Enhancing rare-earth recovery from lamp phosphor waste

© 2019 The Authors In the present work rare-earth recovery was performed from a residue of a hydrometallurgical process based on sulphuric acid leaching of lamp phosphor waste by which the red phosphor Y 2 O 3 :Eu 3+ was removed for further recovery. The undissolved residue is rich in lanthanum, cerium and the valuable terbium, present as phosphates and aluminates in the green and blue phosphors. The process here proposed is based on an integrated pyro-hydrometallurgical approach involving a thermal treatment (roasting in the presence of sodium carbonate)aimed at converting rare-earth phosphates into oxides, which can be more easily leached by mineral acids (HCl and H 2 SO 4 )in a further leaching step. Rare-earth recovery from the leachate was then performed by solvent extraction with the extractant di-(2-ethylhexyl)phosphoric acid, D2EHPA, followed by precipitation with oxalic acid and calcination. 82% Ce, 75% La and 82% Tb were recovered as mixed La 2 O 3 + CeO 2 oxide (99% purity)and Tb 4 O 7 (64% purity).

Publication year:2019

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Authors:International

Authors from:Higher Education

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