Gradient chromatographic elution of sulphur anions

The distribution coefficient of sulphide, sulphite, sulphate and thiosulphate anions between different concentrations of aqueous alkali metal chloride solutions and the anion exchanger Dowex 1X8 is studied. The obtained distribution deportment of these anions is explained in the light of water-water, anion-cation and ion-ion interactions as well as the different tendencies of the alkali ions to hydration. Based on the separation factors encountered between adjacent anions, a chromatographic method is adopted for isolation of the sulphur anions by gradient elution. This method is further compared with the chromatographic procedures so far reported for separation of the investigated anions.     

Highly efficient separation of lithium chloride from seawater

A complexing reagent composed of two bipyridine moieties enabled the efficient separation of lithium chloride through liquid membrane from seawater, in which 0.005% lithium chloride is contained (more than 99% metal chlorides are NaCl, KCl, MgCl2, and CaCl2). That is, two separations by our liquid membrane changed the molar ratio of LiCl from 0.005% to 80%. The striking characteristic of this compound is that the lithium ion is separated efficiently from alkali and alkaline earth metal ions without the lipophilic anion. Thus this new membrane system contructed by us offers a low-energy, low-cost, and environmentally friendly method to enable the routine use of lithium chloride separation from seawater.     

Interaction between anionic polyelectrolytes and anion exchange membranes and change in membrane properties

Electrodialytic transport properties of anion exchange membranes were measured after formation of anionic polyelectrolyte layers on the membrane surfaces: relative transport number of various anions to chloride ions, current efficiency and apparent diffusion coefficients of neutral molecules. The anionic polyelectrolyte layers were formed by immersing the membrane into an aqueous solution of polycondensation product of sodium naphthalene sulfonate and formaldehyde or polystyrene sulfonic acid.

The change in the relative transport number between anions was remarkable in the anion exchange membrane with high ion exchange capacity by forming the layer. Results were: the relative transport number of sulfate ions to chloride ions decreased and those of nitrate ions to chloride ions, fluoride ions to chloride ions and bromide ions to chloride ions increased compared with the corresponding membrane. Although the apparent diffusion coefficient of neutral molecules suggested clogging of the membrane pores by the polyelectrolyte, anions with higher hydrated ionic diameter were able to permeate through the membrane easily. This means that difference of electrostatic repulsion force against two anions is effective on the change in the relative transport number of anions.     

Mechanism of anodic dissolution of copper in aqueous acidified solutions of different anions

The potentials of copper anodes were measured as a function of current density in aqueous acidified solutions of different anions. Tafel lines were obtained, whose slopes depend on the nature of the anion. This denoted the participation of the anion in the anodic dissolution of the metal. Hence, mechanisms were suggested based on the formation of intermediate cuprous compounds, which are further oxidized electrochemically, or undergo chemical disproportionation to cupric salts.The results in phosphate solutions indicated that the second electrochemical oxidation is the rate determining step. In chloride, nitrate and sulphate solutions, both the second electrochemical step and the disproportionation reaction govern the overall reaction rate.Measurements in acidified copper salt solutions showed that Cu²⁺ ions affect the reaction mechanism. Thus, in chloride and sulphate solutions, the disproportionation reaction becomes predominating, whereas in nitrate solutions the intermediate is mainly oxidized electrochemically. An interpretation is provided, based on the adsorption of Cu²⁺ ions.     

Solubilities in the Ternary System Alkali Metal Halide–Glucose–Water

The solubility of glucose was measured in aqueous saturated alkali metal halide (NaF, NaCl, NaBr, NaI, KCl, KBr, and KI) solutions at 30°C. The solubility of glucose in saturated sodium halide solutions is lower than that in water. On the contrary, the solubility of glucose in saturated potassium halide solutions is higher than that in water. The determinations of glucose solubility were also carried out in some unsaturated NaCl or KCl solutions at 30°C. In the case of NaCl, the glucose solubility curve is not simple. It increases slightly at lower NaCl concentrations then decreases gradually with increases NaCl concentration. In the case of KCl, the curve is simple, the solubility of glucose increasing with increases KCl concentration. The determinations of alkali metal chloride solubilities were also carried out in the presence of glucose at 30°C.     

Voltammetry of Mn(III) Porphyrin in Trihexyl(tetradecyl)‐phosphonium Tris(pentafluoroethyl)trifluorophosphate Supported Toluene in Contact with an Aqueous Electrolyte

Voltammetry of manganese tetraphenylporphyrinato chloride in trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate solution in toluene reveals its unexpectedly low diffusion coefficient. UV‐vis spectra confirm significant Cl^? exchange with large phosphate anion at the axial position of the complex. Experiments performed with a glassy carbon electrode covered by a liquid film of the same solution and immersed in an aqueous electrolyte solution show a peak potential dependence on the nature and concentration of the aqueous electrolyte anion described by a Nernst type equation. Electron transfer is followed by anion expulsion where the anion effect results from the lability of the axial coordination site of the porphyrin and from spontaneous ion exchange.     

