A method for preparing a defoamer for wastewater treatment

Abstract

This invention discloses a method for preparing a defoamer for wastewater treatment, belonging to the technical field of wastewater treatment additive preparation. The defoamer comprises polyether-modified organosiloxane, dispersant, composite emulsifier, composite component, and water, obtained by mixing the emulsion of the polyether-modified organosiloxane with the composite component. The polyether-modified organosiloxane includes a siloxane-terminated polypropylene oxide prepolymer with a weight average molecular weight of 12,000, and 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, and further improving the defoaming performance and defoaming efficiency.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment additive preparation technology, specifically to a method for preparing a defoamer for wastewater treatment. Background Technology

[0002] Wastewater treatment involves using physical, chemical, and biological methods to purify wastewater, reduce pollution, recycle wastewater, and fully utilize water resources. High organic matter content in wastewater, sludge aging due to aeration and mixing, and the presence of various surfactants can all lead to foaming problems. Foaming can cause several problems: foam covering the water surface can easily overflow and pollute; it can affect normal wastewater treatment operations, including interfering with instrument displays, causing system malfunctions, creating false liquid level readings, and posing difficulties for the operation and management of wastewater treatment systems. For example, in the pulping process of papermaking, the natural substances such as fatty acids and resin acids contained in the pulping raw materials react with the added chemicals such as caustic soda and sodium sulfide to produce foaming substances such as fatty acid soaps and resin acid soaps. Meanwhile, the raw materials contain high molecular weight substances such as cellulose, which have a foam-stabilizing effect. This causes a large amount of stable foam to be generated during the flow and mixing of the pulp, which brings great difficulties to the subsequent washing, conveying, and bleaching processes, and causes floating pulp and reduces the quality of the pulp. At the same time, the black liquor obtained from the washing process in the pulping process also contains high concentrations of foaming and foam-stabilizing substances such as fatty acid soaps and resin acid soaps. The generation of foam is not conducive to the alkali recovery of the black liquor.

[0003] In recent years, research on defoamers has mainly focused on compound defoamers such as the combination of organosilicon compounds and surfactants, the combination of polyethers and organosilicones, and the combination of water-soluble or oil-soluble polyethers and silicone-containing polyethers. However, while the introduction of polyethers increases compatibility, it also reduces defoaming efficiency. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing a defoamer for wastewater treatment.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing an antifoaming agent for wastewater treatment includes the following steps:

[0007] S1. Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 100-150℃, keep warm and stir for 1-2 hours. After cooling to below 70℃, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained.

[0008] The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is (30-50):(6-12):(8-15):(48-65);

[0009] S2. The mixed emulsion is mixed with the composite components to obtain the desired product;

[0010] The composite component includes a first component, and the preparation method of the first component includes the following steps:

[0011] Weigh out polyethylene glycol derivative, alkyl carboxylic acid and tetrabutyl titanate respectively and mix them. Stir and react at 25-40℃ for 1-30 min to obtain a suspension. After sealing the suspension, keep it at 90-110℃ for 20-40 h and cool it to obtain the first component.

[0012] The polyethylene glycol derivative is polyethylene glycol, polyethylene glycol-acetic acid, polyethylene glycol-amino, or DOTA-polyethylene glycol-amino; the alkyl carboxylic acid is butyric acid, valeric acid, hexanoic acid, heptanoic acid, or octanoic acid.

[0013] In some preferred embodiments, the polyether-modified organosiloxane comprises 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, wherein the monomers of the polyether-terminated segments are ethylene oxide and propylene oxide.

[0014] In some preferred embodiments, the mixing mass ratio of the siloxane-terminated polypropylene oxide prepolymer to the polyether-modified silicone oil is (3-5):25.

[0015] In some preferred embodiments, the dispersant is nano-silica; the composite emulsifier is a mixture of one or more of Span-20, Span-60, Span-80, Tween-60, Tween-80 or AEO3 with a hydrophilic-lipophilic balance value between 7 and 10.

[0016] In some preferred embodiments, the mass ratio of the polyethylene glycol derivative to the alkyl carboxylic acid and the tetrabutyl titanate is 10:(0.1-0.2):(0.18-0.22).

