Sodium Borates Research Articles

Synthesis of Known and Previously Inaccessible Poly(pyrazolyl)Borates under Mild Conditions.

Poly(pyrazolyl)borate ligands have been obtained through the reaction of highly reactive haloboranes with in situ formed pyrazolides under very mild conditions. This versatile synthetic method allows the selective synthesis of bis-, tris-, or tetrakis(pyrazolyl)borates. Furthermore, the method is compatible with the use of functional groups on the heterocyclic moieties of the poly(pyrazolyl)borates that were not accessible to date. Strongly encumbered sodium and thallium(I) poly(pyrazolyl)borates with a reduced donating ability have been obtained for the first time.

СИНТЕЗ И ИССЛЕДОВАНИЕ ФИЗИКО-ХИМИЧЕСКИХ И ТЕРМОДИНАМИЧЕСКИХ СВОЙСТВ В СИСТЕМЕ Na2O-BaO-B2O3

38 samples were synthesized in the Na2O-BaO-B2O3 system, some of which were glasses, some crystallized. The degree of interaction of the initial reagents in the synthesis process was controlled by X–ray phase analysis on a DRON-3M diffractometer using CuKa radiation. Crystal phases were identified using X–ray phase analysis on a DRON-3M diffractometer using CuKa radiation and the PDF–2 powder diffractometry database. The following crystalline phases were identified in the crystallized samples: β-BaВ2O4, NaBO2, NaBaB9O15. Density, microhardness, refractive index were measured for glassy samples of the system under study and melting/liquidus temperatures were determined. It is established that the nature of the dependence of the above properties on the content of sodium oxide with a constant content of boron oxide is linear. The study of vaporization processes and thermodynamic properties of the Na2O-BaO-B2O3 system was carried out by differential high-temperature mass spectrometry on the MS–1301 mass spectrometer. The studied samples were evaporated from a twin Knudsen molybdenum effusion cell. The heating of the cell was carried out by electronic bombardment, the temperature was measured with an optical pyrometer EOP–66. It was shown that as a result of the interaction of Na2O, BaO and B2O3 oxides, sodium and barium borates are formed in the condensed phase. It is established that the studied system is characterized by selective evaporation of NaBO2 in the temperature range of 1290–1350 K. The activity values of NaBO2 and B2O3 were determined depending on the composition of the condensed phase at a temperature of 1330 K. The activity of BaB2O4 was calculated using the Gibbs-Dugem equation. The obtained values of the Gibbs mixing energies and excess Gibbs energies indicate significant deviations of the Na2O-BaO-B2O3 system from the ideal behavior.

Electroprecipitation of inorganic borates, with different solubility, within monumental stones to avoid fungal colonization

Biodeterioration is a serious threat to the preservation of cultural heritage. Currently, the chemical treatments used to combat it must fulfil a series of restrictions to ensure that they are not harmful to humans or the environment. Borates satisfy these conditions but due to its high degree of leaching its application is limited to indoor areas. The use of electroprecipitation may to increase the range of applicability by allowing to precipitate, along the entire section of the stony materials, of a mixture of boron salts with different solubility (zinc, magnesium, and sodium borates) to cover a wide range of moisture conditions. The results obtained show that electroprecipitation not only increases the penetration depth of boron compounds but also allows the formation of compounds of different solubility, which allows the treatment to last over time. Furthermore, the treatment increased the mechanical properties and reduced the porosity of the stones treated, all without causing significant aesthetic changes.

The structure of glasses M2O-B2O3 (М – Li, Na, K): Estimation of thermodynamic characteristics of alkali borates and physicochemical modeling

The paper presents results of structural calculations carried out on the alkali borate glasses using physicochemical modeling based on Gibbs energy minimisation. Standard heat capacity, entropy and enthalpy of formation values for lithium, sodium and potassium borates are estimated by regression analysis for use as the input data for the models taking into account the error of the initial data. The correction of the physicochemical model was made using results of Raman spectroscopy. The dependence of the maximum of the “borate anomaly” on the number of non-bridging oxygen atoms was shown. It was found that the most obvious changes in the dependence of properties occur in the regions of N1 and N2 compositions, which are characterized by the appearance of asymmetric triangles BØ2O− and BØO22− in glasses, correspondingly.

