Bacterial Reduction of Hexavalent Chromium from Contaminated Overburden Soil

This study was focused for the bioreduction of Cr(VI) from chromite mine overburden soil using a highly tolerant Bacillus sp. isolated from chromite mine soil. Under the optimized conditions of pH ~7.0, Bacillus sp. (4.05 x 107 cell mL-1) reduced more than 98% of Cr(VI) from the soil sample in 16 h at 60% pulp density(PD). The exponential rate equation yielded rate constants in the range 4.923×10-1 h-1 – 2.141×10-1 h-1 for 20% and 60% PD respectively, which decreased with increase in Cr(VI) concentration. The bio-reduction was also carried out in absence of media at the higher pulp density (60%) as used in the chromite ore beneficiation plant. After bio-reduction the samples were characterized using FT-IR for the leaching of other valuable metals using bio-organic acids.