Research on the preparation of ettringite from total solid waste and its application in the treatment of industrial wastewater containing Pb²⁺

Treatment of heavy metal wastewater, especially effluent containing highly toxic Pb²⁺, is essential for ecological security. Ettringite (AFt) is a promising material for heavy metal immobilization due to its open-channel crystal structure and high ion-exchange activity, but traditional synthesis depends on expensive reagents and carbon-intensive processes. Based on the "waste-treats-waste" concept, this study synthesized high-performance ettringite (Waste-AFt) from multiple metallurgical solid wastes (desulfurization ash, fly ash, steel slag powder, and GGBS) through a solution reaction method. Synthesis parameters were optimized, and its performance was compared with chemically synthesized ettringite (Chem-AFt). The optimal conditions were 30 °C and pH 11.5, producing Waste-AFt with 70.2% phase purity and well-developed hexagonal columnar morphology, while 90 °C significantly suppressed ettringite formation. Waste-AFt showed comparable Pb²⁺ removal efficiency to Chem-AFt, with removal rates exceeding 99% at 4 g/L dosage. Adsorption kinetics followed the pseudo-second-order model and equilibrium data fitted the Langmuir isotherm, with maximum adsorption capacities of 257.27 mg/g and 269.11 mg/g for Waste-AFt and Chem-AFt, respectively. Multi-scale characterizations confirmed lattice isomorphous substitution as the dominant mechanism, where Pb²⁺ replaced Ca²⁺ in the ettringite lattice. This work proves the feasibility of preparing high-value adsorbents from bulk industrial solid wastes for wastewater remediation, with both environmental and economic advantages.

重金属废水（尤其是含剧毒铅离子（Pb²⁺）的废水）的治理，对生态安全至关重要。钙矾石（Ettringite，AFt）因具有开放通道的晶体结构与较高的离子交换活性，是一种极具应用前景的重金属固定化材料，但传统合成工艺依赖高成本试剂且碳排放强度较高。本研究基于“以废治废”理念，采用溶液反应法，以多种冶金固废（脱硫灰、粉煤灰、钢渣粉及粒化高炉矿渣粉（GGBS））为原料，合成了高性能钙矾石（Waste-AFt）。研究优化了合成工艺参数，并将其性能与化学合成钙矾石（Chem-AFt）进行对比。最佳合成条件为30℃、pH=11.5，此时制备的Waste-AFt物相纯度达70.2%，且形貌为发育良好的六方柱状；而90℃会显著抑制钙矾石的生成。Waste-AFt对Pb²⁺的去除效率与Chem-AFt相当，当投加量为4g/L时，去除率均超过99%。吸附动力学符合准二级动力学模型，吸附平衡数据符合朗缪尔等温线，Waste-AFt与Chem-AFt的最大吸附容量分别为257.27 mg/g和269.11 mg/g。多尺度表征结果证实，晶格同晶取代是该吸附过程的主导机制，即Pb²⁺取代钙矾石晶格中的钙离子（Ca²⁺）位点。本研究证实了利用大宗工业固废制备高价值吸附剂用于废水修复的可行性，兼具环境与经济双重优势。