Electrostatically cleaned oil water gels, method for preparing and use thereof

Abstract

The present application relates to the technical field of electrostatic oil cleaning materials, and discloses an electrostatic oil cleaning hydrogel, a preparation method and application thereof. The electrostatic oil cleaning hydrogel comprises the following raw materials in mass fractions: 1-6 parts of lignin sulfonate, 5-8 parts of chitosan, 50-85 parts of acrylic acid, 130-200 parts of strong alkali solution, 1-3 parts of initiator, 0.1-0.3 parts of crosslinking agent and 100-150 parts of water. The lignin sulfonate, chitosan and acrylic acid are used as main raw materials, and the raw materials are crosslinked into polymers under the action of the initiator and the crosslinking agent to obtain the electrostatic oil cleaning hydrogel. By limiting the raw material components and the ratio, the synergistic effect of the raw materials is effectively exerted, the electrostatic oil cleaning hydrogel has excellent hydrophilicity and oleophobicity, has strong mechanical stability and recycling ability, can be applied to various extreme use conditions, is suitable for large-scale industrial production, and has high market application value.

Description

Technical Field

[0001] This invention relates to the field of electrostatic oil-purifying materials technology, and in particular to an electrostatic oil-purifying hydrogel, its preparation method, and its application. Background Technology

[0002] As the primary insulating medium in oil-filled electrical equipment, the performance of insulating oil directly affects the safe operation of the equipment. Currently, with the continuous increase in the capacity of power transmission equipment, the importance of its safe and reliable operation is also increasing. During transformer operation, transformer oil (whose main components include cycloalkanes, alkanes, and aromatics) is prone to aging under the influence of external physicochemical factors, producing moisture, oxygen, and various oxides. This significantly reduces its physical, chemical, and electrical properties, especially its insulating performance, and may even force it to be scrapped.

[0003] Moisture content is a key parameter for evaluating transformer oil performance, and its level significantly impacts the oil's properties. Therefore, removing trace amounts of water from the oil to below the national standard (GB / T7595-2017 "Quality Standard for Operating Transformer Oil", 25 mg / L) can effectively improve the performance of waste transformer oil and is a crucial step in the waste oil regeneration process. Compared to traditional oil-water separation processes, wetting materials offer advantages such as energy saving, simple operation, high separation efficiency, and wide applicability. Researchers have used methods such as chemical grafting, physical blending, surface coating, or in-situ growth to introduce hydrophilic groups into electrostatic oil purification materials, enhancing their hydrophilicity and thus improving separation efficiency. However, currently used industrial dehydration technologies have some drawbacks, such as long dehydration times, large footprints, inability to operate continuously, introduction of new impurities, and high energy consumption. Therefore, there is an urgent need to develop an electrostatic oil purification material with excellent mechanical stability, which can not only save energy and reduce consumption but also significantly increase the dehydration effect on waste oil. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an electrostatic oil-removing hydrogel, its preparation method, and its application. By limiting the raw material components and proportions of the electrostatic oil-removing hydrogel, the hydrophilicity and oleophobicity of the electrostatic oil-removing material and its mechanical stability are improved, significantly increasing its dehydration effect on waste oil.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, the present invention provides an electrostatic oil-removing hydrogel comprising the following raw materials in parts by weight: 1 to 6 parts of lignin sulfonate, 5 to 8 parts of chitosan, 50 to 85 parts of acrylic acid, 130 to 200 parts of strong alkaline solution, 1 to 3 parts of initiator, 0.1 to 0.3 parts of crosslinking agent, and 100 to 150 parts of water.

