobi- 185

lizedfungalbiomasswererespectivelyputintophenolsolutions 186

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Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption V.Farkasetal./ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx 3

Fig.1.Stereomicroscopicview(a)ofCa–alginatebead,freebiomass,andimmobilizedbiomass.Scanningelectronmicroscopicimageof(b)theCa–alginatebead(at70×

magnification),(c)ofthesurfaceoftheCa–alginatebead(at1000×magnification)and(d)ofthehyphalstructureoffreePh.chrysosporiumbiomass.Diametersofthebeads areabout5mm.

withinitialconcentrations from 10 to100mgL1. Theconcen-

187

trationof biosorbentwas0.3gL−1,thesuspension volumewas

188

50mL.Theexperimentswerecarriedoutat22.5Ctemperature.

189

Theadsorbedamountofphenolwascalculatedwiththefollowing

190

equation:

191

q=(C0−Ce)V

m (1)

192

whereqistheadsorbedamountofphenol(mgg−1);C0istheinitial

193

phenolconcentration(mgL1);Ce istheequilibriumphenolcon-

194

centration(mgL−1);Visthevolumeofthesolution(L);andmis

195

theweightofthebiosorbent(g).

196

2.5. Analysis

197

HPLC(AgilentTechnologies,USA)wasusedtodeterminethe

198

equilibriumconcentrationofphenolinthesupernatant.TheHPLC

199

systemcontainedadegasser(Agilent1100Series),asystemcon-

200

troller(Agilent1200Series),anautosamplerandinjector(Agilent

201

1200Series).TheChemstationsoftwarewasusedtoevaluatethe

202

chromatographicdata.Theexperimentswereperformedwitha

203

UV/visphotodiodearraydetectoratthewavelengthsof217and

204

270nm.

205

AWatersSymmetryC18column(4.6mm×150mm;5␮mpar-

206

ticlesize) was used. Allthe measurement werecarried out in

207

isocraticmodeusingthemobilephasecomposition60:40%(v/v),

208

methanol:water).Theseparationconditionswerethefollowing:

209

flowrate1mLmin1,columntemperature50C,andinjectionvol-

210

ume20␮Lforboththestandardandsamplesaswell.Calibration

211

curveofthestandardwasmadefromstocksolutionintherangeof

212

10–100mgL1.

