KIPOUROS INTERNATIONAL SYMPOSIUM (8TH INTL. SYMP. ON SUSTAINABLE MOLTEN SALT, IONIC & GLASS-FORMING LIQUIDS AND POWDERED MATERIALS)

The fuel compositions for molten-salt nuclear reactor of the 4th generation are usually fluorides of metals with a small cross-section of neutron capture [1-3]. Сhloride systems, compared to fluoride, have higher vapor pressures and lower thermodynamic stability at high temperatures. At the same time, they are less aggressive in relation to the structure of the material and have lower melting temperatures. Therefore, in order to ensure the more reliable operation of the next generation reactors, it is necessary to consider chemical processes and equilibrium in mutual fluoride-chloride systems. Among the binary systems composed of fluoride or chlorides of alkaline metals and uranium (plutonium) we can say, that all fluoride systems forming ternary M1,M2,U(Pu)||F (M1,M2=Li,Na,K,Rb) are experimentally studied in more or less detail. But the chloride systems M1,M2,U(Pu)||Cl (M1,M2=Li,Na,K,Rb) have been studied much less. And there is no information about the study of ternary reciprocal systems M,U(Pu)||F,Cl (M=Li,Na,K,Rb). Accordingly, the polyhedration of the M1,M2,U(Pu)||F,Cl (M1,M2=Li,Na,K,Rb) quaternary reciprocal systems can only be multivariate, and the construction of 4D computer models T-x-y-z diagrams of the resulting subsystems - virtual. Four variants of the Li,Na,U||F,Cl system polyhedration are discussed and 3 quintets of four- dimensional T-x-y-z diagrams for the quaternary systems have been forecasted. This work was been performed under the program of fundamental research SB RAS (project 0336-2019-0008), and it was partially supported by the RFBR project 19-38-90035.

The interionic forces in molten electrolytes can be classified according to the number of particles entering to the interaction energy. The first group includes the pair interactions: the repulsions at short distances, the London dispersion forces and the Coulomb interactions. The most difficulty is the consideration of the second group, namely, induction interactions, since the charge of a given ion induces dipole moments on neighboring ones, which will not only interact with each other, but also induce dipole moments on other ions. The charge-induced dipole part of the energy can be calculated for molten salts by introducing the dielectric constant to avoid the many-body problem [1]. The difficulty of statistical-thermodynamic calculations is the absence of exact solutions for complicated interaction models (for example, taking into account the induction interactions).
From a physical standpoint, the problem of the thermodynamics of molten alkali halides can be usefully considered in terms of thermodynamic perturbation theory [2], which allows extra terms to pair potentials to be taken into consideration based on analytical statistical mechanics models. Therefore, objectives of this report are to propose the model based on the thermodynamic perturbation theory, which provides the possibility of reducing the charge-induced dipole contribution to the relatively simple pair potential, using the reference system of charged hard spheres and to present the results of calculations for this term to the thermodynamics of alkali halide melts.
The Helmholtz free energy for the reference system of liquid melts included the standard contribution of the ideal-gas mixture [3], the hard-sphere contribution within the Mansoori-Carnahan-Starling-Leland approximation [4], and the Coulombic contribution within the mean spherical approximation [5]. The perturbation to the free energy due to the charge-induced dipole interactions was taken into account through Gibbs-Bogoliubov approach of the thermodynamic perturbation theory.
We will demonstrate, that the fraction of the ion-dipole contribution to the free energy is not more than 10 percent, while its absolute values for alkali halides lies in the range of 30–60 kJ/mol. The discrepancy between the calculated and available experimental enthalpies do not exceed 10 percent for most considered halides. Moreover, the calculated temperature dependences of enthalpy almost completely correspond to the experimental data on its base trend, when the enthalpy of the melts slightly increases with heating. The report will present and analyze the results of modeling the temperature dependences of the free energy, the enthalpy and other thermodynamic characteristics for molten alkali halides.
The reported study was funded by RFBR, projects number 19-33-90180 and number 18-03-00606.

