Anode Slime Research Articles

Cross-section Analysis of Anode Slime Generated on Sn Anode Containing Sb and Bi for Elucidating passivation mechanism

Cross-section Analysis of Anode Slime Generated on Sn Anode Containing Sb and Bi for Elucidating passivation mechanism

Heterogenizing MnO2 nanostructure with industrial impurity ions for lead leakage-preventable anodes in zinc electrowinning

γ-MnO2 precoated lead (Pb)-based anodes have shown high initial activity in heavy-metal pollution reduction and production improvement for zinc electrowinning in laboratory. However, the accumulated impurity ions (M) in industrial MnO2-precursors restrict its industrial application. Herein, the heterostructure-induced rich oxygen-vacancies for M-MnO2 and its higher activity (Pb/Co-MnO2>Pb/Ni-MnO2>Pb/Fe-MnO2≈Pb/Cu-MnO2>Pb/MnO2) was reported. However, it reached a concentration threshold and afterwards provided the inhibited activity. Moreover, the Pb2+ diffusion-induced lead leakage is the dominant factor in the inactivation of anodes before extrinsic mechanical effects manifest, which follows: Pb/Fe-MnO2>Pb/Cu-MnO2>Pb/MnO2≈Pb/Ni-MnO2≈Pb/Co-MnO2. Instead, due to the enhanced activity and suppressed lead leakage, Pb/Co-MnO2 avoided about 12.4% and 72.3% lead-containing anode slime in comparison with Pb/MnO2 and Pb/Fe-MnO2 and minimized the contamination of zinc products by lead. Such complex effects also provide a cost-effective and environmental-friendly strategy for lead-leakage preventable Pb-based anodes in zinc electrowinning as it can reduce the exogenous dopants usage while still delivering competitive electrooxidation activity-stability.

Liquid-liquid extraction of selenium (IV) ions from hydrochloric acid solution using Aliquat 336 dissolved in kerosene.

Solvent extraction of selenium(IV) ions from highly concentrated hydrochloric acid using 0.4mol/L Aliquat 336 dissolved in kerosene was investigated. As a modifying agent, 1-octanol (10% v/v) was added to the organic phase to avoid the third phase formation. The effect of different parameters affecting the liquid-liquid extraction of selenium(IV) such as the acid concentration, shaking time, metal ion concentration in the aqueous phase, loading capacity, diluents, and temperature, was studied. The results indicate that selenium(IV) is extracted efficiently by 0.4mol/L Aliquat 336 dissolved in kerosene. It was noticed that the extraction increased with the increase in the acid and Aliquat 336 concentrations, reaching an extraction percentage of about 92% at 8mol/L HCl and 97.1% at 1mol/L extractant. The extracted organic species is postulated to be [H2SeO2Cl2.2R4NCl]org by using the slope analysis method, and the value of Kex for selenium(IV) extraction was found to be 26.17 ± 2 M- 2. The structure of the extracted organic species was confirmed by FT-IR. The effect of diluents using various aliphatic and aromatic diluents indicated that kerosene is the most preferred diluent. This is owing to safety ground purpose, economic consideration, the lower cost, availability, and lower toxicity. Thermodynamic parameters indicate the endothermic nature for the solvent extraction of selenium(IV) for the investigated system according to the positive value obtained of the enthalpy change (ΔH). Depending on the obtained results, the method was used to recover selenium(IV) from a simulated solution synthesized in hydrochloric acid medium, which is expected in anode slime leach liquor solution.

Mechanism and kinetics of scorodite formation in arsenic-bearing solutions using Fe(OH)3 as a solid iron source

