Pb-Ag Anode Research Articles

Boosting effect of ultrasonication on the oxygen evolution reaction during zinc electrowinning

In this study, the electrochemical and anodic behaviors of Pb-Ag anodes during ultrasound-assisted zinc electrowinning were meticulously examined. The oxygen evolution reaction (OER) occurring at the Pb-Ag anodes in a 150 g L-1 aqueous H2SO4 solution was studied in the absence (silent) and presence of ultrasonication (40 kHz, 100 % acoustic amplitude). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and zinc electrowinning tests were conducted to analyze the electrochemical behavior of the Pb-Ag anodes during zinc electrowinning. Compared with that under silent conditions, the OER was greatly enhanced under ultrasonic conditions, and the overpotential reduction was found to be 108 mV at 35 °C at a current density of 50 mA cm−2. A significant reduction in the bath voltage was achieved during ultrasound-assisted prolonged zinc electrowinning, with a difference of approximately 50 mV compared with that of the control. The integration of ultrasonic technology into the realm of zinc electrowinning leverages the physical and chemical effects of ultrasonication to significantly improve the efficiency and kinetics of the OER. Smaller PbO2 grains and a larger silver exposure area appeared on the Pb-Ag plate surface during ultrasonic-assisted electrowinning, which is beneficial for the OER chemically. The generated oxygen bubbles merged more rapidly and detached from the electrode surface with greater alacrity under ultrasonication conditions, which reinforced the OER in terms of mass transfer kinetics. Furthermore, more fine zinc products can be obtained during ultrasound-assisted zinc electrowinning. By harnessing the power of ultrasonic technology, more sustainable and cost-effective zinc electrowinning can be achieved.

Designing and structuring MnO2 coating compositions for efficient and clean zinc electrowinning production

Lead-silver (Pb-Ag) anodes in the zinc electrolysis have resulted in significant environmental pollution and waste of valuable resources due to the influence of the lead corrosion reaction (LCR). Herein, the composition and interfacial structure of manganese dioxide (MnO2) coatings were designed and regulated by controlling the electrodeposition nucleation process using a Pb-Ag anode as the substrate. MnO2 coatings with a three-dimensional spherical bicrystalline-phase (β/γ) hydrophilic structure were synthesized. The introduction of γ-MnO2 not only increased the hydrophilicity of the coating, but also increased the content of the active substances Mn3+ and Oabs, thus improving the intrinsic OER activity of the MnO2 anode. Furthermore, density functional calculations have demonstrated that γ-MnO2 reduces the energy barrier of the determining step and increases the adsorption capacity of OH*, which is conducive to promoting the OER process. It was also demonstrated that the MnO2-coated anode could suppress the generation of Pb4+, thus inhibit the LCR process. Long-term electrolysis experiments have shown that the β/γ-MnO2 composite phase-coated anode can not only improve the oxygen evolution reaction (OER) rate and reduce energy consumption, but also effectively mitigate the generation of lead pollution and further reduce the impurity content of zinc products. This approach can simultaneously achieve economic benefits and environmental protection.

A novel CF/Ti/β-PbO2 composite anode for zinc electrowinning: preparation, electrochemical properties and application

The CF/Ti/β-PbO2 composite was prepared for the first time by thermal decomposition and electrodeposition. Compared with the Pb–Ag anode, the current efficiency and service life of the CF/Ti/β-PbO2 anode increased by 14.92% and 232%, respectively.

Influence of polarisation time and Mn2+ on the electrochemical behaviour of different lead silver anodes

ABSTRACT The influence of polarisation time and Mn content on the electrochemical behaviour of different lead silver anodes in sulphuric acid electrolyte during decay periods has been studied. After 1, 5 and 10 h polarisation followed by one hour decay in zinc electrolyte in the presence of Mn2+, the corrosion current density of Pb-0.5% Ag was higher than that of Pb-0.6% Ag anode and even higher than that of Pb-0.7% Ag anode. It was also found that during 1 h of decay after 5 h polarisation study in the presence and the absence of Mn2+, the Pb–Ag anodes containing different silver contents have better oxide film and less corrosion current density than that of 1 and 10 h of polarisation. Electrochemical impedance results confirmed the mentioned tendency with and without Mn2+ additions. Scanning electron microscope (SEM) analysis shows that the presence of MnO2 on the anode surface provides a protective barrier against leakage of Pb2+ ions into the solution.

