Bioremediation of CR(VI) from Contaminated Chromite Mine Overburden Soil and its Management

Abstract

Extensive mining of chromite ores from Sukinda area of Orissa has resulted in pollution due to natural oxidation of chromite from the stockpiled overburden dumps affecting the nearby areas with the toxic Cr(VI) species. Amongst the various physico-chemical treatment approaches, native microorganisms which are already adapted to toxic metal stress conditions can play a significant role in bio-remediation of Cr(VI) from contaminated mine soil. An attempt was made for the bioreduction of Cr(VI) 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 mV') reduced more than 98% of Cr(VI) from the soil sample in 16 h at 60% pulp density(PD). The fitting of time course reduction data to the exponential rate equation yielded rate constants in the range 4.923x10-1 h-1 - 2.141 x10-1 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.