Hierarchical oil-water separation membrane using carbon fabrics decorated with carbon nanotubes

The study adopts an efficient spin-coating method to disperse fluorinated carbon nanotubes (CNTs) onto carbon fabrics (CFs) as hierarchical oil-water separation membrane. The topography observation indicates that multi-walled CNTs with an average diameter of 30-50 nm are coated over the CF surface, forming a nano/submicron scaled roughness. The CNT-CF membrane exhibits superhydrophobic behavior (water contact angle: 165°), low wetted surface fraction (5.5%), and low work of adhesion (Wad: 2.5 mJ/m2). The oil-water separation efficiency of CNT-CF membrane can reach to 99.7%, better than the CF membrane without the CNT decoration. The robust design of CNT-CF membranes enhances not only the oil-water separation efficiency but also the permeability. The enhanced efficiency can be ascribed to the fact that the decoration of fluorinated CNTs is capable of lowering roll-off kinetic energy barrier, proved by the oil-water separation mechanism. Accordingly, the difference of Wad values between oil and water droplets can be taken into account as a crucial index for evaluating the separation efficiency, favoring the development of oil-water separators and filtration units in the future.