Industrial tests of composite porous Pb-Ag anode in zinc electrowinning plant

Industrial tests of composite porous Pb-Ag anode in zinc electrowinning plant

Manganese removal from zinc sulfate electrolyte by electro-oxidation using Pb-Ag anode

ABSTRACT The optimum conditions for manganese dioxide (MnO2) removal were investigated in two simulated conditions, purification and electrowinning, using a Pb-0.7 wt.% Ag electrode. Linear sweep voltammetry and Cyclic voltammetry tests were conducted to study the effect of temperature and concentrations. SEM-EDS and XRD were employed to study the surface characterisations and chemical compositions. The results revealed that the electrowinning operating conditions are more appropriate than the purification conditions for MnO2 removal. The highest current efficiency of manganese removal was 21% which was obtained in the EW electrolyte at 125 A m−2 at 40°C after 2 h of electrolysis. The Current Efficiency was increased significantly at lower Mn ion concentrations (0.1–1.0 g L−1) while it stayed constant beyond the concentration of 1.0 g L−1. The results showed that an increase in temperature depolarised the oxygen evolution reaction and the addition of Mn2+ suppressed formation of PbO2 on anode surface.

PbO2 modified with TiO2-NTs composite materials with enhanced OER electrocatalytic activity for Zn electrowinning.

The high oxygen evolution overpotential of the Pb–Ag anode is one of the main reasons for the high energy consumption in Zn electrowinning. PbO2, owing to its high conductivity, good corrosion resistance and low cost, is widely used as an excellent coating material. In present research, a novel composite Ti/TiO2-NTs/PbO2 material was synthesized through a facile anodization, annealing, electrochemical reduction and galvanostatic deposition. The surface morphology, internal structure and the mechanisms of TiO2-NTs enhancing electrochemical performance were discussed. The results show that the self-organized high aspect ratio TiO2-NTs with diameter of ∼120 nm and length of ∼8 μm were obtained on Ti substrate. The Ti/TiO2-NTs/PbO2 composite material exhibits excellent oxygen evolution performance and good stability in Zn electrowinning simulation solution (50 g L−1 Zn2+, 150 g L−1 H2SO4) at 35 °C. Its oxygen evolution overpotential is only 630 mV under current density 50 mA cm−2, which is 332 m lower than that of Pb-0.76 wt% Ag (η = 962 mV) and only increases 22 mV after 5000 cycles of CV scanning. Its outstanding electrochemical performance is mainly ascribed to the introduction of TiO2-NTs in Pb(CH3COO)2 media since it refines the crystal grains, increases the electrochemical surface area, greatly reduces the charge transfer resistance (25.4 Ω cm2 to 2.337 Ω cm2) and enhances corrosion resistance. Therefore, the Ti/TiO2-NTs/PbO2 material prepared in Pb(CH3COO)2 medium may be an ideal anode for Zn electrowinning.

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

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.

