Copper Cathode Research Articles

Effect of Thiourea on Copper Cathode from Simulated Leachate of Copper and Cadmium Residues by Cyclone Electrowinning Technology

Effect of Thiourea on Copper Cathode from Simulated Leachate of Copper and Cadmium Residues by Cyclone Electrowinning Technology

Enhanced Stability of Tin Halide Perovskite Photovoltaics Using a Bathocuproine—Copper Top Electrode

AbstractUnencapsulated organo‐tin halide perovskite photovoltaic (PV) devices exhibiting record stability (for organo‐tin perovskite PV devices) when tested under continuous one sun solar illumination in ambient air and under electrical load are reported. This exceptional stability is made possible by the use of a bathocuproine | copper cathode in an inverted device architecture. A series of experiments designed to elucidate the underlying reasons for the high stability show that, compared to conventional silver electrodes, compact copper electrodes are far more resistant to corrosion by I2 gas (evolved when organo‐tin halide decomposes) and toward adverse morphological evolution and ingress of oxygen and water molecules through the top electrode into the device. The findings of these experiments show that copper should be the metal of choice for the reflective cathode in inverted tin perovskite PVs when the material interfacing the metal interacts strongly with it, enabling compact film formation and a stable interface toward copper diffusion into the adjacent charge transport layer.

Implementation of digital automated control systems at electrolytic copper refining plants in Vietnam

The work aims to develop digital control and management systems of copper electrolytic refining processes when addressing energy efficiency issues. Thermal imaging scanners can be used to monitor the process state of an electrolytic cell. In this regard, the experience in the automation and control systems of OJSC Novgorod Metallurgical Plant was considered. Mathematical research methods and a stochastic model developed in the MatLab software were used. This model was applied at the Lao Cai copper-smelting plant (Vietnam). The proposed algorithm is based on the temperature variation in electrolyte depending on the heating of cathode and anode sections during short circuits due to dendritic growth, as well as process disturbance time. The algorithm was developed using the Visual BasicScript programming languages. The temperature rise in short circuit areas was recorded using a thermal imaging scanner immediately after the colour change of the cathode surface. It was shown that the duration of a short circuit depends on the amount of sludge deposited in an electrolytic cell. The sludge formed following the destruction of intergrown dendrites contains precious metals. The developed measures, along with those of digitisation, are necessary for effective management, taking into account the functional and kinetic characteristics of the copper refining process. The proposed solutions and control algorithms will allow remote access systems with augmented reality elements when creating a digital twin. This will reduce the specific power consumption by 20 –25% while decreasing the number of electrode short circuits. Controlling the composition and level of electrolyte and sludge will reduce material losses and maintain the concentration of noble metals in the electrolyte. To improve the control quality of automation during the electrolytic production of cathode copper, a number of technical measures were proposed that provide additional points of control to expand the process database. Furthermore, the proportion of manual periodic measurements of process parameters is reduced.

Copper Cathode Contamination by Nickel in Copper Electrorefining

Nickel behavior has a significant role in the electrorefining of copper, and although it has been extensively studied from the anode and electrolyte point of view over the past decades, studies on nickel contamination at the cathode are limited. In the current paper, three possible contamination mechanisms—particle entrapment, electrolyte inclusions and co-electrodeposition—were investigated. Copper electrorefining (Cu-ER) was conducted at the laboratory scale, and the cathodes were analyzed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and flame atomic absorption spectroscopy (AAS). Particle entrapment was studied by adding NiO and Fe2O3 to the system to simulate nickel anode slime, and the experiments were replicated with industrial anode slime material. The possibility of electrolyte entrapment due to nodulation was explored through the addition of graphite to produce nodules on the cathode. Co-electrodeposition was analyzed by experiments that utilized a Hull cell. The results indicate that particle entrapment can occur at the cathode and is a major source of the nickel contamination in Cu-ER, whereas nickel compounds were not shown to promote nodulation. Inclusions of bulk electrolytes within the surface matrix were observed, proving that electrolyte entrapment is possible. As co-electrodeposition of Ni in Cu-ER is thermodynamically unlikely, these experimental results also verify that it does not occur to any significant extent.

