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In this work, Ti/PbO2‐MWCNTs anodes modified with different amount with different amount of Tween 80 (0.0–2.0 g/L) were prepared by the direct current electrodeposition method used as anode materials for Zinc electrowinning. The MWCNTs were dispersed in a lead nitrate solution with Tween 80, and the effects of the amount of added Tween 80 on the morphology, phase composition and electrocatalytical performance of lead dioxide coating were investigated. Physical characterizations show that with the increase of the amount of Tween 80, both grain size of PbO2 and carbon content in PbO2 layer firstly increased and then decreased, the preferential orientation and crystallinity of the PbO2 grain growth in the deposition process changed. Electrochemical tests demonstrate that the optimal modified electrode achieved the minimum Eo value and maximum j0 of 2.038 V and 3.781×10−4 A, respectively, an increase of capacitance to 368.8 μF cm−2, and a decrease of charge transfer resistance to 92.74 Ω cm2, which is mainly attributed to the PbO2 electrode modified with Tween 80, coupled with the synergistic effects of MWCNTs doping. [ABSTRACT FROM AUTHOR]

The integration of selectivity and electron transfer ability remains a primary challenge in developing electrode materials for uranium electroextraction. Herein, a phenanthroline‐based supramolecular organic framework (MPSOF) is elaborately constructed as a pioneering cathode material through the hydrogen bond‐driven self‐assembly of melamine and 1,10‐phenanthroline 2,9‐dicarboxylic acid (PDA) for selective and continuous electrochemical uranium extraction (EUE). PDA moieties selectively capture UO22+, while the hydrogen bond‐supporting frameworks provide an efficient electron transfer channel for the redox of UO22+. These structural features enable the rapid formation and spontaneous shedding of uranium precipitate from MPSOF, allowing for the regeneration of the selective adsorption sites. As a result, MPSOF‐mediated EUE exhibits a high extraction capacity of 7311 mg U g−1 at a low voltage of −3.5 V but does not reach equilibrium. Cyclic EUE is employed to uranium extraction from simulated high‐salt radioactive effluents and attains high selectivity for uranium. The electroextraction mechanism is confirmed, wherein uranium species transform into (UO2)O2·4H2O. This work not only provides an efficient electrode material for uranium electroextraction, but also presents a novel electrochemical strategy for separation and adsorption of other radionuclides and contaminant ions. [ABSTRACT FROM AUTHOR]

The performance of the anode varies from the impurity ions in the copper electrowinning process. This work focused on the variation of the electrochemical behavior of the Pb-0.06%Ca-1.2%Sn anode as the Fe ions (Fe3+ and/or Fe2+) existed in the electrolyte by electrochemical characterization. Copper electrodeposition experiments were conducted under a current density of 300 A/m2, with the Fe ion concentration in the electrolyte controlled within the range of 0 to 20 g/L and the Cu ion concentration maintained at 45 g/L at a temperature of 45 °C. The variation in the corrosion resistance, catalytic activity, and structural composition of the anode film layer was analyzed in-depth according to the presence of Fe ions. The results show that the structure of PbO2 on the surface of the film was changed as Fe ions doped into the anode film, and the oxygen evolution activity of the anode was also improved. However, the corrosion resistance decreased with increasing Fe3+ concentration. Furthermore, the addition of 2 g/L Fe2+ in the electrolyte containing 2 g/L Fe3+ led to an elevation in the corrosion resistance of the anode to some extent and further increased the oxygen evolution activity. [ABSTRACT FROM AUTHOR]

Fast technological progress in the electronics industry leads to an ever-growing generation of electronic waste or e-waste. Proper recycling of e-waste is, therefore, of great importance, not only for ecological reasons but also to valorize its material content. With gold being the most valuable metal in electronic waste, it is the main driver for recycling, even though it is only present in minor concentrations compared to base metals like copper and iron. This study presents a continuous flow module for potential-controlled electrowinning of gold out of AuCl4− complexes from a multi-metal solution containing nickel, copper, iron, and gold ions, as a representative solution of a typical Printed Circuit Board leachate after a pre-washing and gold leaching step. Concentrations as low as 0.1 mM of AuCl4− were selectively reduced to metallic gold on a glassy carbon plate in a continuous flow cell for 4 h with a maximum recovery of up to 86%. Both electrochemical and engineering parameters were investigated, such as the impact of the flow rate, potential, presence of competing reactions from other ions in the solution, and the addition of turbulence promoters in an attempt to optimize the electrowinning. An increase in recovery was observed by raising the flow rate, whereas the potential showed an optimum at + 0.4 V vs Ag/AgCl, with lower potentials leading to more side reactions and lower current efficiencies. Addition of turbulence promoters mainly played a role in the surface utilization and crystal growth, leading to similar overall recoveries but with a more homogeneous deposit and lower variation. With this technique, it is demonstrated that selective gold electrowinning from small concentrations in the presence of base metals, such as copper, nickel, or iron, is feasible in an efficient manner. [ABSTRACT FROM AUTHOR]

The optimization of the cobalt electrowinning process is crucial to enhance the quality of metallic deposits, as cobalt plays a fundamental role in the manufacturing of high-tech materials. Thus, the effect of the additives sodium lauryl sulfate (SLS), boric acid, and Cl− ions on the physical and chemical properties of cobalt deposits obtained by electrowinning are scarce in the literature. The present study investigated the effect of additive concentrations on current efficiency (CE), specific energy consumption (SEC), and the physical and chemical properties of cobalt deposits (crystalline phases, grain and crystallite sizes, morphology, purity, and microhardness) produced through electrodeposition tests in presence of a cobalt sulfate solution at 200 A m−2, 60 °C, and pH 4. The results indicated that the presence of 0.05 g L−1 of SLS in the solution led to the best values for CE (95.5 pct) and SEC (1.80 kWh kg−1), as well as the production of uniform deposits. Cracks were identified in the cross-sectional area of the metallic deposits under all evaluated conditions, with the detection of oxygen in these areas, except for Cl− ions. Higher concentrations of SLS and boric acid resulted in the production of deposits with low microhardness and less fragility, attributed to the increased of crystallite and grain sizes. The predominant crystalline phase for all deposits was hexagonal close-packed (HCP), but the presence of SLS and Cl− ions led to the rise of significant percentages of the face-centered cubic (FCC) phase. Furthermore, the increase of Cl− ions concentration led to an increase of residual deformations in the crystalline structure of cobalt deposits, while the increase of SLS and boric acid concentrations led to a decrease of these residual deformations. [ABSTRACT FROM AUTHOR]

