Borate Ions Research Articles

Shapes of Polyelectrolyte Titration Curves. 2. The Deviant Behavior of Labile Polyelectrolytes

Hydroxypropyl guar (HPG), a nonionic water soluble polymer, becomes an anionic polyelectrolyte in the presence of borate or boronate ions which bind to HPG. However, the charge groups on the HPG−borate are labile which complicates the interpretation of polyelectrolyte titration behavior. Specifically, polyelectrolyte complex formation between HPG−borate and cationic poly(diallyldimethyl ammonium chloride), PDADMAC, stimulates further borate binding to HPG. We propose that labile polyelectrolytes such as HPG−borate are new class of polylelectrolytes that fall outside conventional “strong” or “weak” polyelectrolyte behavior.

Boron Isotope Fractionation in Column Chromatography with Glucamine Type Fibers

Glucamine type polymers have specific affinity toward boric acid and borate ion. Among them, Chelest Fiber GRY-L showed larger fractionation for boron isotopes than other polymers in our previous study. For this study, we used Chelest Fibers with different fiber lengths (1.0 mm, 0.5 mm, and 0.3 mm) as column packing materials to perform chromatographic separation of boron isotopes. The shorter fiber has larger packing density when packed into the column using a dry method. The 0.3-mm-long fiber has a larger backpressure than fibers of other lengths. Boron adsorption capacities were measured using the breakthrough operation. At this time, the 0.5-mm-long fiber showed the highest capacity. When we measured the isotope ratio profile for fibers of different length using column chromatography, 0.5-mm-long fibers displayed the highest boron isotope fractionation. The 0.5-mm-long fiber is promising as a packing material of column chromatography for boron isotope separation. We also changed operation methods. The lower eluent concentration and the slower flow rate are suitable for boron isotope separation.

Isotope and Ion Selectivity in Reverse Osmosis Desalination: Geochemical Tracers for Man-made Freshwater

A systematic measurement of ions and 2H/1H, 7Li/6Li, 11B/10B, 18O/ 16O, and 87Sr/86Sr isotopes in feed-waters, permeates, and brines from commercial reverse osmosis (RO) desalination plants in Israel (Ashkelon, Eilat, and Nitzana) and Cyprus (Larnaca) reveals distinctive geochemical and isotopic fingerprints of fresh water generated from desalination of seawater (SWRO) and brackish water (BWRO). The degree of isotope fractionation during the passage of water and solutes through the RO membranes depends on the medium (solvent-water vs. solutes), chemical speciation of the solutes, their charge, and their mass difference. O, H, and Sr isotopes are not fractionated during the RO process. 7Li is preferentially rejected in low pH RO, and B isotope fractionation depends on the pH conditions. Under low pH conditions, B isotopes are not significantly fractionated, whereas at high pH, RO permeates are enriched by 20 per thousand in 11B due to selective rejection of borate ion and preferential permeation of 11B-enriched boric acid through the membrane. The specific geochemical and isotopic fingerprints of SWRO provide a unique tool for tracing "man-made" fresh water as an emerging recharge component of natural water resources.

Saline-alkali soils of Russia

Diagnostics, methods of evaluation, and geography of saline-alkali (soda) soils are discussed. The saline-alkali soils include soils of different genetic types with the following chemical properties: the pH of the water suspensions equal to or higher than 8.5; the total alkalinity exceeding 1.4 meq/100 g of soil and the sum of water-soluble calcium and magnesium; and the presence of soluble “alkaline” salts in the soil profiles, the hydrolysis of which results in the alkaline reaction of the soils. The chemical properties of the saline-alkali soils are largely related to the presence of soda (Na2CO3, NaHCO3) in the soils. According to their morphological properties, saline-alkali soils are divided into two groups: alkaline soils with an undiferentiated profile and without a morphologically pronounced solonetzic (natric) horizon, and alkaline soils with a pronounced natric horizon (solonetzes). Solonetzes, in turn, are divided into (a) alkaline solonetzes (with soda or with soda and neutral salts), (b) solonetzes salinized with neutral salts (saline soils) with increased alkalinity in the solonetzic and lower lying horizons, (c) saline solonetzes throughout the profile, and (d) leached solonetzes containing no soluble salts in the profile and almost no exchangeable sodium in the soil exchange complex (SEC) (“dead” solonetzes). The latter two groups of solonetzes cannot be ranked among the alkaline soils. The alkalinity of the saline-alkali soils under study is due to carbonate and bicarbonate ions (carbonate alkalinity), organic acid anions (organic alkalinity), and borate ions (borate alkalinity). The carbonate alkalinity is due to both soda (Na2CO3, NaHCO3) and CaCO3.