[0007] Compared to existing technologies, the electrostatic oil-removing hydrogel provided by this invention uses lignin sulfonate, chitosan, and acrylic acid as main raw materials. Under the action of an initiator and a crosslinking agent, the raw materials are crosslinked into polymers to obtain the electrostatic oil-removing hydrogel. Lignosulfonate and chitosan, as crosslinked organic compounds that react with acrylic acid, both have extremely strong water absorption properties and are the main raw materials for dehydrating waste oil. Acrylic acid is the main monomer for forming the hydrogel, and strong alkaline solutions can neutralize acrylic acid, providing conditions for the polymerization of organic compounds.

[0008] This invention, by limiting the raw material components and proportions, effectively leverages the synergistic effect of each raw material, resulting in an electrostatic oil-removing hydrogel with excellent hydrophilic and oleophobic properties. Furthermore, the electrostatic oil-removing hydrogel provided by this invention also possesses strong mechanical stability and recyclability, making it suitable for various extreme operating conditions, large-scale industrial production, and high market application value. Example results show that applying the electrostatic oil-removing hydrogel to industrial oil dehydration can reduce the trace water content in waste transformer oil from 32 mg / L to below 23 mg / L. The maximum volume expansion rate of the electrostatic oil-removing hydrogel reaches 57.5 times, demonstrating excellent water absorption capacity and a highly significant dehydration effect, providing a new direction and industrialization approach for the field of oil dehydration.

[0009] Preferably, the lignin sulfonate includes sodium lignin sulfonate.

[0010] Preferably, the strong alkaline solution comprises a 20wt% to 50wt% aqueous solution of potassium hydroxide.

[0011] Preferably, the initiator comprises potassium persulfate.

[0012] Preferably, the crosslinking agent comprises N,N'-methylenebisacrylamide.

[0013] In this invention, potassium persulfate, as an initiator for the crosslinking reaction, has a strong oxidizing effect and can generate free radicals after reacting with monomers, thereby promoting the chain initiation process of the organic crosslinking reaction. N,N'-methylenebisacrylamide has unique functional groups that can link acrylic acid monomers with chitosan to form a gel polymer with a mesoporous structure.

[0014] For example, the water is deionized water.

[0015] Preferably, the electrostatic oil-removing hydrogel has a mesoporous structure.

[0016] Preferably, the specific surface area of ​​the electrostatic oil-removing hydrogel is 36 m². 2 / g~42m 2 / g, pore volume 0.01m 3 / g~0.113m 3 / g.

[0017] Preferably, the electrostatic oil-removing hydrogel is prepared from the raw material by the sol-gel method.

[0018] Secondly, the present invention provides a method for preparing the electrostatic oil-removing hydrogel, comprising the following steps:

[0019] S1. Weigh each raw material according to the design ratio, add acrylic acid to a strong alkaline solution to carry out a neutralization reaction, and obtain an acrylate solution.

[0020] S2, lignin sulfonate, chitosan, initiator and crosslinking agent are added to water to obtain a mixed solution;

[0021] S3, the acrylate solution and the mixed solution are mixed and cross-linked at 70℃~90℃ to obtain an electrostatic oil-removing hydrogel.

[0022] It should be noted that there is no specific order between S1 and S2.

[0023] The present invention provides a method for preparing electrostatic oil-removing hydrogels. This method synthesizes hydrophilic and oleophobic electrostatic oil-removing hydrogels via a simple sol-gel method. The process is simple, requires no complex equipment or excessive energy consumption, reduces preparation costs, and is suitable for large-scale production. Extensive experiments have revealed that excessively high crosslinking temperatures lead to the inactivation of acrylic monomers, preventing the formation of hydrogel polymers; while excessively low crosslinking temperatures result in insufficient and incomplete reactions, slow reaction rates, and low efficiency.

[0024] Preferably, in S1, the temperature of the neutralization reaction is 5℃~40℃, and the reaction time is 0.5min~1.5min.

[0025] In this invention, a sufficient amount of strong alkaline solution can rapidly neutralize acrylic acid to produce acrylate and water, and the neutralization reaction can generally be completed within 1 minute.

[0026] For example, in S1, after the neutralization reaction is complete, cooling to room temperature is also included.

