At present, rapid population growth, global warming, indiscriminate drain of industrial wastewater and oil spill incur dwindling resources of available fresh water, devastatingly affecting our living environment. Hence, oil/water separation has attracted considerable attention due to the serious water pollution caused by oil spill accidents and oily wastewater from industries, etc. This has led to active researches for the improvement of oil/water separation efficiency.
Superhydrophilic-superoleophobic membranes are not fouled by oil, which means high separation efficiency and long lifetime. Hence, they are a main target for the fabrication of oil/water separation membranes.
There are many superhydrophilic-superoleophobic materials available such as fabrics, metal meshes and polymer filtration membranes. Since they are usually hydrophobic, their wettability characteristics should be improved to be superhydrophilic-superoleophobic. Dopamine has attracted much attention recently due to its potent adhesion property. Based on the strong adhesion behaviour and the intrinsic capacity for facile secondary treatments, a great number of approaches have been put forward for surface modification of solid materials.
Kim Myong Hak, a researcher at the Faculty of Chemical Engineering, has proposed a novel method to improve the hydrophilicity of stainless steel mesh by coating a polydopamine (PDA) as a transition layer on the surface of a hydrophobic stainless steel mesh and modifying a hydrophilic triblock copolymer onto the surface.
The water contact angle on the triblock copolymer-modified mesh in the air is 0°, which proves the mesh to be superhydrophilic. The oil (dichloromethane) contact angle on the surface of the modified mesh in water is 155°, exhibiting greater underwater superoleophobicity than on the surface of mesh with only a polydopamine layer.
The triblock copolymer/polydopamine modified mesh could selectively separate oil from immiscible oil/water mixtures with high separation efficiency of above 96%.