Pure Salts Research Articles

Catalysis of the Thermal Decomposition of Transition Metal Nitrate Hydrates by Poly(vinylidene difluoride).

Poly(vinylidene difluoride) (PVDF) doped with transition metal nitrate hydrates are cast into thin films giving a high β-phase content. Analysis of the thermal behavior of the doped PVDF shows that the decomposition of the metal (II) nitrate hydrates to metal (II) oxides is catalyzed by the PVDF, as evidenced by reduction in the decomposition temperature by as much as 170 °C compared to the pure metal salts. In contrast, there is little to no apparent catalysis for the decomposition of the metal (III) nitrate hydrates. The FTIR spectra of the gas phase decomposition products show H2O and NO2 are the major components for both PVDF-doped material and the pure metal nitrate hydrates. A mechanism for the role of PVDF is proposed that uses the internal electric field of the ferroelectric phase to orient the nitrate ions and polarize the N–O bonds.

Facile Fabrication of Highly Stable and Wavelength-Tunable Tin Based Perovskite Materials with Enhanced Quantum Yield via the Cation Transformation Reaction

Metal halide perovskites have attracted great attention for their superior light energy conversion applications. Herein, we demonstrated a facile synthesis of zero-dimensional Sn2+ perovskite Cs4-xMxSnBr6(M = K+ and Rb+) material through the cation transformation reaction at room temperature. Cs4SnBr6 NCs was mixed with pure metal bromide salts (KBr and RbBr) via the mechanochemical process to successfully synthesize Cs4-xMxSnBr6 perovskite where transformation of Cs to mixed Cs/Rb and mixed Cs/K was achieved. By substituting different cations, the bright fluorescence of the Cs4-xMxSnBr6 was tuned from dim green to greenish-cyan while achieving the photoluminescence (PL) quantum yield of ∼39%. The crystal structure of Sn based perovskite with the substitution of K+ or Rb+ cations was determined by X-ray diffraction (XRD). Moreover, the Cs4-xMxSnBr6 demonstrated superior air stability and exhibited a better photocatalytic activity for CO2 reduction reaction (CO2RR) with high selectivity of CH4 gas with a higher yield rate compared to the pristine Cs4SnBr6 NCs.

Ternary chloride salt–porous ceramic composite as a high-temperature phase change material

In this study, a ternary salt/porous Si3N4 composite was prepared as a high-temperature shape-stabilized phase change material by pressure impregnation. In this composite, the ternary salt composed of 50 wt% sodium chloride (NaCl), 30 wt% potassium chloride (KCl), and 20 wt% magnesium chloride (MgCl2) was acted as the high-temperature phase change material. A porous Si3N4 ceramic was acted as the skeleton material and heat transfer enhancer. The porosity infiltration ratio of the pores reached 89.19%, demonstrating the good chemical compatibility of Si3N4 with chloride salts. The thermal conductivity of the composite was over six times greater than that of pure ternary salts. The thermal physical properties of the composite were stable even after 300 thermal cycles. The coefficients of thermal conductivity obtained by theoretical analysis and calculation were compared to the experimental values. All the results showed that this composite is a promising candidate as a shape-stabilized high-temperature phase change heat storage material.

Volumetric and viscosity properties of water-in-salt lithium electrolytes: A comparison with ionic liquids and hydrated molten salts

