Thermodynamic study of Fe2O3-Fe2(SO4)3 equilibrium using an oxyanionic electrolyte (Na2SO4-I)

The emf of the cell, Pt, Ar + O₂ + SO₂ + SO₃/Na₂SO₄-I/Fe₂O₂ + Fe₂(SO₄)₃, Pt, has been measured in the temperature range 800 to 1000 K, using a gas mixture of known input composition as the reference electrode. The equilibrium composition of the reference gas at the measuring temperatures was computed using the thermodynamic data on the gaseous species reported in the literature. A mixture of ferric oxide and sulfate was kept in a closed system to ensure establishment of equilibrium partial pressure at the electrode. The cell was designed to avoid physical contact between Fe₂(SO₄)₃ and Na₂SO₄ electrolyte. Uncertainties arising from the formation of sulfate solid solution were thus eliminated. The Gibbs’ energy of formation of ferric sulfate calculated from the emf is discussed in comparison with data reported in the literature. There is no evidence for the formation of oxysulfates in the Fe-S-0 system. Based on the results obtained in the present study for Fe₂(SO₄)₃ and literature data for other phases, chemical potential diagrams have been constructed for the Fe-S-O system at 900 and 1100 K.     

Cu（OH）2-CuSO4-H2O系热力学平衡研究

根据热力学平衡原理,绘得Cu（OH）₂-CuSO₄-H₂O体系在298.15 K条件下的平衡pc-pH图。pc-pH图描述了不同铜离子的平衡浓度与pH值关系:pH值在3.49～4.76时,CuSO₄的溶解度最小;pH值在7.32～10.68时,Cu（OH）₂的溶解度最小。同时查明了Cu（OH）₂和CuSO₄在水中共同存在时对溶解度相互影响的规律。研究结果可为含铜废液的处理及铜的回收利用提供理论依据。     

Water and solute activities in the aqueous H2SO4 -(NH4)2SO4 solutions

The activities of water in H₂SO₄-(NH₄)₂SO₄-H₂O solutions, the concentrations of which ranged from 0.1 to 4.0 mol kg_-1 H₂SO₄ and 0.1 to 5.0 mol kg_-1 (NH₄)₂SO₄, were determined by an isopiestic method at 298 K. The experimentally determined water activities showed considerable deviation from the Zdanovskii rule. The activities of water were not in agreement with those calculated from the Robinson-Bower equation, even though the formation of sulfato-complexes of NH₄(I) and the dissociation of sulfuric acid were taken into consideration. The behavior of H₂SO₄-(NH4)₂SO₄ solu-tions is quite different from other systems. Water activities of aqueous solutions of H₂SO₄-Li₂SO₄ and H₂SO₄-Na₂SO₄ can be calculated from the Robinson-Bower equation with satisfactory accuracy. The interesting behavior of (NH₄)₂SO₄ can be attributed to the water structure-breaking property of NH₄ ⁺ ions. An additivity equation for estimating the water activity of aqueous H₂SO₄ solutions con-taining (NH₄)₂SO₄ was proposed by considering the contributing effects of solutes on the structure of water. The proposed equation satisfactorily described the solution system under investigation. The mean activity coefficients of H₂SO₄ and (NH₄)₂SO₄ in the solution system, H₂SO₄-(NH₄)₂SO₄-H₂O, at 298 K, were calculated by the McKay-Perring method using the water activities experimentally determined. It is believed that the calculated values for concentrated solutions of more than one sol-ute are sufficiently accurate since the mean activity coefficients of H₂SO₄ agree with the values measured by the emf method.     

H_2O_2-Fe_2(SO_4)_3-H_2SO_4体系中辉铜矿的浸取研究

以H_2O_2和Fe_2(SO_4)_3为氧化剂、NaCl为助浸剂,在H_2SO_4溶液中浸出辉铜矿中的铜。结果表明,在反应温度85℃,反应时间180 min,H_2O_2、Fe_2(SO_4)_3、NaCl、H_2SO_4浓度分别为0.2、0.25、0.5、0.5mol/L的条件下,铜浸出率可达94.33%。采用XRD和EDS等手段对不同反应时间浸出残渣进行了表征与分析,初步揭示了辉铜矿浸取反应历程。     

Tl2SO4的研制

采用硫酸溶解、自然重结晶方法制备Tl2SO4。     

Calculation of equilibrium species for the aqueous solution systems of UO2SO4−U(SO4)2−H2SO4−HF and UO2Cl2−UCl4−HCl−HF at 298 K

