Experimental study on solidification and remediation of lead–zinc tailings based on microbially induced calcium carbonate precipitation (MICP)

With the development of industry, the human demand for lead and zinc is increasing gradually, and the heavy metal pollution caused by the mining process of lead–zinc tailings is becoming more and more serious. To alleviate the pollution problem, microbially induced calcium carbonate precipitation (MICP) technology has been used to solidify and remedy lead–zinc tailings containing heavy metals based on the multi-shell curing method. Based on unconfined compression strength (UCS) and the parameters of heavy metal ions leaching concentration, exploring the addition of lead–zinc tailings on the impact of microbially induced calcium carbonate precipitation on solidifying and repairing lead–zinc tailings, using SEM, XRD, FTIR, EDS and XPS tests, and revealing the mechanism of MICP to solidify lead–zinc tailings. The results of the experiment showed that MICP had a good solidifying and repairing effect on heavy metals in lead–zinc tailings. When the thickness of lead–zinc tailings was 2 cm, the unconfined compression strength of the specimen was the maximum up to 0.93 MPa and the calcium carbonate content was up to 7.41 %. At the same time, Fe3+, Zn2+, Pb2+, Cu2+ and Cd2+ in the leaching solution could be completely removed, and the removal of Mn2+ and Cr3+was up to 98.24 % and 95.56 % respectively, which was the best condition for solidification. The samples of lead–zinc tailings being solidified and repaired based on MICP showed that calcium carbonate was primarily precipitated as the commonly crystal forms of aragonite, calcite, and vaterite, with strong cohesiveness, which made lead–zinc tailings particles connected together. At the same time, the CO32– and alkaline substances produced by microbial metabolism made the heavy metal ions released by the lead–zinc tailings mainly precipitate in the form of metal carbonate, which reduced the pollution to the environment. This technology provides a new method for solidifying and repairing lead–zinc tailings.