Wang Xinyang, Xue Yongjie
Shandong Hi-Speed Engineering Test Co., Ltd., Jinan 250098, China.
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel). 2024 Jul 6;17(13):3353. doi: 10.3390/ma17133353.
Pb-contaminated soil poses serious hazards to humans and ecosystems and is in urgent need of remediation. However, the extensive use of traditional curing materials such as ordinary Portland cement (OPC) has negatively impacted global ecology and the climate, so there is a need to explore low-carbon and efficient green cementitious materials for the immobilization of Pb-contaminated soils. A red mud/steel slag-based (RM/SS) geopolymer was designed and the potential use of solidifying/stabilizing heavy metal Pb pollution was studied. The Box-Behnken design (BBD) model was used to design the response surface, and the optimal preparation conditions of RM/SS geopolymer (RSGP) were predicted by software of Design-Expert 8.0.6.1. The microstructure and phase composition of RSGP were studied by X-ray diffractometer, Fourier transform infrared spectrometer, scanning electron microscopy and X-ray photoelectron spectroscopy, and the immobilization mechanism of RSGP to Pb was revealed. The results showed that when the liquid-solid ratio is 0.76, the mass fraction of RM is 79.82% and the modulus of alkali activator is 1.21, the maximum unconfined compressive strength (UCS) of the solidified soil sample is 3.42 MPa and the immobilization efficiency of Pb is 71.95%. The main hydration products of RSGP are calcium aluminum silicate hydrate, calcium silicate hydrate and nekoite, which can fill the cracks in the soil, form dense structures and enhance the UCS of the solidified soil. Pb is mainly removed by lattice immobilization, that is, Pb participates in geopolymerization by replacing Na and Ca to form Si-O-Pb or Al-O-Pb. The remaining part of Pb is physically wrapped in geopolymer and forms Pb(OH) precipitate in a high-alkali environment.
铅污染土壤对人类和生态系统构成严重危害，急需修复。然而，普通硅酸盐水泥（OPC）等传统固化材料的广泛使用对全球生态和气候产生了负面影响，因此需要探索用于固定铅污染土壤的低碳高效绿色胶凝材料。设计了一种基于赤泥/钢渣的（RM/SS）地质聚合物，并研究了其固化/稳定重金属铅污染的潜在用途。采用Box-Behnken设计（BBD）模型设计响应面，并通过Design-Expert 8.0.6.1软件预测RM/SS地质聚合物（RSGP）的最佳制备条件。通过X射线衍射仪、傅里叶变换红外光谱仪、扫描电子显微镜和X射线光电子能谱研究了RSGP的微观结构和相组成，揭示了RSGP对铅的固定机理。结果表明，当液固比为0.76、RM质量分数为79.82%、碱激发剂模量为1.21时，固化土样的最大无侧限抗压强度（UCS）为3.42 MPa，铅的固定效率为71.95%。RSGP的主要水化产物为钙铝硅酸盐水合物、硅酸钙水合物和硅钙石，它们可以填充土壤中的裂缝，形成致密结构，提高固化土的UCS。铅主要通过晶格固定去除，即铅通过取代钠和钙参与地质聚合反应，形成Si-O-Pb或Al-O-Pb。铅的其余部分被物理包裹在地质聚合物中，并在高碱环境中形成Pb(OH)沉淀。