Titanium (Ti) is the ninth-most abundant element of the Earth’s crust. Ti and its alloys have excellent characteristics, such as high specific strength and high corrosion resistance; however, their use is currently limited in specific areas because of their high production costs. Feeding Ti scraps with virgin Ti for ingot production is an approach to reduce these costs. In this process, scrap dosages are limited to avoid increasing the O concentration of the ingot. Reducing the concentration of O in Ti and its alloys is a significant challenge due to high affinity of Ti for O and high solubility of O in Ti. To increase scrap dosage, we developed a new deoxidation process for Ti and its alloys. In this work, Ti and Ti alloys were deoxidized in a molten salt electrolyte using rare-earth metals (e.g., Y, La, and Ho) as reducing agents[1–10]. By utilizing the formation of rare-earth oxyhalides, we demonstrated that the O concentration in Ti could be decreased to less than 100 mass ppm, lower than that in the virgin metals (Sponge Ti). Therefore, we named this process the “upgrade recycling process,” and have implemented it for Ti alloys. We believe this new method is a promising technique to promote the recycling of Ti and its alloys, lowering the price of Ti products in the future.

KEYWORDS: Molten salts; Conductivity; LiCl-KCl; SrCl₂.
In the course of the pyrochemical reprocessing of spent nitride nuclear fuel (SNF), multicomponent molten mixtures based on the LiCl-KCl eutectic are formed. It is impossible to measure electrical conductivity of all multicomponent mixtures, that is why a common model, which allows calculating the electrical conductivity of complex mixtures according to the electrical conductivity of binary mixtures, should be developed. The present work is a part of works aimed at the development of a model for calculation of the electrical conductivity of complex melts based on LiCl-KCl eutectic, containing components of spent nuclear fuel. In continuation of our previous studies [1, 2] in the present work the electrical conductivity of 13 compositions of (3LiCl-2KCl) - SrCl₂ mixtures was measured at the temperatures of 616-1198 K in the concentration range of 0-100 mol. % with the increment of ~ 10 mol. % of SrCl₂ using capillary quartz cells with platinum electrodes. The AC-bridge method at the input frequency of 75 kHz was used. The liquidus line of the system was plotted based on the conductivity data.
The values of electrical conductivity of all melts increase as the temperature increases and they decrease as the concentration of SrCl₂ increases. The specific electrical conductivity (κ, S/cm) of several molten mixtures is exemplified below:
κ = -4.6316 + 1.0862*10^-2T - 3.6361*10^-6T² , (625-1150 K) 10 mol.% SrCl₂;
κ = -4.4607 + 9.0791*10^-3T - 2.6880*10^-6T² , (773-1151 K) 40 mol.% SrCl₂;
κ = -5.3748 + 9.7550*10^-3T - 2.8376*10^-6T² , (983-1158 K) 70 mol.% SrCl₂.
The molar conductivity was calculated using previously proposed equations for density of MCl-MeCl₂ (M - alkali metals; Me - divalent metals) systems [3]. The molar conductivity of molten mixtures decreases gradually from (LiCl-KCl)_eut. to pure SrCl₂ with a blurred mild minimum around 70 mol.% of SrCl₂ (1150 K).
The results were interpreted in terms of coexistence and mutual influence of the complexes formed by the Li⁺ and Sr²⁺ cations.

