Design of a high-performance ternary LDHs containing Ni, Co and Mn for arsenate removal

To cope with the current serious arsenate pollution problem, a new ternary layered double hydroxides (LDHs) containing Ni, Co and Mn with good performance was developed, guiding by DFT calculations. First, Ni, Co and Mn were screened as the metal sources to constitute the LDHs, due to their high ionic charge density. Then, Ni(II), Co(II) and Mn(III)-O octahedra were selected as the primary units for structuring the LDHs, because of their good chemical activity. Meanwhile, the ratio of metals in the ternary LDHs, favoring for arsenate removal, was optimized at 1:2:1. In addition, the synergistic effect among various metals in the LDHs was considered. The results suggested that in the case of single doping, all three metals can act as the center to promote chemical activity independently. On the contrary, when combined together, there is only one unilateral active center. Moreover, the existence of ligand covalent bonds between arsenate and LDHs was confirmed. Finally, a promising new NiCo₂Mn-LDHs with the maximum adsorption capacity of 407.23 mg/g for arsenate removal had been prepared.