Montmorillonite-coupled microbially induced carbonate precipitation (MICP) enhanced contaminant removal and carbon capture in cyanide tailings

Microbial induced carbonate precipitation (MICP) technology is an effective method for immobilization of heavy metals in tailings. However, how to sustainably improve the removal of contaminants and the carbon capture capacity of tailings is a current concern. In this study, montmorillonite-coupled MICP (Mt-MICP) process is proposed to solidify cyanide tailings by improving mineralization properties, heavy metal and cyanide removal, and carbon capture. The results showed that Mt -MICP increased the amount of mineralized precipitation by 0.16–1.33 times; Total cyanide (T-CN) and free cyanide (F-CN) concentrations were reduced by 82.00 and 97.14 %, respectively; Cr, Zn, Cu and Pb leaching concentrations were reduced by 87.18, 42.85, 60.56 and 88.79 %, respectively. Characterizations results such as X-computed tomography (X-CT) confirmed that Mt enhanced the uniformity of the bio-cementation. Furthermore, the Mt-MICP process increased CO2 capture from tailings by 27.15∼34.55 %. Density Functional Theory (DFT) and thermogravimetry (TG) showed that Mt increased the adsorption energy of tailings for CO2 and was converted to CaCO3 by urea catalysis. This work provided new insights into the harmless treatment of CT and microbial carbon capture. [Display omitted] •Mt as a bacterial carrier enhanced MICP mineralization.•Mt-MICP improved the immobilization of heavy metals and degradation of cyanide.•Mt-MICP enhanced bio-mineralization through CO2 capture.•Mt-MICP enhanced tailings curing and uniformity.