Researchers from the Dept. of Chemical Engineering of KU Leuven (Belgium; www.cit.kuleuven.be), in collaboration with KU Leuven chemists, have discovered a method to separate two rare-earth elements — europium and yttrium — with ultraviolet (UV) light. The study, published earlier this year in Green Chemistry, promised to be a simpler and “greener” alternative to liquid-liquid extraction, which requires a solvent and multiple steps to achieve adequate separation, due to its low efficiency.
In early 2015, KU Leuven chemists developed ionic liquid technology to recycle europium and yttrium from collected fluorescent lamps and low-energy light bulbs. Their method recycles the red lamp phosphor as a whole to reuse the powder in lamps. For other applications, however, it is necessary to separate europium and yttrium from the rare-earth mixture.
In the new method, the aqueous solution of Eu+3 and Y+3 ions is irradiated with UV light. The Eu+3 ions are selectively reduced to Eu+2, which then precipitates as EuSO4, leaving the Y+3 ions in solution. The EuSO4 is then filtered. More than 95% of the Eu is recovered as EuSO4, which has a purity of 98.5%. A similar purity was obtained with industrial mixtures. The researchers are now working to improve the purity and optimize the process.
The research is part of the KU Leuven activities in the knowledge platform RARE3 (www.kuleuven.rare3.eu), a collaboration involving chemists, chemical technologists and material engineers, among others, to investigate the recycling of rare earth and other critical metals.