Combined electric discharge “arc + discharge with liquid electrolyte cathode”

A combination of an electric arc and discharge with a liquid electrolyte cathode in a single discharge gap has been created. The plasma column of discharge with liquid electrolyte cathode formed a “hollow cylinder”. The electric arc was burned in a vapor-gas environment inside the “hollow cylinder”. The gas discharge current with liquid electrolyte cathode was set in the range of 5-10 A, and the arc current varied in the range of 1-10 A. Aqueous solutions of sodium chloride with a specific electrical conductivity of 10-15 mS/cm were used as a liquid electrolyte. Spectral studies have been carried out in the visible range of radiation. In the experiments, copper and duralumin metal cathodes were used.

Recent Progress in Molten Salt Electrolysis Using a Liquid Metal Cathode and Vacuum Distillation for the Production of Ultra-High-Purity Mg Metal from MgO

In order to produce ultra-high-purity magnesium (Mg) metal from magnesium oxide (MgO), a novel and environmentally-sound process via molten salt electrolysis using a liquid metal cathode and vacuum distillation has been developed. The molten salt electrolysis of MgO in magnesium fluoride (MgF2) – lithium fluoride (LiF) molten salt is conducted at 1053 K using a tin (Sn), copper (Cu), or silver (Ag) cathode and a carbon (C) or platinum (Pt) anode for the production of Mg alloys. Subsequently, vacuum distillation of the obtained Mg alloys is carried out at 1200 – 1300 K to produce Mg metal with a purity of 99.999 %. In this study, the influence of the electrolysis temperature, concentration of Mg in the Mg alloys, and current density of the cathode on the faradaic efficiency was investigated. In addition, the reaction between the Mg alloys cathode and alumina (Al2O3) in contact with the cathode was analyzed. Recent results obtained by scale-up of the developed electrolytic and vacuum distillation processes and the use of secondary resources containing MgO as a feedstock for robustness and extension of the process will also be discussed. This study demonstrates the feasibility of an effective and environmentally-friendly Mg production process using MgO. Figure 1

Fundamental Study of Electrolysis of MgO in MgF2 - LiF - KCl Molten Salt Using Cu Cathode

For the commercial production of magnesium (Mg) metal using the electrolytic method, anhydrous magnesium chloride (MgCl2) is used as a feedstock. However, preparation of anhydrous MgCl2 is energy-intensive and toxic chlorine (Cl2) gas is generated during electrolysis. In order to resolve these problems, a novel molten salt electrolysis of magnesium oxide (MgO) using copper (Cu) cathode was investigated in this study. The effect of the electrolysis temperature, the size of the Cu metal pellets used for the cathode, the concentration of Mg in the Mg – Cu alloy, and the cathodic current density on the current efficiency were investigated. In addition, the reaction between the Mg – Cu alloy cathode and the alumina (Al2O3) crucible containing the Mg alloy during the electrolysis was analyzed. In the experiments, the electrolysis of MgO was conducted in a magnesium fluoride (MgF2) – lithium fluoride (LiF) – potassium chloride (KCl) molten salt using Cu cathode and carbon (C) anode by applying current in the range of 1.42 – 2.15 A at 1043 – 1173 K for 9.50 – 27.5 h in an argon gas atmosphere. After the electrolysis, the Mg – Cu alloys with a mixture of Cu2Mg and Cu (Mg) were obtained with 87.8 – 92.0 % current efficiency under certain conditions. Therefore, it was demonstrated that the green and effective electrolytic Mg production method using MgO, developed in this study, is feasible.

Copper recovery from sludges generated in the electrolyte treatment plant of a pyrometallurgical complex

