Recycling Arsenic from Gallium Arsenide Scraps through Sulfurizing Thermal Treatment

Due to its superior electronic properties, gallium arsenide (GaAs) is widely used in integrated circuits which are the core elements of most electric and electronic equipment. With the obsolescence of this equipment, a large amount of GaAs scraps is generated, which may possess potential threats to human beings and the environment if treated improperly. In this paper, an integrated process combining sulfurization and evaporation is proposed to recycle arsenic from GaAs scraps. The sulfides of arsenic can be easily evaporated and recycled. More importantly, the environmental requirements are satisfied because of the low toxicity of the arsenic sulfides. Using solid sulfur as the sulfurizing agent, 88.2% of arsenic can be extracted from GaAs scraps under the optimized conditions of 5 K/min heating rate, 453 K midsection temperature, 40 min midsection holding time, 1073 K final temperature, and 60 min corresponding holding time. The behavior of arsenic during the sulfurizing thermal process is discussed in details. After the instrument examinations of X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray phototelectron spectroscopy (XPS), the sulfurizing mechanism is explored and the reaction equation is deduced as 2GaAs + (2x + 3)S → 2AsS_x + Ga₂S₃. This research can provide the theoretical foundation for recycling arsenic from GaAs scraps or other e-waste containing arsenic.