Hydrophobic modified glycinin-based flocculant as well as preparation method and application thereof

Abstract

The invention belongs to the field of water and slurry treatment agents, and discloses a hydrophobic modified glycinin-based flocculant as well as a preparation method and application thereof. The preparation method comprises the following steps: dissociating soybean protein subunits under alkaline and nitrogen protection; pre-emulsified octenyl succinic anhydride or dodecyl glycidyl ether is added for a grafting reaction; adjusting the pH to terminate the reaction and aging; and washing and drying to obtain the product. The flocculant has a hydrophobic association three-dimensional network structure, can efficiently capture particles in water, generates a self-extrusion drainage effect in slurry dehydration, is high in dehydration efficiency and environment-friendly, and is suitable for purification of high-turbidity water and dehydration of building slurry.

Description

Technical Field

[0001] This invention belongs to the field of water and mud treatment agents, specifically relating to a hydrophobically modified soybean globulin-based flocculant, its preparation method, and its application. Background Technology

[0002] Flocculation, as the most crucial and efficient method in solid-liquid separation, is widely used to reduce water turbidity, achieve mud drying and volume reduction, and promote water resource recycling. However, currently widely used flocculation technologies still have significant limitations in terms of environmental friendliness and process adaptability.

[0003] Currently, the flocculants widely used in the industrial sector are still mainly synthetic organic polymers such as polyacrylamide (PAM) and its derivatives. Although these agents have strong bridging capabilities, their potential ecological risks have attracted significant attention: First, acrylamide monomers remaining during synthesis or generated during environmental degradation have significant neurotoxicity and teratogenicity, easily threatening human health through water reuse systems or soil infiltration; second, the carbon chain structure of these polymers is extremely stable and has poor biodegradability, leading to the accumulation of recalcitrant organic matter in the ecological chain with long-term use. To address this challenge, natural biomass-modified flocculants, represented by starch, cellulose, and chitosan, have been rapidly developed. However, these polysaccharide-modified biomass products often exhibit drawbacks such as a single adsorption mechanism and excessively rigid molecular chains when dealing with high-turbidity water and complex slurries, resulting in loose floc structures, poor shear resistance, and high water content. This is particularly problematic during mechanical pressure filtration dewatering, where floc breakage and filter cake adhesion to the filter cloth are common technical challenges.

[0004] Among numerous bio-based materials, soy protein isolate (SPI) stands out as an ideal monomer for preparing high-performance green flocculants due to its unique molecular architecture and high designability. Unlike single-chain linear polysaccharides such as sodium alginate and starch, soy protein is a globular protein aggregate composed of 7S (β-conglycinin) and 11S (glycinin) subunits with a complex quaternary structure. Its molecular chains are densely packed with various active sites, including amino, carboxyl, hydroxyl, and thiol groups, providing strong potential for chemical grafting. Developing a soy protein-based modified flocculant with excellent ecological safety and good treatment performance has significant technological and social value for ensuring the safety of water resource reuse and promoting the resource utilization of construction solid waste. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of low treatment efficiency of existing biomass flocculants and poor environmental friendliness of traditional synthetic flocculants, and provides a hydrophobically modified soybean globulin-based flocculant, its preparation method and application.

[0006] The preparation method provided in the first aspect of the present invention includes the following steps: S1: Prepare an aqueous solution of soy protein isolate with a mass concentration of 35-50 g / L, adjust the pH to 9.5-11.5 with an alkaline solution, and stir for at least 25 minutes at 45-55℃ under nitrogen protection. This alkaline condition and temperature control help the 7S and 11S globulin subunits to fully dissociate and expose their internal active sites, laying the foundation for efficient grafting.

[0007] S2: Under nitrogen protection, a pre-emulsified hydrophobic modified monomer emulsion and an activated catalyst are added to the system, and the grafting reaction is carried out at 45-55°C for 4.5-6 hours. The hydrophobic modified monomer is selected from octenyl succinic anhydride (OSA) or dodecyl glycidyl ether (AGE). The mass ratio of soy protein isolate to hydrophobic modified monomer is 1:(0.08-0.25). This step introduces the hydrophobic long chain into the protein backbone through covalent grafting, which is crucial for constructing the amphiphilic structure.

[0008] S3: Add an acidic neutralizing agent to adjust the pH of the system to 6.0-7.5 to terminate the reaction. The resulting product is allowed to stand at room temperature for 3-5 hours for aging. The pH adjustment induces the protein molecule to refold, encapsulate hydrophobic groups, and initially form hydrophobic microdomains. The aging process promotes the stability of the structure.

