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.     

A mathematical model for the solution mining of primary copper ore: Part I. leaching by oxygen-saturated solution containing no gas bubbles

An unsteady-state, one-dimensional model which simulates the solution mining of a rubblized copper ore body deeply buried below the water table has been developed. Leaching is accomplished by pumping water saturated with oxygen into the bottom of the flooded rubble chimney. The physical processes incorporated in the present model include the axial convective transport of mass and heat, axial dispersion of mass, mass transfer between the bulk fluid and solid surface, and pore diffusion within the ore fragments. The solution withdrawn from the top of the chimney is recycled through the bottom of the chimney, and the temperature of the chimney is allowed to build up by means of the heat generated during leaching. The coupled model equations are solved numerically by an implicit finite-difference method. Model calculations for the leaching process are made for two different modes of operation: (1) constant flow-rate and (2) variable flow-rate of the leach solution during leaching. The calculated results from both modes of operation indicate that thefractional recovery of copper increases with decreasing ore particle size, ore grade, pyrite/chalcopyrite molar ratio, and shape factor. Copper recovery is rather insensitive to the chimney porosity under typical operating conditions.     

碱性氧化铜矿产氨菌浸出特性

为了研究碱性氧化铜矿产氨菌浸出特性,分析了产氨菌浸矿过程对矿石的作用.将云南某矿的碱性氧化铜矿置于含菌培养液、去菌培养液和氨水等5种浸矿溶液中,在同一条件下进行摇瓶浸矿实验,剖析溶液中各可能的浸矿因子.研究结果表明:产氨菌产氨能力较强,尿素培养液中氨质量浓度最大达8.93 g·L-1;产氨量与细菌含量呈正相关关系,细菌含量越高,产氨量越大;产氨菌主要通过产氨间接浸矿,此外产氨菌和其代谢产物都能直接作用于矿石,浸矿能力细菌产氨 > 细菌 > 细菌代谢产物,三者比值约为12:5:4.      

Mixed-control kinetics of oxygen leaching of chalcopyrite and pyrite from porous primary ore fragments

The leaching of individual copper ore fragments was investigated under oxygen pressure of 690 to 3100 kPa. After 500 hours of leaching at 90°C under 3100 kPa oxygen pressure, 50 pct of copper was extracted from an ore particle of 0.57 cm size, while 1300 hours were needed to extract 90 pct of copper under the same experimental conditions. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains and the pore diffusion of dissolved oxygen within the ore fragment was formulated to interpret the experimental results. Both chemical reaction and diffusion were found to be important to the overall leaching rate in the particle size range tested. The model can also be used to predict the leaching behavior of particles of different sizes at different temperatures and oxygen partial pressures. H. K. LIN, formerly Graduate Student in the Department of Metallurgy and Metallurgical Engineering, University of Utah     

类砂岩型矿石浸出液质量浓度混沌时序重构与浸矿周期预测

以河砂、水泥和盐为原料制作类砂岩型矿石试件,采用水浸的方式对不同品位矿石进行浸矿试验,对浸出液质量浓度进行监测.考察了浸出液质量浓度和浸出率随浸矿时间演变规律;将浸出液质量浓度时间序列进行相空间重构,用混沌理论揭示了不同品位矿石浸出液质量浓度在相空间中相点距演化规律;利用灰色理论,建立了浸出液质量浓度相点距演化预测模型,确定合理的浸矿周期.研究发现:浸出液质量浓度表现出混沌特性,对其进行相空间重构处理后,细微变化特征得以放大,内部规律得以充分展现;不同品位矿石表现出不同的非线性动力学行为;利用基于相空间重构的残差修正灰色模型预测了浸矿周期,为溶浸采矿理论与技术提供了一种新的研究和探讨方法.      

Evaluation of velocity-dependent in situ leaching processes: Single-porosity model

A methodology to characterize processes of in situ leaching is developed to study various parameters that may affect the recovery of a valuable mineral and to assure a successful application of the in situ leaching technology. A leaching kinetics model is first derived based on the concept of representative elementary volume (REV) in porous ore deposits. Every parameter in the model is clearly defined and may be easy to obtain in practice. Then the governing equations are obtained for transport of both the reagent and the dissolved mineral in porous ore deposits. These equations are solved by a fully three-dimensional computer simulator. Effects on the mineral recovery of parameters such as lumped rate constant, ore porosity, injection flux, and macrodispersivities are investigated through the three-dimensional case with one injection well. It is found that all of these four parameters, interconnected through the ore porosity, significantly affect the effectiveness of the in situ leaching. Furthermore, the flow velocity of leach solution within an ore deposit may be the key parameter to the design of a real leaching mine because all of the other three parameters are site specific.     

