Method for synthesizing composite film by nmp-induced surface self-corrosion assisted rapid spin coating and application thereof

Abstract

The application belongs to the technical field of environmental material synthesis, and particularly relates to a method for synthesizing a composite film by means of NMP-induced surface self-corrosion assisted rapid spin coating and application thereof; the steps are as follows: firstly, PDI and PEDOT are prepared, then a photocatalyst is prepared by means of a microwave method and a surface imprinting technology, and then the photocatalyst is embedded in surface pores of a PVDF film by means of NMP-induced surface self-corrosion assisted rapid spin coating to prepare an imprinting composite film with high stability and high permeability; the imprinting PDI / PEDOT photocatalyst is firmly embedded in the surface pores of the PVDF film, the stability is effectively improved, and a high water flux and a high light degradation activity are maintained. In addition, the construction of a heterojunction structure and the existence of imprinting cavities endow the imprinting composite film with good self-cleaning performance, photocatalytic performance and significant selectivity, and the imprinting composite film has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental material synthesis technology, specifically relating to a composite film synthesized by an NMP-induced surface self-corrosion-assisted rapid spin-coating method and its application in the efficient selective adsorption and photocatalytic degradation of tetracycline. Background Technology

[0002] Currently, tetracycline (TC) is widely used in human medicine and animal husbandry due to its low cost, high efficiency, and hyperspectral properties. However, the overuse of TC not only results in a large amount of residual pollutants being released into the environment, causing serious pollution, especially to the aquatic environment, but also hinders the progress of water treatment. It also has serious adverse effects on human health and ecosystems. Therefore, there is an urgent need for a low-cost, environmentally friendly technology to selectively remove low concentrations of highly toxic TC from a wide range of high-concentration, low-toxicity, or even non-toxic substances. Photocatalytic membrane technology stands out among many treatment technologies due to its high efficiency and environmental friendliness. This technology solves problems such as difficulties in separating and recovering powder materials, large degradation losses, and secondary pollution, while also endowing photocatalytic membranes with self-cleaning capabilities, thus solving the problem of membrane fouling.

[0003] Furthermore, to address the issue of selective TC removal, surface imprinting technology has been introduced. Imprinted materials prepared using this technology possess abundant imprint cavities, enabling selective adsorption of target pollutants. Therefore, combining surface imprinting technology with photocatalytic membrane technology allows photocatalytic materials to specifically adsorb TC and photodegrade it into non-toxic or non-toxic intermediates.

[0004] Photocatalytic membranes can be prepared using techniques such as vacuum filtration, phase inversion, sol-gel, electrospinning, liquid phase deposition, and spin coating. Among these, rapid spin coating relies on centrifugal force and gravity generated by adjusting the spin speed to spread the spin coating solution and material across the entire surface of the substrate membrane. This method offers advantages such as ease of operation, speed, and relatively uniform coating thickness. Composite membranes prepared using traditional spin coating solutions, such as CA, embed the photocatalytic powder material within a relatively dense spin coating layer, reducing direct contact between the photocatalyst and the target pollutant, thus leading to decreased photocatalytic degradation activity and water flux. However, 1-methyl-2-pyrrolidone (NMP) solvent has a corrosive effect on the PVDF membrane surface. Through the rapid spin coating process, NMP can only damage the surface layer of the PVDF membrane, causing the pore walls on the PVDF membrane surface to collapse. This pore wall collapse fixes the photocatalyst spin-coated at the pores on the PVDF membrane surface, protecting and stabilizing the photocatalyst. The composite membrane prepared by NMP-induced surface self-corrosion-assisted rapid spin-coating method lacks the dense spin-coating layer of composite membranes prepared by conventional spin-coating solutions. Furthermore, it enables effective contact between the photocatalyst embedded in the pores of the PVDF membrane surface and the target pollutant, thereby improving photocatalytic activity and flux. Currently, no research has been reported on the preparation of composite membranes using the NMP surface self-corrosion-assisted rapid spin-coating method. Summary of the Invention

