Incorporation of green synthesized ZnO with the support of rGO sheets into PVDF membranes to improve their filtration and antifouling properties for wastewater treatment

Abstract

The growing scarcity of clean water necessitates urgent interventions in wastewater treatment. Polymeric membranes are prevalent in this domain. However, due to their hydrophobic behaviour, they become more prone to fouling. To address this issue, we synthesized hydrophilic nanomaterials as additives to prepare polymer nanocomposite membranes with enhanced hydrophilicity. The eco-friendly zinc oxide (ZnO) nanomaterial was synthesized via a green route, and reduced graphene oxide (rGO) and a rGO/ZnO composite were synthesized using a chemical process and characterized using FESEM, FTIR, XRD, and zeta potential techniques. The synthesized nanomaterials were incorporated into PVDF membranes, and the prepared membranes were characterized using FESEM with EDX, FTIR, and contact angle measurements, along with mechanical strength determination. The filtration properties of the membranes were evaluated using a dead-end filtration module. The FESEM images revealed the finger-like structure in the membranes, which increases with the incorporation of nanomaterials. The results demonstrated that among all the membranes, the rGO/ZnO-PVDF showed the highest membrane permeability due to increased membrane porosity, pore size, and finger-like macrovoid sponge structures. The rejection of BSA protein and CBB dye increased due to the negative charge provided by the ZnO in the rGO/ZnO nanocomposite. The antifouling study reveals that the rGO/ZnO-PVDF membrane had the highest FRR value of ∼50.05% among the various synthesized membranes. The disk diffusion data of the synthesized nanomaterials and nanocomposite membranes confirms their antibacterial activity and suggests that the addition of rGO/ZnO nanomaterial can provide anti-biofouling behaviour to the polymer membranes by minimizing the adhesion of bacteria on the surface of the membrane. The results showed that the rGO/ZnO-PVDF membrane possesses antifouling and anti-biofouling behaviour, useful for minimising the pollutants from wastewater.