A novel bird-nest-like air superoleophobic/superhydrophilic Cu(OH)2-based composite coating for efficient oil—water separation

An air superoleophobic/superhydrophilic composite coating with a unique structure was fabricated by oxidation and further modification of the copper mesh, and its design principle was clarified. This unique bird-nest-like configuration gives it instant superhydrophilicity due to the high surface roughness and high polar surface free energy components, while air superoleophobicity is caused by its extremely low dispersive surface free energy components. Furthermore, a water-resistance mechanism was proposed whereby a polyelectrolyte plays a critical role in improving the water-resistance of fluorosurfactants. It can separate oil—water mixtures with high efficiency (98.72%) and high flux (25185 L·m−2·h−1), and can be reused. In addition, our composite coating had certain anti-acid, anti-alkali, anti-salt and anti-sand impact performance. More importantly, after being soaked in water for a long time or being exposed to the air for a long time, it still retained ultra-high air oil contact angle and showed excellent stability, which provided the possibility for practical applications. Thus, these findings offer the potential for significant practical applications in managing oily wastewater and marine oil spill incidents.