Three Generations of Polystyrene-Type Strong Acid Cation Exchangers: Textural Effects on Proton/Cadmium(II) Ion Exchange Kinetics

Proton/cadmium(II) ion exchange kinetics on sulfonated polystyrene resins of type gel, macroporous, and hypercross-linked were investigated using a potentiometric method in conditions favoring a particle diffusion-controlled mechanism. The data were modeled with different quasi-homogeneous resin phase kinetic models and with the Ruckenstein et al. bidisperse pore model. The interdiffusion and self-diffusion coefficients were obtained and reported. The diffusion coefficients on resins with different texture slightly decrease in the series hypercross-linked >=gel > macroporous resins. The evaluated ratio between the sulfonic groups grafted in micro- and macropores was 1/60 for the macroporous resin and 1/100 for the hypercross-linked one. The evaluated Cd2+ self-diffusion coefficients were 8.4 × 10^-12, 6.4 × 10^-12, and 9.1 × 10^-12 m^2 s^-1, while the evaluated H+ self-diffusion coefficients were 1.7 × 10^-10, 1.4 × 10^-10, and 4.1 × 10^-10 m^2 s^-1 on gel, macroporous, and hypercross-linked resins, respectively.