A membrane process for removing ammonia and nitrogen

Abstract

The present application relates to a kind of membrane ammonia nitrogen removal process, belong to wastewater treatment technical field.The process of the present application includes injecting acid solution into circulating acid storage tank, absorbing ammonia nitrogen in ammonia nitrogen wastewater by modified hollow fiber membrane, returning to circulating acid storage tank again for secondary absorption, complete ammonia nitrogen wastewater treatment and generate inorganic ammonium salt solution.Among them, modified hollow fiber membrane is prepared by polyvinylidene fluoride, sodium silicate, nano silicon dioxide through specific steps, with excellent ammonia nitrogen absorption performance.In the process, ammonia nitrogen wastewater is treated by aeration after adjusting pH value by lye, then absorbs ammonia nitrogen by modified hollow fiber membrane, realizes high-efficiency denitrification.In addition, the present application specifies acid solution, lye type and concentration, aeration treatment parameters in detail, to ensure treatment effect.Finally, inorganic ammonium salt solution is discharged from system by blowdown pump for subsequent treatment.The present application process is simple, easy to operate, high denitrification efficiency, suitable for various ammonia nitrogen-containing wastewater treatment, with wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a membrane-based ammonia nitrogen removal process. Background Technology

[0002] Ammonia nitrogen wastewater treatment is a crucial issue in the environmental protection field. With the acceleration of industrialization, the discharge of ammonia nitrogen wastewater is increasing year by year, causing serious pollution to the aquatic environment. Traditional ammonia nitrogen wastewater treatment methods suffer from problems such as low treatment efficiency, high cost, and secondary pollution. Therefore, developing efficient, economical, and environmentally friendly ammonia nitrogen wastewater treatment technologies is of paramount importance.

[0003] Membrane-based ammonia nitrogen removal technology, as a novel treatment method, boasts advantages such as high treatment efficiency, small footprint, and ease of operation, and has gradually become a research hotspot in the field of ammonia nitrogen wastewater treatment. However, existing membrane-based ammonia nitrogen removal technologies still face some challenges in practical applications, such as the selection of membrane materials, membrane modification, and optimization of the treatment process. These issues limit the widespread application of membrane-based ammonia nitrogen removal technology.

[0004] This invention provides an improved membrane-based ammonia nitrogen removal process. By employing a specific modified hollow fiber membrane and a recyclable absorbent, it enhances the absorption efficiency of ammonia nitrogen and reduces the formation rate of inorganic ammonium salts, while simultaneously lowering treatment costs and environmental impact. This invention aims to address the problems existing in current membrane-based ammonia nitrogen removal technologies, providing a highly efficient, economical, and environmentally friendly method for treating ammonia nitrogen wastewater to meet increasingly stringent environmental requirements and industrial production needs. Summary of the Invention

[0005] The purpose of this invention is to provide a membrane-based ammonia nitrogen removal process with high ammonia nitrogen removal efficiency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A membrane-based ammonia nitrogen removal process flow, the specific steps of which are as follows:

[0008] S1: Inject an acid solution with a mass fraction of 10-30% into the circulating acid storage tank, start the circulation, and pass the dilute acid solution into the modified hollow fiber membrane in the ammonia nitrogen wastewater pool;

[0009] S2: The wastewater containing ammonia nitrogen is introduced into the ammonia nitrogen wastewater tank, and the pH value is adjusted with alkaline solution. The pH value of the ammonia nitrogen wastewater is tested. After it meets the standard, the wastewater is aerated.

[0010] S3: The ammonia nitrogen wastewater after aeration is absorbed by a modified hollow fiber membrane to generate an inorganic ammonium salt solution. The generated inorganic ammonium salt solution is then returned to the circulating acid storage tank for secondary absorption by a circulating pump to complete the treatment of ammonia nitrogen wastewater.

[0011] S4: The inorganic ammonium salt solution is discharged from the system via a sewage pump for subsequent product separation and purification.

[0012] Furthermore, the preparation method of the modified hollow fiber membrane in S1 is as follows:

[0013] S1.1: Heat polyvinylidene fluoride to 165-180℃ to make it melt, add N,N-dimethylacetamide (DMAC) at a mass ratio of 1:1, and stir at 200 r / min for 1 h to obtain a uniformly mixed solution A.

[0014] S1.2: Dissolve sodium silicate in deionized water to obtain a sodium silicate aqueous solution with a mass fraction of 20-30%. Disperse nano-silica in the sodium silicate aqueous solution with a solid-liquid mass ratio of 1:2. Then add 2 wt% of silane coupling agent KH550 to the solid-liquid mixture and stir at 300 r / min for 1-2 h to obtain solid-liquid mixture B.

