Chemical equilibrium studies on the iron(III)-sulfuric acid/β-alkenyl 8 hydroxy-quinoline-xylene system

A thermodynamic equilibrium model is developed for the distribution of iron(III) between phases of the system ferric sulfate-sulfuric acid/β-alkenyl-8-hydroxyquinoline in xylene. Equilibrium data are obtained in the range [Fe]_T (0.01 to 0.20 mol/dm³), pH (0.2 to 2.0), [HR] (0.02 to 0.06 mol/dm³) and temperatureT(298 to 323 K). The best fit of the data from a linear regression results in the following equation: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaO% qaaiGacYgacaGGUbWaaSaaaeaadaWadaqaamaanaaabaGaamOraiaa The regression analysis employs the aqueous phase ionic concentration of [Fe⁺³] and [H⁺], which are obtained by consideration of pertinent aqueous phase species equilibria. This model includes the effects of ionic strength on the aqueous phase equilibrium concentration. The stoichiometry of the given reaction is established using the method of continuous variation. Presence of only one species in the organic phase is also determined by the method of continuous variation. The results indicate that the enthalpy of the reaction and the entropy change are −21.8 kJ/mole and −0.05 J/mole K, respectively.     

Selective separation of copper and nickel by solvent extraction using LIX 984N

Selective separation of copper and nickel from ammoniacal/ammonium carbonate medium was carried out by using LIX 984N diluted with deodourised kerosene. The study of the influence of equilibration time, equilibrium pH, extractant concentration and selective stripping of copper and nickel has been optimized. It was found that both the metal extractions were unaffected by the changes in pH. Nickel extraction equilibrium was reached at a longer contact time than that for copper and nickel extraction depends greatly on the extractant concentration in the organic phase. Co-extraction, ammonia scrubbing and selective stripping of copper and nickel were performed for a solution containing 3 g dm^− 3 each of copper and nickel and 60 g dm^− 3 ammonium carbonate. The extraction and the percentage of stripping for nickel and copper were almost quantitative.     

Solvent extraction equilibria of copper and nickel with SME 529

Distribution equilibria in the extraction of copper and nickel from 1.0 mol/dm³ aqueous ammonium nitrate solution by anti-2-hydroxy-5-nonylacetophenone oxime, the active species of SME 529, in MSB 210 diluent were studied at 30°C. The extraction equilibrium constants for copper and nickel were determined to be 1.9 × 10¹ and 3.2 × 10⁵, respectively. The aqueous solubility of the oxime was also examined, resulting in a measurement of the partition coefficient of the monomeric oxime between the aqueous and organic phases, its dissociation constant in the aqueous phase and its dimerization constant in the organic phase as 2.2 × 10^?4, 0.53 nmol/dm³ and 31 dm³/mol, respectively. It was found that the extraction of copper is decreased by the addition of p-nonylphenol due to adduct formation. The equilibrium constant of the adduct formation between the oxime and p-nonylphenol was determined to be 6.6 dm³/mol. It was observed that nickel is extracted by p-nonylphenol.     

Extraction and Concentration Effect on Dimerization of Copper(II) Caprate

Extraction of copper(II) with capric acid in chloroform was investigated at 25°C and aqueous ionic strength of 0.33 mol dm^–3 (Na₂SO₄). The composition of the complex extracted was determined using the slope analysis method. Copper(II) complex exists as a monomeric species CuL₂.2HL in the lower concentration range of capric acid and a dimeric species (CuL₂.HL)₂ in the higher concentration range, while both monomer and dimer were extracted at a total capric acid concentration of 0.1–0.2 mol dm^–3. Extraction and dimerization constants of the above species were also determined. UV-Visible and FT-IR spectroscopy have also been applied for the study of the ligand and their copper(II) species. Electronic spectrum of the organometallic complexes suggests the octahedral geometry.     

