A method of purifying graphene oxide

Abstract

The application relates to the technical field of a new material graphene, and discloses a method for purifying graphene oxide. The method comprises the following steps: (1) contacting paste A1 with water to obtain a graphene oxide diluent; (2) mixing the graphene oxide diluent with active agent B1 to obtain electrolyte C1, then performing power supply treatment on the electrolyte C1 in an electrolytic cell provided with a cathode and an anode to obtain concentrated graphene oxide D1; (3) sequentially adding paste An and active agent Bn into the electrolytic cell to obtain electrolyte Cn respectively, and sequentially performing power supply treatment on the electrolyte Cn to obtain concentrated graphene oxide Dn; and (4) performing filter pressing on the concentrated graphene oxide D1... the concentrated graphene oxide Dn, and then sequentially performing dispersion and drying on the product obtained through the filter pressing to obtain purified graphene oxide. The method can reduce the impurity content in the graphene oxide, and has high purification efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of graphene, a novel material, and specifically to a method for purifying graphene oxide. Background Technology

[0002] Graphene oxide, as a newly developed two-dimensional material, possesses many excellent properties. The thermal conductivity of a single layer of defect-free graphene can reach 5300 W / mK, far exceeding that of metallic thermally conductive materials such as copper (398 W / mK). Currently, the main method for producing graphene oxide is the oxide intercalation exfoliation method based on Hummers' process. This method has low production costs, high yield, and a high graphene monolayer ratio, making it suitable for large-scale industrial production. However, the graphene oxide slurry produced by the oxide intercalation method contains a large number of impurity ions.

[0003] Existing methods for purifying graphene oxide involve multiple dilutions and washings with large amounts of pure water to reduce impurities. The washing conditions are typically acidic dilute hydrochloric acid solutions, which are inefficient, produce poor results, and result in highly acidic products. Consequently, the produced graphene oxide products have low purity and poor quality.

[0004] CN102626591A discloses a method and apparatus for purifying graphene oxide / graphene solution. The method involves inputting the graphene oxide / graphene solution to be purified into a dialysis chamber placed between an anode and cathode. The dialysis chamber has a graphene oxide / graphene solution channel in the middle, and a solvent flow channel between the dialysis chamber and the anode and cathode. The graphene oxide / graphene solution to be purified enters from one end of the dialysis chamber and, under the influence of the electric field between the anode and cathode, ions and charged particles in the solution migrate through the dialysis chamber wall towards the oppositely charged electrodes and are carried away by the solvent flow. The remaining purified graphene oxide / graphene solution flows out of the dialysis chamber. However, purifying graphene oxide / graphene solution through electrolysis and dialysis suffers from problems such as long processing time, low efficiency, high overall cost, and poor purification effect.

[0005] CN 104118872A discloses a method and apparatus for purifying graphene oxide / graphene solution. The method includes: pumping the graphene oxide / graphene solution to be purified into the channel of at least one filter tube; placing the filter tube between at least one set of cathode and anode electrodes in an electrolytic cell; and providing an auxiliary liquid channel between the cathode / anode electrodes and the filter tube. Under the influence of the electric field between the cathode and anode electrodes, ions and charged particles in the graphene oxide / graphene solution to be purified undergo electrode migration, filtering impurities out of the filter tube and carrying them away by the auxiliary liquid. The remaining purified graphene oxide / graphene solution is then pumped from the filter tube into another water tank, forming a filtration cycle. However, the filter tube in this apparatus has a micron-sized pore size, which is difficult to manufacture, requires replacement with filter tubes of different pore sizes, and is complex, cumbersome, and has a high overall cost. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as low efficiency, poor washing effect, and high acidity of the product in the graphene oxide washing process.

[0007] To achieve the above objectives, the present invention provides a method for purifying graphene oxide, the method comprising the following steps:

[0008] (1) Provide n graphene oxide pastes numbered A1, A2...An, and refer to them as paste A1, paste A2... paste An respectively; contact the paste A1 with water to obtain a diluted graphene oxide solution; provide n surfactants numbered B1, B2... Bn, and refer to them as surfactant B1, surfactant B2... surfactant Bn respectively; wherein, n ≮ 2;

[0009] (2) The graphene oxide dilution solution is mixed with the activator B1 to obtain electrolyte C1. Then, in an electrolytic cell equipped with a cathode and an anode, the electrolyte C1 is subjected to electric current treatment to obtain concentrated graphene oxide D1.