This study outlines findings from an investigation into the development of a hydrometallurgical process for manufacturing various forms of zinc perrhenate, entirely from waste from recycling and from the Zn–Pb industry. Scraps of Re-bearing Ni-based superalloys and acidic waste, circulating zinc solutions generated during the production of Zn by the electrolytic method and which contain >45 g/dm3 of Zn, Na, Mn, and Mg, were used in the research. In the publication, the conditions for the production of three types of zinc perrhenate, i.e., Zn(ReO4)2·4H2O, Zn(ReO4)2, and Zn(ReO4)2·2H2O, are presented. As a result of the analysis of the obtained results, it was concluded that to obtain the above-mentioned forms of zinc perrhenate, zinc carbonate can be used, precipitated from acidic, waste, and multi-component solutions after their prior neutralization to pH 4.0 and partial purification from Mn, Mg, and Na using metallurgical zinc oxide. Zinc carbonate should be precipitated using Na2CO3 at pH 6.3 and subsequently purified from other impurities, i.e., Mg, Na, and Mn, using aqueous ammonia solutions. As a result, zinc carbonate was obtained, which was used in a reaction with an aqueous solution of HReO4 to produce zinc perrhenate. The precipitated forms of Zn(ReO4)2 were obtained by appropriately drying the crude and hydrated Zn(ReO4)2 to obtain its tetrahydrate, dihydrate, and anhydrous forms, respectively, using drying temperatures of 55, 135, and 185 °C. The developed technology has been submitted for a patent and is an example of a technology founded on the principles of sustainable development, with a particular emphasis on the minimalization of loss of rhenium and zinc at all stages of its realization. [ABSTRACT FROM AUTHOR]

The global gold ore grade has been decreasing, and the mineralogy is now more diverse and complex. This has necessitated the utilization of low-grade ores previously not used. During the cyanidation process of such ores, copper cyanide complexes form that are competitively adsorbed with gold onto activated carbon. Therefore, to decrease the amount of copper in the pregnant electrowinning electrolyte, a series of copper adsorption experiments were done to limit the amount of copper that adsorbs onto activated carbon. Tests on selective copper cold stripping were also conducted to selectively elute copper from loaded head carbon before the elution process. The results showed that increasing the solution pH from 9 to 11 decreased the copper adsorption from about 15.1% to 8.2%, but on the other hand the gold adsorption decreased from 98.7% to 95.1%. The optimal determined cold stripping parameters were 2% cyanide strength, 1% sodium hydroxide, 27 g/L carbon concentration and 4 h residence time. This experimental procedure effectively reduced the amount of copper in the gold leaching process and has potential to be used in large-scale applications. [ABSTRACT FROM AUTHOR]

The possibility of extracting Cu compounds through adsorption using galvanic sludge modified with solutions of humic acids was investigated. The chemical and structural composition of rigid galvanic sludge from printed circuit board production was examined. The primary phase-forming element is Fe compounds in the form of β-FeOOH, constituting up to 45% of the sludge mass. X-ray phase analysis of the sludge revealed the presence of two main phases: akaganeite (β-FeOOH) and an atacamite-like crystalline phase of copper hydroxychloride (Cu(OH)3Cl) in quantities exceeding 10%. The conditions for leaching Cu compounds from the sludge and the effect of thermal treatment on the sludge adsorption capacity were determined. Copper was leached from galvanic sludge using an H2SO4 solution within the pH range of the equilibrium solution of 3–5.5. This allowed for the leaching of up to 97% of copper, with minimal dissolution of Fe compounds. The Cu concentration in the leaching solution reached 10–15 g/dm3, while the concentration of Fe ions did not exceed 1 mg/dm3, enabling the subsequent utilization of these solutions for Cu electroextraction. The modification of the sludge with humic acid solutions increases its adsorption capacity for copper ions by more than threefold. [ABSTRACT FROM AUTHOR]

Due to the excellent activity and stability of MnCo 2 O 4 toward the oxygen evolution reaction (OER) in acidic solution, a Pb–MnCo 2 O 4 composite anode for zinc electrowinning was prepared by embedding dispersed MnCo 2 O 4 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–MnCo 2 O 4 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–MnCo 2 O 4 composite anodes. Compared with that on the Pure-Pb anode, the oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable in a 160 g L−1 H 2 SO 4 solution containing 4 g L−1 Mn2+. Consequently, the Pb–MnCo 2 O 4 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 PbO 2 content of the oxide layer, the Pb–MnCo 2 O 4 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 anodic potential of Pb–MnCo 2 O 4 composite anode is 70 mV than the Pure-Pb anode. • The oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable. • Pb–MnCo 2 O 4 exhibits a smaller tafel slope and lower charge transfer resistance of OER. • The incorporation of MnCo 2 O 4 significantly reduces the production of anode slime. [ABSTRACT FROM AUTHOR]

