Mixed Salts Research Articles

Microstructure Evolution and Molten Salt Corrosion Resistance Dependent on Pre-Oxidation Treatment of NiAl Coatings

The chloride-infused molten salt shows the most potential as the medium for the upcoming generation of concentrated solar power system. However, the molten salt put for ward higher corrosion resistance demand on the critical components of concentrated solar power system. The application of NiAl coating proves to be a highly efficient method for preventing corrosion. In this paper, the microstructure, adhesion, and corrosion resistance of NiAl coatings on 310S stainless steel with/without pre-oxidation treatment were studied. The coating predominantly consisted of β-NiAl phase nanocrystals with an Al content of 41.0 at.%. Continuous α-Al2O3 oxide film was formed and no obvious cracks were observed after pre-oxidation. The adhesion strength of NiAl coating was increased by about 70% to 40.0 N through pre-oxidation. Importantly, the corrosion results of NiAl coatings by pre-oxidation treatment in the mixed salt of NaCl/MgCl2/KCl at 1073.15 K for 10 h showed no obvious diffusion of molten salt elements into the coatings. Compared to 310S stainless steel, the pre-oxidized coating sample exhibited a significant reduction of 50.2% in corrosion mass loss. The pre-oxidation of the NiAl coating creates an Al2O3 oxidation layer that effectively blocks corrosion, offering a new method for protecting stainless steels in concentrated solar power system plants.

Influence of pore size distribution and applied cross-flow on ion rejection and separation

To improve the understanding of the separation mechanism of ions through membrane filtration, ion transport through a membrane with non-uniform pore sizes is investigated theoretically by solving the coupled Poisson-Nernst-Planck and Navier-Stokes equations under various conditions. The model focuses on a membrane with pore sizes following a log-normal distribution and considers the flow interaction between pores. The rejection performance for different pore arrangements is addressed for a rational assessment of the best ion rejection and selectivity in membrane filtration processes. In addition to the dead-end setting, a cross-flow is applied on the feed side to alleviate the concentration polarization effect. In the presence of positively charged nanopore surfaces, both the cases of a single salt (NaCl) and mixed salts (NaCl, MgCl2) present in the liquid are considered. We show that the uniform pore system outperforms non-uniform ones in terms of the overall rejection and selectivity between salts. When pore size polydispersity is present, the arrangement among the larger and smaller pores impacts the local rejection and volumetric flux of pores. Moreover, the competitive transport between cationic co-ions makes Mg2+ demonstrate generally higher rejection in all the pore arrangements considered. As uniform pores show lower flow rates, the separation efficiency of ions may be improved by pore size polydispersity at the same concentration and pressure difference.

Effect of the SiO2 instead of Al2O3 in the embedding powder on the microstructure and hot corrosion behavior of silicon-modified aluminide coatings

The effects of Si and SiO2 content in the embedding powder on the equilibrium partial pressure of halide gas were compared by material thermodynamic calculation, and higher SiO2 content facilitated the preparation of silicon-modified aluminide coatings. The microstructure and hot corrosion behavior of silicon-modified aluminide coating prepared by different SiO2 contents were studied. As the SiO2 content in the embedding powder increased, the Al, Si, and Cr content was elevated in the prepared coating surface, which promotes the Cr9.1Si0.9 phase precipitate in the coating. Besides, the corrosion weight loss of the coating was the lowest, after 50 wt% NaCl + 50 wt%Na2SO4 mixed molten corrosion at 900 °C for 100 h, showing the excellent corrosion resistance. At the initial corrosion stage, the higher Si content induces the formation of a SiO2 oxide film on the coating surface, which could resist the mixed molten salt reaction. As the corrosion process, the SiO2 oxide film and the below Al2O3 oxide film peel off due to thermal expansion mismatch. Meanwhile, the coating relies on the dispersed precipitation below the oxide film to hinder the corrosive elements and the consumption of Al elements at the final corrosion stage.

