Abstract
ZnSO4∙7H2O was prepared using a filter cake enriched in calcium and magnesium that was generated during the process of zinc hydrometallurgy. The study was optimized to obtain process parameters. The results show that the optimal acid leaching parameters are a solid-to-liquid ratio of 1:3.5, a sulfuric acid concentration of 16%, an acid leaching time of 20 min, a final pH of 4.1–4.4, a cooling and settling time of 120 min, an oxidation time of 20 min, a stirring speed of 300 r/min, a H2O2 dosage of 25 mL/L, a crystallization temperature of 20 °C, and a crystallization time of 60 min. The ZnSO4∙7H2O content in the product is 98.6%, and the zinc recovery efficiency is 97.5%. This process is characterized by simple flow and low cost, while the circulation and accumulation problems with calcium and magnesium ions in the zinc hydrometallurgy process are also solved.
Highlights
During the hydrometallurgical process of zinc, calcium and magnesium enter into the system with the raw materials in the form of sulfate and cannot be removed like Cu, Co, Cd, etc1., which are generally removed by cementation onto zinc
Ca and Mg cannot be removed in this whole operation, so the underflow generated at the end of the process enriched in zinc, calcium and magnesium
Preparation of ZnSO4∙7H2O using the filter cake enriched in calcium and magnesium is an appropriate strategy to conserve energy and to reduce emissions[4]
Summary
Physical and chemical characteristics of the material. The filter cake consists of white powder and a certain amount of water. In this process, ferrous ions were oxidized to ferric ions, and the balanced chemical reaction is shown in equation (7). The removal efficiency of Fe leaching increased considerably with an increasing oxidation time from 5 to 30 min, after which the amount of Fe leached levels off.
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