TRANSPORT PHENOMENA IN ULTRAFILTRATION - MEMBRANE SELECTIVITY AND BOUNDARY-LAYER PHENOMENA

Retention characteristics of UF membranes are delineated through comparison of the combined viscous flow and frictional model with the Ferry-Faxen equation. The molecular weight cut-off concept is discussed using calculations of how sharp cut-off curves one can expect of UF membranes with uniform pore sizes and how heteroporosity will affect such curves. Experimental retention-flux curves for different macromolecules have been measured. From these data the molecular weight cut-off curves at varying pressure levels can be determined and by comparing with the model an average pore radius can be calculated.