[0010] (3) The paste A2 and the activator B2...the paste An and the activator Bn are sequentially added to the electrolytic cell to obtain electrolyte C2...electrolyte Cn, and the electrolyte C2...electrolyte Cn are sequentially subjected to electrolysis to obtain concentrated graphene oxide D2...concentrated graphene oxide Dn;

[0011] (4) The concentrated graphene oxide D1, the concentrated graphene oxide D2...the concentrated graphene oxide Dn are subjected to pressure filtration, and the products obtained by pressure filtration are dispersed and dried in sequence to obtain purified graphene oxide.

[0012] In step (1), the weight ratio of the paste A1 to the water is 1:20-300.

[0013] For any single 100g of graphene oxide paste, the amount of any single surfactant is 0.01-1g; the conditions for the electrochemical treatment each independently include: a current density of 0.01-1000mA / cm². 2 The voltage is 0.1-50V, the energizing frequency is 5-15min / time, and the number of energizing cycles is 2-5 times;

[0014] In step (3), the content of graphene oxide in any one of the electrolytes C2 to Cn is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1.

[0015] During their research, the inventors of this invention discovered that adding a surfactant to the reaction system can promote the separation of graphene oxide from impurities. Then, by utilizing the principle that graphene oxide and impurity ions carry different charges and move towards opposite electrode directions, the graphene oxide in the solution can be enriched and concentrated on the electrode surface, thereby achieving the purification of graphene oxide.

[0016] The present invention has the following advantages through the above technical solution:

[0017] (1) The method for purifying graphene oxide provided by the present invention can significantly reduce the impurity content in graphene oxide and improve the purification efficiency of graphene oxide; and the purification process does not generate a large amount of acidic wastewater, and the purification cost is low.

[0018] (2) The method for purifying graphene oxide provided by the present invention uses less water and has high purification efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow for purifying graphene oxide according to one embodiment of the present invention. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] As mentioned above, the present invention provides a method for purifying graphene oxide, the method comprising the following steps:

[0022] (1) Provide n graphene oxide pastes numbered A1, A2...An, and refer to them as paste A1, paste A2... paste An respectively; contact the paste A1 with water to obtain a diluted graphene oxide solution; provide n surfactants numbered B1, B2... Bn, and refer to them as surfactant B1, surfactant B2... surfactant Bn respectively; wherein, n ≮ 2;

[0023] (2) The graphene oxide dilution solution is mixed with the activator B1 to obtain electrolyte C1. Then, in an electrolytic cell equipped with a cathode and an anode, the electrolyte C1 is subjected to electric current treatment to obtain concentrated graphene oxide D1.

[0024] (3) The paste A2 and the activator B2...the paste An and the activator Bn are sequentially added to the electrolytic cell to obtain electrolyte C2...electrolyte Cn, and the electrolyte C2...electrolyte Cn are sequentially subjected to electrolysis to obtain concentrated graphene oxide D2...concentrated graphene oxide Dn;

[0025] (4) The concentrated graphene oxide D1, the concentrated graphene oxide D2...the concentrated graphene oxide Dn are subjected to pressure filtration, and the products obtained by pressure filtration are dispersed and dried in sequence to obtain purified graphene oxide.

[0026] In step (1), the weight ratio of the paste A1 to the water is 1:20-300.

[0027] For any single 100g of graphene oxide paste, the amount of any single surfactant is 0.01-1g; the conditions for the electrochemical treatment each independently include: a current density of 0.01-1000mA / cm². 2 The voltage is 0.1-50V, the energizing frequency is 5-15min / time, and the number of energizing cycles is 2-5 times;

[0028] In step (3), the content of graphene oxide in any one of the electrolytes C2 to Cn is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1.

[0029] During their research, the inventors of this invention discovered that the method for purifying graphene oxide provided by this invention has a higher pH value in the dispersion before drying, resulting in a lower impurity content in the final purified graphene oxide; furthermore, it uses less water during the purification process and has higher purification efficiency.

[0030] In this invention, the graphene oxide paste refers to graphene oxide containing impurities such as Fe, Mn and Na; the n graphene oxide pastes are all of the same type, with a pH value of 1-3, and the content of graphene oxide is 40-45 wt%, the content of impurities is 1.5-5 wt%, and the content of water is 52-58 wt%.

[0031] In this invention, all n surfactants are of the same type.

