Electrochemical oxidation and removal of arsenic using water-soluble polymers

Abstract

In this work, the electrochemical oxidation of arsenite and its subsequent removal was studied using water-soluble poly[glycidyl methacrylate N-methyl-d-glucamine], P(GMA–NMG), and poly[2-(acryloyloxy)ethyl]trimethylammonium chloride, P(ClAETA). In the first stage, the electroanalysis of arsenic (via oxidation of arsenite to arsenate) by cyclic voltammetry in the presence of water-soluble polymers was conducted. The type of polymer, electrode (gold or platinum), polymer concentration, and pH were evaluated. The study indicated that using P(GMA–NMG) and a gold electrode, oxidation peaks were obtained at approximately +0.5 V versus Ag/AgCl. In the case of P(ClAETA), wide oxidation peaks were obtained at +0.8 V versus Ag/AgCl using a platinum electrode. The optimum concentration for both polymers was 0.05 mol L−1. For P(GMA–NMG), the oxidation potential was influenced by a change of pH. The quantitative oxidation of As(III) to As(V) was conducted using metallic electrodes with higher surface areas. The conversion of arsenic as a function of applied potential was also evaluated. The results showed an efficient oxidation in the presence of both water-soluble polymers. Finally, 60 % of the As(V) could be removed through polymer-enhanced ultrafiltration. The results demonstrated an increase in the removal of pre-oxidized arsenic.