Home – Home – Jornals – Chemistry for Sustainable Development 2021 number 3

Results of the experimental investigation of the filtration of natural waters and gel-forming solutions through sand under the conditions simulating the aeration zone in the area of ground storage facilities of the Siberian Chemical Combine (SCC). Model porous media from natural sand ground samples of the aeration zone in the area of SCC surface storage facilities in the first aquifer from the surface were used in the experiments. Sorption and plugging properties of anti-filtration gel barriers (screens) formed by various thermotropic gel-forming systems were evaluated. Low-viscosity gel-forming compositions were pumped into the model porous medium. They were transformed into gels directly in the porous medium according to the mechanism of hydroxopolycondensation of aluminium ions or phase transitions of the polymers with lower and upper critical dissolution temperatures with the formation of anti-filtration barriers. The anti-migration properties of anti-filtration gel screens on the migration path of polluted waters in the first aquifer from the surface were investigated. Solutions of cesium and strontium salts were used as simulators of radioactive contaminants. To enhance the anti-migration properties of the gel barriers, we used preliminary impregnation of the rock with a sodium tetraborate solution, as well as the introduction of potassium alum into the gel-forming compositions. It was established that the anti-filtration gel screen based on polyvinyl alcohol (PVA) has also anti-migration properties. On the basis of the results of experimental studies, the PVA-based composition is recommended for making anti-filtration and anti-migration barriers on the migration path of contaminated water in the area of ground storage facilities of the SCC. It is reasonable to pump a portion of the solution of sodium tetraborate before and after injection of the composition.

Some examples of the technological developments implemented at the Experimental Chemical Plant of the Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, in collaboration with the Rosatom State Corporation, for application in various areas are considered. The technology for the synthesis of basic polyfluoroaromatic compounds (hexafluorobenzene, chloropentafluorobenzene and isomeric dichlorotetrafluorobenzenes) was developed. The key stage of the process is the substitution of chlorine atoms in hexachlorobenzene under the action of anhydrous potassium fluoride in an autoclave at 450-550 °C. The production of grand lots of a number of high-purity crown ethers was developed and optimized, which allowed their use in actual industrial processes for selective extraction of some metals. A commercially available biologically active preparation accelerating the growth, development and general stability of plants to diseases was created as a result of fundamental studies of triterpene compounds extracted from Siberian larch.

Advances in the scientific directions launched by A. A. Kovalsky, an outstanding expert in Physics and Physical Chemistry, participant of the works on the Atomic Project, the first Director of the Institute of Chemical Kinetics and Combustion SB RAS are considered. The works aimed at the development and investigation of the properties of new types of energy materials and inhibitors of combustion proceed on the basis of the notions on the mechanisms of ignition and combustion formulated by A. A. Kovalsky. Aerosol studies that were initiated within the framework of the Atomic Project for protection from irradiation formed the basis for the development of aerosol-based method to protect forests and agricultural plants from pests. Works initiated by Kovalsky gave rise to new aerosol-related directions: methods and instruments for measuring the characteristics of aerosol particles are under development, methods are elaborated for the generation of aerosol with necessary particle sizes and concentrations for various applications including nanoaerosol pharmaceutical forms, chemical properties and biological effects of nanosized substances are under investigation. Perspectives for further progress in these areas are outlined.

The microsphere composites were prepared by covering microsphere glass-crystalline supports with as-synthesized crystalline zirconium molybdate (Mo/Zr = 1.7) and pre-synthesized microporous sodium zirconium silicates of hilairite and gaidonnayite structural types. Narrow fractions of coal fly ash cenospheres with (SiO₂/Al₂O₃)_wt of 2.7 and 3.0 were used as precursors of the supports. The composites were studied by means of SEM, EDX and PXRD. The efficiency for Cs⁺ and Sr²⁺ removal from simulated wastewater was evaluated on the basis of parameters, such as the distribution coefficient K _d (for low Cs⁺/Sr²⁺ concentrations) and the maximum sorption capacity a _m (for high Cs⁺/Sr²⁺ concentrations) determined from the Langmuir sorption isotherms. It was established that the composites trap Cs⁺ and Sr²⁺ with K _d of up to 10⁴ mL/g. The influence of zirconium molybdate and sodium zirconium silicate composition and structure on their sorption abilities was demonstrated. The proposed resource-saving approach to the preparation of composite sorbents along with their high sorption parameters favours their application for decontamination of ¹³⁷Cs and ⁹⁰Sr bearing wastewater including aquatic environment and technological solutions.

