Salt Systems Research Articles

Influence of sodium chloride on corrosion resistance of ever silver vessels in the presence of curd rice

The present work is undertaken to investigate the corrosion resistance of ever silver in the presence of water, water+curd system, water+curd+rice system, water+curd+rice+Salt system. The corrosion resistance has been evaluated by AC impedance spectra . AC impedance spectra have been employed to investigate the corrosion resistance of ever silver electrode when it is immersed in various test solutions like water, curd, curd rice recipe, curd rice recipe with salt (sodium chloride 500 ppm). The corrosion resistance of ever silver electrode when it is immersed in various test solutions like water, water+curd, water+curd+rice and water+curd+rice+salt have been evaluated by AC impedance spectroscopy. If a protective film is formed, the charge transfer resistance increases, impedance value increases, phase angle value increases and double layer capacitance (Cdl) value decreases. When Ever silver electrode is immersed in water + curd rice system + 500ppmsodium chloride system, the corrosion resistance of ever silver electrode decreases. This is due to the presence of chloride ion introduced into the curd rice system. It implies that when curd rice is packed in vessels made of ever silver, we should avoid adding salt to the curd rice. It is better to keep the salt and curd rice separately. It is to be noted that this corrosion resistance is better than the corrosion resistance in water alone. The corrosion resistance decreases in the following order: Water + Curd + Rice system > Water + Curd + Rice + Salt system (sodium chloride 500ppm) > Water+ Curd system > Water

Development of an Attenuated Total Reflectance-Ultraviolet-Visible Probe for the Online Monitoring of Dark Solutions.

Optical spectroscopy is a valuable tool for online monitoring of a variety of processes. Ultraviolet-visible (UV-vis) spectroscopy can monitor the concentration of analytes as well as identify the speciation and oxidation state. However, it can be difficult or impossible to employ UV-vis-based sensors in chemical systems that are very dark (i.e., have a high optical density), requiring exceedingly short path lengths (for transmission approaches) or an effective means of backscattering (for reflectance approaches). Examples of processes that produce highly absorbing solutions and that would benefit significantly from the diagnostic potential of optical sensors include used nuclear fuel recycling and molten salt systems with high concentrations of dissolved uranium. Utilizing an attenuated total reflectance (ATR) UV-vis approach can overcome these challenges and allow for the measurement of solutions orders of magnitude more concentrated than transmission UV-vis. However, determining ideal sensor specifications for various processes can be time-consuming and expensive. Here, we evaluate the ability of a novel ATR-UV-vis probe to measure very concentrated solutions of Co(II) and Ni(II) nitrate as well as organic dyes (methylene blue, acid red 1, and crystal violet). This sensor design provides a modular method for exploring possible "path lengths" by altering the length of the ATR fiber that was submerged within solution during spectral measurements. Measurements within the ATR sensor cell were compared to measurements gathered by transmission UV-vis of samples within a commercially available 1 cm optical cuvette. The ATR-UV-vis probe was capable of measuring absorbance of solutions with a chromophore concentration 600 times greater than that in the 1 cm cuvette. Advanced data analysis in the form of multivariate curve resolution (MCR) was used to analyze the speciation of methylene blue over a large concentration range. The application of this novel ATR-UV-vis probe to the investigation of dark solutions is a promising avenue for use in online monitoring of nuclear processes.

Volumetric Determination of Densities of Molten Salts for CSP Applications

The densities of molten salt mixtures are determined by direct volumetric measurements providing uniform thermal conditions, defined gas atmosphere above the sample and direct observation of the sample during the measurement. Three nitrate/nitrite salt systems are examined: NaNO3-KNO3 (40:60 by mass, solar salt), KNO3-NaNO3-NaNO2 (53:7:40 by mass, Hitec) and two alternative compositions of KNO3-NaNO3-Ca(NO3)2 (45:7:48 and 43:15:42 by mass, Hitec XL) are examined. Linear fits of the density are presented derived from the experimental data

Cu(II) Stability and UV-Induced Electron Transfer in a Metal-Organic Hybrid: An EPR, DFT, and Crystallographic Characterization of Copper-Doped Zinc Creatininium Sulfate.