Valorization of agitated thin film dryer (ATFD)-mixed-salt from textile wastewater for its application in leather manufacturing – a sustainable approach

ABSTRACT The textile industry uses sodium chloride and sodium sulphate during the dyeing process to improve the fixation of dyes on fabrics. After wastewater treatment, the reject stream is dried resulting in mixed salts as solid wastes that are not reused. The leather industry also uses a vast quantity of salt for temporary preservation of skins/hides and as swelling-suppressing agent during the pickling (acidification) process. Thus, an attempt was made to utilize the mixed salt obtained from the textile industry to replace sodium chloride in leather processing. It was found that a 40% w/w offer of ATFD salt was able to preserve the skins for 3 months, which was on par with the preservation carried out using a similar quantity of sodium chloride in conventional preservation process. Likewise, for the pickling process, an offer of 10% w/w ATFD salt provided sufficient deswelling action when compared to conventionally used sodium chloride. However, the residual colour of the mixed salts affected the quality of the leather obtained. To overcome this, an electro-oxidation treatment was carried out to obtain decolourized salts. The COD measurements showed that the 1% solution of ATFD-3 salt reduced from 471 ± 25 to 88 ± 16 ppm. A similar trend was also seen in BOD reduction from 80 ± 12 to 18 ± 10 ppm. These results confirmed that the colour removal could be due to the degradation of the organic contaminants present in the ATFD salt. Thus, the treated ATFD salt can be reused for leather processing without affecting leather quality, thus promoting the concept of circular economy.

Preparation of porous carbon with high performance as lithium-ion battery anode utilizing FeCl3/ZnCl2 as modifying agents

The anode materials for lithium-ion batteries (LIBs) are prepared by one-step carbonization using urea-impregnated cotton stalk (CS) as a carbon precursor and ZnCl2 and FeCl3 as an activator and catalyst, respectively. The addition of ZnCl2 contributes to the development of mesopore. Incorporating FeCl3 improves the graphitization of porous carbon, but has no significant effect on layer spacing. In addition, FeCl3 catalysis can increase the specific surface area and pore volume of porous carbon, especially the development of pore structure below 10 nm. In terms of electrochemical performance, the porous carbon is prepared at CS: ZnCl2: FeCl3 = 1:1:1 and possessed the best performance, with a reversible capacity of 487.7 mAhg−1 after 100 charge–discharge cycles at 0.1 Ag−1 and specific capacity retention of 83.61 %. This study greatly improves the cycling stability of the battery while reducing the amount of mixed salt, which is extremely significant for subsequent research.

Time for mixing: Mixed dicationic energetic salts based on methylene bridged 4-hydroxy-3,5-dinitropyrazole and tetrazole for tunable performance

Various types of materials have been explored in the pursuit of high energy density materials (HEDMs) that have balanced energy and stability. Among them, energetic salts show numerous advantages, such as lower vapor pressures, high physical stabilities, and the opportunity for favorable tuning by careful selection of cations/anions. Nitrogen-rich bases are generally used as cations for energetic salt formation. While the synthesis of salts with larger cations lowers the sensitivity, smaller cations aid better energetic performance. A combination of both in the same ionic moieties might help in the formation of a superior explosive. In this work, a facile route for the synthesis of mixed dicationic energetic salts based on 1-((1H-tetrazol-5-yl)methyl)-3,5-dinitro-1H-pyrazol-4-ol (compound 1) has been explored by various combinations of bigger and smaller cations (compounds 4–10). All the synthesized energetic salts showed high positive heats of formation, energetic performance comparable to TATB, excellent stability towards impact and friction, and acceptable thermal stabilities. This improved technique will provide an additional option for fine-tuning the energetic properties of HEDMs and will facilitate in exploring the role of various cations in the overall performance of the energetic compounds.

Genome-Wide Identification of the Pectate Lyase Gene Family in Potato and Expression Analysis under Salt Stress.

Pectin is a structural polysaccharide and a major component of plant cell walls. Pectate lyases are a class of enzymes that degrade demethylated pectin by cleaving the α-1,4-glycosidic bond, and they play an important role in plant growth and development. Currently, little is known about the PL gene family members and their involvement in salt stress in potato. In this study, we utilized bioinformatics to identify members of the potato pectate lyase gene family and analyzed their gene and amino acid sequence characteristics. The results showed that a total of 27 members of the pectate lyase gene family were identified in potato. Phylogenetic tree analysis revealed that these genes were divided into eight groups. Analysis of their promoters indicated that several members' promoter regions contained a significant number of hormone and stress response elements. Further, we found that several members responded positively to salt treatment under single salt and mixed salt stress. Since StPL18 exhibited a consistent expression pattern under both single and mixed salt stress conditions, its subcellular localization was determined. The results indicated that StPL18 is localized in the endoplasmic reticulum membrane. The results will establish a foundation for analyzing the functions of potato pectate lyase family members and their expression under salt stress.