The present work is focused on the recovery of pure copper metal from leach liquor of discarded printed circuit boards (PCBs) using solvent extraction and electrowinning techniques. Leach liquor containing copper was produced from PCBs of scrap computers using pretreatment followed by the leaching technique. The obtained leach liquor contained 19.35 g/L of copper and 6 M concentration of nitric media. From the obtained leach liquor, systematic solvent extraction and electrowinning studies were carried out for maximum extraction of copper, leaving other metals to be present as impurities. Various process parameters of solvent extraction viz. effect of pH, contact time, phase ratio, and so on were studied and optimized. McCabe–Thiele diagram was plotted, which shows that complete recovery of copper can be achieved in three stages using 40% LIX 84IC and O/A ratio 1/1 at equilibrium pH 2.2 in a mixing time of 20 min. The loaded copper was stripped using 10% H2SO4. The obtained strip solution containing 19.35 g/L Cu was electrowinned at the optimized condition, i.e., 8 hours' time and 205 A/m2 cathode density with 99.99% current efficiency. 99.8% pure copper metal was obtained. The developed process is environmentally sustainable and has potential to be commercialized after scale-up studies. [ABSTRACT FROM AUTHOR]

Dynamic process models present an opportunity to investigate optimization and control strategies for the energy-intensive copper electrowinning process. In this paper, a dynamic semi-empirical model of the copper electrowinning process was developed to predict the copper yield, current efficiency, and specific energy consumption. The model uses input variables readily measured in industrial tankhouses and incorporates the ability to induce step or pulse disturbances in the electrolyte composition or flow rate. Dynamic bench-scale electrowinning data were used to show how the model may be calibrated and validated for use in predicting electrowinning performance. Overall, the performance of the developed dynamic model lends credence to the application thereof for operator training, process monitoring, and early fault detection. The model also represents a further step towards investigating advanced control strategies for the electrowinning process. [ABSTRACT FROM AUTHOR]

The effects of thallium(I) ions on the surface morphology, cathode current efficiency, cathode potential, polarization behavior, and electrochemical impedance spectroscopy of zinc electrowinning were studied by scanning electron microscopy and electrochemical measurements. The results showed that with increasing thallium(I) ion concentration in the electrolyte, the hydrogen evolution reaction and the galvanic effect produced during zinc electrowinning increased. When the concentration of thallium(I) ions in the electrolyte was 0.6 mg L-1, the exchange current density of the zinc electrowinning process was maximum and the polarization was minimum. At this time, the Rct of the equivalent circuit was minimum, the CPE value was minimum, and the charge transfer rate was maximum. The cathodic current efficiency decreased from 80% to 55% when the thallium(I) ion concentration was 1.5 mg L-1. The presence of thallium(I) ions also affected the surface macro- and microstructure of the zinc deposits. This result confirmed that thallium(I) ions have a significant negative influence on the electrowinning of zinc. [ABSTRACT FROM AUTHOR]

In Northern Chile, large amounts of highly corrosive solutions are currently generated in the process of cathode washing after completing the electrowinning or electrorefining process of copper. This study investigates the electrochemical behavior of ASTM A36 carbon steel in pregnant-leach-solution (PLS) wash water. Measurements of electrochemical impedance spectroscopy and linear sweep voltammetry, complemented with weight loss measurements, were performed. Four ratios of PLS containing reverse osmosis (RO) water are evaluated, considering both quiescent and rotating conditions of the steel specimen. The results indicate that oxygen reduction, hydrogen evolution, and iron oxidation reactions are all involved during the corrosion of carbon steel in pure RO water, with the corrosion rate increasing up to 4 times under rotating conditions. In the case of corrosion in RO wash water containing PLS, a galvanic process occurs whereby copper is reduced at the expense of iron oxidation, superimposed on former partial reactions. The deposited copper induces notable corrosion inhibition of steel, observed as a significant drop in corrosion rate from high initial to constant residual values. Morphological and X-ray analyses support that corrosion is affected by oxide layer formation and galvanic copper deposition, confirming the results obtained from electrochemical analysis and weight loss measurements. [ABSTRACT FROM AUTHOR]

During hot-dip galvanization, wastes such as bottom dross, zinc ash, spent pre-treatment solutions, and galvanizing flue dust (GFD) are generated. In scientific publications, research devoted to GFD waste recycling is absent, and companies generating this waste require a solution to this complex problem. GFD is often landfilled in hazardous waste landfills. However, it is possible to process this waste hydrometallurgically, where GFD is first leached, the solution is refined, and finally, zinc metal is obtained by electrowinning. During specific environmentally friendly leaching, not all solid GFD is dissolved, and the aim of this study is to process the remaining solid GFD residue. The analysis shows that the GFD residue material mainly contains zinc (42.46%) in the form of oxides, but there is also a small amount of polluting elements such as Al, Fe, and Pb. This study examines the leaching of the samples in HCl and H2SO4 under different conditions with the aim of obtaining a solution with a high concentration and high leaching efficiency of zinc. The L/S ratio of 3, 4 M H2SO4, and ambient temperature proved to be optimal for the leaching of the GFD residue, where 96.24% of zinc was leached out, which represents a zinc concentration of 136.532 g/L. [ABSTRACT FROM AUTHOR]

A manganese and manganese dioxide co-tank electrodeposition process was developed to investigate the effect of four factors by using a one-factor test, enhance cathode and anode current efficiencies, and reduce energy consumption. Response surface methods was adopted to examine the relationship among the four variables temperature, anode and cathode electrodeposition efficiency, compartment sulfuric acid concentration, and cathode ammonium sulfate concentration. A quadratic regression fitting model was developed to determine the optimal electrolysis conditions. A cathode ammonium sulphate concentration of 107. 11 g/L, an anode sulphuric add concentration of 2. 8 mol/L, a septum chamber concentration of 0. 516%, and a temperature of 40. 2 _ were the bes--optimized factor combinations leading to the best cathode current efficiency of 84.79% and anode current efficiency of 68.43% .The study showed that ammonium sulphate concentration and temperature significantly impacted cathode electrolysis efficiency. In contrast, sulphuric acid concentration and temperature had the most significant impact on anode electrolysis efficiency. The electrolytic manganese metal is securely deposited, and the electrolytic manganese dioxide particles are unholy. [ABSTRACT FROM AUTHOR]

