Thiosulphate leaching of gold in the presence of carboxymethyl cellulose (CMC)

Carboxymethyl cellulose (CMC) was introduced as a surfactant in the leaching of pure gold as well as a sulphide ore using ammoniacal thiosulphate medium. Competing with thiosulphate anions to complex with the cupric ion at the axial coordinate sites, CMC in small quantities reduced the consumption of thiosulphate in the ammoniacal thiosulphate leaching system. The dissolution of pure gold in thiosulphate solution was enhanced in the presence of CMC, and this beneficial effect became more pronounced with an increase in the CMC concentration up to a certain level. Extraction rates of gold and silver from the sulphide ore were improved greatly, while the consumption of thiosulphate was reduced in the presence of CMC especially at a higher CMC concentration. The enhanced leaching performance was attributed to the stabilisation of thiosulphate, likely reduced leaching passivation and the dispersion of mineral particles in the slurry system. Addition of CMC facilitates satisfactory gold extraction at low reagent consumption in thiosulphate leaching.     

Thiosulfate leaching kinetics of gold in the presence of copper and ammonia

In recent years a significant amount of research has focused on thiosulfate as an alternative lixiviant for gold. However few fundamental studies have been undertaken due to the complexity of the solution chemistry. This study investigates the effect of various parameters on the gold leaching kinetics and the undesirable homogeneous copper(II) reduction by thiosulfate. The leach kinetics are measured at essentially constant solution conditions using a rotating electrochemical quartz crystal microbalance, which measures mass changes in real time and hence leach rates within minutes. The gold leaching kinetics were found to be chemically controlled and the rate was found to decrease with time as the copper(H) concentration decreased. This can be attributed to passivation of the gold surface by the products of the copper(II)-thiosulfate reaction. Optimum leach conditions derived from this study are 0.4M ammonia, 0.1M thiosulfate, pH > 11.4, and temperature at 30°C.     

含高砷金矿浸金工艺研究现状

针对含高砷金矿中砷的伴生类型、高砷金矿浸出金的工艺特点,介绍了浮选 细菌预氧化法、氧化焙烧法、加压氧化法等主要浸金方法。同时,也对其他一些工艺方法的最新发展动态进行了研究,以便根据具体情况选择适用的工艺方法,使含高砷金矿浸金率得到提高,从而达到最佳经济指标。     

Prospects for underground leaching in gold mines

The authors describe experiments on pretreatment of ore by injection of explosive gases before underground leaching of gold in mine conditions. It is shown that injection of explosive gases into opening micro-fractures enhances efficiency of underground leaching owing to microstructural transformation of ore containing dispersed gold.     

Diagnostic leaching of galena and its oxidation products with EDTA

Many authors have used EDTA as a means of determining the extent of oxidation of flotation pulps. However, there have been few documented studies of the reaction mechanisms in the interaction of EDTA with sulphide minerals and their oxidation products. This paper examines the use of EDTA to extract lead oxidation products from galena. In the first instance, it will be demonstrated that all oxygen containing galena oxidation products (i.e. sulphate, hydroxide, oxide, and carbonate, but not polysulphide or sulphur) are rapidly solubilized in EDTA. Secondly, it is shown that EDTA does not extract lead from un-reacted galena. Continued extraction of lead with increasing conditioning time is due to continued galena oxidation, not to the extraction of lead from galena. Argon gas purging minimises this oxidation whereas the use of air or nitrogen gas purging do not. Using information gathered from these experiments, an improved EDTA extraction technique was developed and compared with other techniques used within the mining industry.     

碱性硫化物浸出含锑金精矿过程中的抑金措施

在含锑难冶炼金矿碱性浸出脱锑生产工艺中的金伴随浸出是一种普遍的现象,此现象使金进入到锑浸出液中,造成了一定的损失。本文根据碱性硫化物在氧化环境中的不稳定性以及碱性多硫化物浓度对于金、锑浸出过程中的反应级数差等理论,并结合实际生产情况,研究了空气氧化、二段浸出对碱性硫化体系浸锑过程中的抑制金浸出的效果。在浸出矿浆中通入4.5L/（L*min）的空气,氧化浸出4h后,Sb浸出率63%,Au浸出率0.86%。采用两段浸出法,Sb浸出率为89%,Au损失率为浸出4.2%,相比一段浸出Au损失率降低6.0%。     

The role of amino acids in the thiosulphate leaching of gold

Amino acids L-valine, glycine, DL-α-alanine and L-histidine were applied in the ammoniacal thiosulphate leaching of a pyrite concentrate. Amino acids formed more stable complexes with cupric ions than does ammonia, resulting in lower thiosulphate consumption due to reduced interaction between thiosulphate and the copper complexes. Overall gold extraction was largely improved by the addition of amino acids, despite lower initial kinetics. Thiosulphate consumption decreased with an increase in the amino acid concentration. Among the amino acids, L-histidine improved overall gold extraction and reduced the thiosulphate consumption to the greatest extent.     

