Simplified engineering models are presented, characterizing Donnan dialysis separations of a single and multicomponent feed solutions by an overall transport coefficient combining mass transfer resistance and membrane diffusion resistance. Full verification of the predictions of the derived models was obtained from experimental data measured at various Reynolds numbers and feed solution concentrations using a NaCl stripping solution. Permeating target ions from single component feed solutions consisted of H2PO4-, NO3-, and HCO3-. Dual component permeation was from feed solutions of the ion pairs H2PO4-/NO3-, and NO3-/HCO3-. Permeation of all ions except the H2PO4- ion was found to be mass transfer controlled.