[0032] The present invention does not impose any particular restrictions on the order in which the graphene oxide paste and the surfactant are provided in step (1). For example, n graphene oxide pastes numbered A1, A2...An can be provided first, and referred to as paste A1, paste A2... paste An respectively; paste A1 is contacted with water to obtain a diluted graphene oxide solution; then n surfactants numbered B1, B2... Bn can be provided, and referred to as surfactant B1, surfactant B2... surfactant Bn respectively.

[0033] According to some embodiments of the present invention, preferably, in step (1), the contact method is selected from at least one of mechanical stirring, ultrasonic dispersion, homogeneous dispersion, and sand mill dispersion.

[0034] The above-described preferred embodiments are beneficial for further reducing the impurity content in graphene oxide and improving the purification efficiency of graphene oxide.

[0035] According to some embodiments of the present invention, preferably, in step (1), the weight ratio of the paste A1 to the water is 1:90-200. This preferred embodiment is advantageous in reducing the impurity content in graphene oxide while further reducing the water consumption in the graphene oxide purification process.

[0036] According to some embodiments of the present invention, preferably, in step (2), the n surfactants are each provided independently in the form of an aqueous surfactant solution, the concentration of which is 0.05-0.2 wt%.

[0037] According to some embodiments of the present invention, preferably, in step (2), each of the n surfactants is independently selected from at least one of sodium dodecyl alcohol polyoxyethylene ether sulfate, ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium secondary alkyl sulfonate, sodium fatty alcohol hydroxyethyl sulfonate, sodium tetrapolypropylene benzene sulfonate, polyacrylamide, sodium carboxymethyl cellulose, triethanolamine lauryl sulfate, polyvinylpyrrolidone, and polyvinyl alcohol. More preferably, each of the n surfactants is independently selected from at least one of sodium dodecylbenzene sulfonate, polyacrylamide, and sodium carboxymethyl cellulose.

[0038] The above-described preferred embodiments are more effective in promoting the separation of graphene oxide from impurities and improving purification efficiency.

[0039] According to some embodiments of the present invention, preferably, step (2) includes the following specific operations:

[0040] (2-1) The graphene oxide dilution solution is mixed with the activator B1 and stirred until the reaction system is stable to obtain electrolyte C1;

[0041] (2-2) Then, in an electrolytic cell equipped with a cathode and an anode, the cathode and the anode are connected to the positive and negative terminals of a DC regulated power supply, respectively, and the electrolyte C1 is energized to obtain concentrated graphene oxide D1.

[0042] (2-3) The concentrated graphene oxide D1 is peeled off.

[0043] The present invention allows for a wide range of choices for the types of cathode and anode, and can use any commonly used cathode and anode in the art. Preferably, in step (2), the cathode and anode may be the same or different, and each is independently selected from platinum, palladium, and rhodium; more preferably, the cathode and anode are the same; even more preferably, both the cathode and the anode are platinum.

[0044] Preferably, the anode has dimensions of 8×80mm-12×120mm and a thickness of 0.05-0.15mm.

[0045] The above-described preferred embodiments are beneficial for further improving the purification efficiency of graphene oxide.

[0046] According to some embodiments of the present invention, step (3) specifically includes:

[0047] (3-1) The paste A2 and the surfactant B2 are added sequentially to the electrolytic cell to obtain electrolyte C2, and the electrolyte C2 is subjected to electrolytic treatment to obtain concentrated graphene oxide D2; the amount of paste A2 and surfactant B2 added is controlled so that the content of graphene oxide in electrolyte C2 is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1;

[0048] (3-2) The paste A3 and the surfactant B3 are added sequentially to the electrolytic cell to obtain electrolyte C3, and the electrolyte C3 is subjected to electrolytic treatment to obtain concentrated graphene oxide D3; the amount of paste A3 and surfactant B3 added is controlled so that the content of graphene oxide in electrolyte C3 is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1;

[0049] (3-3)...

[0050] (3-n) The paste An and the surfactant Bn are added sequentially to the electrolytic cell to obtain electrolyte Cn, and the electrolyte Cn is subjected to electrolytic treatment to obtain concentrated graphene oxide Dn; the amount of paste An and surfactant Bn added is controlled so that the content of graphene oxide in electrolyte Cn is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1.

[0051] Preferably, the conditions for the energizing process each independently include: a current density of 10-30 mA / cm². 2 The voltage is 5-10V, the energizing frequency is 5-10min / time, and the number of energizing cycles is 3-5 times; more preferably, the energizing treatment in step (2) is under the same conditions as the energizing treatment in step (3). By adopting this preferred embodiment, more graphene oxide in electrolyte C1...electrolyte Cn can be enriched and concentrated on the electrode surface, thereby achieving the purification of graphene oxide.

