ZSM-5/Thermoplastic Polyurethane Mixed Matrix Membranes for Pervaporation of Binary and Ternary Mixtures of n-Butanol, Ethanol, and Water

In this work, the performance of a ZSM-5/thermoplastic polyurethane (TPU) mixed matrix membrane (MMM) is presented for pervaporation (PV) of n-butanol and ethanol from dilute aqueous solutions as a cheap and easy to fabricate replacement for the benchmark polydimethylsiloxane (PDMS) membranes. When compared to other PDMS alternatives, such as HTPB-PU, HBPE, or PEBA, the developed ZSM-5/TPU MMM has superior separation performance in many cases. ZSM-5 loadings were varied from 0 to 30 wt % in an effort to enhance the overall selectivity and permeability of the MMMs. Binary systems of n-butanol-water and ethanol-water were tested along with a ternary system of n-butanol-ethanol-water. Experimental results indicated that the 20 wt % ZSM-5/TPU MMM displayed the best selectivity and separation factor. By varying the operating conditions, it was also discovered that n-butanol's flux is more sensitive to temperature changes when compared to water. Further analysis revealed that n-butanol permeability was dissolution-dominated, while water permeability was diffusion-dominated. PV of n-butanol-water had a maximum selectivity and separation factor of 2.24 and 12.77, respectively. For the ethanol-water mixture, a maximum selectivity and separation factor of 0.20 and 2.27 were obtained, respectively. PV of the ternary mixture yielded maximum selectivities of 1.97 and 0.23 for n-butanol and ethanol, respectively, with the corresponding separation factors of 11.53 and 2.55. This study provides valuable evidence for further research into TPU MMMs as an easy-to-fabricate, robust, and economical competitor for PV due to their superior separation performance when compared to other alternatives.