Deep Eutectic Solvents for the Leaching of Cobalt from Oxide Ores

Cobalt (Co) exhibits unique properties that make it fundamentally important for a wide range of modern materials and applications, such as rechargeable batteries, magnets, and superalloys, which are all essential to the development of strategic sectors, including net-zero-emission, defence, and aerospace. The majority of Co is sourced as a by-product of copper (Cu) and nickel (Ni) production from stratiform sediment-hosted (SSH) Cu and Ni laterite deposits, respectively. Conventional processing of these ores is currently extremely energy-intensive and/or utilises toxic mineral acids, whilst the high degree of variability of Co ore mineralogy and geochemistry makes its extraction inefficient and technically challenging. As a result, there is a growing need for more efficient and environmentally compatible processing of Co ores. To address this, this thesis examines the application of deep eutectic solvents (DESs) as a new approach for the extraction of Co from its ores. The work focussed on two ‘world-class’ Co-bearing ores types: a SSH Cu ore and a Ni(Co) laterite ore. Analysis using XRD, QEMSCAN®, and EPMA shows that a considerable proportion of Co was hosted within high-valent Mn-oxides that require reductive processes in order to be liberated. Given this property, subsequent leaching experiments centred around the use of Type III ChCl-based DESs composed of carboxylic acids, which serve as reducing/complexing agents, and therefore likely to exhibit a propensity for selective Co dissolution. Batch leaching tests were applied across a range of temperatures and time. Analysis of metal concentrations within leachates using ICP–OES show that by tailoring the HBD, the acidity, redox potential, and ligand strength of the DES can be modulated to enhance the selective leaching of target minerals over gangue. When applied to ores for 90 hours at a low temperature (20 °C), 85 % Co was selectively leached from cupro-asbolane and kolwezite in SSH Cu ore using ChCl–lactic acid. Under identical conditions, 71 % of Co was leached from asbolane in laterite ore; however, the laterite required a more powerful DES in ChCl–oxalic acid to dissolve additional Co hosted in FeOOH minerals. Overall, this study demonstrates that DESs offer a highly promising alternative to conventional routes for Co extraction from its ore due to their ability to selectively extract Co under ambient temperature, which is enhanced by adjusting the properties of the HBD component of the DES to suit the ore mineralogy.<p></p>

Author dc:creator

• Rupert Heathcote (21041303)

• deep eutectic solvent
• cobalt
• copper
• nickel
• manganese
• leaching
• oxide ore

Statement dc:rights

• All rights reserved
• Open Access after 2027-06-02

Identifier

10779/exe.32560044.v1

OAI identifier oai:identifier

oai:figshare.com:article/32560044