Effects of Ag+ in diaphragm electrolysis on oxygen evolution and corrosion behaviors of Pb and Pb[sbnd]Ag anodes

In this study, the effects of Ag+ (140 mg/L) in an electrolyte on the oxygen evolution and corrosion behaviors of Pb and PbAg (0.6 wt%) anodes in diaphragm electrolysis were investigated by utilizing a variety of tests and analyses, including galvanostatic polarization, mass increment, ion concentration, anodic polarization curve, phase analysis, and scanning electron microscopy of the oxide layer and substrate. The results show that an ion exchange membrane can effectively prevent Ag+ and Pb2+ from penetrating into the cathode chamber and depositing on the cathode. The addition of Ag+ in diaphragm electrolysis significantly lowers the overpotential of oxygen evolution reaction and improves the corrosion resistance of Pb and PbAg (0.6 wt%) anodes. This is mainly attributed to the formation of Ag2O2 on the surface of the anode, which provides good catalytic activity for the oxygen evolution reaction (Ag2O2 can form Ag2O2 hydrate in sulfuric acid solution, Ag2O2 hydrate loses electrons and H+ during electrification, and then Ag2O2 is formed again after electron rearrangement).

Oxygen evolution behaviours of novel porous MnxSiy electrodes for metal electrowinning

In this study, three types of novel porous MnxSiy oxygen electrodes for metal electrowinning were prepared by elemental powders reactive synthesis. The electrocatalytic activity and corrosion resistance of the porous MnxSiy electrodes were evaluated. The results demonstrated that the electrodes with lower silicon content presented lower potential during a 24-h polarization period and that the corrosion resistance of MnxSiy electrodes was enhanced as the Si content increased. Among these prepared oxygen electrodes, the porous Mn5Si3 electrode exhibited the highest catalytic activity towards oxygen evolution reaction (OER) in 1.63 mol l−1 sulfuric acid solutions. The influence of the electrode active surface on electrocatalytic activity was also studied, and the results showed that large active surface greatly promoted the electrocatalytic performance of the electrodes. The porous MnxSiy electrodes were also tested in conditions which simulate industrial zinc electrowinning and compared to conventional Pb and Pb-Ag (0.8 wt%) anodes. The current efficiency of porous Mn5Si3 electrode reached 85.7%, which was comparable to that of Pb and Pb-Ag (0.8 wt%) anodes. Moreover, the zinc cathode exhibited much lower impurity content. Besides, the addition of Mn2+ ions was also found to result in blockage of pores and increase of potential.

Electrochemical corrosion behaviors of Pb-Ag anodes by electric current pulse assisted casting

Electric current pulse was for the first time applied during the casting of PbAg (0.6wt%) anode to have successfully improved its anti-corrosion property and lowered the overpotential of oxygen evolution. It was proven that the electric current pulse applied during the casting has promoted the grain growth of formed equiaxed crystals. Moreover, this treatment contributed to the formation of compact oxide layer which was the reason of the improved corrosion resistance. It was also found that Ag was concentrated at the boundary regions, which well explained the phenomenon that corrosion happened faster along the grain boundaries.

Electrochemical Behaviors of Powder-Processed Pb-Ag Anodes

Pb-based anodes with different Ag contents (0 wt.%, 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.%) were prepared by the powder-processed (PP) method. Electrochemical behaviors of Pb-Ag anodes in the sulfuric acid solution were studied by performing tests of cyclic voltammetry, galvanostatic polarization and anodic polarization. Morphologies and phases of the anode oxide layer after polarization were studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. When the Ag fraction is > 0.4 wt.%, stable oxygen evolution potentials of PP Pb-Ag anodes are lower than those of the cast Pb-Ag (0.6 wt.%) anode. As the Ag fraction increases, the stable potential of the alloy anode decreases while average grain sizes of oxides on anode surfaces increase. However, when the Ag content is > 0.4 wt.%, its effect on surface grain growth becomes insignificant.

