Nanoflocculant, its preparation method and application

Abstract

This invention discloses a nano-flocculator, its preparation method, and its applications. The preparation method includes: preparing a protein amyloid cellulose solution; adding a zirconium salt compound and mixing to obtain a zirconium-loaded protein amyloid cellulose composite solution; and mixing with a polydimethyldiallyl ammonium chloride solution. The nano-flocculator provided by this invention can be stored for a long time at room temperature, is easy to use, and is suitable for improving both sedimentation efficiency and phosphorus removal in municipal and industrial wastewater treatment processes, showing broad engineering application prospects and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a nano-flocculator, its preparation method, and its application. Background Technology

[0002] Currently, in wastewater treatment processes, phosphorus removal is the core objective to control eutrophication and meet total phosphorus discharge standards. Traditional phosphorus removal pathways primarily focus on biological phosphorus removal (such as A...). 2 While both the O process and chemical phosphorus removal (such as adding iron or aluminum salts) are used, phosphorus often remains in the supernatant or coexists with difficult-to-settle particles in the mixed liquor during enhanced phosphorus removal. Studies have shown that some soluble and colloidal phosphorus easily escapes from the main reaction zone and accumulates in the secondary sedimentation tank effluent, becoming one of the important reasons for excessive TP in the effluent. Therefore, achieving simultaneous enhanced phosphorus removal in the secondary sedimentation tank stage can not only supplement the upstream phosphorus removal methods but also improve the overall stability and redundancy of the system. Especially during high-load operation or influent fluctuations, the secondary sedimentation tank becomes the "last line of defense." The common practice is to add Fe or aluminum salts at the upstream end of the secondary sedimentation tank for coagulation and phosphorus removal.

[0003] Meanwhile, accelerating the settling speed of sludge in the secondary sedimentation tank is also crucial for ensuring the normal operation of the wastewater treatment system. Insufficient settling speed often leads to problems such as rising sludge levels, incomplete sludge-water separation, sludge inclusion in the effluent, and increased suspended solids in the effluent, affecting the final effluent quality and even causing sludge spillage accidents, reducing the system's treatment load and stability. The settling bottleneck in the secondary sedimentation tank is particularly prominent under adverse conditions such as a sudden increase in influent flow, low temperature, or sludge expansion. Therefore, achieving a rapid and stable sludge settling process is essential for ensuring the continuous and stable operation of the wastewater treatment plant to meet standards. Generally, phosphorus removal and natural sludge settling are two-step processes. Due to water quality and process technology, it often requires repeated adjustments to the solution pH environment and large amounts of chemicals, especially in winter. Some wastewater treatment plants often need to add coagulants such as polyacrylamide multiple times to reduce sludge retention time, resulting in high costs. If a one-step process can achieve simultaneous and efficient sludge settling and phosphorus capture, it can significantly reduce the system's discharge risk, improve the overall effluent quality, and reduce process costs.