Single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopic experiments, complemented by quantum chemical DFT calculations, were carried out on the copper-doped metal-organic hybrid and Tutton salt analogue zinc creatininium sulfate to determine its crystal structure, to characterize the electronic structure of the doped Cu(II) binding site, and to propose a pathway for an excited-state, proton-coupled electron transfer (PCET) process in UV-exposed crystals. The crystal structure is isomorphous to that of cadmium creatininium sulfate, which has the transition ion, not in direct coordination with the creatinine, but forming a hexahydrate complex, which is bridged to a creatininium through an intervening sulfate ion. The EPR g (2.446, 2.112, 2.082) and copper hyperfine (ACu: -327, -59.6, 10.8 MHz) tensor parameters are consistent with doped copper replacing host zinc in the metal-hexahydrate complex. These parameters are similar to those observed for copper hexahydrate in doped Tutton salt systems at low temperature, where the unpaired electron occupies mainly the copper 3dx2-y2 orbital. At room temperature in the Tutton systems, vibration couplings stemming from a dynamic Jahn-Teller effect cause tensor averaging which results in a reduction in their maximum g-tensor and hyperfine tensor values. However, like for the doped isomorphous Cd creatinine crystal, the Cu(II) EPR exhibits little, or no room temperature averaging compared to its low temperature pattern. Samples exposed to 254 nm UV light generate a carbon-centered free radical species, characterized by an isotropic g-tensor (g = 2.0029) and an alpha-proton hyperfine coupling (-24 -14 +4 G). These parameters identify it as a creatinine radical cation formed by the oxidative release of one of its C2 methylene hydrogens. DFT calculations confirm the unpaired electronic structures of both the Cu(II) site and free radical. The growth in radical concentration with an increase in the UV exposure time coincides with a decrease in the copper EPR signal, indicating a coupled light-induced oxidation reduction process. A comparison of the crystal structure with the EPR parameters and DFT results provides evidence for a UV-induced PCET.

Comprehensive consideration of screening fluoride electrolyte for electrodeposition of rare earth cerium

Molten salt is an indispensable medium for the electrochemical extraction of rare earth metal cerium (Ce). However, the existing molten salt system is incapable of meeting the low-cost requirement of industrial production. The selection of molten salt electrolyte is closely related to its thermodynamic properties and its influence on electrolytic extraction in terms of electrochemical reaction and kinetics. Herein, the constructed potential fluoride electrolyte systems (CeF3-LiF-BaF2, CeF3-LiF-NaF, CeF3-LiF-KF, and CeF3-LiF-NaF-KF melts) were systematically investigated with respect to theoretical electrochemical window, exchange current density at the molten salt/electrode interface during electrolytic reduction, and the effect of density in rare earth deposition. From a comprehensive point of view, the choice of molten salt system for electrolysis should combine the electrochemical reaction properties of rare earth metal ions in it and the physicochemical properties of the molten salt itself. The CeF3-LiF-BaF2 electrolyte was considered as the most promising molten salt system due to its various outstanding parameters (diffusion coefficients: 6.74×10−7 cm2 s−1, exchange current density: 0.649 A cm−2, density: 4.046 g·cm−3). This work provides new insights into fluoride electrolyte design screening.

