The objective of this work is to characterize the kinetics of Donnan dialysis process by a simple model. The Nernst–Planck equation is simplified by neglecting the membrane swelling pressure and assuming an average diffusion coefficient for all ions. Experimental data are presented on the permeation of monovalent phosphate ions from a KH2PO4/NaH2PO4 feed solution to a NaCl receiver solution using two different anion exchange membranes: a low flux membrane (Fumasep FAB) and a high flux membrane (Selemion AMV). Measurements indicate a brief initial ion exchange process in which the membrane is loaded with phosphate ions. Phosphate transport data fit the predicted correlations and provide values of the overall kinetic coefficient. The kinetic coefficients derived from both membranes were found to increase linearly with the membrane phosphate concentration. The phosphate dialysis data of the low flux membrane were found to be controlled by a diffusive process, while the data of the high flux membrane were found to be mass transfer controlled. The increase of the kinetic coefficient with phosphate concentration is shown to be related to the increase in membrane ion diffusivity with its solution concentration.