TNTindustrywastewatertreatmentusingcombinedzeroval

JournalofHazardousMaterials168(2009)1065–1069ContentslistsavailableatScienceDirectJournalofHazardousMaterialsjournalhomepage:∗,FlávioT.Silvab,TeresaC.B.PaivabaFederalTechnologicalUniversityofParaná–UTFPR,ViadoConhecimentos/n,km01BairroFraron,CEP85501-970,PatoBrancoPR,BrazilbLorenaEngineeringSchool–EEL/USP,EstradaMunicipaldoCampinho,s/n,CEP12602-810,LorenaSP,BrazilarticleinfoArticlehistory:Received6September2008Receivedinrevisedform26February2009Accepted26February2009Availableonline21March2009Keywords:TNTindustrywastewaterZero-valentironFentonprocessabstractThisworkexplorestheoptimizationofcombinedzero-valentironandfentonprocessesforthetreatmentofTNTindustrywastewater,aresiduewithrecognizedpollutingpotentialduetoitshighconcentrationof2,4,6-trinitrotolueneandextremelyacidicpHdueofthenatureoftheproductpurificationprocess.TheresultsoftheoptimizationstudyindicatethatthemostefficientconditionforreducingtheconcentrationofTNTalsogeneratessufficientamountsofiron(II)forthesubsequentoxidativetreatmentthroughtheFentonreaction.Ingeneral,itwasobservedthatthetreatmentwashighlyefficientintermsofmeetingthemainassociatedenvironmentalparameters,sinceitreducedacutetoxicity,removed100%ofTNT,100%oftheorganicnitrogenand95.4%oftheCOD.©2009ElsevierB.V.Allrightsreserved.1.IntroductionWithaglobalproductionestimatedat108tons/year,nitroaro-maticcompoundsareusedintensivelyinseveraldifferentindustrialsegments,includingforproductionofinks,plastics,pharmaceuticalandveterinarianproducts,dyes,polyurethanefoams,herbicides,insecticidesandexplosives[1].Thesecompoundsaregenerallyrecalcitranttobiologicaltreatmentandconstituteasourceofpollu-tionduetoboththeirtoxicandtheirmutageniceffectsonhumans,fish,algaeandmicroorganisms[2–5].Themainsourceofnitro-compoundcontaminationisassociatedwithindustrialprocesses,storageoperationsanduseinmilitaryinstallations[1,2].Thedis-chargeofresiduesgeneratedduringexplosivemanufacturingandprocessingaswellastheassociatedlevelofcontaminationvarieswidely,dependingontheintensityofthemanufacturingoperationsandtheeffectivenessofthetechnologiesusedtotreattheresidues[6].Withinthiscontext,conventionalbiologicalwastewatertreat-mentprocesses(e.g.,activatedsludge)arenoteffectiveintreatingtheresiduesbecausetheelectron-withdrawingnitroconstituentsintheseexplosivesinhibittheelectrophilicattackthroughenzymes[7].Chemicaloxidationmethods(e.g.,advancedoxidationpro-cesses)arealsonotconsideredeffectivebecausethenitrofunctionalgroupsinhibitoxidation[8].Currently,oneofthemorecommonlyusedmethodsisincineration.Althoughefficient,itsapplicabilityisquestionedduetotheemissionofgaseouspollutants[7].Recent∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](M.Barreto-Rodrigues).studieshaveshownthatTNTcouldbebiologicallytransformedintotriaminotoluene(TAT)throughintermediates(e.g.,aminon-itrotoluenesandhydroxyaminotoluenes)usingpureandmixedculturesunderanaerobicconditions[9,10].Inthesesstudies,itwasfoundthatTATwasunstableandcouldbetransformedintophenolicproducts,dependingonthepH.Thesecompoundswerefurtherdegradedabioticallyintoformaldehyde,methanol,nitrousoxideandwater[11].Additionally,someresearchershaveconsid-eredthatreductiveprocessesmediatedbyironwoolcanfacilitatetheconventionaltreatmentsofnitroaromaticcompoundsduetotheirtransformationintocompositesofalargerbiodegradability[12–15].ArNO2+3Fe0+H+→ArNH2+3Fe2++2H2O(1)Fe2++H2O2→Fe3++OH−+OH•(2)Thisworkpresentsthestudyandoptimizationofcombinedzero-valentiron(ironwool)phenolicproductsandFentonpro-cessesforthetreatmentofTNTindustrywastewater,whichisaresiduecalledyellowwaterwithrecognizedpollutingpotentialduetoitshigh2,4,6-trinitrotolueneconcentrationandextremelyacidicpHresultingfromthenatureofitsmanufacturingprocess.Thecentralideaofthisworkwastousethephysical–chemicalcharacteristicsoftheeffluenttoenhancethetreatmenteffi-ciency.Inotherwords,inadditiontopromotingareductionofthe2,4,6-trinitrotolueneinchemicalspecieswithanincreasedsusceptibilitytooxidativedegradationasaminoaromaticcom-pounds,theacidleachingprocesspromotedbytheeffluentcanalsogeneratesufficientamountsofiron(II)inanacidsolution,therebysatisfyingthenecessaryconditionsforcomplement-0304-3894/$–seefrontmatter©2009ElsevierB.V.Allrightsreserved.doi:10.1016/j.jhazmat.2009.02.1721066M.Barreto-Rodriguesetal./JournalofHazardousMaterials168(2009)1065–1069ingthistreatmentthroughtheFentonreaction(Eqs.(1)and(2)).2.Materialandmethods2.1.ChemicalsandsuppliesAllchemicalswereofanalyticalgradeorhigherandwerepur-chasedfromMerckorSigmareagent.ThesamplesofwastewaterwerecollectedatIMBEL,BelicsMaterialsIndustry,locatedinSãoPauloState,Brazil.ThewastewateroriginatingfrompreliminarilywashingsinvolvedintheTNTpurificationprocess.ThiseffluentisalsocalledyellowwaterandhasapH1.0,CODof638mgL−1and156mgL−1of2,4,6-trinotroluene[2].2.2.IronwoolForcharacterizationeffects,theX-rayfluorescenceofthei