Role of solution acidity on ferrous ions mineralization process at low temperature of 393.15 K, 408.15 K, and 423.15 K

Here, a clean, low-temperature hematite process using a neutralizer was proposed to remove iron ions from a zinc leaching solution and reutilize iron removal residue. The results showed that the solution acidity played a crucial role in this process. For a ZnSO4 solution with an Fe2+ concentration of 12-14 g/L and an initial pH > 3.0, the iron ion concentration decreased to 20 mg/L within 95 min when using the low-temperature hematite process with pure ZnO (10-13 g/L) added as a neutralizer in the temperature range of 408.15-423.15 K. The iron removal efficiency reached 99%. Increasing the initial pH of the initial solution significantly improved the iron removal efficiency, and it was necessary to control the pH above 3.0. After ferrous ion mineralization, the re-sidual iron concentration in the solution was inversely proportional to the final pH. The precipitated hematite products contained an Fe content of >55%, with a Zn loss of <1% and S contamination level of <3%. These hematite products can be sold as raw materials for ironmaking to solve the environmental issues associated with the storage of iron removal residue. The results showed that zinc oxide dust could not be used as a neutralizer because it resulted in the loss of valuable metals such as Pb, Ag, and In. Compared with the hematite process (453.15-473.15 K, reaction time of 3.0 h) used by the Iijima Refinery of Akita Zinc Co. in Japan, the ferrous ion mineralization in this study was shortened to <100 min. This significantly increased the treatment capacity of the low-temperature hematite process for zinc leaching solutions. The low-temperature hematite process could be performed at 393.15 K, 408.15 K, and 423.15 K, which can realize energy savings and consumption reduction.