Salt Systems Research Articles

Experimental investigation and thermodynamic modelling assessment of the AECl2-NdCl3 (AE = Sr, Ba) systems.

The thermodynamic and thermo-physical properties of the binary salt systems AECl2-NdCl3 (AE = Sr, Ba) have been investigated using an experimental and modelling approach. The binary salt systems both include a single intermediate salt, i.e. Sr9Nd5Cl33 and Ba3Nd2Cl12, respectively. The structure of these intermediates has been investigated with X-ray diffraction (XRD). Furthermore, these systems exhibit mutual solubility of NdCl3 in BaCl2 and SrCl2. The investigation of these solid solutions has been performed using quenching experiments and subsequent post-characterisation by XRD. Phase diagram equilibria have also been investigated using differential scanning calorimetry (DSC). Using the aforementioned information on phase transitions, intermediate compound formation, and solid solubility, thermodynamic assessment of the systems has been performed using the CALPHAD method. The model for the Gibbs energy of the liquid solution is the quasi-chemical formalism in the quadruplet approximation, while the model for the Gibbs energy of the solid solutions is the two-sublattice polynomial model.

Influence mechanism of interfacial organic matter and salt system on carbon dioxide hydrate nucleation in porous media

CO2 carbon sequestration in marine gas hydrate occurrence areas is a potential way to mitigate the continued growth of CO2 in the atmosphere. The organic matters of marine sediment can affect the phase equilibrium conditions of CO2 hydrate in salt system, and the organic salt system in pore medium has effect on the nucleation growth of CO2 hydrate. The organic matters on the surface of the sediment is mainly composed of lipids, proteins, carbohydrates, and unsaturated hydrocarbon organic compounds, and these polar functional groups weaken the inhibitory effect of salt ions on hydrates through coordination bonds and Ca ion complexation. The nucleation kinetics of CO2 hydrate under organic salt system in pore medium in marine environment is an important parameter determining the carbon sequestration of hydrate. In addition, experimental results show that clay surface organic matters (CSOM) can reduce the surface tension of pore water, and thus pore water migration occurs during hydrate growth and expansion. The basic background in our findings will bring a much better recognition of phase equilibrium conditions among the offshore marine sediment CO2 sequestration process and further assess the location of potential marine CO2 storage sites.

Coupled Computational Fluid Dynamics and Computational Thermodynamics Simulations for Chemically Reacting Flows with Phase Transformations: A Fluoride Volatility Process Example

This study presents the development of a novel computational capability for chemically reacting flows with phase transformation that can be applied to complex multi-component systems. This is done by coupling Computational Fluid Dynamic (CFD) using OpenFOAM and Computational Thermodynamics (CT) using Thermochimica and the Joint Research Centre Molten Salt Database (JRCMSD). To illustrate this capability, the Fluorite Volatility Process (FVP) is modelled because it is the first step to clean up irradiated fuel salt in the Molten Salt Fast Reactor design and needs to be better understood. Local chemical equilibrium is assumed, which means that chemical kinetics is solely governed by mass transport. FVP recovers nuclear fuel UF4(liq) by injection of fluorine gas (F2), forming UF6(gas). The vaporization rate of UF4 is investigated on four different molten salt systems, using different dynamic viscosities and temperatures. The vaporization rate was shown to be clearly dependent on both thermochemical and thermophysical properties. Higher viscosities promoted larger bubbles, which delayed the chemical reaction. Results were compared to already available experimental data, showing good agreement. The applicability of coupling CFD with Thermochimica showed to be promising and expands interpretations on multiphysics systems and will be later applied to more complex scenarios.

Pulse Electrodeposition in the Presence of Corrosion Reactions during the Off-Time

