Recovery of silver from slags generated by melting precipitates from the Merrill–Crowe process

Slag that is produced from induction furnaces that use the Merrill–Crowe process still contains precious metals. In this study, a pyrometallurgical treatment was performed for their recovery in order to realise economic savings and reduce environmental concerns. An analysis was performed to determine the effect of two fluxes (sodium carbonate and anhydrous borax) on the recovery of silver at different temperatures (1373, 1423 and 1473?K). Experiments that used 20% by weight of anhydrous borax at 1473?K showed recoveries up to 99.68% of silver in the metal phase. However, it also showed an increment of impurities in the doré. On the other hand, the silver recovery was 97.2% when 20% of sodium carbonate was used at the same temperature. Additionally, the sodium carbonate flux produced a better quality doré.     

The dissolution behavior of metals from Ag/Cu and Ag/Au alloys in acidic and cyanide solutions

The dissolution behavior of silver, copper, and gold from silver/copper and silver/gold alloys in acid and cyanide solutions has been investigated using a rotating disc. Oxygen or ferric ion was used as an oxidant. The effect of composition of alloys, rotation speed, concentration of lixiviants, and temperature on the overall dissolution kinetics of these metals has been studied. The dissolution rate of silver was reduced due to galvanic effect, when it was leached from a silver/copper alloy disc in acidic media at relatively low oxidation potentials. On the other hand, when the oxidation potential was high, the galvanic effect of the dissolution rate became less pronounced. In the case of the silver/gold system in cyanide solutions, the effect of alloy composition on the dissolution rate of gold and silver was not as much as in the case of silver/ copper alloy systems. This may be attributed to the fact that both gold and silver are noble, and therefore, the electromotive forces of these two metals are not significantly different. Formerly with the South Dakota School of Mines and Technology Formerly Visiting Professor, South Dakota School of Mines and Technology     

Extension of solid solubility during massive transformations

Recent studies of massive transformations in systems based on copper or silver have shown that the degree to which the primary solid solution,a, may be extended into the two-phase field,α+β), during a composition invariant massive transformation, varies from system to system, and depends upon a number of factors. A systematic study of this point was performed in the Cu-Zn, Cu-Al, and Ag-Cd systems, using quenching and heating techniques. In each system a series of alloys, increasing by small intervals (0.1 at. pct) of solute content, was examined. Particular care was taken in the control of composition and homogeneity of these alloys. The results show that the highest solute content for which the massively-formed phase can be identified metallographically exceeds the equilibriuma-phase boundary value by about 0.45 and 1.2 at. pct in the Cu-Zn and Cu-Al systems, respectively, and by several atomic percent in the Ag-Cd system. In the latter case, extension of solid solubility into the two-phase region occurs both from the fcca and the hcp ζ equilibrium phase fields. It is suggested that these findings may be interpreted in terms of local nonequilibrium conditions at the massive transformation interface. Formerly Fellow, Metal Physics Laboratory, Mellon Institute of Science, Carnegie-Mellon Univ.     

Selective oxidation of copper from liquid copper-silver alloys

In this work, the oxygen refining of liquid copper-silver alloys with a borosilicate slag was studied. First, a comprehensive thermodynamic analysis was performed using the data available in the literature. The results indicate that since silver oxide is relatively unstable in silicate-based slags, then it should be thermodynamically feasible to oxidize copper from copper-silver alloys with a very low silver loss to the silicate slag. In actual practice, although relatively low copper levels can be achieved in the metal phase, the silver losses to the slag are excessive. Therefore, in the present work, both kinetic and equilibrium experiments were performed on a molten copper-silver alloy containing 12.68 mass pct silver in order to elucidate the mechanism of silver loss to the slag. The kinetic experimental results indicated that copper levels of less than 2 mass pct could be achieved with silver recoveries of about 95 pct after relatively short refining times of 15 minutes. In the equilibrium experiments, the copper contents of the metal were less than 1 mass pct, and these values were in good agreement with those which were calculated from the data of previous researchers. In order to explain the relatively high silver losses to the slag, a model was developed which is based on the transport of silver from the metal phase to the slag phase both in metallic form and as silver oxide in the copper oxide oxidation product. The copper and silver oxides and the metallic copper-silver alloy are all transported into the slag by the oxidizing gas bubbles. It is proposed that once in the slag, the silver oxide is unstable and decomposes into metallic silver which is not easily recovered in the metal phase. Also, the transfer of the copper-silver alloy into the slag, by the gas bubbles, promotes the slag-metal exchange reaction, which again results in the generation of silver particles in the slag.     