Atmospheric leaching characteristics of nickel and iron in limonitic laterite with sulfuric acid in the presence of sodium sulfite

Atmospheric leaching of nickel from limonitic laterite ores is regarded as a promising approach for nickel production, despite its low nickel recovery and slower leaching rate than high pressure acid leaching. Sulfur dioxide can enhance the sulfuric acid leaching of laterite, but its behavior for enhancing atmospheric sulfuric acid leaching was uncertain due to SO₂ losses and emission. In this study, sodium sulfite was used as a substitute for SO₂ gas in the leaching and the sulfuric acid leaching characteristics of Ni and Fe from a limonitic laterite in the presence of sodium sulfite were investigated. A linear correlation exists between the extraction of Ni and Fe, indicating the difficulty in selective leaching of Ni over Fe. Most nickel is isomorphically substituted within the goethite and it is difficult to dissolve in a high oxidation–reduction potential solution environment, resulting in a low nickel recovery. SO₂(aq) generated from the reaction of sodium sulfite in sulfuric acid solution, lowers the potential for the reducing reaction of FeOOH to give Fe²⁺, accelerating the iron extraction and nickel liberation from goethite.     

The cyanide leaching of gold in solutions containing sulfide

A large proportion of the gold processed in the 21^st century will be recovered from sulfide ores. Since the sulfide minerals are to some extent soluble in cyanide solutions, there will always be some sulfur species present in the leach solution. It has been shown that soluble sulfide hinders the rate of gold leaching, forming a protective layer of the type Au/S_x. Electrochemical studies of the constituent half reactions: gold oxidation; and oxygen reduction, were consistent with this view. The effect of sulfide and cyanide concentrations on the leaching reaction were investigated, and it was shown that the sulfur formed is chemically attacked by cyanide, resulting in higher leach rates at higher cyanide concentrations. The effect of lead was also studied and is discussed in detail.     

两段脱砷金焙砂的硫酸熟化酸解对氰化浸金过程的影响

针对两段焙砂中赤铁矿包裹造成渣含金过高的问题,结合铁氧化物包裹金的研究现状,重点研究了两段焙砂硫酸熟化过程的热重差热和微观结构变化以及对水浸渣的提金效果和氰化钠消耗量的影响。结果表明,生成水合硫酸盐过程主要发生在127.8~249.1℃,该过程中,物料的微观形貌由疏松多孔蜂窝状转变成疏松片状。两段焙砂用浓度75%的硫酸在250℃熟化90 min,水浸除铁率达91.69%,水浸渣氰化浸金率达95.54%,比焙砂直接氰化提高了近11%,氰化尾渣金品位由直接氰化浸出的9.10 g/t降至5.88 g/t,氰化钠消耗量也降低了近一半。研究结果对提高两段焙砂中金浸出率具有重要意义。     

含硫试剂浸金技术的研究现状

本文介绍了含硫试剂的发展现状,对硫脲、硫代硫酸盐、硫氰酸盐、石硫合剂四种含硫非氰试剂的浸金机理及应用进行了系统论述,含硫浸金试剂具有无毒或低毒性、对砷、碳、铜等杂质元素适应性强、浸出效率高等优点,分析了含硫试剂对不同类型的难处理金矿的浸出效果及适应性,对难处理金矿的清洁高效开发,建设绿色环保矿山具有一定指导意义。     

Productivity of chemical-electrochemical gold leaching from rebellious ore

The authors describe experimental research findings on chemical-electrochemical leaching of gold from rebellious minerals. A laboratory-scale plant has been designed for studying the leaching kinetics. Rational parameters of chemical-electrochemical leaching are specified (duration of the process, electrode current density, NaCl concentration). The researchers analyze the changed microstructure and phase composition of arsenopyrite surface after the leaching and substantiate the leaching improving practices.     

山东某金矿氰化浸出金的研究

针对矿石风化严重、具有多孔状结构的细粒自然金的特点,采用氰化浸出工艺回收金.用石灰作为保护碱,氰化钠作为浸出剂,通过优化工艺条件,在原矿金品位为4.45g/t时,可获得金浸出率为97.30％的指标.     

