Insight into the effect of pressure on the CO₂ capture capacity and kinetics by a biochar-ionic liquid composite

Agave bagasse fibers-derived biochar (BCw) impregnated with 1-butyl-3-methylimidazolium acetate ionic liquid (IL) exhibited a considerably CO2 capture capacity at atmospheric (1.47 mmol/g at 25 degrees C and 1 bar) and moderately high pressure (1.32 mmol/g at 25 degrees C and 8.5 bar) under dynamic and static systems, respectively. Biochar-IL composites improved the CO2 capture capacity, kinetics, and selectivity (CO2/N-2) by 4-90% compared with than of the bulk adsorbents. By increasing the working manometric pressure from 1 to 8.5 bar in a static high-pressure system, the CO2 capture capacity and kinetics of impregnated-biochar improved 2 times. Additionally, the biochar-IL composites were regenerated under a pressure swing adsorption (PSA) arrangement, where more than 70% of the desorption was attributed to the depressurization of the system. The proposed CO2 sorption mechanism suggests gas-solid physisorption and gas-liquid chemisorption at low pressure. At moderately high pressure (>= 1 bar), the textural properties of the adsorbent play an important role. Moreover, this study provided evidence that the CO2 capture is not only related to the textural properties of the biochar, but also to its surface chemistry. The biochar-IL composite materials reported herein could be an option for CO2 capture at low and moderate pressures, which could reduce operating costs if implemented at large scale for CO2 separation from flue gases under a PSA design.