Long-acting defoaming agent for wastewater treatment and preparation method thereof

Abstract

This invention discloses a long-lasting defoaming agent for wastewater treatment and its preparation method, belonging to the field of defoamer technology. The long-lasting defoaming agent for wastewater treatment comprises the following raw materials in parts by weight: 12-16 parts modified silicone oil, 1.5-3 parts modified silica, 8-12 parts dimethyl silicone oil, 4-6 parts nonionic emulsifier, 0.2-0.5 parts stabilizer, and 60-75 parts deionized water. The modified silicone oil is prepared by the following method: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane reacts with hydrogen-terminated silicone oil to obtain a hyperbranched polymer; the hyperbranched polymer reacts with octadecyl vinyl ether and allyl polyoxyethylene ether methyl ether to obtain the modified silicone oil. The defoamer for wastewater treatment prepared by this invention has excellent rapid defoaming performance and long-lasting defoaming performance.

Description

Technical Field

[0001] This invention relates to the field of defoamer technology, specifically to a long-acting defoaming agent for wastewater treatment and its preparation method. Background Technology

[0002] Wastewater typically contains large amounts of surfactants, proteins, oils, and other pollutants, which easily accumulate at the gas-liquid interface and form stable foam under conditions such as aeration, oxygenation, and mechanical stirring. Excessive foam not only occupies space in the reaction tank, leading to wastewater overflow, but also hinders oxygen transfer, reduces the degradation efficiency of aerobic microorganisms, and thus affects the stability of the wastewater treatment system. Therefore, defoamers are commonly used in wastewater treatment to suppress foam generation and aggregation. Currently, commonly used wastewater treatment defoamers mainly include mineral oil-based, polyether-based, and silicone-based defoamers. Among them, mineral oil-based defoamers have lower costs but limited defoaming efficiency, require larger dosages, and easily increase the COD load of the wastewater system; polyether products have certain foam-suppressing properties, but lower defoaming efficiency; silicone-based defoamers have a fast defoaming speed but insufficient persistence, making it difficult to meet the long-term, stable defoaming requirements of modern wastewater treatment processes.

[0003] Chinese invention patent CN117101190A discloses a method for preparing a defoamer for wastewater treatment. The defoamer includes a polyether-modified organosiloxane, a dispersant, a composite emulsifier, a composite component, and water. The polyether-modified organosiloxane includes a siloxane-terminated polypropylene oxide prepolymer with a weight average molecular weight of 12,000 and a single- or double-terminated polyether-modified silicone oil. The composite component includes an assembly product of polyethylene glycol derivatives, alkyl carboxylic acids, and tetrabutyl titanate. This invention modifies the components of existing polyether-modified organosiloxanes through composite modification, further reducing the impact of polyether modification on the defoaming and foam-suppressing performance of the defoamer. However, its foam-suppressing performance still needs to be improved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a long-lasting defoaming agent for wastewater treatment and its preparation method.

[0005] A long-lasting defoaming agent for wastewater treatment comprises the following raw materials in parts by weight: 12-16 parts modified silicone oil, 1.5-3 parts modified silica, 8-12 parts dimethyl silicone oil, 4-6 parts nonionic emulsifier, 0.2-0.5 parts stabilizer, and 60-75 parts deionized water; The modified silicone oil is prepared by the following method: S1: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane reacts with hydrogen-terminated silicone oil under the action of catalyst one to obtain a hyperbranched polymer; S2: Modified silicone oil is obtained by reacting hyperbranched polymer with octadecyl vinyl ether and allyl polyoxyethylene ether methyl ether under the action of catalyst II.

[0006] In step S1, the mass ratio of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane to hydrogen-terminated silicone oil is (0.06-0.07):1.

[0007] In step S2, the mass ratio of the hyperbranched polymer to octadecyl vinyl ether and allyl polyoxyethylene ether methyl ether is 1:(0.04-0.06):(0.03-0.04).

[0008] Both catalyst one and catalyst two are platinum catalysts.

[0009] The modified silica is obtained by grafting silica with a silane coupling agent.

[0010] The silane coupling agent is dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

[0011] The mass ratio of the silane coupling agent to silica is 1:10.