Electrolytic sludge is generated in the last stage of the electrolyte decontamination treatment plant in the manufacture of cathodic copper (> 99.99 % Cu). Currently, this sludge is recycled back to the process due to the high concentration of copper, although its recirculation involves a serious problem of arsenic accumulation in the industrial process. This negatively affects the quality of commercial copper. Therefore, the main focus of this study was the recovery of copper contained in the electrolyte sludge as copper (II) sulfate pentahydrate (CuSO4∙5H2O) for its return to the industrial process and/or commercialization. The remaining waste, which contains mainly As and other toxic chemical species, were eliminated in a controlled repository. To this end, an exhaustive characterization of the electrolytic sludge was performed to determine its chemical composition, mineral phases, and particle size. The main results indicated that the sludge was composed of very fine particles (~ 99 % < 100 μm), containing mostly Cu (~ 54 %) (Cu3As, Cu2O, Cu and CuSO4∙xH2O), As (~ 10 % as Cu3As) and S (~ 7 % as CuSO4∙xH2O). More than 90 % of the Cu contained in the sludge was recovered as very pure copper sulfate (≥ 99.5 %) by an evaporative crystallization process. In addition, around 70 % of the As was removed in the process as a solid (> 99 % in As2O3). The rest of pollutants remained in the final solution, which ultimately will be treated in the liquid effluent treatment plant. Therefore, valorization of the electrolytic sludge was achieved by copper recovery as CuSO4∙5H2O using evaporative crystallization; this process was an effective way for both recovering Cu and removing the As contained in the electrolytic sludge generated in the electrolyte treatment plant.

Mitigating dendrite formation and electrolyte decomposition via functional double layers coating on copper current collector in anode-free lithium metal battery

BackgroundAnode-free lithium metal batteries (AFLMBs) are promising power sources. However, Li dendrite and dead Li formation hindered it from practical applications. These challenges mainly result from inhomogeneous Li plating and fragile SEI due to the rough bare copper (bare Cu) surface and commonly used carbonate electrolytes. MethodsHerein, we designed a two-step modification on the copper surface with synthesized Ag nanoparticles wrapped with polydopamine (Ag@P) and an artificial protection film (APF) to introduce an interface functional double layers. The first layer serves as Li-seeds for uniform Li nucleation and deposition. The latter (PVDF-HFP/LiTFSI) encapsulates the deposited Li to promote the formation of an anion-derived compact SEI film and minimize the inevitable electrolyte decomposition with Li. Significant findingsIt is found that the double-layer coating on copper enables homogenous and Li dendrite-free morphology. The anode-free cell with double layer-coated copper and NMC cathode maintains a superior coulombic efficiency (CE) of 98.15% and over 70 cycles at 40% capacity retention (CR) compared to the CE of 96.18% after 25 cycles at 40% CR on the bare Cu under 0.2 mA cm−2. These prominent achievements stem from the synergetic role of the lithiophilic Ag nanoparticles and the generation of an anion-derived robust LiF-rich SEI film. This study offers an alternative approach for current collector surface modification for the feasibility of AFLMBs.

Granulometric Characteristics Study for the Particles of the Cu&lt;sub&gt;2-x&lt;/sub&gt;S - Fe&lt;sub&gt;x+1&lt;/sub&gt;S System

The electrolysis of granular matte is a new alternative method for processing sulphide copper materials with the production of cathode copper and the conversion of sulfur to the elemental state. For the first time were established the regularities for the Cu2-xS – Fex+1S granules distribution by the size classes of obtained granulations for the Cu - Fe - S melt at temperatures of 1200, 1250, 1300 and 1350 °C. The maximum amount of Cu2-xS – Fex+1S material of size class 5.0 + 2.5, -2.5 + 1.6 and-1.6 + 1.0 mm, which corresponds to the conditions of following electrochemical processing and estimated as 72.5%, was obtained by granulation of the melt at 1200 °C. The granulometric characteristics of Cu2-xS – Fex+1S granules were estimated. With an increase in the overheating temperature of the Cu - Fe - S melt, granules with a large value of the average diameter were obtained, also the root-mean-square deviation of the particle size from the average value increases and the degree of polydispersity of the granules decreases. The duration of cooling for Cu2-xS – Fex+1S granules from the melt temperatures at 1200, 1250, 1300 and 1350 °C was calculated. In the entire considered temperature range, the particle cooling time is much longer than the spheroidization time, which contributes to the formation of spherical particles.

