SELECTIVE ULTRAFILTRATION

This paper reviews data on the selective properties of porous membranes in the light of the polarization sieving (PS) model of ultrafiltration (suggested by the author). In accordance with such a model, the gel polarization of ultrafiltration membranes, instead of complete overlapping of pores by a gel layer, produces a decrease of pore sizes by a constant value ΔR required for the corresponding reduction of filtration flow. In the pores of decreased dimensions, the sieve separation of molecules by size proceeds as before, which explains the preservation of the sieving nature of ultrafiltration in conditions of gel polarization. The PS model has been validated by means of calibration using model protein mixtures and chromatographic analysis. The proposed model also explains the log-normal nature of retention curves for ultrafiltration membranes. © 1990.