Cathodic Current Efficiency Research Articles

One-step recovery of valuable metals from spent Lithium-ion batteries and synthesis of persulfate through paired electrolysis

• The paired electrolysis reduces energy consumption in the recycling of spent LIBs. • Synchronously recovering Co 2+ as cobalt metal and synthesizing persulfate. • Simultaneous desalting in the recycling process of spent LIBs. The application of electrochemical methods on the recycling of valuable metals from spent lithium-ion batteries, and the removing of pollutant from wastewater by persulfate have attracted widespread attention in recent years. However, high energy consumption resulting from side electrochemical reactions constrains its application. Herein, a paired electrolysis method was designed to achieve the recycling of valuable metals from the spent LIBs and the synthesis of persulfate synchronically. In the process, high purity cobalt metal (>99.9%) was obtained from the leachate (catholyte) of the spent LIBs, and valuable persulfate were synchronically synthesized anolyte through a diaphragm electrolyzer. The prepared persulfate was directly thermally activated for pollutant degradation. Two important synthesis process are conducted in one step. About 30% energy consumption is reduced through paired electrolysis to produce valuable products of equal quality and the cathodic current efficiency is also enhanced about 4% compared with the single cobalt electrolysis system at same stage. Additionally, Li + is recycled as Li 2 CO 3 through precipitation from the electrolyte. As a green method, paired electrolysis will own a wide application prospects in the waste recycling and other hydrometallurgical fields because of low energy consumption and high valuable products.

Towards the Stability of Low-Temperature Aluminum Electrolysis

The results of several different tests related to the low-temperature aluminum electrolysis were considered in this work. The role of mass transfer processes in the anode-cathode space was recommended to be significant during electrolysis in the low-temperature KF-AlF3 and NaF-AlF3-based melts. The stationary polarization and voltammetry methods were applied in order to study the kinetics of the electrode processes on the carbon and metal electrodes in the KF-AlF3-Al2O3 melts and to select the electrolysis parameters. The schemes of electrode processes were suggested on the basis of electrochemical tests, the flows of substances in the anode-cathode distance were analyzed and the main reasons of the cathode current efficiency decrease during the low-temperature electrolysis in the KF-AlF3-Al2O3 and KF-NaF-AlF3-Al2O3 melts were discussed. It was revealed that the cathode current density should not exceed 0.4–0.55 A cm−2 during the electrolysis at 750 °C–800 °C.

Impact of ionic liquid [FPIM]Br on the electrodeposition of Ni and Co from an aqueous sulfate bath

A novel ionic liquid, namely, 1-(4-fluorobenzyl)-3-(4-phenoxybutyl)imidazole-3-ium bromide [FPIM]Br, was used as an additive for cobalt (Co) and nickel (Ni) electrodeposition from acidic sulfate and Watts baths, respectively. The effect of [FPIM]Br on the electrodeposition mechanism of the coatings was investigated by a variety of electrochemical methods (potentiodynamic cathodic polarization, cyclic voltammetry, and anodic linear stripping voltammetry) as well as by morphologic techniques (XRD, SEM, EDX and AFM). The inhibition of Co2+ and Ni2+ ions deposition in the presence of [FPIM]Br was found to lead to finer-grained deposits. Adsorption of [FPIM]+ on the copper substrate is shown, and the process obeys the Langmuir adsorption isotherm. The cathodic current efficiency (CCE%), hardness and corrosion resistance for Co2+ and Ni2+ deposition in the electrodeposition bath were found to increase when additive was included. The resultant surface morphologies demonstrated that the [FPIM]Br additive served as an effective brightener that can produce highly uniform and smooth Co and Ni deposits.

Electrodeposition of Zn-Co Alloy from an Acid Sulphate Bath Containing Triethanolamine and Thiaminehydrochloride

Electrodeposition of Zn-Co alloy from an acid sulphate bath has been carried out in this research work. The effects of metal ion ratio in the bath, pH current density, temperature, stirring, thickness and concentrations of triethanolamine and thiaminehydrochloride on the alloy composition and on cathodic current efficiency have been investigated. The deposition potentials of Zn-Co alloy are less noble of zinc and cobalt. The structure of Zn-Co alloy was investigated by X-ray diffraction indicates zinc structure. The surface morphology of alloy deposits is found to depend on the percentage of cobalt in the alloy. Under the optimum operating conditions, Zn-Co alloy deposition follows anomalous co-deposition.

