Tentacle-type dication modified tannin-based organic flocculant as well as preparation method and application of whisker-type dication modified tannin-based organic flocculant

Abstract

The invention relates to the technical field of water treatment, in particular to a whisker type dication modified tannin-based organic flocculant as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) adding tetrabutylphosphonium bromide into an alkaline solution of tannic acid, and reacting at 50-80 DEG C for 2-4 hours; (2) dispersing the precipitate in water, continuously introducing nitrogen, adding a first free radical initiator at 50-80 DEG C for reaction, then adding dimethyl diallyl ammonium chloride and a second free radical initiator, and reacting for 2-4 hours; and (3) extracting by using a mixed solution of acetone and ethanol to obtain a precipitation product, filtering and washing to obtain the product. The quaternary phosphonium salt and the quaternary ammonium salt which have strong cationic property and good water solubility are grafted to the tannic acid step by step, so that the water solubility and the flocculation effect of the tannic acid are remarkably improved, meanwhile, the biodegradability and the environmental friendliness of the tannic acid are kept, and the technical effects of efficiently removing algae and cooperatively removing algal toxins can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a tentacle-type dicationically modified tannin-based organic flocculant and a preparation method and application thereof. Background Art

[0002] In recent years, eutrophication of water bodies has occurred frequently. The "2022 China Environmental Bulletin" pointed out that among the 204 key lakes (reservoirs) for nutrient status monitoring, lakes (reservoirs) in eutrophic and mesotrophic states accounted for 29.9% and 60.3% respectively. In water supply treatment with surface water as the water source, the excessive reproduction of algae caused by eutrophication of water bodies in summer poses a serious threat to the water supply safety of water plants. As algae grow, reproduce and die, the released algal toxins continue to enter the water body, further affecting the water quality of the water supply. Algal toxins are secondary metabolites of algae, which have a strong carcinogenic (liver cancer) effect. Once ingested by the human body, they can cause damage to the liver, kidneys, gastrointestinal tract, reproductive system, immune system and nervous system. How to efficiently remove algal toxins in the algae removal process is a difficult problem in the field of water treatment.

[0003] At present, the commonly used algae removal processes mainly include filtration algae removal, biological algae removal and chemical algae removal. Chemical algae removal mainly includes algaecide algae removal, oxidant algae removal and coagulant algae removal. It does not require additional structures and is easy to operate, and has received widespread attention. However, commonly used algaecides contain copper, which is harmful to human health; oxidants can cause algae cell lysis, leading to the release of intracellular algae toxins and increasing the generation potential of disinfection by-products. Coagulant algae removal has the advantages of low cost, high algae removal efficiency, low algae cell damage rate, and no toxic and harmful intermediates. It is currently the most widely used process in water plants. Traditional coagulation processes can effectively remove algae cells, suspended particles, colloidal substances and macromolecular organic matter, but the removal effect of algae toxins with small molecular weight and high solubility is poor. Coagulation is the most commonly used primary treatment unit in conventional water plants, and the coagulation efficiency directly affects the operating load of all downstream treatment units. Therefore, breaking through the bottleneck problem of poor removal effect of coagulation process on algae toxins is the most economical and simple strategy to improve water quality.

[0004] Tannic acid, as a polyphenolic compound, has abundant phenolic hydroxyl groups and good biodegradability, and can effectively remove algae cells through allelopathic action. It can combine with biomacromolecules such as proteins, enzymes, nucleic acids on the surface and inside of algae cells, interfere with cell material transport, metabolic regulation, gene expression and protein synthesis, inhibit algae growth and reproduction, and reduce the production of intracellular organic matter and algae toxins from the source; it can also cross-link with algae cell walls and cell membrane components, interfere with algae photosynthesis, reduce light energy absorption and conversion efficiency by affecting related pigments, proteins and electron transport chains, inhibit algae from obtaining energy and substances, and thus reduce algae toxin synthesis and release.

[0005] However, the uneven molecular weight distribution and inherent electrical defects of tannic acid seriously limit its practical application in the field of flocculation and algae removal. The molecular weight of tannic acid is usually in the range of 500-3000 Da, and its flocculation performance is nonlinearly related to the molecular weight. Low molecular weight tannic acid cannot effectively bridge multiple algae cells to form large-sized flocs due to its short molecular chain, resulting in low flocculation efficiency; while high molecular weight components have longer molecular chains and more adsorption sites, but their solubility in water is significantly reduced, making it difficult to quickly diffuse to the surface of algae cells. At the same time, too high a molecular weight will induce a "steric hindrance effect". After adsorption, the tannic acid molecules hinder the adjacent algae cells from approaching due to their large size, and instead inhibit the aggregation of flocs.

