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To reduce the limitations of the chemical washing method due to soil texture, the freezing technique has been used to enhance the mass transfer efficiency between the eluent and heavy metal contaminants. With the optimized water supplement and cooling conditions, a large-scale model experiment was conducted. Results show that the optimized method is prone to enhancing the eluent intake of clayey soil, leading to an increase in the amount of soil frost heave, which has a feedback effect by breaking the soil structure and enhancing the eluent intake. The synergistic effect of the two is responsible for the improvement of washing efficiency. In addition, after four freeze-thaw and washing cycles, the total removal rates of the metallic elements Pb and Cd reach 58.73% and 69.04%, respectively, satisfying the soil environmental quality standard. The soil bioavailability is effectively reduced by alternating the eluent with ethylenediaminetetraacetic acid (EDTA) and water, thereby reducing the bioavailability of Pb and Cd by 66.01% and 74.18%, respectively. This remediation strategy for heavy metals in clayey soils utilizes alternate freezing and thawing (natural cold energy) in seasonally frozen regions, which is beneficial for constructing an ecological civilization and protecting the environment. • WSL-GC-CS method for remediation of heavy metal in contaminated clayey soil was proposed. • The new method can solve the problem of poor efficiency for clayey soil in field remediation. • The method can reduce energy consumption and promote sustainable economic development. [ABSTRACT FROM AUTHOR]

For the improved washing efficiency of clayey soil, utilized magnetization technology was used in this study to enhance the physicochemical properties (e.g., viscosity, surface tension, and contact angle) of the eluent. Lead- and cadmium-contaminated clayey soil was used as the research subject in an experimental study aimed to enhance the heavy metal removal efficiency through a magnetized modified eluent and freezing-thawing effect by using EDTA as the eluent. The magnetization test results indicate that the EDTA solution's viscosity, surface tension, and contact angle decrease after magnetization, thus improving the wettability, enhancing the eluent's full contact with heavy metal pollutants, and consequently increasing the removal rate. The results of the freezing–thawing and washing column test show that magnetization reduced the viscosity of eluent, decreased soil seepage or migration resistance, and increased moisture migration during freezing. After three cycles of freezing-thawing and washing, the removal rates for Cd and Pb were 79.35% and 70.38%, respectively. The technology of magnetized eluent is facile to operate and serves as an efficient, cost-effective, and eco-friendly auxiliary method for increasing the efficiency of freezing–thawing–washing processes, offering a novel approach for soil remediation. • The combined magnetization technology and soil washing method for remediation of heavy metal contaminated clay soils is proposed. • Based on enhance the physicochemical properties of the eluent to improve removal efficiency. • To provide basis for remediating heavy metal by magnetization technology. [ABSTRACT FROM AUTHOR]