[0012] The nonionic emulsifier is a mixture of Span 80 and Tween 80 in a mass ratio of 1:(2-3).

[0013] The stabilizer is xanthan gum.

[0014] A method for preparing a long-acting defoaming agent for wastewater treatment includes the following steps: (1) Weigh out the following by weight: 12-16 parts modified silicone oil, 1.5-3 parts modified silica, 8-12 parts dimethyl silicone oil, 4-6 parts nonionic emulsifier, 0.2-0.5 parts stabilizer, and 60-75 parts deionized water; (2) Mix modified silicone oil, modified silica and dimethyl silicone oil, heat and stir to mix evenly, disperse at high speed, add nonionic emulsifier and stir to mix evenly to obtain mixed oil phase; mix deionized water and stabilizer evenly to obtain water phase; add mixed oil phase to water phase, stir at high speed, and sieve to obtain defoamer for wastewater treatment.

[0015] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include: The defoamer for wastewater treatment prepared by this invention has good rapid defoaming performance and long-lasting foam suppression performance. Attached Figure Description

[0016] Figure 1 Fourier transform infrared spectra of the hyperbranched polymer and modified silicone oil prepared in Example 2.

[0017] Figure 2 The image shows the 1H NMR spectrum of the modified silicone oil prepared in Example 2.

[0018] Figure 3 The image shows a scanning electron microscope (SEM) image of the modified silica prepared in Example 4.

[0019] Figure 4 Fourier transform infrared spectra of the silica and modified silica prepared in Example 4. Detailed Implementation

[0020] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments.

[0021] Example 1: Preparation of Modified Silicone Oil S1: Under nitrogen protection, 100g of hydrogen-terminated silicone oil and 0.4g of Karstedt platinum catalyst were added to a reaction flask, stirred and heated to 80℃, and 6g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane was added dropwise. After the addition was completed in 30min, the temperature was raised to 110℃ and the reaction was carried out for 5h. Then, 0.1g of Karstedt platinum catalyst was added and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain the hyperbranched polymer. S2: Under nitrogen protection, 100g of hyperbranched polymer and 0.4g of Karstedt platinum catalyst were added to a reaction flask and stirred and heated to 80℃. 6g of octadecyl vinyl ether and 4g of allyl polyoxyethylene ether methyl ether were stirred at 60℃ for 20min to form a uniform dispersion, which was then added dropwise to the reaction flask. The addition was completed in 30min. The temperature was raised to 110℃ and the reaction was carried out for 7h. 0.1g of Karstedt platinum catalyst was added, and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain modified silicone oil.

[0022] Example 2 Preparation of modified silicone oil S1: Under nitrogen protection, 100g of hydrogen-containing silicone oil and 0.4g of Karstedt platinum catalyst were added to a reaction flask, stirred and heated to 80℃, and 6.5g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane was added dropwise over 30min. The temperature was then raised to 120℃ and reacted for 4h. 0.1g of Karstedt platinum catalyst was added, and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain the hyperbranched polymer. S2: Under nitrogen protection, 100g of hyperbranched polymer and 0.4g of Karstedt platinum catalyst were added to a reaction flask and stirred to 80℃. 5g of octadecyl vinyl ether and 3.5g of allyl polyoxyethylene ether methyl ether were stirred at 60℃ for 20min to form a uniform dispersion, which was then added dropwise to the reaction flask. The addition was completed in 30min. The temperature was raised to 120℃ and the reaction was carried out for 6h. 0.1g of Karstedt platinum catalyst was added, and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain modified silicone oil.

[0023] Figure 1 The figures show the Fourier transform infrared spectra of hyperbranched polymers and modified silicone oils. As can be seen from the figures, the hyperbranched polymers exhibit high activity in the 1020-1090 cm⁻¹ range. -1 A distinct Si-O-Si stretching vibration absorption peak appears at 1260 cm⁻¹. -1 and 800cm -1 The presence of a characteristic Si-CH3 absorption peak nearby indicates that it maintains the polysiloxane backbone structure; simultaneously, at 2160 cm⁻¹... -1 The presence of weak Si-H stretching vibration peaks nearby indicates that some Si-H active sites are still retained in the hyperbranched polymer. Modified silicone oil exhibits peaks in the 1020-1090 cm⁻¹ range. -1 The area still exhibits characteristic Si-O-Si absorption peaks, while the 2160 cm⁻¹ peak... -1 No obvious Si-H absorption peaks were observed nearby, indicating that the remaining Si-H further participated in the grafting reaction; at 2920 cm⁻¹ -1 and 2850cm -1 The nearby methylene CH stretching vibration peaks are enhanced. These results indicate that the hyperbranched polymer and modified silicone oil were successfully prepared.

