Zinc Electrowinning Process Research Articles

Constructing a multilayered film β[sbnd]PbO2[sbnd]ZrO2 electrode for energy-efficient zinc electrowinning

The zinc electrowinning process demands considerable energy, prompting the quest for energy-efficient solutions to curtail costs. Hence, the development of energy-saving anode materials for zinc hydrometallurgy is an important issue. Herein, multilayered PbO2 film materials were prepared through thermal decomposition and composite electrodeposition, yielding a new PbO2–ZrO2 electrode featuring ZrO2 particles as the second phase for energy-saving zinc electrowinning. The introduction of ZrO2 leads to reduced PbO2 crystal size, heightened the specific surface area of the electrode, and preferential growth of crystal planes. Electrochemical tests underscore that the PbO2–ZrO2 electrode manifests a reduced charge-transfer resistance (Rct) and overpotential alongside a 46.15 % extension in service life compared to the pure PbO2 electrode. Simulated zinc electrowinning experiment affirms PbO2–ZrO2 electrode has a 3.63 % surge in the current efficiency and a substantial 244.61 kWh/t reduction in energy consumption relative to the traditional Pb–0.6wt%Ag anode. This study provides a strategic framework for designing and developing cost-efficient, cost-effective anode materials, promoting advancements in energy conservation and consumption reduction within zinc electrowinning processes.

Integrated Optimal Control for Electrolyte Temperature With Temporal Causal Network and Reinforcement Learning.

The electrowinning process is a critical operation in nonferrous hydrometallurgy and consumes large quantities of power consumption. Current efficiency is an important process index related to power consumption, and it is vital to operate the electrolyte temperature close to the optimum point to ensure high current efficiency. However, the optimal control of electrolyte temperature faces the following challenges. First, the temporal causal relationship between process variables and current efficiency makes it difficult to estimate the current efficiency accurately and set the optimal electrolyte temperature. Second, the substantial fluctuation of influencing variables of electrolyte temperature leads to difficulty in maintaining the electrolyte temperature close to the optimum point. Third, due to the complex mechanism, building a dynamic electrowinning process model is intractable. Hence, it is a problem of index optimal control in the multivariable fluctuation scenario without process modeling. To get around this issue, an integrated optimal control method based on temporal causal network and reinforcement learning (RL) is proposed. First, the working conditions are divided and the temporal causal network is used to estimate current efficiency accurately to solve the optimal electrolyte temperature under multiple working conditions. Then, an RL controller is established under each working condition, and the optimal electrolyte temperature is placed into the controller's reward function to assist in control strategy learning. An experiment case study of the zinc electrowinning process is provided to verify the effectiveness of the proposed method and to show that it can stabilize the electrolyte temperature within the optimal range without modeling.

Effect of thallium (I) ions on the zinc electrowinning process

Effect of thallium (I) ions on the zinc electrowinning process

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.

The combined effect of highly variable DC current – Simulated from solar irradiance data – And electrolyte quality on zinc electrowinning

This paper is the second in a series of two papers focusing on the applicability of highly variable direct current (DC) for the production of high quality cathodes by electrowinning. Different current profiles were simulated from solar irradiance data and then applied to electrowinning cell using a precision programmable power supply. The simulated DC current was applied to the zinc electrowinning process, which was chosen as a case study due to its intensive energy consumption. The present work discusses the combined effect of highly variable current with the concentration of magnesium ions (Mg2+) in the zinc sulfate electrolyte. The impact of this impurity is relevant due to the complex mineralogy of the zinc ores available for processing (i.e., magnesium is one of the major elements contained in low-grade silicate ores). The results showed that even over a wide range of applied current densities (highest average value = 697 A m−2; highest peak value = 1486 A m−2), the average values of current efficiency calculated for the process, according to the different types of solar irradiance variability, are comparable. The lowest value (90.3% for intermittent day) could be explained by high amplitude variations in the intensity of the current density, which enhances the hydrogen evolution rate. The average values of current efficiency decreased with increasing impurity concentration in the electrolyte; decreases of 0.8–2.0% units in the average value of current efficiency were calculated at 15 g L−1 Mg2+. At this concentration, an increase of 2.1–6.8% in the average values of specific energy consumption was calculated, which was explained by the observed decrease in current efficiency and a slight increase in the cell voltage due to a decrease in the electrolyte conductivity. The deposits formed in the presence of 15 g L−1 and 30 g L−1 Mg2+ in the electrolyte showed a relatively greater number of pores, which, however, did not cause them to fracture or break during stripping.

