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.     

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.     

Chemical equilibrium studies on the copper-sulfuric acid-kelex 100-xylene system

A thermodynamic equilibrium model is developed for the distribution of copper between the phases for the system copper-sulfuric acid-xylene-/3-alkenyl 8-hydroxyquinoline. Chemical equilibrium data were obtained for the range of experimental parameters of [Cu] _{aq, i} ^T (0.005 to 0.02 mol/dm³), [S]^T (0.05 to 0.2 mol/dm³), extractant (0.02 to 0.06 mol/dm³), and temperature (20 to 50 ?C). The nonlinear regression analysis best fit model is ln(Dαo/γCusu++) = 3.83 + 642(1/T - 1/308) +2 ln([HR]/[H⁺]γ_H ⁺) whereD is the distribution coefficient, α_o is the reciprocal of the degree of formation of copper ion, and γ refers to activity coefficients of ionic species. The analysis of the data considers the aqueous phase ionic equilibria and a technique to estimate the impurities present in the reagent. The results indicate that the enthalpy of the reaction and the entropy change are -5338 J/mol and 14.5 J/mol · K, respectively. Also, the stoichiometric coefficient of two, determined for the extractant with cupric ion, is in agreement with other investigators.     

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 extraction of hafnium (IV) by some organophosphorus reagents in the presence of two mineral acids

Extraction of hafnium (IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids of constant total acidity 2, 4, 6 and 8 M and c_Hf ? 4 × 10^?4mol l^?1. The organic phase consisted of solutions of various acidic or neutral organophosphorus reagents including di-n-butylphosphoric acid, di-n-amylphosphoric acid, di-n-octylphosphoric acid, n-decylphenylphosphonic acid, tri-n-butylphosphine oxide, tri-n-octylphosphine acid (TOPO), tri-n-phenylphosphine oxide, and tri-n-butylphosphate (TBP); or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. Pronounced synergic extraction of hafnium occurs only with organophosphorus reagents from aqueous phases whose acidity is not lower than 3 M (HClO₄ + HNO₃) or 5 M (HClO₄ + HCl). The synergic effect was not affected markedly by variation of the initial concentration of hafnium in the range 1 × 10^?8 ?4 × 10^?4 mol l^?1, but it decreased with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H⁺ ions. No synergism was observed for the extraction of hafnium from mixtures of perchloric and sulphuric acids. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.     

Solvent extraction of base metals by mixtures of organophosphoric acids and non-chelating oximes

The effect of non-chelating oximes on the extraction of several transition and nontransition metals by solutions of organophosphoric acids (H₂A₂) in xylene has been investigated. Synergistic enhancements of extraction of divalent transition metal ions were found with the oximes of aliphatic aldehydes, the enhancements of extraction increasing in the order VO²⁺ < Mn²⁺ < Mn²⁺ < Co²⁺ < Cu²⁺ < V²⁺ < Ni²⁺. Large synergistic effects were also found for copper(I) and silver(I). Among the divalent non-transition metals studied (Mg, Ca, Zn, Cd, Sn, and Pb), only cadmium showed a synergistic effect. No significant synergism was found for any of the trivalent metal ions studied (Fe, Cr, V, Al, Bi, La, Ce, and Nd). The extracted complexes of copper, cobalt, and nickel were shown to be octahedral in structure, with the compositions Cu(HA₂)₂(oxime)₂, Co(HA₂)₂(oxime)₂, and NiA(HA₂)(oxime)₃, respectively, in which HA₂^? acts as a bidentate ligand. Extraction rates were found to be rapid, even for nickel, and complete stripping of metal-loaded organic phases was effected by contact with 0.5 M mineral acid. Some practical applications, such as the recovery of nickel from acidic leach liquors, are envisaged.     

Extraction of ammonia by commercial copper chelating extractants

The extraction of ammonia by commercially available hydroxyoxime, β-diketone and quinoline sulphonamide extractants in the absence and presence of copper and nickel has been studied as a function of pH, diluent type and metal loading. Ammonia appears to be extracted by hydroxyoximes directly as the species RH·NH₃ and the data suggest that only the monomeric oxime is involved. Nonylphenol, used in the synthesis of the hydroxyoximes, was found to extract ammonia quite strongly and variation in uptake by various hydroxyoximes may be due to a combination of different nonylphenol contents and degree of oxime dimerisation. Metal loading of the organic phases with copper or nickel reduces the ammonia content. While neither the β-diketone reagent LIX 54 nor the sulphonamide reagent LIX 34 extracted ammonia in appreciable quantities in the absence of copper and nickel, copper loading caused a small increase in ammonia content and nickel loading caused a considerable increase in ammonia content with nickel: ammonia ratios suggesting the extraction of a nickel ammine complex.     

