Transition Metal Salt Solutions Research Articles

Dielectric properties of iPP and aPS nanocomposites with core‐shell particles obtained by treatment in transition metal salt solutions

AbstractThe dielectric properties of nanocomposites based on isotactic polypropylene (iPP) and atactic polystyrene (aPS) obtained by novel, simple, and environmentally friendly treatment technique have been analyzed in this study. The best treatment conditions to obtain nanocomposites with embedded core‐shell particles with enhanced dielectric properties were considered. Treatment of polymer matrices in water solution iron(II)‐chloride had the most pronounced precipitation effect, that was directly related to the appearance of higher transition metal concentrations in the iPP and aPS matrices, in comparison to treatments in the other two transition metal salts, MnCl2 and NiCl2. Relative dielectric constant and loss tangent have been studied in the frequency range from 20 Hz to 9 MHz. Embedded core‐shell nanoparticles (from 15 to 150 nm in diameter) in a very small amount (1.72E‐8 mol/cm3 to 1.17E‐5 mol/cm3) resulted in significant improvement (2.5% up to 9.1%) and stabilization of relative dielectric constant value toward higher frequencies and also lowering loss tangent in compare to starting polymer matrices. These properties indicate that materials obtained with the presented treatment technique can be applied as microelectronic packing and with further development of the method in order to obtain a higher concentration of metal ions as energy storage devices.

Metal nanoparticles decorated sodium alginate‑carbon nitride composite beads as effective catalyst for the reduction of organic pollutants

Herein, a simple method is used for fabrication of carbon nitride (g-C3N4) incorporated sodium alginate (Alg) beads. The alginate carbon nitride beads (Alg-CNBs) were prepared by introducing the g-C3N4 dispersed Alg aqueous solution to a divalent Ca2+ ions solution. Alg-CNBs were further treated with different transition metal salt solutions. The surface coated transition metal ions on Alg-CNBs were reduced to zero-valent state (M0), through strong reducing agent NaBH4, and used for the catalytic reduction of different organic dyes. The surface morphology of all catalysts was investigated by FE-SEM and metal uptake capacity was investigated by ICP-OES. The prepared M0/Alg-CNBs (where M0 = Ag0, Ni0, Fe0 and Cu0) catalysts were tested against the reduction of 4-nitrophenol (4-NP) to recognize the fastest one. Among all the catalysts, the Cu0/Alg-CNBs efficiently reduced 4-NP to 4-aminophenol (4-AP). Cu0/Alg-CNBs was used further for the reduction of methyl orange (MO), congo red (CR), 2-nitrophenol (2-NP) and 2,6-dinitrophenol (2,6-DNP). The MO, CR and 4-NP was reduced with rate constant of 0.135, 0.077 and 0.384 min−1, respectively. For large scale and continuous reduction of 4-NP to 4-AP, the column was packed with 0.15 g catalyst and the reducible reactants were passed through it. A reduction of 4-NP up to 97–99% was achieved by simply passing it through column packed with catalyst under gravity. Similarly, effects of changing initial dye concentration, catalytic dosage and NaBH4 performance has been investigated for the reduction process. Also, the prepared catalyst beads can be easily prepared, recovered simply by discarding the dye after completion of the reaction, recyclable and its good catalytic activity.

Y-Type Zeolites Modified by Transition Metal Nanoparticles for Separating Argon from a Mixture with Oxygen

Based on NaY and HY granular synthetic zeolites without binding agents, adsorbents containing transition metal nanoparticles and characterized by the selectivity for argon at adsorption from a mixture with oxygen have been fabricated. Modification has been performed by the interaction with reverse micellar solutions of silver nanoparticles, as well as by ion exchange with transition metal salt solutions and subsequent reduction of metal ions until the achievement of nanoparticles in liquid media under the effect of ultrasound. The actual sizes of metal particles and their distribution over the surface of the modified samples of zeolites have been determined by the method of transmission electron microscopy (TEM). The samples’ equilibrium adsorption capacities for oxygen and argon at 25°С and atmospheric pressure and the partition coefficients of the argon–oxygen mixture as a ratio of the Henry coefficients have been determined. It has been demonstrated that samples of the NaY zeolite modified with silver nanoparticles have the highest selectivity for argon during its separation from a mixture with oxygen. The partition coefficient value of the argon–oxygen gas mixture was equal to 1.5–1.6.