213

2.6. Morphologicalstudywithscanningelectronmicroscope 214

(SEM) 215

SEMstudieswereconductedintheCentralElectronMicroscope 216

Laboratory,FacultyofMedicine,UniversityofPécs.AJeolJSM-6300 217

(JeolLtd.,Japan)scanningelectronmicroscopewasusedinthis 218

study. 219

Sampleswerelyophilizedasadryingprocedure.Nofurtherfixa- 220

tionproceduresweredoneduringthesamplepreparationprotocol. 221

Beforethesampleshadbeencoveredwithgold,dehydratedgran- 222

uleswerefixedonamicroscopeslide(Fig.1). Q2 223

3. Resultsanddiscussion 224

3.1. TheeffectofinitialpHonphenolbioadsorptionon 225

Ca–alginate,immobilizedandfreePh.chrysosporiumbiomass 226

EarlierstudiesonbiosorptionhaveshownthatpHisanimpor- 227

tantparameteraffectingthebiosorptionprocess[30].Theeffect 228

ofthepHoftheinitialsolutiononthephenoluptakecapacityof 229

theadsorbents(Ca–alginateblankbeads,Ca–alginateimmobilized 230

Ph.chrysosporiumbiomass,and free Ph.chrysosporiumbiomass) 231

wasstudiedinthepHrange2.0–7.0atasuspensionconcentration 232

of0.3gL−1.OnecanseeinFig.2a–cthatthebiosorptionofphe- 233

nolfirstincreasesfrompH2.0andthendeclineswiththefurther 234

increaseofpH.ForCa–alginatebeads,themaximumequilibrium 235

phenoluptake wasfoundat 1.21and2.22mgg−1,respectively, 236

for25 and50mgL1 atpH6(Fig.2a)Foralginateimmobilized 237

fungalbiomass,themaximum equilibriumuptakewasfoundat 238

2.06 and 3.93mgg−1, respectively, for 25 and 50mgL−1 phe- 239

nol concentrations atpH6 (Fig. 2b).For free Ph.chrysosporium 240

biomass, the maximum equilibrium uptake was foundat 2.82 241

and5.25mgg−1,respectively,forphenolconcentrationsof25and 242

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Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption on immobilized white-rot fungus Phanerochaete chrysosporium from aqueous solution, Colloids Surf. B: Biointerfaces (2012), http://dx.doi.org/10.1016/j.colsurfb.2012.09.029

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Fig.2.TheeffectofpHonphenolbiosorptionprocessby(a)Ca–alginate,(b)immobi- lizedPh.chrysosporiumbiomassand(c)freebiomassatinitialphenolconcentrations of25and50mgL−1inaqueoussuspension.Thebiomassconcentrationis0.3gL−1. Errorbarrepresentsstandarddeviation(SD);n=3.

50mgL−1(Fig.2c).DuringtheadsorptionprocesstheadjustedpH

243

valueofthesuspensionsdidnotsignificantlyvaried.

244

Similar trends were observed for two initial concentrations

245

in the case of Ca–alginate, immobilized and free biomass.

246

Withincreasinginitialconcentration,thephenoluptakecapacity

247

increasedinallcases.Inthecaseoffreebiomassandimmobilized

248

biomass,inthenaturalstateofpH5.0–6.0,theadsorptionofphenol

249

wasatthemaximumlevel.InthecaseofCa–alginateimmobilized

250

biomass,theadsorptionwasatmaximumatpH6.0.Thebioadsorp-

251

tionwasslightlyreducedinalkalineandacidicmedium.Theeffect

252

ofpHonphenolbioadsorptionwasnotsignificantinthepHrangeof

253

6.0–8.0,andtheuptakeofphenolinthatpHrangewaslargerthan

254

atotherpHvalues.ThepHofthesolutioninfluencesboththecell

255

surfacebindingsitesandchemistryinwater.Earlierstudiesfound 256

thattheadsorbedamountcorrelated withthedissociation con- 257

stantofphenolderivatives[7,15,19].Theionicfractionofphenolate 258

ionincreaseswithincreasingpHandthesurfacechargeoffungal 259

biomassispredominantlynegativeatpH3.0–10.0[7,15,19,31].It 260

wasalsoreportedthattheelectrostaticforcesbetweenthecharged 261

fungalsurfaceandphenolplayedanimportantroleinthebioad- 262

sorptionprocess. 263

Inourearlierstudy,theinfluenceofpHonphenolbioadsorp- 264

tionwasalsoinvestigatedonfreedeadPh.chrysosporiumbiomass, 265

buttheculturalmediumhadadifferentcompositionwithasimple 266

constitution.ThemaximaluptakecapacitywasobtainedatpH5.5. 267

Inthepresentstudy,theculturalmediumforfungalbiomasshasa 268

complexcomposition[32].WuandYu[25,33]foundthatthemax- 269

imumuptakecapacityfor2,4-dichlorophenolwasatpH5.0–6.0for 270

bothfreeandimmobilizedfungalbiomass. 271

3.2. BioadsorptionkineticsofphenolonCa-alginatebeads, 272 immobilizedPh.chrysosporiumbiomass,andfreebiomassfrom 273

aqueoussuspension 274

Thebiosorptiontime ofphenolonto Ca–alginatebeads(2%), 275

alginate immobilized Ph. chrysosporium biomass, and free Ph. 276 chrysosporium biomass was evaluated with a solution contain- 277