[0027] For example, in S2, lignin sulfonate can be added to water first, and after it is completely dissolved, chitosan, initiator and crosslinking agent can be added and mixed evenly to obtain a mixed solution.

[0028] Preferably, in step S3, the crosslinking reaction takes 2 to 3 hours.

[0029] For example, in S3, after the crosslinking reaction is completed, washing and drying are also included. The hydrogel (brown) after the crosslinking reaction can be washed with an alcohol solution until the washing solution is colorless, such as washing 3 to 4 times with anhydrous ethanol, and then placed in a constant temperature vacuum drying oven at 60℃ to 70℃ and 700Pa to 800Pa for vacuum drying for 3 to 4 hours.

[0030] Thirdly, the present invention provides an application of the electrostatic oil-removing hydrogel described above in the dehydration of industrial oils.

[0031] Fourthly, the present invention provides a method for using the electrostatic oil-removing hydrogel, comprising the following steps:

[0032] The electrostatic oil-purifying hydrogel is mixed with the circulating oil to be purified for purification.

[0033] Preferably, the volume ratio of the electrostatic oil-purifying hydrogel to the oil to be purified is (7.5–8.5) cm³. 3 10L.

[0034] Preferably, the electrostatic oil-purifying hydrogel is placed at least at one of the positive electrode plate, negative electrode plate, between the positive and negative electrode plates, or at the oil inlet of the electrostatic oil-purifying reactor.

[0035] In this invention, the electrostatic oil-purifying hydrogel can be placed at any of the locations mentioned above in the electrostatic oil-purifying reactor, and the trace water content of waste transformer oil can be reduced to below 25 mg / L, which meets the requirements of the national standard GB / T7595-2017 "Quality Standard for Operating Transformer Oil".

[0036] More preferably, the electrostatic oil-purifying hydrogel is placed at least one of the positive or negative electrode plates of the electrostatic oil-purifying reactor.

[0037] By placing electrostatic oil-purifying hydrogel on the electrode plate of the electrostatic oil-purifying reactor, the addition of electrostatic oil-purifying hydrogel to the reactor also increases the roughness and non-uniformity of the electrode plate, thereby indirectly increasing the electric field gradient and making the purification effect better.

[0038] Preferably, the purification temperature is 35℃~55℃.

[0039] Preferably, the purification process uses a DC voltage of 12kV to 16kV.

[0040] Preferably, the circulation velocity of the oil to be purified is 0.1 m / s to 0.3 m / s.

[0041] The present invention can control the circulation rate of the oil to be purified by installing a flow regulating pump on the oil pipeline.

[0042] Preferably, the purification time is 25 min to 40 min.

[0043] Through extensive experimentation, this invention has found that by controlling the above-mentioned purification conditions, the oil purification effect can be optimized. Attached Figure Description

[0044] Figure 1 The images shown are SEM images of the hydrogels of Examples 1-3 and Comparative Example 1 of the present invention; wherein, a represents the SEM image of the hydrogel of Comparative Example 1, b represents the SEM image of the electrostatic oil-removing hydrogel of Example 1, c represents the SEM image of the electrostatic oil-removing hydrogel of Example 2, and d represents the SEM image of the electrostatic oil-removing hydrogel of Example 3.

[0045] Figure 2 The mechanical property test diagrams are for the hydrogels of Examples 1-3 and Comparative Example 1 of this invention;

[0046] Figure 3 This is the N2 adsorption and desorption curve of the electrostatic oil-removing hydrogel of Example 1 of the present invention;

[0047] Figure 4 This is a diagram showing the specific surface area and pore size analysis of the electrostatic oil-removing hydrogel of Example 1 of the present invention;

[0048] Figure 5 This is the N2 adsorption and desorption curve of the electrostatic oil-removing hydrogel of Example 2 of the present invention;