Kinetics model for leaching of ion-adsorption type rare earth ores

This paper aims to establish a mathematical model that can analyze the whole leaching kinetics process of ion-adsorption type rare earth ores. This leaching process is composed of three steps: (1) ammonium ions arrive at the ore particle surface through the diffusion layer; (2) ammonium ions exchange with rare earth ions; and (3) rare earth ions enter into the external solution through the diffusion layer. In the leaching process, it is hypothesized that the ore particle size remains constant. The process of ammonium ions and rare earth ions passing through the diffusion layer was described by the Fick law, and the reversible ion exchange process between ammonium ions and rare earth ions was described by the Kerr model. A leaching kinetics model of rare earth ions by ammonium ions was constructed. Accuracy of this kinetics model was verified with laboratory tests. It is found that the correlation coefficients of all data are greater than 0.9000. The proposed kinetics model is therefore feasible for kinetics analysis throughout the leaching process.     

Model for ferric sulfate leaching of copper ores containing a variety of sulfide minerals: Part I. Modeling uniform size ore fragments

A computer model was constructed for bacterial ferric sulfate leaching of the major sulfides found in porphyry copper deposits. Leaching occurs by reactions with ferric ion diffusing into the rock fragment. The model incorporates the reaction kinetics of the individual minerals and keeps material and energy balances. The model is needed to aid in the design of modifiedin situ leaching operations and combines desirable features found in previous models with extensions needed for the described study ofin situ leaching. In modeling the leaching of single ore fragments, it is shown that the rate of ferric ion generation by bacteria can limit the rate of copper recovery. The transition from kinetic to diffusion rate limitation is different for each mineral and ore fragment size. The width of the leaching reaction zone is different for each mineral, and many reaction zones cannot be considered narrow. Minerals do not leach in proportion to their concentration in ore fragments.     

云南某难处理硫化银矿石氰化浸出试验研究

对云南某难处理硫化银矿石进行氰化浸出及锌粉置换工艺试验研究。通过对其影响因素进行探讨,得出最佳试验条件,且可获得68.41%的银浸出率,高于理论浸出率;将锌粉用质量分数1%的硝酸铅溶液浸泡10 min后,过滤清洗,再进行贵液置换,银的置换率达86.79%,指标相对较好,而锌粉的处理方式是影响贵液置换的关键因素。     

A mathematical model for the solution mining of primary copper ore: Part II. leaching by solution containing oxygen bubbles

The one-dimensional model developed previously to simulate thein situ leaching of copper from deeply-buried low-grade copper ore deposits is used to simulate thein situ operation in which the oxygen-saturated solution containing oxygen bubbles is introduced at the bottom of the chimney. The physical and chemical processes incorporated in the present model include the axial convective transport of mass and heat, axial dispersion of mass, mass transfer between the liquid and gas phases, fluid-solid mass transfer, diffusion of oxygen in the pores of ore fragments, and the dissolution of sulfide minerals. The coupled model equations are solved numerically by an implicit finite-difference method. Calculations have been made for various values of the volume fraction of oxygen bubbles (up to 0.1) in the fluid just downstream of the oxygen sparging nozzle. Calculated results indicate that, for a specific chimney considered, the total amount of copper extracted increases with increasing volume fraction of undissolved oxygen bubbles in the inlet fluid and increasing superficial velocity of the solution (up to 20 m per day). However, a further increase in the superficial velocity of liquid or undissolved oxygen bubbles does not enhance copper extraction. Calculated results also indicate that the total fractional recovery of copper increases with decreasing pyrite to chalcopyrite molar ratio, ore grade, particle size, and shape factor.     

Bacterial succession in bioheap leaching

Bioheap leaching of secondary copper ores is applied commercially at operations in Chile, Australia, and Myanmar. Bioheap leaching of sulfidic refractory gold ores has been demonstrated at large scale. There is limited comprehension of what actually occurs microbiologically in full-scale bioheap operations, despite the commercial achievement of copper ore bioheap leaching and the anticipated technical and commercial success of gold ore bioheap leaching. Copper bioheaps are typically inoculated with the bacteria contained in the raffinate or intermediate leach solution, whereas, sulfidic refractory gold ore bioheaps can be inoculated with bacteria developed in a separate reactor. Chemical and physical conditions within bioheaps change radically from the time the bioheap is stacked and inoculated until bioleaching is completed. Redox, acidity, temperature, oxygen and solution chemistry conditions vary widely during the oxidation period. Such conditions likely select for microorganisms or may, in fact, effect a succession of organisms in portions of the bioheap. Bioheap solutions are recycled and constituent build-up over time also affects the microbiology. Organic entrapment in the raffinate from the solvent extraction circuit may influence microbial activity. Heterotrophic microorganisms may also play some role in bioheap leaching. Understanding the microbiology of bioheaps is key to advancing commercial bioheap applications. Such knowledge will increase the ore types as well as the diversity of mineral deposits that can be processed by bioheap technology. It will also enable better control of conditions to improve leach rates, metal recoveries and costs. This paper briefly explains commercial practices, describes chemical, physical and microbiological monitoring of bioheaps, considers conditions that control microbial populations in bioheaps, and examines the types of ore deposits that could be bioleached, if the microbiology was elucidated.     

