A modified FeOOH / PVDF molecularly imprinted composite film, its preparation method and application

Abstract

This invention belongs to the field of new materials technology and relates to a method for preparing a modified FeOOH / PVDF molecularly imprinted composite membrane, comprising the following steps: preparing a modified FeOOH / PVDF base membrane using a wet phase inversion method; immersing the modified FeOOH / PVDF base membrane in a photoinitiator solution, removing it, and then drying it; immersing the modified FeOOH / PVDF base membrane with the adsorbed photoinitiator in a mixture containing a template molecule-functional monomer complex, a crosslinking agent, and a photoinitiator for photo-initiated polymerization, followed by elution to obtain the modified FeOOH / PVDF molecularly imprinted composite membrane; wherein the template molecule is an organic pollutant, and the photoinitiator is benzophenone. Compared with the prior art, the modified FeOOH / PVDF molecularly imprinted composite membrane prepared by this invention has reusability, photocatalytic properties, and self-cleaning properties. It can reduce the use of organic solvents in the regeneration process of the molecularly imprinted composite membrane, achieve specific enrichment of target molecules, and completely eliminate organic pollutants serving as template molecules through light irradiation.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a modified FeOOH / PVDF molecularly imprinted composite membrane, its preparation method and application, and particularly to a molecularly imprinted composite membrane that is easy to operate, can selectively separate organic pollutants and has high reusability. Background Technology

[0002] Antibiotics are organic substances produced by microorganisms or higher plants and animals during their life processes that selectively inhibit or affect the functions of other cells. Based on their chemical structure, they are mainly classified into quinolone antibiotics, β-lactam antibiotics, macrolides, and aminoglycoside antibiotics. Antibiotics are widely used in medicine, animal husbandry, aquaculture, and agriculture, and in enormous quantities. Once these antibiotics enter the environment, they can lead to drug resistance in pathogens and induce antibiotic resistance genes in food animals, causing extremely serious harm to aquatic organisms and even human health. Furthermore, most antibiotics are physically and chemically stable, do not readily degrade, and have long half-lives. Therefore, their excessive use leads to antibiotic residues in some environments, especially in soil and water bodies.

[0003] Currently, adsorption and extraction methods are mainly used to remove organic pollutants such as antibiotics from water. Adsorption primarily utilizes porous solid adsorbents such as activated carbon to adsorb pollutants onto their surface for removal. The steps include adding powdered activated carbon to the water to be treated, mixing thoroughly, and separating the activated carbon from the water through sedimentation or filtration. This method is simple to operate and can remove multiple pollutants simultaneously, but it is difficult to achieve specific enrichment of target molecules. Furthermore, the continuous accumulation of various pollutants on the activated carbon surface causes the activated carbon to deactivate in a short time, thus requiring regeneration of the adsorbent material. Common regeneration methods include high-temperature incineration and organic reagent elution. High-temperature incineration can eliminate organic pollutants but generates other organic pollutants, while organic reagent elution can enrich organic pollutants, but it only involves phase transfer and does not truly remove the organic pollutants, and it requires a large amount of organic solvents.

[0004] Extraction methods primarily utilize the difference in solubility of soluble organic compounds in a two-phase reaction to remove organic pollutants from water. The method involves adding a water-immiscible organic solvent to the aqueous phase, shaking to allow the organic pollutants to enter the organic phase, separating the organic phase, and repeating the extraction process multiple times. The combined organic phases are then washed with a saturated sodium chloride solution, dried with a drying agent, filtered, and the solvent is removed by rotary evaporation before subsequent operations such as column chromatography. This method can separate and enrich both low- and moderate-volatility organic pollutants in water, but it requires large amounts of organic solvent, the extract is difficult to purify, the operation is complex, and it is difficult to achieve specific enrichment of target molecules.

[0005] Therefore, these two methods only transfer organic pollutants in the water to activated carbon or the organic phase, and further treatment is required to remove the organic pollutants. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a modified FeOOH / PVDF molecularly imprinted composite membrane for removing organic pollutants.

[0007] The modified FeOOH / PVDF molecularly imprinted composite film was prepared by the following method:

[0008] Step 1: Prepare modified FeOOH / PVDF base film using a wet phase inversion method;

[0009] Step 2: Immerse the modified FeOOH / PVDF base film in a photoinitiator solution, then remove and dry it;

[0010] Step 3: The modified FeOOH / PVDF base film with adsorbed photoinitiator is immersed in a mixture containing template molecule-functional monomer complex, crosslinking agent and photoinitiator, photoinitiated polymerization is carried out, and then the modified FeOOH / PVDF molecularly imprinted composite film is obtained by elution;

[0011] The template molecule is an organic pollutant, and the photoinitiator is benzophenone.

