Hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment and preparation method thereof

Abstract

The present application relates to the technical field of ammonia nitrogen removal in sewage treatment, and particularly relates to a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment and a preparation method thereof, which comprises the following steps: S1, a porous support layer with polyvinylidene fluoride as a base material is prepared by a phase inversion method; S2, a coating liquid comprising polydimethylsiloxane and silicon dioxide is prepared, and a metal organic framework material is loaded to obtain a hybrid coating liquid; S3, the porous support layer is immersed in the hybrid coating liquid and solidified to obtain a composite degassing membrane; S4, an etching flow channel is formed on the inner surface of a membrane module flow channel substrate by laser etching; and S5, the composite degassing membrane is installed in a degassing membrane module flow channel surrounded by the membrane module flow channel substrate to obtain a composite degassing membrane module. Through the synergistic effect of the surface roughness of the SiO2 nanoparticles of the hybrid coating and the hydrophobic main chain of the PDMS, the contact angle of the membrane surface is increased, the water permeation is significantly reduced, and the ammonia gas selectivity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ammonia nitrogen removal in sewage treatment, and in particular to a hydrophobic composite degassing membrane for high ammonia nitrogen wastewater treatment and a preparation method thereof. BACKGROUND

[0002] High ammonia nitrogen wastewater (such as semiconductor wastewater, aquaculture wastewater, landfill leachate, coking wastewater, etc.) has high ammonia nitrogen concentration, and direct discharge will cause water eutrophication, water quality deterioration and ecological destruction. The traditional treatment methods (such as stripping method, biological method, chemical precipitation method) have problems such as high energy consumption, great risk of secondary pollution, or low treatment efficiency. Membrane separation technology (especially degassing membrane) has become a research hotspot for high ammonia nitrogen wastewater treatment due to its low energy consumption, simple operation and environmental friendliness.

[0003] The existing degassing membranes are mostly hydrophilic or weakly hydrophobic materials (such as polypropylene, polysulfone, polyether sulfone), which have the following problems:

[0004] Strong affinity for water, easy to cause membrane pore wetting due to water penetration in wastewater, reducing ammonia gas selectivity;

[0005] Insufficient hydrophobicity, easy to be polluted by organic matter, colloid, etc. in wastewater after long-term operation, and significant flux decay;

[0006] Single membrane structure, low ammonia gas permeation flux, difficult to meet the treatment needs of high concentration wastewater;

[0007] Flow channel design leads to large liquid flow boundary layer thickness and serious concentration polarization, further reducing mass transfer efficiency. SUMMARY

[0008] Therefore, the present application provides a hydrophobic composite degassing membrane for high ammonia nitrogen wastewater treatment and a preparation method thereof to overcome at least one of the technical problems in the background art.

[0009] To achieve the above-mentioned purpose, on the one hand, the present application provides a preparation method of a hydrophobic composite degassing membrane for high ammonia nitrogen wastewater treatment, comprising:

[0010] Step S1, preparing a porous support layer with polyvinylidene fluoride (PVDF) as a base material by phase inversion method;

[0011] Step S2, preparing a coating liquid comprising polydimethylsiloxane (PDMS) and silicon dioxide, and loading metal organic framework material (MOFs) to obtain a hybrid coating liquid;

[0012] Step S3, immersing the porous support layer in the hybrid coating liquid, and solidifying to obtain a composite degassing membrane;

[0013] Step S4, forming etching flow channels on the inner surface of the membrane module flow channel substrate by laser etching;

[0014] Step S5, installing the composite degassing membrane into the degassing membrane module flow channel surrounded by the membrane module flow channel substrate to obtain a composite degassing membrane module.

[0015] Among them, the etching flow channel array is arranged in multiple groups, and the etching depth of the etching flow channel is set to be different for different regions of the composite degassing membrane.

[0016] In the above technical effects, the porous support layer takes polyvinylidene fluoride (PVDF) as the base material and is prepared by phase inversion method, with a porosity of 60% to 75% and an average pore size of 0.5 μm to 2 μm, and has a three-dimensional interconnected finger-shaped hole and sponge-shaped hole structure to provide mechanical support for the subsequent coating. The hybrid coating liquid is coated on the surface of the porous support layer, which obtains regular channels (pore size 0.5 nm to 1 nm) and high specific surface area to specifically adsorb NH3 molecules, and at the same time, the coating micropores are filled with SiO2 nanoparticles to form a gradient pore structure, thereby improving the ammonia permeation flux.

