In Situ Oxidation and Efficient Simultaneous Adsorption of Arsenite and Arsenate by Mg–Fe–LDH with Persulfate Intercalation

Abstract

Inorganic arsenic occurs mainly in As(III) and As(V) states in water environment, but arsenite is more toxic and difficult to remove than arsenate by usual adsorption processes. To achieve the in situ oxidation of As(III) and simultaneous removal of both As(III) and As(V) in water, a novel-layered double hydroxide (Mg–Fe–S2O8–LDH) with the intercalation of persulfate has been designed and synthesized by a calcination-reconstruction method. The arsenic adsorption performances and removal mechanism with the Mg–Fe–S2O8–LDH material were studied. The experimental result showed that, since the strong oxidation ability of the exchangeable persulfate ions from the LDH, the As(III) species in water were almost completely oxidized to the As(V) state and simultaneously adsorbed onto the Mg–Fe–S2O8–LDH. It was found that the maximum adsorption capacity for As(III) and As(V) in single-pollutant system was 75.00 and 75.63 mg·g−1, respectively. When the adsorbent dosage was 0.5 g·L−1 for a mixed As(III) and As(V) solution, the batch experiment showed that the residual arsenic concentration can be reduced from 1 mg·L−1 to lower than the limit value of drinking water standard recommended by WHO. It indicated that the synthesized Mg–Fe–S2O8–LDH is a potential attractive adsorbent for simultaneous removal of As(III) and As(V) in water.