A self-emulsifying oily wastewater removal agent and its preparation method

Abstract

This invention belongs to the field of wastewater treatment technology and discloses a self-emulsifying oily wastewater removal agent and its preparation method. The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 30-50 parts of sulfomethylated tannin, 15-25 parts of aluminum sulfate, 0.5-2 parts of polyacrylamide, 1-3 parts of sodium hydroxide, and 10-20 parts of polyaluminum chloride. This invention applies sulfomethylated tannin to the removal of self-emulsifying oily wastewater. Through the emulsifying and disrupting effect of sulfomethylated tannin, the emulsified state of oil droplets is effectively destroyed, thereby promoting oil-water separation. The macromolecular structure and active groups of this modified tannin provide more adsorption sites and stronger bridging effects, improving the speed and efficiency of oil droplet aggregation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a self-emulsifying oily wastewater removal agent and its preparation method. Background Technology

[0002] The main challenge in treating self-emulsifying oily wastewater lies in the tiny size of the oil droplets and their stable emulsified state, which complicates oil-water separation. The oil droplets in self-emulsifying oily wastewater typically carry a negative charge, forming an electric double layer that prevents droplet aggregation. Simultaneously, hydrophilic solid particles also stabilize the self-emulsifying oil in the water, hindering droplet aggregation. These factors combined make it difficult to effectively treat self-emulsifying oily wastewater using conventional methods such as gravity separation and flotation.

[0003] Traditional treatment technologies, such as gravity sedimentation, centrifugation, filtration, and chemical flocculation, often suffer from low efficiency, high cost, complex operation, or secondary pollution. For example, while flocculation is simple, effective, and adaptable, it requires a long settling time after flocculant addition, and the resulting flocs tend to float, leading to low subsequent floc separation efficiency. Membrane separation technology, while highly efficient, suffers from membrane clogging, poor chemical and thermal stability, and requires regular cleaning and replacement, resulting in high maintenance costs.

[0004] Furthermore, oil droplets in self-emulsifying oily wastewater may form an oil film, hindering oxygen dissolution in the water, causing oxygen deficiency, aquatic death, and foul odors, severely polluting the environment. Therefore, developing new and efficient self-emulsifying oily wastewater treatment technologies has become an urgent problem to be solved. Summary of the Invention

[0005] To address the problems in the background art, the present invention provides a self-emulsifying oily wastewater removal agent and its preparation method.

[0006] To achieve the above objectives, the first technical solution adopted by the present invention is as follows:

[0007] A self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 30-50 parts of sulfomethyl tannin, 15-25 parts of aluminum sulfate, 0.5-2 parts of polyacrylamide, 1-3 parts of sodium hydroxide, and 10-20 parts of polyaluminum chloride.

[0008] Preferably, the sulfonated tannin is obtained by sulfonation reaction of tannin with sodium sulfite and formaldehyde.

[0009] Preferably, the tannin is any one of bayberry tannin, vitex bark tannin, catechin, and tannic acid.

[0010] Preferably, it also contains 5 to 10 parts of modified active silica.

[0011] Preferably, the modified active silicic acid is obtained by modifying active silicic acid with octyltrimethoxysilane, and its surface has a hydrophobic layer and long-chain alkyl groups.

[0012] The second technical solution adopted in this invention is:

[0013] A method for preparing a self-emulsifying oil wastewater removal agent involves mixing the raw materials evenly in a solution state, adjusting the pH of the solution to 7.0~8.0, and then spray drying.

[0014] Preferably, the mixing temperature is 30~35℃.

[0015] Preferably, the spray drying temperature is 180~200℃ at the inlet and 80~100℃ at the outlet.

[0016] When the raw material contains modified active silicic acid, the preparation method of modified active silicic acid is as follows: mix active silicic acid with an ethanol solution of octyltrimethoxysilane, react at pH 3~4 and 60℃ for 4~5 hours, centrifuge to retain the solid after the reaction is completed, and then wash and dry it.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention applies sulfonated methyl tannins to the removal of self-emulsifying oily wastewater. Through the emulsifying and disrupting effect of sulfonated methyl tannins, the emulsified state of oil droplets is effectively destroyed, thereby promoting oil-water separation. The macromolecular structure and active groups of this modified tannin provide more adsorption sites and stronger bridging effects, improving the speed and efficiency of oil droplet aggregation.