A kinetic study on the pressure leaching of sphalerite

The dissolution of sphalerite (ZnS) in sulfuric acid solution under oxygen pressure was investigated. Effects of temperature, percent solids, agitation, sample size, oxygen partial pressure and foreign ions were evaluated. The effect of hydrogen pretreatment on sphalerite leaching rate was also examined. Leaching of sphalerite at 90°C and 150 psi oxygen pressure was found to occur at a constant rate. This rate was determined from the experimental data observed under the different leaching conditions mentioned above. The constant leaching rate was attributed to the chemical reaction occurring on the surface of the flat-plate type sphalerite sample. The rate-controlling step of the reaction was determined to be the oxidation of hydrogen sulfide to elemental sulfur. Oxidation of hydrogen sulfide was studied through the addition of iron and through the observation of the change in iron concentration during leaching. The oxidation was concluded to be by reaction with ferric ion rather than by direct oxygen oxidation. Leaching tests run with samples pretreated with hydrogen do not show any increase in the rate of zinc extraction. M. T. HEPWORTH, formerly with University of Denver.     

硫氧混合铅锌矿中锌的氧化氨浸动力学

常压低温条件下在NH₃-（NH₄）₂SO₄体系中使用过硫酸铵作为氧化剂对硫氧混合铅锌矿中的锌进行浸出实验,系统研究了搅拌速度、浸出剂浓度、氧化剂浓度与温度对于锌浸出率的影响.结果表明,在最优条件下锌的浸出率可达93.2%,且浸出过程中几乎没有其他离子进入溶液,实现了锌的选择性高效浸出,从而简化了后续的浸出液净化与材料制备过程.动力学研究表明,硫氧混合铅锌矿中锌的氧化氨浸过程遵循固体产物层扩散控制的未反应核收缩模型,浸出反应的表观活化能为17.89 kJ·mol-1.      

高磷鲕状铁矿酸浸脱磷

研究了酸浸处理高磷铁矿脱磷及其影响因素.实验用鄂西鲕状高磷矿Fe的质量分数为51.7%,P的质量分数约0.5%,S的质量分数为0.34%.通过硫酸浸出,浸出矿中磷的质量分数降低至0.07%左右,而铁损只有0.18%,S的质量分数为0.35%,满足钢铁生产的要求.通过扫描电镜观察和能谱分析表征了高磷矿中磷的脱除,在实验酸度下能明显看出磷灰石溶解,而铁相基本不反应,并得到了热力学计算证明.实验确定了最佳的酸浸条件:浸出时间1 h,液固比100mL:8 g,酸度0.2 mol·L-1,振荡频率150 Hz.通过微波加热预处理,高磷铁矿中产生微裂纹,增加了矿石的比表面积,但是这并没有明显促进酸浸脱磷的进行.通过补酸的方式循环利用酸浸液处理高磷铁矿能得到较好的脱磷效果,脱磷率稳定在80%,能有效减少酸耗、保护环境.      

矿堆非饱和渗流中的界面作用

为探明矿堆非饱和浸出渗流规律,以界面作用为切入点,分析了浸出液的运动状态.矿堆中吸力由界面作用产生的基质吸力和吸收扩散产生的渗透吸力组成.孔隙中介质分布的不均匀性和矿石形状的随机性是导致界面作用多样性以及浸出液运动状态复杂的原因.采用毛细上升实验很好地证明了矿堆中吸力的存在,在驱动力的作用下,浸润初期的液面上升速度较快,浸润后期液面上升相对平缓.通过拟合得知液面毛细上升高度与浸润时间符合幂函数关系.理论研究表明可以通过改变固相、液相和气相的物理性质来实现对矿堆非饱和渗流中界面作用的调控.      

