Robust design of reinforced superhydrophobic FEP-SiO2@PTFE hollow fiber membrane for waste lubricating oils treatment

The shortage of petroleum resources brings the regeneration of used lubricating oils (ULOs) to a major issue, and hence the superhydrophobic membranes attract extensive attention derived from lotus-effect and capillary forces. In this paper, a superhydrophobic FEP-SiO2@PTFE hollow fiber composite membrane (HFCM) based on a facile step-by-step adhesive bonding method with a water contact angle up to 154.1°. The multilayered structure with superhydrophobic separation layer, microporous structure transition layer, and high strength supporting layer could be constructed. The lubricant permeate flux of membrane was as high as 814.5 L·m−2·h−1·bar−1 at 100 °C, with separation efficiencies of 99.3 % and 98.9 % for lubricants containing activated carbon and SiO2, respectively. Meanwhile, the flux of the membrane was stabilized at 430.9 L·m−2·h−1·bar−1 after 200 h of operation, and showed an initial permeation of 680.1 L·m−2·h−1·bar−1 after 5 cycles. Prominent mechanical properties and thermal-resistance (breaking strength of about 165.0 MPa, thermal decomposition temperature was up to 380℃) are another excellent performance of the membrane. As a result, the membrane provided another preferred option for the recycling of heavy oils, such as ULOs, at high temperatures or in various harsh environments.