Biomass derived low-cost microporous adsorbents for efficient CO2 capture

• Low-cost microporous carbon materials are obtained from lignocellulosic feedstock.
• Microporous carbon materials exhibit exceptionally high CO2 uptake (3.71 mmol g−1).
• Microporous carbon materials adsorbed CO2 rapidly and had excellent cyclability.
• Surface chemistry and microstructure properties are reasons behind CO2 capture.

Low-cost carbonaceous adsorbents with microporous structures and large specific surface area (up to 2511 m2 g−1) were prepared from a lignocellulosic feedstock by novel hydrothermal carbonization coupled with chemical activation for CO2 capture. In-depth spectroscopic and microscopic analyses of these adsorbents were performed to gain insights into their structural, morphological and textural characteristics. The microporous carbons have a remarkable CO2 uptake capacity (3.71 mmol g−1) at 25 °C and at a pressure of 1 atm. These materials also feature good selectivity for CO2 over N2 gas and are composed of a hydrophobic core making them favorable as adsorbents for CO2 capture. The Freundlich equilibrium model well correlated with the experimental data obtained from the adsorption isotherms and classical micropore diffusion model described the adsorption kinetics satisfactorily. The Henry’s law constant calculated using Virial model indicates the presence of strong electrostatic interactions and dispersion forces between CO2 and porous carbons. Furthermore, these carbon-based adsorbents can be used repeatedly up to 10 times for CO2 adsorption without significant loss of adsorption capacity. Overall, the results suggest that prepared microporous adsorbents provide a feasible option for capturing CO2 from post-fossil fuel combustion processes due to their potentially low costs, environmentally benign nature, and elevated CO2 capture capacity.

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