Chiral Ionic Liquids: Synthesis, Properties, and Enantiomeric Recognition

We have synthesized a series of structurally novel chiral ionic liquids which have a either chiral cation, chiral anion, or both. Cations are an imidazolium group, while anions are based on a borate ion with spiral structure and chiral substituents. Both (or all) stereoisomeric forms of each compound in the series can be readily synthesized in optically pure form by a simple one-step process from commercially available reagents. In addition to the ease of preparation, most of the chiral ILs in this series are liquid at room temperature with a solid to liquid transformation temperature as low as -70 degrees C and have relatively high thermal stability (up to at least 300 degrees C). Circular dichroism and X-ray crystallographic results confirm that the reaction to form the chiral spiral borate anion is stereospecific, namely, only one of two possible spiral stereoisomers was formed. Results of NMR studies including 1H{15N} heteronuclear single quantum coherence (HSQC) show that these chiral ILs exhibit intramolecular as well as intermolecular enantiomeric recognition. Intramolecularly, the chiral anion of an IL was found to exhibit chiral recognition toward the cation. Specifically, for a chiral IL composing with a chiral anion and a racemic cation, enantiomeric recognition of the chiral anion toward both enantiomers of the cation lead to pronounced differences in the NMR bands of the cation enantiomers. The chiral recognition was found to be dependent on solvent dielectric constant, concentration, and structure of the ILs. Stronger enantiomeric recognition was found in solvent with relatively lower dielectric constants (CDCl3 compared to CD3CN) and at higher concentration of ILs. Also, stronger chiral recognition was found for anions with a relatively larger substituent group (e.g., chiral anion with a phenylmethyl group exhibits stronger chiral recognition compared to that with a phenyl group, and an anion with an isobutyl group has the weakest chiral recognition). Chiral anions were also found to exhibit intermolecular chiral recognition. Enantiomeric discrimination was found for a chiral IL composed of a chiral anion and achiral cation toward another chiral molecule such as a quinine derivative.

Metastable Phase Equilibria of the Reciprocal Quaternary System Containing Sodium, Potassium, Chloride, and Borate Ions at 308.15 K

The metastable solubility of the reciprocal quaternary system containing sodium, potassium, chloride, and borate ions and the physicochemical properties corresponding to density, viscosity, pH value, and refractive index at 308.15 K have been studied with the isothermal evaporation method. According to the experimental data, the metastable equilibrium phase diagrams of dry salt and the water phase diagram of the system were plotted. In the dry-salt phase diagram, there are two invariant points, five univariant curves, and four crystallizing regions corresponding to sodium chloride, potassium chloride, borax (Na2B4O7·10H2O), and potassium tetraborate tetrahydrate (K2B4O7·4H2O). The crystallized region of borax is the largest, while the phase region of NaCl is the smallest with the highest concentration and a strong salting-out effect to borax. There are neither double salts nor solid solutions formed in the metastable system. When compared with the stable phase diagram at 298.15 K of the system, the areas of both metastable phase regions of borax and potassium chloride are enlarged, while other metastable phase regions are decreased. The calculated values of densities and refractive index in the metastable quaternary system with the empirical equations are in good agreement with the experimental values.

Irreversible inhibition of aldolase by a phosphorylated α-dicarbonyl compound

The preparation of a phosphorylated α-dicarbonyl compound designed to specifically react with arginine residues of enzymes accepting phosphorylated compounds as effectors is reported, and shown to inhibit rabbit muscle aldolase in a time-dependent and irreversible manner. This irreversible inhibition occured in a buffer devoid of borate ions, suggesting that the presence of the phosphate moiety contributes in the stabilization of the adduct formed with arginine residues. Under the same conditions, the metalloenzyme iron superoxide dismutase, in which an arginine is known to be critical for the catalytic function, is not significantly inhibited.

