Results Of Thermodynamic Modeling Research Articles

Preparation of dilute solutions of rare earth metal trichlorides by chlorination of their oxides in a molten NaCl-KCl equimolar mixture

The article is devoted to the study and thermodynamic justification of the method for obtaining dilute solutions of rare earth metal trichlorides by chlorination of their oxides in a molten equimolar mixture of NaCl – KCl. And the effectiveness of this method is demonstrated by the example of lanthanum (III) and neodymium (III) oxides. Gibbs free energy of the reactions of La2O3 and Nd2O3 chlorination by different chlorinating agents has been calculated. The interaction of lanthanum (III) and neodymium (III) oxides in the molten equimolar mixture NaCl – KCl depending on the chlorination time and the material of reaction vessel (beryllium oxide and glass-carbon) has been studied experimentally. The results of thermodynamic modelling of the chlorination reactions of La2O3 and Nd2O3 by gaseous chlorine in this salt melt are presented. In the case of using a molten equimolar mixture of NaCl – KCl, a significant shift of the Gibbs energy to the negative region is observed compared with chlorination without the use of a salt medium. The effectiveness of chlorine as a chlorinating agent in the melt is based on the fact that in liquid NaCl-KCl Ln3+ ions form complexes with very small activity coefficient. The removal of synthesized lanthanum trichloride from the chlorination reaction zone due to its solubility in a low-viscosity NaCl-KCl melt has a beneficial effect on the rate of its flow. It has been shown that the formation of rare earth metal trichlorides occurs through the formation of LaOCl and NdOCl oxychlorides. The advantages of the proposed method of chlorination of rare earth metal oxides (REM) in the synthesis of solutions of their trichlorides in molten salts are shown.

The estimation of desulphurization property of boron-containing slags of the reduction period of the AOD process

Now the main industrial method for producing stainless steel is smelting in an argon-oxygen decarburization (AOD) furnace, therefore the paper presents the results of thermodynamic modeling of the desulfurization process of low-carbon semi-finished stainless steel during the reduction period of AOD process by treating it with boron-containing slags. The use of boron oxide as a fluxing material instead of fluorspar reduces the environmental harm and decrease the viscosity of the formed slags. Using the simplex lattice method of experiment planning, a matrix was constructed containing 16 compositions of the oxide system СаО–SiO2–(3-6%)В2О3–12%Cr2O3–3%Al2O3–8%MgO with variable basicity of 1.0–2.5. Based on the generalization of the thermodynamic modeling results, approximating mathematical models in the form of a reduced third-degree polynomial were constructed. The adequacy of the models is verified by three control points not included in the experimental design matrix using the t-criterion at a significance level of 0.01. The results of mathematical modeling are presented graphically in the form of diagrams of the dependence of the equilibrium sulfur distribution on the slag composition at temperatures of 1600 and 1700°C. The constructed diagrams made it possible to quantitatively estimate the effect of temperature, basicity and boron oxide content on the equilibrium interphase distribution coefficient of sulfur. It is found that an increase in slag basicity from 1.0 to 2.5 in the considered range of boron oxide content (3.0–6.0%) improves the metal desulfurization process, ensuring an increase in the equilibrium interphase distribution coefficient of sulfur from 0.1 to 5.0–7.0 at temperatures of 1700 and 1600°C. It’s shown that the process of metal desulfurization in slags with low basicity of 1.05–1.15 is accompanied by a slight decrease in the sulfur content in the metal. At the same time, the concentration of boron oxide has virtually no negative effect on the process of metal desulfurization. Slags with increased basicity up to 2.0–2.5 have more favorable refining properties. The sulfur concentration in the metal during their formation decreases from 0.015 to 0.007–0.008%.

