Enhancing membrane performance by blending ATRP grafted PMMA–TiO2 or PMMA–PSBMA–TiO2 in PVDF

• TiO2 was modified by ATRP grafting with PMMA or co-grafting with SBMA.
• The modified TiO2/PVDF membrane had higher flux and better antifouling property.
• With SBMA, the flux was further increased as compared to TiO2 PMMA/PVDF.
• Optimal grafting time was 5 h, optimal ratio of KH550 to TiO2 was 3:1.
• Optimal molar ratio of PMMA to SBMA is 2:1.

To improve PVDF (polyvinylidine fluoride) membrane property, TiO2 nano-particles can be blended in casting solutions to form composite membranes. In this study, TiO2 nano-particles were modified by coupling with γ-aminopropyl triethoxy silane (KH550), then grafted with PMMA (Polymethyl methacrylate) or co-grafted with PMMA and more hydrophilic PSBMA (polysulfobetaine methacrylate) via ATRP (atom transfer radical polymerization). ATRP grafting time and weight ratio of KH550 to TiO2 were two main identified factors affecting TiO2 modification and membrane hydrophilicity, flux and antifouling properties. These were shown by Scanning electron microscopy (SEM) characterization, contact angles measurements and filtration tests with yeast suspensions. The grafted TiO2–PMMA nano particles formed after coupling at 3:1 weight ratio of KH550 to TiO2 and 5 h grafting, once composited with PVDF, formed a membrane with higher flux (up to 50%), higher flux recovery rate (FRR, 93.5%) and lower irreversible fouling (5.37%) than PVDF membrane composited with unmodified TiO2. Blending TiO2 co-grafted with PMMA and zwitterionic polymer PSBMA resulted in even better antifouling membranes (even lower Rir < 2% and even higher FRR 99%). When the molar ratio of MMA to SBMA was 2 to 1, the highest steady flux and the highest FRR were obtained.