ICP-AES法测无铅焊锡中的银铜铅等元素

用ICP-AES法测无铅焊锡中的元素,改进了样品溶解方法,用硝酸盐酸混酸溶解样品,加入硫脲稳定溶液中的银离子.     

The catalytic action of cupric and ferric ions in nitric acid leaching of Ni3S2

The kinetics of dissolution of synthetic Ni₃S₂ in nitric acid solution containing ⩽ 2.0 M HNO₃ in the presence of cupric and ferric ions was investigated. The effects of stirring, particle size, temperature and concentration of cupric and ferric ions were examined. Solid residues at various levels of nickel extraction were examined by SEM, X-ray diffraction, electron microprobe and chemical analysis. The constant dissolution rate of Ni₃S₂ was attributed to the electrochemical reaction occurring on the surface of flat-plate type Ni₃S₂ particles. The reaction kinetics were found to be independent of both cupric and ferric ion concentrations up to 1 mM. Cupric ion did not act as a catalyst at temperatures below 60°C. At 80°C cupric and ferric ions show the same catalytic activity. The activation energy in the presence of ferric ions was 103.6 ± 4.2 kJ/mol. A mechanism for Ni₃S₂ dissolution in the presence of cupric and ferric ions is proposed.     

Leaching behavior of ilmenite with sulfuric acid

A study of the rate of dissolution of ilmenite in sulfuric acid solutions has been carried out. The effects of temperature, particle size, stirring speed, and concentration of sulfuric acid on the rate of dissolution of ilmenite has been investigated. Temperature range studied in this investigation was 88° to 115°C, and the Arrhenius activation energy was found to be 64.4 kJ (15.4 kcal) per mole. The rate of dissolution increased with concentration of sulfuric acid up to about 14 M sulfuric acid and decreased beyond this concentration. The maximum recovery at 14 M H₂SO₄ can be explained partially by the fact that H⁺ ion concentration peaks at about this concentration. Furthermore, reaction products, TiOSO₄ and FeSO₄, cover the surface of ilmenite when high concentrations of sulfuric acid are used, while these products are dissolved in water and removed from the surface when diluted sulfuric acid is involved. Based on the results obtained in this study, it can be concluded that the overall leaching of ilmenite with sulfuric acid at 88° to 115°C is described best by surface chemical reaction limiting with an order of 0.55 with respect to sulfuric acid concentration.     

Solubility of uranous sulfate in aqueous sulfuric acid solution

To provide important thermodynamic data for use in uranium hydrometallurgy, solubilities of uranous sulfate were determined as a function of free acid concentration and temperature. Two sets of experiments were performed in this study. One set was the precipitation experiments of uranous sulfate crystals, in which concentrated uranous sulfate solution was mixed with sulfuric acid solution of suitable concentration. The other set was the dissolution experiments of uranous sulfate crystals in aqueous sulfuric acid solutions. It is noteworthy that good agreement exists between the solubilities determined by the two methods. At elevated temperatures, say, 363 K, the presence of free sulfuric acid is required to avoid precipitation of uranous hydroxide resulting from the hydrolysis of uranous sulfate. Generally speaking, however, an increase in free sulfuric acid concentration results in a slight decrease in uranous sulfate solubility. The elevation of solution temperature causes a decrease in solubility of uranous sulfate. It should be noted that the solid uranous sulfates equilibrated with saturated solutions at 298 K were U(SO₄)₂ 2H₂O in dilute sulfuric acid solution and U(SO₄)₂ 4H₂O in concentrated sulfuric acid solution, while those at 333 K and 363 K were mainly U(SO₄)₂ 4H₂O. Formerly Director, Mining and Ore Processing Division, Ningyo-toge Works, Power Reactor and Nuclear Fuel Development Corporation, is Director, Ningyo-toge Nuclear Service Company, Tomata-gun, Okayama Prefecture 708-06, Japan.     

