Reaction Kinetics of magnesite ore in dilute ethanoic acid

The leaching of naturally occurring magnesite in dilute ethanoic acid is achieved to optimize the reaction conditions affecting the reaction kinetics. In the current study effect of various reaction parameters (The particle size of ore, concentration of leaching agent, the reaction temperature and rate of stirring) on the dissolution of magnesium carbonate ore with aqueous solutions of acetic acid is probed. It is inferred that the rate of leaching reaction of magnesium carbonate ore in the aqueous solutions of acetic acid rises with a rise in temperature of reaction medium, acetic acid solution strength and decreases with the increase in particle size of the magnesite ore samples. The analysis of kinetic data done by the application of graphical and statistical approaches reveals that the leaching kinetics of magnesite ore in dilute solutions of acetic acid follows a surface chemically controlled mechanism. The calculated value of energy of activation for the dissolution reaction of magnesium carbonate in acetic acid is 46.39 kJ mol^–1.     

磷矿中稀土浸出的动力学研究

研究了硝酸浸出磷矿中稀土的动力学,考察了温度、浓度、粒度对稀土浸出率的影响。结果表明,提高温度和浓度、减小粒度均能提高稀土浸出率。浸出过程符合未反应收缩核模型,受界面化学反应控制,表观活化能为70.6 kJ/mol,表观反应级数为0.83级。     

Leaching kinetics of copper from natural chalcocite in alkaline Na4EDTA solutions

The leaching behavior of copper from natural chalcocite (Cu₂S) particles in alkaline Na₄EDTA solutions containing oxygen was examined at atmospheric pressure. The EDTA leaching process took place with consecutive reactions, where the solid product of the first reaction, covellite (CuS), became the reactant for the second. The copper leached into the alkaline solutions was immediately consumed by the chelation of copper (II) with EDTA, and the mineral sulfur was completely oxidized to sulfate ion. The experimental data for the leaching rate of copper were analyzed with a familiar shrinking-particle model for reaction control. The conversion rate of chalcocite to covellite was found to be about 10 times as high as the dissolution rate of covellite. The time required for complete dissolution of covellite was directly proportional to the initial particle size and was inversely proportional to the square root of the product of the hydroxide ion concentration and the oxygen partial pressure, but it was independent of the Na4EDTA concentration in the presence of excess Na₄EDTA. The observed effects of the relevant operating variables on the dissolution rate were consistent with a kinetic model for electrochemical reaction control. The kinetic model was developed by applying the Butler-Volmer equation to the electrochemical process, in which the anodic reaction involves the oxidation of covellite to copper (II) ion and sulfate ion and the cathodic reaction involves the reduction of oxygen in alkaline solution. The rate equation allowed us to predict the time required for the complete leaching of copper from chalcocite in the alkaline Na4EDTA solutions.     

含碳酸盐脉石氧化铜矿的酸浸动力学

针对碳酸盐脉石对氧化铜矿酸浸动力学的影响进行探讨,研究了温度、酸度、矿石粒径、液固质量比、振荡速度等因素对含碳酸盐脉石氧化铜矿浸出的影响.结果表明,高温、高酸度、高液固质量比、小粒径和高振荡速度利于矿石的浸出,但碳酸盐脉石使得酸耗增加.考虑浸出成本确定合理的浸出条件为温度303 K、酸度35 g·L-1、矿石粒径0.074~0.125 mm、液固质量比3∶1以及振荡速度180 r·min-1,浸出180 min后铜浸出率达53.6%.对浸出前后矿石表面形貌进行分析.结果显示碳酸盐脉石与酸反应后在矿石表面形成CaSO₄·2H₂O沉淀,覆盖在颗粒表面,限制了矿石颗粒孔裂隙的发育.基于收缩未反应核模型对浸出动力学进行分析,发现碳酸盐脉石反应生成的沉淀阻碍了浸出反应,固体产物层扩散为浸出反应的控制步骤,反应的表观活化能为8.65 kJ·mol-1.      

