Rare earth elements (REEs) are key materials for the development of renewable energy devices such as high-power magnets for wind turbines, electric vehicles, or fuel cells for hydrogen generation, aiming to fulfill the objectives of the European Green Deal for a carbon-neutral economy. The increased demand for REEs and their criticality strongly require the improvement of their extraction technologies from primary resources and the enhancement of their circularity reuse rate from secondary resources. The aim of this paper is to focus attention on the possibilities offered by emerging methods such as microwave (MW) treatment and mechanochemistry in waste electric and electronic equipment (WEEE) processing and the reuse of end-of-life (EoL) magnets, directed toward the tailoring of rational REE material flows. The discussed investigation examples explore some key features of conventional and new methods for efficient, environmentally friendly, and scalable REE extraction and reuse, with the final goal of producing recycled NdFeB powders, with potential use in the redesign and fabrication of new REE-based magnets.
According to their composition, the NdFeB permanent magnets form the following main groups: NdFeB magnets manufactured into either resin-bonded alloys (containing usually 10% epoxy resin or a polymer), or into fully dense sintered magnets with the magnetic matrix NdFeB [ 26 ]. At this time, both types of REE scrap are expected to become more available with the increasing collection of EoL goods. Thus, the rising opportunity for recycling a variety of products containing NdFeB magnets allows a systematic approach to recycling scrap magnets as a potential secondary resource [ 8 ]. Different treatment approaches for recycling REE-containing spent magnets [ 27 ] or scrap have been extensively investigated [ 28 30 ]. Rare earth permanent magnets usually contain more than 30 wt.% of the REEs [ 19 21 ]. They can be classified into three main types, samarium cobalt (SmCo), samarium iron nitrogen (SmFeN), and neodymium iron boron (NdFeB) [ 22 ]. Due to their better performance and good price, NdFeB permanent magnets have been incorporated into a wide range of products, such as wind turbines, electric vehicles, magnet resonance imaging devices, industrial robots, light means of transport, cooling generators, heat pumps, electric motors, industrial electric pumps, automatic washing machines, tumble dryers, microwaves, vacuum cleaners, and dishwashers, as well as a huge variety of smart and electronic devices [ 23 25 ]. The high value of the REEs for the preparation of advanced materials [ 7 ] is strongly connected with their unique magnetic, optic, electronic, and conductive properties, which are highly desirable for a broad range of technological applications [ 8 10 ]. The main fields of REE application currently include the production of new and high-technology materials such as magnets, catalysts, metal alloys, electronics, NiMH batteries, fluorescent lamps, glass, and ceramics. According to the published statistics, the biggest share in these high-tech applications of…
Cherkezova-Zheleva, Burada, Sobetkii, Slobozeanu, Anca Elena, Paneva, Fironda, Sabina Andreea, Piticescu, Zara Cherkezova-Zheleva