Phosphorus removal agent for sewage treatment and preparation method thereof

Abstract

The present invention belongs to the field of water treatment technology, and specifically relates to a phosphorus removal agent for sewage treatment and a preparation method thereof. The preparation method of the phosphorus removal agent for sewage treatment comprises the following steps: activating an iron / zinc bimetallic organic framework and reacting it with a bilirubin solution to prepare a modified bimetallic organic framework; then adding the modified bimetallic organic framework to a quaternized silk fibroin solution, ultrasonically shaking, standing, and freeze-drying to obtain the phosphorus removal agent. The present invention sequentially modifies the iron / zinc bimetallic organic framework with bilirubin and quaternized silk fibroin, and the resulting phosphorus removal agent can efficiently remove phosphorus through multiple mechanisms, and can achieve the removal and recovery of phosphate radicals by utilizing the light response characteristics of bilirubin. The structure is stable and the reusability is strong.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and particularly relates to a dephosphorization agent for sewage treatment and a preparation method thereof. Background Art

[0002] Due to human interference, large amounts of untreated phosphorus-containing domestic and industrial wastewater are discharged directly into rivers and lakes. The phosphorus concentrations far exceed the water's self-purification threshold, directly triggering a eutrophication crisis. As an essential element for living organisms, excessive accumulation of phosphorus not only threatens human drinking water safety, potentially inducing algal toxin poisoning and the release of carcinogens, but also disrupts the balance of aquatic ecosystems. For example, explosive algae growth can lead to oxygen depletion in the water, which can suffocate and kill fish.

[0003] Currently, mainstream phosphorus removal technologies, both domestically and internationally, include biological and chemical methods. While biological methods can avoid reagent costs, they suffer from long bacterial acclimation cycles, weak resistance to shock loads, and a sharp drop in phosphorus removal efficiency at low temperatures. While chemical methods can achieve highly efficient phosphorus removal, reducing phosphorus concentrations to below 0.5 mg / L, they carry high reagent costs. For example, the dosage of iron and aluminum salts typically requires 50-200 mg / L. They also produce large amounts of sludge, with chemical sludge containing >99% moisture. Developing new phosphorus removal agents to reduce wastewater phosphorus removal costs and ensure that wastewater meets discharge standards remains a key research topic.

[0004] Therefore, there is an urgent need for an environmentally friendly and effective phosphorus removal agent to cope with the increasingly serious problem of water eutrophication. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the first object of the present invention is to provide a method for preparing a phosphorus removal agent for sewage treatment.

[0006] The second object of the present invention is to provide a phosphorus removal agent for sewage treatment obtained by the above preparation method, which has a large adsorption capacity, a high phosphorus removal rate, a stable structure, and is reusable.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a phosphorus removal agent for sewage treatment comprises the following steps:

[0009] (1) Mixing ferric nitrate, zinc nitrate, N,N-dimethylformamide, ethanol and water to obtain a mixed solution, adjusting the pH to 3.5-4.5, and then adding 2,3-dihydroxyterephthalaldehyde and stirring to obtain a precursor solution; adding the precursor solution to a high-pressure reactor and heating for reaction; cooling after the reaction, centrifuging, washing, and drying to obtain an iron / zinc bimetallic organic framework;

[0010] (2) heating and activating the iron / zinc bimetallic organic framework, cooling it to room temperature, adding it to a bilirubin solution, heating and stirring it under an argon atmosphere and in the dark, centrifuging, washing, and drying it to obtain a modified bimetallic organic framework;

[0011] (3) Add the degummed silk fibroin to a lithium bromide aqueous solution, stir at 60-70°C until dissolved, then add tributyl methylammonium chloride, adjust the pH to 8-10 with alkali solution, and then keep warm for reaction; reduce the reaction solution to 0-5°C and dialyze in water, and adjust the concentration to obtain a quaternized silk fibroin solution;

[0012] (4) The modified bimetallic organic framework obtained in step (2) is added to the quaternized silk fibroin solution obtained in step (3), and the solution is subjected to ultrasonic vibration, allowed to stand, and freeze-dried to obtain the phosphorus removal agent.

