The adsorption of Fe2+ and Fe3+ ions on 2-vinylpyridine-divinylbenzene copolymer and acrylonitrile-methyl methacrylate-divinylbenzene terpolymer was investigated. In general, the adsorption of Fe2+ and Fe3+ in both resins increased with the enhancement of hydrochloric acid and metal concentration. The metal adsorption on the terpolymer increased sharply with the addition of small portions of ethanol, whereas the adsorption on the copolymer practically was not affected by the presence of the alcohol. An increase in temperature produced a small increase in iron adsorption for both resins. Fourier transform infrared spectra showed that nitrile and ester groups of the terpolymer did not suffer hydrolysis during metal adsorption, even for the highest HCl concentration and the highest temperature applied. A mechanism of iron adsorption through the ion exchange of chloride anions by tetrahedral [FeCl4](2-) or [FeCl4](-) anions is proposed. (C) 2003 Wiley Periodicals, Inc.