Thermodynamic modeling of converter sludge sintering

Currently, a promising area is the development of technologies for sintering or briquetting of converter sludge. Recycling of this sludge into production will allow solving a number of important tasks for modern metallurgy in the utilization of man-made waste, saving raw materials and reducing the cost of steel. The efficiency of utilizing useful components in the composition of briquettes is significantly higher than in any other state (in a fine or polydisperse fraction, in sorted form). In this paper, we consider the development and justification of an integrated approach to thermochemical sintering of converter sludge based on conditioning of iron-containing sludge by non-thermal adsorption dehydration and thermochemical sintering with simultaneous reduction of iron from oxides. Adsorption dehydration to a moisture content of 2 – 3 % is provided by a short-term contact of iron-containing slimes with a porous energy carrier, brown coal semi-coke, which is separated by pneumoseparation and sent for energy technological use, and the iron-containing product mixed with coals is subjected to thermo-oxidative coking. Coking is carried out in an annular furnace with a rotating hearth, where, when temperatures reach 1050 – 1100 °C, a large and durable lump material is formed with 55 – 60 % of the iron-containing product with almost complete reduction. Thermodynamic modeling of converter sludge sintering with coals was carried out. A tool for performing computational experiments using methods of thermodynamic modeling of the studied object was the Terra software package designed to calculate the thermodynamic properties and composition of the phases of equilibrium state of arbitrary systems with chemical and phase transformations. The results of thermodynamic modeling were fully confirmed by the experimental studies. The obtained material is an analog of ferrocox containing 35 – 39 % of iron and 45 – 49 % of carbon, while the zinc oxide content does not exceed 0.017 %.

Solubility of NaCl in water vapor at 400–700 °C

Water significantly impacts the chemical evolution of the Earth’s crust, affecting environments from volcanic settings to hydrothermal systems. These fluids transport elements essential for geological processes, such as metal ore deposit formation. At high temperatures, as water transitions from liquid to vapor, its molecular structure changes, drastically reducing its capacity to dissolve solids and solvate ions. Here, we report experimental results of halite (NaCl(s)) solubility in water vapor at 400–700 °C and 30–300 bar using a novel U-tube flow-through reactor system. The results show that halite solubility is low (xNaCl,tot = 3.2 × 10−9 to 2.9 × 10−4 mol/mol) and increases with temperature and pressure, attributed to the dissolution of NaCl followed by its hydration according to the reaction:NaCl(s)+nH2O(g)⇋NaCl·H2On(g)Thermodynamic modeling of the experimental results indicates a preference for specific hydrated species, including NaClg, NaCl·H2O4g, NaCl·H2O6g and NaCl·H2O8g. The less hydrated gaseous NaCl species become more prevalent with increasing temperature and decreasing pressure. At temperatures below 600 °C and pressures above 50 bar, halite solubility is close to stoichiometric, whereas at higher temperatures and lower pressures, the hydrolysis of NaCl(s) to form NaOH(lq,s) or a NaClxOH(1-x)(lq,s) (x < 1) solid solution is evident, resulting in the formation of HCl(g). The logarithm of the halite equilibrium solubility constant (logKn) ranges from −10.18 to −4.19 for NaCl(g), and from −13.12 to −11.94, −15.90 to −17.28, and −19.67 to –22.73 for NaCl·H2O4(g), NaCl·H2O6(g) and NaCl·H2O8(g), respectively. Standard thermodynamic properties derived from this data reveal a temperature-independent enthalpy (ΔHn,ro), entropy (ΔSn,ro) and heat capacity (ΔCp,n,ro) of reaction for each NaCl species. While the enthalpy of reaction is nearly constant, the entropy and heat capacity decrease with an increasing degree of hydration, indicating the decreasing stability of these species with increasing temperature. Our thermodynamic model results and gas species stoichiometries are in excellent agreement with previous density functional theory (DFT) calculations (Suleimenov et al., 2006). The halite solubility data obtained here compare well with prior studies and thermodynamic models for the NaCl-H2O system.

Technological Aspects of Sintering Low-Quality Wolframite Concentrate with Potassium Carbonate

The loss of quality of wolframite concentrates determines the need to improve their processing method that ensures maximum conversion of tungsten into water-soluble wolframate and a reduction in water-soluble impurities. The results of thermodynamic modeling of the sintering of wolframite concentrate with sodium and potassium carbonates indicate a greater efficiency of K2CO3: The reagent consumption required for complete conversion of tungsten into solution decreases from 170% from stoichiometric sintering with Na2CO3 to 110% for K2CO3, as well as the proportion of soluble silicates up to 0.1%. In addition, sintering with K2CO3 is accompanied by the formation of compounds with a higher melting point, preventing melting and coating formation during the process. Mathematical sintering models were obtained by the method of probabilistically deterministic planning of this experiment. Optimal parameters have been determined: The extraction of tungsten into a solution of more than 95% is achieved by sintering with K2CO3 in an amount of 105–110% according to the stoichiometric requirements for the formation of K2WO4, K2MoO4, and K2SO4 at temperatures of 1073–1123 K for 100–120 min. Pilot tests have confirmed the effectiveness of the process. The possibility of sintering a cinder of wolframite concentrate with K2CO3 without the introduction of recycled materials has been established. Sintering under optimal conditions ensures the transition of tungsten to water-soluble tungstate by 97.5%.

