Trace contaminant removal using adsorption and membrane methods

This dissertation includes two parts and aims to contribute to trace contaminants removal of the Environmental Control and Life Support (ELLS) program of the National Aeronautics and Space Administration for long duration space missions. The first part is prediction of adsorption equilibrium for pure organic compounds and their binary mixtures with water vapor on BPL activated carbon using modified Dubinin-Radushkevich (D-R) equations. We propose to use the properties of organic compounds such as V_b, the molar volume as liquid at the normal boiling point, P_s, the vapor pressure as saturated liquid at the adsorption temperature, and the solvatochromic parameters π*, α_m and β_m to predict the adsorption equilibria.; The second part of this dissertation is a hybrid membrane/adsorption process for carbon dioxide removal and comparison with current four-bed molecular sieve technology (4BMS). In this part, we developed a hybrid membrane/adsorption process, which combines a membrane unit with the 4BMS technology to remove water vapor and recover carbon dioxide from the spacecraft cabin air. We tested the drying performances of single- and multi-tube membrane modules under various operational conditions and measured and obtained a functional formula for the dependence of water permeability on the water content level of the membranes. We developed an effective mathematical model for a membrane process to remove water vapor from nitrogen gas. The model simulations for the membrane modules matched experimental data well over a wide range of operating conditions. We have also compared the energy consumption of the hybrid membrane/adsorption process with that of the 4BMS technology for recovering carbon dioxide from the cabin air. The new process is potentially more energy efficient.