Chemistry of the Ca–Se(IV)–H2O and Ca–Se(VI)–H2O systems at 25 °C

The Ca–Se(IV)–H₂O and Ca–Se(VI)–H₂O systems were studied by contacting either selenious acid or selenic acid solution with calcium oxide to attain equilibrium at 25 °C for one month. Analysis of the final solid phases and the associated solution, together with X-ray diffraction analysis and a study into the graphed relationships, showed the existence of three calcium selenites in the Ca–Se(IV)–H₂O system — Ca₂SeO₃(OH)₂·2H₂O (Se(IV) = 4.8 × 10^− 5–2.8 × 10^− 4 M); CaSeO₃·H₂O (Se(IV) = 2.8 × 10^− 4–0.86 M) and Ca(HSeO₃)₂·H₂O (Se(IV) > 0.86 M). It also showed four calcium selenates in the Ca–Se(VI)–H₂O system — Ca₂SeO₄(OH)₂ (Se(VI) = 0.21–0.39 M); CaSeO₄·2H₂O (Se(VI) = 0.40–9.1 M); CaSeO₄ (Se(VI) = 10.2 M) and CaSe₂O₇ (Se(VI) > 10.8 M). The X-ray diffraction analyses reported and SEM analyses indicate a high degree of crystallinity of all seven compounds. The stability and solubility regions for these compounds were defined versus pH, and the conventional solubility constants and conditional free energies of formation for the less soluble CaSeO₃·H₂O, Ca₂SeO₃(OH)₂·2H₂O, CaSeO₄·2H₂O and Ca₂SeO₄(OH)₂ were calculated from solubility data obtained.     

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.     

Identification of arsenato antimonates in copper anode slimes

It was found that, in copper electrolyte, the combination of As(V) and Sb(V) can form arsenato antimonic acid (AAAc) and, the reactions of AAAc with As(III), Sb(III), and Bi(III) can produce the precipitates of arsenato antimonates. During copper electrorefining, the As, Sb, and Bi deposited into the anode slime from the electrolyte are dominant in the forms of arsenato antimonates. It is extremely difficult to separate pure arsenato antimonates from copper anode slimes, while it is easy to synthesize arsenato antimonates using H₂O₂ to oxidize As(III) and Sb(III) in copper refining electrolyte. The composition and structure of the arsenato antimonates were determined with chemical analysis, IR and XRD techniques. The characteristic bands in the IR spectra of arsenato antimonates are δ of As–OH and Sb–OH at 1126.8 cm^− 1, ν_as of As–OH at 1029.7 cm^− 1, ν_as of As–OX(X = As, Sb) at 819.5 cm^− 1, ν_as of Sb–OH at 618.4 cm^− 1, ν_as of Sb–OY(Y = As, Sb) at 507.2 cm^− 1, and ν_as of Sb–OBi at 470 cm^− 1.The arsenato antimonates form irregular masses of amorphous structure because there are many OH groups in AAAc, the OH groups bond with As(III), Sb(III), and Bi(III) at random, which makes the arsenato antimonates formed in copper refining electrolyte have no fixed ratios for As/Sb/Bi. The formation of the arsenato antimonates can be expressed as follows:aH₃AsO₄ + bH[Sb(OH)₆] + cMeO ⁺ →Me_cAs_aSb_bO_{(3a+5b+c/2+1)}H_{(a+5b−2c+2)}·xH₂O + cH⁺ + (a + b + c / 2 − 1 − x)H₂O, where Me = As(III), Sb(III) and Bi(III); a ≥ 1, b ≥ 1, c ≤ (3a + b)     

Leaching of waste battery paste components. Part 2: Leaching and desulphurisation of PbSO4 by citric acid and sodium citrate solution