[0004] To overcome the limitations of traditional flocculants, in recent years, technical solutions have emerged that improve sludge settling efficiency and flocculation performance through nano-processing and inorganic-organic composite strategies. For example: (1) Nano-flocculators based on the composite of polyferric chloride and polydimethyldiallyl ammonium chloride have a certain settling-promoting effect, but mainly rely on electrostatic neutralization and surface charge enhancement, lacking the ability to deeply treat soluble pollutants and have weak removal function for nutrients such as phosphorus. In addition, its structure and function are relatively simple, and its stability is limited, which cannot meet the needs of multi-target pollution synergistic treatment. (2) In-situ energy-enhancing nano-flocculators are formed by combining nano-iron powder and ferrous ions with polydimethyldiallyl ammonium chloride. Although this combination can improve the sludge settling speed, there is a reaction system that strongly depends on reducing agents such as NaBH4. The reaction conditions are unstable, and there are safety hazards in storage and use. At the same time, the phosphorus removal mechanism still depends on the iron ion precipitation process, and it has poor adaptability to high-concentration phosphorus systems or water bodies with pH fluctuations. (3) Fe-MOF composite polymer targeted flocculants improve flocculation by constructing metal-organic framework structures, but their technical solutions have the following drawbacks: the synthesis conditions of MOFs are harsh, involving long-term high-temperature reactions and organic solvent systems, resulting in long preparation cycles and environmental unfriendliness; the stability of the MOF framework is poor, and Fe exists. 3+ There are risks of reverse leaching; the phosphorus removal mechanism still relies on iron ion coordination precipitation, which has poor targeting and does not introduce multifunctional sites to achieve simultaneous adsorption and complexation. Furthermore, other systems such as multivalent aluminum or aluminum-iron synergistic inorganic flocculants, while promoting sedimentation to some extent, rely primarily on precipitation reactions for phosphorus removal, lacking flexible framework support and structural controllability. Chitosan-modified flocculants, although possessing biodegradability advantages, have low adsorption site density and slow sedimentation rates. While ZrO2 nanoparticle-based technologies use Zr as the core, they primarily rely on direct particle addition without constructing a composite system to improve adsorption stability. In summary, while existing technologies each have their strengths, they all suffer from complex structures, insufficient environmental friendliness, single function, or poor stability, making it difficult to simultaneously meet the comprehensive technical requirements of efficient sludge sedimentation, deep phosphorus removal, and environmental friendliness. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a nano-flocculator, its preparation method, and its applications. The nano-flocculator provided by this invention is a multifunctional nanoscale composite flocculant composed of zirconium ions, polydimethyldiallylammonium chloride, and amyloid fibers, possessing both highly efficient flocculation and sedimentation and deep phosphorus removal functions. On one hand, the amyloid fibers have an ultra-high aspect ratio (diameter 2-5 nm, length exceeding 10 micrometers), enabling them to self-assemble with polydimethyldiallylammonium chloride to form a cage-like high-density charged structure, possessing charge neutralization, adsorption, and bridging capabilities, thus accelerating sludge sedimentation. The fiber template fully complexes with Zr, forming a charged confinement structure. Zr ions can collect suspended small flocs in the sludge to form large particles, facilitating synergistic sludge sedimentation. Furthermore, under fiber confinement, the fiber cage-like charged structure can enrich phosphate and synergistically react with sub-5 nm zirconium oxide (zirconia particle size less than 5 nm) colloids to react with water and Zr. 4+ Ions rapidly form highly stable zirconium phosphate species, thereby simultaneously achieving rapid removal of phosphates.

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

[0007] On one hand, the present invention provides a method for preparing a nano-flocculator, comprising the following steps:

[0008] (1) Preparation of protein amyloid fiber solution;

[0009] (2) Add zirconium salt compound and mix to obtain a protein amyloid fiber composite solution loaded with zirconium ions;

[0010] (3) The protein amyloid fiber composite solution in step (2) is mixed with polydimethyldiallylammonium chloride solution to obtain the nano-flocculator.

[0011] As a preferred embodiment, in step (1), the method for preparing the protein amyloid cellulose solution is as follows: dispersing protein powder in water, adjusting the pH to 2-4, and heating at 90-100°C for 4-10 hours.

[0012] In a preferred embodiment, in step (1), the protein powder is selected from at least one of bovine serum albumin, lactoglobulin, and lysozyme protein.

[0013] In a preferred embodiment, in step (1), the mass fraction of protein powder in the protein amyloid cellulose solution is 1% to 4%.

[0014] In a preferred embodiment, in step (2), the zirconium salt compound is a soluble Zr. 4+ Salts; such as zirconium oxychloride, zirconium nitrate, or zirconium sulfate.

[0015] And / or, in step (2), the mass fraction of zirconium in the protein amyloid fiber composite solution is 1% to 5%.

[0016] As a preferred embodiment, in step (2), a zirconium salt compound is added, the pH is adjusted to 2-4, and the solution is shaken at 20-40°C for 0.5-4 hours to obtain the protein amyloid fiber composite solution.

[0017] In a preferred embodiment, in step (3), the solid content of the polydimethyldiallylammonium chloride solution is 20% to 40%, and the viscosity is 5000 to 13000 mPa·s.

[0018] And / or, in step (3), the mass ratio of the protein amyloid fiber composite solution to the polydimethyldiallylammonium chloride solution is 1.2 to 2:1.

[0019] And / or, in step (3), the mixing time is 2 to 5 hours.

[0020] On the other hand, the present invention provides a nano-flocculator obtained by the above preparation method.

[0021] In another aspect, the present invention provides the application of the above-mentioned nano-flocculator in wastewater treatment.

[0022] Preferably, it is used in phosphorus removal from wastewater.

[0023] In the technical solution of this invention, the nano-flocculator is stable and can be stored for a long time at room temperature; it is used after dilution. In some specific embodiments, the nano-flocculator is mixed with sludge from the secondary sedimentation tank, and when the sludge concentration is 3000-15000 mg / L, the amount of nano-flocculator used is 40-4000 μL / L.

