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The adsorption–desorption of water vapours on swelling layer silicate is considered in the framework of the Brunauer-Emmett-Teller (BET) and Frenkel-Halsey-Hill (FHH) formalisms. The theoretical dependencies calculated with reasonable and consistent values of model parameters are shown to agree quite satisfactorily with the experimental data. Based on these equations, the description of the adsorption hysteresis related to Type III adsorption isotherms is proposed, which also yields a good reproduction of the experimentally observed values.

For qualitative and quantitative description of adsorption equilibrium and hysteresis in open slit-like micropores, theoretically rigorous equations are proposed based on the theory of volume filling of micropores which imply the physical and formal analogy between the volume filling of micropores and capillary condensation. The applicability of the proposed equations for description of the hysteresis in such systems is demonstrated for water adsorption/desorption isotherm on the fibrous carbon material AUVM-Dnepr which possesses micro- and mesoporous structure.