My talk will focus on the many apparent similarities that exist between glassy polymers and carbon molecular sieve (CMS) membranes, and describe how on a fundamental level, the mechanisms behind these observations are entirely different. CMS membranes are derived via high temperature (>500 ̊C) pyrolysis of polymer precursors and provide excellent separation performance for many challenging gas-pairs. Examples include CO2/CH4, C2H4/C2H6, C3H6/C3H8, O2/N2 and CO2/N2 separations and for all these cases, CMS membranes exceed the so-called “polymer performance upper bound”. Beyond excellent separation properties, CMS membranes have the advantage of being processable into hollow fiber formats, which are the preferred membrane configurations for large-scale gas separations.
Both glassy polymers and CMS membranes show physical aging – a phenomenon by which the membrane loses its productivity with time. Unlike the “free-volume theory” commonly used to explain physical aging in glassy polymers, CMS membranes age due to tightening of a specific structural feature – viz. slit bypass pores. Moreover, transport in glassy polymers is described by dual-mode sorption and transport theory, which is also applicable to CMS, yet the physical origin of this mechanism is unique in the case of CMS. The discussion about these features would essentially highlight the most recent fundamental discoveries in CMS membranes. Additionally, I will touch upon how these features could be leveraged to create membranes with unprecedented performance for emerging separation challenges.
Dr. Oishi Sanyal is an Assistant Professor in Chemical Engineering at West Virginia University leading a research program focused on membranes for water treatment and gas separation. Her group’s current efforts are directed towards advanced membrane manufacturing strategies as well as establishing membranes as the next generation separation tools for newer applications beyond traditional desalination. Prior to WVU, she was a postdoctoral researcher at Georgia Tech (Advisor – Prof. Bill Koros) where she worked on the fundamentals of carbon molecular sieve membranes for gas separation. Oishi received her PhD in Chemical Engineering from Michigan State University (Advisor – Prof. Ilsoon Lee) where she developed polyelectrolyte-based membranes for ion rejection and wastewater treatment. She is currently on the Early Career Editorial Board of Separation and Purification Technology (Elsevier) and a Topic Editor for Sustainability (MDPI).