A high-flocculation-strength sludge dewatering flocculant, its preparation method, and its application in sludge treatment.

Abstract

This invention discloses a high-flocculation-strength sludge dewatering flocculant, its preparation method, and its application in sludge treatment, relating to the field of wastewater treatment technology. The flocculant prepared by this invention is composed of acrylamide, vinylphosphonic acid, N-vinylimidazolium copolymer, ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriaminepentamethylphosphonic acid grafted modified chitosan. The flocculant prepared by this invention can effectively form flocs during sludge dewatering, maintain filter cake water flow channels, reduce filtration resistance, improve dewatering efficiency, and trigger polymer chain degradation under reducing conditions, reducing environmental residues. The flocculant provided by this invention is suitable for the dewatering treatment of various types of sludge, including municipal sludge and industrial sludge.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a high-flocculation-strength sludge dewatering flocculant, its preparation method, and its application in sludge treatment. Background Technology

[0002] Sludge dewatering is a crucial step in wastewater treatment, aiming to reduce sludge moisture content and volume, thus facilitating subsequent transportation, disposal, or resource utilization. Flocculants, as the core agents in sludge dewatering, directly determine dewatering efficiency and filter cake moisture content. Currently, flocculants used for sludge dewatering are mainly classified into three categories: inorganic flocculants, organic flocculants, and composite flocculants. Inorganic flocculants, such as polyaluminum chloride and polyferric sulfate, have strong charge neutralization capabilities, but the flocs are loose, require large quantities, and residual metal ions may cause secondary pollution. Organic flocculants, such as polyacrylamide polymers, have excellent adsorption bridging effects, but their charge density is relatively low, and the flocs formed by linear polymers are easily destroyed by shear forces during mechanical dewatering, leading to floc breakage and decreased dewatering efficiency. To address these issues, researchers have attempted to prepare composite flocculants by physically combining or chemically grafting inorganic and organic components, aiming to simultaneously leverage the advantages of charge neutralization and adsorption bridging.

[0003] However, existing composite flocculants still face the following technical challenges. First, in most composite flocculants, the inorganic and organic components are only physically mixed or weakly interacting, making them prone to phase separation under hydraulic shear conditions, leading to unstable flocculation performance. Second, the introduction of covalent cross-linked structures to improve floc strength results in cross-linked polymers that are difficult to degrade in the natural environment, causing flocculant residues to accumulate in the sludge and affecting subsequent resource utilization. Third, during filter press dewatering, existing flocculants tend to densify and clog the water flow channels inside the filter cake after compression, increasing filtration resistance and limiting further improvements in dewatering efficiency. Fourth, sludge composition is complex, with significant differences in charge properties and organic matter content among sludge from different sources; single-mechanism flocculants often struggle to adapt to these varied sludge characteristics.

[0004] Therefore, developing a flocculant that combines high flocculation strength, good dewatering performance, and biodegradability, while also being able to adapt to different sludge characteristics and maintain the permeability of the filter cake, is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-flocculation-strength sludge dewatering flocculant, its preparation method, and its application in sludge treatment, so as to solve the problems mentioned in the background art.

[0006] In a first aspect, the present invention provides a high-flocculation-strength sludge dewatering flocculant, comprising the following raw materials in parts by weight: Acrylamide 70-85 parts; Vinylphosphonic acid 5-15 parts; 5-15 parts of N-vinylimidazole; 0.1-0.5 parts of mercaptoethanol; Ammonium persulfate 0.1-0.3 parts; Sodium bisulfite 0.05-0.15 parts; 150-250 parts deionized water; Ferrous tartrate 0.5-3 parts; 0.1-0.5 parts of tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex; 0.5-3 parts of basic magnesium sulfate whiskers; 0.2-1 parts of diethylenetriamine pentamethylphosphonic acid grafted modified chitosan.

