Composite defoaming agent for sewage treatment and preparation method thereof

Abstract

The present application relates to the technical field of chemical materials, and discloses a composite defoaming agent for sewage treatment and a preparation method thereof. The composite defoaming agent comprises raw materials such as epoxy group polyether modified polysiloxane, propyl gallate, zinc lactate and quaternary phosphonium salt modified cationic polymer. Through a multi-step chemical reaction of 'grafting-complexing-assembly', the propyl gallate is first covalently grafted to the polysiloxane main chain, then a 'polysiloxane-polyphenol-zinc' complex structure is formed through zinc ion coordination complexing, and finally the quaternary phosphonium salt modified cationic polymer is anchored and assembled on the complex structure by using coordination bonds, electrostatic interaction and hydrogen bonds, so as to construct a 'polysiloxane-polyphenol-zinc-quaternary phosphonium salt polymer' composite system with stable structure. The problems of single function and easy stratification failure of physical compounding of the existing defoaming agent are solved, multi-effect synergy and long-term stability of defoaming, sterilization and flocculation are realized, and the composite defoaming agent is suitable for high salinity oilfield sewage treatment scenes.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials technology and relates to a composite defoamer for wastewater treatment and its preparation method, which is particularly suitable for wastewater treatment scenarios in oilfields with high mineralization and oil content. Background Technology

[0002] During oilfield extraction, gathering and transportation, and wastewater treatment, large amounts of stable and persistent foam are easily generated in the system due to fluid agitation, gas escape, and the addition of large quantities of surfactants. This foam occupies the effective treatment volume, affects the efficiency of oil-water separation and solid-liquid sedimentation, leads to a decrease in the processing capacity of subsequent equipment, and may even cause safety accidents such as tank overflow. Therefore, high-efficiency defoamers are indispensable additives in oilfield water treatment processes.

[0003] Currently, commonly used defoamers mainly include mineral oils, polyethers, and organosilicones. However, in oilfield wastewater with complex composition, especially under conditions of high mineralization and high oil content, traditional defoamers generally have the following problems: (1) low defoaming efficiency and short foam suppression time, making it difficult to cope with systems that continuously generate foam; (2) poor compatibility with the system, which may lead to secondary pollution or interfere with the function of the main agent; (3) single function, only having defoaming function, unable to synergistically treat microorganisms or emulsified oil droplets that cause foam; (4) most products are physically compounded, lacking chemical interaction between components, and are prone to stratification and failure during storage and use.

[0004] Therefore, developing an environmentally friendly composite defoamer with long-lasting defoaming ability and synergistic treatment effect is of great significance for improving the overall water treatment efficiency of oilfields and reducing comprehensive operating costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a composite defoamer for wastewater treatment and its preparation method. Through a multi-step chemical reaction of "grafting-complexing-dynamic assembly," the defoaming main chain, polyphenol complexing nodes, and quaternary phosphonium salt modified polyethyleneimine are constructed into a structurally stable "polysiloxane-polyphenol-zinc-quaternary phosphonium salt polymer" composite system via covalent and coordination bonds. This achieves multi-effect synergy and long-term stability of defoaming, foam suppression, demulsification, flocculation, and sterilization, and ensures the product's excellent performance in complex water quality and long-term storage.

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

[0007] This invention provides a composite defoamer for wastewater treatment, comprising the following raw materials in parts by weight: 10-25 parts of epoxy-modified polysiloxane, 2-6 parts of propyl gallate, 1-3 parts of zinc lactate, 3-8 parts of quaternary phosphonium salt-modified cationic polymer, 0.1-0.5 parts of catalyst, 0.5-2 parts of buffer, 5-12 parts of environmentally friendly solvent, and 45-75 parts of deionized water.

[0008] Further, the epoxy-based polyether modified polysiloxane comprises the following raw materials: hydrogen-containing silicone oil, allyl polyoxyethylene ether, chloroplatinic acid, epichlorohydrin, and tetrabutylammonium bromide. The preparation method is as follows: hydrogen-containing silicone oil, allyl polyoxyethylene ether, and chloroplatinic acid catalyst are added to a reaction flask and reacted at 90-110°C for 4-6 hours to obtain hydroxyl-terminated polyether modified polysiloxane. Then, the temperature is lowered to 60-80°C, epichlorohydrin and phase transfer catalyst tetrabutylammonium bromide are added, and the reaction is carried out for 2-4 hours to obtain epoxy-based polyether modified polysiloxane.

