Robust and switchable superwetting sponge-like membrane: Towards on-demand emulsion separation and aqueous pollutant degradation

Abstract

There remains a great challenge to integrate reversible separation of emulsified oil/water mixtures and treatment of organic contaminants in complex oily wastewaters. Herein, sponge-like Co(OH)2 nanosheets coated stainless steel mesh (SSM) was designed through electrodeposition route within only 20 min. Due to the highly porous hierarchical architecture, the membrane displays superhydrophilicity and underwater superoleophilicity with water contact angle of nearly 0° and underwater oil contact angle greater than 160.1°, achieving high-efficient separation of surfactant-stabilized oil-in-water emulsion (≥99.9%) and fast permission flux up to 540 L m−2 h−1. Interestingly, reversible wettability transition for on-demand emulsified oil/water separation can be easily manipulated for at least 10 cycles by the alternation treatment with stearic acid and NaOH/tetrahydrofuran in turn. The membrane reveals outstanding superwetting stability against mechanical abrasion, heat treatment and harsh corrosive conditions. Importantly, the Co(OH)2/SSM exhibits a high catalyzing potential to effectively oxidize the aqueous contaminant (i.e. Acid Orange 7) with a maximum degradation efficiency of almost 100% in 6 min. All these attractive features make the smart membrane a promising candidate for potential extensive application in oil spill cleanup and industrial emulsified oily wastewater treatment.