Selective CO2 Separation from CO2−N2 Mixtures by Immobilized Carbonate−Glycerol Membranes

Abstract

Separation of carbon dioxide from a humid mixture of CO2−N2 through membranes containing immobilized solutions of Na2CO3−glycerol in porous and hydrophilic poly(vinylidene fluoride) (PVDF) substrate was experimentally studied for use as a venting membrane in space-walk applications. The effects of Na2CO3 concentration, CO2 partial pressure, and feed stream relative humidity (RH) were investigated. The carbonate concentration was in the range of 0−4.0 mol/dm3. The feed gas RH range was 49−100%; the sweep gas was dry helium. CO2 partial pressure (pCO2,f) range was 0.007−0.77 atm. Addition of Na2CO3 increased the CO2 permeability drastically at lower carbonate concentrations; at higher Na2CO3 concentrations, this permeability increase is partly compromised by increased solution viscosity and salting-out effect. N2 permeability coefficient decreased with an increase in Na2CO3 concentration. Very high CO2/N2 selectivities were observed at high Na2CO3 concentrations. Higher CO2/N2 selectivities were observed at...