Development of highly efficient electrochemical devices is as a desirable approach to hydrogen industries. Hydrogen depolarization anode (HDA), is considered as an advanced approach to dramatically reducing the high energy consumption for hydrometallurgy. To evaluate the feasibility of HDA technology in zinc electrowinning and its technical features, we prepare two kinds of HDAs. After 48 h operation in industrial electrolyte, the low cell voltage (below 1.5 V), low power consumption (below 1320 kWh/t) and high Faraday efficiency (above 95%) confirm the good technical prospect of this hydrogen-participated hydrometallurgy. Besides, the anode degradation should also be paid attentions. The lower hydrophobicities (i.e., PVDF-bonded HDA), leading a better electrolyte wettability, make a better initial electrocatalysis performance but a faster degradation. Through the structural changes of electrodes before and after electrowinning operations, the degradation behaviors seem different on their corrosion regions of PVDF-bonded HDA (mainly on platinum-carbon interface) and PTFE-bonded HDA (carbon supports). Whereas, we also provide some insights into materials selections, structural states, and operation conditions for the future development of using HDA technologies for hydrometallurgies, with the expectation of increasing ability to design and tailor highly efficient electrochemical devices. [Display omitted] • Hydrogen depolarization anodes are prepared for the zinc electrowinning. • The low cell voltages endow a promising application of hydrogen depolarization. • The different hydrophilicities led different performance and corrosion regions. • Some insights were given for the further development. [ABSTRACT FROM AUTHOR]

The utility of molten chloride salts in concentrating solar power (CSP) is dependent on the ability to maintain low corrosive impurities. Without proper purification, the corrosion rates of containment alloys exceed the industry standard of corrosion—under 20 μm/year. An extensive body of literature focuses on the initial purification stage of molten chloride salts. However, occurrences such as maintenance, leaks, and so forth expose the salt to the atmosphere and reintroduce impurities. Therefore, it is critical to develop a purification strategy that can control impurity levels during CSP plant operation. Here we present the design and fabrication of a purification vessel to continuously remove impurities out of flowing molten salt.

A major concern in cobalt electrowinning is the generation of H2 along with cobalt deposition on the cathode, which results in current efficiency drop, specific energy consumption increase, as well as poor deposit quality. In this paper, the influence of initial pH, temperature, current density, and Co2+ ions concentration on current efficiency and specific energy consumption for cobalt electrowinning in a batch cell for 24-h electrolysis was investigated through a two-level factorial design. Preliminary analysis from cyclic voltammograms and current-time curves indicated a current efficiency of 86.2%, with 60 g/L of Co2+ at pH 4.0. The statistical study indicated that temperature presented the greatest significant contribution for the response variables. The best result was achieved with initial pH 4.0, 70°C 100 A/m2 and 60 g/L of Co2+, leading to a current efficiency of 78.8% and a specific energy consumption of 2.3 kWh/kg. As the pH drops considerably during the tests, its influence demands further studies. [ABSTRACT FROM AUTHOR]

In zinc electrowinning, small amounts of manganese ions additives are needed in the electrolyte to reduce the corrosion of anodes and minimize the contamination of cathodic zinc by dissolved lead. However, excess manganese oxide could cover the dimensionally stable anodes (DSA) surface and decrease their service life. Additives of phosphoric acid are put in the electrolyte to complex the manganic Mn3+ ion and hence reduce its disproportionation to MnO2. In the investigation, phosphoric acid was added to sulfuric acid or zinc electrolytes, and conventional and recent electrochemical measurements were carried out to examine electrochemical behaviour of DSA (Ti/IrO2-Ta2O5) anode during zinc electrolysis at 48 mA/cm2 and 39°C. It was observed that the anodic potentials of DSA anodes were lower by 27 mV after 5 h polarization in the zinc electrolyte containing 35 g/L phosphoric acid at 39°C. Electrochemical impedance measurements show that the addition of 35 ml/LH3PO4 to the zinc electrolyte can increase impedance resistances of the DSA mesh anodes. Cyclic voltammogram studies (CV) at a scan rate of 5 mV/s without agitation show that the oxidation peak in the solution with 35 ml/L phosphoric acid addition is highest, followed by that with 17 ml/L phosphoric acid addition and that without addition of phosphoric acid. [ABSTRACT FROM AUTHOR]

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The leaching of Cu in ammoniacal solutions has proven an efficient method to recover Cu from waste printed circuit boards (WPCBs) that has used by many researchers over the last two decades. This study investigates the feasibility of a counter-current leaching circuit that would be coupled with an electrowinning (EW) cell. To accomplish this objective, the paper is divided into three parts. In Part 1, a leaching kinetic framework is developed from a set of experiments that were designed and conducted using end-of-life waste RAM chips as feed sources and Cu(II)-ammoniacal solution as the lixiviant. Various processing parameters, such as particle size, stirring rates, initial Cu(II) concentrations, and temperatures, were evaluated for their effects on the Cu recovery and the leaching rate. It was found that the particle size and initial Cu(II) concentration were the two most important factors in Cu leaching. Using a 1.2 mm particle size diameter and 40 g/L of initial Cu(II) concentration, a maximum Cu recovery of 96% was achieved. The Zhuravlev changing-concentration model was selected to develop the empirically fitted kinetic coefficients. In Part 2, kinetic data were adapted into a leaching function suitable for continuously stirred tank reactors. This was achieved via using the coefficients from the Zhuravlev model and adapting them to the Jander constant concentration model for use in the counter-current circuit model. Part 3 details the development of a counter-current circuit model based on the relevant kinetic model, and the circuit performance was modeled to provide a tool that would allow the exploration of maximum copper recovery whilst minimizing the Cu(II) reporting to electrowinning. A 4-stage counter-current circuit was modeled incorporating a feed of 35 g/L of Cu(II), achieving a 4.12 g/L Cu(II) output with 93% copper recovery. [ABSTRACT FROM AUTHOR]