[0012] Compared with existing technologies, the modified FeOOH / PVDF molecularly imprinted composite membrane prepared by this invention has reusability, photocatalytic properties, and membrane self-cleaning properties. It can reduce the use of organic solvents in the regeneration process of molecularly imprinted composite membranes, achieve specific enrichment of target molecules, and completely eliminate organic pollutants used as template molecules through light irradiation.

[0013] Furthermore, the soaking time in step 3 is 15 minutes, and the polymerization initiation includes 15 cycles of direct irradiation of the modified FeOOH / PVDF base film immersed in the mixed solution by a 1000W high-pressure mercury lamp.

[0014] Furthermore, the soaking time in step 2 is 30 minutes, and the concentration of the photoinitiator is 0.15 mol / L.

[0015] Further, step 1 includes: dispersing PVDF and FeOOH in DMF, fully dissolving them to obtain a casting solution, degassing the casting solution, and then using a wet phase inversion method to form a membrane. The membrane is then washed and dried to obtain a modified FeOOH / PVDF base membrane.

[0016] Furthermore, the mass ratio of FeOOH to PVDF is 1:12, and the degassing treatment includes heating and stirring at 75°C for 1.5 hours and vacuum drying at 40°C for 16 hours.

[0017] Furthermore, the preparation method of FeOOH includes adjusting the pH of a 1 mol / L FeCl3 aqueous solution to about 12 with a 10% NaOH solution, stirring at room temperature for 30 min, and then taking the precipitate and reacting it at 180℃ for 24 h to obtain FeOOH.

[0018] Furthermore, the template molecule-functional monomer complex in step 3 is obtained by mixing the template molecule and the functional monomer, wherein the template molecule is gatifloxacin, the functional monomer is AMPS, and the crosslinking agent is MBAA.

[0019] Furthermore, the concentration of the template molecule is 5–15 mM, the concentration of the functional monomer is 30–70 mM, and the concentration of the crosslinking agent is 200–400 mM.

[0020] Instruction manual illustrations

[0021] Figure 1 This is a schematic diagram illustrating the formation process of the modified FeOOH / PVDF molecularly imprinted composite film of the present invention.

[0022] Figure 2 The image shows a comparison of XRD patterns between FeOOH powder and FeOOH / PVDF substrate film prepared in Example 1 of this invention.

[0023] Figure 3 The infrared spectra of the FeOOH / PVDF base film and the modified FeOOH / PVDF molecularly imprinted composite film prepared in Example 1 of this invention are shown.

[0024] Figure 4 The graph shows the relationship between the concentration of functional monomers and the binding amount of MIM and NIM during the preparation of MIM and NIM in Examples 1 to 7 of this invention.

[0025] Figure 5 The graphs show the relationship between the crosslinking agent concentration and the binding amount of MIM and NIM during the preparation of MIM and NIM in Examples 1-7 of this invention.

[0026] Figure 6 This is a graph showing the substrate concentration-binding amount relationship of the MIM prepared in Example 1 of the present invention.

[0027] Figure 7 This is a graph showing the adsorption time-binding amount relationship of MIM prepared in Example 1 of the present invention.

[0028] Figure 8 This is a comparison chart of the binding amounts of MIM prepared in Example 1 and B-MIM prepared in Comparative Example 8.

[0029] Figure 9 The graph shows the self-cleaning performance of the MIM membrane prepared in Example 1 of this invention. Detailed Implementation

[0030] To address the shortcomings of existing methods for removing organic pollutants, such as difficulty in achieving specific enrichment of target molecules, failure to degrade organic pollutants, poor reusability of adsorbents, secondary pollution, and the generation of large amounts of organic reagent waste, this invention considers using modified adsorbents to specifically enrich organic pollutants in water, followed by degradation treatment of the enriched organic pollutants using an elimination agent. Based on this concept, this invention first designs an environmentally friendly organic pollutant elimination membrane. This membrane can adsorb organic pollutants in water, and then eliminate the adsorbed organic pollutants through photocatalytic oxidation technology, achieving complete degradation of organic pollutants in the water, allowing for recycling without complex regeneration processes.

[0031] This invention designs the structure of the organic pollutant removal membrane by modifying the surface of the carrier membrane with an adsorbent layer doped with the eliminator. Then, it further studies the preparation method of the organic pollutant removal membrane by using an eliminator with photocatalytic properties to modify the carrier membrane, and then using photo-initiated polymerization to form an adsorbent that specifically adsorbs template molecules onto the modified carrier membrane, forming a molecularly imprinted composite membrane.

