Study of solidification and stabilization of heavy metals by passivators in heavy metal-contaminated soil

Abstract

In this study, the indoor constant temperature culture experiment was used to explore the mutual transformation of different forms of heavy metals. Appropriate types of passivating agents were screened, and the optimal addition amount was determined to realize the solidification and stabilization of heavy metals. The results showed that the dissolved copper (Cu), zinc (Zn), and lead (Pb) contents of the zeolite-treated soil decreased to the lowest. They were 219, 819, and 40 g/kg, respectively, which were 31.2, 6.5, and 38.5% lower than no passivating agent added (the control); the dissolved Cu, Zn, and Pb content gradually increased with the extension of time; 5% zeolite (Z4) treatment had the highest average content of Cu, Zn, and Pb in the residue state, respectively, 24, 48, and 19 mg/kg; and at the end of the test, the residual Zn content of Z4 treatment reached 50 mg/kg, which was 72.4% higher than that of the control. A comprehensive analysis of the changes in the dissolved state of the four heavy metals in the soil shows that Cu, Zn, cadmium (Cd), and Pb treated with zeolite have the best effect, followed by sepiolite, and finally palygorskite. Therefore, 5% zeolite can be used for the passivation restoration of heavy metals Cu, Zn, Cd, and Pb in the soil.

Keywords

• heavy metals
• contaminated soils
• solidification and stabilization
• passivators
• constant temperature culture