Preparation method for tubular gas-permeable membrane for wastewater treatment and denitrification process

Abstract

Disclosed in the present invention are a preparation method for a tubular gas-permeable membrane for wastewater treatment and a denitrification process. The preparation method for a tubular gas-permeable membrane of the present invention comprises: slitting a flat-sheet denitrification membrane into strips, and then successively subjecting the strip-shaped flat-sheet denitrification membrane to winding, laminating, bonding, tube making and cutting to form a tubular gas-permeable membrane. The preparation method of the present invention is based on original flat-sheet denitrification membranes and an optimized winding process. Compared with traditional gas-permeable membranes, the prepared tubular gas-permeable membrane has higher ammonia mass transfer efficiency. In addition, the tubular gas-permeable membrane uses a closed columnar membrane structure, so that the ammonia leakage rate can be significantly reduced, greatly improving the denitrification efficiency of wastewater. The preparation method for a tubular gas-permeable membrane and the denitrification process provided by the present invention have a wide range of application and high denitrification efficiency, can recover ammonia nitrogen resources while treating ammonia nitrogen wastewater, and have good economic and environmental benefits.

Description

A method for preparing a tubular gaseous membrane for wastewater treatment and a denitrification process Technical Field

[0001] This invention relates to a method for preparing a tubular gaseous membrane and a denitrification process for wastewater treatment, belonging to the field of wastewater denitrification technology. Background Technology

[0002] Physical nitrogen removal technologies such as ammonia stripping, struvite removal, and gaseous membrane processes have been widely applied for ammonia nitrogen recovery from wastewater. These technologies can separate and extract NH3-N from wastewater and convert it into usable ammonium salts. They also reduce the NH3-N content in wastewater, adjusting the C / N ratio and facilitating subsequent biological treatment. Ammonia stripping is highly effective at removing NH3-N from wastewater, but its gas-liquid ratio and energy consumption are relatively high, and scaling on the inner walls of the stripping or ammonia stripping tower is a significant problem. The struvite process is simple and rapid, has good ammonia nitrogen removal efficiency, and its byproducts have high economic value. However, for wastewater lacking phosphorus and magnesium, large amounts of magnesium and phosphate salts need to be added, resulting in higher costs.

[0003] The gas-permeable membrane (GPM) process utilizes a microporous hydrophobic membrane to isolate the ammonia-nitrogen-containing feed solution from the acidic absorbent solution, placing them on opposite sides of the membrane. This increases the pH of the feed solution, allowing ionic NH4+ to be released. + The NH3 is transformed into free gaseous NH3, and under the driving force of mass transfer (mainly the partial pressure difference of NH3 on both sides of the membrane), the NH3 passes through the microporous membrane and is absorbed by the absorbent, and undergoes an acid-base neutralization reaction to form ammonium salt. Compared with the ammonia stripping method, the gaseous membrane method does not require a large amount of air or water vapor to strip off NH3, nor does it require the use of large stripping towers and absorption towers, resulting in lower denitrification costs.

[0004] Based on the form or arrangement of the membrane, the commonly used denitrification membrane modules are mainly: tubular membrane modules, hollow fiber membrane modules, and flat-sheet membrane modules. Single modules or multiple modules can be assembled into membrane separators for use in factories and laboratories. The applicant's previously filed and granted patent, "A flat-sheet denitrification membrane for wastewater treatment and its preparation method" (ZL202010862209.4), developed a flat-sheet denitrification membrane. This denitrification membrane solved the technical problem of fouling in denitrification membrane modules. However, existing denitrification membranes and membrane modules still have problems such as low denitrification efficiency and ammonia leakage.

[0005] Summary of the Invention

[0006] The purpose of this invention is to improve the denitrification efficiency of traditional denitrification membranes and their components, and to solve technical problems such as ammonia leakage. This invention provides a method for preparing a tubular gaseous membrane and a denitrification process for wastewater treatment. Compared with traditional gaseous membranes, the tubular gaseous membrane prepared by the method of this invention has a higher ammonia mass transfer efficiency. Moreover, the tubular gaseous membrane adopts a closed columnar membrane structure, which can significantly reduce the ammonia leakage rate. Therefore, the wastewater denitrification efficiency is greatly improved.

