Preparation and benchmarking of thin film supported PTMSP-silica pervaporation membranes

Abstract

Supported silica filled poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were optimised in terms of silica filler loading and top layer thickness, and applied in the pervaporative separation of dilute aqueous ethanol and butanol mixtures (5 wt.%). Addition of hydrophobic silica clearly increased the permeate flux at the expense of the alcohol/water selectivity. Based on its maximal pervaporation separation index (PSI) an optimum was found for a 25 wt.% silica filled membrane with a PTMSP separating layer of 2.4 μm thickness. This membrane exhibited a flux of 9.5 kg m−2 h−1 in combination with an ethanol/water separation factor of 18.3. In the pervaporation of a butanol/water mixture, a flux of 9.5 kg m−2 h−1 and accompanying separation factor of 104 was obtained. A benchmark of this optimised supported PTMSP-silica nanohybrid membrane against two commercially available PDMS-based membranes clearly demonstrated the superior flux/selectivity combination of the prepared thin film silica filled PTMSP membranes in the removal of alcohols from dilute aqueous mixtures. Compared to the commercial membranes, a 4- and 3-fold increase in flux and a 2- and 3-fold increase in alcohol/water separation factor was observed for the optimised supported PTMSP-silica membrane in the separation of a 5 wt.% ethanol/water and butanol/water mixture, respectively.