A review of the current progress in recycling technologies for gallium and rare earth elements from light-emitting diodes

摘要

End-of-life light-emitting diodes are electronic waste containing valuable and critical metals such as rare earth elements (REE) and gallium. These metals face the risk of supply disruption with increasing demand and the difficulty of their extraction and separation through mineral and metallurgical processing. Hence, this study aims to provide a descriptive insight into recovery techniques of light-emitting diodes (LED) waste using examples from other e-waste such as fluorescent lamps, liquid crystal displays, and LED production dust. An investigation was conducted following scoping searches, and a gap in research on LED recycling technologies was found. It was noticed that the possible technologies to recover gallium and REE from LED are physical processes, pyrolysis, bioleaching, and acid leaching, followed by purification processes such as solvent extraction and precipitation. The advantages and disadvantages of each method for industrial application were addressed in terms of efficiency in recovery of gallium and REE, selectivity, and energy consumption. Based on this analysis, hydrometallurgical processing has been identified as the most suitable method to recover gallium and REE from LEDs due to its high efficiency in recovering metals from low-grade secondary raw material. Despite the energy consumption, a first pyrometallurgical step is recommended for gallium recovery. Furthermore, the selection of recovery processes must be consistent with the light-emitting products due to differences in LEDs composition. Overall, the future perspective for LED recycling is to exploit the economic potential of this e-waste, aiming at a circular economy that enables the conservation of natural resources.