A novel pearls-like hierarchical porous silica aerogel monolith for efficient oil/water separation

Oil pollution poses serious threat to environment and ecological system. Using porous materials for absorption and separation is an effective method to treat oil polluted water. In this study, a methyltriethoxysilane (MTES) based flexible silica aerogel monolith with novel pearls-like hierarchical porous structure was prepared via ambient pressure drying. The robust and high-porosity aerogel network was composed of macropores and three-dimensionally interconnected pearls-like secondary silica particles that possess both micropores and mesopores. The hierarchical porous aerogel exhibited remarkable hydrophobic/oleophilic and oil absorption/desorption properties, with a high oil separation rate and a high absorption capacity of 5.5–8 g/g for various oils. The aerogel also showed good durability and excellent recyclability in different oil absorption/desorption test cycles. Furthermore, the absorbed oil could be effectively and rapidly removed by evaporation or pumping to realize the continuous oil/water separation. The largest flux of n-hexane pumped out from the aerogel was evaluated to be 4350 ml/h, and the separation efficiency was as high as 97.8–99.2%, indicating that the flexible pearls-like hierarchical porous silica aerogel could be a promising choice for oil/water separation.