锌丝置换氰化镀银废水中低浓度银的研究及应用

氰化镀银工艺产生了大量的含银清洗废水,采用锌丝置换氰化镀银漂洗废水中的低浓度银有助于节约资源、保护环境。考察了锌丝用量、反应时间、温度、pH值、搅拌速度对银回收率的影响。最佳置换条件为,锌丝用量1 g/200 mL,pH值8~9,温度30 ℃,搅拌速度400 r/min,反应时间30 min,银置换率99.44%。动力学分析表明,氰化镀银漂洗废水中银的置换反应符合一级动力学,扩散为控制步骤,以反应Arrhenius方程计算出反应活化能为19.95 kJ/mol。参考研究结果,设计了回收装置,银回收率99%,回收成本比树脂法低。     

亚硫酸钠浸出-甲醛还原回收氯化渣中的银

为了改善氰化金泥湿法精炼过程中氯化渣铁粉置换工艺熔炼粗银时的工作环境,提高银的回收率,采用亚硫酸钠浸出-甲醛还原方法处理氯化渣。结果表明,在pH=8.5、液固质量比为20:1、35℃的条件下用浓度为250g/L的亚硫酸钠溶液浸出氯化渣3h后,银浸出率大于99%;浸银液在40%甲醛与银比例为5:2 (mL/g)、50℃的条件下还原1.5 h,银还原率达99%以上。浸出渣返回金泥氯化分金流程,浸银液还原后可再生循环使用,银综合回收率可达98%以上。     

选冶联合流程回收铜银金的工艺

采用ＤＸ 低碱度抑制剂， 用ＮａＯＨ 调节ｐＨ， 在ｐＨ＝ ９ ～１０ 的范围内浮铜抑硫， 使混合精矿中的有价金属与黄铁矿分离， 再选精矿产率２０ ％ ～３０ ％ ， 尾矿含金低于３ ．０ ｇ／ｔ。在较低的压力下（ 氧压０ ．４ ～０ ．６ ＭＰａ） 对所得精矿进行氧压氨浸， 使硫转化为硫酸铵， 铜进入溶液， 金银留在浸渣中。分选中金、银、铜回收率分别为９５ ％ ，９０ ％ 和８５ ％ ； 分选条件为ｐＨ＝ ９ ．５ ， 捕收剂用量２００ ｇ／ｔ， ＤＸ 抑制剂３ｋｇ／ｔ。低压氨浸铜浸出率为９５ ％ ， 浸出压力０ ．５ ＭＰａ， 温度１２０ ℃， 时间３ ｈ ， 氨浓度４５ ｇ／Ｌ。氰化浸出金、银浸出率为９７ ％ 和９５ ％ ， 置换率９９ ％ 和９８ ％ 。金、银、铜总回收率分别为９４ ％ ，８４ ％ 和８１ ％ 。     

锌粉置换回收锑精矿碱浸液中的金

锑精矿碱浸液是湿法处理锑精矿产生的中间产物含有少量的金，必须回收。以山东某公司锑精矿碱浸液为原料，经多种提取剂对比，采用锌粉置换回收其中的金。考察了锌粉用量、料液pH、浸出温度、时间的影响，得到的最佳工艺条件为:锌粉用量4.0 kg/m³，溶液pH=11，反应时间3 h，反应温度80 ℃，多批次试验金回收率88%。工艺过程简单，经济性可行，有效解决了资源浪费问题，为锑精矿碱浸液回收金提供了一条新的工艺。     

As(Ⅲ)在酸性水溶液中与金属铁的反应行为

从热力学分析和试验两方面研究As(Ⅲ)在酸性水溶液中与金属铁的反应行为。热力学计算结果表明:在酸性水溶液中,As(Ⅲ)与金属铁作用,分别生成As元素或As H3气体的反应在热力学上均是可行的。试验结果表明:在温度为20~80℃、溶液初始p H值为-0.31~4、溶液初始浓度ρ[As(Ⅲ)]为1~20 g/L、铁粉大量过剩的条件范围内,由于动力学方面的原因,生成As H3的反应实际并不会发生,铁粉仅能使As(Ⅲ)还原为As元素。铁粉"过量"系数、溶液p H值和温度对沉砷率有显著影响,提高铁粉"过量"系数和温度,可使沉砷率增大,在溶液p H值为3的条件下,沉砷效果最佳。在酸性溶液中,铁粉置换As(Ⅲ)生成As的反应难以进行到底的原因,可能是由于还原的As在铁粉表面沉积阻滞了反应的延续。而在初始p H值为3或较高温度条件下能达到较高的沉砷率,是由于在这些条件下,置换的砷呈疏散形态沉积,未能对铁粉表面形成紧密包裹,使得反应得以延续。     