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] (1) Process innovation: Compared with the existing two-step treatment process of removing phosphate by iron salt and aluminum salt and accelerating sludge settling by flocculants such as polyacrylamide, the nano-flocculant with protein amyloid fiber as the core provided by the present invention has the dual effects of one-step deep phosphorus removal and accelerated sludge settling.

[0026] (2) The present invention uses protein amyloid fibers with ultra-high aspect ratio as core template material. On the one hand, protein amyloid fibers (highly charged amino acid components) can self-assemble with polydimethyldiallylammonium chloride to form a three-dimensional highly charged confined cage structure, which can rapidly enrich and capture sludge flocs. Through charge neutralization and polymer spatial confined network capture-bridging effect, sludge sedimentation is accelerated. On the other hand, amino acids at the protein amyloid fiber interface complex with Zr ions, enriching trace small flocs and forming large particles, thereby synergistically accelerating sedimentation.

[0027] (3) The nano-flocculator provided by this invention has significant advantages over conventional phosphorus removal agents in simultaneous phosphorus removal: amyloid fibers self-assemble to form a three-dimensional, highly charged confined cage structure, which can complex with Zr ions. By adjusting the pH, a biphasic Zr species is formed, namely, sub-5nm zirconium oxide particles induced by the fiber template and Zr charged species coordinated on the fiber surface. On the one hand, the ultra-high aspect ratio structure of the fiber can fully expose active sites, while its cage-like fiber structure can enrich phosphate to Zr sites. Under a highly concentrated confined environment of phosphate, the sub-5nm zirconium oxide particles and the Zr charged species coordinated on the fiber surface fully react with phosphate to form highly stable zirconium phosphate species. Unlike conventional zirconium oxide phosphorus removal which relies on weak core coordination, the amyloid fiber confined structure can change the interaction between Zr and phosphate from weak core coordination to strong, highly stable zirconium phosphate, increasing the phosphorus removal depth and correspondingly increasing the adsorption capacity by 3-5 times.

[0028] (4) The nano-flocculator provided by this invention has high stability and is easy to store for a long time; its application process is simple, requiring only simple dilution and addition, without the need for complex activation steps, adapting to the needs of rapid on-site reaction, and significantly improving operational convenience and application flexibility. At the same time, this material avoids the Fe2+ formation that is prone to occur in traditional iron-based flocculants during long-term storage. 2+ / Fe 3+ This nano-flocculator addresses issues such as precipitation and oxidative denaturation, ensuring long-term stability of the agent's performance and facilitating bulk procurement and continuous application in practical engineering projects. Furthermore, it has a wide range of applications: suitable for various water bodies including urban sewage, industrial wastewater, and aquaculture effluent, and is particularly well-suited for use in enhanced secondary sedimentation tanks to simultaneously address the challenges of excessive phosphorus levels and sludge settling control. Detailed Implementation

[0029] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0031] Example 1

[0032] Dissolve 1.5g of bovine serum albumin lyophilized powder in 100mL of deionized water, adjust the pH to 3, and heat in a 95℃ water bath for 6 hours to form a protein amyloid cellulose solution.

[0033] Zirconium oxychloride (ZrOCl2·8H2O) was added, the zirconium mass fraction was controlled at 3%, and the pH was adjusted to 3; the reaction was shaken at 30℃ for 40 minutes to obtain a protein amyloid fiber composite solution loaded with zirconium nanoparticles.

[0034] Add 1.5 mL of polydimethyldiallyl ammonium chloride solution with a solid content of 30% and a viscosity of 8000 mPa·s. The mass ratio of the protein starch-like fiber composite solution to the polydimethyldiallyl ammonium chloride solution is 1.5:1. Stir at room temperature for 3 hours to obtain the nano-flocculator.

[0035] The nano-flocculator was diluted 10 times and added to a municipal wastewater treatment system with a sludge concentration of 5000 mg / L at a dosage of 200 μL / L. The settling time was measured to be less than 10 minutes, and the total phosphorus concentration in the effluent was reduced to 0.21 mg / L.

[0036] Example 2

[0037] Weigh 2.0g of lysozyme protein powder and dissolve it in 100mL of deionized water. Adjust the pH to 2.5 and heat in a 90℃ water bath for 8 hours to obtain a protein amyloid cellulose solution.

