METHOD FOR PURIFYING ASH GRAPHITE Russian patent published in 2016 - IPC C01B31/04 

FIELD: energy.

SUBSTANCE: invention can be used for production of structural materials for nuclear power engineering, heat engineering, as well as raw material for producing colloidal graphite, graphite oxide and expanded graphite. Method for purifying ash graphite involves treatment of graphite with aqueous solution of ammonium bifluoride salt. After that, the mixture is heated to 190-200 °C at the rate of about 1°/min, maintained until ammonium bifluoride will react with the main part of silicon dioxide SiO₂, present in the graphite, for example, 30 minutes. Then the temperature is increased to 400 °C at the rate of about 2-5°/min and maintained until the end of sublimation of ammonium silicofluoride formed during fluorination of silicon dioxide with ammonium bi-fluoride, for example 2 h. Obtained product is cooled to the room temperature and is repeatedly treated with ammonium bi-fluoride. After that the mixture is heated at the rate of about 2-5°/min to 190-200 °C and maintained until the decomposition of aluminium silicates, present in the graphite, and the remaining silicon dioxide, for example 2 h. Then the graphite is cooled to the room temperature and leached at heating with 10% solution of hydrochloric acid at solid to liquid ratio = 1:8 or 15 % solution of nitric acid at solid to liquid ratio = 1:5, washed with water to obtain a neutral medium. Obtained mixture is filtered, the residue is washed with water and dried. Purity of produced graphite is 99.97-99.98 %.

EFFECT: production of structural materials.

6 cl, 2 ex