Recently, solid iron sources have been used for scorodite synthesis in arsenic-bearing wastewater from nonferrous metallurgy. Immobilising arsenic-solution as scorodite via iron hydroxide (Fe(OH)3) solid iron source is an important method for controlling arsenic pollution. The evolution behavior of scorodite during its formation in high arsenic solution have been rarely investigated. In this paper, the mechanism and kinetics of scorodite formation using Fe(OH)3 in arsenic-bearing solution were investigated. This work was divided into three parts. Firstly, the influencing parameters were investigated, revealing that the dissolution of Fe(OH)3 and scorodite generation accelerated at lower initial pH and higher reaction temperature. Increasing Fe/As ratio delayed scorodite crystallisation, which was in turn enhanced by elevating arsenic concentration. Secondly, the mechanism of scorodite formation was investigated, revealing that Fe(OH)3 underwent acidic dissolution to form a precursor. Subsequent scorodite formation had a ΔrGmθ ranging from −69.39 kJ·mol−1 to −15.64 kJ·mol−1. Residual As was absorbed and converted into Fe(OH)3@scorodite. Thirdly, the chemical kinetics were investigated, showing that activation energy (Ea) for Fe(OH)3 dissolution was 72.54 and 105.37 kJ·mol−1 at Stages I and II, respectively, whereas it was 105.97 kJ·mol−1 for residual As absorption-conversion at Stage III outweighing the Ea of As-Fe coprecipitation. The restrictive steps were Fe(OH)3 dissolution and residual arsenic absorption-conversion. This proposed method can be applied for environment-friendly treatment of 10－40 g/L of arsenic-bearing industrial effluent for scorodite formation. Overall, this research confirmed the formation of scorodite via Fe(OH)3 and can potentially provide feasible schemes for eliminating arsenic-bearing acidic waste, dust, and anode slime from nonferrous metallurgical processes.

Study on separation and purification of titanium alloys (TC4-6Al-4V) by molten salt electrolysis

With the widespread expansion of titanium applications and its significant increase in usage, the issue of recycling titanium resources after consumption has emerged. Focusing on titanium alloys with high usage, such as TC4 (Ti-6Al-4V), this article proposes a titanium separation and recovery method based on molten salt electrolysis. This method thoroughly analyzes the characteristics of elements in TC4 and electrochemical principles, ensuring that vanadium in the TC4 alloy does not undergo electrochemical dissolution when the electrolysis potential is below 0.3 V vs Pt. Subsequently, through electrochemical analysis, it was discovered that the precipitation of aluminum ions is influenced by concentration. Therefore, by controlling the concentration of aluminum in the eutectic molten salt, such as increasing the electrolyte concentration and shortening the electrolysis time, the precipitation of aluminum can be effectively avoided. Under the experimental conditions mentioned above, vanadium elements deposit at the bottom of the crucible in the form of anode slime, while aluminum dissolves and remains in the electrolyte. Meanwhile, titanium ions in the cathode region undergo electron reduction and deposit in the cathode area in the form of titanium, thus achieving precise separation of alloy elements. Experimental verification shows that the purity of the obtained titanium reaches 99.17 atomic percent. Therefore, this molten salt electrolysis method, which combines the physical properties of alloy elements with electrochemical principles, not only provides a new perspective for the separation and recovery of titanium and other critical metals, but also offers new research directions for the recovery technology of other alloy elements.

Effect of APMImBr ionic liquid on the migration of silver in copper electrorefining

As the grade of copper concentrate decreases and its composition becomes increasingly complex, the silver content in the anode plate casting after fire refining increases. This leads to a high silver content in the copper cathode during electrorefining and a substantial loss of precious metals. This study investigated the effect of 1-aminopropyl-3-methylimidazolium bromide (APMImBr) ionic liquid on the migration of silver during high-silver anode plate electrorefining. The results show that APMImBr is adsorbed on the anode surface by reacting with Ag+ released from the anode to form AgBr precipitates, thereby preventing Ag+ ions from entering the electrolyte. Simultaneously, agglomerates of fine Ag–Se compounds and AgBr particles form, resulting in anode slime particles that are sufficiently large to settle quickly to the bottom of the cell, thus inhibiting fine silver-containing particles from adhering to the cathode. Furthermore, APMImBr adsorbs onto the cathode surface, forming CuBr intermediates and inhibiting Cu2+ electrodeposition. This facilitates the refinement of the surface grains and flattens the copper cathode surface. The Ag content of the cathode decreased continuously as the concentration of APMImBr increased. The Ag content of the cathode decreased by 41.67% from 6.0 ppm (no additives) to 3.5 ppm upon the addition of the optimal concentration of 300 mg/L of APMImBr.

