Experimental study on remediation of low permeability Cu–Zn contaminated clay by vacuum enhanced leaching combined with EDTA and hydrochloric acid

To improve the washing efficiency for low permeable clay, the method of vacuum enhanced washing technology was proposed. In this study, ethylene diamine tetraacetic acid (EDTA) and hydrochloric acid (HCl) as eluents, the experiments of remediation of Cu–Zn contaminated cohesive soil by traditional soil column leaching and vacuum enhanced leaching was carried out. Results show that compared with traditional leaching method, the vacuum enhanced leaching method can significantly shorten the leaching time and prominently improve the removal rate of heavy metals Cu–Zn. When concentration of EDTA is 0.1 mol/L, the removal rate of Cu–Zn can reach 95.7% and 82.9%, respectively by vacuum-enhanced leaching. When concentration of HCl is 0.2 mol/L, the removal rate of Cu–Zn by vacuum enhanced leaching method can reach 96.2% and 90.2%, respectively. Whereas, the higher the concentration of EDTA and HCl, the slower the leaching rate. At the same concentration, the leaching rate of HCl was faster. After HCl leaching, the soil structure was seriously corroded, and the relative content of mineral composition changed considerably. After EDTA leaching, the corrosion of soil structure is light, and the relative content of mineral composition changes little. The conclusions obtained are of crucial theoretical value and technical support for environmental engineering.