An environmentally friendly and high current efficiency acid mist inhibitor for zinc electrowinning

Acid mist inhibitor is an effective additive for suppressing the generation of acid mist during electrowinning process. However, the traditional acid mist inhibitor has a low current efficiency, leading to high energy consumption. Thus, novel acid mist inhibitors are crucial for the development of the electrowinning industry. In this paper, three new acid mist inhibitors (Famigo® FS-101, Famigo® FS-301, and Famigo® FS-401) are used in zinc electrowinning process, while the mechanism of action in suppressing the generation of acid mist is characterized by the volume of bubble attached on the cathode surface and surface tension. The impacts of the concentration of the acid mist inhibitors on the bath voltage, current efficiency, power consumption, and electrochemical properties, as well as the enhancement mechanism on the current efficiency, are studied. The obtained results demonstrate that an adequate concentration of Famigo®FS-101, Famigo®FS-301, and Famigo®FS-401 allows to increase the cathode current efficiency and decrease the energy consumption, from 3219 kWh t−1 in zinc electrolyzer to 2948 kWh t−1, 3090 kWh t−1, and 2884 kWh t−1 using a concentration of 5 mg l−1 of Famigo®FS-101, Famigo®FS-301, and Famigo®FS-401, respectively. The proposed inhibitors have high acid mist inhibition efficiency and current efficiency in the zinc electrowinning process. Furthermore, if engineered, they may contribute to the development of the electroposition industry.

Synthesis and study of TiMn2 intermetallic compound anode materials with different structures for zinc electrowinning

In the zinc electrowinning process, lead anodes have been the main cause of lead pollution, resulting in environmental and ecological imbalances. To address this issue, this study prepared high purity bulk and porous TiMn2 intermetallic compound lead-free anodes through elemental reaction synthesis and investigated their electrochemical properties and electrolytic performance. The Tafel slopes of the bulk and porous TiMn2 anodes were found to be 351.85 and 741.9 mV·dec−1, respectively, with oxygen evolution overpotentials of 0.952 and 0.704 V in 160 g L−1 H2SO4 solutions. Both bulk and porous TiMn2 anodes exhibited long-time stability of 4210 and 960 h, respectively, during simulated electrolysis at 500 A m−2. Additionally, porous TiMn2 anodes exhibited lower potential than lead in simulated electrowinning experiments, while maintaining the quality of the deposited Zn conforming to the Zn-1 standard according to ISO 752–2004, with higher electrowinning efficiency than lead anode. Therefore, this study proposes a new intermetallic compound anode system that shows great potential and application in electrowinning, while reducing lead pollution and promoting environmental and ecological balance.

Effects of F− ions on the electrochemical and interface behavior of cathodes in zinc electrowinning

The increasing use of Zn metal in the energy and industrial sectors necessitates a higher level of research into the zinc electrowinning process. In this work, the effects of fluoride ions (F−) in zinc electrolyte on the cathodic kinetics and zinc product quality during zinc electrodeposition was systematically investigated via a series analysis. The results revealed that the addition of F− in the electrolyte showed a polarization effect, with an increase in the apparent cathodic exchange current density increased by 104 orders of magnitude, and a decrease in the zinc deposition overpotential by 46 mV at a concentration of 400 mg/L. However, F− also reduces the hydrogen evolution overvoltage, when the electrolyte contains 400 mg/L F−, the hydrogen evolution overvoltage on aluminum cathode and zinc cathode decreases by 121 mV and 97 mV, respectively. The promoted hydrogen evolution kinetics increases energy consumption and surface porosity. Additionally, F− ions corrode the Al2O3 oxide film on the cathode surface, accelerating the corrosion of the aluminum cathode plate. This results in increased adhesion of zinc deposition to the damaged aluminum substrate, making it difficult to peel off.

