The possibility of oxidizing As(III) to As(V) in aqueous solutions by means of heterogeneous oxidants, i.e. synthetic macromolecular redox compounds, was studied. The materials contain N-chlorosulfonamide functional groups in the sodium form: [P]-SO2NClNa (R/ClNa, 2.1 mmol/g) or in the hydrogen form: [P]-SO2NClH (R/ClH. 2.4 mmol/g), attached to a cross-linked macroporous poly(styrene-divinylbenzene) matrix. They were obtained through the transformation of Amberlyst 15 (Rohm and Haas) commercial cation exchanger's sulfonic functional groups. The experiments were conducted in the H2O and 0.01 M NaOH environment (R/ClNa) and in the H2O and 0.01 M H2SO4 environment (R/ClH), using the batch process and the column process and NaAsO2 solutions (93-375 mg As(III)/dm(3)). The experiments showed that the two copolymers' capacity to oxidize As(III) is high and depends on the process conditions. In the column process experiments, conducted using NaAsO2 solutions with a concentration of similar to 93 mg As(III)/dm(3) at a flow rate of 4 BV/h (R/ClH) and 6 BV/h (R/ClNa), a breakthrough (defined as the exceedance of 0.05 mg As(III)/dm(3) in the effluent) would occur after the solutions amounting to about 400 bed volumes had been passed through the column. (C) 2011 Elsevier B.V. All rights reserved.