Ultrafiltration membrane for wastewater treatment and method for preparing the same

Abstract

The application relates to the technical field of wastewater treatment, and discloses an ultrafiltration membrane for wastewater treatment and a preparation method thereof.The preparation method of the ultrafiltration membrane for wastewater treatment comprises the following steps: polyvinylidene fluoride is dissolved in an organic solvent and anhydrous ethanol; photocatalytic nanomaterials are subjected to calcination modification and immersion modification, and then the modified photocatalytic nanomaterials are dispersed in anhydrous ethanol; carbon nanotubes are subjected to immersion modification, and then the modified carbon nanotubes are dispersed in anhydrous ethanol; a polyvinylidene fluoride solution, photocatalytic nanomaterial dispersion liquid, carbon nanotube dispersion liquid and FeCl3 solution are mixed and electrospun; NaBH4 solution is added dropwise on the surface of the spun film to obtain the ultrafiltration membrane for wastewater treatment.The ultrafiltration membrane for wastewater treatment prepared by the method has good physical properties and wastewater treatment performance, and has good wastewater treatment performance on different water qualities of printing and dyeing wastewater, and can meet the needs of different printing and dyeing plants.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to an ultrafiltration membrane for wastewater treatment and its preparation method. Background Technology

[0002] Dyeing and printing wastewater refers to the wastewater discharged during the pretreatment, dyeing, printing and finishing processes of cotton, wool, linen, silk, chemical fiber or blended products. Dyeing and printing wastewater is characterized by large volume, high content of organic pollutants, high alkalinity and large variation in water quality, and belongs to the category of difficult-to-treat industrial wastewater.

[0003] Membrane treatment, as a highly efficient separation technology, utilizes the principle of selective permeability of membrane materials to separate, concentrate, and recover pollutants in wastewater, thereby achieving wastewater treatment. Statistics show that using tubular and hollow fiber polysulfone ultrafiltration membranes to treat dyeing and printing wastewater achieves a decolorization rate of 95%–98% and a COD reduction rate of [missing information]. Cr The removal rate is 60%–90%, and the dye recovery rate is greater than 95%.

[0004] However, practical applications have revealed that the water flux of membrane treatment processes gradually decreases over time. This is because the organic matter trapped by the membrane material adsorbs and accumulates in the pore structure of the membrane material, leading to pore blockage and reduced water flux, which is detrimental to further wastewater treatment. In addition, practical applications have also shown that when the content of small organic molecules in dyeing and printing wastewater is high, the effectiveness of membrane treatment processes is significantly reduced. This is because some small organic molecules in the wastewater can permeate through the membrane material and are not effectively trapped, thus reducing the wastewater treatment effect.

[0005] Therefore, those skilled in the art urgently need a membrane material that can simultaneously retain and decompose organic matter in wastewater, and effectively treat small-molecule organic matter in wastewater, in order to improve the treatment effect of membrane treatment processes on dyeing and printing wastewater. Summary of the Invention

[0006] The purpose of this invention is to provide an ultrafiltration membrane for wastewater treatment and its preparation method. The ultrafiltration membrane for wastewater treatment provided by this invention can retain and decompose organic matter in wastewater, and can effectively treat small molecule organic matter in wastewater, thereby improving the treatment effect of membrane treatment process on dyeing and printing wastewater.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the technical solutions of this invention:

[0009] A method for preparing an ultrafiltration membrane for wastewater treatment includes the following steps:

[0010] 1) Dissolve polyvinylidene fluoride in an organic solvent and anhydrous ethanol to obtain a polyvinylidene fluoride solution;

[0011] 2) The photocatalytic nanomaterials were calcined and impregnated to obtain modified photocatalytic nanomaterials. The modified photocatalytic nanomaterials were then dispersed in anhydrous ethanol to obtain a photocatalytic nanomaterial dispersion.

[0012] 3) The carbon nanotubes were impregnated and modified to obtain modified carbon nanotubes, and then the modified carbon nanotubes were dispersed in anhydrous ethanol to obtain a carbon nanotube dispersion.

[0013] 4) Mix the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 2), the carbon nanotube dispersion obtained in step 3), and the FeCl3 solution in a volume ratio of 10:(3-5):(1-3):(0.5-1.5), and electrospin the mixture into a film.

[0014] 5) Add NaBH4 solution to the surface of the spun membrane obtained in step 4) to obtain the ultrafiltration membrane for wastewater treatment.

