硫代硫酸盐法浸出废旧IC芯片中金的试验研究

介绍了当前电子废弃物中常用的浸金方法及其优缺点, 分析了电子废弃物中硫代硫酸盐法浸金的研究现状。针对这一研究现状, 本文采用碱性Na₂S₂O₃溶液中添加Cu²⁺的方法, 对废旧IC(integrated circuit)芯片中金的浸出进行了试验研究。通过对IC样品进行机械预处理、粒度分析、解离度分析、化学预处理和浸金试验, 探讨了Na₂S₂O₃浓度、Cu²⁺浓度、NH₃浓度、浸出温度、浸出时间和反应液固比6个因素对金浸出率的影响。试验得出最佳浸金条件为:Na₂S₂O₃浓度0.3mol/L, Cu²⁺浓度0.03mol/L, NH₃浓度0.5mol/L, 添加3.5g/L的Na₂SO₃作为稳定剂, 浸取温度50℃, 浸取时间2.5h, 液固比10:1, 在最佳浸出条件下, 金的最高浸出率为92.25%。与传统方法相比, 该方法具有浸出速度快、浸出液无毒、操作简单等优点, 是一种具有开发潜力的电子废弃物浸金方法。     

An electrochemical study of the dissolution of gold in thiosulfate solutions Part I: Alkaline solutions

The anodic dissolution of gold in alkaline thiosulfate solutions has been studied by using a rotating gold disc. Experimental results have shown that the gold dissolves at measurable rates in thiosulfate solutions at potentials above 0.2 V. It has been confirmed that dissolution occurs in parallel with oxidation of thiosulfate with a dissolution current efficiency that varies with time and with the experimental conditions and which is generally in the range of 0.3 to 0.6. Although oxygen could be used as an oxidant for gold in the thiosulfate system, the rate of the cathodic reduction of oxygen in the relevant potential region is too slow for practical purposes. It was found that in the potential region investigated, thiosulfate ions undergo oxidative decomposition leaving a sulfur-like film on the surface of gold, which inhibits the rate of dissolution of gold and results in a low anodic current efficiency for the dissolution of gold. The factors (temperature, pH, thiosulfate concentration and ammonia) have been found to have positive effects on the kinetics of gold dissolution. The rates of gold dissolution in oxygenated alkaline thiosulfate solutions have been estimated to be much lower than in the copper–ammonia–thiosulfate and cyanide systems.     

An electrochemical study of the dissolution of gold in thiosulfate solutions. Part II. Effect of Copper

Thiosulfate has been considered as one of the most promising of the non-toxic alternatives to cyanide for the leaching of gold and much work has been carried out with the aim of understanding and improving the ammoniacal thiosulfate leaching process. In particular the behaviour of gold in thiosulfate solutions containing copper in the absence of ammonia has received little attention. It has been shown in this study involving electrochemical and leaching tests that copper ions catalyze not only the oxidation of thiosulfate but also the dissolution of gold in alkaline thiosulfate solutions. Electrochemical studies have shown that copper has a positive effect on the anodic dissolution of gold with increasing concentrations of copper resulting in higher dissolution rates of gold at a potential of 0.3V. Studies on the dissolution of gold powder in alkaline oxygenated thiosulfate solutions containing low concentrations of copper have shown that the role of copper in enhancing the dissolution rate of gold is possibly associated with the formation of a copper–thiosulfate–oxygen intermediate which is more reactive in terms of cathodic reduction than dissolved oxygen. The electrochemical experiments have been complemented by a leaching study which has shown that milling of gold powder in the presence of copper (added as ions, metal, or oxide) assists with the dissolution of gold in thiosulfate solutions.     

