ADSORPTION CHARACTERIZATION OF HYDROFLUOROCARBONS ON CLAY MATERIALS.

□ Adsorption properties (enthalpy of adsorption, entropy of adsorption, and free energy of adsorption) of several hydrofluorocarbons (HFCs) on natural and surfactants modified clay minerals (bentonites, rectorite clays, and activated clays) were evaluated over the temperature range of 40–100°C by inverse gas chromatography. The differences of thermodynamic parameters of HFCs on different clay minerals mainly depended on the surface polarity and the interlayer spacing of clay mineral. When the clay minerals were modified by surfactants, such as cetyltrimethylammonium bromide, sodiumdodecyl benzene sulfonate, and tetrabutyl ammonium bromide, the adsorption values for the HFCs were weaker. However, the free energies of adsorption on natural and modified clay mineral were negative, implying the adsorptive processes of HFCs on clay were spontaneous at these temperatures. These results may have implications to reduce the atmospheric lifetimes of HFCs. [ABSTRACT FROM AUTHOR]