Effect of fluoride complexation by aluminium ions on the corrosion behaviour of aluminium cathodes used in zinc electrowinning

Fluoride (F−) impurity at 20 mg L−1 in the zinc sulphate electrolyte increased by 73% and 98% the corrosion rate of Al-1050 and Al-1070 alloys, respectively, which are used as cathode in zinc electrowinning process. The addition of aluminium ions, Al3+, to the electrolyte reduced the corrosion rate by about 21% for the Al-1050 alloy and about 28% for the Al-1070 alloy. The effect was ascribed to the formation of AlF2+ and AlF2+ complexes, thus decreasing fluoride activity. Electrochemical impedance spectroscopy demonstrated that the corrosion resistance of Al alloys is increased in the presence of Al3+. Scanning electron microscopy indicated uniform corrosion of the Al surface, the degree of which depends on fluoride concentration. The higher corrosion resistance of Al-1050 was related to its coarser microstructure, which is less susceptible to corrosion in a non-passivating media. The selection of effective complexing agent for fluoride ion and the consequent reduction in the corrosion rate of aluminum cathodes are relevant in scenario of increasing co-processing of secondary zinc sources.

Effect of the Sn Addition on the Electrochemical Properties of Al/Pb Anodes and Its Application in Zinc Electrowinning

Al/Sn/Pb composite anode materials were prepared by the hot-pressing diffusion method to improve their electrochemical properties. The bonding interface, electrochemical properties, and application properties in the zinc electrowinning process of the composite electrode materials were tested and analyzed. The results indicate that an improvement of the corrosion resistance of the electrode material, a more uniform distribution of the surface potential, and an enhancement of the electrochemistry have been achieved by changing the structure of the electrode. The cell voltage of the Al/Sn/Pb composite anode decreased by 0.169 V compared with that of the Pb alloy electrode in the zinc electrowinning engineering experiment. Its current efficiency is increased by 8.5%, its specific electric energy consumption is reduced by 11.4%, and its corrosion rate is reduced by 57.3%. The surface quality of the cathode-precipitated products is good, the impurity content is low, and the impurity Pb content is decreased by 35.59% compared to the Pb alloy electrode.

Pb-Zn recovery from a malic leach solution of a carbonate type ore flotation tailing by precipitation and solvent extraction

The recovery of zinc and lead from a malic leach solution of a carbonate type ore flotation tailing by precipitation with sulfuric acid followed by solvent extraction using di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant was investigated. The separation of lead via precipitation was essentially complete from the malic acid leach solution by adding sulphuric acid to reach a pH of 0.25 at 25 °C. The precipitate product was identified by XRD as anglesite (PbSO4). The pregnant leach solution after lead precipitation was then subjected to solvent extraction using D2EHPA. The optimum solvent extraction conditions were determined as 10% D2EHPA concentration, 25 °C temperature, 10 min contact time and phase ratio of unity. Under these conditions, 99.3% of zinc was extracted into the organic phase at a pH of 4.2 in a single contact alongside a substantial amount of Ca (76.6%), and minor amounts of Fe (19.2%) and Mg (18%). Complete stripping of zinc and calcium from the loaded organic solution along with 47.8% of Mg was achieved at a pH 0.5 under room temperature. No iron stripping was observed from the loaded organic. The zinc content in the loaded strip solution could be enriched and then sent to the electrowinning (EW) stage. It is noted that the calcium and magnesium impurities in the loaded strip solution had no adverse effect on the zinc EW process. Based on the experimental results, a flowsheet was proposed for the recovery of Pb and Zn from the malic acid leach solution. With the proposed precipitation and solvent extraction process, two different material streams are produced.