[0015] Further, in step 1), the mass-to-volume ratio of the polyvinylidene fluoride, organic solvent, and anhydrous ethanol is 1g:6mL:2mL.

[0016] Further, in step 2), the photocatalytic nanomaterial is nano-titanium dioxide or graphite-like carbon nitride;

[0017] Further, in step 2), the calcination modification is performed by calcining at 200–500°C for 1–3 hours;

[0018] Furthermore, when the photocatalytic nanomaterial is nano-titanium dioxide, the calcination modification is performed by calcining at 200–400°C for 1–3 hours; when the photocatalytic nanomaterial is graphite-like carbon nitride, the calcination modification is performed by calcining at 300–500°C for 1–3 hours.

[0019] Further, in step 2), the impregnation modification involves placing the calcined and modified photocatalytic nanomaterials in an alkaline solution and impregnating them at room temperature for 20–40 minutes.

[0020] Furthermore, the alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution;

[0021] Further, in step 2), the mass-to-volume ratio of the modified photocatalytic nanomaterial to anhydrous ethanol is 1 g: 20 mL.

[0022] This invention adds photocatalytic nanomaterials to an ultrafiltration membrane for wastewater treatment. The purpose is to use the photocatalytic nanomaterials to degrade organic matter in the water and release free radicals. Then, the released free radicals are used to oxidize microorganisms in the water, thereby further improving the wastewater treatment performance.

[0023] This invention modifies photocatalytic nanomaterials through calcination and impregnation, aiming to improve the wastewater treatment performance and hydrophilicity of ultrafiltration membranes used in wastewater treatment. Specifically, calcination modification allows the photocatalytic nanomaterials to form more microporous structures, effectively improving the membrane material's adsorption capacity for organic matter, thereby enhancing wastewater treatment performance. Impregnation modification allows the formation of hydrophilic groups on the surface of the ultrafiltration membrane, which plays an important role in improving the hydrophilicity of the membrane material.

[0024] Further, in step 3), the impregnation modification involves placing carbon nanotubes in an alkaline solution and impregnating them at room temperature for 20–40 minutes.

[0025] Furthermore, the alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution;

[0026] Further, in step 3), the mass-to-volume ratio of the modified carbon nanotubes to anhydrous ethanol is 1 g: 20 mL.

[0027] This invention adds carbon nanotubes to an ultrafiltration membrane for wastewater treatment, aiming to improve the membrane material’s adsorption capacity for organic matter and provide sufficient space for the subsequent introduction of nano-zero valent iron.

[0028] This invention modifies carbon nanotubes by impregnation, aiming to improve the hydrophilicity of ultrafiltration membranes used for wastewater treatment. Carbon nanotubes have high hydrophobicity. If carbon nanotubes are used directly for wastewater treatment, a water film is easily formed on the surface of the membrane material, which is not conducive to water permeation and retention of organic matter, thereby reducing the wastewater treatment performance of the ultrafiltration membrane.

[0029] Further, in step 4), the concentration of the FeCl3 solution is 0.5 mol·L⁻¹. -1 ;

[0030] Further, in step 4), the electrospinning parameters are: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, pouring speed: 3mL / h, and roller speed: 25r / min.

[0031] Furthermore, in step 5), the dropping rate of the NaBH4 solution is 20 d / min;

[0032] Further, in step 5), the NaBH4 solution is prepared at a concentration of 0.5 mL / cm³.-2 Add dropwise;

[0033] Further, in step 5), the concentration of the NaBH4 solution is 0.05 mol / L.

[0034] This invention involves adding FeCl3 solution to an ultrafiltration membrane used for wastewater treatment, and utilizing NaBH4 solution to remove Fe... 3+ By reducing iron to zero valent iron, nano-iron is introduced into the ultrafiltration membrane. The introduction of nano-iron can first react with metal ions in wastewater to reduce the content of heavy metal ions and improve the pH of the wastewater. Secondly, nano-iron itself can improve the photocatalytic performance of photocatalytic nanomaterials, promote the degradation of organic matter by photocatalytic nanomaterials, and release free radicals. Moreover, the heavy metal element obtained after the reduction reaction of iron will also promote the photocatalytic performance of photocatalytic nanomaterials, thus achieving highly efficient wastewater treatment performance.

[0035] The second technical solution of this invention:

[0036] The ultrafiltration membrane for wastewater treatment prepared by the above-mentioned method is an ultrafiltration membrane for wastewater treatment.

