PECASE: Kinetics of Adsorption in Nanoporous Structures

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This CAREER award by the Chemical and Biological Separations program supports work by Professor Maria Mercedes Calbi at Southern Illinois University at Carbondale to develop theoretical models and methods that can provide a basic understanding of how and how fast different atoms or molecules can gain access into nanoporous structures and become bound (adsorbed) to their surfaces. Since different atoms adsorb differently on a structure (either because they are attracted to its surfaces with different strength, or they are adsorbed at different speeds, or both), adsorption processes have been widely used for separating gases from a mixture. This project is focused on a particular nanostructure, a carbon nanotube bundle, which is a collection of hollow, very long tubes that gather spontaneously forming bundles or ropes. The small diameter of the tubes and the presence of different kinds of adsorbing spaces make a nanotube bundle a unique nanostructure in which to study these adsorption processes. Moreover, carbon nanotubes have recently emerged as promising materials for separation and membrane applications. Gas separation devices have an extensive impact on society due to their wide use for gas recovery (including H2 production, a significant challenge toward a hydrogen-based economy), air purification systems and environmental remediation. In this project, computer simulations and statistical mechanical models will be implemented in order to: 1) Explore the conditions and identify the parameters that lead to the actual accessibility of adsorption sites in nanoporous structures, 2) Assess the ability of nanotube-based systems for separation and transport applications, and 3) Elucidate the unique dynamical behavior that is expected as a consequence of the restriction on the adsorbed atoms to move in effectively lower dimensional spaces (surfaces and channels). From a wider perspective, these results will provide the basis to understand these phenomena in more complicated systems (other porous materials and/or more complex adsorbates) and to envision new kinds of structures with optimal performance for separation and transport applications. This project also comprises an important educational component through the following activities: 1) Students participating in the project acquire basic research skills while learning specific theoretical and computational techniques, 2) The PI participates in an interdisciplinary program in Materials Research that brings students from underrepresented groups to engage in research projects at SIUC, 3) A new course, entitled "Surface Phenomena in Nanostructures", is implemented to fill educational gaps in the current curriculum and strengthen the recently approved doctoral program in Applied Physics. As an outreach activity, aimed at increasing the female enrollment in STEM (Science, Technology, Engineering and Math) careers, the PI leads a workshop to make a critical intervention in junior high school girls to increase the awareness of math-based careers, to present information about the paths to those careers and, most importantly, to provide successful career role models.