[0007] In order to solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a tubular gaseous membrane for wastewater treatment, comprising: cutting a flat sheet denitrification membrane into strips, and then sequentially winding, stacking, bonding, tube making and cutting the strip-shaped flat sheet denitrification membrane to form a tubular gaseous membrane.

[0009] The flat-plate denitrification membrane comprises a nonwoven fabric substrate layer and a gas permeation layer bonded together; the nonwoven fabric substrate comprises 60-90 wt% polypropylene fiber, 5-30 wt% cellulose fiber and 5-15 wt% carbon fiber; the gas permeation layer is an expanded polytetrafluoroethylene film.

[0010] Preferably, the quantitative range of the flat-plate denitrification membrane is 50-100 g / m³. 2 The thickness is 100-250μm, the air permeability is 0.05-1.5m / s, the average pore size is 0.05-4.5μm, and the contact angle is 110-140°.

[0011] Preferably, the width of the slit strip-shaped flat denitrification membrane is 10-20 mm.

[0012] Preferably, the winding diameter of the strip-shaped flat denitrification membrane is 5-10 mm, and the edges of the denitrification membrane are overlapped during the winding process, with the width of the overlapped area set to 0.5-2 mm.

[0013] Preferably, the bonding is performed using an ultrasonic-assisted thermosetting bonding process, specifically including: uniformly applying a chemical adhesive to the overlapping area of ​​the film edges during winding, and then performing ultrasonic-assisted heating curing treatment; the chemical adhesive is an aqueous dispersion of acrylonitrile multi-component copolymer; the frequency of the ultrasound is 15-40kHz, and the temperature of the heating curing is 150-250℃.

[0014] Preferably, the tubular membrane manufacturing process includes: cooling the tubular membrane formed by bonding, wherein the cooling temperature is 5-20°C; and the inner diameter of the tubular membrane is 5-10 mm.

[0015] A second aspect of the present invention provides a tubular gaseous membrane prepared by the preparation method described in the first aspect of the present invention.

[0016] A third aspect of the present invention provides the application of the tubular gaseous membrane described in the second aspect of the present invention in the preparation of tubular gaseous membrane modules and wastewater denitrification treatment.

[0017] A fourth aspect of the present invention provides a tubular gaseous membrane assembly comprising the tubular gaseous membrane described in the second aspect of the present invention.

[0018] Preferably, the method for preparing the tubular gaseous membrane module includes: cutting the tubular gaseous membrane to a suitable length and the required filling quantity, then filling it sequentially into the encapsulation tube, and then performing potting and curing treatments to produce the tubular gaseous membrane module.

[0019] A fifth aspect of the present invention provides the application of the tubular gaseous membrane module described in the fourth aspect of the present invention in wastewater denitrification treatment.

[0020] A sixth aspect of the present invention provides a method for wastewater denitrification treatment using a tubular gaseous membrane module as described in the fourth aspect of the present invention, comprising the following steps:

[0021] Step 1): Adjust the pH of the ammonia nitrogen wastewater to alkaline;

[0022] Step 2): After adjusting the temperature of the ammonia nitrogen wastewater, pump it into the tubular gas membrane module and adjust the flow rate on the membrane surface.

[0023] Step 3): Pump the acid absorbent from the acid tank into the shell side of the tubular gas membrane module, and then return it to the acid tank to maintain the circulation state;

[0024] Step 4): Under the mass transfer of ammonia inside the tubular gas membrane module, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules. Discharge begins after the ammonia nitrogen in the wastewater is reduced to the discharge standard.

[0025] Step 5): The concentration of ammonium salt in the acid absorption solution gradually increases with the extension of the circulation time until the ammonium salt solution in the acid tank reaches saturation.

[0026] Step 6): Evaporate and crystallize the saturated ammonium salt solution to obtain solid ammonium salt, thereby realizing the recovery of ammonia nitrogen resources.

[0027] Preferably, the concentration of ammonia nitrogen wastewater in step 1) is 10-5000 mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 10-12 by adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide.

[0028] Preferably, in step 2), the temperature of the ammonia nitrogen wastewater is adjusted to 5-40℃, and the membrane flow rate is set to 1-100m / min.