The extraction of nickel from ammoniacal media and its separation from copper,cobalt and zinc using hydroxyoxime extractants I. SME-529

Nickel extraction from ammoniacal media, containing, initially, 0.03 mol dm^?3 of nickel, by 10% v/v Shell metal extractant 529 in MSB 210 or Shellsol A, has been studied as a function of pH, counter anions (nitrate or sulphate), ammonium salt concentration, temperature (10 to 50°C), and the presence of copper, cobalt and zinc. The extraction of copper as a function of pH was studied in the presence of nickel. The pH for maximum nickel extraction decreased from 8.2 to 7.4 as the ammonium sulphate concentration increased from 0.1 to 3.4 mol dm^?3. Nickel extraction was lower from sulphate than from nitrate media and with Shellsol A, and at higher temperature. The enthalpy and entropy of extraction were negative. The presence of copper, cobalt and zinc decreased nickel extraction. Separation factors between copper and nickel are reported as a function of pH and indicate that initial removal of copper is desirable.From a consideration of the equilibrium, the extraction of nickel (with MSB 210 diluent) at 25°C could be expressed by the equation:

$\text{log}\text{D}{}_{\mathrm{<mtext>Ni</mtext>}}\text{= ?9.25 +}\text{log}\text{α}{}_0\text{+ 2}\text{log}\text{(C}{}_{\mathrm{HR}}\text{?2[}\text{Ni}\text{]}{}_{\mathrm{<mtext>org</mtext>}}\text{) + 2}\text{pH}$

where D_Ni represents nickel distribution coefficient, C_HR the total extractant concentration, [Ni]_org the organic nickel concentration (both in mol dm^?3) and α₀, the fraction of uncomplexed nickel in the aqueous phase calculated from the overall stability constants of Ni(NH₃)_i²⁺ complexes and the formation constant of NiSO₄ ion pairs.The limiting slope of ?1 for long D_Ni versus log [NH₃]_free plots indicated an average co-ordination number of 3 for nickel by ammonia in the aqueous phase.The uptake of SO₄^2?, NO₃^? and water by the organic phase was negligible. The uptake of ammonia was dependent upon pH and the ammonia content of the aqueous phase, and was negligible in the absence of metal.     

Determination of the association constant of sulfuric acid

The activities of HC1 and H₂SO₄ in aqueous solutions of HC1-H₂SO₄ and H₂SO₄-HC1O₄, respectively, were measured at 298 K by an electromotive force (emf) method. Using the activity data, the association constant,K*_{H 2SO 4} was calculated as a function of the effective ionic strength of the solution by a method similar to that proposed by Johnson and Pytkowicz. The association constant of H₂SO₄, which corresponds to the reciprocal value of the first ionization constant of H₂SO₄, decreased with an increase in the effective ionic strength and was correlated to the effective ionic strength,I _e (mol dm⁻³), as follows: logK*_{H 2SO 4} = 0.42 - 0.91I_e, 0 I_e1 The mean free activity coefficients of H₂SO₄ were calculated from the association constant of H₂SO₄ and were found to decrease with an increase in the effective ionic strength. Formerly Graduate Student, Department of Metallurgy, Kyoto University.     

Principal processing flowsheet of copper–brass wastes of metallurgical brass production

The process flowsheet of dusty wastes forming during metallurgical brass production with the use of two-stage leaching is proposed. The production solution, which contains the main amount of zinc ions (0.46 mol/L) and a small amount of copper ions (less than 0.02 mol/L) is formed at the first stage during the dust dissolution with the 0.5 mol/L sulfuric acid solution. Copper and zinc are sequentially electrochemically isolated from this solution at the current density of 0.1 A/dm² and 5.0 A/dm², respectively. A dry residue (cake) is subjected to copper–ammonia leaching, due to which copper completely transfers into the solution, while accompanying metals remain undissolved. To recover copper from the formed solution, liquid extraction with the solution of 0.34 mol/L DX-510A in kerosene is applied. Copper ions are recovered from the organic phase by reextraction with the 2.0 mol/L sulfuric acid solution. Cathodic copper is isolated from the sulfuric acid electrolyte at the current density of 1.5–2.0 A/dm². The advantages of the proposed flowsheet are an increase in environmental safety due to the use of recirculation of solutions at all process stages, as well as minimization of wastes of the whole process of processing of dusty metallurgical slime.     

