Carrier-mediated, thermal energy-coupled, non-isothermal membrane transport. II. A gaseous system

Abstract

The non-isothermal facilitated transport of CO 2 through a sulfonic cation exchange membrane (Permion 5010) containing organic diamine counter-ion carrier (EDA) has been studied experimentally and confronted with a theoretical model based on the Nernst-Planck flux equation, with good agreement between the two approaches. Discussions also took into account measurements at different temperatures of isothermal passive and facilitated transports, membrane conductivity and corresponding Arrhenius plots, the stability constant of the permeant-carrier complex determined with a new technique and of heat of reaction (Δ H) obtained from Van't Hoff plots. Steady state fluxes of carbon dioxide were measured at different temperature gradients (Δ T) and partial pressures in mixtures with N 2. A permeability of 7.4×10 −7 mmol/cm/s/atm was obtained for a Δ T of 8 K around 295 K at a steady state flux of 4 × 10 −7 mmol/cm/s for 1% CO 2 in the mixture. Facilitation factors as well as thermal gradient amplification factors are presented. It is concluded that the effect of the thermal gradient on the flux is mediated by the modification of the concentration gradient inside the membrane. Stimulation or hindering are dependent on the sign of Δ H and of the orientation of Δ T relative to the gradient of partial pressure.