Oxidation method and application of graphite

Abstract

The present invention relates to a graphite oxidation method, which comprises: mixing graphite, a concentrated acid and potassium permanganate, carrying out a heating reaction, mixing the mixed material and hydrogen peroxide, carrying out a heating reaction, and carrying out solid-liquid separation to obtain graphite oxide and a filtration waste liquid, carrying out hydrothermal treatment on the filtered waste liquid, and separating and taking out a solid-phase material to obtain manganese oxide; wherein the mass ratio of the addition amount of the hydrogen peroxide to the addition amount of the graphite is (20-500): 1, and the mass concentration of the hydrogen peroxide is 0.01-5%; the mass ratio of potassium permanganate to graphite is (1-6): 1. According to the preparation method disclosed by the invention, the manganese oxide is produced in the graphite oxide preparation process, the use amount of potassium permanganate in the graphite oxide preparation process is relatively low, sodium nitrate is not added in the reaction process, the preparation cost of the graphite oxide and the manganese oxide is reduced, and meanwhile, the content of manganese ions and the like in the wastewater can be remarkably reduced; the problem that sewage discharge pollutes the environment in the graphite oxidation process is solved.

Description

Technical Field

[0001] The present invention belongs to the field of graphite oxidation, and in particular relates to a graphite oxidation method and application thereof. Background Art

[0002] Graphite is a transitional crystal between atomic crystals, metal crystals and molecular crystals. However, because the carbon atoms on the same plane layer are strongly bonded and extremely difficult to destroy, the melting point of graphite is also very high and its chemical properties are stable. Graphite can be oxidized by strong oxidants such as concentrated nitric acid, potassium permanganate and other strong oxidants, and the product after oxidation is graphite oxide. The formal name of graphite oxide is graphite oxide or graphitic acid. It is a compound composed of carbon, hydrogen and oxygen elements in an uncertain ratio of moles. Graphite oxide is an important type of graphite product, which can be used to prepare downstream popular products such as expanded graphite and graphene. At present, the main method of producing graphite oxide is to oxidize graphite using strong oxidants such as concentrated acid and potassium permanganate, but the wastewater generated by the existing graphite oxidation method is difficult to treat. Summary of the invention

[0003] The purpose of the present invention is to provide a graphite oxidation method and its use. The present invention utilizes an oxidation method to prepare graphite oxide and can simultaneously produce manganese oxide, which can significantly reduce the content of manganese ions and the like in the preparation wastewater, and solve the problem of wastewater discharge polluting the environment.

[0004] In order to achieve the above object, the first aspect of the present invention provides a method for oxidizing graphite, wherein the method comprises:

[0005] S1: mixing graphite, concentrated acid and potassium permanganate, heating and reacting to obtain a mixed material;

[0006] S2: mixing the mixed material with hydrogen peroxide and heating them for reaction, and obtaining graphite oxide and filtering waste liquid through solid-liquid separation;

[0007] S3 performs hydrothermal treatment on the filtered waste liquid to separate and take out the solid phase material to obtain manganese oxide;

[0008] The mass ratio of the amount of hydrogen peroxide added to the amount of graphite added is (20-500):1, and the mass concentration of the 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 the added amount of the hydrogen peroxide to the added amount of the graphite is (50-200):1, the mass concentration of the hydrogen peroxide is 0.05-1%; the mass ratio of the potassium permanganate to the 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 more than 95% by weight, an ash content of less than 5%, and a mesh size of 20 to 200 meshes.

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

[0014] A 0 Any concentration between M-10% and M+10%, preferably A 0 Any concentration between M-5% and M+5%, A 0 is the concentration of the concentrated acid, and M is the maximum concentration of the analytical pure reagent grade of the concentrated acid.

[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 comprises:

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

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

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

[0021] The second aspect of the present invention provides a manganese oxide prepared by the method provided by the first aspect of the present invention.

[0022] Optionally, in the XRD spectrum of the manganese oxide, characteristic peaks exist 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-peak 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 to 30 m 2 / g, preferably 15 to 25 m 2 / g, and the pore volume is 0.01-0.1 ml / g, preferably 0.02-0.08 ml / g.