[0009] Furthermore, the mass ratio of the hydrogen-containing silicone oil, allyl polyoxyethylene ether, chloroplatinic acid, epichlorohydrin and tetrabutylammonium bromide is 1:2:0.001:0.3:0.005.

[0010] Furthermore, the quaternary phosphonium salt modified cationic polymer is prepared by dehydration condensation of tetramethylolphosphonium sulfate and polyethyleneimine. The specific preparation method is as follows: (a) Polyethyleneimine is dissolved in deionized water to prepare a polymer solution with a mass fraction of 10%; (b) The polymer solution is heated to 55°C, and tetramethylolphosphonium sulfate is slowly added under stirring. The mass ratio of tetramethylolphosphonium sulfate to polyethyleneimine is 1:3-5. The reaction is carried out at 65°C with constant temperature stirring for 4-6 hours, so that the hydroxymethyl group of tetramethylolphosphonium sulfate undergoes a condensation dehydration reaction with the primary and secondary amino groups on the polyethyleneimine molecular chain, and the quaternary phosphonium salt structure is covalently grafted onto the polyethyleneimine molecular chain; (c) After the reaction is completed, the mixture is distilled under reduced pressure at 60-70°C and 0.095 MPa for 30 min to remove unreacted small molecules and obtain the quaternary phosphonium salt modified cationic polymer.

[0011] Furthermore, the catalyst is either triphenylphosphine or imidazole.

[0012] Furthermore, the buffer is a phosphate buffer.

[0013] Furthermore, the environmentally friendly solvent is any one of anhydrous ethanol, propylene glycol, and glycerin.

[0014] The present invention also provides a method for preparing the above-mentioned composite defoamer for wastewater treatment, comprising the following steps:

[0015] S1 base material pre-dispersion: Mix environmentally friendly solvent with 1 / 3 weight of deionized water evenly, add epoxy polyether modified polysiloxane, and stir and disperse at 40-50℃ and 300-500rpm for 20-30min to obtain a uniform polysiloxane dispersion.

[0016] S2 Grafting Reaction: Add a catalyst to the polysiloxane dispersion obtained in S1, adjust the pH of the system to 7.0-8.0, add propyl gallate, and stir at a constant temperature of 50-60℃ and 400-600rpm for 2-3 hours to allow the terminal epoxy group of the epoxy-modified polysiloxane to undergo a ring-opening addition reaction with the phenolic hydroxyl group in the propyl gallate molecule, thereby covalently grafting propyl gallate onto the polysiloxane molecular chain to obtain a polysiloxane-polyphenol graft dispersion;

[0017] S3 Metal-Polyphenol Complexation Reaction: Add a buffer to the polysiloxane-polyphenol graft dispersion obtained in S2, adjust the pH of the system to 5.8-6.2, add zinc lactate under continuous stirring, and react at a constant temperature of 45-55℃ for 1-1.5h, so that the zinc ions in zinc lactate can undergo a coordination complexation reaction with the ortho-phenolic hydroxyl groups in the propyl gallate molecule on the graft to form a "polysiloxane-polyphenol-zinc" metal complex structure, and obtain an intermediate dispersion;

[0018] S4 electrostatic synergistic assembly: The quaternary phosphonium salt modified cationic polymer was pre-dissolved in 1 / 3 of the weight of deionized water, and then slowly added dropwise to the intermediate dispersion obtained in S3 under stirring. The addition time was controlled at 20-30 min. After the addition was completed, the overall pH of the system was slowly adjusted to 7.5-8.0 with a buffer, and the reaction was continued to be stirred for 0.5-1 h. During this process, the unprotonated amino groups in the quaternary phosphonium salt modified cationic polymer donated lone pairs of electrons to coordinate with the empty coordination orbitals of zinc ions in the metal complex structure, forming a dynamic coordination bond of "amino-zinc". At the same time, the positive charge of the protonated amino groups on the polymer chain was electrostatically attracted to the lactate anions in the system and formed multiple hydrogen bond crosslinks with the ether oxygen atoms of the polysiloxane chain segments, realizing the stable assembly of the bactericidal-demulsifying flocculant component and the defoaming main chain at the molecular level, and obtaining the complex dispersion.

