Difference in dissolution between germanium and zinc during the oxidative pressure leaching of sphalerite

The difference in dissolution between germanium and zinc during oxidative pressure leaching of germanium-bearing sphalerite was evaluated in laboratory-scale experiments. The effect of temperature and time on germanium hydrolysis, coprecipitation with silica, and coprecipitation with iron oxides was investigated. Experimental results show coprecipitation with silica is the most important factor, followed by coprecipitaion with iron, and finally germanium hydrolysis, causing germanium losses of 9%, 5% and 2%, respectively.     

Oxidative acid leaching of mechanically activated sphalerite

The pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44?kJ?mol^?1 as the activation time increased from 0 to 30, 60, and 120?min, respectively. The reaction orders for the H₂SO₄ solutions of the sphalerite samples activated for 0, 30, 60, and 120?min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H₂SO₄ could be reduced by means of mechanical activation.     

A kinetic study of the leaching of chalcopyrite at elevated temperatures

A study of the rate of dissolution of chalcopyrite (CuFeS₂) in acidic solutions under oxygen overpressures was carried out by measuring the rate of formation of cupric ions in solution. Effects of temperature, oxygen partial pressure, surface area, and concentration of sulfuric acid were evaluated. A sized batch of chalcopyrite was leached in the temperature range of 125 to 175° and in the pressure range of 75 to 400 psi of oxygen. In 0.5N H₂SO₄ all products of reaction went into solution except for trace amounts of elemental sulfur. The dissolution of chalcopyrite followed linear kinetics and was essentially independent of hydrogen ion concentration for H₂SO₄ concentrations between 0.2 and 0.5 JV. The oxygen dependence indicated adsorption approaching limiting values with increasing oxygen pressure. The linear mechanism was explained in terms of steady-state adsorption of oxygen at the chalcopyrite surface followed by a surface reaction. The enthalpy of activation for adsorption of oxygen was found to be approximately 33 kcal per mole. An activation enthalpy of approximately 9 kcal per mole was observed for the surface reaction. Charge transfer reaction are not rate controlling in the process.     

Reaction kinetics of the ferric chloride leaching of sphalerite—an experimental study

Chloride leaching processes have significant potential for treating complex sulfides. One advantage of chloride leaching is fast dissolution rates for most sulfide minerals. This experimental study is concerned with ferric chloride leaching of sphalerite, a common component of many complex concentrates. The effects of stirring, temperature, ferric ion concentration, and particle size have been examined. In addition, reaction residues at various levels of zinc extraction were examined by SEM, and the products of reaction were identified by energy dispersive X-ray analysis and X-ray diffraction. These observations indicated that the dissolution reaction is topochemical. Moreover, the leaching results fit a surface reaction control model. The activation energy was calculated to be 58.4 kJ/mole which is reasonable for a rate limiting surface reaction. The order of the reaction was 0.5 with respect to Fe³⁺ at low concentrations and zero at high concentrations. The change in reaction order occurred at similar Fe³⁺ concentrations for various particle sizes. This is believed to be indicative of an electrochemical reaction mechanism at low Fe³⁺ and an adsorption mechanism at higher Fe³⁺. A kinetic model for the ferric chloride leaching of sphalerite was also obtained for the lower Fe³⁺ concentrations and is given by: (ie5-01) This model is in excellent agreement with the experimental results for fractions of zinc extracted up to 0.95.     

Kinetics of biochemical leaching of sphalerite concentrate

The paper deals with bacterial leaching of sphalerite. The data include progress curves for leaching of the concentrate in terms of Zn, Cu, and Cd solubilization. Plots of the Zn and Cu data followed a relationship predicted by a chemical rate equation. Reaction rates for Zn and Cu were inversely related to initial particle size of the concentrate. A pulp density in excess of 2 pct caused a decrease in percent Zn leached in 31 days, presumably due to oxygen limitation. The leaching of Zn and Cu followed first order kinetics.     

