Abstract: Alkaline industrial wastes have been widely used for soil heavy metal remediation. They can be combined, processed and modified to stabilize heavy metals in the soil, thereby reducing the toxicity of heavy metals. In this study, we investigated the stabilization effect of blast furnace slag (FG) and iron tailing sand (T) on heavy metal-contaminated soil, and combined SEM-EDS and XRD to reveal the passivation mechanism of heavy metals in soil. The products WFG and HFG were obtained after washing and high-temperature calcination of blast furnace slag materials, while the product HT was obtained after high-temperature calcination of iron tailing sand. The results showed that the application of stabilizing materials significantly increased soil pH, and did not affect EC value. Soil pH declined after soil was stabilized for 40 d. The contents of Cd, Pb and Zn in DTPA extracted soil decreased after 40 d of treatment with stabilizing materials, and the HFG-10% treatment had the best effect on Cd and Zn, with stabilizing rates of 66.04% and 92.21%, respectively. HT-10% had the best stabilizing effect on Pb, with a stabilizing rate of 69.67%. The application of stabilization materials first increased and then decreased the content of heavy metals in the soil in the residual and reducible states over time. The assessment of ecological risk index showed that the risk index of Cd, Pb and Zn in the soil decreased by one level after application of 10% blast furnace slag materials (FG, WFG and HFG). Overall, the HFG-10% treatment had the best stabilization effect on Cd, Pb and Zn in soil, and the heavy metal passivation mechanisms mainly included surface adsorption and complexation reactions.

Key words: blast-furnace slag, iron tailing, soil heavy metal, stabilization, mechanism