Geopolymer is an environment-friendly cementitious material, which can effectively immobilize heavy metals. However, the existing study on solidification/stabilization (S/S) of heavy metal contaminated soil using geopolymer is very limited. In order to investigate the effects of geopolymer produced by activating fly ash (FA) and ground granulated blast-furnace slag (GGBS) (FA + GGBS) with composite activator of Na₂SiO₃ and NaOH on environmental and engineering properties of Pb²⁺ and Cd²⁺ contaminated soil, a series of tests including soil pH, leachate pH and electrical conductivity (EC), toxicity leaching, UCS and pH-dependent tests were conducted at different curing times. Additionally, scanning electron microscopy/energy dispersive spectroscope (SEM/EDS), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were performed to analyze the micro mechanism of FA + GGBS based geopolymer solidified contaminated soil. The results indicated that the UCS and pH of soil increased steadily with FA + GGBS content and curing time increasing. Moreover, as FA + GGBS content and curing time increased, the leached Pb²⁺, Cd²⁺ concentration decreased significantly, and the concentration was closely related to the pH of leachate. Compared with Cd²⁺, the solidification ratio of FA + GGBS based geopolymer for Pb²⁺ was lower. Besides, the leached Pb²⁺ and Cd²⁺ concentrations decreased first and then increased with increasing pH of extraction fluid. Microscopic analysis showed that the gel products of FA + GGBS based geopolymer were mainly C-(N)-A-S–H gels. However, the geopolymer structure became looser due to the existence of Pb²⁺ or Cd²⁺. The formation of Cd(OH)₂ was the primary solidification mechanism of Cd²⁺, while Pb²⁺ was mainly immobilized in geopolymer structure by ion exchange. The MIP results showed that the volume of inter-aggregate pores between 0.01 and 1 μm reduced with increasing FA + GGBS content of solidified soil.

地聚合物是一种环保胶凝材料，可有效固定重金属。然而，现有的利用地质聚合物对重金属污染土壤进行固化/稳定（S/S）的研究非常有限。为了研究用Na ₂ SiO ₃和NaOH复合活化剂活化粉煤灰(FA) 和磨碎的高炉矿渣(GGBS) (FA + GGBS) 生产的地质聚合物对Pb ^{2+ 的}环境和工程性能的影响和镉²⁺针对受污染土壤，在不同的固化时间进行了一系列测试，包括土壤 pH 值、渗滤液 pH 值和电导率（EC）、毒性浸出、UCS 和 pH 依赖性测试。此外，还进行了扫描电子显微镜/能谱仪（SEM/EDS）、X射线衍射（XRD）和压汞孔隙率（MIP）测试，分析了基于FA+GGBS的地质聚合物固化污染土壤的微观机理。结果表明，随着FA+GGBS含量和固化时间的增加，土壤UCS和pH值稳步上升。此外，随着FA+GGBS含量和固化时间的增加，浸出的Pb ²⁺、Cd ²⁺浓度显着降低，且该浓度与浸出液的pH值密切相关。与 Cd ²⁺相比, FA + GGBS 基地质聚合物对 Pb ²⁺的凝固率较低。此外，浸出的Pb ²⁺和Cd ²⁺浓度随着萃取液pH值的增加而先降低后升高。显微分析表明，FA+GGBS基地质聚合物的凝胶产物主要是C-(N)-AS-H凝胶。然而，由于Pb ²⁺或Cd ²⁺的存在，地质聚合物结构变得松散。Cd(OH) ₂的形成是 Cd ²⁺的主要凝固机制，而 Pb ²⁺主要通过离子交换固定在地质聚合物结构中。MIP 结果表明，随着固化土壤中 FA + GGBS 含量的增加，0.01 到 1 μm 之间的团聚体孔隙体积减小。