Use of X-ray diffraction in a study of ammonia leaching of multimetal sulfides

X-ray diffraction has been used to study the changes in mineralogy that occur during ammonia leaching of sulfide minerals and complex bulk sulfide concentrates. Leaching results in high extraction rates (>90 pct) of copper from chalcopyrite, zinc from sphalerite, and lead from galena. However, under experimental leaching conditions (temperature, 115 °C to 135 °C; par-tial pressure of oxygen, 1.5 kg/cm²; pH ∼ 10.0), the pyrite grains are practically inert. Ap-parently, the amount of pyrite in leach residue is constant in absolute terms. However, its relative percentage changes because the amount of copper and zinc minerals is reduced in the leach residue during progressive leaching. The products formed during the leaching reaction, such as goethite and lead sulfate, tend to increase the weight of the leach residue, and thus the relative weight of pyrite remains nearly unchanged. The ratios of selected line pair intensities of pyrite lines and characteristic (selected) lines of chalcopyrite, sphalerite, and galena are used to establish the oxidative ammonia leaching kinetics of Cu-Zn-Pb bulk concentrates. That is, the variation in the line pair intensity ratios, with time, correlates with the changes in the el-emental concentrations in the leach liquor.     

Pressure leaching of a sulphide copper concentrate with simultaneous regeneration of the leaching agent

An experimental study is presented of leaching of a sulphide copper concentrate with aqueous ferric sulphate under oxygen pressure. The effects of oxygen pressure, sulphuric acid concentration and ferrous iron additions on the copper leaching rate have been determined. Partial pressure of oxygen has been found to govern the rate of copper leaching while the concentration of sulphuric acid only slightly influences this rate. Oxygen enhances the leaching rate mainly by oxidizing ferrous iron to ferric iron — the major leaching agent — and not by direct action on the minerals.Leaching of a sulphide copper concentrate under oxygen pressure with aqueous ferric sulphate leads to a three-fold reduction of both the necessary leaching time and ferric sulphate concentration in the leaching solution over those for conventional leaching with concentrated aqueous ferric sulphate.     

A kinetic study on nonoxidative dissolution of sphalerite in aqueous hydrochloric acid solutions

The nonoxidative leaching of sphalerite in aqueous acidic solutions was studied from a kinetic point of view. Also the selective nonoxidation leaching in a hydrochloric acid solution containing a large amount of sodium chloride was examined for a Pb-Zn sulfide bulk concentrate. The dissolution rates of sphalerites from five different mines appeared to be controlled by a chemical reaction on the surface of sphalerite. The dissolution rate of sphalerite is of the first order with respect to the hydrogen ion activity of the solutions. It is also considerably affected by the iron content of the sphalerite sample; a linear relationship was observed between iron content of the sphalerite and its dissolution rate. The addition of sodium chloride to the hydrochloric acid solutions greatly enhanced dissolution rates. Compared to the dissolution rates of galena, which were reported in a previous paper, the dissolution rates of sphalerite were found to be far slower. The difference in the dissolution rates between these two minerals becomes greater with the addition of sodium chloride to the hydrchloric acid solutions. Based on these findings, the selective leaching of Pb-Zn bulk concentrate in a hydrochloric acid solution containing a large amount of sodium chloride was examined. The experimental results clearly showed that the galena was selectively leached, leaving a residue of sphalerite. NORIO MISAKI formerly Graduate student, Kyoto University     

A Visual Insight into the Oxidation of Sulfide Minerals During Bioleaching and Chemical Leaching of a Complex Ore

