MgAl layered double hydroxides with chloride and carbonate ions as interlayer anions for removal of arsenic and fluoride ions in water

Layered double hydroxides (LDHs) are regarded as effective adsorbents to remove arsenic and fluoride ions in water. Compared to thorough research on calcined LDHs, very few works have focused on the adsorption properties and mechanisms of LDHs themselves for these ions. In this manuscript, three-dimensional hierarchical flower-like MgAl layered double hydroxides (MgAl-LDHs) with chloride and carbonate ions as interlayer anions were synthesized via a solvothermal method without any surfactant. When tested as adsorbents for removal of As(V) and F- ions, these hierarchical MgAl-LDHs showed maximum capacities of 125.8 and 28.6 mg g(-1), respectively, under neutral conditions. The adsorption mechanisms for As(V) and F- of hierarchical MgAl-LDHs were elucidated by X-ray diffraction patterns, Fourier transformed infrared spectra, X-ray photoelectron spectroscopy and energy dispersive spectra. The results suggested that ion exchange between interlayer anions in hierarchical MgAl-LDHs and As(V) or F- ions was the main adsorption mechanism. Chloride and carbonate ions intercalated in the MgAl-LDHs layers were exchanged with As(V), while only chloride ions were exchanged with F- during adsorption.