Thin film nanocomposite nanofiltration hollow fiber membrane fabrication and characterization by electrochemical impedance spectroscopy

Nano-TiO₂ nanoparticles were incorporated into thin film nanocomposites (TFN) formed on hollow fiber support membranes composed of a blend of polysulfone and multi-walled carbon nanotubes. Three different TiO₂ nanoparticles (0.01%, 0.05% and 0.2% w/v) in the thin film composite were investigated. Formation of the nanocomposite polyamide layer was confirmed by the results of FTIR and scanning electron microscopy. Double-layer capacitance values obtained from electrochemical impedance spectroscopy results showed that effective surface area of the membranes was enhance by the incorporation of nano-TiO₂. Nanofiltration membrane performance was examined using solutions of MgSO₄ and NaCl under cross-flow system with hollow fiber nanofiltration modules. Fouling of the membrane was evaluated with solutions of humic and tannic acids. The permeate flux of TFN 0.05 composite membranes was improved nearly 12 times with the incorporation of TiO₂ with rejections of MgSO₄ and NaCl salts of 22% and 5%, respectively. The rejections of the NF membranes for HA and TA were 84% and 74%, respectively, with improved antifouling properties compared to the thin film composite membrane without TiO₂, the latter being attributed to increased hydrophilicity of membrane surface.