LEACHING OF PRECIOUS METALS FROM COMPLEX SULPHIDE ORES——2.DIRECT LEACHING OF Cu SULFIDE CONCENTRATE BY ACIDIC THIOUREA SOLUTIONS

Recovery of gold and silver from a sulphide concentrate by thiourea leaching was investigat-ed.The effects of various parameters on the process,such as oxidants,the initial concentrationof thiourea and acidity in solutions as well as reaction temperature,were systematically exam-ined.From the results it was confirmed that(a)oxidants had no significant influence on the dis-solution of gold and silver at a fixed initial concentration of thiourea;(b)the initial concentra-tion of thiourea and acidity affected the dissolution rate only in the earliest period of leaching;(c)the rate of the process was controlled by reagent diffusion.The optimum operations wereworked out for the thiourea leaching process of the concentrate.     

Differences of cyanide leaching between calcine and dust from refractory gold concentrates

Differences of cyanide leaching between the calcine and the dust from a refractory gold concentrate were investigated by comparative method. Results showed that gold leaching efficiencies of the calcine and the dust were 85.31% and 54.30%, respectively, with direct cyanidation. Contents and existing forms of arsenic and carbon were the main reasons for those differences. The maximum gold leaching efficiencies of the calcine and the dust were 87.70% and 58.60%, respectively, with cyanidation after NaOH pre-leaching. Harmful elements removal, gold loss in NaOH pre-leaching and iron oxides hindrance codetermined gold leaching efficiencies of the calcine and the dust. After H₂SO₄ pre-leaching, the maximum gold leaching efficiencies of the calcine and the dust achieved 94.96% and 80.40%, respectively. The effect of carbonaceous matter was the main reason for differences for leaching efficiencies of the calcine and the dust. Based on those differences, two proper gold extraction processes were put forward, and gold leaching efficiencies for the calcine and the dust achieved 94.91% and 91.90%, respectively.     

Alkaline sulfide pretreatment of an antimonial refractory Au-Ag ore for improved cyanidation

This paper presents the alkaline sulfide pretreatment of an antimonial refractory gold and silver ore. In the ore, gold occurs mainly as gold-silver alloys and as associated with quartz and framboidal pyrite grains, and, to a small extent, as the inclusions within antimonial sulfides. Silver is present extensively as antimonial sulfides such as andorite. Alkaline sulfide pretreatment was shown to allow the decomposition of the antimonial sulfide minerals (up to 98% Sb removal) and to remarkably improve the amenability of gold (e.g., from <49% up to 83%) and silver (e.g., from <18% up to 90%) to subsequent cyanide leaching. An increase in reagent concentration (1–4 mol/L Na₂S or NaOH) and temperature (20–80°C), and a decrease in particle size seem to produce an enhancing effect on metal extraction. These findings suggest that alkaline sulfide leaching can be suitably used as a chemical pretreatment method prior to the conventional cyanidation for antimonial refractory gold and silver ores.     

Characterization of refractory behaviour of complex gold/silver ore by diagnostic leaching

The amenability of a refractory ore to the extraction of gold and silver by cyanide leaching was investigated. Diagnostic leaching tests were also performed to shed light on the refractory characteristics of ore. The leaching tests show that the extraction of gold and silver is consistently low, i.e. ≤47% and ≤19.2%, respectively, over a leaching period of 24 h. Even fine grinding (e.g. ＜38 μm) does not improve the recovery of gold and silver. Diagnostic leaching approach provides information into the cause of the refractoriness of the ore. The findings suggest that the refractoriness is induced by the dissemination and encapsulation of the very fine gold and silver particles largely in the carbonates, oxides and sulfides and, to a small extent, with silicates present in the ore matrix. These findings highlight the practical importance of diagnostic leaching for the understanding of the refractory characteristic of such an ore and for the identification of possible pretreatment options to overcome its refractoriness prior to cyanide leaching.     