ing 50mgL−1 of phenolat pH 5.5 in natural state withoutpH 278

adjustment.Thebiosorbentconcentrationwas0.3gL1,thecon- 279

centrationofPh.chrysosporiumbiomasswas1.25%inthealginate 280

beads.Theinitialphenolconcentrationwas50mgL−1.Thechange 281

ofphenolconcentrationinthesupernatantispresentedinFig.3a. 282

In Fig.3b, theadsorbedamounts of phenol, and in Fig. 3cthe 283

adsorptionefficiency(inpercent) ispresentedagainstthesorp- 284

tion time. Fig. 3a–c demonstrate that the adsorption rate was 285

initially highin the very first minutes,and thesaturation was 286

reachedaftersixtyminutesforalltheadsorbentsstudied.Beyond 287

thattime,theamountofadsorbedphenoldidnotincreasesignif- 288

icantlywithsorptiontime.Atthebioadsorptionequilibriumwith 289

initialphenolconcentrationof50mgL−1,theadsorptioncapacity 290

was2.78mgg−1 on Ca–alginatebeads, 3.33mgg−1 onimmobi- 291

lizedbiomassand6.73mgg1onfreebiomass.Fig.3calsoshows 292

thatapproximately13.45%ofphenolequilibriumuptakecouldbe 293

reachedwithinfortyminutesonfreefungalbiomass,andthatthe 294

correspondingphenolequilibriumuptakewas6.66%and4.85%for 295

immobilizedfungalbiomassandblankCa–alginatebeads,respec- 296

tively.Thissuggeststhattheadsorptionrateofphenolontothe 297

immobilizedfungalbeadswasslowerthanthatontothefreefun- 298

galbiomassintheinitialbiosorptionperiod.Inourstudy,thelow 299

adsorptionefficiencycan beexplainedwiththelow biosorbent 300

dosage.Wuand Yu[25] reportedthatapproximately78.03% of 301

2,4-DCPequilibriumuptakecouldbeachievedwithin30minon 302

thefreefungalbiomass,andthatthecorresponding2,4-DCPequi- 303

libriumuptakewas68.04%and71.24%fortheimmobilizedfungal 304

biomassandCa–alginatebeads,respectively,inthecaseofbiomass 305

dosageof5gL−1 andinitialconcentrationof40mgL−1.Wehave 306

toconsiderthattheadsorptionincreaseswithdecreasingwater 307

solubilityofthemoleculeandwithincreasingoctanol–waterparti- 308

tioningcoefficient.Thefreebiomasshaditsbindingsitesexposedto 309

phenol,whereastheentrappedbiomasswasretainedintheinterior 310

oftheimmobilizedbeads[20,25].Thetimeof60minwasconsid- 311

eredtobesufficientforphenolbiosorptiontoreachequilibriumfor 312

alltheadsorbentsstudied. 313

3.3. Kineticmodeling 314

Thereare severalkineticmodelsregardingtheadsorptionof 315

heavy metals, dyes and chlorophenols[3,7,31,32,34]. To evalu- 316

atethebioadsorptionkineticsofphenol,twokineticmodelswere 317

(8)

Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption V.Farkasetal./ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx 5

Fig. 3. Time courses of phenol biosorption by Ca–alginate, immobilized Ph.

chrysosporiumbiomassbeadsandfreebiomassatpH5.5,T=22.5C.(a)Thephenol concentrationsarepresentedagainstthesorptiontime.(b)Theadsorbedphenol amountsarepresentedagainstthesorptiontime.(c)Theadsorptionefficiencyval- uesarepresentedagainstthesorptiontime.Theinitialphenolconcentrationis 50mgL−1andthebiomassdosageis0.3gL−1.Thebiomassconcentrationinalginate beadsis1.25%.ErrorbarrepresentsSD;n=3.

usedtofittheexperimentaldataobtainedonCa–alginatebeads,

318

Ca–alginateimmobilizedPh.chrysosporiumbiomass,andfreePh.

319

chrysosporiumbiomass.