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

[0026] Through the above technical scheme, the present invention utilizes an oxidation method to prepare graphite oxide and can simultaneously produce manganese oxide, and the amount of potassium permanganate used is relatively small, and no additional manganese source needs to be added, and no sodium nitrate is added during the reaction process, thereby reducing the preparation cost of manganese oxide. At the same time, the prepared graphite oxide and manganese oxide show excellent performance in the process of treating wastewater, and can significantly reduce the content of manganese ions and the like in the wastewater, thereby 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is the XRD pattern of the manganese oxide prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0031] A first aspect of the present invention provides a method for oxidizing graphite, wherein the method comprises:

[0032] S1: mixing graphite, concentrated acid and potassium permanganate, heating and reacting to obtain a mixed material;

[0033] S2: mixing the mixed material with hydrogen peroxide and heating them for reaction, and obtaining graphite oxide and filtering waste liquid through solid-liquid separation;

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

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

[0036] The preparation method of the present invention comprises the following steps: firstly mixing graphite with concentrated acid and potassium permanganate, heating and reacting the mixture for a certain time, then adding hydrogen peroxide, mixing and heating the mixture for a certain time, and then subjecting the filtered waste liquid to a hydrothermal reaction after solid-liquid separation, so as to prepare manganese oxide while oxidizing graphite. In the process of graphite oxidation, the amount of potassium permanganate used is relatively small, and no sodium nitrate is added during the reaction process, so that the process safety is greatly improved, and it is conducive to the subsequent preparation of manganese oxide and wastewater treatment, and the cost of graphite oxidation and preparation of manganese oxide is significantly reduced.

[0037] In a 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 5% or less, preferably 0.1% by weight or less, and a mesh size of 20 to 200 meshes, preferably 50 to 100 meshes.

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

[0040] A 0 Any concentration between M-10% and M+10%, preferably A 0 Any concentration between M-5% and M+5%, A 0 is the concentration of the concentrated acid, and M is the maximum concentration of the analytical pure reagent grade of the concentrated acid.

[0041] In a 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-mentioned embodiment, the performance of the prepared graphite oxide is improved by selecting the preferred types, carbon content and concentration of graphite and concentrated acid.

[0043] In a 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 the present invention has a moderate oxygen content and has significant advantages in fire retardancy and the like after thermal expansion and exfoliation.

[0045] In a specific embodiment of the present invention, the method further comprises:

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

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

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

[0049] The second aspect of the present invention provides a manganese oxide prepared by the method provided by the first aspect of the present invention.

[0050] The invention produces manganese oxides while oxidizing graphite, and the method can significantly reduce the content of manganese ions and the like in wastewater, thereby solving the problem of wastewater discharge polluting the environment when preparing graphite oxide.

[0051] In a specific embodiment of the present invention, the XRD spectrum of the manganese oxide has characteristic peaks at 2θ of 12.1±0.5°, 24.6±0.4°, 36.9±0.4° and 66.2±0.4°, respectively; and the half-peak 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 to 30 m 2 / g, preferably 15 to 25 m 2 / g, and the pore volume is 0.01-0.1 ml / g, preferably 0.02-0.08 ml / g.

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

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

[0056] The reagents used in the present invention are all commercially available analytically pure reagents.

[0057] Example 1

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

[0059] b. Then, 25 g of potassium permanganate was added into the mixed solution obtained in step a in 5 batches, and the mixture was stirred at 15° C. for 1 h to obtain a mixed material;

[0060] c. Stir the mixture obtained in step b at 45° C. under autogenous pressure for 2 h to obtain a mixed slurry after reaction;

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

[0062] e. The waste liquid filtered in step d is subjected to hydrothermal treatment at 160° C. and autogenous pressure for 24 hours to separate the solid and liquid and remove the manganese oxide.

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

[0064] Example 2

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

[0066] Example 3

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

[0068] Example 4

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

[0070] Example 5

[0071] The preparation method in Example 1 was adopted, except that in step c, the reaction temperature 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 adopted, except that, in step b, potassium permanganate is added once to the mixed solution obtained in step a.

[0078] Comparative Example 1

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

[0080] Comparative Example 2

[0081] The preparation method in Example 1 was adopted, except that in step d, 15 ml of hydrogen peroxide solution 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 hydrogen peroxide with a mass concentration of 6% was added.

[0084] Test Case

[0085] The XRD spectrum of the sample was obtained by a Rigaku D / MaxA-ⅢA X-ray diffractometer. Test conditions: Cu target Kα radiation, voltage 30 kV, current 20 mA, step scan, scanning range 5°~80°.

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

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

[0088] The effects of the manganese oxide prepared in the examples of the present invention and the comparative examples as formaldehyde adsorption and removal agents are as follows: at room temperature and pressure, 500 mg of manganese oxide is placed in the middle of a fixed bed reaction tube with a diameter of 10 mm, quartz wool is filled at both ends, and a 1.0 mg / m 3 The remaining formaldehyde concentration after 1h and 12h of reaction was detected, and the formaldehyde removal rate was calculated. The results of the formaldehyde removal rate after 1h of reaction and the formaldehyde removal rate after 12h 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 the present invention is shown in Figure 1 shown.