[0019] S5 Stabilization and Dispersion: Add the remaining deionized water to the composite dispersion obtained in S4 to adjust the solid content, continue stirring for 15 minutes and then stop the reaction. Cool to room temperature and filter through a 100-mesh filter to obtain the composite defoamer for wastewater treatment.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) Functional synergy is achieved through chemical structural innovation, breaking through the technical bottleneck of simple compounding. This invention constructs a composite structure of "polysiloxane-polyphenol-zinc-quaternary phosphonium salt" through a stepwise chemical reaction of "grafting-complexation-assembly". In this structure, zinc ions act as a "chemical bridge", with one end fixed to the defoamer skeleton through coordination bonds, and the other end anchored to the quaternary phosphonium salt modified cationic polymer through coordination bonds and electrostatic interaction, thereby transforming the bactericide from a water-soluble small molecule that is easily lost into a "fixed" state. This structure achieves deep coupling of defoaming, sterilization, and flocculation functions: the defoamer skeleton delivers the bactericide to the bubble interface, precisely killing foam-producing microorganisms and inhibiting foaming from the source; at the same time, the immobilization of the bactericide greatly extends its action time in the system, solving the problem of rapid dilution and failure of bactericides after addition and poor persistence in traditional sewage treatment; and the polyethyleneimine skeleton in the quaternary phosphonium salt modified cationic polymer itself has both demulsification and flocculation functions, working together with the defoaming main chain to achieve oil-water separation and suspended solids sedimentation.

[0022] (2) The construction of a multi-dimensional network structure significantly improves the stability and applicability of the product. This invention constructs a multi-dimensional network stable structure through "covalent bonds-coordinate bonds-electrostatic / hydrogen bonds": covalent bonds ensure the permanent fixation of polyphenol components on the polysiloxane backbone; coordinate bonds strengthen the interaction between metal ions and polyphenols and bactericidal-flocculating components, improving structural rigidity; electrostatic attraction and multiple hydrogen bonds construct a dynamic and reversible protective network, effectively buffering changes in the external environment. Compared with the existing silicone defoamers that are prone to demulsification, stratification, and failure under high temperature, high mineralization, or high shear conditions, the multi-dimensional network structure of this invention effectively buffers changes in the external environment, ensuring that the product can maintain excellent defoaming and foam suppression performance under complex water quality conditions such as wide pH value and high oil content, and that there is no stratification or precipitation during long-term storage, significantly improving the environmental adaptability and service life of the product.

[0023] (3) In step S4 of this invention, by precisely controlling the pH transition range, the unprotonated amino groups in polyethyleneimine provide lone pairs of electrons to the empty orbitals of zinc ions to form a dynamic coordination bond of "amino-zinc". At the same time, multiple hydrogen bonds are used for cross-linking, anchoring the large demulsifying and bactericidal polymer chain to the periphery of the defoaming main chain in a "coiled and bound state". During static storage, this bound state does not increase the viscosity of the system, ensuring low-resistance spreading of the defoamer molecules; when it enters the sewage treatment tank and is subjected to mechanical stirring and shearing force, the weaker dynamic coordination bonds are specifically broken, triggering the decoiling and release of the polymer chain in a feedback manner, instantly exerting the demulsifying and flocculating effects.

[0024] (4) The selection of raw materials is scientific and reasonable, optimizing the controllability and environmental friendliness of the reaction system. This invention uses propyl gallate instead of traditional tannic acid as the source of polyphenols. Its molecular structure is clear and the number of phenolic hydroxyl groups is moderate, avoiding the excessive cross-linking and product gelation problems caused by too many reaction sites in tannic acid, and significantly improving the water solubility and dispersion stability of the product. At the same time, the selected zinc lactate, quaternary phosphonium salt and propyl gallate are all environmentally friendly and non-toxic materials. While achieving efficient defoaming and sterilization functions, they avoid the introduction of harmful substances such as heavy metal chloride ions, which meets the development requirements of green water treatment agents and has significant safety and environmental protection advantages. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0026] Figure 1 The graph shows the test results of the defoaming and foam suppression performance of the defoamers obtained in Examples 1-3 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0029] In the following embodiments, the epoxy-based polyether modified polysiloxane and the quaternary phosphonium salt modified cationic polymer used were prepared according to the method described in the invention. Unless otherwise specified, all other materials used were new materials purchased from the market.

