Flexible nanofiber composite membrane with photothermally induced switchable wettability for different oil/water emulsions separation

[Display omitted] •A nanofibrous composite membrane with photothermally induced reversible wettability is prepared.•PNIPAM improves the interfacial interaction and hence the durability of the nanofiber composite.•The composite membrane can separate different oil/water mixtures and emulsions with excellent recyclability. How to quickly, conveniently and efficiently separate different kinds of oil–water mixtures and emulsions remains a great challenge. Herein, we fabricate a photo-thermally responsive nanofiber composite membrane with switchable superwettability by carbon nanotubes (CNTs) adsorption onto electrospun polyurethane (PU) nanofibers and then poly (N-isopropyl acrylamide) (PNIPAM) modification. The PNIPAM enhances the interfacial interaction between CNTs and PU nanofibers without sacrificing the flexibility of the membrane. The outstanding photothermal conversion behavior endows the nanofiber composite with quick reversible conversion of superhydrophilicity and good hydrophobicity. The nanofiber composite membrane can successfully separate the oil/water mixture with different oil densities, oil-in-water emulsions at room temperature and water-in-oil emulsions under the assistance of the infrared light, with both high liquid permeation flux and separation efficiency. In addition, the PNIPAM/CNTs@PU shows superior cyclic separation performance. This multi-functional composite membrane exhibits promising applications in intelligent, smart and controllable separation of oil contaminated wastewater.