Abstract: Heavy metal contamination is a growing problem with increasing industrial and urbanization processes. This has created a requirement for field-applicable and effective stabilization/solidification (S/S) methods. Therefore, the long-term leaching behavior and leaching mechanism of zinc from activated magnesium oxide (MgO) carbonation-cured contaminated soils in strong (pH = 3), weak (pH = 5), and neutral (pH = 7) environments were investigated. The semi-dynamic leaching test method was used to evaluate the effect of S/S treatment under different pollution concentrations, active MgO dosages, and carbonation times by effective diffusion coefficient (De) and leachability index (Lx). The results showed that the dissolution of Zn ions in the strongly acidic (pH = 3) environment was significantly greater than that in the weakly acidic (pH = 5) and neutral (pH = 7) environments, both of which were 4−5 orders of magnitude lower than that in the untreated contaminated soil samples. The De of the carbonation-treated soils were all less than 3×10−13 m2/s, and the Lx were all more than 9, fulfilling the condition of controlling the contaminated site underutilization. Under prolonged acid attack, the carbonated Zn was eventually leached out by dissolution. Based on these findings, the remediation of Zn-contaminated soils by the activated MgO carbonation method lays a solid foundation for safely treating and reusing heavy metal-contaminated land resources.

Key words: carbonation, activated magnesium oxide, semi-dynamic leaching test, effective diffusion coefficient, leachability index