Transport mechanisms and modelling in liquid membrane contactors

This paper discusses the use of liquid membrane contactors for extraction o f fermentation and pharmaceutical products using different types of carrier s. It intends to emphasise the importance of understanding the transport me chanisms involved in liquid membrane extraction with different carriers and also to discuss relevant aspects of the mathematical modelling involved in these extraction processes. Using the extraction of organic acids, namely amino acids, as a case study it is shown how the supramolecular organisatio n of the extractant determines the solute transport mechanisms involved. Ad ditionally, the resolution of racemic mixtures using chiral carriers is als o discussed. The modelling work analyses two different aspects of extractio n using membrane contactors with microporous membranes: (i) the importance of using a correct description of solute partition between the feed and the extractant phase (use of a variable partition description versus constant partition); (ii) the correct development of mass transfer correlations in h ollow fibre contactors. For the development of mass transfer correlations t he calculation method proposed by Wilson has been universally used. Given t he currently available mathematical tools, that enable the analytical manip ulation of equations and fittings with complex expressions, a new calculati on methodology is discussed. (C) 2000 Elsevier Science B.V. All rights rese rved.