Comparative leaching of a sulfidic gold ore in ionic liquid and aqueous acid with thiourea and halides using Fe(III) or HSO5 oxidant

The leaching of gold, silver and base metals from a sulfidic gold ore in the presence of an oxidant (peroxomonosulfate (HSO₅⁻) or iron(III)) and leaching agent (thiourea, chloride, bromide or iodide) is compared in 1-butyl-3-methylimidazolium hydrogen sulfate (bmimHSO₄) and chloride (bmimCl) ionic liquids, as well as in aqueous saturated K₂SO₄ as the solvent medium. Over 85% of gold and silver was recovered in the presence of HSO₅⁻/ thiourea at 25–50 °C in both bmimHSO₄ and bmimCl, with silver recovery significantly enhanced compared with that from aqueous sulfate medium. The leaching efficiency with HSO₅⁻ was similar to that with Fe(III) as oxidant in bmimHSO₄ and was far superior in bmimCl. With HSO₅⁻ /halide ion (Cl⁻, Br⁻, I⁻) as leaching agent, gold and silver recovery in bmimHSO₄, bmimCl or saturated aqueous K₂SO₄ improved from Cl⁻ to Br⁻ to I⁻, but only I⁻ gave a high recovery in the bmimCl ionic liquid due to the particular stability of the iodo complex anion in this medium. However, recovery was significantly higher than in an aqueous medium. Negligible recovery of base metals occurred in the ionic liquid medium, making it highly selective for Au and Ag. Concentration dependence studies with respect to halide and oxidant have defined optimum conditions for gold and silver recovery.     

硫脲法处理银精矿的研究

以某厂湿法炼锌浸出渣浮选所得的银精矿为原料,用硫脲对其进行络合浸出,并用锌粉分步还原回收浸出液中的银和铜。结果表明,银浸出率保持在90%左右,锌粉分步还原可得到含银80%左右的银绵和含铜60%左右的铜渣。银绵经火法处理得粗银锭,再经电解可得精银,二次还原后液可直接返回浸出流程,可使硫脲得到循环利用。经生产中试,该工艺可应用于工业生产并取得较好的经济效益。     

从锌冶炼废渣中回收银的生产实践

介绍陕西锌业有限公司年产10t银锭的生产运行情况。含银0.015%的酸浸底流矿浆经过浮选,得到含银0.5%的银精矿。银精矿经硫脲浸出,浸出率达90%。7个月生产含银99.99%的银锭7t,取得了良好的经济和社会效益。     

Copper recovery from chalcopyrite concentrates by the BRISA process

The technical viability of the BRISA process (Biolixiviación Rápida Indirecta con Separación de Acciones: Fast Indirect Bioleaching with Actions Separation) for the copper recovery from chalcopyrite concentrates has been proved. Two copper concentrates (with a copper content of 8.9 and 9.9 wt.%) with chalcopyrite as the dominant copper mineral have been leached with ferric sulphate at 12 g/L of ferric iron and pH 1.25 in agitated reactors using silver as a catalyst. Effects of temperature, amount of catalyst and catalyst addition time have been investigated. Small amounts of catalyst (from 0.5 to 2 mg Ag/g concentrate) were required to achieve high copper extractions (>95%) from concentrates at 70 °C and 8–10 h leaching. Liquors generated in the chemical leaching were biooxidized for ferrous iron oxidation and ferric regeneration with a mixed culture of ferrooxidant bacteria. No inhibition effect inherent in the liquor composition was detected. The silver added as a catalyst remained in the solid residue, and it was never detected in solution. The recovery of silver may be achieved by leaching the leach residue in an acid-brine medium with 200 g/L of NaCl and either hydrochloric or sulphuric acid, provided that elemental sulphur has been previously removed by steam hot filtration. The effect of variables such as temperature, NaCl concentration, type of acid and acidity–pulp density relationship on the silver extraction from an elemental sulphur-free residue has been examined. It is possible to obtain total recovery of the silver added as a catalyst plus 75% of the silver originally present in concentrate B (44 mg/kg) by leaching a leach residue with a 200 g/L NaCl–0.5 M H₂SO₄ medium at 90 °C and 10 wt.% of pulp density in two stages of 2 h each. The incorporation of silver catalysis to the BRISA process allows a technology based on bioleaching capable of processing chalcopyrite concentrates with rapid kinetics.     

高硫银金精矿碱浸预处理试验研究与生产实践

针对湖北鑫荣矿业有限公司高硫银金精矿氰化浸出过程中银、金出现“返沉淀”的现象,对精矿采用高锰酸钾进行碱浸氧化预处理,有效地消除了银、金的“返沉淀”现象,银、金的氰化浸出率比预处理前分别提高4．65％和1．43％。     

Kinetics of reductive leaching of manganese oxide ore with molasses in nitric acid solution

The kinetics of reductive leaching of manganese from a low grade manganese ore in dilute nitric acid in the presence of molasses is examined. The rate is controlled by diffusion through the “product” layer composed of the associated minerals. The leaching process follows the kinetic model 1 − 2/3X − (1 − X)^2/3 = kt with an apparent activation energy of 25.7 kJ/mole. It is concluded that the concentration of HNO₃ and molasses as well as temperature are the main factors influencing the leaching rate. The results indicate a reaction order of 1.2 for HNO₃ concentration and 1.9 for molasses concentration.     