Determination and correlation of the solubility of magnesium sulfate in ethanol solutions with different concentrations: Application to the removal of magnesium from zinc electrolytic waste solution

In this study, the solubility of anhydrous magnesium sulfate (MgSO4) in ethanol solutions with concentrations ranging from 10 % to 50 % was determined at 15–50 °C. Next, the results were correlated by using the Apelblat model, polynomial empirical equation, ideal solution equation of state model, and Van’t Hoff–Jouyban–Acree model. The results indicated that all four models exhibited correlation coefficients greater than 97 %, and average relative deviations of 3.82 %, 4.24 %, 3.96 %, and 3.96 %, respectively. Notably, the Apelblat model was found to be more accurate and reliable in correlating the solubility of MgSO4 in ethanol solutions with different concentrations. Further, the Van’t Hoff equation was applied to determine the enthalpy and entropy of dissolution. Herein, a certain amount of anhydrous ethanol was added to the zinc (Zn) electrolytic waste solution (ZEWS) to crystallize Zn2+ and Mg2+ through the solvent crystallization method, with the precipitation rates reaching 20.13 % and 39.38 %, respectively. The concentration of Mg2+ reduced to below 15 g⋅L−1, meeting the quality standard of ZEWS. The XRD, TG, and SEM analyses of the output salt mix crystallization confirmed the primary components to be MgSO4·7H2O and ZnSO4·7H2O, with the morphological features primarily consisting of short rods and some crystal agglomerates. This study shows that the removal of Mg2+ from Zn smelting process can be effectively achieved by the proposed solvent crystallization method.

Ekman-driven salt transport as a key mechanism for open-ocean polynya formation at Maud Rise.

Open-ocean polynyas formed over the Maud Rise, in the Weddell Sea, during the winters of 2016-2017. Such polynyas are rare events in the Southern Ocean and are associated with deep convection, affecting regional carbon and heat budgets. Using an ocean state estimate, we found that during 2017, early sea ice melting occurred in response to enhanced vertical mixing of heat, which was accompanied by mixing of salt. The melting sea ice compensated for the vertically mixed salt, resulting in a net buoyancy gain. An additional salt input was then necessary to destabilize the upper ocean. This came from a hitherto unexplored polynya-formation mechanism: an Ekman transport of salt across a jet girdling the northern flank of the Maud Rise. Such transport was driven by intensified eastward surface stresses during 2015-2018. Our results illustrate how highly localized interactions between wind, ocean flow and topography can trigger polynya formation in the open Southern Ocean.

Effect of changing the proportion of C16:0 and cis-9 C18:1 in fat supplements on rumen fermentation, glucose and lipid metabolism, antioxidation capacity, and visceral fatty acid profile in finishing Angus bulls

This study evaluated the effects of different proportions of palmitic (C16:0) and oleic (cis-9 C18:1) acids in fat supplements on rumen fermentation, glucose (GLU) and lipid metabolism, antioxidant function, and visceral fat fatty acid (FA) composition in Angus bulls. The design of the experiment was a randomized block design with 3 treatments of 10 animals each. A total of 30 finishing Angus bulls (21 ± 0.5 months) with an initial body weight of 626 ± 69 kg were blocked by weight into 10 blocks, with 3 bulls per block. The bulls in each block were randomly assigned to one of three experimental diets: (1) control diet without additional fat (CON), (2) CON + 2.5% palmitic calcium salt (PA; 90% C16:0), (3) CON + 2.5% mixed FA calcium salts (MA; 60% C16:0 + 30% cis-9 C18:1). Both fat supplements increased C18:0 and cis-9 C18:1 in visceral fat (P < 0.05) and up-regulated the expression of liver FA transport protein 5 (FATP5; P < 0.001). PA increased the insulin concentration (P < 0.001) and aspartate aminotransferase activity (AST; P = 0.030) in bull's blood while reducing the GLU concentration (P = 0.009). PA increased the content of triglycerides (TG; P = 0.014) in the liver, the content of the C16:0 in visceral fat (P = 0.004), and weight gain (P = 0.032), and up-regulated the expression of liver diacylglycerol acyltransferase 2 (DGAT2; P < 0.001) and stearoyl-CoA desaturase 1 (SCD1; P < 0.05). MA increased plasma superoxide dismutase activity (SOD; P = 0.011), reduced the concentration of acetate and total volatile FA (VFA) in rumen fluid (P < 0.05), and tended to increase plasma non-esterified FA (NEFA; P = 0.069) concentrations. Generally, high C16:0 fat supplementation increased weight gain in Angus bulls and triggered the risk of fatty liver, insulin resistance, and reduced antioxidant function. These adverse effects were alleviated by partially replacing C16:0 with cis-9 C18:1.

