Optimized Hydrometallurgical Route to Produce Ultrafine Zinc Powder from Industrial Wastes in Alkaline Medium

A hydrometallurgical process for producing ultrafine zinc powder from industrial wastes containing zinc was proposed. This process consists of alkaline leaching, purification stage, and electrowinning section. Firstly, affecting factors, such as leaching condition and waste sample composition were studied. In the alkaline medium, the leaching extractions of Zn and Pb are above 80% and 90%. Moreover, the residue was detoxified completely. In the purification section, the Pb, Sn and Al were separated by adding Na2S, Zn and CaO, respectively. Experiments were performed to obtain the optimal condition. Hence, more than 90% of metal impurities could be removed. Finally, zinc electrowinning was undertaken with addition of the Pb, Sn and Al. Morphology and size distribution of Zn particles were characterized by Scanning Electron Microscopy and Laser Particle Size Analyzer. The electrowinning results show that metal impurities could evidently reduce the size of zinc particle under optimum condition. Through this process, ultrafine zinc powders with a mean diameter of around 10 μm, containing less than 100 ppm of metallic impurities, could be obtained.