KEYWORDS: Molten SnCl₂; Electrical conductivity maxima.
The electrical conductivity of molten SnCl₂ was measured in a wide temperature range (∆T = 763 K) from 551 K to temperature as high as 1314 K that is 391 degrees above the boiling point of the salt. The studied temperature range is extended by 79 degrees towards higher temperatures in comparison with the available data [1] and thereby the presence of the maximum in the electrical conductivity polytherm (2.815 S/cm at 1143 K) is confirmed.
Due to the fact that under our experimental conditions the values of vapor pressure above the melts reached several tens of atmospheres, the measurements were carried out in a specially constructed capillary type cell, designed to operate at high pressures. The cell was made of quartz with graphite electrodes [2, 3]. For conductivity measurements an AC bridge with the input frequency of 10 kHz was used.
Our data (∆T = 551–1314 K) are well approximated by the following equation:
k = -4.02417 + 1.19270*10^-2T - 5.19936*10^-6T², S/cm; T, K. (1)
The “dome” area of the conductivity polytherm of molten SnCl₂ (our data, ∆T = 968–1314 K) is approximated more precisely by the following equation:
k = -3.92031 + 1.17428*10^-2T - 5.11853*10^-6T², S/cm; T, K. (2) After 1143 K the electrical conductivity decreases as the temperature increases. The fastest rate of reduction of the melt conductivity should be in the vicinity of a critical point of SnCl₂: T_c = 1459 K and P_c = 12 MPa, as the melt becomes more and more gas-like.
The reasons for the appearance of maxima on the conductivity polytherms of molten stannous chloride are discussed.

KEYWORDS: Molten salt; Mixtures; KCl-ZrCl₄; KCl-HfCl₄; Electrical conductivity. To perfect the technological processes of electrodeposition and electrorefining of zirconium and hafnium, information on the electrical conductivity of ZrCl₄ and HfCl₄ solutions in molten alkali metal chlorides is needed. The electrical conductivity of KCl-MCl₄ (M = Zr or Hf) melts, containing volatile ZrCl₄ and HfCl₄ up to 25–30 mol. %, was studied in the temperature range of 900-1100 K, at which the vapor pressure above the melt is less than 1 atm. Such melts are of interest for industrial use.
It was found that the electrical conductivity increases as the temperature increases and that it decreases as the MCl₄ concentration increases. When interacting with molten KCl, the ZrCl₄ and HfCl₄ molecules ionize with the formation of strong octahedral ZrCl₆^2- and HfCl₆^2- anions [1]. Thus, as the concentration of MCl₄ in molten alkali metal chlorides increases, the concentration of nonmobile MCl₆^2- complexes containing six strongly bound chlorine anions increases. This leads to a decrease in the concentration of electricity carriers. The proportion of K⁺ and, especially, Cl^- - ions decreases and, accordingly, decreases the conductivity of the melts. The specific electrical conductivity (κ, S/cm) isotherms at 1073 K of KCl-ZrCl₄ and KCl-HfCl₄ molten mixtures is exemplified below depending on the concentration of ZrCl₄ or HfCl₄ (mol. %), respectively:
k = 2.2394 - 7.7639*10^-2 [ZrCl₄] + 1.3656*10^-3 [ZrCl₄]²,
k = 2.2373 - 7.7800*10^-2 [HfCl₄] + 1.2902*10^-3 [HfCl₄]².
The relative decrease in electrical conductivity with increasing MCl₄ concentration is more pronounced in the case of HfCl₄, since Hf(IV) forms stronger complex chloride anions than Zr(IV) in molten KCl.
It has been established that the values of electrical conductivity of the melts studied in this work are significantly higher (0.89–1.65 S/cm) than those of the previously studied low-melting mixtures of zirconium tetrachloride with KCl (0.23–0.33 S/cm) with the high ZrCl₄ content of 65-72 mol. % [2, 3], which are also promising for industrial use.

Carbamide melts have found applications as electrolytes for electrochemical treatment of metals [1, 2]. The possibility of electrodeposition of cobalt from carbamide melts at 408 K has been examined for tungsten as an example. When studying the electrochemical behaviour of cobalt oxide in molten carbamide, it can be concluded that maximum limiting currents are typical of the system (NH2)2CO-CoO. Cobalt coatings on nickel cathodes have been obtained by the electrolysis of the molten system (NH2)2CO-CoO at current densities of 20-30 mA/cm².