Predicting the Release Mechanism of Amorphous Solid Dispersions: A Combination of Thermodynamic Modeling and In Silico Molecular Simulation

Background: During the dissolution of amorphous solid dispersion (ASD) formulations, the drug load (DL) often impacts the release mechanism and the occurrence of loss of release (LoR). The ASD/water interfacial gel layer and its specific phase behavior in connection with DL strongly dictate the release mechanism and LoR of ASDs, as reported in the literature. Thermodynamically driven liquid-liquid phase separation (LLPS) and/or drug crystallization at the interface are the key phase transformations that drive LoR. Methods: In this study, a combination of Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) thermodynamic modeling and in silico molecular simulation was applied to investigate the release mechanism and the occurrence LoR of an ASD formulation consisting of ritonavir as the active pharmaceutical ingredient (API) and the polymer, polyvinylpyrrolidone-co-vinyl acetate (PVPVA64). A thermodynamically modeled ternary phase diagram of ritonavir (PVPVA64) and water was applied to predict DL-dependent LLPS in the ASD/water interfacial gel layer. Microscopic Erosion Time Testing (METT) was used to experimentally validate the phase diagram predictions. Additionally, in silico molecular simulation was applied to provide further insights into the phase separation, the release mechanism, and aggregation behavior on a molecular level. Results: Thermodynamic modeling, molecular simulation, and experimental results were consistent and complementary, providing evidence that ASD/water interactions and phase separation are essential factors driving the dissolution behavior and LoR at 40 wt% DL of the investigated ritonavir/PVPVA64 ASD system, consistent with previous studies. Conclusions: This study provides insights into the potential of blending thermodynamic modeling, molecular simulation, and experimental research to comprehensively understand ASD formulations. Such a combined approach can be leveraged as a computational framework to gain insights into the ASD dissolution mechanism, thereby facilitating in silico screening, designing, and optimization of formulations with the benefit of significantly reducing the number of experimental tests.

The precipitation mechanisms of scheelite from CO2-rich hydrothermal fluids: Insight from thermodynamic modeling

Scheelite and wolframite are two main tungsten-bearing ore minerals in tungsten deposits. Compared to wolframite formed mostly by NaCl–H2O fluids, scheelite in many but not all tungsten deposits is associated with CO2–bearing hydrothermal fluids, but its precipitation mechanisms from these fluids are poorly understood. The replacement of wolframite by scheelite is common among tungsten deposits where these two tungstates coexist, but how CO2, as the pH-buffering agent, affects their replacement remains unclear. To answer these questions, we first tested the pH-buffering effect of CO2 by comparing available experimental pH values of H2O–CO2±NaCl solutions at 200–280 °C and the corresponding thermodynamic modeling results. The mean absolute errors between the calculated and experimental pH values are 0.14 log units in H2O–CO2 solutions and 0.13 log units in H2O–CO2–NaCl solutions, indicating that the calculated acitivities of H+ in CO2-bearing solutions are reliable. Then, the solubilities of scheelite, scheelite-ferberite, and scheelite-hübnerite in NaCl–H2O–CO2 systems were modeled in this study. Our modeling results suggest that scheelite solubility in CO2-rich fluids is highly dependent on fluid pressure but is insensitive to fluid temperature. A decrease in fluid pressure from lithostatic to hydrostatic levels at a depth of 3–8 km causes CO2 escape and pH rise and precipitates over 70 % of tungsten contents in fluids on average. Therefore, CO2 escape is an efficient mechanism for precipitating scheelite from CO2–rich hydrothermal fluids. The independence of scheelite solubility on temperature at high pressures and the slightly retrograde solubility at low pressures allows CO2–rich hydrothermal fluids to carry a great amount of tungsten far away from its sources. This may be one of reasons why some scheelite deposits occur at greater distances (>500 m) from the granite or extend along its strike for several kilometers. Similar to the cases in NaCl–H2O systems, two mechanisms for scheelite replacing wolframite in CO2–rich fluids are identified, a single decrease in fluid pressure or simple cooling plus an increase in the ratios of total Ca contents to total Fe (or Mn) contents in fluids.

