Mechanism of gold dissolving in alkaline thiourea solution

Reaction mechanism of gold dissolving in alkaline thiourea solution was studied by electrochemical methods,such as cyclic voltammetry,chronopotentiometry,AC impedance,linear sweep voltammetry.Apparent activation energy of anodic process of gold electrode dissolving in alkaline thiourea solution is 14.91 kJ/mol.Rate determining step is the process of gold thiourea complex diffusing away from electrode surface to solution.The results of AC impedance and chronopotentiometry indicate that thiourea adsorbs on gold electrode surface before dissolving in solution.There does not exist proceeding chemical reactions.Formamidine disulfide,the decomposed product of thiourea,does not participate the process of gold dissolution and thiourea complex.Species with electro-activity produced in the process of electrode reaction adsorbs on the electrode surface.In alkaline thiourea solution,gold dissolving mechanism undergoes the following courses:adsorption of thiourea on electrode surface;charge transfer from gold atom to thiourea molecule;Au[SC(NH2)2]ads receiving a thiourea molecule and forming stable Au[SC(NH2)2]2 ;and then Au[SC(NH2)2]2 diffusing away from the electrode surface to solution,the last step is the rate-determining one.     

Electrochemical kinetics of gold dissolving in alkaline thiourea solution

1 INTRODUCTIONEssentially , determination of electrode reac-tion mechanism is just the determination of thecourse of electrode reaction and the rate-determi-ning step[1 5]. Based on the previous results[6 11],gold dissolution mechanism undergoes the follow-ing courses in alkaline thiourea solution: adsorp-tion of thiourea on active points of electrode sur-face and formation of Au[SC(NH2)2]ads; chargetransfer fromactive gold atomto thiourea moleculeand formation of Au[SC(NH2)2]a+ds; Au-…     

Study on mechanism of gold leaching by thiourea in the presence of sodium sulphite

Ｃｙａｎｉｄａｔｉｏｎｈａｓｂｅｅｎｕｓｅｄｆｏｒｍｏｒｅｔｈａｎｏｎｅｈｕｎ ｄｒｅｄｙｅａｒｓｉｎｇｏｌｄｉｎｄｕｓｔｒｙｓｉｎｃｅｔｈｅｆｉｒｓｔｐａｔｅｎｔｂｙＭａｃＡｒｔｈｕｒａｎｄｔｈｅＦｏｒｒｅｓｔｓｉｎ 1889[1] ,ａｎｄｓｔｉｌｌｒｅｍａｉｎｓｔｈｅｍｏｓｔｐｏｐｕｌａｒｏｐｔｉｏｎｆｏｒｐｒｏｃｅｓｓｉｎｇｇｏｌｄｏｒｅｓｂｅｃａｕｓｅｏｆｉｔｓｐｒｏｃｅｓｓｓｉｍｐｌｉｃｉｔｙａｎｄｏｐｅｒａｔｉｏｎｅｃｏｎｏｍｙ .Ｎｅｖｅｒｔｈｅ ｌｅｓｓ,ａｐｐｌｉｃａｔｉｏｎｏｆｔｈｅｔｅ…     

Effects of sulfurous acid on anodic process of gold electrode in thiourea solution

Thioureaitselfisunstableunderanappropriateoxidizingconditionandcanbeoxidized .Theoxida tion productsofthioureadependontheoxidants ,suchashydrogenperoxide ,ferriciron .Itwasreport edthatwithferricironetc ,thioureadecomposedasfollows[7] .2SC(NH2 ) 2 (SC(NH)NH2 ) 2 + 2H++ 2e(2 )ThepotentiodynamicpolarizationcurvesshowninFig .1wereobtainedin 0 .0 5mol/Lthiourea(TU )solutionforafreshlygroundstationarygoldelectrodestartsfrom 0to 1.2 0VvsSCE .FromFig .1itcanbeseenthatthefirstanodicshoulderais…     