In this study, as part of developing a new process that can avoid both smelting and electro-winning, citric acid based reagents were reacted with PbSO₄, in aqueous media for achieving lead recovery simultaneously with desulphurisation. PbSO₄ is the main component in a spent battery paste (accounting for nearly 50% by weight). Recovery of the two oxides PbO and PbO₂, which together account for the remaining 50% of the paste, has been discussed in Part 1 in a separate paper. Leaching of PbSO₄ with a solution containing C₆H₅Na₃O₇·2H₂O alone was neither effective in removing the sulphate or in synthesising uncontaminated lead citrate. When both C₆H₅Na₃O₇·2H₂O and C₆H₈O₇·H₂O reagents were used together, it was possible to achieve effective recovery of lead precursor as lead citrate while simultaneously removing sulphur as Na₂SO₄. The lead citrate product was characterised by SEM and XRD analysis. Conditions for achieving a recovery of 99% of the lead precursor crystallites have been experimentally deduced by varying the concentrations of various reagents, time and temperature of the reaction, and the starting ratio of solid to liquid.     

The precipitation of ammonium uranyl carbonate (AUC): Thermodynamic and kinetic investigations

The aim of this study is to determine the predominant chemical reaction during precipitation of ammonium uranyl carbonate (AUC) based on thermodynamic analysis and to investigate its kinetics. Four chemical reactions were considered. The Gibbs free energies, Δ_rG°(T) derived from the Ulich calculations as a function of temperature have been determined between 293.15 K and 353.15 K. The predominant chemical reaction of AUC precipitation was UO₂(NO₃)₂·6H₂O_(aq) + 6NH_3(g) + 3CO_2(g) → (NH₄)₄UO₂(CO₃)_3(s) + 2NH₄NO_3(aq) + 3H₂O_(l). According to the AUC precipitation kinetics results, the reaction best fits a second order rate equation. The rate constants k₂ were calculated at 313.15 K and 330.15 K and the activation energy E_a determined using the Arrehenius equation was found as 17.4 kJ/mol.     

Kinetics and mechanism of stripping of Mn(II)–D2EHPA complex by sulphuric acid solution

The kinetics of stripping of Mn(II)–D2EHPA chelate (MnA₂.HA.H₂A₂) existing in kerosene phase by aqueous sulphuric acid solutions at constant sulphate ion concentration of 0.50 M have been investigated by the constant interfacial area stirred (Lewis) and non-stirred (Hahn) cells. Both pseudo-rate constant (q) or (rate / area) and flux (F) methods of the rate data treatment have been applied. The empirical rate equations have been derived. Results have been compared among themselves and other published works on Mn(II)–D2EHPA chelate stripping kinetics. Rate constants obtained from (q) or (rate / area) and (F) methods differ in magnitude and units and an explanation of this has been given.An analysis of rate equations obtained from the Lewis cell experimentation (F_b = 10^− 4.1[MnA₂.HA.H₂A₂]_(o)(1 + 0.005[H⁺]_(i)^− 1)^− 1 (1 + 7.94[H₂A₂]_(o)^0.5)^− 1) suggests that the process is chemically controlled at lower aqueous acidity and higher free D2EHPA concentration regions; whereas, it is diffusion-controlled at higher aqueous acidity and lower free D2EHPA concentration regions. In the investigated D2EHPA concentration and aqueous acidity regions, majority of data fall in the intermediate controlled region. The suggested mechanisms are supported by the values of activation energy (E_a). In the kinetic regime, the reaction step: MnA⁺ → Mn²⁺ + A⁻ occurring in the bulk aqueous phase is the slowest step which proceeds through S_N2 mechanism as indicated by the comparable higher negative value of ΔS^± in the stated condition.In Hahn cell technique, the empirical rate equation is: F_b = 10^− 5.9[MnA₂.HA.H₂A₂]_(o)(1 + 0.0025[H⁺]_(i)^− 1)^− 1(1 + 2.8[H₂A₂]_(o)^0.5)^− 1. Analysis of this equation together with the E_a value of 12–42 kJ/mol indicate that the stripping process is completely diffusion controlled in the low pH and extractant concentration region and in other parametric condition, that is intermediate controlled. For both cells, the ratio of (k_f) to (k_b) equals almost to K_ex of 10^− 2.44 obtained from the distribution study.     

