Ionic transport in a continuous donnan dialyzer with two parallel-plate channels

Ionic transport in a continuous Donnan dialyzer with two parallel-plate channels was studied for a biionic exchange system. A theoretical model of the system was formulated on the basis of diffusion equations in terms of diffusion, migration and convection of each ion. Theoretical solutions were obtained by numerical calculations using a finite-difference technique. Simultaneously, continuous Donnan dialytic experiments with a cation-exchange membrane were conducted for the K⁺-H⁺ and Ca²⁺-H⁺ exchange systems. The validity of the model and the numerical calculations was confirmed by comparison with experimental results for mean dialytic rates. The numerical calculation also provided distributions of ionic concentrations in both the channels and the membrane, and the electric potential in the channels. An effectiveness factor was introduced to investigate the proportion of the mass transfer resistance in the membrane phase or the liquid phase to its overall value. The influence of Reynolds number, channel height and valence of counter-ion on the mean dialytic rates and on the effectiveness factor was also discussed.