Pulse electrodeposition of metals and alloys offers one route to enhance or tune material properties. However, an often-neglected period during pulse plating is the off-time, which may also influence deposit properties. Traditionally it is considered a relatively unimportant, allowing, for example, relaxation of concentration gradients, desorption of additives, recrystallization and discharge of the double later capacitance. Over the past few decades, however, studies have shown that it is possible to have ‘internal current’ processes occurring in the off-time which can strongly influence the deposit properties and composition. For example, in the pulse electrodeposition of binary alloys from aqueous solutions, displacement (corrosion) reactions have been observed in the off-time that can significantly alter the alloy composition. This has also been observed in many aqueous and molten salt systems, and appears a very general phenomenon. More recently we have observed corrosion arising from a comproportionation reactions during the pulse plating of copper from a deep eutectic solvent (DES) and noted some of their effect on deposit properties.The main purpose of this paper is to examine some of the similarities and differences in off-time corrosion caused by displacement and comproportionation processes during pulse electrodeposition. As is shown in the figure, corrosion may occur due to the presence of oxygen, or due the presence of a noble material leading to displacement reactions, as well as the presence of a stable species of differing valency in solution leading to comproportionation reactions. These differing mechanisms can produce different effects on the deposit. We will discuss how these different mechanisms can be understood and the influence on the deposit and their characteristics. Figure 1

Synthesis of Ternary and Quaternary Group III-Arsenide Colloidal Quantum Dots via High-Temperature Cation Exchange in Molten Salts: The Importance of Molten Salt Speciation.

Colloidal semiconductor nanocrystals are an important class of materials which have many desirable optoelectronic properties. In their bulk phases, gallium- and aluminum-containing III-V materials such as GaAs, GaP, and Al1-xGaxAs represent some of the most technologically important semiconductors. However, their colloidal synthesis by traditional methods is difficult due to the high temperatures needed to crystallize these highly covalent materials and the extreme reactivity of Ga- and Al- precursors toward organic solvents at such high temperatures. A recently developed paradigm shift in the synthesis of these materials is to use molten inorganic salts as solvents to prepare Ga- containing III-V colloidal nanocrystals by cation exchange of the corresponding indium pnictide (InPn) colloidal nanocrystals. There have been several successful applications of molten salt solvents to prepare III-phosphide colloidal nanocrystals. However, little is known about the nature of these reaction environments at the relevant reaction conditions and synthesis of III-arsenide colloidal nanocrystals remains challenging. Herein we report a detailed study on cation exchange of InPn nanocrystals using nominally Lewis basic molten salt solvents with added gallium halides. Surprisingly, these salt systems phase separate into two immiscible phases, and the nanocrystals preferentially segregate to one of the phases. Using a suite of in situ spectroscopy tools, we identify the phase the nanocrystals segregate to as Lewis neutral alkali tetrahalogallate molten salts. We apply in situ high-temperature Raman spectroscopy to identify the chemical species present in several molten salt compositions at experimentally relevant reaction conditions to elucidate a molecular basis for the reactivity observed. We then employ Lewis neutral KGaI4 molten salts to prepare high-quality In1-xGaxAs and In1-xGaxP nanocrystals and demonstrate that deviation from Lewis neutral conditions accelerate nanocrystal decomposition in the case of III-arsenide materials. Further, we expand to KAlI4-based molten salts to prepare In1-x-yGaxAlyAs nanocrystals which represent an example of solution-synthesized quaternary III-V nanocrystals. These insights provide a molecular basis for the rational development of molten salt solvents, thus allowing the preparation of a diverse array of multicomponent III-V colloidal nanocrystals.

Effect of the template particles size on structure and piezoelectric properties of 〈0 0 1〉‐textured BNT‐based ceramics

AbstractThis research investigated the effect of Bi4Ti3O12 (BiT) template particles size on the structure and piezoelectric properties of 〈001〉‐textured (Bi0.5Na0.5)TiO3 (BNT)‐based lead‐free piezoelectric ceramics. Results of X‐ray diffractometer analyses and scanning electron microscopy observations showed that high purity BiT template particles could be obtained with the KCl as the molten salt system. Highly 〈001〉‐textured (~87%) BNT‐based ceramics prepared with large size BiT templates (7.75 µm) exhibited a high inverse piezoelectric constant d33* (1100 pm/N), which was ∼3.38‐fold larger than that with 1.91 µm (325 pm/N). In addition, we have found that too small the template size can make it difficult to align the orientation of the template during the casting process, whereas too large the size can create problems such as too much hysteresis (∆S/Smax = 67%). This study has demonstrated that the use of high purity large size BiT template particles could provide a feasible route to fabricate BNT‐based textured ceramics with desired electro‐strain properties.

