Experimental Study on the Preparation of High Purity Graphite by Alkali-acid Method

Experiments were carried out on a fine flaky graphite flotation concentrate in Heilongjiang Provence by alkali-acid purification method. The optimum technological parameters were investigated. The results showed that under the conditions of NaOH dosage 3.0 g (ratio of alkali to solid 0.6:1), roasting temperature 750℃, roasting time 40 min, leaching water dosage 50 mL, acid leaching HCl concentration 1.0 mol/L, dosage 40 mL and acid leaching time 40 min, the fixed carbon content in graphite was increased from 95.89% to 99.94% by the process of alkali fusion roasting-water leaching-acid leaching. As the reaction proceeds and the phase changes, the impurities are eventually transformed into soluble matters and are washed with pure water. Maintaining a weak alkaline environment during water leaching is beneficial to the dissolution of sodium silicate.