[0015] S1.3: Mix solid-liquid mixture B and mixed solution A at a volume ratio of 1:(2-4), increase the rotation speed to 800 r / min, stir for 2 h, add 5 wt% trifluoroacetic acid solution and 7 wt% p-toluenesulfonyl fluoride, continue stirring for 0.5 h to obtain casting solution;

[0016] S1.4: Using a hollow fiber membrane spinning machine with a spinning machine temperature of 30-40℃, the casting solution is extruded through a hollow spinneret. Nitrogen gas is injected at the same time as the extrusion. The extruded membrane is immersed in deionized water at 20-30℃ for coagulation to form a hollow fiber membrane structure.

[0017] S1.5: The prepared hollow fiber membrane is rinsed to remove residual solvents and additives, and dried at 80°C in a nitrogen atmosphere. After drying, a 10% polydimethylsiloxane solution is coated on the surface, and the membrane is allowed to stand and dry at room temperature to obtain the modified hollow fiber membrane.

[0018] Furthermore, the acid solution in S1 is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid.

[0019] Furthermore, the pH value in the circulating acid storage tank in S1 is 1 to 2.

[0020] Furthermore, the trifluoroacetic acid in the trifluoroacetic acid solution in S1.3 has a mass fraction of 3-5%.

[0021] Furthermore, in step S1.4, the nitrogen gas is introduced at a flow rate of 5 m / s and a pressure of 0.2–0.3 MPa.

[0022] Furthermore, the alkaline solution in S2 is one or more of calcium hydroxide, sodium hydroxide, and sodium carbonate.

[0023] Furthermore, the mass fraction of the alkaline solution in S2 is 30-50%.

[0024] Furthermore, the pH value of the ammonia nitrogen wastewater in S2 is >10.

[0025] Furthermore, the aeration parameters in S2 are an aeration duty cycle of 100% and an aeration flow rate of 2.5 m³ / s. 3 / L, airflow temperature 50℃.

[0026] In this invention, the acidic circulating solution in the circulating acid storage tank enters the modified hollow fiber membrane under the action of the circulating pump, and absorbs NH3 generated by ammonia nitrogen wastewater in the ammonia nitrogen wastewater pool, thereby reducing the ammonia nitrogen concentration. The ammonia nitrogen concentration is continuously reduced through circulation. The circulating acid storage tank is replenished with acid to maintain the pH value of the acidic circulating solution between 1 and 2. The ammonia nitrogen wastewater pool is replenished with alkaline solution to make the pH of the ammonia nitrogen wastewater > 10, thereby improving the ammonia nitrogen removal effect.

[0027] This invention achieves highly efficient ammonia nitrogen removal by injecting an acid solution into a circulating acid storage tank and utilizing a modified hollow fiber membrane to effectively absorb ammonia nitrogen wastewater, generating an inorganic ammonium salt solution. The use of a modified hollow fiber membrane for ammonia nitrogen absorption improves absorption efficiency and selectivity, while simultaneously forming a closed-loop circulation system, reducing wastewater discharge and improving resource utilization. Furthermore, the process flow of this invention further optimizes the treatment effect by precisely adjusting the wastewater pH and aeration treatment.

[0028] Aeration devices are used to aerate ammonia nitrogen wastewater, ensuring that suspended solids in the influent are evenly separated, reducing the accumulation of suspended solids on the membrane surface, and removing pollutants from the membrane surface, thereby improving the ammonia nitrogen removal efficiency and enabling the treatment of ammonia nitrogen wastewater with high concentrations of suspended solids.

[0029] The modified hollow fiber membrane prepared by this invention exhibits significant advantages in membrane-based ammonia nitrogen removal processes. This membrane not only possesses highly efficient ammonia nitrogen absorption capacity, effectively reducing the ammonia nitrogen content in wastewater, but also demonstrates good chemical stability and mechanical strength, ensuring long-term stable operation.

[0030] During the preparation process, various additives play a crucial role. Polyvinylidene fluoride (PVDF), as the base material of the membrane, provides excellent mechanical support and chemical inertness, and is a major component of the membrane structure. N,N-dimethylacetamide (DMAC), as a solvent, helps to form a homogeneous solution of PVDF, laying the foundation for the subsequent spinning process.

