Osmotic pressure and diffusion coefficients were studied experimentally and theoretically in order to facilitate fully quantitative descriptions of ultrafiltration processes. These parameters may be incorporated in the solution of the equations for hydrodynamics and mass transfer in the filtration module. Theoretical descriptions are presented to allow calculation of osmotic pressure, taking account of the electrostatic repulsive interactions, London Van Der Waals forces, configurational entropy and additional interactions of unknown source. Approaches of constant zeta potential and charge regulation conditions were investigated for BSA, lactoferrin and silica colloidal dispersions. An experimental technique for measuring osmotic pressure was established and verified by comparison of the measured osmotic pressure with known data using BSA protein dispersions. The measured osmotic pressures of BSA solutions also agreed well with the theoretical predictions. Osmotic pressures of the commercially important protein lactoferrin solutions were also measured. Using the experimental results further refinement of the charge regulation model was made by modifying the expression of the extra attractive force, which is probably caused by interaction between sugar molecules on the protein surfaces. The refined model gives greatly improved prediction of osmotic pressure as well as ultra-filtration rate over a wide range of solution conditions. Osmotic pressures of silica dispersions were also measured and a charge regulation model was developed for the silica colloidal system. This model gives a good description of the experimental results over the conditions studied. The gradient diffusion coefficients of BSA solutions were measured by the modified Taylor's capillary method and compared with light scattering data. An analysis of electrokinetic effects in membrane pores containing electrolytes has also been carried out. The analysis uses a numerical solution of the non-linear Poisson-Boltzmaan equation and allows for the mobilities of anions and cations to be individually specified. It is shown that it is very important to use such an approach to calculate zeta-potentials from the basic electrokinetic data.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636202 |
| Date | January 2000 |
| Creators | Cao, X. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0377 seconds