Optimal Limestone Content on Hydration Properties of Ordinary Portland Cement with 5% Ground Granulated Blast-Furnace Slag.

In this study, the effect of limestone content on the mechanical performance and the heat of hydration of ordinary Portland cement (OPC) was investigated. Changes in the phase assemblage were analyzed through XRD and thermodynamic modeling. The purpose of the study was to identify the optimal limestone content in OPC. As a result of the experiment, all samples were found to have equal fluidity. Increasing the limestone content accelerated the hydration of the cement before approximately 13 h and shortened the setting time due to the acceleration of the initial hydration reaction. The compressive strength of the cement mortar showed a dilution effect, with lower compressive strength compared to the reference sample at an early age, but it gradually recovered at a later age. This is because, as shown in the XRD and thermodynamic modeling results, the carboaluminate phases formed due to the chemical effect of limestone contributed to the development of compressive strength. As a result, within the scope of this study, it is believed that maintaining the limestone content in OPC within 10% is optimal to minimize quality degradation.

Textural and compositional evolution of quartz and cobalt-bearing minerals from the Wubaoshan Deposit, Jiangxi Province, South China: Implications for cobalt mineralization

Cobalt resources are primarily derived from hydrothermal-related deposits; however, our understanding of the mechanisms governing cobalt transportation and deposition, particularly for cobalt arsenides and sulfarsenides within hydrothermal fluids, remains limited. In this study, we present a comprehensive investigation into the Wubaoshan cobalt deposit located in the Qin-Hang ore Belt, South China. This deposit exhibits mineralization associated with multiple hydrothermal fluids, resulting in complex paragenesis and the formation of cobalt minerals. By employing a combination of petrographic and geochemical observations, we explore the conditions of the ore-forming fluid and the hydrothermal mechanisms underlying cobalt mineralization. Our analysis reveals three distinct hydrothermal stages of mineralization: Stage 1 is characterized by quartz-arsenopyrite-pyrite assemblages formed at relatively high temperatures (352–390 °C), neutral pH, and high fS2 (log fS2 = −6.9 ∼ −8.8); Stage 2, the pivotal stage for cobalt mineralization, displays various sulfides-sulfarsenides formed at lower temperatures (229 ± 6.0 °C), under acidic conditions, and low fS2 (log fS2 = −12.0 ∼ −14.0); and Stage 3 comprises minor sulfides and carbonates formed at relatively lower temperature and pH. Sulfur isotope analysis of pyrite from Stage 1 (+13.49 to +14.30 ‰) and sphalerite from Stage 2 (+5.53 to +9.21 ‰) suggests a mixed sulfur source derived from both Permian seawater sulfate and related magmatic rocks. Additionally, our results reveal that a transformation from cobalt arsenide to sulfarsenide during Stage 2, likely influenced by the change of As/S ratio in ore fluids, which is affected by the influx of external sulfur from magmatic hydrothermal fluids. Our findings, together with the previous thermodynamic modelling results, indicate that the variations of the ore fluid condition, particularly temperature and pH, govern the precipitation and dissolution of mineral during cobalt mineralization. These findings contribute to our understanding of the formation processes of the Wubaoshan deposit and provide valuable insights into the mechanisms of cobalt enrichment.

Correlation between Thermodynamic Studies and Experimental Process for Roasting Cobalt-Bearing Pyrite

Cobalt is a critical metal widely distributed in nature, but cobalt ore has hardly been found as an independent mineral. Cobalt-bearing pyrite tailings separated from iron ore is one of the resources for recovering cobalt. In the following study, roasting is carried out to oxidize cobalt-bearing pyrite tailings for preparing and recovering the cobalt by acid leaching. The further aim of the research is to determine and control the optimal technological regime for roasting by using thermodynamic modeling. The phase transition in Fe–S–O and Co–S–O systems and its mechanism are analyzed under the partial pressure of oxygen and sulfur dioxide at constant temperatures. Thermodynamic modeling proves that iron and cobalt sulfides can be intensively oxidized at a relatively high temperature (&gt;900 °C) under an atmosphere of logp(O2) &gt; −5, leading to the formation of SO2 (logp(SO2) &lt; 0). The results of the roasting experiment indicate 98% desulfurization degree upon holding for about 4–5 h and at &gt; 1000 °C. Based on these thermodynamic modeling and experimental results, the roasting of cobalt containing pyrite can be optimized with substantial productivity with regard to the metal oxide and cobalt thereof. Oxidative roasting also allows the elimination of environmentally hazardous gases such as sulfur during the process.