[0017] Further, the porous support layer is prepared by the following steps,

[0018] Step one, preparation of PVDF casting solution: dissolve PVDF (molecular weight 80,000 to 120,000) in N-methyl pyrrolidone (NMP), with PVDF mass fraction of 15% to 20%, and add polyvinylpyrrolidone (PVP, molecular weight 30,000 to 50,000) as a pore former, with PVP mass fraction of 5% to 8%, stir at 60°C to 70°C for 4 to 6 hours until completely dissolved to obtain a uniform casting solution.

[0019] Step two, phase inversion film forming: pour the casting solution on a clean glass plate, use a doctor blade to prepare a liquid film with a thickness of 150 μm to 250 μm, immediately immerse in deionized water at 20°C to 25°C for phase inversion, and solidify for 10 to 20 minutes to obtain a nascent membrane; immerse the nascent membrane in deionized water for 24 hours to remove residual solvents and pore formers, and obtain a porous support layer.

[0020] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, in the step S2, the preparation of the hybrid coating liquid comprises the following steps:

[0021] Step S21, disperse the silicon dioxide nanoparticles modified by APTES in anhydrous ethanol to obtain a modified silicon dioxide suspension;

[0022] Step S22, mix the polydimethylsiloxane prepolymer with TEOS and DBTDL to obtain a prepolymer mixture;

[0023] Step S23, mixing the modified silica suspension with the prepolymer mixture, and then adding a metal organic framework material suspension, and ultrasonic dispersion to obtain the hybrid coating solution.

[0024] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, in the step S2, the mass ratio of the polydimethylsiloxane to the silica is (8-10):1, and the mass fraction of the metal organic framework material is 5%-15% of the total mass of the polydimethylsiloxane and the silica.

[0025] Further, the step S21 specifically comprises: dissolving tetraethyl orthosilicate (TEOS) in anhydrous ethanol, the mass fraction of TEOS being 10%-15%, adding ammonia water (mass fraction 25%) as a catalyst, the molar ratio of the ammonia water to TEOS being (1-1.2):1, stirring and reacting at room temperature for 4-6 hours to generate a SiO2 sol; adding γ-aminopropyl triethoxysilane (APTES) to the sol, the mass ratio of APTES to TEOS being 1:10, and continuing to stir for 2 hours to obtain an amino-modified SiO2 nanoparticle suspension.

[0026] Further, the step S22 specifically comprises:

[0027] Mixing the PDMS prepolymer (viscosity 2000-5000 mPa·s) with a crosslinking agent (tetraethyl orthosilicate, TEOS) at a mass ratio of 10:1, adding a catalyst (dibutyltin dilaurate, DBTDL, mass fraction 0.5%-1%), and stirring at room temperature for 1-2 hours to obtain a PDMS prepolymer mixture.

[0028] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, in the step S23, the metal organic framework material is selected from one or more of MIL-101(Cr), ZIF-8, or UiO-66, and the partial synthesis method comprises:

[0029] Synthesis of MIL-101(Cr): dissolving Cr(NO3)3·9H2O (0.8 mmol) and terephthalic acid (0.4 mmol) in 20 mL of DMF, adding 0.2 mL of H2BDC (as a regulator), reacting at 110°C for 8 hours, centrifuging and washing after cooling, and drying at 80°C for 12 hours to obtain MIL-01(Cr);

[0030] Synthesis of ZIF-8: dissolving 2-methylimidazole (0.34 g) in 10 mL of methanol, adding a methanol solution (5 mL) of zinc nitrate (0.12 g), stirring at room temperature for 24 hours, centrifuging and washing, and drying at 60°C for 6 hours to obtain ZIF-8.

