Selective flotation separation mechanism of LFPs and graphite electrode materials using CMC as inhibitor

Economical and efficient separation and utilization of spent lithium iron phosphate powder is the key to lithium-ion battery recycling. Flotation, as a low-cost physical enrichment method, has attracted much attention due to its promising advantage of separating graphite before the metallurgical extraction of lithium iron phosphate. However, high-efficiency flotation separation reagent is still challenging. In this work, low-viscosity carboxymethyl cellulose (CMC) was used as a selective flotation inhibitor in the separation of graphite and lithium iron phosphate electrode materials (LFPs). With the addition of 100 mg/L 25 mPa·s CMC, the recoveries of graphite and LFPs were 96.37% and 3.47%, respectively, indicating excellent separation efficiency. The adsorption analysis and wettability measurement indicated that CMC is more favorable adsorbed on the surface of LFPs and graphite, and also greatly improved the wettability and hydrophilicity of LFPs. Meanwhile, the turbidity and particle size analysis showed that CMC could effectively disperse LFPs particles, reducing the particle entrapment caused by heterocoagulation. Furthermore, XPS and FT-IR studies confirmed that CMC could chemisorb on LFPs and physically adsorb on graphite electrode material. The study results could provide a promising physical enrichment method for the green and efficient recycling of spent lithium iron phosphate batteries.