[0049] Figure 6 This is a diagram showing the specific surface area and pore size analysis of the electrostatic oil-removing hydrogel of Example 2 of the present invention;

[0050] Figure 7 This is the N2 adsorption and desorption curve of the electrostatic oil-removing hydrogel of Example 3 of the present invention;

[0051] Figure 8 This is a diagram showing the specific surface area and pore size analysis of the electrostatic oil-removing hydrogel of Example 3 of the present invention;

[0052] Figure 9 The images show the water absorption effect of the electrostatic oil-removing hydrogels in Examples 1-3 of this invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0054] Example 1

[0055] This embodiment provides an electrostatic oil-removing hydrogel, comprising the following raw materials in parts by weight: 1 part sodium lignosulfonate, 6 parts chitosan, 65 parts acrylic acid, 160 parts of 35wt% potassium hydroxide aqueous solution, 2 parts potassium persulfate, 0.2 parts N,N'-methylenebisacrylamide, and 120 parts deionized water.

[0056] The preparation method of the above-mentioned electrostatic oil-removing hydrogel includes the following steps:

[0057] S1. Weigh each raw material according to the design ratio, add acrylic acid to a 35wt% potassium hydroxide aqueous solution, and carry out a neutralization reaction at room temperature for 1 minute to obtain an acrylate solution.

[0058] S2, add sodium lignosulfonate to deionized water, dissolve it completely, then add chitosan, potassium persulfate and N,N'-methylenebisacrylamide, mix well to obtain a mixed solution;

[0059] S3. The acrylate solution and the mixed solution were mixed and cross-linked at 80°C for 2.5 h. The brown hydrogel after the cross-linking reaction was washed with anhydrous ethanol until the washing solution was colorless. Then it was placed in a constant temperature vacuum drying oven at 65°C and 750 Pa and vacuum dried for 3.5 h to obtain electrostatic oil-removing hydrogel.

[0060] Example 2

[0061] This embodiment provides an electrostatic oil-removing hydrogel, comprising the following raw materials in parts by weight: 2 parts sodium lignosulfonate, 8 parts chitosan, 85 parts acrylic acid, 200 parts of 50wt% potassium hydroxide aqueous solution, 3 parts potassium persulfate, 0.3 parts N,N'-methylenebisacrylamide, and 150 parts deionized water.

[0062] The preparation method of the above-mentioned electrostatic oil-removing hydrogel includes the following steps:

[0063] S1. Weigh each raw material according to the design ratio, add acrylic acid to 50wt% potassium hydroxide aqueous solution, and carry out neutralization reaction at room temperature for 1 minute to obtain acrylate solution.

[0064] S2, add sodium lignosulfonate to deionized water, dissolve it completely, then add chitosan, potassium persulfate and N,N'-methylenebisacrylamide, mix well to obtain a mixed solution;

[0065] S3. The acrylate solution and the mixed solution were mixed and cross-linked at 90°C for 2 hours. The brown hydrogel after the cross-linking reaction was washed with anhydrous ethanol until the washing solution was colorless. Then it was placed in a constant temperature vacuum drying oven at 70°C and 800Pa and vacuum dried for 3 hours to obtain electrostatic oil-removing hydrogel.

[0066] Example 3

[0067] This embodiment provides an electrostatic oil-removing hydrogel, comprising the following raw materials in parts by weight: 5 parts sodium lignosulfonate, 5 parts chitosan, 50 parts acrylic acid, 130 parts of 23wt% potassium hydroxide aqueous solution, 1 part potassium persulfate, 0.1 parts N,N'-methylenebisacrylamide, and 100 parts deionized water.

[0068] The preparation method of the above-mentioned electrostatic oil-removing hydrogel includes the following steps:

[0069] S1. Weigh each raw material according to the design ratio, add acrylic acid to 23wt% potassium hydroxide aqueous solution, and carry out neutralization reaction at room temperature for 1 min to obtain acrylate solution.

