Research subject: Water source pollution on a global scale exhibits a concerning growth trend. Among these, effluents containing oil pollutants present a major environmental challenge. To address this issue, various purification methods have been developed, with membrane separation technology being one of the most effective. Furthermore, a significant portion of research in membrane separation has thus far concentrated on simple oil-water two-phase mixtures, and the impact of salinity parameters on membrane performance has not been comprehensively investigated. The presence of salts can fundamentally alter the fouling mechanisms and permeability of membranes. Despite considerable advancements in the design and fabrication of oil-water separation membranes, achieving high water flux, satisfactory oil removal, and anti-fouling performance remains a formidable challenge.
Research approach: In this research, layered nanocomposite membranes were designed and fabricated utilizing phosphorous-functionalized graphene oxide nanosheets (P-GO) through a pressure-assisted layer-by-layer self-assembly method. The functionalization process of GO using phosphoric acid resulted in the formation of the P-GO structure with a significant increase in the content of oxygen-containing functional groups. Subsequently, these engineered nanosheets were deposited onto a polyethersulfone (PES) substrate, which had been pre-treated with polydopamine (PDA) to enhance adhesion and compatibility, at three different concentrations (25, 50, and 100 mg/mL) in order to evaluate the effect of nanosheet concentration on the final membrane performance.
Main results: Based on the experimental results, the mP-GO50 membrane exhibited optimal water absorption (87.61%), desirable water permeability (output flux of 81.66 L/m²·h), and 99.6% vegetable oil removal, while also demonstrating improved anti-fouling properties due to the higher negative charge of P-GO, maintaining 95.5% oil removal after ten cycles. Additionally, the effect of adding different NaCl concentrations (0, 25, 50, and 100 mg/mL) to the feed solution was investigated. With increasing NaCl concentration, the oil removal capability of the mP-GO50 membrane decreased by 1.49%, but it still showed favourable performance with 98.12% oil removal at the highest salt concentration (100 mg/mL).