[0013] Furthermore, the molar ratio of ferric nitrate, zinc nitrate and 2,3-dihydroxyterephthalaldehyde in step (1) is 1: (0.5-1): (1-2.5); and the concentration of ferric nitrate in the mixed solution is 0.02-0.05 mol / L.

[0014] Furthermore, the stirring time in step (1) is 0.5-2 h; the temperature of the heating reaction is 100-140° C., and the time is 10-20 h.

[0015] Furthermore, the specific process of the heating activation in step (2) is: heat-activating the iron / zinc bimetallic organic framework for 1-2 h at 120-150 °C under argon atmosphere.

[0016] Furthermore, the mass ratio of bilirubin to the iron / zinc bimetallic organic framework in the bilirubin solution in step (2) is 1:(3-6); the concentration of the bilirubin solution is 3-8 mg / mL; the heating and stirring temperature is 50-70°C, and the time is 0.5-1 h.

[0017] Furthermore, in step (3), the mass ratio of the degummed silk fibroin, tributylmethylammonium chloride, and lithium bromide aqueous solution is 1: (0.1-0.4): (5-10); the alkali solution is sodium hydroxide solution or potassium hydroxide solution; the concentration of the lithium bromide aqueous solution is 9-10 mol / L; and the insulation reaction time is 5-10 h.

[0018] Furthermore, the dialysis time in step (3) is 40-80 h; and the concentration of the quaternized silk fibroin solution is 4-10 w / v%.

[0019] Furthermore, in step (4), the ratio of the modified bimetallic organic framework to the quaternized silk fibroin solution is (0.05-0.08) g: 1 mL; the ultrasonic oscillation temperature is 35-45 ° C, and the time is 5-10 min.

[0020] A phosphorus removal agent for sewage treatment is prepared by the above-mentioned method for preparing the phosphorus removal agent for sewage treatment.

[0021] The beneficial technical effects of the present invention are:

[0022] 1. The present invention first modifies an iron / zinc bimetallic organic framework (BiOMF) with bilirubin to produce a modified BiOMF, which is then compounded with a quaternized silk fibroin solution to prepare a phosphorus removal agent. The phosphorus removal agent prepared in the present invention exhibits a stable structure, high adsorption capacity, high phosphorus removal rate, and good reusability.

[0023] 2. In the process of preparing the phosphorus removal agent of the present invention, the modified metal-organic framework obtained has the characteristics of high porosity, low density and large specific surface area, and the metal ions therein can form Fe-OP / Zn-OP bonds with phosphates through ligand exchange, thereby improving the adsorption capacity of phosphate and the phosphorus removal effect; the introduced bilirubin has a light-responsive property. Under light irradiation, its olefin bond undergoes a configurational transition from cis to trans, increasing the molecular rigidity, blocking part of the pores of the metal-organic framework, and more effectively intercepting phosphate ions; when the light is stopped, the bilirubin can return to the flexible cis structure, allowing the pores of the metal-organic framework to open again, realizing the removal of phosphate ions, and facilitating the recovery and reuse of the phosphorus removal agent.

[0024] 3. Since silk fibroin has a special hydrophilic-hydrophobic block structure, the hydrophilic light chain can form an amorphous random coil or α-helix structure, while the hydrophobic heavy chain can form a β-folded structure, which can form a fiber network structure. Silk fibroin is rich in amino acids such as glycine, alanine and serine, and its hydroxyl and amino groups can be combined with phosphate groups through hydrogen bonds or electrostatic effects to achieve adsorption and retention of phosphate groups. The present invention uses quaternary ammonium salts to graft cationic groups on silk fibroin, which can further enhance its selectivity and adsorption strength for phosphate groups. The quaternized silk fibroin hydrogel formed has a large specific surface area and good mechanical strength, which can enhance the adsorption capacity and adsorption stability of the dephosphorylation agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the phosphorus removal agent prepared in Example 1;

[0026] Figure 2 This is a scanning electron microscope image of the dephosphorization agent prepared in Comparative Example 3. DETAILED DESCRIPTION

[0027] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it is not intended that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, without departing from the inventive concept, several simple deductions or replacements can also be made, all of which should be considered to belong to the scope of protection of the present invention. The specific conditions not indicated in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0028] The preparation method of degummed silk fibroin in the following examples and comparative examples is as follows: immersing the silk fibroin in a sodium carbonate aqueous solution and boiling for 90 minutes to degummed the silk fibroin, washing the degummed silk fibroin three times with distilled water to remove sericin on the surface of the silk fibroin, and keeping the degummed silk fibroin in an oven at 60°C for 12 hours after washing to remove moisture, thereby obtaining degummed silk fibroin.

