Enhanced CO₂ capture by cupuassu shell-derived activated carbon with high microporous volume

Here, we report the preparation of microporous-activated carbons from a Brazilian natural lignocellulosic agricultural waste, cupuassu shell, by pyrolysis at 500 ºC and KOH activation under different experimental conditions and their subsequent application as adsorbent for CO₂ capture. The effect of the KOH:precursor ratio (wt/wt%) and the activation temperature on the porous texture of activated carbons have been studied. The values of specific surface area ranged from 1132 to 2486 m²/g, and the overall micropore volume ranged from 0.73 to 1.02 cm³/g. Carbons activated with 2:1 ratio of KOH and activation temperature of 700 ºC presented a CO₂ adsorption at 1 bar of 7.8 and 4.4 mmol/g at 0 °C and 25 ºC, respectively. The isosteric heat of adsorption, Q_st, was calculated for all samples by applying the Clausius–Clapeyron approach to CO₂ adsorption isotherms at both temperatures. The values of CO₂ adsorption capacities are among the highest reported in the literature, especially for activated carbons produced from biomass.