The density and viscosity of LiTf, LiTFSI and LiTFSI + LiTf (mole ratio 3:1) aqueous solutions have been measured at temperatures between 25 °C and 55 °C, over a wide range of concentrations covering the Water-in-Salt (WiS) region, where no free water is present in the system. As it was observed in mixtures of ionic liquids with water and mixtures of melted salt hydrates, the molar volumes of these WiS electrolytes are linear functions of the salt mole fraction. We propose a new procedure to calculate the intrinsic volume of the salts in the WiS solutions, corresponding to the volume of the hypothetical supercooled pure salts. The contributions of electrostriction and conformational changes of the anion to the partial molar volume of the WiS are discussed. The presence of Li+ ions in the salts free of water (supercooled salts) produces a large contraction of the Tf− and TFSI− volumes as compared with ionic liquids containing the same anions in contact with bulky cations. In terms of the apparent partial molar volume of water we could identify a dilute regime (x ≤ 0.1) where the volumetric properties are dominated by the water electrostriction, and a WiS regime (x > 0.1), without free-water, where the molar volume is determined by the volumes of the hydrated Li+ ion and the corresponding dehydrated anion, compatible with a proposed WiS structure formed by a percolating network of anions embedded by Li(H2O)n+ cations.The excess volume of the ternary WiS (LiTf + LiTFSI) is very small at all temperatures and concentrations, while the excess viscosity is positive and small, but increases near the solubility limit. The viscosity of the WiS electrolytes exhibit a normal Arrhenius dependence, but simple extrapolation to the glass transition temperature indicates that the WiS electrolytes behave as fragile fluids.

Helicity: A Non-Conventional Stereogenic Element for Designing Inherently Chiral Ionic Liquids for Electrochemical Enantiodifferentiation.

Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conventional ionic liquids (IL)s. It was prepared, purified, and separated into enantiomers by preparative HPLC on a chiral stationary phase. Enantiomerically pure quaternary salts of 1 with appropriate counterions were prepared and fully characterized. N-octyl-5-aza[6]helicenium bis triflimidate (2) was tested in very small quantities as a selector in achiral IL media to perform preliminary electrochemical enantiodifferentiation experiments on the antipodes of two different chiral probes. The new organic salt exhibited outstanding enantioselection performance with respect to these probes, thus opening the way to applications in the enantioselective electroanalysis of relevant bioactive molecules.

Comparing the effect of Cu-based fungicides and pure Cu salts on microbial biomass, microbial community structure and bacterial community tolerance to Cu

The effect of Cu on three different microbial endpoints was studied using different Cu sources, in order to check the usefulness of pure Cu salts to estimate the toxicity of commercial Cu fungicides on soil microbes. Cu additions caused similar dose-response curves of substrate induced respiration (SIR) decreases regardless of Cu source, i.e. the use of pure Cu salts to estimate the effect of Cu fungicides on microbial biomass using SIR may be useful. Phospholipid fatty acid (PLFA) analysis showed that the Cu source was more important for the microbial community structure than Cu concentration. Thus, the use of Cu salts to infer the effects of Cu fungicides on microbial community structure using PLFA analysis is not recommended, since effects of Cu concentration will be confounded with Cu source. Analyzing pollution induced community tolerance (PICT) to Cu showed that the use of pure Cu salts may overestimate Cu effects if Cu salt additions modified the soil pH. The highest doses of Cu salts increased bacterial community tolerance to Cu between 300 and 600 times, while commercial Cu fungicide increases were between 20 and 160 times. Therefore, the use of pure Cu salts to estimate the Cu fungicides effects on soil microbes is not recommended for PLFAs analyses, not suitable for PICT at high Cu concentrations, while useful for SIR.

Unified Description of the Specific Heat of Ionic Bulk Materials Containing Nanoparticles.

The specific heat behavior in bulk nanomaterials (NMs) obtained by adding nanoparticles to pure suspending media has attracted a lot interest in recent years. Controversial results about NMs specific heat (cp) have been reported in the literature, where nanoparticles (NPs) of different sizes and materials were suspended in solid and liquid salts at different concentrations and temperatures. However, a unified picture explaining the cp enhancements and diminutions by adding NPs to pure salts is still missing. In this work, we present a general theoretical thermostatic model aimed at describing the cp behavior in two-component ionic bulk nanomaterials containing NPs. The model, designed to work in the dilute regime, divides the NM in three regions: bulk suspending medium (SM), nanoparticles, and interface regions. It includes the effects of temperature, NP size, and NP concentration (mass fraction), allowing us to calculate cp variations with respect to the pure SM and the ideal NM (where NP and SM are assumed to not interact). We then use the model to interpret results of our classical molecular dynamics simulations, which we perform in the solid and liquid phases of NMs representative of three different classes, defined according to the atomic interactions at the interface. The analysis reveals nontrivial and competing effects influencing cp, such as system-dependent atomic rearrangements at the interface, vibrations of the NP as a whole and cp variations coming from the individual NP and SM specific heats. Our study contributes to the interpretation of past controversial results and helps in designing NMs with improved thermal properties, which is highly relevant for industrial applications in thermal energy storage and renewable energy production.

