Durable and Efficient Oil/Water Separation Enabled by Superhydrophilic/Underwater Superoleophobic Polyvinylidene Fluoride/Mesh Binary Composite Membranes

The escalating discharge of oily wastewater presents a considerable threat to both ecological systems and human health, making the development of efficient treatment technologies an ongoing challenge. This study constructed binary composite membranes that effectively integrate polymeric and metallic substrates by integrating a polyvinylidene fluoride (PVDF) membrane with an acid-etched copper mesh (CM). The binary composite membranes were subsequently modified with a polydopamine/polyethylenimine (PDA/PEI) complex to produce superhydrophilic and underwater superoleophobic PVDF/mesh binary composite membranes (PP@PVDF/triethyl phosphate (TEP) n -roughened CM (RCM)). By varying the mass ratio of PVDF to the solvent TEP, the phase separation kinetics were systematically regulated, resulting in five distinct membranes with tailored pore sizes and porosity levels. Among these, PP@PVDF/TEP 30 -RCM exhibited outstanding separation performance for various immiscible oil–water mixtures, achieving separation efficiencies exceeding 99.60% and reaching a maximum of 99.97%. When applied to the separation of surfactant-stabilized oil-in-water emulsions under gravity-driven conditions, PP@PVDF/TEP 30 -RCM demonstrated high permeation fluxes, all above 1010 L·m −2 ·h −1 , coupled with separation efficiencies exceeding 99.10%. Furthermore, PP@PVDF/TEP 30 -RCM maintained high separation efficiency over 15 repeated cycles. The PVDF/mesh binary composite membranes developed in this work combine high separation efficiency with robust durability, making them promising candidates for the sustainable separation of challenging oil/water emulsions.