Sensitivity variation of the electrochemical quartz crystal microbalance in response to energy trapping

The spatial sensitivity of the electrochemical quartz crystal microbalance (EQCM) to deposited mass is known to vary, from a maximum at the electrode centre to a low value at its edge. For small mass loadings, the effects of such spatially non-uniform deposition can be described by simple convolution of the added mass and the spatial sensitivity function; the response is linear with added mass. However, when the added mass is large, the phenomenon of “energy trapping” is significant; the EQCM sensitivity is predicted to be non-linear with locally added mass. These deviations have been found experimentally (via local Cu deposition) to be significant. A model based on the Rayleigh principle of energy balance and energy trapping phenomena is able to describe the observed deviations. Heavy deposits change the shape of the resonator oscillations: their amplitude decreases exponentially from the edge of the deposit with a decay length that depends on the deposit mass. This effect allows one to vary the differential sensitivity of the EQCM in a desirable way while retaining conductivity of the complete electrode surface.     

基于粒子群算法的金矿湿法冶金浸出率优化

各浸出率的合理分配对组织金矿湿法冶金浸出过程生产具有重要作用,当前各浸出率通常由精炼厂氰化车间工程师凭人工经验给出,导致对浸出过程生产的指导具有很大的模糊性与随意性,不能保证调整后的总浸出率最大。为优化确定金矿湿法冶金各浸出率,建立以总浸出率最大为目标的优化模型,并将二阶振荡粒子群算法用于模型的求解。最后通过实验研究验证了模型和算法的有效性。     

Electrochemistry of methanofullerene films: Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance studies

Electrochemical properties of eight methanofullerene films, prepared on electrodes by casting, were examined by means of cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) technique in acetonitrile solution. Compared with C₆₀ film, the film stability with respect to dissolution is associated with the length of the alkyl chains introduced into C₆₀ cage and is strongly dependent on the nature of the cation of the supporting electrolyte. TBA⁺, Li⁺, K⁺, and Na⁺ were selected to observe the effect of countercations on the electrochemical behavior of methanofullerene films. In TBAPF₆ solution, when short chains, such as formic ether or butyl butyrate groups, were introduced into C₆₀ cage, the film stability was less than that of C₆₀. When the length of the alkyl chain was extended to butyl 12 alkanoate group, the film would not dissolve until the third reduction process because the long alkyl chain could inflect and encase the cations into the film. In KPF₆ or NaClO₄ solution, however, the solubility of the salt formed by K⁺ or Na⁺ with methanofullerene anion was higher than that formed by TBA⁺ with methanofullerene anion. Li⁺ (alkali metal) affected the behavior of the films in different ways. The possible electron‐transfer mechanisms of methanofullerene films in various supporting electrolyte solutions were presented. Furthermore, the film images observed by atomic force microscopy indicated that TBA⁺ and Li⁺ affected the behavior of the methanofullerene films in different ways. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3634–3640, 2006     

New electrocatalytic materials based on mixed metal oxides: electrochemical quartz crystal microbalance characterization

An electrochemical Quartz Crystal Microbalance (EQCM) was used to characterize a mixed metal oxide electrocatalyst, Ir_0.15Sn_0.85O₂, for the Oxygen Evolution Reaction (OER) in acidic medium in the potential range of the pseudo-capacitance reaction, from 0.4 to 1.2 V versus Reversible Hydrogen Electrode (RHE). The EQCM gold tip was characterized in H₂SO₄ 0.05 M and HClO₄ 0.1 M. Subsequently, Ir_0.15Sn_0.85O₂ powder, synthesized by a sol–gel route, was supported on the tip gold surface for investigations in the same media. The simultaneous measurements of mass variation and current density as functions of potential led to the identification of the chemical species involved in the mass transfer between the oxide and the acidic solution during the pseudo-capacitance reaction.     

