Microwave-assisted and regular leaching of germanium from the germanium-rich lignite ash

Demand for germanium (Ge) is rapidly growing in recent years in various fields including semiconductors, aerospace, and solar cells. However, the Ge resources are very limited in the world. Hence, in this work, microwave-assisted leaching and conventional leaching methods are employed for the leaching of Ge from the Ge-rich lignite ash (GA). The effects of leaching temperature, leaching time, initial acid concentration, oxidizing agent amount, and stirring speed on leaching of Ge were investigated and microwave-assisted and conventional methods of leaching were compared. Here, HCl solution is used as a leaching agent, and MnO₂ is used as an oxidizing agent. From the results, the leaching rate of Ge was found to be 89.49% in the microwave-assisted method, and 83.62% in the conventional leaching method. The optimal conditions for microwave-assisted method include a leaching temperature of 65°C, a leaching time of 90 min, an oxidizing agent amount of 10 g/l, an initial acid concentration of 10 mol/l, and a stirring speed of 250 rpm. The leaching rate of Ge significantly improved in the microwave-assisted method as compared to the conventional method. Therefore, the microwave-assisted method is a suitable method for the leaching of Ge from the GA and is a novel way for the efficient utilization of Ge concentrate.