[0006] The electrical properties of natural tannic acid are closely related to the dissociation state of its phenolic hydroxyl groups. In neutral water bodies, the phenolic hydroxyl groups of tannic acid partially dissociate, and the surface exhibits a weak negative charge, while algal cells usually carry a strong negative charge due to the presence of carboxylic acid groups and sulfate groups. This like-charge repulsion effect leads to the lack of electrostatic attraction between tannic acid and algal cells, and adsorption relies solely on hydrogen bonds and hydrophobic effects. The binding energy is much lower than the electrostatic effect, resulting in the need to increase the amount of flocculant several times to achieve the same effect. In addition, the electrical properties of tannic acid are highly sensitive to pH. Under acidic conditions, the phenolic hydroxyl group is protonated to make its electrical properties close to neutral. Although it can improve the flocculation efficiency, the strong acidic environment can easily destroy the algal cell wall, induce the release of intracellular toxins, and cause the risk of secondary pollution. These factors combined lead to the unstable flocculation effect of tannic acid when used alone, which is difficult to meet the requirements of high efficiency and stability of flocculants in actual industrial wastewater treatment and other scenarios, thus limiting its wide application in the field of flocculants. Summary of the invention

[0007] In order to solve the technical problem that tannic acid has poor effect when used alone as a flocculant, the present invention provides a tentacle-type dicationic modified tannin-based organic flocculant and a preparation method and application thereof. By grafting quaternary phosphonium salts and quaternary ammonium salts with strong cationicity and good water solubility onto tannic acid in steps, the flocculation effect of tannic acid is significantly improved while maintaining its biodegradability and environmental friendliness, thereby achieving the technical effect of efficient algae removal and synergistic removal of algae toxins.

[0008] In a first aspect, the present invention provides a method for preparing a tentacle-type dicationically modified tannin-based organic flocculant, comprising the following steps: (1) Add tetrabutylphosphonium bromide to an alkaline solution of tannic acid, react at 50-80°C for 2-4 hours, precipitate in an acetone solution, and remove the lower precipitate for washing; (2) dispersing the precipitate in water, continuously introducing nitrogen, adding a first free radical initiator to react at 50-80°C, and then adding dimethyldiallylammonium chloride and a second free radical initiator to react for 2-4 hours; (3) Extract the precipitated product with a mixture of acetone and ethanol, filter and wash.

[0009] Furthermore, in step (1), the alkaline solution of tannic acid is prepared by dissolving tannic acid in a NaOH solution having a concentration of 0.1-0.5 mol / L.

[0010] Furthermore, in step (1), the lower layer of precipitate is washed with ethanol and then washed with deionized water.

[0011] Furthermore, in step (1), the amount of tetrabutylphosphonium bromide added is 0.5-2 mol / mol based on the amount of tannic acid.

[0012] Furthermore, in step (2), the amount of the first free radical initiator added is 0.01-0.1 g / 5 g based on the mass of tannic acid; Based on the mass of tannic acid, the added amount of the second free radical initiator is 0.01-0.1 g / 5 g.

[0013] Furthermore, in step (2), after the first free radical initiator is added, the reaction is continued for 20-40 minutes before adding dimethyldiallylammonium chloride and the second free radical initiator.

[0014] Furthermore, in step (2), the amount of dimethyldiallylammonium chloride added is 1-5 mol / mol based on the amount of tannic acid.

[0015] Furthermore, in step (2), the precipitate is dispersed in water and heated to 50-80° C. in a water bath.

[0016] Further, the first free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate; The second free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate.

[0017] Furthermore, the preparation method of the tentacle-type dicationically modified tannin-based organic flocculant is specifically as follows: (1) Dissolve tannic acid in 170 mL of 0.3 mol / L sodium hydroxide solution, add tetrabutylphosphonium bromide to the alkaline solution of tannic acid, the molar ratio of tetrabutylphosphonium bromide to tannic acid is 1:1, react at 70°C for 3 hours, cool to room temperature, precipitate in acetone solution, remove the lower precipitate, wash with ethanol, and then wash with deionized water 3 times; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced, and the first portion of potassium persulfate was added. The mass ratio of the first portion of potassium persulfate to tannic acid was 0.03:5. After reacting for 20 min, dimethyldiallyl ammonium chloride and the second portion of potassium persulfate were added. The molar ratio of dimethyldiallyl ammonium chloride to tannic acid was 3:1. The mass ratio of the second portion of potassium persulfate to tannic acid was 0.03:5. The reaction was continued for 4 hours. (3) After the reaction is completed, cool to room temperature, extract the precipitated product with a mixture of acetone and ethanol, filter and wash to obtain the product.