THEORETICAL INVESTIGATION OF THERMODYNAMIC PARAMETERS OF TRANSITION METAL SALTS COMPLEXATION WITH ACRYLONITRILE-STYRENE COPOLYMER

Thermodynamic parameters of formation reactions of polymer complexes of transition metals (ZnCl2, CuCl2, NiCl2, СоС12) were obtained using the PBE96/SVP computational level. Chemical processes taking place during both direct copolymerizations in the presence of transition metal salts and at introduction of transition metal salts at final step of polymerization were considered. The success of formation reaction of polymer complexes was theoretically based with the radical polymerization into solutions of transition metal salts in the presence of zink chloride only.

Hydrogen generation by oxidation of “mechanical alloys” of magnesium with iron and copper in aqueous salt solutions

Oxidation processes of magnesium and magnesium “mechanical alloys” with iron and copper (1–15 wt%) in presence of aqueous solutions of sodium, cobalt, nickel and copper chlorides have been investigated. The rate of hydrogen generation increases with the increase of the transition metal content in the “alloys” and levels out for the Mg–Cu system. The overall hydrogen yield does not exceed 92% of theoretical one at the initial solution concentrations of 0.032 M and chloride/Mg molar ratios of 0.0075 (0.85 M and 0.20 for NaCl), but becomes close to 100% at double concentration of the transition metal salt solutions. The electrochemical corrosion mechanism of the magnesium oxidation process has been suggested.

Data on energy-band-gap characteristics of composite nanoparticles obtained by modification of the amorphous potassium polytitanate in aqueous solutions of transition metal salts.

Here we present the data on the energy-band-gap characteristics of composite nanoparticles produced by modification of the amorphous potassium polytitanate in aqueous solutions of different transition metal salts. Band gap characteristics are investigated using diffuse reflection spectra of the obtained powders. Calculated logarithmic derivative quantity of the Kubelka–Munk function reveals a presence of local maxima in the regions 0.5–1.5 eV and 1.6–3.0 eV which correspond to band gap values of the investigated materials. The values might be related to the constituents of the composite nanoparticles and intermediate products of their chemical interaction.

Catalysts for the Electrochemical Conversion of Carbon Dioxide

Currently, there are no large, commercial processes that convert carbon dioxide back to useful chemicals, save for the water-gas shift that leads to the Fischer-Tropsch process, but both of these reactions require a large amount of energy input. Simpler methods exist, such as the electrochemical conversion of carbon dioxide, which can be performed in aqueous solution at room temperature1. This carbon dioxide utilization pathway is not yet fully developed for several reasons: lack of a selective and robust catalyst, large energy input required for desirable products, and low current densities (low yields)2. All of these issues are being addressed by researchers in the field. Copper metal has been found to produce the most desirable products, hydrocarbons, which can be used as fuel3. High surface area nanoporous copper catalysts were prepared using an in-house method. Galvanic displacement reactions using aqueous transition metal salt solutions were used to create nanoporous copper catalysts with a coating of a second transition metal. Electrolysis was conducted using a custom built electrochemical cell and a Princeton Applied Research potentiostat. CO2 reduction products were analyzed in-situ using a gas chromatograph with a mass spectrometer and thermal conductivity detectors. Liquid products were analyzed using nuclear magnetic resonance. Results show unique selectivity for all variations of nanoporous bimetallic copper catalyst tested. The pure nanporous Cu preferentially producing ethylene and ethane with very minimal methane. On a typical polycrystalline copper catalyst, methane and ethylene are the majority hydrocarbon gases while ethane is rarely observed. A significant amount of formate was produced on nanoporous Cu, reaching 10% faradaic efficiency at potentials as low as -0.55 V vs RHE. Selectivity of the catalysts can be significantly altered on bimetallic Cu surfaces. Substantial increase in ethylene and ethane is observed and greater amounts of ethanol and propanol (~5% FE each) were produced. Preliminary experiments using 13CO2 saturated solution have been performed and may provide insight into CO2 reduction pathways. Using mass spectroscopy and NMR, reaction products were monitored. Product species containing the 13C isotope were observed for all CO2 reduction products and a comparison to 12CO2 experiments was made. Differences in the 13C/12C ratio may provide clues as to the carbon species responsible for the measured products.

Polymer-metal complexes of polyacrylonitrile and its copolymers: synthesis and theoretical study

Polyacrylonitrile, poly(styrene-acrylonitrile) and poly(acrylonitrile-butadiene-styrene) complexes with transition metal salts have been synthesized. The synthesis were attempted by carrying out free radical polymerization reactions in aqueous transition metal salt solutions (ZnCl2, CuCl2, CoCl2, CoSO4, NiSO4, CuSO4) and by addition of the transition metal salts to the reaction mixture in the final stage of the polymerization. It is shown experimentally and theoretically that the first method is successful only when zinc chloride is used, while the cobalt, nickel, copper complexes are formed through the addition of the salts to the ready polymers. Reactions that take place during studied complexations were investigated by means of ab initio quantum chemistry calculations, thermodynamic parameters for these reactions were determined.

