Recovery and Electrowinning of Strategic Critical Materials from Molten Salts

Materials scarcity is a complex and global issue. The whole lifecycle of products has to be considered: form mining of materials to recycling of the products at the end of its life time.

Rare earth (RE) elements (lanthanides, yttrium and scandium) are often called "key enablers of green technologies", as they are vital in the development of e.g. hybrid electric vehicles, rechargeable batteries and wind power generators. In addition, RE elements are commonly used in our daily life: flat screens, mobile phones, tablets, economy bulbs, etc. Therefore, the RE metals (REM) have been identified as one of the most critical raw materials, as their forecast scarcity will have a detrimental impact on the economy, society, research and development areas.

Electrolysis from high temperature molten salts (chlorides and fluorides) is the main current industrial route for the production of "light" REM (those with lowest melting point, i.e. Ce, La, Nd, Pr, mischmetal) and their alloys with other transition elements. Today's electrolytic production of REM is mainly carried out in China, using the so-called "Chinese technology", which is rather primitive, little energy effective, and releases environmentally harmful by-products.

Moreover, it is clear that as the demand for raw materials increases, greater efforts will have to be made on recycling, since higher recycling rates will: i) reduce the pressure on demand for primary raw materials; ii) help to reuse valuable materials which would otherwise be wasted, and iii) reduce energy consumption, greenhouse gas emissions and other negative environmental impact from extraction and processing.

In the last years, SINTEF has been involved in investigations related to:

• the improvement of the already existing industrial electrolytic processes for the production of REM and alloys, in terms of energy efficiency and reducing environmental impact.
• the development of effective methods for the extraction of valuable REM from RE-containing wastes/scrap (secondary sources) based on electrolysis technologies.

An insight of the challenges associated to the forecast of RE shortage will be reported. The issues connected to today's electrolytic production of REM and the necessity of innovative extraction processes from end-of-life or scrap products will also be exposed. At the end, the research activities carried out in this field at SINTEF will be described and experimental results will be presented.