Process for the oxidation of graphite and use thereof

Abstract

This disclosure relates to a method for oxidizing graphite, comprising: mixing graphite, concentrated acid, and potassium permanganate, heating and reacting the mixture, then mixing the mixture with hydrogen peroxide and heating and reacting the mixture, followed by solid-liquid separation to obtain graphite oxide and filtrate waste liquid; subjecting the filtrate waste liquid to hydrothermal treatment, separating and removing the solid phase material to obtain manganese oxide; wherein the mass ratio of hydrogen peroxide to graphite is (20-500):1, the mass concentration of hydrogen peroxide is 0.01-5%, and the mass ratio of potassium permanganate to graphite is (1-6):1. This method achieves the simultaneous production of manganese oxide during graphite oxidation, with a low amount of potassium permanganate used and no sodium nitrate added during the reaction, reducing the preparation cost of graphite oxide and manganese oxide. Furthermore, this method can significantly reduce the content of manganese ions in wastewater, solving the problem of environmental pollution caused by wastewater discharge during graphite oxidation.

Description

Technical Field

[0001] This disclosure pertains to the field of graphite oxidation, specifically relating to a method for oxidizing graphite and its applications. Background Technology

[0002] Graphite is a transitional crystal between atomic crystals, metallic crystals, and molecular crystals. However, due to the strong bonding between carbon atoms in the same planar layer, which is extremely difficult to break down, graphite has a high melting point and stable chemical properties. Graphite can be oxidized by strong oxidizing agents such as concentrated nitric acid and potassium permanganate, producing graphite oxide. Graphite oxide, formally known as graphite oxide or graphitic acid, is a compound composed of carbon, hydrogen, and oxygen elements in varying mass ratios. Graphite oxide is an important type of graphite product, used to prepare popular downstream products such as expanded graphite and graphene. Currently, the main method for producing graphite oxide is through oxidation with strong oxidizing agents such as concentrated acid and potassium permanganate; however, the wastewater generated by existing graphite oxide methods is difficult to treat. Summary of the Invention

[0003] The purpose of this invention is to provide a method for oxidizing graphite and its applications. This invention utilizes an oxidation method to prepare graphite oxide while simultaneously producing manganese oxides, significantly reducing the content of manganese ions and other pollutants in the wastewater, thus solving the problem of environmental pollution caused by wastewater discharge.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for oxidizing graphite, wherein the method includes:

[0005] S1 mixes graphite, concentrated acid, and potassium permanganate, and heats the mixture to react, yielding a mixture.

[0006] S2 mixes the mixture with hydrogen peroxide and heats it to react, then separates the solid and liquid components to obtain graphite oxide and filtered waste liquid;

[0007] S3 performs hydrothermal treatment on the filtered waste liquid to separate and remove solid materials to obtain manganese oxides;

[0008] The mass ratio of hydrogen peroxide to graphite is (20-500):1, and the mass concentration of hydrogen peroxide is 0.01-5%.

[0009] The mass ratio of potassium permanganate to graphite is (1-6):1.

[0010] Optionally, the mass ratio of hydrogen peroxide to graphite is (50-200):1, the mass concentration of hydrogen peroxide is 0.05-1%, and the mass ratio of potassium permanganate to graphite is (3-6):1.

[0011] Optionally, the graphite is one or more of natural flake graphite, natural cryptocrystalline graphite, and artificial graphite;

[0012] The graphite has a carbon content of 95% or more by weight, an ash content of less than 5%, and a mesh size of 20 to 200 mesh.

[0013] Optionally, the concentrated acid is selected from one or more of sulfuric acid, nitric acid, and perchloric acid;

[0014] A0 is any concentration between M-10% and M+10%, preferably A0 is any concentration between M-5% and M+5%, where A0 is the concentration of the concentrated acid and M is the highest concentration of the concentrated acid in analytical grade reagent.

[0015] Optionally, the mass ratio of the concentrated acid to the graphite is (10-200):1, preferably (25-100):1.

[0016] Optionally, the carbon-oxygen molar ratio of the graphite oxide is 2 to 4, preferably 2.5 to 3.5.

[0017] Optionally, the method further includes:

[0018] In step S1, potassium permanganate is added in batches to graphite and concentrated acid. The mass ratio of potassium permanganate to graphite in each batch is (0.1-2):1, preferably (0.2-1):1. During the mixing process, the temperature is controlled to be below 40°C, preferably below 30°C, more preferably below 20°C, and the mixing time is 0.1-10 h, preferably 0.5-5 h. The temperature for heating the reaction is 30-60°C, preferably 40-50°C.

