Pervaporation performance of BTESE/TEOS-derived organosilica membrane and its stability in isopropanol aqueous solutions
Organosilica membranes derived from bis(triethoxysilyl)ethane (BTESE) and tetraethyl orthosilicate (TEOS) were prepared by sol-gel method on porous α -Al 2 O 3 supports and applied in pervaporation dehydration of isopropanol (IPA) aqueous solutions. The permeation characteristics of membranes in IPA/water mixture were evaluated for preparation conditions and stability, including long-term stability, acid resistance, and feed concentration. It was observed that the water contact angle of BTESE/TEOS-derived organosilica membrane decreased from (77.74±0.47)° to (36.67±1.05)° as the content of TEOS increased, which proved that the surface property of the membrane could be changed by the part of hydrocarbon units after hydrolysis condensation reaction. As the molar ratio of BTESE to TEOS was 1 : 2, the organosilica membrane showed high pervaporation performance for 90 wt% isopropanol aqueous solutions at 75 °C, with a water permeation flux of 10.580 kg·m −2 ·h −1 and separation factor of 1170. Stability experiments of long-term operation and acid environment in isopropanol aqueous solutions showed slight changes in flux and separation factor, proving that organosilica membranes had better stability. An increase in IPA concentration from 60 wt% to 90 wt% decreased both water flux and water content on the permeate side, suggesting that the effective pore sizes for permeation could be reduced by adsorption of IPA molecules, whereas the membrane remained high permeance in isopropanol aqueous solutions with high water content. The separation mechanism of pervaporation dehydration of isopropanol aqueous solutions by BTESE/TEOS-derived membrane was mainly attributed to the molecular sieve separation effect. The results showed that the BTESE/TEOS-derived organosilica membranes had an application prospect in the dehydration of aqueous-organic mixtures.
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