KEYWORDS: dealloying, molten salts, Ag-Zn alloys
ABSTRACT
Electrochemical dealloying as a promising method for producing metals with a highly developed surface is widely studied in aqueous solutions [1, 2]. However, there are very few works devoted to studying it in liquid salt ionic media at elevated temperatures.The possibilities of using anhydrous high-temperature ionic electrolytes for the production of porous metals have not yet been disclosed, and the regularities of dealloуing in such media have not been clarified.
The purpose of this work is to establish the features of the selective anodic dissolution of zinc from its alloys with silver in еutectic melts of alkali chlorides.Two homogeneous Ag-Zn alloyswere prepared by fusing the components under a layer of molten salts. The zinc content in the alloys was 67 and 46 mol.%, which corresponded to the ε and β phases of the phase diagram and the investigatedtemperature interval was from 300 up to 500 °С. EutecticsLiCl0.57CsCl0.26KCl0.17and CsCl0.455KCl0.245NaCl0.30was used as electrolytes.Three-electrode cell was designed for the experiments. A glassy carbon crucible served as a reservoir for the melt and, at the same time, as the counter electrode. The reference electrode was a silver wire immersed in the same melt with addition of 3 mol. % AgCl in a micro-perforated alundum tube. Selective anodic dissolution of alloys carried out in potentio- and galvanostatic modes varying the voltage and the current density.
Practically full zinc removal was achieved at a current density of about 20 mA/cm2 in the case of the ε phase and 7 mA/cm2 for the β phase in galvanostatic mode. The selectivity of the dealloyng decreased with the increasing current density. Typical homogeneous porous structures obtained on the surface of Zn0.67Ag0.33 alloywith pores and ligaments of approximately the same size lying in the range of 0.5–5 μm. For the Zn0.46Ag0.54, dendritic structures with sizes of silver particles of the order of 0.5–4 and 5–20 μm formed. It was shown that the increase in the process temperature led to the coarsening of the porous structure.
Thus, we have shown the possibility of percolation-type electrochemical dealloying and found the best method for the most dezincification of the alloy. The regularities of the influence of the alloy composition, temperature and electrolysis mode on the composition and structure of the resulting product have been established.
This work was supported by Russian Foundation for Basic Researches (20-03-00267)
REFERENCES:
[1] J. Weissmüller, K. Sieradzki, MRS Bulletin, 43 (2018) 14-19.
[2] J. Zhang, Ch.M. Li, Chem. Soc. Rev., 41(2012)7016–7031.

The peculiarities of the Li₂CO₃ electroreduction in pure carbonate and halide-carbonate melts have been studied by many authors [1-5]. This interest is due to the importance of this process for the production of nano-sized electrolytic carbon with a unique structure and morphology, since the solid-phase carbon deposition was carried out mainly from the salt melts containing lithium carbonate. However, there are wide differences in the obtained results. This is caused by the different research conditions. The authors, as a rule, studied the process at one depolarizer concentration, in a wide temperature, current and potential ranges, on different cathode materials and under the gaseous media of one composition. The purpose of this study was the voltammetric study of this process in a molten equimolar NaCl-KCl mixture in wide ranges of Li₂CO₃ concentrations (1.0-15.0×10^-4 mol·cm^-3) and polarization rates (0.02-0.10 mV·s-1) on platinum and glassy carbon cathodes in different gaseous media (air, in an inert atmosphere of argon and in an atmosphere of CO2) at a temperature of 750 °C.
It was found that the electroreduction of Li2CO3 in air occurs through the stage of a preliminary chemical reaction of acid-base type (Li2CO3 ⇄ Li2O + CO2) to form two electrochemically active particles: CO2 and Li_xCO₃^2-x, which are reduced to elemental carbon at potentials of -0.8 and -1.7 V respectively against Pt|O₂/O^2- reference electrode. Both processes are irreversible, and the electroreduction of Li_xCO₃^2-x takes place with diffusion control of the delivery of the depolarizer to the electrode surface.
Under of argon or carbon dioxide atmosphere over the melt, the process of lithium carbonate dissociation is suppressed; therefore, the deposition of carbon in this case occurs only from the cationized carbonate complex.
X-ray diffraction, SEM and Raman spectroscopy revealed that the cathode product is a high disordered amorphous carbon. Agglomerated particles consist of degraded graphite structures with an approximate crystallite size of 30–40 nm.