Thermodynamic modeling of interphase distribution of chromium and boron in slags of AOD reduction period

The paper presents the results of a thermodynamic modeling of the chromium and boron reduction from slags of reduction period of argon-oxygen decarburization (AOD) by a complex reducing agent containing silicon and aluminum. Using the simplex lattice method, an experiment planning matrix is constructed containing 16 compositions of the oxide system СаО – SiO2 – (3 – 6 %) В2О3 – 12 % Cr2O3 – 3 % Al2O3 – 8 % MgO of variable basicity 1.0 – 2.5. The results of thermodynamic modeling are graphically presented in form of dependence of equilibrium distribution of chromium and boron on the slag composition at temperatures of 1600 and 1700 °C. The constructed diagrams make it possible to quantify the influence of the temperature, basicity and B2O3 in the slag on equilibrium interphase distribution of chromium and boron. It is established that increasing the slag basicity from 1.0 to 2.5 improves the process of chromium reduction, but restores the boron stability. With an increase in B2O3 content in the slag, a slight deterioration of chromium reduction process occurs, while the boron content in the metal increases. With a simultaneous increase in basicity up to 2.5 and a decrease in boron oxide in the slag from 5 to 3 %, the interphase distribution coefficient of chromium is reduced to 1.5·10–3. Changing the process temperature from 1600 to 1700 °C does not have a negative effect on the process of chromium reduction, but worsens the boron reduction conditions. Based on analysis of the formed slag phases and thermodynamics of the reactions of their formation, it is established that chromium is mainly reduced by aliminum with only partial development of silicothermy. The residual silicon content reduces boron, thereby limiting its concentration in the metal. The results of high-temperature experiments showed high correspondence with the results of thermodynamic studies.

Hydration mechanism and microstructure evolution of recycled brick powder blended cement toward low-carbon and cleaner production

Recycled brick powder (RBP) as an aluminosilicate-rich material has shown great potential as a new type of supplementary cementitious material (SCM). However, the interaction mechanism between cement and RBP has not been clarified yet. In this study, the pore solution chemistry, phase assemblage and nano-structures of RBP blended cement paste were revealed. The pore solution chemistry indicated that RBP facilitates the dissolution of C3S and the precipitation of C-S-H, but inhibits the precipitation of CH. Hydration kinetics modelling results showed that RBP accelerates the nuclei formation but retards the growth of hydration products during boundary nucleation and growth process. FIB-TEM and thermodynamic modeling results demonstrated that the additional [Si] and [Al] ions dissolved from RBP contribute to the reactions: (1) the [Si] and [Al] react with the CH to form C-A-S-H gel with Al/Ca and Si/Ca molar ratios of 0.32 and 0.62, respectively; (2) the [Si] and [Al] reorganize to form nano clusters, such as hydrotalcite-like phase, AFt nano-crystals, AFm phase and C-(A)-S-H gel. Therefore, blended mortar with 30–45 % RBP replacing cement has slight or no late-age mechanical properties loss and presents 25.2–30.3 % decrease in chloride ion diffusion coefficients. Additionally, compared to blended cement utilizing traditional SCMs, like FA and GGBFS, RBP blended cement presents a 6.4–26.1 % reduction in cost and 21.4–41.6 % decrease in natural resource consumption, which contributes to great economic and environmental benefits.