载金树脂硫脲硫酸解吸规律的研究

本文对硫酸和氰化钠分步解吸载金树脂上的贱金属离子，以及用硫脲硫酸溶液解吸载金树脂上的金、银络离子的解吸过程进行了研究，并通过现场采集的数据绘制了解吸曲线。     

Pressure leaching of a lead-zinc-silver concentrate with nitric acid at moderate temperatures between 130 and 170 °C

The aim of this investigation was to study the oxidative leaching of lead and silver from a lead-silver concentrate containing galena, sphalerite, pyrite and argentite in nitric acid solutions above the melting point of sulfur (119 °C). The elemental sulfur formed was expected to agglomerate, thereby slowing its oxidation to sulfate and inhibiting the precipitation of lead and silver sulfate.The experimental conditions employed 0.13-0.65 M nitric acid, which is 3 to 15 times the stoichiometric amount needed to form sulfur, at temperatures between 130 and 170 °C. Higher acid concentrations have a favorable effect on silver and lead dissolution at 130 °C with about 90% Ag and 80% Pb extracted into 0.65 M nitric acid within 90 min. However, an increase in temperature caused a decline in the extraction of both metals, due to the greater amount of sulfate produced. Pyrite was found to oxidize directly to akaganeite and sulfate ion and promotes the formation of plumbo- and argento-jarosite. X-ray diffraction analyses of the leach residues show the presence of anglesite (PbSO₄), plumbo-jarosite (PbFe₆(SO₄)₄(OH)₁₂), elemental sulfur (S-β) and akaganeite (FeO(OH)). Enhanced silver extraction was obtained when the oxidation was carried out in the presence of citrate ion which was added to complex with lead and silver ions.     

The dissolution of sphalerite in ferric sulfate media

The dissolution of sphalerite, (Zn,Fe)S, in ferric sulfate media was investigated using closely sized fractions of crushed sphalerite crystals. Linear kinetics were observed, and the rate increased in proportion to the surface area, as the average particle size of the sphalerite decreased. The predominant reaction products are ZnSO₄, FeSO₄, and elemental sulfur. The leaching rate increases with increasing temperature, and the apparent activation energy is 44 kJ/mol. The relatively high apparent activation energy suggests that the rate is chemically controlled, a conclusion supported by the insensitivity of the rate of the rotation speed that was observed in complementary rotating disk experiments. The rate increases as the 0.3 to 0.4 power of the Fe(SO₄)_1.5 concentration, and is nearly independent of the pulp density, in the presence of a stoichiometric excess of ferric sulfate. In 0.3 M Fe(SO₄)_1.5 media, the rate increases with increasing acid concentrations >0.1 M H₂SO₄, but is insensitive to more dilute acid concentrations. In the absence of ferric ions, the rate increases rapidly with increasing H₂SO₄ concentrations, and relatively rapid rates are observed in solutions containing >0.5 M H₂SO₄. The rate decreases with increasing initial concentrations of ZnSO₄, MgSO₄, or FeSO₄ in the ferric sulfate leaching solution, and this emphasizes the importance of maintaining the dissolved iron in a fully oxidized state in a commercial leaching operation.     

Studies on the effect of addition of silver ions on the direct oxidation of pyrite

The nature of the reaction between Ag⁺ and pyrite in 0.25 M H₂SO₄ solutions has been investigated in order to determine whether Ag⁺ can enhance the ferric sulfate leaching of this mineral. Analysis of reacted pyrite particles using scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and low-angle X-ray diffraction (XRD) indicates that elemental silver and elemental sulfur are the primary surface species formed by this interaction. Rest potential measurements of a pyrite electrode immersed in a solution containing 10⁻² M Ag⁺ are also consistent with what is expected for the deposition of metallic silver. Furthermore, the XRD data reveal that, at the most, only minor amounts of Ag₂S are being produced. The presence of Ag₂O has also been detected, but this is due to oxidation of silver after the experiment is complete and while the particles are being transferred for surface analysis. When 1 M ferric sulfate is contacted with pyrite which has been pretreated in a AgNO₃ solution, most of the silver immediately redissolves and does not redeposit while ferric ions are present. This indicates that the kinetics of the transfer reaction between Ag⁺ and pyrite is slower than the reaction between Fe³⁺ and pyrite and suggests that Ag⁺ does not likely enhance the ferric sulfate leaching.     