Statistical analysis of the distribution of impurities during copper electrorefining

Electrolytic copper refining makes it possible to obtain high purity metal, so the analysis of the main ways of impurity transition into electrolysis products is an actual problem. If it is solved, the process can be controlled when changing the composition of raw materials and, as a result, the content of impurities in the anodes. This paper uses the comprehensive analysis and synchronization of a large array of data on impurities concentrations in various process media (anodes, electrolyte, slime, and cathode metal) obtained on the series of commercial cells to identify the directions of impurity flows and relationship between their content in these media. It is shown that the transition of impurities from one process medium (source) to another (receiver) is implemented according to four main patterns: linear increase, no visible dependence, the presence of a limit concentration in the receiver and the presence of a threshold concentration in the source. The paper provides the results obtained in the statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel and silver) belonging to different groups in four main pairs of the impurity source – receiver: anode – solution, anode – slime, slime – cathode, solution – cathode. The coefficients of linear regression equations are determined and their significance is estimated for all dependencies of the impurity concentration in the source on the content in the receiver. The coefficients obtained make it possible to explain the impurity transition paths observed in the commercial cells and predict the quality of cathode copper and the composition of slimes when the anode composition changes. The calculations showed that impurities are accumulated in cathodes due to the occlusion of slime particles and incomplete solution removal from the surface of commercial cathodes rather than due to electrochemical reactions. The copper electrorefining technology should be improved and developed so as to find surface-active additives that would prevent the adsorption of suspended slime particles on the cathode surface, as well as better wash them from the electrolyte.

Correlation between the microstructure and corrosion behaviour of copper/316 L stainless-steel dissimilar-metal welded joints

In this study, the correlation between the microstructure and corrosion behaviour of copper/316 L stainless-steel dissimilar-metal welded joints on an electrolytic copper cathode plate was experimentally investigated. Clear phase separation was noted in the weld metal with the γ- and ε-Cu phase dominating the Fe-rich and Cu-rich zones, respectively. The difference in the corrosion resistance of these zones means that multiple galvanic corrosion couples are formed in different joint areas. Strong galvanic corrosion between the γ and ε-Cu phases caused the shedding of the γ phase particles from the surface, thereby producing corrosion pits and eventually leading to joint failure.

Industrial validation of conductivity and viscosity models for copper electrolysis processes

In copper electrorefining and electrowinning, the conductivity and viscosity of the electrolyte affect the energy consumption, and for electrorefining the purity of cathode copper. Consequently, accurate models for predicting these properties are highly important. Although the modeling of conductivity and viscosity of synthetic copper electrolytes has been previously studied, only a few models have been validated with actual industrial electrolytes. The conductivity and viscosity models outlined in this study were developed using conductivity and viscosity measurements from both synthetic and industrial solutions. The synthetic electrolytes were investigated over a temperature range between 50–70 °C and typical concentrations of Cu (40–90 g/dm3), Ni (0–30 g/dm3), Fe (0–10 g/dm3), Co (0–5 g/dm3), As (0–63.8 g/dm3), H2SO4 (50–223 g/dm3) as well as other solution impurities like Sb in some cases. Validation of the synthetic electrolyte models was performed through industrial measurements at three copper plants across Europe. Generally, the developed models predicted the conductivities and viscosities of industrial solutions with high accuracy. The viscosity models covered extended ranges of both [H2SO4] and [Cu] with percentage errors of only (2.08 ± 0.59) - (2.48 ± 0.61). For conductivity, two different models for low (<142 g/dm3) and high (>142 g/dm3) [H2SO4] electrolytes were utilized. Their error margins were (−1.96 ± 0.84) - (−1.44 ± 0.35) and (1.17 ± 0.27) - (2.52 ± 0.28), respectively. In the case of high [H2SO4] electrolytes, the validations focused on conductivity, and the highest level of accuracy was obtained when the effects of Sb and other minor impurities were considered.

Assessment of possibility of obtaining alloying components in the process of desalting of heavy hydrocarbon raw materials. Part 2

