Remediation of Pb, Cd, and Cu contaminated soil with Mg-Fe-Al layered double hydroxides (LDHs) synthesized from waste red mud

Soils contaminated with multiple heavy metals pose a significant threat to human health and ecosystem functionality. Following a "treat pollution with waste" strategy, we synthesized Mg-Fe-Al ternary layered double hydroxides (LDHs) from waste Bayer red mud for the remediation of heavy metal contaminated soils. Characterization using XRD, FTIR, SEM and EDS methods revealed a characteristic layered structure rich in functional groups, offering reaction sites for heavy metal passivation. Passivation experiments showed that the application of Mg-Fe-Al LDHs (2.5 wt.%) reduced the availability of Pb (29.7%), Cd (64.1%) and Cu (66.0%) in contaminated soil from a sulphide iron ore area in southern Sichuan Province. Simulated acid rain experiments showed leachate concentrations of Pb, Cd, and Cu reduced by 43.3%, 72.7% and 42.4%, respectively. This work provides a reference for the development of high-performance and environmentally friendly adsorption-stabilizing materials for green remediation.