This review discusses the electrochemical principles involved in the recovery of metals from aqueous solutions and fused salt electrolytes. In this article we concentrate on electrolytic processing of different types of metals with an emphasis on the significant role of electrochemical principles together with free energy and activity in electrowinning and electrorefining of common and reactive metals. Based on discharge potentials, metals are classified into three categories with respect to their characteristics of deposition from aqueous electrolytes without hydrogen evolution, under hydrogen over-voltage, and only from fused electrolytes. [ABSTRACT FROM AUTHOR]

For decades, the steel production industry has been one of the largest sources of CO2 emissions, accounting for 7% of global CO2 emissions, of which 70% is emitted in the iron-making process. Currently, the main low-carbon iron production route is hydrogen metallurgy, which uses renewable energy to generate electricity, electrolyze water to produce hydrogen, and reduce iron with hydrogen. Thus, hydrogen metallurgy is also electrometallurgy. In this context, using the green electric energy one-step electrowinning of iron (ERI) will achieve technical route superiority. Developments in new energy generation technologies have led to renewed interest in ERI because of its green and low-carbon properties. In this study, progress in research into ERI was reviewed, and ERI categories, including molten salts, alkaline aqueous solutions, acidic aqueous solutions, and ionic liquids systems, were discussed. On this basis, ERI methods for various systems, including molten oxide electrolysis (MOE), Cambridge process (FFC), electrowinning, and ionic liquids-based methods, were introduced. Finally, the main challenges and possible solutions were summarized, and the development prospects and opportunities were prospected. The present research work will be beneficial to the development of this field. [ABSTRACT FROM AUTHOR]

In recent years, lead dioxide coatings have received extensive attention as promising anode material for electrochemical processes. In the present study, the electrodeposition of PbO2 on a Ti substrate from nitrate bath was investigated to serve as the oxygen evolution anode for electrowinning of nonferrous metals. The effect of predeposition of the α-PbO2 interlayer between the Ti substrate and the β-PbO2 top layer, as well as the use of additives such as copper ions and sodium dodecyl sulfate in the electrolyte was studied. The coatings were characterized using regular and grazing-incidence X-ray diffractometry, and scanning electron microscopy (SEM) techniques. The electrochemical properties of the prepared PbO2-coated Ti electrodes were evaluated and electrocatalytic activity was quantified using imax from cyclic voltammetry, in combination with linear sweep voltammetry, electrochemical impedance spectroscopy, and accelerated life test. It was found out that the Ti/α-PbO2/β-PbO2 electrode produced in a nitrate solution containing NaF, Cu(NO3)2, and SDS exhibited the most favorable electrochemical performance. Under these conditions, a prominent increase in imax (17 times of that for the sample with no additives and interlayer) and a notable decrease in oxygen evolution potential from 2.05 to 1.85 V were achieved. [ABSTRACT FROM AUTHOR]

Nickel-bearing zinc plant residues (cold filtercake, CFC) cause a serious threat to the environment. In this research, nickel deposits from an electrowinning from a nickel sulfate electrolyte containing a high concentration of zinc as an impurity were studied in two sections. In the first, effects of four parameters including Ni2+ concentration, pH, temperature and current density have been studied in a synthetic sulfate electrolyte, and based on current efficiency (CE) and morphological characterizations of the deposits, the optimum conditions were chosen as 30 g/L Ni2+, pH 3.5, 45°C and 200 A/m2. Subsequently, the effect of zinc impurity in the range of 0–600 mg/L was studied in terms of CE and morphology, purity and texture of the nickel deposits. The CE decreased as well as the deposit surface quality and purity by increasing the zinc concentration. Field emission scanning electron microscopy (FESEM) analysis revealed that when the Zn2+ concentration in the electrolytes increased from 0 mg/L to 75 mg/L, a continuous decrease in the nickel particle size was detected. [ABSTRACT FROM AUTHOR]

Iron is one ol the undesired element with high content and dillicult to remove in the raw materials ol zinc hydrometallurgy, and the Fe2+ ions are one ol the impurity that are ol great concern in the zinc electro winning process. The simulated zinc sullate solution containing Fe2+ was used to carry out zinc electrowinning experiments. The effects of Fe2+ concentration, current density, time, electrode distance on the current elliciency, power consumption and zinc morphology were studied systematically. The results showed that the current elliciency was seriously reduced and the power consumption per ton ol zinc was signilicantly increased when the concentration ol Fe2+ in the zinc sullate electrolyte was more than 6 mg/L, meanwhile the cathod zinc was redissolved. As the concentration ol Fe2+ was below 6 mg/L, the optimized operating conditions were current density ol 400 A/m2, electrode distance ol 4 cm and electro winning time of <16 h. More than 90% ol the current elliciency, less than 2 950 kWh ol the per ton zinc power consumption and high quality ol cathode zinc with smooth and Ilat surface was obtained At these optimized conditions. [ABSTRACT FROM AUTHOR]

This study shows the feasibility of recovering copper directly from Pregnant Leaching Solutions (PLS), using the reactive electrodialysis technique, without the need of solvent extraction. The copper PLS contained the following ion concentrations: Cu2+ 2.0–2.5 g/L; pH 1.5–1.8; SO 4 2 − 90–95 g/L; Cl− 8–10 g/L and total iron of 8–10 g/L. The copper electrowinning process is limited by the mass transport capacity of the system and by impurities that decrease the yield. To increase the selectivity and the copperproduction rate, a reactive electrodialysis (RED) cell was developed. The cell contained four compartments, two anion-exchangemembranes and a bipolar electrode to increase the production rate. This cell recovered copper and sulfuric acid at the anolytes. Thebest result was a current efficiency of 99% and specific energy consumption of 2.11 Wh/kg Cu using a current density of 80 A/m2 at 55°C and flow of 100 mL/s. [ABSTRACT FROM AUTHOR]