铅试金重量法测定铜精矿中金和银

采用铅试金重量法测定铜精矿中的金和银时,因铜精矿中的铜含量较高,在高温熔融时,部分铜会与金和银一起保留在铅扣中,造成灰吹时铜会形成氧化铜渣从而使铅扣产生冻结现象进而影响测定。通过优化实验条件消除了试样中铜对测定的影响,最终实现了铅试金重量法对铜精矿中金和银的测定。探讨了铅试金时铅扣中铜量对灰吹效果的影响,结果表明,当铅扣中铜质量小于1g时,铜对金和银的测定结果无影响。对铅试金重量法测定铜精矿中金和银的条件进行了优化,结果表明,通过选择试样量为15g,配料中氧化铅量为135g、硅酸度为0.5,可有效的将铅扣中的铜量控制在1g以下,据此消除了试样中铜对测定的影响。考察了灰吹温度对金和银测定结果的影响,确定灰吹温度为860℃。方法应用于铜精矿实际样品分析,分析结果与国家标准方法 GB/T 3884.1—2012吻合。按实验方法分别对2个铜精矿样品平行测定7次,金测定结果的相对标准偏差(RSD)小于5%,银测定结果的相对标准偏差小于2%。     

铅阳极泥中银的分析-火法试金法

火法试金分析是现今最主要也是最经典分析铅阳极泥中金、银的方法,其中配料是关键.本文针对某公司阳极泥中Ag、Cu、Bi高含量的特点,运用观察法确立铅阳极泥的配料方法.试样与适量的溶剂高温熔融,以铅捕集试样中的金、银形成铅扣.试样中的其他杂质与溶剂生成易熔性的熔渣.通过灰吹使金银与铅分离.得到金、银合粒.利用金不溶于硝酸的性质使金、银分离.用称量法测定银含量.     

Thermochemistry of binary liquid gold alloys: The systems Au-Ni,Au-Co,Au-Fe,and Au-Mn

In this paper we report enthalpy of mixing data for the liquid alloys of gold with manganese, iron, cobalt, and nickel obtained by a Calvet-type calorimeter at 1378 K. The enthalpies of mixing are compared with Gibbs energies calculated from earlier emf and vapor pressure studies to yield information on the excess entropies of mixing. The limiting enthalpies of solution of the liquid transition metals in liquid gold are compared with values predicted from the semi-empirical model of Miedemaet al. and with earlier data for the same transition metals in liquid copper. The calculated values of the excess entropy of solution in liquid gold are compared with the corresponding values in liquid copper near 1400 K. For Ni, Co, and Fe as solutes we observepositive shifts of 5 to 9 J K⁻¹ mol⁻¹ which are attributed to vibrational entropy terms. For Mn there is a strongnegative shift of about 35 J K⁻¹ mol⁻¹. This shift probably is due to “complex” or “associate” formation between gold and manganese atoms.     

Hardening mechanisms and deformation stages in nanograined polycrystals

Strain hardening of nanograined polycrystals is studied using copper-based alloys as an example. The stages of strain hardening are compared for these alloys and for pure metals (copper, gold) having a similar grain size in the range 40–200 nm. The stress σ-strain ɛ dependence demonstrates that the strain hardening of these polycrystalline nanograined materials proceeds, as a rule, in three stages with different hardening mechanisms.     

