In his doctoral research in the field of chemistry at the University of Helsinki, Xu Junhua studied the recovery of rare earth elements, or REE. He developed new ion exchangers based on zirconium phosphate, with which it is possible to recover and separate cobalt, neodymium, and dysprosium from each other.
“China produces the majority of the rare earth elements in the world. The interest of the industry in recycling has varied as the price of the raw material fluctuates, but the most ecological thing would be to reuse the metals used in the components”, Junhua Xu says.
Lately, neodymium permanent magnets (NdFeB) have displaced others thanks to their low price and better magnetic features. In his research, Xu Junhua concentrated on developing recovery methods for the rare earth elements necessary in the production of these magnets.
The doctoral researcher carried out tests on the laboratory scale, where he first managed almost complete metal separation of cobalt, but only partially with the other metals. When repeating the treatment several times, he also managed to separate clean neodymium and dysprosium.
The elements occur in small amounts
“One of the most difficult tasks in inorganic chemistry is separating two REEs from each other. However, we need clean metals for turbines”, says researcher Risto Koivula from the radiochemistry laboratory at the University of Helsinki.
Different methods have been used ever since the times of the Manhattan project that developed the atomic bomb during the Second World War. The hardest thing is to find a method that is efficient enough, as well as cheap enough for the industry to adopt it. The industry’s interest in recycling depends on the world market price for rare earth elements. At the moment, the prices are low enough for production lines based on recycling to have been discontinued.
Junhua Xu has been working within EREAN, an EU-funded Marie-Curie Initial Training Network Project, where 15 researchers from the industry and various research institutes have been studying the lifespan of permanent magnets, and how the recovered components can be used for a new, functioning product.
Junhua Xu will be defending his thesis, "Recovery of rare-earth elements from NdFeB magnets by zirconium phosphate ion exchangers," on 31 August, 2018, at the Faculty of Science at the University of Helsinki. The defense will be held in auditorium A110, the Department of Chemistry, on 31 August 2018. Examiner is Professor Dimitrios Panias, National Technical University of Athens, and custos Professor Anu Airaksinen.
The dissertation is available as an e-publication at the E-thesis service.
M.Sc. Eng. Junhua Xu
Phone: +358 41 4905053
Researcher, group leader Risto Koivula, Ion exchange for nuclear waste treatment and for recycling
Phone: + 358 50 4486640
Science communicator Riitta-Leena Inki
Phone: +358 50 448 5770