Extraction of nickel,cobalt and other metals [Cu,Zn, Fe(III)] with a commercial β-diketone extractant

The extraction of nickel, cobalt, copper and zinc from ammoniacal solutions of ammonium carbonate or ammonium sulphate by solutions of Hostarex DK-16 in kerosene has been investigated as a function of phase contact time, aqueous-phase pH and organicphase reagent concentration. Besides copper, Hostarex DK-16 also partially extracts iron (III) from moderately acidic solutions whereas nickel, cobalt(II), copper and zinc are extracted from neutral or ammoniacal ammonium sulphate and ammonium carbonate solutions. Extraction decreases in the following order of metals: Cu > Co > Ni > Zn. Cobalt(III) is not extracted, but the complex of cobalt(II) with Hostarex DK-16 is slowly oxidized to a cobalt(III) complex which cannot be stripped even when 10 N sulphuric acid is used. Absorption spectra for cobalt complexes with Hostarex DK-16 (purified by preparative thin-layer chromatography) in benzene also suggest oxidation of cobalt(II) to cobalt(III) in the organic phase. Nickel, cobalt(II), zinc and copper can be stripped easily from organic solution with dilute solutions of sulphuric acid. Hostarex DK-16 extracts iron very slowly, nickel moderately rapidly and copper, cobalt(II) and zinc rapidly. Slope analysis and extraction isotherms suggest that the complexes CuR₂, NiR₂ ·HR and CoR₂·HR are present in the organic phase. Nickel can easily be separated from cobalt by extraction with Hosterex DK-16 after oxidation of cobalt in aqueous ammoniacal solution by hydrogen peroxide; however, LIX 64N seems to be a more promising extractant owing to the higher extraction of nickel under analogous conditions and the poorer extraction of zinc in comparison with Hostarex DK-16.     

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.     

Diffusivity of hydrogen in liquid nickel and copper

The diffusivity of hydrogen in liquid nickel was determined from 1468° to 1550°C by a capillary gas-reservoir technique. The diffusion cell was semiinfinite in length and consisted of Specpure nickel in an alumina capillary. An argon and hydrogen gas flow maintained a constant hydrogen potential at the metal/gas interface. A controlled furnace hot zone of length 23 cm was obtained using eight separate windings of Pt-40 pct Rh wire. The temperature profile in this zone was adjusted so that the top of the cell was hotter than the bottom, to eliminate convection. The experiments were terminated by a rapid nonaqueous quench. The diffusion columns were then sectioned and analyzed by vacuum extraction. Diffusivities were calculated using a solution to Fick’s Second Law. At 1468°C,D = 3.17 x 10⁻³ sq cm per sec with σ = ±0.76 × 10⁻³; at 1550°C,D = 3.48 × 10⁻³ sq cm per sec with σ = ±0.54 × 10⁻³. The diffusivity of hydrogen in liquid copper was determined using a shallow melt and analyzing for the total diffusate content; at 1101°C,D = 0.99 x 10⁻³ sq cm per sec with a = ±0.25 × 10⁻³; at 1201°C,D = 1.26 × 10⁻³ sq cm per sec with σ = ±0.16 × 10⁻³. Formerly with the Nuffield Research Group in Extraction Metallurgy at Imperial College, London, England This paper is based upon a thesis submitted by J. H. WRIGHT in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of London.     

Trace detection of Ce3+ by adsorption strip voltammetry at a carbon paste electrode modified with ion imprinted polymers

To develop a convenient method for sensitive and selective determination of Ce3+ in aqueous phase with complicated matrices, a carbon paste electrode(CPE) modified with ion imprinted polymers(IIPs) were fabricated. The polymers were prepared by precipitation polymerization using Ce3+ as template, allyl phenoxyacetate(APA) as monomer, ethylene glycol dimethacrylate(EGDMA) as crosslinker and azobisisobutyronitrile(AIBN) as initiator under the molar ratio of Ce3+, APA and EGDMA as 1:4:40, respectively. Ce~(3+) was detected directly by differential pulse adsorptive stripping voltammetry(DPASV) and its oxidation peak appears at about 0.93 V. All parameters affecting the sensor's response are optimized and a calibration curve is plotted at a linear range of 1.0 × 10~(-6)-1.0 x 10~(-5) mol/L and 1.0×10~(-5)-2.0 × 10~(-4)mol/L with the detection limit of 1.5 × 10~(-7) mol/L. All other rare earth ions have no interference with the determination of Ce~(3+) even at a concentration 500 times higher than that of Ce~(3+).This sensor was successfully applied to determination of Ce~(3+) in two catalyst sample solutions with RSD≤3.3%(n = 5)and recoveries in the range of 99.2%-106.5% at our optimal conditions.     

