Fabrication of underwater superoleophobic metallic fiber felts for oil-water separation

Highlights: • The superhydrophilic and underwater superoleophobic metal felts were fabricated by facile methods. • The as-prepared metal felts can separate both oil/water mixtures and oil-in-water emulsion. • The underwater superoleophobic metal felts possessed high oil/water separation efficiency. Hierarchical nanoneedles-like Cu(OH)₂ structure coated stainless steel fiber felts (SSFF) with underwater superoleophobic (154° ± 2.2°, n-octane, oil contact angle) and low-adhesive properties have been successfully fabricated via simple nanoparticles deposition and electrochemical oxidation methods. Meanwhile, when a water droplet (5 μL) contacted the SSFF/Au/Cu/Cu(OH)₂ surface, it spread out quickly and reached a 0° CA with very short time, suggesting a superior superhydrophilic property. The SSFF/Au/Cu/Cu(OH)₂ was used to separate oil-water mixtures, oil-corrosive salt solution mixtures and oil-in-water emulsions with high efficiency, which allowed water to permeate through while retained oil. In addition, the SSFF/Au/Cu/Cu(OH)₂ still maintained high separation efficiency above 99% after 5 emulsion recycling separation times.