[0031] Further, after the end of the above synthesis, step S23 is performed, which specifically includes:

[0032] The synthesized MOFs (such as MIL-101(Cr), particle size 100-200 nm) are dispersed in anhydrous ethanol, and ultrasonic treatment is performed for 30 minutes to obtain a MOFs suspension with a mass fraction of 5%-10%; the modified silica suspension is mixed with the prepolymer mixed solution, and then mixed with the MOFs suspension at a volume ratio of (9-9.5):1, and stirred for 1 hour to obtain a hybrid coating solution.

[0033] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment, the step S3 specifically includes:

[0034] The porous support layer is immersed in the hybrid coating solution for 40-60 seconds, and after being taken out, it is placed in an oven at 60-80°C for pre-curing for 10-15 minutes; then it is transferred to a vacuum drying box at 120°C-150°C for curing for 2-3 hours, so that the PDMS is completely cross-linked, and at the same time the MOFs remain stably dispersed, forming a surface hydrophobic coating layer, to obtain the hydrophobic composite degassing membrane.

[0035] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment, in the step S4, the etched flow channel is a groove with an Archimedes spiral shape, and multiple groups of etched flow channels are arrayed on the membrane module flow channel substrate, and the curvature radius of the Archimedes spiral corresponding to the groove is 5-10 mm. Through the spiral curvature design of the etched wall surface, the liquid flow is guided to form a vortex, breaking the stability of the boundary layer, reducing the thickness of the boundary layer, and reducing the concentration polarization phenomenon, so that the concentration polarization is reduced.

[0036] Further, the laser etching specifically includes: using an ultraviolet nanosecond laser (wavelength 355 nm, pulse width <10 ns, spot diameter 20-50 μm) to etch the membrane module flow channel substrate, and the etching depth is selected from 1-3 μm based on the following scheme; the flow channel wall surface is designed with an Archimedes spiral curvature (curvature radius 5-10 μm), and the flow rate is 0.5-2 m / s; when the liquid flow flows in the flow channel, a transverse velocity component is induced due to the wall surface curvature, forming a vortex and breaking the stability of the boundary layer. The prepared hydrophobic composite degassing membrane is cut to the appropriate size and wound into a cylindrical module, and the two ends are fixed by sealing glue or hot melt welding to form a complete degassing membrane module.

[0037] As a preferred technical solution of the preparation method of the hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment, the following steps are performed before the step S4 is performed:

[0038] Step S01, winding the composite degassing film to form a cylindrical installation state (in the implementation, the composite degassing film exists direct placement or braiding and other installation methods, the steps S01-S04 of the present scheme are only applicable to the installation state of the composite degassing film wound into a cylindrical shape or stacked into a cylindrical shape, and in the present scheme, the cylindrical area surrounded by the composite degassing film and the film assembly substrate is coaxial and has a fixed distance. For installation states that do not meet steps S01-S04, the same etching depth of the flow channel can be etched directly after step S3), based on the distribution density of the etching flow channel, the surface of the composite degassing film in the installation state is divided into a plurality of control areas, and each control area corresponds to a group of etching flow channels of the film assembly flow channel substrate (satisfying that after the composite degassing film is installed, the position of the control area is opposite to the position of the etching flow channel corresponding thereto);

[0039] Step S02, intermittently rotating the composite degassing film around the shaft, while applying liquid flow impact above the composite degassing film (the impact strength of the liquid flow is the maximum impact strength that occurs during the operation of the composite degassing film assembly of the same structure), until the liquid flow impact is applied to all control areas;

[0040] Step S03, collecting the degree of depression of the composite degassing film when the liquid flow impact is applied and the maximum rebound height of the film body after the liquid flow impact, and recording;

[0041] Step S04, selecting the etching depth of the etching flow channel corresponding to the control area in the preset depth range (the preset depth range is the above range 1µm-3µm) based on the degree of depression and the maximum rebound height.

[0042] Wherein, the etching depth is negatively correlated with the degree of depression (quantified by the depression depth) and positively correlated with the maximum rebound height.

