Experimental study on remediation of cadmium-contaminated tailings using microbial-induced carbonate precipitation

The microbial-induced calcium carbonate precipitation (MICP) is recognized as a promising method for remediating the sites contaminated with heavy metals. The remediation potential of cadmium (Cd)-contaminated tailings using Sporosarcina pasteurii is investigated, assessing the effects of cementation frequency, bacterial concentration, cementation solution concentration and temperature on the leaching properties of tailings. The analyses of microbial community structure shifts and microanalytical techniques are integrated to elucidate the MICP mechanisms in soil remediation. The results demonstrate effective cadmium (Cd²⁺) passivation after 12 MICP treatments. The optimal conditions for calcium carbonate formation include 30 ℃ temperature, OD₆₀₀=1.5 bacterial concentration, and a cementation solution concentration of 0.5 mol/L, ensuring uniform dispersion within pores of tailings. The predominant calcium carbonate form is structurally stable calcite, with Bacterium octococcum spp. comprising 78.68% of the remediated tailings, confirming successful solidification and remediation. The MICP achieves heavy metal passivation through the mechanisms such as biosorption, bioprecipitation, calcium carbonate adsorption, lattice doping (including substitution and interstitial doping) and co-precipitation. The results are of great significance for the optimization of the MICP technology and its application in the remediation of heavy metal-contaminated soils.