Understanding the zinc discharge from sodium sulphate solution in the presence of surfactants

This paper aims to understand the effect of surfactants on zinc discharge in sulphate solutions on a solid electrode and to collect new experimental data that would give a deeper insight into the processes involved in industrial electrolysis. Anionic and cationic coagulants (flocculants) and an anionic frother were used as surfactants. Electrolysis was conducted in the potential region of –1050 to –1250 mV (Ag/АgCl) in stationary and dynamic conditions in sodium sulphate solution under intensive stirring. The authors obtained comparative data on the zinc discharge current in electrolyte with and without frother at the scan velocities of 2 to 100 mV/sec. It is noted that at higher scan velocities (>10–20 mV/sec) and in the initial electrolysis phase the zinc discharge process develops in a mixed mode. In this case, as the study showed, the positive effect of the frother on zinc discharge is most distinguished. A reaction order was designed based on zinc ion with four potentials to prove that the zinc electrowinning process develops in a mixed mode. It is shown that the addition of frother raises the reaction order from 1.2 to 1.5, which is attributed to a larger effective cathode surface area. The data obtained in a galvanostatic mode under intensive stirring conditions indicate that, at the current density of 1.7 mA/cm2, the electrode polarization is 1.6 times lower in the presence of cationic coagulant and almost 3 times lower in the presence of anionic coagulant. The data given in this paper are also indicative of a changing electrolysis mode. Under stirring, a transition is observed from a diffusion mode of zinc ion reduction to a mixed one. The experimental data obtained under intensive stirring conditions in sodium sulphate solution with frother, as well as anionic and cationic coagulants are in line with the theory of electrochemical processes.

Improvements in the selective cementation of Cd and Ni/Co from zinc industrial electrolyte

The selective cementation of cadmium, cobalt, and nickel from synthetic and an industrial zinc sulfate (150–160 g.L−1) electrolyte was investigated. The desired cadmium removal (from 640 to 740 mg.L−1 to <1 mg.L−1) was achieved at ambient temperature, with staged addition of zinc dust, using a Zinc/Metals molar ratio in excess of 300%, which is about 50% lower than typical ratios used in industries. An enriched Cd cement (29% wt. vs. app. 7% wt. in industrial samples) with low nickel (0.05% wt.) content was produced in one purification stage. The zinc content in the Cd cement was 20% lower relative to that in the industrial cement. In a second stage, fast and high cobalt and nickel removals were obtained after the pre-activation of zinc dust with copper and antimony. The presence of 150–160 g.L−1 Zn did not affect cobalt removal but made it difficult for nickel cementation. The industrial specification for the purified solution that feed the zinc electrowinning process was achieved for cobalt (< 0.2 mg.L−1) and nickel (< 0.5 mg.L−1), after 60 min of reaction time. The nature, morphology, and chemical composition of the cementation products were evaluated by X-ray diffraction analyses and electron microscopy techniques. Finally, an alternative two-stage purification flowsheet was proposed to produce a rich cadmium cement with low nickel content (0.05% wt.), and a cobalt‑nickel cement. The process allows for a reduction in the consumption of zinc dust and energy, as well as the reaction time.

Lowering the Energy Consumption of Zinc Electrowinning By Electrocatalysis of the Oxygen Evolution Reaction Using Manganese Oxides

