Production of lead via ammoniacal ammonium sulfate leaching

Laboratory-scale investigations of a novel hydrometallurgical process for lead production are described. The process is based upon the solubility of certain oxidized lead compounds in aqueous ammoniacal ammonium sulfate (AAS) solutions. There are, essentially, five steps in the process, viz: pretreatment to convert lead in the raw material to a suitable oxidized form; dissolution of the lead compounds in an AAS solution at ambient temperatures and pressures; recovery of the lead from solution by electrolysis or precipitation; conversion of the products of the preceding stage to saleable products; treatment of solutions to make them suitable for recycling. This new process avoids many of the difficulties of existing hydrometallurgical processes for lead.     

Pressure leaching of beta-spodumene by sodium chloride

Abstract

The applicability of the pressure leaching technique in the recovery of lithium from a beta-spodumene bearing concentrate has been investigated using sodium chloride as reactant in alkaline medium. Factors such as the concentration of sodium chloride and calcium hydroxide, the temperature, the pulp density, the reaction time and the particle size, which influence the rate and the extent of the lithium dissolution were studied When ever applicable the optimum values were determined. It has been suggested that the kinetics of this reaction are controlled by the diffusion phenomena. This hypothesis is supported by the relatively low activation energy ?H_a=3.6±0.2 Kcal/mol. The possibility of recovering pure lithium chloride from the .leach solutions containing large quantities of sodium chloride is indicated.

Résumé

L'application de la méthode de lixiviation sous pression à l'extraction du lithium d'un concentré de spodumène-beta a été étudiée en employant le chlorure de sodium comme réactif en milieu a1calin. Les principaux paramètres qui affectent la réaction sont: les concentrations du chlorure de sodium et de l'hydroxyde de calcium, la température, la densité de la pulpe, la durée de la réaction et la grosseur des particules. Lorsque possible, l'optimisation des paramètres a été faite. Il est suggéré que la cinétique de cette réaction soit contrôlée par le phénomène de diffusion. En effet, cette hypothèse est supportée par le fait que l' énergie est relativement basse, ?H_a = 3.6 ± 0.2 Kcal/mole. La possibilité de récupération de chlorure de lithium pur à partir de solutions de lixiviation contenant des quantités élevées de chlorure de sodium parait évidente.     

Kinetics of galena leaching in hydrochloric acid-chloride solutions

This article presents a series of studies on the nonoxidative leaching of galena with hydrochloric acid in the presence of a metallic chloride. A systematic study was carried out using a succession of metallic chlorides with cations of different valencies in an attempt to generalize the leaching behavior of these solutions. The reaction order for leaching galena, in terms of the mean ionic activity of HCl, is 3/2 over a wide range of concentration. The addition of soluble chlorides to a HCl solution increases the leaching rate of the galena by augmenting the mean ionic activity of the acid. A reaction order of 3/2 for the mean HCl activity in the solution is maintained for solutions in which the acid concentration is constant and the metallic chloride varies, as well as for the opposite situation. Therefore, the only activity that must figure in the kinetic equation is that of the HCl. The activation energy (58.5 kJ/mole) is independent of the chloride used to increase the activity of the hydrochloric acid. The same is true for the Arrhenius prefactor.     

乙酸根配位浸出硫酸铅的热力学分析

采用热力学平衡计算和验证性实验的方法, 研究乙酸根配位浸出硫酸铅的热力学问题。首先, 通过Pb(OH)₂-H₂O体系的热力学计算评价了Pb(OH)₆4-形成常数的合理性。结果表明, 考虑Pb(OH)₆4-存在时所得计算结果明显不符合Pb(OH)₂两性化合物的性质, 因而不建议采用。然后, 计算并绘制了乙酸根配位浸出硫酸铅的热力学平衡图。结果表明, 在不同总乙酸根浓度下, pH值在6~9的范围对乙酸根浸出硫酸铅更有利, Pb(Ac)₄2-是该pH值区域中铅的主要物种; 并且, 总乙酸根浓度越高, 浸出液中, Pb(Ac)₄2-与游离Ac-的浓度比越高, 表明浸出硫酸铅的乙酸根利用率随之增大。此外, 根据电中性原则、质量守恒原则和同时平衡原理, 计算并绘制了不同HAc和NaAc比例的初始液浸出硫酸铅平衡后各溶解物种的lgc-[Na]/[Ac]_T图, 表明总乙酸根一定时浸出液铅浓度随着初始液乙酸钠比例增加而增加, 验证性实验结果与热力学计算结果趋势上一致。      