Recovery of highly pure copper from waste cupronickel by electrolysis separation with low energy consumption: The role of deep eutectic solvent

The recovery of waste cupronickel not only can solve related environmental concerns but also facilitates the separation of valuable metals and reduces extra exploitation of natural ore resources. Here, high-efficiency and low-energy-consumption separation of copper (Cu) from waste 90/10 cupronickel (Ni ∼ 10 %) by electrolysis was clarified in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES). Electrochemistry showed that Cu can be dissolved feasibly as monovalent Cu(I), forming species such as [CuCl2]− and [CuCl3]2−, while Ni was restrained and entered into anode slime at controlled potential. Compared with Ni(II), Cu(I) can be easily reduced to Cu0, and elevating temperature can accelerate ions transportation and reduction rates. Potentiostatic electrolysis at bath voltage of 0.4 V found that highly pure Cu (99.9918 wt%) was obtained and the current efficiency reached up to 99.71 % with low specific energy consumption (169.18 kW·h·t−1). A separation mechanism model of Cu from waste 90/10 cupronickel was proposed and the role of the DES was revealed, which possessed strong coordination ability and fast transport capacity for Cu(I), as well as significant potential difference between Cu and Ni. This strategy represents a promising and economical technique for recycling waste Cu-based alloy and extracting highly pure metals.

Impact of 5-Amino-1H Tetrazole on Reducing Silver in Copper Cathodes during Electrorefining with High Silver Content Anode Plates

As the grade of the copper concentrate decreases and its composition becomes increasingly complex, the silver content in anode plates cast after fire refining increases, leading to a higher silver content in the copper cathode during electrorefining and a substantial loss of precious metals. This study investigates the impact of 5-amino-1H tetrazole (5-AT) on reducing silver in copper cathodes during electrorefining with high silver content anode plates. 5-AT forms an “adsorption layer” on the anode surface, reacting with Ag+ released by the anode to form a precipitate and prevent Ag+ from entering the electrolyte. This process agglomerates fine Ag-Se compounds and AgCl particles, creating larger anode slime particles that settle quickly, thus inhibiting fine silver-containing particles from adhering to the cathode. Furthermore, 5-AT adsorbs on the cathode, binding with Cu+ and promoting the Cu2+ electrodeposition process while inhibiting Ag+ electrodeposition. This facilitates uniform copper cathode grain growth and reduces inclusions in the copper cathode. The grain size of the copper cathode initially decreases and then increases as the concentration of 5-AT increases. At an optimal 5-AT concentration of 15 mg/L, the Ag content in the copper cathode decreased from 6.9 ppm to 4.7 ppm, indicating the potential efficacy of 5-AT in improving the quality of electrorefined copper.

One step to direct extracted gold and silver from industrial Cu-Ag-Sb-Au alloy by a convenient bimetallic electrolytic separation process

Cu-Ag-Sb-Au alloy produced from lead anode slime reduction smelting through twice vacuum distillation is a high value-added precious metal resource. Currently, using pyrometallurgical process, the antimony and copper elements can be removed respectively by multistage oxidation refining, and then the precious metals are recycled by electrolytic refining. This process has a number of shortcomings such as high energy consumption, high pollution and low direct yield. In this study, a highly efficient new process for extracting precious metals from Cu-Ag-Sb-Au alloy by one-step bimetallic potential-controlled electrolysis is proposed. The electrolytic process of Cu-Ag-Sb alloy is studied by linear scanning voltammetry and electrochemical impedance spectroscopy, and the experimental verification is carried out under the guidance of Cu-Ag-Sb alloy experiments. The results show that gold and silver are enriched in the electrolytic anode slime, while copper and antimony are reduced and deposited on the cathode, which realizes the efficient separation of gold and silver from copper and antimony. The direct yield of precious metals and the anode treatment rate are as high as 99.97 % and 16.02 kg/day·A·m2, respectively, but the energy consumption is 453.90 kW·h/t only. This process strongly supports the treatment of Cu-Ag-Sb-Au alloy with low cost and high efficiency. At the same time, in combination with the vacuum distillation process, the oxidation refining is successfully removed from the lead and copper smelting system, thereby achieving efficient recovery and effective reuse of the precious metals.

