CO2 uptake on fruit wastes-derived activated hydrochars: systematic modeling of adsorption kinetics and isotherms

Abstract Climate change mitigation requires efficient and low-cost approaches for carbon dioxide (CO 2 ) capture, and valorization of fruit waste offers a sustainable pathway to address this challenge. This study establishes a systematic modeling framework for interpreting CO 2 adsorption on activated hydrochars derived from banana and orange peels synthesized via hydrothermal carbonization. Multiple kinetic and isotherm models were evaluated using both the coefficient of determination ( $$\:{R}^{2}$$ ) and the Akaike Information Criterion ( $$\:AIC$$ ) to ensure robust comparison. Kinetic analyses revealed that the pseudo-second-order model ( $$\:{R}^{2}$$ = 0.997, lowest $$\:AIC$$ ) and Elovich model best describe the uptake behavior, indicating chemisorption on heterogeneous surfaces. Equilibrium data were most consistent with the Tóth and Sips models ( $$\:{R}^{2}$$ > 0.99), supporting monolayer adsorption coupled with micropore filling. By combining statistical rigor with mechanistic interpretation, this work advances understanding of the adsorption mechanisms of fruit waste-derived hydrochars and highlights their promise as scalable and sustainable sorbents for CO 2 capture.