320

3.3.1. Pseudofirstorder-Lagergrenmodel

321

Thepseudofirst-orderkineticmodel(Lagergrenmodel)isgen-

322

erallyexpressedasfollows:

323

dq

dt =k1,ad(qeq−q) (2)

324

Fig.4. (a)Linearizedpseudofirst-order kineticmodelfor phenolsorptionby Ca–alginatebeads,immobilizedbiomassinCa–alginateandfreePh.chrysosporium biomass.(b)Linearizedpseudosecond-orderkineticmodelforphenolsorptionby Ca–alginatebeads,immobilizedbiomassinCa–alginateandfreePh.chrysosporium biomass.Theinitialphenolconcentrationis50mgL−1andthebiomassdosageis 0.3gL−1.Thebiomassconcentrationinalginatebeadsis1.25%.Errorbarrepresents SD;n=3.

where k1,ad istheadsorptionrateconstant offirstorderbioad- 325

sorption(min−1),qisadsorbedamount(mgg−1),qeqisadsorption 326

capacity(mgg1)atequilibrium. 327

IntegrationandlinearizationofEq.(2)give 328

log(qeq−q)=logqeq−k1,ad t

2.303 (3) 329

Theplotsoflog(qeq−q)vs.sorptiontimeareshowninFig.4a. 330

Thelinearrelationshipswereobservedonlyfortheinitial30minof 331

sorptionandtheexperimentaldataconsiderablydeviatedfromthe 332

theoreticalonesafterthisinitialperiod.Thesorptionrateconstants 333

k1,adandthetheoreticalvaluesofqeqcalculatedfromtheslopeand 334

interceptofthelinearplotsaresummarizedinTable1,withthe 335

correspondingcorrelationcoefficients. 336

Thesorptionrateconstantk1,advariedintherangeof1.15×102 337

to 6.91×102min1. The first-order rate constants k1,ad are 338

5.13×10−2min−1forCa–alginatebeads,1.15×10−1min−1forthe 339

immobilizedbiomassand6.91×102min1forthefreebiomass. 340

Thetheoreticalvaluesofsorptioncapacityqeqarelowerthanthe 341

experimentalvalues.Thecalculatedadsorptioncapacitiesqeq,calare 342

2.20mgg1forCa–alginatebeads,1.81mgg1fortheimmobilized 343

biomassand2.69mgg1forthefreebiomass. 344

3.3.2. Pseudosecond-orderkineticmodel 345

Thepseudosecond-orderkineticrateequationcanbewritten 346

asfollows: 347

dq

dt =k2,ad(qeq−q)2 (4) 348

(9)

Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption on immobilized white-rot fungus Phanerochaete chrysosporium from aqueous solution, Colloids Surf. B: Biointerfaces (2012), http://dx.doi.org/10.1016/j.colsurfb.2012.09.029

ARTICLE IN PRESS

GModel COLSUB53561–10

6 V.Farkasetal./ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx

Table1

Thepseudofirst-andsecond-orderrateconstantsandthecalculatedequilibriumadsorptioncapacitiesonfreePh.chrysosporiumbiomass,Ca–alginateimmobilizedbiomass, andCa–alginatebeadsatpH5.5.Ca–alginateconcentration:2%,thebiomassconcentration:1.25%.T=22.5C,biomassconcentration:0.3gL−1.

Biosorbent k1,ad(min−1) qeq,cal(mgg−1) R2 k2,ad(min−1) qeq,cal(mgg−1) R2 qeq,exp(mgg−1)

Freebiomass 6.91×10−1 2.69 0.946 4.27 6.85 0.996 6.73

Alginate+biomass 1.15×10−1 1.81 0.963 1.62 3.41 0.999 3.33

Alginate 5.13×10−1 2.20 0.852 5.47×10−1 2.94 0.996 2.78

where k2,ad is the rateconstant of second order bioadsorp-

349

tion(gmg1min1),qistheadsorbedamount(mgg1),qeqisthe

350

adsorptioncapacity(mgg−1)intheequilibrium.

