Calorimetric investigation of adsorption of organic compounds by active carbons

Enthalpies of wetting of two active carbons and one brown coal coke by seve ral pure liquids (mainly homologous series) were measured at 298.15 K with two quasi-isothermal microcalorimeters. Different measuring cells with cavi ties of about 0.5 and 15 cm(3) were used. The advantage of the larger measu ring cell with three independent 15 cm(3) cavities is the higher mass of ac tive carbon, leading to a high reproducibility with standard deviations bel ow 1% and a reduced,measuring time. Experiments were carried out with n-alk anes, 1-alkanols, cycloalkanes and isomers thereof, i.e. 2-propanol, methyl cyclohexane, 2,2,4-trimethylpentane (isooctane and 2-ethyl-1-hexanol, and w ater. Like the polarity, the size and the three-dimensional expansion of th e molecules, the energetic and geometric heterogeneity of the adsorbent inf luences the enthalpy of wetting.