The coating and reduction of graphene oxide on meshes with inverse wettability for continuous water/oil separation

Highlights: • We report a facile, cheap and green way to prepare membranes with inverse wettability. • Both meshes exhibit superior capability for water/oil separation with high efficiency. • Both types of meshes could maintain their original wettability in harsh environment. • A T-shaped bidirectional separation setup was assembled by the two types of membranes. • Continuous separation of water/oil mixtures of any oil density was achieved. We report a mild, inexpensive, environment-friendly method to fabricate graphene oxide (GO) and reduced graphene oxide (RGO) coated meshes with superhydrophilicity/underwater superoleophobicity and superhydrophobicity/superoleophilicity through scrape coating of GO nanosheets onto stainless steel mesh and electrochemical reduction of the GO coated mesh, respectively. The GO coated meshes exhibit high efficiency for unidirectional separation of mixtures of water and various light oils, while the RGO coated meshes show excellent capability of separating various heavy oils from water. Both types of meshes could maintain their original wettability in harsh environments, and demonstrate high efficiency and recyclability for the separation of water/oil mixtures containing boiling water, acid and salt. In addition, a T-shaped bidirectional device was assembled by fixing the two meshes with inverse wettability at the both horizontal ends of a T-tube, which can achieve continuous high-efficiency separation of various mixtures of water and oil regardless of their density relationship.