Synergistic solidification of lead-contaminated soil by magnesium oxide and microorganisms

Although microbially induced carbonate precipitation (MICP) technology effectively promotes the remediation of heavy metal contaminated soils in low concentrations, the high concentration of heavy metals has a toxic effect on microorganisms, which leads to the decline of carbonate yield and makes the soil strength and environmental safety after remediation no up to the standard. This study describes the synergistic curing effect of MgO and microorganisms on soil contaminated with high concentrations of heavy metals. The experimental results with MgO showed 2-6 times increase in unconfined compressive strength (UCS) compared to bio-cemented samples without MgO. Toxicity characteristic leaching procedure experiments indicated that Pb-contaminated soil at 10,000 mg/kg with quantitative MgO for synergistic solidification could meet the international solid waste disposal standards, which leachable Pb²⁺ are less than 5 mg/L. In addition, the microscopic results showed that the introduction of MgO promoted the formation of magnesium calcite and dolomite, improved the solidification efficiency of heavy metal contaminants, and demonstrated the presence of Pb²⁺ in carbonate minerals. This study suggests that MgO and microorganisms have broad application prospects for synergistic solidification of Pb²⁺ soil.