[0037] The third technical solution of this invention:

[0038] The above-mentioned ultrafiltration membranes for wastewater treatment are used in the treatment of wastewater.

[0039] Furthermore, the wastewater includes dyeing and printing wastewater.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] The ultrafiltration membrane for wastewater treatment prepared by this invention has good physical properties. Specifically, its tensile strength can reach 36.07 MPa, its elongation at break can reach 171%, and it has good mechanical properties; its contact angle with water can reach 50°, and it has good hydrophilicity; its acid resistance can reach 5.9 h, its alkali resistance can reach 6.0 h, and it has good weather resistance.

[0042] The ultrafiltration membrane for wastewater treatment prepared by this invention has good wastewater treatment performance; specifically, its COD... Cr The removal rates of SS and BOD5 can all reach over 96%, the pH can be adjusted to neutral, the water flux change in 120 hours is only 4.4%, and the treated dyeing and printing wastewater meets the national wastewater discharge standards.

[0043] The ultrafiltration membrane for wastewater treatment prepared by this invention has good wastewater treatment performance for dyeing and printing wastewater of different water qualities, and can meet the needs of different dyeing and printing plants. Detailed Implementation

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In the following embodiments, the room temperature is 25±2℃;

[0046] The following embodiments illustrate a method for preparing an ultrafiltration membrane for wastewater treatment, comprising the following steps:

[0047] 1) Dissolve polyvinylidene fluoride in organic solvent and anhydrous ethanol according to the mass-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol of 1g:6mL:2mL to obtain polyvinylidene fluoride solution.

[0048] The organic solvents include DMAC, DMF and NMP, and DMF is used as the organic solvent in the following examples;

[0049] 2) The photocatalytic nanomaterials were calcined at 200-500℃ for 1-3 hours, and then the calcined and modified photocatalytic nanomaterials were placed in an alkaline solution and impregnated at room temperature for 20-40 minutes to obtain modified photocatalytic nanomaterials.

[0050] The photocatalytic nanomaterial is either nano-titanium dioxide or graphite-like carbon nitride. When the photocatalytic nanomaterial is nano-titanium dioxide, the calcination modification involves calcination at 200–400°C for 1–3 hours; when the photocatalytic nanomaterial is graphite-like carbon nitride, the calcination modification involves calcination at 300–500°C for 1–3 hours. The alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution;

[0051] 3) The modified photocatalytic nanomaterials obtained in step 2) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a photocatalytic nanomaterial dispersion.

[0052] 4) Place carbon nanotubes in an alkaline solution and immerse them at room temperature for 20–40 min to obtain modified carbon nanotubes;

[0053] The alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution;

[0054] 5) The modified carbon nanotubes obtained in step 4) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a carbon nanotube dispersion.

[0055] 6) Combine the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and a solution with a concentration of 0.5 mol·L⁻¹. -1 FeCl3 solution was mixed in a volume ratio of 10:(3-5):(1-3):(0.5-1.5), and then the mixed solution was placed in an electrospinning machine to form a film by electrospinning.

[0056] The electrospinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, pouring speed: 3mL / h, roller speed: 25r / min;

[0057] 7) On the surface of the spun film obtained in step 6), control the dropping speed to 20 d / min, at a rate of 0.5 mL·cm. -2 A NaBH4 solution with a concentration of 0.05 mol / L was added dropwise to obtain the ultrafiltration membrane for wastewater treatment.

[0058] Example 1

[0059] An ultrafiltration membrane for wastewater treatment

[0060] 1) Dissolve polyvinylidene fluoride in organic solvent and anhydrous ethanol according to the mass-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol of 1g:6mL:2mL to obtain polyvinylidene fluoride solution.

[0061] 2) The nano-titanium dioxide was calcined at 300℃ for 2 hours to modify it, and then the calcined and modified photocatalytic nanomaterials were placed in a solution with a concentration of 1.0 mol·L⁻¹. -1 The modified photocatalytic nanomaterials were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0062] 3) The modified photocatalytic nanomaterials obtained in step 2) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a photocatalytic nanomaterial dispersion.

[0063] 4) Place carbon nanotubes in a solution with a concentration of 1.0 mol·L⁻¹ -1 Modified carbon nanotubes were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0064] 5) The modified carbon nanotubes obtained in step 4) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a carbon nanotube dispersion.