[0017] In some preferred embodiments, the mixing mass ratio of the mixed emulsion to the first component is (2-4):1.

[0018] In some preferred embodiments, the composite component further includes a second component, the preparation method of which includes the following steps:

[0019] (1) Weigh 4,4'-biphenyldicarboxylic acid and dissolve it in a mixed solvent of dichloromethane and toluene. Under a protective atmosphere, add propylene oxide, Salen-Mn(III) and bis(triphenylphosphine)chloroimine as catalysts. After thorough mixing, stir the mixture under a protective atmosphere for 1-30 min. Then, switch the reaction atmosphere to carbon dioxide and continue stirring for 2-8 h. The reaction pressure is 1-10 bar. After the reaction is complete, add the active diluent XY680 and continue stirring the mixture under a carbon dioxide atmosphere for 2-8 h. After the reaction is complete, recrystallize the reaction product in neutral methanol and acidic methanol in sequence. Dissolve the crystallized product in tetrahydrofuran and then recrystallize it in anhydrous diethyl ether. The product is dried under vacuum to obtain the intermediate product.

[0020] (2) Dissolve the intermediate product in anhydrous tetrahydrofuran solvent, add mercaptoacetic acid and initiator, heat to 70-80°C under a protective atmosphere, keep warm and stir for 20-30 h, concentrate under reduced pressure after the reaction is completed, recrystallize in anhydrous diethyl ether, dissolve the product in tetrahydrofuran, add triethylamine and mix to obtain the second component.

[0021] In some preferred embodiments, the mass ratio of the 4,4'-biphenyldicarboxylic acid to the propylene oxide, the Salen-Mn(III), the bis(triphenylphosphine)chloroimine, and the reactive diluent XY680 is (3.6-4.2):10:(2.4-3.4):(1.7-2.3):(5.8-6.5); and the mass ratio of the intermediate product to the mercaptoacetic acid, the initiator, and the triethylamine is 10:(4-10):(0.5-0.7):(1-4).

[0022] In some preferred embodiments, the mass ratio of the first component to the second component is 1:(0.7-1.4).

[0023] Another aspect of the present invention is to provide a defoamer for wastewater treatment, wherein the defoamer for wastewater treatment is prepared by the aforementioned preparation method.

[0024] The beneficial effects of this invention are as follows:

[0025] To address the problem of low defoaming efficiency in existing wastewater treatment defoamers, this invention modifies existing polyether-modified organosiloxanes by performing component composite modification. This reduces the impact of polyether modification on the defoaming and foam-suppressing properties of the defoamer, thereby improving its defoaming performance and efficiency. Specifically, this invention uses polyethylene glycol derivatives and alkyl carboxylic acids as hydrophilic and hydrophobic assembly components, respectively. The first component is prepared by co-assembling these components with an organotitanium precursor. The assembled product possesses both amphiphilic surface activity and the porosity of a general assembly structure. In wastewater treatment, due to the low surface tension of the polyether-modified organosiloxane, the first component readily accumulates on the surface of the wastewater system and embeds itself within the foam. In the foam film, its porosity facilitates the continuous diffusion and permeation of gas within the bubbles under the pressure difference across the film, leading to the formation of larger bubbles and thus promoting bubble elimination and improving defoaming efficiency. Furthermore, due to the wide pH range of wastewater, conventional defoamers have limited pH resistance, restricting their application in various types of wastewater. This invention introduces a second component based on the aforementioned composite components, expanding the applicable pH range of the defoamer. Specifically, this invention uses biphenyl dicarboxylic acid as the center of symmetry, propylene oxide and carbon dioxide polymerization as the hydrophobic chain, and introduces a carboxylic acid-quaternary ammonium salt as a hydrophilic end and pH buffer site through a mercapto-olefin reaction, reducing the pH sensitivity of the defoamer and thus improving its pH resistance. Detailed Implementation

[0026] The present invention will be further described in conjunction with the following embodiments.

[0027] Example 1

[0028] A defoamer for wastewater treatment, the preparation method of which includes the following steps:

[0029] S1. Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 120°C, keep warm and stir for 1 hour. After cooling to below 70°C, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained.

[0030] The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is 40:9:11:55.