The possibility of hydrothermal synthesis of Cs and Sr bearing framework aluminosilicates in the CsNO₃-NaOH-H₂O-(SiO₂-Al₂O₃)_glass and Sr(NO₃)₂-NaOH-H₂O-(SiO₂-Al₂O₃)_glass systems using coal fly ash cenospheres was studied as a low-temperature method to include the water-soluble forms of radionuclides ¹³⁷Cs и ⁹⁰Sr in a mineral-like form. The syntheses were carried out at temperatures in the range of 80-200 °С and autogenous pressure. Narrow fractions of cenospheres with the glass phase content of 90-95 mass % were used as aluminosilicate glass, and compounds of stable isotopes of Cs and Sr were used as imitators of radionuclides ¹³⁷Cs и ⁹⁰Sr. Based on the data obtained in the studies of solid products and post-synthetic solutions by means of X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX) and atomic absorption spectroscopy (AAS), it was established that the Cs bearing analcime-pollucite solid solutions (Na _n Cs_{1- n} )AlSi₂O₆∙ n H₂O are crystallized in the Cs-containing system at 120-150 °C with 98 % Cs⁺ removal from solution to the solid product. The Sr bearing phases of tobermorite and plagioclase structural types are formed in the Sr(NO₃)₂-NaOH-H₂O-(SiO₂-Al₂O₃)_glass system. In this case, the effectiveness of Sr²⁺ extraction from solution is not less than 99.99 %.

An overview of the research of the Boreskov Institute of Catalysis SB RAS in the field of the use of catalytic processes to neutralise the mixed organic waste containing radionuclides is given. An ecologically friendly technology was proposed for ecologically safe neutralization of mixed organic wastes containing radionuclides U, Pu and fission products. This technology is based on flameless lot-temperature oxidation of the organic component of the waste in a fluidised bed of catalyst granules and the transition of radionuclides into the compact solid phase for subsequent processing or disposal. The technological scheme includes a catalytic reactor for waste oxidation and a flue gas purification system. The process was investigated on experimental installations during the catalytic combustion of model mixtures and real radioactive waste containing uranium formed in the production of fuel rods. Various regimes of catalytic combustion of mixed waste and gas purification processes were elaborated. Based on the research conducted, a technological scheme and a technical project of the demonstration plant for the treatment of mixed organic waste were developed. The plant was constructed and assembled at the JSC Novosibirsk Chemical Concentrates Plant. For neutralization of the wastes of extractants containing radionuclides, oxidation in catalytically active melts was investigated. The effect of melt composition, oxygen concentration, load and temperature on process efficiency was studied. Optimal process parameters were determined. On the basis of these results, an experimental installation for processing real liquid organic wastes (worked out extractants) containing U and Pu radionuclides was designed and built at the Siberian Chemical Combine. Installation tests demonstrated the high efficiency of the oxidation of organic components of the wastes and complete absorption of phosphorus and radionuclides U, Pu by the melt.

The main directions of the depleted uranium compounds utilization, modern trends in the use of uranium oxides and complex compounds based on them in catalytic processes, and methods for producing uranium oxides are considered in the review. It is shown that oxygenated uranium compounds are promising in all areas of catalysis, including environmental protection processes, organic synthesis, photocatalysis, electrocatalysis, processes for the production of hydrogen and valuable chemical compounds. The achievements of the Boreskov Institute of Catalysis SB RAS in the development of methods for the production of uranium oxides with different U/O ratios and uranium-containing catalysts for environmental protection and hydrogen production within the framework of the international program “Development of technology for the production of new effective catalysts based on raw materials from depleted uranium oxides” are described in detail. The review includes foreign and domestic publications from 1955 to 2021.