The global warming, caused by the increase in the emission of greenhouse gases, such as carbon dioxide (CO2), methane (CH4) and others, has been recognized as a serious environmental problem of the humanity. At the present time, the annual increase in CO2 is 3200-3600 million tons. According to the calculations of the International Group of Experts on Climate Change (IGECC), if CO2 emissions continue to increase at this rate, the average annual temperature on the Earth will increase by 1.5-4.5 ºC by the end of the 21st century. Therefore, the effective utilization of carbon dioxide is a topical scientific and environmental problem. The CO2 utilization methods can be conditionally divided into biological, chemical and physical ones. Among the chemical methods, the electrochemical method is an efficient but still poorly developed method. It involves the electrochemical decomposition of CO2 at the cathode. Depending on the electrolysis conditions (electrolytic bath composition, temperature, current density, electrode materials), the chemical composition of cathodic products can change dramatically. The electroreduction of carbon dioxide in molten salts can be considered one of the possible ways of solving this problem. A peculiarity of the electroreduction of CO2 dissolved in molten salts is the deposition of a solid carbon phase on the cathode in contrast to aqueous, organic (ionic liquids) and solid-oxide electrolytes. The investigation of this process is dealt with in a large number of original papers and reviews [1-3]. These works contain certain contradictions as to the compositions of electrolysis products; there are also contradictions in the interpretation of obtained data and proposed mechanisms of electrode processes. The aim of this report is to consider the present state of research on the electrochemical conversion of carbon dioxide from different types of electrolytes: aqueous, organic (ionic liquids), solid-oxide and molten salt. The comparative analysis of the effectiveness of using these electrolytes, as well as cathodic products obtained by carbon dioxide decomposition and prospects for their use will be done. Special emphasis is made on the electrochemical decomposition of carbon dioxide in salt melts, several variants of decomposition are shown, the advantages and disadvantages of each variant are analyzed.

Anthropogenic CO2 emission is driving global warming, hence causing a drastic change in earth's geological and ecological systems. One of the solutions to reduce CO2 emission is to capture it from large point sources and store in geological strata or use it in enhanced oil recovery (EOR). Among many technologies, amine-based CO2 capture process is the most mature one and it offers high CO2 capture capacity and rapid kinetics. However, high regeneration energy, degradation and corrosion for the amine systems [1] compelled researchers to find alternate solvents. Ionic liquids (ILs) known as green solvents are molten salts at room temperature fulfil those criteria of low regeneration energy, negligible volatility and high thermal stability.[2] But, low CO2 uptake and high viscosity is the hindrance for deployment in CO2 capture operation [3]. To improve CO2 uptake, researcher have deployed strategies of functionalizing ILs with amines then known as task specific ionic liquids (TSILs)[4], but costly synthesis and purification steps, excessive viscosity forming gel like solids upon CO2 uptake are major obstruction for CO2 capture operation. An alternate strategy of blending the amines with ILs have shown promising results, such blended systems retain the desired properties of ILs but exclude the drawbacks of TSILs such as high synthesis cost and high viscosity. Moreover, the regeneration process requires lower energy as ILs replaces water fully or partially without compromising the absorption performance. A number of blended systems have been reported in the literature, however, in search of better blended systems with higher CO2 capacity but lower viscosity, new blended systems comprising of water, amines (Piperazine (PZ)) and ILs (1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) were investigated.
Herein, the concentration of PZ was kept constant at 15 wt.%, while the concentration of ionic liquid (ILs) was varied from 0 to 60 wt.% by replacing the corresponding amount of water. Experiments were conducted up-to a CO2 partial pressure of 300 kPa at (313 and 333) K. In addition, the density and viscosity of all the blended systems were measured for the temperature range of (303 to 333) K at atmospheric pressure. The results indicated that the CO2 uptake in all blended systems increased with the increase in CO2 partial pressure. In addition, CO2 uptake decreases for all systems with an increase in temperature. No significant change in CO2 uptake was observed for the addition of ILs up to 30 wt.% to aqueous PZ, however a dramatic increase in CO2 uptake was observed for ILs concentration of 60 wt.%. Moreover, it was found that the viscosities of the blended systems are significantly lower than the pristine [Bmim][Ac] as well as other functionalized ionic liquids (TSILs) reported in the literature. The results reveal that aqueous PZ + [Bmim][Ac] blended systems have the potential to overcome the drawbacks of IL/TSILs while retaining superior CO2 capture performance.

