Optimized diffusion-convection compromise for reversible CO2 capture on hydroxylated organo-montmorillonite

Carbon dioxide (CO2) was reversibly captured at room temperature and normal pressure by a low cost hybrid absorbent (NaMt-H30) obtained through Na-montmorillonite intercalation with Boltorn dendrimer H30 (1 wt%). Measurements through thermal programmed desorption between 20 degrees C and 200 degrees C showed variations of the retention capacities of CO2 (CRC) and water (WRC) according to the nitrogen stream throughput, contact time and injected CO2 amount for adsorbent saturation. CRC and WRC modeling as functions of these parameters was achieved using a 33 factorial design involving 27 attempts. Model analysis revealed that the retention of CO2 and water molecules depend not only on the individual effects of each parameters but also on their interactions. High nitrogen throughput and low amount of impregnation resulted in detrimental effects on both CO2 and moisture retention. This was explained in terms of diffusion and mass loss during impregnation through forced convection. An optimum compromise between these factors in correlation with the contribution of moisture content turned out to be an essential requirement for achieving highest CRC levels that express the effective material affinity towards carbon dioxide. These findings provide a useful tool for rigorously optimizing the reversible capture of CO2 by hydroxylated adsorbents.