[0052] Preferably, in step (2), the solid content of the concentrated graphene oxide D1 at 25°C is 3-20 wt%, more preferably 3-10 wt%.

[0053] This invention does not impose any particular limitations on the method of pressure filtration, as long as the pressure filtration can achieve the purpose of this invention. For example, the concentrated graphene oxide D1, the concentrated graphene oxide D2…the concentrated graphene oxide Dn can be combined and introduced into a filter press for pressure filtration.

[0054] The above-described preferred embodiments are beneficial for further reducing the impurity content in graphene oxide.

[0055] According to some embodiments of the present invention, preferably, in step (4), the pressure filtration conditions include: a pressure of 0.5-0.9 MPa and a time of 0.5-1.0 h. This preferred embodiment is beneficial for further reducing the impurity content in graphene oxide.

[0056] According to some embodiments of the present invention, preferably, in step (4), the solid content of the product obtained by pressure filtration at 25°C is 40-60 wt%.

[0057] According to some embodiments of the present invention, preferably, in step (4), the drying method is spray drying; more preferably, in step (3), the conditions for spray drying include: a temperature of 60-180°C and a time of 0.1-5h.

[0058] The above-described preferred embodiments are beneficial for further reducing the water content of graphene oxide, making it easier to package and transport.

[0059] According to a preferred embodiment of the present invention, the method of the present invention is as follows: Figure 1 The process flow diagram shown is as follows:

[0060] (1) Provide n graphene oxide pastes numbered A1, A2...An, and refer to them as paste A1, paste A2... paste An respectively; contact the paste A1 with water to obtain a diluted graphene oxide solution; provide n surfactants numbered B1, B2... Bn, and refer to them as surfactant B1, surfactant B2... surfactant Bn respectively; wherein, n ≮ 2;

[0061] (2) The graphene oxide dilution solution is mixed with the activator B1 and dispersed and stirred until the reaction system is stable to obtain electrolyte C1. Then, in an electrolytic cell equipped with a cathode and an anode, the electrolyte C1 is subjected to electrolytic treatment to obtain concentrated graphene oxide D1.

[0062] (3) The paste A2 and the activator B2...the paste An and the activator Bn are sequentially added to the electrolytic cell in a circulating feeding manner to obtain electrolyte C2...electrolyte Cn respectively. The electrolyte C2...electrolyte Cn are then sequentially subjected to electrolytic treatment to obtain concentrated graphene oxide D2...concentrated graphene oxide Dn.

[0063] (4) The concentrated graphene oxide D1, the concentrated graphene oxide D2...the concentrated graphene oxide Dn are subjected to pressure filtration, and the products obtained by pressure filtration are dispersed and dried in sequence to obtain purified graphene oxide.

[0064] The present invention will be described in detail below through examples.

[0065] In the following examples, unless otherwise specified, all instruments, reagents, and materials used are conventional and can be obtained through legitimate commercial channels. Unless otherwise stated, all reagents used are commercially available analytical grade products.

[0066] n graphene oxide pastes were purchased from Changzhou Sixth Element Materials Technology Co., Ltd., grade SE243PW, with a pH of 1.5. The graphene oxide content was 41.3 wt%, the impurity content was 2.7 wt%, and the water content was 56 wt%.

[0067] Polyacrylamide: Purchased from Jiangsu Zhonghao Yuanda Environmental Engineering Co., Ltd., brand name ZH2310, with a number average molecular weight of 8 million.

[0068] Sodium hydroxymethyl cellulose: purchased from Sinopharm Chemical Reagent Co., Ltd.

[0069] In the following examples, the relevant characteristic parameters were measured using the following methods:

[0070] (1) Impurity content and graphene content in purified graphene oxide: First, the mass M1 of purified graphene oxide is measured, and the purified graphene oxide is placed in a high-temperature furnace for calcination. The resulting ash content M2 is the impurity content, and the difference between M1 and M2 is the graphene content.

[0071] (2) pH value of dispersion: measured by Shanghai Leici PHS-3E tester.

[0072] In the following example, the conditions for powering on in step (2) are the same as those for powering on in step (3).

[0073] Examples 1-6 illustrate the method for purifying graphene oxide provided by the present invention.

