Simple modeling of Donnan separation processes: single and multicomponent feed solutions

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.