[0019] In step S2, the time for heating the graphite and hydrogen peroxide mixture is 0.1 to 6 hours, preferably 0.5 to 3 hours, and the temperature for heating the reaction is 60 to 99°C, preferably 85 to 95°C; no sodium nitrate is added during the reaction.

[0020] In step S3, the hydrothermal treatment conditions include: a temperature of 120–200°C, preferably 150–180°C, and a time of 1–72 h, preferably 12–36 h.

[0021] A second aspect of the present invention provides a manganese oxide prepared using the method provided in the first aspect of the present invention.

[0022] Optionally, the XRD pattern of the manganese oxide has characteristic peaks at 2θ positions of 12.1±0.5°, 24.6±0.4°, 36.9±0.4° and 66.2±0.4°, respectively; and the half-width of the diffraction peak at 12.1±0.5° is greater than 0.4°.

[0023] Based on the mass of the manganese oxide, the mass content of manganese in the manganese oxide is 55-63%; the manganese content in the manganese oxide accounts for more than 95% of the manganese content in the filtered waste liquid;

[0024] The specific surface area of ​​the manganese oxide is 10–30 m². 2 / g, preferably 15-25m 2 / g, with a pore volume of 0.01 to 0.1 ml / g, preferably 0.02 to 0.08 ml / g.

[0025] The third aspect of this invention provides the use of the manganese oxide described in the second aspect of this invention in the field of formaldehyde adsorption and removal.

[0026] Through the above technical solution, the present invention can prepare graphite oxide by oxidation and simultaneously produce manganese oxide. The amount of potassium permanganate used is small, no additional manganese source is required, and sodium nitrate is not added in the reaction process, which reduces the preparation cost of manganese oxide. At the same time, the prepared graphite oxide and manganese oxide exhibit excellent performance in the treatment of wastewater, which can significantly reduce the content of manganese ions and other substances in the wastewater, thus solving the problem of environmental pollution caused by sewage discharge.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 The image shows the XRD pattern of the manganese oxide prepared in Example 1 of this invention. Detailed Implementation

[0030] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0031] The first aspect of this invention provides a method for oxidizing graphite, wherein the method includes:

[0032] S1 mixes graphite, concentrated acid, and potassium permanganate, and heats the mixture to react, yielding a mixture.

[0033] S2 mixes the mixture with hydrogen peroxide and heats it to react, then separates the solid and liquid components to obtain graphite oxide and filtered waste liquid;

[0034] S3 performs hydrothermal treatment on the filtered waste liquid to separate and remove the solid material;

[0035] The mass ratio of hydrogen peroxide to graphite is (20-500):1, preferably (50-200):1; the mass concentration of hydrogen peroxide is 0.01-5%, preferably 0.05-1%; and the mass ratio of potassium permanganate to graphite is (1-6):1, preferably (3-6):1, more preferably (3.5-5.5):1.

[0036] The preparation method of this invention involves first mixing graphite with concentrated acid and potassium permanganate, then heating and reacting for a certain period of time. Next, hydrogen peroxide is added, and the mixture is heated and reacted for another period. After solid-liquid separation, the filtered waste liquid is subjected to a hydrothermal reaction, thus achieving the simultaneous oxidation of graphite and the preparation of manganese oxides. The amount of potassium permanganate used in the graphite oxidation process is relatively small, and no sodium nitrate is added during the reaction, significantly improving process safety and facilitating subsequent manganese oxide preparation and wastewater treatment, thereby significantly reducing the cost of graphite oxidation and manganese oxide preparation.

[0037] In one specific embodiment of the present invention, the graphite is one or more of natural flake graphite, natural cryptocrystalline graphite and artificial graphite, preferably artificial graphite.

[0038] The graphite has a carbon content of 95% by weight or more, preferably 99.9% by weight or more, an ash content of less than 5%, preferably less than 0.1% by weight, and a mesh size of 20 to 200 mesh, preferably 50 to 100 mesh.

[0039] In one specific embodiment of the present invention, the concentrated acid is selected from one or more of sulfuric acid, nitric acid, and perchloric acid;

[0040] A0 is any concentration between M-10% and M+10%, preferably A0 is any concentration between M-5% and M+5%, where A0 is the concentration of the concentrated acid and M is the highest concentration of the concentrated acid in analytical grade reagent.

[0041] In one specific embodiment of the present invention, the mass ratio of the concentrated acid to the graphite is (10-200):1, preferably (25-100):1.

[0042] In the above embodiments, by selecting preferred types of graphite and concentrated acid, as well as their carbon content and concentration, it is beneficial to improve the performance of the prepared graphite oxide.

