Bilayer Superwetting Nickel Foam ( NF ) Composite Used for the Efficient Separation of Oil‐in‐Water Emulsion

ABSTRACT Superwetting materials are increasingly used in the field of oil/water separation due to their special surface wettability. Herein, a single‐layer superhydrophilic/underwater superoleophobic material was rapidly prepared by ultrasound‐assisted and seed‐mediated growth methods using nickel foam (NF) as the carrier, polydopamine (PDA) as the binder, and HKUST‐1 as the filler. Two sheets of modified NF were then laminated into a bilayer HKUST‐1/PDA/NF composite and used for the separation of oil‐in‐water emulsions. The sonication time and HKUST‐1 seed content were optimized during the preparation process, and their effects on the underwater surface wettability, separation flux, and efficiency were thus investigated. The as‐prepared NF composite also exhibited remarkable antifouling performance and excellent thermal and chemical stability. Additionally, the unique three‐dimensional structure of NF enabled its robust and wear‐resistant property. After ultrasonication for about 1 h and 25 mechanical abrasions, the underwater superoleophobic angle still remained above 150°. More notably, under gravity drive, the as‐prepared composite demonstrated superior separation efficiency above 98% for each of the selected oil‐in‐water emulsions. The developed method may offer a fast and facile approach to fabricate stable, chemically and mechanically robust materials with underwater superoleophobicity for the treatment of oily wastewater.