Kinetic study of the dissolution of cuprite in oxyacid solutions

The rates of disproportionation dissolution of three artificial cuprite samples were measured in sulfuric acid and perchloric acid solutions, from which oxygen had been stripped, at different concentrations and temperatures. Samples were prepared by electrolysis, sintering of electro-lytically produced cuprite, and oxidation of hot-rolled copper sheets. The effects of sodium sulfate and sodium perchlorate on the dissolution of cuprite were also examined. Metal copper formed by the disproportionation reaction plays a role as a barrier for further dissolution of cuprite. Apparent activation energies were determined in the temperature range of 293 to 323 K for the initial stage of the disproportionation reaction of cuprites. The values ranged from 14.7 to 24.9 kJ mol^-1 in 0.003 mol dm^-3 sulfuric acid and perchloric acid and from 29.7 to 52.0 kJ mol^-1 in 0.1 mol dm^-3 sulfuric acid and perchloric acid. Judging from the effects of temper-ature, agitation speed, acid concentration, and common salt additions, it is concluded that the adsorption of H⁺ onto the surface site is important in determining the dissolution rate of cuprite in oxyacid solutions. The dissolution behaviors of different cuprite samples were also morpho-logically examined.     

Speciation of the Fe(II)–Fe(III)–H2SO4–H2O system at 25 and 50 °C

This work presents theoretical and experimental results on the speciation of the Fe(II)–Fe(III)–H₂SO₄–H₂O system in concentrated solutions (up to 2.2 m H₂SO₄ and 1.3 m Fe). The aim was to study the chemical equilibria of iron at 25 and 50 °C in synthetic aqueous sulphuric acid solutions that contain dissolved ferric and ferrous ion species. Raman spectroscopy, volumetric titration and conductivity measurements have been carried out in order to study the presence of specific ions and to characterize the ionic equilibrium. A thermochemical equilibrium model incorporating an extended Debye–Hückel relationship was used to calculate the activities of ionic species in solution. Model calculations were compared with experimental results. Model simulations indicate that anions, cations and neutral complexes coexisted in the studied system, where the dominant species were HSO₄⁻, H⁺, Fe²⁺ and FeH(SO₄)₂⁰. This indicated that these solutions showed a high buffer capacity due to the existence of bisulphate ions (HSO₄⁻), which presented the highest concentration. A decrease in the concentration of H⁺ and Fe³⁺ took place with increasing temperature due to the formation of complex species. Standard equilibrium constants for the formation of FeH(SO₄)₂⁰ were obtained in this work: log K_f⁰ = 8.1 ± 0.3 at 25 °C and 10.0 ± 0.3 at 50 °C.     

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol · dm⁻³ FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol · dm⁻³, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe⁻²⁺]² andp _{o 2} exhibiting an activation energy of 51.6 · kJ mol⁻¹. In another path the reaction rate was proportional to [Fe²⁺]², [SO ₄ ^{2 −}], andp _{o 2} with an activation energy of 144.6 kJ · mol⁻¹. A reaction mechanism in which the SO ₄ ^{2 −} ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol · dm⁻³, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² andp _{o 2}, and was also affected by [H⁺] and [SO ₄ ^{2 −}]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).     

