Journal
JOURNAL OF SUPERCRITICAL FLUIDS
Volume 33, Issue 3, Pages 235-241Publisher
ELSEVIER
DOI: 10.1016/j.supflu.2004.08.004
Keywords
supercritical fluid extraction; rare earth elements; luminescent material; TBP complex with HNO3 and H2O; fluorescent lamp
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Rare earth elements were extracted from luminescent material in waste fluorescent lamps using supercritical carbon dioxide (SF-CO2) containing tri-n-butyl phosphate (TBP) complexes with HNO3 and H2O. The determined Y, Eu, La, Cc and Tb in the employed luminescent material were 29.6, 2.3. 10.6, 5.0 and 2.6 wt.%, respectively. Aqueous droplets were generated in an extraction experiment from a reaction with metal oxides and a complex prepared from vigorous mixing of TBP with concentrated nitric acid (15.5 mol dm(-3) (M)). These droplets were generated because the complex was saturated with water and the excess water separated, leading to low recovery yields. The molecular ratio of TBP:HNO3:H2O in the complex was 1.0:1.8:0.6. When the ratio was changed to 1.0:1.3:0.4 by dilution with TBP anhydrate, the separation of water was prevented. Using this complex, extraction efficiencies for Y and Eu increased to over 99% after the static extraction for 120 min at 15 MPa, 333 K. (C) 2004 Elsevier B.V. All rights reserved.
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