Ion-exchange kinetics based on film theory

ABSTRACT The ion‐exchange kinetics in polymer complexes was theoretically formulated. The regeneration of metal species from an ion‐exchange or chelate resin was described as a competitive reaction between metal ions and protons. We considered the ion‐exchange terms and the Langmuir terms to describe the rate of reaction, and film diffusion was also taken into account to describe the profile of the kinetics. In contrast to early methods, the surface concentrations were determined so that the rates of the chemical reactions and diffusion were self‐consistent. Although in the initial stage ion exchange was controlled by diffusion, in the last stage ion exchange was controlled by chemical reactions, particularly under excess acid. The kinetics were supported by experimental data for an iminodiacetic acid chelate resin and amidinourea resins. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39358.