Physicochemical modeling of precipitating and dissolving of gypsum in chloride solutions

Physicochemical modeling is used to study the isolation of sulfate ions as α (β)-CaSO₄ · 2H₂O from aqueous solutions. The equilibrium compositions of liquid, solid, and gas phases of the NA₂SO₄-CaCl₂-CO₂-H₂O system are calculated at 25°C, CO₂ partial pressures of 10^−1.53 kPa, CaCl₂/Na₂SO₄ molar ratios of 0.2–3.0, and CaCl₂ concentrations from 0.01 to 0.15 mol/kgH₂O. The Gibbs energies of formation for α(β)-gypsum were determined from experimental solubility data on the α(β)-gypsum-air-water system by solving the inverse problem of physicochemical modeling. The data obtained are ΔG° _f298 (α-CaSO₄ · 2H₂O) = −1796.446 kJ/mol and G° _f298 (β-CaSO₄ · 2H₂)) = −1797.317 kJ/mol. Published in Russian in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 5, pp. 889–894. This article was translated by the authors.     

Complex Formation on the Surface of Tungsten on Its Chlorination in DMF Medium

IR spectroscopy and chromato-mass spectrometry were used to investigate the surface layer of tungsten after its chlorination in a medium of DMF containing water. The mechanism of this process is similar to that of the previously described chlorination of rhenium and molybdenum and is determined by the participation of a complex formed in the DMF-H₂O-Cl₂ system.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 436–440.Original Russian Text Copyright © 2005 by Trifonova, Mukhanova, Stepanov, N. Drobot, Krenev, D. Drobot.     

Reduction of Metallurgical Wastes in an RF Thermal Plasma Reactor

Recovery of metals from iron and zinc oxides, as well as from zinc-containing metallurgical wastes, such as flue dust from the Siemens–Martin process and sludge from hot galvanizing, has been studied in an rf thermal plasma reactor under reducing conditions. The product composition was estimated by thermodynamic calculations based on the minimization of the Gibbs free enthalpy. Effects of the plate power of rf generator and the feed rate of powder on the chemical and phase composition of products have been investigated in detail. It has been proved that the rf thermal plasma treatment makes possible to produce unstable species in thermodynamic terms: metallic zinc was gained in the reaction of ZnO and hydrogen. The gradient cooling along the plasma reactor led to the segregation of the iron and zinc compounds. Valuable products were made from the particular wastes by a single step thermal plasma processing.     

Physicochemical simulation and experimental study of interactions in the Si-Al-Ca-Mg-Fe-Na-Cr-Cl-H-O system

The interactions in the SiO₂-Al₂O₃-CaO-MgO-Fe₂O₃-FeO-Na₂O-Cr₂O₃-CaCl₂-HCl-H₂O system were studied by physicochemical simulation methods. Conditions for the most complete extraction of chromium into hydrochloric acid solutions were estimated. The equilibrium compositions of reaction products were calculated. The effect of calcium chloride on the solubility of chromium-containing minerals in hydrochloric acid was determined.     

The deformation of a half-space with a gradient elastic coating under arbitrary axisymmetric loading

An analytical-numerical method of solving the Neumann boundary-value problem for an elastic half-space with a gradient elastic coating is proposed. The problem is formulated and the construction of the fundamental solution (Green’s function) is described. The method enables a solution of the problem to be obtained for a fairly wide class of types of non-uniformity of the medium, and effects related to the non-uniformity are investigated analytically. A procedure for calculating the displacement, stress and strain fields is described. Particular attention is devoted to analysing the mechanical characteristics in the transition region from the coating to the elastic substrate.     

Physicochemical modeling and experimental study of the interaction in the Si-Al-Ca-Mg-Fe-Na-K-V-Cl-H-O system

Physicochemical modeling is used to study the interaction in the SiO₂-Al₂O₃-CaO-MgO-Fe₃O₄-Na₂O-V₂O₃(V₂O₅)-HCl-H₂O system. The regions of formation of calcium (magnesium, iron) vanadates and various vanadium oxides are determined. The conditions for the most complete extraction of vanadium into hydrochloric acid solutions are estimated. The data obtained can be used to develop the procedure a the extraction of vanadium during the leaching of basalt with hydrochloric acid. Original Russian Text ? N.V. Kochetkova, N.P. Dergacheva, S.V. Fomichev, V.A. Krenev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1205–1211.     

Oxidative dissolution of refractory metals by chlorination in aqueous organic media

Chlorination of rhenium, tungsten, and molybdenum with gaseous chlorine in a dimethylformamide-water medium was studied. The degree to which the metals pass to the solution is higher in the presence of water. The activating effect of water is attributed to the catalytic properties of solutions of HCl in DMF. The activating effect on metal dissolution increases in the sequence W < Mo < Re.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 262–265.Original Russian Text Copyright © 2005 by N. Drobot, Trifonova, Krenev, D. Drobot.     

Interaction of basalt with orthophosphoric acid

Physicochemical modeling is used to study the decomposition of basalt by orthophosphoric acid. The equilibrium compositions of the liquid and solid phases of the Al-Fe-Ca-Mg-Na-Si-P-O-H system are calculated. The effects of the acid concentration and solid-to-liquid ratio on the composition of reaction products and the degrees of extraction of iron, aluminum, magnesium, calcium, sodium, and silicon into solution are determined. Conditions for selective extraction of the components into liquid phase are estimated.     

Simulation of the precipitation of calcium phosphates,sulfates, and carbonates from aqueous solutions of complex composition

The isothermal evaporation of aqueous solutions containing calcium, magnesium, and sodium carbonates, phosphates, sulfates, and chlorides was studied by physiochemical simulation methods. The equilibrium composition of the Ca(HCO₃)₂-Mg(HCO)₂-H₃PO₄-H₂SO₄-NaCl-CO₂-H₂O system was calculated for T = 25°C, pCO₂ = 10^?1 ? 10³ Pa, pH 7.7–9.4, solution concentration factors of 1–10, H₂SO₄ concentrations of 10^?4?9 × 10^?4 mol/(kg H₂O), an H₃PO₄ concentration of 2 × 10^?5 mol/(kg H₂O), and a NaCl concentration of 10^?3 mol/(kg H₂O). Conditions were determined for calcium precipitation as calcite, dolomite, gypsum, and hydroxylapatite. The results of simulation were used in the development of commercial-scale methods for stabilizing cooling solutions in circulating water supply systems.