Purification of natural graphite by microwave assisted acid leaching

Natural graphite was leached under microwave irradiation by acid mixtures containing HCl (12 mol/L) and HNO3 (16 mol/L). It was found that the purification efficiency was affected by microwave power, reaction pressure, reaction time and the acid ratio. The carbon content of the graphite increased from 95.84 to 99. 43% under optimized leaching conditions with an acid volume ratio of 1∶1, pressure of 1.0 MPa, reaction time of 25 min and microwave power of 800 W. SEM indicated that the morphology remained unchanged and XRD indicated that there was no apparent change in the 2θ peak position, peak height and full width at half maximum after the leaching.