[0030] Example 1: This example provides a composite defoamer for wastewater treatment, comprising the following raw materials in parts by weight: 10 parts epoxy polyether modified polysiloxane, 2 parts propyl gallate, 1 part zinc lactate, 3 parts quaternary phosphonium salt modified cationic polymer, 0.1 parts triphenylphosphine, 0.5 parts phosphate buffer, 5 parts anhydrous ethanol, and 75 parts deionized water.

[0031] The preparation method of the epoxy polyether modified polysiloxane is as follows: 100g of hydrogen-containing silicone oil, 200g of allyl polyoxyethylene ether and 0.1g of chloroplatinic acid are added to a reaction flask. Under nitrogen protection, the temperature is raised to 110°C and stirred for 4 hours to obtain hydroxyl-terminated polyether modified polysiloxane. After the reaction is completed, the temperature is lowered to 80°C, 30g of epichlorohydrin and 0.5g of tetrabutylammonium bromide are added, and the reaction is carried out for 2 hours to obtain epoxy polyether modified polysiloxane.

[0032] The preparation method of the quaternary phosphonium salt modified cationic polymer is as follows: (a) 50g of polyethyleneimine is dissolved in 450mL of deionized water to prepare a polymer solution with a mass fraction of 10%; (b) the polymer solution is heated to 55°C, and 16.6g of tetrahydroxymethylphosphonium sulfate is slowly added under stirring. The reaction is carried out at 65°C with constant temperature stirring for 5 hours; (c) the solution is distilled under reduced pressure at 65°C and 0.095MPa for 30 minutes to remove water and unreacted small molecules, thereby obtaining the quaternary phosphonium salt modified cationic polymer.

[0033] This embodiment also provides a method for preparing the above-mentioned composite defoamer for wastewater treatment, including the following steps:

[0034] S1 base material pre-dispersion: Mix anhydrous ethanol with 25 parts of deionized water evenly, add epoxy polyether modified polysiloxane, and stir and disperse at 40℃ and 300 rpm for 25 min to obtain a uniform polysiloxane dispersion.

[0035] S2 grafting reaction: Triphenylphosphine catalyst was added to the polysiloxane dispersion obtained in S1, the pH of the system was adjusted to 7.0 with 0.1 mol / L sodium hydroxide solution, propyl gallate was added, and the reaction was carried out at 50℃ and 400 rpm for 2.5 h to obtain polysiloxane-polyphenol graft dispersion.

[0036] S3 Metal-Polyphenol Complexation Reaction: Add phosphate buffer to the polysiloxane-polyphenol graft dispersion obtained in S2, adjust the pH of the system to 5.8, add zinc lactate under continuous stirring, and react at 45℃ for 1 h to obtain intermediate dispersion.

[0037] S4 electrostatic synergistic assembly: The quaternary phosphonium salt modified cationic polymer was pre-dissolved in 25 parts of deionized water, and then slowly added dropwise to the intermediate dispersion obtained in S3 under stirring. The addition time was controlled at 25 min. After the addition was completed, the overall pH of the system was slowly adjusted to 7.5 with phosphate buffer, and the reaction was continued to be stirred for 0.8 h to obtain the complex dispersion.

[0038] S5 Stabilization and Dispersion: Add the remaining deionized water to the composite dispersion obtained in S4 to adjust the solid content, continue stirring for 15 minutes and then stop the reaction. Cool to room temperature and filter through a 100-mesh filter to obtain the composite defoamer for wastewater treatment.

[0039] Example 2: This example provides a composite defoamer for wastewater treatment, comprising the following raw materials in parts by weight: 17.5 parts of epoxy polyether modified polysiloxane, 4 parts of propyl gallate, 2 parts of zinc lactate, 5.5 parts of quaternary phosphonium salt modified cationic polymer, 0.3 parts of imidazole, 1.25 parts of phosphate buffer system, 8.5 parts of propylene glycol, and 60 parts of deionized water.

