Copper Electrorefining Research Articles

Impedimetric Thiourea Sensing in Copper Electrorefining Bath based on DC Magnetron Sputtered Nanosilver as Highly Uniform Transducer

Highly uniform sputtered nanostructured silver (Nano-Ag) film on the conductive carbon paper (CP) substrate (Nano-Ag/CP) was applied as a novel approach for thiourea (TU) measurement in copper electrorefining bath. Nano-Ag film was achieved by direct current (DC) magnetron sputtering system at the optimized instrumental deposition conditions. Characterization of the surface structure of Nano-Ag film by field emission-scanning electron microscopy (FE-SEM), exhibits uniform Nano-Ag film as an effective transducer for TU sensing. Step by step monitoring of Nano-Ag/CP electrode fabrication were performed using electrochemical methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Fabricated Nano-Ag/CP electrode was used for TU determination using EIS assessment. The impedimetric results show high sensitivity for TU sensing within 2.0–250ppm.

Experimental studies on impurity particle behavior in electrolyte and the associated distribution on the cathode in the process of copper electrorefining

A three factor 2-level designed set of experiments was performed to determine the effects of inlet flow rate, temperature, and current density on impurity particle behavior in electrolyte and the associated distribution on the cathode in copper electrorefining. Laser-Induced Breakdown Spectroscopy (LIBS) was used to measure the concentration of impurities on the cathode. The results of the experiments were statistically analyzed using Minitab. The inlet flow rate was identified as the most significant factor. All three factors and their two-factor interactions have a significant effect on impurity concentration on the cathode. The impurity concentrations in corner positions of cathodes had higher impurity levels than those in the center position of cathodes. The current density exerts more effect on both impurity concentrations at corner positions than at the center position. A possible explanation for the phenomena observed is proposed.

Simulation and Validation Studies of Impurity Particle Behavior in Copper Electrorefining

A model based in COMSOL Multiphysics consisting of an electrorefining cell was utilized to simulate copper electrorefining. Concentration and electrolyte density profiles were generated as electrochemical simulation results. Fluid velocity field, particle trajectories, and particle distribution maps were generated to study impurity particle behavior in electrolyte. A three factor designed set of boundary conditions was used to determine the effects of inlet flow rate, temperature, and current density on impurity particle behavior in electrolyte and the associated distribution on the cross section (slice) 100 microns away from the front surface of the cathode during copper electrorefining. The number of impurity particles on the cross section was counted for each set of boundary conditions. The model data for impurity particle distribution was compared with measured impurity particle contamination at the cathode surface, and the results show a very good correlation, which suggests the model is reasonable. The model results show the three factors have significant effects on the number of impurity particles on the cross section. The impurity particle counts at the corner positions of the slice are much higher than those at the center position of the slice. Possible explanations for the simulation results are proposed.

Electrolytic recovery of bismuth and copper as a powder from acidic sulfate effluents using an emew® cell

Effective removal of bismuth is a primary concern during copper electrorefining.

Influence of Vitamin C on Copper Electrorefining from Acidic Solution of Copper Sulfate

Influence of Vitamin C on Copper Electrorefining from Acidic Solution of Copper Sulfate

Copper deposition on stainless steel sheets in copper nitrate solution

The aim of this study was to examine factors that influence copper nitrate based electrorefining of copper and to search the best process parameters for high-purity copper deposition on AISI 316L steel blanks. Considering impurities, the most important goal was to minimize sulfur content in a copper cathode. The effect of Cu 2+ concentration, current density, temperature and pH were studied. The best parameters for the best copper purity were sorted out. The most important factors for quality copper deposition are sufficiently low Cu 2+ concentration, low current density, right zone and careful control of pH. Active nitrate ion reduction reactions catalyzed by copper ions are suggested to affect detrimentally both copper deposition current efficiency and purity. Furthermore, nitrate ion reactions seem to elevate an electrolyte pH so that the deposition appears to be dark brow copper oxide. The 6N purity for copper was not reached with this cell construction and it felled behind about 7 ppm (99.9993% Cu). Both, sulfur and silver concentration were slightly above 1 - 2 ppm. To minimize the impurities, electrolyte circulation and filtration are needed. Also, either a separate silver cementation cell or cementation membrane is needed.