Speciation models for aqueous solutions of UO₂SO₄−U(SO₄)₂−H₂SO₄−HF and UO₂Cl₂−UCl₄−HCl−HF were proposed based on chemical reaction equilibria, mass balances, charge balance, and stoichiometry of UF₄(s). The equilibrium concentrations of uranium and fluoride species in these solutions were calculated at 298 K, and are of relevance to the electrolytic reduction of U(VI), followed by the precipitation of UF₄(s). In these calculations, the reduction ratios of U(VI) were set at 25, 50, 75, and 100 pct. In the sulfate system the stable domains of U⁴⁺, U(SO₄) _n ⁴⁻²ⁿ , UF _n ⁴⁻ⁿ , and UF₄(s) as U(IV) species and UO ₂ ²⁺ , UO₂(SO₄) _n ²⁻²ⁿ , and UO₂F _n ²⁻ⁿ , as U(VI) species are strongly dependent on theC _T(F)/C _T(U(IV)) value. On the other hand, the stable domains of U⁴⁺ UCl³⁺, UF _n ^/4−n , and UF₄(s) as U(IV) species and UO ₂ ²⁺ , UO₂Cl⁺, and UO₂F _n ²⁻ⁿ as U(VI) species are also strongly affected by theC _T(F)/C _T(U(IV)) ratio in the chloride system. The initiation and precipitation of UF₄(s) in both the sulfate and chloride systems are a function of the reduction ratio of U(VI). The higher the reduction ratio, the lower theC _T(F)/C _T(U(IV)) values required. Compared to the chloride system, UF₄(s) precipitation in the sulfate system starts at a lower value ofC _T(F)/C _T(U(IV)). The addition of an excess amount of HF does not cause the dissolution of UF₄(s) precipitates because HF is a weak acid. KOJI SATO, formerly Graduate Student, Department of Metallurgy, Kyoto University, Kyoto, Japan     

The morphology and thermal stability of the Cu−Cu2S eutectic system

A study has been made of the morphology of unidirectionally solidified and as-cast Cu?Cu₂S eutectic alloys. The growth morphology of the eutectic is rod-like, consisting of rods of Cu₂S which are circular in cross-section in a copper matrix. Following solidification, the Cu₂S rods neck down, pinch off, and spheroidize in a sequence which has previously been termed “ovulation”. The spheroids subsequently coarsen rapidly by a process which is controlled by the volume diffusion of sulfur in copper.     

Thermodynamic stability of kΒ-alumina

The activity of K₂O in a mixture of α-alumina and KΒ-alumina has been determined using the solid state galvanic cell: ' Ta, Bi-5 mol pct K // α-alumina + KΒ-alumina // In + In₂O₃, Ta in the temperature range 600 to 1000 K. The cell is written such that the right hand electrode is positive. The solid electrolyte consisted of a dispersion of a-alumina (~15 vol pct) in a matrix of KΒ-alumina. The emf of the cell was found to be reversible and to vary linearly with tem-perature. From the emf and auxiliary data on In₂O₃ and K₂O from the literature, the activity of K₂O in the two-phase mixture is obtained as log a_{K 2}O = 2.368 -20,850/T(K) (±0.015) The standard free energy of formation of KΒ-alumina from component oxides is given by K₂O (s) + 9.5 α-Al₂O₃ (s) → K₂O.9.5A1₂O₃ (s) δG‡ = -398,920 + 45.01 T(K) (±1000) J mol^-1     

Thermodynamic properties of SnSb2Te4 ternary compounds

The Gibbs free energy, enthalpy, and entropy of formation for tin monotelluride from its solid compounds and for the ternary compound SnSb₂Te₄ from SnTe and Sb₂Te₃ are determined by measuring the emf of galvanic cells. The thermodynamic functions of ternary compound formation from pure components (solid tin, antimony, and tellurium) are calculated. The enthalpy of formation for tin monotelluride is in good agreement with the results of calorimetric measurements.     

SO2-H2SO4体系中锌浸渣还原浸出锌和铟

以锌浸出渣为对象,研究了在硫酸—二氧化硫体系还原浸出锌浸渣过程中反应温度、转速、液固比、初始硫酸浓度、SO2分压对锌和铟浸出行为及浸出率的影响。结果表明:采用SO2对锌浸渣进行还原浸出能够大幅提高锌和铟的浸出率,在SO2-H2SO4体系下锌浸渣还原过程中的锌和铟的浸出行为及动力学特性符合二级反应方程,浸出过程受到化学反应控制,表观活化能分别为21.72和39.16kJ/mol,提高温度能够显著提高锌和铟的浸出速率,提高液固比和初始硫酸浓度对锌和铟浸出速率影响较小,在一定范围内提高二氧化硫分压对锌和铟浸出速率影响较为显著。在反应温度105℃、转速500r/min、液固比8、初始硫酸浓度120g/L、SO2分压200kPa的条件下反应150min,锌浸出率达到96%以上、铟浸出率达到95%以上。     