Geochemical Thermometry of Ore-Bearing Gabbronorites from the Apophisis of the Yoko-Dovyren Massif: Composition, Amount of Olivine, and Conditions of Sulphide Saturation in the Parental Magma

The temperature and compositional parameters of the parental magma of the ore-bearing apophysis DV10 from the Yoko-Dovyren massif are estimated based on the results of thermodynamic modeling the equilibrium crystallization of melts of 24 samples, following the method of geochemical thermometry. Thermometric calculations were carried out using the COMAGMAT-5.3 program with a step of 0.5 mol. % to a maximum degree of crystallization 75–85% under oxygen fugacity controlled by the QFM buffer. The model order of mineral crystallization corresponds to the sequence: olivine (Ol) + + Cr-Al spinel (Spl) → plagioclase (Pl) → high-Ca pyroxene (Cpx) → orthopyroxene (Opx). Silicate-sulfide immiscibility was modeled to occur mostlybefore the onset of plagioclase crystallization, being consistent with sulfide saturation of the parental magma. The results of calculations demonstrate the convergence and intersection of the model liquid lines of descent at temperatures of about 1185°C. When applied to the average composition of the DV10 apophysis, this temperature indicates the existence of a suspension of the original crystals (52.1 wt. % cumulus olivine (Fo83.6), 2.3 wt. % plagioclase (An79.7), 0.24% clinopyroxene (Mg# 88.8), 1 wt. % aluminochromite (Cr# 0.62)) and about 0.2% sulfide liquid in a moderately magnesian melt (53.6 wt. % SiO2, 7.4 wt. % MgO). At that the solubility of sulfide sulfur (SCSS) was estimated to be 0.083 wt. %. This heterogeneous system had a viscosity of 4.71 log. units (Pa · s) and an integral density of 2929 kg/m3. Such rheological properties do not contradict the possibility of the migration and emplacement of the protocumulus mush from the main Dovyren chamber. However, a more probable scenario includes a localized accumulation of olivine in the trough-like part of the DV10 subchamber, which preceded or occurred in parallel to the accumulation of segregated sulfides.

Production of complex Fe-Si-Mn-Cr ferroalloy using high-ash coal: a sustainable metallurgical approach

The article presents the results of comprehensive thermodynamic modeling and laboratory tests conducted for smelting a complex ferroalloy of silicon, manganese, and chromium (Fe-Si-Mn-Cr) from chromium, medium-grade manganese ores, and high-ash coals from Kazakhstan. Thermodynamic analysis was performed using HSC Chemistry software to model the Fe-Si-Mn-Cr smelting process over a temperature range of 900 °C–1800 °C. This analysis involved six actual charge compositions with solid reductant (Csolid) consumption ranging from 5 to 20 kg per 100 kg of Cr and Mn ore mixture. The mechanism of the combined carbothermic reduction of Cr, Mn, Si, and Fe was investigated using the Cr-Si-Al-Ca-Mn-Mg-O-C system. According to thermodynamic data, the optimal consumption of Csolid per 100 kg of ore mixture is 17 kg, and the optimal temperature range for smelting ferroalloys is between 1600 and 1700 °C. Laboratory tests were conducted in a high-temperature Tamman furnace at 1700 °C, resulting in experimental samples of the new complex ferroalloy with an average composition of 14.85% Fe, 14.05% Si, 7.55% Mn, 57.54% Cr, and 6.01% C, with P < 0.03% and S < 0.02%. The phase composition included (Cr, Fe, Mn)3Si and carbides Cr23C6 and (Fe, Mn)3C. The resulting alloy is suitable for alloying high-carbon and tool steels.

Oligocene melting of subducted mélange and its mantle dynamics in northeast Asia

Melting of subducted mélange can potentially transport mass from the slab-mantle interface to the mantle wedge in subduction zones. The mélange diapir model was primarily proposed from the results of laboratory experiments and thermodynamic modeling. However, the melting mechanisms of mélange diapirs in subduction zones remain unclear. To further constrain the mantle dynamics of a mélange diapir, we studied Oligocene alkaline intermediate rocks on the northeast Asian continental margin. We report whole-rock geochemical and Sr-Nd-Pb-Mg-Zn isotope data and show that these rocks formed by partial melting of mélange. We conclude that a diapir was the mechanism for Oligocene melting of the mélange. We also identified younger rocks formed by melting of mélange in the eastern part of northeast Asia, implying an eastward shift in such magmatism since the Oligocene. Our results and the tectonic setting indicate that melting of mélange diapirs occurred preferentially during tectonic transitions, such as the formation of a back-arc basin triggered by trench-perpendicular mantle flow. The low-viscosity mantle with an incompressible stress field triggered melting of the mélange diapirs. Interactions occurred between the mélange diapirs and carbonated peridotites, constraining the depth of mélange-mantle interactions to the asthenosphere, which is deeper than the depth inferred in previous studies.

