DISSOLUTION THEORY OF GOLD IN ALKALINE THIOUREA SOLUTION(Ⅱ)——Electrochemical Study on Au-Fe Mix Anode in Alkaline Thiourea Solution Containing Na_2SO_3

１ＩＮＴＲＯＤＵＣＴＩＯＮＭａｎｙｓｔｕｄｉｅｓｏｎｔｈｅｅｘｔｒａｃｔｉｏｎｏｆｇｏｌｄｆｒｏｍｏｒｅｏｒｓｃｒａｐｗｉｔｈｔｈｉｏｕｒｅａｗｅｒｅｒｅｐｏｒｔｅｄ［１－３］，ｂｕｔａｌｔｈｏｓｅｗｅｒｅｌｉｍｉｔｅｄｏｎｌｙｉｎａｃｉｄｉｃｍｅｄ...     

亚硫酸钠在碱性硫脲溶金体系中的电化学行为

用电化学工作站测试金电极和铂电极的极化曲线和交流阻抗,研究亚硫酸钠对碱性硫脲溶解金的影响。结果表明,亚硫酸钠对金的腐蚀电位(E_(corr))为-0.776 V,远低于硫脲,腐蚀速率为0.014mm/a,是有效的溶金试剂;在铂电极上测试,硫脲在碱性条件下会发生不可逆氧化分解,但亚硫酸钠对硫脲的氧化分解没有明显抑制作用;当硫脲中添加亚硫酸钠后,E_(corr)降低,腐蚀速率增大,电化学阻抗弧值大大降低,协同促进金的溶解;0.15 mol/L硫脲+0.15 mol/L亚硫酸钠的溶液具有最佳溶金效果。     

DISSOLUTION THEORY OF GOLD IN ALKALINE THIOUREA SOLUTION(I) Anodic Behavior on Gold in Alkaline Thiourea Solution Containing Na2SO3

Anodic polarization behaviors of gold and its associated elements, e.g., silver, copper, nickel and iron, in the alkaline thiourea solution with and without Na2SO3 were examined. The results showed gold is hardly dissolved in the solution with Na2SO3 because of the passivation of elemental sulfur produced by irreversible decomposition of alkaline thiourea; however, the additive Na2SO3 improves the stability of thiourea in alkaline media, greatly increases anodic current of gold and accelerates the selective dissolution of gold in the alkaline thiourea solution, without changing the passivation states of the associated elements of gold. Also the factors affecting the polarization of gold anode were investigated in detail, and it was found that, the Na2SO3obviously decreases polarization potential of gold and the apparent activation energy of gold dissolution, and the controlling step of the dissolution of gold anode in the alkaline thiourea solution is changed from the anode dissolution reaction to the solute diffusion. The mechanism for accelerated dissolution of gold in the alkaline thiourea solution with Na2SO3 was considered as electrochemical reduction and catalysis, over the Na2SO3 concentration of 0.01 ～0.5 mol/L, at the potential of 0.34～0.44 V.     

Anodic dissolution of gold in alkaline solutions containing thiourea, thiosulfate and sulfite ions

Gld dissolves electrochemically in alkaline solutions containing ligands to form complex ions with gold ion.Therefore,selective leaching of noble metals is expected without dissolution of base metals such as steels,aluminum alloys in scrap treatment.Gold electrodes were investigated using linear sweep voltammetry,EQCM method and potentiostatic eclectrolysis in alkaline solutions containing thiourea,Na2SO3 and Na2S2O3.The solution composition,electrode potential affect gold dissolution rate and current efficiency.The gold dissolved from anode electrode forms complex ions,suspension particles as compound precipitates and deposits on cathode electrode as a metal.Anodic efficiency for gold dissolution is between 10% and 22%.This is caused by the oxidation decomposition of sulfite ions and thiourea.The statbility of the alkaline solution containing these elements was also estimated by capillary electrophoresis technique.     

Dissolution theory of gold in alkaline thiourea solution(

The oxidants of gold were investigated in an alkaline thiourea solution containing Na₂CO₃, in which Na₂S₂O₈ is a proper oxidant for dissolving gold because of in such homogeneous sulfur system coexisting complex agent, oxidant and stabilizing agent. The thermodynamic analyses were conducted on the dissolving of gold in the alkaline thiourea solution containing Na₂SO₃ by the oxidants oxygen or Na₂S₂O₈. The results show that the possibility of gold dissolution reduces with increasing pH value, while oxygen acts as oxidant; and when Na₂S₂O₈ acts as the oxidant of gold in the alkaline thiourea solution of pH 12.5, decomposition potential of thiourea decreases from the standard value 0.42 V to -0.32 V, also the dissolution trend of gold enhances with shifting the mix potential of the solution to the positive direction.     