CFD modelling and simulation of industrial-scale copper electrorefining process

Both electrolyte flow and cupric ion concentration fields have been numerically calculated with the computational fluid dynamics (CFD) model in an industrial-scale copper electrorefining cell. In this CFD model, both of the natural convection induced by the electrochemical reactions and the forced convection caused by the electrolyte circulation are taken into account. In order to examine how the difference in the ways of the electrolyte circulation affects the electrolyte flow pattern associated with the concentration field, three different ways of the electrolyte circulation, “bottom inlet to top outlet”, “top inlet to bottom outlet”, and “side inlet to top outlet”, have been modeled.Calculation results have revealed that both “bottom inlet to top outlet” and “top inlet to bottom outlet” circulations have characteristic flow patterns that are locally formed near the inlet. On the other hand, “side inlet to top outlet” circulation forms the inherent two vortex tubes in the space below the electrodes. It is also found that the electrolyte flow patterns in the inter-electrode spaces are formed mainly by the natural convection, and they are insensitive to kinds of the electrolyte circulation way.

Electrorefining of Copper at Inclined Electrodes

Electrorefining of Copper at Inclined Electrodes

Laboratory and Pilot Scale Tests of a New Potential-Controlled Method of Copper Industrial Electrolysis

Copper electrorefining and electrowinning industrial processes are carried out on industrial scale as current-controlled processes practically from the beginning of the commercial exploitation. However, it is the electrode potential which is a driving force of electrochemical process. The copper electrodeposition from industrial electrolytes is in fact a very complex multi-ion process. Consequently, the theoretical analysis of the experimental results should take into account that in concentrated and complex matrix electrolytes migration, convection and diffusion are mass transfer modes. However, there is only very limited number of papers where copper electroreduction from concentrated electrolytes is considered and most of the published theoretical and experimental studies are carried out in diluted electrolytes of relatively simple compositions where only diffusion of copper ions is considered in theoretical analysis. In the present paper some basic aspects of potential-controlled electrolysis of copper in concentrated and industrial electrolytes as a new method of copper electrorefining and electrowinning are presented and discussed. The pilot scale tests results of copper potential-controlled electrolysis are published for the first time. Apart from the possible industrial applications, studies of the electrochemical processes in concentrated electrolytes are very important from the basic research point of view.

異種金属接触による銅電解精製時のAg溶解抑制

異種金属接触による銅電解精製時のAg溶解抑制

Recovering Scrap Anode Copper Using Reactive Electrodialysis

Despite functioning without major operational problems—copper electro-refining does not allow complete use of copper anodes, peaking at 85% of the copper anode in weight. Consequently, the remaining 15% of scrap copper must be recirculated into the copper smelting. The use of reactive electrodyalysis is a system capable of continuously electro-refining scrap, by using a stainless steel basket and a cationic exchanging membrane in order to increase production of copper cathodes at the same percentage; it currently today returns to the copper smelter. In terms of specific energy consumption, this process would use between 3 and 4 times the value of normal electro-refining.

Efecto de la concentración de poliacrilamida sobre la calidad del depósito de cobre obtenido por refino electrolítico

The effect of the additive non ionic polyacrylamide (PAM), was studied at the laboratory level, as refining crystalline grain in the copper electrorefining. Experiments were performed 24 h of electrolysis, using an electrolyte of copper sulphate acid, with 0.5 to 10 mgl -1 polyacrylamide at 55 °C and a current density of 260 Am -2 . The effectiveness of these organic additives in copper electrorefining was determined by directly measuring the surface roughness of the copper deposit and contrasted with the results of other instrumental techniques (SEM and metallographic analysis). The results of the analysis SEM, metallographic analysis and measurement of the surface roughness of the copper deposit, show that to concentrations as low as 0.5 mgl -1 of this additive is manifested its property of tuner of grain. However, in the range of 7 to 10 mgl -1 of polyacrylamide, it reaches an optimum size of grain for the deposit of copper in the cathodes.