Ion exchange properties of polypyrrole studied by electrochemical quartz crystal microbalance (EQCM)

The electrochemical polymerization of pyrrole in aqueous solution was studied as a function of a variety of parameters, such as magnitude of current density and monomer concentration. The possibility of quantitative replacement of counterions by solution anions was studied in detail using the electrochemical quartz crystal microbalance (EQCM) technique. It was found that the polymer structure can be manipulated, even after synthesis. The manipulation was revealed to be dependent on various factors, including the nature of the counterion and of the electrolyte concentration. On the basis of these observations, a two-layer structure is suggested for polypyrrole-based polymers. © 1999 Society of Chemical Industry     

Deposition of selenium thin layers on gold surfaces from sulphuric acid media: Studies using electrochemical quartz crystal microbalance, cyclic voltammetry and AFM

In this paper we report here new considerations about the relationship between the mass and charge variations (m/z relationship) in underpotential deposition (UPD), bulk deposition and also in the H₂Se formation reaction. Nanogravimetric experiments were able to show the adsorption of H₂SeO₃ on the AuO surface prior to the voltammetric sweep and that, after the AuO reduction, 0.40 monolayer of H₂SeO₃ remains adsorbed on the newly reduced Au surface, which was enough to gives rise to the UPD layer. The UPD results indicate that the maximum coverage with Se_ads on polycrystalline gold surface corresponds to approximately 0.40 monolayer, in good agreement with charge density results. The cyclic voltammetry experiments demonstrated that the amount of bulk Se obtained during the potential scan to approximately 2 Se monolayers, which was further confirmed by electrochemical quartz crystal microbalance (EQCM) measurements that pointed out a mass variation corresponding of 3 monolayers of Se. In addition, the Se thin films were obtained by chronoamperometric experiments, where the Au electrode was polarized at +0.10 V during different times in 1.0 M H₂SO₄ + 1.0 mM SeO₂. The topologic aspects of the electrodeposits were observed in Atomic Force Microscope (AFM) measurements. Finally, in highly negative potential polarizations, the H₂Se formation was analyzed by voltammetric and nanogravimetric measurements. These finding brings a new light on the selenium electrodeposition and point up to a proposed electrochemical model for molecule controlled surface engineering.     

Electrodeposition of ternary CuAgSe thin films: Use of the electrochemical quartz crystal microbalance approach for real-time phase quantification

A detailed electrochemical study of the ternary Cu + Ag + Se system on Pt substrate using the techniques of cyclic voltammetry (CV), hydrodynamic voltammetry at Pt-rotated disc electrode (RDE), anodic stripping has identified optimum conditions for the electrodeposition of ternary CuAgSe thin semiconductor films used as active membranes in developing Cu(II)-ion-selective sensors. A combined coulometry-quartz crystal microbalance (EQCM) protocol has been developed which allows real-time phase composition analysis of the target ternary CuAgSe and admixture with either Cu₂Se or Ag₂Se binary selenides. The EQCM data have provided valuable information concerning the mechanistic details of the CuAgSe-electrodeposition. The molar ratio of Cu:Se in the electrolytic bath is shown to be of crucial importance for depositing device quality films. Different mechanisms dominate when this ratio is increased from 1:5 to 1:1, from one-step diffusion-controlled electrochemical process (Cu:Se = 1:5) to a mixed electrochemical and chemical pathway for Ag⁺ assimilation (Cu:Se = 1:1).     

Electropolymerization of chlorinated phenols on a Pt electrode in alkaline solution. Part II: An electrochemical quartz crystal microbalance study

Electropolymerization of phenol and mono-, di-, tri-, pentachlorophenols was studied using EQCM on a Pt electrode at 0.78 V (SHE) in 1 M NaOH solution containing 0.1 M of the corresponding phenol. The highest electropolymerization rate was found for ortho-substituted chlorophenols indicating a weak fouling of the electrode. Low electropolymerization rates for para-substituted chlorophenols suggest a low permeability of the polymer film, resulting in rapid electrode fouling. The EQCM data suggest that electropolymerization of chlorophenols occurs without Cl-elimination for the monomers with unsubstituted ortho and para positions. Dechlorination is most pronounced for electropolymerization of para-substituted isomers. The mechanism of electropolymerization of chlorophenols is discussed.     

