Cation exchange kinetics of pyridinecarboxylic acids

The sorption—desorption kinetics of nicotinic and isonicotinic acids on strong acid cationites (sulfocationite CU-2-8, sulfonated polycalixarene) were considered. The rate of the processes, following both the cation exchange mechanism H⁺ ? Cat⁺ and the ion exchange mechanism accompanied by the chemical reaction of protonation of pyridinecarboxylic acid zwitterions, is determined by a slow diffusion of components in the polymeric phase. The interdiffusion coefficient in sulfocationite CU-2-8 for the process H⁺ ? Cat⁺ was equal to ~1?10^–11 m² s^–1, in sulfonated polycalixarene the corresponding value was in the range of (1—4)?10^–12 m² s^–1.