A Study on the Leaching of Rare Earth Elements from Waste Phosphor Powder

Abstract

This study was carried out to obtain data to design a process to recover rare earth elements, specifically Y(Yttrium), La(Lanthanum), Ce(Cerium), Eu(Europium), Tb(Terbium) from waste phosphor powder. For this purpose, we investigated the effect of temperature, concentration, time and acids on leaching of the rare earth elements. The effect of roasting temperature, roasting time, roasting agent and its dosage on the leaching of rare earth elements were also investigated. 92% of the Yttrium, 70% of the Europium and 8% of the Cerium contained in the waste phosphor powder was leached at the condition of 50 ^oC and 0.3N HCl solution for 3hours. However, Terbium and Lanthanum were never leached at this condition. The leaching ratio increased to 100% of Yttrium and Europium, 98% of Cerium, 92% of Terbium and 89% of Lanthanum by leaching after soda ash roasting. In the leaching experiment with unroasted phosphor at 80 ^oC, the initial leaching reaction rate of Yttrium was 0.035 mol/L·s in 0.3N sulfuric acid solution, 0.033 mol/L·s in nitric acid solution and 0.028 mol/L·s in 0.3N hydrochloric acid solution. And the initial leaching reaction rate of Europium was 0.0017 mol/L·s in 0.3N sulfuric acid solution, 0.00114 mol/L·s in nitric acid solution and 0.00113 mol/L·s in 0.3N hydrochloric acid solution. For Cerium, the initial leaching reaction rate was 0.00019 mol/L·s in 0.3N sulfuric acid solution, 0.00025 mol/L·s in nitric acid solution and 0.00014 mol/L·s in 0.3N hydrochloric acid solution.