Recovery gallium from GaAs waste etching solutions by solvent extraction

Gallium arsenide was widely used in light-emitting diodes and semiconductor industries in the world while. According to USGS, 63 metric ton GaAs wafers were imported to America in 2018. Lots of waste solutions containing gallium arsenide has been generated during the etching process of GaAs wafer. Owing to the great amount of gallium in the waste etching solutions, environmentally friendly technology should be established to treat toxic arsenic when gallium was recovered. In this study, gallium arsenide waste solutions were aqua ammonia medium and were extracted through Cyanex 272. On the other hand, there were numerous GaAs precipitates in the etching solutions. Hence, the precipitates were dissolved through ammonia solutions and nitric acid first by adjusting the pH value and ORP. In the extraction step, the GaAs etching solutions were extracted by using 0.5 M Cyanex 272 solutions in kerosene at the conditions of pH 2 and 0.1 O/A ratio in 5 mins. The extraction efficiency attained 77.4% which had an optimal ratio of concentration. In the stripping step, the organic phase was stripped with 0.5 M hydrochloric acid at 1 O/A ratio in 3 mins. Finally, more than 97.5% gallium was stripped, and the gallium was 7 times the concentration of the etching solutions.