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

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 ۷ molar NaOH solution at a temperature of ۷۵ °C for ۲ hours. During the leaching process, ۸۴% 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 ۸۲ % current efficiency. Subsequently, the cold purification of the industrial zinc sulfate solution is performed using spongy zinc powder. The solution is heated to ۵۰°C and agitated at ۳۰۰ 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 ۶۰ ppm and ۲۵۰ ppm, respectively. The purification process is optimized by adjusting the zinc powder dosage to ۵ grams, resulting in cadmium and nickel concentrations reduced to ۱.۴ and ۱.۵ ppm, respectively, thus meeting the stringent requirements for electrowinning.________________________________________

کلیدواژه ها:

Cold filter cake ، Zinc alkaline leaching ، Basic electrowinning ، Spongy zinc powder ، Cold purification