Separation and Enrichment of Au and Ag from Lead Anode Slime by a Selective Oxidation–Vacuum Volatilization–Carbon Reduction Process

Huge amounts of Au and Ag are recovered from the hazardous waste lead anode slime. The conventional extraction of precious metals from lead anode slime is based on pyrometallurgical and electrolytic processes, which are seriously conditioned by the separation of harmful elements As and Sb. In this paper, an innovative and efficient oxidation–vacuum volatilization–carbon reduction process was proposed to separate and enrich Ag and Au from lead anode slime. Before vacuum volatilization, selective oxidation of the lead anode slime was performed. Then, vacuum volatilization and vacuum carbon reduction were used to obtain a gold- and silver-rich alloy. The feasibility of the process was verified experimentally and theoretically. The effects of temperature and time on vacuum volatilization separation and reduction enrichment were investigated. The experimental results showed that the Ag content in the resulting gold- and silver-rich alloy was as high as 67.58%, Au was as high as 4287 g/t, and the efficiencies for the recovery of Ag and Au from the lead anode slime were 99.25% and 99.91%, respectively. The gold- and silver-rich alloy can be directly used to produce Ag ingots. Moreover, no gas or wastewater was discharged in this process, so Ag and Au were recovered in a sustainable and cleaner manner.

Separation behavior of metal and oxide: Vacuum gasification for metal recovery advanced from lead anode slime

Lead anode slime (LAS), a significant secondary resource, was utilized to separate andrecycle of rare and precious metals such as Te, Au, and Ag, along with essential metals Cu, Pb, and Bi. The conventional pyrometallurgical and hydrometallurgical processes generated hazardous waste, including high levels of As, Sb, smoke, heavy metal waste. Extraction of these key metals is both laborious and ineffective. A novel vacuum gasification technology was employed to explore the separation patterns and migration distribution principles of metal and oxide (MO) in LAS. The theoretical results of phase transition enthalpy change (ΔH), saturated vapor pressure, and molecular average free path investigated the gasification and volatilization potential of MO in LAS. Furthermore, the experimental results revealed separation behavior of MO. As and Sb were evaporated into the gaseous phase to facilitate their separation from other substances at 773 K. Pb and Bi behavior were similar to them at 823 K, As, Sb, Pb and Bi to enter the gaseous phase for the purpose of separation with Ag, Au, and Cu. By exploiting the differences of gasification specificity, it is possible to separate Ag, Au, Cu, and other elements at 1173 K, finally leading to the formation of Ag–Au–Cu alloys.

A water model study on mixing behaviour in a Kaldo furnace using acid–base neutralization decolourization method combined with RGB-based image analysis

Mixing time is usually used as an important parameter for quantifying the mixing performance of multiphase flow in a metallurgical bath. However, the topic of the mixing time of a Kaldo furnace for copper anode slime treatment has received little attention from scholars to date; this concept is important for guiding the optimization of high-efficiency smelting in the Kaldo furnace. In the present work, the mixing behaviour of gas-liquid two-phase flow in a Kaldo furnace was simulated using a scaled-down 1:4.5 water model fabricated from transparent acrylic plastic. A visualization technique and a quantitative characterization method for mixing performance in the Kaldo furnace—acid-base neutralization decolourization combined with RGB-based image analysis—were innovatively proposed. This approach can not only determine the global mixing level η¯(t) and track the frequency distribution of the local mixing performance ξk(t) of the fluid region during the mixing process but also quantify the mixing time. In addition, based on the proposed method and by using dimensional analysis, the effects of operating parameters (such as the gas flow rate Q, injection lance height h, rotation speed ω, liquid volume fraction φ, inclination angle θ, and liquid viscosity μl) on the mixing time of gas-liquid two-phase flow in the molten bath were discussed. On this basis, the empirical equation of the mixing time as a function of h, ω, φ, the modified Froude number (Fr'), μl and θ was established as the first quantitative relationship of the mixing time for the Kaldo furnace.

