A robust superwetting nickel foam with tuning pore features for stable and efficient separation of oil-in-water emulsions

In this study, SiO2-PNF/NiCo, a superhydrophilic nickel foam with tuning pore features was fabricated by introducing SiO2 nanofibers and in situ growing nickel cobaltate (NiCo2O4) micro-nano structures within the nickel foam. The pore size of the nickel foam was adjusted from initial 150–300 µm to modified 20–65 µm, while the porosity was still maintained above 70 %. A self-assembly columnar separator was applied to separate oil and water, with an inner diameter of 1.5 cm and an effective filtration area of 1.77 cm2. With the aid of the separator, the SiO2-PNF/NiCo could rapidly separate the n-hexane/water immiscible mixture with an extremely high flux of over 1.8 × 105 L·m−2·h−1 and an exceptional separation efficiency of over 99 %. For a variety of surfactant-free oil-in-water emulsions, it also demonstrated exceptional separation efficiencies over 99.5 % and high permeation fluxes reaching 4 × 104 L·m−2·h−1. Moreover, different surfactant-stabilized oil-in-water emulsions can also be effectively separated, with a flux up to 3.3 × 104 L·m−2·h−1 and a maximum separation efficiency of 99.76 %. Notably, even after enduring 30 cycles of abrasion, peeling and 48 h of chemical corrosion, the robust nickel foam still retained its high UWOCA (>158°), good surface roughness and stable separation performance, highlighting its potential for industrial wastewater treatment and oil spill remediation.