边磨边浸全泥氰化工艺在北衙金矿的运用

北衙金矿4000 t/d选厂是一座常规全泥氰化炭浆厂。投产后,各项工艺指标基本达到了设计水平,但尾渣金、银品位偏高,金浸出率不到90%,银浸出率不到30%。为了进一步降低尾渣品位,提高金、银浸出率,选厂进行了一系列的工艺技改及试验研究。经过研究得出,采用"边磨边浸"工艺流程可以有效地提高金、银的浸出率。于是选厂进行技改,运用了"边磨边浸"工艺流程。技改后,工艺指标得到了明显的提高,年平均金浸出率提高了2.97%,达到92.40%,银浸出率提高了9.07%,达到35.49%;尾渣金品位下降了0.10 g/t,降至0.16 g/t,尾渣银品位下降了3.43 g/t,每年可为选厂增加5000万元以上的经济效益。     

Solomon某金矿浸出工艺探索研究

本文对Solomon某金矿进行可行性工艺探索性研究,结果表明,混合原矿,矿石粒度为20 mm,柱浸浸出60 d,渣液合计浸出率为73.19%;浮选金精矿,超细磨粒度为P80=13 μm,金浸出率为68.90%,焙烧预氧化-细磨-氰化,可使金的浸出率提高到91.50%;加压预氧化-氰化后金的浸出率可以达到97.02%。     

某铀精矿酸法搅拌浸出氧化剂的选择

对比了二氧化锰、二氧化锰加硫酸亚铁以及硫酸铁3种氧化剂处理某铀精矿的酸法搅拌浸出结果.结果表明,采用硫酸铁作氧化剂后酸耗明显减少、浸出所需温度低、浸出速率快、浸出液中磷和锰含量少.     

The mechanism of leaching of gold from refractory ores

Refractory gold ores commonly contain free gold, submicroscopic gold, base metal sulphides, pyrite, pyrrhorite, labile sulphides and carbonaceous material. The analysis of gold deportment with the diagnostic leaching technique has opened a research field to gain more insight into the fundamentals of the kinetic behaviour of gold dissolution from refractory ores. Hence, more detailed studies on the kinetics of the reactions that occur during leaching with cyanide are now possible.Previous research work has indicated that the dissolution rate of gold during cyanidation becomes depressed after a certain time with no further increase in the rate. However, a second noticeable increase in the gold dissolution rate has been observed after a leaching time of 5 to 12 hours during some of the cyanidations, following the destruction of a mineral with the diagnostic leaching technique. If such a second increase in dissolution rate does not occur, the re-leaching of the filtered solids with a fresh cyanide solution yields an additional gold extraction of 4 to 8 %.Various experimental results have indicated that a passivative film forms on the surface of some of the liberated gold. The selective destruction of the various minerals with oxidative acid leaches destroys and/or decomposes certain minerals which may form films on the gold surface by precipitation. The chemical composition of these films and precipitates depends on the mineralogy of the sample. These films may be oxides, sulphides, carbonates and cyanide complexes.The complexes can be destroyed, depending on the nature of the film, by interstage dilute acid and/or cyanide washes in an agitated vessel. The destruction of the films exposes the gold surface for cyanidation. Whereas most of the previous studies on the leaching of gold have focused on the whole ore, the emphasis in this study was on the leaching behaviour of gold from various ore constituents. This approach of studying the leaching behaviour of different gold bearing minerals has provided reasons why some ores leach better than others.     

Acidic sulphate leaching of chalcopyrite concentrates in presence of pyrite

Copper concentrates with mineralogy dominated by chalcopyrite have slow leaching kinetics at atmospheric pressure in sulphate media because of the formation of passivation layer on its surface during the leaching. To enhance the leaching rate of the copper concentrate, pyrite was added to act as a catalyst. Pyrite and copper sulphide minerals then form a galvanic cell which increases both the copper leaching rate and yield. Effect of parameters such as solution redox potential, temperature, initial acid concentration, solids content, total initial iron concentration and pyrite to copper sulphide minerals mass ratio were investigated. Mineralogical analyses by XRD were performed on selected leach residues and the feed materials. A copper recovery higher than 80% in 24 h was achieved at a redox potential of 410 mV vs Ag, AgCl, a temperature of 85 °C, 15 g/L of initial acid concentration, a solid content of 7.8% (w/v), a total initial iron concentration 5 g/L and pyrite to copper sulphide minerals mass ratio 2:1. XRD patterns on leach residues showed that candidates for surface passivation, i.e. jarosite and elemental sulphur, were formed at high total initial iron concentrations.     

Simulation study of the optimal distribution of cyanide in a gold leaching circuit

The mineral industry has been using cyanidation to recover gold from ores for more than a century; however, a systematic study of the best reactant addition strategy in a cascade of agitated leaching tanks is not available in the open literature. A phenomenological mathematical model of the gold cyanidation process, calibrated with a set of industrial data from an Australian plant, together with an economic performance index is used to analyze this problem. The simulated results show that the best compromise between the two antagonistic effects, cyanide consumption and gold recovery, which are both function of cyanide concentrations, leads to a reagent distribution that depends on the leaching and cyanide consumption kinetics, pulp feed characteristics, and economic factors such as the gold market value. For the specific studied plant, in the operating range of low cyanide consumption and fast gold dissolution, all the cyanide must be added in the first tank; however, in the operating conditions of high cyanide consumption, cyanide has to be distributed in the first, second and third tanks.