[0089] Table 1

[0090] Formaldehyde removal rate after 1h reaction / % Formaldehyde removal rate after 12h 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] According to the test results of Table 1 and Table 2, it can be seen that the manganese oxide material prepared by the method provided by the present invention has a moderate specific surface area and pore volume compared with the comparative example, can effectively remove formaldehyde in the material, and can continue to have excellent formaldehyde removal performance after 12 hours of reaction. No nitrate needs to be added during the reaction process, which reduces the cost of preparing the material. At the same time, the content of manganese in the filtered waste liquid is significantly reduced, solving the problem of wastewater discharge polluting the environment in the graphite oxidation process.

[0095] It can be seen from the test results of Examples 1 to 8 that when the preparation method and the amount of hydrogen peroxide and potassium permanganate are within the specified range of the present invention, the effect and performance of the product prepared by the present invention can be improved. By comparing Example 1 with Examples 2 to 8, it can be seen 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, the heating temperature and the stirring time are all within the preferred specified range of the present invention, the performance of the manganese oxide material prepared by the present invention in removing formaldehyde can be further improved.

[0096] It can be seen from the test results of Comparative Examples 1 to 3 that the amount of potassium permanganate used in Comparative Example 1 is too low, and the manganese content provided by the waste liquid filtered by graphite oxide is low, resulting in a low manganese content in the prepared manganese oxide, a large specific surface area and a large pore volume, and poor product performance. The removal rate of formaldehyde in the material after 1 hour of reaction is significantly worse than that in Example 1, and the performance of removing formaldehyde in the material after 12 hours of reaction is significantly reduced; the amount of hydrogen peroxide used in Comparative Example 2 is not within the specified range of the present invention, so that the oxidation reaction is insufficient, resulting in a large specific surface area and a large pore volume of the prepared manganese oxide, and the quality of the product is reduced. The removal rate of formaldehyde in the material after 1 hour of reaction and after 12 hours of reaction is lower than that of Examples 1 to 9; the use of hydrogen peroxide in Comparative Example 3 is too high, which will cause the specific surface area and pore volume of the prepared manganese oxide to be too small, and the removal rate of formaldehyde after 1 hour of reaction and after 12 hours of reaction is significantly reduced.

[0097] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to 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 further describe various possible combinations.

[0099] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for oxidizing graphite, wherein: The method includes: S1: mixing graphite, concentrated acid and potassium permanganate, heating and reacting to obtain a mixed material; S2: mixing the mixed material with hydrogen peroxide and heating them for reaction, and obtaining graphite oxide and filtering waste liquid through solid-liquid separation; S3 performs hydrothermal treatment on the filtered waste liquid to separate and take out the solid phase material to obtain manganese oxide; The mass ratio of the amount of hydrogen peroxide added to the amount of graphite added is (20-500):1, and the mass concentration of the hydrogen peroxide is 0.01-5%; The mass ratio of potassium permanganate to graphite is (1-6):

1.

2. The method according to claim 1, wherein: The mass ratio of the added amount of the hydrogen peroxide to the added amount of the graphite is (50-200):1, and the mass concentration of the hydrogen peroxide is 0.05-1%; the mass ratio of the potassium permanganate to the 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 more than 95% by weight, an ash content of less than 5%, and a mesh size of 20 to 200 meshes.

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%, preferably A0 is any concentration between M-5% and M+5%, A0 is the concentration of the concentrated acid, and M is the highest concentration of the analytical pure reagent grade of the concentrated acid.

5. The method according to claim 1, wherein: The mass ratio of the concentrated acid to the graphite is (10-200):1, preferably (25-100):

1.

6. The method according to claim 1, wherein: The carbon-oxygen molar ratio of the graphite oxide is 2 to 4, preferably 2.5 to 3.

5.

7. The method according to claim 1, wherein: The method further includes: In step S1, potassium permanganate is added to the graphite and concentrated acid in batches, the mass ratio of potassium permanganate added in each batch to the graphite is (0.1-2):1, preferably (0.2-1):1, the temperature is controlled to be below 40°C, preferably below 30°C, more preferably below 20°C during the mixing process, the mixing time is 0.1-10h, preferably 0.5-5h; the temperature of the heating reaction is 30-60°C, preferably 40-50°C; In step S2, the graphite and hydrogen peroxide are mixed and heated for a reaction time of 0.1 to 6 hours, preferably 0.5 to 3 hours, and the heating reaction temperature is 60 to 99° C., preferably 85 to 95° C.; no sodium nitrate is added during the reaction; In step S3, the conditions of the hydrothermal treatment include: a temperature of 120 to 200° C., preferably 150 to 180° C., and a time of 1 to 72 hours, preferably 12 to 36 hours.

8. Manganese oxide prepared by the method according to any one of claims 1 to 7.

9. The manganese oxide according to claim 8, wherein The XRD spectrum 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-peak 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 to 30 m 2 / g, preferably 15 to 25 m 2 / g, and the pore volume is 0.01-0.1 ml / g, preferably 0.02-0.08 ml / g.

10. Use of the manganese oxide according to claim 8 or 9 in the field of formaldehyde adsorption and removal.

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