[0009] S4: Wash the intermediate with anhydrous ethanol or isopropanol, vacuum dry or freeze dry at 35-45℃, and then pulverize to obtain the final flocculant product. Washing removes unreacted monomers and byproducts to ensure product purity.

[0010] Preferably, the alkaline solution used in step S1 is at least one of sodium hydroxide, potassium hydroxide, or sodium carbonate solution.

[0011] Preferably, in step S2, the pre-emulsification treatment involves mixing the monomer with a nonionic surfactant (such as Tween-80) at a mass ratio of 5:1 to 10:1, and then dispersing the mixture by high-speed shearing and ultrasonication to form a microemulsion with a droplet size of 200-500 nm, so as to improve its dispersibility and reaction efficiency in protein aqueous solution.

[0012] Preferably, the activating catalyst used in step S2 is 4-dimethylaminopyridine (DMAP) or triethylamine, and the monomer emulsion is added in 10-15 minutes.

[0013] Preferably, the acid neutralizing agent used in step S3 is at least one of dilute hydrochloric acid, phosphoric acid, or citric acid.

[0014] A second aspect of this invention provides a hydrophobically modified soybean globulin-based flocculant prepared by the above method. This flocculant possesses a three-dimensional spatial network structure driven by hydrophobic association, giving it unique amphiphilic properties in aqueous solutions.

[0015] A third aspect of this invention provides the application of the above-mentioned flocculant for the purification of high-turbidity water or the deep dewatering of high-cement-content slurry (such as construction waste slurry and tunnel boring machine slurry). When used for slurry dewatering, it is recommended to prepare the flocculant into an aqueous solution with a mass fraction of 0.1%-0.5% and add it to the slurry system at a dosage of 10-60 mg / L.

[0016] The beneficial effects of this invention include: (1) Enhanced dewatering efficiency for high cement content slurry: This invention introduces hydrophobic functional groups on the soybean protein skeleton to construct a hydrophobic association network with physical cross-linking properties. During the slurry treatment process, this structure can not only form large-sized flocs through bridging, but also induce spontaneous collapse inside the flocs during the mechanical pressure filtration stage, expelling the capillary water trapped inside the particle gaps, significantly reducing the moisture content of the slurry cake, and solving the problem of high viscosity and difficult dewatering of traditional biomass flocculants.

[0017] (2) Optimized the utilization efficiency and conformational stability of soybean protein: Unlike simple surface adsorption modification, this invention uses pH to induce the unfolding and directional grafting of 7S and 11S globulin subunits, which preserves the flexibility of the long protein chain to the greatest extent; the hydrophobic association gives the flocculant stronger shear resistance, so that the generated flocs can still maintain structural integrity and are not easily broken and re-dissolved when subjected to high-intensity pumping or pressure filtration shear.

[0018] (3) It has extremely high industrial reuse safety and environmental protection value: the flocculant base is natural soybean protein and the degradation products are amino acids. It is not only environmentally friendly, but also will not introduce the toxic monomer residues or cumulative metal ions (such as aluminum ions) that may remain in traditional PAM agents when applied to industrial water reuse systems. This fundamentally eliminates the potential safety hazards of reused water to subsequent production processes (such as building material quality or industrial synthesis). Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 A flowchart illustrating the preparation method of the hydrophobically modified soybean globulin-based flocculant provided in this embodiment of the invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] Please see Figure 1 As shown, this invention provides a method for preparing a hydrophobically modified soybean globulin-based flocculant, comprising the following steps: S1: Prepare an aqueous solution of soy protein isolate with a mass concentration of 35-50 g / L, adjust the pH to 9.5-11.5 with an alkaline solution, and stir for at least 25 minutes at 45-55℃ under nitrogen protection; S2: Under nitrogen protection, add the pre-emulsified hydrophobic modified monomer emulsion and activated catalyst to the system of step S1, and carry out the grafting reaction at 45-55℃ for 4.5-6 hours. The hydrophobic modified monomer is selected from octenyl succinic anhydride or dodecyl glycidyl ether, and the mass ratio of soy protein isolate to hydrophobic modified monomer is 1: (0.08-0.25). S3: Add an acidic neutralizing agent to adjust the pH of the system to 6.0-7.5 to terminate the reaction. Let the resulting product stand at room temperature for 3-5 hours to age and obtain the intermediate. S4: The intermediate is washed with an organic solvent, dried at 35-45°C and pulverized to obtain the hydrophobic modified soybean globulin-based flocculant.

