Advances in Understanding Metal Electrolysis Process

Advancements in technologies related to the electrorefining and electrodeposition of metals—as important manufacturing process steps—continue to receive significant attention. Specifically, novel ideas that focus on the development of new approaches to the electrochemical synthesis of alloys and composites are important for advancing technologies that can promote increased supply sustainability in the future. This Special Issue, “Advances in understanding metal electrolysis process”, aims at the fundamental level of research with respect to novel approaches in areas of electrolysis and electrochemical mechanisms as well as their impact on the efficiency and quality of metal deposition. It consists of ten papers addressing various issues and their possible solutions around the electrolysis/-deposition of aluminum, copper, indium, rare earth metals, and their alloys, including Zn-Co coatings. One review paper provides an overview of the structure of metal powders produced by electrochemical methods

Electrochemical co-deposition of neodymium and praseodymium from oxyfluoride molten salts

In the present study we aim to provide an understanding of the electrochemical behaviour of neodymium and praseodymium in the fluoride based melts composition containing different LiF concentration. Comparison of the experimental results obtained from chosen electrolyte systems, should enable to precisely incorporate adjustable parameters which could favor more deposited neodymium and praseodymium metal remaining on an inert working substrate.U ovom radu ispitivali smo elektrohemijsko ponašanje neodijuma i prazeodijuma u elektrolitima na bazi fluorida sa različitim koncentracijama LiF. Poređenje dobijenih eksperimentalnih rezultata iz izabranih elektrolita, trebalo bi da nam omogući optimizaciju parametara koji bi favorizovali veći prinos neodijuma i prazeodijuma na inertnoj radnoj elektrodi

Investigation on the Electrochemical Behaviour and Deposition Mechanism of Neodymium in NdF3–LiF–Nd2O3 Melt on Mo Electrode

Neodymium was electrochemically deposited from NdF3–LiF–Nd2O3 molten salt electrolyte onto the Mo electrode at temperatures close to 1273 K. Cyclic voltammetry and chronoamperometry measurements were the applied electrochemical methods. Metallic neodymium is obtained by potentiostatic deposition. The optical microscopy and XRD were used to analyze the electrolyte, the working electrode surface, and the deposit on the electrode. It was established that Nd(III) ions were reduced to Nd metals in two steps: Nd(III) + e− → Nd(II) at potential ≈−0.55 V vs. W and Nd(II) + 2e− → Nd(0) at ≈−0.83 V vs. W. Both of these processes are reversible and under mass transfer control. Upon deposition under the regime of relatively small deposition overpotential of −0.10 V to −0.20 V, and after the electrolyte was cooled off, Nd metal was observed at the surface of the Mo electrode. CO and CF4 were gases registered as being evolved at the anode. CO and CF4 evolution were observed in quantities below 600 ppm and 10 ppm, respectivel

Greenhouse gas emission from the rare earth metals electrolysis

In the present work, we investigated the off-gas emission during the Nd and Pr electrodeposition from oxy- fluoride melts by the in-situ FTIR-spectrometry to understand the nature of the reactions taking place on the anode and the mechanisms behind them

Electrochemical deposition of neodymium and praseodymium on molybdenum from molten fluoride

Neodymium and praseodymium were electrochemically co-deposited onto Mo cathode applying constant potential, from fluoride-based molten salts containing the corresponding rare earth oxides. According to the recorded voltammograms, it appears that in the investigated system, the electrodeposition of neodymium proceeds as a two-step reduction process: Nd(III)→Nd(II) and Nd(II)→Nd(0), whilst the praseodymium deposition proceeds as an one-step reduction process: Pr(III)→Pr(0). However, it was also recognized that at the same time a substantial amount of NdF2 was formed as a result of the disproportionation reaction between the electrodeposited Nd metal and Nd(III) present in the electrolyte. The deposit on the working electrode surface was recorded by optical microscopy and analyzed by X-ray diffraction (XRD). The analysis made upon the applying the potentiostatic deposition regimehas shown Nd/Pr metals present on the molybdenum cathode

Electrochemical study of Nd and Pr co-deposition onto Mo and W from molten oxyfluorides

Electrodeposition processes of neodymium and praseodymium in molten NdF3 + PrF3 + LiF + 1 wt.%Pr6O11 + 1 wt.%Nd2O3 and NdF3 + PrF3 + LiF + 2 wt.%Pr6O11 + 2 wt.%Nd2O3 electrolytes at 1323 K were investigated. Cyclic voltammetry, square wave voltammetry, and open circuit potentiometry were applied to study the electrochemical reduction of Nd(III) and Pr(III) ions on Mo and W cathodes. It was established that a critical condition for Nd and Pr co-deposition in oxyfluoride electrolytes was a constant praseodymium deposition overpotential of ≈−0.100 V, which was shown to result in co-deposition current densities approaching 6 mAcm−2 . Analysis of the results obtained by applied electrochemical techniques showed that praseodymium deposition proceeds as a one-step process involving exchange of three electrons (Pr(III)→Pr(0)) and that neodymium deposition is a two-step process: the first involves one electron exchange (Nd(III)→Nd(II)), and the second involves an exchange of two electrons (Nd(II)→Nd(0)). X-ray diffraction analyses confirmed the formation of metallic Nd and Pr on the working substrate. Keeping the anodic potential to the glassy carbon working anode low results in very low levels of carbon oxides, fluorine and fluorocarbon gas emissions, which should qualify the studied system as an environmentally friendly option for rare earth metal deposition. The newly reported data for Nd and Pr metals co-deposition provide valuable information for the recycling of neodymium-iron-boron magnets