[0040] The preparation method of the epoxy polyether modified polysiloxane is as follows: 180g of hydrogen-containing silicone oil, 360g of allyl polyoxyethylene ether and 0.18g of chloroplatinic acid are added to a reaction flask. Under nitrogen protection, the temperature is raised to 105℃ and stirred for 5 hours to obtain hydroxyl-terminated polyether modified polysiloxane. After the reaction is completed, the temperature is lowered to 75℃, 54g of epichlorohydrin and 0.9g of tetrabutylammonium bromide are added, and the reaction is carried out for 3 hours to obtain epoxy polyether modified polysiloxane.

[0041] The preparation method of the quaternary phosphonium salt modified cationic polymer is as follows: (a) Dissolve 80g of polyethyleneimine in 720mL of deionized water to prepare a polymer solution with a mass fraction of 10%; (b) Heat the polymer solution to 55°C, slowly add 20g of tetrahydroxymethylphosphonium sulfate while stirring, and stir at 65°C for 5 hours; (c) After the reaction is completed, distill under reduced pressure at 65°C and 0.095MPa for 30 minutes to remove water and unreacted small molecules, thereby obtaining the quaternary phosphonium salt modified cationic polymer.

[0042] This embodiment also provides a method for preparing the above-mentioned composite defoamer for wastewater treatment, including the following steps:

[0043] S1 base material pre-dispersion: Mix propylene glycol with 20 parts of deionized water evenly, add epoxy polyether modified polysiloxane, and stir and disperse at 45℃ and 400 rpm for 30 min to obtain a uniform polysiloxane dispersion.

[0044] S2 grafting reaction: Add imidazole catalyst to the polysiloxane dispersion obtained in S1, adjust the pH of the system to 7.5 with 0.1 mol / L sodium hydroxide solution, add propyl gallate, and stir at 55℃ and 500 rpm for 3 h to obtain polysiloxane-polyphenol graft dispersion.

[0045] S3 Metal-Polyphenol Complexation Reaction: Add phosphate buffer to the polysiloxane-polyphenol graft dispersion obtained in S2, adjust the pH of the system to 6.0, add zinc lactate under continuous stirring, and react at 50℃ for 1.2h to obtain intermediate dispersion;

[0046] S4 electrostatic synergistic assembly: The quaternary phosphonium salt modified cationic polymer was pre-dissolved in 20 parts of deionized water, and then slowly added dropwise to the intermediate dispersion obtained in S3 under stirring. The addition time was controlled at 30 min. After the addition was completed, the overall pH of the system was slowly adjusted to 7.8 with phosphate buffer, and the reaction was continued for 1 h to obtain the complex dispersion.

[0047] S5 Stabilization and Dispersion: Add the remaining deionized water to the composite dispersion obtained in S4 to adjust the solid content, continue stirring for 15 minutes and then stop the reaction. Cool to room temperature and filter through a 100-mesh filter to obtain the composite defoamer for wastewater treatment.

[0048] Example 3: This example provides a composite defoamer for wastewater treatment, comprising the following raw materials in parts by weight: 25 parts of epoxy polyether modified polysiloxane, 6 parts of propyl gallate, 3 parts of zinc lactate, 8 parts of quaternary phosphonium salt modified cationic polymer, 0.5 parts of triphenylphosphine, 2 parts of phosphate buffer, 12 parts of glycerol, and 45 parts of deionized water.

[0049] The preparation method of the epoxy polyether modified polysiloxane is as follows: 250g of hydrogen-containing silicone oil, 500g of allyl polyoxyethylene ether and 0.25g of chloroplatinic acid are added to a reaction flask. Under nitrogen protection, the temperature is raised to 90°C and stirred for 6 hours to obtain hydroxyl-terminated polyether modified polysiloxane. After the reaction is completed, the temperature is lowered to 60°C, 75g of epichlorohydrin and 1.25g of tetrabutylammonium bromide are added, and the reaction is carried out for 4 hours to obtain epoxy polyether modified polysiloxane.

[0050] The preparation method of the quaternary phosphonium salt modified cationic polymer is as follows: (a) 100g of polyethyleneimine is dissolved in 900mL of deionized water to prepare a polymer solution with a mass fraction of 10%; (b) the polymer solution is heated to 60°C, and 20g of tetrahydroxymethylphosphonium sulfate is slowly added under stirring. The reaction is carried out at 65°C with constant stirring for 6 hours; (c) after the reaction is completed, the solution is distilled under reduced pressure at 70°C and 0.095MPa for 30 minutes to remove water and unreacted small molecules, thereby obtaining the quaternary phosphonium salt modified cationic polymer.

