(562ab) Cr(VI) Reduction By Fe(II) and Subsequent Regeneration of Fe(II) from Fe(III) By Shewanella Oneidensis MR-1

Hexavalent chromium, Cr(VI) is the predominant contaminant in the subsurface vadose zone and groundwater of Department of Energy’s waste sites such as Hanford, WA, and has detrimental impacts on the environment, ecology, as well as human health. This contaminant can be reduced to nontoxic trivalent chromium, Cr(III) by reacting with Ferrous ion, Fe(II). During that reaction, Fe(II) is oxidized to Ferric, Fe(III), which has no ability to reduce Cr(VI) and the remediation process terminates. But, metal-reducing bacteria, Shewanella oneidensis MR-1, regenerates Fe(II) from Fe(III) with the help of an organic electron donor in an appropriate bacterial media. Thus, in the Cr(VI) chemical remediation process, Fe(II)-Fe(III) conversion is reversed in biological process regenerating Fe(II) and the Cr(VI) chemical remediation process continues in a cyclic fashion. This paper presents the results from regeneration of Fe(II) from pure Fe(III) as well as from the reaction products of Cr(VI) and Fe(II). Both pure Fe(III) and reaction product Fe(III) exhibited the same reduction behavior. Fe(II) production increased with the increase of the initial concentration of Fe(III); almost 80% Fe(II)-regeneration was achieved. In the experimental system, Cr(VI) was reduced first followed by Fe(III) by Shewanella oneidensis MR-1 when both of these species are present. So, Fe(II) regeneration with metal-reducing bacteria has a good potential for application in groundwater and wastewater remediation in reducing Cr(VI) to Cr(III).