Insights into the Composite Scale Formation and Coprecipitation Behavior of CaSO4 and SrSO4 at different salinity level

The dependency of the calcium sulfate (CaSO4) deposit formation on the presence and concentration of co-precipitating ions, is a fundamental question to the advancement of crystallization science. In this paper, the thermodynamics and kinetics of the static precipitation of 47.5 mM calcium sulfate, in isolation and presence of strontium sulfate (SrSO4) as common co-crystallizing salt, are examined at 30°C. The deposition of pure and composite sulfate scales is studied by varying the salinity of the medium from 0.35 to 1.50 M NaCl. To evaluate the effect of the co-precipitating, strontium ion concentration was altered from 0 to 20.0 mM. In order to elucidate the crystallization mechanism in terms of reaction rate and extent, the concentration of the free scaling ions, including that of Ca2+, SO42− and Sr2+, is systematically monitored at different intervals until equilibrium is achieved. Moreover, crystal deposits collected at regular intervals from the isothermal incubation experiments are characterized for changes in their microstructure, morphology, and elemental distribution, to establish correlations with the data obtained on the evolution of the solution composition. The analysis of the crystallographic properties of the deposits substantiates the dependency of the thermodynamics and kinetics of the CaSO4 precipitation process on the salinity and co-existence of supersaturated SrSO4 in the mixture. Particularly, the morphology of calcium sulfate deposits is altered in the presence of SrSO4, which corroborates the assumption of co-crystal interactions. These results indicate that heterogeneous crystal nucleation and growth of the mixed salts can be prompted at temperatures and salinity conditions as low as 30°C and 0.35 M, when the concentration of Sr2+ is increased up to 20.0 mM. Using the Pitzer model derived ion activity coefficients, discrepant thermodynamic solubility product constant (Ksp) values are also determined for the pure salts when these co-precipitate in mixed systems. Reaction kinetics for calcium sulfate crystallization is also highly sensitive to the ionic strength effect as well as to the presence and concentration of strontium ions. Accordingly, these observations confirm the need to account for both contributing and non-contributing ions in assessing the thermodynamics and kinetics of crystal formation.

Quantifying Alloy 625 Crevice Corrosion using an Image Differencing Technique: Part II. A Diffusive Transport Model of Crevice Cation Concentration using Surface Current Density

In this paper we present a diffusive transport model of alloy 625 crevice corrosion for simulated ocean water. The model uses the empirical electrochemical kinetics (local surface current density) and empirical damage profile to determine the source of cations from surface oxidation reactions and then calculates the total cation concentration in the crevice solution as a function of time. To gain insight into the solution speciation at the calculated cation concentrations, a thermodynamic software package was used. In those calculations, it was assumed that the anodic dissolution products of the individual alloy components form their corresponding metal salts in the crevice solution. The calculations, based on activity, predicted that precipitation occurred in the same time frame as the experimentally observed increase in active area, decrease in surface current density and transition to diffusion control. The salts that precipitated out of the model solution were NaCl, at 5.3 m, and NiCl2·6H2O, at 5.7 m. It is shown that the presence of the Cr3+, Fe2+, Mo3+ and Nb5+ in the model crevice solution increase the cation and chloride activities resulting in precipitation at the same Ksp values as in the pure salts, albeit at lower Na+ or Ni2+ concentrations. Implications of the speciation results as they relate to actual crevices are discussed.