湿法从氰化金泥中提取金、银、铜、铅工艺试验研究

提出了一个湿法从氰化金泥中提取金、银、铜、铅的新工艺。该工艺采用WC混合除杂剂,将氰化金泥中的Cu、Pb、Zn、Ag除去,使产品金的含量达到95％以上,然后利用电解精炼制备出99.99％的高纯金,银的品位可达99％以上,且可以回收Cu、Pb。其适于在中小黄金矿山推广应用。     

Measurement of vapor pressure of indium over α ag-ln using atomic absorption

The vapor pressure of indium over seven binary alloys of theα Ag-ln system was measured by atomic absorption. Thermodynamic activity, relative partial molal enthalpy, and partial entropy of indium were calculated from the vapor pressures and their temperature coefficients. The results were used to evaluate an equation derived previously from the rigid band model, giving the composition dependence of the activity coefficient of solutes in terminal solutions to which the Hume-Rothery e/a correlations apply. This treatment ascribes the nonideal behavior of alloy components to electronic factors. The observed behavior is consistent with the linear dependence of In γ_solute on atom fraction predicted by the model; the observed dependence ofd In γ_solute/dX_solute on solute valence also substantiates the model. The results are believed to be the first measurement of the activity of a trivalent solute in solid alloys of copper, silver or gold of the type treated by thee/a correlations. Atomic absorption was found to be suitable for the measurement of vapor pressure of indium, although the reliability of the temperature coefficients was not high because of the restricted temperature range covered.     

Thermochemistry of binary liquid gold alloys: The systems (Au + Cr), (Au + V), (Au + Ti), and (Au + Sc) at 1379 K

This paper reports enthalpy of mixing information for the liquid alloys of gold with scandium, titanium, vanadium, and chromium at 1379 K. The results are compared with corresponding information for the alloys of gold with manganese, iron, cobalt, and nickel, with data for the liquid alloys of the first row transition metals with copper, and with the predictions provided by the semi-empirical theory of Miedemaet al. For Sc, Ti, and V the experimental values are 75 to 100 kJ mol⁻¹ less exothermic than predicted by Miedema. A comparison of the emf data of Eremenkoet al. for the solid solutions of V and Cr in gold allows us to make estimates of the excess entropies of solution of these two metals in liquid gold. The values are positive, but numerically smaller than for the same metals in copper. The possible significance of this difference is discussed.     

氨水提高金精矿氰化金银浸出率的研究与应用实践

采用边磨边浸、富氧氰化工艺处理金精矿,在原生产工艺条件不变情况下,在一段磨矿加入适量的氨水,可以强化银金矿浸出,提高金、银的浸出率,抑制铜浸出和提高氰化钠有效利用率。与不加氨水相比,金氰化浸出率提高了0.47%,银浸出率提高了5.33%,铜浸出率降低了6.50%。     

The mineralogical characterization of tellurium in copper anodes

A mineralogical study of a «normal» commercial copper anode and six tellurium-rich copper anodes from the CCR Refinery of the Noranda Copper Smelting and Refining Company was carried out to identify the tellurium carriers and their relative abundances. In all the anodes, the major tellurium carrier is the Cu₂Se-Cu₂Te phase which occurs as a constituent of complex inclusions at the copper grain boundaries. In tellurium-rich anodes, the molar tellurium content of the Cu₂Se-Cu₂Te phase can exceed that of selenium. Although >85 pct of the tellurium occurs as the Cu₂Se-Cu₂Te phase, minor amounts are present in Cu-Pb-As-Bi-Sb oxide, Cu-Bi-As oxide, and Cu-Te-As oxide phases which form part of the grain-boundary inclusions. About 1 pct of the tellurium content of silver-rich anodes occurs in various silver alloys, but gold tellurides were never detected. Surprising is the fact that 2 to 8 pct of the total tellurium content of the anodes occurs in solid solution in the copper-metal matrix, and presumably, this form of tellurium dissolves at the anode interface during electrorefining.     

