Inhibition of cadmium releasing from sulfide tailings into the environment by carbonate-mineralized bacteria

Abstract

Microbially induced carbonate precipitation (MICP) could be a potential green solution to resolve the issue of heavy metal releasing from the sulfide tailings. However, detailed mechanism of heavy metal-biomineralization in sulfide tailings and impact of procedure parameters on in-situ applications remain unexplored. We systematically investigated the biomineralization process in the column tests for a better understanding of the mechanism and effects on the inhibition of cadmium (Cd) releasing from sulfide tailings. Results revealed that uniform and efficient mineralization in the tailings column occurred under bacterial concentration of 1 × 108 cfu mL−1, bacterial retention time of 3 h, concentration of mineralization solution of 0.25 mol L−1, and flow rate of 1.5 mL min−1. The leachable Cd concentration decreased 80.7% after 7 mineralization cycles. From a suit of characterizations, bacteria can adhere on the tailings and acted as the nucleation sites to induce the mineralization of Ca and Cd (to (Ca0.67, Cd0.33)CO3 and calcite phase); eventually, tailings particles were coated with the growth of mineralized carbonates, resulting in a reduction of exposure for tailings (especially sulfur). And thus, Cd release was inhibited. Results from this study will provide a fundamental basis for future in-situ applications of MICP to mitigate heavy metal pollutions.