Correlation between dielectric properties and aqueous oxidation rate for pulverized sphalerites and zinc concentrates

In a previous paper the dielectric properties, including dielectric constant, dielectric loss tangent, and relaxation time, of six particulate sphalerite samples and four zinc flotation concentrates were measured using a packed bed condenser. In the current study, the same particulate samples were ground to an average size of 8.5 μm, and together with the concentrates underwent oxidation in an acidic sulfate solution, containing 100 g/dm³ H₂SO₄, 10 g/dm³ total Fe, and 30 g/dm³ Zn, at a controlled suspension potential of 0.55 V (Ptvs SCE) and at 90 °C (363 K). Under these experimental conditions, the Fe³⁺ concentration and the suspension potential had little effect on the oxidation rate. The oxidation proceeded mainly in the sulfur-forming type. The results were analyzed using a simplified kinetic expression for spherical particles with a logarithmic normal size distribution. It was found that the rate constant varied in proportion to the 0.6th power of the reciprocal of the equivalent parallel resistances for the dense substance and the packed bed. The rate constant also varied in proportion to the reciprocal of the dielectric relaxation time; however, this variation was influenced by the copper content of the samples. Formerly with National Research Institute for Metals     

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.     

Measurement of pH in the vicinity of a cathode during the chloride electrowinning of nickel

An antimony microelectrode was prepared by quenching a molten Sb-Sb₂O₃ mixture (2 pct Sb₂O₃). The local pH in the vicinity of a nickel-plated copper cathode was directly measured using the microelectrode during the chloride electrowinning of nickel for a MCLE (matte chlorine leach electrowinning) process, where nickel metal is electrodeposited with a high current efficiency, 94 to 97 pct, from low-pH baths. The local pH at 328 K was increased by proton consumption during the electrolysis of aqueous electrolytes containing NiCl₂ (1.20 mol dm⁻³) and NaCl (0.43 mol dm⁻³) with the same concentrations as employed for the MCLE process. The difference in pH between the cathode surface and bulk solution increased with increasing cathodic current density. Nickel deposits with a metallic luster were obtained when the difference was not more than 1.2 pH units. The current efficiency was a maximum for electrolysis with a current density of 265 A m⁻² and bulk pH of 1.0 to 1.5; these optimal conditions coincided with those reported for the MCLE process: temperature 328 to 333 K, bulk pH 1.1 to 1.5, and current density 230 to 260 A m⁻². Electrolytes with lower NiCl₂ and NaCl concentrations resulted in a drop in current efficiency.     

Copper diffusion in iron during high-temperature tensile creep

The diffusion of liquid copper in iron from a notched surface has been studied by metallographic, microanalysis, and sessile drop techniques. The diffusivity of copper was found to be 0.59×10^?6 sq cm per sec at 1100°C and 0.97×10^?6 sq cm per sec at 1130°C. The diffusion factor,D ₀ was 0.78×10^?3 sq cm per sec and the activation energy 19.0 kcal per mole. The predominant mode of copper penetration was along grain boundaries, but when larger volumes of copper at the iron surface were used, surface diffusion increased and grain boundary penetration remained constant. The most frequently occurring dihedral angle for liquid copper was 34 deg at 1100° and 1130°C. The liquid copper/austenite interfacial energy was found to be 444 ergs per sq cm between 1100 and 1130°C. From sessile drop measurements, the contact angle was determined as 35 deg at 1100°C and 28 deg at 1130°C, from which values the respective interfacial energies were calculated to be 387 ergs per sq cm and 301 ergs per sq cm.     

Cyclic strain hardening in polycrystalline copper

Polycrystals of pure copper were cyclically deformed, at room temperature under symmetric tension-compression fatigue at constant total strain amplitude control with an approximate constant plastic strain rate of 10⁻⁴. The relationship between the saturation stress amplitude and strain amplitude over a range of plastic strain from 2 × 10⁻⁷ to 10⁻² reveals three regions of cyclic hardening. A quasi-plateau, where the stresses show a slow constant increase, was observed in the intermediate region extending in the plastic strain range γ_pl, of 1.5 × 10⁻⁵ to 7.5 × 10⁻⁴. In this region, persistent slip bands (PSBs) which consist of “ladder” structures, similar to the case of single crystals, were found in the bulk of the fatigued polycrystals. The fatigue limit was found to be Δσ_s/2 = 73 MPa which corresponds to the plastic strain Δϵ_pl/2 = 1.5 × 10⁻⁵ where PSBs do not form.     