矿浆电解法从复杂银精矿中提取银的研究

进行了矿浆电解法从复杂银精矿中提取银的研究。富含砷、锑、铜的银精矿先经过预处理,再进行矿浆电解,银的浸出率达到95%以上。     

矿浆电解法从复杂银精矿中提取银的研究

进行了矿浆电解法从复杂银精矿中提取银的研究。富舍砷、锑、铜的银精矿先经过预处理，再进行矿浆电解，银的浸出率达到95％以上。     

多金属银矿湿法处理工艺研究

某以银为主的多金属精矿,银以固溶体形态存在于方铅矿及闪锌矿中。直接氰化时,银浸出率小于10%,金浸出率小于50%,因此应先进行预处理以提高金银浸出率。结果表明,对含金、银、铜、铅、锌的多金属精矿,采用氨浸—氰化或氨浸—酸脱铅—氰化方案可以得到良好效果。在85～100℃、0.2MPa氧压条件下进行氨性浸出后,铜、锌浸出率分别达到99%及93.8%,铅转化率94.8%,再进行常规氰化,金、银氰化浸出率分别达到98%及99%。     

The behavior of thiourea and flotation reagents in zinc electrowinning circuits

The effect of thiourea and flotation reagents on the electrowinning of zinc from industrial electrolytes was studied, and all the compounds were found to reduce the zinc deposition current efficiency and to change the properties of the zinc deposits. The effectiveness of activated carbon, two-stage cementation, and hot acid leaching on the destruction/removal of the organic compounds also was addressed. Activated carbon pretreatment of thiourea-containing electrolytes restored the current efficiency for 1-hour zinc deposits to values comparable to those obtained for thiourea-free electrolytes. The activated carbon pretreatment, however, altered the deposit morphology and orientation, but produced a cyclic voltammogram similar to that of the thiourea-free solution. Two-stage cementation did not counteract the harmful effects of thiourea. Hot acid leaching destroyed the thiourea but generated large concentrations of ferrous ion that reduced the current efficiency. The ferrous concentrations, however, were readily controlled by KMnO₄ or MnO₂ oxidation. None of the treatment options (activated carbon, two-stage cementation, or hot acid leaching) was effective in controlling the flotation reagents, and their moderately harmful effect on zinc electrowinning persisted. Even low concentrations of these reagents polarized zinc deposition, and this resulted in a “glue-type” zinc deposit.     

The behavior of thiourea and flotation reagents in zinc electrowinning circuits

The effect of thiourea and flotation reagents on the electrowinning of zinc from industrial electrolytes was studied, and all the compounds were found to reduce the zinc deposition current efficiency and to change the properties of the zinc deposits. The effectiveness of activated carbon, two-stage cementation, and hot acid leaching on the destruction/removal of the organic compounds also was addressed. Activated carbon pretreatment of thiourea-containing electrolytes restored the current efficiency for 1-hour zinc deposits to values comparable to those obtained for thiourea-free electrolytes. The activated carbon pretreatment, however, altered the deposit morphology and orientation, but produced a cyclic voltammogram similar to that of the thiourea-free solution. Two-stage cementation did not counteract the harmful effects of thiourea. Hot acid leaching destroyed the thiourea but generated large concentrations of ferrous ion that reduced the current efficiency. The ferrous concentrations, however, were readily controlled by KMnO₄ or MnO₂ oxidation. None of the treatment options (activated carbon, two-stage cementation, or hot acid leaching) was effective in controlling the flotation reagents, and their moderately harmful effect on zinc electrowinning persisted. Even low concentrations of these reagents polarized zinc deposition, and this resulted in a “glue-type” zinc deposit.     

某难浸金精矿硫脲法浸金试验研究

进行了某富硫高砷金精矿加添加剂CL硫脲浸金试验研究。试验研究结果表明,添加剂CL可以改善硫脲浸金过程,降低浸出所需的硫脲浓度,提高金浸出率,可使该金精矿的金浸出率达到89％以上。试验还探讨了浸出的最佳条件,并分析了添加剂CL对浸金机理的影响。     

某铜金精矿加压氧化-氰化浸出试验研究

本文对某铜金精矿进行了高温加压氧化—氰化工艺试验研究,探讨了浸出时间、浸出温度、氧分压和初始NaCl浓度等工艺参数对铜浸出率的影响以及后续氰化条件对金银浸出率的影响。结果表明,在综合条件下,即粒度-325目占90%、初始NaCl浓度40 g/L、浸出温度180 ℃、氧分压0.6 MPa、液固比5∶1、浸出时间2.5 h以及搅拌速度750 rpm,在氰化条件：振荡氰化、液固比2∶1、NaCN加入量10 kg/t浸铜渣和氰化时间24 h,金、银、铜的浸出率分别为98.3%、94.7%和99.7%。该铜金精矿采用加压酸浸—氰化提取金银铜工艺具有对3种有价金属回收率高、氧化速度快、对矿石中杂质不敏感及对环境污染小等优点,具有较好的工业化前景。     

