Ozonation precipitation for iron removal in zinc hydrometallurgy

Abstract

ABSTRACT Iron is an undesirable constituent and should be removed before zinc electrowinning. Oxidative precipitation using ozone for iron removal from ZnSO4 solution was investigated. Meanwhile, using air as an oxidant was compared at parallel tests. The results indicated that the per centage of iron removal is above two times higher using O3 than using air. With ozone, the effects of important process parameters, such as ZnO mass, temperature, O3 mass flow rate, time, and stirring speed, were systematically investigated. Under optimised conditions, i.e. MZnO/Fe of 1.45, temperature of 90°C, ozone mass flow rate of 3.12 g/h, 30 min, and stirring speed of 300 rev min−1, 99.98% of iron can be removed, causing 0.15% of Zn loss. The precipitate existed as good crystalline phases of FeOOH, MnO2 and ZnSO4·H2O, and composed of rough and dense particles with different size, which is beneficial for solid–liquid separation.