Rare earth removal from pyroprocessing fuel product for preparing MSR fuel

A series of experiments were performed to produce a fuel source for a molten salt reactor (MSR) through pyroprocessing technology. A simulated LiCl–KCl–UCl3-NdCl3 salt system was prepared, and the U element was fully recovered using a liquid cadmium cathode (LCC) by applying a constant current. As a result, the salt was purified with an UCl3 concentration lower than 100 ppm. Subsequently, the U/RE ingot was prepared by melting U and RE metals in Y2O3 crucible at 1473 K as a surrogate for RE-rich ingot product from pyroprocessing. The produced ingot was sliced and used as a working electrode in LiCl–KCl–LaCl3 salt. Only RE elements were then anodically dissolved by applying potential at −1.7 V versus Ag/AgCl reference electrode. The RE-removed ingot product was used to produce UCl3 via the reaction with NH4Cl in a sealed reactor.

Analysis of Factors Affecting the Preparation of Mullite Whiskers from Silica-Rich Slag and Application Studies.

This paper presents an in-depth comparative study of the effects of different molten salt systems, catalyst additions, preparation temperatures, temperature rise rates, and holding times on the properties of mullite whiskers during their preparation process, as well as exploring the enhancement of the toughening effect of mullite whiskers on ceramics. The morphology, crystal structure, and composition of the whiskers were analyzed via SEM, XRD, TG, strength tests, etc. The results show that the best-performing mullite whisker was prepared with an aluminum sulfate molten salt system, with the addition of aluminum fluoride catalyst at 4%, a temperature increase rate of 5 °C, a temperature increase up to 850 °C, and a holding time of 5 h, and its aspect ratio reached 20.64. By adding different contents of mullite whiskers and comparing the toughness strengths and wear rates of the silicon carbide ceramics, it was found that the toughness strength of the ceramics was improved by more than 16.5% and the wear rate was lower than 0.4% when the addition of mullite whisker was more than 3%.

Demonstration of the stabilization of solar salt at 620 C with a semi-closed configuration in a 100 kg-scale

Among the variety of energy storage techniques thermal energy storage (TES), based on molten salts, is already in use for the storage of heat in a gigawatt hour scale. At the time of writing virtually all TES in CSP utilize Solar Salt (60 wt-% NaNO3 and 40 wt-% KNO3) due to its competitively low price, low vapor pressure and non-toxicity. On the downside, the operating temperature is limited to 560 °C based on its thermal stability. However, increasing the operating temperature while maintaining thermal stability of the salt using techniques that are realizable in industrial scale remains one of the main challenges. Up to now this could only be achieved in a small scale by flushing with synthetic purge gas or sealing and pressurizing the system, maintaining the necessary gas atmosphere and shifting the chemical equilibrium to the nitrate side. Both methods are hardly realizable in an industrial scale. In this work we show a new strategy to stabilize Solar Salt at 620 °C by combining the gas-purged configuration and sealed system with maximum pressure of few tens of millibars in a 100 kg scale. The formed gas phase was within the expected range in terms of oxygen and nitrous gases. Additionally, the concentration of the nitrate and nitrite ions aligned well with salt systems with gas-purged atmosphere at 620 °C. We demonstrate the first experiments on long-term thermal stabilization (4000 h) of Solar Salt at 620 °C in a 100 kg technical-scale. These findings represent an important step in the development of modern storage systems.

Machine-learning-driven simulations on microstructure, thermodynamic properties, and transport properties of LiCl-KCl-LiF molten salt

The thermodynamic and transport properties of high-temperature chloride molten salt systems are of great significance for spent fuel reprocessing in the field of nuclear energy engineering. Here, by using machine learning based deep potential (DP) method, we train a high-precision force field model for the LiCl-KCl-LiF system. During force field training, adding new dataset through multiple iterations improves the accuracy of the force field model and its applicability to more configurations. The comparison of density functional theory (DFT) and DP results for the test dataset indicates that our trained DP model has the same accuracy as DFT. Then, we comprehensively investigate the local structure, thermophysical properties, and transport properties of the LiCl-KCl and LiCl-KCl-LiF molten salt systems using the trained DP model. The effects of temperature and LiF concentration on the above properties are analyzed. This work provides guidance for the training of machine learning force fields in molten salt systems and the study of basic physical properties of high-temperature chloride molten salt systems.