Kinetics of galena dissolution in ferric chloride solutions

A leaching investigation of galena with ferric chloride has been carried out as a function of concentration of ferric chloride and sodium chloride, temperature, and particle size. Three size fractions were considered in this investigation, namely, 48 × 65, 35 × 48, and 28 × 35 mesh. The concentration ranges of ferric chloride and sodium chloride used in this investigation were 0 to 0.25 M and 0 to 3 M, respectively. The reaction rate mechanism has been discussed in terms of a shrinking core model developed for cubic systems. Mass transport of ferric chlorocomplex through the product sulfur layer appears to be responsible for establishing the overall leaching rate under most of the conditions used in this investigation. The apparent activation energy for the leaching of 28 × 35 mesh galena with 0.1 M FeCl₃, 1 M HC1, and 3.0 M NaCl was found to be about 8.05 kcal/mol (33.7 kJ/mol), which was partially contributed by diffusion and partially by the heat of reaction of the formation of ferric chlorocomplexes. Rate of dissolution at both 50° and 90 °C is greatly affected by ferric chloride concentration up to 0.2 M and is essentially constant with ferric chloride concentration above this value.     

The solubility of aqueous lead chloride solutions

Data are presented for the solubility of lead in acidic solutions of between 5 and 10 M chloride concentration, present as the salts of copper (II) and either sodium or calcium. Cooling these solutions from boiling point to 20°C precipitates approximately two thirds of the lead as PbCl₂ crystals of >99% purity. The solubility of PbCl₂ is shown to depend upon the activity of the lead and chloride ions in solution, and can be predicted from known thermodynamic constants. This has been tested for solutions containing only one cation, other than lead, at 25°C. This approach accurately predicts the lead solubility in solutions of calcium chloride but needs improving before it can be applied to sodium chloride solutions and hydrochloric acid.     

磷酸钠-氢氧化钠浸出氟化钙动力学研究

针对现行主流氢氧化钠和碳酸钠浸出低品位白钨矿存在浸出剂用量大,浸出率低的弊端,提出磷酸钠-氢氧化钠-氟化钙协同高效浸出低品位白钨矿的新工艺.氟化钙作为固体氟源,在浸出过程中首先发生溶解并释放出游离的氟离子,再参与白钨矿的浸出反应生成氟磷酸钙沉淀.因此,氟化钙的溶解速率对白钨矿浸出速率有较大影响.文章使用等浸出率法,对磷...     

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.     

Kinetics of pyrite oxidation in sodium carbonate solutions

The kinetics of pyrite oxidation in sodium carbonate solutions were investigated in a stirred vessel, under temperatures ranging from 50 °C to 85 °C, oxygen partial pressures from 0 to 1 atm, particle size fractions from −150 + 106 to −38 + 10 μm (−100 + 150 Mesh to −400 Mesh + 10 μm) and pH values of up to 12.5. The rate of the oxidation reaction is described by the following expression:−dN/dt = SbkpO ₂ ^0.5 [OH₋]^0.1 whereN represents moles of pyrite,S is the surface area of the solid particles,b is a stoichiometric factor,k is an apparent rate constant, pO```2`` is the oxygen partial pressure, and [OH⁻] is the hydroxyl ion concentration. The experimental data were fitted by a stochastic model for chemically controlled reactions, represented by the following fractional conversion(X) vs time (t) equation: (1−X)^−2/3−1 =k _STt The assumption behind this model,i.e., surface heterogeneity leading to preferential dissolution, is supported by the micrographs of reacted pyrite particles, showing pits created by localized dissolution beneath an oxide layer. In addition to the surface texture, the magnitude of the activation energy (60.9 kJ/mol or 14.6 ± 2.7 kcal/mol), the independence of rate on the stirring speed, the inverse relationship between the rate constant and the initial particle diameter, and the fractional reaction orders are also in agreement with a mechanism controlled by chemical reaction.     

