The role of doped-Mn on enhancing arsenic removal by MgAl-LDHs

To meet the challenges posed by global arsenic water contamination, the Mg Al Mn-LDHs with extraordinary efficiency of arsenate removal was developed. In order to clarify the enhancement effect of the doped-Mn on the arsenate removal performance of the LDHs, the cluster models of the Mg Al Mn-LDHs and Mg Al-LDHs were established and calculated by using density functional theory(DFT). The results shown that the doped-Mn can significantly change the electronic structure of the LDHs and improve its chemical activity. Compared with the Mg Al-LDHs that without the doped-Mn, the HOMO-LUMO gap was smaller after doping. In addition, the-OH and Al on the laminates were also activated to improve the adsorption property of the LDHs. Besides, the doped-Mn existed as a novel active site. On the other hand, the Mg Al Mn-LDHs with the doped-Mn, the increased of the binding energy, as well as the decreased of the ion exchange energy of interlayer Cl^(-), making the ability to arsenate removal had been considerably elevated than the Mg Al-LDHs. Furthermore, there is an obvious coordination covalent bond between arsenate and the laminates of the Mg Al MnLDHs that with the doped-Mn.