Sodium Borates: Expanding the Electrolyte Selection for Sodium‐Ion Batteries

AbstractSodium‐ion batteries (SIBs) are a promising grid‐level storage technology due to the abundance and low cost of sodium. The development of new electrolytes for SIBs is imperative since it impacts battery life and capacity. Currently, sodium hexafluorophosphate (NaPF6) is used as the benchmark salt, but is highly hygroscopic and generates toxic HF. This work describes the synthesis of a series of sodium borate salts, with electrochemical studies revealing that Na[B(hfip)4]⋅DME (hfip=hexafluoroisopropyloxy, OiPrF) and Na[B(pp)2] (pp=perfluorinated pinacolato, O2C2(CF3)4) have excellent electrochemical performance. The [B(pp)2]− anion also exhibits a high tolerance to air and water. Both electrolytes give more stable electrode‐electrolyte interfaces than conventionally used NaPF6, as demonstrated by impedance spectroscopy and cyclic voltammetry. Furthermore, they give greater cycling stability and comparable capacity to NaPF6 for SIBs, as shown in commercial pouch cells.

Sodium Borates: Expanding the Electrolyte Selection for Sodium-Ion Batteries.

Sodium‐ion batteries (SIBs) are a promising grid‐level storage technology due to the abundance and low cost of sodium. The development of new electrolytes for SIBs is imperative since it impacts battery life and capacity. Currently, sodium hexafluorophosphate (NaPF6) is used as the benchmark salt, but is highly hygroscopic and generates toxic HF. This work describes the synthesis of a series of sodium borate salts, with electrochemical studies revealing that Na[B(hfip)4]⋅DME (hfip=hexafluoroisopropyloxy, OiPrF) and Na[B(pp)2] (pp=perfluorinated pinacolato, O2C2(CF3)4) have excellent electrochemical performance. The [B(pp)2]− anion also exhibits a high tolerance to air and water. Both electrolytes give more stable electrode‐electrolyte interfaces than conventionally used NaPF6, as demonstrated by impedance spectroscopy and cyclic voltammetry. Furthermore, they give greater cycling stability and comparable capacity to NaPF6 for SIBs, as shown in commercial pouch cells.

Cytotoxicity, genotoxicity, oxidative stress, apoptosis, and cell cycle arrest in human Sertoli cells exposed to boric acid

BackgroundBoron, which is used in a range of industries worldwide, is an essential micronutrient for plants and “probably essential” for humans. Conflicting reports have been published regarding the toxicity of boron compounds. Moreover, boric acid and sodium borates are classified as toxic to development and reproduction in the European Union-Classification, Labelling and Packaging Regulation (EU-CLP Regulation). The scope of our study was to ascertain whether boric acid caused the cytotoxic and genotoxic effects, as well as oxidative stress, apoptosis, and cell cycle profiles on human Sertoli cells. MethodsThe possible toxic effects of boric acid on human Sertoli cells were investigated by in vitro methods. The cellular viability and DNA damage were examined by neutral red uptake and alkaline comet assay, respectively. Oxidative stress, apoptosis, and cell cycle arrest profiles were analyzed by flow cytometry. ResultsBoric acid was neither cytotoxic nor genotoxic in a wide concentration range (0.5–1000 μM) on human Sertoli cells. No significant difference in the DNA damage was observed between boric acid-treated and control groups (p > 0.05). Boric acid did not stimulate oxidative stress, apoptosis, and cell cycle arrest within the tested concentrations. ConclusionOur study provides novel insights into the influences of boric acid on human Sertoli cells which are used as a model in male reproductive toxicity studies. The concentrations tested in our study were extremely higher than the blood and semen boron levels reported in epidemiological studies.