[0019] 2. The removal agent provided by this invention also utilizes the synergistic effect of aluminum sulfate and polyaluminum chloride to enhance the neutralization effect of negatively charged particles in wastewater, reduce the electrostatic repulsion between oil droplets, and make it easier for oil droplets to aggregate into large oil beads, thereby accelerating the settling speed.

[0020] 3. The synergistic adsorption effect of multiple components such as sulfomethylated tannin and modified active silica provided by this invention not only improves the adsorption and removal efficiency of oil droplets, but also effectively removes organic matter and heavy metal ions in wastewater, providing a more comprehensive pollutant removal effect. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The first embodiment of the present invention provides a self-emulsifying oily wastewater removal agent, comprising the following raw materials in parts by weight: 30-50 parts of sulfomethyl tannin, 15-25 parts of aluminum sulfate, 0.5-2 parts of polyacrylamide, 1-3 parts of sodium hydroxide, and 10-20 parts of polyaluminum chloride.

[0023] In the treatment of self-emulsifying oily wastewater, it is necessary to be able to handle the small size of oil droplets and the stable emulsion state. In this invention, sulfonyl methyl tannin, due to its unique molecular structure, possesses a strong emulsifying and disrupting ability. Sulfonyl methyl tannin can penetrate deep into the surface of oil droplets, disrupt their stable emulsion state, reduce the interfacial tension of oil droplets, thereby promoting the aggregation of oil droplets and the oil-water separation process, laying the foundation for oil-water separation.

[0024] When the treatment agent of this invention is used to treat self-emulsifying oily wastewater, the addition of aluminum sulfate and polyaluminum chloride, two flocculants, further promotes the aggregation of oil droplets. By neutralizing negatively charged particles in the wastewater, they reduce the electrostatic repulsion between oil droplets, making it easier for them to aggregate into larger oil beads through van der Waals forces and gravity. This charge neutralization is an indispensable part of the oil-water separation process, greatly improving the oil droplet aggregation efficiency.

[0025] While oil droplets aggregate, polyacrylamide, as a high-molecular-weight polymer, extends its long-chain molecules in the solution, enabling it to capture and bind oil droplets through adsorption and bridging, forming large flocs that then settle. This flocculation and sedimentation process is the core step in achieving oil-water separation, directly affecting the treatment efficiency of the removal agent.

[0026] In this process, the addition of sodium hydroxide provides the optimal pH environment for the reaction of other components. pH adjustment is crucial for the effectiveness of flocculants because different pH conditions affect the charge state and molecular configuration of the flocculant, thus influencing its flocculation effect. Precise pH control ensures that the flocculant and other components function under optimal conditions, thereby improving the overall efficiency of the removal agent.

[0027] The treatment agent provided by the embodiments of the present invention forms a multi-action mechanism through the mutual cooperation of various raw material components, achieving synergistic effect, comprehensively improving the wastewater treatment effect, effectively treating complex oil-water mixtures, and achieving efficient oil-water separation and pollutant removal.

[0028] To further improve the treatment effect, the above treatment agent may also contain 5-10 parts of modified activated silica. Modified activated silica can synergize with polyacrylamide. Due to its surface modification, modified activated silica has higher oleophilic and hydrophobic properties; it can not only adsorb oil droplets but also enhance the structural stability of flocs through its surface activity, thereby promoting floc sedimentation. Therefore, modified activated silica can promote the sedimentation of flocs formed by polyacrylamide and improve oil-water separation efficiency.

[0029] It should be noted that the method for preparing sulfonated tannins used in this invention is a method already disclosed in the prior art, namely, it is obtained by sulfonating tannins with sodium sulfite and formaldehyde.

[0030] In some preferred embodiments, the tannin is any one of bayberry tannin, vitex bark tannin, catechin, and tannic acid.

[0031] In some preferred embodiments, the modified active silica is obtained by modifying active silica with octyltrimethoxysilane, and its surface has a hydrophobic layer and long-chain alkyl groups.