Solvent extraction of cadmium from sulfate solution with di-(2-ethylhexyl) phosphoric acid diluted in kerosene

In the present paper, solvent extraction process has been used for extraction of cadmium from sulfate solution using di-(2-ethylhexyl) phosphoric acid (D2EHPA) with 1% isodecanol in kerosene diluent expected from industrial effluents or leaching of ores/secondary materials. Different process parameters such as pH, contact time, extractant concentration, O/A ratio etc. were investigated. Results demonstrated that quantitative extraction of cadmium was feasible from 4.45 mM cadmium feed solution in single stage at equilibrium pH 4.5, time 2 min and O/A ratio 1:1 with 0.15 mM D2EHPA. The extraction mechanism of cadmium from sulfate solution by D2EHPA in kerosene could be represented at equilibrium by Cd²⁺ + 3/2 (H₂A₂)_org ⇔ CdA₂(HA)_org + 2H⁺. The loading capacity of 0.15 mM D2EHPA in sulfate solution was determined to be ∼ 8.9 mM cadmium. The loaded cadmium was effectively stripped using 180 g/L sulfuric acid. The metal or salt could be produced by electrolysis or crystallization from the stripped solution.     

Pressure leaching of copper arsenic-containing mattes with copper sulfate solutions

The topicality is shown to improve the processing technology of complex polymetallic raw material containing a considerable amount of toxic impurities of arsenic and lead. Results on pressure leaching the mattes formed after reduction smelting the dusts of OAO Sredneural’skii Copper Smeltery (SUMZ) by solutions of copper sulfate are discussed. These mattes contain a considerable amount of lead and arsenic. According to the data of X-ray phase analysis of matte samples, phases of sulfides (PbS, PbS ? As₂S₃, Cu₂S, FeS, and (Zn,Fe)S) and arsenides (FeAs₂, Cu₃As, FeAs, and Cu_0.85As_0.15), as well as inclusions of metallic copper, are revealed in them. Optimal parameters of matte leaching by copper sulfate solutions are the temperature of 150–180°C, acidity from 5 to 30 g/dm³, and copper concentration of 14–32 g/dm³. This process made it possible to extract 85% As into the solution, while copper and lead remained in the cake in this case.     

Catalytic-Oxidative Leaching of Low-Grade Complex Zinc Ore by Cu (II) Ions Produced from Copper Ore in Ammonia-Ammonium Sulfate Solution

The catalytic-oxidative leaching of a mixed ore, which consists of low-grade oxide copper ore and oxide zinc ore containing ZnS, was investigated in ammonia-ammonium sulfate solution. The effect of the main parameters, such as mass ratio of copper ore to zinc ore, liquid-to-solid ratio, concentration of lixivant, leaching time, and temperature, was studied. The optimal leaching conditions with a maximum extraction of Cu 92.6?pct and Zn 85.5?pct were determined as follows: the mass ratio of copper ore to zinc ore 4/10?g/g, temperature 323.15?K (50?°C), leaching time 6?hours, stirring speed 500?r/min, liquid-to-solid ratio 3.6/1?cm³/g, concentration of lixivant including ammonia 2.0?mol/dm³, ammonium sulfate 1.0?mol/dm³, and ammonium persulfate 0.3?mol/dm³. It was found that ZnS in the oxide zinc ore could be extracted with Cu(II) ion, which was produced from copper ore and was used as the catalyst in the presence of ammonium persulfate.     

The oxidation of thiosulfates with copper sulfate. Application to an industrial fixing bath

This paper presents the transformation of thiosulfate using Cu(II) salts, such as copper sulfate, at pH between 4 and 5. The nature and kinetics of this process were determined. In the experimental conditions employed, the reaction between thiosulfates and Cu(II) ions produces a precipitate of CuS and the remaining sulfur is oxidized to sulfate, according to the following stoichiometry: 1 mol thiosulfate reacts with 1 mol Cu²⁺ and 3 mol H₂O, generating 1 mol copper(II), 1 mol sulfate and 2 mol H₃O⁺. In the kinetic study, the apparent reaction order was ≈ 0 with respect to H₃O⁺ concentration, in the interval 1.0 · 10^? 4–1.0 · 10^? 5M H₃O⁺; of order 0.4 with respect to Cu²⁺ in the interval 0.21–0.85 g L^? 1 Cu²⁺; and of order 0 with respect to S₂O₃^2? in the interval 0.88–2 g L^?1 S₂O₃^2?. The apparent activation energy was 98 kJ mol^? 1 in the interval 15–40 °C. On the basis of this behavior an empirical mathematical model was established, that fits well with the experimental results. The thiosulfate transformation process using copper(II) sulfate was applied to an industrial fixing bath that proceeded from the photographic industry; after this, the resulting effluent contained less than 10 mg L^? 1 of thiosulfates.     

