Enhancing Pervaporation Performance for Alcohol Recovery from Aqueous Solutions with Silicalite-1/Polydimethyldiethoxysilane (PDMDES) Nanocomposite Membranes

Abstract

This study presented a newly prepared silicalite-1/ polydimethyldiethoxysilane (PDMDES) nanocomposite membrane through the incorporation of nanosized silicalite-1 particles to enhance the pervaporation performance for alcohol recovery from aqueous solutions. Preheating was strategically employed to facilitate the formation of chemical bonds between silicalite-1 and the cross-linking agent vinyltriethoxysilane (VTES), thereby improving the compatibility between silicalite-1 and the PDMDES polymer. Comprehensive characterizations including FT-IR, XRD, TGA, and CA demonstrated a notable increase in hydrophobicity and thermal stability, attributable to the well-incorporated silicalite-1 nanoparticles. FE-SEM observation revealed two distinct cross-sectional morphologies of the nanocomposite membrane: a dense packed structure with uniformly dispersed silicalite-1 nanoparticles within the PDMDES polymer matrix and a loosely accumulated structure where silicalite-1 was adhered by the PDMDES polymer. This phenomenon was linked to the low viscosity of PDMDES during the membrane preparation, which also resulted in the actual loading of silicalite-1 in the prepared nanocomposite membranes being higher than the intended one. The separation performance, influenced by silicalite-1 loading, operating temperature, and feed concentration, was thoroughly evaluated. Accordingly, the separation factor was enhanced by 90% compared to pure PDMDES membrane, and the optimal pervaporation performance was achieved with a 10 wt % silicalite-1 loading in the nanocomposite membrane, manifesting a high total flux of 5.72 kg m −2 h −1 , a PSI of 31.36 kg m −2 h −1 , and an ethanol permeability of 184.3 × 10 −6 mol m −1 h −1 kPa −1 , when separating ethanol from 5 wt % ethanol/water solution at 40 °C. Based on the experimental findings, lower feed concentration and operating temperature were suggested in the applications of the silicalite-1/PDMDES nanocomposite membranes for efficient alcohol recovery from aqueous solution.■ HIGHLIGHTS 1. Innovative preparation of silicalite-1/PDMDES nanocomposite membranes for efficient alcohol recovery from aqueous solutions. 2. Preheating strategy utilized to enhance compatibility between silicalite-1 and PDMDES in membrane preparation. 3. Breakthrough in trade-off balances: the silicalite-1/ PDMDES nanocomposite membrane surpasses pristine PDMDES membrane in separation performance, with 90% enhancement in separation factor and more than 9.6% enhancement in total flux. 4. Low-viscosity PDMDES limits the maximum silicalite-1 loading of 10 wt % and results in exceeding designed silicalite-1 loading in membranes. 5. Exceptional separation performance: the silicalite-1/ PDMDES nanocomposite membrane achieves a high flux of 5.72 kg m −2 h −1 and a PSI of 31.36 kg m −2 h −1 in ethanol recovery.