[0043] In one specific embodiment of the present invention, the carbon-oxygen molar ratio of the graphite oxide is 2 to 4, preferably 2.5 to 3.5.

[0044] The graphite oxide prepared by this invention has a moderate oxygen content and exhibits significant advantages in fire prevention and flame retardancy after thermal expansion and exfoliation.

[0045] In one specific embodiment of the present invention, the method further includes:

[0046] In step S1, potassium permanganate is added in batches to graphite and concentrated acid. The mass ratio of potassium permanganate to graphite in each batch is (0.1-2):1, preferably (0.2-1):1. During the mixing process, the temperature is controlled to be below 40°C, preferably below 30°C, more preferably below 20°C, and the mixing time is 0.1-10 h, preferably 0.5-5 h. The temperature for heating the reaction is 30-60°C, preferably 40-50°C.

[0047] In step S2, the time for heating the graphite and hydrogen peroxide mixture is 0.1 to 6 hours, preferably 0.5 to 3 hours, and the temperature for heating the reaction is 60 to 99°C, preferably 85 to 95°C; no sodium nitrate is added during the reaction.

[0048] In step S3, the hydrothermal treatment conditions include: a temperature of 120–200°C, preferably 150–180°C, and a time of 1–72 h, preferably 12–36 h.

[0049] A second aspect of the present invention provides a manganese oxide prepared using the method provided in the first aspect of the present invention.

[0050] This invention produces manganese oxide while oxidizing graphite, and the method of this invention can significantly reduce the content of manganese ions and other substances in wastewater, thus solving the problem of environmental pollution caused by wastewater discharge during the preparation of graphite oxide.

[0051] In one specific embodiment of the present invention, the XRD pattern of the manganese oxide has characteristic peaks at 2θ positions of 12.1±0.5°, 24.6±0.4°, 36.9±0.4° and 66.2±0.4° respectively; and the half-width of the diffraction peak at 12.1±0.5° is greater than 0.4°.

[0052] Based on the mass of the manganese oxide, the mass content of manganese in the manganese oxide is 55-63%, preferably 58-61%; the manganese content in the manganese oxide accounts for more than 95% of the manganese content in the filtered waste liquid, preferably more than 98%.

[0053] The specific surface area of ​​the manganese oxide is 10–30 m². 2 / g, preferably 15-25m 2 / g, with a pore volume of 0.01 to 0.1 ml / g, preferably 0.02 to 0.08 ml / g.

[0054] The third aspect of this invention provides the use of the manganese oxide described in the second aspect of this invention in the field of formaldehyde adsorption and removal.

[0055] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0056] All reagents used in this invention are commercially available analytical grade reagents.

[0057] Example 1

[0058] First, add 150ml of concentrated sulfuric acid (mass concentration greater than 98%) and 5g of graphite to a beaker and mix to obtain a mixture.

[0059] b. Next, add 25g of potassium permanganate in 5 equal batches to the mixture obtained in step a, and stir and mix at 15℃ for 1 hour to obtain the mixture.

[0060] c. Stir the mixture obtained in step b under autogenous pressure at 45°C for 2 hours to obtain the reacted slurry;

[0061] d. Add 150 ml of 0.05% hydrogen peroxide to the mixed slurry after the reaction in step c. Continue stirring and reacting at 88°C for 1 hour. Then, use a sand filter funnel to directly filter and separate the solid and liquid to obtain graphite oxide solid and filtration waste liquid.

[0062] e. At 160℃ and autogenous pressure, the filtered waste liquid from step d is subjected to hydrothermal treatment for 24 hours, and manganese oxide is extracted by solid-liquid separation.

[0063] The XRD pattern of the prepared manganese oxide is shown in the figure. Figure 1 As shown.

[0064] Example 2

[0065] The preparation method in Example 1 was used, except that in step b, the amount of potassium permanganate used was 10g.

[0066] Example 3

[0067] The preparation method in Example 1 was used, except that in step e, the reaction temperature was 120°C and the hydrothermal treatment time was 2 hours.

[0068] Example 4

[0069] The preparation method in Example 1 was used, except that in step a, 100 ml of concentrated sulfuric acid was added.

[0070] Example 5

[0071] The preparation method in Example 1 was used, except that the reaction temperature in step c was 30°C.

[0072] Example 6

[0073] The preparation method in Example 1 was used, except that in step d, 450 ml of hydrogen peroxide of the same concentration was added.

[0074] Example 7

[0075] The preparation method in Example 1 was used, except that in step d, 150 ml of hydrogen peroxide with a mass concentration of 1.5% was added.

[0076] Example 8

[0077] The preparation method in Example 1 is used, except that in step b, potassium permanganate is added to the mixture obtained in step a all at once.

