Sustainable Graphite Purification: A Comprehensive Review of Eco-Friendly and High-Purity Methods

Graphite purification is essential for producing battery- and nuclear-grade products from natural graphite and for upgrading graphite recovered from spent lithium-ion batteries (LIBs) to a quality suitable for reuse. Conventional routes often involve trade-offs between final carbon purity and recovery and can increase energy demand, chemical consumption, and wastewater generation, thereby constraining industrial scalability. This review classifies graphite purification technologies into physical, chemical, physicochemical, and emerging sustainable purification methods; the last of these are defined as low-hazard approaches designed to reduce hazardous reagent inputs and secondary waste generation while maintaining practical upgrading performance. Using integrated metrics, we compare purification performance in conjunction with environmental and techno-economic considerations and present a dual-axis multicriteria evaluation matrix that links feedstock characteristics to end-use requirements. The proposed decision framework supports application-tailored hybrid flowsheet selection and design, including hydrofluoric acid-free routes and recycling-oriented purification of spent-LIB graphite, while accounting for sustainability and industrial deployability.