Studies on impurity iron removal from zinc electrolyte using MnO2–H2O2

This paper is focused on the iron removal from sulphuric acid–zinc liquors obtained from double leached Waelz oxide. The initial iron concentration in the liquor was around 80 mg/L which must be removed prior to complementary purification stages and zinc electrowinning. Different oxidation agents were studied, operating at room temperature and atmospheric pressure. It was observed that the most suitable oxidation agent was a mixture of MnO2–H2O2. During 20 min at pH 4.5 while adding 2 mL H2O2 and 1.2 g MnO2/L of liquor, an iron removal around 99.6% was achieved, reducing the iron concentration in the liquor to 0.3 mg/L.The proposed process operates well at room temperature and energy saving is achieved with respect to conventional oxidation processes using O2 or H2O2 as oxidation agents, in which temperatures of at least 60–80 °C must be used.

Research Highlights
► Hydrometallurgical iron oxidation-removal at room temperature.
► Iron removal yield achieved around 99.5%.
► A mixture of MnO2 and H2O2 allows this iron oxidation.