Recovery of Gallium, Indium, and Arsenic from Semiconductors Using Tribromide Ionic Liquids

Leaching of semiconductors (GaN, GaAs, and InAs) and light-emitting diodes (LEDs) in a nonvolatile tribromide ionic liquid, and the selective recovery of gallium, indium, and arsenic from this ionic liquid were investigated. To prevent the formation of the highly toxic arsine (AsH 3 ), usually formed when leaching metal arsenides with acids, the hydrophobic trihalide ionic liquid tributyldecylphosphonium tribromide [P 44410 ][Br 3 ] was used to oxidatively leach the semiconductors, avoiding arsine formation. After leaching, a selective stripping procedure was applied to remove and recover arsenic, gallium, and indium. Arsenic and gallium could be stripped using NaBr solutions and pure water, respectively, while indium was removed from the ionic liquid phase via precipitation stripping with a NaOH solution. A mechanistic study was performed to explain this difference in stripping behavior. A flowsheet was proposed and, finally, the procedure was applied to real LEDs.