Laminar Structured Cellulose/Graphene Membranes Constructed from Electrostatic Attraction for Efficient Emulsion Separation

Improperly processed water-in-oil (W/O) emulsions from daily life and production negatively impact the environment. Membrane separation is particularly efficient among various W/O emulsion separation technologies. This study developed a hydrophobic oil-water separation membrane (CGZP) using electrostatic attraction between 1D micro-fibrillated cellulose (MFC) and 2D graphene oxide (GO) flakes. GO is modified with positively charged polyethyleneimine (PEI), and zinc hydroxide nanoparticles (Zn(OH)₂ NPs) are in situ grown on GO (GZP) to enhance its positive charge and dispersibility. The modified positively charged GZP particles and negatively charged MFC formed a stable, uniform multilayer structure through electrostatic attraction. The CGZP membrane with the thickness of only 150 µm, exhibited a tensile strength of 178 kPa. The random stacking of MFC and GZP, along with the spacious gaps between GZP layers, provided sufficient channels for emulsion separation. The CGZP membranes demonstrated high separation permeability (W/O: 5000-18000 L m^-2 h^-1 bar^-1) and efficiency (>99.5%) for various W/O emulsions stabilized by surfactants. Furthermore, this membrane displayed good recycling stability. This study presents a design strategy for cellulose/GO-based membranes with enhanced mechanical properties, offering an eco-friendly, cost-effective use of agricultural waste. The scalable method enables reliable oil-water purification and functional membrane applications in aqueous environments.