Abstract: In recent years, the remediation of heavy metal contaminated soil has become a hot topic, due to the rapid development of industry and technology. In this study, MICP technology combined with adsorption materials was used to repair the zinc-lead composite heavy metal contaminated soil. Through unconfined compressive strength test and toxicity leaching test, the solidification effect of contaminated soil and the stabilization effect of heavy metals before and after treatment were evaluated. Combined with scanning electron microscope (SEM) and X ray diffraction (XRD) detection methods, the repairing mechanism of zinc-lead heavy metal contaminated soil treated by MICP technology was revealed. The results showed that the solidification/stabilization of Zn-Pb heavy metal contaminated soil by MICP technology effectively reduced the leaching of harmful heavy metals from contaminated soil. When the mineralization time was 10 d, the unconfined compressive strength of the sample was 942.5 kPa. The leaching concentration of lead was 4.20 mg/L, which was 44.81% lower than that of the untreated sample. The leaching concentration of zinc was 4.31 mg/L, which was 46.19% lower than that without treatment. On this basis, by adding 10% porous silicon adsorption material, the unconfined compressive strength of the sample could reach 1 021 kPa, and the strength was increased by 8.3%. The leaching concentration of lead was 2.45 mg/L, which was 67.81% lower than that without treatment. Compared with the MICP method alone, the leaching concentration of lead was reduced by 41.67%. The leaching concentration of zinc was only 2.93 mg/L, which decreased by 63.4% compared with that without treatment. Compared with the MICP method alone, the leaching concentration of zinc was reduced by 31.9%. The addition of porous silicon adsorption material significantly improved the remediation effect of MICP technology on zinc-lead composite heavy metal contaminated soil. Due to the immobilization and adsorption of heavy metal ions by porous silicon adsorption material, the leaching concentration of heavy metals in contaminated soil decreased. At the same time, the adsorption material can also be used as the host site for calcium carbonate crystal deposition to accelerate the mineralization reaction. This study provides a new technology for the treatment of heavy metal contaminated soil and reveals its remediation mechanism, which provides a theoretical and experimental basis for the application of MICP technology combined with porous silicon adsorption materials to remediate Zn-Pb composite heavy metal contaminated soil.

Key words: microbially induced calcite precipitation (MICP), zinc-lead composite contaminated soil, porous silicon adsorption materials, solidification/stabilization, remediation mechanisms