Predicting CO2 and H2 Solubility in Pure Water and Various Aqueous Systems: Implication for CO2–EOR, Carbon Capture and Sequestration, Natural Hydrogen Production and Underground Hydrogen Storage

The growing energy demand and the need for climate mitigation strategies have spurred interest in the application of CO2–enhanced oil recovery (CO2–EOR) and carbon capture, utilization, and storage (CCUS). Furthermore, natural hydrogen (H2) production and underground hydrogen storage (UHS) in geological media have emerged as promising technologies for cleaner energy and achieving net–zero emissions. However, selecting a suitable geological storage medium is complex, as it depends on the physicochemical and petrophysical characteristics of the host rock. Solubility is a key factor affecting the above–mentioned processes, and it is critical to understand phase distribution and estimating trapping capacities. This paper conducts a succinct review of predictive techniques and present novel simple and non–iterative predictive models for swift and reliable prediction of solubility behaviors in CO2–brine and H2–brine systems under varying conditions of pressure, temperature, and salinity (T–P–m salts), which are crucial for many geological and energy–related applications. The proposed models predict CO2 solubility in CO2 + H2O and CO2 + brine systems containing mixed salts and various single salt systems (Na+, K+, Ca2+, Mg2+, Cl−, SO42−) under typical geological conditions (273.15–523.15 K, 0–71 MPa), as well as H2 solubility in H2 + H2O and H2 + brine systems containing NaCl (273.15–630 K, 0–101 MPa). The proposed models are validated against experimental data, with average absolute errors for CO2 solubility in pure water and brine ranging between 8.19 and 8.80% and for H2 solubility in pure water and brine between 4.03 and 9.91%, respectively. These results demonstrate that the models can accurately predict solubility over a wide range of conditions while remaining computationally efficient compared to traditional models. Importantly, the proposed models can reproduce abrupt variations in phase composition during phase transitions and account for the influence of different ions on CO2 solubility. The solubility models accurately capture the salting–out (SO) characteristics of CO2 and H2 gas in various types of salt systems which are consistent with previous studies. The simplified solubility models for CO2 and H2 presented in this study offer significant advantages over conventional approaches, including computational efficiency and accuracy across a wide range of geological conditions. The explicit, derivative–continuous nature of these models eliminates the need for iterative algorithms, making them suitable for integration into large–scale multiphase flow simulations. This work contributes to the field by offering reliable tools for modeling solubility in various subsurface energy and environmental–related applications, facilitating their application in energy transition strategies aimed at reducing carbon emissions.

Electrochemical behavior and dissolution processes of lithium metal in the LiCl–KCl–CsCl molten salt system

Electrochemical behavior and dissolution processes of lithium metal in the LiCl–KCl–CsCl molten salt system

Overall mass transfer approach for electrodialysis-based acid recovery

The reclamation of low-concentration waste acid (e.g., pH > 0.5) has garnered significant attention due to its prevalence, substantial output, and considerable potential value. Notably, a further concentration of the separated acid is typically required for practical applications, for which electrodialysis (ED) has been widely acknowledged as an effective method. However, various factors, including proton leakage, complicate the application of ED in acid systems compared to salt systems. This study presents a novel modeling approach for ED-based acid recovery utilizing the overall mass transfer (OMT) methodology for the first time. Importantly, regression models incorporating initial concentration and current density as independent variables have been developed to calculate the OMT coefficients and cell resistance following a quantitative analysis of the effects of acid media and electric field on mass transport phenomena, based on a series of carefully designed experiments. Subsequent predictions regarding a typical ED-based acid recovery process were conducted, yielding results that align closely with experimental data. For instance, the relative deviations for concentration and volume evolution were found to be less than ±8.4 % and ±7.9 %, respectively. Additionally, the relative deviations for energy consumption were recorded at 8.2 % and 3.2 % for the overall process and the ED stack, respectively. Furthermore, simulations were performed to evaluate the impacts of operational conditions on ED performance using the derived models. In conclusion, the efficacy of the OMT approach for modeling the ED process in acid systems has been substantiated. It is reasonable to assert that the developed models will be beneficial for production management and the optimization of operating conditions in ED-based acid recovery processes.