Earlier, the authors had already successfully proposed a method for extracting minerals from crude oil as a first step, to be further developed in this second step in the direction of obtaining solid (metallic and / or oxide) phases of nickel and vanadium. The scientific, practical and strategic importance of the work is clearly-underlined with a general depletion of vanadium and nickel ores. In the current situation of mineral resources with a general depletion of vanadium and nickel ores, it becomes necessary to search for new and alternative resources to obtain these strategic and important metals and their compounds from available resources. Taking into account that vanadium and nickel ores are practically absent in the raw material resources base of some countries, such as Middle East&rsquo;s countries. Thus, a high percentage of imports of this metal product remains, which worsens the economic situation that has developed during political conflicts. The scientific approach was based on a combination of hydrometallurgical and electrometallurgical experiments, consistently carried out through the processes of sorption and desorption during cathodic electrodeposition. Sorption processes for vanadium and nickel were carried out using a mixture of Syrian sorbing materials (incense-type resins and surface-activated natural clays) with finely ground glass SiO2. Cathodic electrodeposition experiments were carried out on a copper cathode plate, and on the other hand, an insoluble glassy carbon electrode was used as the anode. All batch experiments were carried out to determine the best conditions for vanadium and nickel sorption by studying six different parameters affecting the sorption capacity of vanadium and nickel. As a result, the maximum sorption capacity of vanadium and nickel was 87.5 % and 91.3 % consistently under the predetermined conditions. Eventually, 7.6 % Ni (with a purity of 97 %) was recovered from the solution after the desorption process by the electrolytic method (during electrolysis); 15.6 % (99.3 % pure) V2O5 and 11.5 % (79 % pure) NiO chemically.

Assessing Water Footprint of Copper Production by Pyrometallurgy

As an important tool for water resource environmental impact assessment, the application of water footprint assessment method in copper production process is conducive to more accurate assessment of water resource environmental impact in copper production process. The water footprint assessment method released by the Water Footprint Network was used to study the water footprint of the production process of cathode copper products produced by pyrometallurgy. It was found that the water footprint of 1 ton of copper produced by pyrometallurgy was 242m3, of which the blue water footprint accounted for 60%, the grey water footprint accounted for 40%. The direct water footprint accounted for 67% and the indirect water footprint accounted for 33%. The characteristics of water footprint contribution at each process were compared, which provided data support and reference for enterprises to better understand the water resource environmental impact of copper by pyrometallurgy and to choose the water resource utilization mode with their own production characteristics.

МОДЕЛЮВАННЯ ДУГОВОГО РОЗРЯДУ НА МІДНОМУ КАТОДІ ДЛЯ ГЕНЕРАЦІЇ НАНОСТРУКТУР

The paper considers the model of processes acting in the ionization layer of the cathode assembly during plasma generation of nanostructures. In the given model the processes in electrodynamic and gas - dynamic layers of plasma and their coordination are rather densely considered. Therefore, the solution of the model allows to adequately determine the magnitude of the cathode potential jump in the electrodynamic layer, which allows to compensate for all energy losses during the generation of nanostructures, and the magnitude of ion and electron fluxes at the cathode. The calculations were performed at a constant value of the elongation of the ionization layer, because it has little effect on the change in the ion current density along the length of the cathode layers. Also, the calculations confirmed a non-significant dependence of the initial pressure from the ionization layer on the temperature of the electrons. The obtained dependences, the fraction of ionic current at the cathode and the cathode potential drop from the current density at different cathode temperatures, showed that the change in the proportion of ionic current makes it possible to compensate for energy costs to maintain the cathode temperature. And consideration of the equation of energy balance allowed to establish the range of losses of the working fluid at which it is possible not to take into account the energy of evaporation of the working fluid and steam heating. To determine the current density at the cathode, the dependence of the thermoemission current on the cathode temperature and the dependence of the current density on the cathode on the plasma concentration at different cathode drops and different representations of electric field strengths were obtained. This allowed to determine the cathode temperature due to the ionic current density and to estimate the plasma concentration. Depending on the plasma concentration, the electric transfer coefficient for different emission mechanisms and cathode drops is obtained. All this allowed us to determine the dependence of the specific gravity leaving the cathode per unit time per unit area, on the cathode temperature and heat flux density for the copper cathode. Determining the specific gravity and the transfer coefficient makes it possible to determine the life of the cathode during plasma generation of nanostructures.

Time-resolved study of nonlinear photoemission in radio-frequency photoinjectors.

Photoemission is one of the fundamental processes that describes the generation of charged particles from materials irradiated by photons. The continuous progress in the development of ultrashort lasers allows investigation into the dynamics of the process at the femtosecond timescale. Here we report about experimental measurements using two ultrashort ultraviolet laser pulses to temporally probe the electrons release from a copper cathode in a radio-frequency photoinjector. By changing their relative delay, we studied how the release mechanism is affected by two-photon photoemission when tens of GW/cm2 intensities are employed. We evaluated the limits it poses on the achievable beam brightness and analyzed the resulting emission yield in terms of the electronic temperature by modeling the cathode as a two-temperature system.