[0043] In the aforementioned technical effects, the hydrodynamic purpose of etching the flow channel is to generate secondary flows or Taylor vortices within the channel, thereby disrupting the concentration polarization layer. The intensity of the vortex is directly related to the geometric disturbance intensity of the flow channel. However, the vortex cannot be too strong or too weak. Strong vortices can promote more intense fluid mixing, more effectively sweeping high-concentration ammonia nitrogen molecules from the membrane surface, while allowing the feed solution to contact the membrane surface more fully, thus significantly reducing concentration polarization and improving ammonia mass transfer efficiency. However, this also generates greater local shear stress and impact force on the membrane surface. If the membrane itself is relatively soft, there is a risk of membrane damage, flux decline, or increased fouling. With the above scheme, a large indentation indicates that the membrane is relatively soft and has lower mechanical strength. Under the same hydraulic conditions, a gentler flow channel, i.e., a shallower etching depth, is needed to avoid excessive deformation. The maximum rebound height reflects the membrane's elastic recovery capability. A high rebound height indicates that the membrane has good elasticity, can quickly recover its original shape after impact, and has good fatigue resistance. It can withstand more severe periodic impacts from the flow channel. Because deep trenches can generate stronger eddies and improve mass transfer, a deeper etching depth can be selected for them.

[0044] Furthermore, the etching depth D, in μm, is determined in the following way:

[0045] D = 1 + (K + C) * [2 / (Kmax - Kmin)], and D does not exceed the range of 1µm to 3µm;

[0046] Wherein, K is a comprehensive index used to establish a linear mapping relationship between etching depth and maximum springback height and depression depth, K=(h / hmax)-(d / dmax), C=1, Kmax and Kmin are the maximum and minimum values ​​of K in all control regions during the current preparation, h and d are the maximum springback height and depression depth respectively, and hmax and dmax are the maximum values ​​of springback height and depression depth during the current preparation respectively.

[0047] As a preferred technical solution for the preparation method of a hydrophobic composite degassing membrane for treating high ammonia nitrogen wastewater, after determining the etching depth of each of the control regions, the following steps are performed:

[0048] The curing time in step S3 of the next preparation cycle is selected based on the uniformity of the etching depth in each control area.

[0049] The curing duration is negatively correlated with the uniformity of the etching depth (quantified by the variance value of each etching depth). If the variance value of the current preparation is greater than a preset variance value (2 pm in this scheme), the initial curing duration of 2 hours is increased to 2h15min in the next preparation. If the variance value of the subsequent preparation is still greater than 2 pm, the increase gradient of 15min is continued until the upper limit of the curing duration of 3h is reached.

[0050] In another aspect, the application also provides a hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, which is prepared by the preparation method of the hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment according to any one of the above schemes.

[0051] Compared with the prior art, the composite degassing membrane of the application has high hydrophobicity. The surface contact angle of the membrane is increased by the synergistic effect of the surface roughness of SiO2 nanoparticles and the hydrophobic main chain of PDMS, which significantly reduces the water permeation and improves the ammonia gas selectivity.

[0052] Further, the composite degassing membrane of the application has high ammonia gas permeation flux. The gradient pore structure (three-dimensional pores of the support layer + micropores of the coating) and the low surface energy property of PDMS enable the ammonia gas permeation flux to reach more than 1800GPU, meeting the processing requirements of high ammonia-nitrogen wastewater (ammonia-nitrogen concentration >1000mg / L).

[0053] Further, the regular channels and high specific surface area of MOFs (such as MIL-101(Cr)) in the application can specifically adsorb NH3 molecules, and the selectivity of the membrane to NH3 is improved through physical adsorption and chemical interaction, especially under low NH3 partial pressure conditions.

[0054] Further, the bionic flow channel structure etched by laser in the application guides the liquid flow to form a vortex, the transverse secondary flow destroys the stability of the boundary layer, reduces the thickness of the boundary layer, and significantly improves the mass transfer efficiency by reducing the concentration polarization.

[0055] Further, the SiO2 nanoparticle reinforced coating in the application enhances the mechanical strength, and the regular channels of MOFs reduce the risk of organic matter blockage, and the long-term flux decay rate is small.

[0056] Especially, the application establishes a dynamic adaptation relationship between the composite degassing membrane and the etched flow channel, so that each degassing membrane assembly can achieve the optimal solution of mass transfer efficiency within the range allowed by its own material mechanical properties, while greatly improving the reliability and service life of the product. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1The preparation method flow of the hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment in the embodiment of the present application is as follows.