Activities of water and solutes in the solution system H2SO4−Cr2(SO4)3−H2O

The activities of water in the solution systems of Cr₂(SO₄)₃−H₂O and H₂SO₄−Cr₂(SO₄)₃−H₂O were determined at 298 K by an isopiestic method. Properties of the green and violet isomers of Cr₂(SO₄)₃ were considered separately. The activities of water in aqueous solutions containing violet Cr₂(SO₄)₃ alone are considerably smaller than those of the green isomer. The water activities of aqueous H₂SO₄ solutions containing the violet isomer of Cr₂(SO₄)₃ satisfactorily obey the Zdanovskii rule, while those of the green isomer show an upward deviation from the Zdanovskii linearity. The activities of water in these solution systems were also calculated, using the Robinson-Bower empirical equation, and showed satisfactory agreement with the calculated values, whether the formation of the sulfato-complex, CrSO ₄ ⁺ , and the dissociation of H₂SO₄ were taken into consideration or not. The mean activity coefficients of H₂SO₄ and Cr₂(SO₄)₃, for the solution systems studied in this work, were calculated by applying the McKay-Perring method and its modified form, using the measured water activity data of these solution systems. The concentration dependencies of the mean activity coefficients of H₂SO₄ and Cr₂(SO₄)₃ in the solutions containing the green isomer are quite different from those of the violet isomer. Particularly, it was found that the activity values of water and solutes in the solution system of H₂SO₄-violet Cr₂(SO₄)₃−H₂O are similar to those of the solution system of H₂SO₄−Fe₂(SO₄)₃−H₂O. formerly Graduate Student with Kyoto University     

Thermodynamic and application study of complicated extraction system Ce(IV)–HF–H3BO3–H2SO4 using Cyanex 923

This article aims to reduce the environmental pollution while maximizing the recovery of REEs as well as associate resource-fluorine (F) from bastnaesite. This paper investigates the extraction equilibrium process and mechanism of Ce(IV)–HF–H₃BO₃–H₂SO₄ system using Cyanex 923. Extraction equilibrium process of different systems, including HF–H₂SO₄, H₃BO₃–HF–H₂SO₄, and Ce(IV)–HF–H₂SO₄, were studied in detail and the corresponding extraction mechanisms were also determined. It is noteworthy that a synergistic effect between B–F and an antagonistic effect between Ce(IV)–F were discovered first in the extraction process by Cyanex 923. Besides, H₃BO₃ is found to be able to promote the extraction of F in quantitation by Cyanex 923. FTIR and ¹¹B and ¹⁹F NMR were adopted to characterize the different loaded organic phase. Based on these results, the extraction mechanism of complicated system Ce(IV)-HF-H₃BO₃–H₂SO₄ was further determined. Besides, the effect of H₃BO₃ on the extraction and stripping of Ce(IV) in complicated system was studied. Moreover, it shows that the addition of H₃BO₃ has nothing to do with the purity of obtained CeF₃ particle from bastneasite liquor in the practical system. Adding H₃BO₃ into bastnaesite leach liquor, on the one hand, will be beneficial for the recovery yield of Ce and F. On the other hand, it can avoid from environmental pollution caused by emission of F-containing waste water as well as reducing the waste residue.     

The ion-association-interaction approach as applied to aqueous H2SO4-Al2(SO4)3-MgSO4 solutions at 250 °C

A hybrid ion-association-interaction approach is implemented to describe the chemistry and thermodynamics of aqueous H₂SO₄-Al₂(SO₄)₃-MgSO₄ solutions at 250 °C. These solutions are relevant to the sulfuric acid pressure leaching of nickeliferous laterites. Strong complexes in solution are handled via the ion-association approach. Nonidealities, including weak ion pair formations, are treated through the Pitzer ion-interaction theory. The existing complexes in solution and the Pitzer ion-interaction parameters were identified through processing solubility data in the binary (H₂SO₄-Al₂(SO₄)₃ and H₂SO₄-MgSO₄) as well as the ternary (H₂SO₄-Al₂(SO₄)₃-MgSO₄) electrolyte solutions at or near 250 °C. The existing aqueous aluminum-bearing species identified were Al³⁺, Al(SO₄)⁺, and Al₂(SO₄) ₃ ⁰ , with Al₂(SO₄) ₃ ⁰ as the dominant species at moderate to high H₂SO₄ concentrations. The existing aqueous magnesium-bearing species found were Mg²⁺ and MgSO ₄ ⁰ , with Mg²⁺ being dominant except at low concentrations of H₂SO₄. The dominant species identified for Al and Mg explain why a higher H₂SO₄ concentration in solution is required during the processing of high-magnesium laterites.