[0005] To address the challenges of efficient and selective adsorption and removal of tetracycline by membranes, this invention employs an NMP-induced surface self-corrosion-assisted rapid spin-coating method to prepare a highly stable and highly permeable imprinted composite membrane. Since NMP is corrosive to commercially available PVDF membranes, it causes the pore walls on the PVDF surface to collapse. This collapse firmly fixes the imprinted PDI / PEDOT photocatalyst within the surface pores of the PVDF membrane, effectively improving stability. More importantly, this method avoids the dense layer found in membranes prepared using traditional spin-coating solutions. The imprinted PDI / PEDOT photocatalyst is fully exposed within the membrane's surface pores, maintaining high water flux and photodegradation activity.

[0006] Furthermore, the construction of the heterojunction structure and the introduction of the imprinted cavity endow the imprinted composite membrane with excellent self-cleaning properties, good photocatalytic performance, and significant selectivity. The degradation activity of the imprinted composite membrane for TC is 13.47 times that of CIP, and the selectivity coefficients of the imprinted composite membrane relative to the PDI membrane and the non-imprinted composite membrane are 3.96 and 2.02, respectively.

[0007] To achieve the above technical objectives, this invention provides a method for preparing a composite film (type II imprinted PDI / PEDOT heterojunction photocatalytic film) using an NMP-induced surface self-corrosion-assisted rapid spin-coating method, which is carried out according to the following steps:

[0008] Step 1: Preparation of PDI:

[0009] Under nitrogen protection, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 3-aminopropionic acid, and imidazole were mixed and reacted in an oil bath for a period of time. After the reaction was completed, the mixture was cooled to room temperature, and ethanol and HCl were added and stirred overnight. The resulting mixture was centrifuged to obtain a red solid precipitate, which was then dispersed in deionized water and washed until the pH of the dispersion was neutral. The washed precipitate was then collected again and vacuum dried to obtain a red solid. The red solid, TEA (triethylamine), and hydrochloric acid solution were then uniformly dispersed in deionized water, heated in a water bath, and magnetically stirred to obtain a mixed solution. Deionized water was then added to adjust the pH of the mixed solution to neutral. The mixed solution was then centrifuged, and the resulting precipitate was vacuum dried. The dried solid was PDI.

[0010] Step 2: Preparation of PEDOT:

[0011] Sodium bis(2-ethylhexyl)sulfosuccinate was dissolved in n-hexane, and anhydrous FeCl3 solution was added and stirred until a reverse micelle solution was formed. Then, 3,4-ethylenedioxythiophene was added to the above solution and stirred until the solution turned black. The product was washed by centrifugation with anhydrous ethanol, and the precipitate was dried under vacuum. The product obtained is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0012] Step 3: Preparation of imprinted PDI / PEDOT photocatalyst:

[0013] The PEDOT and TC prepared in step 2 were added to dimethyl sulfoxide and ultrasonically treated. After ultrasonic dissolution, a mixed solution was obtained and allowed to stand for a period of time in the dark under nitrogen protection. Then, trimethylolpropane trimethacrylate (TMPTMA), azobisisobutyronitrile and PDI were added to the above mixed solution and ultrasonically dispersed again to obtain a mixed liquid. Subsequently, a microwave reaction was carried out. After the reaction, the solid was obtained by centrifugation and repeatedly centrifuged and washed with deionized water and anhydrous ethanol. The precipitate after washing was then vacuum dried. The product obtained after drying is the uneluted imprinted PDI / PEDOT photocatalyst.

[0014] Uneluted imprinted PDI / PEDOT photocatalyst was placed in deionized water and photoeluted under magnetic stirring, aeration and visible light. After elution, the solid product was collected and washed multiple times with deionized water and anhydrous ethanol. The washed product was then vacuum dried, and the dried product was the imprinted PDI / PEDOT photocatalyst.