[0007] As a preferred embodiment of the present invention, the preparation method of the tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex is as follows: Copper sulfate pentahydrate was dissolved in deionized water, and tetramethylethylenediamine was added. The mixture was stirred at room temperature for 30-45 min to obtain a mixed solution. β-cyclodextrin was dissolved in deionized water, heated to 50-60℃ and stirred for 20-30 min to obtain an aqueous solution of β-cyclodextrin. The mixed solution was added to the aqueous solution of β-cyclodextrin, and stirring was continued for 1-2 h. After cooling to room temperature, the mixture was spray-dried to obtain a tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex. In the mixed solution, the mass ratio of copper sulfate pentahydrate, deionized water, and tetramethylethylenediamine is 1:(50-100):(0.5-1); In the β-cyclodextrin aqueous solution, the mass ratio of β-cyclodextrin to deionized water is (5-10):(100-150); The mass ratio of the mixed solution to the β-cyclodextrin aqueous solution is (51.5-101):(105-160); The spray dryer has an inlet air temperature of 180-200℃, an outlet air temperature of 80-100℃, and a feed flow rate of 5-15mL / min.

[0008] As a preferred embodiment of the present invention, the basic magnesium sulfate whiskers have an aspect ratio of 20-50, a diameter of 0.5-2 μm, a length of 10-100 μm, and a tensile strength of not less than 800 MPa.

[0009] As a preferred embodiment of the present invention, the preparation method of the diethylenetriamine pentamethylphosphonic acid grafted modified chitosan is as follows: Chitosan was dissolved in a 2% (w / w) aqueous solution of acetic acid and stirred until completely dissolved to obtain a chitosan solution. A 45-55% (w / w) aqueous solution of diethylenetriamine pentamethylphosphonic acid was added to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stirred at room temperature for 15-30 min to obtain an activated DTPMPA solution. The activated DTPMPA solution was added dropwise to the chitosan solution, and the reaction was stirred at room temperature for 12-24 h. After the reaction was complete, the mixture was precipitated with acetone, filtered, washed successively with ethanol and water, vacuum dried at 50-60℃, and pulverized through a 100-200 mesh sieve to obtain diethylenetriamine pentamethylphosphonic acid grafted modified chitosan. The degree of deacetylation of the chitosan is not less than 90%; The mass ratio of chitosan to aqueous acetic acid in the chitosan solution is 1:(100-150); The mass ratio of the diethylenetriamine pentamethylphosphonic acid aqueous solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide is (20.5-51.5):(0.2-0.5):(0.1-0.3).

[0010] A second aspect of the present invention provides a method for preparing a high-flocculation-strength sludge dewatering flocculant, comprising the following steps: S1. Add the formulated amounts of acrylamide, vinylphosphonic acid, N-vinylimidazolium, mercaptoethanol, and deionized water to a reaction vessel, stir to dissolve, adjust the pH to 5.5-6.5 with 25% ammonia water, purge with nitrogen gas to remove oxygen for 30 min, and simultaneously heat the water bath to 35-40℃. Add ammonium persulfate and sodium bisulfite respectively, and polymerize at 35-40℃ for 4-6 h. After the reaction is complete, precipitate the reaction solution with acetone, filter, vacuum dry at 50-60℃, and pulverize through an 80-120 mesh sieve to obtain polymer powder. It should be noted that the redox initiation system composed of ammonium persulfate and sodium bisulfite in step S1 can generate free radicals at a relatively low temperature of 35-40℃, initiating a copolymerization reaction of acrylamide, vinylphosphonic acid, and N-vinylimidazolium to generate an acrylamide copolymer with side chains containing both phosphonic acid and imidazole groups. Mercaptoethanol is used as a chain transfer agent to adjust the polymer's molecular weight, ensuring it remains within a suitable range and avoiding either excessively high molecular weight leading to dissolution difficulties or excessively low molecular weight resulting in insufficient bridging ability. After the polymer is subsequently prepared into an aqueous solution, its phosphonic acid groups partially dissociate under the neutral pH conditions of the sludge to form phosphonic acid anions, while the imidazole groups undergo partial protonation to form positively charged imidazole onium ions. The coexistence of these two groups gives the polymer chain a zwitterionic characteristic.

[0011] S2. Add the polymer powder obtained in S1, ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriamine pentamethylphosphonic acid grafted modified chitosan into a three-dimensional mixer and mix for 30-60 minutes. Discharge and seal the product to obtain a high flocculation strength sludge dewatering flocculant.

