KR101095584B1 - Washing method of mixture comprising graphite oxide - Google Patents

Abstract

PURPOSE: A method for cleaning a graphite oxide mixture is provided to improve the efficiency of energy and to be applied for acid-based surface modified carbon materials. CONSTITUTION: A cationic surfactant is introduced into a graphite oxide mixture, and an agitating process and a mixing process are implemented(S110). An organic solvent is introduced into the graphite oxide mixture with the cationic surfactant, and an agitating process and a mixing process are implemented(S120). An organic layer, in which the graphite oxide is dispersed, is separated(S130). The organic solvent and the cationic surfactant are eliminated from the separated organic layer(S140). The cationic surfactant is a quaternary ammonium salt compound.

Description

Washing method of mixture comprising graphite oxide

The present invention relates to a method for cleaning a graphite oxide mixture having excellent energy efficiency since the amount of waste water is significantly reduced in the process of washing the graphite oxide mixture obtained during the production of graphite oxide.

Graphene is a recently discovered two-dimensional carbon nanostructure, a hexagonal crystal lattice in the form of a single plate structure consisting of sp2 hybrid bonds of carbon atoms. The graphene has the same shape as that in which the hexagonal crystal lattice is stacked in a layered structure and the interlayer separation is completely completed in the multilayered graphite.

Graphene oxide, an intermediate of graphene, produced during the production of graphene, is added to the graphite powder and reacted for several days by adding nitric acid and potassium perchlorate to produce graphite oxide. The Stadenmaier method, the Brodie method, and the hummer (Hummer) method and the like are known, and in US Patent No. 2,798,878, the method was improved to reduce the reaction time by using sulfuric acid, nitric acid and potassium permanganate.

Since the graphite oxide thus prepared is dispersed in a solution having strong acid and other ions, it is inevitably accompanied by several washing processes to separate the graphite oxide. At this time, the amount of energy and waste water used is significant, which leads to a high price of the graphene, and it is necessary to improve the washing process causing this problem.

Accordingly, the present inventors have completed the present invention by devising a method of separating graphite oxide from sulfuric acid and other ions using a cationic surfactant while studying to solve the problem of the washing process.

Accordingly, an object of the present invention is to significantly reduce the amount of wastewater generated in the process of washing the graphite oxide mixture obtained during the graphite oxide manufacturing process, and can be treated in a simple manner to provide a method for cleaning the graphite oxide mixture with excellent energy efficiency.

In addition, another object of the present invention to provide an acid-treated surface-modified carbon material washing method using the washing method.

In order to achieve the above object, the present invention is a method for washing a graphite oxide mixture containing graphite oxide, sulfuric acid, hydrogen peroxide and pure water obtained during the graphite oxide manufacturing process, after adding a cationic surfactant to the graphite oxide mixture, stirring And mixing; Adding an organic solvent to the graphite oxide mixture in which the cationic surfactant is mixed, followed by stirring and mixing; Separating the organic layer in which the cationic surfactant-treated graphite oxide is dispersed; And it provides a method for cleaning the graphite oxide mixture comprising the step of removing the organic solvent and cationic surfactant in the separated organic layer.

In addition, the present invention may further include the step of recovering and reusing the removed organic solvent and cationic surfactant.

The cationic surfactant used in the present invention may be a quaternary ammonium salt compound, the compound of formula 1, for example, N-benzyl-N, N-dimethyl-1-octanaminium chloride, N-benzyl-N, N-dimethyl-1-decanaluminum chloride, N-benzyl-N, N-dimethyl-1-dodecanaluminum chloride, N-benzyl-N, N-dimethyl-1-tetradecanaluminum chloride or N-benzyl -N, N-dimethyl-1-octadecanealuminum chloride; Gemini compounds such as the following Chemical Formula 2, for example, bis [triethylammonium 하이드 2-hydroxypropyl] ethylene glycol, bis [dimethylstearylammonium 하이드 2-hydroxypropyl] ethylene glycol, bis [dimethyloctylammonium 2 -Hydroxypropyl] ethylene glycol, bis [tri (hydroxyethyl) ammonium # 2-hydroxypropyl] ethylene glycol; Alkyl dimethyl amine oxide; Alkylcarboxybetaine; Benzalkonium chloride; Benzetonium chloride; Benzyltributylammonium chloride; Benzyltriethylammonium chloride; Benzyltrimethylammonium chloride; 3-chloro-2-hydroxy-propyl trimethylammonium chloride; Tetraethylammonium chloride; Tetramethylammonium chloride; Dodecyltrimethylammonium chloride; Glycidyl trimethylammonium chloride; Cetyltrimethylammonium bromide; Dodecyltrimethylammonium bromide; Tetrabutylammonium bromide; Tetraethylammonium bromide; And a quaternary ammonium salt compound such as benzylpropylammonium bromide, but is not limited thereto. Any cationic surfactant based on quaternary ammonium salts may be used.

