Remediation of heavy metal contaminated soil with appropriate washing agents is crucial to the decline in the harmfulness of contaminated soil by heavy metals to the environment and human health. In this study, citric acid (CA) and water-soluble chitosan (WSCS) as natural and degradable washing agents were used to remove Zn in the soil by two-step washing method. Results indicated that the two-step washing with CA and WSCS were found to be suitable for the removal of Zn from the contaminated soils, which significantly decreased the total concentration of Zn in the soil. After the remediation process with two-step soil washing, the contents of Zn in different chemical species decreased, especially for the carbonate-bound fraction. Therefore, the two-step soil washing with CA and WSCS was advisable for the remediation of Zn-contaminated soils. The washing mechanism could include the acid dissolution, ion exchange and complexation reaction between zinc ions and functional groups such as hydroxyl, carboxyl, amine and amide groups. This study provided the theoretical support for the exploitation and application of suitable washing agents used for the remediation of contaminated soil by heavy metals.

使用合适的清洗剂修复重金属污染土壤，对于降低重金属污染土壤对环境和人类健康的危害至关重要。在这项研究中，柠檬酸（CA）和水溶性壳聚糖（WSCS）作为天然和可降解的洗涤剂，通过两步洗涤法去除土壤中的锌。结果表明，CA和WSCS两步洗涤适用于去除污染土壤中的Zn，显着降低了土壤中Zn的总浓度。经过两步土壤冲洗修复过程后，不同化学物种中Zn的含量下降，尤其是碳酸盐结合部分。因此，建议采用 CA 和 WSCS 两步洗土法修复锌污染土壤。洗涤机理可包括锌离子与羟基、羧基、胺基和酰胺基等官能团之间的酸溶解、离子交换和络合反应。该研究为开发和应用适用于重金属污染土壤修复的洗涤剂提供了理论支持。