[0031] The introduction of sodium silicate aqueous solution and nano-silica significantly enhanced the mechanical strength and pore structure of the membrane. Sodium silicate, acting as an inorganic framework, interacted with nano-silica to form a more robust membrane structure. Simultaneously, the dispersion of nano-silica increased the membrane's surface area and porosity, facilitating the adsorption and transport of ammonia nitrogen molecules. The addition of the silane coupling agent KH550 further improved the compatibility between the inorganic filler and the organic polymer, ensuring the stability and uniformity of the membrane structure.

[0032] Trifluoroacetic acid solution and p-toluenesulfonyl fluoride, acting as surfactants, allowed for precise control of the membrane's surface properties. They could regulate the membrane's pore size and distribution, optimizing its selective absorption of ammonia nitrogen molecules. Beyond their role as surfactants in adjusting membrane surface properties, the addition of trifluoroacetic acid solution and p-toluenesulfonyl fluoride played a more crucial role.

[0033] Trifluoroacetic acid solution exhibits strong hydrophobicity, forming a dense hydrophobic layer on the membrane surface. This effectively prevents water molecule penetration, thereby improving the membrane's antifouling performance and selectivity. Simultaneously, its unique molecular structure interacts with polyvinylidene fluoride (PVDF) molecular chains, enhancing the membrane's stability and mechanical strength. Toluenesulfonyl fluoride primarily functions as a pore regulator, finely controlling the pore structure and distribution within the membrane by influencing the phase separation process of the casting solution. This regulatory effect not only optimizes the adsorption and transport pathways of ammonia nitrogen molecules but also further improves the membrane's separation efficiency and selectivity. The synergistic mechanism between the two lies in the complementary and mutually reinforcing effects of the hydrophobic effect of trifluoroacetic acid solution and the pore-regulating effect of toluenesulfonyl fluoride. The formation of the hydrophobic layer reduces water molecule interference, providing more favorable conditions for pore structure optimization; conversely, pore structure optimization further enhances the effectiveness of the hydrophobic layer, resulting in superior performance of the modified hollow fiber membrane in ammonia nitrogen wastewater treatment.

[0034] This invention also utilizes a polydimethylsiloxane solution to form a hydrophobic layer on the membrane surface, which effectively prevents the penetration of moisture and other impurities, maintaining the stability and efficiency of the membrane's internal structure. This hydrophobic layer not only improves the membrane's durability but also ensures its continued high efficiency in treating ammonia nitrogen wastewater.

[0035] In this invention, polyvinylidene fluoride was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., with a purity of 98%; trifluoroacetic acid was purchased from Jinan Zhonglan Chemical Co., Ltd., with a purity of 99.9%; p-toluenesulfonyl fluoride was purchased from Anhui Zesheng Technology Co., Ltd., with a purity of 98%; and polydimethylsiloxane was purchased from Jinan Longcheng Organosilicon Co., Ltd., with a purity of 99.99%.

[0036] The beneficial effects of this invention are:

[0037] This invention achieves highly efficient removal of ammonia nitrogen from wastewater by employing modified hollow fiber membrane technology. By injecting acid solution into a circulating acid storage tank and utilizing the modified hollow fiber membrane to absorb the ammonia nitrogen wastewater, an inorganic ammonium salt solution is generated, significantly reducing the ammonia nitrogen concentration in the wastewater. Simultaneously, this invention reduces wastewater discharge and improves resource utilization through a secondary recycling system.

[0038] The modified hollow fiber membrane prepared by this invention not only possesses highly efficient ammonia nitrogen absorption capacity but also exhibits excellent chemical stability and mechanical strength, ensuring long-term stable operation. During the preparation process, additives such as polyvinylidene fluoride, N,N-dimethylacetamide, sodium silicate aqueous solution, nano-silica, silane coupling agent KH550, trifluoroacetic acid solution, and p-toluenesulfonyl fluoride played key roles, collectively contributing to the membrane's superior performance. Attached Figure Description

[0039] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0040] Figure 1 Schematic diagram of membrane process for removing ammonia nitrogen. Detailed Implementation

[0041] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0042] Example 1

[0043] S1: Inject a 20% sulfuric acid solution into the circulating acid storage tank. The pH value in the circulating acid storage tank is 2. Start the circulation and pass the dilute acid solution into the modified hollow fiber membrane in the ammonia nitrogen wastewater pool.

[0044] The preparation method of modified hollow fiber membrane is as follows:

[0045] S1.1: Heat polyvinylidene fluoride to 175°C to make it melt, add N,N-dimethylacetamide (DMAC) at a mass ratio of 1:1, and stir at 200 r / min for 1 h to obtain a uniformly mixed solution A.

