One-stage ultrasonic-assisted calcium chloride leaching of lead from zinc leaching residue

Abstract

To efficiently leach Pb from Zn leaching residue, an ultrasonic-assisted one-stage leaching process was developed and compared with a two-stage leaching process under conventional conditions. The results showed that Pb leaching efficiency reached up to 83.8% under the optimized one-stage ultrasonic leaching conditions (including 480 W of ultrasonic power, 100 min duration, 350 g/L of CaCl2, 5:1 of liquid-solid ratio, 35°C, and pH of 3), higher than that under conventional process with same conditions (65.7%). A diffusion model controlled the ultrasonic-assisted leaching process at 7.57 kJ/mol activation energy. X-ray diffraction and scanning electron microscopy showed that the mineral phase of Pb-containing anglesite disappeared during the leaching. By contrast, the Zn-containing franklinite minerals and Zn orthosilicate remained in the leached residue. The possible leaching mechanism of the ultrasonic-assisted effect was related to that the Pb released from Zn leaching residue by forming PbCl42− in the leachate, avoiding PbCl2 precipitation under the conventional method. Moreover, introducing could lower the leaching temperature and reduce the amount of leaching agent, which could potentially be a sustainable technique for increasing the leaching efficiency of Pb from Zn leaching residue.