Numerical analysis of the viscosity of ZrF4–BeF2 molten salts for nuclear transmutation using fusion neutron sources

This study analyzed the influence of ZrF4 on the viscosity of a ZrF4–BeF2 binary salt towards developing BeF2-based molten salts for nuclear transmutation targets. Specifically, we performed molecular dynamics simulation using a polarization ion model and evaluated the viscosity, static structure, and applicability of the Stokes–Einstein equation for ZrF4–BeF2 compared with LiF–BeF2. Our study revealed that ZrF4–BeF2 exhibits higher viscosity than LiF–BeF2 because each ionic bond's longer lifetime extends the structural relaxation time. Furthermore, it is suggested that the ZrF and BeF relaxations contribute to the viscosity mechanism of ZrF4–BeF2. Most of the elements in long-lived fission products (LLFPs) are multivalent ions such as Zr, Pd, and Sn, which bind strongly to anions and are not expected to contribute much to reducing the viscosity of BeF2 mixed salts. In contrast, Cs, also an LLFP, is a monovalent ion, and CsF can reduce the viscosity of these salts. Mixing particular LLFPs with CsF will be one of the principles in designing BeF2-based salts for transmutation.

Negative rejection phenomenon in the mixed salt nanofiltration: Law and mechanism

The negative rejection of certain solutes is an interesting phenomenon often observed in nanofiltration (NF) process, which presents an ideal solute separation effect. In this study, the NF membrane pore size, electric charge property and influent ions composition were controlled to investigate the rule and mechanism of negative rejection phenomenon during SO42−/Cl− mixed salt NF. The results show that the changing of the membrane pore diameter and charge will significantly affect the NF selectivity to SO42−/Cl−, then affect the negative rejection phenomenon. Selective efficiency of Cl−/SO42− can be up to 156.04–283.20 for the negative charged NF membrane with an average pore diameter of 0.62–0.68 nm, and the Cl− was negatively rejected under many influent conditions with the lowest rejection rate of −252.36 %. The substitution of Na+ for Mg2+ and the increase of SO42−/Cl− ratio are beneficial to improve selectivity. The Donnan Steric Pore Model with dielectric exclusion model was used to calculate the rejection curve which is consistent with the experimental results. The analysis of NF mechanism shows that the negative rejection of Cl− is caused by the extra transfer power derived from the NF selectivity to Cl−, which is a compensation for the higher rejection rate of SO42−.

Molecular and electrostatic origins of mixed salt partitioning phenomena in uncharged poly(ethylene oxide)-based membranes

Despite the increasing interest in membranes for water purification and resource recovery from aqueous electrolyte mixtures, few studies rigorously investigate the influence of salt solution composition (e.g., mole fraction and total salt concentration) on membrane material properties such as partition coefficients. Here, we systematically investigate the influence of solution composition on the partitioning of ionic species from binary aqueous salt solutions into crosslinked poly(ethylene glycol) diacrylate membranes at fixed ionic strength. These results are compared to partition coefficients observed for pure salt solutions. We observe large systematic deviations between the pure salt and mixed salt ion partition coefficients, indicating that the single salt partition coefficients that are often reported do not describe the more complex and realistic mixed salt scenario. Free energy calculations from molecular dynamics simulations, coupled with equilibrium thermodynamic modeling, indicate that mixed salt partitioning trends result from (i) different ions exhibiting different affinities for the membrane and (ii) the constraint of global electrical neutrality within the membrane. With this physical insight, we develop a simple approach to predicting the concentration of various ions in a membrane equilibrated with a mixed salt solution which requires no adjustable parameters.

