A major source of germanium recovery and also the source of this research is the by-product of lead and zinc metallurgical process. The primary purpose of the research is to investigate the effects of ultrasonic assisted and regular methods on the leaching yield of germanium from roasted slag containing germanium. In the study, the HCl-CaCl2 mixed solution is adopted as the reacting system and the Ca(ClO)2 used as the oxidant. Through six single factor (leaching time, temperature, amount of Ca(ClO)2, acid concentration, concentration of CaCl2 solution, ultrasonic power) experiments and the comparison of the two methods, it is found the optimum collective of germanium for ultrasonic-assisted method is obtained at temperature 80 °C for a leaching duration of 40 min. The optimum concentration for hydrochloric acid, CaCl2 and oxidizing agent are identified to be 3.5 mol/L, 150 g/L and 58.33 g/L, respectively. In addition, 700 W is the best ultrasonic power and an over-high power is adverse in the leaching process. Under the optimum condition, the recovery of germanium could reach up to 92.7%. While, the optimum leaching condition for regular leaching method is same to ultrasonic-assisted method, except regular method consume 100 min and the leaching rate of Ge 88.35% is lower about 4.35%. All in all, the experiment manifests that the leaching time can be reduced by as much as 60% and the leaching rate of Ge can be increased by 3-5% with the application of ultrasonic tool, which is mainly thanks to the mechanical action of ultrasonic.

The method of microwave strengthens roasting neutral leaching slag contained germanium is put forward. The dielectric properties and temperature rising behavior of neutral leaching slag in the microwave field are analyzed via experimental and theoretical analysis. The experiment used the dielectric constant test device, the microwave roasting device and the temperature measuring device. The neutral leaching slag can absorb microwave energy and transform into heat energy. The specific surface area of the calcined slag containing the neutral leaching slag is increased by microwave roasting, and the microwave energy can reduce the particle size of the mineral particles to some extent. At the same time, cracks can be seen on the surface of the calcined sand after microwave roasting. The surface of neutral leaching slag roasted by microwave reformed cracks which help to open reaction channels making the oxygen to inside takes part in oxidizing reaction significantly improving germanium oxide reaction conditions, besides increasing the leaching process of the reaction area and increasing the leaching rate. The research on the dielectric constants and temperature characteristics of neutral leaching residue can provide the theoretical and experimental basis for microwave strengthen roasting.