Methods of dyeing ceramic brick

The results of a study of the possibility of bulk dyeing of ceramic brick by incorporating manganese and iron ore and metallic slags and sludges from electroplating plants in the pastes are reported. It was found that low-melting clays should first be bleached with chalk or fireclay or kaolin impregnated with solutions of transition metal salts in order to attain a broad color scale for the articles. Using natural raw materials and soluble salts of 3d elements significantly expands the raw-materials base, reduces the cost of the ceramic articles by replacing expensive materials, and combines synthesis of pigments and firing of the articles.

Visible and ultra-violet absorption spectra of aqueous solutions of transition metal salts affected by a high-voltage pulse electric discharge

The effect of a high-voltage pulse electric discharge (HVPED) on the electron spectra of CuSO4, Ni(NO3)2, NiCl2, CoSO4, and Co(NO3)2 aqueous solutions is investigated. It is found that the salt system activation by HVPED can change the configurations of electron shells of molecular ions. It is stated that the processes of post-activation structural relaxation of CuSO4/H2O solution are rather long-term. It is shown that the character of the HVPED effect on the electron spectra of solutions significantly depends on the solution composition and the intensity of interparticle interactions therein.

Inversion of selective binding of transition metal ions by Langmuir monolayers of amphiphilic cyclen

Abstract Selective binding of Cu(II), Ni(II), and Zn(II) from aqueous solutions of transition metal salts and their mixtures by Langmuir monolayers of dicetyl cyclen (DCC) was investigated. A direct relationship between the subphase pH and the selectivity of macrocyclic molecules with respect to particular metal ions was deduced from analysis of the π-A isotherms of DCC monolayers and the X-ray fluorescent spectra of the corresponding Langmuir–Blodgett (LB) films. Unusual inversion of the macrocycle selectivity from preferential binding of Cu 2+ to complex formation with Ni 2+ upon a decrease in subphase pH was revealed for a DCC monolayer.

Phosphoric acid and various transition metal salt solutions as a combined etchant and activator prior to the use of an anaerobic adhesive

Objectives. The objectives of this experiment were to determine whether various transition metal salts in 37% o-phosphoric acid could both activate and etch an enamel surface prior to the use of an anaerobic adhesive. Method. Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case, the enamel was etched and activated using a solution of 37% o-phosphoric acid containing various transition metal sulfates and chlorides. After bench curing, the specimens were shear bond tested to failure and the load at debond recorded in each case. Results. The results were analyzed using mean force to debond (N) and 95% confidence intervals. Kaplan–Meier survival probabilities and log-rank tests were also performed. Conclusions. Under the conditions of this experiment, the sulfate and chloride of copper in acid were the most effective etching/activating solutions. There was no significant difference in the mean force to debond between the copper (II) sulfate and copper (II) chloride. The chloride in acid was, however, the only one of the two to produce a conventional etch pattern on the surface of the enamel. Significance. It is possible to render the enamel surface both retentive and active towards anaerobic adhesives, such that relatively unreactive substrates can be bonded to enamel using such adhesives.

Self-assembled poly(metal tetrathiooxalate) films

Abstract Ultrathin poly(metal tetrathiooxalate) films are described which were prepared by a reactive self-assembly process. The polymer films were prepared upon alternate dipping of a negatively charged substrate into aqueous solutions of transition metal salts (e.g. salts with Cu2+, Ni2+, Co2+ and Pd2+) and tetraethylammonium tetrathiooxalate, which led to sequential adsorption of the metal and tetrathiooxalate ions under simultaneous complexation and formation of poly(metal tetrathiooxalate). The polymer films exhibit a brownish coloration with strong metallic reflection. Optical measurements indicate a very broad absorption extended from the ultraviolet to the near-infrared up to 2000 nm. Scanning force microscopy indicates a rather smooth surface with isolated peaks of a height up to 2 μm. Preliminary studies of the specific surface conductivity of poly(nickel tetrathiooxalate) films indicate a value of 2.5×10−3 S cm−1.