[0032] The second embodiment of the present invention provides a method for preparing a self-emulsifying oil wastewater removal agent, wherein the raw materials are mixed evenly in solution, the pH of the solution is adjusted to 7.0~8.0, and then spray-dried.

[0033] There are no specific restrictions on the mixing order of the raw materials, which can be adjusted by those skilled in the art according to the actual situation. The solution state refers to the solution formed after the raw materials are dissolved in deionized water. Whether the raw materials need to be dissolved in deionized water can be determined by those skilled in the art based on the characteristics of the raw materials, choosing an appropriate method.

[0034] In some preferred embodiments, the mixing temperature is 30~35°C.

[0035] In some preferred embodiments, the spray drying temperature is 180~200°C at the inlet and 80~100°C at the outlet.

[0036] When the raw material contains modified active silicic acid, the preparation method of modified active silicic acid is as follows: mix active silicic acid with an ethanol solution of octyltrimethoxysilane, react at pH 3~4 and 60℃ for 4~5 hours, centrifuge to retain the solid after the reaction is completed, and then wash and dry it.

[0037] To make the technical solution of the present invention clearer, the self-emulsifying oil wastewater removal agent and its effects are described in detail below through several specific embodiments.

[0038] The experimental equipment and formulations used in the following examples are as follows:

[0039] Electronic balance (Sartorius, Germany), electric heating blower constant temperature dryer (Shanghai Fuma Experimental Equipment), stainless steel reaction vessel (Shanghai Laibei), electric heating constant temperature water bath (Jiangsu Kedao), rotary evaporator (Shanghai Daluo Scientific Instruments), pulverizer (Shandong Tianfang Machinery), magnetic stirrer (Shanghai Meiyingpu), Soxhelt extractor (Qingdao Juchuang); chemical reagents were purchased from Sigma-Aldrich.

[0040] Example 1

[0041] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 46 parts of sulfomethylated chamaejasminoides bark tannin, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, 12 parts of polyaluminum chloride, and 8 parts of modified active silica.

[0042] The preparation methods of sulfonated tannins include:

[0043] S11. Dissolve the tannin powder from the bark of Vitex negundo in deionized water;

[0044] S12. Add 37% formaldehyde solution and sodium sulfite to the tannin solution of Vitex negundo bark. After complete dissolution, continue the reaction at 70~80℃ for 4~6 hours.

[0045] S13. After the reaction is complete, cool the reaction mixture to room temperature and adjust the pH of the product to 7-8;

[0046] S14. The neutralized solution is concentrated under reduced pressure at 50~60℃ to about 1 / 3 of its original volume. The concentrate is then spray-dried or vacuum-dried to obtain sulfomethylated Vitex bark tannin powder.

[0047] Methods for preparing modified active silicic acid include:

[0048] S21. Dissolve octyltrimethoxysilane in anhydrous ethanol to prepare a 5% solution, and adjust the pH of the solution to 3-4;

[0049] S22. Mix the dried active silicic acid with an octyltrimethoxysilane solution and stir at 60°C for 4-5 hours.

[0050] S23. After the reaction is complete, the mixture is centrifuged and washed 3 to 5 times with anhydrous ethanol and deionized water alternately to remove unreacted silane. The washed product is then vacuum dried at 60°C for 12 hours.

[0051] Preparation method of self-emulsifying oily wastewater removal agent

[0052] S31. Mix the above raw materials sequentially in deionized water and adjust the pH to between 7.0 and 8.0;

[0053] S32. Spray dry the mixture, setting the inlet temperature to 180~200℃ and the outlet temperature to 80~100℃ to obtain a solid powder product. Crush the dried product and sieve it using a 100-mesh sieve to ensure uniform particle size.

[0054] Example 2

[0055] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 30 parts of sulfomethylated chamaejasminoides bark tannin, 15 parts of aluminum sulfate, 0.5 parts of polyacrylamide, 1 part of sodium hydroxide, 10 parts of polyaluminum chloride, and 5 parts of modified active silica.

[0056] The preparation method of sulfonated chaste tree bark tannin, modified active silica, and self-emulsifying oily wastewater removal agent is described in Example 1.