[0074] Example 1

[0075] (1) Dilution

[0076] First, three graphene oxide pastes, numbered A1, A2, and A3 respectively, are provided and referred to as paste A1, paste A2, and paste A3. Paste A1 (100g) is then contacted with water to obtain a diluted graphene oxide solution. Next, three surfactants, numbered B1, B2, and B3 respectively, are provided and referred to as surfactant B1, surfactant B2, and surfactant B3.

[0077] The weight ratio of ointment A1 to water is shown in Table 1.

[0078] All three surfactants were provided in the form of aqueous solutions of polyacrylamide, with a concentration of 0.1 wt%. The amounts of the three surfactants are shown in Table 1.

[0079] The contact method is mechanical stirring.

[0080] (2) Electrochemical concentration and purification

[0081] (2-1) Mix the above-mentioned graphene oxide dilution with the above-mentioned activator B1 and stir until the reaction system is stable to obtain electrolyte C1;

[0082] (2-2) Then, in an electrolytic cell equipped with a cathode and an anode, the cathode and anode are connected to the positive and negative terminals of a DC regulated power supply, respectively. Then, the electrolyte C1 is subjected to energization to obtain concentrated graphene oxide D1.

[0083] (2-3) Finally, a plastic scraper is used to peel the concentrated graphene oxide D1 adhering to the anode surface into the container;

[0084] The cathode and anode are the same, both being platinum electrodes; the platinum electrodes are 10×100mm in size and 0.1mm thick; the conditions for the energization process are shown in Table 1.

[0085] (3) Circulating concentration and purification

[0086] (3-1) The above-mentioned paste A2 and the above-mentioned surfactant B2 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C2, and the above-mentioned electrolyte C2 is subjected to electrolytic treatment to obtain concentrated graphene oxide D2. The concentrated graphene oxide D2 is peeled into a container; the amount of the above-mentioned paste A2 and the above-mentioned surfactant B2 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C2 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0087] (3-2) The above-mentioned paste A3 and the above-mentioned surfactant B3 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C3, and the above-mentioned electrolyte C3 is subjected to electrolytic treatment to obtain concentrated graphene oxide D3. The concentrated graphene oxide D3 is peeled into a container; the amount of the above-mentioned paste A3 and the above-mentioned surfactant B3 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C3 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0088] The conditions for power-on processing are shown in Table 1.

[0089] (4) Filtration, dispersion and drying

[0090] (4-1) The concentrated graphene oxide D1, the concentrated graphene oxide D2, and the concentrated graphene oxide D3 that were stripped into the container were combined and introduced into a filter press for filtration.

[0091] (4-2) The product obtained by the above pressure filtration is then placed in water and dispersed into a dispersion with a solid content of 0.5 wt% at 25°C;

[0092] (4-3) The product obtained by the above dispersion was spray-dried to obtain purified graphene oxide;

[0093] The conditions for pressure filtration are shown in Table 1; the solid content of the product obtained by pressure filtration at 25℃ is shown in Table 1.

[0094] The conditions for spray drying are: temperature 120℃ and time 2h.

[0095] Example 2

[0096] (1) Dilution

[0097] First, four graphene oxide pastes, numbered A1, A2, A3, and A4 respectively, are provided and referred to as paste A1, paste A2, paste A3, and paste A4. Paste A1 (50g) is then contacted with water to obtain a diluted graphene oxide solution. Next, four surfactants, numbered B1, B2, B3, and B4 respectively, are provided and referred to as surfactant B1, surfactant B2, surfactant B3, and surfactant B4.

[0098] The weight ratio of ointment A1 to water is shown in Table 1.

[0099] All four surfactants were provided in the form of aqueous solutions of sodium dodecylbenzenesulfonate at a concentration of 0.1 wt%. The amounts of the four surfactants are shown in Table 1.

[0100] The contact method is homogeneous dispersion.

[0101] (2) Electrochemical concentration and purification

[0102] (2-1) Mix the above-mentioned graphene oxide dilution with the above-mentioned activator B1 and stir until the reaction system is stable to obtain electrolyte C1;

[0103] (2-2) Then, in an electrolytic cell equipped with a cathode and an anode, the cathode and anode are connected to the positive and negative terminals of a DC regulated power supply, respectively. Then, the electrolyte C1 is subjected to energization to obtain concentrated graphene oxide D1.

[0104] (2-3) Finally, a plastic scraper is used to peel the concentrated graphene oxide D1 adhering to the anode surface into the container;

[0105] The cathode and anode are the same, both being platinum electrodes; the platinum electrodes are 10×100mm in size and 0.1mm thick; the conditions for the energization process are shown in Table 1.