Electrochemical behavior of tantalum ion in LiF-NaF-K2TaF7 molten salt system

It is of great significance to clarify the electrochemical behavior of Ta5+ in LiF-NaF-K2TaF7 molten salt systems for the preparation of tantalum metal by molten salt electrodeposition. The aim of this work was to explore the reaction steps and behavior of the reduction of metal Ta from Ta5+ in fluorine molten salt by electrochemical method. The cyclic voltammetry, square wave voltammetry, chronopotentiometry were used to determine the reduction steps of Ta5+. The results showed that there were two reduction steps which the first reduction step R1 was TaF72−+2e−⇌TaF3+4F− and the second reduction step R2 was TaF3+3e−→Ta+3F−. SEM, XRD and EDS results showed that the reduction product of Ta5+ in molten salt is Ta and the tantalum atom was selectively deposited and grew on the (200) crystal plane in priority.

Natural convection effects in molten LiF-NaF-KF

Understanding mass transfer is of great importance to molten salt electrochemistry. However, natural convection has long been neglected in electrochemical measurements in stagnant molten salt systems due to the complex mathematical treatments. Here we reported the notable natural convection effects in molten LiF-NaF-KF during cyclic voltammetry and chronoamperometry tests. The established model showed that the convection-diffusion layer (CDL) convection dominated mass transfer under long time-scale tests in molten LiF-NaF-KF-EuF3. However, in the case of molten LiF-NaF-KF-K2TiF6, CDL convection predominated at dilute redox concentrations while density-driven convection came into dominance at high redox concentrations, because of the severe coordinate structure change of the redox couple. The derived thickness of the convection-diffusion layer, δconv., ranged from 135 to 183 μm, much higher than that in aqueous solutions (220–250 μm). Moreover, the increase in system temperature greatly enhanced natural convection effects in molten fluorides. Lastly, the use of microelectrode (re<39.7 μm for δconv.=160 μm) was demonstrated to be an effective way to suppress the intense natural convection effects.

The Form of Electrodeposited Iridium Ions in a Molten Chloride Salt and the Effects of Different Iridium Concentrations

A molten salt system was prepared using an optimized method. We studied the complex structure of Ir3+ ions in the molten salt system and the influence their concentration had on the quality of the coatings prepared via electrodeposition. Using TG-DSC and in situ XRD experiments, we studied the high-temperature characteristics and properties of IrCl3 alongside its thermal stability. Using in situ XRD and Raman spectroscopy, we analyzed the Ir ions’ complex structure and the variation in the molten salt system at high temperatures. Finally, the changes in the Ir ion concentration in the molten salt system and the influence of the microstructure of the coatings’ surfaces were investigated under different anode conditions. IrCl3 easily decomposes above 400 °C, and temperature increases accelerate the rate of this decomposition. When the NaCl-KCl-CsCl system is in a high-temperature, molten state, IrCl3 forms stable complex structures (IrCl6)3− and (IrCl6)2−, and the valence state of Ir will be transformed with the increase in temperature. Generating these complex structures is conducive to improving the Ir coating quality. During the electrodeposition process, too few Ir ions in the molten salt can lead to concentration polarization, affecting the quality of the coating. Application of the molten NaCl-KCl-CsCl system is conducive to the electrodeposition of Ir coatings in a suitable temperature range. At the same time, using Ir as the anode can enhance the quality of the coatings.

Shortening a mixed salt and mobile shale system: A case study from East Breaks, northwest Gulf of Mexico