[0015] Step 4: Preparation of the imprinted composite film:

[0016] The imprinted PDI / PEDOT photocatalyst obtained in step 3 was added to NMP solvent and ultrasonically treated until it was uniformly dispersed; the mixed solution was evenly spread on the surface of the PVDF membrane, and the membrane was immediately immersed in deionized water after the spin coating process was completed. Then it was taken out and dried to obtain the imprinted composite membrane.

[0017] Preferably, in step 1, the ratio of the amounts of 3,4,9,10-perylenetetracarboxylic acid dianhydride, 3-aminopropionic acid, imidazole, deionized water, ethanol, and HCl is 1.177g:2.227g:16g:200mL:100mL:250mL; wherein the concentration of HCl is 2M.

[0018] The ratio of the red solid, TEA (triethylamine), hydrochloric acid solution, and deionized water is 0.5g:834μl:30mL:200mL, wherein the concentration of the hydrochloric acid solution is 4M.

[0019] Preferably, in step 1, the oil bath reaction temperature is 100°C and the reaction time is 4 hours; the water bath heating temperature is 60°C and the stirring reaction time is 1 hour.

[0020] Preferably, in step 2, the ratio of sodium bis(2-ethylhexyl)sulfosuccinate, 3,4-ethylenedioxythiophene, n-hexane, and anhydrous FeCl3 solution is 3.8 g: 0.45 g: 15 mL: 0.47 mL; wherein the concentration of the anhydrous FeCl3 solution is 10.2 mol / L.

[0021] Preferably, in step 2, the polymerization stirring time is 12 hours.

[0022] Preferably, in step 3, the ratio of PEDOT, TC, dimethyl sulfoxide, TMPTMA, azobisisobutyronitrile and PDI is 0.15g:0.1g:60mL:1mL:0.01g:0.3g.

[0023] Preferably, in step 3, the time for resting in the dark is 12 hours.

[0024] Preferably, in step 3, the microwave reaction temperature is 60°C, the power is 700W and 800rpm, and the reaction time is 1h.

[0025] Preferably, in step 3, the ratio of unwashed imprinted PDI / PEDOT photocatalyst to deionized water is 0.2g:100mL.

[0026] Preferably, in step 3, the aeration rate during photoelution is 2 mL / min, the visible light is a 250W xenon lamp, the elution temperature is 30℃, and the elution time is 12 h.

[0027] Preferably, in steps 1-3, the drying temperature is 60℃ and the time is 12h.

[0028] Preferably, in step 4, the ratio of the imprinted PDI / PEDOT photocatalyst to NMP is 0.1 g: 10 mL.

[0029] Preferably, in step 4, the mixed solution is evenly spread on the surface of the PVDF membrane, with 0.5 mL of mixed solution used per square centimeter of membrane area; the PVDF membrane is a hydrophilic membrane with a pore size of 220 nm.

[0030] Preferably, in step 4, the device used to evenly spread the mixed solution on the surface of the PVDF membrane is a spin coater, and the working conditions of the spin coater are 500 rpm low speed for 10 seconds and 300 rpm high speed for 10 seconds; the drying temperature is 60℃ and the drying time is 3 minutes.

[0031] The beneficial effects of this invention are:

[0032] (1) The imprinted composite membrane prepared by the NMP-induced surface self-corrosion assisted rapid spin coating method of the present invention has a large number of TC imprinted pores in the imprinted layer, which makes the prepared composite membrane have the ability to selectively adsorb and remove TC. The degradation activity of the membrane for TC is 13.47 times that of CIP. The selectivity coefficients of the imprinted composite membrane relative to the PDI membrane and the non-imprinted composite membrane are 3.96 and 2.02, respectively.

[0033] (2) The imprinted composite film prepared by the NMP-induced surface self-corrosion assisted rapid spin coating method of the present invention, due to the formation of a type II heterojunction structure between PDI and PEDOT, promotes the rapid separation of photogenerated electrons and holes to further enhance the photocatalytic degradation activity of tetracycline.

