Solubilities of salts in the ternary systems NaCl + CaCl<Subscript>2</Subscript> + H<Subscript>2</Subscript>O and KCl + CaCl<Subscript>2</Subscript> + H<Subscript>2</Subscript>O at 75°C

The solubility in the NaCl-CaCl₂-H₂O and KCl-CaCl₂-H₂O systems were determined at 75°C and the phase diagrams and the diagram of physicochemical property vs composition were plotted. One invariant point, two univariant curves, and two crystallization zones, corresponding to potassium chloride, dihydrate (CaCl₂ · 2H₂O) showed up in the phase diagrams of the ternary systems. The mixing parameters θ_{M, Ca} and Ψ_{M, Ca, Cl} (M = Na or K) and equilibrium constant K _sp were evaluated in NaCl-CaCl₂-H₂O and KCl-CaCl₂-H₂O systems by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl, KCl, and CaCl₂ β⁽⁰⁾, β⁽¹⁾, β⁽²⁾, and C ^Φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.     

Solubility in the Na,Ca∥CO<Subscript>3</Subscript>,HCO<Subscript>3</Subscript>–H<Subscript>2</Subscript>O system at 25°C

Solubility in the Na,Ca∥CO₃,HCO₃–H₂O system is studied; its phase diagram at 25°C is plotted.     

Solubility in the ternary system LiCl + MgCl<Subscript>2</Subscript> + H<Subscript>2</Subscript>O at 60 and 75°C

The solubility of ternary system of lithium, magnesium and chloride and refractive indexes have been determined at 60 and 75°C, respectively. Using the experimental results, the phase diagrams of the ternary system were plotted. The single-salt Pitzer parameters of LiCl and MgCl₂ β⁽⁰⁾, β⁽¹⁾ and C ^ϕ were calculated by using the equations reported by Li Y-H and de Lima at different temperatures, respectively. On the basis of Pitzer ion-interaction model and solubility product equation for mixed electrolytes, the mixing parameters θ_{Li, Mg}, Ψ_{Li, Mg, Cl} and equilibrium constant K _sp were evaluated in this system, which were not reported in literature. A complete phase diagram of the ternary system was predicted at 60 and 75°C. The prediction of solubilities in ternary system was then demonstrated. The calculated solubilities agreed well with the experimental values.     

Formation of nanocrystals in the ZrO<Subscript>2</Subscript>–H<Subscript>2</Subscript>O system

Formation of zirconia nanocrystals in the course of thermal treatment of an X-ray amorphous zirconium oxyhydroxide was studied. It was shown that the formation of tetragonal and monoclinic polymorphs of ZrO₂ in the temperature range from 500 to 700°C occurs owing to dehydration and crystallization of amorphous hydroxide. An increase of the temperature up to 800°C and higher activates mass transfer processes and, as a result, activates the nanoparticle growth and increases the fraction of the phase based on monoclinic modification of ZrO₂ due to mass transfer from the nanoparticles with the non-equilibrium tetragonal structure. Herewith, formed ZrO₂ nanocrystals with monoclinic structure have a broad size distribution of crystallites, and the average crystallite size after thermal treatment at 1200°C for 20 min is about 42 nm.     

Solid-Liquid Equilibria in the Quaternary Systems KCl–MgCl<Subscript>2</Subscript>–SrCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O and NaCl–KCl–SrCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O at 348 K

Solid-liquid equilibria in the quaternary systems KCl–MgCl₂–SrCl₂–H₂O and NaCl–KCl–SrCl₂–H₂O at 348 K were measured by the isothermal solution saturation method. The composition of the equilibrium solid phase, solubilities of salts, and densities of saturated solution in the two systems were determined. Phase diagrams, water content diagrams and solution density diagrams of quaternary systems were plotted according to experimental data. The phase diagram of the quaternary system NaCl–KCl–SrCl₂–H₂O has one invariant point, three univariant curves as the boundary of NaCl, KCl and SrCl₂ · 2H₂O. This phase diagrams were simple co-saturation type without complex salt and solid solution. For the quaternary system KCl–MgCl₂–SrCl₂–H₂O, one complex salt KCl · MgCl₂ · 6H₂O (Car) had been found in this system, consisted of five univariant curves, two invariant points and four crystallization regions of MgCl₂ · 6H₂O (Bis), KCl, SrCl₂ · 2H₂O and KCl · MgCl₂ · 6H₂O. And the densities transformation rules were simply discussed. Simultaneously, the solubilities and densities data in invariant point of the quaternary system NaCl–KCl–SrCl₂–H₂O had been compared with the experimental data of previous researchers.     

