Beneficiation of microcrystalline graphite using evaporation assisted film flotation

Abstract

Graphite is considered a critical mineral by many countries due to its strategic importance, especially as an anode material in lithium-ion batteries. Natural graphite is preferred over synthetic forms for its lower carbon footprint. However, it typically occurs with aluminosilicate-based impurities (gangue) and requires beneficiation. With the shift from flake to microcrystalline graphite (MG) ores, traditional froth flotation becomes ineffective due to fine particle size and gangue entrapment, while chemical methods pose environmental and economic concerns. As a result, low-grade MG ores often remain unprocessed.

In this study, we present a novel, environmentally benign beneficiation method based on evaporation-assisted film flotation, which leverages the hydrophobicity of microcrystalline graphite and small size to form a thin film at the liquid–air interface, avoiding gangue entrapment. A low-grade MG ore was characterized, revealing a carbon content of 6.3 at% and natural graphitic flake size of 320 ± 200 nm. One gram of crushed raw ore powder was dispersed in 50 mL of 2.5 M NaOH and stirred at different temperatures (40 °C, 60 °C, and 80 °C) for 12 and 24 h. The optimal condition (60 °C for 24 h) for the current setup yielded a recoverable floating film of 3.01 wt%. Characterization of this film fraction showed a tenfold increase in carbon content (60.9 at%) and particle size of 643 ± 200 nm. These results demonstrate the effectiveness of the proposed film-flotation method for beneficiating low-grade microcrystalline graphite.