Reaction mechanism for the ferric chloride leaching of sphalerite

Reaction mechanisms for the ferric chloride leaching of sphalerite are proposed based on data obtained in leaching and dual cell experiments presented in this work and in a previous study. The results from the leaching experiments show that at low concentrations the rate is proportional to [Fe³⁺]_T ^0.5 and [Cl^-]_T ^0.43 but at higher concentrations the reaction order with respect to both [Fe³⁺]_T and [Cl^-]_T decreases. Using dual cell experiments which allow the half cell reactions to be separated, increased rates are observed when NaCl is added to the anolyte and to the catholyte. The increase in rate is attributed to a direct, anodic electrochemical reaction of Cl^- with the mineral. When NaCl is added only to the catholyte, a decrease in the rate is observed due to a decrease in theE ⁰ of the cathode which is attributed to the formation of ferric-chloro complexes. Several possible electrochemical mechanisms and mathematical models based on the Butler-Volmer relation are delineated, and of these, one model is selected which accounts for the experimentally observed changes in reaction order for both Fe³⁺ and Cl^-. This analysis incorporates a charge transfer process for each ion and an adsorption step for ferric and chloride ions. The inhibiting effect of Fe²⁺ noted by previous investigators is also accounted for through a similar model which includes back reaction kinetics for Fe²⁺. The proposed models successfully provide a theoretical basis for describing the role of Cl^-, Fe³⁺, and Fe²⁺ as well as their interrelationship in zinc sulfide leaching reactions. Possible applications of these results to chloride leaching systems involving other sulfides or complex sulfides are considered.     

A kinetic model for the acid-oxygen pressure leaching of Ni–Cu matte

A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni₃S₂. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O₂ flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O₂ flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase.     

Effect of aging conditions on the leaching of mechanically activated pyrite and sphalerite

The leaching of mechanically activated pyrite and sphalerite exposed to nitrogen (99.999 vol pct) or air at ambient temperature or 573 K was investigated. The results indicate that at the same leaching time, the iron-leaching ratio of mechanically activated pyrite or sphalerite aged in nitrogen at both ambient temperature and 573 K decreases slightly with increasing aging time and remains constant after a certain aging period. The iron-leaching ratio of mechanically activated pyrite exposed to ambient air varies with the exposure period. But, at the same leaching time, the zinc-leaching ratio of mechanically activated sphalerite aged at ambient temperature does not change with the aging atmosphere. The structures of mechanically activated pyrite and sphalerite after being aged were determined. The specific granulometric surface area of mechanically activated pyrite and sphalerite decreases with increasing aging time, but keeps constant after a certain aging period. The X-ray diffraction patterns of mechanically activated pyrites aged in nitrogen do not change with aging time; neither do the X-ray diffraction patterns of mechanically activated sphalerites aged either in air or in nitrogen. For mechanically activated pyrite exposed to ambient air for 3 and 6 months, new phases were found. The lattice distortion and the elemental sulfur content of pyrite and sphalerite mechanically activated in nitrogen were also investigated. The results indicate that the elemental sulfur content of mechanically activated pyrite rises noticeably, and its lattice distortion (ε) rises slightly, with increasing grinding time. The elemental sulfur content of mechanically activated sphalerite remains constant at 0.5 mg elemental sulfur per gram of sphalerite, and its lattice-distortion ratio increases apparently with increasing grinding time. These observations provide further evidence for our opinion that the formation of dangling bonds on the surface of mechanically activated pyrites and the lattice distortion on the surface of mechanically activated sphalerites may mainly result in the enhancement of hydrometallurgical process for corresponding sulfide minerals.     

高铁闪锌矿加压浸出过程中Fe的动力学研究

进行了高铁闪锌矿加压浸出过程Fe的动力学研究。考察了温度、压力、始酸浓度、矿样粒度、溶液中Fe^2＋浓度对Fe浸出率的影响。结果表明，在试验条件下，浸出初期Fe的浸出速率受化学反应控制遵循“未反应核减缩型”表面化学反应控制的动力学规律，浸出后期受固膜扩散控制，浸出中期由二者共同控制。     

高铁闪锌矿加压浸出过程中Fe的动力学研究

进行了高铁闪锌矿加压浸出过程Fe的动力学研究。考察了温度、压力、始酸浓度、矿样粒度、溶液中Fe ~(2+)浓度对Fe浸出率的影响。结果表明,在试验条件下,浸出初期Fe的漫出速率受化学反应控制,遵循“未反应核减缩型”表面化学反应控制的动力学规律,浸出后期受固膜扩散控制,浸出中期由二者共同控制。     

A kinetic study that compares the leaching of gold in the cyanide, thiosulfate, and chloride systems