[0034] (3) This invention relates to an imprinted PDI / PEDOT heterojunction composite membrane prepared by an NMP-induced surface self-corrosion-assisted rapid spin-coating method. NMP is corrosive to the PVDF membrane surface, causing the pore walls of the PVDF surface to collapse. The collapse of the pore walls firmly anchors the imprinted PDI / PEDOT photocatalyst into the surface pores of the PVDF membrane, effectively improving stability and maintaining high water flux and photodegradation activity. This membrane also solves the problems of low water flux, poor photocatalytic degradation activity, and dense spin-coating layer of photocatalytic membranes prepared by traditional spin-coating methods.

[0035] (4) The composite film prepared by the present invention using the NMP-induced surface self-corrosion assisted rapid spin coating method is a novel and unreported research method for preparing composite films. Therefore, the material prepared by the present invention is unique and innovative, and has the advantages of simple operation, low cost, high utilization rate, strong targeting, and good effect. Attached Figure Description

[0036] Figure 1 The images show the morphology of different powder materials and films; where a is PDI, b is imprinted PDI / PEDOT photocatalyst, c is PDI film, d is PVDF film, and e is imprinted composite film.

[0037] Figure 2 The images show the FT-IR spectra of different powder materials; where a represents PDI, b represents PETOT, and c represents imprinted PDI / PEDOT photocatalyst.

[0038] Figure 3 The images show the UV-Vis diffuse reflectance spectra of different powder materials; where a represents PDI, b represents PETOT, and c represents imprinted PDI / PEDOT photocatalysts.

[0039] Figure 4 The images show the FT-IR spectra of different membranes; where a is the PDI membrane, b is the PVDF membrane, and c is the imprinted composite membrane.

[0040] Figure 5 The pure water flux data are for different membranes; where a is PVDF membrane, b is PDI membrane, c is non-imprinted composite membrane, and d is imprinted composite membrane.

[0041] Figure 6 The images show the photodegradation experiments of tetracycline (a) and ciprofloxacin (b) using different membranes. The samples are a PDI membrane, an imprinted composite membrane prepared with conventional CA spin-coating solution, a non-imprinted composite membrane, and an imprinted composite membrane, respectively.

[0042] Figure 7 SEM images, photocatalytic degradation performance, and flux data of membranes prepared by adjusting the time NMP remains on the commercial PVDF membrane after the spin-coating process.

[0043] Figure 8 The diagram shows the cyclic experiment of tetracycline degradation by the imprinted composite membrane and the FT-IR spectra before and after cycling. Detailed Implementation

[0044] The invention will be further explained below with reference to specific implementation examples.

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] Evaluation of the photocatalytic degradation activity of tetracycline:

[0050] One imprinted composite film prepared by NMP-induced surface self-corrosion-assisted rapid spin coating was placed at the bottom of a quartz cup. 100 mL of 20 mg / L tetracycline solution was added. The quartz cup was then placed under a 180 W xenon lamp (with a filter) and magnetic stirring was turned on. The reaction was allowed to proceed in the dark for a period of time until adsorption equilibrium was reached. Then the lamp was turned on and air was introduced (flow rate of 2 mL / min). Samples were taken every 20 minutes until the 120-minute mark. The samples were then labeled as C1, C2, C3, C4, C5, and C6. The solution after adsorption was labeled as C0.

[0051] The solid catalyst was separated by a combination of filtration and high-speed centrifugation (around 8000 rpm / min), and its absorbance (concentration) was measured. All degradation data were used to calculate the degradation rate using the degradation rate formula: (C0-Ci / C0)*100%.

[0052] Example 1:

[0053] (1) Preparation of PDI:

[0054] Under nitrogen protection, 1.177 g of 3,4,9,10-perylenetetracarboxylic acid dianhydride, 2.227 g of 3-aminopropionic acid, and 16 g of imidazole were mixed and reacted at 100 °C for 4 h. After the reaction was completed, the mixture was cooled to room temperature and ethanol (100 mL) and HCl (250 mL, 2 M) were added and stirred overnight. The resulting precipitate was washed with deionized water. After washing, the precipitate was collected and added to deionized water again until the pH of the dispersion was neutral. The washed precipitate was then collected and vacuum dried at 60 °C for 12 h to obtain a red solid.