[0029] Preferably, the concentration of the acid absorption solution in step 3) is 1-20 wt%, and the acid absorption solution is one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The tubular gaseous membrane of the present invention has a double-layer structure of a porous support layer and a microporous hydrophobic layer, which has good chemical resistance. It adopts an ultrasonic-assisted thermosetting bonding process, which has high strength, good corrosion resistance and is not easy to fall off in the overlapping area, greatly improving the sealing performance and service life, and has the effect of long-term stable operation.

[0032] (2) The tubular gaseous membrane module of the present invention has a wide flow channel that is not easy to clog, and the wastewater pretreatment is simple. It allows wastewater with high suspended solids content to enter the membrane module. The closed column membrane structure can avoid secondary pollution.

[0033] (3) The wastewater denitrification process of the present invention adopts cross-flow filtration. The higher cross-flow velocity can reduce the speed at which pollutants such as organic matter adhere to the membrane surface, reduce membrane fouling, and maintain a high denitrification efficiency.

[0034] (4) The tubular gas membrane preparation method and denitrification process provided by the present invention have a wide range of applications and high denitrification efficiency. While treating ammonia nitrogen wastewater, ammonia nitrogen resources can be recovered, which has good economic and environmental benefits. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the preparation process of the tubular gaseous membrane and its components of the present invention.

[0036] Figure 2 is a physical image of the tubular gaseous membrane module prepared according to the present invention, wherein A is a top view and B is a side view.

[0037] Figure 3 is a process flow diagram of the tubular gaseous membrane prepared in this invention for denitrification treatment. Detailed Implementation

[0038] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0039] This invention provides a method for preparing a tubular gaseous membrane and membrane module for wastewater treatment. The preparation process is shown in Figure 1 and includes the following steps:

[0040] Step 1: Cut the flat-plate denitrification membrane into strips. The quantitative range of this flat-plate denitrification membrane is 50-100 g / m³. 2The thickness is set to 100-250μm, the air permeability is set to 0.05-1.5m / s, the average pore size is set to 0.05-4.5μm, the contact angle is set to 110-140°, and the width of the strip-shaped flat denitrification membrane is 10-20mm.

[0041] Step 2: The above-mentioned strip-shaped flat denitrification membrane is wound with a winding diameter of 5-10 mm. During the winding process, the width of the overlapping area of ​​the upper and lower layers of the denitrification membrane is controlled within the range of 0.5-2 mm.

[0042] Step 3: Using an ultrasonic-assisted thermosetting bonding process, a chemical adhesive is evenly applied to the overlapping area of ​​the film edges during the winding process, and then ultrasonic-assisted heating and curing treatment is performed; the chemical adhesive is an aqueous dispersion of acrylonitrile multi-component copolymer; the frequency of the ultrasound is 15-40kHz, and the temperature of the heating and curing is 150-250℃.

[0043] Step 4: The tubular gaseous membrane formed during the tube-making process is subjected to rapid cooling to reduce the membrane temperature to room temperature, with the cooling temperature controlled between 5-20℃. The inner diameter of the tubular gaseous membrane is 5-10mm.

[0044] Step 5: After the tubular gaseous membrane is cut, it is filled into the encapsulation tube, and after potting and curing, a tubular gaseous membrane assembly is formed, as shown in Figure 1.

[0045] In the preparation method of this invention, after multiple attempts, it was found that using acrylonitrile multi-component copolymer as an adhesive combined with ultrasonic-assisted thermosetting bonding process can significantly improve the strength of the membrane lamination area, making it less prone to detachment, and enabling long-term stable operation in acid and alkali media. It also exhibits good resistance to acid and alkali corrosion and oxidation, thereby significantly improving the service life of the membrane and its membrane components.

[0046] The present invention also provides a method for wastewater denitrification treatment using the above-mentioned tubular gaseous membrane module, the process flow of which is shown in Figure 2, and includes the following steps:

[0047] Step 1: Adjust the pH of the ammonia nitrogen wastewater to 10-12 and the temperature to 5-40℃, and pump it into the tube side of the tubular gas membrane module with a membrane surface flow rate of 1-100m / min; pump the acid absorbent into the shell side of the gas membrane module with an acid absorbent concentration of 1-20wt%, and then return it to the acid tank to maintain a circulation state.