[0018] In a second aspect, the present invention provides a tentacle-type dicationically modified tannin-based organic flocculant prepared by the preparation method.

[0019] In a third aspect, the present invention also provides a use of the above-mentioned tentacle-type dicationically modified tannin-based organic flocculant in treating algae liquid.

[0020] The synthesis mechanism of the tentacle-type dicationically modified tannin-based organic flocculant of the present invention is to completely or partially replace the H in each phenolic hydroxyl group of tannic acid with a quaternary phosphonium salt (tetrabutylphosphonium bromide) or a quaternary ammonium salt (dimethyldiallylammonium chloride). The specific synthesis route is as follows: .

[0021] The beneficial effects of the present invention are: 1. The present invention uses tannic acid as a raw material, and grafts quaternary phosphonium groups and quaternary ammonium groups by a two-step method to prepare an organic polymer flocculant with high-efficiency flocculation performance, environmental friendliness and structural stability. Compared with the problems of low grafting rate and insufficient product stability in a single reaction system, the present invention covalently bonds quaternary phosphonium salt (tetrabutylphosphonium bromide) with the phenolic hydroxyl group of tannic acid to form a rigid short-chain quaternary phosphonium group to enhance the charge neutralization ability; and grafts quaternary ammonium salt (dimethyldiallyl ammonium chloride) by free radical polymerization to form a flexible long-chain "tentacle" structure, which provides adsorption charge neutralization, bridging function and hydrophobic association, and enhances the density of sludge flocs. Therefore, the tentacle-type double cationic modified tannin-based organic flocculant provided by the present invention has a "rigid core-flexible tentacle" network, which can significantly improve the removal efficiency of algal cells and algal toxins through the synergistic mechanism of "charge neutralization-bridging-netting".

[0022] 2. The quaternary phosphonium and quaternary ammonium cations in the organic flocculant of the present invention can quickly adsorb the negatively charged algae cell surface through ionic bonds and hydrogen bonds, destroying the stability of the cell membrane; the long chain of polymerized dimethyldiallylammonium chloride can combine with the hydrophobic structure of algae toxins (such as microcystins) and detoxify through hydrophobic action. The tentacle-type structure forms a three-dimensional network, which enhances the ability to encapsulate algae cell clusters and toxins, and has a stable treatment effect on high turbidity and high organic matter water bodies. At the same time, the quaternary phosphonium group and the quaternary ammonium group maintain high charge density under acidic to alkaline conditions, so the pH application range of the flocculant can be expanded to 2-10.

[0023] 3. The main raw material tannic acid used in the present invention is a renewable resource, and the degradation product is non-toxic, thus avoiding secondary pollution. The flocculant has high biocompatibility, and the sludge is easy to dehydrate and can be recycled. Moreover, the monomers of tannic acid, quaternary phosphonium salt and quaternary ammonium salt are all commercially available products, and the cost is controllable. The preparation process is simple, does not require complex equipment, and has mild reaction conditions, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 In a specific embodiment, OD 680 Standard curve for measuring the density of Microcystis aeruginosa.

[0026] Figure 2 This is a transmission electron microscope photograph of the tentacle-type dicationically modified tannin-based organic flocculant of Example 8.

[0027] Figure 3 This is the removal rate curve of algae cells by the tentacle-type dicationic modified tannin-based organic flocculant of Example 8 at different dosages.

[0028] Figure 4 This is the removal rate curve of algae toxins at different dosages of the tentacle-type double cationic modified tannin-based organic flocculant of Example 8.

[0029] Figure 5 This is a scanning electron microscope photograph of flocs after coagulation of the tentacle-type dicationically modified tannin-based organic flocculant of Example 8. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] A method for preparing a tentacle-type dicationically modified tannin-based organic flocculant comprises the following steps: (1) Add tetrabutylphosphonium bromide to an alkaline solution of tannic acid, react at 50-80°C for 2-4 hours, precipitate in an acetone solution, and remove the lower precipitate for washing; (2) dispersing the precipitate in water, continuously introducing nitrogen, adding a first free radical initiator to react at 50-80°C, and then adding a quaternary ammonium salt and a second free radical initiator, and reacting for 2-4 hours; (3) Extracting with a mixture of acetone and ethanol to obtain a precipitated product, filtering and washing to obtain the product; Wherein, the quaternary phosphonium salt is tetrabutylphosphonium bromide, and the quaternary ammonium salt is dimethyldiallylammonium chloride.