Gelation of konjac glucomannan crosslinked by organic borate

A series of thermoreversible konjac glucomannan gels crosslinked by organic borate were prepared. The gel network was formed through the crosslinking reaction between borate ions dissociated from organic borate and the cis-diol hydroxyl groups on the mannose units of polysaccharide chains. The rheological properties of the complex gels were studied by dynamic viscoelastic measurement. The gelation kinetics of the gels were studied and the critical gelation points of the gels were exactly determined by the Winter–Chambon criterion. The effects of temperature and composite ratio on the shear storage modulus ( G ′), the loss modulus ( G ″), and the sol-gel transition points were investigated. The critical gel-sol temperatures of the complex gels were successfully elucidated by Winter–Chambon criterion. The effect of crosslinking density on the critical gelation temperature and the elasticity of the gels were discussed.

Investigation of amphoteric polybenzimidazole (PBI) nanofiltration hollow fiber membrane for both cation and anions removal

The removal of both anions (phosphate, arsenate, arsenite and borate ions) and cations (copper ions) has been investigated by employing a lab-developed amphoteric polybenzimidazole (PBI) nanofiltration (NF) hollow fiber membrane. The amphoteric characteristics are due to the imidazole group within PBI molecules that makes the PBI NF membrane have an isoelectric point near pH 7.0 and show different charge signs based on the media pH. Investigations on the rejection capability of typical anions, e.g. phosphate, arsenate, arsenite, borate anions and typical heavy metal cations, e.g. copper ions, reveal that the PBI NF membrane exhibits impressive rejection performance for various ions removal. However, their rejections are strongly dependent on the chemical nature of electrolytes, solution pHs and the feed concentrations. The experimental results are analyzed by using the Spiegler–Kedem model with the transport parameters of the reflection coefficient ( σ) and the solute permeability ( P). The PBI NF membrane may have potential to be used in industrial removal of various environmentally unfriendly ion species.

In Situ Solid/Liquid Separation Effect for High-Yield Recovery of Boron and Fluorine from Aqueous Media Containing Borate or Fluoroborate Ions

Abstract Detoxification of polluted water and resource recovery of boron and fluorine by using a sampling-type hydrothermal mineralization treatment apparatus was investigated. The hydrothermal mineralization treatment is a geomimetic treatment, which recovers natural minerals from aqueous media under hydrothermal conditions. As a result, hydrothermal mineralization treatment for aqueous solutions containing borate or fluoroborate ions, followed by separation of the reaction solution from precipitate, effectively reduced boron and fluorine concentration in solution, and parasibirskite (Ca2B2O5·H2O) and fluorite (CaF2) formed in high yields. Both the boron and fluorine concentration after the treatment for 2 h at 150 °C was 4 mg dm−3 regardless of its initial concentration (5–3000 mg dm−3) and the ionic species (B(OH)4− or BF4−). Therefore, the hydrothermal mineralization treatment by using a sampling-type apparatus should be an effective method to detoxify the wastewater and ground water containing these ions and recover these ions as reusable mineral.

Reply to comment by K. Caldeira et al. on “Modern-age buildup of CO2and its effects on seawater acidity and salinity”

Reply to comment by K. Caldeira et al. on “Modern-age buildup of CO₂and its effects on seawater acidity and salinity”

Thermoreversible konjac glucomannan gel crosslinked by borax

Dynamic viscoelastic measurements were carried out for novel konjac glucomannan/borax gels. Gel networks were formed through the crosslinking reaction between borate ions dissociated from borax and the cis-diol sites on the polysaccharide chains. At lower oscillation frequencies, the complex gels behave like a liquid, whereas at higher frequency they relax like true gel materials with a predominant elastic relaxation response. An obvious plateau value of storage modulus ( G′) and a maximum and minimum in loss modulus ( G″) were observed on the relaxation spectrum. The characteristic viscoelastic functions were studied as a function of concentrations of konjac glucomannan and borax, strain, and temperature. The storage and loss moduli obey time–temperature superposition by using the empirical shifting factors, which are corresponding to the rheological properties with respect to the longest relaxation time. Relaxation and crosslinking energies for the gels were calculated from the Arrhenius representations of the shift factors. The experimental finding indicates the nature of dynamic crosslinking for the complex gels.

