Zinc Ferrite Conversion Kinetics and Mechanism During Roasting with Calcium Oxide
摘要
Converting zinc ferrite into zinc oxide and dicalcium ferrite through roasting with calcium oxide is the key point for realizing the following efficient separation between zinc and iron in zinc ferrite by leaching. The kinetics of zinc ferrite during roasting with calcium oxide was systematically studied in this work, together with its conversion mechanism investigated through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometer analyses, and results showed that the conversion of zinc ferrite can be divided into two stages. Stage I with activation energy of 48.75 kJ mol−1 is controlled by phase boundary reaction (tridimensional shape), and stage II with activation energy of 101.31 kJ mol−1 is controlled by three-dimensional diffusion (the Ginsteing–Brounshtein equation). The zinc ferrite directly reacts with calcium oxide at the beginning of roasting, and is then affected by the migration of calcium oxide, which can pass the reaction layer. Ultimately, the zinc ferrite is efficiently converted into zinc oxide dicalcium ferrite through reacting with calcium oxide. This work has guiding significance for optimizing the conversion of zinc ferrite.