A comparison of effect mechanisms of chlorination and ozonation on the interfacial forces of protein at membrane surfaces and the implications for membrane fouling control

Abstract

Pre-chlorination and pre-ozonation are the two most common pre-oxidation processes for fouling control of ultrafiltration membranes. However, few studies have explored and compared their effect mechanisms on membrane fouling behavior at the interfacial forces level. Accordingly, bull serum albumin (BSA) was used, and the changes in the interaction forces of BSA at the membrane surface after pre-chlorination and pre-ozonation were investigated. The results were combined with macro/micro analyses to unravel the effect mechanisms of chlorination and ozonation on membrane fouling behavior. Results demonstrated that the changes in the hydrophobic forces, hydrogen bonds and electrostatic repulsive forces between the membrane and BSA and between BSA molecules after pre-chlorination and pre-ozonation, were beneficial for membrane fouling control in theory, but not helpful. These changes in the non-covalent bonds appear to be completely masked by changes in disulfide bonds. The chlorination could break the disulfide bonds between BSA molecules, while ozonation could promote their formation. As a result, the deposition behavior of BSA onto the membrane surface and the structures of corresponding fouling layers after pre-chlorination were quite different from those after pre-ozonation. Finally, two different membrane fouling behaviors were observed that membrane fouling was definitively mitigated by pre-chlorination but enhanced by pre-ozonation.