SELECTIVE SEPARATION AND CONCENTRATION OF CARBON-DIOXIDE BY FLOWING LIQUID MEMBRANES

To remove and concentrate dilute CO2 selectively, a series of experiments on the simultaneous permeation of CO2, O2 and N2 was performed using flowing liquid membrane in which gases permeate a liquid membrane solution which flows in a thin channel between two hydrophobic microporous membranes. Separation factors of CO2 relative to O2 and N2 were high, about 24 and 48 respectively, even when water was used as a membrane liquid. These results were explained by the physical solution-diffusion model in which permeability is dependent on the Henry constant and diffusivity. The separation factor was remarkably increased when potassium carbonste/bicarbonate was used as the carrier of CO2. The permeability of CO2 and pH of the membrane solution at steady state were simulated by a facilitated transport mechanism. Addition of diethanolamine was very effective in enhancing the permeability of CO2, and the separation factor αCO was increased up to 380. By evacuating the strip side of the permeation cell, CO2 in N2 was concentrated from 0.98% to 42%, as expected from the very high separation factor. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.