Phase formation in the system Zn(VO<Subscript>3</Subscript>)<Subscript>2</Subscript>–HCl–VOCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O

The phase and chemical compositions of precipitates formed in the system Zn(VO₃)₂–HCl–VOCl₂–H₂O at pH 1?3, molar ratio V⁴⁺: V⁵⁺ = 0.1?9, and 80°C were studied. It was shown that, within the range 0.4 ≤ V⁴⁺: V⁵⁺ ≤ 9, zinc vanadate with vanadium in a mixed oxidation state forms with the general formula Zn_xV⁴⁺ _yV⁵⁺ _2-yO₅ ? nH₂O (0.005 ≤ x ≤ 0.1, 0.05 ≤ y ≤ 0.3, n = 0.5?1.2). Vanadate Zn_xV₂O₅ ? nH₂O with the maximum tetravalent vanadium content (y = 0.30) was produced within the ratio range V⁴⁺: V⁵⁺ = 1.5?9.0. Investigation of the kinetics of the formation of Zn_xV₂O₅ ? nH₂O at pH 3 determined that tetravalent vanadium ions VO2+ activate the formation of zinc vanadate, and its precipitation is described by a second-order reaction. It was demonstrated that, under hydrothermal conditions at pH 3 and 180°C, zinc decavanadate in the presence of VOCl₂ can be used as a precursor for producing V₃O₇ ? H₂O nanorods 50–100 nm in diameter.     

Phase diagram of the NaCl–MgCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O system at 25–75°C and its application for MgCl<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O purification

The co-saturation line for the solid phases NaCl_(s) and MgCl₂ · 6H₂O_(s) in aqueous solution has been measured by a phase equilibrium at various temperatures. It was found that the Y _b (Y _b = w(NaCl)/(w(NaCl) + w(MgCl₂))) value of the co-saturation line increase with increasing temperature. A new recrystallization approach has been suggested for the purification of MgCl₂ · 6H₂O_(s) containing quite amount of impurity NaCl, i.e., dissolving the crude sample at low temperatures, followed by evaporating and phase separating at high temperatures. Applying the proposed approach a crude MgCl₂ · 6H₂O_(s) sample can be purified to the level of Y _b = 0.17% by only one crystallization process.     

Simulating equilibrium processes in the Ga(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>–H<Subscript>2</Subscript>O–NaOH system

Equilibrium processes in the Ga(NO₃)₃–H₂O–NaOH system are simulated with allowance for the formation of precipitates of various compositions using experimental data from potentiometric titration and theoretical studies. The values of the instability constants are calculated along with the stoichiometric compositions of the resulting compounds. It is found that pH ranges of 1.0 to 4.3 and 12.0 to 14.0 are best for the deposition of gallium chalcogenide films.     

The NaCl–AlCl<Subscript>3</Subscript>–HCl–H<Subscript>2</Subscript>O system at 25°С

Solubility was studied in the system NaCl–AlCl₃–HCl–H₂O at 25°C in the section 28 wt % HCl. The system is of the eutonic type and has an extensive sodium chloride crystallization region. The composition of the eutonic solution is the following, wt %: NaCl, 0.47; AlCl₃ ? 6H₂O, 8.88; HCl, 25.38; and H₂O, 65.27. The lines of saturated solutions were approximated by polynomial equations.     

