Research on the Extraction of Nickel, Cobalt, and Rare Earth Metals from Spent Nickel–Metal Hydride Batteries Using Thiosulfate Method

Spent nickel–metal hydride (Ni–MH) batteries have attracted significant interest due to their high content of valuable metals. In this study, we propose an environmentally friendly thiosulfate leaching system that uses sodium thiosulfate (Na2S2O3) and copper sulfate (CuSO4) in combination to efficiently extract nickel (Ni), cobalt (Co), and rare earth metals (RE) from the electrode materials of spent Ni–MH batteries. Under the catalytic oxidation effect of Cu2+, the efficient and synergistic effective leaching of these valuable metals has been achieved. The experimental results indicate that the leaching efficiencies of Ni, Co, and RE reached 92.53, 95.91, and 98.95%, respectively. Kinetic analysis revealed that the leaching process of Ni was controlled by chemical reactions, whereas the leaching of Co and RE was governed by a mixed control. Moreover, we demonstrate a “waste-to-wealth” strategy by repurposing the sulfur-rich leaching residue as an effective photo-Fenton catalyst, achieving degradation efficiencies of 92.52% for Rhodamine B (RhB) and 70.58% for Methyl Orange (MO). This work provides not only an efficient alternative to traditional hydrometallurgical methods but also new insights into reaction kinetics and closed-loop material flows for sustainable battery recycling.