Enhanced uptake capacities and isosteric heats of CO2and CH4adsorption onspent coffee ground activated carbons loaded with metal ions

Abstract

Low-cost activated carbon (AC) samples obtained from waste coffee grounds were used for CO 2 and CH 4 adsorption. ACs were prepared by chemical activation and carbonized at three different temperatures. AC carbonized at 800 • C showed a relatively high surface area (582.92 m 2 g −1) and high adsorption capacities of 2.6 mmol g −1 and 1.1 mmol g −1 at 25 • C for CO 2 and CH 4 , respectively. Adsorbent samples were prepared by loading of Fe 3+ metal ions onto ACs and their adsorption capacities were compared with those of nonloaded ACs. As expected, the loading of Fe 3+ metal ions increased the adsorption capacities at all temperatures and the adsorption capacity of Fe 3+-loaded AC carbonized at 800 • C was 3.1 mmol g −1 for CO 2 and 1.2 mmol g −1 for CH 4 at 25 • C. The isosteric heats of adsorption were calculated at 0-35 • C with the range of 20-35 kJ mol −1 and 18-23 kJ mol −1 for CO 2 and CH 4 , respectively. According to our findings, bio-based ACs can be used as an effective and alternative adsorbent for capturing different gas molecules.