ComparisonbetweenReductiveDissolutionofJarositebySulfateReducing BacteriaandDissimilatoryIronReducingBacteria

Inthisstudymicrobialreductionofjarosite[KFe3(SO4)2(OH)6],acommonsecondarymineralinacidminedrainage( AMD)area,wasconductedwithadissimilatoryironreducingbacteriumShewanellaputrefaciens CN32andasulfatereducingbacteriumDesulfovibriovulgarisunderneutralanaerobicconditionsinnon- growthmedia.Wetchemistry,X-raydiffraction( XRD)andscanningelectronicmicroscopy(SEM)wereusedtoanalyzethereducedironconcentration,mineralcompositionandmorphologyofthesolidphases. Itwasobservedthatjarositewasfairlystableunderanaerobicconditionswithout microbes.BothfacultativeS.putrefaciens CN32andstrictanaerobicD .vulgaris werecapableofreducingthecrystallized Fe3+ injarosite.Undersimilarconditions,D .vulgarisshowedmuchhighercapabilitytoreducecrystallizedFe3+ withafinal bioreductionextentof16.80%.IncontrastS.putrefaciensCN32canonlyreduce0.37%ofFe3+injarosite.Anthraquinone-2, 6-disulfonate(AQDS)canenhanceFe3+ reductioninD .vulgarisinoculatedsystemswithafinalbioreductionextentof24.30%. NodiagnosticspectrumotherthanthoseofjarositewasobservedinchemicalcontrolandS.putrefaciensCN32inoculatedsystems. InD .vulgarisinoculatedsystems,onlyspectrumofsideriteandjarositeweredetectedwithoutthepresenceofAQDS.In thepresenceofAQDS,jarositepeakswerereplacedbypeaksofsideriteandvivianite.Theelementalanalysisbyenergydispersivespectrometer( EDS)coupledwithSEMalsoconfirmedthepresenceofsideriteinD .vulgarisinoculatedsystems.WeproposethatthehigherFe3+ reductionextentwithD .vulgarisresultedfromthepresenceofSO42- injarosite,whichcanbereducedtoH2SbyD .vulgaris.H2S,astrongreductant,subsequentlyenhancedFe3+ reductionextent.Theobservationofvivianitemightresultfromthedegradationofyeastextractionwhichproducedphosphate. Theresultsclearlydemonstratethehighpotentialofmicrobialreductionofjarositeunderneutral, anaerobicandoligotrophicconditions.Attentionshouldbepaidtothemicrobialactivitiesandthesecondarymineralizationwhenconsideringjarositeasacandidatematerialtoremoveh eavymetalsor storetheradioactivehazards.