[Formula 1]

In Formula 1, R is alkyl selected from C1 to C20.

[Formula 2]

In Chemical Formula 2, R ¹ to R ⁶ are each independently alkyl, alkylene or hydroxy alkyl selected from C1 to C30; R ⁷ is hydrogen or C1 to C5 alkyl; X is selected from the anionic moiety under a solvent of halogen, formic acid, acetic acid and nitric acid; n is an integer from 1 to 30.

Preferably, the cationic surfactant is included in an amount of 1 to 5 parts by weight based on 1 part by weight of the graphite oxide mixture. When the cationic surfactant is included in the content of less than the content range, the surfactant does not function properly and the organic layer and the water layer are separated. May cause problems, and when included in excess of the content range, a problem of wasting of surfactant may be caused.

The organic solvent used in the present invention is methylene chloride, ethylene chloride, trichloroethylene, toluene, di-isopropyl ether, pentane, methyl ethyl ketone, methyl t-butyl ether, hexane, heptane, di-ethyl ether, ethyl Acetate, dichloromethane, 1,2-dichloroethane, cyclohexane, chloroform, chlorochloride, butyl acetate, n-butanol and benzene may be any one selected from the group consisting of, but not limited to, the organic solvent is oxidized 25 to 50 parts by weight, preferably 30 to 45 parts by weight, based on 100 parts by weight of the graphite mixture, the organic solvent is included in the content range below may cause a problem of lack of capture space of graphite oxide, If it exceeds the content range, it may cause a waste of organic solvent.

In one embodiment of the present invention, the graphite oxide treated with the cationic surfactant dispersed in the organic layer may be separated using a separatory funnel, and the organic layer may be heated to remove the organic solvent. The organic solvent can be separated and reused using a concentrator. In addition, the cationic surfactant may be removed through thermal shock reduction, while alcohol, for example, ethanol is added to the separated organic layer and stirred to dissolve the cationic surfactant in alcohol, and then the cationic surfactant and the alcohol are separated to form a cation. The surfactant and ethanol can be reused.

In addition, in the present invention, the graphite oxide mixture includes any graphite oxide mixtures prepared according to Hummer's manufacturing method of graphite oxide ( J. Am. Chem. Soc. , 80 (6), 1339, 1958). As an embodiment 1) preparing a graphite slurry by mixing the graphite powder and sulfuric acid; 2) preparing a KMnO ₄ sulfuric acid solution by mixing KMnO ₄ powder and sulfuric acid; 3) preparing an aqueous hydrogen peroxide solution; 4) introducing the graphite slurry at the start of the channel having a reaction mixture maintained at a constant temperature range and having a start, a reaction part and an outlet; 5) mixing the KMnO ₄ sulfuric acid solution at the beginning of the channel by mixing; 6) maintaining the reaction mixture in the temperature range within the channel; And 7) a graphite oxide mixture prepared according to a process comprising introducing the aqueous hydrogen peroxide solution near the outlet of the channel.

The graphite slurry is a concentrated sulfuric acid such that the graphite powder having a particle size of 1 to 200 μm, preferably 5 to 50 μm, has a weight ratio of graphite and sulfuric acid of 1:10 to 1: 100, preferably 1:30 to 1:50. Preferably, it can be prepared by dispersing in sulfuric acid of 97% or more. If the particle size of the graphite is too low, the expansion effect according to the weight density is low, the graphene due to peeling is not well formed, and if the particle size of the graphite is too large, the transport and mixing of the reactants are not smooth. The higher the concentration of sulfuric acid, the higher the reactivity. Therefore, it is preferable to use concentrated sulfuric acid of 97% or more. If the weight ratio of graphite and sulfuric acid is too high, the viscosity of the graphite slurry becomes high, and the transport and mixing of the reactants in the channel is not smooth. On the other hand, if the weight ratio of graphite and sulfuric acid is too low, the reaction efficiency is low and many waste sulfuric acid by-products are generated. The graphite slurry can be controlled by a metering pump directly connected to the beginning of the channel.

