Enhanced adsorption effect of defect ordering Mg/Al on layered double hydroxides nanosheets with highly efficient removal of Congo red

Abstract

The non-conventional structure layered double hydroxides (LDHs) as pollutant adsorbents with significant adsorption efficiency are promising valuable research topics. In this work, the defect ordering MgAl-LDHs nanosheets for the highly efficient removal of Congo red (CR) are designed and fabricated by a facile environmental-friendly hydrothermal method based on solid insoluble substances magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) as precursors. The decrease of Mg/Al ordering changes the interlayer spacing of LDHs and improves the defect sites with low oxygen coordination on the LDHs laminate, which enhances the removal efficiency of CR from 45.6 to 97.7%. This study reveals that a defect enhancing combined mechanism of surface adsorption and the anion-exchange in MgAl-LDHs can obtain an outstanding adsorption efficiency for removing CR. The reactivity of the Mg/Al disorder with O defect on the LDHs laminate increases with the reduction of frontier orbitals energy gap (ΔEgap), resulting in a high adsorption capacity for CR. The uncover of the defect enhancing adsorption mechanism provides a new strategy to fabricate MgAl-LDHs with high capability for wastewater remediation.