[0048] Step 2: Under the mass transfer of ammonia inside the tubular gas membrane, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules. Once the ammonia nitrogen in the wastewater gradually decreases to the discharge standard, the wastewater is discharged.

[0049] Step 3: The concentration of ammonium salt in the acid absorption solution gradually increases with the extension of the circulation time until the ammonium salt solution in the acid tank reaches saturation; the saturated ammonium salt solution is evaporated and crystallized to obtain solid ammonium salt, thereby realizing the recovery of ammonia nitrogen resources.

[0050] In Examples 1-5, the aqueous dispersion of the acrylonitrile multi-component copolymer chemical adhesive is LA133, a product manufactured by Chengdu Indile Power Technology Co., Ltd. The flat-plate denitrification membrane originates from the applicant's previously filed and authorized invention patent, "A Flat-plate Denitrification Membrane for Wastewater Treatment and Its Preparation Method" (ZL202010862209.4), which is incorporated herein by reference in its entirety. The flat-plate denitrification membrane comprises a nonwoven fabric substrate layer and a gas permeation layer; the nonwoven fabric substrate layer and the gas permeation layer are bonded together; the nonwoven fabric substrate comprises polypropylene fibers, cellulose fibers, and carbon fibers; wherein the polypropylene fibers account for 60-90 wt%, the cellulose fibers account for 5-30 wt%, and the carbon fibers account for 5-15 wt%; the gas permeation layer is an expanded polytetrafluoroethylene film; the polypropylene fibers comprise one or both of single-component polypropylene fibers and two-component polyethylene / polypropylene fibers; the single-component polypropylene fibers... The melting point of the fiber is 150-190℃; the bicomponent polyethylene / polypropylene fiber is a core-sheath fiber, with the outer layer melting point of 90-150℃ and the fiber body melting point of 150-190℃; the beating degree of the cellulose fiber is 30-60°SR; the cellulose fiber is bamboo pulp fiber and wood pulp fiber; the carbon fiber has a temperature resistance greater than 300℃; the expanded polytetrafluoroethylene film has an air permeability of 0.1-5m / s, an average pore size of 0.1-5μm, a porosity of 50-80%, and a contact angle of 110-140°; its preparation method includes the following steps:

[0051] Step 1: Using a wet papermaking process, a mixed fiber slurry composed of polypropylene fiber, cellulose fiber and carbon fiber is formed by papermaking through a paper machine to form the nonwoven fabric substrate; in the papermaking process parameters of the nonwoven fabric substrate, the slurry concentration on the paper machine is set to 0.01-0.5wt%, the drying temperature of the nonwoven fabric substrate is 90-120℃, and the soft calendering temperature is set to 100-130℃.

[0052] Step 2: The non-woven fabric substrate and the expanded polytetrafluoroethylene film are pre-stacked together;

[0053] Step 3: Place the material into a hot press for high-temperature hot pressing. The hot pressing temperature is related to the melting point of the selected polypropylene fiber and the hot pressing pressure. During high-temperature hot pressing, the hot pressing temperature of the denitrification membrane is 140-170℃, and the pressure range is set to 0.5-2.5MPa. The temperature required for the hot pressing process of the flat denitrification membrane has a certain gradient relationship with the temperature required for the drying and soft calendering processes of the non-woven fabric substrate. The drying temperature of the non-woven fabric substrate is 90-120℃ < the soft calendering temperature is 100-130℃ < the hot pressing temperature of the denitrification membrane is 140-170℃.

[0054] Step 4: After hot-pressing and lamination, the membrane is cooled to form a flat denitrification membrane; the quantitative density of the formed flat denitrification membrane is 50-100 g / m³. 2 The thickness is 100-250μm, the air permeability is 0.05-1.5m / s, the average pore size is 0.05-4.5μm, and the contact angle is 110-140°.

