Transport and Critical Behavior in Mesoporous Random Materials

University Of Rochester, Rochester NY

Investigators

Abstract

ABSTRACT CTS-0104323 Chimowitz, Eldred H/ U of Rochester The principal investigators hypothesize that in the near-critical regime the dominant transport mechanism in supercritical fluid-microporous membrane systems will occur by diffusion of surface-bound solute species with little contribution from void regions of the membrane because of the effects of critical slowing-down therein. In this case the principal investigators have argued that his should uniquely lead to highly enriched solute fluxes through the membrane which would be a significant outcome for the proposed research objectives. The specific goal in the first year of the project will be to use computer simulation to study near-critical transport phenomena through microporous membrane systems using a novel relaxation-dynamics simulation technique, particularly suited for calculations in the critical region. The relaxation-dynamics simulation ensemble consists of two chambers, a phenomenological construction chosen to mimic concentration-driven diffusion processes. Each respective chamber's structure can be set up to resemble the membrane of interest. The two chambers are separated initially by an impermeable partition with the two profiles meeting at a discontinuous concentration interface. Once the partition is removed, diffusion between both chambers occurs, and molecular fluxes/selectivities can be directly enumerated as the system relaxes towards its overall equilibrium state at the given thermodynamic conditions. The dynamics in the entire ensemble will be generated by a kinetic Monte-Carlo, particle-exchange algorithm. The main objective of these simulations will be to evaluate this new simulation methodology and use it to study the properties of the near-critical membrane system described above. The principal investigators have currently benchmarked these computational procedures in homogeneous fluid systems and now have the computational resources and theory in had to use them to carry out a systematic study of near critical dynamics in confined structures. They hope to be able to complete a comprehensive investigation of this issue within next year, leading to new results that they intend to write up for publication. These simulation results will be of significant value in providing a conceptual framework for guiding experimental work in this area, which they aim to emphasize during the latter half of the project. The objective here will be to build and commission an experimental system for reliably acquiring data for model solute permeances through mesocale inorganic membranes as supercritical transport conditions. The principal investigators view the ability to do this as central to exploring the viability of the concepts described herein; funds have been requested to facilitate this endeavor. This will require the modification of a high-pressure absorption apparatus, currently in their laboratory, to accommodate a ceramic membrane module, which they intend to purchase from the US Filter Corporation. During this time their dynamic simulation capability in these systems should be fully functional, which will advance their goal of a useful interaction between both simulation and experimental aspects of the project.