Effect of suspension potential on the oxidation rate of copper concentrate in a sulfuric acid solution

A chalcopyrite concentrate containing 17 pct pyrite was oxidized in 1 mol/dm³ sulfuric acid solution at 90 °C (363.2 K). The suspension potential (Ptvs SCE, in the presence of Fe³⁺/Fe²⁺) was maintained constant in the range 0.30 to 0.65 V by controlled additions of KMnO₄ solution. The oxidation appeared to be under surface reaction control. The rate constant was nearly independent of total Fe concentration (0.01 to 0.5 mol/dm³), but increased rapidly with a rise in suspension potential until it reached a maximum at 0.40 to 0.43 V, after which there was marked decrease at around 0.45 V. Chalcopyrite in the concentrate was oxidized to form elemental sulfur over the whole of the suspension potential range, whereas the oxidation of pyrite took place only above 0.45 V and yielded sulfate ion. At 0.40 V the apparent activation energy was 47 kJ/mol. An analogy between the potential dependence of the rate and the Tafel correlation for an electrode process is discussed.     

The heat capacities and heat content of molten cerium by levitation calorimetry

A 15 kva, 450 khz radio frequency generator was used to levitate and melt cerium sam-ples ranging in size from 0.4 gms to 1.7 gms. The molten cerium samples were then drop-ped into a copper block calorimeter contained in isothermal surroundings. The cerium data between 1400 K and 1700 K indicated a nonlinear heat content function as described by the equation:H _T -H _298.15 = -0.01255T ² + 75.305T - 32,995.401 J/mol. The correlation coefficient for the curve fitting process was 0.81. The data between 1700 K and 2500 K indicated a linear heat content function as described by the equation:H _T-H _298.15 ={31.616 ± 0.596}(T - 1077) + {38,917.267 ± 575.049} J/mol. The average percent deviation between this and the experimental values was 0.67. Experi-mental heat contents were corrected for convection and radiation heat losses during the fall of the sample from the levitation chamber into the calorimeter. The maximum esti-mated error for the levitation calorimetry work was ±2.5 pct. Formerly Graduate Assistant, Department of Chemical Engineering, Iowa State University Prepared for the Energy Research and Development Administration under Contract No. W-7405-eng-82.     

Extraction equilibrium conditions of beryllium and aluminium from a beryl ore for optimal industrial beryllium compound production

This study examines the extraction of beryllium and aluminium from a Nigerian beryl ore using Cyanex®272 in kerosene from an aqueous sulphate pregnant solution. Parameters such as extractant concentration and equilibrium pH that dictates the extraction yield were studied. Under the following conditions: temperature 27?±?2°C, phase ratio 1?1, about 45.50 and 46.76% of beryllium and aluminium were extracted by 0.15?mol?L^?1 Cyanex®272 concentration within 30?min. However, the extraction yield of beryllium and aluminium was increased to 91.68% and 97.89% at equilibrium pH of 3 and 4, respectively, for beryllium and aluminium at 27?±?2°C. A 0.05?mol?L^?1 H₂SO₄ solution was found to be adequate for the stripping of about 99.00% Be and 95.40% Al from the loaded organic phase. The pure solutions containing metal ions were accordingly beneficiated to obtain beryllium and aluminium compounds of industrial values.     