Exploring the Electronic Structure of New Doped Salt Hydrates, Mg1–xCaxCl2·nH2O, for Thermochemical Energy Storage

Chloride-based salt hydrates, MgCl2·nH2O and CaCl2·nH2O (n = 0,1,2,4,6), are promising materials for thermochemical heat storage systems due to their high sorption energy capacity. However, both salts have their own shortcoming characteristics within the operational temperature of the thermochemical heat storage applications. While the higher hydrates of CaCl2·nH2O (n = 4,6) have a low melting point, the lower hydrates of MgCl2·nH2O (n = 0,1,2) can form the highly toxic and corrosive HCl gas. Both shortcomings cap the individual use of these salts to a restricted range of the available hydrates. A combination of these two salts showed to have the potential to overcome these shortcomings. The present study focuses on finding stable configurations of potential superior salt hydrate combinations using the evolutionary algorithm USPEX as well as manual mutations of known pristine structures. The newly found structures are less stable than the pure salts, but stable enough to be combined. Extensive electronic density-derived tools, like the Density Derived Electronic and Chemical (DDEC6) bond orders and net atomic charges, as well as Bader topological analysis, are used to predict the HCl gas formation based on the chemical environment in the new metastable structures. We find that doping MgCl2·nH2O with calcium considerably reduces HCl formation compared to its pure form, caused by a combination of the stronger Ca-Cl interaction than Mg-Cl and a less polar H2O molecule in a calcium environment than in a magnesium environment. This provides the possibility to shift the p, T-equilibrium curve of HCl outside the thermal storage operational window.

Determination of the mass fraction of potassium and sodium oxides in the dust of electric furnace filters by atomic emission spectrometry with inductively coupled plasma

A method of measuring the mass fraction of potassium and sodium oxides in the dust filters of electric arc furnaces by atomic emission spectrometry with the inductively coupled plasma (AES-ICP) was developed. Possibilities of atomic emission spectrometers of iCAP series for determination of potassium and sodium in dust of filters of electric arc furnaces are investigated.A method for converting potassium and sodium oxides into solution is proposed. Calibration of the spectrometer was carried out on aqueous solutions with a known concentration of potassium and sodium. For the preparation of calibration solutions, chemically pure potassium and sodium salts were used. Analytical lines of potassium and sodium free from spectral overlays are selected.A good correlation of calibration graphs is obtained. The developed technique is used to determine the mass fraction of potassium and sodium oxides in the dust filters of electric furnaces. Validation of the methodology was carried out. The repeatability of the results was compared with the repeatability of the standardized methodology. iCAP series spectrometers can be used to determine the mass of potassium and sodium oxides in gas cleaning dust.s cleaning dust.

Thermal energy storage characteristics of binary molten salt nanofluids: Specific heat and latent heat

This study aims to examine the thermal energy storage characteristics, in terms of specific heat and latent heat, of nanoparticle-doped binary molten salt nanofluids. Two different binary molten salt mixtures, namely carbonate salts (Li2CO3 and K2CO3) and nitrate salts (NaNO3 and KNO3), were used as base solvents. Graphite nanoparticles were dispersed into the salt mixtures. The chemical compositions (molar fractions) of the two salt components were varied from hypoeutectic to hypereutectic, including eutectic compositions, to investigate their effects on the specific heat and latent heat of both the pure salts and their nanofluids. The specific heat of the carbonate salt nanofluid was enhanced, irrespective of the chemical composition, and the enhancement was proportional to the nanoparticle concentration. However, the specific heat of the nitrate salt nanofluid was decreased by the addition of 0.1 wt% of graphite nanoparticles and increased by the addition of a larger amount of 1 wt%. The latent heat of the nanofluids was enhanced by doping nanoparticles into the salt mixtures and was affected by the chemical composition of the solvent salt mixtures. The distinct behaviors of specific heat and latent heat obtained in this study were discussed based on a compressed liquid (solid-like) layer formed near the nanoparticles. The thermal energy storage capacities of the nanofluids were estimated and compared by using their specific heat and latent heat.

Hydrogen-bonded host\u2013guest systems are stable in ionic liquids

We show that H-bonded host–guest systems associate in ionic liquids (ILs), pure salts with melting point below room temperature, in which dipole–dipole electrostatic interactions should be negligible in comparison with dipole-charge interactions. Binding constants (Ka) obtained from titrations of four H-bonded host–guest systems in two organic solvents and two ionic liquids yield smaller yet comparable Ka values in ionic liquids than in organic solvents. We also detect the association event using force spectroscopy, which confirms that the binding is not solely due to (de)solvation processes. Our results indicate that classic H-bonded host–guest supramolecular chemistry takes place in ILs. This implies that strong H-bonds are only moderately affected by surroundings composed entirely of charges, which can be interpreted as an indication that the balance of Coulombic to covalent forces in strong H-bonds is not tipped towards the former.

