Copper removal from cyanide solutions by acidification

Cyanidation is the most used method to recover gold and silver from their ores. In this process, other metals besides gold and silver may dissolve under certain circumstances and interfere with the efficiency of extraction. Copper is one of these metals, being able to reach concentrations as high as 1000 mg/L. When the cyanide solution contains a high copper concentration, the extraction of precious metals decreases and the operating costs increase. In addition, the control of the process is more complicated because the free cyanide analysis performed by the operators by titration does not represent the actual cyanide available to dissolve gold and silver. This experimental work has two objectives: to evaluate the amount of copper–cyanide complexes that are measured when titration is used for free cyanide analysis, and to develop and propose a method for copper removal from cyanidation solutions. The method consists in the acidification of the solution with sulfuric acid, and the separation of the precipitated solid (CuCN) by filtration. The thermodynamics of the copper–cyanide system is discussed, and the hydrogen cyanide evolution (HCN) at pH acid is evaluated.One of the main operating variables in cyanidation plants is the “free cyanide” concentration, that is, the amount of cyanide available to dissolve the precious metals. The usual method to estimate free cyanide is titration. When copper is present in the cyanide solution, the titration method not only measures the free cyanide but also part of the cyanide that is forming complexes with copper. It was demonstrated from the tests performed in this work, that for cyanide/copper ratios of 1–10, typically found in cyanidation solutions, around 10% of the free cyanide measured by titration corresponds to copper–cyanide complexes and is not available for gold and silver dissolution.In order to recycle the solution to the process, it is necessary to remove part of the copper. A method of copper removal is proposed, based on the precipitation of CuCN when the copper–cyanide solution is acidified. The precipitated solid is separated from the solution by filtration and finally the clear solution is neutralized. The acidification/filtration/alkalinization of cyanidation solutions containing copper permits the removal of most of the copper present in the solution, thus allowing the recycling of the solution. For synthetic solutions containing 200–730 mg/L Cu at different cyanide/copper ratios, it was found that 93–98% of the copper can be removed as CuCN at pH 2.5, releasing free cyanide to the solution. If a flotation stage is considered to remove the solid formed, the HCN formed by acidification should not represent a problem: the amount of HCN gas stripped at pH 2.5 when using the usual flotation gas flow rates (0.17 cm/s, 0.28 L/min, 1 h for our experimental design) was only 6%, which can be easily controlled with conventional equipment.     

季铵盐型抗菌粘胶纤维的抗菌性能研究

以粘胶纤维为基体,通过接枝含季铵基烯类单体制备了一种季铵盐型抗菌纤维材料.使用反射红外、单丝拉伸及热重分析等表征手段,考察了接枝前后粘胶纤维的结构及性能的变化.结果表明,接枝率达31％的改性纤维在200℃内失重也不超过2％,且其力学强度保持在原纤维力学强度的70％以上,能够满足实际使用的要求.抗菌试验显示,该改性抗菌纤维对大肠杆菌、金黄色葡萄球菌及白色念珠菌有优越的抗菌性能,抗菌率均达到了99.99％;经过20次洗涤后该材料的抗菌率仍保持在90％以上.     

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。     

湿法炼锌铜砷渣加压浸铜及同步固砷

针对湿法炼锌冶炼过程中产出的铜砷渣的综合回收利用,在研究铜砷渣矿物学组成及热分解特性的基础上,开展了加压浸出铜及同步固砷工艺与铜、砷元素的行为研究,结果表明,在反应温度为135 ℃、反应时间为4 h、液固比为25、硫酸浓度为50 g/L、氧分压500 kPa、铁砷摩尔比为1的条件下,浸出渣中铜含量仅为2.03%,浸出率达到97.72%,砷含量达到26.06%,浸出率仅为4.02%;浸出液中Cu的浓度达到20.47 g/L,As浓度小于0.63 g/L;铜砷分离效果好。在反应过程中,Cu₃As先发生氧化溶解,铜的浸出需要一定的时间,铜的浸出与砷的沉淀同时进行。浸出液pH值与浸出液中As浓度变化趋势基本一致,在反应前期砷与铁生成臭葱石产生的酸可以补充铜的浸出消耗的酸。     

Recovery of copper cyanide from waste cyanide solution by LIX 7950

The use of the guanidine extractant, LIX 7950, to extract copper cyanide from waste cyanide solution has been investigated. Copper extraction is favorable at low pH while a high cyanide to copper molar ratio tends to suppress copper loading. The extractant also strongly extracted zinc and nickel from cyanide solution, but the extraction of iron was poor. The presence of thiocyanate ion significantly depressed copper extraction, but thiosulfate ion produced negligible impact on copper extraction. The preferential extraction of metal cyanide species to free cyanide has been noticed. The potential application of the recovery technique as a pre-concentration step for the treatment of cyanide effluent has been suggested, by which copper can be extracted and concentrated into a small volume of solution and the barren cyanide solution recycled to the cyanidation process.     

