Determination of the Distribution of Cupric Chloro-Complexes in Hydrochloric Acid Solutions at 298 K

The distribution of metal-chloro complexes in hydrochloric acid solutions is a fundamental aspect of anion exchange reactions that allows ultrahigh purification during hydrometallurgical processes. However, these exchange reactions are not yet understood in detail. To clarify and improve anion exchange separation so as to obtain a more sophisticated purification process, it is necessary to accurately determine the distribution of metal-chloro complexes. In the present work, cupric-chloro complexes were investigated because copper is one of the most important base metals in modern society. The absorption spectra of solutions of these complexes were acquired at 298 K and analyzed by multivariate curve resolution–alternating least squares method (MCR–ALS), a factor analysis technique widely used in chemometrics. The resulting cupric-chloro complex distributions were fitted with a thermodynamic model using appropriate activity coefficients extended to the concentrated solutions. These calculations employed a modified Debye–Hückel model because the distributions acquired through the model-free MCR–ALS analysis were less meaningful, both physically and chemically. It was concluded that five [Cu^IICl _n ]^2?n species, where n = 0–4, are present in the hydrochloric acid solutions. In addition, cumulative formation constants and pure molar attenuation coefficients were obtained.     

Determination of structures of cobalt(II)-chloro complexes in hydrochloric acid solutions by X-ray absorption spectroscopy at 298 K

The anion exchange reaction is fundamental to the adsorption and desorption of a specific species from a solution phase to an extracting phase, and it is widely used for separation and waste fluid treatment in industrial fields. However, the details of the anion exchange reaction are poorly understood. Quantitative thermodynamic analysis needs a precise solution condition before and after the exchange reaction. Identification of species adsorbed on the anion exchanger is also necessary because there are multiple species in the solution phase in general. Cobalt is a base metal that is widely used in modern society. One of the authors determined the distribution of cobalt-chloro complexes in hydrochloric acid solutions. It is necessary to know what species are adsorbed on anion exchangers for the thermodynamic analysis of the anion exchange reaction. The comparison in structures between the species in the solution phase and adsorbed on anion exchangers reveals what species are adsorbed. Therefore, the determination of the structures of cobalt-chloro complexes in the solution phase is the next step for quantitative analysis. X-ray absorption spectroscopy (XAS) was used for the structure analysis. Factor analysis can decompose extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectra consisting of multiple species into individual spectra of single species using the distribution determined using UV-Vis absorption spectra. Fitting EXAFS theoretical models to the decomposed individual spectra determined the structures of three cobalt-chloro complexes: an octahedron of [Co^II(H₂O)₆]²⁺, a distorted octahedron of [Co^II(H₂O)₅Cl]⁺, and a tetrahedron of [Co^IICl₄]^2?. The XANES spectra showed us that the Cl ligand in [Co^II(H₂O)₅Cl]⁺ was attracted to the center atom of Co^II by an electrostatic force, and the bonding system between Cl ligands and Co^II in [Co^IICl₄]^2? involved covalency.

     

Ion-exchange selectivities of amorphous and anatase-types hydrous titanium dioxides and the possible separation of bivalent transition metal ions

Summary Amorphous and anatase-type hydrous titanium dioxides showed typical amphoteric ion-exchange properties. The ion-exchange selectivity for bivalent transition metal ions was studied as a function of both pH and metal ion concentration in ammonium nitrate media. The selectivity series was Co<Ni<Mn<Zn<Cd<Cu for the amorphous and Ni<Co<Mn<Zn<Cd<Cu for the anatase-type material. The separation factor on the anatase-type material is larger than on the amorphous material. Effective group separation of Co–Ni and Zn–Cd–Cu could be achieved on an ion-exchange column containing the anatase-type hydrous titanium dioxide.Part XXIV in a series on synthetic inorganic ion-exchange materials.     

Complex Cauchy Problems with Intersecting Singularities

We consider linear Cauchy problems of order two in a complex domain. We assume that the initial values have singularities along a family of hypersurfaces, which cross pairwise transversally along a single intersection. We study the propagation of the singularities of the solution. We show that the solution may have anomalous singularities, and study the monodromy of the solution.     

