Extraction and kinetic analysis of Pb and Sr from the leaching residue of zinc oxide ore

NH 4 HCO 3 conversion followed by HCl leaching was performed and proven to be effective in extracting Pb and Sr from zinc extracted residual. The mechanism and operating conditions of NH 4 HCO 3 conversion, including molar ratio of NH 4 HCO 3 to zinc extracted residual, NH 4 HCO 3 concentration, conversion temperature, conversion time, and stirring velocity, were discussed, and operating conditions were optimized by the orthogonal test. Experimental results indicate that NH 4 HCO 3 conversion at temperatures ranging from 25 to 85°C follows the shrinking unreacted core model and is controlled by inner diffusion through the product layer. The extraction ratios of Pb and Sr under optimized conditions reached 85.15% and 87.08%, respectively. Moreover, the apparent activation energies of Pb and Sr were 13.85 and 13.67 kJ·mol −1 , respectively.