[0055] Example 1

[0056] A tubular gaseous membrane and its components are prepared as follows: a quantitative 50 g / m³ of gaseous membrane is prepared... 2 The membrane, with a thickness of 100 μm, an air permeability of 0.05 m / s, an average pore size of 0.05 μm, and a contact angle of 110°, is a flat denitrification membrane cut into 10 mm strips. These strips are then wound with a diameter of 5 mm, with two opposite edges overlapped in a 0.5 mm overlap. An aqueous dispersion of an acrylonitrile copolymer binder is uniformly applied to the overlap area, followed by ultrasonic-assisted curing at a frequency of 15 kHz and a curing temperature of 150 °C. The membrane is then cooled at 20 °C to obtain a gaseous membrane tube with an inner diameter of 5 mm. The membrane tube is then cut and filled into a tubing, followed by adhesive filling and curing to form… Tubular gaseous membrane module.

[0057] The process of wastewater denitrification using the above-mentioned tubular gaseous membrane module is as follows: Landfill leachate with an ammonia nitrogen concentration of 10 mg / L is denitrified by adding sodium hydroxide to adjust the pH of the influent to 10 and the temperature to 5°C. The leachate is pumped into the tubular gaseous membrane module at a membrane surface flow rate of 1 m / min, while a 1 wt% sulfuric acid solution is pumped into the shell side of the module and then returned to the acid tank, maintaining a circulation state. The ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the sulfuric acid solution, while the ammonium sulfate concentration in the acid tank gradually increases. The final wastewater denitrification efficiency is 82.9%. The ammonium sulfate in the acid tank is evaporated and crystallized to obtain solid ammonium sulfate with an N content of 20.5 wt%.

[0058] Example 2

[0059] A tubular gaseous membrane and its components are prepared as follows: A quantitative 100 g / m³ gaseous membrane is prepared... 2 The membrane, with a thickness of 250 μm, an air permeability of 1.5 m / s, an average pore size of 4.5 μm, and a contact angle of 140°, is a flat denitrification membrane cut into 20 mm strips. These strips are then wound with a diameter of 10 mm, with two opposite edges overlapped in a 2 mm overlap. An aqueous dispersion of an acrylonitrile copolymer, a chemical adhesive, is uniformly applied to the overlap area. Ultrasonic-assisted curing is then performed at a frequency of 20 kHz and a curing temperature of 250 °C. The membrane is then cooled at 20 °C to obtain a gaseous membrane tube with an inner diameter of 10 mm. The membrane tube is then cut and filled into a tubing, followed by adhesive filling and curing to form… Tubular gaseous membrane module.

[0060] The process of wastewater denitrification using the above-mentioned tubular gaseous membrane module is as follows: Kitchen wastewater with an ammonia nitrogen concentration of 5000 mg / L is denitrified by adding calcium hydroxide to adjust the pH of the influent to 12 and the temperature to 40℃. The kitchen wastewater is pumped into the tubular gaseous membrane module at a membrane surface flow rate of 100 m / min, while a 20 wt% nitric acid solution is pumped into the shell side of the tubular gaseous membrane module and then returned to the acid tank, maintaining a circulation state. The ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the nitric acid solution, while the ammonium nitrate concentration in the acid tank gradually increases. The final wastewater denitrification efficiency is 88.3%. The ammonium nitrate in the acid tank is evaporated and crystallized to obtain solid ammonium nitrate with an N content of 32.4 wt%.

[0061] Example 3

[0062] A tubular gaseous membrane and its components are prepared as follows: a quantitative 80 g / m³ of gaseous membrane is prepared... 2 The membrane, with a thickness of 140 μm, an air permeability of 0.08 m / s, an average pore size of 0.3 μm, and a contact angle of 120°, was cut into 12.5 mm strips and wound to a diameter of 7 mm. During winding, two opposite edges were overlapped in a double-layer configuration with a overlap width of 0.8 mm. An aqueous dispersion of an acrylonitrile copolymer, a chemical adhesive, was uniformly coated onto the overlapped area. Ultrasonic-assisted curing was then performed at a frequency of 25 kHz and a curing temperature of 170 °C. The membrane was then cooled at 10 °C to obtain a gaseous membrane tube with an inner diameter of 7 mm. The membrane tube was then cut and filled into a tubing, followed by adhesive filling and curing to form… Tubular gaseous membrane module.