微细浸染型金矿强化湿法预处理研究

采用两段充气预处理-非氰化工艺浸出微细浸染型金矿,研究了浸出条件对金浸出效率的影响。结果表明,在氧化和碱浸预处理2个阶段充气可提高金浸出率;氧化预处理2 h后,加入氢氧化钠(20 kg/t)碱浸预处理4 h,加入氧化钙(40 kg/t)替代氢氧化钠,用TY-3浸出剂(8 kg/t)浸出4 h,金浸出率可达87.21%。浸出渣的物相分析、扫描电镜观察及X射线能谱分析结果显示,硅酸盐、碳酸盐中的金可被有效浸出,浸出渣中的石英、黄铁矿表面发生腐蚀,部分黄铁矿氧化。     

Mineralogical characterization and pretreatment for antimony extraction by ozone of antimony-bearing refractory gold concentrates

The mineralogical characterization of antimony-bearing refractory gold concentrates and the antimony extraction by ozone in HCl solution were investigated. The mineralogical study shows that there exist stibnite(Sb₂S₃), arsenopyrite(FeAsS), pyrite(FeS₂) and quartz in the concentrates, and the gold is mainly (67.42%) encapsulated in sulfides. The antimony extraction by ozone in hydrochloric acid was employed and the influences of temperature, liquid/solid ratio, HCl concentration and stirring speed on the extraction of antimony were investigated. High antimony extraction (93.75%) is achieved under the optimized conditions. After the pretreatment by ozone, the antimony is recovered efficiently and the gold is enriched in the leaching residue.     

氨氰浸金原理及研究进展

氨氰浸出技术自从发明以来就被认为是从含铜难处枞金矿资源中恒择性回收金的一种有效方法。系统总结了目前国内外氨氰浸金的研究进展,主要包括氨氰浸金的基本原枞、浸出动力学研究、溶液化学研究、氨氰浸金实验室实验及工业应用研究现状,对氨氰浸金过程中存在的问题及其未来的发展趋势做了评价。     

A new extraction process of carbonaceous refractory gold concentrate

A new hydrometallurgical process for a carbonaceous refractory gold concentrate at ambient temperature and pressure was presented, including grinding-leaching, intensified alkaline leaching（IAL）, thiosulfate leaching and cementation by zinc powder. The experimental results show that the grinding-leaching and intensified alkaline leaching process result in the selective oxidation of arsenopyrite and pyrite. The oxidation ratio of As is 96.6%, and 46.7 % for S. The total consumption of NaOH in alkaline leaching is only 28 % of that theoretically calculated under the conditions of full oxidization for the same amount of arsenopyrite and pyrite transforming into arsenates and sulfates, and 83.6% of gold is synchro-dissoluted by thiosulfate self-generated during pretreatment. Since the carbonaceous matter in concentrate possesses a strong capability of preg robbing, the cyanidation process is not suitable for the extraction of gold after pretreatment. However, the gold leaching rate by thiosulfate leaching for 24 h is increased to 91.7% from 0 - 3.2% by ultra-fine grinding without the pretreatment. The recovery of gold by zinc cementation gets to 99.6%. Due to the thiosulfate self-generated during alkaline leaching, the reagent addition in thiosulfate leaching afterwards is lower than the normal one.     

Applications of mixed potential model in leaching of gold

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｉｘｅｄ ｐｏｔｅｎｔｉａｌｍｏｄｅｌ (ＭＰＭ )ｈａｓｒｅｃｅｉｖｅｄｇｒｅａｔｉｎｔｅｒｅｓｔｉｎｓｔｕｄｙｉｎｇｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｃｏｒｒｏ ｓｉｏｎ[1,2 ] .ＭｉｌｔｏｎａｌｓｏｉｎｔｒｏｄｕｃｅｄＭＰＭｔｏｄｉｓｃｕｓｓｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｄｉｓｓｏｌｕｔｉｏｎｏｆｓｕｃｈｍｉｎｅｒａｌｓａｓｕｒａｎｉ ｕｍｄｉｏｘｉｄｅａｎｄｃｈａｌｃｏｐｙｒｉｔｅ[3] .Ｓｉｎｃｅｇｏｌｄｄｉｓｓｏｌｕｔｉｏｎｉｎｌｉｇａｎｄｓｏｌｕｔｉｏｎｓｉｓａｌｓｏ…     

