Simple synthesis of spent coffee ground-based microporous carbons using K2CO3 as an activation agent and their application to CO2 capture

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Microporous carbons were prepared from spent coffee grounds via solid-state K2CO3 activation. Activation temperature and time were changed to manipulate the properties and CO2 adsorption performance of porous carbons. As the activation temperature and time increased, textural properties such as specific surface area and total pore volume increased, reaching 2337 m2 g−1 and 1.15 cm3 g−1, respectively. Among the prepared samples, the highest CO2 uptake (4.54 mmol g−1) at 25 °C and 1 atm was obtained in the porous carbon activated at 700 °C for 5 h. Depending on adsorption temperature and pressure, a dominant factor for CO2 uptake was different. Nitrogen content and narrow microporosity were crucial at the low-pressure, 0.15 atm, and the narrow micropore volume was decisive but the significant pore size range was different depending on the adsorption temperature at atmospheric pressure. In addition to high CO2 uptake, the developed porous carbons showed excellent cyclic stability and good selectivity for CO2 over N2. The high value-added porous carbons prepared from spent coffee grounds using the simple and less hazardous method have a potential of industrial application for CO2 capture.