[0063] The process of wastewater denitrification using the above-mentioned tubular gaseous membrane module is as follows: Metallurgical wastewater with an ammonia nitrogen concentration of 1000 mg / L is denitrified by adding calcium oxide to adjust the pH of the influent to 10.7 and the temperature to 20°C. The metallurgical wastewater is pumped into the tube side of the tubular gaseous membrane module at a membrane surface flow rate of 30 m / min, while a 5 wt% phosphoric acid solution is pumped into the shell side of the tubular gaseous membrane module and then returned to the acid tank, maintaining a circulation state. The ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the phosphoric acid solution, while the ammonium phosphate concentration in the acid tank gradually increases. The final wastewater denitrification efficiency is 87.1%. The ammonium phosphate in the acid tank is evaporated and crystallized to obtain solid ammonium phosphate with an N content of 25.8 wt%.

[0064] Example 4

[0065] A tubular gaseous membrane and its components are prepared as follows: A quantitative 85 g / m³... 2 The membrane, with a thickness of 200 μm, an air permeability of 1.0 m / s, an average pore size of 2.5 μm, and a contact angle of 125°, is a flat denitrification membrane cut into 16.5 mm strips. These strips are then wound to a diameter of 8 mm, with two opposite edges overlapped in a 1.2 mm overlap. An aqueous dispersion of an acrylonitrile copolymer binder is uniformly applied to the overlap area, followed by ultrasonic-assisted curing at 30 kHz and 200 °C. The membrane is then cooled at 15 °C to obtain a gaseous membrane tube with an inner diameter of 8 mm. The membrane tube is then cut and filled into a tubing, followed by adhesive filling and curing to form… Tubular gaseous membrane module.

[0066] The process of wastewater denitrification using the above-mentioned tubular gaseous membrane module is as follows: Photovoltaic wastewater with an ammonia nitrogen concentration of 2800 mg / L is denitrified by adding sodium hydroxide to adjust the pH of the influent to 11 and the temperature to 30°C. The photovoltaic wastewater is pumped into the tube side of the tubular gaseous membrane module at a membrane surface flow rate of 70 m / min, while a 10 wt% hydrochloric acid solution is pumped into the shell side of the tubular gaseous membrane module and then returned to the acid tank, maintaining a circulation state. The ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the hydrochloric acid solution, while the ammonium chloride concentration in the acid tank gradually increases. The final wastewater denitrification efficiency is 85.4%. The ammonium chloride in the acid tank is evaporated and crystallized to obtain solid ammonium chloride with an N content of 21.8 wt%.

[0067] Example 5

[0068] A tubular gaseous membrane and its components are prepared as follows: a quantitative 90 g / m³ of gaseous membrane is prepared... 2The membrane, with a thickness of 200 μm, an air permeability of 1.2 m / s, an average pore size of 3.2 μm, and a contact angle of 128°, is a flat denitrification membrane cut into 18 mm strips. These strips are then wound to a diameter of 8 mm, with two opposite edges overlapped in a 1.5 mm overlap. An aqueous dispersion of an acrylonitrile copolymer binder is uniformly applied to the overlap area, followed by ultrasonic-assisted curing at a frequency of 40 kHz and a curing temperature of 220 °C. The membrane is then cooled at 15 °C to obtain a gaseous membrane tube with an inner diameter of 8 mm. The membrane tube is then cut and filled into a tubing, followed by adhesive filling and curing to form… Tubular gaseous membrane module.

[0069] The process of wastewater denitrification using the above-mentioned tubular gaseous membrane module is as follows: Landfill leachate with an ammonia nitrogen concentration of 3500 mg / L is denitrified by adding sodium hydroxide to adjust the pH of the influent to 11 and the temperature to 35°C. The leachate is pumped into the tube side of the tubular gaseous membrane module at a membrane flow rate of 85 m / min, while a 17.5 wt% sulfuric acid solution is pumped into the shell side of the module, and then returned to the acid tank, maintaining a circulation state. The ammonia nitrogen in the wastewater gradually decreases and is continuously absorbed by the sulfuric acid solution, while the ammonium sulfate concentration in the acid tank gradually increases. The final wastewater denitrification efficiency is 90.3%. The ammonium sulfate in the acid tank is evaporated and crystallized to obtain solid ammonium sulfate with an nitrogen content of 20.8 wt%.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a tubular gaseous membrane for wastewater treatment, characterized in that, include: The flat denitrification membrane is cut into strips, and then the strip-shaped flat denitrification membrane is successively wound, stacked, bonded, made into tubes and cut to form a tubular gas membrane. The flat-plate denitrification membrane comprises a nonwoven fabric substrate layer and a gas permeation layer bonded together; the nonwoven fabric substrate comprises 60-90 wt% polypropylene fiber, 5-30 wt% cellulose fiber and 5-15 wt% carbon fiber; the gas permeation layer is an expanded polytetrafluoroethylene film.

