Studies on Recovery of Valuable Metals by Leaching Lead–Zinc Smelting Waste with Sulfuric Acid

Abstract

Germanium-containing residues (GCR) are a secondary resource rich in zinc (Zn) and germanium (Ge) produced in the Zn pyrometallurgical process and an important raw material for recovering Zn and Ge. To recycle the residue by hydrometallurgy, sulfuric acid is used to leach the residue under normal pressure. In this study, the experimental conditions (leaching temperature, leaching time, liquid/solid (L/S) mass ratio and initial acidity) were optimized through the experimental design to make the optimized experimental conditions consistent with the current industrial production conditions, so as to maximize the leaching rate of Zn and Ge, and the main reasons for the low leaching rate of germanium were analyzed. The results show that the optimum reaction conditions are as follows: initial acidity 160 g·L−1, leaching temperature 90 °C, L/S mass ratio 5:1, leaching time 60 min and stirring speed 400 r·min−1. Under the optimum reaction conditions, the leaching rates of Zn and Ge are 83.22% and 77.29%, respectively. The reason for the low leaching rates of Zn and Ge in GCR was obtained through atmospheric leaching experiment, electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and chemical phase analysis. GCR is mainly composed of phases such as zincite (ZnO), galena (PbS), wurtzite (ZnS) and anglesite (PbSO4), and the main elements are Zn, lead (Pb), germanium (Ge), oxygen (O), sulfur (S), silicon (Si), aluminum (Al) and Fe. This study can provide a certain reference value for researchers, in order to provide a reference for the large-scale recycling of Zn and Ge resources in the future.