[0065] 6) Combine the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and a solution with a concentration of 0.5 mol·L⁻¹. -1 FeCl3 solution was mixed in a volume ratio of 10:4:2:1, and then the mixed solution was placed in an electrospinning machine to form a film by electrospinning.

[0066] The spinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, filling speed: 3mL / h, and roller speed: 25r / min.

[0067] 7) On the surface of the spun film obtained in step 6), control the dropping speed to 20 d / min, at a rate of 0.5 mL·cm. -2 Add 10 mL of a 0.05 mol / L NaBH4 solution to obtain the ultrafiltration membrane for wastewater treatment.

[0068] Example 2

[0069] An ultrafiltration membrane for wastewater treatment

[0070] 1) Dissolve polyvinylidene fluoride in organic solvent and anhydrous ethanol according to the mass-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol of 1g:6mL:2mL to obtain polyvinylidene fluoride solution.

[0071] 2) Graphite-like carbon nitride was calcined at 400℃ for 2 hours to modify it, and then the calcined and modified photocatalytic nanomaterials were placed in a solution with a concentration of 1.0 mol·L⁻¹. -1 The modified photocatalytic nanomaterials were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0072] 3) The modified photocatalytic nanomaterials obtained in step 2) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a photocatalytic nanomaterial dispersion.

[0073] 4) Place carbon nanotubes in a solution with a concentration of 1.0 mol·L⁻¹ -1 Modified carbon nanotubes were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0074] 5) The modified carbon nanotubes obtained in step 4) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a carbon nanotube dispersion.

[0075] 6) Combine the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and a solution with a concentration of 0.5 mol·L⁻¹. -1 FeCl3 solution was mixed in a volume ratio of 10:4:2:1, and then the mixed solution was placed in an electrospinning machine to form a film by electrospinning.

[0076] The spinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, filling speed: 3mL / h, and roller speed: 25r / min.

[0077] 7) On the surface of the spun film obtained in step 6), control the dropping speed to 20 d / min, at a rate of 0.5 mL·cm. -2 Add 10 mL of a 0.05 mol / L NaBH4 solution to obtain the ultrafiltration membrane for wastewater treatment.

[0078] Example 3

[0079] An ultrafiltration membrane for wastewater treatment

[0080] 1) Dissolve polyvinylidene fluoride in organic solvent and anhydrous ethanol according to the mass-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol of 1g:6mL:2mL to obtain polyvinylidene fluoride solution.

[0081] 2) Graphite-like carbon nitride was calcined at 400℃ for 2 hours to modify it, and then the calcined and modified photocatalytic nanomaterials were placed in a solution with a concentration of 1.0 mol·L⁻¹. -1 The modified photocatalytic nanomaterials were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0082] 3) The modified photocatalytic nanomaterials obtained in step 2) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a photocatalytic nanomaterial dispersion.

[0083] 4) Place carbon nanotubes in a solution with a concentration of 1.0 mol·L⁻¹ -1 Modified carbon nanotubes were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0084] 5) The modified carbon nanotubes obtained in step 4) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a carbon nanotube dispersion.

[0085] 6) Combine the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and a solution with a concentration of 0.5 mol·L⁻¹. -1 FeCl3 solution was mixed in a volume ratio of 10:3:1:0.5, and then the mixed solution was placed in an electrospinning machine to form a film by electrospinning.

[0086] The spinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, filling speed: 3mL / h, and roller speed: 25r / min.

[0087] 7) On the surface of the spun film obtained in step 6), control the dropping speed to 20 d / min, at a rate of 0.5 mL·cm. -2 Add 10 mL of a 0.05 mol / L NaBH4 solution to obtain the ultrafiltration membrane for wastewater treatment.

[0088] Example 4

[0089] An ultrafiltration membrane for wastewater treatment

[0090] 1) Dissolve polyvinylidene fluoride in organic solvent and anhydrous ethanol according to the mass-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol of 1g:6mL:2mL to obtain polyvinylidene fluoride solution.

[0091] 2) Graphite-like carbon nitride was calcined at 400℃ for 2 hours to modify it, and then the calcined and modified photocatalytic nanomaterials were placed in a solution with a concentration of 1.0 mol·L⁻¹. -1 The modified photocatalytic nanomaterials were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0092] 3) The modified photocatalytic nanomaterials obtained in step 2) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a photocatalytic nanomaterial dispersion.

