2水业专家网.docx
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2水业专家网.docx
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2水业专家网
TheUseofSomeFoodIndustrialbyProductsforAdsorptiveRemovalofHeavyMetalsFromWasteWater
MohamedbinSalehAlamriandSaadMohamedEl-Said
Buraydah,BuraydahCollegeofFoodandEnvironmentTechnology,SaudiArabia
Dr.amira_ahmed@andahmd_sad@
Tel.No.00966545762999,00966503098331
P.O.266Buraydah,BuraydahCollegeofFoodandEnvironmentTechnology,SaudiArabia
Keywords,Adsorption-batchtechnique-heavymetals-okrawaste-kineticstudies
ABSTRACT
Mostavailabletechnologiesappliedintheremovalofmetalcontaminantsinaqueoussystemsusethewellestablishedprocessesofadsorption.Adsorbentscurrentlyinuseareeithertooexpensiveornotreadilyavailableforwastewatertreatment.Thereisaneedtodevelopnewadsorbentswhicharereadilyavailableatlowcosttoremovemetalcontaminantsinaqueoussystem.Inthiswork,Okrawastesasafoodcanningprocessesbyproductswereusedasapotentialadsorptionofcadmium(II)iron(II)andzinc(II)removalfromvariousaqueoussolutions.QualitativeandQuantitativeanalysisofokrawasteswereinvestigated.Infraredspectraoftheokrawastewasrecordedtodetectthefunctiongroupthatgainedthecapabilitiesofokrawastesformetalionadsorption.Batchstudieswereperformedtoevaluatetheadsorptionprocess,anditwasfoundthattheokrawastewasfoundtoadsorb96.4%ofCadmium(II)93.8%ofiron(II)and79.8%zinc(II),Therateofadsorptionfollowspseudo-second-orderkineticsbeforeattainingequilibrium.ThedesorptionstudiessuggestedthatthedesorptionofCadmium(II)iron(II)andzinc(II)wasthemostdifficultandthedesorptionwaszero.Thisworkprovedthatokrawastescanbeusedasanefficientadsorbentmaterialforremovalofheavymetalsfromwaterandwastewater
1.INTRODUCTION
Thepollutionofwaterresourcesduetothedisposalofheavymetalshasconcernforthelastfewdecades.Itiswellknownthatsomemetalshavebeenresponsibleforseveralhealthproblemswithanimals,plants,andhumanbeings.Cadmium(II)iron(II)andzinc(II)areintroducedintobodiesofwaterfromsmelting,phosphatefertilizer,mining,pigments,stabilizers,alloyindustriesandsewagesludge.ToxicologicalstudieshaveshownpoisoningeffectsthatinLong-termfromCadmium(II)ironandzincIncludeskidneydamageandchangestotheconstitutionofthebone,liver,andblood.Short-termeffectsincludeanumberofacuteandchronicdisorders,suchasrenaldamage,emphysema,hypertension,andtesticularatrophy[5].Chemicalprecipitation,reverseosmosis,electrodialysis,ionexchangeandadsorptionhavebeendevelopedovertheyearstoremovetheseheavymetalsfromwastewater[6].However,thehighpriceoftheadsorbentsisthedisadvantageforadsorptiontreatmentmethod.So,itisnecessarytofindsomeadsorbentswithlowcostandhighefficiencyfortheremovalofhazardoussubstancesfromwastewater.Inrecentyears,Agriculturalby-productshavebeenusedasadsorbentsfortheadsorptionofhazardoussubstancesfromwastewater.Muchworkontheadsorptioncapacitanceofsomeagriculturalby-productssuchas,maizecob,ApricotStones,datestone,,ricebran,andbagasspithhasalsobeencarriedout[7-12].Thisstudymaygenerateusefulinformationfortheutilizationofnativeagriculturalby-productsfortheremovalofcadmium(II)iron(II)andzinc(II)fromwastewater.Okrawastes,asagriculturalbyproductsfromfoodcanningindustries,couldbeheavymetaladsorbentswhichcouldbeselectiveforsomemetalions.Thecapabilitiesofokrawastesformetalionadsorptionweretestedatseveralexperimentalconditions.TheeffectofpH,metalconcentration,adsorbentdose,particlesizeandtemperatureontherateofremovalofcadmium(II)iron(II)andzinc(II)wasinvestigated.
2.MATERIALSANDEXPERIMENTALWORK
2.1.Adsorbent:
Therawmaterialusedinthisworkasanadsorbentwasthefoodindustrialwastes(okrawastes).Thiswasteisobtainedfromfoodcanningprocesses.Okrawastesputinanelectricaloventoatemperatureof60oCfor24hours.Driedokrawasteswasbrokentopowderforminanelectricalmixer.Itwasthensievedintoparticlesizes0.5–4mm.Theinfrared(I.R.)absorptionspectrumapparatuswasusedtoinvestigatethechemicalstructureofokrawastes.
2.1.1Infraredspectraoftheokrawaste
Infraredspectra(IR)ofokrawastewasobtainedusingaPerkin-Elmer621spectrophotometer.Theinfraredspectrumofthesolidsubstancehasbeenrecordedonintheregion400–4000cm-1usingKBrandnujolmulltechniques.Theobservedfrequencieshavebeenassignedintermsofthefundamentals,overtonesandcombinationsassumingD2hpoint-groupsymmetry.
