A facile method to fabricate a double-layer stainless steel mesh for effective separation of water-in-oil emulsions with high flux

Oil wastewater, which is generated by oil discharge from industrial processes and daily human activities, is a major source of water pollution worldwide, which poses a serious threat to the environment and the health of human beings. To date, the separation of emulsified water-in-oil mixtures has remained a challenge owing to the excellent stability displayed by water-in-oil emulsions. Therefore, developing a versatile material that could effectively separate water-in-oil emulsions is highly desirable. In the present study, a double-layer stainless steel mesh (DSSM) was fabricated by modification of a trichlorovinylsilane-pre-coated stainless steel mesh with different polymers, poly-(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(divinylbenzene) (PDVB), for application in the separation of water-in-oil emulsions. The key feature of the DSSM separation device was that it imparted superhydrophobic properties (water contact angle > 150 degrees) to the demulsifying PDMAEMA agent using PDVB. The DSSM thus afforded dual functionalities, i.e., high flux and excellent separation efficiency. The DSSM could effectively break down emulsions with the demulsifying mesh and subsequently allowed oil to pass through the superhydrophobic mesh while water remained on the mesh surface. Furthermore, the entire separation process was easy to operate, with gravity acting as the driving force, and the separation efficiency was thus high. Moreover, the DSSM maintained high separation efficiency even after 10 separation cycles. These outstanding properties make it an ideal candidate for practical application in water-in-oil emulsion separation.