A Comparison of the Conventional and Ultrasound-Augmented Leaching of Zinc Residue Using Sulphuric Acid

This paper attempts to capture the difference between the ultrasound augmented and conventional sulphuric acid leaching of zinc from zinc residue, having a Zn content of 12.31 %, along with other metallic compounds such as Fe, Pb and SiO2. The leaching temperature, sulphuric acid concentration, particle size, Liquid/solid ratio and the ultrasound power have been chosen as parameters for investigation. The shrinking core model is utilized for analyzing the rate controlling step in the leaching process. Only a maximum of 67 % of zinc could be leached using conventional process, while 80 % could be leached with the ultrasound augmentation. For both the processes the rate controlling step is identified to be the diffusion through the product layer. The reaction order with respect to the sulphuric acid concentration is found to be 1.33 and 0.94, while the activation energy being are 13.07 and 6.57 kJ/mol, for the conventional and ultrasound-augmented leaching process, respectively. The raw as well as the leached residue are characterized using XRD and SEM/EDS analyses.