Remediation of Pb- and Cd-contaminated clayey soil via magnetic-enhanced washing

The mass transfer efficiency between the contaminant and the washing eluent is the fundamental factor that limits the efficiency of chemical washing. In this study, the magnetization technique was employed to improve the physicochemical properties of eluent and cross-tests were conducted on clayey soils samples contaminated with lead (Pb) and cadmium (Cd). Furthermore, eluent concentration, magnetization strength, and magnetization time were varied as parameters for enhancing mass transfer efficiency. Results showed that after magnetization, the viscosity, surface tension, and contact angle of ethylene diamine tetraacetie acid (EDTA) decreased, whereas conductivity and pH increased. In particular, the viscosity of high-concentration EDTA increased with higher magnetic field strength and longer magnetization time. The maximum removal of Cd and Pb increased by 64.46% and 35.49%, respectively, compared with the unmagnetized lysate. This result highlighted the efficient mass transfer and synergistic mechanism of the magnetization technique, facilitating better contact between the eluent and the contaminants. Magnetization eluent has been proven to be an efficient, cost-effective, and easily implementable method for enhancing mass transfer efficiency, providing a valuable reference for improving the efficiency of chemical washing for heavy metal-contaminated clayey soil.