The KMnO ₄ sulfuric acid solution is prepared by dissolving concentrated sulfuric acid, preferably KMnO ₄ powder in sulfuric acid of 97% or more, such that KMnO ₄ and sulfuric acid weight ratio is 1: 5 to 1:50, preferably 1:10 to 1:30. Can be. The KMnO ₄ sulfuric acid solution can be easily mixed by adding potassium permanganate to the channel in the form of a sulfuric acid solution, the KMnO ₄ sulfuric acid solution can be supplied by a metering pump connected to the reaction portion of the channel. The amount of KMnO ₄ sulfuric acid solution supplied can be strictly controlled by a quantitative method or the like.

The hydrogen peroxide aqueous solution is not particularly limited in concentration, but may be 1 to 10% by weight, preferably 2 to 7% by weight. The weight ratio of the graphite and the hydrogen peroxide aqueous solution may be added to 1:10 to 1: 100, preferably 1:30 to 1:50. The aqueous hydrogen peroxide solution can terminate the oxidation of the graphite by reducing excess KMnO ₄ . Excessive additions are expensive to wash and dry, and minor additions do not terminate the reaction. After the aqueous hydrogen peroxide solution is added, the holding time may be within several tens of minutes.

The reaction mixture after addition of the KMnO ₄ sulfuric acid solution in the channel should be maintained at a temperature of 0 to 50 ° C, preferably 20 to 35 ° C. At low temperatures the reaction efficiency is low, and at high temperatures the risk of explosion is high. In order to prevent the explosion due to local overheating, in particular the reaction section of the channel must be tightly controlled within this temperature range. The channel is preferably loaded in a heat exchanger having a cooling arrangement to be controlled at a range of temperatures.

The channel may be a tubular reactor having an inner diameter of 1 μm or more and several tens of mm or less, preferably 1 μm or more and 1 mm or less with good thermal conductivity and good corrosion resistance and acid resistance. The channel should have an internal diameter of several tens of mm or less to keep the reaction mixture preferably at 20 to 35 ° C. to prevent explosion due to local overheating. In addition, an inner diameter of several mm or less is preferable in order for the reaction mixture to mix well in the channel so that the reaction efficiency is good. Therefore, for the reaction efficiency and safe driving, the inner diameter is most preferably 1 µm or more and 1 mm or less. The reaction mixture can travel in the channel at a speed of several centimeters to several meters per second, preferably several centimeters to several tens of centimeters per second.

After the KMnO ₄ sulfuric acid solution is added to the sulfuric acid slurry of graphite, it can preferably be maintained for several hours in minutes and most preferably for two hours in minutes.

The graphite slurry, the KMnO ₄ sulfuric acid solution and the hydrogen peroxide aqueous solution may respectively supply the corresponding material to the channel by a metering pump. The graphite slurry and the KMnO ₄ sulfuric acid solution are preferably supplied into the channel at a sufficient pressure and speed so that the reaction mixture forms a vortex in the channel by means of the corresponding metering pump.

In the reaction mixture in which excess KMnO ₄ is reduced by the addition of aqueous hydrogen peroxide solution and the reaction is terminated, the reaction mixture may be discharged to the outlet of the reactor. Reactor The reaction mixture at the outlet exiting the reaction can be washed by treatment with a cationic surfactant such as quaternary ammonium salts before drying. This washing process may be performed in the same manner as described above.

The graphite oxide thus washed may be dried under reduced pressure at 200 ° C. or lower, preferably 80 ° C. or lower, and within 48 hours. Such washing and drying can be carried out separately from the preceding processes or continuously.

In addition, the present invention comprises the steps of adding a cationic surfactant to the surface-modified carbon material by acid treatment, followed by stirring and mixing; Adding an organic solvent to the reaction mixture mixed with the cationic surfactant, followed by stirring and mixing; Separating the organic layer having the cationic surfactant treated carbon material dispersed therein; And removing the organic solvent and the cationic surfactant from the separated organic layer, wherein the acid-treated surface-modified carbon material is washed.