Copper Refining Electrolyte and Slime Processing - Emerging Techniques

Copper electro-refining (Cu-ER) is the principal method for producing >70% of high or 99.97% pure copper cathodes from 97-99% pure blister/fire refined-scrap copper anodes. While the inert and most of less soluble impurities settle as anode slime/sludge, other soluble impurities, particularly the metalloids (group VA/15 elements or Q: As, Sb and Bi) and some transition metals (Mt) co-dissolved with Cu(II). Since the soluble impurities build up in the copper refining electrolyte (CRE) which need monitoring and control to prevent contamination of the cathodes and passivation of the anodes before bleeding for spent CRE reprocessing. There is a high demand for pure electrorefined copper and electrolyte additives are added to the CRE to prevent nodulation or control the chemical and physical properties of copper cathodes. Various hydrometallurgical methods such as precipitation, adsorption, electro-dialysis, electro-winning, ion exchange and solvent extraction have been developed with some success to control the CRE impurities. So some emerging technologies for improved monitoring and control of the metalloid impurities in CRE and slime as well as development of saleable byproduct recovery (As, Sb, Bi) are briefly reviewed with particular emphasis on the precipitation for the metalloid slime resource recycling and product development.

Recovery of tellurium from high tellurium-bearing materials by alkaline pressure leaching process: Thermodynamic evaluation and experimental study

This paper focuses on the recovery of tellurium from high tellurium-bearing material with similar compositions to the anode slime of copper electrorefining, containing about 50% of copper and 34% of tellurium in several different phases. Based on the Pourbaix diagram (Eh-pH) of Cu–Te–Se–H2O in certain conditions, an alkaline pressure leaching process with NaOH as leaching agent was proposed to separate tellurium and selenium selectively from the raw material. Further heterogeneous thermodynamic simulation of the leaching was performed by Factsage 6.3 and the behavior of different species was predicted. The experimental results agree with the simulation results and prove that about 90% of the tellurium can be oxidized to soluble sodium tellurite, while the copper stays in the residue. It is found that selenium is difficult to dissolve with a leaching efficiency of only 20%, which needs more detailed research in the future. For the leaching of tellurium, the established optimal leaching conditions were as follows: L/S ratio of 6:1, free concentration of NaOH of 30–40g/L, time of 6h, total pressure of compressed air of 1.0MPa, temperature of 120±5°C, and agitation speed of 400rpm.

CFD modeling of the electrolyte flow in the copper electrorefining cell of Sarcheshmeh copper complex

Electrolytic refining is the principal method of mass producing high-purity copper in an industrial scale. In this study, a three dimensional computational fluid dynamics simulation together with experimental field measurements was applied to optimize the performance of industrial electrolysis cell in the Sarcheshmeh copper complex, Iran. The continuity, momentum equations with inclusion of buoyancy force and the copper mass concentration equation were solved by finite volume method. In order to calculate the velocity distribution in the cell, the k–ω turbulence flow model has been used. There was a good agreement between the simulation results and the experimental data of the electrolysis cell. After the validation of the model, the effects of flow pattern, copper mass concentration distribution, current density, volumetric flow rate of feed and the distance between the electrodes on the performance of the cell using CFD were studied. The results of CFD modeling show that along the cathode and anode surfaces, there were a down flow and an up flow due to natural convection, respectively. Increasing the current density caused an increase of copper mass concentration near the anodes and a decrease near the cathodes; that is in accordance with Faraday's law. Increasing the volumetric flow rate of feed caused an increase of vertical velocity near the anodes and cathodes. Decreasing the distance between electrodes caused a decrease of the natural convection between the anodes and the cathodes and increasing of copper mass concentration near the anodes.