Separation of fission products from high-level waste salt systems by partial crystallization: CsCl-NaCl-LiCl-KCl study

Pyroprocessing refers to a series of high-temperature molten-salt processes used to manage and recycle nuclear materials to reduce the waste volume and hazardous environmental impact of the final waste products. Fission products with high halide affinity, including cesium (Cs-137) with a half-life of 30 years, are dissolved into a molten-salt bath. The separation and recovery of cesium can benefit waste-stream minimization because Cs-137—a strong gamma-ray emitter—is a potential source of environmental contamination. This work proposes the recovery of Cs+ from a chloride-salt matrix using a thermally controlled solid-liquid separation. Thermodynamic calculations for the CsCl-NaCl-LiCl-KCl system were performed to predict the partitioning of Cs+ into liquid and solid phases as functions of salt composition and temperature. The selected composition simulated the formulation of high-level salt waste from used fuel treatment. These calculations showed that once the solidus temperature was reached, Cs+ partitions to the liquid phase. According to the thermodynamic calculations, a thermally controlled liquid-solid separation holds the potential to recover up to 92.8 % of the initial cesium chloride. The phase transition temperatures of the sample, including the solidus and liquidus temperatures, were determined using differential scanning calorimetry. The phase composition of the system was studied at various temperatures using high-temperature X-ray diffraction. A laboratory-scale crystallization apparatus was used to melt the sample partially, allowing the collection of the liquid fraction for elemental analysis. All results demonstrated that Cs+ in this system concentrates in the liquid phase and confirmed the viability of recovering CsCl through thermally controlled solid-liquid separation.

Molten salt-assisted carbonized zeolite imidazolate framework on nickel foam for highly efficient iodide capture in fluoride molten salts

Removing radioactive iodide ions from molten salt nuclear fuel in fourth-generation molten salt reactors is essential for nuclear and environmental safety. In the present work, a synthesis strategy as synthesised in molten salt was utilized by employing. A two-dimensional nanoscale carbon membrane with a hierarchical pore structure (HNPC@NF) was successfully prepared via molten salt-assisted carbonized three-dimensional ZIF-8 grown in situ on nickel foam, which showed the maximum adsorption capacity of 55.6 mg/g for iodide ions in LiF-BeF2 molten salt within 8 h under static adsorption experiments. HNPC@NF was capable of effectively adsorbing iodide ions even in the presence of various cations and anions such as Cs+, Sr2+, Nd3+, Sm3+and Br- and also adsorbed coexisting ions. The different-sized pores of HNPC@NF act as filters, sieving, and occluding for these ions. Radioactive tracer experiments have confirmed that HNPC@NF could adsorb 131I in simulated spent nuclear fuel salt and captured radionuclides 99mTc, 99Mo, 239Np, and 132Te within 4 h without interacting with 237U. The adsorption mechanism was determined by combining kinetic fitting, XRD, XPS, and simulation calculations using the Adsorption Locator and CASTEP module of BIOVIA Materials Studio based on density functional theory (DFT). On the macroscopic scale, iodide ions covered by molten salt diffused the surface of HNPC@NF through physisorption and occluded in the pores. On the atomic scale, charge-shift bonds formed between carbon atoms and iodide ions, allowing for stable adsorption at the hollow sites within the carbon network. The coexistence of cations increased the adsorption energy of iodide ions, which benefited the reaction. Based on these results, HNPC@NF showed the potential application as an adsorbent for radioactive iodide in the fluoride molten salt system.

Evaluation of Ni–B alloy electroplated with different anionic groups

In order to study the effects of the main nickel salt on the electroplated nanocrystalline Ni–B alloy coating, the deposition rates, surface morphology, crystallinity, grain sizes, hardness, and corrosion resistance of the Ni–B films electrodeposited with plating baths containing separately nickel sulfate (NS) and nickel sulfamate (NSA) under various temperatures and current densities were compared. Under all conditions, the NSA bath system offered higher deposition rates and lower B contents than the NS counterpart because of the formation of Ni-ammonium complex, which can be adsorbed faster than nickel ions. These two groups of coatings had similar surface morphology and crystallinity under all plating conditions except for those plated with the NS bath system at 60 °C, wherein significant changes in surface texture and preferred crystal orientation as well as an abrupt increase in grain size occurred. The coating hardness was optimized by reducing the grain size and increasing the boron content because of the combined effects of grain refinement strengthening and solid solution strengthening. The differences between the two main salt systems can be explained by the presence of ammonium ions in the NSA bath, which not only increased the deposition rate but also maintained the preferred orientation in Ni (111) at high temperature. Our results indicate that, under high current density and high temperature operation conditions, the NSA main salt plating system is a more favorable option for obtaining higher quality Ni–B alloy coatings.

