Exploring a promising technology for the extraction of gallium from coal fly ash

The coal fly ash (CFA) in the present study contains a high content of gallium, which is categorized as a strategic metal. Gallium extraction from CFA is an important step toward its reutilization. Two different processes for gallium extraction were systematically investigated and compared. The effects of mixed acid, microwave power, microwave digestion time, the amount of HNO3, HF, and HCl were studied. The results revealed that although both open wet digestion and microwave-assisted digestion could successfully leach gallium, the former method consumed a longer time. The microwave-assisted digestion was a time-saving way but required the use of HCl. Compared to previous studies, the processes proposed in this article can greatly reduce environmental pollution and cost as they halved the use of acids.