The effects of the chemical activation agent and the chemical/nutshell ratio (ranging from 15–500 mass%) on the pore-size distribution (PSD) of macadamia nutshell-based activated carbons have been investigated in this study. The adsorption isotherm data of two series of activated carbons prepared from macadamia nutshell by chemical activation with potassium hydroxide and zinc chloride were used. The three widely used models of Dubinin–Stoeckli, Stoeckli and Horvath–Kawazoe were applied for characterizing these porous solids. Although the results showed some differences amongst these models arising from the fundamental assumptions on which they are based, in general they were comparable. Thus, at the same chemical ratio, samples activated by ZnCl2 showed more adsorption capacity than those from KOH. Moreover, the pore volumes increased as the impregnation ratio in each series increased. In addition, with increasing impregnation ratio (up to 100%) in the ZnCl2 series, the micropores were widened and a further increase in ZnCl2 content caused the micropores to change to mesopores. In the KOH series, increasing KOH created more micropores in the carbon structure over the whole range of chemical/nutshell ratio studied.

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