某微细粒砷黄铁矿包裹金矿的非氰浸出研究

采用非氰浸化剂(石硫合剂)对含金为2.47 g/t的甘肃某微细粒砷黄铁矿包裹金矿进行浸出试验,研究预处理方式和浸出工艺对金浸出率的影响。结果表明,石硫合剂对金的直接搅拌浸出率低于30%,该矿属难浸金矿石;采用边磨边浸-搅拌浸出的方式,浸出率可提升至68.4%;增加碱式预氧化处理,可将金的浸出率进一步提升到80%以上。采用最优的工艺,边磨边碱式预氧化36 h,经石硫合剂搅拌浸出5 h,金的浸出率可达到91.5%。     

Use of ferricyanide for gold and silver cyanidation

Low gold and silver leaching kinetics has been commonly observed in traditional gold-silver cyanidation process, especially in heap leaching and in situ leaching operations. The different mineralogy of gold and silver in the ores is suspected to be the main reason, e.g., the occurrence of low solubility acanthite (Ag2S) typically results in low overall silver extraction. Due to the low solubility of oxygen in cyanide solution, the reactivity and availability of oxidant is believed to be the critical limitation for gold and silver dissolution. The use of ferricyanide as the auxiliary oxidant for gold and silver cyanidation has been examined. The rotating disc test results prove the assistant effect of ferricyanide on increasing the dissolution rate of gold and silver. The potential use of ferricyanide in gold/silver cyanidation process is proposed based on the leaching results of actual ores.     

从废弃印刷线路板中回收金的试验

试验研究了采用硫脲法有效地从废弃印刷线路板中回收金。试验结果表明，硫脲回收金的主要影响因素有：温度、硫脲质量浓度、Fe^3＋质量分数、浸出时间、硫酸体积分数；合适的浸出条件是：固液比为1：5，浸出温度为35℃，硫脲质量浓度为10g／l，Fe^3＋抖质量分数为0．3％，浸出时间为1h，硫酸体积分数为5％。     

四川丹巴铜炉房金矿床矿石选冶方法研究

通过多次对金矿石的选冶试验研究工作,使金精矿经沸腾焙烧预处理后Au、Ag、Cu、S的浸出回收率均得到显著提高,其中硫脲法Au、Ag、Cu的浸出率分别为99.4%、95.8%、98.0%;氰化法 Au、Ag、Cu的浸出率分别为:99.4%、89.4%、93.3%.最终确定矿石的最佳选冶方案为:原矿破碎→球磨→浮选富集→金、银、铜精矿→沸腾焙烧→烟气制硫酸,焙砂经硫酸浸出萃取电解回收铜后,再经硫脲法回收金银.     

草酸配位浸出二段焙砂中包裹金的赤铁矿

草酸根(ox^2-)对三价铁具有强的配位能力，可用草酸配位浸出二段焙砂中包裹金的赤铁矿，提高金的回收率。考察了草酸用量、液固比、浸出温度和时间对二段焙砂中铁浸出率的影响。结果表明，用1.17倍理论量的草酸在液固比为12 mL/g时于90℃浸出2 h，铁浸出率达到75.8%以上。除铁渣进一步氰化浸出，渣中金品位为8.8 g/t，低于直接氰化浸出渣12.3 g/t的金品位。草酸浸出液主要成分为具有光催化活性的Fe(ox)⁺和Fe(ox)2^-，可采用光催化法回收铁、再生草酸，再生的草酸可返回浸铁过程。     

Co-intensification of cyanide leaching gold by mercury ions and oxidant

The effects of mercury ions on gold cyanidation were studied. The results show that under low cyanide concentration, gold cyanide process is controlled by CN^? transfer, while at higher cyanide concentration, there forms passivation on gold surface. Therefore, chemical oxidation of gold in cyanide solution of higher concentration is controlled by surface reaction. Small quantity of additions of mercury ions bring about great increases in anodic gold dissolution rate, decreases the passivation and reduces the equilibrium activated energy. In addition, they also markedly change the effect pattern of cyanide concentration. Mercury ions show positive effects on cathodic reduction of oxygen and raise the rate of electrochemical step of the cathodic reduction of oxygen. Addition of a certain amount of hydrogen peroxide is confirmed to be an effective way for intensification of cathodic process on gold electrode. Active potential range and current peak on anodic dissolution are enlarged when being co-intensified with Hg²⁺ and hydrogen peroxide. Co-intensifying effect may be obtained and gold leaching rate is considerably increased on cyanide leaching of gold from gold concentrates.     