[0029] (1) Implementation

[0030] Example 1

[0031] Example 1 provides a method for preparing a phosphorus removal agent for sewage treatment, the specific steps are as follows:

[0032] (1) Adding ferric nitrate and zinc nitrate to a mixed solvent consisting of N,N-dimethylformamide, ethanol and deionized water in a ratio of 1 mmol:0.8 mmol:2 mmol:15 mL:10 mL:10 mL of ferric nitrate, zinc nitrate, 2,3-dihydroxyterephthalaldehyde, N,N-dimethylformamide, ethanol and deionized water to obtain a mixed solution; adjusting the pH of the mixed solution to 4 with acetic acid, adding 2,3-dihydroxyterephthalaldehyde and stirring for 1 h to obtain a precursor solution; transferring the precursor solution to a high-pressure reactor (filling degree <70%), reacting at 120 °C for 15 h, cooling after the reaction, centrifuging, washing and drying to obtain an iron / zinc bimetallic organic framework;

[0033] (2) Under an argon atmosphere, the iron / zinc bimetallic organic framework was activated at 130 °C for 1 h. After the activation, it was cooled to room temperature. A bilirubin solution with a concentration of 5 mg / mL was mixed with the activated iron / zinc bimetallic organic framework at a mass ratio of bilirubin to iron / zinc bimetallic organic framework of 1:4. Under an argon atmosphere, it was stirred in the dark at 60 °C for 0.8 h. After heating and stirring, the modified bimetallic organic framework was separated, washed, and dried to obtain the modified bimetallic organic framework.

[0034] (3) The degummed silk fibroin was added to a 9 mol / L lithium bromide aqueous solution at a mass ratio of 1:0.3:8 among degummed silk fibroin, tributyl methylammonium chloride, and lithium bromide aqueous solution. The solution was stirred at 60°C until dissolved. Tributyl methylammonium chloride was then added and the pH was adjusted to 9 with sodium hydroxide. The solution was kept warm for 8 h. The reaction solution was cooled to 3°C and dialyzed in pure water for 60 h. After adjusting the concentration, a quaternized silk fibroin solution with a concentration of 8 w / v% was obtained.

[0035] (4) The modified bimetallic organic framework was added to the quaternized silk fibroin solution at a ratio of 0.06 g:1 mL, and ultrasonically shaken at 40 °C for 8 min. After standing for 30 min, the solution was freeze-dried to obtain a phosphorus removal agent.

[0036] Example 1 provides a phosphorus removal agent for sewage treatment, which is prepared by the above preparation method.

[0037] The scanning electron microscope image of the phosphorus removal agent prepared in this embodiment is as follows Figure 1 shown.

[0038] Example 2

[0039] Example 2 provides a method for preparing a phosphorus removal agent for sewage treatment, the specific steps are as follows:

[0040] (1) Adding ferric nitrate and zinc nitrate to a mixed solvent consisting of N,N-dimethylformamide, ethanol and deionized water in a ratio of 1 mmol:1 mmol:2.5 mmol:10 mL:5 mL:5 mL of ferric nitrate, zinc nitrate, 2,3-dihydroxyterephthalaldehyde, N,N-dimethylformamide, ethanol and deionized water to obtain a mixed solution; adjusting the pH of the mixed solution to 4.5 with acetic acid, adding 2,3-dihydroxyterephthalaldehyde and stirring for 2 h to obtain a precursor solution; transferring the precursor solution to a high-pressure reactor (filling degree <70%), reacting at 140 °C for 20 h, cooling after the reaction, centrifuging, washing and drying to obtain an iron / zinc bimetallic organic framework;

[0041] (2) Under an argon atmosphere, the iron / zinc bimetallic organic framework was activated at 150 °C for 2 h. After the activation, it was cooled to room temperature. A bilirubin solution with a concentration of 3 mg / mL was mixed with the activated iron / zinc bimetallic organic framework at a mass ratio of bilirubin to iron / zinc bimetallic organic framework of 1:6. Under an argon atmosphere, the mixture was stirred in the dark at 70 °C for 1 h. After heating and stirring, the modified bimetallic organic framework was separated, washed, and dried to obtain the modified bimetallic organic framework.

