Mechanism and Optimization of Polyepoxysuccinic Acid in Washing Cd-, Pb-, and Zn-Contaminated Soils

Soil washing is an important technique for remediating metal-contaminated soils, and screening promising eluant and optimizing its washing conditions can enhance the restoration efficiencies. Biodegradable polyepoxysuccinic acid (PESA) was employed to remove Cd, Pb, and Zn from two contaminated soils. FTIR analysis suggested that PESA washing process may be dominated by dispersion effect and associated with chelating function. The effects of PESA concentration, pH of solution, and washing time on heavy metal removal were conducted. Single-factor experiments showed that Cd, Pb, and Zn removal was 72.8, 75.7, and 47.7% for soil A and 61.1, 70.2, and 43.3% for soil B at PESA concentration of 30.0 mmol L −1 , pH 3.0, and washing time of 2.0 h. Furthermore, rotatable orthogonal central combination design (ROCCD) was conducted to optimize the washing parameters. The optimal experiment intervals of PESA concentration, pH, and washing time were 38.0–39.0 mmol L −1 , 3.0, and 2.0–2.4 h. Under these conditions, Cd, Pb, and Zn could be removed 80.4, 66.0, and 47.8% from soil A and 64.9, 67.4, and 43.3% from soil B, respectively. Therefore, PESA is a potential extracting agent to remove heavy metals from contaminated soils, and ROCCD is an effective reliable tool for optimization washing parameters. Graphical abstract