[0046] S1.2: Dissolve sodium silicate in deionized water to obtain a sodium silicate aqueous solution with a mass fraction of 30%. Disperse nano-silica in the sodium silicate aqueous solution with a solid-liquid mass ratio of 1:2. Then add 2 wt% of silane coupling agent KH550 to the solid-liquid mixture and stir at 300 r / min for 2 h to obtain solid-liquid mixture B.

[0047] S1.3: Mix solid-liquid mixture B and mixed solution A at a volume ratio of 1:3, increase the rotation speed to 800 r / min, stir for 2 h, add 5 wt% trifluoroacetic acid solution and 7 wt% p-toluenesulfonyl fluoride, wherein the mass fraction of trifluoroacetic acid solution is 5%, and continue stirring for 0.5 h to obtain casting solution;

[0048] S1.4: Using a hollow fiber membrane spinning machine with a spinning machine temperature of 35℃, the casting solution is extruded through a hollow spinneret. Nitrogen gas is injected at the same time as the extrusion, with a flow rate of 5m / s and a pressure of 0.3MPa. The extruded membrane is then immersed in deionized water at 25℃ for solidification to form a hollow fiber membrane structure.

[0049] S1.5: The prepared hollow fiber membrane is rinsed to remove residual solvents and additives, and dried at 80°C in a nitrogen atmosphere. After drying, a 10% polydimethylsiloxane solution is coated on the surface, and the membrane is allowed to stand and dry at room temperature to obtain the modified hollow fiber membrane.

[0050] S2: Wastewater containing ammonia nitrogen is introduced into an ammonia nitrogen wastewater tank, and the pH value is adjusted using a 30-50% (w / w) calcium hydroxide solution. The pH value of the ammonia nitrogen wastewater is then tested. If the pH value is >10, meeting the standard, the wastewater is aerated. The aeration parameters are: aeration duty cycle of 100% and aeration flow rate of 2.5 m³ / h. 3 / L, airflow temperature 50℃;

[0051] S3: The ammonia nitrogen wastewater after aeration is absorbed by a modified hollow fiber membrane to generate an inorganic ammonium salt solution. The generated inorganic ammonium salt solution is then returned to the circulating acid storage tank for secondary absorption by a circulating pump to complete the treatment of ammonia nitrogen wastewater.

[0052] S4: The inorganic ammonium salt solution is discharged from the system via a sewage pump for subsequent product separation and purification.

[0053] Example 2

[0054] S1: Inject a 10% phosphoric acid solution into the circulating acid storage tank. The pH value in the circulating acid storage tank is 1.5. Start the circulation and pass the dilute acid solution into the modified hollow fiber membrane in the ammonia nitrogen wastewater pool.

[0055] The preparation method of modified hollow fiber membrane is as follows:

[0056] S1.1: Heat polyvinylidene fluoride to 165°C to make it melt, add N,N-dimethylacetamide (DMAC) at a mass ratio of 1:1, and stir at 200 r / min for 1 h to obtain a uniformly mixed solution A.

[0057] S1.2: Dissolve sodium silicate in deionized water to obtain a sodium silicate aqueous solution with a mass fraction of 20%. Disperse nano-silica in the sodium silicate aqueous solution with a solid-liquid mass ratio of 1:2. Then add 2 wt% of silane coupling agent KH550 to the solid-liquid mixture and stir at 300 r / min for 1 h to obtain solid-liquid mixture B.

[0058] S1.3: Mix solid-liquid mixture B and mixed solution A at a volume ratio of 1:4, increase the rotation speed to 800 r / min, stir for 2 h, add 5 wt% trifluoroacetic acid solution and 7 wt% p-toluenesulfonyl fluoride, wherein the mass fraction of trifluoroacetic acid solution is 3%, and continue stirring for 0.5 h to obtain casting solution;

[0059] S1.4: Using a hollow fiber membrane spinning machine with a spinning machine temperature of 30℃, the casting solution is extruded through a hollow spinneret. Nitrogen gas is injected at the same time as the extrusion, with a flow rate of 5m / s and a pressure of 0.3MPa. The extruded membrane is then immersed in deionized water at 30℃ for solidification to form a hollow fiber membrane structure.

[0060] S1.5: The prepared hollow fiber membrane is rinsed to remove residual solvents and additives, and dried at 80°C in a nitrogen atmosphere. After drying, a 10% polydimethylsiloxane solution is coated on the surface, and the membrane is allowed to stand and dry at room temperature to obtain the modified hollow fiber membrane.