[0055] 0.5 g of the above red solid, 834 μl of TEA, and 30 mL of 4M HCl were uniformly dispersed in a flask containing 200 mL of deionized water. The mixture was heated in a water bath at 60 °C with magnetic stirring for 1 h. After the reaction, deionized water was added to adjust the pH of the mixed solution to neutral. The product was then vacuum dried at 60 °C for 12 h. The solid obtained after drying was PDI.

[0056] (2) Preparation of PEDOT:

[0057] 3.8 g of sodium bis(2-ethylhexyl)sulfosuccinate was dispersed in 15 mL of n-hexane, and 0.47 mL of anhydrous FeCl3 solution was added. The mixture was stirred for 12 h to form a reverse micelle solution.

[0058] Subsequently, 0.45 g of 3,4-ethylenedioxythiophene was added to the above reverse micelle solution and stirred until the solution turned black. The solid product was collected and then centrifuged and washed with anhydrous ethanol. The precipitate was then vacuum dried at 60°C for 12 hours. The product obtained after drying is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0059] (3) Preparation of imprinted PDI / PEDOT photocatalyst:

[0060] 0.15g PEDOT and 0.1g TC were added to 60mL of dimethyl sulfoxide and sonicated until TC dissolved. The resulting mixed solution was then stored in the dark under nitrogen protection for 12h.

[0061] After standing, 1 mL of TMPTMA, 0.01 g of azobisisoheptanenitrile and 0.3 g of PDI were added to the above mixed solution. The mixture was then ultrasonically dispersed to ensure uniform dispersion. The resulting mixture was then subjected to microwave polymerization at 60 °C, 700 W and 800 rpm for 1 hour under nitrogen protection. After the reaction, the mixture was centrifuged. The resulting solid was washed three times by centrifugation with deionized water and anhydrous ethanol. The precipitate after washing was then vacuum dried at 60 °C for 12 hours. The product obtained after drying was the uneluted imprinted PDI / PEDOT photocatalyst.

[0062] The dried, uneluted imprinted PDI / PEDOT photocatalyst was placed in a photoreaction flask containing 100 mL of deionized water. Photoelution was performed under magnetic stirring, aeration (2 mL / min), and a 250 W xenon lamp (with a filter). Filtering was performed once per hour. The filtered solid was then added back to a photoreaction flask containing 100 mL of deionized water for cyclic elution. The elution temperature was 30°C, and the elution time was 12 h.

[0063] The absorbance was measured by taking approximately 6 mL of the filtrate each time until the absorbance intensity showed no significant change, at which point the elution process was considered complete. The solid product was washed three times with deionized water and anhydrous ethanol, and then dried under vacuum at 60°C for 12 hours. The resulting solid was the imprinted PDI / PEDOT photocatalyst.

[0064] (4) Preparation of non-imprinted PDI / PEDOT photocatalysts:

[0065] The method is consistent with (3), but the steps of adding TC and eluting TC are omitted.

[0066] (5) Preparation of imprinted composite films:

[0067] 0.1 g of imprinted PDI / PEDOT photocatalyst was added to 10 mL of NMP solvent and sonicated until it was uniformly dispersed. 2 mL of the above mixed solution was dropped onto a PVDF membrane, which is a hydrophilic membrane with a pore size of 220 nm. The membrane was then spin-coated at a low speed of 500 rpm for 10 s and a high speed of 300 rpm for 10 s using an NMP-induced surface self-corrosion assisted rapid spin-coating method. Immediately after the spin-coating process, the membrane was immersed in deionized water, removed, and dried at 60 °C for 3 min.

[0068] (6) Preparation of PDI film: Same as (5), except that the imprinted PDI / PEDOT photocatalyst is replaced with PDI.

