Magnetic fields can make separating ‘rare earth’ materials from one another less wasteful, according to the University of Pennsylvania.

Used in displays, lasers and magnets, the rare earths are chemically similar and therefore challenging to separate – they tend to be found in the earth in mixtures, and can also presented for recycling in mixtures.

The standard approach for separating such mixtures, according to the university, is to dissolve the whole lot and exploit the slight chemical differences between the the different rare earths.

Unfortunately, many chemical properties, such as solubility or reactivity with other elements, are similar between rare earths, leading to time-consuming and energy-consuming processing.

“It works well when you do it 10,000 times, but each individual step is poorly efficient,” said U Penn chemist Eric Schelter.

The materials are also paramagnetic, and differently so, but it has proved difficult to couple their paramagnetism with a chemical reaction to improve separation.

That is until now, according to the university, as its team has combined a third effect – a temperature gradient – and caused the ions of different rare earths to crystallise at different rates.

“We use lower temperatures to crystallise a lot of our materials,” said lead researcher Robert Higgins. “It was one of the things I could potentially use, but didn’t realise at the beginning how important that was actually going to be.”

Using its chemical-magnetic-thermal approach, heavy rare earths like terbium and ytterbium have been separated from lighter metals such as lanthanum and neodymium.

“The most striking result was taking a 50/50 mixture of lanthanum and dysprosium and getting back 99.7% dysprosium in one step”, according to the university – doubling the effectiveness compared to the same method without a magnetic field.

“The faster we can find new ways of performing separations more efficiently, the faster we can improve some of the geopolitical and climate issues that are associated with rare earth mining and recycling,” claimed Higgins.