(2025) Science of the Total Environment_Insect-derived biochar for CO2 adsorption under humid conditions: Elucidating adsorption mechanisms and competitive interactions with water molecules

Kim J.Y.; Lee D.-J.; Park J.; Lee T.; Kwon E.E.

(489697) Science of the Total Environment ISSN:  Vol.959 Issue. Article No.178304 DOI: 10.1016/j.scitotenv.2024.178304

The CO₂ adsorption capacity of biochar depends on the type of biomass used and its physicochemical properties; various sorption parameters including temperature, CO₂ concentration, and humidity affect the CO₂ adsorption capacity. Biochar derived from defatted black soldier fly larvae (BSFL) biomass was investigated for direct CO₂ capture and exhibited a hydrophilic/mesoporous structure that contained high concentrations of alkali and alkaline metals (>10 wt%), which contribute to CO₂ chemisorption. The CO₂ adsorption efficiency was higher at 25 °C compared with that at 30 °C and 35 °C, probably due to reduced Brownian motion of CO₂ molecules at lower temperatures. The adsorption process followed the Langmuir isotherm, suggesting monolayer adsorption. Kinetic modeling indicated that physical and chemical adsorption mechanisms were involved; physisorption predominated. The presence of water molecules resulted in competitive adsorption with CO₂, with 2.5 water molecules competing for adsorption sites at 70 % relative humidity and 1200 ppm CO₂. In the cyclic adsorption-desorption tests, the CO₂ adsorption capacity decreased by approximately 11 % after the first cycle, probably because a portion of the chemically adsorbed CO₂ did not fully desorb during regeneration. The findings of this study could aid in the development of more efficient biochar-based materials for CO₂ capture. © 2024 Elsevier B.V.

This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education(RS-2023-00272302).This study was supported by an NRF grant funded by the Korean Government (MSIT) (No.RS 2023-00219667). Elsevier B.V.