Membrane-based and other Advanced Separations

This special issue on “Membrane-based and other Advanced Separations” is a collation of exciting research ranging from advanced membrane materials to novel processes for protein purification. The contribution of Wu (2019) challenges the standing of the well-established Spiegler-Kedem (S-K) model for dense membranes, at least as it is conventionally presented. Noting that its application has led to counter-intuitive outcomes in the area of pressure retarded osmosis, she has initiated a re-evaluation. The outcome of this may have implications for forward osmosis and possibly reverse osmosis modelling. Hyun et al (2019) review the current state of the art and the potential of 2D-enabled membrane separation processes which would, if successfully implemented at scale, have a significant impact of the energy-efficiency of important separation processes. The motivation for Liu et al (2019) study was similar and their simulations have concentrated upon the development of microporous materials for Noble gas separation. Complementing these in silico studies, the papers of Chuah and Bae (2019) and Kirk et al (2019) both address experimental challenges. The former showed that the incorporation of nanocrystals can dramatically increase the permeability of polymeric membranes used for oxygen – nitrogen separation whilst the latter examined the application to pervaporation of polymers of intrinsic microporosity (PIMs) and 2D materials such as graphene. The two classes of applications were the separation of alcohols and other volatile organic compounds from aqueous solution, and organic/organic separations such as methanol/ethylene glycol and dimethyl carbonate/methanol mixtures. These two classes cover the areas where pervaporation has yet to achieve commercial success. The Collection concludes with two papers relating to protein purification. Vicente et al (2019) explored the application of a two-step approach combining an aqueous two-phase system and an aqueous micellar two-phase system, both based on the thermo-responsive copolymer Pluronic L-35, to the purification of proteins. Pluronic triblock copolymers are non-ionic surfactants. Harvey et al (2019) examine an advanced approach for improving the control of the chromatographic process. In this process step changes in modulator properties such as pH, solvent strength, or ionic strength are used to facilitate desorption of proteins and other chemicals. Harvey et al (2019) developed the general equations for the Standing-Wave Design of non-isocratic and non-ideal systems and showed that this method allows for fast and efficient design of Simulated Moving Bed systems. The examples given indicate that significant increases in productivity can thereby be achieved.

Keywords: Membrane separations, Spiegler-Kedem, gas separation, polymers of intrinsic microporosity (PIMs), protein purification


  • Robert Field

    Robert Field studied chemical engineering at the University of Cambridge. His research has concentrated upon the physical phenomena governing the performance, particularly limitations to performance, of both pressure driven and activity driven membrane processes. His world-leading contribution to the development of the concepts of critical flux and threshold flux for porous membrane processes has brought renown and most importantly helped to lead a revolution in industrial membrane operation.

Articles (7 in this collection)