The preparation of electrospun PVDF membranes and their applications in the removal of dyes, heavy metals and oil-water separation

The PVDF/PVP/SiO 2 /CS nanofibrous membrane was synthesized using polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), nanosilica (SiO 2 ), and chitosan (CS) as raw materials through a one-step electrospinning process, specifically developed for the treatment of complex oily wastewater. The membrane exhibited exceptional hydrophilicity, underwater oil repellency, self-cleaning properties, and a porous fiber structure. Its pure water flux reached 7894.50 L·m −2 ·h −1 ·bar −1 , with an average fiber diameter of 130 nm and an underwater oil contact angle exceeding 140°. The hydration layer enabled the membrane to effectively separate oil–water mixtures and emulsions composed of engine oil, carbon tetrachloride (CCl 4 ), toluene (C 7 H 8 ), soybean oil, cyclohexane (C 6 H 12 ), and other oil agents from water, achieving an efficiency greater than 99 %. Furthermore, the PVDF/PVP/SiO 2 /CS nanofiber membrane successfully captured dyes and heavy metal ions through hydration, hydrogen bonding (HB), electrostatic interactions (ESI), π-π interactions, and chelation mechanisms. The retention efficiencies of the membrane for Rhodamine B (RB), chromium ions (Cr 6+ ), methyl orange (MO), methylene blue (MB), malachite green (MG), and lead ions (Pb 2+ ) were 71.4 %, 74.0 %, 83.3 %, 85.6 %, 88.5 %, and 95.1 %, respectively. After filtration, the membrane flux values were 6042.64, 6653.40, 5689.85, 5865.40, 5732.68, and 6652.70 L·m −2 ·h −1 ·bar −1 , with a maximum membrane flux loss of no more than 25 %. The membrane demonstrated retention efficiencies of 72.4 %, 75.3 %, 79.4 %, 81.2 %, 84.3 %, and 92.3 % for the removal of RB, Cr 6+ , MO, MB, MG, and Pb 2+ from wastewater containing dual pollutants of oil–water emulsions with heavy metal ions and dyes. The separation efficiency for oil–water emulsions in the dual-pollutant wastewater exceeded 99 %.