N. E. Gordina

Effect of ultrasound on the synthesis of low-modulus zeolites from a metakaolin

It was studied the effect of ultrasonic processing (22kHz) of the aqueous suspension of metakaolin, sodium hydroxide and alumina with a molar ratio 2Al2Si2O7:12NaOH:2Al2O3 on the low-modulus zeolite synthesis processes. To investigate the XRD, SEM, IR, EDS had been used. It was shown that after ultrasonic processing, sodium aluminates are formed, what leads to a change in process of further synthesis. It was found that without ultrasonic processing on the stage of thermal treatment at 650°C, SOD zeolite (|Na6|[Al6Si6O24]) and sodium aluminosilicate (Na6Al4Si4O17) are synthesized. In the sample after ultrasound during thermal treatment, only sodium aluminosilicates of cubic syngony (Na6Al4Si4O17 and Na8Al4Si4O18) are formed. It was demonstrated that sodium aluminosilicates are precursors for the formation of LTA zeolite (|Na12|[Al12Si12O48]). As a result zeolitization of sodium aluminosilicates after the hydrothermal crystallization in alkaline solution, the sonicated sample contained 97wt% LTA. Without ultrasonic processing, the product of synthesis contained 50wt% SOD and 40wt% LTA.

Investigation of mechanochemical synthesis of zeolite NaA made of metakaolin in the mills with shock-shear type of strain

The possibility of obtaining of the NaA zeolite using dry mixture in a mill with a shock-shear type of strain with anhydrous raw ingredients, metakaolin, aluminium oxide, sodium aluminate was examined. The optimal time of mechanical activation was found.

Visible emission from Ag+ exchanged SOD zeolites

Broad visible emissions dominant at green or red have been observed for the thermally-treated Ag(+) exchanged SOD zeolites, determined by the Ag(+) loading contents and the excitation wavelengths. Contrary to the notable reversible green/red dominant emission evolution in the Ag(+) exchanged LTA zeolites upon hydration/dehydration in air (or water vapor)/vacuum, emission spectra of the Ag(+) exchanged SOD zeolites are insensitive to the environmental change. This is most probably due to the difficult H2O permeation in SOD zeolites in comparison with LTA zeolites. By combining the environment dependent emission spectra of the Ag(+) exchanged LTA and SOD zeolites, we proposed the following emission mechanisms for Ag(+) exchanged LTA and SOD zeolites: the green emission is due to the transition from ligand-to-metal (framework O(2-)→ Ag(+)) charge transfer state to the ground state and the red emission is due to the transition from the metal-metal (Ag(+)-Ag(+)) charge transfer state to the ground state. The insensitive environment dependent emission characteristics of Ag(+) exchanged SOD zeolites may have potential applications as robust phosphors.

Natural Mechanisms of Mechanochemical Interactions in Oxide Powders

The effect of hydroxyl and other functional groups on mechanochemical interactions in oxide powders is shown. The general rules of non-covalent mechanochemical synthesis are established. Phenomenological models are discussed and the kinetic equations of mechanochemical synthesis are presented.

A study of thermal treatment and hydrothermal crystallization stages in production of granulated NaA zeolite from mechanically activated metakaolin

NaA zeolite was synthesized from mechanically activated granulated mixtures of metakaolin, sodium hydroxide, and aluminum oxide. The thermal treatment and hydrothermal crystallization processes were studied. It is shown that the optimal temperature of thermal treatment of grains based on a mechanically activated metakaolin is 600°C at a NaA zeolite content of about 65 wt %. Raising the calcination temperature leads to a decrease in the content of the zeolite and to formation of nepheline. It was found that the optimal concentration of the crystallization solution of NaOH is 2–4 M. Under these conditions, the content of the zeolite exceeds 90 wt %. Raising the alkali concentration leads to a decrease in the content of the zeolite and to its recrystallization into sodalite.

