CO2 capture on KOH-activated carbons derived from yellow mombin fruit stones

Activated carbons derived from the stones of yellow mombin, an abundant tropical fruit, were prepared at 500 and 700 degrees C (referred to here as BP5 and BP7, respectively). The carbons were further activated with KOH and the resulting materials (referred to as CAK5 and CAK7) were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman scattering measurements. The microporous network architecture was evaluated by the Dubinin-Astakhov equation and the non-local density functional theory, assuming slit-shaped pores. In general, the graphitization process of the activated carbons decreased and the microporous volume increased significantly when the pyrolysis temperature was elevated from 500 to 700 degrees C. The temperature of 500 degrees C favored the production of activated carbons with high pore volumes in the range of 0.85-1.0 nm, which has been considered a key feature affecting CO2 capture at low pressures. Therefore, the carbon sample activated with KOH at 500 degrees C (i.e. CAK5) adsorbed 10.5 mmol CO2/g at 0 degrees C, 7.3 mmol CO2/g at 25 degrees C and 4.9 mmol CO2/g at 75 degrees C. The adsorption efficiency of the samples increased as: BP5 < BP7 < CAK7 < CAK5, with values ranging from 30.8 to 46.2%. CO2 capture on activated carbons proved highly stable after 10 adsorption-desorption cycles at 75 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.