[0032] As a preferred embodiment of the present invention, in step (1), the alkaline solution of tannic acid is prepared by dissolving tannic acid in a NaOH solution with a concentration of 0.1-0.5 mol / L. Tannic acid molecules contain a large number of phenolic hydroxyl groups (-OH). Under alkaline conditions, the hydroxide ions (OH⁻) provided by NaOH can promote the dissociation of phenolic hydroxyl groups into phenolic oxide anions (-O⁻). This ionized form significantly enhances the nucleophilicity of phenolic hydroxyl groups, making it easier to undergo nucleophilic substitution reactions with quaternary phosphonium groups in tetrabutylphosphonium bromide, thereby improving the grafting efficiency of quaternary phosphonium groups. Controlling the NaOH concentration at 0.1-0.5 mol / L can ensure sufficient generation of phenolic oxide anions and avoid excessive alkalinity leading to destruction of the tannic acid structure, thereby balancing the reaction activity and product stability.

[0033] As a preferred embodiment of the present invention, in step (1), ethanol is used to wash the lower precipitate, and then deionized water is used to wash it. Ethanol can effectively remove the residual reaction impurities and acetone in the precipitate, and deionized water further washes ethanol and other water-soluble impurities, thereby improving the purity of the product, ensuring that the subsequent reaction proceeds smoothly, and avoiding the adverse effects of impurities on the product performance.

[0034] As a preferred embodiment of the present invention, in step (1), the amount of tetrabutylphosphonium bromide added is 0.5-2 mol / mol, based on the amount of tannic acid. Within this addition amount range, it can ensure that an appropriate amount of tetrabutylphosphonium bromide is fully covalently bonded to the phenolic hydroxyl group of tannic acid to form a sufficient number of rigid short-chain quaternary phosphine groups. If the addition amount is too small, the number of quaternary phosphine groups is insufficient and the charge neutralization ability is limited; if the addition amount is too large, it may cause a waste of raw materials and affect the product structure and performance.

[0035] As a preferred embodiment of the present invention, in step (2), the amount of the first free radical initiator added is 0.01-0.1 g / 5 g, based on the mass of tannic acid. This dosage range can effectively initiate free radical polymerization reaction and promote the successful grafting of dimethyldiallylammonium chloride onto the tannic acid derivative. The amount of the second free radical initiator added is 0.01-0.1 g / 5g, which can effectively initiate the chain growth process and form a flexible long-chain "tentacle" structure. If the amount added is too small, the initiation efficiency is low and the grafting reaction is incomplete; if the amount added is too large, the reaction is too violent, which may lead to uneven molecular weight distribution of the product and homopolymerization of the organic monomer, affecting the performance of the flocculant.

[0036] As a preferred embodiment of the present invention, in step (2), the first free radical initiator is added and reacted for 20-40 minutes before adding dimethyldiallyl ammonium chloride and the second free radical initiator. The time interval of this reaction can allow the first free radical initiator to fully initiate the active sites on the tannic acid derivative, and when dimethyldiallyl ammonium chloride and the second free radical initiator are subsequently added, chain polymerization and chain growth reactions can be carried out more efficiently, ensuring the orderly construction of the flexible long chain "tentacle" structure and improving the product quality.

[0037] As a preferred embodiment of the present invention, in step (2), the amount of dimethyldiallylammonium chloride added is 1-5 mol / mol, based on the amount of tannic acid. This amount can ensure the formation of flexible long-chain "tentacles" of sufficient length and quantity, providing sufficient adsorption sites and bridging functions for the flocculant. If the amount added is too little, the "tentacle" structure is insufficient, and the adsorption and bridging effects are weak; if the amount added is too much, it may lead to side effects such as overly complex product structure, high homopolymer content, and long chain agglomeration, affecting solubility and flocculation effect.

[0038] As a preferred embodiment of the present invention, in step (2), the precipitate is dispersed in water and heated to 50-80° C. by water bath heating. Water bath heating can heat the reaction system evenly, facilitate accurate control of the reaction temperature at 50-80° C., provide a stable and suitable reaction environment for the free radical polymerization reaction, and help ensure the consistency of the reaction and the stability of the product, thereby improving the product quality.

