A pair of MnO2 nanocrystal coatings with inverse wettability on metal meshes for efficient oil/water separation

Abstract Water contamination arising oil spill and industrial oily wastewater discharge has posed a severe threat to ecological environment and human health. To address the issues, the metal meshes with superwetting performance for selective oil/water separation have received extensive attention. But, it is still a great challenge to fabricate durable meshes with special wettability and high liquid intrusion pressure, which can be utilized for oil/water separation under harsh environments. Herein, two types of MnO2 nanocrystal coated meshes with inverse wettability, namely superhydrophobicity and underwater superoleophobicity, were fabricated via a single hydrothermal strategy or combining dipping modification. The resulting superhydrophobic mesh and underwater superoleophobic mesh are suitable for removing heavy oil and light oil from water, respectively. The oil/water separation efficiencies of greater than 96.2% are achieved for the two meshes. Importantly, both meshes exhibit quick separation rate for the permeable liquid and high intrusion pressure (>1.38 kPa) for the intercepted liquid, and can maintain excellent superwetting performance and high oil/water separation efficiency under harsh environments (acidic, alkakine and high-concentration salt solutions). We believe the as-fabricated meshes are promising and effective filters for purifying oil-polluted water.