The effect of the salting-out agent, aluminium nitrate (Al(NO₃)₃), on the extraction properties of hexavalent uranyl and plutonyl nitrates (UO₂(NO₃)₂ and PuO₂(NO₃)₂) is studied. It is shown that in 4-8 М HNO₃ solutions (aqueous phase) with an increase in Al(NO₃)₃ concentration from 0.1 to 1 M, uranium distribution coefficient increases sharply during extraction in 30 % solution of tributyl phosphate (TBP) in a hydrocarbon solvent (organic phase). In the presence of aluminium nitrate, the distribution coefficient of Pu⁶⁺ increases most significantly in comparison with other valence forms of Pu. The efficiency of salting-out action increases with an increase in TBP concentration in the organic phase: in the presence of 0.1-2.0 М Al(NO₃)₃, the distribution coefficient of Pu⁶⁺ in a 30 % solution of TBP increases three times faster than in its 4.5 % solution. The efficiency of reductive stripping of hexavalent plutonium (Pu⁶⁺) by tetravalent uranium (U⁴⁺) increases in the presence of aluminium nitrate. In the presence of 1 M Al(NO₃)₃, the coefficient of PuO₂²⁺ distribution does not exceed 1.0 even at low concentrations of U(NO₃)₄ (50 g/L) and HNO₃ (0.5 M). The concentration of HNO₃ in the aqueous phase strongly affects the change in Pu⁶⁺ distribution coefficient. However, with an increase in the concentration of U(NO₃)₄ in the stripping solution, the rate of a decrease in the coefficient of Pu⁶⁺ distribution drops down. With an increase in U(NO₃)₄ concentration from 50 to 150 g/L, this parameter decreases by a factor of 2.6, and in more concentrated U(NO₃)₄ solutions (150-250 g/L) it decreases by a factor of 1.1.

An overview of the research carried out at the Boreskov Institute of Catalysis SB RAS on the application of catalytic technologies to develop energy-efficient designs of high-temperature fuel cell (FC) batteries is provided. The catalysts for high-temperature combustion of methane and catalytic burners for efficient fuel combustion in the reformers of installations operating on fuel cells were developed. Internal reformers with active and durable catalytic coatings have been developed, allowing the formation of synthesis gas directly inside the battery of high-temperature molten carbonate and solid oxide FC, providing a compact and energy-efficient design of power plants.

One of the most complicated tasks in spent nuclear fuel reprocessing is the separation of rare earth elements (REE) from transplutonium elements (TPE). This is due to the proximity of the extraction and sorption properties of REE and TPE. One of the most efficient and industrially tested methods of separating REE from TPE is extraction with tributyl phosphate in the presence of complexones. The difficulty in developing an effective technology for REE separation from TPE is that these elements are capable to form many complex compounds both in the aqueous phase and in the extractant. Moreover, almost any change in the extraction system (pH, type of salting-out agent, concentration of the target component, etc .) leads to a change of the dominant reactions and significantly changes the distribution coefficients. These features of the behaviour of the elements under consideration have led to the fact that the effective development of the technology of REE and TPE separation is practically impossible without designing a multifactor computer model of the process The formal system of equations of chemical thermodynamics (CTD) is a convenient element for presenting and processing data during modeling such systems. Relying on this postulate, we have developed a new specialized numerical method for calculating the composition of equilibrium chemical systems through the iterative solution of the formal system of CTD equations. The developed program based on this numerical method was used to optimize the technology of extraction separation of REE and americium.

Sodium-ion batteries (SIB) are the nearest alternative to lithium ion batteries (LIB) for stationary energy storage devices. However, at the moment, SIB are inferior to LIB in energy density due to the lower efficiency of sodium-containing electrode materials, which encourages the emergence of new developments in this field. The review provides examples of some promising sodium-containing cathode materials obtained by mechanochemically assisted solid-state synthesis. It is shown that this approach is an energy- and eco-efficient method for the synthesis of single-phase, nanostructured cathode materials. An increase in their electron conductivity is achieved through surface modification with an electrically conductive carbon at the stage of synthesis. A complex of modern physicochemical methods was used to study their crystal and local structure, morphology, and electrochemical properties during cycling in both Na and Li electrochemical cells. The specific energy was compared with that of the known lithium-containing cathode materials.