[0051] This embodiment also provides a method for preparing the above-mentioned composite defoamer for wastewater treatment, including the following steps:

[0052] S1 base material pre-dispersion: Glycerin and 15 parts of deionized water are mixed evenly, epoxy polyether modified polysiloxane is added, and the mixture is stirred and dispersed at 50℃ and 500rpm for 30min to obtain a uniform polysiloxane dispersion.

[0053] S2 grafting reaction: Triphenylphosphine catalyst was added to the polysiloxane dispersion obtained in S1, the pH of the system was adjusted to 8.0 with 0.1 mol / L sodium hydroxide solution, propyl gallate was added, and the reaction was carried out at 60℃ and 600 rpm for 3 h to obtain polysiloxane-polyphenol graft dispersion.

[0054] S3 Metal-Polyphenol Complexation Reaction: Add phosphate buffer to the polysiloxane-polyphenol graft dispersion obtained in S2, adjust the pH of the system to 6.2, add zinc lactate under continuous stirring, and react at 55℃ for 1.5h to obtain intermediate dispersion;

[0055] S4 electrostatic synergistic assembly: The quaternary phosphonium salt modified cationic polymer was pre-dissolved in 15 parts of deionized water, and then slowly added dropwise to the intermediate dispersion obtained in S3 under stirring. The addition time was controlled at 30 min. After the addition was completed, the overall pH of the system was slowly adjusted to 8.0 with phosphate buffer, and the reaction was continued for 1 h to obtain the complex dispersion.

[0056] S5 Stabilization and Dispersion: Add the remaining deionized water to the composite dispersion obtained in S4 to adjust the solid content, continue stirring for 15 minutes and then stop the reaction. Cool to room temperature and filter through a 100-mesh filter to obtain the composite defoamer for wastewater treatment.

[0057] Comparative Example 1: This comparative example provides a comparative defoamer, whose raw materials are the same as those in Example 2. The difference is that the preparation method is a simple physical mixing, that is: all raw materials are added to a four-necked flask at one time, and stirred and mixed at 500 rpm for 2 hours in a 50°C water bath until completely dissolved. Then, heating is stopped, stirring is continued, and the mixture is cooled to room temperature. The resulting mixture is filtered through a 100-mesh filter to obtain the comparative defoamer.

[0058] Comparative Example 2: This comparative example provides a conventional polyether-modified polysiloxane defoamer, which differs from Example 2 in that: the raw materials for preparation omit propyl gallate, zinc lactate, and quaternary phosphonium salt modified cationic polymer, i.e., the raw materials for preparation are: 18g of epoxy polyether-modified polysiloxane, 0.3g of imidazole, 1.2g of phosphate buffer, 8g of propylene glycol, and 70g of deionized water; the preparation method retains only the S1 base material pre-dispersion step and the S5 stabilization dispersion step, resulting in a conventional polyether-modified polysiloxane defoamer.

[0059] Comparative Example 3: This comparative example provides a comparative defoamer, which differs from Example 2 in that: an equal weight of unmodified polyethyleneimine is used instead of quaternary phosphonium salt modified cationic polymer, while the other raw materials and preparation methods remain unchanged.

[0060] To verify the effectiveness of the composite defoamer described in this invention, performance tests were conducted on the products obtained in Examples 1-3 and Comparative Examples 1-3 above:

[0061] Defoaming and foam suppression performance test: Referring to GB / T26527-2024, take oily wastewater, let it stand to remove the surface oil, and use it as the test water sample. Measure 100mL of wastewater sample and place it in a 500mL stoppered graduated cylinder. Use a stopwatch to time the test and shake it vigorously up and down at a frequency of 60 times / minute for 30 seconds to fill the graduated cylinder with foam. Quickly add 0.1g of the defoamer sample to be tested and record the time required for the foam volume to drop to the original liquid level (i.e., the foam volume is 0mL). This is the defoaming time. After the defoaming test, shake the graduated cylinder again at the same frequency 30 times and record the foam volume generated in the graduated cylinder at this time. The smaller the volume, the better the foam suppression performance.