Synthesis of Hexagonal Boron Nitride Coatings Using Concentrated Solutions of Alkali Metal Borates

Continuous nanocrystalline coatings of hexagonal boron nitride (h-BN) with a thickness of ~1000‒350 nm are prepared from highly concentrated aqueous solutions of lithium and sodium borates, which display good film-forming properties. The borate solutions were applied on silicon substrates by spin coating followed by drying in air and treatment in ammonia at a temperature of 1300°C. This method is deemed promising for creating protective coatings (e.g., for protecting carbon products from oxidation at elevated temperatures).

Получение покрытий гексагонального нитрида бора из концентрированных растворов боратов щелочных металлов

The continuous hexagonal boron nitride (h-BN) coating with the ~100-350 nm thickness was produced from the aqueous solutions of the lithium and sodium borates. The saturated solution was applied on the silicon support by the spin coating, dried under the normal conditions and treated in the ammonia atmosphere under 1300 °C. Such method is a promising way for the fabrication of protection coating. For example, for the protection of the carbon products from an oxidation under high temperature atmosphere.

Effects of boron compounds on decomposition of chlorides to control clinkers under solid refuse fuel combustion conditions

The chlorides of sodium and potassium and other mineral salts are often present in solid refuse fuel (SRF) in concentrations of at least 1–2%. These salts can generate clinker during combustion and cause serious operational problems, such as blocking of the gas passage, reduction in boiler operational efficiency, and corrosion of the heat exchanger tubes in the boiler. Although many solutions have been proposed to control clinker formation in boilers, herein we investigated the effects of boron compounds (boric acid and borax) on the decomposition of the mineral salts present in SRF to control the formation of fly ash. Using a laboratory-scale reactor, isothermal reactions between the boron compounds and the chlorides were performed at 900 °C for 10 h. HCl gas was released during the decomposition reactions, indicating that a chemical reaction had occurred on the surfaces of the boron compounds. Peaks related to sodium and potassium borates were observed in X-ray diffraction patterns, suggesting that these compounds had been formed during the reactions. Scanning electron microscopy images of the reaction products showed clusters of the mineral salts on the matrix of the borax particles, indicating that changes in the morphology owing to physical adsorption had also occurred during the reactions.

Structural response of alkali metal borates at Fe2O3 sliding interface: The effect of alkali cations

Structural transformation and chemical reaction induced by sliding motion is an interesting topic in material science and tribochemistry. In this paper, we used density functional theory (DFT) to study the adaptation of molecular and electronic structures at the iron oxide–alkali borate interface. Sodium borates with different sodium concentrations and two other common alkali metal borates of lithium and potassium have been confined between two Fe2O3 surfaces and subjected to the sliding at 1 and 38GPa. The results suggest a significant impact of alkali elements on the energy shape and bonding behavior in the systems. The low energy variation was obtained in the systems with sodium borate at 33% and 50% concentration of Na2O. Meanwhile, high variation energy was encountered with the sodium borate with low Na2O concentration (25% Na2O), lithium borate and potassium borates at 3 GPa. The formation of an “easy-shear” pattern was found in the lowest energy variation system with 50% Na2O at 1 GPa. The high variation energy was closely related to the dissociation of iron atoms from the oxide surface and the subsequent rupture of Fe−O bonds of the surface. Based on the current simulations, the possible interfacial layering has been proposed to rationalize experimental findings on the friction and wear of borate lubricated iron oxide surfaces.

