磷酸盐固化剂封闭高浓度复合重金属污染黏土的机理及稳定性研究

The solidification/stabilization technique has been widely used in remediating heavy metals-contaminated soils. Recently, solidification/stabilization of the soils with high concentration levels of multi- heavy metals has been concerned by both researchers and engineers. It is significant to note that very few studies have systematically investigated the effects of thaw-freeze cycling and carbonization on the leachability and mechanical properties of the solidified soils with high concentration levels of multi- heavy metals. In this project, a comprehensive laboratory tests and theoretical analysis of phosphate-based binder solidified soils with high concentration levels of multi- heavy metals (Pb, Cd, Cu, Zn) are undertaken to: (1) reveal the mechanisms of the interaction between phosphate-based binder and contaminated soils based on the analysis of the physico-chemical and microstructural characteristics of the soils, and chemical speciation of the metals; (2) analyze the leaching properties of heavy metals and assess the effects of heavy metal concentration levels, binder contents, and curing times on the leaching diffusion coefficients of metals using a series of leaching tests including TCLP leaching tests, L/S- and pH- dependent leaching tests, and semi-dynamic leaching tests; (3) assess the durability under the circumstances of thaw-freeze cycling and carbonization; and, (4) evaluate the effects of rainfall intensities on the leaching of heavy metals from the stabilized contaminated soils and its impact to the sustainability of surrounding environment, using numerical modeling and advection-diffusion test results. The results obtained from this project will remarkably facilitate the design of solidification/stabilization technique for the heavy metal-contaminated soils; and provide feasible scientific guidance and theoretical support to promote the wide utilization of the solidification/stabilization technology in China.

固化稳定化技术广泛用于重金属工业污染土的修复领域。现有研究尚未探明高浓度复合重金属污染土的固化机理、溶出特性和耐久性能。本项目以磷酸盐固化剂和高浓度复合重金属污染黏土为研究对象，通过室内试验和理论分析，拟解决以下关键问题：① 系统研究固化污染土的物理化学性质、微观结构、重金属赋存形态随重金属浓度和类型、固化剂掺量的变化规律，揭示磷酸盐固化剂-污染土相互作用机理；② 通过系列溶出试验，查明液固比、浸提液类型和pH、固化剂掺量对固化污染土重金属溶出量的影响规律；③ 通过冻融循环和碳化试验，明确固化污染土在复杂环境下耐久性能、重金属溶出量和扩散系数的变化特征；④ 综合柔性壁渗透扩散试验及数值模拟，定量评价在降雨环境下，固化污染土体重金属溶出运移特征及其对周边环境的影响。研究成果可完善现有固化污染土的环境安全性和耐久性评价体系，为提高我国污染土的固化技术水平提供重要的科学依据和理论支撑。

固化稳定化技术广泛用于重金属工业污染土的修复领域。现有研究尚未探明高浓度复合重金属污染土的固化机理、溶出特性和耐久性能。本项目以磷酸盐固化剂和高浓度复合重金属污染黏土为研究对象，通过室内试验和理论分析，解决了以下关键科学问题：①研究了固化污染土的物理化学性质、微观结构、重金属赋存形态随重金属浓度和类型、固化剂掺量的变化规律，揭示了磷酸盐固化剂-污染土相互作用机理；②通过系列浸出试验，查明了固化剂类型和掺量、养护龄期、土体pH对固化污染土强度和重金属浸出量的影响规律；③通过冻融循环和碳化试验，明确了固化污染土在复杂环境下耐久性能、重金属溶出量和扩散系数的变化特征；④综合土柱降雨模型试验和数值计算，定量评价了降雨环境下，固化污染土体重金属浸出运移特征及其对周边环境的影响。研究成果可完善现有固化污染土的环境安全性和耐久性评价体系，为提高我国污染土的固化技术水平提供重要的科学依据和理论支撑。