A scanning electron microscope (SEM) study was performed to provide a visual insight into the oxidation patterns of sulfide minerals during chemical and bacterial leaching of a complex ore for 3 days. The mineral grains were studied under SEM before and after bacterial and chemical leaching with or without the addition of ferrous iron to generate ferric iron in situ by bacteria or chemical oxidant (MnO₂). Both mesophilic and moderately thermophilic cultures of bacteria were used in bioleaching tests. A limited oxidation of sphalerite and pyrite, similar to those in acid leaching (control), was observed to occur when no ferrous iron was added. However, the initial addition of ferrous iron into bioleaching media was shown to significantly improve the oxidation of sphalerite and pyrite. Galena was readily oxidized in the presence or absence of bacteria. Sphalerite was oxidized more extensively/selectively than chalcopyrite and pyrite, consistent with their respective nobility/electrochemical activity. Provided that chemical/biological oxidation of sphalerite was intensive, a sulfur-rich layer appeared to form on mineral surface. But, no such layer on pyrite surfaces was discernable. Supplementary bioleaching data were also provided to support SEM observations and to further elucidate the bioleaching characteristics of these sulfide phases. It can be inferred from this study that the oxidation of sulfides proceeds most discernibly via “indirect mechanism” and the generation of ferric iron by bacteria in sufficient quantity is essential for the effective oxidation of sulfide minerals.     

高铟高铁闪锌矿加压酸浸工艺研究

介绍高铟高铁闪锌矿精矿加压酸浸提取锌铟试验研究情况,重点考察精矿粒度、硫酸用量、时间、氧气分压力对铟、铁浸出率的影响。结果表明,采用二段加压浸出,既可以保证高的锌、铟浸出率,又能够实现锌、铟与铁的选择性浸出,降低浸出液的酸度。     

Pressure oxidation of arsenopyrite and pyrite in alkaline solutions

Alkaline pressure oxidation of a sulfide concentrate assaying 60% arsenopyrite and 40% pyrite was investigated. A comparative analysis of the effect of pH, temperature, oxygen partial pressure and particle size on the oxidation rate of both sulfides is presented. The results show that the reaction rates are extremely favored by the increase of pH up to a value of 13.5. The oxidation rate of pyrite increases as oxygen partial pressure increases, while the oxidation rate of arsenopyrite becomes nearly independent of this variable above 202.6 kPa. Apparent activation energies equal to 15.0 and 27.2 kJ/mol were determined for arsenopyrite and pyrite, respectively. High levels of oxidation were achieved working with relatively coarse particle sizes (−212 + 150 μm), under moderate temperature (393 K) and oxygen partial pressure (405.2 kPa).Microprobe analysis revealed that porous layers of iron oxides precipitate on the sulfide particles at high pH, while thin and apparently dense oxide coatings are formed under neutral conditions. Hematite is the main iron oxide formed in all experimental conditions. Sulfates and arsenates were detected only during precipitation from neutral or slightly acid solutions.     

高铁硫化锌精矿氧压酸浸过程分析

论述和分析了高铁闪锌矿氧压酸浸过程中在氧压反应釜中浸出反应过程和可能的浸出机理,并对浸出过程中控制铁以赤铁矿法沉铁的可能性进行了分析。     

含砷烟尘的综合利用

采用氢氧化钠碱性浸出分离回收含砷烟尘中的砷,在优化试验条件下,砷、锑、铅的浸出率分别为99.27%、1.83%和0.20%;砷浸出液经氧化—冷却结晶回收砷酸钠后返回浸出过程循环利用,整个脱砷工艺闭路循环。采用硫化钠浸出—空气氧化法分离回收含砷烟尘碱浸渣中的锑并制备焦锑酸钠,碱浸渣中锑的浸出率为93.03%,锑浸出液中锑沉淀率为98.51%。采用硫酸浸出—铝板置换分离回收硫化钠浸出渣中的铟并制备海绵铟,铟的浸出率为71.83%。硫酸浸出渣中铅的主要以PbS的形式存在,可以作为铅冶炼的原料返回铅厂回收铅。     

加压氧化浸出工艺的机理研究

加压浸出法具有流程短、砷浸出率高、浸出时间短及无SO2等有毒物质产生的优点,是预处理含硫、砷金矿石或金精矿的有效手段.在酸性介质中,硫化物、铁化合物与砷化物发生高温氧化的主要反应包括3种形式:硫化物全部被氧化成硫或硫酸盐,反应过程中产生的Fe2+被氧化成Fe3+,砷被氧化成砷酸盐.随着易处理矿石资源日益减少,加压浸出法...     