Oxidation of ferrous sulfate in acid solution by a mixture of sulfur dioxide and oxygen

The oxidation of ferrous sulfate with oxygen-sulfur dioxide mixtures in aqueous sulfuric acid has been investigated. In the presence of excess oxygen, sulfur dioxide produces fast oxidation of ferrous ion probably because of the formation of reactive radicals such as HSO₃, HO₂, and OH. The catalytic effect of cupric ion and activated carbon on the rate of oxidation has also been studied. By appropriately adjusting the SO₂/O₂ in the gas and Fe⁺³/Fe⁺² in the liquid phase, any of the following reactions can be favorably carried out: 1) oxidation of ferrous ion, 2) reduction of ferric ion, and 3) generation of sulfuric acid. Formerly with Martin Marietta Laboratories     

The dissolution of chalcopyrite in ferric sulfate and ferric chloride media

The literature on the ferric ion leaching of chalcopyrite has been surveyed to identify those leaching parameters which are well established and to outline areas requiring additional study. New experimental work was undertaken to resolve points still in dispute. It seems well established that chalcopyrite dissolution in either ferric chloride or ferric sulfate media is independent of stirring speeds above those necessary to suspend the particles and of acid concentrations above those required to keep iron in solution. The rates are faster in the chloride system and the activation energy in that medium is about 42 kJ/mol; the activation energy is about 75 kJ/mol in ferric sulfate solutions. It has been confirmed that the rate is directly proportional to the surface area of the chalcopyrite in both chloride and sulfate media. Sulfate concentrations, especially FeSO₄ concentrations, decrease the leaching rate substantially; furthermore, CuSO₄ does not promote leaching in the sulfate system. Chloride additions to sulfate solutions accelerate slightly the dissolution rates at elevated temperatures. It has been confirmed that leaching in the ferric sulfate system is nearly independent of the concentration of Fe³⁺, ka[Fe³⁺]^0.12. In ferric chloride solutions, the ferric concentration dependence is greater and appears to be independent of temperature over the interval 45 to 100 °C.     

Enhancement of chalcopyrite leaching by ferrous ions in acidic ferric sulfate solutions

The effects of ferrous ions on chalcopyrite oxidation with ferric ions in 0.1 mol dm⁻³ sulfuric acid solutions were investigated by leaching experiments at 303 K in nitrogen. With high cupric ion concentrations, the chalcopyrite oxidation was enhanced by high concentrations of ferrous ions and copper extraction was mainly controlled by the concentration ratio of ferrous to ferric ions or the redox potential of solutions. Ferrous ions, however, suppressed the chalcopyrite oxidation when cupric ion concentrations were low. A reaction model, which involves chalcopyrite reduction to intermediate Cu₂S by ferrous ions and oxidation of the Cu₂S by ferric ions, was proposed to interpret the results.     

The kinetics of dissolution of enargite in acidified ferric sulphate solutions

Abstract

Over the temperature range 60° to 95°C, sintered discs of synthetic enargite (Cu₃AsS₄) were dissolved slowly in acidified ferric sulphate solutions, yielding both elemental and sulphate sulphur, together with soluble copper and arsenic. The dissolution kinetics were linear and this was interpreted as indicating rate control by a reaction occurring on the surface of this sulphosalt. The activation energy associated with this reaction was 13.3 kcal/mole. The rate of copper extraction increased according to the 0.55 power of the ferric sulphate concentration and the 0.20 power of the sulphuric acid concentration. The rate decreased in a complex manner with increasing strengths of the ferrous sulphate reaction product. Natural enargite dissolves like the synthetic sulphosalt and at approximately the same rate.

