CO₂ removal in humid environment by ion-exchange membranes

Many CO₂ sorbents have performance degradation issues in humid environment. The recently developed moisture swing sorbent, initially used for CO₂ capture from ambient air, faces the same problem of high moisture sensitivity in the adsorption environment with very dilute CO₂ concentration (i.e., air). However, the performance of the sorbent, especially its moisture sensitivity, at relative high concentrations of CO₂, is still unknown. In this work, the adsorption performance of a resin-based ion-exchange membrane loaded with CO₃²⁻ (a typical moisture swing sorbent) was investigated in a series of isothermal equilibrium experiments at varying CO₂ concentrations and relative humidity. The results showed that the moisture sensitivity of the adsorption capacity of the ion-exchange membrane decreased with the initial CO₂ concentration, especially when the initial CO₂ concentration was above 4%. The competition mechanism of H₂O and CO₂ molecules in the membrane material was analyzed by the modified dynamic adsorption model. The present work indicates that the resin-based ion-exchange membrane could be used for carbon dioxide removal in a lot humid environments with relatively high CO₂ concentration, such as fruit and vegetable storage room, raw natural gas, and flue gas.