Dissolution theory of gold in alkaline thiourea solution(Ⅲ) ——Thermodynamics on dissolution of gold in alkaline thiourea solution containing Na _2SO_3

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｅｃｈａｎｉｓｍａｎｄｃｈｅｍｉｃａｌｐｒｏｃｅｓｓｆｏｒｄｉｓｓｏｌｖｉｎｇｇｏｌｄｉｎａｃｉｄｉｃｔｈｉｏｕｒｅａｓｏｌｕｔｉｏｎｗｅｒｅｓｔｕｄｉｅｄｂｙｍａｎｙｒｅｓｅａｒｃｈｅｒｓ［１～５］，ｗｈｏｇｅｎｅｒａｌｌｙｔｈｏｕｇｈｔｔｈａｔｔｈｉｏｕｒｅａａｓａｓｔｒｏｎｇｌｉｇａｎｄｃｏｍｐｌｅｘｅｓｓｅｌｅｃｔｉｖｅｌｙｗｉｔｈｇｏｌｄｉｏｎｔｏｆｏｒｍｓｔａｂｌｅｃｏｍｐｌｅｘｉｏｎＡｕ［ＣＳ（ＮＨ２）２］＋２，ａｎｄｓｏｍｅｏｘｉｄａｎｔｓ…     

低品位铁锰型金银矿的硫脲浸出研究

对铁锰型金银矿采用预先浸锰工艺,使被二氧化锰包裹金银裸露出来,同时降低硫脲浸出金银时的氧化还原电位,有效减少了硫脲消耗量.结果表明,当矿样为200g,经浸锰预处理后,在pH =1.5,电位300mV,亚硫酸钠6g,浸出时间4h的最佳条件下,金、银的浸出率分别为98%、45%,硫脲消耗仅为6kg/t.     

Electrochemical Catalytic Oxidation Performance of a Nanoporous Gold Electrode

对纳米多孔金电极的电化学催化活性进行了研究,在1 mol/L LiPF6非水溶液中室温下采用电化学合金化/去合金化方法制备了纳米多孔金电极,然后使用循环伏安方法和计时电流方法研究了电极对乙醇的电化学催化活性。研究显示,在0.5 mol/L KOH + 1.0 mol/L CH3CH2OH 溶液中,制备的多孔电极在0和400 mV (vs SCE)对乙醇的电化学催化氧化电流密度超过光滑金电极的100倍以上,分别达到3.7和6.1 mA·cm-2。表明制备的纳米多孔金电极对乙醇具有良好的电化学催化氧化活性。     

Electrochemical oxidation of pyrrhotute in aqueous solution

The anodic surface oxidation of natural pyrrhotite in 0.3 mol/L KCI and HCI solution （pH 4.0） and 0.1 mol/L Na2B4O7 solution （pH 9.18） respectively was investigated by using cyclic voltammetry, Tafel plot, and chronoamperometry. In 0.3 mol/L KCl and HCl solution （pH 4.0）, at potential less than 0.5 V（vs SHE）, the production of anodic oxidation on pyrrhotite surface can not maintain a stable phase to form a passive film. In 0.1 mol/L Na2B4O7 solution （pH 9.18）, when the electrode potential increases to more than 0.5 V （vs SHE）, part of S is oxidized to sulfate, making the passive film somewhat porous, but elemental S and metal oxidates Fe（OH）3 still remain on the electrode surface, and the passive film can not be broken down totally. According to PARCalc Tafel analysis, the corresponding corrosion current density （J0） is 5.34 μA/cm^2 , which is also the exchange current density of the oxidation reaction on pyrrhotite electrode surface in 0. 1 mol/L Na2B4O7 solution （pH 9. 18）. The electrochemical dynamics equation of the oxidation was determined.     

硫脲浸金电化学行为研究

采用循环伏安法(CV)、Tafel曲线和差分脉冲伏安法(DPV)等电化学方法对模拟硫脲浸金体系进行了研究。结果表明,硫脲浓度范围为0.005～0.04 mol/L,浓度增大有利于金的浸出;在Fe~(3+)浓度为0.01～0.08 mol/L范围内,随着Fe~(3+)浓度的增大,金腐蚀电位负移,腐蚀电流变大;适度升温可以提高金的腐蚀。实际矿物浸出验证试验表明,金的浸出率随Fe~(3+)浓度(0.02～0.08 mol/L)增大而增大,最高达到了53.21%;金的浸出率随硫脲浓度(0.005～0.05 mol/L)增大而增大,最高达到了78.67%,与电化学分析结论基本一致。     

N503萃淋树脂分离富集金

研究了N_(503)萃淋树脂的合成方法及其分离富集金的条件.N_(503)萃淋树脂是萃取色层分离富集金的新固定相.2%硫脲、1%亚硫酸钠水溶液均可以定量解脱柱床上的金.经矿样验证,金的测定结果与717离子交换树脂吸附法一致.红外光谱表明该萃取色层与N_(503)液液萃取金有相同的机理.     

