Adsorptive Removal of Arsenic(III) and Arsenic(V) from Aqueous Solution using Nickel–Zinc Hydroxyl Double Salts

Nickel-zinc hydroxyl double salt (NiZn) with acetate in the interlayer was synthesized by a hydrothermal method for the adsorptive removal of toxic As(III) and As(V) from aqueous solution. Adsorption of As(III) and As(V) using NiZn was greater than that using commercial hydrotalcite (MgAl), and adsorption of As(V) using NiZn was around 100% at pH 6.4-10.6. Among coexisting anions tested, only phosphate decreased the adsorption of As(V). The adsorption of As(III) and As(V) was influenced by their dissolved chemical species and was high when H2AsO3- and H2AsO4- were the major species. The maximum adsorption capacity of NiZn for As(III) and As(V) was 1.24 mmol.g(-1) and 1.05 mmol.g(-1), respectively. On the basis of d(001) values in XRD, the interlayer distance of NiZn decreased from 1.3 to 0.91 nm after adsorption of As(V). In the FT-IR spectra after adsorption of As(V) on NiZn, the absorption peak originating from acetate decreased, and the weak absorption peak originating from As-O appeared at 854 cm(-1). These results confirmed that arsenic was removed by ion-exchange with acetate anions in the interlayer. However As(III) seemed to be adsorbed on the surface of NiZn at pH 6.2 +/- 0.5. NiZn was found to be effective for the adsorptive removal of As(V) from neutral aqueous solution and for removal of As(III) from alkaline aqueous solution.