Electrolysis of iron with oxygen gas evolution from molten sodium borate electrolytes

ABSTRACT Molten oxide electrolysis can be used to reduce the carbon dioxide emissions from ironmaking. In this paper, we electrochemically decompose iron oxide (Fe2O3) into iron (Fe) and oxygen (O2) using boron trioxide and sodium oxide (B2O3–Na2O) as the molten oxide electrolyte at 1000°C that is less than the temperature of other molten oxide electrolysis. The formation of Fe at the cathode and O2 at the anode is identified by analysing products from both electrodes. The results suggest that the cathodic current efficiency of electrolysis at 2 V is about 54.7%, energy consumption is about 5.27 kW h kg–1 of Fe at 2 V electrolysis, and purity of the reduced Fe was more than 97 mol.%. With respect to the process temperature and product yield, B2O3–Na2O molten oxide has potential as a supporting electrolyte to reduce Fe2O3 to Fe without consuming any carbon.

Effects of Cuprous Ion on Electrodeposition of Aluminum from AlCl3-BMIC Ionic Liquid

The effect of Cu(I) ions on electrodeposition of aluminum from AlCl3-BMIC (AlCl3-1-butyl-3-methylimidazolium chloride) ionic liquid was investigated. The cyclic voltammetry and cathodic polarization analyses showed that Cu(I) ions obviously decreased the nucleation overpotential of Al and promoted the reduction reaction of Al (III). The analysis of thechronoamperometric transients indicated that the presence of Cu(I) does not change the nucleation and growth mode of Al deposition, but affects nucleation rate. Besides, the addition of Cu(I) slightly decreased the cathodic current efficiency (CE), increased the power consumption (PC), and reduced the purity of Al deposit. X-ray diffractogram revealed the presence of Cu(I) ions in electrolyte affected the preferred orientations of the electrodeposited Al by promoting the growth of (220) plane. SEM images showed that the grain of the Al deposit was refined with the increase of Cu(I) ions.

Physico-Chemical Properties of Zn-Fe Alloy Deposits from an Acid Sulphate Bath Containing Triethanolamine

The composition, properties, structure and morphology of electrodeposited Zn-Fe alloy deposits obtained from an acid sulphate bath containing triethanolamine have been investigated. A bath containing less zinc (20%) produced an alloy deposit with higher zinc content (80%), i.e. anomalous co-deposition process. The composition of alloy remained constant with pH of the plating bath and thickness of the alloy deposit. The cathodic current efficiency depends on plating variables. The shift in deposition potentials of Zn-Fe alloy is a chief cause in the co-deposition process to produce alloy of varying composition. Phase structure determination by X-ray diffraction studies showed a wide variety of inter metallic phases. Zn-Fe alloy showed a superior corrosion resistance than zinc coatings. An alloy containing greater than 40% Fe showed a good paintability. Hardness of the alloy deposits increased with increase in iron content in the alloy. Smooth, uniform and fine grained deposits were obtained for the Zn-Fe alloy containing 20% Fe.

Electrochemical Behaviors of MnO2 on Lead Alloy Anode during Pulse Electrodeposition for Efficient Manganese Electrowinning

The electrochemical performances of deposited MnO2 on lead alloy anode by pulse current (PC) and direct current (DC) electrodeposition in manganese sulfate solution were investigated by performing measurements of galvanostatic polarization, cyclic voltammetry (CV), and Tafel tests. The composition and morphology of MnO2 were observed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The anode deposited with MnO2 layers by PC electrodeposition presented a lower anodic potential of 60 mV and more uniform potential oscillating attractor with fractal dimension of 1.0337 compared with those of DC electrodeposition. In addition, MnO2 layers exhibited excellent corrosion resistance because less intermediate oxide Mn(III) appeared in anode deposits. Furthermore, the cathodic current efficiency improved by 3.11∼3.77% and energy consumption decreased by 5.30∼8.17% after galvanostatic electrolysis for 2∼8 h by using PC instead of DC for manganese metal electrodeposition. As an external control method, PC electrodeposition not only regulated the structure and surface morphology of MnO2 but also affected the anode electrochemical behaviors and cathode manganese metal deposition. Electrochemical oscillations and other characteristics of anode reaction described in this study could inspire future work on promoting the whole electrowinning process.