In situ analysis of bismuth telluride electrodeposition using combined spectroscopic ellipsometry and electrochemical quartz crystal microbalance

Electrodeposition of bismuth telluride (Bi₂Te₃) in an acidic medium with Arabic gum by galvanostatic polarization has been investigated. Simultaneous in situ spectroscopic ellipsometry and gravimetric measurements have been performed to study the morphological evolution of the compound. A progressive covering stage was demonstrated and revealed that a 40 nm thick film has already acquired morphological and optical behavior similar to that of thicker films. The optical thickness and electrochemical quartz crystal microbalance (EQCM) mass are coherent with a density of 7.06. Combined gravimetric and coulometric data confirm the formation of Bi₂Te₃ by determining the ratio m/z.     

Electrochemical and spontaneous deposition of ruthenium at platinum electrodes for methanol oxidation: an electrochemical quartz crystal microbalance study

PtRu electrodes with Ru surface concentration ranging from 20 to 50% were prepared by electrolysis of Ru(NO)(NO₃)₃ at a constant potential and/or by spontaneous Ru deposition performed at open circuit potential from a RuCl₃ solution. The amount of either spontaneously or electrochemically deposited ruthenium on the platinum electrode was determined by means of an electrochemical quartz crystal microbalance (EQCM). The effect of the Ru surface concentration on the rate of methanol electrooxidation was also investigated and correlated to the EQCM measurements.     

Investigation of cobalt deposition using the electrochemical quartz crystal microbalance

Electrodeposition of cobalt from sulfate solutions at different pH values was investigated using the EQCM technique coupled with cyclic voltammetry. The results show that cobalt hydroxide is formed simultaneously with cobalt deposition during the early stages of reduction due to the pH variation near the electrode surface caused by the parallel hydrogen evolution reaction (HER). This result was confirmed using M/z values calculated using the Sauerbrey equation and Faraday's law, which showed the presence of cobalt hydroxide in the electrodeposits. A flux model was developed and it assumes a direct reduction of cobalt, simultaneous HER and the formation of cobalt hydroxide during the early stages of deposition at pH 4.10. When the solution pH is decreased to 3.33 only the direct cobalt reduction is observed without any hydroxylated species formation.     

Multi-stage economic model predictive control for a gold cyanidation leaching process under uncertainty

In order to dynamically operate the gold cyanidation leaching process (GCLP) under uncertainty, a multi-stage economic model predictive control (EMPC) is proposed for GCLP for the transient and steady-state economic optimization. The proposed multi-stage EMPC is composed of two steps. In the first step, the unmeasurable uncertain parameters are estimated by using Tikhonov regularization based method, so as to avoid amplification and propagation of the noise measurements into the estimation. Based on the estimated results, the scenario tree for multi-stage EMPC is generated from the historical data using a data-driven approach, and the control inputs are obtained from solving the resulting large nonlinear programming problem (NLP) at each sampling point. The resulting uncertainty model and the probability of each scenario are more consistent with the actual industrial GCLP, and the solutions are less conservative. The efficiency of the proposed multi-stage EMPC is verified through a simulated industrial GCLP. Compared with other EMPC methods, including classic EMPC and multi-stage EMPC with box uncertainty region, the proposed method can reduce the economic cost while accounting for the constraints at the same time.     

Electrochemical quartz crystal microbalance studies of polymerization and redox process of poly(1,8-diaminocarbazole) in protic and aprotic solutions

Electropolymerization and doping/undoping process of poly(1,8-diaminocarbazole) (PDACz) were investigated by cyclic voltammetry combined with electrochemical quartz microbalance (EQCM), in aqueous solution of 0.1 M HClO₄ and in 0.1 M LiClO₄ in acetonitrile. The results demonstrated that protonation of the polymer in HClO₄ strongly influences the gravimetric response obtained during polymerization as well as the mechanism of redox process of the polymer in the monomer-free solution. The data are discussed in terms of the presence of protons and ClO₄⁻ counter ions in the reduced (neutral) polymer matrix. In aprotic acetonitrile containing LiClO₄ as the supporting electrolyte, the polymer doping/undoping occurs according to the simple mechanism with exchange of anions. The gravimetric results obtained in acidic aqueous solution allowed for some revision of the scheme of the redox process proposed by the authors in the previous paper.     