Investigation of Electrowinning of Mg from MgO Using a Liquid Metal Cathode in MgF2-CaF2-NaF or MgF2-LiF Molten Salt

A novel magnesium (Mg) production process utilizing an electrolytic method was investigated for the direct reduction of magnesium oxide (MgO). Electrolysis of MgO was carried out with an applied voltage of 3.0 V using a copper (Cu), silver (Ag), or tin (Sn) cathode and carbon (C) or platinum (Pt) anode in magnesium fluoride (MgF2)−calcium fluoride (CaF2)−sodium fluoride (NaF) at 1273 K or MgF2− lithium fluoride (LiF) at 1083−1093 K. After the electrolysis of MgO in MgF2−CaF2−NaF molten salt, Mg alloys such as Mg2Cu, Cu2Mg, or Mg2Sn phases were produced with current efficiencies of 75.8−85.6% when the concentration of Mg in Mg alloys was 9.1−14.6 mass%. In addition, when the electrolysis of MgO was conducted in MgF2–LiF molten salt, Mg alloys such as Mg2Cu or AgMg phase were produced with current efficiencies of 76.2−81.7% when the concentration of Mg in the Mg alloys was 12.5−13.2 mass%. In addition, to produce high-purity Mg metal from Mg alloys, vacuum distillation was conducted. When vacuum distillation was conducted at 1100−1400 K for a duration of 5 h, the concentration of Mg in the Mg alloys feed decreased from 30.2−34.1 mass% to 0.64−1.75 mass%, and Mg metal with a purity of 99.998−99.999% was obtained under certain conditions. Therefore, the molten salt electrolysis using liquid metal cathode (MSE-LMC) process developed here is feasible for the direct reduction of MgO using an effective and environmentally sound method.

In vitro study of the antibacterial properties of amorphous copper-doped carbon coatings

A deposition technology of amorphous carbon coating (a-C), doped with copper (C-$$$Cu), has been developed. The C-Cu coating deposition was performed with the simultaneous operation of arc- and pulse-arc sources with copper and graphite cathodes, respectively. There was studied the antibacterial activity of the a-C and C-Cu against E. coli, S. aureus and P. aeruginosa. The copper-doped coating has bactericidal activity against P. aeruginosa. The number of bacterial colonies is five times lower in compare with a-C and Ti.

Removal of Sb Impurities in Copper Electrolyte and Evaluation of As and Fe Species in an Electrorefining Plant

Antimony and arsenic concentrations and their oxidation states (Sb(III), Sb(V), As(III) and As(V)) in copper electrorefining electrolyte can affect copper cathode quality through the formation of floating slimes. A laboratory-scale pilot plant was operated to remove Sb from commercial electrolyte. The pilot plant consisted of a pre-treatment process with copper shavings followed by ion exchange. The results indicated that Sb(III) was removed from copper electrolyte completely, while Sb(V) was partially eliminated. The concentrations of As(III) and As(V) were not affected, and the poisoning of the ion exchange resin by Fe(III) was avoided by pre-reduction to Fe(II) by copper shavings. The operation configuration of the pilot plant was applied to the design of an industrial plant for Sb/Bi removal at the Atlantic Copper Refinery in Huelva, Spain. The evolution of Sb, Fe and As species in the commercial electrolyte was monitored prior to and after the installation of the Sb/Bi removal plant. The results show a ca. 45% decrease in total Sb content (from 0.29 g L−1 to 0.16 g L−1) in the electrolyte. This reduction is more noticeable for Sb(III), whose concentration decreased from 0.18 g L−1 to 0.09 g L−1, whereas Sb(V) concentration diminished from 0.11 g L−1 to 0.07 g L−1. The resin also retained ca. 75% of the Bi content (0.15–0.22 g L−1). The total As increased during the study period (from 7.7 to 9.0 g L−1) due to changes in plant inputs. Arsenic was predominantly As(V) (ca. 93–95%). The total Fe concentration experienced little variation (0.9–1.1 g L−1) with Fe(II) being the main species (ca. 94–96%).