[0038] Add ZrOCl2·8H2O, with a zirconium mass fraction of 5%, adjust the pH to 2, and shake and mix at 40℃ for 30 minutes to form a protein starch-like fiber composite solution loaded with nano-zirconium; mix this solution with polydimethyldiallylammonium chloride solution (solid content 35%, viscosity 8500 mPa·s) at a mass ratio of 2:1 and stir at room temperature for 4 hours to obtain a nano-flocculator.

[0039] When this nano-flocculator is diluted 10 times and used in livestock and poultry wastewater at a dosage of 300 μL / L, the total phosphorus removal rate exceeds 64.7%, and the floc stability is good.

[0040] Example 3

[0041] 2.5g of bovine serum albumin was dissolved in 100mL of deionized water, the pH was adjusted to 3, and the mixture was heated in a water bath at 95℃ for 6 hours. ZrOCl2·8H2O was added to make the zirconium mass fraction 4%, the pH was adjusted to 3, and the mixture was shaken at 35℃ for 30 minutes. Subsequently, it was mixed with a polydimethyldiallylammonium chloride solution with a solid content of 25% and a viscosity of about 7000mPa·s at a mass ratio of 1.5:1 and stirred for 3 hours to obtain a nano-flocculator.

[0042] The nano-flocculator was diluted 10 times and added to a fine chemical wastewater end-of-pipe treatment system. The sludge concentration was 9000 mg / L, the dosage was 500 μL / L, the sedimentation interface was clear, and the total phosphorus in the effluent decreased from 1.4 mg / L to 0.26 mg / L.

[0043] Example 4

[0044] 2.0 g of lysozyme protein powder was dissolved in 100 mL of deionized water, the pH was adjusted to 2.5, and the solution was treated in a 90℃ water bath for 8 hours to obtain a protein amyloid fiber solution. ZrOCl2·8H2O was added to make the zirconium mass fraction 3%, the pH was adjusted to 4, and the solution was reacted at 30℃ for 35 minutes to form a protein amyloid fiber composite solution loaded with nano-zirconium. Then, polydiallyldimethylammonium chloride solution (solid content 40%, viscosity 12000 mPa·s) was added. The mass ratio of the protein amyloid fiber composite solution to the polydiallyldimethylammonium chloride solution was 1.6:1. The solution was stirred at room temperature for 4 hours to obtain a nano-flocculator.

[0045] When the nano-flocculator was diluted 10 times and added to the effluent section of the SBR process system, TP decreased from 0.9 mg / L to 0.22 mg / L and SS decreased from 18 mg / L to 7 mg / L, and the effluent was stable and qualified.

[0046] Example 5

[0047] Dissolve 4g of lactoglobulin powder in 100mL of deionized water, adjust the pH to 2, and heat in a 100℃ water bath for 5 hours to form a protein amyloid cellulose solution.

[0048] Zirconium oxychloride (ZrOCl2·8H2O) was added, with the zirconium mass fraction controlled at 2.5% and the pH adjusted to 2. The mixture was shaken and reacted at 30°C for 2 hours to obtain a protein amyloid fiber composite solution loaded with nano-zirconium. Then, a polydimethyldiallyl ammonium chloride solution with a solid content of 30% and a viscosity of 8000 mPa·s was added, with the mass ratio of the protein amyloid fiber composite solution to the polydimethyldiallyl ammonium chloride solution being 2:1. The mixture was stirred at room temperature for 3 hours to obtain a nano-flocculator.

[0049] This nano-flocculator can be used for emergency addition during sudden increases in flow rates at urban wastewater treatment plants during heavy rain. When sludge concentration reached as high as 12000 mg / L, an addition of 600 μL / L resulted in a significant decrease in sludge level, with total phosphorus (TP) dropping from 0.56 mg / L to 0.28 mg / L, effectively controlling sludge floating and the risk of effluent exceeding standards.

[0050] Example 6

[0051] Dissolve 1.8g of bovine serum albumin lyophilized powder in 100mL of deionized water, adjust the pH to 3, and heat in a 95℃ water bath for 6 hours to form a protein amyloid cellulose solution.

[0052] Zirconium oxychloride (ZrOCl2·8H2O) was added, the zirconium mass fraction was controlled at 1.5%, the pH was adjusted to 3, and the reaction was shaken at 30℃ for 40 minutes to obtain a protein amyloid fiber composite solution loaded with zirconium nanoparticles.

