FUNCTIONALIZATION OF CARRIER TRANSPORT MEMBRANES BY THE CONTROL OF MICROSTRUCTURE

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1. The effects of reaction rate constant and equilibrium constant of the reaction between CO_2 and amine on the permeability of CO_2 were successfully formulated on the basis of facilitated transport theory. An amine with moderate chemical equilibrium constant was found to be favorable to obtain high CO_2 permeability.2. The effect of the characteristics of microporous support membrane was examined by the facilitated transport model. It was found that the thickness, porosity and tortuosity of the support are the important factors which influence the facilitated transport rate if the support has no electric charge.3. Ion exchange membranes (PE-g-AA membrane) were prepared by grafting acrylic acid (AA) onto microporous polyethylene (PE) membranes using low temperature plasma. Facilitated transport membranes (PE-g-AA-EDA) prepared by impregnating the PE-G-AA membranes with monoprotonated ethylenediamine (EDAH^+) showed very high selectivity of CO_2 over CH_4. This was due to high mobility of carrier in the membrane resulting from high water content of PE-g-AA membrane and also due to high carrier concentration resulting from high ion site (COO-) concentration of AA graft-layr. The membrane was stable because the carrier (EDAH^+) was held in the membrane by the electrostatic force. The facilitated transport rate of CO_2 was simulated by the proposed model by considering the diffusivity of the carrier in the ion exchange membrane.4. Microporous ion exchange membranes having sulfonic acid groups were prepared by plasma graft polymerization method. The prepared membranes were found to be very effective as the supports of facilitated transport of C2H4 using silver nitrate as the carrier.5. The effects of cross-linking ratio, water content and fraction of unfrozen water in PVA gel membranes impregnated with (EDAH^+) on the facilitated transport of CO_2 could be elucidated by the DSC measurement and the diffusivity and solubility of CO_2 measured by time-lag method.