In recent years, tungsten carbides are extensively used in engineering applications, such as cutting and mining tools, surface coatings, chemical and electronic industries [1]. Also, tungsten carbides (especially nanoscale) are widely used as a catalytic material [2, 3]. Most modern methods of producing tungsten carbides are hindered by either multi-stage processes or their high energy costs. One of the most attractive methods for producing nanoscale materials is by means high-temperature electrochemical synthesis (HTES). The essence of the method of HTES is the use of electrochemical processes for the decomposition of the carbon and tungsten precursor with further interaction of reduction products and the formation of carbides. This paper is devoted to the production of nanoscale tungsten carbides by the method of HTES. Taking into account specific features of partial and joint electrochemical reduction of carbon and tungsten in different systems, we chose optimum conditions for obtaining highly dispersed tungsten carbides. A high yield of nanopowders of hexagonal α-WC with nano-dimensional carbon structures could be obtained using the NaCl–KCl–Li₂CO₃ (2*10^-3 mol/cm³)–Na₂W₂O₇ (6*10^-4 mol/cm³) molten salt system with pressure of CO₂ 10 atm. at 750 °C. The current density is 0.2 A/cm². The particles were characterized using XRD, SEM, TEM, Raman spectroscopy, BET and DTG methods. The size of WC and W2C can be less than 8 nm with the specific surface area of the powders 25–30 m²/g. Based on SEM images, it has been found that the WC nanoparticles are connected together into conglomerates, which are enveloped in a “fur coat” and which apparently consist of carbon. Four types of particles have been established: curdled, slightly coherent conglomerates, layered particles individual nanofibers and nanorods. These properties allow the use of electrolytic tungsten carbides as a electrocatalyst. The electrocatalytic properties of the synthesis carbides for the hydrogen evolution reaction (HER) in acid solution were investigated by using the electrochemical techniques of cyclic voltammetry. Investigations have shown that it is possible to produce by the HTES nanosized powders of tungsten carbides which can be used as electrode material for the HER in the solution of H₂SO₄.

New Research Lines in the Synthesis of Alloys and Compounds via the FFC-Cambridge Electro-deoxidation Process
Carsten Schwandt
Department of Materials Science and Metallurgy, University of Nizwa,
Birkat Al Mouz Initial Campus, 616 Nizwa, Sultanate of Oman;
Department of Materials Science and Metallurgy, University of Cambridge,
27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom;
carsten@unizwa.edu.om, cs254@cantab.net
Abstract
The FFC-Cambridge process is a generic molten salt electrolytic method that was invented at the Department of Materials Science and Metallurgy of the University of Cambridge almost two decades ago. It makes possible the direct conversion of metal oxides into the corresponding metals through the cathodic polarisation of the oxide in a molten salt electrolyte based on calcium chloride [1]. The process is rather universal in its applicability, and numerous studies on metals, alloys and intermetallics have since been performed at the place of its invention and worldwide [2].
This presentation will first give an introduction into the fundamentals of the FFC-Cambridge process and will then feature some of the more recent and ongoing research lines. Their overarching theme is the harnessing of this process for the synthesis of multinary materials that are difficult to achieve via conventional metallurgical methods. Specific systems of interest include high-entropy alloys [3], high-entropy carbides [4], biomedical alloys based on beta-titanium [5], and nano-structured silicon carbide [6]. Also touched upon will be the possibility of the combined generation of metals and oxygen from lunar materials [7].

