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 (W_ad: 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 W_ad 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.