Electrochemical approaches for selective recovery of critical elements in hydrometallurgical processes of complex feedstocks

Abstract

Summary Critical minerals are essential for the ever-increasing urban and industrial activities in modern society. The shift to cost-efficient and ecofriendly urban mining can be an avenue to replace the traditional linear flow of virgin-mined materials. Electrochemical separation technologies provide a sustainable approach to metal recovery, through possible integration with renewable energy, the minimization of external chemical input, as well as reducing secondary pollution. In this review, recent advances in electrochemically mediated technologies for metal recovery are discussed, with a focus on rare earth elements and other key critical materials for the modern circular economy. Given the extreme heterogeneity of hydrometallurgically-derived media of complex feedstocks, we focus on the nature of molecular selectivity in various electrochemically assisted recovery techniques. Finally, we provide a perspective on the challenges and opportunities for process intensification in critical materials recycling, especially through combining electrochemical and hydrometallurgical separation steps.

Selective cobalt and nickel electrodeposition for lithium-ion battery recycling through integrated electrolyte and interface control

“…Our strategy is to control speciation along with an integrated view of leaching and recovery. In hydrometallurgical processes, the recovery step can benefit from a preceding leaching step in relation to solution chemistry and speciation control 25 . Concentrated chloride has been used as a ligand for integrated leaching and recovery (e.g., concentrated LiCl, ionic liquids and deep eutectic solvents for ionometallurgy) 39 – 43 .…”

“…As an alternative, electrochemical methods have been suggested as a promising approach, which, in combination with renewable sources, allow for sustainable and distributed processes for metal recycling 25 . Among various electrochemically driven techniques, electrodeposition is a versatile and simple method with tunability in nucleation and growth, morphology, and deposit composition 26 – 28 .…”

“…Among various electrochemically driven techniques, electrodeposition is a versatile and simple method with tunability in nucleation and growth, morphology, and deposit composition 26 – 28 . Electrodeposition has been useful for the separation and recovery of metals from multicomponent mixtures 29 – 31 , with the reduction potentials of component metals being the most crucial parameter dictating selectivity 25 . Reduction potentials of cobalt and nickel have been systematically investigated in high temperature eutectic mixtures of molten LiCl–KCl and NaCl–KCl 32 , 33 .…”

Imidazolium-type anion exchange membranes for improved organic acid transport and permselectivity in electrodialysis

“…Manipulating the molecular interactions between the cation head group and target species are one tool that can be used for designing selective membranes for electrochemical separations. Another notable approach in electrochemical separations are redox active polymers using capacitive deionization platforms [34][35][36] , but these materials have not been investigated for organic acid capture and purification.…”

Ion Exchange Conversion of Na-birnessite to Mg-buserite for Enhanced Cu2+ Removal via Membrane Capacitive Deionization (MCDI)

“…Recently, capacitive deionization (CDI) has been demonstrated as a promising technique for ion separations, offering an attractive and prospective platform for desalination, [8][9][10] selective ion removal, [11][12][13][14] and recovery of high-value elements. [13][14][15][16] Carbon-based materials such as carbon aerogels, activated carbon, carbon nanotubes, carbon nanofibers, graphene, mesoporous carbon, and carbide-derived carbon are the most widely used electrodes for the removal of ions (e.g., Na + , Cl − , and heavy metals) from aqueous solutions via ion electrosorption and the formation of Helmholtz electric double layer (EDL) inside the CDI cells. 3,6,[17][18][19][20][21] More recently, it has been shown that hybridization of the conventional carbon electrodes with Faradaic/redox-active materials can greatly enhance the salt adsorption capacity (SAC) and selectivity for heavy metal ions (e.g., Cu 2+ , Pb 2+ , etc.…”