Preparation and Application of Stabilizing Agents for Solidification of Heavy Metal-Contaminated Soil under Low-Temperature Conditions

Abstract

Stabilization/solidification (S/S) is an effective method used to reduce the leaching of heavy metals from soils, which is a serious environmental problem when soil is contaminated with heavy metals. In this study, a new stabilizing agent consisting of acetate-ethylene copolymer emulsion (VAE)-hydrated calcium silicate-polycarboxylate (V-CSH-PCE), water-soluble thiourea-formaldehyde (WTF) resins, cement, and fly ash was prepared for the solidification of heavy metal-contaminated soil under low-temperature conditions. The results showed that the agents significantly enhanced the compressive properties of the soil. When 10% cement, 8% fly ash, 1.5% V-CSH-PCE, and 0.5% WTF were added, the compressive strength of the subsoil after 1 day of curing was 0.3755 MPa, which was nearly 12 times higher compared with a blank sample. Meanwhile, the leaching concentrations of Cu2+, Zn2+, Pb2+, and Cr3+ in the substrate were 2.52, 1.12, 1.32, and 0.51 mg/L, respectively, which were lower than the leaching standard of “Hazardous Waste Identification Standard Leaching Toxicity Identification (GB 5085.3-2007)”. In addition, the compressive strength of the soil after 1 day of curing at a low temperature (4 °C) was 0.2915 MPa, which was 30.9% higher compared with the soil without the V-CSH-PCE. The results showed that the cement-fly ash-(V-CSH-PCE)-WTF mixture has good application prospects in improving the compressive strength of soil and stabilizing heavy metal ions.