Multiple Anchor Sites of CaFe-LDH Enhanced the Capture Capacity to Cadmium, Arsenite, and Lead Simultaneously in Contaminated Water/Soil: Scalable Synthesis, Mechanism, and Validation

Heavy metal pollution is a global challenge to human health and ecosystems, and various strategies have been developed to eliminate these hazardous pollutants. However, due to the contrasting biogeochemical behavior of cadmium (Cd) and arsenic (As), the efficient and simultaneous removal of these substances is still a major challenge. Here, we demonstrated that the synthesized CaFe-layered double hydroxide (CaFe-LDH) can provide various active sites for the simultaneous removal of Cd 2+, AsO 2 –, and Pb 2+ with removal efficiencies of >95% in 5 min and >99% within 60 min. The combination of energy-dispersive X-ray elements and structural characterizations indicated that Cd 2+ was anchored in the lattice of the layer through isomorphous substitution with Ca, AsO 2 – was trapped by amorphous FeOOH, while Pb 2+ was removed via the precipitation route. At the same time, we provide a scalable (100 g/batch in the lab and 500 kg/batch in the pilot plant) and effective strategy to produce CaFe-LDH using only Ca(OH) 2 and FeCl 3 as building blocks. Moreover, hydroponics and potting experiments have shown that CaFe-LDH can not only significantly suppress the migration of the above-mentioned heavy metals from the soil into plants (the reduction efficiencies for Cd 2+, AsO 2 –, and Pb 2+ are up to 98.7, 99.4, and 94.9%, respectively) but also have a positive effect on plant growth. Therefore, our work opens the possibility of scalable production of CaFe-LDH and offers a new perspective for the simultaneous removal of Cd 2+, AsO 2 –, and Pb 2+ from contaminated wastewater and soil.