Yttrium and europium recycling from phosphor powder of waste tube light by combined route of hydrometallurgy and chemical reduction

Abstract

This paper deals with the recovery of yttrium and europium from waste tube light phosphor powder leach liquor using solvent extraction and chemical reduction route. Hydrochloric acid (2 mol/L) is used as the leachant to generate the leach liquor. From the leach liquor, the separation of Y(III) and Eu(III) is carried out with three types of extractants (acidic, neutral and ionic liquid) with extractant concentration and pH variation. Highest separation factor of 60.6 is achieved with 0.1 mol/L D2EHPA at aqueous phase pH of 2.56. The quantitative extraction of yttrium from the leach liquor is achieved in two counter current stages at O:A ratio of 1:1.5 at pH 2.56. After extraction of yttrium, yttrium oxalate is prepared by precipitation stripping with 0.4 mol/L oxalic acid. The stability and reusability of the extractant is also investigated. The reduction process with zinc helps to reduce 78% of Eu (III) to Eu (II) but 16% Y(III) is precipitated as yttrium sulfate along with Eu(II) precipitation. A tentative flow-sheet is developed for the whole process.