Preparation and characterization of low fouling novel hybrid ultrafiltration membranes based on the blends of GO-TiO₂ nanocomposite and polysulfone for humic acid removal

In this work, graphene oxide (GO)-TiO₂ nanocomposite was synthesized by in situ sol-gel reaction at pH=2 using GO nanosheets suspension and titanium isopropoxide precursor. The synthesized GO-TiO₂ nanocomposite was explored as a filler to fabricate improved antifouling novel hybrid ultrafiltration membranes for removal of humic acid from aqueous solution. Membranes were fabricated from polymer blend solutions containing polysulfone and GO-TiO₂ with varied loading amount (0-5 wt%) by the non-solvent induced phase separation (NIPS) method. Contact angle, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and outer surface zeta potential studies were conducted in order to characterise the membranes in terms of roughness, structure, surface properties and charge. The porous hydrophilic hybrid membranes were shown to have an asymmetric structure with improved surface roughness. The water permeability and antifouling capacity of hybrid membranes with 10 ppm HA solution were dependent on the loading amount of GO-TiO₂. Incorporation of GO-TiO₂ nanocomposite was found to improve the antifouling characteristics of the membranes when challenged with HA solutions. Irreversible HA fouling was substantially reduced with increased loading of GO-TiO₂ nanocomposite (wt%). The lowest irreversible fouling ratio (3.2%) was obtained for the membrane containing 5 wt% nanocomposite (to total wt% of PSf, MG-5). Ultrafiltration of HA solutions of varied concentrations using hybrid membranes was studied at pH=7 and 1 bar feed pressure. The removal efficiency of hybrid membranes for HA was controlled by the membrane surface charge concentration, porosity and HA exclusion. The membrane MG-5 had the highest HA removal efficiency for 10 ppm HA solution at pH=7.