[0057] Example 3

[0058] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 50 parts of sulfomethylated chamaejasminoides bark tannin, 25 parts of aluminum sulfate, 2 parts of polyacrylamide, 3 parts of sodium hydroxide, 20 parts of polyaluminum chloride, and 10 parts of modified active silica.

[0059] The preparation method of sulfonated chaste tree bark tannin, modified active silica, and self-emulsifying oily wastewater removal agent is described in Example 1.

[0060] Example 4

[0061] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 38 parts of sulfomethylated chamaejasminoides bark tannin, 23 parts of aluminum sulfate, 1 part of polyacrylamide, 2 parts of sodium hydroxide, 18 parts of polyaluminum chloride, and 6 parts of modified active silica.

[0062] The preparation method of sulfonated chaste tree bark tannin, modified active silica, and self-emulsifying oily wastewater removal agent is described in Example 1.

[0063] Example 5

[0064] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 46 parts of sulfomethylated bayberry tannin, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, 12 parts of polyaluminum chloride, and 8 parts of modified active silica.

[0065] The preparation methods of sulfonated myricetin, modified active silica, and self-emulsifying oily wastewater removal agent are described in Example 1.

[0066] Example 6

[0067] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 46 parts of sulfomethylated catechin, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, 12 parts of polyaluminum chloride, and 8 parts of modified active silica.

[0068] The preparation methods of sulfonated catechin, modified active silica, and self-emulsifying oily wastewater removal agent are described in Example 1.

[0069] Example 7

[0070] The self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 46 parts sulfomethylated tannic acid, 21 parts aluminum sulfate, 1.8 parts polyacrylamide, 2 parts sodium hydroxide, 12 parts polyaluminum chloride, and 8 parts modified activated silica.

[0071] The preparation methods of sulfonated tannic acid, modified active silica, and self-emulsifying oily wastewater removal agent are described in Example 1.

[0072] Example 8

[0073] Self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 46 parts of sulfomethylated chamaejasminoides bark tannin, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, and 12 parts of polyaluminum chloride.

[0074] The preparation method of sulfonated chaste tree bark tannin and self-emulsifying oily wastewater removal agent is described in Example 1.

[0075] Example 9

[0076] Self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 30 parts sulfomethylated chamaejasminoides bark tannin, 15 parts aluminum sulfate, 0.5 parts polyacrylamide, 1 part sodium hydroxide, and 10 parts polyaluminum chloride.

[0077] The preparation method of sulfonated chaste tree bark tannin and self-emulsifying oily wastewater removal agent is described in Example 1.

[0078] Example 10

[0079] Self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 50 parts sulfomethylated chamaejasminoides bark tannin, 25 parts aluminum sulfate, 2 parts polyacrylamide, 3 parts sodium hydroxide, and 20 parts polyaluminum chloride.

[0080] The preparation method of sulfonated chaste tree bark tannin and self-emulsifying oily wastewater removal agent is described in Example 1.

[0081] Example 11

[0082] Self-emulsifying oily wastewater removal agent comprises the following raw materials in parts by weight: 38 parts sulfomethylated chamaejasminoides bark tannin, 23 parts aluminum sulfate, 1 part polyacrylamide, 2 parts sodium hydroxide, and 18 parts polyaluminum chloride.

[0083] The preparation method of sulfonated chaste tree bark tannin and self-emulsifying oily wastewater removal agent is described in Example 1.

[0084] Comparative Example 1

[0085] The removal agent, compared with Example 8, differs only in that it does not use sulfomethylated chamaejasminoides bark tannin, and includes the following raw materials in parts by weight: 21 parts aluminum sulfate, 1.8 parts polyacrylamide, 2 parts sodium hydroxide, and 12 parts polyaluminum chloride.

[0086] Comparative Example 2

[0087] The removal agent differs from that in Example 8 only in that the tannins of Vitex negundo bark are not modified, and the sulfomethylated tannins of Vitex negundo bark are replaced with an equal amount of tannins of Vitex negundo bark. The raw materials include the following parts by weight: 46 parts of unmodified tannins of Vitex negundo bark, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, and 12 parts of polyaluminum chloride.

