Ion-exchange polymers were used successfully in water-treatment operations. In this study, three ion-exchange resins based on 4-vinylpyridine and divinylbenzene functionalized with N-oxide groups were obtained. Their ion-adsorption properties were measured in solutions containing chromium at concentrations of 4 and 500 ppm with column and batch equilibrium techniques. The removal efficiency of the chromium ions with HCl was observed to increase after the protonation of the N-oxide groups. The resins could be reused after 10 cycles with the metal removal efficiency maintained at higher than 95%. These studies evidenced a strong correlation between the morphology and ionic group content in the resin and its chromium ion sorption capability. (C) 2007 Wiley Periodicals, Inc.