Developing effective ways to recycle rare earth elements (REEs) is essential for reducing Europe’s dependence on primary raw materials. Within the HARMONY project, researchers have taken an important step by scaling up hydrometallurgical recycling processes from laboratory experiments to a small pilot operated in an industrial laboratory environment.
At Technische Universität Clausthal, a HARMONY research team processed REE-containing slag using hydrometallurgical methods. The team scaled up a process that was first developed at laboratory scale. In total, approximately 42.5 kg of slag was treated. As a result, the process produced 10 kg of rare earth oxalates, marking a significant milestone for secondary raw material recycling.
The pilot system combines continuous leaching and selective precipitation and achieves extraction and recovery efficiencies of over 90%. First, the team validated key process parameters in a single reactor. They then transferred these parameters to a three-reactor continuous system, which allows controlled operation under industrially relevant conditions.
Beyond the quantities produced, the demonstration shows that hydrometallurgical recycling of rare earth elements can be operated continuously. Moreover, the system enables precise control over temperature, pH, and residence time. Therefore, it provides valuable insight into how such processes behave beyond batch laboratory experiments. This step is important for evaluating future scalability, while remaining firmly within a research setting.
“This milestone shows that rare earth recycling is no longer confined to laboratory conditions,” explains the research team. “It demonstrates a practical pathway to secure critical raw materials through efficient and scalable processes.”
This pilot-scale achievement highlights how collaborative applied research within the HARMONY consortium can translate laboratory innovation into tangible progress. In particular, it supports circular economy approaches and contributes to Europe’s strategic autonomy in critical raw materials.