Recovery of Crude Silver and Valuable Metals from Tin Anode Slime

Recovery of Crude Silver and Valuable Metals from Tin Anode Slime

Activity Calculation and Vacuum Separation Theoretical Research concerning Ag–Cu, Ag–Sb and Cu–Sb Binary Alloys

The Ag–Cu–Sb system is a key component of lead anode slime and boasts an exceptionally high economic recovery value. In this work, six models, including the Molecular Interaction Volume Model (MIVM), Modified Molecular Interaction Volume Model (M-MIVM), Wilson equation, Miedema model, Regular Solution Model (RSE) and Sub-Regular Solution Model (SRSE), are used to calculate the predicted values of the activity and its deviations with experimental data for binary alloys in the Ag–Cu–Sb system for the first time. The result reveals that the overall means of the average relative deviation and average standard deviation of the M-MIVM are 0.01501 and 3.97278%, respectively, which are about two to six times smaller than those of the other five models, indicating the stability and reliability of the M-MIVM. In the meantime, the predicted data of the Cu–Ag binary alloy at 1423 K, Sb–Ag binary alloy at 1250 K and Sb–Cu binary alloy at 1375 K calculated from the M-MIVM are more reliable and pass the Herington test. Then, the separation coefficient–composition (β–x), temperature–composition (T–x–y) and pressure–composition (P–x–y) of the Cu–Ag, Sb–Ag and Sb–Cu binary alloys are plotted based on the M-MIVM and vacuum theories, showing that the Cu–Ag binary alloy is relatively difficult to separate and that high temperatures or high copper contents are detrimental to obtaining high-purity silver. Meanwhile, theoretical data of the T–x–y diagram are consistent with the available experimental data. These results can guide vacuum separation experiments and industrial production concerning Ag–Cu, Ag–Sb and Cu–Sb binary alloys.

Leaching Behavior of the Main Metals of Decopperized Anode Slime

Leaching Behavior of the Main Metals of Decopperized Anode Slime

Application of side-submerged combustion smelting(SSC) process in recovery of lead smelting by-products

The treatment of lead smelting by-products,such as anode slime and antimony-containing dust and slag is an important process, which is not only related to improvement the rate of comprehensive recovery of resources, but also plays a very important role in improving the economic benefits of plant. The existing by-product treatment technology and current situation were introduced in first. Combined with the current treatment process and characteristics of by-products, this paper focuses on the characteristics of the oxygen-enriched submerged combustion side-blown smelting technology and the application of by-products treatment. Based on the engineering practice and relevant technical and economic indicators of treating 5812t anode slime annually, compared with the conventional technology, this technology has obvious advantages in operation cost, treatment efficiency and environmental protection.

Enhancing the oxygen evolution activity and stability of Pb anode in Mn2+-containing acidic solution by embedding MnCo2O4 particles

Due to the excellent activity and stability of MnCo2O4 toward the oxygen evolution reaction (OER) in acidic solution, a Pb–MnCo2O4 composite anode for zinc electrowinning was prepared by embedding dispersed MnCo2O4 particles into a Pb matrix in a powder metallurgy process. In this work, the phase structure, chemical composition, and morphology of the oxide layers formed on Pure-Pb and Pb–MnCo2O4 were analyzed by XRD, SEM, and EDS. Galvanostatic polorization, Tafel tests, and EIS measurements were performed to investigate the anodic potential variation and OER kinetics of the Pure-Pb and Pb–MnCo2O4 composite anodes. Compared with that on the Pure-Pb anode, the oxide layer on Pb–MnCo2O4 is thinner, more compact, and more stable in a 160 g L−1 H2SO4 solution containing 4 g L−1 Mn2+. Consequently, the Pb–MnCo2O4 composite anode exhibited a much lower anode slime production (8.7 mg) during 72 h of the simulated zinc electrowinning process. Despite the smaller surface area and lower PbO2 content of the oxide layer, the Pb–MnCo2O4 composite anode presented preferable OER kinetics with a lower OER charge transfer resistance (0.729 Ω cm2) and a smaller Tafel slope (90.74 mV dec−1), which contributed to a 70 mV reduction in the anodic potential compared with that of the Pure-Pb anode.

