Green and rapid fabrication of superhydrophilic and underwater superoleophobic coatings for super anti-crude oil fouling and crude oil-water separation

The development of surfaces with super anti-crude oil-fouling behavior and crude oil-water separation properties is still a global challenge owing to the high viscosity of crude oil. Herein, superhydrophilic and underwater superoleophobic surfaces were successfully prepared by a simple, green and environmentally friendly one-step dip coating method. In the whole process, microcrystalline cellulose with hydrophilic hydroxyl functional groups was introduced into the coating with the help of inorganic adhesives, water was the only solvent, and no other organic solvents or surface modifiers was added. Besides being highly resistant to low viscosity oils and achieving effective oil-water separation (more than 98.3% separation efficiency after 30 cycles), the surface effectively resisted crude oil adhesion and achieved high viscosity crude oil-water separation. In addition, the underwater oil contact angle can still reach 147.5° and 152.5° after 20 cycles of sandpaper friction tests and 50 cycles of finger pressure tests, respectively, which indicates excellent durability. Furthermore, the method can achieve excellent superhydrophilicity and underwater superoleophobicity on varieties of substrates (such as copper foil, aluminum sheet and glass), showing very extensive applicability. It is expected that such fabrication strategy can provide a low cost, green and environmentally friendly approach to construct a series of superhydrophilic and underwater superoleophobic surfaces to achieve super anti-crude oil-fouling and (crude) oil-water separation. • Superhydrophilic and underwater superhydrophobic coatings were fabricated by a simple one-step dip coating method. • Water is the only solvent, and the methodology is green, environmentally friendly and versatile. • Both super anti-crude oil fouling and crude oil-water separation are achieved by the coatings. • The obtained surfaces are durable and robust.