[0022] In step S1, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide, or sodium carbonate solution.

[0023] In step S2, the pre-emulsification treatment is as follows: hydrophobic modified monomers and nonionic surfactants are mixed at a mass ratio of 5:1-10:1, and then dispersed by high-speed shearing and ultrasonication to form a microemulsion with a droplet size of 200-500 nm.

[0024] The nonionic surfactant is selected from at least one of Tween-20, Tween-80, Span-20, Span-80 or polyethylene glycol.

[0025] In step S2, the activating catalyst is 4-dimethylaminopyridine or triethylamine; the hydrophobic modified monomer emulsion is added over a period of 10-15 minutes.

[0026] In step S3, the acid neutralizing agent is at least one of dilute hydrochloric acid, phosphoric acid, or citric acid.

[0027] In step S4, the organic solvent is anhydrous ethanol or isopropanol; the drying is vacuum drying or freeze drying.

[0028] The present invention also provides a hydrophobically modified soybean globulin-based flocculant, which is prepared by the aforementioned preparation method.

[0029] Furthermore, the flocculant can form a three-dimensional network structure in an aqueous system through hydrophobic association.

[0030] The present invention also provides an application of the hydrophobically modified soybean globulin-based flocculant for the purification of high-turbidity water or the deep dewatering of high-cement-content slurry; when used for the deep dewatering of high-cement-content slurry, the flocculant is prepared into an aqueous solution with a mass fraction of 0.1%-0.5% and added at a dosage of 10-60 mg / L; the high-cement-content slurry includes construction waste mud and shield tunneling mud.

[0031] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0032] Example 1: Preparation of Octenylsuccinic Anhydride (OSA) Modified Flocculant and its Application in High Turbidity Water Treatment Preparation: Weigh 40g of soy protein isolate (SPI) and dissolve it in 1L of deionized water to prepare a 40 g / L solution. Adjust the pH to 10.5 with 2.0 mol / L NaOH. Incubate the solution in a 50℃ water bath with stirring at 300 rpm, then purge with nitrogen gas for 30 minutes to fully expose the active sites of the protein.

[0033] A microemulsion was prepared by emulsifying 4g OSA and 0.4g Tween-80 under high-speed shear for 15 minutes. Under nitrogen protection, 0.1g DMAP catalyst was first added to the SPI solution, followed by the addition of the OSA emulsion over 12 minutes. The reaction was carried out at 50°C for 5 hours to achieve efficient and uniform grafting of hydrophobic monomers.

[0034] After the reaction was completed, 1.0 mol / L citric acid was added dropwise to adjust the pH to 7.0 to terminate the reaction. The mixture was then allowed to stand at room temperature for 4 hours to age, inducing the formation of a stable hydrophobic microdomain structure.

[0035] Add 3 times the volume of anhydrous ethanol to the aged product to precipitate, filter, and wash 3 times with ethanol. Dry the solid under vacuum at 40°C to constant weight, pulverize and pass through a 100-mesh sieve to obtain flocculant SPI-OSA-1, finally obtaining a pure and easy-to-store solid product.

[0036] Application Test: Mine wastewater with an initial turbidity of 1200 NTU was collected. SPI-OSA-1 was prepared into a 0.2% solution and added at a concentration of 12 mg / L. The results showed that the effluent turbidity decreased to 17.8 NTU, the removal rate reached 98.5%, and the flocs were large, dense, and settled quickly.

[0037] Example 2: Preparation of dodecyl glycidyl ether (AGE) modified flocculant and slurry dewatering Preparation: Weigh 50g of SPI and dissolve it in 1L of deionized water (50 g / L). Adjust the pH to 11.0 with NaOH. Stir at 55℃ and purge with nitrogen for 40 minutes. Under nitrogen protection, add 1.5g of triethylamine. Slowly add 10g of AGE after ultrasonic emulsification (SPI to monomer mass ratio 1:0.2), and react at 55℃ for 6 hours. Terminate the reaction by adjusting the pH to 6.8 dropwise with dilute hydrochloric acid, and allow to stand for 5 hours. Wash the precipitate with isopropanol, dry under vacuum at 45℃, and grind to obtain flocculant SPI-AGE-2.

