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Separation efficiency of membranes in biotechnology - an experimental and mathematical study of flux control

: McDonogh, R.M.; Bauser, H.; Chmiel, H.; Stroh, N.


Chemical Engineering Science 47 (1992), No.1, pp.271-279 : Abb.,Lit.
ISSN: 0009-2509
Journal Article
Fraunhofer IGB ()

Feeds containing proteins and proteins with cells have been filtered using a range of membranes of largely different pore sizes. It has been observed that the differences in operating behaviour in the longer term, across the range, are not so great as would be expected from the membrane specifications. For any particular feed solution, the observed fluxes for range membranes, with pore sizes from 10 nm to 1 Mym, are within an order of magnitude or less, even though the pure solvent fluxes of these membranes vary from 200 l/qm h to 10,000 l/qm h. By observing the operation of the membranes on a microscopic scale, using novel radio-tracer and infra-red optical techniques, it has been observed that the similarity of behaviour of these membranes goes down to the microscopic scale. Mathematical modelling describing the filtration processes in terms of the mass transfer is used to explain the governing mechanisms. This modelling, whose validity is supported by good comparison with experiment - both on the macroscopic and microscopic level-indicates that the governing factors in filtration of solutions containing a range of species - such as proteins and biological particles like cells - are the highly diffusive species. The overall performance can be described in terms of the concentration polarisation layer existing above the membrane, and direct consideration of pore blockage etc. is not warranted, once effects of interaction between such species and the membrane are described by a single phenomenological term - the rejection.