Osmosis: a bimodal theory with implications for symmetry

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Abstract

A theory is advanced that volume transfer across a membrane pore during osmosis takes place in two modes: if solute is sterically excluded from the pore a pressure gradient is set up and viscous flow of solvent results; if solute can enter the pore then osmotic flow is a diffusive phenomenon, and there is no pressure gradient in any part of the pore to which solute has access, even at low concentration due to a repulsive wall field. As a consequence the reflexion coefficients σ s and σ f for osmosis and ultrafiltration are not equal, although equality is usually assumed to result from an underlying thermodynamic reciprocity; instead, the two coefficients represent essentially different processes. These results follow from three basic thermodynamic considerations which have usually been overlooked: (i) there is a qualitative difference between a permeable pore and an impermeable one, the latter having a discontinuity of solute activity at the mouth, which the former does not; (ii) the osmotic pressure within the pore is determined by the activity of solute not the concentration; (iii) the effective resistance to flow through a channel depends upon the nature of the régime, being different for diffusive and viscous flow. An expression for σ s is derived and shown to be compatible with experimental data on polymer membranes and homoporous bilayers.

Publisher

The Royal Society

Subject

General Medicine

Reference35 articles.

1. Mechanism of Osmotic Flow in Porous Membranes

2. Bean C. P. 197a The physics of porous membranes - neutral pores. In Membranes (ed. G. Eisenman) vol. 1 pp. 1-54. New York: Dekker.

3. Hindrance of solute diffusion within membranes as measured with microporous membranes of known pore geometry;Beck R. E.;Biochim.,1972

4. Statistical-mechanical theory of passive transport through partially sieving or leaky membranes

5. Crank J. 1956 The definition and measurement of diffusion coefficients. The mathematics of diffusion ch. 11. London: Oxford University Press.

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