Fabrication and characterization of a novel polyvinyl alcohol-graphene oxide-sodium alginate nanocomposite hydrogel blended PES nanofiltration membrane for improved water purification

Novel asymmetric microporous polyethersulfone (PES)/polyvinyl alcohol-graphene oxide-sodium alginate (PVA-GO-NaAlg) nanocomposite hydrogel (HG) blended nanofiltration membranes with preferable characteristics were fabricated with the phase inversion induced by immersion precipitation technique. The hydrophilic PVA-GO-NaAlg nanocomposite hydrogel with carboxyl, hydroxyl, carboxylate ions and epoxy groups was in situ formed by chemical crosslinking in presence of the saturated boric acid and CaCl₂ curing solution and characterized with SEM, XRD and FTIR analyses. Distinct quantities of the nanocomposite hydrogel were applied in the PES doping solutions for modifying membrane characteristics and the results were compared by pristine PES and PES/polyvinyl pyrrolidone (PVP) membranes. The prepared membranes characterization was performed using SEM, AFM, ATR-FTIR, water contact angle, overall porosity and mean pore radius measurement. Pure water flux, antifouling ability and dye rejection properties were also studied. By HG concentrations enhancement up to 1 wt%, the permeability of the membranes were improved and also antifouling ability of membranes were improved. The hydrogel blended membranes showed Lanasol blue 3R dye rejection more than 83%. Results of comparing PVP additive with HG indicated that the HG could increase hydrophilic property of membrane and result in permeability and antifouling ability improvement. On the other hand, the PVP additive has effective efficiency in membranes porosity and permeability improvement. Hence, the membrane by 1 wt% PVP and 1 wt% HG was fabricated for studying the coupling effect of these two additives, which indicated better solution flux and antifouling properties.