Adsorption of CO₂on palm shell based activated carbon modified by deep eutectic solvent: Breakthrough adsorption study

Adsorption process technology using solid adsorbents in capturing CO2 is an alternative approach to solve the global greenhouse issue. As such, cost-effective, environmentally friendly and high-performance adsorbents have been developed to this end. This paper describes the preparation of adsorbents derived from palm shell waste with high carbon content, which is then functionalized with deep eutectic solvent (DES) a mixture of choline hydroxide:urea and choline hydroxide:glycerol to enhance the CO2 adsorption capacity. Adsorbents are characterized by their structural, morphological, and chemical properties using XRD, FTIR, SEM, EDX, and BET surface area. The relationship between adsorbent surface characteristics and CO2 adsorption performance was studied. CO2 breakthrough experiments were carried out in a fixed-bed adsorption column at different adsorption temperatures (25-55 °C), feed flow rates (200-600 mL/min), and the initial CO2 concentrations (10-20%). It was found that the amount of CO2 uptake decreased with an increase in adsorption temperature, and feed flow rate. It was observed that DES-based activated carbon with a mixture of choline hydroxide:urea (ACDES 9) exhibited the highest CO2 adsorption capacity (37.2 mg/g) at an adsorption temperature of 25 °C, feed flow rate of 200 mL/min, and CO2 concentrations of 10%. Furthermore, the modified adsorbent still showed good performance even after 11 adsorption-desorption cycles.