Characterization of end-of-life LED lamps for the recovery of precious metals and rare earth elements

Abstract

LED (Light Emitting Diode) lamps have been replacing conventional light bulbs (fluorescent and incandescent) due to their lifetime, luminescence power, and energy saving, and thus, the generation of end-of-life LED lamps is increasing. Unpublished data on their composition, focusing in the precious metals and rare earth elements, is presented and is extremely important for future studies involving recycling processes. From samples comminuted in ring mills, loss-on-ignition as well as digestion in aqua regia and nitric acid were used. The results showed that LED lamps had 8 wt.% and 14 wt.% of inorganics, 34 wt.% and 36 wt.% of polymers, and 50 wt.% and 58 wt.% of metals when leached by aqua regia and nitric acid, respectively. Two traditional e-waste leaching agents were used for comparison purposes, and although aqua regia was reported as efficient for the leaching of precious metals, rare earth elements were only verified for leaching with nitric acid. Antimony, silver, aluminum, and copper presented statistically significant differences between the two leaching agents used. The characterization also allowed for identifying the presence of arsenic, which is considered a harmful substance to health. Compared to other types of lamps (fluorescent and incandescent), only LED lamps contain gold, which makes them economically attractive. In this sense, it was concluded that LED lamps must be recycled both from the environmental point of view, regarding the presence of arsenic and the increasing waste generation, and the economic point of view, due to the presence of critical metals and recovery potential.