Zinc has a wide range of commercial applications including but not limited to galvanizing iron and steel and production of various metal alloys such as brass and bronze. In hydrometallurgical processes, zinc electrowinning from sulfate-based electrolytes is the last step of zinc extraction in which high purity metallic zinc is electrodeposited from a highly acidic solution on an aluminum cathode. The electrowinning stage is very energy-intensive and responsible for approximately 80% of the power requirement of a zinc refinery (1). Thus, improving the energy efficiency and lowering the operating costs of zinc electrowinning are of primary significance. The oxygen evolution reaction (OER) overpotential on conventional lead-silver (Pb-Ag) anodes contributes to nearly 25% of the total electrowinning cell potential (2). Therefore, the high anodic OER overpotential places a heavy financial burden on zinc refining plants.The present study aims to evaluate novel anodic electrocatalysts incorporating MnO x in order to lower the anodic OER overpotential of the zinc electrowinning process. Anodically electrodeposited MnO x catalysts on Pb-Ag electrodes were prepared using galvanostatic and potentiodynamic polarizations. The OER catalytic activity and stability of MnOx electrodeposited Pb-Ag electrodes were evaluated in 160 g/L sulphuric acid solution with 3 g/L of manganese (II) and in the absence and presence of 0.3 g/L of chloride ion at 35°C, using a standard three-electrode setup. The electrolyte composition and operating conditions were selected such that to be directly applicable to the industrial zinc electrowinning process. The OER activity of the MnOx electrodeposited electrodes was investigated through potentiodynamic polarization and 72-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density. Finally, the activity of MnOx electrodeposited Pb-Ag electrodes was explored in a full zinc electrowinning cell through 24-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density.The OER potential variations of the bare Pb-Ag and MnO x electrodeposited Pb-Ag anodes during the 72-hour galvanostatic polarization are shown in Fig. 1. In the absence and presence of chloride ions, the three MnO x electrodeposited Pb-Ag electrodes are observed to reduce the anodic potential by maximum of 150 mV and 80 mV, respectively. Investigation of these novel electrodes in the full-cell zinc electrowinning operation corroborated the half-cell experiments, revealing a maximum of 130 mV reduction in cell potential at 50 mA/cm2 superficial current density and in the presence of 0.3 g/L of chloride ion. Thus, this work demonstrates that MnO x electrodeposited Pb-Ag anodes have great capacity to lower the power consumption of the zinc electrowinning process.Fig. 1. OER activity and stability comparison under galvanostatic polarization for four anodes: bare Pb-Ag (baseline) and three MnOx electrodeposited Pb-Ag anodes prepared via linear scan voltammetry (LSV), constant current density (CCD), and cyclic voltammetry (CV). Superficial current density: 50 mA/cm2. Electrolyte:160 g/L H2SO4 with 3 g/L Mn2+ and 0.3 g/L Cl- at 35°C.References A. C. Scott, R. M. Pitbaldo, G.W. Barton, A. R. Ault, J. Appl Electrochem, 18, 120–127 (1988). Schmachtel, M. Toiminen, K. Kontturi, O. Forsen, M. H. Barker, J. Appl Electrochem, 39, 1835–1848 (2009). Figure 1

Recovery of Cobalt from the Residues of an Industrial Zinc Refinery

The electrolytic production of metallic zinc from processing zinc sulfide concentrates generates a residue containing cadmium, copper, and cobalt that need to be removed from the electrolytic zinc solution because they are harmful to the zinc electro-winning process. This residue is commonly sent to other parties that partly recover the contained elements. These elements can generate revenues if recovered at the zinc plant site. A series of laboratory tests were conducted to evaluate a method to process a zinc plant residue with the objective of recovering cobalt into a salable product. The proposed process comprises washing, selective leaching, purifying and precipitation of cobalt following its oxidation. The process allows the production of a cobalt rich hydroxide precipitate assaying 45 ± 4% Co, 0.8 ± 0.2% Zn, 4.4 ± 0.7% Cu, and 0.120 ± 0.004% Cd at a 61 ± 14% Co recovery. Replicating the whole process with different feed samples allowed the identification of the critical steps in the production of the cobalt product; one of these critical steps being the control of the oxidation conditions for the selective precipitation step.

