Alkaline acid extraction of graphite

The alkali-acid method includes two reaction processes: alkali melting process and acid leaching process. The alkali melting process uses the molten alkali and the acidic impurities in the graphite to undergo a chemical reaction under high temperature conditions, especially silicon-containing impurities (such as silicates, aluminosilicates, quartz, etc.) to generate soluble salts, and then After washing to remove impurities, the purity of graphite can be improved. The basic principle of the acid leaching process is to use acid to react with metal oxide impurities. This part of the impurities does not react with alkali during the alkali fusion process. The metal oxide is converted into a soluble salt, and then washed to separate it from the graphite. The combination of alkali fusion and acid leaching has a good effect on graphite purification.

A variety of alkaline substances can remove graphite impurities. The stronger the alkaline, the better the purification effect. The alkaline acid method mostly uses NaOH with a small melting point and strong alkalinity. The acid used in the acid leaching process can be HCl, H2SO4, HNO3 or a mixture of them. Among them, HCl is more used.