Effects of boric acid on cell death and oxidative stress of mouse TM3 Leydig cells in vitro

BackgroundBoron (B) is an abundant element on earth and presents at physiological pH in the form of boric acid (BA). It has both positive and negative effects on biological systems. BA and sodium borates have been considered as being toxic to the reproduction system in animal experiments. Unfortunately, the molecular mechanism underlying the toxic effects of BA is not fully understood. MethodsHere, we demonstrate the influence of BA on mouse TM3 Leydig cells which are male reproductive system cells targeted by BA exposure. The cytotoxicity was evaluated by MTT and NRU assays. Annexin V-FITC/PI double staining kit, mitochondria membrane potential (ΔΨm) assay kit with JC-1 and caspase-3 colorimetric assay kit were used to indicate the cell death pathway. To estimate the role of oxidative stress in BA induced toxicity, glutathione (GSH) level, catalase (CAT) and superoxide dismutase (SOD) activities were measured manually. ResultsThe cell viability assays showed that BA was not cytotoxic within the tested concentrations up to 1000 μM. Sub-toxic concentrations were used for detecting oxidative stress status. BA exposure was significantly reduced GSH level at 1000 μM and CAT activity in a concentration-dependent manner. However, SOD activity was increased at the tested concentrations (100–1000 μM). Moreover, ΔΨm was significantly decreased at 500 and 1000 μM of BA, while caspase-3 activity was not changed apparently. ConclusionThese findings demonstrated that BA is not cytotoxic and apoptotic but may slightly induces oxidative stress in TM3 Leydig cells at higher concentrations.

The Conversion Kinetics of Tincal to Boric Acid in Nitric Acid Solutions

Pure borax and various boron compounds are produced from the solutions in which tincal is dissolved with various reagents. Economically important boron compounds such as boric acid, borax, boric oxide, and refined hydrated sodium borates and perborates are produced from boron-containing ores. The production of boric acid by using nitric acid from tincal is more advantageous because it evaluates by-product NaNO3 as fertilizer production. In this study, the conversion kinetics of tincal to boric acid in nitric acid solutions were investigated by such parameters as particle size, 300-1500 µm; acid concentration,0.5-4 mol/L; solid-to-liquid ratio 0.04-0.10 g/mL; stirring speed 20.93-62.8 s-1, and reaction temperature, 30-60 oC. The conversion was found to increase with decreasing particle size and solid-to-liquid ratio and while it increased with increasing reaction temperature, acid concentration, and stirring speed. The conversion kinetics was examined using the heterogeneous and pseudo-homogeneous reaction models. The experimental results were found to be in better agreement with the correlation given in the following equation and the activation energy being 37.5 kJ/mol.

Precise and rapid isotopic analysis of lithium in refractory materials using NaLiBO2+ by thermal ionization mass spectrometry (TIMS)

6Li/7Li isotopic ratio was determined in lithium based compounds and refractory materials by TIMS using a novel approach. The method involved fusion of the samples such as Lithium Aluminate (LiAlO2), Lithium Titanate (Li2TiO3), Lithium Carbonate etc, with Sodium Borate flux directly on the loading filament to produce NaLiBO2+ ions at m/z 71,72 and 73 and Na2BO2+ at m/z 88 and 89. 6Li/7Li was determined by monitoring NaLiBO2+ ions at m/z 71, 72 and 73. Contributions from isotopes of boron to the ion intensity at m/z 71–73, were accounted by sequentially monitoring Na2BO2+, at m/z 88 and 89 during same analysis. L-SVEC Li2CO3was used for the initial investigations to identify the optimum composition of the analyte, sodium borate mixture required for obtaining precise 6Li/7Li ratio and the possible ion formation mechanism. Fusion of the lithium compounds with boron rich sodium borates having compositions such as Na2O·5B2O3 and Na2O·10B2O3 resulted in strong and stable molecular ion intensities for both NaLiBO2+ and Na2BO2+. Average 6Li/7Li isotopic ratio obtained for L-SVEC lithium from ten measurement using this technique was 0.08277 ± 0.00006 (S.D). Refractory compounds Li2TiO3 and LiAlO2 and lithium salts such as Li2CO3 (lithium source for the refractory compounds) and Li2B10O16 were analysed for 6Li/7Li isotopic ratio with precision of better than 0.07% (% R.S.D). Agreement between the 6Li/7Li isotopic ratio of the refractory compound and the starting material signified that there is no matrix induced mass bias. This technique not only resulted precise values for 6Li/7Li isotopic ratio but has also simplified the procedure for isotopic analysis of Li in refractory materials by circumventing the dissolution and purification step that would have been otherwise required for established mass spectrometric methods.