[0078] Comparative Example 1

[0079] The preparation method in Example 1 was used, except that in step b, the amount of potassium permanganate used was 4g.

[0080] Comparative Example 2

[0081] The preparation method in Example 1 was used, except that in step d, 15 ml of hydrogen peroxide of the same concentration was added.

[0082] Comparative Example 3

[0083] The preparation method in Example 1 was used, except that in step d, 150 ml of 6% hydrogen peroxide was added.

[0084] Test case

[0085] The XRD patterns of the samples were obtained using a Rigaku D / MaxA-ⅢA X-ray diffractometer (Japan). Test conditions: Cu target Kα radiation, voltage 30 kV, current 20 mA, step scan, scan range 5°–80°.

[0086] The elemental content of the samples was determined by XPS on a VGESCA-LABS X-ray photoelectron spectrometer, using Mg Kα X-rays as the laser source, and the binding energy of each element in the species on the surface of the desulfurizer was calibrated by the C1s binding energy of the carbon contaminants on the surface.

[0087] The temperature nitrogen adsorption-desorption (BET) test was performed using a JW-BK200C specific surface area and pore size analyzer from Beijing Jingwei Gaobo Co., Ltd. Specific surface area and pore volume were calculated using the two-parameter BET equation, and pore distribution was calculated using the BJH method.

[0088] The effects of manganese oxide prepared in the embodiments and comparative examples of the present invention as formaldehyde adsorption and removal agents are demonstrated. The specific steps are as follows: At room temperature and atmospheric pressure, 500 mg of manganese oxide was packed into the middle of a fixed-bed reaction tube with a diameter of 10 mm, and both ends were filled with quartz wool. A concentration of 1.0 mg / m³ was introduced at a flow rate of 10 ml / min. 3 The formaldehyde (with the remainder being air) was measured, and the residual formaldehyde concentration was detected after 1 hour and 12 hours of reaction to calculate the formaldehyde removal rate. The formaldehyde removal rates after 1 hour and 12 hours of reaction are shown in Table 1. Other characterization results of the prepared samples are shown in Table 2. The XRD pattern of the manganese oxide prepared in Example 1 of this invention is shown in... Figure 1 As shown.

[0089] Table 1

[0090] Formaldehyde removal rate (%) after 1 hour of reaction Formaldehyde removal rate (%) after 12 hours of reaction Example 1 96.4 96.1 Example 2 92.2 88.7 Example 3 89.6 83.5 Example 4 90.1 85.2 Example 5 90.7 82.6 Example 6 86.4 86.2 Example 7 85.8 85.1 Example 8 89.6 86.8 Comparative Example 1 87.1 71.5 Comparative Example 2 85.3 68.2 Comparative Example 3 77.5 69.4

[0091] Table 2

[0092]

[0093]

[0094] As can be seen from the test results in Tables 1 and 2, the manganese oxide material prepared by the method provided by this invention has a moderate specific surface area and pore volume compared with the comparative example, which can effectively remove formaldehyde from the material. It can maintain excellent formaldehyde removal performance even after 12 hours of reaction, and no nitrate needs to be added during the reaction process, which reduces the cost of the prepared material. At the same time, it significantly reduces the manganese content in the filtration waste liquid, thus solving the problem of wastewater discharge polluting the environment during the graphite oxidation process.

[0095] The test results of Examples 1-8 show that when the preparation method and the amounts of hydrogen peroxide and potassium permanganate are within the limits defined by this invention, the effect and performance of the product prepared by this invention can be improved. A comparison of Examples 1 and Examples 2-8 shows that when the amount and mass concentration of hydrogen peroxide, the amount of potassium permanganate, the type and amount of concentrated acid, the amount and batch of potassium permanganate added, the heating temperature, and the stirring time are all within the preferred limits defined by this invention, the formaldehyde removal performance of the manganese oxide material prepared by this invention can be further improved.

[0096] The test results of Comparative Examples 1-3 show that in Comparative Example 1, the amount of potassium permanganate was too low, resulting in a low manganese content in the graphite oxide filtration waste liquid. This led to a low manganese content in the prepared manganese oxide, a large specific surface area and pore volume, and poor product performance. The formaldehyde removal rate after 1 hour of reaction was significantly worse than that in Example 1, and the formaldehyde removal performance significantly decreased after 12 hours of reaction. In Comparative Example 2, the amount of hydrogen peroxide was outside the limits of this invention, resulting in an insufficient oxidation reaction. This led to a large specific surface area and pore volume in the prepared manganese oxide, resulting in a decrease in product quality. The formaldehyde removal rate after 1 hour and 12 hours of reaction was lower than that in Examples 1-9. In Comparative Example 3, the concentration of hydrogen peroxide was too high, resulting in a small specific surface area and pore volume in the prepared manganese oxide. The formaldehyde removal rate significantly decreased after 1 hour and 12 hours of reaction.