Studies on Sodium Borohydride for Energy Systems

This paper describes a process for synthesising a sodium borohydride solution using a two-compartment electrolytic cell with conversion of borate ions to borohydride ions. This occurs in the catholyte to produce the sodium borohydride solution from which the borohydride material may be extracted. The electrolyte carrier may be an aqueous or a non-aqueous solution, namely a room-temperature ionic liquid. Novel permselective membrane separators are considered. The borohydride stepwise hydrolysis is analysed and proposals are advanced to minimise the resulting hydrogen generation. It is disclosed that sodium borohydride may be used for reversible hydrogen storage, for fuel of direct borohydride fuel cells (DBFC), for high power density cells, and for other relevant energy systems with multifunctional applications, namely in spacecraft.

Potentiometric Sensor for the High Throughput Determination of Tetramisole Hydrochloride

The electrochemical response characteristics of poly(vinyl)chloride (PVC) based membrane sensors for determination of tetramisole hydrochloride (TmCl) is described. The membranes of these electrodes consist of tetramisole-tetraphenyl borate (Tm-TPB), chlorophenyl borate (Tm-ClPB), and phosphotungstate (Tm(3)-PT) ion associations dispersed in a PVC matrix with dibutylpthalate as a plasticizer. The electrodes were fully characterized in terms of composition, life span, usable pH range, and working concentration range and ionic strength. The electrodes showed Nernstian response over the concentration ranges of 7.4 x 10(-7) to 1.0 x 10(-2) M, 1.7 x 10(-6) to 1.0 x 10(-2) M, and 5.6 x 10(-6) to 1.0 x 10(-2) M TmCl, respectively, and were applied to the potentiometric determination of tetramisole ion in pure solutions and pharmaceutical preparations. The potentiometric determination was also used in the determination of tetramisole in pharmaceutical preparations in four batches of different expiration dates. The electrodes exhibited good selectivity for TmCl with respect to a large number of excipients such as inorganic cations, organic cations, amino acids, and sugars. The solubility product of the ion-pair and the formation constant of the precipitation reaction leading to the ion-pair formation were determined conductometrically. The new potentiometric method offers the advantages of high-throughput determination, simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions.

Optimization of conditions for the determination of boron by a ruthenium(II) complex having diol moiety: A mechanistic study

Two ruthenium(II) complexes, [Ru(bpy) 2(dhbpy-H −1)] + and [Ru(bpy) 2(dhphen)] 2+ (bpy = 2,2′-bipyridine, dhbpy = 3,3′-dihydroxy-2,2′-bipyridine, dhphen = 5,6-dihydroxy-1,10-phenanthroline) were examined for use as a colorimetric reagent for the determination of boron. The reactions of boric acid with these two complexes were thermodynamically and kinetically studied in detail in order to specify the reactive species and to set up optimum condition for the determination of boron. The detailed analysis of the kinetic data for the reaction of the latter water-soluble complex showed that both boric acid and borate ion were reactive in an alkaline solution. The thermodynamically and kinetically optimum pH for the determination of boron was ca. 9 at 25 °C. A spectrofluorimetric determination of boron with the latter complex was attempted at 600 nm with excitation at 360 nm, and at pH 8.9 using CHES ( N-cyclohexyl-2-aminoethanesulfonic acid) buffer. It was found that a trace amount of boron as low as ca. 2 × 10 −5 M (∼1 ppm) could be detectable.

Role of PbO substitution by PbF2 on structural behavior and luminescence of rare earth-doped lead borate glass

Structural behavior and luminescence properties of rare earth ions (Pr 3+ , Eu 3+ , Er 3+ ) in oxide and oxyfluoride lead borate glasses have been studied using X-ray diffraction and spectroscopic methods. Substitution of PbO by PbF 2 results in decreasing of the number of tetrahedral BO 4 units, which was observed for Pr 3+ and Eu 3+ ions in lead borate glasses using infrared spectroscopy. In contrast to oxyfluoride lead borate glasses, several diffraction lines due to crystalline ErBO 3 phase were identified for Er-doped oxide sample. Luminescence spectra for rare earth ions in lead borate based glasses have been analyzed, where PbO was totally substituted by PbF 2 .