[0039] As a preferred embodiment of the present invention, the first free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate; the second free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate. These free radical initiators can effectively decompose and generate free radicals in the reaction system to initiate the polymerization reaction of tannic acid derivatives and quaternary ammonium salts. They are stable in nature, high initiation efficiency, and have good compatibility with other components of the system under reaction conditions, which helps to ensure the reliability of the preparation process and the stability of product performance.

[0040] A tentacle-type dicationic modified tannin-based organic flocculant prepared by the above preparation method can be used for treating algae liquid, and the treatment work specifically refers to removing algae cells and / or algae toxins in the algae liquid.

[0041] Example 1 Coagulation efficiency of tentacle-type organic flocculants under different pH conditions (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, dimethyldiallyl ammonium chloride solution was added, based on the amount of tannic acid, the amount of dimethyldiallyl ammonium chloride added was 2 mol / mol, 0.03 g potassium persulfate was added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type dicationically modified tannin-based organic flocculant.

[0042] According to the same preparation method, the concentration of the sodium hydroxide aqueous solution in step (1) was adjusted to 0.1 mol / L, 0.2 mol / L, 0.4 mol / L or 0.5 mol / L to obtain five groups of different tentacle-type dicationic modified tannin-based organic flocculants, and their treatment effects on algae liquid were compared to determine the optimal concentration of the sodium hydroxide aqueous solution in step (1). The specific method is as follows: To 10 7After adding 30 mg / L of tentacle-type organic flocculant to 100 cell / mL Microcystis aeruginosa liquid (pH=8.5±0.5), stir at 250 r / min for 1 min, then at 35 r / min for 15 min, and then settle for 30 min. After sedimentation, take the supernatant and measure OD with a UV spectrophotometer. 680 , through the standard curve (such as Figure 1 The algae cell concentration after treatment was calculated by HPLC-MS / MS, and the removal rate was calculated. The algae toxin content was detected by HPLC-MS / MS. The results are shown in Table 1.

[0043] Table 1 Coagulation effect of organic flocculants at different sodium hydroxide aqueous solution concentrations

[0044] The results show that when the concentration of the sodium hydroxide aqueous solution in step (1) is 0.3 mol / L, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0045] Example 2 On the basis of Example 1, the concentration of the sodium hydroxide aqueous solution in step (1) was selected to be 0.3 mol / L, and then the amount of tetrabutylphosphonium bromide added in step (1) was adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, adding tetrabutylphosphonium bromide solution, based on the amount of tannic acid, the amount of tetrabutylphosphonium bromide added is 0.5 mol / mol, 1 mol / mol, 1.5 mol / mol or 2 mol / mol, controlling the reaction temperature at 70°C, and reacting for a total of 3 hours; after the reaction is completed, cooling to room temperature, precipitating in acetone solution, taking the lower precipitate, washing with ethanol, and then washing with deionized water three times; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, dimethyldiallyl ammonium chloride was added in an amount of 2 mol / mol based on the amount of tannic acid, and 0.03 g of potassium persulfate was added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type dicationically modified tannin-based organic flocculant.

[0046] The treatment effects of the four groups of different tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal amount of tetrabutylphosphonium bromide added in step (1), and the test method was the same as that in Example 1. The results are shown in Table 2 below.

[0047] Table 2 Coagulation effect of organic flocculants at different addition amounts of tetrabutylphosphonium bromide

[0048] The results show that when the amount of tetrabutylphosphonium bromide added in step (1) is 1 mol / mol, based on the amount of tannic acid, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0049] Example 3 On the basis of Example 1 and Example 2, the concentration of the sodium hydroxide aqueous solution in step (1) is selected to be 0.3 mol / L, the amount of tetrabutylphosphonium bromide added is selected to be 1 mol / mol tannic acid, and then the reaction temperature in step (1) is adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, adding tetrabutylphosphonium bromide solution, the amount of tetrabutylphosphonium bromide added is 1 mol / mol based on the amount of tannic acid, controlling the reaction temperature at 50°C, 60°C, 70°C or 80°C, and reacting for 3 hours in total; after the reaction is completed, cooling to room temperature, precipitating in acetone solution, taking the lower precipitate, washing with ethanol, and then washing with deionized water three times; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, dimethyldiallyl ammonium chloride was added in an amount of 2 mol / mol based on the amount of tannic acid, and 0.03 g of potassium persulfate was added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type quaternary phosphine-modified tannin-based organic flocculant.