Characterization of the iron arsenate–sulphate compounds precipitated at elevated temperatures

To help clarify the nature of the iron arsenate–sulphate compounds produced during the autoclave treatment of refractory gold ores and concentrates, systematic synthesis studies were undertaken; in addition to scorodite and Fe(SO₄)(OH), two other compounds, designated as Phase 3 and Phase 4, were identified. Whereas Fe(SO₄)(OH) is predominantly an orthorhombic compound, Phase 3 can have the same composition but is predominantly the monoclinic polytype, the formation of which is promoted by the solid-solution uptake of As; substitution of As results in a corresponding decrease in the OH required to maintain the charge balance; e.g., Fe[(SO₄)_0.60(AsO₄)_0.40]_∑1.00[(OH)_0.6(H₂O)_0.4]_∑1.00. Phase 4 corresponds to Fe(AsO₄)·¾H₂O. In 0.4 M Fe(SO₄)_1.5 (22.3 g/L Fe), 0.41 M (40 g/L) H₂SO₄, 0.09 M (7 g/L) As(V) solutions, sulphate-containing scorodite was formed at 150–175 °C. Phase 3 precipitated at 175–210 °C, but mixtures of Phase 3 and Fe(SO₄)(OH) formed above 210–220 °C. The Fe content of Phase 3 is about 30 mass %, whereas the AsO₄ and SO₄ contents vary widely and in an inversely proportional manner, reflecting the extensive mutual structural substitution of these anions. At 205 or 215 °C, Fe(SO₄)(OH) was precipitated from 0.4 M Fe(SO₄)_1.5 (22.3 g/L Fe), 0.41 M (40 g/L) H₂SO₄ solutions containing < 0.03 M (2 g/L) As(V). Increasing As(V) concentrations enhance the precipitation of Phase 3, but only Phase 4 was precipitated from solutions containing > 0.33 M (25 g/L) As(V). The composition of Phase 4 is nearly constant and it contains < 1 mass % SO₄. Acid concentrations > 0.2 M H₂SO₄ had little effect on the composition of the precipitates. At 205 °C in 0.41 M (40 g/L) H₂SO₄, 0.09 M (7 g/L) As(V) media, mixtures of scorodite and Phase 4 precipitated from 0.0–0.1 M Fe(SO₄)_1.5 (0.0–5.6 g/L Fe) solutions; for Fe(SO₄)_1.5 concentrations > 0.1 M, only Phase 3 formed. To provide a preliminary indication of the solubility of Phase 3 and Phase 4 in tailings impoundments, the various precipitates were leached at room temperature for 40 h in water. The As concentrations dissolved from Phase 3 were consistently < 0.1 mg/L, which suggests that Phase 3 might be an acceptable medium for arsenic disposal. In contrast, the soluble As concentrations from Phase 4 were 1–3 mg/L.     

Corrosion protection of magnesium alloys anode by cerium-based anodization coating in magnesium-ait battery

CeN₃O₉·6H₂O(0.5,1.0,1.5,and 2.0 g/L) was added into an 8.0% NaCl electrolyte solution to investigate this electrolyte for use in a Mg-air battery.The effects of the amount of CeN₃O₉-6H₂O on the corrosion resistance of an AZ31 Mg alloy anode and battery performance were investigated using microstructure,electrochemical(dynamic potential polarization method and electrochemical impedance spectroscopy),and battery measurements.The re ...     

Carrier-mediated transport of uranium from phosphoric acid medium across TOPO/n-dodecane-supported liquid membrane

