A Review on Recycling of End-of-Life Light-Emitting Diodes for Metal Recovery

The generation of end-of-life light-emitting diodes (LEDs) requires efforts to minimize waste and recycle critical raw elements (gallium, indium, and rare earths). This review critically analyzes recycling processes such as physical, hydrometallurgical, and pyrometallurgical treatments. An insight into gallium compounds (GaN, GaAs) and their influence on recycling strategies is provided. Pre-treatment plays a critical role in dissociating the rigid structure of GaN. The major gaps in recycling are identification, segregation, selective recovery, and limited studies on the elemental flow of toxic arsenic. It is calculated that the processing of 1 ton of LEDs is equivalent to 7.8 tons, 3.2 tons, and 42 tons of primary Ga ore, In ore, and Au ore in metallurgical value, respectively. The market value calculations revealed significant economic values of Au, Ag, and REEs. A recycling flowsheet based on the literature for the holistic recovery of Ga, In, Au, and REEs is proposed.