Spectroscopic and fluorescence properties of Sm~(3+)-doped zincfluorophosphate glasses

Optical absorption and fluorescence spectra of Sm3＋-doped zincfluorophosphate glasses with molar composition of 44P2O5＋17K20＋9Al2O3＋（30-χ）ZnF2＋χSm2O3 （χ=0.01 mol.%, 0.05 mol.%, 0.1 mol.%, 0.5 mol.%, 1.0 mol.%, 2.0 and 3.0 mol.%） referred as PKAZFSm were prepared by melt quenching technique and were characterized through Raman, absorption, emission and decay curve analysis. From the absorption spectra, Judd-Ofelt intensity parameters were determined and were used to predict radiative properties such as transition probabilities （AR, radiative lifetimes （τR）, branching ratios （βR）, effective bandwidths （△λeff） and stimulated emission cross-section （σ（λp）） for the excited 4G5/2 luminescent level. The decay curve for the 4G5/2 level was single exponential for lower concentration and became non-exponential for higher concentrations. The non-exponential nature of the decay curves of the 4G5/2 level increased with increase in Sm3＋ ions concentration accompanied by decrease in lifetime due to energy transfer processes among the Sm3＋ ions. The non-exponential decay curves was well fitted to the generalized Inokuti-Hirayama model for S=6, indicating that the energy transfer among optically active ions was of dipole-dipole interaction. The cross-relaxation mechanism responsible for the quenching of lifetimes and the effect of variation of concentration on the spectroscopic properties were also discussed.     

Substitution Recovery of Gold from Copper-Ethylenediamine-Thiosulfate Leaching Solution with Copper Power

The substitution method of recovering gold from thiosulfate-ethylenediamine (en)-Cu²⁺ leaching solution using copper powder was studied. The effects of reaction time, stirring speed, pH, thiosulfate concentration, en/Cu²⁺ molar ratio, Cu/Au⁺ mass ratio, and temperature on gold recovery were systematically examined. The experimental results showed that reaction time, stirring speed, thiosulfate concentration, en/Cu²⁺ molar ratio, Cu/Au⁺ mass ratio, and temperature have a significant influence on the recovery rate of gold, whereas the pH has little effect. A high gold recovery rate of 95.38% was achieved in 0.2 mol/L thiosulfate at 40°C after 40 min with a stirring speed of 400 rpm, pH of 11, en/Cu²⁺ molar ratio of 6, and Cu/Au⁺ mass ratio of 150. A kinetic study revealed that the reduction of gold-thiosulfate complex ions (Au(S₂O₃) ₂ ^3- ) on the surface of copper powder follows a first-order kinetics model with an apparent activation energy of 39.82 kJ/mol.     

The scaling of nucleation rates

The homogeneous nucleation rate,J, forT → T _c can be cast into a “corresponding states” form by exploiting scaled expressions for the vapor pressure and for the surface tension, δ. In the vapor-to-liquid case with δ= δ₀[T _c -T], the classical cluster energy of formation /kT = [16π/3] ? ?³ [T _c -1]³/(lnS)² = [x₀/x]², where ? ≡ δ₀/[k ñ^2/3] and ñ is liquid number density. [1] The ?≈ 2 for normal liquids. (A similar approach can be applied to homogeneous liquid to solid nucleation and to heterogeneous nucleation formalisms using appropriate modifications ofσ and ?.^[2]) The above [x₀/x]² is sufficiently tenable that in some cases, one can use it to extract approximate critical temperatures from experimental data.^[3,4] In this work, we point out that expansion cloud chamber data (for nonane, toluene, and water) are in excellent agreement with lnJ ≈ const. -[x₀/x]² [centimeter-gram-second (cgs) units], and that the constant term is well approximated by ln (Γ_c), whereT _c is the inverse thermal wavelength cubed per second atT =T _c . The ln (Γ_c) is ≈ 60 in cgs units (74 in SI units) for most materials. A physical basis for the latter form, which includes the behavior at smalln, the discrete integer behavior ofn, and a configurational entropy term, τ ln (n), is presented.