ABSTRACTThe rate of ion exchange of Eu(III) from semi-infinite bath containing dilute nitric acid solution was studied on a macroporous bifunctional phosphinic acid resin. The influence of particle size, concentration of nitric acid and temperature on the uptake of Eu(III) was examined. The kinetic data were fitted into the Reichenberg approximate solution, based on the Nernst–Planck resin diffusion model, that relates the fractional attainment of equilibrium (Ut) and internal diffusion coefficient (DA). The measured DA was of the order of 10−13 m2/s, and it was found to increase with the increase of temperature, and decrease with the increase of particle size of the resin and concentration of nitric acid.