[0024] Figure 2 The figure shows the 1H NMR spectrum of the modified silicone oil. As can be seen from the figure, the strong absorption peak at δ -0.03-0.10ppm belongs to the Si-CH3 protons in the polysiloxane and cyclosiloxane structures, the peak at δ 0.5-1.0ppm belongs to the Si-CH2- protons formed after hydrosilylation, the absorption peak at δ 1.0-1.4ppm belongs to the terminal methyl and methylene protons in the octadecyl segment, and the peak at δ 3.2-3.8ppm belongs to the -CH2-O-CH2- protons. The above results indicate that the modified silicone oil was successfully prepared.

[0025] Example 3 Preparation of modified silicone oil S1: Under nitrogen protection, 100g of hydrogen-terminated silicone oil and 0.4g of Karstedt platinum catalyst were added to a reaction flask, stirred and heated to 80℃, and 7g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane was added dropwise. After the addition was completed in 30min, the temperature was raised to 130℃ and the reaction was carried out for 3h. 0.1g of Karstedt platinum catalyst was added, and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain the hyperbranched polymer. S2: Under nitrogen protection, 100g of hyperbranched polymer and 0.4g of Karstedt platinum catalyst were added to a reaction flask and stirred and heated to 80℃. 4g of octadecyl vinyl ether and 3g of allyl polyoxyethylene ether methyl ether were stirred at 60℃ for 20min to form a uniform dispersion, which was then added dropwise to the reaction flask. The addition was completed in 30min. The temperature was raised to 130℃ and the reaction was carried out for 5h. 0.1g of Karstedt platinum catalyst was added, and the reaction was continued for 1h. The mixture was then cooled to room temperature to obtain modified silicone oil.

[0026] Example 4 Preparation of modified silica Add 50 ml of 90 wt% ethanol aqueous solution and 5 g of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride to a reaction flask, stir and mix well, adjust the pH to 4 with 5 wt% acetic acid aqueous solution, stir for 30 min to obtain silane coupling agent solution; add 50 g of silica to 500 ml of 90 wt% ethanol aqueous solution, sonicate at 30 kHz and 200 W for 30 min, then add all the silane coupling agent solution prepared above, stir and heat to 70 ℃ for 5 h, cool to room temperature, filter, wash with anhydrous ethanol (3 × 100 ml), and vacuum dry at 90 ℃ for 5 h to obtain modified silica.

[0027] Figure 3 The image shows a scanning electron microscope (SEM) image of the modified silica. As can be seen from the image, the modified silica exhibits a spherical structure with a relatively uniform particle size distribution and good particle dispersion. It does not form large hard agglomerates and has a relatively rough surface, which is related to the grafting and coating of coupling agent on the particle surface.

[0028] Figure 4 The figures show the Fourier transform infrared spectra of silica and modified silica. As can be seen from the figures, compared to silica, modified silica retains more wavelengths around 3440 cm⁻¹. -1 The nearby OH stretching vibration peak is relatively broad, at 1100 cm⁻¹. -1 The nearby Si-O-Si antisymmetric stretching vibration peak and the 800 cm⁻¹ peak -1 Nearby Si-O-Si symmetric stretching vibration peaks; simultaneously at 2920 cm⁻¹ -1 and 2850cm -1 Nearby, antisymmetric and symmetric stretching vibration peaks appear at 1460 cm⁻¹. -1 The presence of CH bending vibration peaks nearby confirms that quaternary ammonium salt-type long-chain silane coupling agents have been successfully grafted onto the silica surface.

