Some Factors Affecting the Formation, The Decomposition and the Acid Solubility of Zinc Ferrite

Aspects of the formation, decomposition and acid solubility of zinc ferrite were examined to find potential ways of increasing the recovery of zinc from a calcination process of mineral concentrates. Ferrite can begin to form within 2 hours at 450¦C. while complete reaction can occur after 35 minutes at 700¦C. The nature of the starting materials has a pronounced effect on the rate of formation and below 700¦C. ZnSO4 and Fe2O3 proved to be the least reactive of the materials investigated. It is possible that iron in a mineral admixed h sphalerite can be converted to a relatively inactive form, however, it does not seem possible to prevent zince f formation when iron is in the sphalerite lattice. At the two temperatures examined, 650¦C. and 700¦C, the presence of SO2 in the atmosphere accelerate .e formation of ferrite. Prolonged exposure to such atmospheres, however, caused the ferrite to decompose to ZnSO4 and Fe203. The optimum temperature for decomposition was 650¦C. and it was virtually complete within 2 hours in an atmosphere of 10% SO2 in air. Zinc ferrite was also decomposed by CO at low concentrations, and by heating with limestone at 1000¦C. for at least 2 hours. The solubility of zinc ferrite in acid was influenced by the starting materials used. As both the reaction temperature and the time at temperature increased the acid solubility decreased. The acid solubility was a minimum when the ___i_.. n - I -r~...................c -..... F, fe..i+e --A frn... A01- +^ Z(lo/