Abstract
Determination of the extractive behavior of ionic species from lateritic ore leachates is complex, since the leachates are pregnant with tens of different ions in, as a rule, multiple oxide states. To examine the possible pathways of intrinsic electrochemical extraction of the crucial elements Ni and Co, it was necessary to make model solutions of these elements and to subject them to electrochemical examination techniques in order to obtain a benchmark. Beside Ni and Co, the model system for Fe had to be evaluated. Iron, as a dominant ore component by far, is the main interfering factor in the extraction processes of Ni and Co in rather low amounts from leaching solution. The leachate examination results were compared to separate model solutions, as well as to their combinations in concentrations and to pH values comparable to those of the leachate. The separation of the leachate components was initially performed by continuous increase in pH upon leaching with NaOH solution, and afterwards the pH-adjusted solutions were subjected to electrochemical investigation. With the purpose of connecting and quantifying the visual changes in leachate upon increase in pH, conductometric measurements were performed. Reactions of oxidation/precipitations were indicated, which led to the essential Fe removal by precipitation. Resulting solutions were found suitable for Ni and Co electrochemical extraction.
Highlights
IntroductionNickel has already been used in batteries, such as nickel–cadmium or nickel–metal-hydride, but its use in lithium-ion batteries caused rising interest in this metal, since it is able to deliver a higher energy density and more storage capacity to these batteries
Cobalt and nickel are considered both strategic and critical raw materials [1]
Cobalt is still essential for the manufacturing of Li-ion batteries and its compounds for supercapacitor electrodes due to the high specific capacitance and high energy density as well as better cyclic stability of Co oxide [3]
Summary
Nickel has already been used in batteries, such as nickel–cadmium or nickel–metal-hydride, but its use in lithium-ion batteries caused rising interest in this metal, since it is able to deliver a higher energy density and more storage capacity to these batteries. Nickel has become the most important for the lithium-ion battery cathodes, enabling the reduction the use of cobalt, which is scarce and more expensive [2]. With an outbreak of electric vehicle production, global demand for cobalt and nickel has been growing. Global demand for these metals in electric vehicle batteries from 2018 to 2025 is forecasted to increase by 10 times [4,5,6]
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