硫化锌精矿氧压酸浸液中和除铁新工艺研究与生产实践

针对常规硫化锌精矿一段加压浸出釜外中和—氧化—黄钾铁矾法除铁工艺流程冗长、作业时间长、能耗大等问题,提出了硫化锌精矿氧压酸浸液釜内中和除铁的新工艺。即在一台压力釜内完成硫化锌精矿的浸出后,借助其内部温度、氧化气氛等条件,结合新加入的氧化锌物料和碱盐的作用将浸出液中铁脱除,除铁后的浸出液经液固分离上清液达到中性上清液质量标准,可直接供净化工序除杂。通过生产实践表明该工艺可行,且经济效益显著。     

硫化镍精矿低酸高温氧压浸出研究

采用低酸高温氧压浸出工艺从硫化镍精矿中提取镍,考察硫酸起始浓度、氧分压、浸出温度、时间和液固比对镍浸出率的影响。结果表明,在下述最佳条件下镍浸出率可以达到95%:起始酸度50g/L,氧分压0.9～1.0MPa,温度130～150℃,时间6h,液固比5∶1。     

镁离子对低品位硫化镍矿氧化浸出电化学行为的影响

低品位硫化镍矿中含镁硅酸矿物易被酸溶解出Mg^2+而影响其有价金属提取。采用不同氧化浸出体系研究了Mg^2+对硫化镍矿中Ni、Cu、Mg、Fe浸出的影响,利用循环伏安、动电位极化、交流阻抗等方法研究了Mg^2+影响硫化镍矿中硫化矿物氧化溶解电化学行为。结果表明,试验范围内,低品位硫化镍矿中硫化矿物氧化浸出受氧化产物扩散影响控制,含镁矿物被酸溶解释放出Mg^2+进入溶液,游离的Mg^2+受硫化矿物表面负电性离子吸引而吸附在矿石表面,降低矿物表面氧化溶解双电层电荷转移内阻,加速电荷转移过程;另一方面,由于Mg^2+吸附影响,使得硫化镍矿表面氧化产物膜致密生长而显著负影响硫化矿物浸出,致使硫化矿物自腐蚀速率随Mg^2+浓度增加而降低。Mg^2+对含S物种电对间转化不利,与Fe^3+协同影响硫化矿物氧化浸出效率,低Mg^2+浓度促进Fe^3+/Fe^2+循环,而高Mg^2+浓度引起硫化矿物腐蚀产物层致密生长而降低矿物被溶解的速率。硫化镍矿在不同体系氧化浸出时,初始含Mg^2+条件下,Ni、Cu、Fe浸出效率低于无Mg^2+体系。     

富钴结壳湿法冶金工艺中硫化渣的加压浸出

富钴结壳活化硫酸浸出液经过中和除铁、硫化沉淀后得到的渣采用加压浸出工艺处理,考察了温度、压力、酸度、液固比等因素对加压浸出过程的影响,确定了加压浸出条件,此时镍、钴的浸出率大于99.8%,铜的浸出率大于98%,加压浸出得到的镍、钴、铜混合溶液可进一步萃取分离得到纯净的金属溶液。     

Oxidation of dense iron sulfide

Oxidation of stoichiometric iron sulfide was investigated. Rectangular plates of dense FeS were oxidized in an Ar-O₂ gas mixture at 1023 to 1123 K. Oxygen partial pressure was varied between 1.01 × 10³ and 2.03 × 10⁴ Pa. During the initial five minutes of oxidation, a magnetite layer of about 10 μm in thickness was formed on the surface without the evolution of SO₂ gas. Diffusion of iron from the interior of the sulfide to the sulfide/magnetite interface controlled the oxidation rate. Mass transfer through the gaseous boundary layer at the sample surface also affects the oxidation rate at lower oxygen partial pressures. Following this rapid formation of magnetite, the magnetite layer continued to grow for several hours in accordance with the parabolic rate law. Diffusion of iron through the magnetite layer controlled the oxidation rate during this stage. A thin layer of hematite was also formed on the outer surface of magnetite. When the composition of the inner sulfide core reached Fe_0.9S, the oxidation proceeded irregularly into the interior of the remaining sulfide. Porous oxide was formed and SO₂ gas was evolved. Former Graduate Student     

