VANADIUM(V) REDUCTION IN THIOBACILLUS THIOOXIDANS CULTURES ON ELEMENTAL SULFUR

We describe the reduction of vanadium (V) to vanadium (IV) in cultures of Thiobacillus thiooxidans on elemental sulfur, for initial vanadium (V) concentrations up to 5 mM. The vanadium (V) is reduced by interme diate compounds generated by bacterial oxidation of elemental sulfur. The limit of initial vanadium (V) allowing bacterial action seems to b e related to the inhibition caused by such vanadium species, rather th an connected to the vanadium (IV) species, which did not show inhibito ry effects up to concentrations of about 0.1 M. This reduction mechani sm of vanadium (V) is potentially applicable in the recovery of vanadi um from spent solid catalysts, by a low-cost methodology.