Preparation of eco-friendly adsorbent for enhancing CO₂ adsorption capacity

The aim of this study was to investigate the potential of adsorbent derived from agricultural by-product-based activated carbon (AC) functionalized by deep eutectic solvents (DESs) for CO₂ capturing application. Three types of DES, namely Tetrabutylammonium Bromide (TBAB), Methyltriphenylphosphonium Bromide (MTPB), and Triethlyene Glycol (TEG) were synthesized and functionalized with AC using the impregnation method. The characteristics of the prepared adsorbents were analyzed, including the freezing/melting point, viscosity, surface morphology, elemental composition, and BET surface area. Following the characterization, the CO₂ breakthrough adsorption analysis was performed in a packed-bed reactor. The results revealed that the modified AC with the combination of TBAB and TEG showed the maximum CO₂ adsorption capacity of 16.5 mg/g compared to other adsorbents mixtures. The maximum adsorption capacity was achieved at a breakthrough time, temperature, gas flow rate and CO₂ concentration of 11.5 minutes, 25^◦C, 200 mL/min, and 10%, respectively. Furthermore, the adsorption process was thermodynamically favorable and spontaneous under exothermic reaction as indicated by the negative values of both the Gibbs free energy (∆G°) and enthalpy (∆H°). The regeneration evaluation also demonstrated that the modified AC sample was recyclable and reusable for more than nine cycles.