Polyheptylmethylsiloxane—A Novel Material for Removal of Oxygenates from Water by Pervaporation

A new membrane for the removal of oxygenates from wastewater by pervaporation has been prepared on the basis of polymethylsiloxane bearing 1-heptene as a substituent on the side chain. The synthesized membrane material has been characterized using Fourier-transform IR spectroscopy, and its sorption properties with respect to C2–C4 alcohols have been examined. It has been found that polyheptylmethylsiloxane (PHepMS) has a greater affinity for the C3 and C4 alcohols to be separated than its closest analogue known from the literature (polyoctylmethylsiloxane (POMS)), which makes the PHepMS membrane promising for the pervaporative separation of aqueous solutions of these alcohols. The pervaporation properties of PHepMS have been studied for the first time, and its separation characteristics have been compared with those of the commercial highly permeable membrane polymer polydimethylsiloxane (PDMS) and POMS in relation to the problem of recovery of n-butanol, n-propanol, and ethanol from dilute aqueous solutions by vacuum pervaporation. It has been shown that PDMS has the highest separation efficiency for n-propanol–water mixture and PHepMS is the most promising membrane material for the pervaporative separation of water–butanol mixtures. Having a butanol flux comparable to that through PDMS, the PHepMS membrane demonstrates a record-breaking value of butanol/water separation factor of 97.