Recovery of rare earth element from waste cathode ray tube phosphors by concentrated sulfuric acid directional transformation-water leaching

Abstract

A process for recovering both Eu and Y from the discarded cathode ray tube (CRT) display was introduced. The developed process involved a directional transformation of waste CRT phosphors with concentrated sulfuric acid followed by leaching with water. Rare earth metal ions combined with sulfate to form rare earth sulfates and then were extracted by water leaching, while S²⁻ was oxidized to form sulfur, which was volatilized in gaseous form, thus avoiding the formation of the highly toxic gas H₂S. This study showed that in the optimized conditions, the ratio of concentrated sulfuric acid to sample was 8:5 mL/g and transformation time for 30 min under 85 °C, the liquid-to-solid ratio was 10:1 mL/g and leaching time was 30 min under 85 °C. The leaching solution with Y concentration of 8.26 g/L and Eu concentration of 0.57 g/L was obtained and the average leaching efficiencies of Y and Eu were 99.77% and 99.24%, respectively.

Keywords

rare earth / waste CRT phosphor / recovery / oxidative comproportionation / leaching

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