Process Simulation for the Metallurgical Industry: New Insights into Invisible Phenomena

In order to demonstrate how advanced process simulation can help to understand metallurgical process details and thus to improve industrial productivity, a number of examples are shown and discussed. The paper covers recent simulation results gained at the Chair of Simulation and Modeling of Metallurgical Processes, namely (i) the flow and shell formation in thin slap casting of steel, (ii) multiphase flow and magneto-hydrodynamic during Electro-Slag-Remelting, (iii) mold filling, surface wave dissipation and solidification during horizontal centrifugal casting of rolls, and (iv) forced and natural convection during electro-refining of copper in an industrial-size tankhouse cell.

Copper nucleation and growth patterns on stainless steel cathode blanks in copper electrorefining

Surface properties of stainless steel on nucleation and growth of copper under electrorefining conditions were studied using AISI 316L type stainless steel in rotating disc electrodes (RDE), stationary electrodes and Hull cell, and also worn industrial cathode blanks. The aim was to find correlations between surface topography and nucleation and growth using deposition tests, microscopy, and image analysis. Deposition tests were done galvanostatically using synthetic copper electrorefining electrolyte and current density 330 A/m2 typical in electrorefining. On the as-received stainless steel with 2B finish, nucleation happened at grain boundaries. Wet grinding resulted in deposition on the ridges and valleys of rough surface and ridges of smooth surface. The nucleation density was in the order of 106 nuclei/cm2 in RDE and Hull cell tests, and 105 nuclei/cm2 in stationary electrode tests. Used industrial blanks did not show the same deposition patterns on grain boundaries and scratch marks, and copper deposited on edges of larger damages. The nucleation density on industrial blanks was in the order of 103 nuclei/cm2.

New Technology for Electrorefining of Copper

New electrorefining technology utilizes a novel manifold electrolyte inlet, which allows improving productivity and production in new and existing tankhouses at high current efficiency and very good cathode quality. Two installation examples—Montanwerke Brixlegg AG, Brixlegg, Austria (upgrade existing tankhouse) and Xiangguang Copper, Yanggu, China (new tankhouse)—demonstrate the use of current densities above 400 A/m2 at very high current efficiency in electrorefining.

The oxidation of arsenic from As(III) to As(V) during copper electrorefining

The oxidation of arsenic from As(III) to As(V) during copper electrorefining was studied. Experimental results showed that during copper electrorefining, the precipitation of impurities As, Sb and Bi in the electrolyte has strong relation with the oxidation. When As(III) and AsT were 5.00g/L and 10.00g/L respectively in the initial electrolyte, after copper electrolysis carried out with current density 235A/m2 at 65°C for 168h, the concentrations of Sb and Bi were decreased 35.0% and 18.2% respectively, while without As(III) in the initial electrolyte, under the same conditions, the concentrations of Sb and Bi weren't decreased but increased 12.5% and 9.1% respectively. It was found that the oxidation of arsenic from As(III) to As(V) plays an important role in the precipitation of impurities As, Sb and Bi in copper electrolyte as well, and the oxidation is applicable to the pseudo-first order kinetic model.

Removing arsenic from anode slime by vacuum dynamic evaporation and vacuum dynamic flash reduction

In crude lead or copper electrorefining, the by-product anode slime is an important material of recycling precious metals. However, the existing methods for treating arsenic-rich anode slime are less than satisfactory not only for the removal effect of arsenic but also for the environment protection. Therefore, a new technology for treating arsenic-rich anode slime was proposed in this paper, namely the two-step process of vacuum dynamic evaporation (VDE) and vacuum dynamic flash reduction (VDFR). Through this two-step process, silver from the anode slime was left behind in distilland as the silver alloy, and the trivalent oxide of arsenic was evaporated in the distillate. The experimental results showed that the removal ratio of arsenic was 99.96%. Moreover, these vacuum technologies offer improvements in metallurgical and environmental performance.