Due to the increasing environmental and public concerns over cyanidation, there has been a large amount of research into viable alternative lixiviants. This article presents a detailed kinetic study of gold leaching in cyanide, ammonia/thiosulfate, and chloride/hypochlorite solutions. The gold leach rates were measured using a rotating electrochemical quartz crystal microbalance (REQCM). This instrument allows the mass of a gold sample to be measured in situ, with a sensitivity of less than 10 ng. It will be shown that for the cyanide system, the leach rate of a gold/silver alloy is substantially higher than that of pure gold; for the gold/silver alloy, the reaction is diffusion controlled. For the thiosulfate system, reaction rates which are substantially higher than those for cyanide can be achieved with freshly prepared solutions containing copper(II), although the leach rate decreases as the copper(II) reacts with thiosulfate. A steady-state copper(II) concentration is obtained once the rate of copper(II) reduction by thiosulfate matches the rate of copper(I) oxidation by oxygen; at these steady-state concentrations of copper(II), the leach rates are slower than those obtained for cyanide. It will also be shown that reaction rates similar to the cyanide system can be readily achieved in chloride media at pH 3 with 2.5 mM hypochlorous acid; under these conditions, the reaction is limited by the diffusion of HClO.     

Column leaching of lanthanides from Abu Tartur phosphate ore with kinetic study

The dynamic leaching of lanthanides from a west desert phosphate ore, Egypt (Abu Tartur) by hydrochloric acid, nitric acid and sulfuric acid solutions was investigated in this study as a function of acid concentration, flow rate and the presence of some additives such as boric acid. Also the kinetics of leaching of lanthanides was investigated as a function of temperature. It was found that the leaching process could be described by a shrinking-core model, with activation energy about 5.9, 13.8 and 21.9 kJ/...     

锌精矿常压浸出与加压浸出工艺比较

比较了常压浸出与加压浸出两种工艺的机理、流程、技术经济指标、投资以及存在的问题。试验和生产数据表明,加压浸出在技术上和工艺上都更具有吸引力。     

锌精矿常压浸出与加压浸出工艺比较

比较了常压浸出与加压浸出两种工艺的机理、流程、技术经济指标、投资以及存在的问题。试验和生产数据表明,加压浸出在技术上和工艺上都更具有吸引力。     

铜锌混合矿加压浸出的试验研究

进行了铜锌混合矿加压浸出的试验研究,分析了氧分压、酸度、温度、反应时间、添加剂等因素对铜锌浸出率的影响。试验结果表明,在氧分压0.4MPa、酸度240g/L、温度140℃、浸出时间150min、添加剂用量0.10%￣0.22%的条件下浸出,铜、锌的浸出率均可达97%。     

铜锌混合矿加压浸出的试验研究

进行了铜锌混合矿加压浸出的试验研究，分析了氧分压、酸度、温度、反应时间、添加剂等因素对铜锌浸出率的影响。试验结果表明，在氧分压0.4MPa、酸度240g／L、温度140℃、浸出时间150min、添加剂用量0．10%-0．22％的条件下浸出，铜、锌的浸出率均可达97％。     

A simple kinetic model for sulfuric acid leaching of copper from chrysocolla

Experimental results obtained in room temperature laboratory leaching studies of lowgrade chrysocolla are interpreted by a kinetic equation of the form 1?(1?R)^1/3=(1/αKr _c) ln (αkKC ₀t+1) derived on the basis of a special form of the shrinking-core model and assuming chemical-reaction control. The experimental program encompasses a large range of particle sizes and reaction times and significantly extends previous experimental data on similar ore systems. The kinetic model, shown to be consistent with the experimental data, assumes the ore-particle structure to be characterized by pores and channelized regions which extend from the outer surface through a reacted zone into the unreacted core. Scanning electron microscope observations of unreacted particle surfaces as well as reacted particle surface structures lend support to this concept of leaching. The reaction rate is observed to vary inversely with initial mean particle radius, and diffusion in any form appears to be negligible by comparison with surface reaction phenomena.     

低品位氧化钼精矿常压碱浸试验研究

根据钼精矿品位低、钼的氧化率高的特点,进行了常压碱浸条件试验研究,钼的浸出率达到95%以上,氧化钼基本全部漫出.同时进行了钼的连续浸出试验研究,结果表明,碳酸钠在浸出过程中对钼的漫出起作用而且并未消耗,以此制定了多段连续浸出工艺,使碳酸钠的用量下降,浸出液的钼浓度得到提高.