Sorption Equilibria and Kinetics of CO₂, N₂, and H₂O on KOH-Treated Activated Carbon

The equilibria and kinetics of CO₂, N₂, and H₂O on KOH-treated activated carbon (KOH-AC) were evaluated. The isotherms for the pure components were correlated with the Langmuir, dual-site Langmuir, Sips, and Brunauer–Emmett–Teller models. The saturated adsorption amounts followed the order qH₂O > qCO₂ ≫ qN₂. When simulated gas composition of postcombustion CO₂ capture (15 vol % CO₂, 4 vol % H₂O, and balanced N₂) was simulated by the ideal adsorption solution theory, the adsorbed amount of H₂O was much higher than those of CO₂ and N₂. The adsorption amount of CO₂ dropped when H₂O was present. The CO₂ uptake curves were well correlated with a nonisothermal kinetic model because the adsorption kinetics were controlled via heat generation and transfer. At the same temperature and pressure, the adsorption rates followed the order H₂O > CO₂ > N₂. Understanding the adsorption behaviors of flue gas including H₂O is important in designing adsorptive CO₂ capture processes using KOH-AC.