Incorporation of electrochemically exfoliated graphene oxide and TiO2 into polyvinylidene fluoride-based nanofiltration membrane for dye rejection

Abstract

In this work, the novel direct synthesis method of dimethylacetamide-based graphene oxide (GO) was performed through electrochemical exfoliation assisted by commercially available single-tail sodium dodecyl sulphate (SDS) surfactant. Then, the synthesised GO (SDS–GO) was incorporated into polyvinylidene fluoride (PVDF) solution to produce a nanofiltration (NF) membrane through the phase immersion method. The addition of GO into the preparation of membrane solution alters the membrane morphology and improves the hydrophilicity. TiO2 was also used as an additive for the NF membrane fabrication to further increase the membrane hydrophilicity. The fabricated PVDF/SDS–GO/TiO2 and PVDF/SDS–GO NF membranes were compared with pure PVDF membrane. Then, the fabricated NF membranes were tested for methylene blue (MB) rejection with 10 ppm MB concentration. On the basis of the dead-end cell measurement operated at the pressure of 2 bar, the PVDF/SDS–GO/TiO2 presents high MB rejection (92.76%) and the highest dye flux (7.770 L/m2 h). This dye flux value was sevenfold higher than that of pure PVDF membrane (1.146 L/m2 h) which was due to the utilisation of both GO and TiO2 that improved the membrane hydrophilicity as indicated by the lowest contact angle (64.0 ± 0.11°). High porosity (57.46%) also resulted in the highest water permeability (4.187 L/m2 h bar) of the PVDF/SDS–GO/TiO2 NF membrane.