Title: Influence of Hydrazine Sulfate on the Redox Chemistry and Selective Dissolution of Zinc, Iron, Copper, and Cadmium from Metallurgical Wastes
Authors: Khojiev Sh.T., Kholikulov D.B., Khaydaraliev Kh.R., Javliyev S.S., Movlanov A.S.
Volume: 9
Issue: 11
Pages: 132-138
Publication Date: 2025/11/28
Abstract:
This study investigates the selective hydrometallurgical leaching of zinc-containing waste cakes generated during the technological processes of the Almalyk Mining and Metallurgical Combine (AMMC), with particular emphasis on the role of hydrazine sulfate (N?H?SO?) as a selective reducing agent. Chemical and mineralogical analyses using X-ray diffraction and atomic absorption spectroscopy revealed that the main metallic components of the cakes are Zn, Fe, Cu, and Cd. Laboratory-scale experiments were carried out in sulfuric acid solutions (0.5-3.0 mol/L) at temperatures ranging from 60 to 90 °C, with process parameters such as leaching time, pH, and stirring rate strictly controlled. The results showed that adding hydrazine sulfate significantly enhances process selectivity, increasing zinc dissolution up to 95%, while sharply reducing the concentrations of Fe, Cu, and Cd in the leach solution by two to four orders of magnitude. Phase modeling and 3D surface analyses confirmed that hydrazine transforms the chemical environment, promoting preferential zinc extraction while suppressing the dissolution of impurity metals. Additionally, precious metals such as gold, silver, and lead remained in the solid residue, allowing for subsequent recovery through separate metallurgical routes. Overall, the study establishes that the application of hydrazine sulfate provides a scientifically grounded, environmentally safe, and industrially applicable approach to selective leaching of zinc-bearing materials, enabling high-purity zinc recovery and cleaner process solutions for further electrolysis or crystallization stages.