[0058] Figure 2 The contact angle test control chart in the embodiment of the present application is as follows.

[0059] Figure 3 The ammonia gas permeation flux test control chart in the embodiment of the present application is as follows. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0061] Embodiment 1:

[0062] 1. Preparation of porous support layer: PVDF 18 g was dissolved in 82 g of NMP, PVP 6 g was added, and stirring was carried out at 65℃ for 5 hours; the coating thickness was 200 μm, phase inversion was carried out by immersing in deionized water at 25℃ for 15 minutes, and immersion was carried out for 24 hours to obtain a porous support layer (porosity 70%, average pore size 1.2 μm).

[0063] 2. Preparation of PDMS-SiO2 coating solution: TEOS 12 g was dissolved in 90 g of anhydrous ethanol, ammonia water (25%) was added for catalytic reaction for 5 hours, and APTES 1.2 g was added for modification of SiO2; PDMS prepolymer 10 g was mixed with TEOS 1 g, DBTDL 0.08 g was added, and stirring was carried out for 1 hour; the modified SiO2 suspension (solid content 6%) was added to the PDMS mixture, ultrasonic dispersion was carried out, and the mass ratio of SiO2 to PDMS was 1:9.

[0064] 3. Preparation of composite membrane: the porous support layer was immersed in the PDMS-SiO2 coating solution for 45 seconds, pre-curing was carried out at 65℃ for 12 minutes, vacuum curing was carried out at 130℃ for 2.5 hours to obtain a composite degassing membrane, as shown in Figure 2 and Figure 3 , the contact angle was measured to be 145°, and the ammonia gas permeation flux was 1650 GPU.

[0065] Embodiment 2:

[0066] Preparation of composite membrane containing MOFs and laser etching biomimetic flow channel

[0067] The preparation flow shown in Figure 1 was used to prepare a composite membrane assembly, and the preparation steps were specifically as follows:

[0068] 1. Preparation of porous support layer: same as example 1, PVDF support layer with porosity 70%, average pore size 1.2 μm was obtained.

[0069] 2. Preparation of hybrid coating solution:

[0070] PDMS-SiO2 coating solution (without MOFs) was prepared according to the procedure of example 1, step 1;

[0071] MIL-101(Cr) (particle size 150 nm) was dispersed in anhydrous ethanol and ultrasonicated for 30 minutes to obtain a suspension with mass fraction of 8%;

[0072] PDMS-SiO2 coating solution was mixed with MIL-101(Cr) suspension in a volume ratio of 9.5:1, and stirred for 1 hour to obtain PDMS-SiO2-MIL-101(Cr) hybrid coating solution (MOFs mass fraction about 10%).

[0073] 3. Preparation of composite membrane: the porous support layer was immersed in the hybrid coating solution for 50 seconds, pre-cured at 65°C for 12 minutes, and vacuum cured at 130°C for 2.5 hours to obtain a composite degassing membrane (contact angle 158°, ammonia permeation flux 1950 GPU, selectivity coefficient NH3 / H2O for NH3 > 15).

[0074] 4. The control area was divided and subjected to water flow impact test, and after the test, a UV nanosecond laser (wavelength 355 nm) was used to select and etch the etching depth and etch the flow channel;

[0075] 5. The composite degassing membrane was sealed and fixed in the flow channel assembly.

[0076] It was measured that the concentration polarization was reduced by 42%, and the ammonia permeation flux was increased to 2200 GPU. Compared with example 1, due to the addition of MOFs, the contact angle of the composite degassing membrane was increased, the ammonia permeation flux was increased, the concentration polarization was reduced after laser etching flow channel, and the contact angle and ammonia permeation flux were further increased.

[0077] The technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.

