United States – A group of scientists at the US University of Pennsylvania has hit upon a breakthrough in rare earths recycling, specifically the treatment of metals used to create ‘neo magnets’. They have succeeded in separating neodymium and dysprosium from each other, which could open up fresh potential for their recovery from loudspeakers, headphones and even wind turbines.
The novel process relies on a special nitroxide ligand that is added to the salts of the metals, explains project leader Dr Eric J. Schelter. This ligand is an organic molecule that grasps an individual metal ion in a coordination complex like a clamp with ‘three arms’, he has stated in the German journal ‘Angewandte Chemie’.
If the bound metal ions have a large radius, like neodymium, pairs of these complexes tend to form a dimer; in contrast, complexes with small metal ions like dysprosium barely form any dimers at all. As a result, the neodymium complex is ’50 times more soluble’ in benzene than the dysprosium complex.
With a ‘minimal amount’ of benzene, the researchers managed to leach the neodymium complex out of a 1:1 mixture to around 95% purity. ‘The solid left behind contained about 95% of the dysprosium complex,’ the scientists note.
According to Schelter, it is possible to increase the purity of both fractions after further purification steps with benzene. This innovative technique may also be applied to various other rare-earth elements, he adds.