A study on the extension of correlation functions obtained from molecular dynamics simulations by the Ornstein–Zernike theory for modeled molten salts

We extend the correlation functions obtained by molecular dynamics (MD) simulation for a molten salt modeled as a superposition of the Lennard-Jones (LJ) and Coulomb potentials using the hybrid closure method, which employs the Ornstein–Zernike (OZ) theory coupled with a closure relation. An appropriate distance for switching the short-range MD part and the long-range OZ part is determined by monitoring the isothermal compressibility, excess internal energy, and pressure. The Kobryn–Gusarov–Kovalenko (KGK) closure relation is mainly employed for the hybrid closure method (MD–KGK hybrid closure). The hybrid closure with either the hypernetted chain (HNC) or Kovalenko–Hirata (KH) closure was also tested to confirm that the performance was almost equivalent to one another among the MD–HNC, MD–KH, and MD–KGK methods. The bridge function for the model molten salt is extracted using the MD–KGK hybrid closure method. At a high-density state, the bridge function shows a steep increase in the repulsive core region, as is often observed for simple fluids, whereas when the density is relatively low, the bridge function for the cation–anion pair shows a downward-sloping behavior. Furthermore, the accuracies of excess internal energy, pressure, and isothermal compressibility were also examined for the HNC, KH, and KGK approximations. For molten salt systems, these approximations exhibited a similar behavior to those for monatomic LJ fluids, especially in the high-density state. The analysis of the integrand for excess internal energy and pressure is also discussed.

Optimization and Evaluation of the Thermodynamic Model of the LiF–[CaF2/YbF3] Molten Salt System

Optimization and Evaluation of the Thermodynamic Model of the LiF–[CaF2/YbF3] Molten Salt System

Design of spherical agglomeration via salt-induced liquid–liquid phase separation

In this study, a novel strategy for spherical agglomeration via salt-induced liquid–liquid phase separation (SI–SA) was developed. SI–SA technology achieves phase separation in the miscible binary anti-solvent crystallization system by adding certain amounts of salts, avoiding the use of toxic bridging liquids. Water–organic solvent–salt systems that induced phase separation were selected using phase separation experiments. The wetting performance of the organic solvent was estimated by droplet experiments, and organic solvents with stronger wettability for crystals than water would be selected for further verification. Spherical agglomeration experiments were designed based on the ternary phase diagrams of these selected systems. Water–organic solvent–salt systems of benzoic acid were selected, starting with six organic solvents and four salts. A total number of 16 water–organic solvents–salt systems were effectively predicted using the SI–SA strategy. The in-situ process analysis tool indicated that the formation of spherical particles of benzoic acid underwent a process of crystallization, phase separation, wetting, two-step agglomeration, and consolidation. The stirring rate and mass ratio of salt to final crystals were found to be important for controlling the morphology and particle size of the spherical crystals. The spherical particles of aspirin and salicylic acid were successfully predicted in different systems via SI–SA technology, demonstrating the universality and potential usage of SI–SA technology in industry.

A predictive approach for the compositional and temperature representation of thermal conductivity in multicomponent molten salt systems for advanced energy applications

This study presents a theoretical model, based on kinetic theory, for accurately predicting thermal conductivity in molten salt mixtures, a vital factor in designing advanced energy systems such as concentrating solar power, thermal energy storage, and advanced nuclear reactors. Applicable to non-complex, non-reciprocal systems, the model represents thermal conductivity with respect to composition and temperature. We evaluated the model using molecular dynamics simulations on binary systems from fluoride, chloride, bromide, iodide salt families. The model predictions were also compared against existing experimental datasets for those families as well as binary nitrates and carbonates. The model demonstrated an improvement in predictive accuracy over the ideal linear estimation and showed reasonable agreement with the reliable experimental data. Deviations from ideal conductivity, analyzed using the Redlich-Kister method, pointed to the molecular weight and thermal conductivity of individual compounds as primary influencing factors. When applied to predict the thermal conductivity of higher order eutectic salt mixtures relevant to energy applications, the model showed predictive accuracy comparable to empirical methods. The model was further applied to generate compositional mapping to quantify deviations from ideality over the compositional space. This advance enhances new molten salt mixtures evaluation efficiency and extends the model to complex mixtures.

