ANALYSIS OF DIALYSIS COUPLED WITH ULTRAFILTRATION IN CROSS-FLOW MEMBRANE MODULES

Analytical solution of solute concentration for the systems of dialysi s coupled with ultrafiltration in cross-flow membrane modules was obta ined by the method of perturbation, and thus separation efficiencies c ould be calculated for various operating and design conditions. The ov erall mass transfer coefficient was assumed to be constant and the con centration polarization and pressure drop on both compartments were ne glected in solving this problem. Moreover, the mean values of permeati on flux and sieving coefficient were taken and were treated as constan t. It was found that increasing the flow rate in retentate phase is mo re beneficial to the mass transfer than increasing in dialysate phase. The performance of dialysis can be improved significantly by the effe ct of ultrafiltration, especially for the systems with low mass transf er coefficient. The present analysis could be applied to all kinds of configurations, such as parallel-flow, radial-flow and spiral-wound ty pes, but with the limitations of laminar flow and low viscosity and hi gh diffusivity of the fluids.