[0061] S2: Wastewater containing ammonia nitrogen is introduced into an ammonia nitrogen wastewater tank, and the pH value is adjusted using a 30% sodium hydroxide solution. The pH value of the ammonia nitrogen wastewater is then tested. If the pH value is >10, meeting the standard, the wastewater is aerated. The aeration parameters are: aeration duty cycle of 100% and aeration flow rate of 2.5 m³ / h. 3 / L, airflow temperature 50℃;

[0062] S3: The ammonia nitrogen wastewater after aeration is absorbed by a modified hollow fiber membrane to generate an inorganic ammonium salt solution. The generated inorganic ammonium salt solution is then returned to the circulating acid storage tank for secondary absorption by a circulating pump to complete the treatment of ammonia nitrogen wastewater.

[0063] S4: The inorganic ammonium salt solution is discharged from the system via a sewage pump for subsequent product separation and purification.

[0064] Example 3

[0065] S1: Inject a 30% nitric acid solution into the circulating acid storage tank. The pH value in the circulating acid storage tank is 1.5. Start the circulation and pass the dilute acid solution into the modified hollow fiber membrane in the ammonia nitrogen wastewater pool.

[0066] The preparation method of modified hollow fiber membrane is as follows:

[0067] S1.1: Heat polyvinylidene fluoride to 180°C to make it melt, add N,N-dimethylacetamide (DMAC) at a mass ratio of 1:1, and stir at 200 r / min for 1 h to obtain a uniformly mixed solution A.

[0068] S1.2: Dissolve sodium silicate in deionized water to obtain a sodium silicate aqueous solution with a mass fraction of 30%. Disperse nano-silica in the sodium silicate aqueous solution with a solid-liquid mass ratio of 1:2. Then add 2 wt% of silane coupling agent KH550 to the solid-liquid mixture and stir at 300 r / min for 1 to 2 hours to obtain solid-liquid mixture B.

[0069] S1.3: Mix solid-liquid mixture B and mixed solution A at a volume ratio of 1:2, increase the rotation speed to 800 r / min, stir for 2 h, add 5 wt% trifluoroacetic acid solution and 7 wt% p-toluenesulfonyl fluoride, wherein the mass fraction of trifluoroacetic acid solution is 5%, and continue stirring for 0.5 h to obtain casting solution;

[0070] S1.4: Using a hollow fiber membrane spinning machine with a spinning machine temperature of 30℃, the casting solution is extruded through a hollow spinneret. Nitrogen gas is injected at the same time as the extrusion, with a flow rate of 5m / s and a pressure of 0.2MPa. The extruded membrane is then immersed in deionized water at 20℃ for solidification to form a hollow fiber membrane structure.

[0071] S1.5: The prepared hollow fiber membrane is rinsed to remove residual solvents and additives, and dried at 80°C in a nitrogen atmosphere. After drying, a 10% polydimethylsiloxane solution is coated on the surface, and the membrane is allowed to stand and dry at room temperature to obtain the modified hollow fiber membrane.

[0072] S2: Wastewater containing ammonia nitrogen is introduced into an ammonia nitrogen wastewater tank, and the pH value is adjusted using a 50% sodium carbonate solution. The pH value of the ammonia nitrogen wastewater is then tested. If the pH value is >10, meeting the standard, the wastewater is aerated. The aeration parameters are: aeration duty cycle of 100% and aeration flow rate of 2.5 m³ / h. 3 / L, airflow temperature 50℃;

[0073] S3: The ammonia nitrogen wastewater after aeration is absorbed by a modified hollow fiber membrane to generate an inorganic ammonium salt solution. The generated inorganic ammonium salt solution is then returned to the circulating acid storage tank for secondary absorption by a circulating pump to complete the treatment of ammonia nitrogen wastewater.

[0074] S4: The inorganic ammonium salt solution is discharged from the system via a sewage pump for subsequent product separation and purification.

[0075] Comparative Example 1

[0076] In this comparative example, sodium silicate was not added during the preparation of the modified hollow fiber membrane, and the remaining steps were the same as in Example 1.

[0077] Comparative Example 2

[0078] In this comparative example, no nano-silica was added during the preparation of the modified hollow fiber membrane, and the remaining steps were the same as in Example 1.

[0079] Comparative Example 3

[0080] In this comparative example, trifluoroacetic acid solution was not added during the preparation of the modified hollow fiber membrane, and the remaining steps were the same as in Example 1.

