The removal of oil from the water surface is vital to protect the environment and living organisms against the threats posed by industrial oily wastewater and offshore oil spills. High cost, low efficiency, and environmental pollution limit the widespread use of the commercial methods of oil-water separation. In this study, the prewetting polypropylene-wood pulp fiber composite nonwoven fabric (PWNF) has been used in the gravity-driven separation of the oil-water mixture. The prewetting PWNF displayed superior underwater oleophobic properties, and the underwater kerosene contact angle was 137.65° ± 4.27°. The oil-water interfacial tension in the microchannels among the PWNF fibers prevented the oil from passing through the microchannels; however, it allowed the passage of water. The PWNF membrane maintained an excellent oil-water separation performance after repeated separation and long-term soaking cycles. The separation membrane maintained 75% and 50% of the initial separation performance after 40 repeat cycles and water immersion for more than 20 days, respectively. The separation rate of the PWNF membrane was also investigated as a function of salt solution concentration, temperature, and pH. Meanwhile, the influences of prewetting time, prewetting temperature, and different dyeing condition of the mixture on the separation rate were clarified. The destruction of the oil-water contact interface was suggested as the main failure mode of the developed PWNF separation membrane. The maximum kerosene height that the PWNF separation membrane could sustain was 800 mm. The obtained results confirmed that the PWNF separation membrane exhibited the high potential of widespread use in various environments for achieving efficient and stable separations, especially for the oily wastewater treatment.
Keywords: PWNF; oil−water separation; prewetting; separation rate; underwater oleophobic.