Fluoride-Ion Donor Properties of AsF5

Fluoride-Ion Donor Properties of AsF₅

High-temperature dry sliding friction and wear behavior of in-situ (Al3Zr+ZrB2)/AA6016 aluminum matrix composites

Aluminum alloy, a lightweight material, has poor friction and wear properties at high temperatures. Therefore, aluminum matrix composites were prepared by in-situ autogenous method to enhance the high-temperature friction and wear capability of aluminum alloys. (ZrB2+Al3Zr)/AA6016 in-situ aluminum matrix composites were prepared by in-situ reaction with the addition of mixed salts of potassium fluoborate (KBF4) and potassium fluozirconate (K2ZrF6). The materials were characterized by XRD, SEM, and EBSD. The friction and wear properties were investigated mainly by high-temperature friction and wear experiments combined with SEM and XPS. The results show that the wear resistance of (ZrB2+Al3Zr)/AA6016 aluminum matrix composites far exceeds that of their alloys under severe conditions of high temperature. The wear of AMCs first decreases and then increases with increasing temperature. The lowest wear rate was observed at an ambient temperature of 100°C, where the wear rate of AMCs was reduced by a factor of 2.7 compared to that of aluminum alloys. In addition, the enhancement effect of hard and heat-resistant particles was also due to the oxide film generated during friction on the abrasive scar surface layer of AMCs under this condition and the self-lubricating substance (H3BO3). The composite wear mechanism of AMCs was dominated by abrasive, oxidative, and adhesive wear as the test temperature increased.

Surface and Bulk Stabilization of Silicon Anodes with Mixed-Multivalent Additives: Ca(TFSI)2 and Mg(TFSI)2.

Silicon is drawing attention as an emerging anode material for the next generation of lithium-ion batteries due to its higher capacity compared with commercial graphite. However, silicon anions formed during lithiation are highly reactive with binder and electrolyte components, creating an unstable SEI layer and limiting the calendar life of silicon anodes. The reactivity of lithium silicide and the formation of an unstable SEI layer are mitigated by utilizing a mixture of Ca and Mg multivalent cations as an electrolyte additive for Si anodes to improve their calendar life. The effect of mixed salts on the bulk and surface of the silicon anodes was studied by multiple structural characterization techniques. Ca and Mg ions in the electrolyte formed relatively thermodynamically stable quaternary Li-Ca-Mg-Si Zintl phases in an in situ fashion and a more stable and denser SEI layer on the Si particles. These in turn protect silicon particles against side reactions with electrolytes in a coin cell. The full cell with the mixed cation electrolyte demonstrates enhanced calendar life performance with lower measured current and current leakage in comparison to that of the baseline electrolyte due to reduced side reactions. Electron microscopy, HR-XRD, and solid-state NMR results showed that electrodes with mixed cations tended to have less cracking on the electrode surface, and the presence of mixed cations enhances cation migration and formation of quaternary Zintl phases stabilizing the bulk and forming a more stable SEI in comparison to baseline electrolyte and electrolyte with single multivalent cations.

Theoretical and experimental study on the recovery of bromide by crystallization from pesticide production wastewater

Brominated wastewater from the propyl bromide pesticide production rich in ammonium, sodium and bromine salts at a high concentration of 11 %. For the recycling of chemical resources of this mixed brine salt system, this paper proposes a method for the separation of bromide from bromine-containing chemical wastewater by crystallization. According to the process design needs of the new method, and because 298 K and 323 K are two common temperatures in industrial practice, in this paper, the solubility data of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K and 323 K, as well as its ternary subsystems, NaBr-NH4Br-H2O and NH4Cl-NH4Br-H2O at 323 K were determined by the isothermal solubilization method, and the corresponding phase diagrams were drawn. The solubility of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K was also calculated using the Pitzer model, and the calculated results were in good agreement with the experimental measurements. Finally, based on the theoretical analysis of the phase diagrams of the 298 K and 323 K NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary systems and combined with the phase diagrams of the 298 K NaBr-NaCl-CH3OH system, this paper proposes and designs a salt extraction process route for the brominated wastewater of the propyl bromide pesticide production. Through the separation experiment, the new process proved to be technically feasible and produced NaCl with 100 % purity, Na(Br,Cl) with 98.23 % NaBr, and NH4(Cl,Br) with 99.18 % and 97.57 % NH4Cl, respectively. The new process realizes the resourceful utilization of bromine-containing wastewater, and has the significant advantages of production safety and no emission of three wastes.