Synergistic strategy of solute environment and phase control of Pb-based anodes to solve the activity-stability trade-off

The contradiction between the activity and stability of metal anodes exists extensively, especially in acid electrooxidation under industrial-level current density. Although the anode modification enhanced the initial activity of anodes, its long-term activity is limited by anode slime accumulation. Herein, a synergistic strategy, coupling the solute environment with the phase control of anodes, is proposed to achieve the trade-off between activity and stability of Pb-based anodes in concentrated sulfuric acid electrolysis. Non-exogenous Mn2+ motivated a series of positive behaviours of reactive-oxygen-species capture, anode reconstruction and corrosion-dependent activity alleviation. The synergistic effects, which are crystal phase-dependent, mainly benefit from the continuous self-healing ability of the specific crystal phase of MnO2 on the anodes by the coexisted Mn2+. Compared with Mn2+/α-MnO2, Mn2+/γ-MnO2 exhibited outperformed activity and stability in boosting oxygen evolution reaction (OER) and reducing hazardous pollutants, which resulted from the energy difference in the rate-determining step of OER and in the selectivity priority of Mn2+/MnO2 oxidation pathway. Interestingly, the pre-coated γ-MnO2 on the anode also presents excellent inheritance, guaranteeing the unchanged crystal phase of MnO2 and the high performance in ultra-low hazardous slime generation in subsequent Mn2+ oxidation. The sustainability of Mn2+/γ-MnO2 was proved in the operating hydrometallurgy conditions on Pb-based anodes. This strategy offers a promising approach for this common issue in electrooxidation-related areas.

Vacuum thermal decomposition behavior of Ag2Te

Silver and tellurium are crucial valuable metallic elements in anode slimes. During pyrometallurgical processing, tellurium exists in the alloy as the stable compound Ag2Te. The current process of separating tellurium from silver-tellurium compounds in crude silver by oxidizing tellurium into slag leads to undesirable loss of silver, low recovery rates of tellurium, and considerable slag. An environmentally friendly and efficient vacuum thermal decomposition process of Ag2Te was proposed, and the effects of temperature, pressure, and holding time on the decomposition of Ag2Te were investigated. The Experimental temperature was thermodynamically calculated to be in the range of 1473–1673 K and pressure in the range of 1–100 Pa. As the temperature increases, especially above 1573 K, the silver volatiles increase significantly, and silver and tellurium vapors react strongly to form stable silver-tellurium compounds. Investigating the volatilization and condensation mechanisms of silver and tellurium highlights the importance of inhibiting silver volatilization to achieve efficient separation of silver and tellurium. Volatiles containing 98.85% tellurium mainly as tellurium monomer, and a remained melt consisting of 95.56% silver primarily as silver monomer were produced at 1523 K, 50 Pa, and an 8-h holding time.

Detachment and flow behaviour of anode slimes in high nickel copper electrorefining

Most of the world’s copper is produced via copper electrorefining, where nickel is the most abundant impurity in the process. Previously it has been suggested that nickel affects the adhesion of anode slimes on the anode as well as the porosity of the slime layer that forms. This paper investigates the effects of nickel, oxygen, sulphuric acid and temperature on the detachment of anode slimes from the anode surface. The detachment of particles as a function of both anode and electrolyte composition was studied on laboratory scale using a camera connected to a Raspberry Pi, and particle detection and movement analysed using TrackPy. The results revealed four different slime detachment mechanisms: cloud formation, individual particle detachment, cluster detachment and avalanche. These were found to be dependent on the electrolyte (0, 10, 20, 30 g/dm3 Ni2+ & 100, 200 g/dm3 H2SO4), with increasing nickel concentration promoting cluster detachment and increasing sulphuric acid concentration favouring detachment of individual particles. Anode composition (0.05-0.44 wt% O and 0.07-0.64 wt% Ni) was shown to affect the flow direction of anode slimes, with increasing nickel leading to more upward-flowing slimes. Typical particle movement velocities were from -0.5 to 1.0 mm/s regardless of the electrolyte and anode composition, and regardless of the operating temperature (25 °C & 60 °C) for small particles (<0.5 mm). The results also support previous findings that increasing the nickel concentration of the electrolyte leads to a more porous anode slime layer on the anode.