The coexistence of two low-shear strength layers in a continental margin, such as salt and shales, conditions the resulting structural style and also constitutes a challenge for seismic imaging and energy resource exploration. We have analyzed the 3D structure of a mixed salt-shale system in the western Gulf of Mexico, in the East Breaks foldbelt, by interpreting a depth-migrated seismic data set. Overlying the allochthonous Sigsbee canopy and pierced by isolated salt diapirs, the Oligocene shale-prone sequences were shortened during the Miocene through pervasive deformations, developing a major suprasalt detachment system associated with duplexes below and different fold and thrust systems above. Oligocene shales locally reach a critical state and flow, resulting in: (1) inflated shale-cored detachment anticlines, with the stacking of allochthonous mobile shale domains; (2) detached lift-off anticlines with shale bulbs and fishtail thrusted welds; (3) allochthonous shale sheets at the upper tip of thrusts, fed by fluidized material migrating along associated fault zones; (4) hourglass shale diapirs; and (5) Christmas trees and vertical mud pipes connected to small mud volcanoes. The salt diapirs deformed simultaneously, as did the shales. Salt accommodated the shortening through localized subvertical welds that isolated them from the allochthonous Sigsbee canopy and through weld thrusts formed by fault-bounded blocks with highly sheared salt and mobile shales. Mobile shale structures wrap around the squeezed salt diapirs, presenting a unique pattern that has not yet been documented in experimental models with precursor salt diapirs deformed under contraction. Mixed salt-shale systems are a new challenge for structural analysis and experimental models, as well as for seismic model building in situations where there is a high dispersion of seismic energy due to the unique properties of mobile shales.

Investigation of the electrochemical behaviour of praseodymium ions in a LiF-PrF3-Pr6O11 molten salt system

Understanding the electrochemical of paseodymium ions in molten salt is essential to improve electrolytic efficiency. To elucidate the electroreduction mechanism of praseodymium ions and overcome the limitations associated with regulating the yield of praseodymium metal in the industrial praseodymium electrolysis process, the electrochemical behaviour of praseodymium on the W working electrode surface in the LiF-PrF3-Pr6O11 molten salt system was determined by square–wave voltammetry, chronoamperometry, cyclic voltammetry and potentiometry analyses. The results indicated that the reduction of Pr3+ on the W cathode is a one-step quasireversible Pr3+/Pr reduction process controlled by diffusion of the LiF-PrF3 and (LiF-PrF3)eut-Pr6O11 electrolytes at 1223 K Pr3+ in the LiF-PrF3-Pr6O11 molten salt has a diffusion coefficient of DPr3+/Pr = 0.20 × 10−8–4.11 × 10−8 cm2·s−1. The incorporation of Pr6O11 increased the electrochemical activity of Pr3+ in the LiF-PrF3 system. Pr crystallization on the W electrode was achieved by three-dimensional progressive nucleation.

Study on the Effect of Complex Organics on the Phase Equilibrium of the Multicomponent Salt Systems in the High Saline Wastewater of Coal Chemical Industry

Study on the Effect of Complex Organics on the Phase Equilibrium of the Multicomponent Salt Systems in the High Saline Wastewater of Coal Chemical Industry

Quantum Chemical Calculation on ScCl3-NaCl-KCl Molten Salt System

Background: The study of the ionic structure of the ScCl3-NaCl-KCl molten salt system is of guiding significance for the production of metal Sc and Sc alloy by molten salt electrolysis using ScCl3-NaCl-KCl molten salt system as electrolyte. However, limited research has been conducted on the structural analysis of molten salt within this system using Raman spectroscopy. Methods: The Gaussian and GaussView programs are used to simulate Sc-Cl ionic groups that may exist in the ScCl3-NaCl-KCl molten salt system based on density functional theory (DFT) and calculate their theoretical Raman spectra. Then, the wave function analysis of these Sc-Cl ionic groups is carried out using the Multiwfn program. Results: When the ScCl3-NaCl-KCl system is used as the electrolyte, it is considered that the 8 Sc atom in ScCl74− ionic groups is most easily reduced by electrochemistry at the cathode when the concentrations of eight Sc-Cl ionic groups are the same. In Sc2Cl7− Sc2Cl82− and Sc2Cl93− ionic groups, the sites that are most likely to attract electrophiles to attack and react are 1Cl and 7Cl, respectively, and the two Sc atoms located in the "chlorine bridge" structure contribute the most to LUMO orbitals, and nucleophiles will preferentially attack the Sc atoms located in the "chlorine bridge" structure. For Sc2Cl7−、Sc2Cl82− and Sc2Cl93− ionic groups, which have two Sc atoms, the bonds formed between Sc and Cl in the "chlorine bridge" structure have the smallest bond order, so the bonds formed by Sc and Cl in the "chlorine bridge" structure break first during the reaction, and then the bond formed by Sc and Cl located at both ends of the whole structure breaks Conclusion: The key information, such as bond length, point group structure, and theoretical Raman spectral characteristic peak after optimization, are obtained by the Gaussian and GaussView programs. The net atomic charge in each ionic group, the direction of electron migration during the formation of the ionic groups, the sites where electrophilic and nucleophilic reactions are most likely to occur in each ionic group, and the order of bond breaking during chemical reactions are obtained by the Multiwfn program.

