Adsorption of C60 fullerene from its toluene solutions on active carbons: Application of flow microcalorimetry Original Research Article

The adsorption of C60 from its toluene solutions onto active carbons has been investigated. A flow adsorption microcalorimetry method was used to determine the amounts of adsorption and the corresponding enthalpies of displacement at 293 K for three active carbons: S-51 MB, S-51 WTX and Darco G-60. For S-51 MB the adsorption was measured at 5 different concentrations. For the remaining two carbons the measurements were made only at a C60 concentration of 0.5 g L−1. The amounts of C60 adsorbed and desorbed in two consecutive adsorption-desorption cycles, and the related integral molar enthalpies, were compared with those for a graphitised carbon black (Graphon). The BET specific surface areas, micropore volumes and mesopore surfaces, polar and apolar surface sites, and basal plane areas were estimated for all samples from the nitrogen adsorption isotherms (the BET plot and t-plot), enthalpies of adsorption of n-butanol from n-heptane and water, and enthalpies of adsorption of n-dotriacontane from n-heptane, respectively. Fullerene adsorption is a two-step process. At very low surface coverages strong irreversible adsorption of a small amount of C60 produces a large molar integral enthalpy effect. At higher coverages, a weaker reversible component dominates the process and the enthalpy of displacement decreases with increasing density of adsorption, approaching a limited steady value. Darco G-60 has the highest adsorption capacity and irreversible component of adsorption at a given concentration of the equilibrium bulk phase (i.e. 0.5 g L−1). For Graphon, the adsorption of C60 is completely reversible.