Arsenic species interactions with a porous carbon electrode as determined with an electrochemical quartz crystal microbalance

The interactions of arsenic species with platinum and porous carbon electrodes were investigated with an electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry in alkaline solutions. It is shown that the redox reactions in arsenic-containing solutions, due to arsenic reduction/deposition, oxidation/desorption, and electrocatalyzed oxidation by Pt can be readily distinguished with the EQCM. This approach was used to show that the arsenic redox reactions on the carbon electrode are mechanistically similar to that on the bare Pt electrode. This could not be concluded with just classical cyclic voltammetry alone due to the obfuscation of the faradaic features by the large capacitative effects of the carbon double layer.For the porous carbon electrode, a continual mass loss was always observed during potential cycling, with or without arsenic in the solution. This was attributed to electrogasification of the carbon. The apparent mass loss per cycle was observed to decrease with increasing arsenic concentration due to a net mass increase in adsorbed arsenic per cycle that increased with arsenic concentration, offsetting the carbon mass loss. Additional carbon adsorption sites involved in arsenic species interactions are created during electrogasification, thereby augmenting the net uptake of arsenic per cycle.It is demonstrated that EQCM, and in particular the information given by the behavior of the time derivative of the mass vs. potential, or massogram, is very useful for distinguishing arsenic species interactions with carbon electrodes. It may also prove to be effective for investigating redox/adsorption/desorption behavior of other species in solution with carbon materials as well.     

An electrochemical quartz crystal microbalance study into the deposition of manganese dioxide

An electrochemical quartz crystal microbalance (EQCM) has been used to study the effects of electrolyte composition (MnSO₄ and H₂SO₄ concentrations) and anodic current density on the electrodeposition of manganese dioxide. The EQCM, in tandem with the electrode voltage during deposition, has been used to characterize features of the deposition mechanism such as the relative lifetime of the Mn(III) intermediate, the rate of soluble Mn(III) hydrolysis to form MnOOH, and the porosity of the resultant manganese dioxide deposit as a function of crystal nucleation. The connection between the results obtained here and commercial electrodeposition of manganese dioxide were also discussed.     

过氧化钙的工业化制备及在浸金中的应用

通过加入新型稳定剂磷酸盐,研究了常温水相中合成过氧化钙的新工艺,讨论了原料配比、温度、稳定剂加入量等因素对过氧化钙产率和纯度的影响。采用双桨叶与盘式干燥机进行两级干燥,可减少物料在湿态下的活性氧损失,过氧化钙质量分数达到了60%以上,双氧水利用率≥70%。应用此法生产的过氧化钙能显著提高金的浸出率,降低氰化物消耗,提高金的浸出速度。在相同的条件中,使用此法生产的过氧化钙可节约氰化物近30%。     

Electrodeposition of CdS from acidic aqueous thiosulfate solution—Invesitigation of the mechanism by electrochemical quartz microbalance technique

Electrochemical quartz crystal microbalance was used to study mechanism of cathodic electrodeposition of CdS from acidic aqueous solutions containing 0.01 M Cd(ClO₄)₂ and 0.1 M Na₂S₂O₃ as a source of sulfur. Experiments were performed by means of cyclic voltammetry and potentiostatic method. A comparison of gravimetric and current responses at pH 3 and 4 allowed for determination of the potential range in which side reactions of reduction of SO₃²⁻ and H⁺ ions compete most strongly with formation of CdS. The film thickness was determined by means of two methods: from AFM profiles and EQCM measurements.