A new adsorption–desorption model for water adsorption in activated carbon

A new model is developed to describe the adsorption and desorption branches of water adsorption in activated carbon. This model is an extension of a previous adsorption model proposed by Do and Do [Do DD, Do HD. A new model for water adsorption in activated carbon. Carbon 2000;38:767–73] to account for desorption. The desorption branch is resulted from the relaxation of water clusters inside the micropore to form superclusters because of the presence of neighbouring clusters. The rates of formation and decomposition of these superclusters are low enough to reflect the relaxation process, and the large hysteresis observed experimentally is resulted from the decomposition of the superclusters to smaller clusters before they are desorbed from the micropores. We test this model against a number of experimental data, and the description is reasonable and the dependence of the model parameters on treatment (oxidation or reduction) is discussed.