Stripping of copper from CYANEX® 301 extract with thiourea–hydrazine–sodium hydroxide solution

The stripping of copper from the organic extract of bis(2,4,4-trimethylpentyl) phosphinodithioic acid, CYANEX® 301, using an aqueous mixture of thiourea, hydrazine and sodium hydroxide has been investigated. The optimal concentrations of the aqueous solution were found to be 1.0 M, 5 × 10^− 2 M and 5.0 M, respectively which led to 95% stripping of copper from CYANEX 301 with concomitant regeneration of the extractant. The characterization of the stripped copper product was done using a combination of microanalyses, cyclic voltammetry and X-ray diffractometry (XRD). The product was made up of two non-stoichiometric copper sulfides, Cu_xS with x = 1.60 and 1.77. Cu_1.60S was the major product. Hydrazine appears to play the role of reducing the disulfide species of CYANEX 301, R₂P(S)S–S(S)PR₂, formed during the extraction step, back into CYANEX 301, whereas thiourea provides a source of sulfur in the formation of the stripping products.     

Nonuniformity of NaOH concentration and effective bubble diameter in CO2 injection into aqueous NaOH solution

Mixed CO₂-N₂ gas was blown into an aqueous NaOH solution through a submerged nozzle of 3 mm ID, and the net absorption rate of CO₂ from the gas bubbles during their ascent was determined. The size distribution and the rising velocity of bubbles were also measured. The enhancement factor was estimated from the reported reaction rate constant as 1.16 to 8.20 at the NaOH concentration from 0.01 to 0.3 mol · dm^-3. It was deduced that NaOH concentration in the plume zone in which gas bubbles ascended was markedly lower than that of the bulk solution when NaOH concentration of the bulk solution was lower than 0.1 mol · dm^-3. The measured size distribution of bubbles had two peaks at approximately 0.15 and 2.3 cm. However, the effective bubble diameter defined as mean diameter based on the amount of absorbed CO₂ was 2.3 cm and it was close to the mean of larger bubbles.     

Activation parameters of high-temperature creep in polycrystalline nickel at ambient and high pressures

Polycrystalline specimens of pure nickel were deformed in uniaxial compression at temperatures of 1000–1550 K, strain rates of 1×10⁻⁵-3×10⁻³s⁻¹ and pressures of 0.1–1500 MPa, in order to determine the activation parameters of high temperature creep. Experiments at 0.1 MPa were conducted in an MTS apparatus with the specimen immersed in a molten heat-treating salt to prevent oxidation. The data show a decreasing power-law stress exponent with decreasing normalized steady-state flow stress (σ/G), approaching the “natural law” value of n=3 at normalized stresses <10⁻⁴. In contrast, the activation energy is constant over our range of temperatures (T/T_m = 0.55−0.90), and is indistinguishable from the activation energy of self-diffusion (284 kJ/mol). High pressure experiments were conducted in a modified piston-cylinder apparatus using the same molten heat-treating salt for the confining medium. The small activation volume could not be resolved; however, the trend of the high pressure data parallels that of the 0.1 MPa data with a systematic offset, and is consistent with the measured activation volume of self diffusion. Specimens deformed at 0.1 MPa exhibited significant strain-enhanced grain growth; this effect is greatly reduced under hydrostatic pressure, whereas subgrain size was less affected.     

Extraction mechanism of copper by versatic 10

The extraction mechanism of copper from an aqueous ammonia-ammonium nitrate mixture by an n-hexane solution of Versatic 10 was studied from the standpoints of the equilibrium distribution of copper between aqueous and organic phases, the aqueous solubility and interfacial adsorption equilibrium of Versatic 10 and the extraction rate of copper.The equilibrium relations of the distribution of copper and the aqueous solubility and the interfacial adsorption of Versatic 10 were interpreted quantitatively and these equilibrium constants were evaluated.The extraction rate of copper was found to be proportional to the copper concentration in the aqueous phase, inversely proportional to the hydrogen ion concentration and independent of the Versatic 10 concentration in the organic phase. From the experimental results of the extraction rate and the interfacial adsorption equilibrium, it was inferred that the extraction rate was controlled by the elementary reaction between the copper ion in the aqueous phase and the anionic species of Versatic 10 adsorbed at the interface.