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Molecular and Macromolecular Sieving by Asymmetric Ultrafiltration Membranes

机译：不对称超滤膜的分子筛和大分子筛分

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The sieving of dilute solutions of low molecular weight saccharides, proteins, and a polysaccharide, dextran, by several asymmetric ultrafiltration membranes has been studied principally as a function of transmembrane pressure drop or solvent flux (J(sub v)) in a stirred cell device. Scanning or transmission electron microscopy were used to examine the skin layer and substructure of each membrane. For each solute/membrane system studied, solute adsorption to the ultrafilter was not apparent, and solute sizes were characterized by Stokes-Einstein hydrodynamic radii. For polydisperse dextrans, gel permeation chromatography of filtrate and retentate solutions was used to determine the observed rejection coefficients, or fractional retention, of specific dextran mixture components. Concentration polarization, or the accumulation of retained solutes at the membrane surface can mask membrane behavior; accordingly, the flow patterns and specific mass transfer characteristics of the Amicon 52 stirred cell were studied under the turbulent flow conditions employed in all experiments. A one-dimensional mass transfer model was found adequate to describe the boundary layer concentration polarization, thereby permitting the intrinsic membrane rejection coefficient (R) to be related to the experimentally measured rejection coefficient.

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