Results of fundamental research carried out at the Institute of Solid State Chemistry and Mechanochemistry SB RAS on the development of technologies for extracting lithium from both mining and hydromineral raw materials are presented. In the 50s of the last century, the Institute was the first in Russia to develop a technology for processing spodumene concentrate to obtain lithium compounds. In order to develop a technology for extracting lithium from hydromineral raw materials, the processes of lithium chloride intercalation into the crystal structure of aluminium hydroxide have been studied. It has been shown that the intercalation process is accelerated when disordered Al(OH)₃ is used. In order to create a technology for extracting lithium from brines, double compounds of aluminium and lithium were obtained using amorphous aluminium hydroxide. These compounds possess the ability to partially deintercalate lithium chloride when treated with water and to restore the composition again in lithium-containing salt media. This reversible process is the basis for the development of a selective sorbent for the sorption of lithium chloride from highly mineralized multicomponent brines.

The effect of electron-beam treatment with doses up to 450 kGy on the properties of triaminotrinitrobenzene (TATB) was studied. A linear dependence of the number of paramagnetic centres on the treatment dose and their stability upon heating have been revealed. It is shown that electron beam treatment leads to an increase in the interlayer distance in the crystal structure of TATB, causes a significant increase in its volatility and a decrease in the temperature of the onset of intense decomposition by 20 ^oС.

The matrix material based on NdAlO₃ was obtained by means of self-propagating high-temperature synthesis of the NiAl intermetallic compound by diluting the mixture of Ni and Al components with Nd₂O₃-Al₂O₃ oxides. Nd₂O₃ was used as a simulator of actinoids in high-level radioactive wastes. The influence of the batch parameters of the initial components on the synthesis process was studied and optimal conditions for preparation were determined: the density of the system should not exceed 5.2 g/cm³ and the content of the included radioactive waste simulator should not exceed 40 mass %. The composition of the final product and its properties were studied using a complex of physicochemical methods. According to the data of XRD analysis, the maximum possible formation of the NdAlO₃ phase is observed for the sample containing 40 mass % Nd₂O₃-Al₂O₃, with the density of 5.15 g/cm³, obtained by pressing at a pressure of 30 MPa. The studies of the material characteristics have shown the simulator maximum leaching rate 2.66 · 10^-9 g/(cm² · day) . The limits of matrix characteristics variations were determined through the simulation of the storage of matrix material in geological formations by irradiation with neutron fluxes in a research reactor. For instance, a decrease in hydrolytic stability was 10-13 % and a decrease in compressive strength was 7 % on average. The general regularities of structural changes in the matrix material under the influence of ionizing radiation fluxes were considered. Insignificant destruction of the crystal structure was observed due to the appearance of various defects. The limiting value of the changes in sample volume was 4.3 %. However, the characteristics of the samples meet all the requirements to materials intended for the immobilization of radioactive waste.

Results of the works on the development of the technology of phloroglucinol production are presented. Phloroglucinol is a known multipurpose organic reactant that has gained wide and diverse applications, in particular as the starting compound for the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene. A review of the known methods of phloroglucinol synthesis is presented. The method which is most promising from the standpoint of commercialization is studied. The method is based on the reduction of nitroaromatic precursors - 2,4,6-trinitrobenzoic acid and 1,3,5-trinitrobenzene - to 1,3,5-triaminobenzene, followed by its hydrolysis. Alternate approaches to the synthesis of 2,4,6-trinitrobenzoic acid from 2,4,6-trinitrotoluene are proposed. The catalytic hydrogenation of 2,4,6-trinitrobenzoic acid and 1,3,5-trinitrobenzene over palladium-containing catalysts was studied in detail, and the effect of various process parameters on the yield of the reaction product 1,3,5-triaminobenzene was determined. Hydrolysis of triaminobenzene to form phloroglucinol is considered.