A. I. Zhukova

Interaction of water and other polar substances with hydrophilic centres on the surface of hydrophobic adsorbents

The adsorption of water and other polar substances on to the surface of graphitized carbon black and macroporous silica modified by polymethylhydride silicone has been studied using gas chromatography. The adsorption heat values of the substances studied were determined and the concentration of surface hydrophilic centres estimated. Conclusions have been drawn concerning the number of water molecules adsorbed on to hydrophilic centres at low surface occupation values. In the case of water adsorption on the graphitized carbon black surface, the chromatographic data for the adsorption heat have been compared with the energy of water molecule interaction with the surface clusters modelling the micropores existing on the basal surface of carbon black particles as calculated using quantum chemical methods.

Chromatographic and molecular statistical studies of structural and energy characteristics of surface micropores of silicates and silica adsorbents

A comprehensive approach to the investigation of structural and adsorption-selective characteristics of surface-porous silicates end silica adsorbents is developed, combining the chrometogrephic measurements and molecular statistical calculations involving the model pore structure and the detailed molecule-surface interaction potential. The method is capable to describe the non-specific and weak specific adsorption on microporous surface and can be applied to the wide class of microporous adsorbents.

Study of the Structure of a Surface-porous Adsorbent using the Gas Chromatographic Version of the Molecular Probe method

Results are presented of structural studies of a silica-based surface-porous adsorbent. It is shown that a reliable estimate of the size of the surface micropores of this adsorbent can be obtained using the gas chromatographic version of the molecular probe method. This is based on a comparison of the thermodynamic properties for the adsorption of substances of known molecular size on the surface-porous adsorbent with those characteristic for the adsorption of the same substances on to a non-porous adsorbent of a similar chemical nature.

Statistical-mechanical derivation of generalised langmuir equation and its application for the interpretation of chromatographic data for the adsorption of water and methanol on non-porous carbon materials

The chromatographic method is applied to the study of water and methanol adsorption on non-porous carbon materials—graphitised carbon black and thermally expanded graphite. It is shown that the processing of the experimental isotherms in coordinates of the classic Langmuir equation results in their linearization in two ranges of relative pressure, indicating the presence of two types of adsorption centres on the surface, which can be identified as the carboxyl and phenolic hydroxyl groups, respectively. A generalised Langmuir equation based on a statistical-mechanical approach is proposed, capable for the description of both monomolecular and polymolecular adsorption on the surface. It is shown that this equation provides for a better description of the adsorption of polar molecules on non-porous carbon materials.

Gas chromatographic, quentum-chemical, and molecular statistical studies of cluster adsorption of water and methanol molecules on hydrophilic surface sites of hydrophobic adsorbents

The comprehensive theoretical and experimental study of the adsorption of water and methanol molecules on active sites (carboxyl and phenol hydroxyl groups) on the graphitized thermal carbon black is performed. It is shown that microclusters formed upon the adsorption of these molecules on such sites are characterized by the cyclic structure comprising 4–5 molecules similar to that whose existence was revealed previously in liquid water and on the surface of silver iodide. The analysis of the studied adsorption clusters demonstrated that the formation of such cycles is governed primarily by the hydrogen bonding; however, a definite role is played also by energy effects associated with the changes in the state of molecular motion during adsorption. It is shown that the generalized Langmuir equation derived from molecular statistical considerations provides for better reproducing of the experimental isotherm within a wider surface coverage range, thus making it possible to consistently interpret data on structural and energetic characteristics of adsorption systems obtained by gas chromatography and quentum-chemical method.

Adsorption studies of organosubstituted laminated silicates

The hysteresis of sorptive deformation of sorbents has been studied for the first time. Based on the results obtained, it is assumed that the deformation of sorbents could be the universal reason for the sorptive hysteresis.

Adsorption studies of organosubstituted laminar silicates. 1. Adsorption deformation of organosubstituted laminar silicates

A dilatometric method was used to determine the deformations of organosubstituted Pyzhevsk montmorillonite and synthetic fluorohectorite upon the adsorption of water, hexane, and benzene vapor. These results were compared with the adsorption calorimetry data. The dilatometric method was shown to be highly sensitive to structural changes of the laminar silicates.