[0029] Example 5 Preparation of defoamer for wastewater treatment (1) Weigh: 12g of modified silicone oil (prepared in Example 1), 1.5g of modified silica (prepared in Example 4), 8g of dimethyl silicone oil, 4g of nonionic emulsifier (1g Span 80, 3g Tween 80), 0.2g of stabilizer (xanthan gum), and 60g of deionized water; (2) Mix modified silicone oil, modified silica and dimethyl silicone oil, heat to 60°C, stir at 500 rpm for 20 min, then disperse at 5000 rpm for 20 min, add nonionic emulsifier and stir at 500 rpm for 20 min to obtain mixed oil phase; mix deionized water and stabilizer, heat to 60°C, stir at 800 rpm for 60 min to obtain water phase; slowly add mixed oil phase to water phase, stir at 5000 rpm for 15 min, stir at 500 rpm for 10 min, cool to room temperature, pass through 150 mesh sieve to obtain defoamer for wastewater treatment.

[0030] Example 6 Preparation of defoamer for wastewater treatment (1) Weigh: 14g of modified silicone oil (prepared in Example 2), 2.5g of modified silica (prepared in Example 4), 10g of dimethyl silicone oil, 5g of nonionic emulsifier (1.5g Span 80, 3.5g Tween 80), 0.4g of stabilizer (xanthan gum), and 70g of deionized water; (2) Mix modified silicone oil, modified silica and dimethyl silicone oil, heat to 65°C, stir at 500 rpm for 20 min, then disperse at 5000 rpm for 20 min, add nonionic emulsifier and stir at 500 rpm for 20 min to obtain mixed oil phase; mix deionized water and stabilizer, heat to 65°C, stir at 800 rpm for 60 min to obtain water phase; slowly add mixed oil phase to water phase, stir at 5000 rpm for 15 min, stir at 500 rpm for 10 min, cool to room temperature, pass through 150 mesh sieve to obtain defoamer for wastewater treatment.

[0031] Example 7 Preparation of defoamer for wastewater treatment (1) Weigh: 16g of modified silicone oil (prepared in Example 3), 3g of modified silica (prepared in Example 4), 12g of dimethyl silicone oil, 6g of nonionic emulsifier (2g Span 80, 4g Tween 80), 0.5g of stabilizer (xanthan gum), and 75g of deionized water; (2) Mix modified silicone oil, modified silica and dimethyl silicone oil, heat to 70°C, stir at 500 rpm for 20 min, then disperse at 5000 rpm for 20 min, add nonionic emulsifier and stir at 500 rpm for 20 min to obtain mixed oil phase; mix deionized water and stabilizer, heat to 70°C, stir at 800 rpm for 60 min to obtain water phase; slowly add mixed oil phase to water phase, stir at 5000 rpm for 15 min, stir at 500 rpm for 10 min, cool to room temperature, pass through 150 mesh sieve to obtain defoamer for wastewater treatment.

[0032] Comparative Example 1 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silicone oil added to the components is replaced with an equal weight of modified silicone oil prepared by the following method: The preparation method of the modified silicone oil is basically the same as that in Example 2, except that 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in step S1 is replaced with 8g of tris(vinyldimethylsiloxy)methylsilane.

[0033] Comparative Example 2 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silicone oil added to the components is replaced with an equal weight of modified silicone oil prepared by the following method: The preparation method of the modified silicone oil is basically the same as that in Example 2, except that 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in step S1 is replaced with an equal weight of tetramethyltetravinylcyclotetrasiloxane (CAS: 27342-69-4).

[0034] Comparative Example 3 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silicone oil added to the components is replaced with an equal weight of modified silicone oil prepared by the following method: The preparation method of the modified silicone oil is basically the same as that in Example 2, except that 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in step S1 is replaced with 7.5g diallyltetramethyldisiloxane.

[0035] Comparative Example 4 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silicone oil added to the components is replaced with an equal weight of modified silicone oil prepared by the following method: The preparation method of the modified silicone oil is basically the same as that in Example 2, except that the amount of octadecyl vinyl ether added in step S2 is replaced with 3.6g and the amount of allyl polyoxyethylene ether methyl ether added is replaced with 5g.

[0036] Comparative Example 5 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silicone oil added to the components is replaced with an equal weight of modified silicone oil prepared by the following method: The preparation method of the modified silicone oil is basically the same as that in Example 2, except that the amount of allyl polyoxyethylene ether methyl ether added in step S2 is replaced with 1g; and the amount of octadecyl vinyl ether added is replaced with 6g.

