Solvent-nonsolvent regulated nano-functionalization of super-wetting membranes for sustainable oil/water separation

Super-wetting membranes with nano-functionalized surfaces hold great potential for oil/water separation, but it is still a challenge to construct layered nanostructures on hydrophobic PES matrix via the traditional nonsolvent induced phase separation (NIPS) technique. Herein, we propose a method that modulates the phase transition behavior of polyvinylpyrrolidone (PVP) and tannic acid (TA) during the exchange process between solvent and non-solvent, leading to in-situ construction of antifouling membranes with the nano-functionalized surface. By studying the phase transition thermodynamics between polyethersulfone (PES) and PVP-TA systems in different solvents, the formation mechanism of nanostructures was unraveled. Benefiting from the antifouling barrier constructed by the nano-layered structure, the prepared membrane exhibits superhydrophilic/underwater superoleophobic properties and high efficiency in separating oil-in-water emulsions (flux > 2800 L·m−2·h−1·bar−1, rejection rate > 99.5 %) and good recyclability. We believe that this study is expected to provide new insights for the design of nano-functionalized membranes by conventional NIPS technology.