The effect of modified TiO2 nanoparticles on the polyethersulfone ultrafiltration hollow fiber membranes

Addition of nanoparticles to polymer solution in membrane fabrication process has the potential to improve membrane separation performance, Recently, the mechanical and chemical modifications of TiO2 nanoparticles have shown to provide improvements in reducing the nanoparticles agglomeration and fouling in flat sheet membranes. In this study, hollow fiber PES membranes with 2 wt.% mechanically and chemically modified TiO2 were fabricated. The effect of chemical and mechanical modifications on the titania nanoparticles was compared with the effect of mechanical modification only and membranes without nanoparticles additives. The results showed that the migration of nanoparticles toward outer layer only occurred after mechanical modifications, whereas the migration and size of agglomerations reduced significantly after both the chemical and mechanical modifications of particles. Higher thermal resistance, stiffness and lower elasticity were observed in fibers made with chemically and mechanically modified particles. Enhancement in initial pure water flux due to lower intrinsic membrane resistance and bigger pore size was also observed. While the rejection of BSA remained similar and lower overall ultrafiltration resistance was observed, the benefits of particles modifications on flux recovery after cleaning of hollow fiber membranes was not observed, possibly due to a significant change in pore structure and initial permeabilities.