Enhanced CO2 capture kinetics by using macroporous carbonized natural fibers impregnated with an ionic liquid

In this research a new hybrid material was prepared to improve the kinetics and CO2 sorption capacity of an ionic liquid supported on the macroporous structure of carbonized agave bagasse fibers, which are low-cost renewable materials. The ionic liquid was 1-butyl-3-methylimidazolium acetate that has high affinity for CO2. The CO2 capture was assessed in a dynamic mode at atmospheric pressure by monitoring the weight change of the fibers in a thermogravimetric analyzer when passing a CO2 gas stream. The CO2 capture was evaluated on carbonized fibers (CF), acid washed carbonized fibers (CFw) and carbonized fibers impregnated with ionic liquid (IL) using a mass ratio that ranges from 1:10(-3) to 1:1 (wt CFw: wt IL). The BET surface area of CF was 75 m(2)/g that decreased after the acid wash to 2 m(2)/g. However, after impregnation with IL, the surface area was maintained at 2 m(2)/g when using the lowest impregnation ratio (1:10(-3)). The impregnated sample with a mass ratio of 1:10(-3) (CFwIL1:10(-3)) exhibited the highest sorption capacity (1.29 mmol CO2/g evaluated at 50 min of CO2 exposure) and sorption rate of 0.02 mmol CO2/min*g. These values were superior to those obtained by the IL (0.77 mmol CO2/g and 0.012 mmol CO2/min*g), which showed the synergy between the IL and the support in the CO2 capture. Finally, the cycles of CO2 capture (25 degrees C, 50 min) and thermal desorption (80 degrees C, 50 min, under nitrogen atmosphere) reported that the IL captured up to 1.07 mmol CO2/g but released only 41.5%, in contrast the impregnated carbon fibers (CFwIL1:10(-3)) captured 1.13 mmol CO2/g and released 91%. The rapid CO2 sorption-desorption processes and high reversibility of the impregnated carbon fibers suggest that this material could be used in CO2 concentrators. (C) 2022 Elsevier B.V. All rights reserved.