V. E. Polyakov

Obtaining and properties of clinoptilolite modified by manganese dioxide

We have found optimal conditions for obtaining an effective sorbent—catalyst based on natural clinoptololite with chemosorbed manganese dioxide for removing Mn2+ ions from water. Using a complex of sorption-analytical, structure-sorption, electron-microscopic methods we have studied the properties of the modifying δ-MnO2-film. The mechanism of its sorption-catalytic effect on Mn2+ has been discussed.

Study of the reaction of water vapors with carbon fibers by an adsorption-calorimetric method

The isotherms and differential heats of adsorption of water vapor on two samples of activated carbon fiber material (CFM) have been measured. The adsorption of water vapor on CFM has been found to take place virtually over the entire range of surface occupation with thermal effects lower than the heat of condensation. The appearance of endothermic thermal effects on the thermograms made it possible to establish the hitherto unknown submicroscopic swelling of carbon fibers caused by water vapors.

Microcalorimetric Study of the Interaction between Water and Cation-Substituted Clinoptilolites

Heats of ion exchange and adsorption of water vapors on cation-substituted clinoptilolites are studied by microcalorimetry. Based on the results obtained, the composition of hydrates of Na+, Cs+, Co2+, and Ba2+ ions on various ion-exchange sites of clinoptilolite is determined. Their structure is identified using the combined analysis of calorimetric and X-ray diffraction data. The usefulness of energy–stoichiometry approach to the discussion of the results of adsorption calorimetry study of the interaction between water and cation-substituted clinoptilolites is demonstrated.

Equilibria and heats of exchange of alkaline-earth metal ions on the Na form of mordenite

Sorption-analytic studies of ion exchange equilibria combined with direct calorimetric measurements of the heats of ion exchange sorption of the Ca2+, Sr2+, and Ba2+ cations were performed over the whole range of solid phase fillings with sorbed cations on the Na forms of two mordenites prepared from natural specimens rich in Na+ and Ca2+ cations. Ion exchange constants were determined and the Gibbs energies and entropies of ion exchange were calculated. The thermodynamic characteristics obtained were analyzed taking into account the preferable localization of alkaline-earth metal ions on certain exchange centers in the structure of mordenite. The presence of natural mordenite memory effects with respect to extra-framework Ca2+ cations in the presence of which these zeolites were crystallized in nature was established.

The heats of exchange of transition metal ions on the Na form of clinoptilolite

Direct calorimetric measurements were used to determine the heats of exchange of the Mn2+, Co2+, Cu2+, and Ni2+ cations on the Na form of clinoptilolite over the entire range of solid phase fillings with sorbed cations. In parallel, ion exchange isotherms for the systems were measured by the sorption-analytic method. The integral free energies and entropies of ion exchange were calculated. It was shown that the solution phase of the clinoptilolite-electrolyte solution two-phase system contributed significantly to the total thermodynamic characteristics of ion exchange. The differentiation of the dependence of the integral enthalpy on the degree of filling was performed to show that the clinoptilolite structure contained at least two types of exchange sites having different interaction energies with transition metal ions.

Selectivity of Low- and High-Silica Clinoptilolites with Respect to Alkali and Alkaline–Earth Metal Cations

The ion-exchange equilibria involving K+ and Ca2+ cations were studied using the Na-forms of nine different clinoptilolite samples. The high-silica (in the native state, sodium–potassium form) clinoptilolites were shown to have the increased selectivity with respect to K+ ions, whereas the low-silica (in the native state, calcium form) clinoptilolites to Ca2+ ions. The phenomenon found is interpreted as a structural memory of clinoptilolites with respect to alkali and alkaline-earth metal ions which had been present during zeolite crystallization under natural conditions.

A study of cetylpyridinium cation sorption on Na-vermiculite

The sorption of cetylpyridinium on Na-vermiculite has been studied by the adsorption, calorimetry, and X-ray diffraction methods. The ion-exchange component of cetylpyridinium sorption on Na-vermiculite has been distinguished and analyzed. Variations in the integral heat of ion exchange of cetylpyridinium cations on Na-vermiculite have been determined as depending on the amount of absorbed cetylpyridinium by the calorimetry method. X-ray diffraction analysis of cetylpyridinium-Na-vermiculite organomineral complexes with different contents of exchange cations has been carried out in parallel. The formation of monolayer (interlayer spacing Δd = 20.25 Å) and bilayer (Δd = 37.27 Å) intercalation structures with a tilt angle of cetylpyridinium ions to the silicate basal surface of ≈57° has been revealed.

Comprehensive ion-exchange and adsorption study of the distribution of exchanging inorganic cations over the interlayer gaps of vermiculite

The exchange of Co2+ ions on Na-vermiculite has been comprehensively studied by the ionexchange, adsorption, and X-ray diffraction methods. It has been shown that vermiculite is distinguished by high selectivity to Co2+ cations and Kielland dependence log

Ion-exchange equilibriums involving single-charged cations on saponite

\tilde K_m (\theta )

A Study of Water Interaction with γ-Al2O3Surface by Adsorption Calorimetry

increasing with filling of ion-exchange sites with sorbed cations rather than a decreasing one that is observed for common systems. It has been established that the ion exchange is accompanied by segregation of Na+ and Co2+ cations in separate interlayer gaps of vermiculite with the final formation of a disordered layered “cake” composed of separate silicate layers and interlayer gaps enriched with Na+ and Co2+ ions.