Exploring the influence mechanism of ozonation on protein fouling of ultrafiltration membranes as a result of the interfacial interaction of foulants at the membrane surface

Abstract

Ozonation was widely used before ultrafiltration processes, but its effect mechanism on protein fouling is still controversial. Ozonation of bovine serum albumin (BSA) solutions was performed in the present work. The interfacial forces of BSA at the membrane surface were measured before and after ozonation. The adsorption behaviour of BSA onto the membrane surface and the fouling layer structures under different ozone dosages were also investigated. These results were combined with the membrane fouling behaviour to identify the effect of ozonation on protein fouling. The results showed that ozonation could weaken the interaction forces between the membrane and BSA effectively, but this did not have any effect on membrane fouling. In contrast, in terms of membrane fouling behaviour after pre-ozonation, the contribution of the changes in the covalent disulfide bonds between BSA molecules outweighs those of the non-covalent bonds. The number of disulfide bonds gradually increased as the O3:DOC ratio increased from 0 to 0.3, and began to decline when the O3:DOC ratio was further increased to 0.45 and 0.6. This could have altered the deposition rate of foulants onto the membrane surface and the structure of the fouling layers, and may have caused the membrane fouling first to be enhanced and then to decline with increasing ozone dosages.