[0031] S2. The mixed emulsion and the composite components are mixed at a mass ratio of 3.2:1 to obtain the final product;

[0032] The composite component is composed of a first component, and the preparation method of the first component includes the following steps:

[0033] Polyethylene glycol-acetic acid, hexanoic acid, and tetrabutyl titanate were weighed and mixed, and stirred at room temperature for 2 min to obtain a suspension. The suspension was sealed and kept at 100°C for 24 h. After cooling, the first component was obtained. The mass ratio of polyethylene glycol-acetic acid to hexanoic acid and tetrabutyl titanate was 10:0.18:0.22.

[0034] The polyether-modified organosiloxane is a mixture of dual-terminated polyether-modified silicone oil and siloxane-terminated polypropylene oxide prepolymer in a mass ratio of 25:4. The dual-terminated polyether-modified silicone oil has a viscosity of 3000 mPa·s (25℃) and a cloud point of 45℃. The weight-average molecular weight of the siloxane-terminated polypropylene oxide prepolymer is 12000.

[0035] The dispersant is hydrophobic nano-silica; the composite emulsifier is a 1:1 mixture of sorbitan monostearate and polyoxyethylene sorbitan monostearate, with an HLB value of 8-9.

[0036] Example 2

[0037] A defoamer for wastewater treatment, the preparation method of which includes the following steps:

[0038] S1. Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 120°C, keep warm and stir for 1 hour. After cooling to below 70°C, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained.

[0039] The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is 40:9:11:55.

[0040] S2. The mixed emulsion and the composite components are mixed at a mass ratio of 3.2:1 to obtain the final product;

[0041] The composite component is composed of a second component, and the preparation method of the second component includes the following steps:

[0042] (1) Weigh 4,4'-biphenyldicarboxylic acid and dissolve it in a mixed solvent of dichloromethane and toluene (v / v = 1:1). Under a protective atmosphere, add propylene oxide, Salen-Mn(III) and bis(triphenylphosphine)chloroimine as catalysts. After thorough mixing, stir the mixture under a protective atmosphere for 5 min. Then, switch the reaction atmosphere to carbon dioxide and continue stirring for 4 h. The reaction pressure is 2 bar. After the reaction is complete, add the active diluent XY680 and continue stirring the mixture under a carbon dioxide atmosphere for 3 h. After the reaction is complete, recrystallize the reaction product in neutral methanol and acidic methanol in sequence. Dissolve the crystallized product in tetrahydrofuran and then recrystallize it in anhydrous diethyl ether. The product is dried under vacuum to obtain the intermediate product.

[0043] The mass ratio of the 4,4'-biphenyl dicarboxylic acid to the propylene oxide, the Salen-Mn(III), the bis(triphenylphosphine)chloroimine, and the reactive diluent XY680 is 4:10:2.9:2.1:6.2.

[0044] (2) Dissolve the intermediate product in anhydrous tetrahydrofuran solvent, add mercaptoacetic acid and azobisisobutyronitrile, heat to 70-80°C under a protective atmosphere, keep warm and stir for 24 hours, concentrate under reduced pressure after the reaction is completed, recrystallize in anhydrous diethyl ether, dissolve the product in tetrahydrofuran, add triethylamine and mix to obtain the second component.

[0045] The mass ratio of the intermediate product to the mercaptoacetic acid, the azobisisobutyronitrile, and the triethylamine is 10:6.4:0.5:3.1.

[0046] The polyether-modified organosiloxane is a mixture of dual-terminated polyether-modified silicone oil and siloxane-terminated polypropylene oxide prepolymer in a mass ratio of 25:4. The dual-terminated polyether-modified silicone oil has a viscosity of 3000 mPa·s (25℃) and a cloud point of 45℃. The weight-average molecular weight of the siloxane-terminated polypropylene oxide prepolymer is 12000.

[0047] The dispersant is hydrophobic nano-silica; the composite emulsifier is a 1:1 mixture of sorbitan monostearate and polyoxyethylene sorbitan monostearate, with an HLB value of 8-9.

[0048] Example 3

[0049] A defoamer for wastewater treatment, the preparation method of which includes the following steps:

[0050] S1. Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 120°C, keep warm and stir for 1 hour. After cooling to below 70°C, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained.

