Chemical Kinetics and Interfacial Electron Transfer in the Hydrazine Reduction of Zinc Ferrite

This study investigates the hydrazine-assisted reduction of zinc ferrite (ZnFe₂O₄), a major phase in zinc hydrometallurgical residues, with the aim of developing an energy-efficient and selective decomposition process. The experimental results revealed that the reduction follows a pseudo-first-order kinetic model with respect to hydrazine concentration and a surface-controlled mechanism with an activation energy of approximately 45 kJ mol⁻¹. Spectroscopic analyses confirmed the conversion of Fe³⁺ to Fe²⁺ and the formation of Zn(OH)₂ and Fe(OH)₂ phases, which significantly improve subsequent acid leaching efficiency. The proposed interfacial electron-transfer mechanism demonstrates that hydrazine can effectively decompose zinc ferrite under mild conditions (60–90 °C), producing only nitrogen and water as by-products. This approach provides a sustainable solution for improving metal recovery and minimizing environmental impact in zinc hydrometallurgical operations.