Lead-silver anode behavior for zinc electrowinning in sulfuric acid solution

Abstract In recent years, a renewed interest in studying the electrochemical corrosion behavior of lead anodes during zinc electrowinning is probably due to the particularly high sulfuric acid concentrations in zinc electrolyte where lead alloy anodes have high cell voltage and high corrosion rate of lead. The high corrosion rate of lead alloy resulted in Pb contamination on zinc deposit. In zinc electrometallurgy, the electrolyte from a zinc-rich ore contains a significant amount of Mn2+. Mn2+ in the zinc electrolyte results in forming an oxide film on lead anodes during electrolysis. Pb-0.7% Ag anode is generally used in the zinc industry. To improve the technical performance and decrease product cost, other anodes, such as Pb-Ca or Pb-Ag-Ca or Pb-Ag-Ti or Pb-Ag-Se alloys were tested. Till now, none of them has succeeded in the substitution of Pb-Ag anodes in the zinc electrowinning. As an alloying element, silver in small quantities is considered because of the benefits that generates on the anode during electrolysis. During zinc electrolysis, lead dissolution into the zinc electrolyte can be harmful to the quality of zinc deposit. However, the lead silver alloy anode can decrease the lead content in the zinc deposit by pre-treated methods such as blasting and preconditioning.

Oxygen evolution and corrosion behavior of Pb-CeO2 anodes in sulfuric acid solution

Pb-CeO2 composite anodes with different CeO2 contents were prepared by a powder metallurgy method. For comparison, pure Pb and Pb-Ag (0.8 wt%) anodes were also prepared as references by melt casting. The oxygen evolution and corrosion behaviors of the anodes were evaluated by performing measurements of galvanostatic polarizations, Tafel curves, anodic polarization curves, mass increments, and ion concentrations. The morphologies and phase compositions of the anode oxidation layers after polarization were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results showed that as the content of CeO2 increased, the stabilized potential of the composite anodes gradually decreased; the Pb-CeO2 (>1.5 wt%) composite anode exhibited lower stabilized potential and higher electrocatalytic activity than the Pb-Ag anode during galvanostatic polarization. The Pb-CeO2 (>0.5 wt%) composite anode showed better corrosion resistance than the pure Pb and Pb-Ag (0.8 wt%) anode. The increase in CeO2 content improves the compactness and thickness of the oxide layer formed on the anode surface, but excess CeO2 leads to high porosity of the anode, thus deteriorating the performance. The Pb-CeO2 (2.5 wt%) anode showed comprehensively improved electrochemical performance and corrosion resistance.

Effect of ionic liquid additives on oxygen evolution reaction and corrosion behavior of Pb-Ag anode in zinc electrowinning

Three ionic liquid salts, 1-Ethyl-3-methylimidazolium chloride [EMIM]Cl, 1-Ehyl-3-methylimidazolium bromide [EMIM]Br, and 1-Ehyl-3-methylimidazolium ethyl sulfate [EMIM]ESO4 were chosen as additives in order to examine their effects on the oxygen evolution reaction (OER) and corrosion of Pb-0.7%Ag anode in zinc electrowinning. Results of 24 h of anodic polarization showed that the presence of these additives depolarized the OER. A reduction of 25 mV of anodic potential was obtained by addition of 5 mg L−1 of [EMIM]ESO4 to that obtained from free-addition electrolyte. Corrosion measurements employing linear polarization technique revealed that corrosion rate of Pb-0.7%Ag was decreased by ∼25–42% by the addition of [EMIM]ESO4 or [EMIM]Br. Corrosion current was found to be decreased in the order of [EMIM]ESO4 < [EMIM]Br < Gelatin ≤ Blank < [EMIM]Cl. Electrochemical impedance spectroscopy demonstrated that addition of ILS to the zinc sulfate electrolyte increased the charge transfer resistance of the anodic dissolution reaction except for [EMIM]Cl. Zero resistance ammeter and scanning reference electrode techniques showed the same corrosion tendency obtained from other techniques and proved that no localized corrosion was observed in the presence of Cl¯ ions.