Present studies deals with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium. Tri-n-octyl phosphine oxide (TOPO)/n-dodecane is used as a carrier and ammonium carbonate as a receiving phase for the separation of uranium (VI) from the phosphoric acid medium. Throughout the study PTFE membranes are used as a support. The studies involve the investigation of process controlling parameters like feed acidity of phosphoric acid, carrier concentration and stripping agents. The effect of nitric acid and sodium nitrate in feed is also studied. It is found that there is negligible transport of uranium (VI) from pure phosphoric acid medium but it increases to very significant amount if 2 M nitric acid is added to feed phase. More than 90% uranium (VI) is recovered in 360 min using 0.5 M TOPO/n-dodecane as carrier and 1.89 M ammonium carbonate as stripping phase from the mixture of 0.001 M H₃PO₄ and 2 M of HNO₃ as a feed. The flux and permeability coefficient are found to be 9.21 × 10^− 6 mol/m² s and 18.26 × 10^− 5 m/s, respectively. Lower concentration of phosphoric acid with 2 M HNO₃ and higher concentration of carrier is found to be the most suitable condition for maximum transport of uranium (VI) from its low-level sources like commercial phosphoric acid.     

Effect of temperature and alumina/caustic ratio on precipitation of boehmite in synthetic sodium aluminate liquor

In Bayer process gibbsite (alumina trihydrate, Al₂O₃·3H₂O) is precipitated from sodium aluminate liquor for production of alumina by calcination. Precipitation of boehmite or alumina monohydrate (Al₂O₃·H₂O) is an alternative method for production of alumina. Boehmite is also a good precursor material for production of different activated aluminas. At present this boehmite precipitation process is in the early stage of development. This process if developed would reduce the energy consumption for making alumina. The present work is aimed to carry out boehmite precipitation under atmospheric pressure conditions. Parameters such as alumina/caustic (A/C) ratio and temperature are varied to precipitate out boehmite from synthetically prepared sodium aluminate liquor. It was found that boehmite precipitation could be possible at normal pressure only when boehmite seed was added to the supersaturated sodium aluminate solution keeping the alumina/caustic ratio at either 1.1 or 1.0 and temperature at ≥ 85 °C. By decreasing the A/C ratio to 0.95 and below, it was possible to precipitate out boehmite at 60 °C.     

Experimental study of phase equilibria in the systems PbO x -CaO and PbO x -CaO-SiO2

The reported experimental work on the systems PbO _x -CaO and PbO _x -CaO-SiO₂ in air is part of a wider research program that combines experimental and thermodynamic computer modeling techniques to characterize zinc/lead industrial slags. Extensive experimental investigation by high-temperature equilibration and quenching techniques followed by electron probe microanalysis was carried out in the temperature range 640 °C to 1500 °C (913 to 1773 K) and in the composition ranges 0 to 65 mol pct SiO₂ and 0 to 42 mol pct CaO. Liquidus and solidus data were reported for most of the primary phase fields. Liquidus surfaces in the systems CaO-Pb-O and PbO _x -CaO-SiO₂ in air were completely reconstructed. Extensive solid solutions of PbO in α′ dicalcium silicate and Ca₂Pb₃Si₃O₁₁ were measured.     

Leaching of a sphalerite concentrate with H2SO4–HNO3 solutions in the presence of C2Cl4

The enhanced leaching of sphalerite concentrates in H₂SO₄–HNO₃ solutions and the extraction of sulfur with tetrachloroethylene were studied. Variables of the process were investigated including leaching temperature, reaction time, liquid / solid ratio, and tetrachloroethylene concentration. The number of cycles that tetrachloroethylene could be recycled did not have a significant effect on zinc extraction. The results indicated that 99.6% zinc extraction was obtained after three hours of leaching at 85 °C and 0.1 MPa O₂, when 20 g of sphalerite concentrate were leached in a 200 ml solution containing 2.0 mol/L H₂SO₄ and 0.2 mol/L HNO₃, in the presence of 10 ml C₂Cl₄. Leaching rates were significantly improved under these conditions.     

Leaching kinetics of synthetic CaWO4 in HCl solutions containing H3PO4 as chelating agent

In this study, the dissolution kinetics of synthetically prepared CaWO₄ in HCl solutions containing H₃PO₄ was studied. The effects of process parameters such as stirring speed, temperature and acid concentrations on the dissolution rate of CaWO₄ were investigated. The reaction rate was found to be of 1 / 3 and 2 / 3 order with respect to HCl and H₃PO₄ concentrations, respectively, and the activation energy for the dissolution reaction to be 60 kJ mol^− 1. The rate equation for the dissolution reaction was derived using the Avrami equation and the rate determining step was the chemical reaction on the surface of solid particles.     