紫外分光光度法测定金硫脲浸出液中的铜

确定了在硫脲 ( Tu)介质中用紫外分光光度法测定铜的条件 .在λ=30 0 nm处 ,Cu2 +-Tu络合物具有较强吸收 ,而 Tu无紫外吸收 .当硫脲含量在 5 0 0 mg/ L,p H2 .0 ( HCl)时 ,Cu2 +质量浓度在 0 .5～ 1 0 mg/ L范围内遵守比尔定律 .Na+、K+、Ca2 +、Mg2 +、Cl-、NO- 3 、SO42 -、F-等不干扰测定 ,Au3 +、Ag+干扰较小 ,Fe3 +的干扰可用 F- 离子掩敝 .应用该法测定了几种金矿硫脲浸出液中铜的含量 ,与原子吸收法进行比较 ,相对偏差不大于± 3% .     

硫代硫酸盐法添加氯化钠、十二烷基磺酸钠浸取金矿研究

对湖北氧化铁型金矿,进行了Na_2S_2O_3法添加NaCl而不加Cu~(2+)的浸取条件优化研究,当[S_2O_3~(2-)]=0.8mol/L、[NH_3]=1～2mol/L、[NaCl]=1.0mol/L,浸取温度50℃,浸取时间3h,浸出率达到98％。对硫化矿(广东河台金矿、山东招远金矿)进行了浸取研究,[S_2O_3~(2-)]=0.8mol/L、[NH_3]=2mol/L、[NaCl]=1.0mol/L、十二烷基磺酸钠为11.0mmol/L,浸取温度50℃,时间3h,浸取率分别达到96％和93％。     

二次回归正交法碱性蚀刻废液除铅剂配方设计及除铅方程

利用工业品CaCl2和Na2CO3生成的CaCO3与工业品FeCl3·6H2O的协同作用,制得除铅效率高而成本低的碱性蚀刻废液除铅剂。利用二次回归正交设计得到脱铅率的二元二次方程,最佳配比是CaCl2 10．66g/L（相应的Na2CO3 10．18g／L）,FeCl3·6H2O 1．38g／L。绘出了脱铅率的等高线图,为设计除铅剂的配比提供了直观有效的方法。     

难处理金矿浸出预处理过程的FeS2-FeAsS-H2O系电位-pH图

难处理金矿中,金为微细浸染型嵌布在黄铁矿和毒砂的晶格中而不能被充分浸出.本文通过热力学计算绘制了298.15KFeS2-FeAsS-H2O系的电位-pH图,由图可知黄铁矿和毒砂均可以被O2等氧化剂分解.FeAsS的稳定区完全包含在FeS2的稳定区范围内,说明在酸性条件下毒砂比黄铁矿的稳定性差,更容易被分解.当电位及酸度较高时,黄铁矿及毒砂中的硫以稳定的HSO4-、SO42-形式存在,而砷以H3AsO4的形式存在,表明预处理过程能够将包裹在金表面的硫化矿物解离脱除.热力学计算的结果为难处理金矿的浸出预处理过程提供了理论依据.     

NH_3-(NH_4)_2SO_4体系浸析PCB污泥中铜的研究

利用NH3-(NH4)2SO4体系,对印刷电路板(printed circuit boards,PCB)生产过程中产生大量的含铜污泥中的铜进行浸析。对PCB污泥中重金属的质量分数进行了测定,其中铜在污泥中的质量分数为33.500%,其余金属质量分数较小。重点探讨了氨-硫酸铵浓度及pH、浸析时间、液固比、温度等条件对浸析率的影响。NH3-(NH4)2SO4体系对PCB污泥中铜浸析的最优条件为氨、硫酸铵浓度分别为3.0mol/L和1.5mol/L,液固比为20mL/g,浸析时间为180min,浸析温度为25℃。在最优条件下进行了浸析应用试验,结果表明铜的浸析率可达到97.5%,此方法的相对标准偏差(relative standard deviation,RSD)为0.63%。