(671b) Novel Omniphobic Membrane Distillation Process Development for Low-Carbon Ethanol Extraction

The food and beverage industry, comprising of the alcoholic beverage industry, is an energy intensive sector and accounts for 10% of total industrial carbon emissions. An attempt to decrease total energy consumption could not only lead to energy savings but also lower emissions. In the alcoholic beverage industry 70-85% of the total energy consumption is accounted for by separation processes like ethanol distillation. Membrane processes offer a low cost, robust and energy efficient alternative to the existing separation techniques which use boiling point difference for separation. Using a membrane-based process while still leveraging the difference in boiling point could be an ideal substitute for this separation technique. Membrane distillation (MD) offers a unique solution to the aforementioned problem. MD employs a hydrophobic membrane which can block water, soluble salts and minerals but allows vapor to be extracted which is perfect for volatile components like methanol and ethanol with a heated feed stream. The temperature required for separation is much lower than the boiling points of individual components at ambient pressure which can be achieved through low-grade waste heat, easily available in industry. Another important consideration for the MD system’s heat management which involves loss of the feed heat leading to a decrease in process efficiency. In this work we develop a novel Omniphobic thermally resistant membrane for the membrane distillation of ethanol and water. A two-step modification process is employed to make these novel membranes. The 1st step involved fabrication of the Omniphobic layer on the feed side and the 2^nd step involved development of a thermally resistant coating on the permeate side. The Omniphobic membrane is developed by functionalization of surface using diatomaceous earth with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane group leading to a super-hydrophobic surface (contact angle >180º). The thermally resistant coating was achieved by employing TiO₂ pigments which have shown to improve heat reflective properties. The membrane fabrication was characterized by pore sizes, contact angles and surface properties. The membrane showed an enrichment of ethanol from 10% to >40% through a flux of 0.6 L m² h^-1 and a selectivity of >4 which is 20% and >40% improvement as compared to present day commercial membranes in use at 65 ºC. This membrane-based process, when employed with waste heat could also contribute to lower the 70% reduction in carbon intensity and 80% savings from energy usage