EVALUATING MICROBIALLY MEDIATED IMMOBILIZATION OF VANADIUM IN A SHALE ORE
We investigated V biogeochemistry in batch and column incubation studies in order to track the mobility of V associated with a shale ore in the presence of Shewanella putrefaciens CN-32, a dissimilatory metal-reducing bacteria. This ore was obtained from a vanadium mine in Nevada. Vanadate salts were used for comparison in each study.
In batch treatments, soluble sodium vanadate and V-ore treatments were incubated under anaerobic conditions for ~30 days. Na-vanadate treatments with bacteria showed a blue colour change within 24 hours, while controls without bacteria remained colourless. This was indicative of bacterial mediated V reduction. The ore masked colour changes that could be associated with reduction. However, soluble V decreased in the presence of bacteria, but increased in solution without bacteria. Transmission electron microscope images coupled with energy dispersive spectra also indicated that V was sorbed to the bacteria.
For column studies, glass columns were either packed with coarse sand and relatively insoluble calcium vanadate, which gave columns a yellow hue, or were packed with the V ore. S. putrefaciens CN-32 in suspension was introduced to the columns. Ca-vanadate columns with bacteria showed a colour change to greenish-blue after several hours, indicating V reduction. Controls without bacteria retained their yellow hue and had a higher V mobilization than treatments with bacteria. Results are pending for column treatments with V-ore. The outcome of these studies can be used to help predict V mobility through soil, sediment and ore tailings.