【作者】 王剑；

【导师】 谢锋；

【作者基本信息】 东北大学 ， 有色金属冶金， 2020， 博士

【摘要】 在过去的一百余年中,氰化法作为黄金工业最主要的矿石提金方法已实现大规模的工业化应用。近年来,随着环保法律法规的不断出台与完善以及人们环保意识和公共安全意识的不断增强,氰化法的工业应用正面临着前所未有的阻碍与挑战。硫代硫酸盐因价格便宜、安全无毒、浸出速率快,能够有效处理氰化法难以处理的铜金矿和炭质金矿,被公认为是最有可能取代氰化物的浸金试剂之一。然而,传统铜-氨-硫代硫酸盐体系因氨的使用所引起的毒性、氨氮废水和试剂消耗等问题已严重阻碍了硫代硫酸盐浸金工艺的发展和应用。针对以上问题,本文提出了铜-柠檬酸盐-硫代硫酸盐浸金体系,并对该体系开展热力学、体系稳定性、浸金动力学和实际矿物浸出等研究,从而阐明了铜-柠檬酸盐-硫代硫酸盐浸金体系的浸出机理并确定了浸出工艺的技术可行性。基于本试验所获得的研究结果,主要结论如下:通过热力学计算绘制了铜-柠檬酸盐-硫代硫酸盐浸金体系的电位-pH图与物种分布图,并结合热力学研究结果确定了该体系的浸金机理。热力学研究结果表明:一价铜离子、二价铜离子和一价金离子可分别以Cu（S₂O₃）₃^5-、Cu₂（Cit）₂H_-2^4-和Au（S₂O₃）₂^3-配合物的形式稳定存在于铜-柠檬酸盐-硫代硫酸盐溶液中。铜-柠檬酸盐-硫代硫酸盐体系的浸金机理为:柠檬酸根通过与Cu（Ⅱ）形成Cu₂（Cit）₂H_-2^4-配合物来稳定溶液中的铜;金以Au（S₂O₃）₂^3-配合物的形式浸出;Cu₂（Cit）₂H_-2^4-配合物对金的浸出过程起催化氧化作用。考察了不同条件下铜-柠檬酸盐-硫代硫酸盐溶液的稳定性。结果表明:日光照射对溶液的稳定性没有影响;提高溶液的初始pH值和柠檬酸盐的浓度可增强铜-柠檬酸盐-硫代硫酸盐溶液的稳定性;提高温度、铜浓度和硫代硫酸盐的浓度可使铜-柠檬酸盐-硫代硫酸盐溶液的稳定性变差。探究了金盘在铜-柠檬酸盐-硫代硫酸盐溶液中的浸出动力学。研究结果表明:金盘在70℃的铜-柠檬酸钠-硫代硫酸钠溶液中的溶金速率为0.1616 μmol·m-2·s-1,约为同温度硫代硫酸钠溶液的10倍。金盘的转速（0-400 rpm）对金的浸出速率无明显影响。金盘的浸出速率随温度（30-90℃）、铜浓度（0.01-0.20 mol/L）和硫代硫酸盐浓度的增加（0.01-0.20 mol/L）而加快;随柠檬酸盐浓度的增加（0.10-0.40 mol/L）而变慢。适当增加溶液的初始pH值（9.00-11.00）可加快金盘的浸出速率;过高的初始pH值（12.00）则不利于金盘的浸出。动力学拟合结果表明:金盘的浸出过程表观活化能为49.74 kJ/mol,受化学反应控制。以易处理金矿为研究对象,探究了实际金矿在铜-柠檬酸盐-硫代硫酸盐溶液中的浸出特性。研究表明:铜-柠檬酸盐-硫代硫酸盐体系的浸金率与氰化法相近,9.0小时的浸金率可达96.1%,其浸出速率远快于氰化法。金矿的浸金率随浸出温度（30-90℃）和硫代硫酸盐浓度（0.01-0.20 mol/L）的提高而增加。适当提高铜和柠檬酸盐的浓度可促进金矿的浸出,过高的铜和柠檬酸盐浓度将会使金矿的浸金率略微下降。基于动力学分析,金矿的浸出过程表观活化能为34.48kJ/mol,受产物层扩散控制。金矿浸出过程中硫代硫酸盐的消耗量随温度、铜浓度和硫代硫酸盐浓度的提高而增加,随溶液初始pH值和柠檬酸盐浓度的提高而减少。此外,高浓度的柠檬酸盐、低温和低浓度的硫代硫酸盐可显著增强矿浆中Cu₂（Cit）₂H_-2^4-配合物的稳定性。结合相应的预处理方法,对三种难处理金精矿在铜-柠檬酸盐-硫代硫酸盐溶液中的浸出工艺进行了研究。同时,对微波焙烧预处理方法改善浸金的作用机理也进行了探究。对于炭质灰岩型金精矿,铜-柠檬酸盐-硫代硫酸盐体系的浸出能力与传统氰化或铜-氨-硫代硫酸盐体系相同。当浸出条件为0.05 mol/L CuSO₄、0.20 mol/L Na₃Cit、0.05 mol/L Na₂S₂O₃、70℃、初始pH值11.00和9.0小时,浸金率为67.1%,硫代硫酸盐消耗量为10.25 kg/t。研究表明:铜-柠檬酸盐-硫代硫酸盐体系相较于铜-氨-硫代硫酸盐体系具有安全无毒、稳定性强、硫代硫酸盐消耗量低、浸出条件范围宽和试剂使用量低等优点。微波焙烧的作用机理为:使炭质灰岩型金精矿颗粒表面产生裂隙,在打开包裹金的同时促进浸出剂对金精矿颗粒的渗透性。金精矿经500℃的微波焙烧处理后,浸金率可提高至90.1%,硫代硫酸盐的消耗量可降低至4.81 kg/t。对于含铜金精矿,当浸出条件为0.10 mol/L CuSO₄、0.20 mol/L Na₃Cit、0.10 mol/L Na₂S₂O₃、70℃、初始pH值9.00和7.0小时,浸金率为69.7%,硫代硫酸盐消耗量为33.20 kg/t。微波焙烧工艺能将含铜金精矿中部分黄铁矿氧化为磁铁矿,并在金精矿颗粒表面形成大量细小裂纹。微波焙烧处理后,含铜金精矿的浸金率可提高至94.5%,硫代硫酸盐的消耗量可降低至11.38 kg/t。对于高砷高硫金精矿两段焙烧后的焙砂样品,当浸出条件为 0.05 mol/L CuSO₄、0.20 mol/L Na₃Cit、0.10 mol/L Na₂S₂O₃、70℃、初始 pH 值11.00和7.0小时,浸金率为82.8%,硫代硫酸盐消耗量为8.66 kg/t。与传统的氰化或铜-氨-硫代硫酸盐体系相比,柠檬酸盐的使用提供了一种更经济、安全和绿色环保的浸金方法。本文中铜-柠檬酸盐-硫代硫酸盐体系的应用基础研究将为硫代硫酸盐浸金体系的发展和工业化应用提供技术支撑。更多还原

【Abstract】 Over the past 100 years,cyanidation as the main method for gold extraction from ores has been successfully applied in the gold industry on a large scale.In recent years,the environmental laws and regulations have been enacted and the awareness of public security and environmental protection among people has been enhanced,which have seriously limited and challenged the industrial application of cyanidation.Thiosulfate is considered to be one of the most promising alternatives to cyanide due to its nontoxicity,low price,high leaching rate and excellent leaching characteristics for carbonaceous gold and copper-gold ores.However,some issues and barriers caused by the use of ammonia in the conventional copperammonia-thiosulfate system have greatly hindered the application and development of thiosulfate leaching process,such as toxicity,ammonia-nitrogen