[0070] S2, add sodium lignosulfonate to deionized water, dissolve it completely, then add chitosan, potassium persulfate and N,N'-methylenebisacrylamide, mix well to obtain a mixed solution;

[0071] S3. The acrylate solution and the mixed solution were mixed and cross-linked at 70°C. After keeping warm for 3 hours, the brown hydrogel after the cross-linking reaction was washed with anhydrous ethanol until the washing solution was colorless. Then, it was placed in a constant temperature vacuum drying oven at 60°C and 700Pa and vacuum dried for 4 hours to obtain electrostatic oil-removing hydrogel.

[0072] The specific surface area and pore size of the electrostatic oil-removing hydrogels provided in Examples 1-3 were analyzed, and the results are as follows: Figures 3-8 As shown. From Figure 3 , 5 As can be seen from Figure 7, the N2 adsorption-desorption curves of the electrostatic oil-removing hydrogel belong to type IV isotherms (mesoporous adsorption). After capillary condensation, a hysteresis loop occurs, which can be specifically classified as a type IVa isotherm (hysteresis begins to occur when the pore width exceeds a certain critical width). The adsorption characteristics of mesoporous structures are determined by the interaction between the adsorbent and the adsorbate, as well as the intermolecular interactions in the condensed state. Figure 3 , 5 The curves in the knee-shaped portions of Figure 7 are all gradual bends, lacking sharp inflection points, indicating that the monolayer coverage and the initial amount of multilayer adsorption are superimposed, rather than multilayer adsorption occurring only after monolayer adsorption has completely ended; subsequently, condensation occurs in the channels (the gas condenses into a liquid-like phase in the channels when the pressure P is less than its liquid saturation pressure P0). Furthermore, a typical type IV isotherm is characterized by the formation of a plateau at final adsorption saturation, the length of which can vary. Figure 3 , 5 No obvious plateau was observed in either of the samples 7 and 8, indicating that the adsorption has not yet reached saturation.

[0073] from Figure 4 , 6As can be seen from Figures 8 and 9, the pores of the electrostatic oil-removing hydrogels are all mesoporous structures with widths ranging from 2 nm to 50 nm. The electrostatic oil-removing hydrogel of Example 2 has the largest pore structure, which is the reason for its obvious adsorption-desorption hysteresis loop (compared to the electrostatic oil-removing hydrogels of Examples 1 and 3). The electrostatic oil-removing hydrogel of Example 3 has the smallest pore size of 8.055 nm and the largest specific surface area of ​​40.808 m². 2 / g, with a maximum pore volume of 0.11192cm³. 3 / g, from a microscopic perspective, it can be determined that it has the best adsorption performance, which is consistent with the results of the subsequent water absorption test.

[0074] Take 0.4cm respectively 3 The electrostatic oil-removing hydrogels provided in Examples 1-3 were subjected to water absorption tests, and the results are as follows: Figure 9 As shown. From Figure 9 As can be seen, the electrostatic oil-removing hydrogel of Example 3 exhibits the best water absorption performance. This can be attributed to the addition of sodium lignosulfonate altering the surface structure of the gel, making its surface rough and porous, thus increasing the contact area with water molecules. It shows a high water absorption rate within 30 minutes of water absorption. However, after 30 minutes of water absorption, its volume expansion rate is similar to that of the electrostatic oil-removing hydrogels of Examples 1 and 2. Due to the rough and porous surface of the gel and excessive water absorption, the gel expands and breaks down after 60 minutes of water absorption. (It should be noted that the electrostatic oil-removing hydrogel can maintain structural stability in pure water for up to 60 minutes, and it hardly breaks down due to excessive water absorption in transformer oil with low water content.) The electrostatic oil-removing hydrogel of Example 3 has the largest volume expansion rate, expanding to 23.0 cm³ after 65 minutes of water absorption. 3 The expansion rate was 57.5 times, and it still showed strong water absorption. The water absorption rate of the electrostatic oil-removing hydrogel in Example 1 was uniform and stable, and it showed a relatively uniform volume expansion rate within 65 minutes of water absorption.

