Chloride/sulfate ion exchange kinetics at high solution concentration

Kinetics of chloride-sulfate exchange and reverse exchange and sulfate self-exchange at high salinity on three acrylate-base anion exchange resins with quaternary ammonium, tertiary amine, and secondary amine groups, respectively, have been examined. In all cases, evidence points to rate control by intra-particle diffusion. At low conversion, rates are slightly lower than predicted on the basis of the Nernst-Planck equations; this is attributed to initial retardation by film diffusion. For forward and reverse exchange (sulfate and chloride, respectively, taken up by the resin), but not for isotopic sulfate exchange, rates at high conversion tend to be somewhat higher than predicted; this is tentatively attributed to changes in water content of the resins in the course of conversion.