351

TheintegratedandlinearizedformofEq.(4)is

352

t q= 1

k2,adq2eq

+ t

qeq (5)

353

Fortheutilizationofthismodel,theexperimentalvalueofqeqis

354

notnecessarytobeestimatedapriori.Straightlineswereobtained

355

byplotting t/qagainstt for Ca–alginatebeads, for immobilized

356

biomassinCa–alginate,and freebiomass(Fig.4b).Thesecond-

357

order rate constants, k2,ad and qeq, are summarized in Table 1

358

andweredeterminedfromtheslope andinterceptof theplots

359

(Fig.4aandb).Thesorptionrateconstantk2,advariesintherange

360

of5.47×10−1to4.27gmg−1min−1.

361

The second-order rate constants, k2,ad, are

362

5.47×101gmg1min1 for Ca–alginate, 1.62gmg1min1

363

fortheimmobilizedbiomassand4.27gmg−1min−1 forthefree

364

biomass.Thelargestsecond-orderratevalue(4.27gmg1min1)

365

was obtained for the free biomass. The Ph. chrysospo-

366

rium biomass immobilized in Ca–alginate exhibits a higher

367

rate constant (1.62gmg−1min−1) than the alginate beads

368

(5.47×101gmg1min1).

369

Thetheoreticaladsorptioncapacitiesqeq,calare2.94mgg−1for

370

Ca–alginatebeads,3.41mgg−1 fortheimmobilizedbiomass,and

371

6.85mgg1forthefreebiomass.Thecalculatedadsorptioncapac-

372

ities agreed well with the experimental data. The correlation

373

coefficientsforthepseudofirst-orderkineticsmodelwerelower

374

thanforthepseudosecond-orderone.

375

Fromthecomparisonofthetwokineticmodels,wecanconclude

376

that thebiosorption process of phenol onto the surface of Ca-

377

alginate,immobilizedPh.chrysosporiumbiomass,andfreebiomass

378

followsthepseudosecond-orderkinetics.DursunandKalayci[35]

379

studiedthephenoladsorptiononchitinfromaqueoussolutionat

380

abiosorbentdosageof1gL−1(29).Theyfoundthattheadsorp-

381

tion process followed pseudo second-order kinetic model, and

382

theadsorptionrateconstantvariedintherangeof3.9×10−3to

383

4.510−3gmg−1min−1at20,30and40C.

384

3.4. BioadsorptionisothermsofphenolonCa–alginatebeads,

385

immobilizedPh.chrysosporiumbiomass,andfreebiomassfrom

386

aqueoussuspension

387

Thebiosorptionisotherms of phenolonto Ca–alginatebeads

388

(2%),immobilizedPh.chrysosporiumbiomassinCa–alginate,and

389

freePh.chrysosporiumbiomassweredeterminedbyvaryingtheir

390

initialconcentrationsintherangeof10–100mgL1 withacon-

391

stantadsorbentdosageof0.3gL−1atpH5.5innaturalstatewithout

392

pHadjustment.ThePh.chrysosporiumbiomassconcentrationwas

393

1.25%intheCa–alginatebeadsandtheCa–alginateconcentration

394

was2%.InFig.5aandbthechangeofadsorbedamountofphenol

395

onalltheadsorbentsarepresentedagainstequilibriumconcen-

396

trations.Thefreebiomasshasahigheradsorptioncapacitythan

397

theimmobilizedbiomassin Ca–alginateand theblankbiomass.

