Remediation of the lead–zinc composite-contaminated soil using stabilization reagent in an industrial region of Nanjing, China

Heavy metal pollution in soils has posed severe environmental threats to humans through various pathways due to their persistent and toxic nature. In the present study, a new cost-effective type of soil heavy metal solidification and stabilization reagent was synthesized and ratio-optimized, and applied in the remediation of the lead–zinc composite-contaminated soil, collected from the industrial region of Nanjing, China. The solidification/stabilization mechanism as well as the optimized conditions for the remediation of Pb and Zn from soil were also explored. In results, the stability analysis of single metal solidification after the solidifying reaction showed that the addition of a solidification stabilizer can greatly enhance the Pb/Zn precipitation efficiency. In the XRD analysis of the precipitation after a series of adsorption, precipitation, and co-precipitation processes, the precipitation contained an array of substances of quite low solubility and high stability. The orthogonal test analysis indicated that the optimal amount of the clay mineral material, industrial waste, and phosphate-based material was 3.2, 0.8, and 0.6 g, respectively, in the solution of 100 mL Pb and Zn ions, and the most suitable pH condition was alkaline.