碱性硫脲浸金的研究现状与发展趋势

阐述了可能取代氰化浸金的高效、无毒碱性硫脲浸金的研究现状。相比酸性硫脲浸金,碱性硫脲浸金具有溶金选择性好,溶液的再生及净化工序相对容易等优点。阐明了碱性硫脲浸金原理及金在碱性硫脲溶液中的溶解机理,对碱性硫脲溶液中的稳定剂及氧化剂的选择做了详细探讨。最后,指明了碱性硫脲浸金所取得的成果及需要解决的问题,并展望了其发展趋势。     

Si/BDD电极在酸/碱电解条件下的电化学氧化性能变化

目的 探究Si/BDD电极在酸性、碱性2种电解条件下的性能变化特征,阐明BDD电极在酸、碱溶液中电化学氧化性能的变化与失效机理。方法 通过HFCVD技术制备Si/BDD电极,分别在1 mol/L H₂SO₄、1 mol/L NaOH溶液中进行加速寿命实验,以活性蓝19(RB-19)模拟染料废水,进行电化学氧化降解实验。使用扫描电子显微镜、拉曼光谱、接触角测试仪、紫外分光光度计及电化学工作站对电极的表面形貌、成分及电化学性能进行表征。结果 在1 mol/L NaOH溶液中,当电解时间为195 h时,电极表面部分区域发生了明显的脱落现象;在1 mol/L H₂SO₄溶液中,当电解时间达到600 h时,电极表面仍未出现明显的脱落现象,电极表面形貌由清晰转为模糊,晶粒尺寸细化,且在晶界处存在明显的腐蚀现象;在酸溶液中,BDD电极对RB-19的降解效果随着电解时间的延长而提高,而在碱溶液中,其降解效果与电解10 h的降解效果基本一致。结论 与酸溶液相比,Si/BDD电极更易在碱溶液中发生腐蚀。     

Corrosion and corrosion inhibition of Cu-20%Fe alloy in sodium chloride solution

The electrochemical behavior of copper (Cu), iron (Fe) and Cu-20%Fe alloy was investigated in 1.0 M sodium chloride solution of pH 2. The effect of thiourea (TU) addition on the corrosion rate of the Cu-20%Fe electrode was also studied. Open-circuit potential measurements (OCP), polarization and electrochemical impedance spectroscopy (EIS) were used. The results showed that the corrosion rates of the three electrodes follow the sequence: Cu < Cu-20%Fe < Fe. Potentiostatic polarization of the Cu-20%Fe electrode in the range −0.70 V to −0.45 V (SCE), showed that iron dissolves selectively from the Cu-20%Fe electrode surface and the rate of the selective dissolution reaction depends on the applied potential. At anodic potential of −0.45 V, thiourea molecules adsorb at the alloy surface according to the Langmuir adsorption isotherm. Increasing thiourea concentration (up to 5 mM), decreases the selective dissolution reaction and the inhibition efficiency η reach 91%. At [TU] > 5 mM, the dissolution rate of the Cu-20%Fe electrode increases due to formation of soluble thiourea complexes. At cathodic (−0.6 V), the inhibition efficiency of thiourea decreases markedly owing to a decrease of the rate of the selective dissolution reaction and/or desorption of thiourea molecules. The results indicated that thiourea acts mainly as inhibitor of the selective dissolution reaction of the Cu-20%Fe electrode in chloride solution.     

铜阳极泥处理过程中中和渣中碲的提取与制备

采用硫酸浸出二氧化硫还原方法从中和渣中制取单质碲。研究表明:采用硫酸浸出中和渣,当反应温度为30℃、反应时间为0.5 h、硫酸浓度为53.9 g/L、硫酸用量为理论用量的1.5倍时,碲浸出率为99.99%;采用亚硫酸钠还原酸浸液中碲时,碲(Ⅳ)发生水解生成二氧化碲;采用二氧化硫还原酸浸液中碲时,当反应温度为75℃、反应时间为2 h、盐酸浓度为3.2 mol/L、二氧化硫流量为0.4 L/min时,碲回收率达到99.84%。X射线衍射(XRD)分析表明二氧化硫还原得到的产物为单质碲,电感耦合等离子体发射光谱(ICP)分析表明,碲粉中碲含量为98.27%。扫描电子显微系统(SEM)分析表明,碲粉的形态为针形。     

