The effects of mechanical and chemical modification of TiO2 nanoparticles on the surface chemistry, structure and fouling performance of PES ultrafiltration membranes

Recently, TiO2nanoparticles blended within polymeric membranes have shown to provide improvements in foulingperformance. However, agglomeration of nanoparticles remains as one of the major obstacles for generating a uniform surface, and also the mechanisms for improved foulingperformance has yet to be elucidated. In this study, mechanical and chemicalmodification approaches were adapted using Degussa P25 TiO2nanoparticles to improve their dispersion. Afterward, modified TiO2nanoparticles were incorporated into polyethersulfone based in-house membranes and their effect on microstructure, surfacechemistry, and foulingperformance were investigated. Different techniques such as SEM, EDX, TGA, DSC, AFM, FTIR, contact angle goniometry, molecular weight cut-off, static protein absorption and surface free energy measurement were applied to characterize and explore the effect of different factors on foulingperformance. The results showed that good dispersion of nanoparticles in the membrane was achieved after both chemical and mechanicalmodifications of particles, as a result of less agglomeration. The combination of chemical and mechanicalmodifications was found to have significant effects on surface free energy, roughness, surface pore size and protein absorption resistance as well as hydrophilicity. While previous researchers believe that the increase in hydrophilicity is the most likely reason for improvement in foulingperformance, these other parameters such as changes in membrane morphology and local surfacemodifications may contribute just as much to greater fouling resistance when the effects of unmodified and modified titania were compared.