[0038] Application Test: A sample of tunnel boring machine (TBM) slurry (initial moisture content 260%) was taken. A 0.5% SPI-AGE-2 solution was prepared and added at 45 mg / L. After rapid stirring for 1 minute, the mixture was filtered. After 15 minutes of filtration, the moisture content of the filter cake decreased to 62%, the filtrate was clear, and the filter cloth did not stick.

[0039] Comparative Example 1 The wastewater in Example 1 was treated using unmodified SPI at a dosage of 12 mg / L. The effluent turbidity was 145 NTU, the removal rate was 87.9%, the flocs were small and loose, the settling was slow, and the effluent COD increased.

[0040] Comparative Example 2 The slurry in Example 2 was treated with commercially available cationic polyacrylamide (CPAM, molecular weight 12 million) at a dosage of 45 mg / L. After filtration for 15 minutes, the slurry cake had a moisture content of 86%, exhibited strong viscoelasticity, and was difficult to peel off.

[0041] The above embodiments demonstrate that the flocculant provided by the present invention is significantly superior to unmodified natural proteins and traditional synthetic flocculants in terms of flocculation efficiency and dehydration performance.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrophobically modified soybean globulin-based flocculant, characterized in that, Includes the following steps: S1: Prepare an aqueous solution of soy protein isolate with a mass concentration of 35-50 g / L, adjust the pH to 9.5-11.5 with an alkaline solution, and stir for at least 25 minutes at 45-55℃ under nitrogen protection; S2: Under nitrogen protection, add the pre-emulsified hydrophobic modified monomer emulsion and activated catalyst to the system of step S1, and carry out the grafting reaction at 45-55℃ for 4.5-6 hours. The hydrophobic modified monomer is selected from octenyl succinic anhydride or dodecyl glycidyl ether, and the mass ratio of soy protein isolate to hydrophobic modified monomer is 1: (0.08-0.25). S3: Add an acidic neutralizing agent to adjust the pH of the system to 6.0-7.5 to terminate the reaction. Let the resulting product stand at room temperature for 3-5 hours to age and obtain the intermediate. S4: The intermediate is washed with an organic solvent, dried at 35-45°C and pulverized to obtain the hydrophobic modified soybean globulin-based flocculant.

2. The method for preparing the hydrophobically modified soybean globulin-based flocculant according to claim 1, characterized in that, In step S1, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide, or sodium carbonate solution.

3. The preparation method of the hydrophobically modified soybean globulin-based flocculant according to claim 1, characterized in that, In step S2, the pre-emulsification treatment is as follows: hydrophobic modified monomers and nonionic surfactants are mixed at a mass ratio of 5:1-10:1, and then dispersed by high-speed shearing and ultrasonication to form a microemulsion with a droplet size of 200-500 nm.

4. The preparation method of the hydrophobically modified soybean globulin-based flocculant according to claim 3, characterized in that, The nonionic surfactant is selected from at least one of Tween-20, Tween-80, Span-20, Span-80, or polyethylene glycol.

5. The method for preparing the hydrophobically modified soybean globulin-based flocculant according to claim 1, characterized in that, In step S2, the activating catalyst is 4-dimethylaminopyridine or triethylamine; the hydrophobic modified monomer emulsion is added over a period of 10-15 minutes.

6. The method for preparing the hydrophobically modified soybean globulin-based flocculant according to claim 1, characterized in that, In step S3, the acid neutralizing agent is at least one of dilute hydrochloric acid, phosphoric acid, or citric acid.

7. The method for preparing the hydrophobically modified soybean globulin-based flocculant according to claim 1, characterized in that, In step S4, the organic solvent is anhydrous ethanol or isopropanol; the drying is vacuum drying or freeze drying.

8. A hydrophobically modified soybean globulin-based flocculant, characterized in that, It is prepared by the method of any one of claims 1 to 7 for preparing the hydrophobic modified soybean globulin-based flocculant.

9. The hydrophobically modified soybean globulin-based flocculant according to claim 8, characterized in that, It can form a three-dimensional network structure in aqueous systems through hydrophobic association.

10. The application of the hydrophobically modified soybean globulin-based flocculant as described in claim 8 or 9, characterized in that, It is used for the purification of high turbidity water or the deep dewatering of high cement content slurry; when used for the deep dewatering of high cement content slurry, the flocculant is prepared into an aqueous solution with a mass fraction of 0.1%-0.5% and added at a dosage of 10-60 mg / L; the high cement content slurry includes construction waste mud and shield tunneling mud.

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