Layered double hydroxides (LDH) are the cost-effective and high-efficiency materials for remediation of potentially toxic elements (PTEs) in contaminated soil and groundwater. Herein, the effectiveness and mechanisms of a ternary Ca–Mg–Al LDH (CMAL) for the synergistic remediation of As, Cd, and Pb were investigated in contaminated soils and simulative groundwaters for the first time. The immobilization efficiencies of As, Cd, and Pb in both black soil (BS) and red soil (RS) amended by CMAL at 5 wt% were all > 75%. CMAL amendment transferred more mobile As, Cd, and Pb fractions in soils to immobile species than did Ca–Al LDH and Mg–Al LDH treatments. Furthermore, using a pump-and-treat technology, 82–98% of these 3 PTEs from contaminated groundwater were successfully immobilized in both CMAL treated BS and RS top-soils. Meanwhile, leaching of Ca, Mg, and Al from CMAL was minimal indicating the material was stable. The excellent immobilization performance of CMAL for these PTEs was attributed to the coating of soil microparticles by CMAL nanosheets that allowed complexation of Ca–O–As/Cd or Mg–O–As/Cd/Pb formation, co-precipitation of Ca/Fe–As and Cd(OH)₂, and formation of Ca-bridged ternary complex (FeO–Ca–As/Cd). The adverse effect of oppositive pH/Eh-dependence between As and Cd/Pb was overshadowed by these mechanisms and thus allowed As immobilization. Immobilization of As, Cd, and Pb by CMAL amendment was more favorable for RS soil due to its lower reduction potential and more participation of metal-(hydr)oxides for complexation. Overall, the ternary-LDH is a promising synergistic remediation strategy for multi-PTEs contaminated soil and groundwater.

层状双氢氧化物 (LDH) 是用于修复受污染土壤和地下水中潜在有毒元素 (PTE) 的经济高效的材料。在此，首次在污染土壤和模拟地下水中研究了三元 Ca-Mg-Al LDH (CMAL) 协同修复 As、Cd 和 Pb 的有效性和机制。5 wt% CMAL 修正的黑土（BS）和红土（RS）中As、Cd 和Pb 的固定化效率均> 75%。与 Ca-Al LDH 和 Mg-Al LDH 处理相比，CMAL 修正将土壤中更多的可移动 As、Cd 和 Pb 组分转移到固定物种。此外，使用泵送处理技术，来自受污染地下水的这 3 种 PTE 中有 82-98% 成功地固定在 CMAL 处理的 BS 和 RS 表层土壤中。同时，从 CMAL 中浸出的 Ca、Mg 和 Al 最少，表明该材料是稳定的。CMAL 对这些 PTE 的优异固定性能归因于 CMAL 纳米片对土壤微粒的包覆，使 Ca-O-As/Cd 或 Mg-O-As/Cd/Pb 形成络合，Ca/Fe 共沉淀–As 和 Cd(OH)₂ , 形成钙桥三元络合物 (FeO-Ca-As/Cd)。As 和 Cd/Pb 之间的阳性 pH/Eh 依赖性的不利影响被这些机制所掩盖，因此允许 As 固定。CMAL 改良剂对 As、Cd 和 Pb 的固定对 RS 土壤更有利，因为它具有较低的还原电位和更多的金属-（氢）氧化物参与络合。总体而言，三元-LDH是一种很有前景的协同修复多PTEs污染土壤和地下水的策略。