2.1.2Chemicalanalysis
Thechemicalanalysisofokrawastewasmeasuredtodetectitsmaincontentsusinghigh-performanceliquidchromatography(HPLC).AShimadzuLC-6Ahigh-performanceliquidchromatographyequippedwithaRheodyneModel7125injectorandaHitachiModelF-1050fluorescencespectrophotometerwasused.Also,QualitativeandQuantitativecarbohydrateanalysisofokrawastewasmeasuredusing(HPLC).
2.2.Adsorptionprocess
Thesorptionofcadmium(II)iron(II)andzinc(II)ionshasbeenstudiedbybatchexperiments.SolutionsofCd2+ions(20mg/L),Fe2+ions(20mg/L)andZn2+(20mg/L)werepreparedfrom1g/Lstocksolutionofeachsaltusingdistilledwater,respectively.Whenthesolutionvolumeforbothcationswasfixedat100mL,theadsorptionpercentageofCd(II),Fe(II)andZn(II)ionsasafunctionofshakingtimewasinvestigatedatashakingspeedof(220±5)min−1.Afterthefiltration,theconcentrationsofCd2+,Fe2+andZn2+ionsinfiltratewaterweredeterminedbyhigh-performanceliquidchromatography-hydridegenerationatomicabsorptionspectrophotometry(HPLC-HGAAS).Theadsorptionpercentageisdeterminedas
η=100xC0-Ce/C0………………………………
(1)
whereηistheadsorptionpercentageofcationsC0andCearetheinitialandtheequilibriumconcentrationsofcations,respectively,mol/l.Theaverageofadsorptionpercentageisadoptedeverywhereinthisworkafterthreemeasurements.
2-3Desorptionstudy
Desorptionexperimentsoftheinvestigatedmetalswascarriedoutonloadedokrawasteadsorbentresultingfromtheequilibriumsorptionexperiments.Desorptionprocesswasstudiedtakingintoconsiderationtheeffectofunabsorbedsolutionremainingincorporatedwithinthenaturalmaterialsample.Thissolutioncan’tbecompletelywithdrawn,where1mlofclearsupernatantwasleftinthebottletogetherwithsolidphase9mlofdesorbedsolutionwasaddedandtheclosedpolyethylenebottleswhereshakenforthedescriedtime.Thebottlewascentrifugedfor15min.anddesorptionwasevaluatedusingthefollowingformula:
D%={(Ca–XCe)/(Co-Ce)}100………………………..
(2)
whereCa:
theactivityofdesoprtionsolutionX:
isthevolumefractionleftinitiallywithnaturalmaterialsample.
3.RESULTSANDDISCUSSIONS
3.1.Infraredanalysis
TheamountofinformationthatcanbeobtainedfromtheIRspectrumofokrawasteisratherlimited.Thespectra(Figure1)arereportedprincipallyforanyfutureidentification,sincetheabsorptionbandsforsuchcomplexcompoundsareusuallybroadanddiffuse[1].Figure1wasshowedthechemicalgroupscorrespondingthewavenumberofbondscm-1Apartfromtheusualbandsforhydroxyl(3500cm-I)andestercarbonyl(l730cm-l)groups,Nitrogenofprotein(1550cm-I),amidedeformation(1630cm-I)andethergroup(1220cm-I)canbedistinguished.TheOkrawasteswashasahigh.percentageof[O..H],[C=O..],[N..],[C-..O..-C]and[C=C].Lonepairofelectrons(..)thatexistatoxygenandnitrogenatomrepresentahighnegativecharge.Hence,Okrawastesbecomehighlynegativelychargedandcapabletoabsorbthepositivelychargedmetalsofcadmium(II)iron(II)andzinc(II)
3.2.Chemicalanalysis
Theresultsofthechemicalanalysisofokrawasteareusefulingivingahintofrelativeproportionsofthedifferentcomponents.Thecontentsofcellulose,proteinandmineralsaregiveninTable1fortheokrawaste.So,themainconstituentofokrawasteareα-celluloseandprotein.Thiscouldindicateahighadsorptioncapacityofokrawastewhichreferredtothe–veNandOofα-celluloseandproteinthatabsorb+vemetal(figure2).Qualitativeandquantitativecarbohydrateanalysisofokrawastesolutionswerealsoanalyzedforrhamnose,galactoseandglucose,andtheseresultsaresummarizedinTable
3.4.Adsorptionprocess
Theadsorptionofinvestigatedmetalsbyokrawastecouldbeattributedtothecellulose,protein,ligninandsugarscomponentoftheokrawastewheresite-bindingadsorptionmightbeoccurring.Thiscouldbeduetothesurfacecomplexationphenomenonoffunctionalgroupspresentintheokrawastes(figure1).TheremovalofCd(II),Fe(II)andZn(II)ions,thereforeisprobablyduetothemixedeffectofionexchangeandsurfacecomplexationonthesurfaceofokrawastes.TheeffectsofshakingtimeontheadsorptionCd2+,Fe2+andZn2+ionsareshowninFig.3,whichindicatesthattheremovalofcationbyokrawasteisimprovedwithincreasingshakingtime.Theadsorptionreachesequilibriumatabout90minutesonokrawasteandthemaximumadsorptionpercentageis96.4%,93.8%and79.8%forCd(II),Fe(II)andZn(II)respectively(Fig.3).Thesepreliminaryexperimentsforadsorptionofmetalionsontheokrawasteshowedahighrelativelyionexchangecapacity.Thisisduetothefactthatokrawastewashaveahighsugar,cellulose,ligninandproteincontents,(containinghigherpercentageofN,PandO).Hence,Okrawastesbecomehighlynegativelychargedtoabsorbthepositivelychargedmetals
3.5.Adsorptionkinetics
AccordingtoFig.3,theadsorpt
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