Sustainable CO₂ capture using phosphoric acid-activated carbon from the novel biomass Chamaerops humilis: experimental optimization, characterization and DFT insight into the adsorption mechanism

In this study, a sustainable activated carbon (AC-CH) was synthesised from Chamaerops humilis biomass by chemical activation with phosphoric acid (H₃PO₄) with the aim of efficient carbon dioxide (CO₂) capture. Response surface methodology (RSM) was used to optimise the preparation parameters, namely impregnation time (8-24 h), activation temperature (550-750 °C) and impregnation ratio (1:1 to 3:1). The optimal material exhibited a high specific surface area (600 m²/g) and a maximum adsorption capacity of CO₂ reaching 115 mg/g. The study of isotherms showed that Toth's model best fits the experimental data, indicating a monomolecular-type adsorption on heterogeneous surface. In addition, DFT analyses highlighted the interaction mechanisms between CO₂ molecules and activated carbon functional groups, identifying active sites favourable to adsorption. The combination of experimental and theoretical approaches confirms the potential of AC-CH carbon as a low-cost, high-performance biosourced adsorbent for industrial CO₂ capture applications.