Recycle Gallium and Arsenic from GaAs-Based E-Wastes via Pyrolysis-Vacuum Metallurgy Separation: Theory and Feasibility

This work proposed a novel method of pyrolysis and vacuum metallurgy to recycle gallium and arsenic from GaAs-based e-wastes, which may cause arsenic contamination and gallium waste if treated improperly. As a typical GaAs-based e-waste, the light-emitting diode (LED) was studied in this paper. Pure GaAs chips were first adopted to study the vacuum separation behavior of gallium and arsenic. Then, GaAs chips and packaging materials were mixed together to study the effect of packaging material pyrolysis on the subsequent vacuum metallurgy separation behavior of GaAs chips. This indicated that gallium and arsenic can be recycled efficiently at the heating temperature of 1273 K, the holding time of 60 min, and the vacuum pressure of ∼20 Pa, and the total recovery efficiency can reach 95 wt %. The recovered gallium and arsenic were condensed and collected in respective zones. However, because of the effect of organic material pyrolysis, some gallium was oxidized as gallium oxides, while arsenic was influenced little. This study will reveal the speciation transformation of gallium and arsenic during vacuum heat treatment, which can provide the theoretical foundation for recycling gallium and arsenic from LEDs and other GaAs-based e-wastes through pyrolysis and vacuum metallurgy separation.