Scalable and Sustainable Zinc (II) Ions‐Glue‐Assisted Conversion of Biomass Waste Bits into Carbon Aerogels for Efficient Uranium Extraction

AbstractCarbon aerogels (CAs) have garnered significant attention due to their multifunctional applications. Biomass waste, abundantly generated by agriculture and industry, serves as a primary carbon source. However, developing a facile, sustainable, and efficient method to produce CAs from biomass waste remains challenging. In this study, a one‐step Zn2+ ion‐glue‐assisted carbonization technique was developed to produce large‐scale, high‐performance CAs. Various biomass materials (wood bits, peanut shells, bamboo bits, and straw waste) were treated in a molten salt system (ZnCl2/KCl) at 300 °C for 2 h to obtain large‐block CAs derived from biomass bits. Zn2+ ions cleave cellulose hydrogen bonds in natural biomass, facilitating the dehydration crosslinking reaction among cellulose, hemicellulose, and lignin, thus reconstructing the entire block structure. The resulting CAs exhibited high porosity (95 %) and low density (0.078 g/cm3). Numerous hydroxyl and carbonyl groups were preserved during the low‐temperature treatment, facilitating chemical modification for diverse applications. For instance, amidoxime functionalized CAs were utilized as filters for selective and highly efficient extraction of U(VI) from wastewater. The adsorption capacity and extraction efficiency reached 801.2 mg/g and 95 % with a flux rate of 6.1×103 L/m2 ⋅ h.

Scalable and Sustainable Zinc (II) Ions-Glue-Assisted Conversion of Biomass Waste Bits into Carbon Aerogels for Efficient Uranium Extraction.

Carbon aerogels (CAs) have garnered significant attention due to their multifunctional applications. Biomass waste, abundantly generated by agriculture and industry, serves as a primary carbon source. However, developing a facile, sustainable, and efficient method to produce CAs from biomass waste remains challenging. In this study, a one-step Zn2+ ion-glue-assisted carbonization technique was developed to produce large-scale, high-performance CAs. Various biomass materials (wood bits, peanut shells, bamboo bits, and straw waste) were treated in a molten salt system (ZnCl2/KCl) at 300 °C for 2 h to obtain large-block CAs derived from biomass bits. Zn2+ ions cleave cellulose hydrogen bonds in natural biomass, facilitating the dehydration crosslinking reaction among cellulose, hemicellulose, and lignin, thus reconstructing the entire block structure. The resulting CAs exhibited high porosity (95 %) and low density (0.078 g/cm3). Numerous hydroxyl and carbonyl groups were preserved during the low-temperature treatment, facilitating chemical modification for diverse applications. For instance, amidoxime functionalized CAs were utilized as filters for selective and highly efficient extraction of U(VI) from wastewater. The adsorption capacity and extraction efficiency reached 801.2 mg/g and 95 % with a flux rate of 6.1×103 L/m2 ⋅ h.