Phase and extraction equilibria in H<Subscript>2</Subscript>O–sulfonol–HCl (H<Subscript>2</Subscript>SO<Subscript>4</Subscript>) and H<Subscript>2</Subscript>O–sodium dodecyl sulfate–HCl (H<Subscript>2</Subscript>SO<Subscript>4</Subscript>) systems

Solubility isotherms of water–sulfonol–hydrochloric (or sulfuric) acid and water–sodium dodecyl sulfate–hydrochloric acid systems at 75°C and a water–sodium dodecyl sulfate–sulfuric acid system at 50°C are constructed. Regions of two-phase liquid equilibrium suitable for use in extraction are found. Concentration parameters for extraction are determined. The interfacial distribution of a series of metal ions with and without such additional complexing reagents as diantipyrylmethane and diantipyrylheptane is studied.     

Phase equilibria in system LiCl–NaCl–H<Subscript>2</Subscript>O at 308 and 348 K

The solubilities and densities of the solutions in the ternary system LiCl–NaCl–H₂O at 308 and 348 K were determined by the method of isothermal dissolution equilibrium. There are one invariant point, two univariant isotherm dissolution curves, and two crystallization regions corresponding to monohydrate (LiCl · H₂O) and NaCl, respectively. This system at both temperatures belongs to hydrate type I, and neither double salt nor solid solution was found. A comparison of the phase diagram for the ternary system at 273–348 K shows that the area of crystallization region of LiCl · H₂O is decreased with the increasing of temperature, while that of NaCl is increased obviously. The solution density of the ternary system at two temperatures changes regularly with the increasing of LiCl concentration.     

Solubility and Ionic Interaction of the CaF<Subscript>2</Subscript>–CaSO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O System at 298.1 K

Solubility isotherms of the sparingly soluble salts CaF_2(s) and CaSO₄·2H₂O_(s) in their mixed aqueous solutions have been measured at 298.1 K. It was found that the CaF_2(s) solubility decreases with increasing CaSO₄ concentration in the solution and reaches about 1/3 of the CaF_2(s) solubility in pure water in the CaSO₄·2H₂O_(S) saturated solution. A thermodynamic model was developed to predict the CaF_2(s) solubility isotherm in this system, in which the short range interactions of the species in the aqueous solution are represented by ion-association constants reported in literature, and the long range interaction, i.e., the electrostatic term, is represented by the well known Davies equation. The predicted solubility isotherm reasonably agrees with the experimental results. The contributions of the long-range term and the short-range term to the calculated solubility isotherm were investigated. It was concluded that the ionic association combining with the Davies equation is sufficient to represent the excess interaction of the CaF₂ + CaSO₄ aqueous solution at 298.15 K. This model approach could be applicable for other dilute mixed electrolyte systems in which component activity coefficients are lacking and model parameters are difficult to determine.     

Solid–Liquid Metastable Phase Equilibria in the Ternary System (MgCl<Subscript>2</Subscript> + MgSO<Subscript>4</Subscript> + H<Subscript>2</Subscript>O) at 323.15 K

The solubilities and the densities in the aqueous ternary system (MgCl₂ + MgSO₄ + H₂O) at 323.15 K were determined by the isothermal evaporation method. The phase diagram was drawn for this system at 323.15 K. The phase diagram consists of two invariant points, three univariant curves, and three crystallization regions corresponding to bischofite (MgCl₂ · 6H₂O), tetrahydrate (MgSO₄ · 4H₂O) and hexahydrite (MgSO₄ · 6H₂O). Neither double salts nor solid solution was found. Based on the Pitzer and Harvie–Weare (HW) model, the solubility equilibrium constants for the salts were fitted with the solubilities in this research work, and the solubilities of the ternary system at 323.15 K were calculated. Comparisons between the calculated and measured solubilities show that the predicted data agree well with the experimental results.     

Phase equilibria in the NaCl–NaBO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>–KCl quaternary system

The phase diagrams of the ternary systems NaCl–NaBO₂–KCl, NaCl–KCl–Na₂CO₃, and KCl–NaBO₂–Na₂CO₃ and the quaternary system NaCl–NaBO₂–Na₂CO₃–KCl were studied by the calculation–experimental method and differential thermal analysis. Analytical models of phase equilibria were obtained, and the coordinates of ternary eutectics and a quaternary eutectic. It was shown that low-melting eutectic melts can be used as media for synthesizing oxide tungsten bronzes.     