从银电解液中提取铂和钯的新方法

研究了从大量银存在的弱酸性硝酸溶液中选择性沉淀提取钯的反应,提出了一个用丁基黄药作沉淀剂从银电解液中提取铂和钯非常有效的方法。此法对含铂和钯以及含钯不含铂的两种银电解液均适用,选择性很高,当沉淀剂用量从不过量到过量10％,反应温度80～85℃,时间1小时,铂和钯的沉淀率可达99％,银的共沉淀率一般均在2％以内。     

氰渣综合利用提取金银的试验研究

通过正交试验详细考察了矿浆浓度、硫酸过剩系数、反应温度和反应时间等因素对氰渣浸铁率的影响.结果表明矿浆浓度为35%、硫酸过剩系数为1.3、反应温度为100℃、反应时间为2.5 h的试验条件下,铁的浸出率最高,可达97.80%.对比氰渣和浸铁渣金、银的氰化浸出效果发现氰渣再氰化金、银的浸出率分别为5%和10%,而浸铁渣再氰化金、银的浸出率则分别高达87%和80%,因此氰渣浸铁再氰化是提高金、银回收率的有效途径之一.     

富贵锑控电位氯化浸出选择性分离贱金属

为实现从富贵锑中富集提取金的目的,提出采用控电位氯化浸出方法选择性分离富贵锑中贱金属。详细考察了各因素对贱金属浸出率的影响,查明了最优条件下贵金属的溶解行为,采用富贵锑粉置换回收浸出液中的贵金属。结果表明:提高盐酸浓度、增加液固比、提高反应温度和减小双氧水的加入速度均可以提高贱金属的浸出率;但增大双氧水过量系数会导致金属氧化沉淀。在最优条件下,铜、镍、锑和铅的浸出率均大于99.0%,金和银的浸出率分别为0.16%和84.40%,浸出渣中金含量达到96.0%。浸出液冷却结晶过程会析出氯化铅,金和银的置换率均达到99.0%以上。该方法实现了富贵锑中贱金属有效分离和金高效富集的双重目的。     

银阳极泥硝酸浸出液中铂和钯的还原富集

银阳极泥在硝酸浸出时,大部分铂和钯会进入溶液,最终返回熔炼系统,铂钯直收率因此偏低。研究了亚硫酸氢钠还原沉淀硝酸浸出脱银液中铂和钯的工艺条件。结果表明,还原剂用量、硝酸浓度、反应温度和时间均对铂和钯沉淀率有影响。在优化条件下,铂和钯的沉淀率分别可达到99.5%和99.7%,所得精矿中铂和钯含量分别为1.70%和13.59%。     

液氯化法从难处理金精矿加压氧化渣中浸金的研究

针对国内某难处理金精矿的加压氧化渣进行液氯化法浸金的热力学计算及浸出单因素实验,考察pH值、氯化钠浓度、反应温度及反应时间等因素对浸金率的影响。结果表明,金氯化浸出反应的热力学条件为:pH值小于8、电位大于0.9V;液氯化法浸金最佳实验条件为:pH值4、电位1.0V以上、氯化钠浓度75g/L、反应温度40℃、液固比3:1、搅拌速度300r/min、反应时间120min,浸金率为96.54%。此方法显著地提高浸金率,并且具有试剂消耗少、污染少、反应速度快等优点。     

难处理金矿预处理及金回收技术进展

随着优质金矿不断被开发消耗,难处理金矿占比不断地提高,从难处理金矿中回收金是金产业未来发展的必然趋势。本文简要分析了难处理金矿浸出困难的原因,介绍了焙烧氧化法、热压氧化法、生物氧化法、机械活化法、微波法5种预处理技术和氰化法、硫脲法、硫代硫酸盐法、卤素法、火法5种金回收技术的研究进展,并比较了5种预处理技术和4种湿法金回收技术的优势与不足。在此基础上对难处理金矿预处理和金回收技术的前景进行了展望。     

