The internal porosity and swelling/shrinking of a chelating iminodiace
tic type ion exchange resin have been experimentally studied during th
e uptake of copper onto it. The swelling of the particle could be anal
yzed with a modified model on th basis of the unreacted core model (UC
M), including the influence of chemical equilibrium. The ion exchange
kinetic results in batch experiments are used with the UCM to calculat
e the effect of pH on the internal diffusion coefficients. Results fro
m shallow bed experiments with mixed internal and external diffusion c
ontrols have shown the applicability of the above model to analyze ion
exchange with low external velocities.