Mechanisms of Pressure-Induced Structural Transformation in Confined Sodium Borate Glasses.

In this paper, density functional theory simulations were conducted to investigate the structural adaptation of sodium borates xNa2O·(100-x)B2O3 (x = 25, 33, 50, and 60 mol %) during the compression/decompression between 0 and 10 GPa. The sodium borates are confined between two Fe2O3 substrates and undergo the compression by reducing the gap between the two surfaces. The results reveal the borate response to the load through a two-stage transformation: rearrangement at low pressure and polymerization at high pressure. The pressure required to initiate the polymerization depends directly on the portion of fourfold-coordinated ([4]B) boron in the sodium borates. We found that the polymerization occurs through three different mechanisms to form BO4 tetrahedra with surface oxygen and nonbridging and bridging oxygen. The electronic structure was analyzed to understand the nature of these mechanisms. The conversions from BO3 to BO4 are mostly irreversible as a large number of newly formed BO4 remain unchanged under the decompression. In addition, the formation of a sodium-rich layer can be observed when the systems were compressed to high pressure. Our simulation provides insight into sodium borate glass responses to extreme condition and the underlying electronic mechanisms that can account for these behaviors.

Specialties of the structure and conductivity of the non-aqueous electrolytes based on alkali metal bis (salicyl) borates and bis (oxalate) borates

The structure and coordination environment of non-aqueous electrolytes based on bis(salicyl)borates of lithium, sodium, potassium, tetramethylammonium (MeBSB) and bis(oxalato)borates from lithium to cesium (MeBOB) using NMR spectroscopy have been investigated. Bis(salicyl)borates (BSB) and bis(oxalate)borates (BOB) of alkali metals and organic cations are considered as promising electroconductive components of electrolytes of modern chemical sources of current (lithium, sodium ion batteries and super-capacitors). The salts were synthesized by the microwave radiation method. The 13C and 11B NMR spectra analysis determined the presence of symmetric structure in BOB anion and the presence of two optical conformations of the BSB anion with labile coordination environment of boron. The conformations of the BSB are the result of the ion contact pairs formation. In the case of tetramethylammonium cation the presence of conformations are depended on the reactive medium. The conformational lability of the coordination sphere of NaBSB dissolved in DMAA is connected with increasing of the integral intensity of carboxyl group singles relatively signals of carbon atoms in fragments of another functional affiliation when the time delay between radio frequencies varies within 2-15 seconds. The difference in the structure of these anions leads to a change in the thermal dependence of the electrical conductivity of BSB and the transport of ions in non-aqueous solvents. Maximum electrical conductivity of salt solutions in DMFA is achieved at close concentrations of 0.75 m for KBSB and 0.77-1 m for NaBSB. The solubility of BSB is better than the BOB. Based on the measurements of the conductivity and the data of electrochemical impedance spectroscopy (the angle of inclination of spectra in the Nyquist coordinates in the low frequency range, the phase angle shift at a frequency) it was proposed the existence of two ways of ions and charge transfer in the electrolytes: diffusion and relay transport. The possibility of formation of a labile salt complex with a solvent due to hydrogen bonds is established.

Specialties of the structure and conductivity of the non-aqueous electrolytes based on alkali metal bis (salicyl) borates and bis (oxalate) borates