[0069] (7) Preparation of non-imprinted PDI / PEDOT heterojunction photocatalytic film: The method is the same as in (5), except that the imprinted PDI / PEDOT photocatalyst is replaced with a non-imprinted PDI / PEDOT photocatalyst.

[0070] Figure 1 Figures show the morphology of different powder materials and films. As shown, the self-assembled PDI is a needle-like nanofiber structure with a diameter of approximately 30 nm and a length of approximately 150-400 nm. The PDI nanofibers intertwine with the imprinted PEDOT, forming a more stable imprinted PDI / PEDOT photocatalyst structure. Figures c, d, and e are SEM images of the PDI film, PVDF film, and imprinted composite film, respectively. The images reveal that the original PVDF film contains abundant and uniform pores. Compared to the PVDF film, the surfaces of the PDI film and the imprinted composite film show significant changes. This is due to the corrosion effect of NMP and the introduction of the photocatalyst.

[0071] Figure 2 The images show the FT-IR spectra of different powder materials; the samples are PDI, PEDOT, and imprinted PDI / PEDOT photocatalysts, respectively. The figure shows the 1693 cm⁻¹ spectrum of the imprinted PDI / PEDOT photocatalyst. -1 and 1658cm -1 The tensile vibration bands at 1589 cm⁻¹ are caused by the C=O groups of the carboxylic acid moiety and the ketone functional group in PDI, respectively. -1 The absorption band at this point corresponds to the C=C group in the aromatic carbon skeleton. It is approximately at 1089 cm⁻¹. -1 and located at 1517cm -1 The absorption bands correspond to the C=C rings in COC and PEDOT thiophene, respectively. The absorption peak of CS is at 982 cm⁻¹. -1 The characteristic peaks of both can be found in the imprinted PDI / PEDOT photocatalyst, proving the successful preparation of the imprinted PDI / PEDOT photocatalyst.

[0072] Figure 3 The figures show the UV-Vis diffuse reflectance spectra of different powder materials; the samples are PDI, PEDOT, and imprinted PDI / PEDOT photocatalysts, respectively. As shown in the figure, both PDI and PEDOT exhibit strong light absorption in the UV-vis region. Therefore, the imprinted PDI / PEDOT photocatalyst also has good UV-vis response.

[0073] Figure 4 The images show the FT-IR spectra of different films; characteristic peaks of PDI, PEDOT, and PVDF can be observed in all of them. This also proves that the imprinted PDI / PEDOT photocatalyst has been successfully immobilized in the pores on the surface of the PVDF film.

[0074] Figure 5 The data show the pure water flux of different membranes; the samples are PVDF membrane, PDI membrane, non-imprinted composite membrane, and imprinted composite membrane. Compared with PVDF membrane, the water flux of other photocatalytic membranes is lower. This is because the size of some photocatalysts is smaller than the pore size of PVDF membrane, resulting in some pores on the membrane surface being filled or covered. The imprinted composite membrane has the highest water flux among the photocatalytic membranes, which also indicates that the imprinted composite membrane has better permeability.

[0075] Figure 6 Figure a shows the photodegradation experiments of tetracycline and ciprofloxacin using different membranes. The samples are a PDI membrane, an imprinted composite membrane prepared with conventional CA spin-coating solution, a non-imprinted composite membrane, and an imprinted composite membrane. Figure a shows that the imprinted composite membrane achieves a TC degradation rate of 61.57%, which is 1.85 times that of the PDI membrane and 1.11 times that of the non-imprinted composite membrane, respectively. However, it exhibits the lowest degradation rate for CIP. Therefore, this membrane demonstrates good selectivity. Compared to PDI, the improved performance of the imprinted PDI / PEDOT photocatalyst may be due to the formation of a heterojunction after the introduction of PEDOT. Compared to PDI and non-imprinted PDI / PEDOT photocatalysts, the imprinted PDI / PEDOT photocatalyst, synthesized using TC as a template molecule, possesses the ability to increase its selective adsorption of TC through imprinted cavities. Because these imprinted cavities match TC, and there are significant differences in the molecular structure and size between TC and CIP, I-PDI / PEDOT exhibits the highest selective photodegradation activity. Furthermore, the photocatalytic degradation rate of TC by the imprinted composite membrane prepared using conventional CA spin-coating solution was only 33.58%. This is because the conventional CA spin-coating solution forms a dense spin-coating layer on the PVDF membrane, embedding the photocatalyst in the spin-coating layer, which further reduces the direct contact between the photocatalyst and the target pollutant, thereby reducing the photocatalytic activity of the composite membrane.

