Nanoflower-branched layered double hydroxide (LDH)-wrapped electrospun membrane synthesized with ZIF-67 templates for oil-containing emulsified wastewater separation

Designing hierarchical micro/nanostructures on the surface of a membrane to endow it with underwater superoleophobic properties and oil-fouling resistance, poses a considerable challenge. In this study, we propose an elaborate method for depositing layered double hydroxides (LDHs) on a ZIF-67 surface grown along nanofibers, resulting in a nanoflower-branched nanofibrous membrane (ZnCo-LDH@PAN) with an abundant cavity structure. The ZnCo-LDH@PAN membrane exhibited excellent mechanical and superdrophilic/underwater superoleophobic properties, reaching an outstanding separation efficiency (>99.0 %) for crude oil emulsion and various sodium dodecyl sulfate (SDS) stabilized oil/water emulsions, and a separation flux of up to 5434.8 L m−2 h−1 under a low-pressure drive. In the continuous separation of 1700 mL emulsion, the efficiency remained relatively stable, and the FRR (flux recovery rate) can be as high as 97.8 %. Further, the ZnCo-LDH@PAN membrane exhibited good mechanical and chemical stabilities. Overall, this study presents an advanced approach for designing separation membranes by combining LDHs with nanofiber-derived materials.