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Separation Through Dialysis

Application ID: 258

Dialysis is frequently used membrane separation process. An important application is hemodialysis, where membranes are used as artificial kidneys for people suffering from renal failure. Other applications include the recovery of caustic colloidal hemicellulose during viscose manufacturing, and the removal of alcohol from beer.

In the dialysis process, specific components are preferentially transported through a membrane. The process is diffusion-driven, that is, components diffuse through a membrane due to concentration differences between the dialysate and the permeate sides of the membrane. Separation between solutes is obtained as a result of differences in diffusion rates across the membrane arising from differences in molecular size and solubility.

This example looks at a process aimed at lowering the concentration of a contaminant component in an aqueous stream. The dialysis equipment is made of a hollow fiber module, where a large number of hollow fibers act as the membrane. Fully developed laminar flow is assumed within the model geometry. The model also accounts for the partition equilibriums between the different parts of the fiber that cause discontinuities in the concentration of the transported species.