398

Theexperimental maximumadsorbed amountwas3.27mgg−1

399

forblankalginatebeads,7.81mgg1forimmobilizedbiomassin

400

Ca–alginateand13.50mgg−1 forthefree biomassattheinitial

401

phenolconcentrationof100mgL1.Theexperimentalresultsare 402

compared withother studiessuchas bioadsorbentand adsorp- 403

tioncapacityinTable2.Biosorptionof2,4-dichlorophenolbyfree 404

Ph.chrysosporiumbiomass,immobilizedbiomassinalginate(2%) 405

andalginatebeadsfromaqueoussuspensionswerestudiedbyWu 406

andYu[25].Thetheoreticalmaximumadsorptioncapacitiesdeter- 407

minedfromtheLangmuirmodelwere1.63,4.55,and7.15mgg1 408

fortheblankCa–alginate,immobilized,andfreefungalbiomass, 409

respectively. 410

3.5. Modelingtheequilibriumofbioadsorption 411

Among the zillions of two- and three-parameter isotherm 412

equations, two simple models are frequently used to describe 413

biosorptionprocesses[3].Toevaluatethebiosorptionisotherms 414

ofphenol,weusedtheFreundlich,Langmuir,andanti-Langmuir 415

[36]modelstofittheexperimentalequilibriumdatadetermined 416

onblankCa–alginatebeads,immobilizedbiomassinCa–alginate 417

beads,andfreePh.chrysosporiumbiomass.Inthisstudy,thenon- 418

linearleast-squaresestimationandthelinearizedpresentationof 419

isothermequationswereusedfortheevaluationofbioadsorption 420

equilibrium.Intheresearchfieldofbiosorption,thelinearizedpre- 421

sentationofisothermequationshasbeenfrequentlyusedforthe 422

determination ofbioadsorptionconstants despiteofits hazards 423

[3,37].Wepresentacomparisonoftheequilibriumconstantscal- 424

culatedfromthelinearizedand original,nonlinearformsofthe 425

isothermequations. 426

3.5.1. Freundlichisothermmodel 427

Thewell-knownFreundlichmodelisexpressedasfollows: 428

qeq=KFCe1/n (6) 429

whereqeqistheadsorbedamountintheequilibrium(mgg1);KF 430

istheFreundlichconstant(mgg−1);Ceequilibriumconcentration 431

ofphenol(mgL1) 432

LinearizationofEq.(6)gives 433

logqe=logKF+1

nlogCe (7) 434

Theplotsoflogqe againstlogCe areshowninFig.6a.Wehave 435

comparedtheFreundlichconstantscalculatedfromthelinearized 436

presentationof theisotherms with thenonlinear least-squares 437

estimates(Fig.5aanda,Table3)[37].ThevaluesoftheFreund- 438

lichconstant KFand theexponent n calculatedby Eqs.(6) and 439

(7), respectively, and the correspondingcorrelation coefficients 440

aresummarizedinTable3.Fromthelinearizedpresentationthe 441

Freundlichconstant,KFvariedintherangeof0.023–0.203mgg1. 442

The Freundlich constants KF are 2.03×10−1mgg−1 for free 443

biomass, 4.73×102mgg1 for the immobilized biomass, and 444

2.30×102mgg1forblankCa–alginatebeads.Theorderofmag- 445

nitude of KF was: free fungal biomass>immobilized fungi in 446

Ca–alginatebeads>blankCa–alginatebeads.Thisorderindicates 447

ahigheradsorptioncapacityofthefreeandimmobilizedfungal 448

beadsovertheblankCa–alginatebeads.Forfreebiomass,thenval- 449

uesweregreaterthanunity,indicatingafavorableadsorption.For 450

immobilizedfungalbiomassandblankCa–alginate,thenvaluesare 451

closetounity.Thevaluesofexponentnare1.16forfreebiomass, 452

(10)

Please cite this article in press as: V. Farkas, et al., Comparative study of the kinetics and equilibrium of phenol biosorption V.Farkasetal./ColloidsandSurfacesB:Biointerfacesxxx (2012) xxx–xxx 7

Fig.5.(a)Fittedphenolbioadsorptionisothermsfromnonlinearleast-squareestimationusingFreundlichequation(b)datafromnonlinearleast-squareestimationusing LangmuirequationbyCa–alginatebeads,immobilizedPh.chrysosporiumbiomassbeadsandfreebiomassatpH5.5,T=22.5C.(c)PresentationoftheFreundlichand(d) Langmuirisothermsusingcalculateddata.Theadsorbedphenolamountsarepresentedagainsttheequilibriumconcentrationofphenolafterthebiosorptionprocess.Error barrepresentsSD;n=3.

