Bilayer Compounded Polytetrafluoroethylene Membrane for Enhanced Oil-Water Emulsion Separation

In order to achieve efficient and durable oil-water emulsion separation, the membranes possessing high separation efficiency and mechanical strength attract extensive attention and are in great demand. In present study, a kind of polytetrafluoroethylene (PTFE)-based bilayer membrane was fabricated by electrospinning fibrous PTFE (fPTFE) on an expanded PTFE (ePTFE) substrate. The morphological observation revealed that the fibrous structure of the fPTFE layer could be tailored by controlling the formulation of spinning solution. The addition of appropriate polyoxyethylene (PEO) would make the fibers in the fPTFE layer finer and more uniform. As a result, the compounded membrane exhibited a small pore size of approximately 1.25 µm and a substantial porosity nearing 80%. This led to super-hydrophobicity, characterized by a high water contact angle (WCA) of 149.8°, and facilitated rapid oil permeation. The water-in-oil emulsion separation experiment further confirmed that the compounded membrane not only had a high separation efficiency closing 100%, but such an outstanding separation capacity could be largely retained, either through multiple cycles of use or through strong acid (pH=1), strong alkali (pH=12), or high-temperature (100 °C) treatment. Additionally, the mechanical behavior of the bilayer membrane was basically contributed by that of each layer in terms of their volume ratio. More significantly, the poor creep resistance of fPTFE layer was suppressed by compounding with ePTFE substrate. Hence, this study has laid the groundwork for a novel approach to create PTFE-based compounded membranes with exceptional overall characteristics, showing promise for applications in the realm of emulsion separation.