Mineralogical characteristics and treatment of refractory gold ores

Refractory gold ores and concentrates are characterised by low gold recoveries and high cyanide consumptions when subjected to direct cyanide leaching. Therefore an oxidation pretreatment step is required before cyanidation that will break up the sulphide lattice and render gold particles accessible to cyanide ions. The main three options for the treatment of refractory ores and concentrates include the traditional oxidation roasting, the modern pressure oxidation and the bacterial oxidation which is still at an advanced experimental stage. The present work focuses on the mineralogical factors influencing the refractoriness of gold, the main characteristics and developments of each process and provides economic comparative data from various operations worldwide. Environmental considerations are also briefly discussed.     

浅谈含砷金矿提金前的预处理工艺及合理选择

对含砷金矿难浸的原因和预处理的必要性，以及用干法和湿法预处理工艺处理含砷金矿的现状等进行了论述，并提出了合理选择含砷金矿预处理工艺的看法     

Diagnostic pre-treatment procedure for simultaneous cyanide leaching of gold and silver from a refractory gold/silver ore

This study investigates the optimization of simultaneous dissolution of gold and silver from a refractory gold ore through determination of pre-treatment stages. Based on the mineralogical studies (thin layer and polished section) and chemical analysis on the ore sample, a “diagnostic leaching” procedure was designed. Results from diagnostic leaching suggest that the most effective pre-treatment agents for gold and silver are ferric chloride and sulfuric acid media, respectively. Optimum conditions for the simultaneous dissolution of gold and silver were determined using a two factorial design technique. Pre-treatments with sulfuric acid and ferric chloride reagents increased the efficiency of the dissolution of gold from 54.7% to 82% and silver from 37.4% to 81.6%.     

川西某金矿选矿试验探索

对川西某金矿的矿石特征进行了研究,在此基础上进行了全泥氰化试验和单一浮选试验。全泥氰化浸渣金品位为0.46 g/t,浸出率为87.5%,另外矿石中金属硫化物较多,且金的粒度细小,有碍于氰化的砷矿物含量较高,不利于金矿物的提取。相对而言,单一浮选工艺流程更适合该金矿床,原矿金品位为3.86 g/t,经过一次粗选、两次精选、两次扫选,获得的精矿金品位为65 g/t,金回收率91.7%。     

Fungal pretreatment of sulfides in refractory gold ores

This study assessed the capability of the fungus, Phanerochaete chrysosporium, to decompose pyrite, arsenopyrite and a sulfide-containing flotation concentrate in an effort to develop a microbial process for pretreating refractory gold ores. The extent of biotransformation was monitored by analyzing for iron, sulfur and arsenic in incubation solutions, and for sulfide sulfur in the residual solids. The results were then expressed as percentages of the initial weights. For arsenopyrite, 1.5 wt.%, 7.2 wt.% and 10.3 wt.% of iron, arsenic and sulfur respectively were present as soluble constituents in the incubation solution within 21 days of fungal treatment, whereas for pyrite, there was 1.2 wt.% iron and 6.0 wt.% sulfur. For the same processing period in the case of the flotation concentrate, 1.8 wt.%, 6.1 wt.% and 10.7 wt.% respectively of iron, arsenic and sulfur remained in solution. Overall, the decomposition of sulfide sulfur in the samples was 15 wt.%, 35 wt.% and 57 wt.% respectively for pyrite, arsenopyrite and the flotation concentrate. Changes in sulfide sulfur concentration and the formation of oxide phases during fungal treatment were confirmed using Raman spectroscopy and X-ray diffraction analysis. These results suggest that P. chrysosporium is a potential microorganism for oxidative decomposition of metal sulfides associated with refractory gold ores.     

On gold extraction from rebellious ores

The paper generalizes research findings on application of chemical additives to stage-by-stage processing of rebellious gold-bearing ores. The designed stages of gold extraction intensification are the controlled mineral alteration by preparation, use of conventional and specific collecting agents to prepare mineral surface to sorption to intensify flotation, creation of selective collecting agents, and cyanation optimization by introducing additional oxidation agents. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 102–109, March–April, 2009.     

Study of cryogenic disintegration of gold-quartz ores to intensify the heap leaching of gold

It is shown how the airy and nival conditions of cryogenic eolation affect the structural changes and weakening of gold-qnartz sulfide ores under cyclic exposure to frost-penetration and thaw. It is revealed that leaching of ores after cryogenic eolation in the nival conditions and additional pretreatment is more intensive, by 25%, than leaching of ores that were not prepared by cryogenic eolation. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 102–110, January–February, 2006.     

Microwave heating of gold ores for enhanced grindability and cyanide amenability

In leaching processes, the mass transport of lixiviants from the bulk of the solution to the site of the mineral of interest is usually the slowest step. Diffusion becomes slower when the particles to be leached are occluded in host minerals. Access to the mineral of interest is enhanced by micro-crack formation within the host minerals as it enhances percolation and migration of lixiviants. Micro-crack formation also augments grinding and allows size reduction and liberation at a lower stress level. In this research, microwave pretreatment was used to augment the grinding of a free-milling gold ore containing quartz, silicates and iron oxides. Under microwave irradiation, selective heating of the different mineral components resulted in thermal stress cracking. Microwave processing enhanced the grindability of the ore, and crushing strength was reduced by 31.2%. The presence of micro-cracks improved leaching rate, and over 95% extraction was achieved within 12 h as against 22 h for the non-microwaved sample. Such a strategy can be used to maximize recovery and man-hours on processing plants.     

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.     