A Study on the Application Characteristics of the Insoluble MMO (Mixed Metal Oxide) Electrode for Energy Reduction of Zinc Electrowinning Process

Objective : The zinc electrowinning industry is one of the high energy consumption industries where energy saving is required. In the zinc electrowining process, electrode is a high energy consuming part. In order to reduce energy use in the electrolytic smelting industry, a comparative study was conducted on the current usage of Pb+Ag alloy electrode and insoluble composite metal oxide (MMO) electrode.Methods : In this study, a comparative evaluation of energy consumption was conducted between the generally used Pb+Ag alloy electrode and an insoluble MMO electrode. Aluminum was used as a reducing electrode. The actual on-site zinc electrowinning solution and ZnSO₄ simulated solution were prepared to estimate the electrode potential, voltage, zinc deposition efficiency, and lifetime characteristics under the current density of 500 A/m².Results and Discussion : The overvoltage of the insoluble MMO electrode was 28.9% lower and the voltage was 15.0% lower than that of Pb+Ag alloy electrode. The zinc deposition efficiency of the insoluble MMO electrode was higher 1.9% in the actual on-site zinc electrowinning solution and 6.3% in the simulated solution. Compared with the Pb+Ag alloy electrode in use, the insoluble composite metal oxide electrode exhibited low overvoltage, good voltage characteristics, and high current efficiency characteristics.Conclusions : When the energy consumption of the Pb+Ag alloy and the insoluble MMO electrodes was compared, The insoluble MMO electrode showed 17.0% lower energy consumption in the actual on-site zinc electrowinning solution and 23.8% lower in the ZnSO₄ simulated solution than Pb+Ag alloy electrode.

Hydrometallurgical stepwise recovery of copper and zinc from smelting slag of waste brass in ammonium chloride solution

A new process for recycling zinc and copper from the smelting slag of waste brass was investigated in this study. The zinc and copper present in the smelting slag were dissolved in a ZnCl2–NH4Cl solution system. To recycle copper, the lixivium was purified by a novel method termed as electrochemistry and chemistry synergetic (ECS) purification. After deep purification of the ECS-treated lixivium by zinc powder cementation, zinc in the lixivium was extracted by electrowinning to obtain a zinc plate. The effects of the leaching temperature, reaction time, and liquid–solid ratio on the extraction percentages of zinc and copper were examined. The results revealed that the extraction percentages of zinc and copper were 88.37% and 90.85%, respectively, at a leaching temperature of 95 °C, reaction time of 90 min, and liquid–solid ratio of 8:1 mL/g. Further, effects of the current density, temperature, and reaction time on the recovery ratio of copper by ECS method were examined. The results revealed that 98.51% of copper could be extracted from the lixivium and that the purity of the extracted copper was 96.7% at a temperature of 70 °C and cathode current density of 75 A/m2 after a reaction for 4 h. In the deep purification process, 0.3 g/L zinc powder was used to completely remove impurities from the ECS-treated lixivium. In the zinc electrowinning process, a current efficiency of 95.79% was achieved at 70 °C and 400 A/m2; the purity of the obtained zinc product was greater than 99.95%, and the direct energy consumption was 2966.59 kW·h/t-Zn.

Lowering the Energy Consumption of Zinc Electrowinning By Electrocatalysis of Oxygen Evolution Reaction Using Manganese Oxides