Uranium Electrorefining in 3LiCl-2KCl Based Melts

Molten halides can be effectively employed for electrorefining of refractory and radioactive metals with relatively negative reduction potentials and high melting temperatures. In the present study electrorefining of uranium was studied for developing pyrochemical reprocessing technology of metallized spent nuclear fuels. 3LiCl-2KCl molten salt was chosen as the working electrolyte. Uranium containing electrolytes were prepared by dissolving UCl3 in the solvent salt melt in an argon filled glove box to obtain various desired concentrations of uranium in the electrolyte. The working temperature in the refining experiments varied between 450 and 750 °C.The experiments on uranium electrorefining were carried out in a stainless steel semi-industrial water-cooled electrolyser. Crude uranium metal was loaded in a specially designed molybdenum anodic basket. Glassy-carbon crucible was used to hold the melt. Molybdenum rod was employed as a cathode.The main goal of the electrolytic refining process is obtaining high-purity uranium metal. Specific energy consumption is also very important. The results of the electrolytic refining depend on various parameters. In the present study current density, temperature, uranium concentration in the electrolyte, and specific quantity of electricity passed through the cell were selected as variables, and the current efficiently was chosen as a response factor.Dense and compact uranium deposits were obtained under low current densities, while application of relatively high current densities led to the formation of uranium dendrites. Intermediate values of current density allowed producing more coherent deposits that could be easily scraped off the cathode. Increasing temperature led to a sharp change of the cathodic deposits morphology. The reason for this is the formation of tetragonal beta-uranium instead of the low-temperature orthorhombic alpha modification.The values of cathodic current efficiency in the most of experiments confirmed the three-electron scheme of uranium reduction. Cathodic current density under certain conditions exceeded 95 %. The amount of salt retained in the cathodic deposit varied from 7 to 25 %, values typical for dendrite electrolytic metals.

Part I: Ni-Co alloy foils electrodeposited using ionic liquids

The Ni-Co alloy co-electrodeposit from a sulfate bath including two new ionic liquids 1-methyl-3-(2-oxo-2-((2,4,5 trifluorophenyl) amino) ethyl)-1H-imidazol-3-ium iodide [MOFIM]I and 1-(4-fluorobenzyl)-3-(4-phenoxybutyl) imidazol-3-ium bromide [FPIM]Br as additives was characterized using the SEM, EDS, EDS mapping, XRD, AFM and microhardness measurement techniques. The resultant surface morphologies in acidic sulfate baths on a copper substrate demonstrated that both the [MOFIM]I and [FPIM]Br additives served as effective leveling agents. The Ni-Co alloy co-deposit morphology in the [MOFIM]I bath was more enhanced (non-grained coating, Ra of 28 nm and Rt of 35.5 nm) than that in the [FPIM]Br bath (grain size 225 nm, Ra of 51. 1 nm and Rt of 65.7 nm) owing to the molecular structure. The co-deposition of Co and Ni from the acidic baths was of the anomalous type. Moreover, the anomalous behavior of the Ni-Co co-deposition was alleviated after [MOFIM]I and [FPIM]Br were introduced in the bath. To determine the optimal bath conditions, the cathodic current efficiency (CCE%) value was calculated during the Ni-Co alloy co-electrodeposition process under three different compositions and different operating conditions. Under the composition of Ni 70% and Co 30% (Ni70%-Co30% alloy deposit), the CCE% values increased considerably, with maximum values of 99.8% and 97.07% in the baths including [MOFIM]I and [FPIM]Br, respectively.

Electrodeposition of Zn-Fe Alloy from Non-Cyanide Alkaline Sulphate Bath Containing Tartarate

Electrodeposition of Zn-Fe alloy from an alkaline sulphate bath containing tartarate has been carried out. The effect of plating variables on the composition of alloy and on cathodic current efficiency was studied. The cyclic voltammetric studies carried out to know the mutual co-deposition of zinc and iron. Hardness and the surface morphology of the alloy deposits were found to be dependent on the iron content in the alloy. An alloy containing 20% wt. Fe showed smooth, uniform and finer grained deposits. Under the optimum composition and operating conditions, Zn-Fe alloy deposition from alkaline sulphate bath containing tartarate followed anomalous depositing process.

Simulated process integration of wastewater electrooxidation with recuperated micro gas turbine for energy recovery

Electrooxidation (EO) is a promising wastewater treatment technology that is plagued with high energy consumption. This study simulates the energy recovery potential from EO by process integration with recuperated micro gas turbine (RMGT). Gainful utilization of hydrogen produced at cathode is key to it. Percent recoverable energy (PRE) from EO would be strongly influenced by the cathodic current efficiency (CCE) and interelectrode potential (IP) and was likely to vary from a high of 46% to a low of 14%. Simulations suggested that process integration with RMGT could potentially recover 72.4% of this energy – 30.7% as electricity and 41.7% as thermal energy in the form of hot water at 353 K. This translated to 6.3%–9.7% electricity saved in EO besides recovered thermal energy. Energy dynamics was found to be highly sensitive to recuperator performance of the RMGT. Better recuperator performance made energy recovery through process integration more electricity driven at the cost of recovered heat and total energy recovery.

