Light-Assisted Transport of Gases Across Supported Liquid Membranes (Carrier-Mediated, Facilitated, Diffusion).

Reversible photochemical reactions can be combined with mass transport in membranes containing carrier solutions to facilitate the flux of the gaseous species taking part in the reaction. These membranes are called "carrier-mediated photodiffusion membranes" and exploit the change in the equilibrium constant with light intensity for their operation. The membranes are produced by differentially illuminating two ends of a membrane s and wich containing the carrier solution. The transport equations for carrier-mediated photodiffusion consist of nonlinear second order differential equations of the boundary value type and a technique based on the method of orthogonal collocation on finite elements is used for their solution. The method is found to give very accurate results. The simulation results for light-assisted transport of carbon monoxide across membranes containing hemoglobin solutions indicate that for these membranes containing hemoglobin solutions indicate that for these membranes a net flux can be obtained even in the absence of a concentration gradient. In the limit of zero flux, a concentration gradient of the permeant across the membrane can be supported by the light energy. Thin membranes at low degress of illumination are found to be the most efficient in the usage of the light energy. Experiments based on using the nitrosyl chloride (NOCl) decomposition reaction in the photomembrane configuration are described. Results on the dissociation of nitrosyl chloride solutions in bulk indicate that the photostationary state equilibrium constant for this reaction can be changed by a factor of 400. This result is utilized in the construction of photodiffusion membrane based on this reaction. The experimental results for the transport of nitric oxide across membranes containing NOCl solution indicate that the facilitation ratios (under no flux condition) of up to 15 can be obtained for this system. The facilitation ratio increases with the increase in NOCl concentration and the light intensity, and with the decrease in NO concentration. The phenomenon can be used for the concentration and the separation of the gaseous species involved in the photochemical reaction as well as in the storage of solar energy.PhDChemical engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160078/1/8415009.pd