Scalable preparation of graphene from graphite ore via mechano-chemical ball milling

Mechanical exfoliation can generate graphene, but a consistent and scalable preparation of few-layer
graphene (FLG) continues to be a challenge. We employed a mechanochemical milling technique to
achieve maximum shear and frictional force by dual drive mode operation for preparation of FLG directly
from beneficiated graphite ore. Low-grade graphite ore from Jharkhand, India, with a carbon content of
9%, was subjected to primary beneficiation by froth flotation technique using the naturally hydrophobic
property of graphite as opposed to the associated impurities. The obtained graphite concentrates with an
enriched carbon content above 90% after flotation was subjected to chemical treatment process including
alkali roasting and acid leaching, which yielded an enriched graphite powder with fixed carbon of
about 98.16%. A comparative study regarding the leaching efficiency was carried out between sulfuric
acid and hydrochloric acid. The few-layered graphene was successfully prepared by mechanical milling of
beneficiated graphite ore with oxalic acid at 20 hours with optimized critical speed. At various milling
hours, the amplitude of the peak (002) decreased continuously, suggesting that the graphite size and
thickness had decreased. Raman Spectroscopy confirmed the 20 h milled graphite is having single and
few layered (<4 layers) graphene sheets.