Characterizations of Activated Carbon-Methanol Adsorption Pair Including the Heat of Adsorptions

This paper presents adsorption isotherms and isosteric heats of adsorption for methanol vapor adsorption for two commercially available activated carbon samples - 207EA granules and WS-480 pellets (Calgon Carbon, U.S.A.) - which were also fully characterized using nitrogen sorption at 77 K. The heat of adsorption of methanol as a function of loading was determined using the Clausius-Clapeyron approach with isotherms obtained at 5 °C, 15 °C, and 25 °C. The isosteric heats of adsorption increased sharply at the small coverage due to increasing effect of condensation heat with coverage. The heat reached a maximum and then varies little with loading, with the average values at around 46.6 kJ/mol for 207EA and 45.1 kJ/mol for WS-480. The higher heats of adsorption for the former activated carbon reflect its more microporous nature (around 78 % compare to 62 % for WS-480 activated carbon). The heat of adsorption data is also comparable to that obtained elsewhere for other activated carbons.