A Novel Procedure for Comprehensive Recovery of Zinc Fluoride, Manganese Fluorides, Manganese Dioxide, and Carbon Powder from the Electrode Powder of Spent Alkaline Batteries

Abstract

In this paper, a novel procedure is proposed for comprehensively recovering zinc fluoride (ZnF2), manganese fluorides [MnFx(x = 2, 3)], manganese dioxide (MnO2), and carbon powder from the electrode powder of spent alkaline batteries. Firstly, hydrofluoric acid (HF) leaching is conducted on the electrode powder of spent alkaline batteries. Secondly, potassium permanganate (KMnO4) is introduced into the leachate to selectively precipitate manganese (Mn) ions to recover MnO2. Subsequently, the water content in the leachate is evaporated to recover ZnF2. Finally, the leaching residue is leached again by using HF, after which the water content in the leachate is evaporated to recover MnFx. The results indicated that under optimal conditions of a HF concentration of 4 M, a leaching time of 15 min, and a liquid–solid ratio of 5 mL/g, the optimal leaching selectivity for Zn and Mn was achieved and the leaching efficiencies of Zn and Mn were 97.83% and 39.94%, respectively. When KMnO4 with a dosage (KMnO4/Mn ion molar ratio) of 0.5:1 was added to the leachate, MnO2 with a grade of 91.68% and a Mn recovery of 39.07% was obtained. In addition, ZnF2 with a grade of 97.98% and a Zn recovery of 96.15% was also obtained after removing the water content from the leachate via evaporation. Under the optimal conditions of a HF concentration of 2 M, a leaching time of 15 min, and a liquid–solid ratio of 10 mL/g for the leaching residue, followed by removing the water content in the leachate via evaporation, MnFx with a grade of 94.20% and a Mn recovery of 59.46%, was obtained. The residue of the releaching process was carbon powder. The effectiveness of the proposed recovery procedure was confirmed.