Arsenite-arsenate separation analysis technique using anion exchange resin

Abstract

Arsenite-arsenate separation analysis technique using a commercial anion exchange resin column with quaternary ammonium cations as anion exchange groups was studied. The selection of the optimum conditions for the valence-dependent separation of inorganic arsenic and the influence of coexisting anions were examined experimentally. By calculation based on the first dissociation constants of arsenite and arsenate, the optimum pH range of the test solution for valence separation of arsenic was estimated to be 4.3 to 7.1. When the test solution adjusted to the above pH was passed through the column, the arsenic in the test solution was separated appropriately by valence, because the arsenite is not adsorbed and the arsenate is adsorbed on the resin. Also, the arsenate adsorbed on the resin could be easily recovered almost completely by using HCl or HNO₃. The strength of the inhibition effect of coexisting anions on the recovery of arsenic was clarified to be “CH₃COO^－ << Cl^－ < NO₃^－ < SO₄^2－”. The arsenite-arsenate separation analysis technique proposed in this study separated and recovered arsenite and arsenate with an experimental error of about 6％under the experimental conditions.