In this article, square wave voltammetry was used to investigate both anodic and cathodic reactions in manganese electrowinning systems. The generated trivalent manganese ions on the anode would enter the solution and undergo a hydrolysis-disproportionation reaction in neutral or weakly acidic solutions. Nevertheless, permanganate ions would form on the electrode surface under strongly acidic conditions, which would subsequently form manganese dioxide through comproportionation reaction. At the cathode, selenium reduction is a crucial process for the deposition of manganese metal and concentration of hydrogen ions exerts a vital influence on this process by affecting the acid–base balance. Analytical methods derived from this study could also be useful for other electrometallurgical processes. [ABSTRACT FROM AUTHOR]

The paper describes a small full-scale plant based on the Gold-REC 1 process, designed and patented by the University of L'Aquila; the hydrometallurgical process allows the treatment of printed circuit boards (PCBs). The first step is a mechanical treatment to reduce the size of the scraps below 2 mm. The extraction of base metals occurs in a first reactor by a sulfuric acid/hydrogen peroxide solution. After filtration, the solid is leached again with thiourea and ferric sulfate in a sulfuric acid solution to extract gold and silver. This second solution is sent to an electrolytic cell where gold is recovered as metal powder. The resulting solution undergoes a second electrowinning, where silver is deposited on the cathode. The first pregnant solution undergoes recovery of Cu and Sn. A simulation was developed using lab-scale trial results. The 350 tons PCBs/year, running in a batch operating mode, produces around 43.8 kg/year of gold, 85.8 kg/year of silver, 42.4 tons/year of copper, and 7.2 tons/year of tin oxide. The results show the profitability of the process: the net present value is EUR 10.7 M, with an internal rate of return of 150% and a discounted payback time of 2 years. [ABSTRACT FROM AUTHOR]

Zinc is an important non-ferrous metal material, of which the hydrometallurgy process has requirements for anode materials. In the present work, Pb-0.6%Sb/α-PbO 2 /β-PbO 2 -MnO 2 (CNTs) composite electrodes with different proportions of α/β-PbO 2 were obtained and compared before and after zinc electrolytic simulation process. The optimal one was contrasted with traditional Pb-0.8 wt%Ag anode in long-period zinc electrowinning application. It was found that α-PbO 2 transition layer could effectively improve the electrodeposition distortion of β-PbO 2 surface and make the corrosion resistance better. Novel composite anode with more β-PbO 2 proportion showed weaker internal resistance and greater OER electrocatalytic activity. The anode obtained by controlling the electrodeposition time of α&β-PbO 2 phases at 1.5 h & 1 h had the best physical and chemical properties. Its cell voltage value (2.833 V) was 299 mV lower than that of traditional Pb-0.8 wt%Ag anode (3.132 V) in zinc electrodeposition. In addition, the compactness of the composite anode was improved under the function of active particles. The energy-saving effect of novel composite anode in long-period zinc electrowinning application was obvious. • The characteristics of Pb-0.6%Sb/α-PbO 2 /β-PbO 2 -CNTs novel composite anode were examined. • The performance of the novel composite anode and traditional Pb-0.8 wt%Ag anode were compared. • A long-term (8 days) zinc electrowinning experiment was conducted. [ABSTRACT FROM AUTHOR]

The gallium electrowinning process is always accompanied by hydrogen evolution reaction that results in low current efficiency (CE). In this manuscript, cyclic voltammetry and chronoamperometry studies were carried out to investigate the gallium cathode behavior under various conditions and explore the parameter that is beneficial to improve the CE. The CE of the lead and copper cathodes was higher, while gallium deposited on the titanium, SUS316, and SUS304 cathodes was readily separated. Increasing the overpotential and gallium concentration or decreasing the pH within a certain range was all beneficial to improve the CE, while the temperature had no significant effect on the CE. Kinetic studies of gallium electrodeposition were carried out. The gallium electrodeposition process was determined as mixed control and forced convection is expected to further improve the CE. The apparent activation energy and kinetic current from the electrochemical reactions were determined to be 23.335 kJ mol−1 and 47.6 mA, respectively. [ABSTRACT FROM AUTHOR]

The anode material is one of the determining factors for the success of the electrowinning process. This study aims to coat the graphite substrate with β-PbO2 to produce an inert graphite/β-PbO2 composite material with low cost and good quality. The graphite/β-PbO2 synthesis is expected to be used as an anode for inert composites for electrowinning processes. The β-PbO2 deposition layer was prepared on the surface of the graphite substrate by an electrodeposition process using a sulfuric acid electrolyte. The effect of electrolyte concentration and voltage on graphite/β-PbO2 synthesis was investigated using a potentiodynamic polarization test through Tafel analysis. Experimental data have shown that there is an increase in the current density value at the beginning of the process and then a decrease due to passivation; this is due to anodic polarization in the graphite/β-PbO2 synthesis process. Suitable conditions can effectively increase the rate of formation of β-PbO2. The results of scanning electron microscopy with energy-dispersive X-ray spectroscopic analysis of the formed crystal structure showed that the β-PbO2 deposition layer obtained had a well-formed tetragonal structure at a voltage of 9 V. [ABSTRACT FROM AUTHOR]

The paper deals with the torsional rigidity of homogenous and orthotropic beam with rectangular cross section. The torsional rigidity of the considered beam is defined in the framework of the Saint-Venant theory of uniform torsion. Exact and approximate solutions are given to the determination of the torsional rigidity. The shape of cross section is determined which gives maximum value of the torsional rigidity for a given cross-sectional area. The dependence of torsional rigidity as a function of the ratio shear moduli of beam is also studied. [ABSTRACT FROM AUTHOR]

