Transport across homoporous and heteroporous membranes in nonideal, nondilute solutions. II. Inequality of phenomenological and tracer solute permeabilities
For pt.I see ibid., vol.34, p.535, 1981. The phenomenological solute permeability (ωp) of a membrane measures the flux of solute across it when the concentrations of the solutions on the two sides of the membrane differ. The relationship between ωP and the conventionally measured tracer permeability (ωT) is examined for homoporous and heteroporous (parallel path) membranes in nonideal, nondilute solutions and in the presence of boundary layers. For a homoporous membrane, the two permeabilities become equal as the solutions become ideal and dilute. For heteroporous membranes, ωP is always greater than ωT. An upper bound on ωP-ωT is derived to provide an estimate of the maximum error in predicted solute flux. This bound is also used to show that the difference between ωP and ωT demonstrated earlier for the sucrose-Cuprophan system can be explained if the membrane is heteroporous. The expressions developed for ωP support the use of a modified osmotic driving force to describe membrane transport in nonideal, nondilute solutions
