Recovery of Metals from Secondary Raw Materials by Coupled Electroleaching and Electrodeposition in Aqueous or Ionic Liquid Media

Abstract

This paper presents recent views on a hybrid process for beneficiation of secondary raw materials by combined electroleaching of targeted metals and electrodeposition. On the basis of several case studies with aqueous solutions or in ionic liquid media, the paper describes the potential and the limits of the novel, hybrid technique, together with the methodology employed, combining determination of speciation, physical chemistry, electrochemistry, and chemical engineering. On one hand, the case of electroleaching/electrodeposition (E/E) process in aqueous media, although often investigated at the bench scale, appears nevertheless relatively mature, because of the developed methodology, and the appreciable current density allowed, and so it can be used to successfully treat electrode materials of spent Zn/MnO 2 batteries or Ni/Cd accumulators and Waelz oxide. On the other hand, the use of ionic liquids as promising media for the recovery of various metals can be considered for other types of wastes, as shown here for the case of electrodes of aged fuel cells. The combined (E/E) technique could be successfully used for the above waste, in particular by the tricky selection of ionic liquid media. Nevertheless, further investigations in physical chemistry and chemical engineering appear necessary for possible developments of larger-scale processes for the recovery of these strategic resources.

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

“…Recently, the term "ionometallurgy" was introduced by Abbott et al for metallurgical processes using ionic solvents [44]. One of the interesting features of using ionic solvents is that an electrochemical process for the dissolution and the purification of metallic species can be implemented thanks to their large electrochemical window [45].…”

Recent Studies on Ionic Liquids in Metal Recovery from E-Waste and Secondary Sources by Liquid-Liquid Extraction and Electrodeposition: a Review

“…4-ILs were selected due to low volatility, good thermal stability, relatively lower operating temperature, relatively high electrochemical window, provided a non-aqueous media with low electrical resistance, and less viscous and hygroscopic. (Leclerc et al 2018) 1-Butyl-1-ethyl-piperidinium bis(trifluoromethylsulfonyl)imide In/InCl3 vs. In(III) without Cl-1-In the presence of chloride, a complex voltammogram was observed due to the formation of a complex between indium and Cl-as well as a change in the ratio of these two ions during electrodeposition:…”

“…One of the challenges of working with some ILs in electrodeposition is that their viscosity is high. To solve this problem, low viscosity ILs are used or a combination of different ILs is used with each other and or a wide range of diluents can be used to reduce viscosity and with a variety of diluents can even make changes in the oxidation and conductivity properties and control the deposited layer (Leclerc et al 2018;Matsumiya et al 2020). In the extraction of metals in this way, in the face of multi-compounds, the use of potential controlling reagents such as the effect of salts and some different diluents and electrodeposition in several stages can be effective (Popescu et al 2018;Matsumiya et al 2020;Popescu et al 2020).…”

Structural Changes of Au(111) Single‐Crystal Electrode Surface in Ionic Liquids

“…Ionic liquids (ILs) are organic salts in the liquid state even at room temperature and are characterized by a nearly zero vapor pressure, high intrinsic electrical conductivity, and a broad (up to 4–6 V wide) electrochemical stability window . Due to their excellent physico‐chemical properties, ILs have a unique potential as electrochemical media, which makes them a key material for a wide range of technologies: electroplating, batteries, supercapacitors, electrocatalysis and electrosynthesis, or recovery of metals from secondary raw materials . Despite the great interest in ILs, the use of ILs in electrochemical applications is largely hindered by the lack of a detailed understanding of the electrode/IL interface properties .…”

“…[2] Due to their excellent physico-chemical properties, ILs have a unique potential as electrochemical media, which makes them a key material for a wide range of technologies: electroplating, [3] batteries, [4] supercapacitors, [5] electrocatalysis and electrosynthesis, [6][7][8] or recovery of metals from secondary raw materials. [9][10] Despite the great interest in ILs, the use of ILs in electrochemical applications is largely hindered by the lack of a detailed understanding of the electrode/IL interface properties. [1,11] So far, a variety of different spectroscopic techniques has been employed to characterize the corresponding electrode/IL interfaces, e. g. infrared, Raman, X-ray, sum frequency generation or impedance spectroscopy.…”