Kinetics of pyrite oxidation in sodium hydroxide solutions

The kinetics of pyrite oxidation in sodium hydroxide solution were investigated in a stirred reactor, under temperatures ranging from 50 °C to 85 °C, oxygen partial pressures of up to 1 atm, particle size fractions from -150 + 106 to -38 + 10μm (-100 + 150 mesh to -400 mesh + 10 μ), and pH values of up to 12.5. The surface reaction is represented by the rate equation:-dN/dt = Sbk″pO^0.5 ₂[oH^{- 0.25}/(1 +k‴ pO₂ ^0.5) where N represents moles of pyrite, S is the surface area of the solid particles,k″ andk″ are constants,b is a stoichiometric factor, pO₂ is the oxygen partial pressure, and [OH^-] is the hydroxyl ion concentration. The corresponding fractional conversion (X) vs time behavior follows the shrinking particle model for chemical reaction control: 1 - (1 -X)^1/3 =k _ct The rate increases with the reciprocal of particle size and has an activation energy of 55.6 kJ/mol (13.6 kcal/mol). The relationship between reaction rate and oxygen partial pressure resembles a Langmuir-type equation and thus suggests that the reaction involves adsorption or desorption of oxygen at the interface. The square-root rate law may be due to the adsorption of a dissociated oxygen molecule. The observed apparent reaction order with respect to the hydroxyl ion concentration is a result of a complex combination of processes involving the oxidation and nydrolysis of iron, oxidation and hydrolysis of sulfur, and the oxygen reduction. Formerly Graduate Student, Department of Mineral Engineering, Pennsylvania State University     

Kinetics of leaching of zinc ferrite in aqueous hydrochloric acid solutions

The dissolution of synthetic samples of zinc ferrite in aqueous hydrochloric acid is stoichiometric. The rate appears to be controlled by a chemical reaction on the solid surface, and dependence of the dissolution rate on hydrochloric acid activity is of the first order. Activation energy of 83 kJ mol^-1 was found. Zinc ferrite leaching is a slow solubilization process in the hydrochloric acid treatment of dead-roasted Iberian pyrite ashes. The most favorable conditions are 0.5-1 M HC1 at 90 to 100 ‡C, when preferential solubilization of the spinel phases takes place on the hematitic matrix. Extensive extraction of zinc (~90 pct of total zinc) in one to two hours and low solubilization of iron (~8 pet of total iron) results under these conditions.     

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.     

Cupric chloride leaching of a complex copper/zinc/lead ore

A complex Cu/Zn/Pb ore from Cayeli, Turkey, was reacted with cupric chloride solutions under different conditions. Energies of activation were calculated for dissolution of copper (37 kJ mol^?1), iron (33 kJ mol^?1, zinc (26 kJ mol^?1) and lead (7.5 kJ mol^?1, values which indicate diffusion control of the reaction, probably through the sulphur layer formed round each particle. Particle size/leaching relationships corroborated microscopic assessments and indicated that chalcopyrite dissolved at a very low rate. Calculation of Fe:Cu ratios of metal leached showed considerable dissolution of pyrite from finely-ground ($\text{d}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{≈ 3?5 μ}\text{m}$) ore. Examination of residues using SEM X-ray fluorescence line scan techniques revealed little attack of large pyrite crystals, suggesting that fine pyrite particles in complex relationship with the sphalerite and chalcopyrite were dissolving.     

Electrodeposition of lead from aqueous acetate and chloride solutions

Electrodeposition of Pb from electrolyte containing CH₃COONH₄, CH₃COOH, and Cl^- was in-vestigated at 25 ‡C in stirred and quiescent solutions on different substrates: Pb, Cu, Al, and C. The deposited lead from the acetate bath was crystalline and showed a marked tendency to form dendrites. The addition of organic additives, phenol, ethyl alcohol, and gelatine, was found necessary in order to obtain a bright, smooth, and compact lead deposit on Pb and Cu electrode. Even with the additives, dendritic lead was observed on Al and C electrodes. Systematic studies of electrodeposition of Pb from these media—such as investigation of the effect of concentration of chemicals in the electrolyte, the effect of temperature, the effect of current density, and the nature of the subtrates—were carried out. Electrochemical techniques such as cyclic voltammetry, potentiodynamic studies, chrono-amperometry, and chronopotentiometry have been employed to shed light on the nature of the reaction mechanism. The deposit quality and purity was examined by X-ray diffraction analysis, SEM, and Auger spectroscopy. The results were compared with those obtained from a fluoborate bath. The quality of a lead deposit from fluoborate bath proved to be similar to that obtained from acetate bath in the presence of organic additives where the deposit was always of a compact, dense, and smooth form.     

