Experimental Study on the Removal of Fe²⁺ and Mn²⁺ from Zinc Sulfate Water by Micro-nano Ozonation

In the production process of zinc sulfate, the presence of Fe and Mn had an adverse effect on the crystallization process of zinc sulfate production and reduce the purity of MgSO₄·7H₂O. Traditional chemical treatment methods are costly and easy to introduce new impurity ions. To obtain high-quality zinc sulfate, it is essential to develop a new Fe²⁺ and Mn²⁺ removal process. In this experiment, micro-nano bubble and ozone oxidation combined technology was used to explore the influence of different gas sources, temperature, CaCO₃ dosage method and dosage on the oxidation effect of Fe²⁺ and Mn²⁺, and to analyze the feasibility of the technology in a practical production application. Results showed that the removal rate of Fe²⁺ and Mn²⁺ was more than 99.5% with ozone as the gas source, which was much higher than that with air and oxygen as the gas source. The increase of temperature had an effect on the stability of micro and nano bubbles and the solubility of ozone, which was not conducive to the oxidation of Fe²⁺ and Mn²⁺. The treatment time of Mn²⁺ at the maximum temperature of 18℃ was shortened by 12.5% compared with that at 24℃. The addition of CaCO₃ significantly improved the removal efficiency of Fe²⁺ and Mn²⁺ by micro-nano ozone. When the relative dosage of 0.44 g/L CaCO₃ was added every 15 min, the adequate total amount of CaCO₃ was 17.6 g, and the complete Removal of Fe²⁺ and Mn²⁺ took about 50 min, which shortened the treatment time by 33% compared with the treatment time without CaCO₃. Effect of intermittent dosing was better than that of one-time dosing, and the amount of CaCO₃ consumed was more petite.