Résumé

A des températures variant entre 60°C et 95°C, des disques frittés d'énargite synthétique (Cu₃AsS₄) ont été dissous lentement dans des solutions acides de sulfate ferrique, pour produire du soufre élémentaire et sous forme de sulfate, ainsi que du cuivre et de l'arsenic soluble. Les cinétiques de dissolution suivent une loi linéaire, due à la réaction qui a lieu en surface de ce sulfosel et qui, semble-t-il, contrôlerait la dissolution. L'énergie d'activation associée à la réaction est de 13.3 kcal/mole. Le taux d'extraction du cuivre croît comme la puissance 0.55 de la concentration en sulfate ferrique et la puissance 0.20 de la concentration en acide sulfurique. La vitesse décroît de façon complexe lorsque augmente la concentration du produit de la réaction du sulfate ferreux. L'énargite naturelle se dissout de la même manière que le sulfosel synthétique, et à sensiblement la même vitesse.     

Silver ion catalysis in nitric acid dissolution of Ni3S2

The dissolution of Ni₃S₂ in nitric acid solutions in the presence of silver ions was investigated. The effect of stirring, particle size, temperature and silver ion concentration were examined. In addition, the reaction residues at various levels of nickel extraction were examined by SEM, X-ray diffraction, electron microprobe and chemical analysis. These observations indicated that the dissolution reaction is topochemical and fits a surface reaction control model. The activation energy was calculated to be 52.6 ± 3.6 kJ/mol, which is reasonable for a rate-limiting surface reaction. The order of the reaction was 0.2 with respect to Ag⁺ concentration. An electrochemical reaction between nitric acid and the intermediate product Ag₂S occurring on the surface of Ni₃S₂ appears to be the rate-determining step.     

The kinetics of dissolution of chalcopyrite in ferric ion media

The kinetics of dissolution of chalcopyrite (CuFeS₂) in ferric chloride-hydrochloric acid and in ferric sulfate-sulfuric acid solutions have been investigated using the rotating disk technique. Over the temperature range 50 to 100‡C, linear kinetics were observed in the chloride media while nonlinear kinetics were noted in the sulfate system. The apparent activation energy in the chloride system was about 11 kcal/mole. The rate increased with increasing ferric chloride concentrations but was insensitive to the concentrations of hydrochloric acid, the ferrous chloride reaction product and “inert≓ magnesium or lithium chlorides. Cupric chloride substantially accelerated the rate. Small amounts of sulfate in an otherwise all chloride system greatly reduce the chalcopyrite leaching rate; still larger amounts of sulfate make the system behave essentially like the slower-reacting ferric sulfate medium.     

Silver-catalyzed bioleaching of low-grade copper ores. Part II: Stirred tank tests

A study of the effect of different variables (inoculation, aeration, silver complexants, [Ag], [Fe³⁺], temperature and chemical activation stage) on the silver-catalyzed bioleaching of two different low-grade copper ores has been carried out in stirred tanks. The catalyzed bioleaching process was greatly affected by bacterial activity. Aeration and the use of different complexing agents (thiosulfate and thiosulfate plus cupric ions) did not enhance but also did not inhibit the copper kinetics in the silver-catalyzed process. On the contrary, the presence of 5 g/L Cl⁻ inhibited the catalytic effect of silver. The effect of silver concentration was tested on two different low-grade copper ores in the range between 10 and 500 mg Ag/kg for the lower K-ore and between 1.4 and 35.7 g Ag/kg Cu for the PVD ore, the former with a higher content of copper. Silver catalysis was effective for both ores but the PVD ore was basically unaffected by silver concentration in the range studied. Maximum copper extractions and copper dissolution rates were obtained with a very small amount of silver (3.6 g Ag/kg Cu). In all cases, the copper recovery was at least twice that in the absence of silver (∼ 30%). High ferric concentrations have been tested in the absence and in the presence of silver. The presence of silver was essential to improve the copper extraction from chalcopyrite in acidic ferric sulfate solutions. However, bioleaching experiments conducted with silver and 1 g/L Fe³⁺ produced lower copper extractions (20%) compared to experiments where ferric iron was absent (55%). The copper dissolution in the silver-catalyzed lower K-ore bioleaching is temperature dependent, with an optimum temperature around 35 °C. The activation energies of the copper dissolution process were 109.7 and 20 kJ/mol in the ranges of temperature between 15 and 28 °C and 28 and 45 °C respectively. The chemical activation stage establishes optimum conditions that promote higher copper extractions in the presence of silver.     

