Leaching Kinetics of Secondary Zinc Oxide in a NH3–NH4HCO3–H2O System

Autor: Hui Li, Linfei Zhao, Le Wang, Jinglong Liang, Hongyan Yan, Jinrui Liu
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Crystals, Vol 11, Iss 5, p 496 (2021)
Druh dokumentu: article
ISSN: 2073-4352
DOI: 10.3390/cryst11050496
Popis: Secondary zinc oxide (SZO), which comes from the zinc industry, is an important secondary resource of zinc and other valuable metals. In this study, the production feasibility and rationality of a cleaner zinc recovery process using SZO and a hydrometallurgical method were described. Zinc extraction is promoted by the addition of ammonium bicarbonate to a NH3–H2O system, and the maximum recovery of zinc could be close to 80% at the optimum leaching conditions of a stirring rate of 400 rpm, an ammonia/ammonium ratio of 7:3, a total ammonia concentration of 4 mol/L, and a liquid/solid ratio of 7 mL/g for 30 min at 35 °C. The kinetics of leaching were modeled using the shrinking core model of constant-size particles, and the rate-controlling step was determined to be the diffusion through the product layer. The apparent activation energy of the reaction was estimated to be 11.04 KJ·mol−1, while the order of reaction with respect to total ammonia concentration was 1.53 and the liquid/solid ratio was 2.26. The analysis results of the initial residue and the leached residue indicated that lead was transferred from PbCl2 to PbCO3 and that ZnFe2O4 was not leached in the NH3-NH4HCO3-H2O system.
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