Decomposition of mixed rare earth concentrate by NaOH roasting and kinetics of hydrochloric acid leaching process

A new clean extraction technology for the decomposition of Bayan Obo mixed rare earth concentrate by NaOH roasting is proposed.The process mainly includes NaOH roasting to decompose rare earth concentrate and HCl leaching roasted ore.The effects of roasting temperature,roasting time,NaOH addition amount on the extraction of rare earth and factors such as HCl concentration,liquid-solid ratio,leaching temperature and leaching time on the dissolution kinetics of roasted ore were studied.The experimental results show that when the roasting temperature is 550℃ and the roasting time is 60 min,the mass ratio of NaOH:rare earth concentrate is 0.60:1,the concentration of HCl is 6.0 mol/L,the ratio of liquid to solid(L/S) 6.0:1.0,and the leaching temperature 90℃,leaching time 45 min,stirring speed 200 r/min,and the extraction of rare earth can reach 92.5%.The relevant experimental data show that the process of HCl leaching roasted ore conforms to the shrinking core model,but the control mechanism of the che mical reaction process is different when the leaching temperature is different.When the leaching temperature is between 40 and 70℃,the chemical reaction process is controlled by the diffusion of the product through the residual layer of the inert material.The average surface activation energy of the rare earth element is E_a=9.96 kJ/mol.When the leaching temperature is 75-90℃,the chemical reaction process is controlled by the interface transfer across the product layer(product layer interface mass transfer) and diffusion.The average surface activation energy of rare earth elements is E_a=41.65 kJ/mol.The results of this study have certain significance for the green extraction of mixed rare earth ore.     

Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate

Manganese compounds, such as manganese sulfate, can be obtained from pyrolusite, a manganese ore. Low-grade manganese ores is usually treated by hydrometallurgical methods. In this study, the leaching and recovery of manganese from pyrolusite ore in sulfuric acid solutions containing sawdust as reducing agent was investigated. The effects of experimental parameters, such as sulfuric acid concentration, sawdust amount, solid-to-liquid ratio, stirring speed, particle size, reaction temperature, and leaching time, on the manganese extraction from ore were examined. The results showed that the leaching rate of pyrolusite ore increased with an increasing sulfuric acid concentration, sawdust amount, stirring speed, reaction temperature and leaching time, and decreasing in solid to liquid ratio and particle size. The kinetic analysis of leaching process was carried out, and it was determined that the reaction rate was controlled by diffusion through the product layer under the experimental conditions in this work. The activation energy was found to be 22.35 kJ mol^?1. Manganese can be recovered as manganese sulfate by the evaporative crystallization of the purified leach liquor.     

Cupric chloride leaching of model sulfur compounds for simple copper ore concentrates

To learn more about the leaching characteristics of simple copper ore concentrates, the leaching behavior of cupric sulfide (CuS) and cuprous sulfide (Cu₂S) was studied. These compounds serve as model compounds for covellite and chalcocite, respectively. With aqueous saline cupric chloride solutions above 100 °C, dissolution of both compounds is rapid, but does not proceed to completion on a stoichiometric basis. The course of the leaching can be explained with a solution model based on thermodynamic considerations and recognition of certain side reactions. The model is based on consideration of the complexes formed by various ionic species in solution and their effect on the observed extent of reaction near equilibrium. The leaching process was found to be enhanced by elevated temperatures, high chloride concentrations, and acidity. Limited leach times also were found to be advantageous. At dilute copper concentrations, leaching reactions could be driven closer to completion than with higher concentrations, as predicted by the model. For process reasons, it is desirable to convert all copper (II) in solution to copper (I). Routes for accomplishing this are reviewed.     

Investigation of Leaching Kinetics of Copper from Malachite Ore in Ammonium Nitrate Solutions

The production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303?K to 323?K [30?°C to 50?°C]) and diffusion through a porous product layer (323?K to 343?K [50?°C to 70?°C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50?kJ/mol, respectively.     

Kinetic study of nonoxidative leaching of cinnabar ore in aqueous hydrochloric acid-potassium iodide solutions

Results obtained in a kinetic study of nonoxidative leaching of cinnabar ore in aqueous hydrochloric acid-potassium iodide solutions and the basic reactions in a new process of cinnabar treatment for obtaining mercury are presented. Experiments were performed at stirring speeds fast enough to eliminate the effect of this variable in the overall reaction rate. Under these experimental conditions the dissolution rate appears to be controlled by chemical reaction on the cinnabar surface. An activation energy of 42.3 kJ/mole was found. The dissolution rate is of the first order with respect to hydrochloric acid activity and of second order with respect to potassium iodide activity. The reaction rate in the different leaching conditions was established through weight loss of very pure cinnabar spheres submerged in the attack solution for known periods of time.