[0075] Comparative Example 1

[0076] This comparative example provides a hydrogel whose raw material composition and ratio are similar to those of Example 3, except that the raw material does not contain sodium lignosulfonate.

[0077] The method for preparing the above-mentioned hydrogel includes the following steps:

[0078] S1 is the same as in Example 3, and will not be described again;

[0079] S2, add chitosan, potassium persulfate and N,N'-methylenebisacrylamide to deionized water and mix well to obtain a mixed solution;

[0080] S3. The acrylate solution and the mixed solution were mixed and cross-linked at 70°C. After keeping warm for 3 hours, the brown hydrogel after the cross-linking reaction was washed with anhydrous ethanol until the washing solution was colorless. Then, it was placed in a constant temperature vacuum drying oven at 60°C and 700Pa and vacuum dried for 4 hours to obtain the hydrogel.

[0081] Electron microscopy was performed on the electrostatic oil-removing hydrogels provided in Examples 1-3 and the hydrogel provided in Comparative Example 1. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, the surface of the hydrogel without sodium lignosulfonate is smooth. After adding sodium lignosulfonate, the surface of the hydrogel shows wrinkles of varying degrees. When the amount of sodium lignosulfonate added is 5 parts (Example 3), the surface roughness is the greatest.

[0082] Mechanical properties were tested on the electrostatic oil-removing hydrogels provided in Examples 1-3 and the hydrogel provided in Comparative Example 1. The test results are as follows. Figure 2 As shown. From Figure 2 As can be seen, the tensile stress of the electrostatic oil-removing hydrogel is 20MPa to 30MPa, and the elongation at break is 35% to 50%. After adding sodium lignosulfonate, the tensile stress of the hydrogel is slightly increased.

[0083] Comparative Example 2

[0084] This comparative example provides a hydrogel whose raw material composition and ratio are similar to those of Example 3, except that chitosan is replaced with an equal mass of sodium alginate.

[0085] The method for preparing the above-mentioned hydrogel includes the following steps:

[0086] S1 is the same as in Example 3, and will not be described again.

[0087] S2, add sodium lignosulfonate to deionized water, dissolve it completely, then add sodium alginate, potassium persulfate and N,N'-methylenebisacrylamide, mix well to obtain a mixed solution;

[0088] S3. The acrylate solution and the mixed solution were mixed and cross-linked at 70°C. After keeping warm for 3 hours, the brown hydrogel after the cross-linking reaction was washed with anhydrous ethanol until the washing solution was colorless. Then, it was placed in a constant temperature vacuum drying oven at 60°C and 700Pa and vacuum dried for 4 hours to obtain the hydrogel.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a hydrogel, comprising the following steps:

[0091] S1. Weigh each raw material according to the design ratio (the raw material composition and ratio are similar to those in Example 3, except that the 23wt% potassium hydroxide aqueous solution is replaced with the same mass of deionized water). Add sodium lignosulfonate to 230 parts of deionized water and dissolve it completely. Then add chitosan, potassium persulfate and N,N'-methylenebisacrylamide and mix evenly to obtain a mixed solution.

[0092] S2, acrylic acid was added to the mixed solution and crosslinked at 70°C. After holding at this temperature for 3 hours, it was found that hydrogel could not be obtained.

[0093] Comparative Example 4

[0094] This comparative example provides a method for preparing a hydrogel, comprising the following steps:

[0095] S1. Weigh each raw material according to the design ratio (the raw material composition and ratio are similar to those in Example 3, except that the 23wt% potassium hydroxide aqueous solution is replaced with the same mass of 23wt% sodium bicarbonate aqueous solution). Add acrylic acid to the 23wt% sodium bicarbonate aqueous solution and carry out a neutralization reaction at room temperature for 1 minute to obtain an acrylate solution.