[0093] 4) Place carbon nanotubes in a solution with a concentration of 1.0 mol·L⁻¹ -1 Modified carbon nanotubes were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0094] 5) The modified carbon nanotubes obtained in step 4) are dispersed in anhydrous ethanol at a mass-to-volume ratio of 1g:20mL to obtain a carbon nanotube dispersion.

[0095] 6) Combine the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and a solution with a concentration of 0.5 mol·L⁻¹. -1 FeCl3 solution was mixed in a volume ratio of 10:5:3:1.5, and then the mixed solution was placed in an electrospinning machine to form a film by electrospinning.

[0096] The spinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, filling speed: 3mL / h, and roller speed: 25r / min.

[0097] 7) On the surface of the spun film obtained in step 6), control the dropping speed to 20 d / min, at a rate of 0.5 mL·cm. -2 Add 10 mL of a 0.05 mol / L NaBH4 solution to obtain the ultrafiltration membrane for wastewater treatment.

[0098] Comparative Example 1

[0099] An ultrafiltration membrane for wastewater treatment

[0100] Same as Example 2, except that step 2) is: placing graphite-like carbon nitride in a solution with a concentration of 1.0 mol·L⁻¹ -1 Modified photocatalytic nanomaterials were obtained by impregnation and modification in NaOH solution at room temperature for 30 min.

[0101] Comparative Example 2

[0102] An ultrafiltration membrane for wastewater treatment

[0103] Same as Example 2, except that step 2) is: calcining graphite-like carbon nitride at 400°C for 2 hours to obtain modified photocatalytic nanomaterials.

[0104] Comparative Example 3

[0105] An ultrafiltration membrane for wastewater treatment

[0106] Same as Example 2, except that steps 4) and 5) are omitted, in which carbon nanotubes are directly dispersed in anhydrous ethanol.

[0107] Comparative Example 4

[0108] An ultrafiltration membrane for wastewater treatment

[0109] Same as Example 2, except that the addition of FeCl3 solution in step 6) and step 7) are omitted.

[0110] Comparative Example 5: An ultrafiltration membrane for wastewater treatment

[0111] Same as Example 2, except that in step 6), the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and the solution with a concentration of 0.5 mol·L⁻¹ are all different. -1 The volume ratio of the FeCl3 solution is 10:2:0.5:0.25.

[0112] Comparative Example 6

[0113] An ultrafiltration membrane for wastewater treatment

[0114] Same as Example 2, except that in step 6), the polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 3), the carbon nanotube dispersion obtained in step 5), and the solution with a concentration of 0.5 mol·L⁻¹ are all different. -1 The volume ratio of the FeCl3 solution is 10:6:4:2.

[0115] Effect verification

[0116] I. Physical Properties

[0117] The physical properties of the ultrafiltration membranes for wastewater treatment prepared in Examples 1-4 and Comparative Examples 1-6 were tested, and the test results are shown in Table 1.

[0118] Table 1 Physical Properties

[0119]

[0120]

[0121] Note: The acid resistance test method is to place the prepared wastewater treatment ultrafiltration membrane in a 1M HCl solution and record the time required for the tensile strength to change by 5%; the alkali resistance test method is to place the prepared wastewater treatment ultrafiltration membrane in a 1M NaOH solution and record the time required for the tensile strength to change by 5%.

[0122] As shown in Table 1, the ultrafiltration membrane for wastewater treatment prepared by this invention has good physical properties. Specifically, its tensile strength can reach 36.07 MPa, and its elongation at break can reach 171%, indicating good mechanical properties. Its contact angle with water can reach 50°, indicating good hydrophilicity. Its acid resistance can reach 5.9 h, and its alkali resistance can reach 6.0 h, indicating good weather resistance.

[0123] As can be seen from Examples 1 and 2, compared with nano-titanium dioxide, using graphite-like carbon nitride as a photocatalytic nanomaterial enables the prepared ultrafiltration membrane for wastewater treatment to have better physical properties.

[0124] As can be seen from Comparative Examples 1 to 6, omitting any step in this invention or changing the ratio of each solution will have an adverse effect on the physical properties of the final prepared ultrafiltration membrane for wastewater treatment.

[0125] II. Wastewater Treatment Performance

[0126] The wastewater treatment performance of the ultrafiltration membranes prepared in Examples 1-4 and Comparative Examples 1-6 was tested, and the test results are shown in Table 2.

