Recovery and purification of graphite from spent lithium-ion batteries through flotation and subsequent leaching

Abstract

The purpose of this research is to recover and recycle graphite from spent lithium-ion batteries through the application of flotation and acid leaching. This is to promote the circular economy in the battery manufacturing industry and reduce environmental pollution by waste lithium-ion batteries. This study investigated the effects of collector dosage, pH, and roasting time on the separation of graphite and lithium metal oxides through flotation from black mass of spent lithium-ion batteries. The work also involved the purification of recovered graphite through leaching with HCl. The best flotation conditions were found to be a roasting time of 1 h, collector dosage of 200 g/ton, and pH of 7, resulting in a froth product containing 67.3% fixed carbon (FC). The product was leached with 3 M HCl at 80 °C for 4 h. The final product contained Co, Al, and Cl at concentrations of 6.1%, 0.9%, and 0.7%, while other elements were present at concentrations less than 0.5%. X-ray Diffraction (XRD) showed existence of carbon in multiple phases, with a dominant peak at 2θ = 26.65 ° for raw froth product and 26.48 ° for leached product. Scanning Electron Microscope- Dispersive X-ray Spectroscopy (SEM-EDS) revealed that leaching resulted in a smoother material surface. Raman spectroscopy indicated that crystallinity of the recovered graphite was reduced after leaching, with D-band intensity divided by G-band intensity (ID/IG) ratio increasing to 0.51 for the leached product from 0.24 for raw froth product. The leached product had FC, ash, volatile matter, and moisture contents of 92.5%, 3.6%, 3.9% and 0.2%, respectively. • Graphite can be recovered and purified from spent LIBs through flotation. • Leached froth product contains Co and Al as major impurities. • Leaching results in graphite losing its crystallinity. • The leached froth product has a fixed carbon content of 92.45%. • The recycled graphite has carbon as 5 crystalline phases.