[0037] Comparative Example 6 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: The preparation method of modified silica is basically the same as that in Example 4, except that dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride is replaced with an equal weight of n-octadecyltriethoxysilane.

[0038] Comparative Example 7 The raw material composition and preparation method of the defoamer for wastewater treatment are basically the same as in Example 6, except that the modified silica added to the components is replaced with an equal weight of modified silica prepared by the following method: The preparation method of modified silica is basically the same as that in Example 4, except that dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride is replaced with an equal weight of dodecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride.

[0039] The dimethyl silicone oil used in the examples and comparative examples of this application is model QL-201-350, produced by Jiangsu Quanli Chemical Co., Ltd.; the platinum content in the Karstedt platinum catalyst is 2wt%; the silica is model HL-200, produced by Hubei Huifu Nanomaterials Co., Ltd.; the hydrogen-terminated silicone oil is model RH-H6, with a hydrogen content of 0.1%, produced by Ningbo Runhe High-Tech Materials Co., Ltd.; the xanthan gum is model KELTROL®CG-T; the number average molecular weight of the allyl polyoxyethylene ether methyl ether is 800; and the CAS number of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is 3901-77-7.

[0040] The defoamers prepared in the examples and comparative examples were tested for defoaming, foam suppression and dispersion stability. The test results are shown in Table 1.

[0041] The defoaming performance was tested according to the vertical oscillation method in GB / T 26527-2024 for the defoamers (emulsion type defoamers) prepared in the examples and comparative examples, and the average time taken for the foam to disappear completely in the last three tests was recorded; the foam suppression performance was tested according to the air blasting method in GB / T26527-2024.

[0042] Dispersion stability test: Weigh 200g of deionized water into a 500ml sealed bottle, add 1g of the wastewater treatment defoamer prepared in the examples and comparative examples, stir at 1000rpm for 5min to make the defoamer sample uniformly dispersed, seal and let stand at 70℃ for 48h, and observe whether there is any precipitation or oil floating phenomenon in the solution.

[0043] Table 1 Performance Test Data

[0044] As can be seen from the data in Table 1, the defoamer for wastewater treatment prepared by the present invention has a short defoaming time and a low sustained foam height, indicating that it has good rapid defoaming performance and long-term foam suppression performance. The main reason is the synergistic effect between modified silicone oil, modified silica and emulsion stabilization system.

[0045] This invention synthesizes a modified silicone oil with a hyperbranched structure by grafting long-chain vinyl alkyl groups and vinyl polyethers onto trifunctional cyclic siloxanes containing double bonds and difunctional hydrogen-terminated silicone oils. The hyperbranched structure allows the modified silicone oil to maintain low surface tension and interfacial spreading ability, thus achieving better long-lasting antifoaming effects. The introduced long-chain alkyl groups enhance the hydrophobicity and interfacial drainage capacity of the modified silicone oil, improving defoaming efficiency. The introduced polyether segments improve the dispersibility of the modified silicone oil in wastewater systems, enabling the active defoamer component to spread rapidly and exert its effect continuously. Modified silica acts as solid defoaming particles, interfering with the foam liquid film, lowering the energy barrier for the active defoamer component to enter the liquid film, and promoting local drainage and rupture. The grafted quaternary ammonium salt structure enables the modified silica to maintain dispersion stability in wastewater systems. The octadecyl chain linked to the quaternary ammonium salt improves the hydrophobicity of the modified silica surface, and synergistically enhances the defoaming performance through hydrophobic interactions with the long-chain alkyl groups in the modified silicone oil.

[0046] Furthermore, dimethyl silicone oil reduces the surface tension of the system and improves the flow and spreadability of the defoamer; the combination of Span 80 and Tween 80 forms a nonionic emulsion system, enabling the defoamer to form an oil-in-water emulsion; polyether-modified silicone oil improves the interfacial compatibility between the oil and aqueous phases and promotes the wetting and dispersibility of modified silica in the silicone oil system; xanthan gum increases the viscosity and suspension stability of the aqueous phase, reducing stratification, sedimentation, and oil separation during emulsion storage. The synergistic effect of these components gives the defoamer excellent dispersion stability and allows it to quickly disrupt the foam film and inhibit foam regeneration.