[0050] The treatment effects of four different groups of tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal reaction temperature of step (1), and the test method was the same as that of Example 1. The results are shown in Table 3 below.

[0051] Table 3 Coagulation effect of organic flocculants at different reaction temperatures

[0052] The results show that when the reaction temperature of tannic acid and tetrabutylphosphonium bromide in step (1) is 70°C, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0053] Example 4 On the basis of Examples 1 to 3, the concentration of the sodium hydroxide aqueous solution in step (1) is selected to be 0.3 mol / L, the amount of tetrabutylphosphonium bromide added is 1 mol / mol tannic acid, the reaction temperature is 70°C, and then the types of the first free radical initiator and the second free radical initiator in step (2) are adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of the first free radical initiator was added and the reaction was continued for 20 min. -6 mol / s, dimethyldiallyl ammonium chloride was added in an amount of 2 mol / mol based on the amount of tannic acid, 0.03 g of the second free radical initiator was added again, and the reaction was continued for 4 hours; The first free radical initiator and the second free radical initiator are both potassium persulfate, ammonium persulfate or cerium ammonium nitrate; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type quaternary phosphine-modified tannin-based organic flocculant.

[0054] The treatment effects of three different groups of tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal reaction temperature of step (1), and the test method was the same as that of Example 1. The results are shown in Table 4 below.

[0055] Table 4 Coagulation effect of organic flocculants under different free radical initiators

[0056] The results show that when potassium persulfate is selected as the first free radical initiator and the second free radical initiator in step (2), the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0057] Example 5 On the basis of Examples 1 to 4, the concentration of the sodium hydroxide aqueous solution in step (1) is selected to be 0.3 mol / L, the amount of tetrabutylphosphonium bromide added is 1 mol / mol tannic acid, the reaction temperature is 70°C, the first free radical initiator and the second free radical initiator in step (2) are potassium persulfate, and then the amount of dimethyldiallylammonium chloride added in step (2) is adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, adding dimethyldiallyl ammonium chloride solution, based on the amount of tannic acid, the amount of dimethyldiallyl ammonium chloride added is 1 mol / mol, 2 mol / mol, 3 mol / mol, 4 mol / mol or 5 mol / mol, adding 0.03 g of potassium persulfate again, and continuing the reaction for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type dicationically modified tannin-based organic flocculant.

[0058] The treatment effects of five different groups of tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal amount of dimethyldiallylammonium chloride added in step (2). The test method was the same as that in Example 1. The results are shown in Table 5 below.

[0059] Table 5 Coagulation effect of organic flocculants at different addition amounts of dimethyldiallylammonium chloride

[0060] The results show that when the amount of dimethyldiallylammonium chloride added in step (2) is 3 mol / mol, based on the amount of tannic acid, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0061] Example 6 On the basis of Examples 1 to 5, the concentration of the sodium hydroxide aqueous solution in step (1) is selected to be 0.3 mol / L, the amount of tetrabutylphosphonium bromide added is 1 mol / mol tannic acid, the reaction temperature is 70°C, the first free radical initiator and the second free radical initiator in step (2) are potassium persulfate, and the amount of dimethyldiallylammonium chloride added is 3 mol / mol tannic acid, and then the amount of the first free radical initiator added in step (2) is adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.01 g, 0.03 g, 0.05 g, 0.07 g, and 0.1 g of potassium persulfate were added and reacted for 20 min. 1×10 -6 mol / s, dimethyldiallylammonium chloride solution was added, and the amount of dimethyldiallylammonium chloride added was 3 mol / mol based on the amount of tannic acid. 0.03 g of potassium persulfate was added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type dicationically modified tannin-based organic flocculant.

[0062] The treatment effects of five different groups of tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal addition amount of the first free radical initiator in step (2), and the test method was the same as that in Example 1. The results are shown in Table 6 below.