Brines from industrial water recycling: new ways to resource recovery

Abstract Stricter environmental regulation policies and freshwater as an increasingly valuable resource have led to global growth of zero liquid discharge (ZLD) processes in recent years. During this development, in addition to water, the recovery of recyclable materials, e.g. salts, from industrial wastewater and brines is considered more frequently. Within the framework of the HighCon research project, the subject of this study, a new ZLD process with the goal of pure single-salt recovery from industrial wastewater has been developed and investigated in a demonstrational setup at an industrial site. With regard to pure salts recovery, separating organic components is of great importance during the treatment of the concentrate arising from used water recycling. The removal of COD and of ions responsible for scaling worked very well using nanofiltration. The nanofiltration permeate containing the monovalent ions was pre-concentrated using electrodialysis and membrane distillation before selective crystallization for single-salt recovery was performed. An example economic case study for the newly developed ZLD process – based on demonstration results and considering optimization measures for a full-scale design – indicates that the costs are equal to those of a conventional ZLD process, which, however, does not provide inter alia the aforementioned benefit of single-salt recovery.

Increased Antibacterial and Antibiofilm Properties of Silver Nanoparticles Using Silver Fluoride as Precursor

Silver nanoparticles were produced with AgF as the starting Ag(I) salt, with pectin as the reductant and protecting agent. While the obtained nanoparticles (pAgNP-F) have the same dimensional and physicochemical properties as those already described by us and obtained from AgNO3 and pectin (pAgNP-N), the silver nanoparticles from AgF display an increased antibacterial activity against E. coli PHL628 and Staphylococcus epidermidis RP62A (S. epidermidis RP62A), both as planktonic strains and as their biofilms with respect to pAgNP-N. In particular, a comparison of the antimicrobial and antibiofilm action of pAgNP-F has been carried out with pAgNP-N, pAgNP-N and added NaF, pure AgNO3, pure AgF, AgNO3 and added NaF and pure NaNO3 and NaF salts. By also measuring the concentration of the Ag+ cation released by pAgNP-F and pAgNP-N, we were able to unravel the separate contributions of each potential antibacterial agent, observing an evident synergy between p-AgNP and the F− anion: the F− anion increases the antibacterial power of the p-AgNP solutions even when F− is just 10 µM, a concentration at which F− alone (i.e., as its Na+ salt) is completely ineffective.

Catanionic Surfactant Self-Assembly in Protic Ionic Liquids.

Mixing of cationic and anionic surfactants in water can result in pseudo-double-tailed catanionic surfactant ion pairs that form lamellar phases or vesicles that are unstable toward electrolyte addition. Here we show that despite the very high ionic strengths, catanionic surfactants counterintuitively form a wider variety of self-assembled aggregates in pure ionic liquids (ILs, pure salts in a liquid phase) than in water, including micelles, vesicles, and lyotropic phases. Self-assembled structures only form when the IL is sufficiently polar to drive self-assembly through electrostatic interactions and/or H-bond networks, but the catanionic effect is manifested only when the IL does not itself exhibit pronounced amphiphilic nanostructure. This enables the type of catanionic aggregate formed to be designed by changing the hydrogen bonds between the ions through variation of the structures of the cation and anion. These results reveal an entirely new way of controlling catanionic surfactant self-assembly under nonaqueous and high-salt conditions.

Experimental Kinetic Analysis of Potassium Extraction from Ultrapotassic Syenite Using NaCl-CaCl2 Salt Mixture.

