The Royal Society of Chemistry’s Chemistry World reported that two scientists at the University of Leuven in Belgium have collaborated to separate phosphor rare earths europium and yttrium from red lamp phosphor extracted from light bulb waste.
As quoted in the publication:
Tom Van Gerven, at the University of Leuven in Belgium, is interested in how light and other alternative energy sources can boost chemical processes. Koen Binnemans, at the same university, is a chemist who has previously applied ionic liquids to rare earth recycling, successfully extracting red lamp phosphor, a mixture of europium and yttrium, from light bulb waste. Together they realised that they could use photochemistry to go a step further and separate europium and yttrium from each other. ‘In the work on the ionic liquid you extract the europium and yttrium in the same ratio as they were in the red lamp phosphor, so you can only use this mixture again for red lamp phosphors. Whereas in our case we are separating the europium and yttrium … so we can use those streams for any purpose we like,’ explains Van Gerven.
Both elements exist as trivalent (Eu3+ and Y3+) ions in solution, but europium is also stable in the divalent state (Eu2+). Absorbing light of the correct wavelength reduces Eu3+ to Eu2+, which can then be precipitated out of solution as europium sulfate. For artificial Eu–Y mixtures, the Leuven team removed nearly all of the europium, and almost no yttrium, using a low pressure mercury lamp.