Study of Pore Texture of Sorbents Based on Kaolin Clay

Acid modification of clay from the Veselovskoe deposit to obtain a sorbent with a developed pore structure and low mechanical strength was studied. The compositions modified with liquid glass and the joint acid and alkali treatment were considered.

The Adsorption of Undesirable Impurities from Sunflower Oil on the Granulated Sorbents Based on Kaolin Clay

Abstract Modifying processes of clay of Veselovskoe deposits with acetic acid (AA) and liquid sodium glass and adsorption of undesirable impurities from sunflower oil on granulated sorbent in a dynamic mode were studied. It was shown that the modification of clay with AA increases the number of Brönsted sites and yields granulated sorbent with a mesopore structure. The composition of clay and liquid glass is characterized by the basic sites. The composition of the clay modified with AA and the liquid glass produces all kinds of surface sites and yields the bipore structure. It was established that the modification of clay with liquid glass provides highest degree of adsorption of the fatty acid (84.6–87.7%), and the modification of clay with AA leads to increasing adsorption of the peroxide compounds (70.0–81.7%). Both acid and alkaline modification of clay allows increasing the phosphorated substances extraction degree to 77.2–89.4%.

Production of Granulated NaP Zeolite without Binder

Possibility was examined of synthesizing zeolites granulated without a binder with the use of a preliminary ultrasonic treatment of the suspension at a frequency of 22 kHz from mixtures of sodium metasilicate and aluminum and silicon oxides with various Si: Al ratios. It was found that, after the preliminary treatment, extrusion of grains, and calcination at 650°C, crystalline phases Na6Al4Si4O17, Na8Al4Si4O18, Na2Al2O4, and Na2SiO3 phases are formed in the sample with Si: Al = 1. These phases are precursors for synthesis of NaA and NaP zeolites and sodalite via hydrothermal crystallization in a NaOH solution with concentration of 2 M. Upon a similar treatment of a sample with Si: Al = 2, there are crystalline phases α- and β-Na2Si2O5, from which only NaP zeolite is formed in the course of crystallization. The hydrothermal crystallization in a 6 M alkali solution yields sodalite, irrespective of the Si: Al ratio. It was shown that an ultrasonic treatment gives a gel-like system at Si: Al = 1 and a powdered material at Si: Al = 2, which yields by the end of synthesis samples with cactus-like or wool-like morphology, respectively.

Use of ultrasonic treatment for obtaining a sorbent based on zinc compounds and gibbsite

Processes occurring in ultrasonic treatment of aqueous suspensions of gibbsite and zinc oxide of basic zinc carbonate were studied. It was found that, in treatment of suspensions of gibbsite and zinc oxide, ZnO particles become coarser, whereas in mixtures of gibbsite and Zn4CO3(OH)6·H2O, articles of basic zinc carbonate are dispersed. The size of gibbsite particles in both formulations remains nearly unchanged. It was shown that a preliminary ultrasonic treatment of sorbent components make it possible to raise the static capacity for HCl vapor. It was found that Zn5(OH)8Cl2·H2O (mixture with zinc oxide) or Zn2OCl2·2H2O (mixture with basic zinc carbonate) is formed in this case, which leads to a higher sorption capacity of the latter.

Co-Grinding of Three-Component Compositions of Al, Ca, Zn, Mg Compounds

The grinding of the compositions ZnO/CaO/Al(OH)3, Zn4CO3(OH)6 /CaO/Al(OH)3, and MgO/CaO/Al(OH)3 in a vibrating mill is studied by means of x-ray diffraction, IR spectroscopy, and scanning electron microscopy. It is found that a new phase Ca(Zn2(OH)6) in the form of prismoidal crystals forms in mixtures containing ZnO. The grinding process is accompanied by surface hydration of the particles, which is the reason for the equalization of the main properties of the compositions. It is shown that the amount of gibbsite in a composition affects the character of the change in the parameters of the crystal structure of gibbsite.