[0053] Add 1.5 mL of polydimethyldiallyl ammonium chloride solution with a solid content of 35% and a viscosity of 10000 mPa·s. The mass ratio of protein starch-like fiber composite solution to polydimethyldiallyl ammonium chloride solution is 1.4:1. Stir at room temperature for 3 hours to obtain nano-flocculator.

[0054] This nano-flocculator can be used for end-of-pipe enhanced treatment of integrated rural domestic sewage facilities. The influent TP is 2.5 mg / L, and the effluent TP is stable at 0.21-0.29 mg / L, which is significantly better than the control group without the drug. SS and color are also significantly improved.

[0055] Example 7

[0056] Dissolve 1.6g of protein powder in 100mL of deionized water, adjust the pH to 3, and heat in a 90℃ water bath for 6 hours to form a protein amyloid cellulose solution.

[0057] ZrOCl2·8H2O was added, the zirconium mass fraction was controlled at 2.5%, the pH was adjusted to 2, and the reaction was carried out at 25℃ with shaking for 1 hour to obtain a protein amyloid fiber composite solution loaded with nano-zirconium; then a polydimethyldiallyl ammonium chloride solution with a solid content of 20% and a viscosity of 5000 mPa·s was added, and the mass ratio of the protein amyloid fiber composite solution to the polydimethyldiallyl ammonium chloride solution was 1.8:1; the mixture was stirred at room temperature for 4 hours to obtain a nano-flocculator.

[0058] This nano-flocculator can be used in industrial wastewater reuse treatment. Under the condition that the phosphorus content of the reused water is required to be <0.3mg / L, the dosage is only 250μL / L, which can stably meet the water quality requirements, proving that it also has promotional value in high-standard reclaimed water treatment systems.

[0059] Performance testing:

[0060] The nano-flocculator from Example 1 was stored in a light-protected environment at 25°C, and samples were taken on days 1, 7, and 15 for performance testing. The results showed that the nano-flocculator exhibited good stability, with no precipitation or significant color change. Subsequently, it was added to the secondary sedimentation tank at the end of the SBR system in the industrial park, with a sludge concentration of 8000 mg / L and a dosage of 400 μL / L. The effluent SS decreased from 26 mg / L to 9 mg / L, and total phosphorus decreased to 0.27 mg / L. The system sludge level decreased, and the operation became more stable. Furthermore, after three months of storage at 25°C in the dark, no precipitation or decrease in activity was observed. Repeat testing after dilution showed that the phosphorus removal rate remained essentially the same as the initial value, verifying its good storage stability and engineering adaptability.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nano-flocculant, characterized by, The method comprises the following steps: (1) preparing a protein amyloid fiber solution; (2) adding a zirconium salt compound, and mixing to obtain a protein amyloid fiber complex solution loaded with zirconium ions; (3) mixing the protein amyloid fiber complex solution in step (2) with a polydimethyl diallyl ammonium chloride solution to obtain the nano-flocculant; In step (1), the method for preparing the protein amyloid fiber solution is: dispersing protein powder in water, adjusting the pH to 2-4, and heating at 90-100°C for 4-10 hours; In step (2), the zirconium salt compound is added, the pH is adjusted to 2-4, and the mixture is oscillated at 20-40°C for 0.5-4 hours to obtain the protein amyloid fiber complex solution.

2. The production method according to claim 1, characterized by, In step (1), the protein powder is selected from at least one of bovine serum albumin, lactoglobulin and lysozyme protein.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass fraction of the protein powder in the protein amyloid fiber solution is 1%-4%.

4. The method of claim 1, wherein, In step (2), the zirconium salt compound is soluble Zr 4+ salt; And / or, in step (2), the mass fraction of zirconium in the protein amyloid fiber complex solution is 1%-5%.

5. The production method according to claim 1, characterized by, In step (3), the solid content of the polydimethyl diallyl ammonium chloride solution is 20%-40%, and the viscosity is 5000-13000 mPa·s; And / or, in step (3), the mass ratio of the protein amyloid fiber complex solution to the polydimethyl diallyl ammonium chloride solution is 1.2-2:1; And / or, the mixing time is 2-5 hours.

6. The nano-flocculant obtained by the preparation method of any one of claims 1-5.

7. The nano-flocculant of claim 6 for use in wastewater treatment.

8. Use according to claim 7, characterized in that, In the application of phosphorus removal in wastewater.