Exploring NaCl-PuCl3 molten salts with machine learning interatomic potentials and graph theory

Actinide molten salts are the basis of the liquid fuels used in molten salt reactors. Due to the inherent difficulties associated with high temperature and hazardous conditions, experimental investigations of fundamental properties of these materials are usually challenging. In this work, we describe the structure and transport of NaCl-PuCl3 mixtures using computational techniques. Three compositions were considered (16, 25, and 36 mol% PuCl3) over a temperature range (730 – 1257 K) using ab initio molecular dynamics, which provided the necessary data sets for training machine learned interatomic potentials. Molecular dynamics simulations based on these potentials were then used to determine structure and transport properties. A substantial change was noted in the structure factor when increasing the PuCl3 content from 25 to 36 mol%. This change is linked to the aggregation of larger Pu3+ clusters. In addition, the similarity of the atomic environments of metal cations in molten salt systems to their solid states counterparts was investigated using an unsupervised learning technique. Finally, graph theory was employed to explore the structure and size of actinide networks. Consistent with the structure factor, a dense Pu3+ intermolecular structure is observed within the 36 mol% PuCl3 mixture. The structure of cation-cation inter-junctions is also discussed. In all cases, the diffusion of Pu3+ is significantly lower than that of Na+ and Cl−.

The deoxygenation mechanism of biomass thermal conversion with molten salts: Experimental and theoretical analysis

Utilizing molten salt for biomass pyrolysis has emerged as a pivotal technology for enhancing product value and has become a crucial alternative to traditional pyrolysis methods. However, there remains a dearth of research on the deoxygenation mechanism of biomass during molten salt thermal treatment. This study focuses on investigating the deoxygenation characteristics of biomass during molten salts thermal treatment through a comprehensive analysis involving experimental and density functional theory (DFT) study. Our experimental results revealed that, compared to traditional pyrolysis, molten salt (NaNO3–NaNO2) significantly increased oxygenated gas products, favoring deoxygenation during biomass conversion. Formic acid was employed as a simplified oxygen-containing model compound to investigate the decomposition characteristics with and without the presence of molten salts using DFT calculations. DFT studies of formic acid decomposition revealed lower activation energies on NaNO3 (234.39 kJ/mol) and NaNO2 (84.11 kJ/mol) surfaces compared to homogeneous reactions (234.63 kJ/mol). This indicates that NaNO2 has a more pronounced promotional effect, facilitating formic acid decomposition. Furthermore, kinetic calculations show that both homogeneous and heterogeneous reaction rate constants for formic acid decomposition increase with temperature. The reaction rate constants on the surface of NaNO3 are similar to homogeneous reactions, while it is much higher two on NaNO2 surfaces. These findings highlight the critical role of NaNO2 in formic acid decomposition within the NaNO3–NaNO2 molten salt system. The experimental and computational results elucidate the deoxygenation mechanism of biomass thermal conversion using molten salts and establish a theoretical foundation for the high-value utilization of pyrolysis products.

Natural Convection in Molten Salt Electrochemistry.

Molten salt electrochemistry has been widely used in many fields, especially for metal extraction/refinement. The understanding of mass transfer in molten salts under harsh operation conditions is of great importance to reveal reaction mechanisms and advance fine technologies. It has been generally assumed that natural convection is negligible in stagnant molten salt electrochemistry. Herein, we report an abnormal natural convection in molten LiCl-KCl, with the arising time from 2.37 s at 873 K to 10.13 s at 673 K. Using the concentration correction factor, the derived thickness of the natural convection-diffusion layer (δconv.) was found to be ranging from 128 to 163 μm, much thinner than those in aqueous solutions (∼200 μm). The simulations showed that the notable natural convection resulted from convection-diffusion layer (CDL) convection dominated over the density-driven convection even at high redox concentrations, implying the severe vibration of molten salt systems. To suppress the intense natural convection, we predicted that the use of microelectrodes (with radii less than 23.2 μm for δconv. = 150 μm) would be a promising tool, regardless of their inferior stabilities in high-temperature molten salts at this stage. These innovative findings offer insights into the impact of natural convection on mass transfer in molten salts that have not been previously revealed.