Application of biochar derived from olive, peach, and apricot stones for CO2 capture: A statistical physics and thermodynamic investigation

Abstract

This study evaluated the application of biochar derived from agro-industrial waste, such as olive, peach, and apricot stones, for CO₂ capture, offering a sustainable approach for gas adsorption. The biochar activation was carried out using water vapor, and the process was analyzed using CO₂ adsorption isotherms at temperatures from 303 to 353 K. To understand the interaction between CO₂ and the surface of the adsorbents, four statistical physics models were used. The thermodynamics of the process was evaluated from the perspective of statistical physics theory. The models were thoroughly analyzed using statistical criteria and parameter analysis. It was found that the best model to describe the CO₂ interaction with olive and peach stones biochar was the two-layer formation model with two adsorption energies, while for apricot stones biochar, the multilayer model with saturation was the most suitable. Analysis of the parameters revealed that the number of CO₂ molecules per site is between 0.5 and 1, indicating that the molecules are positioned parallel and not parallel to the surface of the adsorbents. The adsorption energy showed that the process is predominantly physisorption (<30 kJ mol⁻¹). Thermodynamic analysis indicated that the process is spontaneous and exothermic and that increasing the temperature impairs the CO₂ removal. The present study demonstrates that biochars derived from agro-industrial waste are promising for CO₂ capture, offering an efficient and sustainable solution, and the application of statistical physics models offers a deeper understanding of the adsorbent-adsorbate interactions, offering insights that go beyond the limitations of traditional models.