Evaluation of adsorption properties of a porous carbon material from coffee waste

• DOI: 10.17277/jamt.2023.03.pp.207-216
• Publication Date: 2025-04-25T07:29:03Z
• Authors: Anastasia Memetova; Nariman Memetov; Andrey Zelenin

The article investigates and evaluates the adsorption properties of a new highly porous carbon material in a wide range of pressures at temperatures above the critical level. It has been shown that the activated carbon material obtained from coffee waste is an effective adsorbent for CH4. So, in this study, carbonized coffee grounds were used as a precursor to obtain a highly porous carbon material (HPCM5), by chemical activation at 750 °C for efficient CH4 adsorption. Porometry shows that the obtained adsorbent is micromesoporous with a narrow pore size distribution, having a BET specific surface area of 3456 m2⋅g–1 and a pore volume of 1.604 cm3⋅g–1. The adsorption of CH4 on the resulting carbon material was studied at temperatures of 298.15–323.15 K and pressures up to 100 bar. HPCM5 demonstrates a high CH4 adsorption capacity of 19 mmol⋅g–1 at 10 MPa and 298.15 K. Experimental data on CH4 adsorption on HPCM5 were analyzed using typical Langmuir and Freundlich adsorption models in the temperature range 298.15–323.13 K. The results show that CH4 adsorption on HPCM5 in the range of temperatures and pressures considered in this study correspond to the Langmuir adsorption; this is confirmed by the obtained values of the correlation coefficients equal to 0.99 and the average relative deviations between the experimental results and the results obtained with the Langmuir model, which are less than 3 %. The values of isosteric heats were calculated for different absolute amounts of CH4 adsorption on the resulting HPCM5, which are in the range from ~10.0 to 17.0 kJ⋅mol–1. This characterizes the process as a physical adsorption, and the bond strength between the CH4 molecule and adsorbent surface refers to the van der Waals force. The adsorption isotherm data and thermodynamic parameters evaluated in this study are useful for designing adsorption-based gas storage systems.