Solubility of some phenolic compounds in aqueous alkali metal nitrate solutions from (293.15 to 318.15) K

This paper is continuation of the study concerning the solubility-temperature dependence data for some phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in two nitrate salts (KNO₃ and NaNO₃) aqueous solutions. The solubilities of PhC were determined in the temperature ranging from (293.15 to 318.15) K. It has been observed that the solubility, in aqueous nitrate solutions, increases with increasing temperature. Results showed that alkali metal nitrate has a salting-out effect on the solubility of PhC. The effect of the anion of the electrolyte on the solubility of PhC is observed by comparing these results with values reported in the previous papers for the effect of LiCl, NaCl and KCl. For each cation, the solubilites of the phenolic compounds are higher with nitrate anion than with chloride anion. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The solubility data were accurately correlated by a semi empirical equation. The standard molar Gibbs free energies of transfer of PhC (Δ_trG^°) from pure water to aqueous solutions of the nitrate salts have been calculated from the solubility data. The decrease in solubility is correlated to the positive Δ_trG^° value which is mainly of enthalpic origin.     

Diffusion coefficients of lithium chloride and potassium chloride in hydrogel membranes derived from acrylamide

Diffusion of non-associated electrolytes (potassium chloride and lithium chloride) in concentrated aqueous solutions (0.1-1.0 mol dm⁻³) has been studied in hydrogels derived from acrylamide and methyl methacrylate to study the mechanism of electrolyte transport. The preparation of two gels with different monomer ratio compositions resulted in obtaining membranes of substantially different hydrophilic character with polymer fractions of 0.3 and 0.5.Cukier hydrodynamic model was applied to explain the dependence of the diffusion coefficients of KCl and LiCl on the electrolyte concentration in hydrogel obtained experimentally. It was shown that the increase of the diffusion coefficients is accompanied with a decrease of the mean distance of approach of the ions. This can be explained by the formation of ion-pairs, resulting in a further contribution to diffusion once there is a decrease in the hydrodynamic resistance of the medium to the diffusing particles. Parameters, which characterise such a behaviour quantitatively, are different for different electrolytes and depend on water content in the gel.     

A novel transformation of O-methyldalbergin

O-methyldalbergin and related 4-phenylcoumarins are markedly different from ordinary coumarins in their behaviour towards alkali. They are stable in boiling alkali and on addition of mercuric oxide yield coumarilic acids. Phenyl-coumarilic acids undergo decarboxylation readily when boiled with aqueous alcoholic mercuric chloride to yield phenyl substituted coumarones.     

Supercooling of aqueous NaCl and KCl solutions under acoustic levitation

The supercooling capability of aqueous NaCl and KCl solutions is investigated at containerless state by using acoustic levitation method. The supercooling of water is obviously enhanced by the alkali metal ions and increases linearly with the augmentation of concentrations. Furthermore, the supercooling depends on the nature of ions and is 2-3 K larger for NaCl solution than that for KCl solution in the present concentration range: Molecular dynamics simulations are performed to reveal the intrinsic correlation between supercoolability and microstructure. The translational and orientational order parameters are applied to quantitatively demonstrate the effect of ionic concentration on the hydrogen-bond network and ice melting point. The disrupted hydrogen-bond structure determines essentially the concentration dependence of supercooling. On the other hand, the introduced acoustic pressure suppresses the increase of supercooling by promoting the growth and coalescence of microbubbles, the effective nucleation catalysts, in water. However, the dissolved ions can weaken this effect, and moreover the degree varies with the ion type. This results in the different supercoolability for NaCl and KCl solutions under the acoustic levitation conditions.     

Diffusion potential is induced by coupled transport of ions through liquid membrane: nonlinear response to pH change in a reverse permeation system

