Abstract
Two processes applying green solvents for recovering rare earth elements (REEs) from different types of aluminate phosphors are demonstrated in this report. For magnesium aluminate-type phosphors, a pretreatment with peroxide calcination was implemented first, and then followed by a supercritical fluid extraction (SFE) process. Supercritical carbon dioxide (sc-CO2) provides an effective and green medium for extracting REEs from dry materials. With the addition of a complex agent, tri-n-butyl phosphate-nitric acid complex, highly efficient and selective extraction of REEs using supercritical carbon dioxide can be achieved. The highest extraction efficiency was 92% for europium from the europium doped barium magnesium aluminate phosphor (BAM), whereas the highest extraction selectivity was more than 99% for the REEs combined from the trichromatic phosphor. On the other hand, for strontium aluminate type phosphors, a direct acid leaching process is suggested. It was found out that acetic acid, which is considerably green, could have high recovery rate for dysprosium (>99%) and europium (~83%) from this strontium aluminate phosphor materials. Nevertheless, both green processes showed promising results and could have high potential for industrial applications.
Highlights
Rare earth elements (REEs) have grown much in interest and demand in recent years due to their unique properties, which are irreplaceable in making modern electronic devices [1,2,3]
Yttrium has the highest composition in the phosphor materials, while europium, cerium and terbium have lower contents
Two processes applying green solvents for recovering REEs from different aluminate phosphor materials have been successfully demonstrated in this report
Summary
Rare earth elements (REEs) have grown much in interest and demand in recent years due to their unique properties, which are irreplaceable in making modern electronic devices [1,2,3]. The phosphor materials in the spent lamps can be recycled for reuse as some recycling facilities have developed technologies aimed for such applications [9]. Another approach is to recover the REEs present from the phosphor materials collected from the spent lamps [10,11,12,13,14]. This approach cannot be done on an industrial scale yet since it requires economically viable extraction technologies to achieve
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