(6io) Morphology Engineering of Carbon Molecular Sieve Membranes for Advanced Separations

The high “energy penalty” associated with traditional separation techniques like distillation and amine scrubbing has motivated interest in advanced membrane based novel materials and processes. These membranes are useful for a wide range of applications such as post-combustion CO₂ capture, natural gas purification and olefin-paraffin separation in petrochemical streams. My research will focus on advanced Carbon Molecular Sieve (CMS) membranes in highly productive hollow fiber configurations. CMS membranes, formed via pyrolysis of specialty polymeric precursors under various atmospheres, can be tuned to address all of the above-mentioned separations. Engineering of a bimodal distribution of micropores and ultramicropores in CMS membranes, provides high penetrant flux and extraordinary angstrom-level molecular discriminating ability.

I will tackle the core fundamental issues to facilitate the development of these membranes as the preferred tools to revolutionize large scale energy intensive separations. To achieve this goal, advanced material characterization methods are needed to complement transport-based analyses. This ambitious undertaking will begin by pursuing the following three proposed thrusts, ideally in collaboration with experts in advanced complementary methods.

Proposal 1- The goal of the first project will be to not only clarify but also control the “precursor to carbon” formation pathway to create new CMS membranes. Besides extensive transport characterization and analysis, microscopic and spectroscopic techniques will be the main tools to achieve the goals of this thrust. A specific objective of this project involves precise control of the “defect ultramicropores” present in the CMS structure. Achieving this control can allow fine-tuning of the diffusivity of penetrant molecules without significantly reducing the overall sorption capacity of the membranes.

Proposal 2- To implement CMS membranes practically, configuration into asymmetric hollow fiber formats with high surface area to volume ratios is paramount. The presence of a “hyperskin” at the outermost selective CMS surface layer reduces productivity, without improving molecular selectivity. Understanding the mechanism behind the formation of this “hyperskin” and developing strategies to eliminate it, will be the primary aim of the second proposal. Techniques like Positron Annihilation Lifetime Spectroscopy (PALS) will be used in conjunction with transport studies and processing to elucidate and control the “hyperskin” properties.

Proposal 3- Unlike the hyperskin, avoiding large scale substructure collapse involves attention to the macroporous support that has no separation function, per se. Such collapse during the pyrolysis process in asymmetric CMS fibers, lowers overall membrane productivity. Existing solutions to overcome the support collapse fail at high pyrolysis temperatures that are needed for many applications. My third research proposal will address this higher pyrolysis temperature regime using alternate anti-collapse strategies. This project will enable creation of next generation asymmetric CMS membranes for diverse applications not accessible by current approaches.

Research Background

I have worked on both liquid and gas separation membranes during my doctoral and postdoctoral research. As part of my postdoctoral research with Prof. William J. Koros at Georgia Tech, I have focused on CMS hollow fiber membranes. At GT, I discovered and analyzed the presence of a “hyperskin” in CMS membranes. I also worked on approaches to mitigate physical aging in CMS membranes, which can cause undesirable loss in productivity over time. This work helped clarify the existence of non-slit larger ultramicropores in CMS membranes which may be used as tools to precisely engineer the membrane performance.

During my PhD research with Prof. Ilsoon Lee at Michigan State University, I surface modified commercial nanofiltration membranes using the layer-by-layer assembly of polyelectrolytes. My surface modified membranes showed higher permeability than commercially available membranes, but with equivalent or higher perchlorate ion removal. I next extended the use of these to more complicated systems like actual aggressive wastewater. These membranes were modified further with addition of clay-nanoplatelets to improve their fouling resistances.

Teaching Interests:

Based on my background in Chemical Engineering, I can teach most of the core courses like Kinetics, Thermodynamics, Mass Transfer, and Transport Phenomena. I would include a section on membrane materials and processes in the Mass Transfer curriculum, if given an opportunity to teach that course. If there is enough interest, I would also like to introduce an Advanced Separations or Membrane Materials and Processes course as graduate elective courses. During my PhD research, I served as the Teaching Assistant (TA) for Transport Phenomena and during my postdoctoral research, I worked as the TA for introductory sophomore class- Chemical Process Principles. I have also mentored 8 undergraduate researchers during my PhD and postdoctoral research and found this opportunity to be highly rewarding.

Selected Publications

• Sanyal, O.; Hicks, S.T.; Bhuwania, N.; Hays, S, Kamath, M.J.; Karwa, S.; Swaidan, R.; Koros, W.J. “Cause and Effects of Hyperskin Features on Carbon Molecular Sieve (CMS) Membranes,” Journal of Membrane Science 551C, 113-122, (2018).
• Sanyal, O.; Zhang, C.; Wenz, G. B.; Fu, S.; Bhuwania, N.; Xu, L.; Rungta, M.; Koros, W.J. “Next Generation Membranes-Using Tailored Carbon,” Carbon, 127, 688-698, (2018).
• Sanyal, O.; Liu, Z.; Yu, J; Meharg, B. M.; Hong J. S; Liao, W.; Lee, I. “Design of fouling-resistant clay-embedded polyelectrolyte multilayer membranes for wastewater effluent treatment,” Journal of Membrane Science, 512, 21-28, (2016).
• Sanyal, O.; Liu, Z.; Meharg, B. M.; Liao, W.; Lee, I. "Development of polyelectrolyte multilayer membranes to reduce the COD level of electrocoagulation treated high-strength wastewater,” Journal of Membrane Science, 496, 259-266, (2015).
• Sanyal, O.; Sommerfeld, A.N.; Lee, I. "Design of ultrathin nanostructured polyelectrolyte-based membranes with high perchlorate rejection and high permeability," Separation and Purification Technology145, 113-119, (2015).
• Sanyal, O.;Lee, I. "Recent progress in the application of layer-by-layer assembly to the preparation of nanostructured ion-rejecting water purification membranes," Journal of Nanoscience and Nanotechnology 14, 2178-2189, (2014).