Experiments performed under chemical and flow conditions representative of pressurized water reactors (PWR) primary fluid purification by ion exchange resins (Amber lite IRN9882) are modeled with the OPTIPUR code, considering ID reactive transport in the mixed-bed column with convective/dispersive transport between beads and electrodiffusive transport within the boundary film around the beads. The effectiveness of the purification in these dilute conditions is highly related to film mass transfer restrictions, which are accounted for by adjustment of a common mass transfer coefficient (MTC) on the experimental initial leakage or modeling of species diffusion through the bead film by the Nernst-Planck equation. A detailed analysis of the modeling against experimental data shows that the Nernst-Planck approach with no adjustable parameters performs as well as, or better than, the MTC approach, particularly to simulate the chromatographic elution of silver by nickel and the subsequent enrichment of the solution in the former metal.