Irregularities of semilinear hyperbolic equations

We consider local solvability of semilinear hyperbolic Cauchy problems for Gevrey functions. To obtain a general result, we define the notion of irregularities, and we give a criterion for the local solvability. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of structures of cupric-chloro complexes in hydrochloric acid solutions by UV-Vis and X-ray absorption spectroscopy

Structural Chemistry - Ultrahigh-purity metals are indispensable to understanding the nature of materials, but the purity of contemporary metals is insufficient for determining their intrinsic...     

Growth of high-quality ZnO single crystals by seeded CVT using the newly designed ampoule

The high-quality ZnO single crystals were grown by seeded chemical vapor transport (CVT) in a newly designed ampoule using carbon as a transport agent. The well-faceted crystal of about 5×5×5 mm³ can be grown reproducibly. Secondary ion mass spectroscopy (SIMS) analysis, X-ray rocking curve (XRC) and photoluminescence (PL) measurements demonstrate that the grown single crystal is of high purity and high crystallinity.     

Growth of ZnO crystal by self-flux method using Zn solvent

Zinc oxide (ZnO) single crystal was grown, for the first time, by the self-flux method using a high-purity zinc solvent saturated with oxygen. ZnO crystals were successfully grown in the solvent by moving a growing crystal slowly, at about 17 mm/day along a temperature gradient (1.5 °C/mm) in a furnace, from 1050 to 500 °C. Hexagonal single crystals 1–3 mm in length and 0.5–1 mm in thickness were obtained. Energy-dispersive X-ray diffraction, secondary ion mass spectrometry, and photoluminescence confirmed that the purity and crystallinity of the ZnO crystals grown in this work were high.     

Determination of the Distribution of Cobalt-Chloro Complexes in Hydrochloric Acid Solutions at 298 K

Knowledge of the distribution of metal-chloro complexes in hydrochloric acid solutions is fundamental for understanding the anion-exchange reaction. Anion-exchange separation allows ultrahigh purification during hydrometallurgical processes. However, at present the exchange reactions are not understood in detail. A more sophisticated purification needs improvement of the anion-exchange separation process. The process is based upon anion-exchange reactions and the distribution of metal-chloro complexes. The present work deals with cobalt-chloro complexes which exhibit a beautiful deep blue color in a concentrated hydrochloric acid solution. The intensity of the absorption attributed to the deep blue color is so strong that it is hard to obtain meaningful results by factor analysis. Another absorption band was chosen to be used in factor analysis and the attempt was successful. The number of cobalt-chloro complexes in hydrochloric acid solutions was determined to be three, and the cumulative formation constants were fitted to absorption spectra decomposed by factor analysis. During the optimization of the cumulative formation constants, a modified Debye–Hückel model for estimation of the activity coefficients of \(\hbox {Cl}^{-}\) was used. It was found that there are three cobalt complexes \([\hbox {Co}^{\mathrm{II}}(\hbox {H}_{2}\hbox {O})_{6}]^{2+}\), \([\hbox {Co}^{\mathrm{II}}\hbox {Cl}(\hbox {H}_{2}\hbox {O})_{5}]^{+}\), and \([\hbox {Co}^{\mathrm{II}}\hbox {Cl}_{4}]^{2-}\), and the two cumulative formation constants were optimized such that \(\log _{10}\beta _{1} = -\,0.861\) and \(\log _{10}\beta _{4} = -\,7.40\). The geometries of the complexes are proposed by assignment of absorption bands using ligand field theory. A qualitative assessment of the relationship between the acquired distribution of cobalt-chloro complexes and the adsorption function of cobalt species from hydrochloric acid solutions to anion-exchange resin was made.     

Microdifferential equations with non-involutory factors

For some microdifferential equations with variable characteristics, we show that the singularities of the solutions do not propagate toward some directions, although those directions are characteristic.