Simultaneous super-stable mineralization of Pb2+, Cd2+ and Cu2+ using MIL-101(Fe)@MgFe-LDH

The Pb2+, Cd2+ and Cu2+ co-existing pollution in battery and smelting industries have posed a significant threat to ecosystem and human health. Herein, we reported the fabrication of MIL-101(Fe)@MgFe-LDH successfully using in-situ nucleation and transformation strategy. The MIL-101(Fe)@MgFe-LDH exhibited maximum saturated adsorption capacities of 1408.57, 568.18 and 366.30 mg g−1 towards Pb2+, Cd2+ and Cu2+ in aqueous solution, respectively, and the adsorption data for each of these heavy metals can be well-fitted with pseudo-second-order kinetic and Langmuir isotherm models. Moreover, when MIL-101(Fe)@MgFe-LDH was applied for 300 mg kg−1 of Pb2+, Cd2+ and Cu2+ co-existing soil, the extremely low concentration of 1.24, 6.88 and 1.08 mg kg−1 for Pb2+, Cd2+ and Cu2+ can be reached in 7 days of column leaching experiment. Note that the release of Mg2+ from MIL-101(Fe)@MgFe-LDH was shown to promote pea seedling growth by acting as magnesium fertilizer. Detailed quasi-situ characterization and DFT calculation revealed the mechanism of isomorphic substitution of Mg2+ by Cu2+ accompanied by in-situ conversion to CuFe-LDH, while the formation of CdCO3 and Pb3(CO3)2(OH)2 can be demonstrated. Consequently, simultaneous super-stable mineralization of multiple heavy metals in water and soil can be accomplished.