In addition, the washing method may further include the step of recovering and reusing the removed organic solvent and cationic surfactant.

The carbon material may be a carbon material having a graphite or graphite structure, preferably carbon nanotubes (CNT), carbon fiber (Carbon fiber), carbon black or Fullerene (Fullerene).

In addition, the specific cleaning method of the acid-treated surface-modified carbon material is the same as the cleaning method of the graphite oxide mixture described above, a description thereof will be omitted.

When the cleaning method according to the present invention is used for the cleaning process of the graphite oxide mixture obtained in the graphite oxide manufacturing process, the amount of waste water can be significantly reduced, the energy efficiency is excellent, and the time required for the cleaning can be reduced, thereby economically and simply oxidizing. In addition to cleaning the graphite mixture, this cleaning method is equally applicable to acid treated surface modified carbon materials.

1 relates to a schematic process diagram for producing graphite oxide as an embodiment of the invention,
2 is a schematic exploded perspective view and a partially exploded enlarged perspective view showing the configuration of the microchannel of FIG.

The present invention will be described in detail with reference to the drawings. These descriptions are only intended to illustrate the present invention in more detail, and should not be construed as limiting the protection scope of the present invention.

1 and 2, a method and apparatus for producing graphite oxide will be described as an embodiment of the present invention. The micro reactor 8 comprises a plurality of micro channel modules 8a, 8b, 8c, 8d, 8e, 8f, 8g loaded in the heat exchanger 17 to form one connected microchannel (a few mm diameter at 1 μm). It consists of The micro channel leads to the beginning, reaction parts 8a, 8b, 8c, 8d, 8e, 8f, 8g and outlet.

The graphite sulfuric acid slurry is supplied from the sulfuric acid tank 1b and the graphite tank 6 by sulfuric acid and graphite powder from the liquid metering pump 4b and the powder metering pump 3b, respectively, and mixed by the premixer 7. Is forced to the beginning of the microchannel 20. The KMnO ₄ sulfuric acid solution is supplied from sulfuric acid tank (1a) and KMnO ₄ tank (2) by sulfuric acid and KMnO ₄ respectively from liquid metering pump (4a) and metering pump (3a) and mixed by premixer (5). , Forced injection at the beginning. The micro reactor 8 consists of a plurality of micro channel modules 8a, 8b, 8c, 8d, 8e, 8f, 8g surrounded by a heat exchanger to precisely control the temperature. Each micro channel module 8a, 8b, 8c, 8d, 8e, 8f, 8g has a channel 20, an inlet 18a and an outlet 18b, which are connected to each other to form one channel 20. .

Each micro channel plate 16 is inserted between two plate heat exchangers 17 having a heat medium inlet 19a and an outlet 19b to form a respective micro channel module (eg 8c). Each micro channel module 8a, 8b, 8c, 8d, 8e, 8f, 8g is preferably stacked again to save space. If necessary, insulation plates may be placed between the modules. Since the mixing is more important than the reaction rate near the beginning of the microchannel, it is preferable to operate at a relatively low temperature of 0 to 35 ° C in consideration of the variable due to the inflow fluctuations, and the latter part of the reactor (for example, 8 g) increases the reaction rate. In order to maintain stability, it is preferable to operate at the same temperature near 35 degreeC.

The graphite sulfuric acid slurry and the KMnO ₄ sulfuric acid solution are mixed in the channel 20 of the reactor 8 and held for about 20 minutes to the outlet. The outlet of the reactor 8 is first connected to the pure water tank (9) to add water to the reaction mixture, and then the reaction mixture is introduced into the hydrogen peroxide mixing tank (11) and the metering pump (4d) from the aqueous hydrogen peroxide solution tank (10) 3% aqueous hydrogen peroxide solution was added and mixed to terminate the oxidation reaction.