[0106] (3) Circulating concentration and purification

[0107] (3-1) The above-mentioned paste A2 and the above-mentioned surfactant B2 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C2, and the above-mentioned electrolyte C2 is subjected to electrolytic treatment to obtain concentrated graphene oxide D2. The concentrated graphene oxide D2 is peeled into a container; the amount of the above-mentioned paste A2 and the above-mentioned surfactant B2 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C2 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0108] (3-2) The above-mentioned paste A3 and the above-mentioned surfactant B3 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C3, and the above-mentioned electrolyte C3 is subjected to electrolytic treatment to obtain concentrated graphene oxide D3. The concentrated graphene oxide D3 is peeled into a container; the amount of the above-mentioned paste A3 and the above-mentioned surfactant B3 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C3 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0109] (3-3) The above-mentioned paste A4 and the above-mentioned surfactant B4 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C4, and the above-mentioned electrolyte C4 is subjected to electrolytic treatment to obtain concentrated graphene oxide D4. The concentrated graphene oxide D4 is peeled into a container; the amount of the above-mentioned paste A4 and the above-mentioned surfactant B4 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C4 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0110] The conditions for power-on processing are shown in Table 1.

[0111] (4) Filtration, dispersion and drying

[0112] (4-1) The concentrated graphene oxide D1, concentrated graphene oxide D2, concentrated graphene oxide D3, and concentrated graphene oxide D4 that were stripped into the container were combined and introduced into a filter press for filtration.

[0113] (4-2) The product obtained by the above pressure filtration is then placed in water and dispersed into a dispersion with a solid content of 0.5 wt% at 25°C;

[0114] (4-3) The product obtained by the above dispersion was spray-dried to obtain purified graphene oxide;

[0115] The conditions for pressure filtration are shown in Table 1; the solid content of the product obtained by pressure filtration at 25℃ is shown in Table 1.

[0116] The spray drying conditions are: temperature 150℃, time 1.5h.

[0117] Example 3

[0118] (1) Dilution

[0119] First, five graphene oxide pastes, numbered A1, A2, A3, A4, and A5 respectively, are provided and designated as Paste A1, Paste A2, Paste A3, Paste A4, and Paste A5. Paste A1 (100g) is then contacted with water to obtain a diluted graphene oxide solution. Next, five surfactants, numbered B1, B2, B3, B4, and B5 respectively, are provided and designated as Surfactant B1, Surfactant B2, Surfactant B3, Surfactant B4, and Surfactant B5.

[0120] The weight ratio of ointment A1 to water is shown in Table 1.

[0121] All five surfactants were provided in the form of aqueous solutions of sodium carboxymethyl cellulose at a concentration of 0.2 wt%. The amounts of the five surfactants are shown in Table 1.

[0122] The contact method is ultrasonic dispersion.

[0123] (2) Electrochemical concentration and purification

[0124] (2-1) Mix the above-mentioned graphene oxide dilution with the above-mentioned activator B1 and stir until the reaction system is stable to obtain electrolyte C1;

[0125] (2-2) Then, in an electrolytic cell equipped with a cathode and an anode, the cathode and anode are connected to the positive and negative terminals of a DC regulated power supply, respectively. Then, the electrolyte C1 is subjected to energization to obtain concentrated graphene oxide D1.

[0126] (2-3) Finally, a plastic scraper is used to peel the concentrated graphene oxide D1 adhering to the anode surface into the container;

[0127] The cathode and anode are the same, both being platinum electrodes; the platinum electrodes are 10×100mm in size and 0.1mm thick; the conditions for the energization process are shown in Table 1.

[0128] (3) Circulating concentration and purification

[0129] (3-1) The above-mentioned paste A2 and the above-mentioned surfactant B2 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C2, and the above-mentioned electrolyte C2 is subjected to electrolytic treatment to obtain concentrated graphene oxide D2. The concentrated graphene oxide D2 is peeled into a container; the amount of the above-mentioned paste A2 and the above-mentioned surfactant B2 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C2 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0130] (3-2) The above-mentioned paste A3 and the above-mentioned surfactant B3 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C3, and the above-mentioned electrolyte C3 is subjected to electrolytic treatment to obtain concentrated graphene oxide D3. The concentrated graphene oxide D3 is peeled into a container; the amount of the above-mentioned paste A3 and the above-mentioned surfactant B3 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C3 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0131] (3-3) The above-mentioned paste A4 and the above-mentioned surfactant B4 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C4, and the above-mentioned electrolyte C4 is subjected to electrolytic treatment to obtain concentrated graphene oxide D4. The concentrated graphene oxide D4 is peeled into a container; the amount of the above-mentioned paste A4 and the above-mentioned surfactant B4 are controlled so that the content of graphene oxide in the above-mentioned electrolyte C4 is the same as the content of graphene oxide in the above-mentioned electrolyte C1, and the content of surfactant is the same as the content of surfactant in the above-mentioned electrolyte C1.

