Process and kinetics of ammonium sulfide removal of zinc, nickel and cobalt from manganous sulfate electrolyte

• Published in: Separation and purification technology 2025-02, Vol.354, p.128706, Article 128706
• Main Authors: Mu, Panpan, Zhang, Xiaoguang, Jiang, Guosai, Tan, Zhe, Yan, Haile, Pan, De’an
• Format: Article
• Language: English
• Subjects: (NH4)2S; Impurities metals ions; Kinetic; MnSO4 electrolyte
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.128706

This study clarified the process and kinetics of ammonium sulfide removal of zinc, nickel and cobalt from manganous sulfate electrolyte. Under the premise of ensuring little Mn loss, the manganese impurity ratio in the MnSO4 electrolyte was increased from 9.2 to 80. [Display omitted] •(NH4)2S can not only remove Zn, Ni, and Co in a high proportion but also control the loss rate of Mn.•Compared with the existing sulfide precipitation process, the reaction rate is improved by magnitude.•The effect of (NH4)2SO4 on the activation energy of Zn, Ni, and Co in the sulfidation process was discussed. In producing electrolytic manganese and manganese-based lithium batteries, Manganous sulfate solution serves as a crucial intermediate material. During the preparation of manganese sulfate solution by acid leaching, the removal of impurities such as zinc, nickel, and cobalt ions by sulfide precipitation is essential for obtaining high-quality metallic manganese and high-purity manganese sulfate. The results show that when the temperature is 45 °C, the pH is 5.60, the ammonium sulfide dosage is 40 %, the time is 5 min, and the rotation speed is 650 rpm, the sulfidation rates of zinc, nickel and cobalt are 99.07 %, 89.30 %, and 87.70 % respectively. At this time, the loss rate of manganese in the solution after sulfide impurity removal is 11.45 %, and the manganese-impurity ratio is 80.00. Response surface methodology analysis revealed that temperature, pH, and ammonium sulfide concentration significantly affected the manganese loss rate. After process optimization, at a temperature of 32.70 °C, a pH of 5.20, and an ammonium sulfide concentration of 32.73 %, the manganese loss rate decreased to 6.05 %, while the removal rates of Ni, Co, and Zn were 75.35 %, 60.80 %, and 99.51 %, respectively. In the Manganous sulfate electrolyte with or without ammonium sulfate, the sulfide precipitation processes of zinc, nickel and cobalt ion are all first-order reactions, and the reaction order is zinc > nickel > cobalt. More importantly, the density functional theory (DFT) calculation results also confirmed the formation sequence of zinc sulfide > nickel sulfide > cobaltous sulfide, which supported the experimental results well. This study will lay the foundation for process optimization and mechanism elucidation of impurity ions in ammonium sulfate electrolyte precipitated by ammonium sulfate.