Modification of ceramic membrane surfaces using phosphoric acid and alkyl phosphonic acids and its effects on ultrafiltration of BSA protein

Abstract Surface properties are known to play an important role in ultrafiltration processes. Phosphoric acid and alkyl phosphonic acid were linked to the surface of titania and zirconia membranes to modify the interactions between the membrane and the molecules in the bulk solution. The adsorption mode of the phosphate derivatives was characterised by direct analysis using infrared spectroscopy. BSA filtrations were performed using an ultrafiltration titania membrane with different surface modifications. The contributions of both the electrostatic interactions between the protein and the membrane surface, and the competitive reactions between BSA and ions in solution, were separated. The competitive reactions of BSA and phosphate ions on the titania surface have to be managed to reach the maximum adsorption of phosphate before the protein filtration. Increase in membrane hydrophobicity also improves BSA rejection.