0.93fortheimmobilizedbiomassand0.91forblankCa–alginate

453

beads.

454

The estimated values of constant KF using nonlin-

455

ear least-squares fitting are 2.92×102mgg1 for free

456

biomass, 8.73×103mgg1 for the immobilized biomass, and

457

3.70×10−2mgg−1 for blank Ca–alginate beads. The estimated

458

values of exponent n are 0.75 for free biomass, 0.67 for the

459

immobilized biomassand 1.01for blankCa–alginatebeads. For

460

bothfittingmethodsthecorrelationcoefficientsareratherhigh.

461

InFig.5c,theexperimentallydeterminedandthefittedisotherms

462

–using theFreundlichconstants calculatedfromthelinearized

463

isothermequation–arepresented.Nevertheless,wecanconclude

464

thatthenonlinearleast-squaresestimationusingtheFreundlich 465

modelgivesbetterfitandmoreauthenticresults(Fig.5aandc) 466

thanthelinearization. 467

3.5.2. Langmuirandanti-Langmuirisothermmodel 468 TheLangmuirmodelisvalidformonolayeradsorptionontoa 469

surfacecontaininglimitednumberofidenticalsites[3].TheLang- 470

muirisothermmodeliswritteninthefollowingform: 471

qeq=qmax KLCe

1+KLCe (8) 472

Table2

Comparisonofbiosorptioncapacityonvariousbiosorbentsforphenolanditsderivatives.

Typeofadsorbents Pollutant Equilibrium

time

Pollutant/adsorbent concentration(gL−1)

pH Adsorptioncapacity References

Pseudomonasputida Phenol 48h 0.6/1 7.0 22%phenolremoval [38]

Caulerpascalpelliformis Phenol 6h 0.1/6 6.0 20.1 [39]

Fumaliatrogii Chloro-phenol 6h 0.5/20 8.0 289.1 [40]

Pleurotussajorcaju Chloro-phenols 4h 0.5/0.2 6.0 0.95–1.89 [41]

Activatedcarbon Phenol 10days 1 6.0 1–31 [42]

Bacillussubtilis Phenol 30min 0.015/25 7.0 0.06 [43]

Chitosan–calciumbeads Phenol,chloro-phenol 4h 0.3/1 7.0 116.31 [44]

Aspergillusniger Phenol 24h 0.001/2 5.1 0.6 [31]

Driedsewagesludge Phenol 24h 0.1/5 6.5 17.3 [45]

Phanerochaetechrysosporium Phenol 24h 0.1/0.3 6.0 13.5 Presentstudy

Ca–alginatebeads(2%) Phenol 24h 0.1/0.3 6.0 3.27 Presentstudy

ImmobilizedPhanerochaetechrysosporium Phenol 24h 0.1/0.3 6.0 7.81 Presentstudy

Phanerochaetechrysosporium 2,4-DCP 6h 0.04/5 5.0 3.22 [25]

Ca–alginatebeads(2%) 2,4-DCP 6h 0.04/5 5.0 0.93 [25]

ImmobilizedPhanerochaetechrysosporium 2,4-DCP 6h 0.04/5 5.0 2.13 [25]

Ábra

Fig. 1. Stereo microscopic view (a) of Ca–alginate bead, free biomass, and immobilized biomass
Fig. 2. The effect of pH on phenol biosorption process by (a) Ca–alginate, (b) immobi- immobi-lized Ph
Fig. 3. Time courses of phenol biosorption by Ca–alginate, immobilized Ph.
Fig. 5. (a) Fitted phenol bioadsorption isotherms from nonlinear least-square estimation using Freundlich equation (b) data from nonlinear least-square estimation using Langmuir equation by Ca–alginate beads, immobilized Ph
+2

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