石煤提钒碱浸过程动力学研究

研究了石煤空白焙烧料NaOH溶液浸出过程中液固比、NaOH溶液初始浓度、反应搅拌速率、矿石粒径、温度对浸出速率的影响,确定了石煤提钒碱浸过程动力学方程式,计算了反应的表观活化能.结果表明:液固比、反应搅拌速率对浸出速率的影响不大,NaOH溶液初始浓度、矿石粒径、浸出温度对浸出速率的影响显著;V2O5的浸出动力学适用于收缩未反应芯模型,浸出反应服从化学反应控制过程;根据Arrhenius公式,使用曲线拟合法,近似求得该反应表观活化能约为58.5 kJ·mol-1,进一步表明该反应属于化学反应控制.     

Leaching behaviour of low-grade copper ore in the presence of organic acid

This study investigated the kinetics of copper leaching from malachite ore using formic acid as an organic leaching reagent. The analysis was carried out to determine the effect of the following parameters: particle size, acid concentration, leaching time, formic acid/malachite ratio, reaction temperature and stirring speed. Based on the experimental results, the optimum leaching parameters are as follows: particle size, +75?30?µm; formic acid concentration, 0.4?mol?L^?1; leaching time, 90?min; formic acid (volume)/malachite (weight) ratio, 10?mL?g^?1; temperature, 25°C; and stirring speed, 200?rev min^?1. Copper extraction was 70.25% under optimum experimental conditions. Furthermore, a kinetic model was used to indicate the effects of these parameters on the leaching of copper from malachite ore in formic acid solution. It was observed that the leaching process was controlled by film diffusion through a product layer. In conclusion, formic acid can be utilised as an organic leaching reagent in the leaching process of other ores that are similar in structure and composition to malachite.     

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.     

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.     

Dissolution behaviour of a beryl ore for optimal industrial beryllium compound production

This study involves the leaching of the beryl ore with sulphuric acid (H₂SO₄) solution for predicting optimal beryllium extraction conditions with the aim of assessing the importance of leachant concentration, reaction temperature and particle size on the extent of dissolution. A kinetic model to represent the effects of these variables on the leaching rate was developed. It was observed that the dissolution of beryl ore increases with increasing H₂SO₄ concentration, temperature, decreasing particle size and solid to liquid ratio. At optimal leaching conditions, 89.3% of the ore was reacted by 1.25?mol/L at 75°C temperature and 120 minutes with moderate stirring, where 1612.0?mg/L Be²⁺, 786.7?mg/L Al³⁺, 98.1?mg/L Fe³⁺ and 63.4?mg/L Ag⁺ were found as major species in the leach liquor. The unleached products constituting about 10.7% were examined by X-ray diffraction (XRD) and found to contain primarily, siliceous compounds such as Xonotlite, Antigorite, Chrysolite and Kaolinite.     

Leaching Kinetics of Willemite in Ammonia-Ammonium Chloride Solution

The leaching kinetics of willemite in ammonia-ammonium chloride solution was investigated. The effects of the ammonia-ammonium ratio, particle size, temperature, and total ammonia concentration on the leaching rate of willemite were determined. The results show that the optimum ammonia-ammonium ratio is 1:2 over the studied range. The zinc extraction increases with the reduction of particle size and with the increase of temperature and the total ammonia concentration. Leaching kinetics indicate that the grain pore model could be adopted to describe the leaching process, and diffusion is the main rate-controlling step. The apparent activation energy was determined to be 54.47 ± 6.39 kJ/mol and a reaction order with respect to NH₃(aq) was 3.16 ± 0.40, both of which are likely a result of the parallel nature of the chemical reaction and diffusion in porous solids, even if the chemical reaction is not the rate-controlling step.     

Kinetics of Dissolution of Tenorite in Ammonium Media

In this work, the dissolution kinetics of tenorite (CuO) in a NH₄OH-H₂O system was studied. The studied temperature range was 5–55°C, ammonium hydroxide concentration between 0.1 and 0.75 M, and a particle size range of 5–24 µm. The stirring speed, pH of the ammonia solution, and various agents were also studied. The results indicated that the leaching of tenorite occurred quickly with a particle size of 5 µm in a 0.45 M solution of NH₄OH for a pH value equal to 10.5. Dissolution of CuO also increases as temperature and the concentration of NH₄OH increase. For concentrations less than 0.10 M, there is almost no leaching tenorite. By decreasing the particle size, the dissolution of CuO increase. Results show the stirring speed had no significant effect on the leaching rate of tenorite for values above 250 rpm. Leaching kinetics was analyzed using the model of the surface chemical reaction. The reaction rate was of the order of 2.2 with respect to the concentration of ammonium hydroxide and inversely proportional to the initial particle size. Activation energy of 59 kJ/mol was estimated for the temperature range of 5–55°C.     