[0096] S2 is the same as in Example 3, and will not be described again.

[0097] S3, an acrylate solution was added to the mixed solution and a cross-linking reaction was carried out at 70°C. After keeping it at this temperature for 3 hours, it was found that no hydrogel could be obtained.

[0098] Application Example 1

[0099] This application example provides a method for using an electrostatic oil-removing hydrogel, including the following steps:

[0100] The electrostatic oil-purifying hydrogel from Example 1 was placed at the inlet of the electrostatic oil-purifying reactor and mixed with the circulating oil to be purified (waste transformer oil with a water content of 32.0 mg / L). Purification was performed using a direct current voltage. The volume ratio of the electrostatic oil-purifying hydrogel to the oil to be purified was 8.5 cm³. 3 The capacity is 10L. The temperature of the electrostatic oil purification reactor (i.e., the purification temperature) is 35℃, the DC voltage is 16kV, the circulation flow rate of the oil to be purified is 0.1m / s, and the purification time is 30min (1 cycle).

[0101] Tests showed that the water content of the oil to be purified was 23.8 mg / L.

[0102] Application Example 2

[0103] This application example provides a method for using an electrostatic oil-removing hydrogel, including the following steps:

[0104] The electrostatic oil-purifying hydrogel from Example 2 was placed between the positive and negative electrode plates of the electrostatic oil-purifying reactor and mixed with circulating oil to be purified (waste transformer oil with a water content of 32.0 mg / L). Purification was performed using a direct current voltage. The volume ratio of the electrostatic oil-purifying hydrogel to the oil to be purified was 7.5 cm³. 3 The capacity is 10L. The temperature of the electrostatic oil purification reactor (i.e., the purification temperature) is 55℃, the DC voltage is 12kV, the circulation flow rate of the oil to be purified is 0.3m / s, and the purification time is 30min (1 cycle).

[0105] Tests showed that the water content of the oil to be purified was 23.2 mg / L.

[0106] Application Example 3

[0107] This application example provides a method for using an electrostatic oil-removing hydrogel, including the following steps:

[0108] The electrostatic oil-purifying hydrogel from Example 3 was attached to the positive electrode plate of the electrostatic oil-purifying reactor and mixed with circulating oil to be purified (waste transformer oil with a water content of 32.0 mg / L). Purification was performed using a direct current voltage. The volume ratio of the electrostatic oil-purifying hydrogel to the oil to be purified was 8 cm³. 3 The capacity is 10L. The temperature of the electrostatic oil purification reactor (i.e., the purification temperature) is 45℃, the DC voltage is 14kV, the circulation flow rate of the oil to be purified is 0.2m / s, and the purification time is 30min (1 cycle).

[0109] Tests showed that the water content of the oil to be purified was 22.9 mg / L.

[0110] Application Example 4

[0111] This application example provides a method for using an electrostatic oil-purifying hydrogel, similar to Application Example 3, except that the purification time is extended to 300 minutes (10 cycles). Other conditions are the same as in Application Example 3 and will not be repeated here.

[0112] Tests showed that the water content of the purified oil was 21.0 mg / L. Furthermore, the performance of the electrostatic oil-purifying hydrogel did not show a significant decrease.

[0113] Application Comparative Example 1

[0114] This comparative example provides a method of using a hydrogel, similar to Application Example 3, except that the electrostatic oil-removing hydrogel of Example 3 is replaced with the hydrogel of Comparative Example 1. All other conditions are the same as in Application Example 3 and will not be repeated here.

[0115] Tests showed that the water content of the oil to be purified was 26.0 mg / L.

[0116] Application Comparative Example 2

[0117] This comparative example provides a method of using a hydrogel, similar to Application Example 3, except that the electrostatic oil-removing hydrogel of Example 3 is replaced with the hydrogel of Comparative Example 2. All other conditions are the same as in Application Example 3 and will not be repeated here.