[0132] The above-mentioned paste A5 and the above-mentioned surfactant B5 are respectively added to the above-mentioned electrolytic cell to obtain electrolyte C5. Electrolyte C5 is then subjected to electrolytic treatment to obtain concentrated graphene oxide D5. The concentrated graphene oxide D5 is then exfoliated into a container. The amount of paste A5 and surfactant B5 added is controlled so that the content of graphene oxide in electrolyte C5 is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1.

[0133] The conditions for power-on processing are shown in Table 1.

[0134] (4) Filtration, dispersion and drying

[0135] (4-1) The concentrated graphene oxide D1, concentrated graphene oxide D2, concentrated graphene oxide D3, concentrated graphene oxide D4, and concentrated graphene oxide D5 that were stripped into the container were combined and introduced into a filter press for filtration.

[0136] (4-2) The product obtained by the above pressure filtration is then placed in water and dispersed into a dispersion with a solid content of 0.5 wt% at 25°C;

[0137] (4-3) The product obtained by the above dispersion was spray-dried to obtain purified graphene oxide;

[0138] The conditions for pressure filtration are shown in Table 1; the solid content of the product obtained by pressure filtration at 25℃ is shown in Table 1.

[0139] The spray drying conditions are: temperature 110℃, time 3h.

[0140] Example 4

[0141] Following the method of Example 1, except that the weight ratio of paste A1 to water was different (see Table 1), all other aspects were the same, and purified graphene oxide was obtained.

[0142] Example 5

[0143] Following the method of Example 1, except for the different conditions of the electro-treatment (see Table 1), all other conditions were the same, and purified graphene oxide was obtained.

[0144] Example 6

[0145] Following the method of Example 1, except that the pressure filtration conditions were different (see Table 1), all other conditions were the same, and purified graphene oxide was obtained.

[0146] Comparative Example 1

[0147] Following the method of Example 1, except that the weight ratio of paste A1 to water was different (see Table 1), all other aspects were the same, and purified graphene oxide was obtained.

[0148] Comparative Example 2

[0149] Following the method of Example 1, except that the amount of surfactant was different (see Table 1), all other aspects were the same, and purified graphene oxide was obtained.

[0150] Comparative Example 3

[0151] Following the method of Example 1, except that the conditions for electro-treatment were different (see Table 1), all other conditions were the same, and purified graphene oxide was obtained.

[0152] Comparative Example 4

[0153] In this comparative example, the traditional method of washing graphene oxide was adopted, and the specific operation steps are as follows:

[0154] (1) Dissolve the graphene oxide paste in dilute hydrochloric acid solution, then filter by pressure, repeat the above steps 5 times to obtain graphene oxide filter cake I.

[0155] (2) The above graphene oxide filter cake I is washed with water. The specific operation is as follows: the above graphene oxide filter cake I is placed in an aqueous solution for dispersion, and then the resulting dispersion is filtered by pressure. The above steps are repeated 3-5 times to obtain graphene oxide filter cake I.

[0156] (3) The above graphene oxide filter cake ⅠⅠ was diluted again with an aqueous solution and then spray-dried to obtain purified graphene oxide.

[0157] Table 1

[0158]

[0159] Note: Usage by weight 1 The weight ratio of paste A1 to water is given, and graphene D1 is concentrated graphene oxide D1.

[0160] Table 1 (continued)

[0161]

[0162] Note: Usage by weight 1 The weight ratio of paste A1 to water is given, and graphene D1 is concentrated graphene oxide D1.

[0163] Test case

[0164] The graphene oxide content and impurity content in the purified graphene oxide in the examples, the pH value of the dispersion, and the water consumption and time consumed in the purification process were evaluated, and the results are shown in Table 2.