[0063] Table 6 Coagulation effect of organic flocculants at different first free radical initiator addition amounts

[0064] The results show that when the amount of the first free radical initiator added in step (2) is 0.03 g, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0065] Example 7 On the basis of Examples 1 to 6, the concentration of the aqueous sodium hydroxide solution in step (1) is selected to be 0.3 mol / L, the amount of tetrabutylphosphonium bromide added is 1 mol / mol tannic acid, the reaction temperature is 70°C, the first free radical initiator and the second free radical initiator in step (2) are potassium persulfate, the amount of dimethyldiallylammonium chloride added is 3 mol / mol tannic acid, the mass ratio of the first free radical initiator to tannic acid is 0.03 g:5 g, and then the amount of the second free radical initiator added in step (2) is adjusted to prepare a tentacle-type dicationically modified tannin-based organic flocculant. The specific scheme is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, dimethyldiallyl ammonium chloride solution was added, based on the amount of tannic acid, the amount of dimethyldiallyl ammonium chloride added was 3 mol / mol, and 0.01 g, 0.03 g, 0.05 g, 0.07 g, and 0.1 g of potassium persulfate were added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type quaternary phosphine-modified tannin-based organic flocculant.

[0066] The treatment effects of five different groups of tentacle-type dicationically modified tannin-based organic flocculants on algae liquid were compared to determine the optimal addition amount of the second free radical initiator in step (2), and the test method was the same as that in Example 1. The results are shown in Table 7 below.

[0067] Table 7 Coagulation effect of organic flocculants at different addition amounts of second free radical initiator

[0068] The results show that when the amount of the second free radical initiator added in step (2) is 0.03 g, the coagulation effect of the finally prepared tentacle-type dicationically modified tannin-based organic flocculant is the best.

[0069] Example 8 Based on Examples 1 to 7, the best method for preparing the tentacle-type dicationically modified tannin-based organic flocculant is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution was added, the amount of tetrabutylphosphonium bromide added was 1 mol / mol based on the amount of tannic acid, the reaction temperature was controlled at 70°C, and the reaction was carried out for 3 hours in total; after the reaction was completed, it was cooled to room temperature, precipitated in acetone solution, the lower precipitate was taken, washed with ethanol, and then washed three times with deionized water; (2) The precipitate was dispersed in water and placed in a water bath at 70°C. Nitrogen was continuously introduced. 0.03 g of potassium persulfate was added and reacted for 20 min. 1×10 -6 mol / s, a predetermined mass of dimethyldiallyl ammonium chloride solution was added, and the amount of dimethyldiallyl ammonium chloride added was 3 mol / mol based on the amount of tannic acid, and 0.03 g of potassium persulfate was added again, and the reaction was continued for 4 hours; (3) After the reaction is completed, the mixture is cooled to room temperature, and the precipitated product is extracted with a mixed solution of acetone and ethanol, filtered and washed to obtain a tentacle-type dicationically modified tannin-based organic flocculant.

[0070] Since the flocculant has good water solubility, it can rely on its polymer structure to interact with pollutants and then destabilize and precipitate them. Therefore, the morphology of the tentacle-type quaternary phosphinated modified tannin-based organic flocculant in water was observed under a transmission electron microscope. Figure 2 As shown in the figure, the flocculant molecule has a long chain structure, and its chain structure is highly branched and presents a tentacle-like structure. This molecular configuration can provide more adsorption sites and is more conducive to contact and flocculation with pollutants.

[0071] The treatment effect of the dosage of tentacle-type double cationic modified tannin-based organic flocculant on algae liquid was studied. The specific method is as follows: To 10 7 After adding 5-30 mg / L of tentacle-type organic flocculant to the 100 cell / mL Microcystis aeruginosa liquid, stir at 250 r / min for 1 min, then at 35 r / min for 15 min, and then settle for 30 min. After sedimentation, take the supernatant and measure the OD with a UV spectrophotometer.680 The concentration of algal cells after treatment was calculated by the standard curve, and then the removal rate was calculated; and the content of algal toxins was detected by high performance liquid chromatography-mass spectrometry.

[0072] Figure 3 The removal rate of algae cells at different dosages is shown. The results show that when 20-30 mg / L flocculant is added, the removal rate of algae cells can reach more than 90%, especially when the dosage is above 25 mg / L, the removal rate can reach more than 95%, and the removal effect tends to be stable.

[0073] Figure 4 The removal rate of algae toxins at different dosages is shown. The results show that when 25-30 mg / L flocculant is added, the removal rate of algae toxins can basically reach more than 35%.

[0074] Figure 5 The flocs after coagulation were observed under a scanning electron microscope. It can be seen that the algal cells are basically intact, thus avoiding the release of a large amount of intracellular algal toxins.