Characterizing gold in refractory sulfide gold ores and residues

Gold is present in refractory sulfide gold ores mainly in arsenian pyrite and arsenopyrite, where it occurs in both the chemically bonded state and as nano-size grains of metallic gold. During roasting or pressure oxidation, the sulfide matrix is destroyed and essentially all the gold is converted to the metallic form. The liberated gold is readily dissolved in conventional cyanide media, although a few residual gold particles, commonly encapsulated by films of silica-rich gel or by calcium sulfate, are detected. Chloridecontaining gold ores can generate soluble gold chlorocomplexes during hydrometallurgical processing and the dissolved gold can be sequestered on the surfaces of associated carbon particles, resulting in reduced gold recoveries.     

An investigation of gold/ceramic and gold/glass interfaces

This paper describes how various characterisation methods can be used to investigate the physicochemical and spectral properties of gold films in contact with glass or ceramic. The interface between the metal and substrate has been given special attention. The examples chosen to illustrate this include: liquid gold films (decorated and fired) or inlayed gold layers on ceramic wares and “sandwich” gold foils between two glass sheets for mosaic application. Characterisation methods include: microanalytical scanning electron microscopy, X-ray diffraction, ion beam analyses (PIXE: particle induced X-ray emission; RBS: Rutherford back-scattering spectrometry), photo-spectrometry and colorimetry. The adhesion mechanism and colour behaviour of the coated objects is discussed.     

Silicon microsegregation in 14K yellow gold yellow gold

Phase equilibria have been used to construct a simplified model of 14 karat (14K) yellow jewelry alloys. In this model, silicon has a reduced solubility in solid 14K (Au-Cu-Ag-Zn) alloys compared to its solubility in pure copper. This reduced solubility results in low values of the partition coefficient for silicon in these alloys. The microsegregation of silicon in 14K yellow gold jewelry casting alloys was evaluated based on the principles of non-equilibrium solidification. The dynamics of non-equilibrium freezing described by the Gulliver-Scheil equation predict the build-up of silicon in the liquid phase to such an extent that unexpected, silicon-rich phases and compounds may appear in the solidification structure. These phases can have deleterious effects on mechanical properties and limit the use of certain types of grain refiners in (Au-Cu-Ag-Zn) families of alloys. The practical limits of silicon levels in 14K yellow gold alloys which do not allow the formation of Cu-Si intermetallics are estimated.     

Electrocatalytic oxidation of glucose on gold–platinum nanocomposite electrodes and platinum-modified gold electrodes

Electrochemical oxidation of glucose on gold–platinum nanocomposite electrodes and platinum-modified gold electrodes was investigated with cyclic voltammetry. Gold–platinum nanoparticles were prepared by reducing aqueous solutions containing chlorauric acid and chloroplatinic acid, and the electrodes were obtained by depositing the gold–platinum nanoparticles from the colloidal solutions onto substrates. The gold–platinum nanocomposite electrodes display high electrocatalytic activity for the glucose oxidation in alkaline solution, showing 0.30–0.35 V negative shift in peak potential as compared with bare gold electrodes, and maintain stable catalytic activity in the reaction. The results of experiments indicate that both gold and platinum act as the dehydrogenation site and gold also functions to regenerate platinum from poisoned platinum. Surface modification of gold electrodes by platinum deposition also increases electrocatalytic activity of the electrodes for the glucose oxidation, showing about 0.10 V negative shift in peak potential, but a gradual decline in reactivity is observed.     

Doped and low-alloyed gold bonding wires

Fine gold wires with diameters down to 15μm are used for bonding semiconductor devices. Increasing miniaturization of electronic circuits calls for smaller wire diameters. This requires the development of gold wires with increased mechanical strength and good bondability to replace thicker wire diameters without detriment to their functionality. The first gold bonding wires were pure gold, and then doped gold wires of high purity were developed because of their stabilized and improved mechanical characteristics. Nowadays and in the near future low alloyed gold wires are increasingly replacing doped gold wires. This paper gives an overview of the mechanical characteristics of doped and low-alloyed gold bonding wires and their bondability.     

Diffusion in gold and Au-Ag alloys

The self-diffusion coefficients of gold in pure gold and alloys of gold and silver have been measured over a range of temperatures. Chemical interdiffusion coefficients have been measured on pure metal and incremental couples, but are of lower accuracy because of the development of porosity. The results are compared with earlier work and internally on the basis of Darken’s equations.