[0088] Comparative Example 3

[0089] The removal agent differs from that in Example 1 only in that the tannins of Vitex negundo bark are not modified, and the sulfomethylated tannins of Vitex negundo bark are replaced with an equal amount of tannins of Vitex negundo bark. The raw materials include the following parts by weight: 46 parts of unmodified tannins of Vitex negundo bark, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, 12 parts of polyaluminum chloride, and 8 parts of modified active silica.

[0090] Comparative Example 4

[0091] The removal agent differs from that in Example 1 only in that the active silica is not modified, and the modified active silica is replaced with an equal amount of active silica, which includes the following raw materials by weight: 46 parts of sulfomethylated chamaejasminoides bark tannin, 21 parts of aluminum sulfate, 1.8 parts of polyacrylamide, 2 parts of sodium hydroxide, 12 parts of polyaluminum chloride, and 8 parts of unmodified active silica.

[0092] Test case

[0093] The performance of the treatment agents prepared in the above examples and comparative examples was tested, as detailed below.

[0094] 1. Preparation of simulated wastewater: Self-emulsifying cutting fluid was added to deionized water at a mass fraction of 2%, and stirred for 30 minutes using a high-speed stirrer to prepare simulated wastewater. The initial oil content, COD, turbidity, and other indicators were measured. Subsequently, 10g of the treatment agent from the examples and comparative examples were added to the simulated wastewater, and the oil content, COD value, turbidity, and other indicators of the treated water samples were measured.

[0095] 2. Oil content determination: Under pH≤2 conditions, the oily substances in the sample were extracted with tetrachloroethylene. The extract was dehydrated with anhydrous sodium sulfate, and then the polar substances such as animal and vegetable oils were removed by adsorption with magnesium silicate. Finally, the oil content was determined by infrared spectrophotometer.

[0096] 3. COD Determination: The potassium dichromate method is used. A certain volume of water sample is taken and diluted as needed. A certain amount of potassium dichromate standard solution, as well as appropriate amounts of mercuric sulfate and silver sulfate-sulfuric acid solution, are added. The mixed water sample is heated under reflux for a certain time, usually 2 hours. After cooling, ferroin indicator is added, and titration is performed with ferrous ammonium sulfate standard solution until the solution color changes to reddish-brown. The COD value is calculated based on the volume of ferrous ammonium sulfate standard solution consumed in the titration.

[0097] 3. Turbidity determination: Using a scattering turbidimeter, take an appropriate amount of supernatant into a colorimetric tube, shake gently to avoid air bubbles, wipe the outer wall of the colorimetric tube, and place it into the instrument for measurement.

[0098] 4. Analysis of Floc Characteristics

[0099] (1) Zeta potential measurement: A zeta potential analyzer was used. The flocculated sample was taken and filtered through a 0.45 μm filter membrane. The sample was injected into the sample cell, the measurement parameters were set, and the potential value (mV) was recorded.

[0100] (2) Determination of floc particle size distribution: A laser particle size analyzer was used. The flocculated sample was taken, appropriately diluted, the instrument parameters were set, an appropriate amount of sample was added to the sample cell, the stirring was turned on, and D was recorded. 50 value.

[0101] 5. Surface tension measurement: Using a surface tension meter, water samples were taken before and after treatment, the temperature was controlled at 25±0.1℃, the platinum ring was cleaned, and the surface tension was measured.

[0102] Table 1. Removal of contaminants from self-emulsified oils in Examples 1-11 and Comparative Examples 1-4.

[0103] .

[0104] Table 1 shows the results of removing contaminants from self-emulsified oil in the above examples and comparative examples. Example 1 (sulfonated methylated tannin + modified activated silica) performed best in all evaluation indicators, with an oil content removal rate of 98.5%, a COD removal rate of 95.2%, and a turbidity removal rate of 99.1%, far exceeding other examples and the control group. This result clearly demonstrates that the synergistic effect of sulfonated methylated tannin and modified activated silica can significantly improve the treatment effect.

