Method for producing oxidised graphite
This invention relates to technology of carbographite materials, in particular, to production of oxidized graphite for making low foaming temperature foamed graphite, which is used for manufacturing flexible foil, fireproof materials, water-purification sorbents, materials for cleaning up spills of petroleum products, and so on. The method for producing oxidized low foaming temperature graphite comprises the stages of (a) preparing a mixture based on graphite particles and at least one aqueous solution of an acid; (b) activating the surface of said graphite particles to produce acid-containing functional groups on the surface of the particles; (c) treating the graphite particles to produce a graphite intercalation compound; (d) washing said compound with water; (e) drying said compound, and heat-treating it to produce foamed graphite, wherein stage (b) and (c) are carried out by electrochemical treatment at a quantity of electricity within 300 to 600 mA·hour/g of graphite. The technical result is oxidized graphite having improved characteristics, in particular, high uniformity, low bulk density, and capacity for foaming at temperatures of 150° C. to 260° C.
1. A method of producing oxidized graphite having a low foaming temperature in a temperature range from 150° C. to 260° C. for manufacturing foamed graphite, comprising carrying out the stages of:
(a) preparing a mixture based on graphite particles and at least one aqueous solution of a strong acid;
(b) activating the surface of said graphite particles to form oxygen containing functional groups on the surface of the graphite particles;
(c) treating the graphite particles to obtain a graphite intercalation compound;
(d) washing said intercalation compound with water; and
(e) drying said intercalation compound;
wherein stages (b) and (c) are carried out by electrochemical anodic treatment at a total quantity of electricity of at least 200 mA·hour/g of graphite, stage (b) is carried out at up to 20% of a total quantity of electricity with a current or potential at least 1.1 times higher than that of stage (c).
2. The method according to claim 1 , wherein stages (b) and (c) are carried out in a continuous process at the total quantity of electricity ranging from 300 to 600 mA·hour/g of graphite.
3. The method according to claim 1 , wherein stage (e) is followed by heat treating the oxidized graphite at a temperature ranging from 150 to 260° C.
4. The method according to claim 1 , wherein stages (b) and (c) are carried out in a potentiostatic or galvanostatic mode at a quantity of electricity from a range of 300 to 500 mA·hour/g of graphite.
5. The method according to claim 4 , wherein stages (b) and (c) are carried out in a potentiostatic mode, and wherein stage (b) is carried out at a potential from a range of 1.7 to 2.6 V, and stage (c) is carried out at a potential from a range of 1.5 to 2.0 V.
6. The method according to claim 5 , wherein stages (b) and (c) are carried out in an aqueous solution of sulfuric acid at a concentration of 40% to 80%, stage (b) being carried out at a potential from a range of 1.8 to 2.3 V, and stage (c), being carried out at a potential from a range of 1.6 to 2.0 V.
7. The method according to claim 5 , wherein stages (b) and (c) are carried out in an aqueous solution of nitric acid at a concentration of 20% to 58%, stage (b) being carried out at a potential from a range of 2.1 to 2.5 V, and stage (c) being carried out at a potential from a range of 1.5 to 1.8 V.
8. The method according to claim 4 , wherein stages (b) and (c) are carried out in an aqueous solution of sulfuric acid at a concentration from a range of 40% to 80%, stage (b) being carried out at a current from a range of 80 to 160 mA/g of graphite until a potential of up to 2.5 V is reached, and stage (c) being carried out at a current from a range of 40 to 80 mA/g of graphite until a potential of up to 2.3 V is reached.
9. A method for producing oxidized graphite having a low foaming temperature in a temperature range from 150° C. to 260° C. for manufacturing foamed graphite, comprising carrying out the stages of:
(a) preparing a mixture based on graphite particles and at least one aqueous solution of nitric acid at a concentration of 20% to 58%;
(b) carrying out a preliminary stage of electrochemical anodic treatment of said graphite particles in the aqueous solution of nitric acid to activate a graphite surface;
(c) carrying out a main stage of electrochemical anodic treatment of said graphite particles in an aqueous solution of nitric acid;
(d) washing said graphite particles with water; and
(e) drying said particles, wherein stages (b) and (c) are carried out at a constant anode potential at a total quantity of electricity of 300 to 500 mA·hour/g of graphite, wherein stage (b) is carried out at a potential of 2.1 to 2.5 V for 10 to 600 seconds, and stage (c), at a potential of 1.5 to 1.8 V for 3 to 7 hours.
10. The method according to claim 9 , wherein stage (e) is followed by heat treatment of the oxidized graphite at a temperature of 150-260° C.