[0062] Antibacterial performance testing: Sulfate-reducing bacteria, saprophytic bacteria, and iron bacteria, commonly found in oilfield wastewater treatment, were used as test species. Sulfate-reducing bacteria (SRB): The dilution method was used. The defoamer sample to be tested was diluted with sterile water to the specified concentration, inoculated into a sulfate-reducing bacteria test bottle, and anaerobically cultured at 35℃ for 14 days. The color change of the test bottle (the formation of a black precipitate) was observed, and the minimum inhibitory concentration (MIC) was calculated. Saprophytic bacteria and iron bacteria: The inhibition zone method was used. The bacterial solution was evenly spread on a nutrient agar plate, and 6mm diameter holes were punched in the plate using a sterile punch. 50μL of the defoamer sample to be tested was added into the holes, and the plate was then placed in a 37℃ incubator for 24 hours. The diameter of the inhibition zone was measured using calipers. Each sample was tested in triplicate.

[0063] Table 1. Results of antibacterial performance test

[0064]

[0065] Storage stability test: Each sample was placed in a 50mL stoppered transparent glass bottle and placed in a constant temperature drying oven at 54±1℃ for accelerated storage test. After 7 days, the sample was taken out, cooled to room temperature, and the state of the sample was observed and recorded, such as whether there was layering, precipitation, discoloration, etc. The pH value before and after acceleration was measured with a pH meter, and the defoaming time was re-measured according to the aforementioned defoaming performance test method. The defoaming performance retention rate was calculated.

[0066] Table 2 Storage stability test results

[0067]

[0068] Demulsification and flocculation performance test: Select wastewater from Huachi Oilfield Station, measure 100mL of water sample and place it in a 250mL stoppered conical flask, add 0.005g of the defoamer sample to be tested, shake and mix up and down 20 times to ensure that the agent and water sample are in full contact, then place the conical flask in a 45℃ water bath and let it stand for 30 minutes to settle, take the clear liquid 2cm below the liquid surface, and measure the following indicators: oil content, suspended solids content, and COD.

[0069] Table 3 Results of demulsification and flocculation performance tests

[0070]

[0071] from Figure 1 It can be seen that the defoaming time of the examples is significantly shorter than that of Comparative Example 2, and the foam suppression is extremely low. This indicates that the present invention, through grafting modification and molecular assembly, introduces hydrophilic bactericidal and flocculating groups without affecting the spreading rate of the defoaming main chain. On the contrary, it achieves the effect of "rapid defoaming and long-lasting foam suppression" by enhancing dispersibility. Comparative Example 1 (physical mixing) showed a significant decrease in defoaming performance due to poor compatibility, proving the necessity of "chemical reaction assembly". Observing Table 1, it was found that the composite defoamer of the present invention has excellent antibacterial properties. Although Comparative Example 1 contains the same antibacterial components, it has not undergone the grafting, complexation and assembly process of the present invention, and each component exists in a free state, resulting in a significant decrease in antibacterial effect. Comparative Example 3 uses unmodified polyethyleneimine, which only shows weak antibacterial activity, proving that the introduction of the quaternary phosphonium salt structure is the core factor for endowing it with high-efficiency antibacterial properties. After accelerated testing at 54°C, the composite defoamers prepared in Examples 1-3 all maintained a defoaming performance retention rate of over 91%, had stable pH values, and exhibited a uniform appearance without stratification. Comparative Example 1 (physical mixing) exhibited severe stratification and performance degradation, demonstrating that the "grafting-complexing-electrostatic assembly" process successfully "anchored" each functional component within the system, ensuring the long-term stability of the product. Table 3 shows that Examples 1-3 significantly outperformed Comparative Examples 1-3 in treating oilfield wastewater, proving that the composite defoamer of this invention possesses excellent demulsification and flocculation functions. Comparative Example 2 showed almost no demulsification and flocculation effect, demonstrating that this invention successfully endowed the product with additional flocculation function by introducing propyl gallate, zinc lactate, and quaternary phosphonium salt-modified cationic polymers. Comparative Example 3, using unmodified polyethyleneimine, showed a significantly weaker demulsification and flocculation effect than Example 2, proving that quaternary phosphonium salt modification and molecular-level assembly significantly improved the flocculation efficiency of cationic polymers. While Comparative Example 1 had the same components as the examples, without the specific process of this invention, the components could not form a stable composite structure, resulting in a significant decrease in demulsification and flocculation effect, further demonstrating the crucial role of the preparation process in achieving synergistic effects.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0073] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A composite defoamer for wastewater treatment, characterized in that, The composite defoamer comprises the following raw materials in parts by weight: 10-25 parts of epoxy polyether modified polysiloxane, 2-6 parts of propyl gallate, 1-3 parts of zinc lactate, 3-8 parts of quaternary phosphonium salt modified cationic polymer, 0.1-0.5 parts of catalyst, 0.5-2 parts of buffer, 5-12 parts of environmentally friendly solvent, and 45-75 parts of deionized water; The epoxy-based polyether modified polysiloxane comprises the following raw materials: hydrogen-containing silicone oil, allyl polyoxyethylene ether, chloroplatinic acid, epichlorohydrin, and tetrabutylammonium bromide; The quaternary phosphonium salt modified cationic polymer is prepared by dehydration condensation of tetrahydroxymethylphosphonium sulfate and polyethyleneimine. The specific preparation method is as follows: (a) dissolve polyethyleneimine in deionized water to prepare a polymer solution; (b) heat the polymer solution and then add tetrahydroxymethylphosphonium sulfate to it and stir to react; (c) after the reaction is completed, distill under reduced pressure to obtain the quaternary phosphonium salt modified cationic polymer.