[0051] The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is 40:9:11:55.

[0052] S2. The mixed emulsion and the composite components are mixed at a mass ratio of 3.2:1.8 to obtain the final product.

[0053] The composite component consists of a first component and a second component in a mass ratio of 1:0.8. The preparation method of the first component is the same as in Example 1; the preparation method of the second component is the same as in Example 2.

[0054] The polyether-modified organosiloxane is a mixture of dual-terminated polyether-modified silicone oil and siloxane-terminated polypropylene oxide prepolymer in a mass ratio of 25:4. The dual-terminated polyether-modified silicone oil has a viscosity of 3000 mPa·s (25℃) and a cloud point of 45℃. The weight-average molecular weight of the siloxane-terminated polypropylene oxide prepolymer is 12000.

[0055] The dispersant is hydrophobic nano-silica; the composite emulsifier is a 1:1 mixture of sorbitan monostearate and polyoxyethylene sorbitan monostearate, with an HLB value of 8-9.

[0056] Example 4

[0057] A defoamer for wastewater treatment, the preparation method of which includes the following steps:

[0058] Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 120°C, keep warm and stir for 1 hour. After cooling to below 70°C, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained.

[0059] The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is 40:9:11:55.

[0060] The polyether-modified organosiloxane is a mixture of dual-terminated polyether-modified silicone oil and siloxane-terminated polypropylene oxide prepolymer in a mass ratio of 25:4. The dual-terminated polyether-modified silicone oil has a viscosity of 3000 mPa·s (25℃) and a cloud point of 45℃. The weight-average molecular weight of the siloxane-terminated polypropylene oxide prepolymer is 12000.

[0061] The dispersant is hydrophobic nano-silica; the composite emulsifier is a 1:1 mixture of sorbitan monostearate and polyoxyethylene sorbitan monostearate, with an HLB value of 8-9.

[0062] Experimental Example

[0063] Defoaming performance comparison: Foaming liquid was prepared according to GB / T26527-2011 "Organic Silicone Defoamer", and the defoaming performance was measured. The foaming force and foam suppression performance were measured using a circulating bubble meter.

[0064] Preparation of foaming solution: Weigh 5g of nonylphenol polyoxyethylene ether and 5g of sodium dodecylbenzenesulfonate and dissolve them in 990mL of water. Mix and stir until a uniform transparent liquid is formed. At the same time, adjust the pH to prepare acidic (pH=3), neutral (pH=7), and alkaline (pH=11) foaming solutions respectively.

[0065] Foaming power test: Thoroughly clean the instrument, pour 200 mL of foaming solution into a graduated cylinder, and maintain the water bath temperature at 40°C. Record the volume of foam formed after 80 s, 3 min, and 5 min of circulation bubbling. If the volume of foam is less than 800 mL after 5 min, it needs to be prepared again. If it exceeds 800 mL, record the volume of foam at 1 min, 2 min, and 3 min after circulation bubbling stops. If the foaming power of the test foaming solution is less than 800 mL after 3 min, it needs to be prepared again.

[0066] Defoaming performance test: Measure (50±0.5) mL of standard foaming solution with a stoppered graduated cylinder, add 0.2 g of defoamer, keep the temperature in a water bath to 50℃, stopper the bottle, shake the graduated cylinder vertically up and down 10 times and 100 times with an amplitude of (30~35) cm at a frequency of 2 times per second, let it stand and start timing with a stopwatch, record the time taken for the foam to disappear until the liquid surface appears, in seconds.

[0067] Defoaming performance test: When the foam height in the circulating bubbler reaches the 800mL mark, stop bubbling, add defoamer solution and start timing. After 1 minute, turn on the circulating bubbler and record the foam height at 30 minutes as the defoaming height.

