The development of quantitative predictive models is of great significance for the successful application of membrane separation processes in the process industries. Successful models exist for the ultrafiltration of macromolecules and particles with sizes 2 to 5nm and 500nm to 10μm, respectively. None of the approaches could predict colloidal ultrafiltration rates in the intermediate size range of 5 to 500nm. This is due to interparticle interactions, especially electrostatic interactions which play an important role and which have been widely neglected or even overlooked by many membrane scientists. As a result of such interactions, changes in the ionic environment and particle zeta potential give <i>order of magnitude</i> changes in the rate of ultrafiltration. However, there has been no rigorous mathematical model for the ultrafiltration of colloids in this range that takes into account such interparticle interactions. The aim of the present dissertation was to develop and test rigorous mathematical models for membrane ultrafiltration of charged colloidal particles, which include quantitative calculations of particle-particle interactions within filter cakes, which are responsible for controlling permeation rates. This has been realized by two approaches: 1) an extended pairwise summation of interaction energies due to electrostatic or double layer forces and London-van der Waals forces through the DLVO theory and 2) by a multiparticle interaction approach based on the use of a Wigner-Seitz cell model to calculate the grand canonical electrostatic potential energy of a concentrated particle system. Dynamic ultrafiltration models for filter cakes of charged particles have been developed ('<i>From Physics To Filtration</i>') based on disjoining pressure calculations between hexagonal close packed particle layers which take the former interaction calculations into proper account. The models require no adjustable parameters. A comparison with experimental ultrafiltration results revealed that the dynamic model based on pairwise summation of interaction energies was in good agreement with the experimental filtration flux over a limited range of conditions, whereas the cell model predictions were in excellent quantitative agreement over a wide range of ionic and zeta potential conditions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637422 |
| Date | January 1994 |
| Creators | Jenner, F. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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