Thermodynamic phase equilibria study of Hythane (methane + hydrogen) gas hydrates for enhanced energy storage applications

Hydrogen blending with natural gas has become an effective technique for incorporating the characteristics of natural gas and facilitating the storage and transportation of hydrogen gas. The transportation of hydrogen and natural gas (methane) blend, also referred to as Hythane, presents numerous challenges, advantages, and disadvantages that differ based on the technology employed. The current research showcased a thorough examination of the thermodynamics involved in studying the three phase equilibrium analysis of gas hydrate technology for storing Hythane gas mixtures. Three different Hythane compositions varying in hydrogen percentage were selected, and the isochoric gas hydrate phase equilibria study was performed. The experimental results of phase equilibria and thermodynamic modelling using CPA EOS in software were compared. A similar study was also conducted in the presence of a 5.56 mol % THF solution to understand the reduction in the pressure requirement for the phase equilibria. Results from the mixed Hythane+THF gas hydrate findings suggested stable gas hydrate formation at much lower pressure requirements, increasing the credibility of storing Hythane mixtures in gas hydrates at moderate conditions. The gas compositions for each experiment were analyzed using gas chromatography to evaluate the presence of the desired gas in the hydrate phase. Heat exchange during the gas hydrate dissociation was analyzed using a high pressure differential scanning calorimeter (DSC). The change in the heat release temperature also indicates the stability of the gas hydrate, and with increasing hydrogen gas in the blend, the gas hydrate stability decreased. The Clausius-Clapeyron equation was employed to compute the heat of gas hydrate dissociation, and a comparison was made with the heat of dissociation obtained from the DSC study. The experimental investigations on Hythane gas hydrates were performed to find the hydrogen storage inside the gas hydrate phase and compare it with the previous studies of pure hydrogen hydrates. To demonstrate the Hythane gas transportation, Hythane gas hydrate pellets were formed, followed by their storage in a controlled environment to observeany changes in pressure and temperature. The Hythane gas hydrate pellets demonstrated exceptional stability of Hythane gas presenting an intriguing prospect for utilizing gas hydrate technology in Hythane gas transportation.

Adsorption of Levofloxacin onto Graphene Oxide/Chitosan Composite Aerogel Microspheres.

The removal of pharmaceutical residues from water resources using bio-based materials is very important for human safety and health. Bio-based graphene oxide/chitosan (GO/CS) aerogel microspheres were fabricated with emulsification and cross-linking, followed by freeze drying, and were used for the adsorption of levofloxacin (LOF). The obtained GO/CS aerogel microspheres were characterized with scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and thermogravimetry (TG). The effects of GO content, pH value, and temperature on their adsorption capacity were investigated. With the incorporation of 40 wt% GO, the adsorption capacity increased from 9.9 to 45.6 mg/g, and the highest adsorption capacity, 51.5 mg/g, was obtained at pH = 8 and T = 25 °C. In addition, to obtain deeper insight into the adsorption process, the thermodynamics and kinetics of the process were also investigated with four different models of LOF adsorption. The thermodynamic modeling results revealed that LOF adsorption is exothermic, and the kinetic investigation demonstrated that LOF adsorption is generally consistent with a pseudo-first-order rate law.

Development of Thermodynamic Criteria for Determining the Composition of Duplex Stainless Steels with High Corrosion Resistance.

One of the most popular methods for ranking duplex stainless steels (DSSs) and predicting their corrosion properties is the calculation of the pitting resistance equivalent number (PREN). However, since DSSs are two-phase materials with a significant fraction of secondary phases and precipitates, the application of the PREN can be highly limited. This article attempted to use a new approach to describe the corrosion resistance of these steels. The corrosion resistance of two DSSs of the same class was investigated. Under identical solution heat treatments in the temperature range of 1050-1200 °C, the crevice corrosion resistance of one steel increased, while that of the other decreased. It was demonstrated that the amounts of austenite and ferrite changed similarly in these steels, and the different corrosion resistances were associated with the behaviors of secondary phases: niobium carbonitride and chromium nitride. SEM-EDS analysis was conducted to analyze the redistribution of elements between phases in both cases, showing good agreement with the thermodynamic modeling results. The PREN was calculated for each phase depending on the treatment temperature, and a method for calculating the effective PREN (PRENeff), accounting for phase balance and secondary phases, was proposed. It was shown that this indicator described corrosion properties better than the classical PREN calculated for the average steel composition. This study demonstrated how the calculation of critical temperatures (the temperature of equal amounts of ferrite and austenite, the temperature of the beginning of chromium nitride formation, and the temperature of the beginning of σ-phase formation) could describe the corrosion resistance of DSSs. Maximum possible deviations from these temperatures were defined, allowing the attainment of the required corrosion properties for the steels. Based on the conducted research, an approach for selecting new compositions of DSSs was proposed.

