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 (CO2) capture, and valorization of fruit waste offers a sustainable pathway to address this challenge. This study establishes a systematic modeling framework for interpreting CO2 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 () and the Akaike Information Criterion () to ensure robust comparison. Kinetic analyses revealed that the pseudo-second-order model (= 0.997, lowest) and Elovich model best describe the uptake behavior, indicating chemisorption on heterogeneous surfaces. Equilibrium data were most consistent with the Tóth and Sips models (> 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 CO2 capture.