Synthetic Polymeric Membranes: Practical Applications —Past, Present And Future

Abstract

The past decade has seen the rapid development of important laboratory and industrial applications of permselective, synthetic polymeric membranes, the majority of which involve molecular separations which in earlier times have been costly, difficult, or impossible to accomplish by other means. The hydraulic-pressure-activated treatment of aqueous solutions and process streams via the techniques of reverse osmosis and ultrafiltration, making use of controllably permselective, asymmetric membranes, constitutes the most advanced application of membrane technology today; such processes are no in idespread use for ater-demineralization, aste-ater treatment, food by-product recovery, and for isolation and purification of biologicals. Membrane ultrafiltration has also revolutionized preparative and analytical methods in experimental molecular biology and biochemistry, and has led to significant improvements in diagnostic laboratory practices for the assay of biological fluids such as urine, plasma and cerebrospinal fluid. Hemodialysis continues to be the most important extracorporeal membrane-separation process in medical practice. Recent membrane developments promise at last to permit efficient dialytic removal of “middle-molecule” impurities from blood, and to utilize ultrafiltration as a safe and improved alternative to dialysis for blood purification. Novel membranes with high 02/C02permeability are being evaluated for use in efficient hemoxygenators or “artificial lungs”. Synthetic polymeric membranes are no embodied into novel pharmaceutical products called Therapeutic Systems, which deliver drugs to specific body sites at precisely controlled rates for prescribed periods of time, for safer, more effective, and more reliable disease treatment. Separation of gaseous and volatile liquid mixtures by membrane permeation continues to be a subject of intensive research, although practical large-scale separation processes of this type remain to be developed. Permselective gas-separation membranes are being used to increase the sensitivity arid accuracy of gas-chromatographic analytical instrumentation. Ionically permselective membranes (of the classical ion-exchange, or diffusible ion-carrier type) are being used industrially in such processes as electrodialysis, and as the detecting elements of potentiometric ion-analyzers. The relatively ne concepts of “facilitated diffusion carrier membranes”, of immobilized-enzyme-containing membranes, and of “ionic mosaic membranes”, hose origins stem from our increasing aareness of the structure and function of biological membranes, are today receiving intensified research and development interest, with potential application to gas- and electrolyte- separation and recovery, to detection and analysis of biological substances, to ne methods of electric poer generation, and the like. Pressures on human survival relating to environment, energy, nutrition, and health are certain in coming years to evoke applications of membrane science and technology which ill make current progress in the field look primitive by comparison. © 1976, Walter de Gruyter. All rights reserved.