EXPERIMENTAL AND THEORETICAL STUDY OF THE BEHAVIOR OF GALLIUM IN A DISCHARGE PLASMA AT ICP-AES DETERMINATION

In the case of inductively coupled plasma atomic emission determination of gallium in metallurgical materials, matrix components can have a significant influence on the determination results. In addition to matrix spectral interference, there may also be non-spectral interference from macrocomponents. The element present in the discharge plasma at high concentrations can lead to a change in the conditions for excitation of the emission spectra, which will lead to a distortion of the intensity of the spectral lines of gallium. It has been established that the spectral lines of gallium are not free from spectral overlap from macrocomponents (iron, chromium, molybdenum, tungsten, nickel and cobalt). As a result, experimental study of non-spectral interference using gallium spectral lines is impossible. Using thermodynamic modeling, a quasi-analyte element was selected, which was proposed to be used to study the non-spectral matrix effect on the analytical signal of gallium during its atomic emission determination with inductively coupled plasma. Indium was proposed as a quasi-analyte. Based on the results of thermodynamic modeling, it was established that when varying the operating parameters of the atomic emission spectrometer (plasma temperature, argon and aerosol flow rate), the spectral behavior of gallium and the proposed indium quasi-analyte in argon plasma is similar. In this case, there is no spectral interference from the quasi-analyte on the spectral lines of gallium, and the increase in the value of the matrix interference estimate observed in some cases is random, which may be due to the time drift of the operating parameters of the atomic emission spectrometer. Thus, it is proposed to use indium as a quasi-analyte for the experimental study of non-spectral interference from matrix components (iron, chromium, molybdenum, tungsten, nickel and cobalt) instead of detectable gallium in metallurgical materials.

THERMODYNAMIC AND EXPERIMENTAL SIMULATION OF THE SMELTING PROCESS OF MEDIUM CARBON FERROMANGANESE WITH THE USE OF ZHEZDINSKY MANGANESE ORES

This article presents the results of a complete thermodynamic modeling and experimental study of the process of smelting medium-carbon ferromanganese using Zhezdinsky manganese ores. Full thermodynamic modeling of the process of smelting medium-carbon ferromanganese was carried out in the HSC Chemistry 6 software package. Thermodynamic modeling of the smelting process was carried out in the temperature range of 898–1989 K. Thermodynamic analysis for modeling the smelting process was carried out for four real charge compositions depending on the basicity of the slag (CaO/SiO2 – 1,4; 1,6; 1,8; 2,0). Based on the obtained thermodynamic data, an experimental study was carried out on the smelting of medium-carbon ferromanganese in a Tamman laboratory high-temperature furnace. В качестве шихтовых материалов были использованы марганцевая руда Manganese ore MnTot. was used as charge material – 48,23 %, SiO2 – 12.48 %, Al2O3 – 2,76 %, Fetot. – 3,45 %, ferrosilicomanganese grade SMn-17, not less than 90 % lime CaO. According to thermodynamic data, the optimal composition of the slag was established, which provides the highest extraction of manganese into the alloy and metal-slag separation. The chemical composition of the metal obtained in the laboratory is as follows, %:Mn – 83–84; Si – 1,5-3; C – 0,95-1,68; P –0,13-1,6; which corresponds to GOST 4755-91. Slag chemical composition, %: MnO – 10,92-17,90; SiO2 19,02-21,45; CaO 36,92-40,43; FeO – 0,33-0,77. Keywords: ferromanganese, ferrosilicomanganese, thermodynamics, manganese ore, laboratory smelting, slag basicity.