The potentiodynamic experiments of the nickel effects on the zinc electrodeposition have been done to understand the impact of Ni impurities on the electrowinning of Zn from spent pickling liquor. The nickel chloride solutions of Ni concentrations 90 and 1 g/dm3 were used as the electrolytes. The latter was also mixed with 90 g/dm3 Zn in the experiments. All the runs were carried out at room temperature with 40 mV/s continuous polarization speed and with 1/s sampling rate. It was observed that nickel electrodeposition from chloride media containing 90 g/dm3 Ni started with the generation of hydrogen bubbles, entirely blocking the cathode surface. Only a slight current development was observed until the polarization potential ~ -0,8 V. The visual observation showed bubbles also formed at the anode, which may represent chlorine and/or oxygen evolution. While, in the electrodeposition of nickel with only 1 g/dm3 Ni concentration in the electrolyte, metal deposition was hardly observed, but visible hydrogen bubbles constantly blocked the cathode surface. A similar tendency was observed in the mixed-solution electrolysis cell; the initial tiny bubbles accumulated at the cathode surface more than in the pure Zn solution. The enhancement of H2 evolution indicates how nickel deposition may contribute to the loss of useful current in the process of Zn electrodeposition. The mass of nickel deposited from the mixed solutions significantly decreases as the Ni concentration decreases in the electrolyte, while the mass of deposited zinc is relatively constant. It means that the purity of the produced Zn is appreciably higher - with respect to Ni - if nickel is efficiently eliminated from the solution before electrowinning. [ABSTRACT FROM AUTHOR]

This study aimed to recover copper and gold from a waste printed circuit board (WPCB) using monosodium glutamate (MSG) supplemented with a clean oxidizer(s) under 30 °C, 150 rpm, and an initial pH of 7.00. The solder mask of WPCBs needed to be removed before leaching. At the first leaching, 93% of copper was selectively leached from solder–mask–free WPCBs within 3 h using 0.75 M MSG with 0.50% (w/v) H 2 O 2 . Then, gold (86%) was extracted from the first residue for 3 h by 1 M MSG with 0.25% (w/v) H 2 O 2 . In the downstream process, 98–100% copper could be directly recovered within 5–6 h from the first leachate by electrowinning (EW). However, gold in the second leachate required separation and purification processes before EW. At 4 h, 98% gold was adsorbed onto the activated carbon. Most impurities were removed from gold-loaded activated carbon by pre-elution using 0.05 M EDTA for 0.5 h without gold release. Afterward, 99% gold was eluted by diluted aqua-regia within an hour. Finally, the gold could be harvested perfectly using EW for 2 h. This complete copper and gold recycling process delivers an innovative concept for hydrometallurgical study and has the potential to develop into a practical industry. [ABSTRACT FROM AUTHOR]

The amount of waste electrical and electronic equipment (WEEE) has been intensely increasing over the recent decades. In this view, the efficient recovery of metals from WEEE will allow a secure supply of raw materials and will contribute to a circular economy. Among many factors currently affecting the contribution of recycling, is the lack of suitable technologies for WEEE treatment in an environmentally friendly way. Current trends in eco-friendly technologies applied for gold, silver, copper, and tin recovery by electrowinning are reviewed in this paper. In addition, a case study on the perspectives of tin electrowinning has been evaluated. Tin can be present in rather high quantities in WEEE; moreover, its price is about three times higher than that for copper. The electrorecovery of tin has been carried out in cooperation with JSC "Elektronikos perdirbimo technologijos". The eco-friendly process based on electrowinning from citric acid-containing leachates is elaborated. The citrate-based solutions have been chosen because citric acid is considered to be an environmentally friendly component. A high deposition rate and current efficiency have been achieved at a deposition potential −0.85 V at 60 °C. However, additional steps would be beneficial to diminish the interference of metals present in the scraps, such as Pb(II) and Cu(II), on tin electrorecovery. [ABSTRACT FROM AUTHOR]

The pulsed electric field (PEF) was applied to improve the extraction yield and properties of rice bran proteins from two rice varieties ("Kum Chao Mor Chor 107" and "Kum Doi Saket"). As compared to the conventional alkaline extraction, PEF treatment at 2.3 kV for 25 min increased the protein extraction efficiency by 20.71–22.8% (p < 0.05). The molecular weight distribution detected by SDS-PAGE and amino acid profiles of extracted rice bran proteins was likely unchanged. The PEF treatment influenced changes in the secondary structures of rice bran proteins, especially from the β-turn to the β-sheet structure. Functional properties of rice bran protein including oil holding capacity and emulsifying properties were significantly improved by PEF treatments by about 20.29–22.64% and 3.3–12.0% (p < 0.05), respectively. Foaming ability and foam stability increased by 1.8- to 2.9-fold. Moreover, the in vitro digestibility of protein was also enhanced, which was consistent with the increment of DPPH and ABTS radical-scavenging activities of peptides generated under in vitro gastrointestinal digestion (37.84–40.45% and 28.46–37.86%, respectively). In conclusion, the PEF process could be a novel technique for assisting the extraction and modification of the protein's digestibility and functional properties. [ABSTRACT FROM AUTHOR]

The main characteristics of electrolytic reduction applied to indium recovery from aqueous chloride solutions were considered theoretically and examined experimentally. Also other media were considered for comparison. Potentiodynamic examinations pointed out that chloride electrolytes are superior to sulphuric and nitric acid-based ones for efficient indium deposition. The optimum conditions, allowing higher than 90% cathodic current efficiencies, were determined by galvanostatic experiments. In contrast, similar sulphate electrolytes could only yield lower than 50% efficiencies because of a stronger hydrogen evolution. The galvanostatic results confirmed the findings of the potentiodynamic study. The cathodic polarisation curves revealed the major characteristics of the deposition process, implying a reduction of the electroactive In3+ ions. Coupled processes are the dynamic transformations of complex species and various rates of simultaneous hydrogen evolution. The structure and the elemental composition of the—relatively dense—cathodic deposits were examined by scanning electron microscopy and energy-dispersive X-ray analysis. Various levelling agents were also tested, and gelatine (up to a concentration of 1 g/dm3 in the chloride electrolyte) was found efficient in grain refining. [ABSTRACT FROM AUTHOR]