Surface Effects in Sulfidation Reactions

Abstract

Pure iron and an Fe–41 wt% Ni alloy are reacted at temperatures in the range 793–1073 K with H₂–H₂S–N₂ atmospheres corresponding to equilibrium P _S2 levels from 6.5 × 10^?5 to 0.65 Pat The kinetics of iron sulfidation are intermediate in form to linear and parabolic rate laws. The instantaneous parabolic rate constant is found to increase with extent of reaction until a constant value is reached. For fixed equilibrium sulfur pressures, the instantaneous rate increases with hydrogen sulfide partial pressure; for fixed hydrogen sulfide partial pressure, the instantaneous rate decreases as the equilibrium sulfur pressure is increased. It is demonstrated that hydrogen sulfide is the reactant species. A Langmuir-Hinshelwood kinetic model based on the slow dissociation of adsorbed hydrogen sulfide accounts satisfactorily for the unusual gas-phase compositional effects, and also for the rate at which the reacting system approaches steady state. Similar effects are found for the Fe–41%Ni alloy, where nickel sulfide whisker formation results from localized catalysis of the hydrogen sulfide dissociation reaction.     

硫化锌精矿低温低压中和除铁试验研究及生产应用

试验研究了在低温低压条件下将硫化锌精矿作为中和剂对一段加压酸浸液进行中和除铁,在一定的中和温度、中和时间、氧分压、浸出前液铁离子浓度、液固比等的条件下,较好的实现了在低温除铁,有效解决硫磺的包裹问题,硫的氧化率降低,且以元素硫的形式进入渣中,后液达到了净化除铁前液的标准要求,可供净化除铁使用。     

An electrochemical model for the leaching of a sphalerite concentrate

The leaching of a sphaleritic flotation concentrate in an acidic ferric sulphate solution is described by an electrochemical charge-transfer model in which the mineral surface potential is approximated by the solution redox potential for the ferrous-ferric redox couple. The oxidation of ferrous ions by dissolved oxygen is described by a model consistent with previously reported models, and the leaching of the sphalerite in the presence of dissolved iron and oxygen is described by the simultaneous integration of the two individual rate expressions.     

硫化锌精矿氧压浸出过程硫的酸化研究

硫化锌精矿氧压浸出工艺生产实践表明,如果没有严格控制氧压浸出过程中硫组元的酸化程度,将造成锌冶炼系统的酸过量问题,进而影响各项技术经济指标。针对氧压浸出系统容易出现酸根过高的现象,探索氧压浸出工艺中二段终酸浓度、反应温度、氧分压及浸出时间对硫组元的酸化效果和锌浸出的影响,在较优的工艺条件下,锌浸出率高达98%以上,硫酸化率仅10%左右。     

镍钼矿加压酸浸新工艺研究

提出一种加压酸浸处理镍钼矿的新工艺,考察温度、氧分压、液固比、时间等对镍钼转化率和浸出率的影响。结果表明,在液固比为5,氧分压为0.4 MPa,150℃反应2h的条件下,钼转化率可以达到98.3%以上,镍浸出率达到98.7%。     

锌精矿中伴生铟的提取

采用两段加压酸浸-萃取新工艺从含铟高铁闪锌矿回收伴生铟,结果表明,铟的浸出率、萃取率、反萃率和铟置换率分别达92.98%、96.58%、99.32%、99.5%;从原料含铟高铁闪锌精矿至海绵铟各工序处理后,经计算铟的直收率为88.74%。与传统提取方法相比,伴生铟的回收率提高了约38.74个百分点,同时,锌浸出率大于99.25%,说明采用该新工艺能够很好地提取有价金属。