Enthalpies of formation of chromium carbides

Adiabatic oxygen combustion calorimetry has been used to determine the enthalpies of combustion of the chromium carbides Cr₂₃C₆, Cr₇C₃ and Cr₃C₂ to be—15,057.6±12.4 kJ ·mole⁻¹,—4985.3±3.8 kJ ·mole⁻¹ and—2400.5±0.9 kJ ·mole⁻¹ respectively. The products of combustion in all cases were Cr₂O₃ and CO₂. Using standard data for Cr₂O₃ and CO₂, the enthalpies of formation of the carbides have been calculated to be:fΔH ₂₉₈ ^o Cr₂₃C₆=−290.0±27.6 kJ·mole⁻¹ fΔH ₂₉₈ ^o Cr₇C₃=−149.2±8.5 kJ·mole⁻¹ fΔH ₂₉₈ ^o Cr₃C₂=−81.1±2.9 kJ·mole⁻¹     

Product inhibition by sulphide species on biological sulphate reduction for the treatment of acid mine drainage

It is well recognised that the product of sulphate reduction, i.e. the sulphide species formed, may inhibit the biological process. In this paper, we further the kinetic study of biological sulphate reduction using the mixed population of complete oxidisers growing on acetate for which kinetic data has been reported previously as a function of sulphate concentration, temperature, dilution rate and volumetric sulphate loading using chemostat culture by Moosa et al. to provide kinetic insight into this inhibition.The effect of a feed sulphide concentration in the range 0.50 to 1.25 kg m^− 3 on the biological sulphate reduction process is established using chemostat culture at pH 7.0 ± 0.2. Further, the chemical speciation of sulphide as undissociated H₂S or dissociated HS⁻ on process inhibition is reported through the variation of operating pH across the range pH 6.0 to pH 7.5 at a sulphate feed concentration of 2.5 kg m^− 3. It is clearly shown that inhibition is chiefly mediated by the undissociated H₂S sulphide species, rather than the total sulphide concentration. This inhibition was shown to affect the maximum specific growth rate constant and the death rate constant in the Contois rate equation presented previously while having negligible effect on KS describing substrate affinity.     

Sorption behaviour and mechanism of ytterbium(III) on imino-diacetic acid resin

The sorption behaviour and mechanism of a novel chelate resin, imino-diacetic acid resin (IDAAR), for Yb(III) has been investigated in HAc–NaAc medium. The sorption of Yb(III) obeys the Freundlich isotherm. Optimum sorption for Yb(III) on IDAAR is at pH 5.13 and the statically saturated sorption capacity is 187 mg/g resin at 298 K. Yb(III) can be eluted using 1~2 mol L^− 1 HCl and the resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k₂₉₈ = 1.57 × 10^− 5 s^− 1; the apparent activation energy is 13.8 kJ mol^− 1 and the enthalpy change ΔH of IDAAR for Yb(III) is 29.8 kJ mol^− 1. The sorption mechanism of IDAAR for Yb(III) was examined by using chemical methods and IR spectrometry. The molar coordination ratio of the functional group of IDAAR to Yb(III) is 3:1 with the coordination compound formed between oxygen atoms in the functional group of IDAAR and Yb(III).     

Stability of 3CaO · Al2O3 · 6H2O in KOH + K2CO3 + H2O system for chromate production