2. The preparation method according to claim 1, characterized in that, The quantitative range of the flat-plate denitrification membrane is 50-100 g / m³. 2 The thickness is 100-250μm, the air permeability is 0.05-1.5m / s, the average pore size is 0.05-4.5μm, and the contact angle is 110-140°.

3. The preparation method according to claim 1, characterized in that, The width of the strip-shaped flat denitrification membrane after slicing is 10-20 mm.

4. The preparation method according to claim 1, characterized in that, The strip-shaped flat denitrification membrane has a winding diameter of 5-10 mm. During the winding process, the edges of the denitrification membrane are overlapped, and the width of the overlapped area is set to 0.5-2 mm.

5. The preparation method according to claim 1, characterized in that, The bonding process employs an ultrasonic-assisted thermosetting bonding technique, specifically including: uniformly applying a chemical adhesive to the overlapping area of ​​the film edges during winding, followed by ultrasonic-assisted heating and curing; the chemical adhesive is an aqueous dispersion of an acrylonitrile multi-element copolymer; the ultrasonic frequency is 15-40kHz, and the heating and curing temperature is 150-250℃.

6. The preparation method according to claim 1, characterized in that, The tube fabrication process includes: cooling the tubular membrane formed by bonding, wherein the cooling temperature is 5-20℃; and the inner diameter of the tubular membrane is 5-10mm.

7. The tubular gaseous membrane prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the tubular gaseous membrane according to claim 7 in the preparation of tubular gaseous membrane modules and wastewater denitrification treatment.

9. A tubular gaseous membrane module, characterized in that, Including the tubular gaseous membrane as described in claim 7.

10. The tubular gaseous membrane module as described in claim 8, characterized in that, The method for preparing the tubular gaseous membrane module includes: cutting the tubular gaseous membrane to a suitable length and the required filling quantity, then filling it sequentially into the encapsulation tube, and then performing potting and curing treatments to produce the tubular gaseous membrane module.

11. The application of the tubular gaseous membrane module according to claim 9 in wastewater denitrification treatment.

12. A method for wastewater denitrification treatment using the tubular gaseous membrane module as described in claim 9, characterized in that, Includes the following steps: Step 1): Adjust the pH of the ammonia nitrogen wastewater to alkaline; Step 2): After adjusting the temperature of the ammonia nitrogen wastewater, pump it into the tubular gas membrane module and adjust the flow rate on the membrane surface. Step 3): Pump the acid absorbent from the acid tank into the shell side of the tubular gas membrane module, and then return it to the acid tank to maintain the circulation state; Step 4): Under the mass transfer of ammonia inside the tubular gas membrane module, the ammonia nitrogen in the wastewater enters the acid absorption liquid in the form of NH3 molecules. Discharge begins after the ammonia nitrogen in the wastewater is reduced to the discharge standard. Step 5): The concentration of ammonium salt in the acid absorption solution gradually increases with the extension of the circulation time until the ammonium salt solution in the acid tank reaches saturation. Step 6): Evaporate and crystallize the saturated ammonium salt solution to obtain solid ammonium salt, thereby realizing the recovery of ammonia nitrogen resources.

13. The method as described in claim 12, characterized in that, The concentration of ammonia nitrogen wastewater in step 1) is 10-5000 mg / L, and the pH value of the ammonia nitrogen wastewater is adjusted to 10-12 by adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide.

14. The method as described in claim 12, characterized in that, In step 2), the temperature of the ammonia nitrogen wastewater is adjusted to 5-40℃, and the membrane flow rate is set to 1-100m / min.

15. The method as described in claim 12, characterized in that, In step 3), the concentration of the acid absorption solution is 1-20 wt%, and the acid absorption solution is one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

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