Gold leaching with elemental sulfur in alkaline solutions under oxygen pressure

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｙａｎｉｄａｔｉｏｎｐｒｏｃｅｓｓ ,ｃｈａｒａｃｔｅｒｉｚｅｄｂｙｅｆｆｅｃｔｉｖｅｎｅｓｓａｎｄｌｏｗｏｐｅｒａｔｉｎｇｃｏｓｔ,ａｓａｃｏｎｖｅｎｔｉｏｎａｌｔｅｃｈｎｏｌｏｇｙｆｏｒｇｏｌｄｅｘｔｒａｃｔｉｏｎｆｒｏｍｏｒｅｓ ,ｈａｓｂｅｅｎｕｓｅｄｉｎｉｎｄｕｓｔｒｙｆｏｒｏｖｅｒ 10 0ｙｅａｒｓ .Ｈｏｗｅｖｅｒｔｈｅｃｙａｎｉｄｅｉｓａｈｉｇｈｌｙｔｏｘｉｃｃｈｅｍｉｃａｌ,ａｎｄｃｏｍｍｅｒｃｉａｌｃｙａｎｉｄａｔｉｏｎｐｒｏｃｅｓｓｉｓｌｉｍｉｔｅｄｉｎｔ…     

一种新的添加剂(Re-1)在硫脲浸金中的应用

报道了一种用于硫脲法浸金过程的新的Re－1型溶金添加剂,实验证实该添加剂可以改善硫脲浸金液状态,降低浸液硫脲浓度,提高金出率。可使含砷硫化原生矿的一次金浸出率达到89％以上。同时,测定了工艺的最佳条件并讨论了Re－1添加剂对浸金机理的影响。     

硫脲在0.5mol/L硫酸溶液中对A3钢缓蚀作用的电化学研究

为研究硫脲在硫酸溶液中对A3钢的缓蚀作用,并为实际生产中选用硫脲作为缓蚀剂的可行性评价提供参考,采用稳态极化曲线和电化学阻抗谱图(EIS)方法分别研究了A3钢在0.5mol/L硫酸溶液和0.5mol/L硫酸溶液+0.3g/L硫脲混合介质中的腐蚀行为.对硫脲在0.5mol/L硫酸溶液中对A3钢的缓蚀作用给出了评价,证明了硫脲在防止腐蚀的过程中对阴阳两极极化过程均有显著作用,并得出其为一种混合抑制型缓蚀剂的结论.     

Surface modification of indium tin oxide films with Au ions implantation: Characterization and application in bioelectrochemistry

Indium tin oxide (ITO) thin film coated glass substrates have been implanted with 21 keV Au ions at a fluence of 1.0 × 10¹⁷ ions/cm² at room temperature. The resulting gold film was characterized with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectra and electrochemical methods. The results reveal that the implanted Au atoms were in the zero-valent metallic state and these Au atoms precipitated to form nanoclusters on the ITO surface whose average radius was estimated between 2 and 5 nm. The preferentially growing orientation was Au (111) plane during the formation process of gold film and the value of gold active surface area normalized by the geometric electrode areas was 0.48 for Au ion implanted ITO (Au/ITO) electrode. The potential utility of Au/ITO films was investigated. The Au/ITO electrode exhibited effective catalytic responses towards biomolecules such as ascorbic acid (AA) oxidation and lowered oxidation potential of AA by 0.6 V when compared with the bare ITO electrode. Myoglobin (Mb) was also successfully immobilized on the Au/ITO electrode and the direct electron transfer between proteins and electrode surface was realized. It was demonstrated that the Au/ITO film offered a favorable microenvironment for the orientation of biomolecules. New biomaterials with specific electrocatalytic and electrochemical features could be fabricated using this method.     

电沉积 CuS 镀液的电化学性能及镀膜相组成

目的获得结晶好、连续均匀的CuS薄膜。方法采用电沉积方法制备CuS薄膜,研究络合剂、硫源及铜硫离子比例对镀液电化学性能的影响,分析不同沉积电位下所得薄膜的相组成。结果柠檬酸钠的络合效果最好,EDTA最差;硫代硫酸钠作为硫源时,其还原电位较硫脲为硫源时正,氧化电位较负,水平距离值较小,更容易实现共沉积;铜硫离子比例为1时,施镀最合适。沉积电位为-0.8 V时,薄膜的XRD图谱中有氧化亚铜的衍射峰;当沉积电位在-0.9 V时,生成了Cu2S相;沉积电位在-0.9~-1.2V时,生成了目标产物CuS,并且-1.2 V时的衍射峰强度比较高,结晶良好。结论最佳沉积条件如下:柠檬酸钠为络合剂,硫代硫酸钠为硫源,铜硫离子比为1,沉积电位为-1.2 V。