Application of quasi-isothermal thermogravimetry for estimation of some properties of hydration layers in mesoporous adsorbents

The quasi-isothermal thermogravimetric analysis method was applied to study the structure of water layers adsorbed on the carbon-silica adsorbent surface. These adsorbents were prepared by means of modification of mesoporous silica gel by acetyloacetone pyrolysis. A new way of interpretation of the data obtained using the quasi-isothermal thermogravimetric method to characterise energetic and structural heterogeneity of adsorbent surfaces was suggested. Adsorbents under investigation were characterised on the basis of changes in the free energies of adsorbed water layer during their desorption as well as dependence of the effective radius of a drop evaporated from the surface on the adsorbed water concentration. Dependence dG/dM(H2O)(C-H2O) was examined under conditions of low coverage of the adsorbent surface with the adsorbed water, which can sl;ow formation of various types of water clusters on the heterogeneous surfaces. (C) 2001 Elsevier Science B.V. All rights reserved.