Electrochemical studies on the corrosion resistance of Zn–Ni–Co coating from acid chloride bath

Anticorrosive deposits are a valuable approach to defending against corrosion from mild steel structures/machinery equipment. The Zn–Ni–Co coating has been deposited on low carbon steel surfaces using environment friendly optimized acidic chloride bath with ZnCl2·6H2O, NiCl2·6H2O, CoCl2·6H2O, sulphanilic acid (C6H7NO3S) and gelatin (C6H8O6). The standard Hull cell technique has been adopted for the optimization of bath components and experimental conditions, for the superior corrosion resistant coating. The corrosion test with potentiodynamic polarization method was performed to investigate the role of pH on the film quality and corrosion performances of the films. Further, the effect of current densities on corrosion resistance, thickness and hardness, have been investigated. Cyclic voltammetry technique has been used to test the electrochemical properties of the Zn–Ni–Co coating in acidic solutions. The results revealed that the increase in the current density favoured the increase in Ni and Co content in the deposit, showed higher corrosion resistance and higher cathodic current efficiency. The structural and morphological characteristics of the alloy coating have been obtained through scanning electron microscopy and X-ray diffraction techniques. The atomic force microscope was used to examine the topographic structure of the coating. X-ray Photoelectron spectroscopy was used to determine the chemical composition of alloy coatings and verified by energy dispersive X-ray analysis. The results indicate that a new and low-cost chloride bath for Zn–Ni–Co coating exhibit superior corrosion resistance properties and can be implement in various industrial applications such as automobiles, machine tools etc.

Uranium Electrorefining in 3LiCl-2KCl Based Melts

The process of uranium electrorefining in 3LiCl–2KCl based melts was investigated. Dense and compact uranium deposits were obtained at low current densities, while application of relatively high current densities led to the formation of uranium dendrites. Cathodic current efficiency in the majority of experiments confirmed the three-electron scheme of uranium reduction. Cathodic current efficiency under certain conditions exceeded 95%. The amount of salt retained in the cathodic deposit varied from 7 to 26%, these values typical for dendrite electrolytic metals.

Methods to Determine the Current Efficiency in AC Electrolysis

The paper presents several methods (analytical, electromechanical and electronic) for determining the cathodic current efficiency of the metal deposition processes carried out by AC or pulse current. Based on the results of own experimental researches (for indium, cadmium, nickel, tin and zinc), the appropriate equations are given and the distribution of both faradaic and non-faradaic parts of charge (charging of the electrode double layer) is calculated.

Preparation, characterisation and electrochemical study of crack-free nanocrystalline electrodeposited Co-W alloy coating of high hardness

ABSTRACT In this work, a lustrous metallic grey nanocrystalline Co-W alloy thin coating was successfully fabricated on copper substrates via galvanostatic deposition from an acidic glycine complexing bath. The impacts of various operating conditions e.g. glycine concentrations, applied current, pH and temperature on the cathodic polarisation behaviour, anodic stripping voltammetry, cathodic current efficiency (CCE%), and alloy composition were examined. This gave the opportunity to establish the operating conditions for producing various Co-W alloys. It was found that the W content in the alloy was in the range of 7.7–13.8 wt.% depending on the operating conditions. Moreover, the CCE% of the deposited alloy was characterised by relatively high values (up to 97.0%) in comparison with other baths. The XRD analysis indicates that the Co-W alloy consists of a hexagonal close-packed (hcp) Co lattice crystalline structure of nanosized grains, of average size 15.44 nm, using 25 g L−1 glycine, at 25°C and the highest current density tested.. The microhardness of Co-W alloy coatings is comparable to or even higher than that of hard chromium coatings (∼ 963–1119 kgf mm−2). The Co-W alloy coatings are crack-free as shown from SEM investigations. The glycine bath used for Co-W alloy codeposition is environmentally friendly.

