PROCESS FOR RECOVERING RARE EARTH OXIDES FROM PHOSPHORS, FLUORESCENT LAMPS AND LIGHT BULBS, CATHODE RAY TUBES AND OTHER INDUSTRIAL WASTES

摘要

The present disclosure broadly relates to a novel process for the recovery of rare earths oxides from phosphors, fluorescent lamps and light bulbs, cathode ray tubes and other industrial wastes containing rare earths elements in the form of halophosphates, tri-band phosphors and other fluorescent materials, the process comprising: a) submitting the wastes or spent materials to either caustic fusion or hot alkaline leaching; b) submitting the solidified melt to hot alkaline leaching step to produce insoluble solid residues and a barren alkaline leaching solution; c) crystallizing the tri-sodium phosphate from the barren solution; d) oven-drying or calcining the residues; e) acid leaching the oven-dried or calcined solids; f) recovering the cerium (IV) oxide from insoluble solids; g) reducing the cerium-free solution, precipitating, acid leaching, precipitating, calcining and recovering the europium (III) oxide; h) precipitating the remaining rare earths as oxalates; i) calcining the rare earths oxalates and dissolving the rare earths oxides in acid; j) separating the yttrium, gadolinium, terbium and erbium by ion exchange (IX) or solvent extraction (SX); h) precipitating and calcining to yield pure yttrium (III) oxide, gadolinium (III) oxide, terbium (III, IV) oxides, and erbium (III) oxide; i) regenerating and recycling the spent alkaline solution after causticization with calcium oxide or hydroxide.