Spongy Zinc Powder Production from Cold Filter Cake to Use in Cold Purification Stage

Behnajady, Bahram; Karimi, Saeid; Moghaddam, Javad

doi:10.22111/jesm.2025.52012.1027

Spongy Zinc Powder Production from Cold Filter Cake to Use in Cold Purification Stage

Document Type : Original Research Paper

Authors

¹ Faculty of Materials Engineering, Sahand University of Technology, Sahand New Town, Tabriz, Iran. Postal Code: 5331817634

² Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, 65169-13733, Iran

³ Materials and Metallurgical Engineering Department, University of Zanjan, Zanjan, Iran

10.22111/jesm.2025.52012.1027

Abstract

The hydrometallurgical extraction of zinc often involves a crucial cold purification stage to remove impurities such as cadmium, cobalt, and nickel from the zinc sulfate electrolyte. The efficiency of this purification hinges on the availability of high-quality zinc dust as a cementation agent. A cost-effective approach to procuring this vital reactant involves processing cold filter cake (CFC), a byproduct of the leaching and purification processes. This study focuses on the production of zinc powder from CFC and its application in the cold purification stage of impure zinc sulfate solutions. The research begins with the alkaline leaching of CFC using a 7 molar NaOH solution at a temperature of 75 °C for 2 hours. During the leaching process, 84% of zinc was dissolved while keeping cadmium and nickel mostly in the residue. The filtrate from the leaching process was then used as an electrolyte in an electrowinning process to produce spongy zinc powder with around 82 % current efficiency. Subsequently, the cold purification of the industrial zinc sulfate solution is performed using spongy zinc powder. The solution is heated to 50°C and agitated at 300 rpm. A pre-determined quantity of spongy zinc powder is introduced to facilitate the cementation of impurities, specifically cadmium and nickel, which are present at concentrations of 60 ppm and 250 ppm, respectively. The purification process is optimized by adjusting the zinc powder dosage to 5 grams, resulting in cadmium and nickel concentrations reduced to 1.4 and 1.5 ppm, respectively, thus meeting the stringent requirements for electrowinning.________________________________________

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