[0165] Table 2

[0166]

[0167] The results above show that the method for purifying graphene oxide provided by this invention results in a higher pH value of the dispersion before drying, leading to a lower impurity content in the final purified graphene oxide. Furthermore, this method uses less water and takes less time during purification. This demonstrates that the method for purifying graphene oxide provided by this invention can significantly reduce the impurity content in graphene oxide, requires less water, and has high purification efficiency.

[0168] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for purifying graphene oxide, characterized in that, The method includes the following steps: (1) Provide n graphene oxide pastes numbered A1, A2...An, and refer to them as paste A1, paste A2...Paste An respectively; contact the paste A1 with water to obtain a graphene oxide dilution; provide n surfactants numbered B1, B2...Bn, and refer to them as surfactant B1, surfactant B2...Surfactant Bn respectively; wherein, n≮2; (2) The graphene oxide dilution solution is mixed with the activator B1 to obtain electrolyte C1. Then, in an electrolytic cell equipped with a cathode and an anode, the electrolyte C1 is subjected to an electric current treatment to obtain concentrated graphene oxide D1. (3) The paste A2 and the activator B2...the paste An and the activator Bn are sequentially added to the electrolytic cell to obtain electrolyte C2...electrolyte Cn respectively, and the electrolyte C2...electrolyte Cn are sequentially subjected to electric current treatment to obtain concentrated graphene oxide D2...concentrated graphene oxide Dn; (4) The concentrated graphene oxide D1, the concentrated graphene oxide D2...the concentrated graphene oxide Dn are subjected to pressure filtration, and the products obtained by pressure filtration are dispersed and dried in sequence to obtain purified graphene oxide. In step (1), the weight ratio of the paste A1 to the water is 1:20-300. For any single 100g of graphene oxide paste, the amount of any single surfactant is 0.01-1g; the conditions for the electrochemical treatment each independently include: a current density of 0.01-1000mA / cm². 2 The voltage is 0.1-50V, the energizing frequency is 5-15min / time, and the number of energizing cycles is 2-5 times; In step (3), the content of graphene oxide in any one of the electrolytes C2 to Cn is the same as the content of graphene oxide in electrolyte C1, and the content of surfactant is the same as the content of surfactant in electrolyte C1.

2. The method according to claim 1, characterized in that, In step (1), the weight ratio of the paste A1 to the water is 1:90-200.

3. The method according to claim 1, characterized in that, In step (2), each of the n surfactants is provided independently in the form of an aqueous surfactant solution with a concentration of 0.05-0.2 wt%.

4. The method according to any one of claims 1-3, characterized in that, In step (2), each of the n surfactants is independently selected from at least one of sodium dodecyl alcohol polyoxyethylene ether sulfate, ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium secondary alkyl sulfonate, sodium fatty alcohol hydroxyethyl sulfonate, sodium tetrapolypropylene benzene sulfonate, polyacrylamide, sodium hydroxymethyl cellulose, triethanolamine lauryl sulfate, polyvinylpyrrolidone, and polyvinyl alcohol.

5. The method according to claim 4, characterized in that, Each of the n surfactants is independently selected from at least one of sodium dodecylbenzenesulfonate, polyacrylamide, and sodium hydroxymethyl cellulose.

6. The method according to any one of claims 1-3, characterized in that, In step (2), the cathode may be the same as or different from the anode, and each is independently selected from platinum, palladium, and rhodium.

7. The method according to claim 6, characterized in that, The cathode is the same as the anode.

8. The method according to claim 7, characterized in that, Both the cathode and the anode are platinum.

9. The method according to any one of claims 1-3, characterized in that, The conditions for the energizing process each independently include: a current density of 10-30 mA / cm². 2 The voltage is 5-10V, the power-on frequency is 5-10min / time, and the number of power-on cycles is 3-5 times.

10. The method according to any one of claims 1-3, characterized in that, In step (2), the solid content of the concentrated graphene oxide D1 at 25°C is 3-20 wt%.

11. The method according to claim 10, characterized in that, The concentrated graphene oxide D1 has a solid content of 3-10 wt% at 25°C.

12. The method according to any one of claims 1-3, characterized in that, In step (4), the pressure filtration conditions include: pressure of 0.5-0.9 MPa and time of 0.5-1.0 h.

13. The method according to any one of claims 1-3, characterized in that, In step (4), the solid content of the product obtained by pressure filtration at 25°C is 40-60 wt%.

14. The method according to any one of claims 1-3, characterized in that, In step (4), the drying method is spray drying.

15. The method according to claim 14, characterized in that, The conditions for spray drying include: a temperature of 60-180℃ and a time of 0.1-5h.

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