Abstract:The transformation behavior of ferrous sulfate was examined during hematite precipitation for iron removal in hydrometallurgical zinc. Specifically, the effects of the method used for oxygen supply (pre-crystallization or pre-oxidation of ferrous sulfate) and temperature (170–190 °C) on the redissolution and oxidation–hydrolysis of ferrous sulfate were studied. The precipitation characteristics and phase characterization of the hematite product were investigated. The results showed that the solubility of ferrous sulfate was considerably lower at elevated temperatures. The dissolution behavior of ferrous sulfate crystals was influenced by both the concentrations of free acid and zinc sulfate and the oxydrolysis of ferrous ions. Rapid oxydrolysis of ferrous ions may serve as the dissolution driving force. Hematite precipitation proceeded via the following sequential steps: crystallization, redissolution, oxidation, and precipitation of ferrous sulfate. The dissolution of ferrous sulfate was slow, which helped to maintain a low supersaturation environment, thereby affording the production of high-grade hematite.

Key words: hydrometallurgical zinc; crystallization of ferrous sulfate; hematite precipitation for iron removal