Risk assessment of antimony-arsenic contaminated soil remediated using zero-valent iron at different pH values combined with freeze-thaw cycles

Abstract

Soil in mining wastelands is seriously polluted with heavy metals. Zero-valent iron (ZVI) is widely used for remediation of heavy metal-polluted soil because of its excellent adsorption properties; however, the remediation process is affected by complex environmental conditions, such as acid rain and freeze-thaw cycles. In this study, the effects of different pH values and freeze-thaw cycles on remediation of antimony (Sb)- and arsenic (As)-contaminated soil by ZVI were investigated in laboratory simulation experiments. The stability and human health risk of the remediated soil were evaluated. The results showed that different pH values coupled with freeze-thaw cycles could promote stabilization remediation of Sb- and As-contaminated soil by ZVI. Among them, ZVI significantly reduced the leaching toxicity and bioavailability of Sb and As in soil (both about 60.00%) after 32 rounds of freeze-thaw cycle treatment under water sample conditions of pH=1 (F1). However, Compared with soil not treated with freeze-thaw cycles, freeze-thaw cycles increased the leaching concentration of unstable forms of As. Bioavailability calculations based on Sb and As in remediated soil that alkaline soil there were no health or carcinogenic risks for children and adults, but the health risks and carcinogenic risks of Sb in acidic soil remained high for children. These findings provide a theoretical basis for the remediation of Sb- and As-contaminated soil using ZVI, and also highlight the importance of considering pH and freeze-thaw conditions in the remediation process to ensure effective and safe treatment.