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ENERGIX-Stort program energi

Low Energy Anodes for Sustainable Electrowinning

Alternative title: Energieffektive anoder for bærekraftig metallframstilling

Awarded: NOK 10.4 mill.

Modern society rests on the availability of materials derived directly or indirectly from mineral resources in the earth's crust. Metals constitute a particularly important class of materials, not only as a construction material for things such as cars, planes, and buildings, but also ever more in sophisticated devices such as computers and smart phones. This has led to increased and shifting demands for metals such as nickel, zinc, copper and cobalt. Most metals are not freely available in nature but must be extracted from the naturally occurring mineral. Nickel, cobalt, copper, and zinc are extracted in Norway by a process called electrolysis. During electrolysis an electric current is passed between two electrodes in a solution so that a metal forms at one of the electrodes. This requires large amounts of electrical energy. In Norway the production of copper, cobalt, nickel, and zinc corresponds to approximately 1 % of the total consumption of electrical energy. In view of the pending climate challenges it becomes imperative to reduce this energy consumption as much as possible. In the LEAn project NTNU and SINTEF collaborate with Glencore Nikkelverk (copper, nickel, and cobalt), Boliden Odda (zinc) and Permascand (catalysts) to reduce the energy consumption in electrowinning through development of novel electrocatalysts. In this first project period the project has designed and built special cells for the measurement of both catalyst performance and of the rates of degradation processes; degradation is an important but often overlooked aspect of catalyst development. However, a catalyst that does not have the required lifetime will not be applicable in an industry context whatever its initial performance. The LEAn project therefore pays particular attention to the characterization of degradation processes both in existing catalysts and catalysts developed directly in the project. This enables a direct comparison between existing catalysts and the new ones developed in the project in terms of a broad range of industry-relevant parameters.

Metal electrowinning is the process of extracting a metal from its ore by electrochemical processes. In aqueous electrowinning the ore from which the metal is to be extracted is dissolved into an electrolytic solution containing two electrodes. A voltage is applied between the two electrodes, and the metal is deposited at the negative electrode. Typically, oxygen is evolved at the positive electrode, i.e. at the anode. The annual energy consumption associated with this industry in Norway is on the scale of TWh. The energy consumption associated with the process is substantial, particularly at the anode, but can be brought down by employing catalysts. Thus, if the lead anodes that currently dominate the industry are replaced by anodes containing iridium, the energy consumption may be reduced by 15 %. However, iridium is costly (115 € per gram) and scarce (annual global production < 10 ton); facing soaring iridium prices and an anode lifetime of only 5 years, it may pay off for companies to continue their use of the cheaper lead anodes and sustain the accompanying energy loss. The LEAn project pursues alternative, energy efficient anodes with a catalytic activity that matches that of iridium-based anodes, but with a longer lifetime and that avoids the use of costly and scarce elements. Since only anode compositions that are at the outset expected to be stable under the rather harsh conditions of metal electrowinning, durability is built into the development work from the start. The challenges consist of finding compositions that are in addition both conductive, catalytically active, and have other necessary properties required for the application, including aspects of bath impurities and gas evolution. A range of sophisticated experimental and theoretical methods will be employed to achieve the goals. For risk mitigation, the project will include iridium in the composition space to be investigated, in this part of the project focusing on iridium thrift.

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ENERGIX-Stort program energi