The technological development propitiates the rapid replacement of electrical and electronic equipment, which makes it indispensable to develop recycling processes for the treatment of this equipment when discarded. Printed circuit boards (PCBs) are fundamental components of electrical and electronic equipment. PCBs are composed of ceramics, polymers, and metals. Copper is the metal that is present in the greatest percentage of mobile phone PCBs. The objective of this study was to recover copper in the form of metallic deposits from a copper solution extracted from comminuted PCBs through supercritical CO2 in the presence of cosolvents (H2O2 and H2SO4). A synthetic CuSO4 solution was employed to determine the ideal current density in the range of 250 to 540 A/m2. The electrowinning of the leachate solution from PCBs was performed at the determined current density. Using the current density of 250 A/m2, pH equal to 4, and temperature of 25 °C, a current efficiency of around 100% was achieved for the real solution. The deposit obtained showed a copper concentration of 95.97 wt%, recovering 40% of the copper contained in the solution in 300 min of electrowinning. It was observed that for a longer electrowinning time, the percentage of copper recovery could increase. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Metallic Mn was produced in H+ exchange membrane electrolytic cell. • Coated titanium anode was applied through a satisfactory way. • Specific energy consumption of 4189 kW·h/t was achieved. • H+ ions was individually separated and recycled from anolyte. • Recyclable spent electrolyte containing 15.2 g/L H 2 SO 4 was produced. Coated Titanium Anodes (CTAs) exhibit significant potential in addressing the high energy consumption challenge inherent in current manganese electrowinning processes. However, the electrodeposition of manganese dioxide (MnO 2) at the anode limits the utilization of CTAs in conventional manganese electrolytic cells. Herein, a novel H+ exchange membrane (HEM) electrolytic cell was proposed and applied to manganese electrowinning employing Ti/IrO 2 − RuO 2 − SiO 2 anode. The HEM electrolytic cell is a three-chamber electrolytic reactor consisting of cathode chamber, acidification chamber and anode chamber separated by woven terylene diaphragm and HEM. The results indicated that after 24 h of electrowinning, the cathodic current efficiency (CE) of 85.1 % was achieved, along with a specific energy consumption (EC) of 4189 kW·h/t. Compared to conventional industrial electrowinning technology, this represents an increase in CE by more than 15 % and a reduction in EC by over 1400 kW·h/t. The unique structure of the HEM electrolytic cell effectively prevents MnO 2 deposition, ensuring the functionality of the CTAs and eliminating the generation of anode mud. Additionally, the H+ from the oxygen evolution reaction at the anode is collected and concentrated in the acidification chamber. This resulted in a spent electrolyte with 15.2 g/L H 2 SO 4 , enabling its reuse in extracting manganese ores. Employing the HEM electrolytic cell with a Ti/IrO 2 − RuO 2 − SiO 2 anode for manganese electrowinning is therefore considered an energy-efficient and clean approach. It is highly recommended for saving energy and reducing carbon emissions in industrial processes. [ABSTRACT FROM AUTHOR]

• Ni-doped Mn 5 O 8 peach-like microspheres modifying PbO 2 layered electrode was prepared through coprecipitation coupling with anodic codeposition process. • The OER overpotential at 50 mA cm−2 of the modified PbO 2 layered electrode was as low as 583 mV in 1.53 M H 2 SO 4 medium. • The modified PbO 2 electrode had a long accelerated service life of 64 h when tested at 1.5 A cm−2 in strong acidic solution. • Comparing with the industrial Pb-(0.76 wt%)Ag electrode, the energy consumption for producing one-ton zinc of the modified PbO 2 electrode was decreased by 530.13 kW h in zinc electrowinning simulated electrolyte. Developing anodic electrocatalysts with superior activity and durability suitable for acidic oxygen evolution reaction (OER) remains a challenge to overcome. Herein, a layered Pb-(0.76 wt%)Ag/α-PbO 2 /β-PbO 2 electrode modified with Ni-doped Mn 5 O 8 particles (PA/PbO 2 -NMO) is successfully synthesized by a coprecipitation coupling with anodic codeposition process. The physical characterization demonstrated that the surface of electrode is composed by β-PbO 2 and portion NMO that embedded in the deposit. In addition, it presents a layer structure, in which PA serving as support, α-PbO 2 as the mid layer enforcing the adherence, and β-PbO 2 -NMO function as active layer. Benefiting from the above unique layered structure, the as-fabricated PA/PbO 2 -NMO electrode with a layered structure exhibits the outstanding acidic OER performance (583 mV, 139.04 mV dec–1) at 50 mA cm−2 in 1.53 M H 2 SO 4. Meanwhile, the responding accelerated corrosion life at 1.5 A cm−2 is up to 64 h, indicating its robust anticorrosion ability. As for the applied performance in zinc electrowinning simulation electrolyte (1.53 M H 2 SO 4 + 0.31 M ZnSO 4), the current efficiency of the PA/PbO 2 electrode is promoted to 93.8 % after the modification with NMO. Moreover, the cell voltage and one-ton zinc energy consumption of the modified PA/PbO 2 electrode are diminished by 14.32 %, 17.75 % compared with the industrial Pb-(0.76 wt%) Ag (PA) electrode. Therefore, this study offers a new horizon on the development of the anodic electrocatalyst for both strongly acidic watersplitting and non-ferrous metals electrowinning. [ABSTRACT FROM AUTHOR]