Comparative analysis of the dissolution kinetics of galena in binary solutions of HCl/FeCl3 and HCl/H2O2

A comparative study of the dissolution kinetics of galena ore in binary solutions of FeCl3/HCl and H2O2/HCl has been undertaken.The dissolution kinetics of the galena was found to depend on leachant concentration,reaction temperature,stirring speed,solid-to-liquid ratio,and particle diameter.The dissolution rate of galena ore increases with the increase of leachant concentration,reaction temperature,and stirring speed,while it decreases with the increase of solid-to-liquid ratio and particle diameter.The activation energy (Ea) of 26.5 kJ/mol was obtained for galena ore dissolution in 0.3 M FeCl3/8.06 M HCl,and it suggests the surface diffusion model for the leaching reaction,while the Ea value of 40.6 kJ/mol was obtained for its dissolution in 8.06 M H202/8.06 M HC1,which suggests the surface chemical reaction model for the leaching reaction.Furthermore,the linear relationship between rate constants and the reciprocal of particle radius supports the fact that dissolution is controlled by the surface reaction in the two eases.Finally,the rate of reaction based on the reaction-controUed process has been described by a semiempirical mathematical model.The Arrhenius and reaction constants of 11.023 s-1,1.25×104 and 3.65×102 s-1,8.02×106 were calculated for the 0.3 M FeCl3/8.06 M HCl and 8.06 M H202/8.06 M HCl binary solutions,respectively.     

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.     

硫铁矿-木炭湿法浸出高铁氧化锰矿的研究

针对两矿法浸出高铁氧化锰矿存在生成大量单质硫并覆盖在矿物颗粒表面,降低了反应速率的问题,研究采用在浸出过程中添加木炭粉的方法吸附单质硫以改善浸出效果。考察了木炭粉添加量、硫铁矿用量、硫酸浓度、浸出温度和浸出时间对高铁氧化锰矿中锰浸出率的影响。在高铁氧化锰矿用量10.0g、硫铁矿用量5.0g、木炭粉添加量0.1g、硫酸浓度1.36mol/L、浸出温度70℃和浸出时间4h的条件下,锰浸出率达到96.7%。     

Leaching of zinc sulfide concentrate from the ganesh-himal deposit of nepal

The leaching of zinc concentrate obtained from the zinc ore located in the Ganesh-Himal region of Nepal has been carried out in the presence of ammonium persulfate (APS) as an oxidant. Leaching variables such as time, temperature, acid, and oxidant concentration, E _h , and particle size of sphalerite concentrate were studied to optimize the condition and to understand the mechanism of the reaction. The zinc extraction increased up to a temperature of 333 K and a further rise in the temperature to 343 K resulted in lowering of metal extraction. A decrease in particle size and increase in oxidant concentration enhanced the dissolution rate of zinc. The leaching data best fitted to the mixed controlled kinetic model. An activation energy of 43 kJ/mol was obtained for the dissolution of zinc in the temperature range 303 to 333 K with APS. The leaching mechanism was further established by characterizing the original concentrate and the leach residue by X-ray diffraction (XRD) phase identification and scanning electron microscopy (SEM) studies.     

