Separation of Magnesium by Fluorination from Zinc Sulfate Solution Through Surface Charge Control

Economically and conveniently removing Mg²⁺ from ZnSO₄ solution has become increasingly important in view of the economic significance of zinc extractive metallurgy. In this paper, the role of surface charge in the removal of Mg²⁺ by the fluorination method to form MgF₂ was investigated. According to the experimental results, both positively charged and negatively charged MgF₂ surfaces resulted in an increased zinc loss ratio. At the point of the zero-charged MgF₂ surface, when the pH is 2.3, the minimum zinc loss ratio of only 3.6% can be achieved and the removal ratio of Mg²⁺ can reach 81.0%. Furthermore, the role of surface charge on the size of colloidal MgF₂ particles was clarified. Finally, the effect of centrifugation parameters on the separation of MgF₂ colloids from ZnSO₄ solution was investigated and the optimized conditions were 4000 rpm and 10 min.