Selective silver electroseparation from ammoniacal thiosulfate leaching solutions using a rotating cylinder electrode reactor (RCE)

A systematic electrochemical study at controlled potential, using a rotating cylinder electrode reactor, was carried out on a synthetic solution with composition 0.2mol/L Na₂S₂O₃, 0.05mol/L CuSO₄, 0.025mol/L EDTA, 0.6 mo/L NH₃, 1 × 10^{− 3}mol/L AgNO₃, which simulates actual leaching solution, to determine the conditions which permit the selective silver electroseparation with a minimum interference from the copper ions. The presence of 10 ppm of gold (5 × 10^{− 4}M Au(I)) was found to enhance the gold–silver alloy deposition, with negligible effect on the copper ions. Those results were compared to that obtained with solutions originating from a previously characterized sulfide concentrate leach, in order to determine the influence of other impurities present in the pregnant solution, on the selective silver electrodeposition, obtaining averaging current efficiencies of 80%, with 90% of silver in the formed deposit and less than 5% of both, copper and lead, with only minor quantities of iron and zinc. Additionally, it was shown that the resulting solution could be recycled back to the leach stage, obtaining similar performances to those produced by the fresh solution, implying that it was not significantly altered in its composition, by the electroseparation process.     

氰化尾渣中铁的浸出对金银浸出率的影响

对难处理金精矿两段焙烧提金流程中的氰化尾渣进行强化酸浸,酸浸过程中氧化铁矿物的溶解而使其中包裹的金得到解离并裸露,在氰化浸出过程中容易被浸出。研究表明,随着焙砂中氧化铁相包裹体的逐步酸溶,其酸浸渣中的金、银的氰化浸出率也随之显著提高。该预处理方法为提高难处理金精矿中金、银的浸出回收率提供了一种有效的途径。     

某金精矿氰化浸出液中金的测定

文中使用100g／L的硫脲络合某金精矿氰化浸出液中的银,消除其对金测定的干扰．分析测定结果准确可靠,使尾渣和浸出液分别计算金的回收率基本一致。     

湿法炼锌渣酸浸—浮选富集银试验研究

某高酸锌冶炼渣中银品位为360g/t,存在形式复杂,绝大部分被黄钾铁矾包裹。研究了用硫酸加热浸出除锌、铁—浮选富集银,得到的银精矿品位为3 201g/t,银回收率为82.58%。     

从含砷金精矿二段焙烧酸浸渣中氰化浸出金银的试验研究

进行了从含砷金精矿二段焙烧酸浸渣中氰化浸出金银的工艺试验研究.研究表明,采用RMD对含砷金精矿的二段焙烧酸浸渣进行预处理,可除去大部分砷和部分铅,使金、银的氰化浸出率比常规工艺分别提高4.51%和51.30%,其经济效益显著.     

提高含砷铜金精矿焙烧-氰化工艺金、银、铜回收率的试验研究

提出了一种提高含砷铜金精矿焙烧-氰化工艺金、银、铜回收率的新方法。该方法是将金精矿加入硫化钠后进行焙烧预处理,可有效地提高金、银、铜的回收率。试验结果表明,金、银、铜的浸出率分别提高8．22％,57．43％,7．82％,且不影响制酸和电解铜工艺。     

Improvement of Silver Extraction by Ultrafine Grinding Prior to Cyanide Leaching of the Plant Tailings of a Refractory Silver Ore

Ultrafine grinding (UFG) was proposed as a pretreatment method prior to cyanide leaching of old plant tailings of a refractory silver ore. Direct cyanidation of the as-received tailings (d₈₀: 100 µm) led to a low silver extraction of only ≤43% over 24 h. A size-based diagnostic study has demonstrated that the refractoriness of the tailings is essentially physical in character. Therefore, effects of particle size/UFG (d₉₉: 5–75 µm), concentrations of NaCN (0.75–2.25 g/L) and Pb(NO₃)₂ (0–500 g/t) on the extraction of silver were investigated using a Box–Behnken design. The statistical analysis of the experimental data (%Ag extraction at 1 h) revealed that particle size/UFG was the most significant parameter for the extraction of silver, which was substantially improved after UFG. A positive effect of increasing the concentration of NaCN was also observed particularly at finer particle sizes while the effect of concentration of Pb(NO₃)₂ was insignificant. Almost complete extraction for silver (i.e., ≥99%) was demonstrated to be possible at even higher concentrations of cyanide (>2.25 g/L NaCN) when using the finest material (d₉₉: 5 µm) over only 1 h of leaching. Albeit, the consumption of cyanide tended to increase with UFG or increasing the initial concentration of cyanide. The findings showed that UFG can be used as a suitable and environmentally sound pretreatment method to improve the extraction of silver from the refractory silver ore tailings. The diagnostic approach adopted in the current study has proved to be a useful analytical tool to determine the amenability of the ore to ultrafine-grinding as a pretreatment process.