[0127] Table 2 Wastewater Treatment Performance

[0128]

[0129] As shown in Table 2, the ultrafiltration membrane for wastewater treatment prepared by this invention has good wastewater treatment performance; specifically, its COD... Cr The removal rates of SS and BOD5 can all reach over 96%, the pH can be adjusted to neutral, the water flux change over 120 hours is only 4.4%, and the treated dyeing and printing wastewater meets the national wastewater discharge standards.

[0130] III. Pilot Application

[0131] The wastewater treatment ultrafiltration membrane prepared in Example 2 was used to treat dyeing wastewater from three textile dyeing and printing factories. The treatment results are shown in Table 3.

[0132] Table 3 Wastewater Treatment Pilot Projects

[0133]

[0134] As shown in Table 3, the ultrafiltration membrane for wastewater treatment prepared by this invention has good wastewater treatment performance for dyeing and printing wastewater of different water qualities, and can meet the needs of different dyeing and printing plants.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an ultrafiltration membrane for wastewater treatment, characterized in that, Includes the following steps: 1) Dissolve polyvinylidene fluoride in an organic solvent and anhydrous ethanol to obtain a polyvinylidene fluoride solution; 2) The photocatalytic nanomaterials are subjected to calcination modification and impregnation modification. The impregnation modification is carried out by placing the calcined photocatalytic nanomaterials in an alkaline solution for impregnation modification to obtain modified photocatalytic nanomaterials. Then, the modified photocatalytic nanomaterials are dispersed in anhydrous ethanol to obtain a photocatalytic nanomaterial dispersion. 3) The carbon nanotubes are impregnated and modified by placing the carbon nanotubes in an alkaline solution to obtain modified carbon nanotubes, and then dispersing the modified carbon nanotubes in anhydrous ethanol to obtain a carbon nanotube dispersion. 4) The polyvinylidene fluoride solution obtained in step 1), the photocatalytic nanomaterial dispersion obtained in step 2), the carbon nanotube dispersion obtained in step 3), and the FeCl3 solution are mixed in a volume ratio of 10:(3-5):(1-3):(0.5-1.5) and electrospun into a film. 5) Add NaBH4 solution to the surface of the spun membrane obtained in step 4) to obtain the ultrafiltration membrane for wastewater treatment.

2. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 1, characterized in that, In step 1), the mass-to-volume ratio of polyvinylidene fluoride, organic solvent and anhydrous ethanol is 1g:6mL:2mL.

3. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 1, characterized in that, In step 2), the photocatalytic nanomaterial is nano-titanium dioxide or graphite-like carbon nitride; the calcination modification is calcination at 200-500℃ for 1-3 hours; the impregnation modification is impregnation modification at room temperature for 20-40 minutes; the mass-volume ratio of the modified photocatalytic nanomaterial to anhydrous ethanol is 1 g: 20 mL.

4. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 3, characterized in that, The photocatalytic nanomaterial is nano-titanium dioxide, and the calcination modification is performed by calcination at 200–400°C for 1–3 hours; the photocatalytic nanomaterial is graphite-like carbon nitride, and the calcination modification is performed by calcination at 300–500°C for 1–3 hours; the alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution.

5. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 1, characterized in that, In step 3), the impregnation modification is performed at room temperature for 20-40 minutes; the mass-to-volume ratio of the modified carbon nanotubes to anhydrous ethanol is 1 g: 20 mL.

6. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 5, characterized in that, The alkaline solution has a concentration of 1.0 mol·L⁻¹. -1 NaOH solution.

7. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 1, characterized in that, In step 4), the concentration of the FeCl3 solution is 0.5 mol·L⁻¹. -1 The electrospinning parameters are as follows: spinning voltage: 30kV, slide speed: 100cm / min, receiving distance: 25cm, pouring speed: 3mL / h, and roller speed: 25r / min.

8. The method for preparing an ultrafiltration membrane for wastewater treatment according to claim 1, characterized in that, In step 5), the NaBH4 solution is added at a rate of 20 drops / min; the NaBH4 solution is added at a rate of 0.5 mL / cm³. -2 The solution is added dropwise; the concentration of the NaBH4 solution is 0.05 mol / L.

9. An ultrafiltration membrane for wastewater treatment prepared by the method for preparing an ultrafiltration membrane for wastewater treatment as described in any one of claims 1 to 8.

10. The application of the ultrafiltration membrane for wastewater treatment as described in claim 9 in the treatment of wastewater.

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