[0012] A third aspect of the present invention provides an application of a high-flocculation-strength sludge dewatering flocculant in sludge treatment, the application method of which is as follows: Prepare a flocculant solution with a mass fraction of 0.3-0.5%, stir and dissolve for 1-2 hours, add the solution to the sludge to be treated, and add 2-8 kg of the solution per ton of dry sludge. Stir at 60-80 r / min for 3-5 minutes, and then put the solution into a mechanical dewatering device for dewatering.

[0013] It should be noted that during the preparation of the aqueous solution of the high-flocculation-strength sludge dewatering flocculant, the polymer chains gradually extend, while ferrous tartrate dissolves and releases ferrous ions. The phosphonic acid groups on the polymer side chains have a high coordination affinity for ferrous ions, and their coordination constants are significantly higher than those of tartaric acid for ferrous ions. Therefore, after dissociating from the tartaric acid complex, the ferrous ions re-coordinate with the phosphonic acid groups. Simultaneously, the nitrogen atom on the imidazole group also participates in the coordination with ferrous ions, forming a bidentate or multidentate coordination structure of phosphonic acid-ferrous-imidazolium. This coordination effect allows the originally linear polymer chains to form a three-dimensional network structure through ferrous ion bridging. This process occurs in situ on the surface of sludge particles and between sludge particles. Unlike covalent crosslinking, this coordination bond is reversible, with bond energies between covalent and hydrogen bonds. It can dynamically adjust during dewatering to adapt to hydraulic shear conditions, providing high floc strength while avoiding brittle fracture caused by excessive crosslinking.

[0014] It should be further explained that the basic magnesium sulfate whiskers are interspersed within the flocs. Their rigid framework structure can resist compression deformation during mechanical dewatering, maintain water flow channels in the filter cake, reduce filtration resistance, and form a composite reinforcement system that combines rigidity and flexibility with the coordination cross-linking network. The diethylenetriamine pentamethylphosphonic acid grafted modified chitosan molecular chain contains multiple phosphonic acid groups and amino groups. Its phosphonic acid groups can participate in the coordination competition of ferrous ions, synergistically forming denser coordination sites with the phosphonic acid groups of the polymer side chains. At the same time, the amino groups on the chitosan backbone become positively charged after protonation under acidic conditions, which can neutralize the charge of sludge particles and assist flocculation. The tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex in the flocculant remains inert during the dewatering stage and does not participate in the flocculation reaction. When the dewatered sludge filter cake enters a reducing environment or when a reducing agent is added artificially, the cyclodextrin inclusion complex structure disintegrates, releasing copper ions that are reduced to monovalent copper. Monovalent copper reacts with dissolved oxygen to generate free radicals, which can cleave the carbon-carbon bonds in the polymer backbone, causing the cross-linked network to disintegrate and the polymer chain to degrade into smaller molecular fragments. The phosphonic acid groups and amino groups in diethylenetriamine pentamethylphosphonic acid-grafted modified chitosan have a certain coordination stabilizing effect on copper ions, which can slow down the release rate of copper ions, making the degradation process more gradual and controllable. This flocculant achieves efficient flocculation and dewatering of sludge particles through a coordination cross-linking mechanism. The resulting flocs have high shear resistance while retaining the potential to trigger degradation under reducing conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a phosphonic acid-ferrous-imidazolium coordination crosslinking mechanism to replace the traditional covalent crosslinking. The resulting flocs have high shear strength and reversibility, and can adapt to the hydraulic shearing during mechanical dewatering, thus reducing floc breakage.

[0016] (2) The present invention introduces basic magnesium sulfate whiskers as a rigid skeleton, which together with the coordination crosslinking network form a composite reinforcement system that combines rigidity and flexibility. During the filter press process, the filter cake water flow channel is maintained, the filtration resistance is reduced, and the dewatering efficiency is improved.

[0017] (3) This invention provides multiple phosphonic acid coordination sites by grafting chitosan with diethylenetriamine pentamethylphosphonic acid, which synergistically increases the crosslinking density with the polymer side chain. At the same time, its amino protonation assists in charge neutralization, enhancing the adaptability to sludge with different charge properties.

