Rapid reversible superwettability transition and controllable oil/water separation based on hierarchical CuO

Abstract

Superwetting interfacial materials have been broadly developed for extensive applications. Reversible superwetting behavior has received a great deal of attention because of the potential applications. In this paper, a hierarchical CuO coating on a stainless steel substrate was fabricated simply by a solution-immersion process at 85 °C. The as-prepared CuO-coated stainless steel surface was superhydrophilic, and obtained superhydrophobicity by modification with tetradecanoic acid for only 15 s. The modified surface converted back into superhydrophilic after being annealed in muffle furnace at 300 °C for 5 min. Moreover, the annealed surface became superhydrophobic again by remodification. A rapid reversible superwetting transition cycle was finished by modification with tetradecanoic acid and annealing treatment for only 5.25 min. When the reversible superwetting transition was applied to the CuO-coated stainless steel mesh, the resulting mesh was switchable between “oil-removing” and “water-removing” modes. Thus, the mesh was suitable for oil/water mixtures whether heavy oil or light oil is involved. After 10 cycles of the superwetting transition or separation for 10 times, the separation efficiency of both meshes remained over 99.9%. The meshes showed the stability and recyclability.