Novel Organic-Inorganic Thin Film Composite Membranes With Separation Performance Surpassing Ceramic Membranes for Isopropanol Dehydration

Novel organic-inorganic thin film composite (TFC) membranes have been developed in this work, with an introduction of an inorganic component 3-glycidyloxypropyltrimethoxy-silane (GOTMS) in the chemical structure of the in-situ synthesized polyamide layer. These membranes exhibit a pervaporation separation performance surpassing most prior polymeric membranes and inorganic ceramic membranes for isopropanol dehydration. Three different modification methods are demonstrated to include GOTMS in the polyamide structure via suitable molecular design, and all resultant organic-inorganic membranes show improved separation performance as compared to the original TFC membrane without GOTMS. The TFC membrane prepared exhibits an optimized flux of 3.5 kg/m²-h with a separation factor of 278 for a feed composition of 85/15 wt% isopropanol (IPA)/water at 50 °C. This high performance can be attributed to the excellent solvent resistance of the inorganic component included and the formation of inorganic cavities in the selective layer. The changes of chemical structures and surface morphology are confirmed and characterized by Fourier Transform Infrared (FTIR) and X-ray energy dispersive spectrometry (EDX). Slow beam positron annihilation spectroscopy (PAS) technique is used to analyze the variation in the fractional free volume of the organic-inorganic TFC membranes. The newly designed and fabricated TFC membranes show a great potential to compete with those commercial inorganic membranes in pervaporation applications.