Controlled crystallization of rare earth elements from deep eutectic solvents for recycling of permanent magnets

This project will develop a combination of two technologies for the separation of critical rare earth elements from permanent magnet waste: selective dissolution using deep eutectic solvents and controlled antisolvent crystallization.

Deep eutectic solvents are a new class of safe, green, low-cost solvents, composed of a hydrogen bond acceptor and donor pair, which have shown remarkable power to dissolve metals in pure and oxide form.

By tuning the chemistry and optimizing conditions, selective dissolution of rare earth oxides from iron and other elements will be investigated. Antisolvent crystallization is a clean, low-temperature method to recover pure metal salts at high yields.

By careful control of the supersaturation generated, in particular locally at the antisolvent feed point, the crystal growth kinetics will be controlled.

The potential to use antisolvent crystallization to selectively separate and obtain REE and Co carboxylate salts from the deep eutectic solvent leach liquor will be investigated, and mechanisms of impurity incorporation will be probed. A complete closed-loop process with full chemical recycling will be evaluated.

In combination, these techniques have great potential to form the core of a sustainable and efficient recycling method for EOL permanent magnets, production scrap and other REE-containing waste. The project is linked to international collaboration and supported by a reference group with industry and academia.