Transport across homoporous and heteroporous membranes in nonideal, nondilute solutions. II. Inequality of phenomenological and tracer solute permeabilities

Abstract

The phenomenological solute permeability (omega p) 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 omega p and the the conventionally measured tracer permeability (omega T) is examined for homoporous and heteroporous (parallel path) membranes in nonideal, nondilute solutions and in the presence of boundary layers. In general, omega p and omega T are not equal; therefore, predictions of transmembrane solute flux based on omega T are always subject to error. For a homoporous membrane, the two permeabilities become equal as the solutions become ideal and dilute. For heteroporous membranes, omega p is always greater than omega T. An upper bound on omega p- omega T 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 omega P and omega T demonstrated earlier for the sucrose-Cuprophan system can be explained if the membrane is heteroporous. The expressions for omega P developed here support the use of a modified osmotic driving force to describe membrane transport in nonideal, nondilute solutions.

Effects of molecular shape on osmotic reflection coefficients

“…In general, one expects intermediate behavior, such that 0 < σ oh < 1. Values of σ oh for various solutes have been measured for cell membranes [4,5], capillary walls [6,7], and synthetic membranes [8][9][10], to cite a few examples. From a thermodynamic viewpoint, osmosis is due to an imbalance in the chemical potential of the solvent.…”

Osmosis: a bimodal theory with implications for symmetry

“…In the absence of osmotic pressure differences, pressure creates a steady state flow for which the equations f Measurements of crs and erf in a heteroporous membrane have been made by Friedman & Meyer (1981), who studied the concentration dependence of the coefficients and concluded that <rs and (Tf converge in dilute solution. However, extrapolation of their data to low concentration does not really show unequivocal convergence, especially in the light of the above discussion that owing to the porosity distribution ers and <rf can be roughly equal in heteroporous polymer membranes without there being any underlying Onsager symmetry.…”

Membrane Transport of Nonelectrolyte Solutions in Concentration Polarization Conditions: Hr Form of the Kedem–Katchalsky–Peusner Equations

“…To describe transport phenomena in biological and technical systems, models developed in the framework of nonequilibrium thermodynamics [8][9][10][11][12], diffusion models [13,14], and friction [15][16][17]; models developed in the framework of statistical physics [18][19][20]; and models developed as part of the network thermodynamics [21][22][23][24][25][26] are used. In order to characterize the relationship between generalized streams of liquid and solutes and their generalized driving forces, which are derived from the electrochemical and/or chemical affinity gradient, the thermodynamics of Onsager are used [9,11,27,28].…”