[0018] (4) This invention utilizes tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex to achieve on-demand triggered degradation. It remains inert during the dehydration stage and initiates polymer chain scission after entering the reducing environment, thus avoiding the environmental residue problem of cross-linked flocculants after sludge treatment. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Preparation Example 1 The preparation method of the tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex is as follows: By weight, 1 part copper sulfate pentahydrate was dissolved in 75 parts deionized water, and 0.75 parts tetramethylethylenediamine was added. The mixture was stirred at room temperature for 40 min to obtain a mixed solution. 7.5 parts β-cyclodextrin was dissolved in 125 parts deionized water, and the mixture was heated to 55°C and stirred for 25 min to obtain a β-cyclodextrin aqueous solution. The mixed solution was added to the β-cyclodextrin aqueous solution, and the mixture was stirred for 2 h. After cooling to room temperature, it was spray-dried with an inlet air temperature of 180°C, an outlet air temperature of 90°C, and a feed flow rate of 10 mL / min to obtain a tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex.

[0021] Preparation Example 2 The preparation method of diethylenetriamine pentamethylphosphonic acid grafted modified chitosan is as follows: By weight, 1 part of chitosan was dissolved in 125 parts of a 2% (w / w) aqueous acetic acid solution and stirred until completely dissolved to obtain a chitosan solution; 0.35 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.2 parts of N-hydroxysuccinimide were added to 36 parts of a 50% (w / w) aqueous solution of diethylenetriaminepentylphosphonic acid and stirred at room temperature for 20 min to obtain an activated DTPMPA solution; the activated DTPMPA solution was added dropwise to the chitosan solution and stirred at room temperature for 18 h; after the reaction was complete, the mixture was precipitated with acetone, filtered, washed successively with ethanol and water, dried under vacuum at 55 °C, and pulverized through a 200-mesh sieve to obtain diethylenetriaminepentylphosphonic acid grafted modified chitosan.

[0022] Example 1

[0023] A high-flocculation-strength sludge dewatering flocculant comprises the following raw materials in parts by weight: Acrylamide 77.5 parts; 10 parts of vinylphosphonic acid; 10 parts of N-vinylimidazole; 0.3 parts mercaptoethanol; Ammonium persulfate 0.2 parts; Sodium bisulfite 0.1 parts; 200 parts deionized water; 1.75 parts of ferrous tartrate; 0.3 parts of tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex; 1.75 parts of basic magnesium sulfate whiskers; 0.6 parts of chitosan grafted with diethylenetriamine pentamethylphosphonic acid.

[0024] A method for preparing a high-flocculation-strength sludge dewatering flocculant includes the following steps: S1. Add the formulated amounts of acrylamide, vinylphosphonic acid, N-vinylimidazolium, mercaptoethanol, and deionized water to a reaction vessel, stir to dissolve, adjust the pH to 6 with 25% ammonia, purge with nitrogen to remove oxygen for 30 min, and simultaneously heat the water bath to 38°C. Add ammonium persulfate and sodium bisulfite respectively, and polymerize at 38°C for 5 h. After the reaction is complete, precipitate the reaction solution with acetone, filter, vacuum dry at 55°C, and pulverize through a 100-mesh sieve to obtain polymer powder. S2. The polymer powder obtained in S1 is added to a three-dimensional mixer along with the formulated amounts of ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriamine pentamethylphosphonic acid grafted modified chitosan. The mixture is mixed for 45 minutes, then discharged, sealed, and packaged to obtain a high flocculation strength sludge dewatering flocculant.

[0025] In this embodiment, some of the raw materials used are the same as those obtained in Preparation Examples 1-2, and the other examples are the same.

[0026] Example 2

[0027] A high-flocculation-strength sludge dewatering flocculant comprises the following raw materials in parts by weight: 85 parts of acrylamide; Vinylphosphonic acid 15 parts; 15 parts of N-vinylimidazole; 0.5 parts mercaptoethanol; Ammonium persulfate 0.3 parts; Sodium bisulfite 0.15 parts; 250 parts deionized water; 3 parts ferrous tartrate; 0.5 parts of tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex; Three parts of basic magnesium sulfate whiskers; One part of chitosan grafted with diethylenetriamine pentamethylphosphonic acid.