Organic Nanoparticles of Cyanine Dye in Aqueous Solution

Abstract Ion-based organic dye nanoparticles ranging from tens to hundreds of nanometers have been prepared in aqueous solution. The synthetic approach is based on “ion-association” (hydrophobic ion-pair formation) in water between the dye cation pseudoisocyanine (PIC) and the anion tetraphenylborate (TPB) or tetrakis(4-fluorophenyl)borate (TFPB) ion. Size tuning of spherical and amorphous PIC nanoparticles was accomplished by varying the molar ratio (ρ) of the loaded anion to the dye cation. Electrophoretic characterization revealed that the increase in surface adsorption of anions onto PIC particles brings about an increase in the negative surface charge density, causing a reduction in the surface tension and the mean size of nanoparticles. We found that the optical absorption properties of the PIC nanoparticles exhibited (i) matrix dependence, that is, the 0–0 band position of the PIC chromophore within similar-sized nanoparticles was dependent on the type of counter anions used, and (ii) size dependence, i.e., the 0–0 band position of the PIC chromophore was dependent on the mean nanoparticle diameter when the particles were prepared using the same counter anion.

Boric acid binding studies with diol containing polyethylenimines as determined by 11B NMR spectroscopy

AbstractThree water‐soluble polymers incorporating increasing levels of 2,3‐dihydroxy propyl attached to polyethylenimine (PEI) backbone were synthesized, characterized by NMR, and investigated for their ability to bind boric acid (BA). 11B NMR spectroscopy showed that BA interacted with the polymeric 2,3‐dihydroxy propyls by forming borate monoester and borate diesters in the boron concentration range of 100–1000 ppm and at 0.0775M polymer. Borate monoester species predominated for low functionalization levels (33% of the PEI amines functionalized), whereas borate diester species dominated for the higher functionalized polymers (66–100% of the PEI amines functionalized). All three polymers showed that 100% of the BA was bound as a mixture of borate mono‐ and diesters at 100‐ppm boron. The overall best performer based on total borate ester formation was the 2/3‐PEI, with a binding Kd of 631 at 200 ppm boron. Borate ion concentration was measured from the 11B NMR chemical shift of the BA/borate peak and it decreased as 1/3‐PEI > 2/3‐PEI > 3/3‐PEI. Variable temperature 11B NMR showed drastic reduction of borate ester species at 65°C. Thus, PEI polymers, as the ones investigated in this work, are reasonable candidates for the selective recovery and recycle of BA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4411–4418, 2006

Energy transfer from the host excitations to Ce 3+ ions in scandium borate

Efficient energy transfer from the host excitations (self-trapped excitons, STE) excited at λ∼160 nm to Ce 3+ impurity ions was observed in scandium borate (ScBO 3). The luminescence and excitation spectra as well as time-resolved emission data were obtained. Energy transfer rates from the STE to Ce 3+ of about 10 8 s −1 are observed and these are within an order of magnitude of estimates based on dipole–dipole energy transfer.

Experimental measurement of boron isotope fractionation in seawater

The boron isotopic composition of marine carbonates is considered to be a tracer of seawater pH. Use of this proxy benefits from an intimate understanding of chemical kinetics and thermodynamic isotope exchange reactions between the two dominant boron-bearing species in seawater: boric acid B(OH) 3 and borate ion B(OH) 4 −. However, because of our inability to quantitatively separate these species in solution, the degree of boron isotope exchange has only been known through theoretical estimates. In this study, we present results of a spectrophotometric procedure wherein the boron isotope equilibrium constant ( 11–10 K B) is determined empirically from the difference in the dissociation constants of 11B(OH) 3 and 10B(OH) 3 in pure water, 0.6 mol kg − 1 H 2O KCl and artificial seawater. Within experimental uncertainty, our results show no dependence of 11–10 K B on temperature, but 11–10 K B at 25 °C in pure water was statistically different than results obtained in solutions at high ionic strength. 11–10 K B of the seawater ( S = 35, B T = 0.01 mol kg − 1 H 2O) at 25 °C is 1.0272 ± 0.0006. This result is significantly larger than the theoretical value used in numerous paleo-pH studies ( 11–10 K B = 1.0194).