The kinetics of dissolution of chalcopyrite in ferric ion media

The kinetics of dissolution of chalcopyrite (CuFeS₂) in ferric chloride-hydrochloric acid and in ferric sulfate-sulfuric acid solutions have been investigated using the rotating disk technique. Over the temperature range 50 to 100?C, linear kinetics were observed in the chloride media while nonlinear kinetics were noted in the sulfate system. The apparent activation energy in the chloride system was about 11 kcal/mole. The rate increased with increasing ferric chloride concentrations but was insensitive to the concentrations of hydrochloric acid, the ferrous chloride reaction product and “inert? magnesium or lithium chlorides. Cupric chloride substantially accelerated the rate. Small amounts of sulfate in an otherwise all chloride system greatly reduce the chalcopyrite leaching rate; still larger amounts of sulfate make the system behave essentially like the slower-reacting ferric sulfate medium.     

A ferric chloride hydrometallurgical process for recovery of silver from electronic scrap materials

A hydrometallurgical method for the recovery of silver from electronic scrap materials is suggested. Electronic scrap materials, containing silver with the accompanying brass and beryllium bronze, are leached at 80°C with ferric chloride. The leaching should be carried out with the concentration of ferric chloride and phase ratio chosen so that in the final phase of leaching the concentration ratio of Fe(III) to Fe(II) is not lower than 1. Under such conditions silver is found to be only slightly solubilized. This was confirmed by electrochemical studies.Potentiodynamic studies of the behaviour of silver in hydrochloric acid demonstrated that at the electrode potential value of 0.77 V, corresponding to the redox potential at 25°C of the solution where the concentration ratio [Fe(III)]/[Fe(II)] = 1, the silver surface is passivated not only by silver chloride but also by silver oxide. This prevents solubilization of silver in chloride solutions owing to the formation of AgCl₂^? and AgCl₃^2? complexes. The lowering of the solution oxidation potential resulting from consumption of Fe³⁺ ions during the leaching process causes a sudden increase in silver concentration in solution.     

Silver leaching from a mechanochemically pretreated complex sulfide concentrate

The intensification of thiourea leaching of silver from a silver-bearing complex sulfide concentrate (Casapalca, Peru) using mechanochemical alkaline leaching as the pretreatment step was investigated. The leaching of “as-received” concentrate in an acid thiourea solution resulted in 5% Ag dissolution. After pretreatment, 90% of the silver was leached within 10 min. The mechanochemical pretreatment resulted in up to 78% of tetrahedrite degrading and an increase in the specific surface area of the concentrate from 0.3 to a maximum of 15.7 m² g⁻¹. The pretreatment was performed in an attritor using variable milling times and sample weights. The physicochemical changes in the concentrate as a consequence of mechanochemical pretreatment had a pronounced influence on the subsequent silver extraction.     

硫化矿的浸金研究—酸性硫脲溶液体系

本文研究了在用酸性硫脲溶液从硫化矿中浸金时,硫酸铁浓度、硫脲浓度、酸度、温度、搅拌速度、浸取时间、矿石粒度及固液比等实验条件对金、银浸出率的影响。并对所得结果进行了讨论。