wastewater and reagent consumption,etc.In this work,the copper-citrate-thiosulfate leaching gold system was proposed.A considerable amount of study including thermodynamic,system stability,leaching kinetics and gold ore leaching was performed for copper-citrate-thiosulfate system,thereby identifying the leaching mechanism and technical feasibility.Based on the results obtained from this study,the main conclusions can be summarized as follow:The Eh-pH and species distribution diagrams for copper-citrate-thiosulfate leaching gold system were drawn by thermodynamic calculation.Based on the results of thermodynamic study,the leaching mechanism was then analyzed.The thermodynamic study indicates that cuprous tri-thiosulfate(Cu（S₂O₃）₃^5-),binuclear cupric-citrate(Cu₂（Cit）₂H_-2^4-)and aurous thiosulfate(Au（S₂O₃）₂^3-)complexes are the most stable form of Cu（I）,Cu（II）and Au（I）in copper-citrate-thiosulfate solutions,respectively.The mechanism for gold leaching in copper-citrate-thiosulfate system is as follow:citrate stabilizes the cupric ion by the formation of Cu₂（Cit）₂H_-2^4-complex,metallic gold is oxidized to aurous ion,then enter the solution as Au（S₂O₃）₂^3-complex,and Cu₂（Cit）₂H_-2^4-complex plays an important catalytic role in accelerating gold leaching process.The stability of copper-citrate-thiosulfate solutions was investigated under the different experimental conditions.The stability of copper-citrate-thiosulfate solutions is independent of sunlight.The stability increases with an increase of initial pH and citrate concentration,but decreases with increasing leaching temperature,copper and thiosulfate concentration.The leaching kinetics of gold disk was studied in copper-citrate-thiosulfate solutions.The dissolution rate of gold disk in copper-citrate-thiosulfate solutions is 0.1616μmol·m-2·s-1 under the leaching temperature of 70℃，which is about ten times as fast as the thiosulfate solutions at the same temperature.The rotating speed of gold disk exhibits insignificant influence on the leaching rate when rotating speed varies from 0 to 400 rpm.The leaching rate of gold disk increases with increasing temperature（30-90℃）,copper（0.01-0.20 mol/L）and thiosulfate concentration（0.01-0.20 mol/L）,but decreases with an increase of citrate concentration（0.10-0.40 mol/L）.A modest increase in initial pH from 9.00 to 11.00 can contribute to gold disk leaching rate,but an excessive initial pH can cause a decrease in leaching rate,such as 12.00.The apparent activated energy of gold disk dissolution in copper-citrate-thiosulfate solutions is 49.74 kJ/mol,indicating the overall reaction rate is controlled by chemical reaction.A free milling gold ore was leached using copper-citrate-thiosulfate solutions.Gold extraction capacity from free-milling gold ore using copper-citrate-thiosulfate system is similar to the conventional cyanidation.The gold extraction can reach to 96.1%after leaching 9.0 hours,and the leaching rate is much faster than that of cyanidation.Increasing temperature（30-90℃）and thiosulfate concentration（0.01-0.20 mol/L）can increase gold extraction form free milling ore.A modest increase in copper and citrate concentrations can contribute to gold extraction,but an excessive increase of