In a cation exchange liquid membrane-aqueous alkali metal chloride system, diffusional flux of alkali metal ion driven by proton was observed. A supported liquid membrane formed on a Teflon filter by impregnating it with stearic acid-doped 1-octanol was used. The internal aqueous phase contained KCl and HCl, and the external aqueous phase also contained KCl. The initial concentrations of K⁺ ions of both phases were 1×10⁻¹ mol dm⁻³ for all the measurements. The concentration of HCl in the internal solution was kept at 1×10⁻² mol dm⁻³. The pH of the external solution was changed successively with HCl, appropriate buffer solution, or KOH. The pH dependence of membrane potential showed hysteresis loop in the range from neutral to alkaline pH, where reverse ion permeation was observed after the flux had been measured in the system with the external solution of an alkaline pH (pH 13). In the acidic range below neutral pH, the hysteresis of the membrane potential as well as reverse ion permeation was not observed. To elucidate the correlation between the appearance of hysteresis loop and the reverse ion permeation driven by proton across the membrane, the time course of the membrane potential in response to pH change was investigated. In the pH range where reverse permeation phenomena appeared, the time dependence of the membrane potential in nonsteady-state showed biphasic behavior. From the time course curve of the membrane potential, the total membrane potential was divided into the Donnan potential and the diffusion potential. From these findings, it was demonstrated that the diffusion potential was generated within the membrane only in the alkaline range where reverse ion permeation occurred. Analyzing the diffusional flux, the diffusion coefficient of potassium ion in the membrane was obtained taking the Donnan potential into account to be much greater than that in the membrane solvent. As a result of comparison of the diffusional fluxes measured by atomic absorption spectrometry and solution conductometry, the flux of the potassium ion was found to be significantly greater than that of the hydrogen ion in the opposite direction, especially at extremely high pH region. This implies the flows of hydroxide ions and neutralization reaction within the membrane facilitate the reverse ion permeation process of potassium ions.     

The reaction of ammonium salts in molten alkali metal nitrites

The thermal decomposition of ammonium chloride and sulphate in molten alkali metal nitrite eutectics cannot be represented by a simple stoichiometry. Nitrous oxide and nitric oxide are produced as well as nitrogen and water.Thermogravimetry is complicated by loss of solid material when the extremely rapid reaction commences at temperatures just below the melting points of the nitrite eutectics and by volatilisation of unreacted ammonium compounds, largely chloride and nitrite/nitrate from reactant solutions of ammonium chloride and ammonium sulphate, respectively.     

ChemInform Abstract: EPR Spectra of Coinage Metal Atoms Trapped in Evaporated Alkali Metal Chloride Matrices at Low Temperatures.

The EPR spectra of Cu, Ag, and Au atoms, trapped directly in vapor-deposited alkali metal chlorides LiCl, NaCl, KCl, and CsCl using the rotating-cryostat technique, show much lower hyperfine interactions than gas-phase metal atoms or atoms in alkali metal chloride single crystals (prepared from the ions in cationic substitutional sites by electron capture).     

Chromatographic behaviour of trace metal ions on a strong base anion exchange resin functionalized by azo ligands

A model which allows the evaluation of the elution volume V(E) and the central point V(C) of the breakthrough curve of a metal ion at trace level on a chromatographic column containing a chelating resin is presented. V(E) and V(C) mainly depend on the complexation properties of the active groups, and on the acidity and composition of the aqueous solution, according to the Gibbs-Donnan model for the resin. The model has been tested in the case of strong base anion exchange resins in chloride form functionalized with two different sulphonated azo ligands (T-azo-C, T-azo-R). The chromatographic behaviour of copper(II) and thorium(IV) is as expected from the formation of a complex with the azo dye in the resin, while that of zinc(II) and cadmium(II) is fully described by also taking into account the formation of anionic chloro complexes inside the resin.     

The interference effect of more than one anion and cation in graphite furnace atomic absorption spectrometry. Part 2: Effect of sodium,magnesium, sulphate and chloride mixtures on the atomization of manganese

Although there are numerous cations and anions in real samples generally, the interference effects of a matrix consisting of one cation and one anion on the atomization of an element in graphite furnace atomic absorption spectrometry (GFAAS) have been investigated. Therefore, it would be more realistic to investigate the interference of a matrix containing more than one cation and anion. In this study, the simultaneous interference effects of sodium, magnesium, sulphate and chlorine, which are the most common and abundant ions in many samples, e.g. sea water, on the atomization of manganese in GFAAS were studied. As a first step, the individual interferences of some possible salts consisting of simple combinations of the ions studied such as sodium chloride, magnesium chloride, sodium sulphate and magnesium sulphate, were investigated. It was found that in the presence of these four ions and in their wide concentration range, sodium chloride and magnesium sulphate are the major salts formed after the drying step which were supported by X-ray diffraction (XRD) studies. Sodium chloride causes a significant depressive effect at low pyrolysis temperatures. The interference of sodium chloride originates from expulsion of the analyte with matrix and gas phase reaction between manganese and chloride ions during atomization. Magnesium sulphate does not cause any depression and in fact higher pyrolysis temperatures compared to matrix-free manganese can be applied without loss of any analyte. The depressive effect of sodium chloride on manganese markedly decreased in the presence of magnesium sulphate due to its protecting effect. The mutual interaction mechanism of these two salts and their effects on manganese have been discussed.     

