Effect of water-soluble thiourea formaldehyde (WTF) on soil contaminated with high copper (Ⅱ) concentration

It is very important to seek a heavy metal soil stabilization/solidification (S/S) agent that has less risk of secondary release and has less impact on the soil. This study explored the repair effect of a new resin repair agent water-soluble thiourea-formaldehyde (WTF), and its stability under indigenous biodegradation and compared the repair effect with sodium sulfide (Na₂S) and hydroxyapatite (HAP). Diethylene triamine pentaacetic acid leaching experiments show that WTF can effectively solidify/stabilize 97.9-84.7% of Cu. At the same time, heavy metal speciation analysis experiments show that WTF does indeed convert the exchangeable Cu in the soil into a non-exchangeable form. Research on soil organic matter, biological carbon and enzyme activity after remediation shows that WTF has a more positive effect on soil function, compared with HAP and Na₂S. Experiments using indigenous microorganisms to decompose the precipitation formed by WTF and Cu show that under the condition of less impact on soil microorganisms, the risk of secondary release of heavy metals caused by soil microorganisms after WTF remediation is less. These findings provide valuable experience for understanding the role of resin structure in preventing the secondary release of heavy metals and restoring soil function.