Experimental study on the remediation of cadmium-contaminated tailings using microbial-induced carbonate precipitation(MICP)

Microbial-induced calcium carbonate precipitation (MICP) represents a viable approach for the remediation of sites contaminated with heavy metals. This study explores the remediation potential of cadmium-contaminated tailings using Sporosarcina pasteurii, examining the influence of cementation frequency, bacterial concentration, cementation solution concentration, and temperature on the leaching properties of the tailings. This investigation is further augmented by an analysis of microbial community structural shifts and microanalytical techniques to elucidate the underlying mechanisms of MICP in soil remediation. Findings indicate that cadmium (Cd2+) within the tailings is effectively passivated following 12 MICP treatments. The induced calcium carbonate, characterized by an optimal crystal size at conditions of 30°C, OD600=1.5, and a cementation solution concentration of 0.5 mol/L, is uniformly dispersed within the tailings' pores. This calcium carbonate predominantly comprises structurally stable calcite, with the abundance of Bacterium octococcum spp. in the remediated tailings reaching 78.68%, thereby demonstrating significant remediation efficacy. Throughout the ongoing mineralization and precipitation process, bacteria facilitate the passivation of heavy metals via mechanisms including biosorption, bioprecipitation, calcium carbonate adsorption, lattice doping (encompassing substitution and interstitial doping), and co-precipitation.