Abstract:In response to the bottlenecks of low efficiency, heavy pollution, and high costs in the traditional purification process of low-grade graphite ore, this study proposes a new flotation-alkali-acid composite gradient purification process, systematically investigating the evolution of impurity occurrence forms and the multi-stage synergistic impurity removal mechanism. By optimizing the ratio of flotation reagents and process parameters, the carbon content in the concentrate was increased from 6.8% in the raw ore to 88.6%; combined with the analysis of alkali fusion reaction kinetics, the quantitative relationship between the silicate decomposition rate and temperature and alkali concentration was revealed, and more than 80% of silicon impurities were removed through alkali fusion treatment at 700℃; a HCl-HF mixed acid synergistic leaching model was constructed to clarify the coupling effect of Cl- complexing metal ions and HF directional etching of silicates, increasing the carbon content to 99.5%; finally, high-temperature purification at 2800℃ achieved a carbon content of 99.99%, with the ash content reduced to 30×10-6. Multiscale characterization reveals that the composite process, by gradient removal of micron-scale gangue, nano-scale oxides, and atomic-scale light element impurities, maintains the integrity of the graphite crystal structure while ensuring surface cleanliness. This provides theoretical support and a technical pathway for the green and efficient utilization of low-grade graphite.