The flotation separation of scheelite from calcite using a quaternary ammonium salt as collector

The flotability of scheelite and calcite was studied with Dioctyl dimethyl ammonium bromide (BDDA). The experiments were conducted on individual and mixed minerals as a function of pH with a micro-flotation cell. And oleic acid was tested for comparison. The flotation results revealed that the performance of BDDA is better than that of oleic acid and the best separation could be achieved with BDDA over the pH range 8-10. Through preliminary analysis, it is concluded that BDDA reacts with scheelite through electrostatic interaction.     

Sulphate ions removal from an aqueous solution: I. Co-precipitation with hydrolysed aluminum-bearing salts

The removal of sulphate ions constitutes one of the main challenges in the mining, metallurgical and chemical industries, among others. Sulphate removal from aqueous streams is by far one of the most difficult and onerous tasks in these industries, and most existing processes are inefficient and costly. This work presents a method to remove sulphate ions in an acidic medium based on co-precipitation with aluminum salts, namely AlCl₃ and a polyaluminum salt (PAC), followed by filtration. Herein, the different Al species react differently with sulphate, forming soluble and insoluble complexes, the latter of which causes insolubility and allows for the removal. The reaction kinetics depend on the activity of the so-called Al_b species (which are classified as polymeric) and was proved here by different techniques. Better results were obtained with the inorganic salt AlCl₃, when compared to PAC, probably because of the higher activity of the Al species. Co-precipitation of sulphate depends highly on the pH (which is optimal at 4.5), the mass ratio between reagents and sulphate ions (which is optimal at 7:1) and time (10 min). Finally, it was concluded that the technique proposed here has good potential for the treatment of sulphate-bearing effluents, including acid mining drainage (AMD).     

The adsorption of precious metals and base metals on a quaternary ammonium group ion exchange resin

Adsorption tests were conducted with a quaternary ammonium group ion exchange resin to determine the equilibrium adsorption of precious- and base metals. The resin used is a macroreticular polystyrene type 1 strong base anion exchange resin. The adsorption was determined for synthetic single metal solutions as well as for multi-component solutions. The effect of the Cl⁻ concentration on the equilibrium adsorption was determined for three different HCl concentrations, i. e. 6, 8 and 10%. The effect of chloride strength in the solution was also determined for mixed and base metal solutions. Pure metals, i.e. platinum, palladium and gold, were dissolved in aqua-regia and diluted to 2000 ppm (as metal) in 4M HCl. Ruthenium, rhodium and iridium were dissolved from pure salts in HCl. A 2000 ppm base-metal solution was prepared by dissolving all the required components, including precious metals, to match an in-plant industrial base-metals solution composition. For each precious metal the equilibrium adsorption was determined for typically two solution concentrations. Data points were established by varying the amount of resin added to the solution. The equilibrium concentrations were determined by ICP analysis after 24 hours exposure using the bottle-roll technique.     

铜电解液电积脱铜制备高纯阴极铜

利用电积法制备高纯阴极铜, 研究了添加剂、电解液温度、电流密度以及Cu²⁺浓度对电积法脱铜制备高纯阴极铜质量的影响。当添加剂(骨胶: 明胶: 硫脲质量比为6∶4∶5)用量为40 mg/L, 电解液温度为55 ℃, 电流密度为200 A/m², 电解液中Cu²⁺浓度从48.78 g/L降至31.71 g/L时, 电积脱铜得到的阴极铜质量达到了高纯阴极铜标准(GB/T 467-1997); 其电流效率达到99.19%, 高纯阴极铜产率达到38.09%。电积脱铜制备高纯阴极铜不仅增加了阴极铜产量, 而且可大大减少电积时黑铜板和黑铜粉。     

生活垃圾沥滤液UASB出水化学沉淀反应中影响总铬去除因素的研究

以厌氧生化(UASB)处理后的生活垃圾沥滤液为对象,研究了水量负荷、总铬浓度、助凝剂种类、还原剂投加量和混凝剂投加量等参数对化学沉淀法除铬效果的影响。研究结果表明,上述参数对总铬去除率影响的程度为:总铬浓度>混凝剂投加量>助凝剂的种类>进水负荷>还原剂的投加量。优化的参数条件为进水负荷1.0 m3/d、总铬浓度1.5 mg/L,助凝剂选用氢氧化钙,还原剂(焦亚硫酸钠)比例1∶4,絮凝剂添加量700 mg/L,在此条件下生活垃圾沥滤液生化出水中总铬去除率达到90%。     

利用铜精矿直接制备超细铜粉

采用高能球磨对铜精矿进行活化预处理, 并通过超声场辅助矿浆电解的方法直接利用铜精矿制备出平均粒度小于10 μm的超细铜粉。超细铜粉经油酸和丙酮的表面改性处理后, 抗氧化性能得到提高。     