Distribution of Gold and Silver between Copper and Matte

The distribution coefficients of silver and gold between copper and matte phases have been measured at 1400 and 1500 K. For 0.07 to 0.13 wt pct silver and 0.0022 to 0.0042 wt pct gold in ironfree matte, the distribution coefficients of silver and gold are independent of concentration. For iron-bearing matte, the distribution coefficients of silver and gold are correlated with iron content of the matte. From the measured values of the distribution coefficients of silver and gold, the activity coefficients of AgS_0.5 and Au in copper-saturated matte have been calculated. The following correlations express these results: log γ°_AgS0.5(1) = -425/T - 0.074 + 0.09N_FeS, log γ°_Au(1) =-7620/T + 7.25 forT = 1400 to 1500 K and N_FeS, mole fraction of FeS = 0 to 0.28. The present values of the activity coefficients of AgS_0.5 must be used exclusively in conjunction with the following Gibbs free energy of formation: 2Ag(l) + 1/2S₂(g) = Ag₂S(l), ΔG° = -23960 + 10.295T (cal/mol). M. Nagamori, formerly Associate Professor of Metallurgy at The University of Utah.     

火试金法测定非浮选铜精矿中金银的条件分析

目前非浮选铜精矿中含杂质种类繁多且含量高,严重干扰金银正常测定,火试金法测定铜精矿中金和银量国家标准方法不能完全适用。文中对火试金方法快速准确分析非浮选铜精矿中金和银量的各种条件进行了分析。     

分金(银)渣氰化工艺的改进

根据对分金（银）渣中金、银物相组成的分析结果，对分金（银）渣氰化工艺进行了相应的改进，消除了铅对金氰化浸出的不利影响，并延长了银的浸出时间，从而显提高了金、银的浸出率。     

Surface composition of ternary cu-ag-au alloys: part i. experimental results

The enthalpies and entropies of segregation for silver and gold, along with equilibrium surface composition measurements on three Cu-Ag-Au ternary specimens, are reported and discussed. The experimentally studied compositions were Cu-0.3 at. pct Ag-2.1 at. pct Au, Cu-0.55 at. pct Ag-6.5 at. pct Au, and Cu-1.09 at. pct Ag-6.9 at. pct Au. The experimental enthalpies of segregation, entropies of segregation, and surface compositions are compared with those of binary alloys having nearly identical bulk solute contents in order to isolate ternary effects on surface segregation. The results indicate that the equilibrium surface composition of the ternary alloys is dominated by site competition with respect to the more weakly segregating species (gold). The surface composition of the more strongly surface-active species (silver) is largely unaffected by ternary bulk gold additions of up to 7 at. pct.     

Diffusion paths and structures in multiphase Cu−Ni−Zn couples at 775°C

Multiphase diffusion was investigated in the Cu−Ni−Zn system at 775°C for the development of diffusion structures involving two interfaces. Selected series of diffusion couples characterized by a common γ (cubic) terminal alloy joined to a set of α (fcc) alloys developed an intermediate β (bcc) phase with two interfaces, α/β and β/γ. The α/β interface showed transitions from planar to nonplanar and back to planar morphology, as the copper concentration of the α terminal alloy was decreased from 100 to about 30 at. pct. Planar β/γ interfaces were observed for all but two of the couples. The compositions on either side of planar α/β interfaces were consistent with those based on equilibrium tielines, while the compositions at nonplanar α/β interfaces differed from those of equilibrium. Selected series of couples assembled with γ and β alloys were also investigated for the development of interface instability at the β/γ interface. The diffusion paths of γ/β couples were consistent with those of γ/α couples.     

Thermochemistry of alloys of transition metals: Part III. Copper-Silver, -Titanium,Zirconium, and -Hafnium at 1373 K

The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: ΔH_mix = ϰ_Agϰ_Cu(17.66 − 5.46 ϰ_Ag) kJ mol⁻¹. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol⁻¹ for Ti, -52.5 kJ mol⁻¹ for Zr, and -46.3 kJ mol⁻¹ for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.     

火试金法测定黑铜中金和银量

建立了一种新的分析方法,试样不进行基体分离,按铜的质量分数进行配料,高温熔融,融态的金属铅捕集试料中的贵金属形成铅扣,试样中的其他物质与熔剂生成易熔性熔渣。将铅扣灰吹,得金银合粒,清除合粒表面黏附杂质,经硝酸分金,用滴定法测定银量,重量法测定金量。