[0028] A method for preparing a high-flocculation-strength sludge dewatering flocculant includes the following steps: S1. Add the formulated amounts of acrylamide, vinylphosphonic acid, N-vinylimidazolium, mercaptoethanol, and deionized water to a reaction vessel, stir to dissolve, adjust the pH to 6 with 25% ammonia, purge with nitrogen to remove oxygen for 30 min, and simultaneously heat the water bath to 38°C. Add ammonium persulfate and sodium bisulfite respectively, and polymerize at 38°C for 5 h. After the reaction is complete, precipitate the reaction solution with acetone, filter, vacuum dry at 55°C, and pulverize through a 100-mesh sieve to obtain polymer powder. S2. The polymer powder obtained in S1 is added to a three-dimensional mixer along with the formulated amounts of ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriamine pentamethylphosphonic acid grafted modified chitosan. The mixture is mixed for 45 minutes, then discharged, sealed, and packaged to obtain a high flocculation strength sludge dewatering flocculant.

[0029] Example 3

[0030] A high-flocculation-strength sludge dewatering flocculant comprises the following raw materials in parts by weight: 70 parts acrylamide; Vinylphosphonic acid 5 parts; 5 parts of N-vinylimidazole; 0.1 parts mercaptoethanol; 0.1 parts of ammonium persulfate; Sodium bisulfite 0.05 parts; 150 parts of deionized water; 0.5 parts of ferrous tartrate; 0.1 part of tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex; 0.5 parts of basic magnesium sulfate whiskers; 0.2 parts of chitosan grafted with diethylenetriamine pentamethylphosphonic acid.

[0031] A method for preparing a high-flocculation-strength sludge dewatering flocculant includes the following steps: S1. Add the formulated amounts of acrylamide, vinylphosphonic acid, N-vinylimidazolium, mercaptoethanol, and deionized water to a reaction vessel, stir to dissolve, adjust the pH to 6 with 25% ammonia, purge with nitrogen to remove oxygen for 30 min, and simultaneously heat the water bath to 38°C. Add ammonium persulfate and sodium bisulfite respectively, and polymerize at 38°C for 5 h. After the reaction is complete, precipitate the reaction solution with acetone, filter, vacuum dry at 55°C, and pulverize through a 100-mesh sieve to obtain polymer powder. S2. The polymer powder obtained in S1 is added to a three-dimensional mixer along with the formulated amounts of ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriamine pentamethylphosphonic acid grafted modified chitosan. The mixture is mixed for 45 minutes, then discharged, sealed, and packaged to obtain a high flocculation strength sludge dewatering flocculant.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is that the tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex prepared in Example 1 was not added; instead, an equal part by weight of cyclodextrin was added.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that the diethylenetriamine pentamethylphosphonic acid grafted modified chitosan prepared in Example 2 was not added; instead, an equal part by weight of chitosan was added.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that ferrous tartrate was not added; instead, an equal part by weight of deionized water was added.

[0035] test: I. Shear Strength Test of Flocs Using a dynamic flocculation testing device, the flocculants prepared in Examples 1-3 and Comparative Examples 1-3 were prepared into a 0.4% aqueous solution according to the application method. The solution was added to the sludge at a dosage of 5 kg per ton of oven-dry sludge. After stirring for 3 min, the flocculants were sheared at a speed of 1000 r / min for 30 s. The median particle size of the flocs before and after shearing was measured using a laser particle size analyzer. The particle size retention rate of the flocs was calculated using the formula: Particle size retention rate (%) = Median particle size after shearing / Median particle size before shearing × 100%.

[0036] II. Sludge Dewatering Performance Test Referring to the test methods in "CJ / T 546-2021 Flocculants for Sludge Dewatering in Urban Wastewater Treatment Plants", the flocculants prepared in Examples 1-3 and Comparative Examples 1-3 were treated according to the application method, and then filtered using a plate and frame filter press at a pressure of 1.2 MPa for 30 min. The moisture content of the filter cake was determined by the gravimetric method in "CJ / T 221-2023 Standard Test Methods for Urban Sludge".

[0037] III. Filter Resistance Test Using a capillary water absorption time tester, the flocculants prepared in Examples 1-3 and Comparative Examples 1-3 were added to the sludge according to the application method. After stirring evenly, 10 mL of sludge sample was injected into the test device, and the capillary water absorption time was recorded in seconds. Each group of samples was tested three times and the average value was taken. The capillary water absorption time was used to evaluate the dewatering performance of the sludge.

