Calorimetric Investigation of Adsorption of Organic Compounds by Active Carbons

Abstract

Enthalpies of wetting of two active carbons and one brown coal coke by several pure liquids (mainly homologous series) were measured at 298.15 K with two quasi-isothermal microcalorimeters. Different measuring cells with cavities of about 0.5 and 15 cm³ were used. The advantage of the larger measuring cell with three independent 15 cm³ cavities is the higher mass of active carbon, leading to a high reproducibility with standard deviations below 1% and a reduced measuring time. Experiments were carried out with n-alkanes, l-alkanols, cycloalkanes and isomers thereof, i.e. 2-propanol, methylcyclohexane, 2,2,4-trimethylpentane (isooctane and 2-ethyl-1-hexanol, and water. Like the polarity, the size and the three-dimensional expansion of the molecules, the energetic and geometric heterogeneity of the adsorbent influences the enthalpy of wetting.