Facile preparation of superhydrophilic and underwater superoleophobic mesh for oil/water separation in harsh environments

An effective solution to separate oil and water is urgently needed owing to the increasingly serious problem of oil pollution. Numerous studies have been done to endow ordinary materials with extreme wettability for oil/water separation. Unfortunately, most of these materials cannot work in harsh environments, resulting in the low stability and practicability in practice. Herein, a facile method was proposed to fabricate superhydrophilic and underwater superoleophobic mesh by immersing ordinary mesh in a mixture of sulfuric acid (H2SO4) and chromium trioxide (CrO3). After immersing for just 1 min, the mesh was endowed with superhydrophilicity (CA = 0°) and underwater superoleophobicity (hexane CA = 151°, SA = 14°). Increasing the immersion time to 3 min, the prepared mesh exhibited better superoleophobicity. A separation device was developed based on the prepared mesh and the separation efficiencies for diverse oil/water mixtures containing acid, alkaline, salt and hot water were above 95%. The device retained a high efficiency after being reused for 20 times and the prepared mesh maintained superoleophobicity after immersing underwater for 72 h and abrasion test of 100 cycles. This oil/water separation method is easy-to-use, inexpensive, power-free and it can be used to separate caustic oil/water mixtures.