Recovery of waste rare earth fluorescent powders by two steps acid leaching

Abstract

The effects of the acid leaching and alkali fusion on the leaching efficiency of Y, Eu, Ce, and Tb from the waste rare earth fluorescent powders were investigated in this paper. The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching, and NaOH is better than Na2CO3 in the alkali fusion. In the first acid leaching, the W loss is 20.94 % when the waste rare earth fluorescent powders are acid leached in H+ concentration 3 mol·L−1 and S/L ratio 1:3 for 4 h due to red powders dissolved. The better results of the alkali fusion can be got at 800 °C for 2 h when the NaOH is used. The blue powders and the green powders can be dissolved into NaAlO2 and oxides such as rare earth oxide (REO). The REO can be dissolved in H+ concentration 5 mol·L−1, S/L 1:10 for 3 h in the second acid leaching. The leaching rates of the Y, Eu, Ce, and Tb are 99.06 %, 97.38 %, 98.22 %, and 98.15 %, respectively. The leaching rate of the total rare earth is 98.60 %.