[0076] Figure 7SEM images, photocatalytic degradation performance, and flux data of membranes prepared by adjusting the residence time of NMP on commercial PVDF membranes after spin coating are shown. The images reveal that the imprinted composite membrane with an NMP residence time of 0 s exhibits abundant pores, high photocatalytic activity, and high water flux. This is because the brief residence time of NMP partially corrodes the PVDF membrane surface, causing slight depressions in the pore walls, firmly fixing the imprinted PDI / PEDOT photocatalyst within the membrane's surface pore walls. After 20 s, NMP further corrodes the PVDF membrane surface, causing further pore wall collapse and the formation of a dense layer, resulting in the lowest membrane flux and activity. When the residence time is extended to 40 s and 60 s, NMP further corrodes the formed dense layer, exposing some pores again. Therefore, the flux and activity of the 40 s and 60 s membranes are similar between 0 s and 20 s. The overall process follows a cyclical pattern of "NMP corrosion—pore wall collapse—NMP corrosion—exposure of pore space." In summary, the imprinted composite membrane has a better pore environment, which is beneficial for flux enhancement and contact between contaminants and the imprinted PDI / PEDOT photocatalyst.

[0077] Figure 8 The figures show the cyclic experimental results of the imprinted composite membrane degrading tetracycline and the FT-IR spectra before and after cycling. The figures demonstrate that the imprinted photocatalytic membrane exhibits good stability and maintains high photocatalytic performance during five cycles of tetracycline degradation. The lack of significant changes in the infrared spectra before and after cycling further indicates the excellent stability of this photocatalytic membrane.

[0078] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, 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 present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating, characterized in that, Includes the following steps: Step 1: Preparation of PDI: Under nitrogen protection, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 3-aminopropionic acid, and imidazole were mixed and reacted in an oil bath for a period of time. After the reaction was completed, the mixture was cooled to room temperature, and ethanol and HCl were added and stirred overnight. The resulting mixture was centrifuged to obtain a red solid precipitate, which was then dispersed in deionized water and washed until the pH of the dispersion was neutral. The washed precipitate was then collected again and vacuum dried to obtain a red solid. The red solid, TEA, and hydrochloric acid solution were then uniformly dispersed in deionized water, heated in a water bath, and magnetically stirred to obtain a mixed solution. Deionized water was then added to adjust the pH of the mixed solution to neutral. The mixed solution was then centrifuged, and the resulting precipitate was vacuum dried. The dried solid was PDI. Step 2: Preparation of PEDOT: Sodium bis(2-ethylhexyl)sulfosuccinate was dissolved in n-hexane, and anhydrous FeCl3 solution was added and stirred until a reverse micelle solution was formed. Then, 3,4-ethylenedioxythiophene was added to the above solution and stirred until the solution turned black. The product was washed by centrifugation with anhydrous ethanol, and the precipitate was dried under vacuum to obtain poly(3,4-ethylenedioxythiophene), which is PEDOT. Step 3: Preparation of imprinted PDI / PEDOT photocatalyst: The PEDOT and TC prepared in step 2 were added to dimethyl sulfoxide and ultrasonically treated. After ultrasonic dissolution, a mixed solution was obtained and allowed to stand in the dark under nitrogen protection for a period of time. Then, trimethylolpropane trimethacrylate, azobisisobutyronitrile and PDI were added to the above mixed solution and ultrasonically dispersed again to obtain a mixed liquid. Subsequently, a microwave reaction was carried out. After the reaction, the solid was obtained by centrifugation and repeatedly centrifuged and washed with deionized water and anhydrous ethanol. The precipitate after washing was then vacuum dried. The product obtained after drying is the uneluted imprinted PDI / PEDOT photocatalyst. Uneluted imprinted PDI / PEDOT photocatalyst was placed in deionized water and photoeluted under magnetic stirring, aeration and visible light. After elution, the solid product was collected and washed multiple times with deionized water and anhydrous ethanol. The washed product was then vacuum dried, and the dried product was the imprinted PDI / PEDOT photocatalyst. Step 4: Preparation of the imprinted composite film: The imprinted PDI / PEDOT photocatalyst obtained in step 3 was added to NMP solvent and ultrasonically treated until it was uniformly dispersed; the mixed solution was evenly spread on the surface of the PVDF membrane, and the membrane was immediately immersed in deionized water after the spin coating process was completed. Then it was taken out and dried to obtain the imprinted composite membrane.

2. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 1, the ratio of 3,4,9,10-perylenetetracarboxylic acid dianhydride, 3-aminopropionic acid, imidazole, deionized water, ethanol, and HCl is 1.177 g: 2.227 g: 16 g: 200 mL: 100 mL: 250 mL; wherein the concentration of HCl is 2 M; the ratio of the red solid, TEA (triethylamine), hydrochloric acid solution, and deionized water is 0.5 g: 834 μl: 30 mL: 200 mL, wherein the concentration of hydrochloric acid solution is 4 M.

3. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 1, the oil bath reaction temperature is 100 °C and the reaction time is 4 h; the water bath heating temperature is 60 °C and the stirring reaction time is 1 h.

4. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 2, the ratio of sodium bis(2-ethylhexyl)sulfosuccinate, 3,4-ethylenedioxythiophene, n-hexane, and anhydrous FeCl3 solution is 3.8 g: 0.45 g: 15 mL: 0.47 mL; the concentration of the anhydrous FeCl3 solution is 10.2 mol / L; and the polymerization stirring time is 12 h.

5. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 3, the ratio of PEDOT, TC, dimethyl sulfoxide, trimethylolpropane trimethacrylate, azobisisobutyronitrile, and PDI is 0.15 g: 0.1 g: 60 mL: 1 mL: 0.01 g: 0.3 g; the light-protected standing time is 12 h; the microwave reaction temperature is 60 ℃, the power is 700 W, the stirring speed is 800 rpm, and the reaction time is 1 h.

6. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 3, the ratio of uneluted imprinted PDI / PEDOT photocatalyst to deionized water is 0.2 g : 100 mL; the aeration rate during the photoelution process is 2 mL / min, the visible light is a 250 W xenon lamp, the elution temperature is 30 ℃, and the elution time is 12 h.

7. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In steps 1-3, the drying temperature is 60 ℃ and the time is 12 h.

8. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 4, the ratio of the imprinted PDI / PEDOT photocatalyst to NMP solvent is 0.1 g: 10 mL; the mixed solution is evenly spread on the surface of the PVDF membrane, with 0.5 mL of the mixed solution used per square centimeter of membrane area; the PVDF membrane is a hydrophilic membrane with a pore size of 220 nm.

9. The method for synthesizing composite films using NMP-induced surface self-corrosion-assisted rapid spin-coating according to claim 1, characterized in that, In step 4, the device used to evenly spread the mixed solution on the surface of the PVDF membrane is a spin coater. The working conditions of the spin coater are 500 rpm low speed for 10 s and 300 rpm high speed for 10 s. The drying temperature is 60 ℃ and the time is 3 min.

10. The composite membrane prepared by the method according to any one of claims 1-9 is used for selective adsorption and photocatalytic degradation of tetracycline.

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