Sustainable ionic liquid functionalized activated carbon for enhanced CO2 capture: Integrated textural properties, adsorption performance and isotherms

Waste materials are major source of environmental degradation. This study targets dual waste mitigation of CO 2 emissions and biomass. Rubber Seed Shell (RSS) biomass was thermochemically converted into Activated Carbon (AC) using K 2 CO 3 and KOH as chemical activators. AC was then surface functionalized for enhanced CO 2 capture using a novel Ammonium-Based Ionic Liquid (AIL), namely Ethanol Ammonium Butyrate [EtOHA][BA] with 10 to 30 wt. % loadings. SEM-EDX, SAP, N 2 adsorption-desorption isotherms, Pore Size Distribution (PSD), Raman spectroscopy, TGA, and DSC were used to characterize the pristine and functionalized AC samples. The characterization indicated that the surface area and pore volume decreased following functionalization of AC, while nitrogen-containing surface functionalities increased. The adsorption and isotherm analyses indicated that the CO 2 adsorption capacity increased with increasing AIL loading, with the Langmuir model providing the best fit to the equilibrium data. Furthermore, the integrated relation of textural properties with adsorption performance and isotherms confirmed that the increase in CO 2 uptake was determined by the combined effects of surface chemistry, textural properties, and adsorption affinity, rather than surface area alone. In addition, sample activated using K 2 CO 3 at 30 wt. % [EtOHA][BA] AIL (ACKC30%) exhibited the highest CO 2 adsorption capacity ranging from 3.71 and 2.49 mmol/gm and CO 2 /N 2 selectivity ranging within 21.59 to 25.94 at 0 and 25 °C, respectively. Furthermore, the isosteric heat of adsorption ranged from 29.7 to 44.2 kJ/mol, and capacity retention for CO 2 was observed to be 99.26% after 10 adsorption-desorption cycles.