Recovery of zinc resources from secondary zinc oxide via composite ammonia leaching: Analysis of Zn leaching behavior

Recovering zinc from typical industrial solid waste secondary zinc oxide (SZO) dust, rich in zinc resources, presents a significant challenge when finding an economical and green approach. This study aimed to investigate the optimal conditions for ammonia leaching of SZO dust using hydrothermal ammonia leaching methods and to explore how impurities affect zinc resource recovery in an ammonia leaching system. The results of SZO characterization before and after leaching confirmed that zinc oxide was the primary component dissolved in the ammonia leaching system. Only a fraction of zinc sulfide, lead oxide, and ferrous oxide entered the liquid phase, while most remained in the leaching slag. The study concluded that ammonium salt acted as a “dipping aid” in the ammonia leaching process and resulted in a 93.40% Zn leaching rate under optimal leaching conditions. Additionally, the study found that while impurities inhibited the leaching of Zinc Oxide in SZO, they promoted the leaching of Zinc Sulfide. Additionally, the leachate was found to contain recoverable amounts of lead and iron. These findings offer a theoretical framework for the efficient and cost-effective recovery of resources from SZO, providing valuable guidance toward achieving this objective.