Evaluation of the Effects of Lime–bassanite–charcoal Amendment on the Immobilization of Cadmium in Contaminated Soil

The effects of amendments, such as lime, bassanite, sodium phosphate, steel slag and charcoal, and their compounds on the immobilization of cadmium (Cd) are investigated. The lime–bassanite–charcoal compound shows the best remediation performance compared to other agents in conducted experiments. The optimum condition for lime–bassanite–charcoal application in contaminated soil is lime–bassanite–charcoal with a mass ratio of 1:1/3:2/3, a dose of 2% of the soil weight, and a liquid-to-solid ratio of 35%–40%; additionally, the agents should be added before water addition. The highest Cd removal rate was 58.94% (±1.19%) with a ∆pH of 0.23, which is much higher than the rates reported in previous studies. The compound amendment was used in a field experiment, demonstrating a Cd removal efficiency of 48.78% (±4.23), further confirming its effectiveness.