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.