The Study Of The Concentration Of Fe/Sb And The Speciation Of Antimony During The Dissimilatory Iron Microbial Reduction

The abundance of iron is considerable in natural environment and iron oxide iswidely distributed in anaerobic condition such as soil, sediments, and groundwater, soiron dissimilation reduction reaction can occur in these environments. There are manydifferent kinds and specitions of heavy metal pollutants existing in these environments,the proess of iron oxide dissimilation reduction can influence the existing speciation ofthese m etals. The difference in the existing s peciation of t he m etals can affect i tsstability a nd toxicity in the se environments directly. And t his w ill le ad the me talsabsorbed on t he surface of iron oxide enter into the environments and it will causepotential pollution to these environments. Sb(III) and Sb(V) are the most usual existingspeciation of antimony in environment. Biogeochemical conditions have great impacton the existing speciation of antimony. And there are large numbers of complex organicmaterials and different kinds of microbes can also influence the existing speciation anddistribution of antimony in the environment greatly.In this experiment, four kinds of materials were used as the study object, the ironoxide coated sand(IOCS)that adsorbed antimony, AQS(anthraquinone-2-sulfonic acidsodium s alt, C14H7NaO5S H2O)which c ontains redox s ensitive f unctional groupstructure, the organic complex EDTA(ethylene diamine tetraacetic acid, C10H16N2O8)and Shewanella m icrobes(Shewanella decolorationis S12). A "microbes-ironoxide-antimony" interaction system was constructed to study the effluence of organicmatters AQS and EDTA on the concentration of Fe/Sb and the changes of Sb speciationin biotic/abiotic and different inoculum density conditions. The study results showedthat t he a ddition of organic matters AQS or EDTA all can accelerate t hedissociation/desorption process of Fe/Sb in the reaction system, the dissociation/desorption rate of Fe/Sb in those systems that contain EDTA or AQS gotequilibrium in300h, in raw system (no organic matter) the rate was less than half of theformer after300h incubation time. The i ncrease of inoculation qu antity of m icrobeplayed different r ole i n di fferent r eaction s ystem, unde r hi gher inoculation qua ntitycondition, the dissociation/desorption rate of Fe/Sb was nearly2times as the lowercondition in raw system. But microbial effect was not obvious in the system that onlyAQS was added and the desorption rate of these systems were even less than its lowinoculation qua ntity system. In t hese systems that c ontained EDTA t hedissociation/desorption rate of Fe/Sb improved significantly, the dissociation/desorptionrate of Fe/Sb of the two systems in higher inoculation quantity conditions were2.089times,1.859t imes a nd1.911t imes,1.861t imes as the lower inoculation qua ntitysystem r espectively after72h i ncubation t ime. In these s ystems that onl y AQS wasadded microbial ir on dissimilation reduction reaction can couple the changes o fantimony speciation, in this process part of the Sb(V) were reduced to Sb(III). In abioticsystems, the a ddition of A QS a nd E DTA ha d weak effluence on thedissociation/desorption rate of Fe/Sb, the desorption rate was far below than that in themicrobial s ystem, these s ystems did not get equilibrium even after840h, i n abioticcondition the desorption rate of the systems contained EDTA were higher than othersystems, but in abiotic systems no changes of Sb speciation were observed, so we canget the conclusion that t he pr ocess of m icrobial i ron di ssimilation r eduction couldaccelerate Sb speciation changes.