This kinetic experimental analysis reports on the application of a eutectic NaCl–CaCl2 salt system for the extraction of potassium from ultrapotassic microsyenite. The reaction parameters, time, temperature, salt composition, and salt to ore ratio, were systematically analyzed. It was found that a salt mixture increases the potassium cation extraction in comparison with using either pure NaCl or pure CaCl2. It was also found that adding CaCl2 into pure NaCl has a considerably stronger effect on increasing the potassium recovery than adding NaCl to pure CaCl2. The salt as a melting agent offers a reduction in the reaction temperature due to its lower melting temperature when compared to pure salts (NaCl or CaCl2). Approximately 70% of K+ in the deposit was extracted at 650 °C. Different characteristic methods have been used to understand the reaction mechanism of the salt mixture and ore, as well as to qualify and quantify the end product mineral phases.

Development of a Precise and Cost-Effective Technique to Measure Deliquescent Relative Humidity of Particulate Contaminants and Determination of the Operating Relative Humidity of a Data Center Utilizing Airside Economization

Abstract A remarkable amount of energy in data centers is consumed in eliminating the heat generated by the information technology (IT) equipment to maintain and ensure safe operating conditions and optimum performance. The installation of airside economizers (ASEs), while very energy efficient, bears the risk of particulate contamination in data centers, hence, deteriorating the reliability of IT equipment. When relative humidity (RH) in data centers exceeds the deliquescent relative humidity (DRH) of salts or accumulated particulate matter, it absorbs moisture, becomes wet, and subsequently leads to electrical short-circuiting because of degraded surface insulation resistance (SIR) between the closely spaced features on printed circuit boards (PCBs). Another concern with this type of failure is the absence of evidence that hinders the process of evaluation and rectification. Therefore, it is imperative to develop a practical test method to determine the DRH value of the accumulated particulate matter found on PCBs. This research is a first attempt to develop an experimental technique to measure the DRH of dust particles by logging the leakage current versus RH% for the particulate matter dispensed on an interdigitated comb coupon. To validate this methodology, the DRH of pure salts like MgCl2, NH4NO3, and NaCl is determined, and their results are then compared with their published values. This methodology was therefore implemented to help lay a modus operandi of establishing the limiting value or an effective relative humidity envelope to be maintained at a real-world data center facility situated in Dallas industrial area for its continuous and reliable operation.

Fidelity of Al2(SO4)3 for the Discharge of Pectin during the Pretreatment of Apocynum Venetum

ABSTRACT During the extraction of fibers from the bast of A. venetum, there is an issue of the existence of undesirable macromolecules, for example, pectins. Separation of these compounds is mostly done by pretreatment with H2SO4 and then by NaOH boiling in the traditional method (Fiber-C). The use of Sulfuric acid for pretreatment may cause harm to both fibers and the environment. In order to overcome these limitations, attempts were made to find a new pretreatment (Fiber-N) method. The hypothetical premise of the new pretreatment strategy dependent on the use of Al2(SO4)3 is presented. Four model solutions were investigated using a method of measuring zeta potential. Furthermore, fibers obtained by pretreatment methods along with the raw fibers of A. venetum had been characterized by Electron spin resonance spectroscopy (ESR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and water retention value (WRV). Results showed that pure salts of Al2(SO4)3 presented improved binding properties with the pectin and causes better swelling and eventually helps to remove pectin than other pretreatment processes. Ultimately, Donnan equilibrium, metal ion complex formation, and Gouy–Chapman–Stern (GCS) model were used to theoretically elucidate the discharging mechanism of pectin macromolecules from A. venetum in the presence of Al3+ ions during pretreatment.

Acetonitrile-Hexane Extraction Route to Pure Sulfonium Salts.

A rapid, simple procedure is described for synthesizing trialkyl, dialkylaryl, and alkyldiaryl sulfonium salts that features a selective extraction procedure to access analytically pure sulfonium salts. Alkylation of dialkylsulfides, alkylarylsulfides, and diarylsulfides followed by partitioning between acetonitrile and hexanes efficiently separates nonpolar reactants and byproducts, the usual impurities, to afford analytically pure crystalline and noncrystalline sulfonium salts. The method is efficient, general, and particularly well suited for the preparation of oily sulfonium salts that are otherwise extremely difficult to purify.