[0042] (3) The degummed silk fibroin was added to a 10 mol / L lithium bromide aqueous solution at a mass ratio of 1:0.4:10 among degummed silk fibroin, tributyl methylammonium chloride, and lithium bromide aqueous solution. The solution was stirred at 70°C until dissolved. Tributyl methylammonium chloride was then added and the pH was adjusted to 10 with potassium hydroxide. The solution was kept warm for 10 h. The reaction solution was cooled to 5°C and dialyzed in pure water for 80 h. After adjusting the concentration, a quaternized silk fibroin solution with a concentration of 10 w / v% was obtained.

[0043] (4) The modified bimetallic organic framework was added to the quaternized silk fibroin solution at a ratio of 0.08 g:1 mL, and the solution was ultrasonically shaken at 45 °C for 10 min. After standing for 40 min, the solution was freeze-dried to obtain a phosphorus removal agent.

[0044] Example 2 provides a phosphorus removal agent for sewage treatment, which is prepared by the above preparation method.

[0045] Example 3

[0046] Example 3 provides a method for preparing a phosphorus removal agent for sewage treatment, and the specific steps are as follows:

[0047] (1) According to the amount ratio of ferric nitrate, zinc nitrate, 2,3-dihydroxyterephthalaldehyde, N,N-dimethylformamide, ethanol and deionized water of 1 mmol:0.5 mmol:1 mmol:20 mL:15 mL:15 mL, ferric nitrate and zinc nitrate were added to a mixed solvent consisting of N,N-dimethylformamide, ethanol and deionized water to obtain a mixed solution; the pH of the mixed solution was adjusted to 3.5 with acetic acid, and 2,3-dihydroxyterephthalaldehyde was added and stirred for 0.5 h to obtain a precursor solution; the precursor solution was transferred to a high-pressure reactor (filling degree <70%), reacted at 100 °C for 10 h, and after the reaction was completed, cooled, centrifuged, washed, and dried to obtain an iron / zinc bimetallic organic framework;

[0048] (2) Under an argon atmosphere, the iron / zinc bimetallic organic framework was activated at 120 °C for 1 h. After the activation, it was cooled to room temperature. The bilirubin solution with a concentration of 8 mg / mL was mixed with the activated iron / zinc bimetallic organic framework at a mass ratio of bilirubin to iron / zinc bimetallic organic framework of 1:3. Under an argon atmosphere, the mixture was stirred in the dark at 50 °C for 0.5 h. After heating and stirring, the modified bimetallic organic framework was separated, washed, and dried to obtain the modified bimetallic organic framework.

[0049] (3) The degummed silk fibroin was added to a 9 mol / L lithium bromide aqueous solution at a mass ratio of 1:0.1:5 among degummed silk fibroin, tributyl methylammonium chloride, and lithium bromide aqueous solution. The solution was stirred at 50°C until dissolved. Tributyl methylammonium chloride was then added and the pH was adjusted to 8 with potassium hydroxide. The solution was kept warm for 5 h. The reaction solution was cooled to 0°C and dialyzed in pure water for 40 h. After adjusting the concentration, a quaternized silk fibroin solution with a concentration of 4 w / v% was obtained.

[0050] (4) The modified bimetallic organic framework was added to the quaternized silk fibroin solution at a ratio of 0.05 g:1 mL, and the solution was ultrasonically shaken at 35 °C for 5 min. After standing for 20 min, the solution was freeze-dried to obtain a phosphorus removal agent.

[0051] Example 3 provides a phosphorus removal agent for sewage treatment, which is prepared by the above preparation method.

[0052] (2) Comparative Example

[0053] Comparative Example 1

[0054] Comparative Example 1 is substantially the same as Example 1, except that step (2) of Example 1 is omitted, and the modified bimetallic organic framework in steps (3) and (4) of Example 1 is replaced by an iron / zinc bimetallic organic framework.