Kinetics of manganese reduction leaching from weathered rare-earth mud with sodium sulfite

The kinetics of manganese reduction leaching in an acidic medium from a weathered rare-earth mud (WREM) were investigated. Using sodium sulfite as a reductant, the effect of reaction temperature, mechanical agitation rate, sulfuric acid dosage, and feed particle size on leaching kinetics were examined. The leaching process can be described by the shrinking-core model. An apparent activation energy of 11.5 kJ/mol for manganese reduction leaching is estimated. The diffusion of reactants and leaching products through a porous ore matrix was found to be the rate-limiting step. An empirical equation relating the manganese leaching rate constant with feed-particle size and leaching temperature was established. It was found that the smaller the feed-particle size or the higher the leaching temperature, the faster the leaching proceeds, as anticipated. The kinetic process exhibited a self-catalysis characteristic of Mn²⁺ in the mud. This finding suggests that Mn(III,IV) in the mud was rapidly reduced to Mn²⁺ during the initial stage of leaching.     

Properties of electrolyte solutions relevant to high concentration chloride leaching I. Mixed aqueous solutions of hydrochloric acid and magnesium chloride

A computer code based on a Pitzer model has been developed for the comprehensive prediction of the thermodynamic properties of MgCl₂–HCl aqueous solutions over a wide range of conditions from 25 to 120 °C and from 0–350 g L^− 1 chloride. This code was applied to the calculation of (i) water activities and mean ionic activity coefficients for mixed aqueous solutions of hydrochloric acid and magnesium chloride over a wide range of concentrations and to 100 °C, (ii) solubilities of MgCl₂·6H₂O in MgCl₂–HCl solutions to 80 °C, (iii) partial pressures of HCl(g) and H₂O(g) over MgCl₂–HCl aqueous solutions at various temperatures and (iv) partial pressures of HCl(g) at the normal boiling point of these mixed electrolyte solutions. The model predictions are in excellent agreement with available experimental data and confirm evidence from the literature that MgCl₂(aq) and HCl(aq) mix almost ideally at constant water activity.     

An investigation into the leaching kinetics of cobaltite ore with ferric sulfate solutions

A method for the extraction of cobalt from cobalt-arsenic-sulfide (cobaltite) ores or concentrates has been identified. The method utilizes an atmospheric oxygen-acidic ferric sulfate leach, at temperatures up to 373 K (100°C), to place the cobalt in solution. Extraction of 80 pct of the cobalt was obtained within 24 h and the tests indicate that greater and more rapid extractions are possible. Experiments were performed to assess the effects of temperature, ferric concentration, acid concentration, particle size, oxygen addition, and silver addition on the kinetics of cobaltite and chalcopyrite dissolution. formerly Graduate Student, University of Idaho     

Representation of the solubility of lead chloride in various chloride solutions with Pitzer’s model

A modified Pitzer’s model^[6] has been applied to the representation of the activities of various species in chloride solutions of lead (II). The parameters associated with the representation were the formation constants of four lead chlorocomplexes as well as Pitzer’s interaction parameters. [7] They were determined by treatment of a data base composed of experimental solubilities of lead in NaCl, NH₄C1, and HC1 solutions at 25 °C. The root mean square (rms) relative deviations obtained for the representation of the experimental solubilities were 7.8 pct, 5.6 pct, and 5.6 pct for the three systems, respectively. The extension of the model to solubilities in a NaClO₄-NaCl solution at an apparent ionic strength of 4 mol/kg water gives a rms relative deviation of 8.9 pct if one parameter involving the perchlorate anion is adjusted. A data treatment of experimental solubilities at other temperatures (from 13 °C to 100 °C) for the systems PbCl₂-NaCl-H₂O and PbCl₂-NH₄Cl-H₂O has been made to determine the temperature derivatives of Pitzer’s parameters involving complexed ions as well as the variation of solubility and complexation constants with temperature. The resulting rms relative deviation is 9.8 pct.     

石煤钠化焙烧料酸浸动力学

研究了石煤钠化焙烧料硫酸浸出过程中,浸出剂初始浓度、搅拌速度和浸出温度对浸出率的影响,并对浸出过程动力学进行了分析.结果表明:浸出剂初始浓度和浸出温度对钒浸出率有显著影响,搅拌速度对钒浸出率影响不大;该浸出过程符合核收缩模型,与化学反应控制动力学方程式相吻合,浸出反应的表观活化能为50.88 kJ·mol^-1,浸出过程控制步骤为化学反应控制.