黑铜渣氧压硫酸浸出脱铜脱砷实验研究

在硫酸体系中通氧加压浸出黑铜渣,结果表明,在硫酸质量浓度180 g/L、浸出温度140 ℃、氧分压0.8 MPa、液固比8 mL/g、浸出时间3 h、搅拌速度600 r/min、黑铜渣粒径178 μm的较优工艺条件下,黑铜渣中Cu、As和Ni浸出率分别为97.59%、95.42%和98.37%,Sb、Bi浸出率分别仅为6.78%和2.31%,实现了黑铜渣中Cu、As、Ni的高效脱除,浸出渣中锑、铋、银等有价金属得到高度富集。     

固定化细胞移动床浸出高硫高铁低铜难选铜矿中铜的研究

利用自制载体将T.f和T.t菌固定起来,并应用于高硫高铁低铜矿的浸出研究中,研究固定化浸矿系统的效果、特点.实验结果表明:在相同的浸提时间(18d)内,T.f和T.t菌混合固定后浸提系统,比非固定化浸系统要高出16.7％;而且固定混合菌群的浸矿效果要优于固定单一菌群的浸矿效果,T.f和T.t菌混合固定的比例为1∶2.     

地下水中氰化物污染状况分析

以异烟酸一吡唑啉酮分光光度法对赤峰市某村30个监测点进行两个月的氰化物监测,采用标准指数法,评价分析该村地下水中氰化物污染现状.通过对氰化物污染空间及时间变化特征的分析得出,离采矿区较近的区域氰化物污染严重;在对氰化物污染未进行处理的情况下,未污染区地下水发生氰化物污染的可能性随着时间增加有增长的可能.为该村地下水污染推荐一些治理措施.     

On-site gold refining of cyanide liquors by solvent extraction

Gold producers are currently being forced to cut costs, to increase plant throughput or to selectively mine out higher-grade areas. Another approach is to produce a value-added product, such as 99.99% gold, currently being produced at some minesites via a chloride re-leach route. There may be an opportunity for the refining of gold directly from cyanide liquors such as eluates and intensive leachates of gravity concentrates. While previous work with solvent extractants has focused on the recovery of gold from leach liquors as a replacement for carbon-in-pulp processing, the present work presents an alternative idea, the notion of on-site refining of gold with no re-leaching step.The current work indicates that it is possible to produce gold of 99.99% purity or higher by direct SX from a cyanide eluate type solution containing high copper tenors (about 200 mg/l Au, 140 mg/l Cu and 2 mg/l Ag). Excellent selectivity can be achieved in the extraction stage for gold over copper and silver. The small amount of co-extracted silver and copper can easily be scrubbed from the gold-loaded organic phase, which is subsequently easily stripped. The gold may then be recovered by electrowinning or reduction.Other work on a mixed-metal intensive cyanide leachate type solution (700 ppm Au, 400 ppm Ag, 200 ppm Cu, 150 ppm Ni, Fe, and Zn) has shown that the process is very selective against base metals such as Ni, Co, Fe and Zn, and that loadings as high as 5000 mg/l gold can be obtained on the organic.This process may well be suited to gold plants at remote sites, or where high copper or silver levels are present. There are several possible advantages over both electrowinning/smelting or chloride re-leach/SX routes, including costs, occupational health and safety (OH&S) and recovery of by-products.     

Comparison of biological ammonium removal from synthetic metal refinery wastewater using three different types of reactor

The use of nitrogen-based compounds as reagents in metal refining has led to high nitrogen compound concentrations in the wastewater generated. Some nitrogen compounds released into the environment are toxic to organisms and lead to eutrophication. Therefore, removal of nitrogen compounds from industrial wastewaters is a priority. A series of experiments was carried out using a synthetic metal refinery wastewater (MRWW) to assess the feasibility of biological ammonium removal from MRWW. A continuously stirred tank reactor, an airlift suspension reactor and a packed bed reactor were used under similar influent conditions with recirculation. Ammonium removal efficiencies over 85%, 90% and 99% were obtained, respectively, during the experimental period of 55 days.     

铜冶炼渣浮选回收铜的研究现状

我国铜冶炼企业每年产生了大量的铜冶炼渣,其中含有大量的有价元素,如金、银、铜、钴、镍等,具有巨大的经济价值。如何经济环保地综合回收这部分有价元素不仅能为企业带来巨大的经济价值,更重要的是能解决铜渣大量堆存的问题。本文综述了目前铜冶炼渣浮选回收铜的研究进展,并在此基础上提出一些想法,为今后的铜渣综合回收提供了参考。     

Activation of sphalerite by Cu ions produced by cyanide action on chalcopyrite

Cyanide used as a depressant for pyrite in the flotation of chalcopyrite from a polymetallic ore was found to result in flotation (activation) of sphalerite. This was thought to be due to leaching of copper ions from chalcopyrite by the cyanide. Copper leached from specimen chalcopyrite and from a Cu-ore sample treated with cyanide was determined for a variety of conditions. A significant increase in Cu release at elevated pulp potential is shown which also enhanced uptake of Cu ions by sphalerite. Activation, it is suggested, is related to release of copper as cuprocyanide and subsequent oxidation to cupric cyanide, which supplies the Cu²⁺ ions.