Kinetics of anion exchange accompanied by fast irreversible reaction

The kinetics of binary anion exchange accompained by a fast irreversible reaction at the exchanger surface was studied. Dowex 1, X‐8, in the hydroxyl form was contacted with a strong acid in a well‐stirred batch reactor and concentration‐time data were obtained by electrical conductivity measurements. The process was analyzed assuming rate control by film diffusion, intraparticle diffusion, and a combination of both mechanisms. The results indicated that models based on the individual mechanisms gave quite satisfactory representations of the data under appropriate conditions, but the combined model appears superior in the nominally intraparticle diffusion controlled range. It was also found that severe particle cracking occurs, particularly with larger resin particles, at high solution concentrations. This results in degradation of the particles as well as apparent intraparticle diffusion coefficients that vary during the exchange process. Care must be taken to avoid or to account for this phenomenon.