Insight into the Simultaneous Super‐Stable Mineralization of AsO₄³⁻, Cd²⁺ and Pb²⁺ Using MgFe‐LDHs.

Multiple‐heavy‐metal contamination in soil, such as the simultaneous presence of AsO43−, Cd2+ and Pb2+, which can reduce crop yields and damage human health, is a serious issue to be addressed. Herein, the MgFe‐LDHs (layered double hydroxides) intercalated with carbonate and nitrate (MgFe‐CO3 and MgFe‐NO3) were synthesized by Separate Nucleation and Aging Steps and ion‐exchange method, respectively. The MgFe‐CO3 demonstrated the maximum saturation adsorption capacity of 55.86, 543.48 and 1597.4 mg g−1 for single AsO43−, Cd2+ and Pb2+ in aqueous solution, while MgFe‐NO3 exhibited 92.50, 387.59 and 869.56 mg g−1, respectively. Kinetic and thermodynamic results for mineralization of single AsO43−, Cd2+ and Pb2+ fitted well with the pseudo‐second‐order kinetic model and Langmuir isotherm model, indicating the occurrence of chemisorption and monolayer adsorption for both MgFe‐CO3 and MgFe‐NO3. Furthermore, simultaneous mineralization of AsO43−, Cd2+ and Pb2+ with >99.0 % efficiency in 240 min in aqueous solution and >81.1 % efficiency in 14 days in soil can be achieved by both MgFe‐CO3 and MgFe‐NO3. Preliminary red bean seedlings cultivation experiments indicated that the released Mg2+ ions from MgFe‐CO3 and MgFe‐NO3 were capable to promote the emergence and growth of red bean seedlings. Detailed XRD and XPS results demonstrated that the AsO43− anions were adsorbed on the laminate of LDHs, whereas the Pb3(OH)2(CO3)2 was the mineralization product for both MgFe‐CO3 and MgFe‐NO3. In terms of Cd2+, CdCO3 was obtained as a mineralization product for MgFe‐CO3, while CdCO3 and Cd(OH)2 can be detected due to the slow transformation of MgFe‐NO3 to MgFe‐CO3 in air. [ABSTRACT FROM AUTHOR]