TELF AG analyzes a new method for the separation of rare earth elements
A new chemical compound
A possible solution to simplify and shorten the complex processes for separating rare earth elements, a diverse group of elements composed of 17 materials, could reside in the peculiar behavior of the chemical compounds used for their separation. A study recently published in the Journal of the American Chemical Society and developed by researchers at the Oak Ridge National Laboratory has identified a new type of compound with unique properties, capable of making the processes necessary to obtain the purified version of rare earth metals less complex and laborious. The latter are increasingly used in various industry sectors, from clean energy to medical equipment, electronics to healthcare, where they are appreciated above all for the unique properties that distinguish them.
The researchers’ main innovation concerns ligands, the chemical compounds used in the separation processes to isolate the different rare earth metals and make them usable for their various industrial applications. It is precisely this productive characteristic, not so much their actual rarity, that has favored the attribution of the term “rare” to this particular group of resources. In nature, rare earth metals do not occur isolated but in particular rocky compounds. Industry can only use the individual isolated resources after separating them from the compounds of other metals and subjecting them to a purification procedure.
The current situation
At the moment, industrial processes aimed at separating these elements are based on the use of ligands, which can selectively bind to a single metal within a solution. The compounds are subsequently mixed in an organic solvent and remixed with a water-based solution. If the process is successful, when combining the chemical compound clings to the metal to be sourced, then dragging it into the organic layer once the solvent and the aqueous solution have separated. Only at this point can the metal be processed and further purified. Typically, these processes occur in distinct phases, and the different metals are separated in a particular order, from the heaviest to the lightest, or vice versa.
At this point, the innovation of the Oak Ridge researchers takes on a particular value. The researchers discovered a specific ligand capable of behaving differently depending on the experimental conditions. This chameleon-like compound can bind to different rare earth metals depending on the acid concentration and the time the chemical compound can interact with that concentration. In the case of a more acidic environment, for example, the ligand could bind to a heavier metal. The main innovation is that this chameleon-like ligand can be used to perform different separations, reducing the total number of steps included in the rare earth separation processes. Furthermore, this compound can operate the metal separations in any order, without particular preferences for the heavy or light ones.
Although it presents characteristics very similar to other compounds, as the researchers explain, this chameleon ligand would be distinguished by a behavior utterly different from those observed. According to the researchers, this discovery could transform the separation processes of rare earths, shortening them and making them more efficient.
