Hydrophobic mesoporous organosilica membranes: Preparation and application in the separation of volatile organic compounds from water

Mesoporous organosilica membranes were synthesized by sol-gel and dip-coating method using 1,2-bis (triethoxysilyl) ethane (BTESE) as precursor, triblock copolymer poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (P123) as surfactant template. After silylated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES,C8) by post-grafting approach, the membranes were used for the separation of hazardous volatile organic compounds (VOCs) from water via pervaporation process. The results show that ethanol-extraction is considerably effective to remove the surfactant template. The membranes show a smooth surface and a sharp pore size distribution centered at 3.5 nm. The hydrophobic property has been enhanced after silylated with PFOTES, leading to a water contact angle of (105 ± 0.1)°. Hydrophobic mesoporous organosilica membranes are selective toward VOCs and show the highest total flux of 0.36 kgm−2h−1 for methyl tert-butyl ether (MTBE) aqueous solution and the highest MTBE/water separation factor of 27.9. The pervaporation performance depends on the affinity between VOCs and grafted C8 groups. Repeated separation experiments reveal that the membranes are durable in aqueous solution due to the presence of water-resistant Si–C bonds within the framework.