Separation and extraction of NH4Br and (K,NH4)2SO4 from 1-Bromooctane production wastewater by crystallization method

This work provides a method for the separation and extraction of bromine salts from bromine-containing wastewater by crystallization. Wastewater from the production of 1-Bromooctane is rich in potassium and bromine salts. This will allow for the recycling of chemical resources in this aqueous salt system. Based on the need for the process design of the new method, the solubility phase equilibrium of the quaternary K+,NH4+//SO42-,Br-–H2O system at 298.15 K and 323.15 K was investigated in this paper by using the isothermal dissolution equilibrium method, and the dry basis phase diagrams were plotted using the experimental data. And the equilibrium solid phase composition was determined by X-ray diffraction. At 298.15 K, the dry phase diagram of the quaternary system K+,NH4+//SO42-,Br-–H2O consists of three invariant points and five crystalline regions (K2SO4, (NH4)2SO4, (K,NH4)2SO4, (K,NH4)Br, (NH4,K)Br). At 323.15 K, there is one invariant point in the phase diagram of this quaternary system and three crystalline regions((K,NH4)2SO4, (K,NH4)Br, (NH4,K)Br). The (K,NH4)Br crystallization zone grows while the (NH4,K)Br crystallization zone decreases with increasing temperature, according to comparisons of the dry basis phase diagrams of this quaternary system at different temperatures. Crystallization zones of solid solution (K,NH4)2SO4 replaced the K2SO4 and (NH4)2SO4 single salt crystallization zones at the same time. The Pitzer model was used to calculate the solubility of this quaternary system at 298.15 K. The results showed that the experimental values were in good agreement with the calculated values. Based on the theoretical analysis of the dry phase diagram of the quaternary system K+,NH4+//SO42-,Br-–H2O, a process route for salt extraction using bromine-containing wastewater generated from the production of 1-Bromooctane was proposed and designed. The new process was experimentally verified to be technically feasible to obtain NH4Br with 99.01 % purity and (K,NH4)2SO4. The process has significant advantages, such as production safety, low input costs and no three-waste emissions.

Novel assessment of molten salt oxidation for cation exchange resin treatment: Effective neutralization of sulfurous gas with Li2CO3-Na2CO3-K2CO3 system

The conventional thermal treatment of cation exchange resin substantially releases sulfurous gases, causing significant equipment corrosion and air pollution. In contrast, the Li2CO3-Na2CO3-K2CO3 as an alkaline molten system effectively neutralizes sulfur gas and mitigates waste gas production inherent in thermal oxidation methods. In the molten salt oxidation process, the volume concentration of SO2 was reduced by 81.7 % compared to that in the traditional thermal oxidation process, and this method reduces the generation of hazardous gases such as CO, CH4, and C2H6. The integration of online gas mass spectrometry and phase stability diagrams for carbonate and sulfur interception products demonstrate excellent thermodynamic stability during the molten salt oxidation (MSO) process. Moreover, a more accurate assessment of the acid gas neutralization capacity of the molten salt system is provided, and the acid gas neutralization capacity of the Li2CO3-Na2CO3-K2CO3 carbonate system can reach 82.58 % at 800 °C. The predominant contributors to acid gas neutralization are Na2CO3 and K2CO3, as evidenced by waste salt composition and ternary phase diagrams. The stable presence of Li2CO3 throughout the MSO process contributes to the lowering of the melting point of the carbonate system to 393 °C.

Technical Overview of Pyro-processing and Policy Considerations

Pyro-processing is an emerging technology crucial to the implementation of a closed nuclear fuel cycle. It is distinguished by its method of extracting and recycling actinides from fission products in spent nuclear fuels, utilizing high-temperature molten salt media. Despite its promise, the technology poses proliferation concerns that underscores the imperative for robust safeguards. While the safeguarding framework for aqueous reprocessing facilities that has been established over decades offers a foundational reference, the unique challenges posed by Pyro-processing necessitate a tailored approach. Amid these concerns, Pyro-processing is heralded as a viable strategy for nuclear waste management, with research increasingly focusing on its selectivity and efficacy within molten salt systems. This paper scrutinizes the proliferation risks inherent in Pyro-processing, delineates the requisite safeguards, and evaluates the feasibility of Pyro-processing, especially within the purview of the 123 Agreements between the United States and South Korea.