Equilibration-time and pore-width dependent hysteresis of water adsorption isotherm on hydrophobic microporous carbons

Effect of pore width (w) and equilibration time on hysteresis of water adsorption isotherm was studied at 303–323 K using hydrophobic activated carbon fiber (ACF). The adsorption isotherm of ACF of w = 1.1 nm has a wide hysteresis loop; the longer the equilibration time from 5 min to 16 h, the narrower the loop width due to a lower pressure shift of the adsorption branch. This fact indicates that adsorption branch stems from a metastable adsorption.