[0081] Comparative Example 4

[0082] In this comparative example, p-toluenesulfonyl fluoride was not added during the preparation of the modified hollow fiber membrane, and the remaining steps were the same as in Example 1.

[0083] Comparative Example 5

[0084] In this comparative example, the surface of the modified hollow fiber membrane was not coated with polydimethylsiloxane solution during preparation; the remaining steps were the same as in Example 1.

[0085] The results obtained from the examples and comparative examples were tested to determine the ammonia nitrogen removal rate from the ammonia nitrogen wastewater. The experimental results are summarized in the table below.

[0086]

[0087]

[0088] Experimental data show that the modified hollow fiber membrane prepared in this invention has a better ammonia nitrogen removal rate.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A membrane process for the removal of ammonia and nitrogen, characterized in that, The process flow comprises the following specific steps, S1: inject an acid solution with a mass fraction of 10-30% into a circulating acid storage tank, start the circulation, and pass the dilute acid solution into the modified hollow fiber membrane in the ammonia-nitrogen wastewater pool; S2: pass the wastewater containing ammonia-nitrogen into the ammonia-nitrogen wastewater pool, adjust the pH value by using lye, detect the pH value of the ammonia-nitrogen wastewater, and after the standard is met, perform aeration treatment on the wastewater; S3: use the modified hollow fiber membrane to absorb ammonia-nitrogen from the aeration-treated ammonia-nitrogen wastewater, and generate an inorganic ammonium salt solution, and return the generated inorganic ammonium salt solution to the circulating acid storage tank again through the action of a circulating pump for secondary absorption, thereby completing the treatment of the ammonia-nitrogen wastewater; S4: discharge the inorganic ammonium salt solution from the system through a blowdown pump, and perform subsequent product separation and purification treatment; The preparation method of the modified hollow fiber membrane in S1 is as follows, S1.1: heat polyvinylidene fluoride to 165-180℃ to make the polyvinylidene fluoride in a molten state, add N,N-dimethylacetamide DMAC at a mass ratio of 1:1, and stir at a speed of 200 r / min for 1 h to obtain a mixed solution A with uniform mixing; S1.2: dissolve sodium silicate in deionized water to obtain a sodium silicate aqueous solution with a mass fraction of 20-30%, disperse nano-silicon dioxide in the sodium silicate aqueous solution, and mix the solid-liquid mixture at a solid-liquid mass ratio of 1:2, then add 2 wt% of silane coupling agent KH550, and stir at a speed of 300 r / min for 1-2 h to obtain a solid-liquid mixture B; S1.3: mix the solid-liquid mixture B and the mixed solution A at a volume ratio of 1:(2-4), increase the stirring speed to 800 r / min, add 5 wt% of a trifluoroacetic acid solution and 7 wt% of p-toluenesulfonyl fluoride after stirring for 2 h, continue stirring for 0.5 h, and obtain a casting solution; S1.4: use a hollow fiber membrane spinning machine, set the spinning machine temperature to 30-40℃, extrude the casting solution through a hollow spinneret while injecting nitrogen, immerse the extruded membrane in deionized water at 20-30℃ for coagulation, and form a hollow fiber membrane structure; S1.5: rinse the prepared hollow fiber membrane to remove residual solvents and additives, dry it in a nitrogen atmosphere at 80℃, and then coat a layer of polydimethylsiloxane solution with a mass fraction of 10% on the surface, and dry it at room temperature to obtain the modified hollow fiber membrane.

2. The process according to claim 1, characterized in that, The acid solution in S1 is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid.

3. The process according to claim 1, characterized in that, The pH value in the circulating acid storage tank in S1 is 1-2.

4. The process of claim 1, wherein, The mass fraction of trifluoroacetic acid in the trifluoroacetic acid solution in S1.3 is 3-5%.

5. The process of claim 1, wherein the process is characterized by, The flow rate of the nitrogen gas in S1.4 is 5 m / s, and the pressure is 0.2-0.3 MPa.

6. The process of claim 1, wherein, The lye in S2 is one or more of calcium hydroxide, sodium hydroxide, and sodium carbonate.

7. The process of claim 1 wherein, The mass fraction of the lye in S2 is 30-50%.

8. The process of claim 1, wherein the process is characterized by, The pH value of the ammonia-nitrogen wastewater in S2 is >10.

9. The process of claim 1, wherein, The parameters of the aeration treatment in S2 are aeration duty cycle 100%, aeration flow rate 2.5 m 3 / L, air flow temperature 50°C.

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