Thermal diffusivity of eutectic of alkali chloride and ice in the freezing-thawing process by temperature wave analysis

Thermal diffusivity of eutectic formed in aqueous alkali chloride solutions (NaCl, KCl, RbCl and CsCl) was determined by temperature wave analysis (TWA) during the freezing-thawing process of aqueous alkali chloride solution. An obvious change of thermal diffusivity in freezing-thawing processes of eutectic was observed with the super-cooling phenomena for each alkali chloride solute. The rate of thermal diffusivity decrease during the eutectic melting in comparison to the total decrease from the solid to the liquid state was observed larger than that of the heat of fusion measured by DSC, especially in the dilute concentration. It was confirmed that thermal diffusivity was sensitively influenced by the highly structure of the coexistence of eutectic crystallization and ice.     

Clipping and stoppering anion templated synthesis of a [2]rotaxane host system

A new [2]rotaxane host system containing nitro-isophthalamide macrocycle and polyether functionalised pyridinium axle components is prepared via clipping and stoppering synthetic methodologies using chloride anion templation. After removing the chloride anion template, (1)H NMR titration experiments reveal the unique interlocked host cavity to be highly selective for binding chloride and bromide in preference to basic oxoanions in competitive aqueous solvent mixtures. The rotaxane host system proved to be a superior anion complexant in comparison to the individual macrocycle and axle components. The anion binding affinity of the novel rotaxane is also investigated via molecular dynamics simulations and in general the structural data obtained corroborates the experimental solution anion recognition behaviour.     

Coadsorbate‐Induced Reversal of Solid–Liquid Interface Dynamics

Coadsorbed anions are well‐known to influence surface reactivity and dynamics at solid–liquid interfaces. Here we demonstrate that the chemical nature of these spectator species can entirely determine the microscopic dynamic behavior. Quantitative in situ video‐STM data on the surface diffusion of adsorbed sulfur atoms on Cu(100) electrodes in aqueous solution covered by bromide and chloride spectators, respectively, reveal in both cases a strong exponential potential dependence, but with opposite sign. This reversal is highly surprising in view of the isostructural adsorbate arrangement in the two systems. Detailed DFT studies suggest an anion‐induced difference in the sulfur diffusion mechanism, specifically an exchange diffusion on the Br‐covered surface. Experimental evidence for the latter is provided by the observation of Cu vacancy formation in the Br system, which can be rationalized by a side reaction of the sulfur exchange diffusion.     

Synthesis, characterization and metal adsorption properties of the new ion exchanger polymer 3-n-propyl(4-methylpyridinium) silsesquioxane chloride

The preparation and anion exchange properties of 3-n-propyl(4-methylpyridinium) silsesquioxane chloride polymer are described. This new polymer was prepared by the sol-gel processing method and is designated as SiPic+Cl-. It is insoluble in water and showed an anion exchange capacity of 1.46x10(-3) mol g-1. The adsorption isotherms of ZnCl2, CdCl2 and HgCl2 were determined from aqueous solutions and the adsorption equilibria simulations fit the model of fixed bidentate centers with the absence of lateral interactions and energetic heterogeneity between them. The metal ions diffuse into the solid solution interface and are dominantly present as MCl2-(4) species for Zn(II), MCl(2-)4 and MCl-3 species for Cd(II) and MCl-3 species for Hg(II).     

Alkali‐Metal Azides Interacting with Metal–Organic Frameworks

Interactions between alkali‐metal azides and metal–organic framework (MOF) derivatives, namely, the first and third members of the isoreticular MOF (IRMOF) family, IRMOF‐1 and IRMOF‐3, are studied within the density functional theory (DFT) paradigm. The investigations take into account different models of the selected IRMOFs. The mutual influence between the alkali‐metal azides and the π rings or Zn centers of the involved MOF derivatives are studied by considering the interactions both of the alkali‐metal cations with model aromatic centers and of the alkali‐metal azides with distinct sites of differently sized models of IRMOF‐1 and IRMOF‐3. Several exchange and correlation functionals are employed to calculate the corresponding interaction energies. Remarkably, it is found that, with increasing alkali‐metal atom size, the latter decrease for cations interacting with the π‐ring systems and increase for the azides interacting with the MOF fragments. The opposite behavior is explained by stabilization effects on the azide moieties and determined by the Zn atoms, which constitute the inorganic vertices of the IRMOF species. Larger cations can, in fact, coordinate more efficiently to both the aromatic center and the azide anion, and thus stabilizing bridging arrangements of the azide between one alkali‐metal and two Zn atoms in an η² coordination mode are more favored.