Selective Recovery of Gallium and Indium from E-Waste via Sulfidation and Distillation

The demand of gallium and indium have increased dramatically in the past decades due to the unique electronic properties of their chemical compounds, which form the backbone of all modern opto-electronic devices. Gallium, in the compounds gallium arsenide and nitride (GaAs, GaN), is the emitter material of light emitting diodes (LEDs); and indium, in the form of indium tin oxide (ITO), is a transparent conductor vital for liquid crystal displays (LCDs) to operate. Although earth abundant, these metals have no concentrated deposits and are recovered as byproducts from within the solid solutions of bauxite (Ga, primary aluminum) and sphalerite (In, primary zinc). One way to lessen the demand on this highly inelastic supply is to increase recovery via recycling of electronic waste (e-waste). However, the chemical environments in which these metals are located in e-waste, as a nitride and ternary oxide, are incompatible with re-introduction to the primary extraction path. Herein we introduce sulfidation followed by vacuum distillation as a pyrometallurgical pathway capable of selectively recovering and concentrating both gallium and indium out of their e-waste compounds. The results of this study have been used to inform the design of a batch reactor capable of recovering 50 g/h (≈ 0.5 tonne/year) of target metal, the results of which are published elsewhere (Benderly-Kremen et al. in JOM 77(11), 2025).