Measurement of mineral solubilities in the ternary systems NaCl−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O and MgCl<Subscript>2</Subscript>−ZnCl<Subscript>2</Subscript>−H<Subscript>2</Subscript>O at 373 K

In this work, the solubilities of the salt minerals and the densities of solution in two ternary systems sodium chloride–zinc chloride–water and magnesium chloride–zinc chloride–water were measured at 373 K using an isothermal solution saturation method. Based on the determined equilibrium solubility data and the corresponding equilibrium solid phase, the phase diagrams and density diagrams of the two systems were plotted. The results show that the two ternary systems are complex and the eutectic points, the univariant solubility curves and the solid crystalline phase regions are shown and discussed. The phase diagram of the ternary system NaCl?ZnCl₂?H₂O at 373 K is constituted of two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to NaCl, ZnCl₂ and 2NaCl · ZnCl₂. And the phase diagram of the ternary system MgCl₂?ZnCl₂?H₂O at 373 K includes two eutectic points, three univariant solubility curves and three solid crystalline phase regions corresponding to MgCl₂ · 6H₂O, MgCl₂ · ZnCl₂ · 5H₂O and ZnCl₂. The experimental results were simply discussed.     

Oxidation of Adamantane with H<Subscript>2</Subscript>O<Subscript>2</Subscript>–CF<Subscript>3</Subscript>COCF<Subscript>3</Subscript> · 1.5 H<Subscript>2</Subscript>O in the Presence of VO(acac)<Subscript>2</Subscript>

The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)₂ to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.     

Crystal structure of Mg pivalate hydrate Mg(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>(Piv)<Subscript>2</Subscript> · 3H<Subscript>2</Subscript>O

Single crystals of Mg pivalate hydrate, Mg(H₂O)₆(Piv)₂ · 3H₂O (HPiv = (CH₃)₃CCOOH) are synthesized and their structure is determined by X-ray diffraction method. The crystals are rhombic: a = 10.917(2) Å, b = 12.625(2) Å, c = 31.394(8) Å, Z = 8, space group Pbca, R ₁ = 0.0525. The Mg atom has octahedral surrounding of the O atoms of water molecules (Mg-O 2.044–2.137 Å). The cationic chains of [Mg(H₂O)₆] _∞ ²⁺ lie in the voids of doubled network anionic layers of [(H₂O)₃(Piv)₂] _∞∞ ^2? . Inside the layer, the pivalate anions alternate with water molecules in the xy plane, being bonded to them by hydrogen bonds. The cationic chains and the anionic layers are united into layered packs by hydrogen bonds between coordinated water molecules and pivalate anions and between coordinated and crystal hydrate water molecules.     

Synthesis of nanopowders and physicochemical properties of ceramic matrices of the LaPO<Subscript>4</Subscript>–YPO<Subscript>4</Subscript>–(H<Subscript>2</Subscript>O) and LaPO<Subscript>4</Subscript>–HoPO<Subscript>4</Subscript>–(H<Subscript>2</Subscript>O) systems

Sol-gel method was used to synthesize nanosize powders in the LaPO₄–YPO₄–(H₂O) and LaPO₄–HoPO₄–(H₂O) systems. Dense ceramic samples with high microhardness (up to 25 GPa) were formed from these powders by sintering at temperatures of up to 1600°C. The isomorphic capacity of the monoclinic LaPO₄ matrix for the second component (yttrium or holmium) simulating radioactive nuclides of the actinide-rare-earth fraction was found to be high. The composites are stable in aqueous solutions, which is indicated by the low concentration of lanthanum and yttrium ions during leaching test (~10^–7 g L^–1). The results obtained in the study can be used to develop new high-efficiency ceramic matrices for solidification of the actinide-rare-earth fraction of liquid wastes formed in processing of the spent nuclear fuel.