[0118] Tests showed that the water content of the oil to be purified was 26.4 mg / L.

[0119] Application Comparative Example 3

[0120] This comparative example provides a method for purifying waste transformer oil, similar to Application Example 3, except that the electrostatic oil-purifying hydrogel of Example 3 is omitted. Specifically, it includes the following steps:

[0121] The circulating oil to be purified (waste transformer oil with a water content of 32.0 mg / L) was purified using DC voltage (no electrostatic oil purification hydrogel was placed in the electrostatic oil purification reactor). The temperature of the electrostatic oil purification reactor (i.e., the purification temperature) was 45℃, the DC voltage was 14kV, the circulation velocity of the oil to be purified was 0.2m / s, and the purification time was 30min.

[0122] Tests showed that the water content of the oil to be purified was 27.4 mg / L.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrostatic oil-removing hydrogel, characterized in that, The raw materials include the following parts by weight: 1 to 6 parts lignin sulfonate, 5 to 8 parts chitosan, 50 to 85 parts acrylic acid, 130 to 200 parts strong alkaline solution, 1 to 3 parts initiator, 0.1 to 0.3 parts crosslinking agent, and 100 to 150 parts water; The electrostatic oil-removing hydrogel has a mesoporous structure; the specific surface area of ​​the electrostatic oil-removing hydrogel is 36 m². 2 / g~42m 2 / g, pore volume 0.01m 3 / g~0.113m 3 / g.

2. The electrostatic oil-removing hydrogel as described in claim 1, characterized in that, The lignin sulfonate includes sodium lignin sulfonate; The strong alkaline solution includes a 20wt% to 50wt% aqueous solution of potassium hydroxide; The initiator includes potassium persulfate; The crosslinking agent includes N,N'-methylenebisacrylamide.

3. The electrostatic oil-removing hydrogel as described in claim 1, characterized in that, The electrostatic oil-removing hydrogel is prepared from the raw material by the sol-gel method.

4. The method for preparing the electrostatic oil-removing hydrogel according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Weigh each raw material according to the design ratio, add acrylic acid to a strong alkaline solution to carry out a neutralization reaction, and obtain an acrylate solution. S2, lignin sulfonate, chitosan, initiator and crosslinking agent are added to water to obtain a mixed solution; S3, the acrylate solution and the mixed solution are mixed and cross-linked at 70℃~90℃ to obtain an electrostatic oil-removing hydrogel.

5. The method for preparing the electrostatic oil-removing hydrogel as described in claim 4, characterized in that, In S1, the temperature of the neutralization reaction is 5℃~40℃, and the reaction time is 0.5min~1.5min; In S3, the cross-linking reaction takes 2 to 3 hours.

6. The application of the electrostatic oil-removing hydrogel according to any one of claims 1 to 3 in the dehydration of industrial oils.

7. The method of using the electrostatic oil-removing hydrogel according to any one of claims 1 to 3, characterized in that, Includes the following steps: The electrostatic oil-purifying hydrogel is mixed with the circulating oil to be purified for purification.

8. The method of using the electrostatic oil-removing hydrogel as described in claim 7, characterized in that, The volume ratio of the electrostatic oil-purifying hydrogel to the oil to be purified is (7.5~8.5) cm³. 3 10L; The electrostatic oil-purifying hydrogel is placed at least at one of the positive electrode plate, negative electrode plate, between the positive and negative electrode plates, or at the oil inlet of the electrostatic oil-purifying reactor.

9. The method of using the electrostatic oil-removing hydrogel as described in claim 7, characterized in that, The purification temperature is 35℃~55℃; The purification process uses a DC voltage of 12kV to 16kV. The circulation velocity of the oil to be purified is 0.1 m / s to 0.3 m / s; The purification time is 25 min to 40 min.

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