铅盐在高铜金精矿氰化提金试验中的应用与工业实践

河台金矿原矿含0 2%～0 3%的铜,以原生硫化铜为主,含硫1%左右,属贫硫化物含铜金矿石。从1989年建厂至1998年一直采用单一混合浮选工艺,生产含铜3%～5%的混合金精矿,这样影响了企业的经济效益。经试验研究采用铅盐预处理工艺获得成功,并建成氰化冶炼厂,本文介绍铅盐在高铜金精矿氰化浸金应用中的试验与工业实践情况。     

难选多金属矿石中提取钴、镍、铜和金的试验研究

青海省某矿区难选含金多金属矿石丰富 ,矿石中富含有 Co、Ni、Cu、Au、Ag、Pb、Zn、Mo、Bi等有用元素 ,应用单一浮选或直接浸出 ,精矿中钴、镍、铜和金品位达不到合理的技术经济指标。采用预处理—湿法浸出工艺技术 ,可使钴、镍、铜和金的浸出率均达到 90 %以上。     

液相氧化剂辅助浸金的试验研究及其作用机理的探讨

对湖南衡阳某地的金矿石进行了氰化浸金的试验研究。结果表明，与通压缩空气相比，过氧化钙与高锰酸钾按重量配比４∶１混合辅助浸金，金的浸出率提高１０．２８％，浸出时间降低４０％，氰化钠耗量降低５０％。借鉴高分子化学的研究成果，对辅助浸金的机理进行了探讨。提出了过氧化物和高锰酸钾等液相氧化剂大幅度缩短氰化浸出时间的原因，可归结为强化了自由基ＨＯ．反应。     

难处理金矿石预处理工艺研究与应用现状

综述了难处理金矿石预处理工艺的基本原理、特点和国内外研究与应用状况。     

黄金尾矿的处理及综合利用

黄金尾矿堆积量逐年增加,带来资源、环境、安全和土地等诸多问题.“十二五”期间,我国将重点推进排放量大、堆存量大、污染严重的固体废弃物大宗利用和高附加值利用.通过对黄金尾矿的特性分析,研究比较了目前黄金尾矿的处理及综合利用方法,为我国尾矿的处理提供重要参考,提升尾矿等大宗废弃物的处理和资源化利用水平.     

High pressure acid leaching of a refractory lateritic nickel ore

This paper describes the experimental findings of the extraction of nickel and cobalt by high pressure acid leaching (HPAL) of a refractory limonitic nickel laterite ore from the Gördes region of Manisa in Turkey. By optimizing the basic HPAL process parameters: leaching at 255 °C with 0.30 sulfuric acid to ore weight ratio with a particle size of 100% −850μ for 1 h of leaching, it was found that 87.3% of nickel and 88.8% of cobalt present in the ore could be extracted into the pregnant leach solution (PLS). However, these extraction results were found to be relatively low compared with other similar studies. In order to understand the possible reasons for this relatively lower extraction, further investigations have shown that together with a problem related to the kinetics of the dissolution reactions, a persistent acid resistant refractory mineral present in this sample also limited the leaching process. Attempts were made with different additives to solve this problem. The effects of chemical additives such as HCl, Na₂SO₄, FeSO₄, Cu⁺ and sulfur were tested and the effect of each addition on the degree of extraction of nickel and cobalt was determined.     

难处理金矿浸出技术的现状与研究

难处理金矿在我国已探明的金矿资源中占到了近1/4,如果直接氰化浸出,浸出率往往很低。本文介绍了3种处理难浸金矿石的方法,目前生产中最常用的是预处理后氰化浸出法。     

Process mineralogy of fluorosilicate minerals in ok tedi ores

The impact of fluorine in copper flotation was relatively unknown until the introduction of skarn ores in the Ok Tedi concentrator. Fluorine in the copper concentrates reports to the gas phase during the smelting stage and forms a corrosive H₂SO₄-HCl-HF acid brine mixture which must be neutralised.This work was aimed at studying the mineralogy of the fluorosilicate minerals contained in the various oretypes present in the Ok Tedi porphyry copper deposit. The electron microprobe was used to analyse for fluorine and hence identify the fluorosilicate minerals in each oretype. This study revealed talc, phlogopite, biotite, clays, amphiboles, fluoroapatite and titanite to be the sources of fluorine in the orebody.Laboratory and plant investigations were conducted to study the flotation response of these minerals. Chemical assaying of the products of these tests was done to determine the bulk assay of fluorine. Using Rietveld analysis, quantitative estimates of the fluorosilicate minerals in these products were generated. Marrying of the bulk assay with the respective mineralogical “assay” enabled the understanding of the flotation behavior of fluorine and it's associated mineralogy. Talc and phlogopite were found to be the causes of the fluorine problem at Ok Tedi.     

金川低品位氧化镍矿的酸法制粒堆浸工艺研究

对于金川有色金属公司低品位的氧化镍矿,目前的火法和湿法冶金工艺,生产成本高,难以回收利用。通过制粒预处理,加入润湿液与矿石中的耗酸组分作用,可以预先破坏碳酸盐和Ca、Mg的氧化物,降低硫酸浸出过程中CO2气体逸出对颗粒的损害。选择N603作为低品位氧化镍矿的黏合剂,有效地改善了堆浸的渗透性,浸出过程中,矿石颗粒未发现严重的破裂和泥化现象。预处理后矿石浸出,每t矿石总用酸量258.8kg,镍浸出率85%以上。如果利用该公司硫酸厂大量的低浓度硫酸来堆浸,则在经济上和环境保护方面都比较合理。     

甘肃某微细粒浸染型难处理金矿选矿试验研究

对甘肃某微细粒浸染型难处理金矿进行了选矿试验研究, 结果表明, 采用阶段磨矿-阶段浮选-尾矿氰化浸金的工艺流程, 可以获得浮选精矿Au品位45.01g/t、回收率82.79%、金总回收率为92.92 %的较好指标。