Adsorption kinetics and thermodynamics of CO2 and CH4 on activated carbon modified by acetic acid

In order to improve the properties of activated carbons in the separation of carbon dioxide/methane mixture, organic acid, namely acetic acid, is used to modify the commercial coconut shell activated carbons. The modified sample 15H‐AC shows greater adsorption capacity than the raw material. To further explore the adsorption mechanism of carbon dioxide and methane on 15H‐AC, adsorption kinetics and thermodynamics are studied and compared with that on R‐AC. According to the results of adsorption kinetic study, it can be observed that the diffusion of both carbon dioxide and methane on 15H‐AC is faster than that on the raw material. The findings obtained in the adsorption thermodynamics indicate that the interaction of both carbon dioxide and methane with the modified sample is stronger and the spontaneity degree is higher. The physical adsorption of carbon dioxide on 15H‐AC indicates that the regeneration of the adsorbents is easy. The modified activated carbon, which possesses higher adsorption capacity, faster adsorption rate and good reproducing property, is promising in the separation of carbon dioxide / methane gas mixtures industrially.