[0047] Comparative Example 1 replaced 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane with tris(vinyldimethylsiloxy)methylsilane, which has a more flexible branched siloxane structure. This reduces rigidity and steric confinement, decreasing molecular chain regularity and interfacial retention, thus reducing defoaming performance. Comparative Example 2 used a tetrafunctional cyclic siloxane containing double bonds, resulting in excessive branching of the silicone oil molecular chain. This reduced the molecular mobility of the modified silicone oil, slowing its migration to the foam gas-liquid interface in the wastewater system and decreasing its rapid spreading and film-breaking ability. Comparative Example 4 used a modified silicone oil with increased grafted polyether segments and decreased long-chain alkyl content, improving aqueous dispersibility but reducing hydrophobic defoaming ability, thus lowering defoaming performance. In Comparative Example 5, the modified silicone oil grafted with a higher amount of long-chain alkyl groups and a lower amount of polyether segments resulted in reduced aqueous dispersibility and emulsification compatibility of the modified silicone oil, leading to a decrease in the effective working area, reduced foam suppression persistence, and decreased storage stability. In Comparative Example 7, the modified silica used had its alkyl chains shortened from C18 to C12, resulting in a reduced degree of hydrophobic modification and decreased compatibility with the silicone oil phase, leading to a decline in defoaming and long-lasting foam suppression performance.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A long-acting antifoaming agent for wastewater treatment of the foam suppressing type, characterized by comprising: The ingredients include the following parts by weight: 12-16 parts modified silicone oil, 1.5-3 parts modified silica, 8-12 parts dimethyl silicone oil, 4-6 parts nonionic emulsifier, 0.2-0.5 parts stabilizer, and 60-75 parts deionized water; The modified silicone oil is prepared by the following method: S1: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane reacts with hydrogen-terminated silicone oil under the action of catalyst one to obtain a hyperbranched polymer; S2: Modified silicone oil is obtained by reacting hyperbranched polymer with octadecyl vinyl ether and allyl polyoxyethylene ether methyl ether under the action of catalyst II.

2. The long-acting anti-foaming agent for wastewater treatment according to claim 1, characterized by, In step S1, the mass ratio of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane to hydrogen-terminated silicone oil is (0.06-0.07):

1.

3. The long-acting anti-foaming agent for wastewater treatment according to claim 1, characterized by, In step S2, the mass ratio of the hyperbranched polymer to octadecyl vinyl ether and allyl polyoxyethylene ether methyl ether is 1:(0.04-0.06):(0.03-0.04).

4. The long-acting anti-foaming agent for wastewater treatment according to claim 1, characterized by, Both catalyst one and catalyst two are platinum catalysts.

5. The long-acting anti-foaming agent for wastewater treatment according to claim 1, characterized by, The modified silica is obtained by grafting silica with a silane coupling agent.

6. The long-acting anti-foaming wastewater treatment defoaming agent according to claim 5, characterized in that, The silane coupling agent is dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride.

7. The long-acting anti-foaming wastewater treatment defoaming agent according to claim 5, characterized in that, The mass ratio of the silane coupling agent to silica is 1:

10.

8. The long-acting anti-foaming wastewater treatment defoaming agent according to claim 1, characterized in that, The nonionic emulsifier is a mixture of Span 80 and Tween 80 in a mass ratio of 1:(2-3).

9. The long-acting defoaming agent for wastewater treatment according to claim 1, characterized in that, The stabilizer is xanthan gum.

10. A method for preparing a long-acting defoaming agent for wastewater treatment as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) Weigh out the following by weight: 12-16 parts modified silicone oil, 1.5-3 parts modified silica, 8-12 parts dimethyl silicone oil, 4-6 parts nonionic emulsifier, 0.2-0.5 parts stabilizer, and 60-75 parts deionized water; (2) Mix modified silicone oil, modified silica and dimethyl silicone oil, heat and stir to mix evenly, disperse at high speed, add nonionic emulsifier and stir to mix evenly to obtain mixed oil phase; mix deionized water and stabilizer evenly to obtain water phase; add mixed oil phase to water phase, stir at high speed, and sieve to obtain defoamer for wastewater treatment.

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