Na+-Mg2+ ion effects on conformation and translocation dynamics of single-stranded RNA: Cooperation and competition

The nanopore-based translocation of a single-stranded RNA (ssRNA) in mixed salt solution has garnered increasing interest for its biological and technological significance. However, it is challenging to comprehensively understand the effects of the mixed ion species on the translocation dynamics due to their cooperation and competition, which can be directly reflected by the ion screening and neutralizing effects, respectively. In this study, Langevin dynamics simulation is employed to investigate the properties of ssRNA conformation and translocation in mixed Na+-Mg2+ ion environments. Simulation results reveal that the ion screening effect dominates the change in the ssRNA conformational size, the ion neutralizing effect controls the capture rate of the ssRNA by the nanopore, and both of them take charge of the different changes in translocation time of the ssRNA under various mixed ion environments. Under high Na+ ion concentration, as Mg2+ concentration increases, the ion neutralizing effect strengthens, weakening the driving force inside the nanopore, leading to longer translocation time. Conversely, at low Na+ concentration, an increase in Mg2+ concentration enhances the ion screening effect, aiding in faster translocation. Furthermore, these simulation results will be explained by quantitative analysis, advancing a deeper understanding of the complicated effects of the mixed Na+-Mg2+ ions.

Concentration effects on dynamic fluctuations in structure and thermodynamic properties of LiCl–AlCl3 molten Salt: Insights from ab initio molecular dynamics

The short–range and mid–range structural features, as well as thermodynamic properties of a LiCl–AlCl3 mixed molten salt at 873 K, were investigated as a function of AlCl3 concentration using ab initio molecular dynamics methods. In all solutions, the short-range structure of Al3+ reveals a regular tetrahedral [AlCl4]– unit. These tetrahedral units exist in isolation within dilute AlCl3 solution and polymerize into dimers or trimers through Al–Cl–Al bridge bonds in concentrated solutions. The dynamic dissociation analysis of Al3+ and Li+ structures indicates that the Al–Cl bond considerably stronger than Li–Cl bond. The polymerization of the [AlCl4]– units leads to the dissociation of the Li+ coordination shells into freely isolated cations. Furthermore, we examined changes in density, self-diffusion coefficient, and ionic conductivity with varying AlCl3 concentration in terms of thermodynamic properties. The conductivity and self-diffusion coefficient of Li+ showed a noticeable peak at 50 % concentration. This peak may be associated with the aggregation of [AlCl4]– units and the dissociation of Li+ coordination shells.

Improving the hot corrosion resistance of additively manufactured Inconel 718 via recrystallization-based grain boundary engineering induced by its residual stress

Metals containing abundant coherent twin boundaries (TBs) can improve corrosion resistance. Tailoring TBs in additive manufacturing (AM)-fabricated metallic materials with lower stacking fault energy, however, has proven impracticable because the traditional grain boundary engineering (GBE) involved in thermomechanical processing is not appropriate for AM-fabricated alloys with complicated geometric shapes. Here, the AM-fabricated Inconel 718 superalloy was successfully utilized to form abundant TBs induced by the intrinsic residual internal stresses, produced by AM processing via direct heat treatment. The microstructural characteristics and corresponding hot corrosion behaviors of different specimens – initial AM-fabricated, directly aged, and GBE-treated specimens – exposed to a mixed salt of 75 wt% Na2SO4 + 25 wt% NaCl at 650 °C were compared and analyzed systematically. The corrosion mechanisms affecting each of the specimens are discussed in detail. The obtained results reveal that the GBE-treated specimen has the most intact surface after the corrosion test, suffering minimum mass loss and having the shallowest corrosion layer depth, exhibiting optimal hot corrosion resistance. This optimal performance is mainly attributed to the penetration of S and O elements that were efficiently impeded by the TBs. This result holds implications for improving hot corrosion resistance in AM-fabricated metallic materials via directly GBE induced by residual stress.