Recycling of Discarded Tubular Lights for Recovery of Rare Earth Values

Abstract

Increasing demand for rare earth elements (REEs) and instabilities in their supply chain requires an alternative source for REEs. Discarded tubular lights have been evaluated in this study as a potential source of REEs. Phosphor dust separated after crushing, and sieving of tubular lights, comprises approximately 34% rare earths (Y, Eu, Ce, Tb) in Y1.90Eu0.10O3 and Al11Ce0.67MgO19Tb0.33 phases. The present study is focused on a two-step recovery of REEs, the recovery of Y and Eu (> 95%) via a leaching route followed by the recovery of Ce (40%) and Tb (> 95%) from leach residue using microwave exposure followed by leaching. The Y and Eu leaching process is optimized using a statistical design to evaluate different leaching parameters, reaction kinetics, while the activation energy was also studied. The leach residue was microwave-treated with NaOH for the dissociation of Ce- and Tb-bearing phases. The material balance reveals that it is possible to recover 52 g of the mixed oxides of Y and Eu and 7 g of the mixed oxides of Tb, Ce, Eu, and Y with purities of over 99% from 100 units of tubular lights.