[0038] IV. Degradability Test The filter cakes obtained after dehydration of the flocculants prepared in Examples 1-3 and Comparative Examples 1-3 according to the application method were treated with sodium thiosulfate to a final concentration of 5 mmol / L. The filter cakes were then placed under anaerobic conditions at 35°C for 7 days. After removal, the percentage of residual high molecular weight of flocculant in the filter cakes was determined by gel permeation chromatography. The degradation rate was calculated based on the high molecular weight before degradation.

[0039] V. Summary of Results Table 1 Test Project Particle size retention rate (%) Filter cake moisture content (%) Capillary water absorption time (s) 7-day degradation rate (%) Example 1 87.3 54.2 28.5 68.4 Example 2 86.5 55.1 29.2 67.2 Example 3 88.1 53.8 27.9 69.5 Comparative Example 1 72.4 63.5 45.6 18.5 Comparative Example 2 75.8 61.2 41.3 71.2 Comparative Example 3 62.3 68.7 52.8 70.8 VI. Discussion of Results As shown in Table 1, the high-flocculation-strength sludge dewatering flocculants prepared in Examples 1-3 of this invention possess excellent floc shear strength, dewatering performance, and biodegradability. The particle size retention rates of Examples 1-3 are all higher than 86%, significantly better than Comparative Example 1 (without tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex), Comparative Example 2 (without diethylenetriamine pentamethylphosphonic acid grafted modified chitosan), and Comparative Example 3 (without ferrous tartrate), indicating that the synergistic effect of the coordination crosslinking mechanism and the rigid framework reinforcement system effectively improves the shear strength of the flocs. The filter cake moisture content of Examples 1-3 is less than 56%, and the capillary water absorption time is less than 30 s, both significantly better than the comparative examples, indicating that this flocculant has good solid-liquid separation efficiency during sludge dewatering. Regarding degradation performance, Examples 1-3 all showed degradation rates of over 67% after 7 days under reducing conditions. Comparative Example 1 showed a significantly reduced degradation rate due to the lack of copper-coordinated cyclodextrin inclusion complexes. Comparative Examples 2 and 3, although exhibiting high degradation rates, had poor dehydration performance. This demonstrates that the present invention achieves the function of triggering degradation on demand while maintaining excellent dehydration performance.

[0040] It should be noted that Comparative Example 2 lacks diethylenetriamine pentamethylphosphonic acid grafted modified chitosan, resulting in lower crosslinking density and looser polymer chains, making it more susceptible to free radical attack, thus leading to a high degradation rate, but at the cost of poor dehydration performance. Comparative Example 3 lacks ferrous tartrate, preventing the formation of a coordination crosslinking network; the polymer exists in a linear form without crosslinking structure, making degradation easier, but at the cost of low floc strength. Examples 1-3 formed a coordination crosslinking network, with crosslinking points providing a certain degree of shielding or hindering free radical attack, resulting in relatively mild and controllable degradation. Simultaneously, their dehydration performance was significantly better than that of Comparative Examples 2-3. Examples 1-3 achieved controllable degradation while maintaining excellent dehydration performance, while Comparative Examples 2-3, although having a slightly higher degradation rate, showed a significant decrease in dehydration performance. This demonstrates the balance achieved by this invention between dehydration performance and degradability; Examples 1-3 maximized the preservation of degradability while ensuring dehydration performance.

[0041] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the scope defined by the invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A high-flocculation-strength sludge dewatering flocculant, characterized in that: Including the following parts by weight of raw materials: Acrylamide 70-85 parts; Vinylphosphonic acid 5-15 parts; 5-15 parts of N-vinylimidazole; 0.1-0.5 parts of mercaptoethanol; Ammonium persulfate 0.1-0.3 parts; Sodium bisulfite 0.05-0.15 parts; 150-250 parts deionized water; Ferrous tartrate 0.5-3 parts; 0.1-0.5 parts of tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex; 0.5-3 parts of basic magnesium sulfate whiskers; 0.2-1 parts of chitosan grafted with diethylenetriamine pentamethylphosphonic acid; The preparation method of the tetramethylethylenediamine-copper coordination cyclodextrin inclusion complex is as follows: Copper sulfate pentahydrate was dissolved in deionized water, and tetramethylethylenediamine was added. The mixture was stirred at room temperature for 30-45 min to obtain a mixed solution. β-cyclodextrin was dissolved in deionized water and heated to 50-60℃ and stirred for 20-30 min to obtain an aqueous solution of β-cyclodextrin. The mixed solution was added to the aqueous solution of β-cyclodextrin and stirred for 1-2 h. After cooling to room temperature, the mixture was spray-dried to obtain a tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex.

2. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: In the mixed solution, the mass ratio of copper sulfate pentahydrate, deionized water, and tetramethylethylenediamine is 1:(50-100):(0.5-1).

3. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: In the β-cyclodextrin aqueous solution, the mass ratio of β-cyclodextrin to deionized water is (5-10):(100-150).

4. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: The mass ratio of the mixed solution to the β-cyclodextrin aqueous solution is (51.5-101):(105-160).

5. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: The spray dryer has an inlet air temperature of 180-200℃, an outlet air temperature of 80-100℃, and a feed flow rate of 5-15mL / min.

6. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: The basic magnesium sulfate whiskers have an aspect ratio of 20-50, a diameter of 0.5-2 μm, a length of 10-100 μm, and a tensile strength of not less than 800 MPa.

7. The high flocculation strength sludge dewatering flocculant according to claim 1, characterized in that: The preparation method of the diethylenetriamine pentamethylphosphonic acid grafted modified chitosan is as follows: Chitosan was dissolved in an aqueous acetic acid solution and stirred until completely dissolved to obtain a chitosan solution. A 45-55% (w / w) aqueous solution of diethylenetriamine pentamethylphosphonic acid was added to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stirred at room temperature for 15-30 min to obtain an activated DTPMPA solution. The activated DTPMPA solution was then added dropwise to the chitosan solution, and the reaction was stirred at room temperature for 12-24 h. After the reaction was complete, the chitosan was precipitated with acetone, filtered, washed successively with ethanol and water, vacuum dried, pulverized, and sieved to obtain diethylenetriamine pentamethylphosphonic acid grafted modified chitosan. The mass ratio of chitosan to aqueous acetic acid in the chitosan solution is 1:(100-150).

8. The high flocculation strength sludge dewatering flocculant according to claim 7, characterized in that: The mass ratio of the diethylenetriamine pentamethylphosphonic acid aqueous solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide is (20.5-51.5):(0.2-0.5):(0.1-0.3).

9. A method for preparing a high-flocculation-strength sludge dewatering flocculant as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. Add the formulated amounts of acrylamide, vinylphosphonic acid, N-vinylimidazolium, mercaptoethanol, and deionized water to a reaction vessel, stir to dissolve, adjust the pH to 5.5-6.5 with 25% ammonia water, purge with nitrogen gas to remove oxygen for 30 min, and simultaneously heat the water bath to 35-40℃. Add ammonium persulfate and sodium bisulfite respectively, and polymerize at 35-40℃ for 4-6 h. After the reaction is complete, precipitate the reaction solution with acetone, filter, vacuum dry at 50-60℃, and pulverize through an 80-120 mesh sieve to obtain polymer powder. S2. Add the polymer powder obtained in S1, ferrous tartrate, tetramethylethylenediamine-copper coordinated cyclodextrin inclusion complex, basic magnesium sulfate whiskers, and diethylenetriamine pentamethylphosphonic acid grafted modified chitosan into a three-dimensional mixer and mix for 30-60 minutes. Discharge and seal the product to obtain a high flocculation strength sludge dewatering flocculant.

10. The application of the high flocculation strength sludge dewatering flocculant as described in claim 1 in sludge treatment, characterized in that: The application method is as follows: Prepare a flocculant solution with a mass fraction of 0.3-0.5%, stir and dissolve for 1-2 hours, add the solution to the sludge to be treated, and add 2-8 kg of the solution per ton of dry sludge. Stir at 60-80 r / min for 3-5 minutes, and then put the solution into a mechanical dewatering device for dewatering.