Zinc has a wide range of commercial applications including but not limited to galvanizing iron and steel and production of various metal alloys such as brass and bronze. In hydrometallurgical processes, zinc electrowinning from sulfate-based electrolytes is the last step of zinc extraction in which high purity metallic zinc is electrodeposited from a highly acidic solution on an aluminum cathode. The electrowinning stage is very energy-intensive and responsible for approximately 80% of the power requirement of a zinc refinery (1). Thus, improving the energy efficiency and lowering the operating costs of zinc electrowinning are of primary significance. The oxygen evolution reaction (OER) overpotential on conventional lead-silver (Pb-Ag) anodes contributes to nearly 25% of the total electrowinning cell potential (2). Therefore, the high anodic OER overpotential places a heavy financial burden on zinc refining plants.The present study aims to evaluate novel anodic electrocatalysts incorporating MnO x in order to lower the anodic OER overpotential of the zinc electrowinning process. Anodically electrodeposited MnO x catalysts on Pb-Ag electrodes were prepared using galvanostatic and potentiodynamic polarizations. The OER catalytic activity and stability of MnOx electrodeposited Pb-Ag electrodes were evaluated in 160 g/L sulphuric acid solution with 3 g/L of manganese (II) and in the absence and presence of 0.3 g/L of chloride ion at 35°C, using a standard three-electrode setup. The electrolyte composition and operating conditions were selected such that to be directly applicable to the industrial zinc electrowinning process. The OER activity of the MnOx electrodeposited electrodes was investigated through potentiodynamic polarization and 72-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density. Finally, the activity of MnOx electrodeposited Pb-Ag electrodes was explored in a full zinc electrowinning cell through 24-hour galvanostatic electrolysis at 50 mA/cm2 superficial current density.The OER potential variations of the bare Pb-Ag and MnO x electrodeposited Pb-Ag anodes during the 72-hour galvanostatic polarization are shown in Fig. 1. In the absence and presence of chloride ions, the three MnO x electrodeposited Pb-Ag electrodes are observed to reduce the anodic potential by maximum of 150 mV and 90 mV, respectively. Investigation of these novel electrodes in the full-cell zinc electrowinning operation corroborated the half-cell experiments, revealing a maximum of 80 mV reduction in cell potential at 50 mA/cm2 superficial current density and in the presence of 0.3 g/L of chloride ion. Thus, this work demonstrates that MnO x electrodeposited Pb-Ag anodes have great capacity to lower the power consumption of the zinc electrowinning process.Fig. 1. OER activity and stability comparison under galvanostatic polarization for four anodes: bare Pb-Ag (baseline) and three MnOx electrodeposited Pb-Ag anodes prepared via linear scan voltammetry (LSV), constant current density (CCD), and cyclic voltammetry (CV). Superficial current density: 50 mA/cm2. Electrolyte:160 g/L H2SO4 with 3 g/L Mn2+ and 0.3 g/L Cl- at 35°C.

Improve the energy efficiency: Effects of additives on longtime zinc electrowinning

In this paper, the theoretical energy consumption required in the zinc electrowinning process was analyzed. The theoretical energy consumption is only a half of the energy consumption in industrial production. To save energy of the production process, we studied five kinds of additives with the industrial electrolyte in the longtime zinc electrowinning process. The results indicated that the presence of non-ionic compound (thiourea) or anionic surfactant (sodium dodecyl sulfonate or sodium dodecylbenzene sulfonate) adversely affected the energy consumption and current efficiency. However, an improvement in energy consumption was observed with the addition of cetyltrimethylammonium bromide. Our results should be helpful for the production of zinc electrowinning.

A method of simultaneously electrodepositing α/β-PbO2 coating materials in methanesulfonic acid and its application in zinc electrowinning

In the present work, nucleation mechanism, preparation conditions, performance testing and application simulation of lead dioxide coating materials prepared by electrodeposition from methanesulfonic acid were studied to improve anodic process in zinc electrowinning process. Phase growth and transformation of lead dioxide were analyzed by anodic polarization curves, X-ray powder diffraction, scanning electron microscopy SEM, electrochemical impedance spectroscopy (EIS) and Tafel curves. The selection of temperature ranges was found to cause a quantitative difference in the formation of α/β-PbO2 phases, as it made interval effects on the overpotential that was the primary control condition to affect transfer process, while without changing the reaction mechanism apparently. In this way, the precise conditions of obtaining α- or β-PbO2 phases by varying temperatures was confirmed and samples were selected to be tested in long-period galvanostatic electrolysis, electrode (deposition time-α&β: 2 h&2 h) showed the best physicochemical properties and could effectively extend the lifetime (70.4 h) compared with the traditional lead dioxide electrodes (32.3 h) in zinc electrowinning.