Ionic liquids for REE recovery from lamp phosphor waste

Within the EU H2020 REMAGHIC project, KU Leuven developed a process to recover yttrium and europium from a mixed oxide obtained by the processing of lamp phosphor waste based on solvent extraction with undiluted thiocyanate ionic liquids. The work is published in the Journal RSC Advances. (Leuven, 18/2/2019)

Spent fluorescent lamps contain a significant amount of the rare earths yttrium and europium, which are present, in particular, in the red phosphor YOX as oxides (Y₂O₃:Eu³⁺). Because the market demand for phosphors has moved to LED lamps, a lot of waste phosphor becomes available and the mutual separation of yttrium and europium is required for their use in other applications.

In this paper we propose an alternative approach compared to the conventional solvent extraction to separate yttrium and europium which is based on the use of undiluted ionic liquids, namely Cyphos IL 101 and Aliquat 336 thiocyanate. The main advantages of this approach are the use of non-volatile and non-flammable organic solvents and the limited number of process steps required to the desired separation.

We observed that the best extraction performances are obtained with [C101][SCN], by using four counter-current extraction stages. The loaded organic phase was afterwards subjected to scrubbing (with a solution of CaCl₂ and NH₄SCN) to remove the co-extracted europium. Yttrium was then stripped by deionised water. Yttrium and europium were finally recovered as hydroxides by precipitation with ammonia and then calcined to the get the corresponding oxides.

The process was first developed by using synthetic solutions and afterwards applied on a leachate obtained from the dissolution of a real mixed oxide. The research presented in this manuscript is relevant also for the recovery of rare earths from end-of-life cathode-ray tube (CRT) phosphors.

Figure 1: Yttrium and europium are separated from a mixed oxide through solvent extraction with undiluted thiocyanate ionic liquids.

Full reference paper

R. Banda, F. Forte, B. Onghena, K. Binnemans, Yttrium and europium separation by solvent extraction with undiluted thiocyanate ionic liquids, RSC Advances, 2019, 9, 4876.

Biography Raju Banda

Raju Banda worked as postdoctoral fellow at (SOLVOMET) KU Leuven, Department of Chemistry. His main interests are in the field of hydrometallurgy and ionometallurgy. In particular, he was involved in the development of solvent extraction processes for rare earths recovery from lamp phosphor waste.

Acknowledgements

This work has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 680629 (REMAGHIC: New Recovery Processes to produce Rare Earth-Magnesium Alloys of High Performance and Low Cost) (project website: http://www.remaghic-project.eu).

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