Agroindustrial waste conversion into ultramicroporous activated carbons for greenhouse gases adsorption-based processes

Activated carbons (ACs) for greenhouse gases adsorption were developed via KOH activation of waste twigs arising from processing of Ilex paraguariensis branches. The effect of KOH/carbonized twigs mass ratio (R =1-3) and temperature (873-1073 K) was examined. The ACs showed BET areas between 1000 and 2150 m2 g1, total pore volumes of 0.3-1.0 cm3 g1, and completely microporous structures with large presence of ultramicropores (<= 1.1 nm). The ACs obtained with R =2 at 873 K attained the highest CO2 adsorption capacity (5.4 mmol g1). An unprecedented correlation to estimate CO2 adsorption capacity in terms of ACs properties was developed. For the best sample, dynamic assays for CO2 and CH4 adsorption from single and binary equimolar gaseous streams were conducted at 101.32 kPa and 303 K. Regeneration showed that the ACs almost kept the initial dynamic adsorption capacity of both gases (1.4 mmol CO2 g1 and 0.4 mmol CH4 g1) after five adsorption-desorption cycles.