2. The composite defoamer for wastewater treatment according to claim 1, characterized in that, The preparation method of the epoxy polyether modified polysiloxane is as follows: add hydrogen-containing silicone oil, allyl polyoxyethylene ether and chloroplatinic acid to a reaction flask, react to obtain hydroxyl-terminated polyether modified polysiloxane, cool down and add epichlorohydrin and tetrabutylammonium bromide to it, react to obtain epoxy polyether modified polysiloxane.

3. The composite defoamer for wastewater treatment according to claim 2, characterized in that, The mass ratio of the hydrogen-containing silicone oil, allyl polyoxyethylene ether, chloroplatinic acid, epichlorohydrin and tetrabutylammonium bromide is 1:2:0.001:0.3:0.

005.

4. The composite defoamer for wastewater treatment according to claim 1, characterized in that, The mass ratio of tetrahydroxymethylphosphonium sulfate to polyethyleneimine is 1:3-5.

5. The composite defoamer for wastewater treatment according to claim 1, characterized in that, The catalyst is either triphenylphosphine or imidazole.

6. The composite defoamer for wastewater treatment according to claim 1, characterized in that, The buffer is a phosphate buffer.

7. The composite defoamer for wastewater treatment according to claim 1, characterized in that, The environmentally friendly solvent is any one of anhydrous ethanol, propylene glycol, and glycerin.

8. A method for preparing a composite defoamer for wastewater treatment according to any one of claims 1-7, characterized in that, Includes the following steps: S1 base material pre-dispersion: Mix environmentally friendly solvent with 1 / 3 weight of deionized water evenly, add epoxy polyether modified polysiloxane, and stir to obtain polysiloxane dispersion; S2 grafting reaction: Add a catalyst to the polysiloxane dispersion, adjust the pH of the system, then add propyl gallate and stir to react, to obtain a polysiloxane-polyphenol graft dispersion; S3 metal-polyphenol complexation reaction: Add a buffer to the polysiloxane-polyphenol graft dispersion, adjust the pH of the system, and then add zinc lactate for constant temperature reaction to obtain intermediate dispersion; S4 electrostatic synergistic assembly: The quaternary phosphonium salt modified cationic polymer was pre-dissolved in 1 / 3 of the weight of deionized water, and then slowly added dropwise to the intermediate dispersion. After the addition was completed, the overall pH of the system was slowly adjusted to 7.5-8.0 with a buffer, and the reaction was continued to be stirred to obtain the complex dispersion. S5 Stabilization and Dispersion: Add the remaining deionized water to the composite dispersion to adjust the solid content, continue stirring and then stop the reaction. After cooling and filtration, the composite defoamer for wastewater treatment is obtained.

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