We examined the kinetic and transport processes involved in Mg production from MgO via electrolysis at circa 1250 K with in a eutectic mixture of MgF2-CaF2 , a Mo cathode, and carbon anode. Exchange current densities, transfer coefficients, and diffusion coefficients of the electroactive species were established with a combination of cyclic and linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The cathode kinetics are described by a concentration dependent Butler Volmer equation. The exchange current density and cathodic transfer coefficient are 11 ± 4 A-cm-2 and 0.5 ± 0.12 respectively. The kinetics of the anode are described by two Tafel equations: at an overvoltage below 0.4 V, the exchange current density is 0.81 ± 0.2 mA-cm-2 with an anodic transfer coefficient of 0.5±0.1; above 0.4 V overvoltage the values are 0.14 ± 0.05 mA-cm-2 and 0.7±0.2 respectively. The diffusion coefficients of the electroactive species are DMg2+ = 5.2 e -5 ± cm2 s-1 and D_(〖Mg〗_2 ) OF_4^(2-) 7.2 ± 0.2 e-6 cm2-s-1. The ionic conductivity of the electrolyte is circa 2.6 S-cm-1. A 3D finite element model of a simple cell geometry incorporating the these kinetic and transport parameters suggest that 30% of the energy required to drive the electrolysis reaction can be supplied thermally for a current density of 0.5 A-cm-2.
Although the work has broad relevance to the vast number of current and developing industrial processes that use or may use molten halide systems, our motivation for doing this work was narrow: the development of a new process for producing Mg from MgO. Phase diagrams (solubility), density, electrical conductivity and viscosity of molten system (MgF2 – CaF2)eut – MgO have been investigated. The phase diagram of (MgF2 – CaF2 – LiF)eut – MgO and (MgF2 – BaF2)eut– MgO and the density of (MgF2 – CaF2 – LiF)eut – MgO have been also investigated. The solubility of MgO was measured by means of thermal analysis, the density by means of a computerized Archimedean method, electrical conductivity by means of a tube–cell (pyrolytic boron nitride) with stationary electrodes and the viscosity of the melt by computerized torsion pendulum method. It was found that the all investigated properties varied linearly with temperature in all investigated mixtures. On the basis of density values, the molar volume of the melts and partial molar volume have been calculated. The coordinates of the eutectic systems has been established as follows: (CaF2 – MgF2)eut – MgO as 0.30 mole % at 972 °C; (CaF2 – MgF2 – LiF)eut – MgO as 0.20 mole % at 941 °C; and (MgF2 – BaF2)eut. – MgO as 0.25 mole % at 883 °C. The density of the molten system of (CaF2 – MgF2)eut – MgO was found to be at 1000 °C: 2.687 g.cm-3 for the system with 0 mole % of MgO; 2.700 g. cm-3 for the system with 0.30 mole % of MgO and 2.728 g.cm-3 for the system with 0.50 mole % of MgO. The density of the molten system of (CaF2 – MgF2 – LiF)eut – MgO was found to be at 1000 °C: 2.875 g cm-3 for the system with 0 mole % of MgO; 2.690 g.cm-3 for the system with 0.20 mole % of MgO and 2.650 g.cm-3 for the system with 0.30 mole % of MgO. The viscosity of basic eutectic mixture of (CaF2 – MgF2)eut at 1000 °C was found to be 7.806 mPa.s.

Currently, in a number of countries, various options for pyrochemical (using molten salts) technologies are being developed. These technologies would ensure efficient disposal of spent nuclear fuel, reduction of radioactive waste, extraction of uranium, plutonium and electrolyte purification for the repeater usage in reactors [1]. In order to assess the possibility of selective evaporation of various components of salt electrolytes, in this work, experimental distillation of chlorides from their molten mixtures under various conditions was carried out. In all cases, CsCl, BaCl₂, SrCl₂, NdCl₃ (1-2 mol%) dilute solutions, as representatives of alkali, alkaline earth and rare earth metal chlorides solutions in the molten eutectic LiCl - KCl mixture, were subjected to evaporation at the reduced (up to ~ 1 Pa) pressures and temperatures of 753-1033 °C. The compositions of sublimates and molten salts before and after the distillation were analyzed.
It was found that in all cases alkali metal chlorides were the main components of vapor condensates, the content of alkali- and rare earth elements or uranium in sublimates was negligible. The distillation rate of salts with continuous evacuation of vapors was many times higher than during evaporation in sealed devices and sealed ampoules [2]. Conclusions about the degree of distillation, the selectivity of evaporation of the components of molten mixtures, and the relative volatility of various chlorides are made. The found dependences can be useful for the development of promising schemes for SNF reprocessing using salt distillation.

