In this paper, adsorption of potassium gold cyanide from water onto three activated carbon samples, four graphites, and two carbon blacks (Graphon and Vulcan) is compared. The present work collects the results of flow microcalorimetric studies for each carbonaceous adsorbent so as to obtain estimates of their polar and accessible apolar graphitic basal plane surface areas. The relative polar and graphitic nature of the carbons is evaluated and related where possible to their capacity of adsorption for gold complexes. Finally, the thermodynamic reversibility of gold adsorption on the carbonaceous adsorbents from an aqueous solution of potassium aurocyanide at room temperature has also been studied. A flow adsorption microcalorimetry method was used to measure the amounts of aurocyanide adsorbed and desorbed in one adsorption-desorption cycle, as well as the corresponding enthalpic changes upon adsorption and desorption. On the basis of the adsorption and enthalpy values obtained in adsorption and desorption cycles, estimates could be made of the reversible and irreversible contributions to the total adsorption capacity and the integral molar enthalpy of adsorption. The degree of adsorption irreversibility ranges from 25% for Graphon to 54% for G212. The irreversible and reversible enthalpy components have respective values of about -50 and -25 kJ mol(-1). A large part of the microporous structure in activated carbons is not accessible to the adsorption of gold complexes. One part of the aurocyanide is believed to irreversibly adsorb as an unpaired anion Au(CN)(2)(-) through electrostatic interactions on the very active surface sites having polar character. The less active sites are occupied by the ion-paired neutral molecular species (KAu(CN)(2)) through the action of van der Waals forces and account for the reversible adsorption. In reversible and irreversible processes, the active sites are thus expected to be associated with the graphitic-like structure containing nonideal aromatic rings and polar structures located at the edge defects in the graphite structure.