Leaching and kinetic modelling of low-grade calcareous sphalerite in acidic ferric chloride solution

The leaching kinetics of a low grade-calcareous sphalerite concentrate containing 38% ankerite and assaying 32% Zn, 7% Pb and 2.2% Fe was studied in HCl–FeCl₃ solution. An L₁₆ (five factors in four levels) standard orthogonal array was employed to evaluate the effect of Fe(III) and HCl concentration, reaction temperature, solid-to-liquid ratio and particle size on the reaction rate of sphalerite. Statistical techniques were used to determine that pulp density and Fe(III) concentration were the most significant factors affecting the leaching kinetics and to determine the optimum conditions for dissolution. The kinetic data were analyzed with the shrinking particle and shrinking core models. A new variant of the shrinking core model (SCM) best fitted the kinetic data in which both the interfacial transfer and diffusion across the product layer affect the reaction rate. The orders of reaction with respect to (C_Fe³⁺), (C_HCl), and (S/L) were 0.86, 0.21 and − 1.54, respectively. The activation energy for the dissolution was found to be 49.2 kJ/mol and a semi-empirical rate equation was derived to describe the process. Similar kinetic behavior was observed during sphalerite dissolution in acidic ferric sulphate and ferric chloride solutions, but the reaction rate constants obtained by leaching in chloride solutions were about tenfold higher than those in sulphate solutions.     

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     

Kinetics of leaching selenium from Ni-Mo ore smelter dust using sodium chlorate in a mixture of hydrochloric and sulfuric acids

The kinetics of leaching selenium from Ni-Mo ore smelter dust in H₂SO₄-HCl-H₂O system was investigated. The effects including leaching temperature and time, particle size of the smelting dust, stirring speed, acid concentration and the coefficient β (the molar ratio of sodium chlorate to selenium in the smelter dust) on leaching of selenium were studied. The results indicated that the leaching of selenium increased sharply with the increase of temperature. The leaching of selenium reached 98% at 95 °C and stirring speed of 350 rpm for 150 min with the particle size of − 0.15 mm, initial [H⁺] concentration of 8 mol/L, the solid/liquid ratio of 1:5 g/mL and the coefficient β of 3.33. The leaching process was controlled by the surface chemical reaction and the kinetics of leaching selenium from Ni-Mo ore smelter dust followed the model of “shrinking core”. The apparent activation energy of leaching selenium was determined to be 44.4 kJ/mol, which was consistent with the values of activation energy reported for the surface chemical reaction control. The kinetics equation of leaching selenium from Ni-Mo ore smelter dust was expressed as , which coincided with the experimental results.     

复杂硅酸盐含钪精矿钪浸出助浸剂试验研究

对复杂硅酸盐含钪矿进行了化学成分分析,钪物相的测定等的研究。研究是在复杂硅酸盐类矿物选钪试验的基础上,进行复杂硅酸盐含钪精矿浸出助浸剂试验研究,通过试验研究找到了合适的浸出液和适当的助浸剂,对有用离子进行浸出富集,对有害的离子使其保留在浸渣中。试样的钪以类质同象分布于多种复杂硅酸盐矿物中,研究采用盐酸添加浸出助浸剂来解离硅酸盐类矿物,把钪元素浸出在盐酸溶液之中。浸出助浸剂是影响钪浸出率的主要因素之一,在盐酸作为浸出试剂基础上,本研究对助浸剂种类、用量、液固比、浸出时间、盐酸浓度、浸出温度及入浸物料粒度等条件进行了试验研究。研究表明:(1)本试样的成分复杂,含众多杂质离子,包含对浸出有很大影响的的活泼金属离子,和对后续萃取有很大影响的钙、镁离子等杂质离子。(2)盐酸加二号助浸剂时钪的浸出效果最佳,其最佳工艺条件为:入浸物料粒度为-0.05 mm,液相中HCl质量分数为15.2%,液固比5:1,添加二号助剂量为4%,温度为90℃,连续搅拌浸出时间为12 h,钪的浸出率达88.33%。     

湖南湘西某钒矿提取五氧化二钒试验研究

研究了湘西某石煤钒矿提取五氧化二钒的工艺条件：分别考察了添加剂种类与用量、焙烧温度、焙烧时间、原矿磨矿粒度、硫酸加入量、浸出时间、浸出温度等对钒浸出率的影响。试验得出结果：空白焙烧870℃、焙烧时间4h、原矿磨矿粒度-74μm≥71％情况下,添加1．8％硫酸,室温浸出1h。在此条件下,钒的提取率可达87％以上。该含钒浸出液用717树脂离子交换一沉钒一煅烧工艺可以提炼出YB／T5304—2006冶金用99钒,该钒矿总回收率为84．5％。