Method for the manufacture of reduced graphene oxide from Kish graphite
A method for the manufacture of reduced graphene oxide from Kish graphite including the pretreatment of kish graphite, the oxidation of pre-treated kish graphite into graphene oxide and the reduction of graphene oxide into reduced graphene oxide, the reduced graphene oxide and the use of the graphene oxide.
1. A method for manufacture of reduced graphene oxide from kish graphite comprising:
A. providing kish graphite,
B. pre-treating the kish graphite including the following successive sub-steps:
i. a sieving step wherein the kish graphite is classified by size as follows:
a) kish graphite having a size below 50 μm,
b) kish graphite having a size above or equal to 50 μm,
the fraction a) of kish graphite having a size below 50 μm being removed,
ii. a flotation step with the fraction b) of kish graphite having a size above or equal to 50 μm and
iii. an acid leaching step wherein an acid is added so that a ratio in weight (acid amount)/(kish graphite amount) is between 0.25 and 1.0,
C. oxidizing the pre-treated kish-graphite obtained after step B) in order to obtain graphene oxide including the following successive sub-steps:
i. preparation of a mixture including the pre-treated kish-graphite, an acid and ammonium nitrate (NH 4 NO 3 ), the mixture being kept at a temperature below 5° C.,
ii. addition of an oxidizing agent into the mixture obtained in step C.i),
iii. after a targeted level of oxidation is reached, addition of a chemical element to stop the oxidation reaction,
iv. optionally, separation of graphite oxide from the mixture obtained in step C.iii) and
v. exfoliation of the graphite oxide from the mixture obtained in step C.iii) into graphene oxide, and
D. reducing of the graphene oxide into reduced graphene oxide.
2. The method as recited in claim 1 wherein in step B.i), a fraction a) of kish graphite having a size below 55 μm is removed and in step B.ii), a fraction b) of kish graphite has a size above or equal to 55 μm.
3. The method as recited in claim 2 wherein in steps B.i) and B.ii), the fraction b) of kish graphite has a size below or equal to 300 μm, any fraction of kish graphite having a size above 300 μm being removed before step B.ii).
4. The method as recited in claim 1 wherein in step B.iii), the acid amount/kish graphite amount ratio in weight is between 0.25 and 0.9.
5. The method as recited in claim 1 wherein in step B.iii), the acid is selected from the group consisting of the following elements: chloride acid, phosphoric acid, sulfuric acid, nitric acid and a mixture thereof.
6. The method as recited in claim 1 wherein in step C.ii), the oxidizing agent is chosen from the group consisting of: potassium permanganate (KMnO4), H 2 O 2 , O 3 , H 2 S 2 O 8 , H 2 SO 5 , KNO 3 , NaClO and a mixture thereof.
7. The method as recited in claim 1 wherein in step C.iii), the chemical element used to stop the oxidation reaction is chosen from the group consisting of: an acid, non-deionized water, deionized water, H 2 O 2 and a mixture thereof.
8. The method as recited in claim 7 wherein the chemical element and a further chemical element chosen from the group are used to stop the oxidation reaction, the element and the further chemical element being used successively.
9. The method as recited in claim 7 wherein the chemical element and a further chemical element chosen from the group are used to stop the oxidation reaction, the element and the further chemical element being used simultaneously.
10. The method as recited in claim 1 wherein in step C.iii), the mixture obtained in step C.ii) is gradually pumped into the element used to stop the oxidation reaction.
11. The method as recited in claim 1 wherein in step C.vii), the exfoliation is performed by using ultrasound or thermal exfoliation.
12. The method as recited in claim 1 wherein step C.iv) is performed and the graphite oxide is separated by centrifugation, by decantation or filtration.
13. The method as recited in claim 1 wherein in step C.i), the acid is selected from the group consisting of the following elements: chloride acid, phosphoric acid, sulfuric acid, nitric acid and a mixture thereof.
14. The method as recited in claim 1 wherein in step D) includes the following sub-steps:
i. reduction of graphene oxide to reduced graphene oxide with a reducing agent,
ii. agitation of the mixture obtained in step D.i),
iii. optionally, washing of the reduced graphene oxide and
iv. optionally, drying of the reduced graphene oxide.
15. The method as recited in claim 4 wherein in step D.ii), the mixture is kept at a temperature between 5° and 120° C.
16. The method as recited in claim 4 wherein in step D.ii), the agitation is performed during less than 24 hours.
17. The method as recited in claim 14 wherein in step D.i), the reducing agent is chosen from the group consisting of: acid ascorbic; urea; hydrazine hydrate; alkaline solution; phenols; alcohols; glycine; sodium citrate and sodium borohydride.
18. The method as recited in claim 17 , wherein the alcohols are one or more of methyl alcohol, ethyl alcohol and isopropyl alcohol.
19. The method as recited in claim 17 , wherein the alkaline solution is a solution of NaOH or KOH.
20. The method as recited in claim 17 , wherein the phenols are one or more of gallic acid, tannin acid, dopamine or tea polyphenol.