[0068] The measurement results are as follows:

[0069]

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a defoamer for wastewater treatment, characterized in that, Includes the following steps: S1. Weigh out the polyether-modified organosiloxane and dispersant separately and mix them. Stir and heat to 100-150℃, keep warm and stir for 1-2 hours. After cooling to below 70℃, add the composite emulsifier and water and stir to emulsify. After cooling and standing, a mixed emulsion is obtained. The mass ratio of the polyether-modified organosiloxane to the dispersant, the composite emulsifier, and the water is (30-50):(6-12):(8-15):(48-65); S2. The mixed emulsion is mixed with the composite components to obtain the desired product; The composite component includes a first component, and the preparation method of the first component includes the following steps: Weigh out polyethylene glycol derivative, alkyl carboxylic acid and tetrabutyl titanate respectively and mix them. Stir and react at 25-40℃ for 1-30 min to obtain a suspension. After sealing the suspension, keep it at 90-110℃ for 20-40 h and cool it to obtain the first component. The polyethylene glycol derivative is polyethylene glycol, polyethylene glycol-acetic acid, polyethylene glycol-amino, or DOTA-polyethylene glycol-amino; the alkyl carboxylic acid is butyric acid, valeric acid, hexanoic acid, heptanoic acid, or octanoic acid.

2. The method for preparing a defoamer for wastewater treatment according to claim 1, characterized in that, 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, wherein the polymerizing monomers of the polyether-terminated segments are ethylene oxide and propylene oxide.

3. The method for preparing a defoamer for wastewater treatment according to claim 2, characterized in that, The mass ratio of the siloxane-terminated polypropylene oxide prepolymer to the polyether-modified silicone oil is (3-5):

25.

4. The method for preparing a defoamer for wastewater treatment according to claim 1, characterized in that, The dispersant is nano-silica; the composite emulsifier is a mixture of one or more of Span-20, Span-60, Span-80, Tween-60, Tween-80 or AEO3, with a hydrophilic-lipophilic balance value between 7 and 10.

5. The method for preparing a defoamer for wastewater treatment according to claim 1, characterized in that, The mass ratio of the polyethylene glycol derivative to the alkyl carboxylic acid and the tetrabutyl titanate is 10:(0.1-0.2):(0.18-0.22).

6. The method for preparing a defoamer for wastewater treatment according to claim 1, characterized in that, The mass ratio of the mixed emulsion to the first component is (2-4):

1.

7. The method for preparing a defoamer for wastewater treatment according to claim 1, characterized in that, The composite component further includes a second component, and the preparation method of the second component includes the following steps: (1) Weigh 4,4'-biphenyldicarboxylic acid and dissolve it in a mixed solvent of dichloromethane and toluene. Under a protective atmosphere, add propylene oxide, Salen-Mn(III) and bis(triphenylphosphine)chloroimine as catalysts. After thorough mixing, stir the mixture under a protective atmosphere for 1-30 min. Then, switch the reaction atmosphere to carbon dioxide and continue stirring for 2-8 h. The reaction pressure is 1-10 bar. After the reaction is complete, add the active diluent XY680 and continue stirring the mixture under a carbon dioxide atmosphere for 2-8 h. After the reaction is complete, recrystallize the reaction product in neutral methanol and acidic methanol in sequence. Dissolve the crystallized product in tetrahydrofuran and then recrystallize it in anhydrous diethyl ether. The product is dried under vacuum to obtain the intermediate product. (2) Dissolve the intermediate product in anhydrous tetrahydrofuran solvent, add mercaptoacetic acid and initiator, heat to 70-80°C under a protective atmosphere, keep warm and stir for 20-30 h, concentrate under reduced pressure after the reaction is completed, recrystallize in anhydrous diethyl ether, dissolve the product in tetrahydrofuran, add triethylamine and mix to obtain the second component.

8. The method for preparing a defoamer for wastewater treatment according to claim 7, characterized in that, The mass ratio of the 4,4'-biphenyldicarboxylic acid to the propylene oxide, the Salen-Mn(III), the bis(triphenylphosphine)chloroimine, and the reactive diluent XY680 is (3.6-4.2):10:(2.4-3.4):(1.7-2.3):(5.8-6.5); the mass ratio of the intermediate product to the mercaptoacetic acid, the initiator, and the triethylamine is 10:(4-10):(0.5-0.7):(1-4).

9. A method for preparing a defoamer for wastewater treatment according to claim 7, characterized in that, The mass ratio of the first component to the second component is 1:(0.7-1.4).

10. A defoamer for wastewater treatment, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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