[0075] Comparative Example 1 Comparative Example 1 provides a method for treating algae liquid using tannic acid alone, specifically, adding tannic acid in an equal molar amount to 10 7 cell / mL Microcystis aeruginosa algae solution, stirred at 250 r / min for 1 min, then stirred at 35 r / min for 15 min, and then precipitated for 30 min. After precipitation, the supernatant was taken and the algae cell removal rate was calculated to be 56.2% and the algae toxin removal rate was 0.9%.

[0076] Comparative Example 2 Comparative Example 2 provides a method for treating algae liquid using a modified tannin-based organic flocculant, wherein the preparation method of the modified tannin-based organic flocculant is as follows: (1) Disperse 5 g of tannic acid in 170 mL of 0.3 mol / L sodium hydroxide aqueous solution and stir at 200 rpm at 1 × 10 -6 mol / s, tetrabutylphosphonium bromide solution is added, based on the amount of tannic acid, the amount of tetrabutylphosphonium bromide added is 1 mol / mol, the reaction temperature is controlled at 70°C, and the reaction is carried out for a total of 3 hours; after the reaction is completed, it is cooled to room temperature and precipitated in an acetone solution, the lower precipitate is taken, washed with ethanol, and then washed three times with deionized water to obtain.

[0077] The modified tannin-based organic flocculant was added to 10 7cell / mL Microcystis aeruginosa algae solution, stirred at 250 r / min for 1 min, then stirred at 35 r / min for 15 min, and then precipitated for 30 min. After precipitation, the supernatant was taken and the algae cell removal rate was calculated to be 49% and the algae toxin removal rate was 1.6%.

[0078] Comparative Example 3 (1) Disperse 5 g of tannic acid in water and place in a water bath at 70 °C. Continue to flow nitrogen gas and stir rapidly (200 rpm) at 1 × 10 -6 mol / s, add dimethyldiallyl ammonium chloride solution, the amount of dimethyldiallyl ammonium chloride added is 2 mol / mol based on the amount of tannic acid, then add 0.03 g potassium persulfate, and react for 4 hours; (2) After the reaction is completed, cool to room temperature, extract the precipitated product with a mixture of acetone and ethanol, filter and wash to obtain the product.

[0079] The modified tannin-based organic flocculant was added to 10 7 cell / mL Microcystis aeruginosa algae solution, stirred at 250 r / min for 1 min, then stirred at 35 r / min for 15 min, and then precipitated for 30 min. After precipitation, the supernatant was taken and the algae cell removal rate was calculated to be 62% and the algae toxin removal rate was 15.1%.

[0080] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person skilled in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and they shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a tentacle-type dicationically modified tannin-based organic flocculant, characterized in that: The steps include: (1) Add tetrabutylphosphonium bromide to an alkaline solution of tannic acid, react at 50-80°C for 2-4 hours, precipitate in an acetone solution, and remove the lower precipitate for washing; (2) dispersing the precipitate in water, continuously introducing nitrogen, adding a first free radical initiator to react at 50-80°C, and then adding dimethyldiallylammonium chloride and a second free radical initiator to react for 2-4 hours; (3) Extract the precipitated product with a mixture of acetone and ethanol, filter and wash.

2. The preparation method according to claim 1, characterized in that In step (1), the lower precipitate is washed with ethanol and then washed with deionized water.

3. The preparation method according to claim 1, characterized in that In step (1), the amount of tetrabutylphosphonium bromide added is 0.5-2 mol / mol based on the amount of tannic acid.

4. The preparation method according to claim 1, characterized in that In step (2), the amount of the first free radical initiator added is 0.01-0.1 g / 5 g based on the mass of tannic acid; Based on the mass of tannic acid, the added amount of the second free radical initiator is 0.01-0.1 g / 5 g.

5. The preparation method according to claim 1, characterized in that In step (2), after the first free radical initiator is added, the reaction is continued for 20-40 minutes before adding dimethyldiallylammonium chloride and the second free radical initiator.

6. The preparation method according to claim 1, characterized in that In step (2), the amount of dimethyldiallylammonium chloride added is 1-5 mol / mol based on the amount of tannic acid.

7. The preparation method according to claim 1, characterized in that: In step (2), the precipitate is dispersed in water and heated to 50-80° C. in a water bath.

8. The preparation method according to claim 1, characterized in that: The first free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate; The second free radical initiator is one of potassium persulfate, ammonium persulfate, and cerium ammonium nitrate.

9. A tentacle-type dicationically modified tannin-based organic flocculant prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the tentacle-type dicationically modified tannin-based organic flocculant as claimed in claim 9 in treating algae liquid.

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