[0055] Comparative Example 2

[0056] Comparative Example 2 is substantially the same as Example 1, except that steps (3) and (4) are omitted, i.e., the phosphorus removal agent is a modified bimetallic organic framework.

[0057] Comparative Example 3

[0058] Comparative Example 3 is substantially the same as Example 1, except that step (3) of Example 1 is omitted, and the quaternized silk fibroin solution in step (4) of Example 1 is replaced by a degummed silk fibroin solution.

[0059] The scanning electron microscope image of the phosphorus removal agent prepared in this comparative example is as follows Figure 2 shown.

[0060] (3) Test examples

[0061] 1. Adsorption rate and adsorption capacity test: 6 mg of each of the dephosphorus removers prepared in Examples 1-3 and Comparative Examples 1-3 was added to 50 mL of a phosphate aqueous solution with an initial concentration of 30 mg / L. The mixture was shaken at a constant temperature of 25°C until adsorption equilibrium was reached. The supernatant was filtered through a 0.45 μm filter membrane, and the phosphate concentration in the filtrate was determined. The adsorption rate and adsorption capacity of the dephosphorus remover were calculated. The results are shown in Table 1.

[0062] Phosphorus adsorption rate R (%) = (C0-C e ) / C0×100%, where C0 is the initial phosphate concentration in the solution before adsorption, mg / L; C e is the residual phosphate concentration in the solution at adsorption equilibrium, mg / L.

[0063] Adsorption capacity Q of phosphorus removal agent e (mg / g) = V (C0-C e ) / m, where V is the volume of phosphate solution, L; C0 is the initial phosphate concentration in the solution before adsorption, mg / L; C e is the residual phosphate concentration in the solution at adsorption equilibrium, mg / L; m is the mass of the dephosphorus remover, g.

[0064] 2. Reusability test: 6 mg of each of the dephosphorus removers prepared in Examples 1-3 and Comparative Examples 1-3 were added to 50 mL of a phosphate aqueous solution with an initial concentration of 30 mg / L, and the mixture was shaken at a constant temperature of 25°C until adsorption equilibrium was reached. The dephosphorus remover and the solution were separated by filtration through a 0.45 μm filter membrane. The dephosphorus remover was placed in an alkaline environment and protected from light for desorption. After filtration, it was washed with deionized water until neutral. After drying, the above adsorption-desorption cycle was repeated 10 times. After the 10th cycle, the molybdenum antimony anti-spectrophotometric method was used again to determine the residual phosphate concentration in the filtrate, and the adsorption rate after 10 cycles was calculated.

[0065] Table 1 Adsorption rate and adsorption capacity of phosphorus removal agents in Examples and Comparative Examples

[0066]

[0067] As can be seen from Table 1, the phosphorus removal agents prepared using Examples 1-3 of the present invention have large adsorption capacity, high phosphorus removal rate, stable structure and good repeatability.

[0068] Compared with Example 1, Comparative Example 1 omits step (2) and only performs quaternary ammonium silk protein modification on the iron / zinc bimetallic organic framework; Comparative Example 2 omits steps (3) (4) and only performs bilirubin modification on the iron / zinc bimetallic organic framework; Comparative Example 3 omits step (3) and replaces the quaternary ammonium silk protein solution with the degummed silk protein solution. The adsorption capacity and adsorption rate are significantly reduced compared with Example 1; further comparison of the initial adsorption rate with the adsorption rate after 10 cycles shows that the adsorption rate difference of Comparative Examples 1-3 is greater than that of Example 1, indicating that the adsorption stability and repeatability of Comparative Examples 1-3 are relatively poor. Specific analysis shows that the modified metal-organic framework in the phosphorus removal agent of the present invention has the characteristics of high porosity, low density and large specific surface area, and the metal ions therein can form Fe-OP / Zn-OP bonds with phosphates through ligand exchange, thereby improving the adsorption capacity of phosphate and the phosphorus removal effect; the introduced bilirubin has a light-responsive property. Under light irradiation, its olefin bond undergoes a configurational transition from cis to trans, increasing the rigidity of the molecule, blocking part of the pores of the metal-organic framework, and more effectively intercepting phosphate ions; when the light is stopped, the bilirubin can return to its flexible cis structure, allowing the pores of the metal-organic framework to open again, realizing the removal of phosphate ions, and facilitating the recovery and reuse of the phosphorus removal agent. In addition, since silk fibroin has a special hydrophilic-hydrophobic block structure, the hydrophilic light chain can form an amorphous random coil or α-helix structure, while the hydrophobic heavy chain can form a β-folded structure, which can form a fiber network structure. Silk fibroin is rich in amino acids such as glycine, alanine and serine, and its hydroxyl and amino groups can be combined with phosphate groups through hydrogen bonds or electrostatic effects to achieve adsorption and retention of phosphate groups. The present invention uses quaternary ammonium salts to graft cationic groups on silk fibroin, which can further enhance its selectivity and adsorption strength for phosphate groups. The formed quaternized silk fibroin hydrogel has a large specific surface area and good mechanical strength, which can enhance the adsorption capacity and adsorption stability of the dephosphorylation agent.