In the novel clean chromate production process, the alkali liquor recycled to decompose the chromite ore mainly consists of KOH and K₂CO₃ which accumulates aluminium impurity and affects the quality of the product greatly. Aluminium impurity can be removed by adding CaO to precipitate as 3CaO · Al₂O₃ · 6H₂O (C₃AH₆). A study of the effects of various parameters, such as KOH concentration, K₂CO₃ concentration and temperature on the behaviour of C₃AH₆ show that C₃AH₆ is decomposed to 3CaO · Al₂O₃ · CaCO₃ · 11H₂O and CaCO₃ below 150 g L^− 1 KOH, and decomposed to Ca(OH)₂ above 150 g L^− 1 KOH. With K₂CO₃ concentration increasing, C₃AH₆ decomposes significantly, which results in more CaCO₃ or 3CaO · Al₂O₃ · CaCO₃ · 11H₂O produced. Temperature has a large positive effect on the decomposition of C₃AH₆ at 45 g L^− 1 KOH but has no significant effect at 150 g L^− 1 KOH. The optimal condition for removing aluminium impurity in the KOH + K₂CO₃ + H₂O system is 150 g L^− 1 KOH, 50 g L^− 1 K₂CO₃ and 80 °C.     

PbO solubility in lead-blast furnace slags

A series of slags in the PbO-CaO-FeO-Fe₂O₃-SiO₂ system has been equilibrated in contact with molten Pb and Pb-Ag alloys in a closed system at 1473 K. The influences of lead activity and the CaO/SiO₂ and ferric/ferrous ion ratios on PbO solubility in slag have been examined. The PbO content is proportional to the lead activity and the ferric/ferrous ratio, but decreases with increasing values of the CaO/SiO₂ ratio. The solubility of lead in the slag can also be characterized by the following empirical equation, whereX _PbO is the lead oxide mole fraction,K ₂ the equilibrium constant for the formation of liquid PbO at 1473 K, andF andG are the calcia/silica and iron/silica weight ratios, respectively. This equation, developed from data in the literature, has been used with the experimental results of this investigation for comparison with values ofp _{O 2}predicted by Hollitt’s structural model. Further comparison with Hollitt’s model has been made with other experimental data in the literature. The values ofp _{O 2}predicted with the structural model are an order of magnitude lower than those predicted by the empirical equation and the values ofp _{O 2} used by other investigators. The reason for this discrepancy may lie in part in the use of questionable assumptions about the behavior of FeO in slag systems; reevaluation of the structural model to include more “basic” FeO improves agreement between the values ofp _{O 2}obtained with the structural model and those obtained with the empirical equation and the partial pressures of O₂ used by other investigators. In addition, the structural model has also been tested with regard to the influence of CaO and FeO additions on the solubility of PbO. The possible effect of interaction between the equilibrating slag melt and the calcia-stabilized zirconia crucible on the system equilibria has also been examined; such an effect may not be as negligible as previous researchers have claimed.     

Thermochemical Study on Coordination Complex of Samarium with Salicylic Acid and 8-Hydroxyquinoline

It is knownthat rare earthions ,8-hydroxyquino-line and salicylic acid are antibacterial[1 ～5].Synthesisand characterization of the rare earth complexes withsalicylic acid were reported by Sun[6].Synthesis andcharacterization of the rare earth complexes …     

Effect of added cobalt ion on electro-deposition of copper from sulfate bath using graphite and Pb–Sb anodes

Effect of added Co²⁺(aq) on copper electro-deposition was studied using Pb–Sb and graphite anodes and a stainless steel cathode. The presence of added Co²⁺(aq) in the electrolyte solution was found to decrease the anode and the cathode potentials. The optimum level of Co²⁺(aq) concentration in the electrolyte, with respect to the maximum saving of power consumption was established. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used to study the influence of added Co²⁺(aq) on the anodic and the cathodic processes in a copper sulfate-sulfuric acid electrolyte. The oxygen-evolution potential is depolarised at lower current densities (≤ 150 A/m²) and attains saturation at [Co²⁺]_o ? 600 ppm; whilst at higher current densities (≥ 300 A/m²) it is depolarised with [Co²⁺]_o ≥ 300 ppm. The presence of Co²⁺ promoted the deposit of a smoother and brighter copper cathode as measured by surface reflectivity. X-ray diffraction (XRD) showed that added Co²⁺ changed the preferred crystal orientations of the copper deposits. Scanning electron microscopy (SEM) indicated that the surface morphology of the copper deposited in the presence of added Co²⁺ has well-defined grains. Analysis of cathode copper deposits found negligible cobalt.