[0078] The above merely illustrates the preferred embodiments of the present application, and is not used to limit the present application; for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, characterized in that, The method comprises the following steps: Step S1, preparing a porous support layer with polyvinylidene fluoride as a base material by a phase inversion method; Step S2, preparing a coating liquid comprising polydimethylsiloxane and silica, and loading a metal organic framework material to obtain a hybrid coating liquid; Step S3, immersing the porous support layer in the hybrid coating liquid, and solidifying to obtain a composite degassing membrane; Step S4, forming etched flow channels on the inner surface of a membrane module flow channel substrate by laser etching; Step S5, mounting the composite degassing membrane in the degassing membrane module flow channel surrounded by the membrane module flow channel substrate to obtain a composite degassing membrane module; In the step S2, the preparation of the hybrid coating liquid comprises the following steps:

2. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 1, characterized in that, Step S21, dispersing silica nanoparticles modified by APTES in anhydrous ethanol to obtain a modified silica suspension; Step S22, mixing polydimethylsiloxane prepolymer with TEOS and DBTDL to obtain a prepolymer mixture; Step S23, mixing the modified silica suspension with the prepolymer mixture, and then adding a metal organic framework material suspension, and ultrasonic dispersion to obtain the hybrid coating liquid. In the step S23, the synthesis method of the metal organic framework material comprises:

3. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 2, characterized in that, Synthesis of MIL-101(Cr): dissolving Cr(NO3)3·9H2O and terephthalic acid in DMF, adding H2BDC regulator, reacting at 110°C for 8 hours, centrifuging and washing, and then drying; And / or, synthesis of ZIF-8: dissolving 2-methylimidazole and zinc nitrate in methanol respectively, mixing and stirring for 24 hours, centrifuging and washing, and then drying. The step S3 specifically comprises:

4. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 1, characterized in that, Step S31, immersing the porous support layer in the hybrid coating liquid, and placing it in an oven for pre-solidification for 10-15 minutes after taking out; Step S32, transferring to a vacuum drying box for solidification for 2-3 hours, so that the polydimethylsiloxane is completely crosslinked, and the metal organic framework material is stably dispersed, forming a hydrophobic coating layer, to obtain the composite degassing membrane. In the step S4, the etched flow channels are grooves in the shape of Archimedes spirals, and a plurality of groups of etched flow channels are arrayed on the membrane module flow channel substrate, and the curvature radius of the Archimedes spiral corresponding to the grooves is 5-10 mm.

5. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 1, characterized in that, Before performing the step S4, the following steps are performed:

6. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 5, characterized in that, Step S01, winding the composite degassing membrane to form a cylindrical mounting state, and dividing the surface of the composite degassing membrane in the mounting state into a plurality of control areas based on the distribution density of the etched flow channels, each control area corresponding to a group of etched flow channels of the membrane module flow channel substrate; Step S02, rotating the composite degassing membrane intermittently around the shaft, and applying liquid flow impact above the composite degassing membrane until the liquid flow impact is applied to all control areas; Step S03, collecting the degree of depression of the composite degassing membrane when the liquid flow impact is applied, and the maximum rebound height of the membrane body after the liquid flow impact, and recording. ​ Step S04, selecting the etching depth of the etching flow corresponding to the control area in the preset depth interval based on the recess degree and the maximum rebound height; Wherein, the etching depth is negatively correlated with the recess degree and positively correlated with the maximum rebound height.

7. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 6, characterized in that, After the etching depth of each control area is determined, the following steps are performed: Selecting the solidification time length in step S3 in the next preparation cycle based on the uniformity of the etching depth of each control area; Wherein, the solidification time length is negatively correlated with the uniformity of the etching depth.

8. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 3, characterized in that, In the step S2, the mass ratio of the polydimethylsiloxane to the silicon dioxide is (8-10):1, and the mass fraction of the metal organic framework material is 5%-15% of the total mass of the polydimethylsiloxane and the silicon dioxide.

9. The method for preparing a hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to claim 3, characterized in that, In the step S23, the preparation of the metal organic framework material suspension includes the following steps: Disperse the synthesized metal organic framework material in anhydrous ethanol, and ultrasonic treat for 30 minutes to obtain a metal organic framework material suspension.

10. A hydrophobic composite degassing membrane for high ammonia-nitrogen wastewater treatment, characterized by, The preparation method of the hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment is prepared by using the preparation method of the hydrophobic composite degassing membrane for high-ammonia-nitrogen wastewater treatment according to any one of claims 1-9.

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