Separation and enrichment of tricolor phosphors in waste phosphors through liquid–liquid–powder extraction method and its benefit evaluation for recovery

Abstract

This study aimed to separate and enrich tricolor phosphors powder including red, blue, and green phosphors in waste phosphors which also contained white phosphors through liquid–liquid–powder extraction method. Kerosene and water were used as the two liquids. Dodecylamine acetate (DAA) was used as the surfactant collector. The operating factors including pH, DAA dosage, kerosene–water volume ratio, solid concentration, extraction temperature, and extraction time, on the enrichment of tricolor phosphors powder were investigated. In addition, the benefit of introducing liquid–liquid–powder extraction method in the recovery procedure of tricolor phosphors from waste phosphors was also evaluated through the comparison of applying hydrochloric acid (HCl) leaching for the separated tricolor phosphors and the waste phosphors.The results indicated that the optimal conditions of liquid–liquid–powder extraction method were that the dosage of DAA was 1.5 kg/ton at pH 3 with a kerosene–water volume ratio of 20/80 (v/v), a solid concentration of 1.25 w/v%, an extraction temperature of 25 °C, and an extraction time of 15 mins. Under these conditions, the grade of tricolor phosphors recovered from the water phase was enriched from its initial grade of 15.0 % in the waste phosphors to 72.5 % with a recovery of 67.4 %. The benefit of introducing liquid–liquid–powder extraction method was that more than 50 % of the reagent cost and nearly 90 % of the wastewater generation were reduced compared to those without liquid–liquid–powder extraction treatment. In addition, white phosphors with a grade of 92.3 % and a recovery of 96.7 % could be recovered from the kerosene phase simultaneously. This study also demonstrates the merit of introducing a physical separation treatment in a resources recovery procedure before chemical treatment.