A reverse membrane emulsification process based on a hierarchically porous monolith for high efficiency water-oil separation

A hierarchically porous monolith with macro-and meso-pores was synthesized via a sol-gel and phase separation process. Due to the surface modification by organic silanes, the wettability of the silica material was effectively controlled. A series of hydrophobic porous silica monoliths (HPSM) were obtained. Using a reverse membrane emulsification process, the HPSM not only cleared oil away from water, but also broke the micro-emulsion efficiently, even when emulsion stabilizer was in the system. As the filtration layer, 1.0 g of HPSM could treat 944 mL of oil containing water or 667 mL of surfactant-stabilized micro-emulsion. HPSM materials could remove at maximum 96.5% of the oil in water and 100% surfactant in the micro-emulsion. In addition, the material could be reused through a simple treatment. The excellent separating effect was kept even after 8 times of regeneration. Special selectivity, easy operation and excellent recyclability make the material have great potential for practical application.