Mechanism and kinetics study on ultrasonic combined with oxygen enhanced leaching of zinc and germanium from germanium-containing slag dust

Abstract

The germanium-containing slag dust (GCSD) contains 49.65% zinc and 620.4 g/t germanium, and has a high recovery value. This work dealt with the leaching behaviors and kinetics of zinc and germanium from GCSD by oxygen-rich acid leaching at ultrasonic environment. The leaching rate (LR) of zinc and germanium are up to 96.66% and 92.96%, which are 4.92% and 9.80% higher than the conventional leaching (CL) method, respectively, indicating that ultrasonic and oxygen have a good synergistic effect. The element correlation fitting analysis shows that germanium has a high correlation with zinc and sulfur, so it is believed that some germanium may exist in ZnS in the form of isomorphism, or occur in the package of ZnS as an independent mineral containing germanium in the body. Characterization analysis studies have confirmed that the combination of ultrasonic waves with oxygen can not only destroy the crystal structure of minerals and reduce the crystallinity of minerals, but also break minerals, open mineral inclusions, leaching sulfides and release encapsulated germanium, and finally improve the LR of zinc and germanium. The analysis of leaching kinetics shows that the leaching reaction process of zinc and germanium is controlled by a mixture of diffusion control and chemical reaction control, and the activation energies of zinc and germanium are 14.996 kJ/mol and 23.133 kJ/mol, respectively. Ultrasound combined with oxygen (UOL) leaching can improve kinetics and reduce reaction activation energy. In addition, the UOL leaching does not bring in impurity ions, and the leaching residue can be used as a raw material for recovering lead and silver, and no toxic and hazardous waste is generated. It is a green, efficient and environmentally friendly method for waste recycling.