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RESEARCHERS at the US Department of Energy’s (DOE) Ames Laboratory are developing a process to recover rare earth metals from magnets using molten magnesium.

The team, led by materials scientist Ryan Ott, have based their process on Ames’ method to produce neodymium-magnesium alloys from neodymium-iron-boron magnet scrap, which was invented in the 1990s. At the time the cost of rare earths was low, so pure recycled metals were not so desirable and were used to add strength to alloys. Between 2009 and 2011, prices rose ten-fold, and Ott’s team has tweaked the process to produce pure rare earth metals.

The magnets Ott and his team can recycle contain neodymium, praseodymium and dysprosium. They first grind them in an automated pestle and mortar until the particles measure around 2–4 mm. The particles are put into a mesh steel box and then into a stainless steel crucible with pieces of magnesium. The furnace is heated with radio waves to a temperature which melts the magnesium, though the magnet particles remain solid. The rare earth metals in the particles, however, diffuse out into the molten magnesium, leaving behind the boron and the iron.

The molten magnesium and rare earth mixture is cast into ingots and cooled, before the team then heat the ingots to boil off the magnesium, leaving behind the rare earths.

“Now the goal is to make new magnet alloys from recycled rare earths. And we want those new alloys to be similar to alloys made from unprocessed rare-earth materials,” says Ott. “It appears that the processing technique works well. It effectively removes rare earths from commercial magnets.”

Ott adds that the team will now work on scaling up the process.