concentrations can cause a slight decrease of gold extraction.Based on the kinetic analysis,the leaching process of gold from free milling ore may be controlled by the product layer diffusion under the experimental conditions,giving an activation energy of 34.48 kJ/mol.In the leaching process of gold ore,the consumption of thiosulfate at any time increases with increasing leaching temperature,copper and thiosulfate concentration,but decreases with increasing initial pH and citrate concentration.Moreover,a high citrate concentration,low temperature and thiosulfate concentration will result in a significant increase in the stability of Cu₂（Cit）₂H_-2^4-complex during the leaching process.Three types of refractory gold concentrates were leached using copper-citratethiosulfate solutions based on the appropriate pretreatment methods.Meanwhile,the mechanism of improving gold extraction by microwave roasting was also investigated.Compared with the conventional cyanidation or copper-ammonia-thiosulfate system,the copper-citrate-thiosulfate leaching system exhibits a similar extraction capability of gold from the carbonaceous gold concentrates.Under optimum experimental conditions of 0.05 mol/L CuSO₄,0.20 mol/L Na₃Cit,0.05 mol/L Na₂S₂O₃,initial pH 11.0 and leaching time of 9.0 hours at 70℃,gold extraction and thiosulfate consumption reach 67.1%and 10.25 kg/t,respectively.Copper-citrate-thiosulfate system offers certain advantages over copperammonia-thiosulfate system,such as non-toxicity,greater stability,wider range of leaching conditions,less reagent usage and consumption,etc.The microwave roasting generates cracks that are noticeable on the concentrate particle surface,which likely to expose encapsulated gold to the lixiviant and facilitate the permeability of the lixiviant,eventually facilitating the gold extraction.When the concentrates are pretreated by microwave roasting at 500℃ gold extraction and thiosulfate consumption reach 90.1%and 4.81 kg/t,respectively.For the gold concentrates containing copper,the gold extraction and thiosulfate consumption can reach 69.7%and 33.20 kg/t under the conditions of 0.10 mol/L CuSO₄,0.20 mol/L Na₃Cit,0.10 mol/L Na₂S₂O₃,initial pH 9.00 and leaching time of 7.0 hours at 70℃.A considerable number of fine cracks are generated on the surface of particles and part of pyrite from gold concentrates containing copper is converted to magnetite during the process of microwave roasting.A maximum gold extraction of 94.5%and minimum thiosulfate consumption of 11.38 kg/t can be achieved for gold concentrates containing copper after microwave roasting.For the calcines of high-arsenic and high-sulfur gold concentrates after two-stage roasting,the gold extraction and thiosulfate consumption are 82.8%and 8.66 kg/t under the conditions of 0.05 mol/L CuSO₄,0.20 mol/L Na₃Cit,0.10 mol/L Na₂S₂O₃,initial pH 11.00 and leaching time of 7.0 hours at 70℃.The use of citrate provides a more economical,secure and eco-friendly leaching gold method than conventional cyanide or copper-ammonia-thiosulfate system.The applied fundamental research on copper-citrate-thiosulfate system will provide technical support for the development and industry application of thiosulfate leaching gold system.更多还原