[0097] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0098] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0099] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for oxidizing graphite, wherein, The method includes: S1. Graphite, concentrated acid, and potassium permanganate are mixed and heated to react, resulting in a mixture. S2 The mixture is mixed with hydrogen peroxide and heated to react, and then graphite oxide and filtered waste liquid are obtained by solid-liquid separation; S3 performs hydrothermal treatment on the filtered waste liquid to separate and remove solid materials to obtain manganese oxides; The mass ratio of hydrogen peroxide to graphite is (20~500):1, and the mass concentration of hydrogen peroxide is 0.01~5%. The mass ratio of potassium permanganate to graphite is (1~6):1; In step S2, the reaction time of the mixture with hydrogen peroxide is 0.1~6h, and the reaction temperature is 60~99℃. In step S3, the conditions for the hydrothermal treatment include: a temperature of 120~200℃ and a time of 1~72h.

2. The method according to claim 1, wherein, The mass ratio of hydrogen peroxide to graphite is (50~200):1, and the mass concentration of hydrogen peroxide is 0.05~1%; the mass ratio of potassium permanganate to graphite is (3~6):

1.

3. The method according to claim 1, wherein, The graphite is one or more of natural flake graphite, natural cryptocrystalline graphite, and artificial graphite. The graphite has a carbon content of 95% or more by weight, an ash content of less than 5%, and a mesh size of 20 to 200 mesh.

4. The method according to claim 1, wherein, The concentrated acid is selected from one or more of sulfuric acid, nitric acid, and perchloric acid; A0 is any concentration between M-10% and M+10%, where A0 is the concentration of the concentrated acid and M is the highest concentration of the concentrated acid in analytical grade reagent.

5. The method according to claim 4, wherein, A0 is any concentration between M-5% and M+5%, where A0 is the concentration of the concentrated acid and M is the highest concentration of the concentrated acid in analytical grade reagent.

6. The method according to claim 1, wherein, The mass ratio of the concentrated acid to the graphite is (10~200):

1.

7. The method according to claim 6, wherein, The mass ratio of the concentrated acid to the graphite is (25~100):

1.

8. The method according to claim 1, wherein, The carbon-oxygen molar ratio of the graphite oxide is 2 to 4.

9. The method according to claim 8, wherein, The carbon-oxygen molar ratio of the graphite oxide is 2.5 to 3.

5.

10. The method according to claim 1, wherein, The method also includes: In step S1, potassium permanganate is added in batches to graphite and concentrated acid. The mass ratio of potassium permanganate to graphite in each batch is (0.1~2):

1. During the mixing process, the temperature is controlled to be below 40°C and the mixing time is 0.1~10h. The temperature of the heating reaction is 30~60°C. In step S2, the mixture of materials and hydrogen peroxide is heated and reacted for 0.5 to 3 hours at a temperature of 85 to 95°C; no sodium nitrate is added during the reaction. In step S3, the hydrothermal treatment conditions include: a temperature of 150~180℃ and a time of 12~36h.

11. The method according to claim 10, wherein, The mass ratio of potassium permanganate to graphite added in each batch is (0.2~1):

1. During the mixing process, the temperature is controlled to be below 30℃, and the mixing time is 0.5~5h. The temperature of the heating reaction is 40~50℃.

12. The method according to claim 11, wherein, Control the temperature to below 20°C during the mixing process.

13. Manganese oxide prepared by the method according to any one of claims 1 to 12.

14. The manganese oxide according to claim 13, wherein, The XRD pattern of the manganese oxide shows characteristic peaks at 2θ positions of 12.1±0.5°, 24.6±0.4°, 36.9±0.4° and 66.2±0.4°, respectively; and the half-width of the diffraction peak at 12.1±0.5° is greater than 0.4°. Based on the mass of the manganese oxide, the mass content of manganese in the manganese oxide is 55-63%; the manganese content in the manganese oxide accounts for more than 95% of the manganese content in the filtered waste liquid; The specific surface area of ​​the manganese oxide is 10~30m². 2 / g, with a pore volume of 0.01~0.1ml / g.

15. The manganese oxide according to claim 14, wherein, The specific surface area of ​​the manganese oxide is 15~25m². 2 / g, with a pore volume of 0.02~0.08ml / g.

16. The use of manganese oxide according to any one of claims 13 to 15 in the field of formaldehyde adsorption and removal.

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