Effect of Process Parameters on Electrodeposited Nanocrystalline Chromium Coatings Investigated by an Orthogonal Experiment

The microporous nanocrystalline chromium coatings were prepared on the H13 steel by electroplating in self-regulating baths. The effects of electroplating parameters including current density, compositions of baths, bath temperature and plating time on the surface quality, thickness of chromium coating and cathode current efficiency were investigated by an orthogonal experiment. Experimental results indicated that the surface quality, thickness of chromium coating and cathode current efficiency can be improved by adjusting these electroplating parameters. Furthermore, bath temperature has the greatest effect on the surface quality of chromium coating, and the high qualified surfaces were only obtained at higher temperatures of 55 and 65°C. Current density was the most significant factor for the thickness of coating and cathode current efficiency. Chromium coating with high surface quality, thickness and cathode current efficiency was obtained at current density 90 A/dm2, CrO3 250 g/L, K2SiF6 10 g/L, SrSO4 1 g/L, bath temperature 65°C and plating time 120 min, which is consisting of pure nanocrystalline chromium with a body-centered cubic structure. And the coating exhibits much higher microhardness and corrosion resistance than for H13 steel.

Nickel-cobalt alloy coatings prepared by electrodeposition Part I: Cathodic current efficiency, alloy composition, polarization behavior and throwing power

A systematic study was carried out to electrodeposit Ni-Co alloy coatings from a complexing acidic glycine bath on copper substrates. The effects of [Co2+]/[Ni2+] ratio, gly concentration, pH, current density and temperature on the current efficiency, Co content in the coatings and on polarization behavior were investigated. It was found that the CCE of these baths has a wide range starting from 55% up to a maximum value of 99.3%, relying on the operating parameters and the bath constituent. However, the CCE decreased from 96.2% to 84.8% when the gly content was enhanced from 25 to 150 g/L. On the other hand, the Co content in the deposit reached 97% (wt%) at [Co2+]/[Ni2+]=0.43, i= 16 mA cm2, t=10 min, T=20 °C. The codeposition of Co and Ni from acidic gly baths obeys the anomalous type of codeposition. The kinetic results indicate that the Tafel slope increased in the case of alloy deposition, while both the transfer coefficient αc and the exchange current i° decreased. Moreover, the obtained results indicated that increasing the Co2+ content in the electrolytic solution has an inhibiting impact on the kinetics of the nickel-cobalt alloy plating. The throwing power is enhanced with enhancing [Co2+]/[Ni2+] ratios, while the addition of gly decreases it. However, the outcomes of macrothrowing power, throwing index and Wagner numbers are in excellent accord.

Corrosion performance of Zinc Based Binary and Ternary Alloy Coatings

Abstract The binary (Zn-Ni, Zn-Co, Zn-Fe) and ternary (Zn-Ni-Co, Zn-Co-Fe) coatings have been developed with sulphamic acid (SA) as an additive using an electrolytic method of sulfate bath. The bath composition, pH, temperature, etc have been optimized using regular Hull cell technique. The effect of current density (C.D) on wt. % of metal, thickness (t), hardness (VHN), and cathode current efficiency (C.C.E) of the plating have been investigated. The potentiodynamic polarization technique has been used to determine corrosion resistances of binary and ternary alloy coatings. The corrosion rate (CR) of ternary Zn-Ni-Co alloy coating is about 18 times and 20 times higher as compared to binary Zn-Ni and Zn-Co alloy coatings and ternary (Zn-Co-Fe) alloy coating is also approximately 27 times and 28 times higher than Zn-Co and Zn-Fe coating at optimized conditions. Thus, ternary coatings can replace conventional binary alloy coatings for many technological applications including aerospace, automobiles etc.

Copper and Antimony Recovery from Electronic Waste by Hydrometallurgical and Electrochemical Techniques.

A strategy for the efficient recovery of highly pure copper and antimony metals from electronic waste (e-waste) was implemented by the combination of hydrometallurgical and electrochemical processes. The focus is on copper recovery as the main component in the leached solution, whereas the antimony recovery process was established as a purification step in order to achieve a highly pure copper deposit. The strategy includes mechanical methods to reduce the size of the wasted printed circuit boards to enhance the efficiency of antimony and copper lixiviation via ferric chloride in acidic media (0.5 M HCl) followed by an electrowinning process. In order to establish the best parameters for copper electrowinning, the leached solution was characterized by cyclic voltammetry and cathodic polarization. Then, an electrochemical reactor with a rotating cylinder electrode was used to evaluate the copper concentration decay, the cathodic current efficiency, the specific energy consumption, and mass-transfer coefficient. Furthermore, antimony was recovered via precipitation by a pH modification in accordance with the Pourbaix diagram. Under this methodology, two valuable products from the e-waste were recovered: a 96 wt % pure copper deposit and 81 wt % pure antimony precipitate. The strategy for recovery of other metal ions, such as lead, present in the e-waste at high concentrations will be reported in further works.