Subsequently, 1 to 5 g of GEMCA 1220A ^TM (purchased from Suyang Comtec Co., Ltd.), which is a cationic surfactant, was added to 230 g (graphite 1 g) of the reaction mixture discharged from the outlet 13 of the hydrogen peroxide mixing tank 11 and mixed with vigorous stirring. 100 g of methylene chloride or ethylene chloride as an organic solvent is added to the reaction mixture, and the mixture is stirred and mixed for 5 minutes. Graphite oxides, cationic surfactants and organic solvents migrate to the organic layer, and sulfuric acid, water, various ions, etc. remain in the aqueous layer to separate the graphite oxide. At this time, the organic layer in which the cationic surfactant-treated graphite oxide is dispersed using a separatory funnel is separated, and the organic oxide and the cationic surfactant are removed from the separated organic layer to wash the graphite oxide. At this time, the organic solvent may be removed by heating, and the cationic surfactant may be removed through a thermal shock reduction process. The graphite oxide thus washed is dried under reduced pressure at 200 ° C or lower, preferably 80 ° C or lower, and within 48 hours.

In the method of washing the graphite oxide mixture according to an embodiment of the present invention, compared to the conventional washing method, for example, a centrifugal separation method and a filter press method, the amount of waste water is markedly reduced as shown in Table 1 below, and energy efficiency is also improved in a short time. There is an advantage to wash.

Graphene
1 kg Wastewater /
Processing cost Used Equipment /
Energy efficiency Time Conventional cleaning method 4000kg /
800,000 won Filter press /
Big energy consumption More than 24 hours Washing method according to the invention 400kg /
80,000 won Starter and Agitator /
Low energy consumption 1 hours

Claims (12)

In the method of washing a graphite oxide mixture containing graphite oxide, sulfuric acid, hydrogen peroxide and pure water obtained during the graphite oxide manufacturing process,
Adding a cationic surfactant to the graphite oxide mixture, followed by stirring and mixing;
Adding an organic solvent to the graphite oxide mixture in which the cationic surfactant is mixed, followed by stirring and mixing;
Separating the organic layer in which the cationic surfactant-treated graphite oxide is dispersed; And
A method for cleaning a graphite oxide mixture, comprising the step of removing the organic solvent and cationic surfactant from the separated organic layer. The method of claim 1, wherein the cationic surfactant is a quaternary ammonium salt compound. The method of claim 2, wherein the cationic surfactant is included in an amount of 1 to 5 parts by weight based on 1 part by weight of the graphite oxide mixture. The method of claim 1, wherein the cationic surfactant is removed by thermal shock reduction. The method of claim 1, further comprising the step of recovering and reusing the cationic surfactant removed from the separated organic layer. The method of claim 1, wherein the organic solvent is methylene chloride, ethylene chloride, trichloroethylene, toluene, di-isopropyl ether, pentane, methyl ethyl ketone, methyl- t-butyl ether, hexane, heptane, di-ethyl ether, ethyl A method of washing a graphite oxide mixture, characterized in that selected from the group consisting of acetate, dichloromethane, 1,2-dichloroethane, cyclohexane, chloroform, carbon tetrachloride, butyl acetate, n-butanol and benzene. The method of claim 1, further comprising the step of recovering and reusing the organic solvent removed from the separated organic layer. The method of claim 1, wherein the graphite oxide mixture
1) preparing a graphite slurry by mixing the graphite powder and sulfuric acid; 2) preparing a KMnO ₄ sulfuric acid solution by mixing KMnO ₄ powder and sulfuric acid; 3) preparing an aqueous hydrogen peroxide solution; 4) introducing the graphite slurry at the start of the channel having a reaction mixture maintained at a constant temperature range and having a start, a reaction part and an outlet; 5) mixing the KMnO ₄ sulfuric acid solution at the beginning of the channel by mixing; 6) maintaining the reaction mixture in the temperature range within the channel; And 7) injecting the aqueous hydrogen peroxide solution near the outlet of the channel. Adding a cationic surfactant to the surface-modified carbon material by acid treatment, followed by stirring and mixing;
Adding an organic solvent to the reaction mixture mixed with the cationic surfactant, followed by stirring and mixing;
Separating the organic layer having the cationic surfactant treated carbon material dispersed therein; And
Removing organic solvent and cationic surfactant from separated organic layer
Acid-treated surface-modified carbon material washing method comprising a. 10. The method of claim 9, wherein the carbon material is a carbon material having a graphite or graphite structure. The method according to claim 9 or 10, wherein the cationic surfactant is a quaternary ammonium salt compound. The method of claim 8 or 9, wherein the cationic surfactant is included in an amount of 1 to 5 parts by weight based on 1 part by weight of the acid treated surface modified carbon material.

Images