Enhanced recovery of rare earth elements from waste phosphors by mechanical activation

Abstract

Rare earth elements (REEs) make up more than 23 wt% of phosphors in fluorescent lamps (FLs). The REEs recovering from waste phosphors is becoming a critical issue since REEs are considered critical elements, being important in future sustainable applications e.g. wind power, electric vehicles, energy efficient lighting, etc., and also, the accelerated generation of waste FLs. In this present study, mechanical activation (MA) was innovatively employed to pre-treat waste phosphors to recover REEs effectively by an acid leaching process. The results showed the feasibility of using MA to enhance the leaching rate of REEs. The leaching rates of terbium (Tb), lanthanum (La) and cerium (Ce) had a significant enhancement of around 90%; and the leaching rates for europium (Eu) and yttrium (Y) were 93.1% and 94.6%, respectively. Moreover, the mechanism for REEs leaching rates enhancement introduced by MA was explored. Substantial physicochemical changes appeared to be the main causes leading to the effectiveness of mechanical activation for phosphors. These changes include structural destruction and compound decomposition, rather than an increase in specific surface area and a reduction in particle size. All these findings and results indicate that this novel application of MA for enhancing the recovery of REEs from waste phosphors is a promising route.