Elektrohemijsko taloženje Nd i Pr na W iz fluoridnih rastopa

Electrodeposition of neodymium and praseodymium metal from molten NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 electrolytes on W was investigated using voltammetry at 1050 °C. The square wave voltammetry confirmed that Nd electrodeposition is a two-step reduction process: first, involving one electron exchange (Nd(III)→Nd(II)) and second, involving two electrons exchange (Nd(II)→Nd(0)). However, praseodymium deposition proceeds as an one-step process involving exchange of three electrons (Pr(III)→Pr(0)). Nd and Pr metals were electrodeposited applying potentiostatic mode. The working electrode surface was analyzed by X-ray diffraction after Nd and Pr co-deposition.Elektrohemijsko taloženje neodijuma i prazeodijuma iz fluoridnog NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 rastopa na W radnoj elektrodi ispitivano je pomoću voltametrijskih tehnika na 1050 °C. Voltametrija sa pravougaonim talasima (SWV, square wave voltammetry) potvrdila je da je elektrohemijsko taloženje Nd proces koji se odvija u dva koraka: prvi, uključuje razmenu od jednog elektrona (Nd(III) → Nd(II)) i drugi korak, uključuje razmenu dva elektrona (Nd(II) → Nd(0)). Međutim, taloženje prazeodijuma uključuje izmenu tri elektrona (Pr(III) → Pr(0)) u jednom koraku. Nd i Pr su elektrohemijski taloženi primenom potenciostatskog režima. Nakon elektrohemijskog taloženja Nd i Pr površina radne elektrode analizirana je rengensko-difrakcionom tehnikom.XII YuCorr International Conference, September 13-16, 2021, Tara Mountain, Serbia, http://sitzam.org.rs/YUCORR

Electrodeposition of Aluminium-Vanadium Alloys from Chloroaluminate Based Molten Salt Containing Vanadium Ions

The Al-V alloys were synthetized by potentiostatic electrodeposition onto a glassy carbon electrode from equimolar AlCl3 + NaCl bath containing vanadium ions at 200 °C. The alloy deposits were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The deposits were identified as Al3V and AlV3 alloys. It was found that intermetallic alloys were synthetized during aluminium underpotential deposition onto vanadium metal that was previously deposited on the glassy carbon electrode by diffusion-controlled overpotential deposition. Alloys were the result of solid-state interdiffusion between the initially deposited vanadium and the subsequently deposited aluminium. As a source to secure a constant concentration of vanadium in the electrolyte during deposition, vanadium anodic dissolution, and VCl3 melt addition were studied. The effect of vanadium ion concentration in the electrolyte on the composition and the surface morphology of the obtained deposits was investigated. The results indicate that controlled vanadium and aluminium codeposition could be a further step to the successful development of an advanced technology for Al3V and AlV3 alloy synthesis

Influence of Rare Earth Oxide Concentration on Electrochemical Co-Deposition of Nd and Pr from NdF3-PrF3-LiF Based Melts

The impact of rare earth oxide (REO) concentration on the deposition process and selective recovery of the metal being deposited from a molten fluoride salt system was investigated by applying deposition of Nd and Pr and varying the concentration of REO added to the electrolyte. A ternary phase diagram for the liquidus temperature of the NdF3-PrF3-LiF system was constructed to better predict the optimal electrolyte constitution. Cyclic voltammetry was used to record three redox signals, reflecting the processes involving Nd(III)/Nd and Pr(III)/Pr transformations. A two-step red/ox process for Nd(III) ions and a single-step red/ox process for Pr(III) ions were confirmed by square-wave voltammetry. The cyclic voltammetry results indicated the possibility of neodymium and praseodymium co-deposition. In order to sustain higher co-deposition rates on the cathode and to avoid increased production of PFC greenhouse gases on the anode, a low-overpotential deposition technique was used for Nd and Pr electrodeposition from the electrolyte with varying Nd2O3 and Pr6O11 concentrations. Co-deposited neodymium and praseodymium metals were characterized by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) analysis. After electrodeposition, concentration profiles of neodymium and praseodymium were recorded, starting from the cathode surface towards the electrolyte bulk. The working temperature of 1050 °C of the molten fluoride salt basic electrolyte, in line with the constructed phase diagram, was validated by improved co-deposition and led to a more effective deposition process

Advances in Understanding Metal Electrolysis Process

Advancements in technologies related to the electrorefining and electrodeposition of metals—as important manufacturing process steps—continue to receive significant attention [...