Novel heterogeneous membranes for enhanced separation in organic-organic pervaporation
Katarzyna Knozowska, Guoqiang Li, Wojciech Kujawski, Joanna Kujawa
Abstract
Novel heterogeneous membranes based on poly(ether block amide) and poly(dimethylsiloxane) were prepared and modified by incorporating the grafted alumina oxides into the polymer matrix. Membranes were subsequently used for separation of organic solvent mixtures (ethyl acetate/ethanol and ethyl acetate/isopropanol). There were four types of grafting compounds applied in this research: octyltriethoxysilane (C6), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FC6), tetradecyltriethoxysilane (C12), 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (FC12). The influence of incorporation of grafted alumina oxide on physicochemical, equilibrium, transport, and separation properties was investigated. Pervaporation results were assessed using thickness-normalized Pervaporation Separation Index (PSIN) and separation factor (β). Additionally, membrane performance and equilibrium properties were discussed using Hansen's Solubility Parameters. It was found that incorporation of grafted alumina oxide improved membranes performances. The best efficiency during the separation of ethyl acetate/ethanol and ethyl acetate/isopropanol mixtures was found for membranes modified by alumina oxides grafted with octyltriethoxysilane (βEtAc/EtOH = 3.9, βEtAc/IPA = 3.4) and 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (βEtAc/EtOH = 4.3, βEtAc/IPA = 3.6). Moreover, the presence of water traces (in the range 0.1–0.3 wt%) in feed and permeate was monitored and correlated to the membrane material features. It was found that the presence of water in permeate depends on the character of the membrane and the filler used. The enrichment factor of water for PDMS/(Al2O3+FC12) obtained during separation of EtAc/EtOH and EtAc/IPA was equal to 1.11 and 0.95, respectively.