Increasing leaching rate of gold cyanide of two-stage calcination generated from refractory ore containing arsenopyrite and pyrrhotite

For the gold locked within hematite in the two-stage calcination, which leads to a low gold leaching rate, the present work is aiming at pretreating the calcination to selectively dissolve hematite. The calcination was pretreated by sulfuric acid with cosolvent B. The factors influencing the hematite dissolution rate were studied, and the pretreatment parameters considered were H₂SO₄ content, B dosage and added time, leaching temperature and time. Simultaneously, mineralogy analysis of the calcination, H₂SO₄ pretreatment residue and cyanide leaching residue were also carried out. Results indicate that the hematite dissolution rate is quicker, the dissolution temperature is lower and the dissolution time is shorter in the role of cosolvent B than without B. At the same time, the gold locked within hematite is effectively released, so the leaching rate of gold cyanide increases about 10 % than that in actual factory production. The results have an actual significance in guiding industrial production.     

采用Na2SO3溶液从硒渣中选择性浸出Se及其动力学

采用SO2还原沉金后液制得硒渣,再用Na2SO3选择性浸出硒渣,使Se得到有效分离;通过研究浸出过程中Se浸出率随时间的变化,建立该反应的动力学方程,确定Na2SO3溶液浓度、液固比、搅拌速度及反应温度对Se浸出率的影响,并计算相应的表观活化能。结果表明:增加Na2SO3溶液浓度和升高反应温度可以较大幅度提高Se的浸出率,液固比和搅拌速度对浸出Se的影响较小;Na2SO3浸出Se过程为Avrami模型混合控制,其特征参数n和表观活化能E分别为0.235和20.847 kJ/mol,Se的浸出率受反应温度的影响较大。     

某难处理金精矿热压预氧化-氰化浸金实验

对某难处理金精矿进行了热压预氧化-氰化浸金实验,探讨热压预氧化温度、时间、氧化分压和矿浆浓度对金浸出率和氰化钠耗量的影响。结果表明,在粒度-44μm占90.74%、温度220℃、矿浆浓度25%、氧分压0.8 MPa和转速750 r/min条件下预氧化2.5 h,砷主要以稳定的结晶状砷酸铁或者臭葱石形式被固定在氧化渣中;预氧化渣在矿浆浓度33%、pH=10~11、初始氰化钠浓度0.3%和活性炭浓度25 g/L条件下氰化浸出24 h,与金精矿直接氰化相比,浸出率由11.21%提高至95.75%,氰化钠耗量从46.99 kg/t降低至1.36 kg/t。     

Zinc removal from hyperaccumulator Sedum alfredii Hance biomass

Leaching of heavy metals from Sedum alfredii Hance biomass was studied with ammonia-ammonium chloride solution as leaching agent. The research was carried out in two phases: 1) a leaching study to determine the zinc extraction efficiency of this leaching agent, and 2) a thermodynamic analysis to identify the likely reactions and stable Zn(II) species formed in the leaching systems. Taguchi orthogonal experiment, with four variable parameters, leaching temperature, molar ratio of NH₄Cl to NH_3, leaching time and solid-to-liquid(L/S) ratio, and each at three levels, was used to optimize the experiment parameters by the analysis of variances. The results indicate that leaching temperature has the most dominant effect on metal extraction performance, followed by molar ratio of NH₄Cl to NH₃, solid-to-liquid ratio and leaching time. The optimum condition was obtained as follows: temperature of 60°C, molecular ratio of NH₄Cl to NH₃ of 0.6, leaching time of 2 h and solid-to-liquid ratio of 5:1. The total zinc leaching efficiency under optimum conditions reaches 97.95%. The thermodynamic study indicates that the dominant species produced by the leaching process should be the soluble Zn(NH₃)₄₂⁺.     

镁热还原法制取金属钛的实验研究

对镁热还原二氧化钛制备金属钛反应过程进行了热力学分析,在此基础上,探索了二氧化钛"真空镁热还原-酸浸除杂"制取钛粉的新工艺.结果表明:镁还原二氕化钛在热力学上是可行的,且反应为教热反应;镁的热还原在实验条件下是压力减小的气固反应:在环境压力为10Pa～30Pa、温度为900℃～1400℃的条件下,低温利于钛粉的生成;过程中氯化钙的添加对还原影响不明显;在反应温度为900℃,反应时间为4h的条件下可得科粉状金属钛.