Model for the determination of diffusion coefficients of heterovalent ions in macroporous ion exchange resins by the zero-length column method

A generalized theoretical model for the measurement of effective diffusion coefficients of heterovalent ions in macroporous ion-exchange resins by the zero-length column method was developed. The model includes the resistance to mass transfer both in the particle and in the film and described ion fluxes with Nernst–Planck equations. Equilibrium was described using the Langmuir type empirical equation. The values of intraparticle diffusivity of Cu2+Cu2+, Cd2+Cd2+, Zn2+Zn2+, and H+H+ on commercial Lewatit TP-207 were obtained by non-linear regression, these values agree fairly well with data reported previously in literature. The following trend was observed: DCu>DZn>DCdDCu>DZn>DCd.