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 surf ace. 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 charac terise energetic and structural heterogeneity of adsorbent surfaces was sug gested. Adsorbents under investigation were characterised on the basis of c hanges in the free energies of adsorbed water layer during their desorption as well as dependence of the effective radius of a drop evaporated from th e surface on the adsorbed water concentration. Dependence dG/dM(H2O)(C-H2O) was examined under conditions of low coverage of the adsorbent surface wit h the adsorbed water, which can sl;ow formation of various types of water c lusters on the heterogeneous surfaces. (C) 2001 Elsevier Science B.V. All r ights reserved.