Durability studies of underwater superoleophobic graphene oxide coated wire mesh.

Due to the increased industrial oily wastewater, developing a successful oil/water separation mechanism is a ubiquitous challenge. As oil/water separation is an interfacial phenomenon, a straightforward way is to utilize the special wettability of novel materials towards oil and water. In this work, we intend to construct a durable membrane/mesh that can have a selective response towards oil and water based on the difference in surface tension. Graphene oxide (GO) is one such material that exhibits in-air hydrophilicity and underwater superoleophobicity. GO-coated wire meshes can act as membranes with excellent efficiency for oil/water separation, but they lack long-term durability for repeated use under different environments. We created GO*-coated wire meshes by dip coating multiple layers of GO with intermediate air plasma treatment. While the multiple steps of coating ensured complete coverage of the mesh with GO, plasma treatment improved the binding of the GO coating to the wire mesh. After coating five GO layers, the mesh is subjected to mild plasma treatment to improve the porosity. The GO*-coated mesh is extremely hydrophilic in air, and the underwater oil contact angles (CA) are ≥125° for different oils. To test the long-term durability, the GO*-coated mesh is continuously immersed underwater in acidic and basic media, and the underwater oil CA is measured at different immersion times. The initial durability results are very promising and show that the GO*-coated mesh retains a significant level of underwater oleophobicity even after 60 days of continuous immersion in water.