Fabrication of Reduced Graphene Oxide-PVDF Composite Membranes via In-Situ Reduction for Enhanced Desalination by Membrane Distillation
摘要
Water scarcity presents a critical challenge to global sustainable development. Membrane distillation (MD) is a promising technology for desalination, yet its performance is often limited to the properties of the hydrophobic membrane. This study reports a facile in-situ reduction strategy to fabricate reduced graphene oxide (RGO)-polyvinylidene fluoride (PVDF) composite membranes for enhanced direct contact MD (DCMD). The composite membranes were designed for robust desalination and potential treatment of hypersaline wastewater. Hydrazine hydrate was employed as the reducing agent within the PVDF casting solution to simultaneously induce phase inversion and the reduction of GO to RGO. The effects of RGO loading on membrane properties were systematically investigated. The optimized membrane (R-4, with a GO precursor concentration of 9 g/L) exhibited a water contact angle of 105.13°, a liquid entry pressure of 2.05 bar, and a high permeate flux of 11.21 kg·m–2·h–1 when treating a 3.5 wt % NaCl solution at 60 °C, representing a 1.46-fold flux enhancement over a commercial PVDF membrane while maintaining stable salt rejection > 99.9% during a 336-hour test. The improved performance is attributed to the synergistic effect of RGO, which simultaneously enhanced membrane hydrophobicity, refined the pore structure towards a more uniform distribution. This work demonstrates the great potential of the in-situ reduction strategy for developing high-performance and robust MD membranes for water treatment applications.