Abstract
basic principles of ion exchange and ion-exchange catalysis on carbon and other sorbents, and study of the surface chemistry of oxide-hydroxide systems. The indicated problems have been pursued at the L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of the Ukrainian SSR. The Institute coordinates investigations performed in the USSR in the area of synthesis, study of the properties and application of inorganic adsorbents (I. E. Neimark, Doctor of Chemical Sciences, chairman of the adsorption section of the Science Council, Academy of Sciences of the USSR). The Institute is a major center for investigation of adsorption problems in the Ukraine, and one of the leading centers in the USSR. Development of theTheory and Methods for Synthesis of Inorganic~ Organos$!icon, and Mixed Adsorbents with Differen t Pore Structures Work on synthesis of adsorbents was begun 30 years ago at the Pisarzhevskii Institute under the direction of M. F. Polyakov, Doctor of Chemical Sciences [i]. He first formulated the idea of forming gel adsorbents with specific adsorption properties with respect to substances in whose presence the gel was prepared. The mechanism of formation of absorbers with specific properties proposed by Polyakov was later confirmed experimentally in the work of American and Italian scientists. The work of Polyakov was further developed at the Institute by V. V. Strelko, Z.Z. Vysotskii, V. A. Kanibolotskii, and V. I. Galinskii [2]. Under the direction of I. E. Neimark, there has been very broad progress in studies on developing theoretical principles for synthesis, control of the pore structure, and modification of the surface of adsorbents, as well as study of selective and other properties of mineral adsorbents. Neimark and coworkers (V. M. Chertov, I. B. Slinyakova, R. Yu. Sheinfain, M. A. Piontkovskaya, Z. Z. Vysotskii, A. I. Rastrenenko, V. G. ll'in, I. M. Samodumova, O. P. Stas', T. F. Makovskaya, et al.) [3-6], as a result of systematic study of the effect ofpreparation conditions for mineral adsorbents (silica gel, hydroxides of aluminum, zirconium, titanium, chromium, iron, etc.) on their pore structure and sorption properties, have developed the theoretical principles for formation of the pore structure and have determined the scientific principles underlying methods for preparation of inorganic adsorbents with prespecified structure. Starting from the concept of a corpuscular structure for gel adsorbents, a mechanism has been proposed for the formation of their pore structure according to which the dimensions of the globules and their packing in the skeleton may vary during genesis of the gel. As the gel ages, changes occur which are connected with the increase in particle size and with the change in their arrangement in the framework. Stabilization of the dispersion of the hydrogel particles is promoted by factors leading to formation of solration shells or protective adsorption layers, hindering the growth of particles and their coalescence. On the other hand, accelerating processes of polycondensation or dissolution of the dispersed phase promote the growth of globules. The character of the porosity of the final xerogel is due to the degree of densification of the hydrogel as it is dehydrated, which depends on the ratio of the capillary pressure developing in this case and the strength of the gel skeleton opposing it. In turn, the capillary pressure is determined by the nature of the intermicellar liquid and its affinity for the gel skeleton, while the strength of the framework depends on the particle size and the degree of crosslinking. *Doctor of Chemical Sciences.
Published Version
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