Anthropogenic emission of carbon dioxide (CO2) is accelerating global warming. One of the technologically advanced techniques for mitigating CO2 emission is to capture CO2 from the major point of sources such as flue-gas and store in geological storage. Apart from the storage in geological formation, captured CO2 can also be used in enhanced oil recovery. Furthermore, CO2 capture process is also used for natural gas sweetening to maintain the quality of natural gas. CO2 capture with the alkanolamine based chemical solvents is the most efficient technique that has been used for long-time, but this technique is still not economical due to high regeneration cost, high amount of solvent degradation and high corrosiveness. Ionic liquids (ILs) which are molten salt with a melting point below 373.15 K [1] have received enormous research emphasis recently as an alternative to reactive solvents as they require much less energy for regeneration and they possess special physical properties such as non-flammable, negligible vapor pressure, high stability, etc.
Previous study showed that the anion part of the ILs has more significant effect on the solubility of gases in ILs and the cation has a minor effect [2]. Moreover, the presence of S=O groups and fluorination in anion increase solubility of CO2 in ILs [3]. Due to the presence of S=O groups and fluorination in bis(trifluoromethylsulfonyl)imide ([Tf2N]) and bis(fluorosulfonyl)imide ([FSI]) anion, four [Tf2N] based ILs and three [FSI] based ILs were selected for this study. The major objectives of this study were to investigate the solubility of carbon dioxide (CO2) and ethane (C2H6) in [Tf2N] and [FSI] anion based ILs, estimate the selectivity towards CO2 over C2H6 for these ILs and compare the solubility of CO2 and selectivity among these ILs.
Solubility of CO2 and C2H6 in [Tf2N] and [FSI] ionic liquids, {N,N-dimethyl-N-ethyl-N-(3-methoxy-propyl)ammonium bis(trifluoromethylsulfonyl)imide, 1-Allyl-3H-imidazolium bis(trifluoromethyl sulfonyl)imide, 1-(3-Hydroxy propyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, N,N-diethyl-N-methyl-n-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, 1-Methyl-1-propylpiperidinium bis(fluorosulfonyl)imide, N-propyl- n-methylpyrrolidinium bis(fluorosulfonyl)imide, and N,n-diethyl-n-methyl-n-propylammonium bis(fluorosulfonyl)imide} were measured at (303.15, 323.15, and 343.15) K and at pressures up to 1.5 MPa with a gravimetric microbalance. Solubility of CO2 and C2H6 in these ILs increased significantly with the increase in pressure in a linear manner and reduced with an increase in temperature. Henry's law constants, enthalpies and entropies for the absorption of CO2 and C2H6 were estimated from the solubility data. Experimental solubility data were correlated with the Peng-Robinson (PR) equation of state. The selectivities towards carbon dioxide (CO2) over C2H6 for these ILs were also estimated. Results showed that [Tf2N] based ILs exhibited higher CO2 solubility compared to [FSI] based ILs, while [FSI] based ILs exhibited higher selectivity towards CO2.

Gipronickel Institute LLC, forming part of Norilsk Nickel MMC PJSC, has developed and patented the solid household and industrial waste management process based on the extensively used Vanukov furnace smelting technology. The process ensures complete destruction of poisonous and toxic compounds as a result of smelting in the actively stirred melt due to high temperatures exposure, the use of oxygen blast and rapid gas cooling. The following can be processed using this technology: stored unsorted solid domestic waste, newly formed unsorted solid household waste, organic part of sorted solid household waste, industrial waste, including chemical waste, and chemical warfare agents. The report presents a comparative analysis of the suggested method with familiar solid waste management processes, outcomes of new process technology pilot testing, and basic technical solutions for project implementation.

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