Influence of Mn2 + on the performance of Pb-Ag anodes in fluoride/chloride-containing H2SO4 solutions

In this study, surface morphology, inner structure and phase composition of anodic layers on Pb-Ag anode in fluoride/chloride-containing H2SO4 solutions were investigated in the presence/absence of Mn2+. Additionally, corrosion morphology of metallic substrate and anodic potential variation of Pb-Ag anodes were studied as well. The influence of Mn2+ on the anodic layer property and corrosion behavior of Pb-Ag anodes in fluoride/chloride-containing H2SO4 solutions was then clarified. The results revealed that in the presence of Mn2+, anodic layer consisted of an external layer in MnO2/PbO2-PbSO4/MnO2 structure and an inner layer adhering to the metallic substrate. Due to the coverage of an external layer, the corrosion of metallic substrate was relieved by the presence of Mn2+ in fluoride/chloride-containing H2SO4 solution. As was demonstrated, Mn2+ decreased PbO2 concentration in the inner layer, especially in fluoride-containing solution. In the presence of Mn2+, the anodic potential was higher than that in solutions without Mn2+ due to larger thickness and resistance of anodic layer. In addition, the anodic potential was characterized by oscillation in Mn2+-containing solution, indicating low stability of anodic layer. Comparatively, the anodic layer formed in the presence of Mn2+ and chloride ion was more stable than that in solutions containing Mn2+ and fluoride ion.

Anodic Reactions at a Pb-Ag Anode in Sulfuric Acid Solutions Containing Manganese(II)

황산용액에 함유된 망간(II)의 농도가 Pb-Ag양극의 산화거동에 미치는 영향을 1.8에서 2.0 V의 범위에서 정전위법으로 조사하였다. 산화전위가 높고 망간의 초기 농도가 낮은 조건에서는 망간(III)의 농도가 높았으며, 산화반응 후 용액을 분광학적으로 분석하여 이를 확인하였다. 1.8과 1.9 V에서는 $MnO_2$ 가 망간(II)...

Review of oxide coated catalytic titanium anodes performance for metal electrowinning

Conventional lead alloys are widely used in the zinc industry, in spite of their high overpotential and Pb contamination of the deposit during zinc electrowinning. The Oxide Coated Catalytic Anodes (OCAs) are considered to improve cathodic zinc purity and decrease cell voltage during zinc electrowinning. Considering the Ti substrate and its coatings such as (70%) IrO2+(30%) Ta2O5 coatings, the composites of OCAs have low overpotentials 400–500mV less than Pb-Ag anode. It was found that the oxygen evolution potential of the Ti/(Ir-Co) is 370mV lower than that of the lead alloy anode. Ta2O5 has more electric resistance than cobalt oxide and can lead to higher overpotentials. Also, RuO2 is an excellent electro-catalytic rutile structure. Considering generally a low cost coating of Ti substrate, Ni is more appreciable than that of zinc for the two systems of Co-Ni and Co-Zn coated over titanium. Addition of certain chemicals to the zinc electrolyte can decrease MnO2 deposition on the OCA anodes during zinc electrolysis. Moreover, the performance of OCA anodes increased with the nanoparticles addition of both IrO2 and the Sb-doped SnO2. To improve the service life of Ti substrate, procedures such as recrystallization, annealing treatment and surface anodic treatment could be employed. A conductive carbon-polymer has been developed to replace the titanium substrate, which is composed of graphite fibre, carbon black and polyolefin. Finally, aluminum has been studied for matrix because of its good electrical conductivity and mechanical strength.

Electrochemical behavior of mesh and plate oxide coated anodes during zinc electrowinning

The catalytic performance of two oxides coated anodes (OCSs) meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 °C. Their electrochemical behaviors were compared with that of a conventional Pb–0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential (OCP) and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/(IrO2–Ta2O5) mesh electrode is the lowest (3.37 μA/cm2) among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm2 and 38 °C, the Ti/MnO2 mesh anode has the highest potential (1.799 V), followed by the Ti/(IrO2–Ta2O5) plate (1.775 V) and Ti/(IrO2–Ta2O5) mesh (1.705 V) anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/(IrO2–Ta2O5) mesh attains the lowest corrosion current density. The Ti/(IrO2–Ta2O5) mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb–Ag anode by about 245 mV.