The structure and coordination environment of non-aqueous electrolytes based on bis(salicyl)borates of lithium, sodium, potassium, tetramethylammonium (MeBSB) and bis(oxalato)borates from lithium to cesium (MeBOB) using NMR spectroscopy have been investigated. Bis(salicyl)borates (BSB) and bis(oxalate)borates (BOB) of alkali metals and organic cations are considered as promising electroconductive components of electrolytes of modern chemical sources of current (lithium, sodium ion batteries and super-capacitors). The salts were synthesized by the microwave radiation method. The 13C and 11B NMR spectra analysis determined the presence of symmetric structure in BOB anion and the presence of two optical conformations of the BSB anion with labile coordination environment of boron. The conformations of the BSB are the result of the ion contact pairs formation. In the case of tetramethylammonium cation the presence of conformations are depended on the reactive medium.
 The conformational lability of the coordination sphere of NaBSB dissolved in DMAA is connected with increasing of the integral intensity of carboxyl group singles relatively signals of carbon atoms in fragments of another functional affiliation when the time delay between radio frequencies varies within 2-15 seconds. The difference in the structure of these anions leads to a change in the thermal dependence of the electrical conductivity of BSB and the transport of ions in non-aqueous solvents. Maximum electrical conductivity of salt solutions in DMFA is achieved at close concentrations of 0.75 m for KBSB and 0.77-1 m for NaBSB. The solubility of BSB is better than the BOB. Based on the measurements of the conductivity and the data of electrochemical impedance spectroscopy (the angle of inclination of spectra in the Nyquist coordinates in the low frequency range, the phase angle shift at a frequency) it was proposed the existence of two ways of ions and charge transfer in the electrolytes: diffusion and relay transport. The possibility of formation of a labile salt complex with a solvent due to hydrogen bonds is established.

Solubilization of palladium in molten mixture of sodium borates and sodium carbonate

Abstract Solubility of palladium in water was enhanced by heating metallic palladium in a molten mixture of sodium borates and sodium carbonate at 1000 °C for 2 h. When 17Na2O − 83B2O3 was used as the sodium borate, 21% of palladium in the obtained product was extracted in water. The solubilization efficiencies differed depending on the chemical composition of the sodium borate. During the heat treatment, oxidation occurred on the palladium surface and the oxidized palladium dissolved in the media.

Behavior of Alkali Metal and Ammonium Salts in Nanofiltration of Their Aqueous Solutions

The behavior of salts (chlorides, nitrates, sulfates, phosphates, borates, ferri- and ferrocyanides) of various alkali metals (Li, Na, K, Cs) and ammonium in the course of nanofiltration (NF) of their aqueous solutions was studied. The NF polymer membrane at high salt concentrations (>30 g dm−3) retains alkali metal and ammonium ions to a low extent (1–5%). At lower salt concentrations, the retaining ability of the NF membrane increases. In nanofiltration of solutions of Na and K salts with anions of different charge, the retaining ability of the NF membrane increases with an increase in the anion charge. The pH dependence of the ability of the NF membrane to retain sodium nitrate was studied. This parameter was constant at pH in the ranges 2.0–5.5 and 7.5–13.0, but at pH in the range 5.5–7.5 the retaining ability decreased approximately by half. Experiments on retention of sodium borates of various compositions showed that the solutions containing bulky polynuclear anions consisting of 4–5 boron atoms were retained by the NF membrane with 45–50% efficiency, whereas neutral boric acid molecules were not noticeably retained by the membrane. Thus, nanofiltration can be used for selective separation of inactive alkali metal salts from radioactive components of liquid radioactive waste.

Evaluation of FSH, LH, testosterone levels and semen parameters in male boron workers under extreme exposure conditions.

Boric acid and sodium borates are currently classified in the EU-CLP regulation as "toxic to reproduction" under "Category 1B", with hazard statement of H360FD. However, so far field studies on male reproduction in China and in Turkey could not confirm such boron-associated toxic effects. As validation by another independent study is still required, the present study has investigated possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions. The mean daily boron exposure (DBE) and blood boron concentration of workers in the extreme exposure group (n = 98) were 47.17±17.47 (7.95-106.8)mgB/day and 570.6±160.1 (402.6-1100)ngB/g blood, respectively. Nevertheless, boron-associated adverse effects on semen parameters, as well as on FSH, LH and total testosterone levels were not seen, even within the extreme exposure group. With this study, a total body of evidence has accumulated that allows to conclude that male reproductive effects are not relevant to humans, under any feasible and realistic conditions of exposure to inorganic boron compounds.