Transition metal salt solutions and anaerobic adhesives in dental bonding

Objectives: The objectives of this experiment were twofold. Firstly to determine whether an anaerobic adhesive could be used to bond steel attachments to etched human enamel, following treatment of this surface with various concentrations of copper (II) sulphate solution. Secondly, to determine the effect of 0.05 M solutions of other transition metal sulphates and chlorides on the same bonding process. Methods: Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel, which had been ground flat, was etched with 37% o-phosphoric acid and then treated with copper (II) sulphate solution prior to bonding. After bench curing for one hour, the specimens were shear tested to failure, and the load at debond recorded in each case. The effect of varying the concentration of copper (II) sulphate solution was determined. Following determination of the optimal copper (II) sulphate concentration, the experiment was repeated using the same concentration of various other transition metal sulphates and chlorides. Results: The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan–Meier survival probabilities and log-rank tests were also performed. Conclusions: Under the conditions of this experiment the optimal concentration of copper (II) sulphate solution was found to be 0.05 M. Of the various transition metal sulphates and chlorides under test, the sulphates appeared to provide a more active surface for the polymerisation of the anaerobic adhesive than the chlorides. Of the sulphate solutions, the most effective was that of copper. Significance: Anaerobic adhesives show promise as dental bonding agents capable of bonding metal attachments to enamel following enamel pretreatment with 0.05 M copper (II) sulphate solution.

Spectrochemistry of solutions. part 29.[1] intrusion ion pairing: Identification of a new form of ion pair in transition metal salt solutions in pyridine through their visible spectra

A new ion associate structure, an “intrusion” ion pair, is reported in which small anions like Cl − and Br − intrude into the hexacoordinate primary solvation sphere of [Ni(py) 6] 2+ in pyridine. This cation-anion interaction is identified by significant spectral shifts to lower frequency of the 3 A 2g( F)- 3 T 2g( F), 3 A 2g( F)- 3 T 1g( F ) and 3A 2 g (F)- 3T 2 g (P) transitions in the d- d spectra compared with the frequencies observed with [Ni(py) 6] 2+ solutions containing the larger anions NO 3 −, BF 4 − and SO 4 2-. A similar spectral shift identifies the presence of an “intrusion” ion pair in Cl − solutions of [Cr(py) 6] 3+ in pyridine versus NO 3 − and NCS-solutions; in the case of the Br − solution of [Cr(py) 6] 3+ the absence of any shift in the positions of the bands due to the 4A- 4T 2(F) and 4A- 4T 1(F) transitions of Cr III indicates that the Br − anion does not enter the primary solvation sphere of [Cr(py) 6]3 3+ to form an “intrusion” ion pair.

Fe-Co-B amorphous alloy powder by chemical reduction

Fine boride powders, prepared by reactions between sodium or potassium borohydride and aqueous (or alcoholic) solutions of transition metal salts have long been known to be good catalysts for hydrogenation reactions. New interest around them has recently grown, because they were found to exhibit amorphous structure. Classical chemical reactions may thus offer a simple route to prepare amorphous metal powders, paralleling more sophisticated methods so far used to reach the same goal. To explore the potential of these reactions, we considered the system Fe-Co-B with the aim of examining the characteristics of the product obtained in the easiest way and without any particular precautions. The structure of the amorphous alloy appears to be different from that of materials with a similar Me/B ratio prepared via melt spinning.

Neutron diffraction study of aqueous transition metal salt solutions by isomorphic substitution

Experiments were initially carried out on 4.3 mol dm–3 MCl2(M = Ni or Mn) and 3.8 mol dm–3 M(ClO4)2(M = Ni or Cu) heavy-water solutions to test the method of isomorphic substitution and see whether Ni, Mn, Cu are suitable isomorphs. The results obtained for chloride solutions are compared with previous results obtained by the technique of isotopic substitution. Good agreement is found between the two techniques; the cation–oxygen and cation–deuterium distances are 2.09±0.02 and 2.69±0.02 Å, respectively. The influence of the different-sized Mn2+ and Ni2+ ions on the results is discussed.

Ligand field stabilization in molten salts: Spectrochemical and nephelauxetic series

Solutions of transition-metal salts in molten alkali salts of the same anion often exhibit different colours from those of the solute or the solid solution. If the intensity is taken into account, one has some indication of the co-ordination of the transition metal ion and might assume complexes to be formed.The examination of the absorption spectra is more informative in that the relative positions of bands and their extinction coefficients yield co-ordination types, whilst their actual energies can yield two parameters Δ and β which characterize (approximately) the electrostatic and covalent interactions respectively.Colours and spectra of several transition metal ions in melts of Br−, Cl−, F−, SO42−, NO3−, CNS− and CN− are reviewed and analysed. The spectrochemical (Δ) and nephelauxetic (β) series of ligands closely resemble those accepted for solid and aqueous systems.