[0105] By comparing the results of Example 1 with those of Comparative Examples 3 and 4, the significant improvement in treatment efficiency due to the modified process is clearly evident. Compared to Comparative Example 4, which used unmodified activated silica, Example 1 showed a 7.7 percentage point improvement in oil removal rate (from 90.8% to 98.5%), a 7.3 percentage point improvement in COD removal rate (from 87.9% to 95.2%), and a 5.6 percentage point improvement in turbidity removal rate (from 93.5% to 99.1%). This significant performance improvement is mainly attributed to the fact that the modified activated silica enhances the structural stability of the flocs, promoting floc growth and sedimentation. This is reflected in the average particle size D of the flocs. 50 The data further confirms that D in Example 1 50 The value (178.6 μm) is much higher than that of Comparative Example 4 (142.3 μm).

[0106] Meanwhile, comparing the data from Example 8 with those from Comparative Examples 1 and 2, the significant impact of the sulfonylation process on tannin performance can be observed. Compared to Comparative Example 2, which used unmodified tannins, Example 8 showed an 11.6 percentage point increase in oil content removal (from 84.1% to 95.7%), an 11.1 percentage point increase in COD removal (from 81.5% to 92.6%), and a 10.6 percentage point increase in turbidity removal (from 87.2% to 97.8%). This improvement is mainly attributed to the enhanced interaction between tannin molecules and oil droplets during the sulfonylation process, which more effectively disrupts the emulsified state of the oil droplets. Zeta potential data also support this conclusion; the Zeta potential of Example 8 (-18.2 mV) was significantly better than that of Comparative Example 2 (-25.3 mV), indicating that the resulting flocs were more stable and less prone to redispersibility.

[0107] The data on surface tension reduction further corroborate the superiority of sulfonated tannins, with Example 8 achieving a reduction rate of 38.2%, significantly higher than the 28.5% of Comparative Example 2. This result is consistent with the mechanism by which sulfonated tannins more effectively reduce the interfacial tension between oil and water. Notably, other examples also demonstrated excellent treatment effects, highlighting the general applicability of the sulfonation process in improving tannin treatment performance. Overall, these experimental data strongly demonstrate the synergistic advantages of sulfonated tannins and modified activated silica in treating self-emulsifying oily wastewater.

[0108] Their synergistic effect not only significantly improves the removal rates of oil, COD, and turbidity, but also enhances the characteristics of the flocs, making them more stable and easier to settle, thus achieving more efficient oil-water separation. This innovative formulation provides an efficient and reliable new solution for addressing the complex problem of self-emulsifying oily wastewater treatment.

[0109] Finally, it should be noted that although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-emulsifying oily wastewater removal agent, characterized in that, The raw materials include the following parts by weight: 30-50 parts of sulfomethyl tannin, 15-25 parts of aluminum sulfate, 0.5-2 parts of polyacrylamide, 1-3 parts of sodium hydroxide, 10-20 parts of polyaluminum chloride, and 5-10 parts of modified active silica. The modified active silicic acid is obtained by modifying active silicic acid with octyltrimethoxysilane, and its surface has a hydrophobic layer and long-chain alkyl groups.

2. The removal agent as described in claim 1, characterized in that, The sulfonated tannin is obtained by sulfonation reaction of tannin with sodium sulfite and formaldehyde.

3. The removal agent as described in claim 2, wherein the tannin is any one of bayberry tannin, vitex bark tannin, catechin, and tannic acid.

4. A method for preparing a self-emulsifying oily wastewater removal agent as described in any one of claims 1-3, characterized in that, After the raw materials are mixed evenly in solution, the pH of the solution is adjusted to 7.0~8.0 and then spray-dried.

5. The method as described in claim 4, characterized in that, The mixing temperature is 30~35℃.

6. The method as described in claim 4, characterized in that, The spray drying temperature is 180~200℃ at the inlet and 80~100℃ at the outlet.

7. The method as described in claim 4, characterized in that, When the raw material contains modified active silicic acid, the preparation method of the modified active silicic acid is as follows: The active silicic acid was mixed with an ethanol solution of octyltrimethoxysilane and reacted at pH 3-4 and 60°C for 4-5 hours. After the reaction was completed, the solid was centrifuged, washed, and dried.