Fruit waste (pomelo peels)-derived activated carbons for biogas upgradation and capture of green house gases from flue gas and low concentration coalbed methane

Abstract

Rising emissions of greenhouse gases, such as CO2 and CH4, due to anthropogenic activities cause several adverse environmental impacts and encourage technological development for their effective capture and separation. The present work addresses a facile hydrothermal approach to impregnate K2CO3 and K2C2O4 into pomelo peels (fruit waste), followed by thermochemical activation for preparing activated carbons, i.e., PKC and PKOX, respectively, as adsorbents for biogas upgradation (CO2/CH4) and capture of greenhouse gases from flue gas (CO2/N2) and low concentration coalbed methane (CH4/N2). The high CO2 sorption capacity of PKC (4.67 mmol.g-1) and PKOX (3.96 mmol.g-1) at 298 K and 1 bar is attributed to their high surface area (1224–1371 m2.g-1), excellent microporosity, nitrogen-based functionalities, and turbostratic structural features. The ideal adsorbed solution theory (IAST) model is applied to estimate separation selectivity for binary gas mixtures, i.e., CO2/N2 (15:85), CO2/CH4 (45:55), and CH4/N2 (30:70) using PKC and PKOX adsorbents. The adsorption selectivity of PKC and PKOX for CO2/CH4 is found to be 143% and 296% higher compared to a widely used commercial activated carbon, signifying the potential of PKOX for biogas upgradation via adsorptive separation of CO2. The adsorption selectivity of PKC and PKOX for CO2/N2 is estimated to be 124% and 119% higher than commercial activated carbon, revealing the potential of both PKC and PKOX for capturing CO2 from flue gas to minimize its release in the atmosphere.