[0069] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. The basic principles and main features of the present invention have been described above using specific implementation schemes. Modifications or substitutions may be made based on the present invention, but such modifications or substitutions do not detract from the essence of the corresponding technical solutions from the scope of protection claimed by the present invention.

Claims

1. A method for preparing a phosphorus removal agent for sewage treatment, characterized in that: The following steps are involved: (1) Mixing ferric nitrate, zinc nitrate, N,N-dimethylformamide, ethanol and water to obtain a mixed solution, adjusting the pH to 3.5-4.5, and then adding 2,3-dihydroxyterephthalaldehyde and stirring to obtain a precursor solution; adding the precursor solution to a high-pressure reactor and heating for reaction; cooling after the reaction, centrifuging, washing, and drying to obtain an iron / zinc bimetallic organic framework; (2) heating and activating the iron / zinc bimetallic organic framework, cooling it to room temperature, adding it to a bilirubin solution, heating and stirring it under an argon atmosphere and in the dark, centrifuging, washing, and drying it to obtain a modified bimetallic organic framework; (3) Add the degummed silk fibroin to a lithium bromide aqueous solution, stir at 60-70°C until dissolved, then add tributyl methylammonium chloride, adjust the pH to 8-10 with alkaline solution, and then keep warm for reaction; The reaction solution was cooled to 0-5°C and dialyzed in water to obtain a quaternized silk fibroin solution after adjusting the concentration; (4) The modified bimetallic organic framework obtained in step (2) is added to the quaternized silk fibroin solution obtained in step (3), and the solution is subjected to ultrasonic vibration, allowed to stand, and freeze-dried to obtain the phosphorus removal agent.

2. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: The molar ratio of ferric nitrate, zinc nitrate and 2,3-dihydroxyterephthalaldehyde in step (1) is 1: (0.5-1): (1-2.5); the concentration of ferric nitrate in the mixed solution is 0.02-0.05 mol / L.

3. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: The stirring time in step (1) is 0.5-2 h; the heating reaction temperature is 100-140 °C and the time is 10-20 h.

4. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein The specific process of the heating activation in step (2) is: heat-activating the iron / zinc bimetallic organic framework for 1-2 hours at 120-150°C in an argon atmosphere.

5. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: The mass ratio of bilirubin to the iron / zinc bimetallic organic framework in the bilirubin solution in step (2) is 1:(3-6); the concentration of the bilirubin solution is 3-8 mg / mL; the heating and stirring temperature is 50-70°C, and the time is 0.5-1 h.

6. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: In step (3), the mass ratio of the degummed silk fibroin, tributylmethylammonium chloride, and lithium bromide aqueous solution is 1: (0.1-0.4): (5-10); the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the lithium bromide aqueous solution is 9-10 mol / L; and the insulation reaction time is 5-10 h.

7. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: The dialysis time in step (3) is 40-80 h; the concentration of the quaternized silk fibroin solution is 4-10 w / v%.

8. The method for preparing a phosphorus removal agent for sewage treatment according to claim 1, wherein: The amount ratio of the modified bimetallic organic framework to the quaternized silk fibroin solution in step (4) is (0.05-0.08) g: 1 mL; the ultrasonic oscillation temperature is 35-45 ° C and the time is 5-10 min.

9. A phosphorus removal agent for sewage treatment, characterized in that: The phosphorus removal agent for sewage treatment is prepared by the preparation method of any one of claims 1 to 8.

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