Pervaporation performance and characterization of organosilica membranes with a tuned pore size by solid-phase HCl post-treatment

Highlight
• BTESE membranes were prepared at 100 to 300 °C by sol–gel method on α-Al2O3 support.
• BTESE membrane fired at 100 °C showed a PV water flux of 3.41 kg m−2 h−1 with α of 230.
• Solid-phase HCl post-treatment was applied to tune BTESE membrane pore size.
• PV water flux kept constant while α increased from 230 to 3960 after HCl treatment.
• PAL and BET results proved successful tuning of pore size via solid-phase HCl treatment.

Organic–inorganic hybrid silica membranes were prepared from 1, 2 bis (triethoxysilyl)ethane (BTESE) by sol–gel processing at temperatures as low as 100 °C, followed by solid-phase HCl-assisted post-treatment to tune the silica network by reducing the pore size. The Brunauer–Emmett–Teller (BET) surface area, thermogravimetric (TG) and positron annihilation lifetime (PAL) showed reduced pore sizes and a densified network structure of BTESE powder after the HCl-assisted treatment. The HCl-assisted treatment increased the permeance ratios of both He-to-N2 and He-to-C3H8, while the permeance of He was decreased. During the pervaporation (PV) dehydration of a 90 wt% (wt%) isopropanol (IPA) aqueous solution at 75 °C, a BTESE membrane fired at 100 °C with HCl treatment showed a stable PV water flux of 2.46 kg m−2 h−1 and a separation factor of 3960 for more than 80 h, confirming the successful preparation of BTESE membranes at low firing temperatures. The BTESE-derived silica networks were successfully and easily controlled by this novel HCl-assisted post-treatment.

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