[0032] Based on this preparation method, iron hydroxyl oxide (FeOOH) was selected as the scavenging agent, and PVDF (polyvinylidene fluoride) microporous filter membrane was selected as the carrier membrane. Under light irradiation, the valence band electrons of FeOOH undergo interband transitions, generating photogenerated electrons and holes, while Fe... 3+ Converted to Fe 2+ O adsorbed on the surface of the photocatalyst 2- Capturing photogenerated electrons to form superoxide anions (·O 2- Then, the holes will absorb the hydroxide ions (OH-) adsorbed on the surface of the photocatalyst. - Fe and water (H2O) are oxidized to hydroxyl radicals (·OH). ·OH has a strong oxidizing ability and can oxidize most organic matter, ultimately converting it into carbon dioxide, water, and inorganic salts, thereby achieving the purpose of harmless treatment of organic pollutants. However, Fe... 2+ It is not easily oxidized by O2 and tends to accumulate in the system, reducing its photocatalytic performance. Adding hydrogen peroxide (H2O2) to an iron-based photocatalytic system forms a photo-Fenton system, where H2O2 can oxidize Fe... 2+ Rapidly converted to Fe 3+ It generates ·OH and hydroxyl oxygen radicals (·OOH), thereby realizing the recycling of iron ion catalysts and improving photocatalytic efficiency.

[0033] Based on this, the specific preparation method of the molecularly imprinted composite membrane for eliminating organic pollutants of the present invention is as follows:

[0034] (1) FeOOH was synthesized by hydrothermal method using water-soluble iron salts as the iron source;

[0035] (2) A casting solution was obtained by mixing DMF (N,N-dimethylformamide), PVDF and FeOOH, and then the casting solution was degassed by drying. The film was prepared by wet phase inversion method, and then the modified FeOOH / PVDF base film was obtained by washing and drying.

[0036] (3) The modified FeOOH / PVDF base film was immersed in a photoinitiator and then dried.

[0037] (4) Then, the template molecule and the functional monomer are mixed to obtain the template molecule-functional monomer complex, wherein the template molecule is an organic pollutant;

[0038] (5) The modified FeOOH / PVDF base film with adsorbed photoinitiator is immersed in a mixture containing template molecule-functional monomer complex, crosslinking agent and photoinitiator. Under ultraviolet light irradiation, the template molecule-functional monomer complex undergoes crosslinking polymerization on the base film surface to form a molecularly imprinted polymer. At the same time, the photoinitiator grafts the molecularly imprinted polymer onto the base film surface, so that there are molecularly imprinted specific recognition sites and recognition channels in the imprinted layer on the base film surface. Finally, the template molecules are eluted to obtain the modified FeOOH / PVDF molecularly imprinted composite film that can specifically adsorb template molecules.

[0039] In this invention, benzophenone is selected as the photoinitiator. Its mechanism of action is as follows: Benzophenone photoinitiators on the surface of the base film are excited to the singlet state S under ultraviolet (UV) irradiation and then rapidly jump to the triplet state T. The triplet benzophenone photoinitiator will undergo a Norrish type II reaction, that is, the carbonyl group on the photoinitiator reacts with the polymer, abstracts hydrogen from the polymer, generates a macromolecular surface free radical, and is reduced to a hydroxyl group. The macromolecular surface free radical reacts with the monomer to be grafted to obtain a covalent polymer, thereby realizing the grafting of the polymer onto the surface of the base film.

[0040] Organic pollutants include quinolone antibiotics, β-lactam antibiotics, macrolides, and aminoglycoside antibiotics. Gatifloxacin, a novel fluoroquinolone antibiotic, is widely used in disease treatment due to its good antibacterial activity and low toxicity. However, its overuse has led to residual pollution in water bodies. Currently, there is no green and efficient method for separating, enriching, and eliminating gatifloxacin.

[0041] Furthermore, this invention targets gatifloxacin, an organic pollutant. Based on the aforementioned method for preparing a molecularly imprinted composite membrane for eliminating organic pollutants, the functional monomer AMPS (2-acrylamide-2-methylpropanesulfonic acid) that interacts with gatifloxacin is screened, and MBAA (N,N-methylenebisacrylamide) is selected as a crosslinking agent to prepare a molecularly imprinted composite membrane for eliminating gatifloxacin. See also... Figure 1 The preparation method of the molecularly imprinted composite membrane that eliminates gatifloxacin is as follows:

[0042] (1) Adjust the pH of 1 mol / L FeCl3 aqueous solution to about 12 with 10% NaOH solution, stir at room temperature for 30 min, and then take the precipitate and react at 180℃ for 24 h to obtain FeOOH.

[0043] (2) PVDF and FeOOH are dissolved in DMF to obtain casting solution, and then the casting solution is degassed by heating and drying. The casting solution is coated on a glass plate by wet phase inversion method to form a homogeneous liquid film of a certain thickness. The film is formed by deionized water coagulation bath, and then washed and dried to obtain modified FeOOH / PVDF base film.

[0044] (3) The modified FeOOH / PVDF base film was immersed in an acetone solution of benzophenone. After immersion, the film was removed and vacuum dried so that benzophenone was adsorbed on the modified FeOOH / PVDF base film.

[0045] (4) Add a certain amount of functional monomer AMPS to gatifloxacin methanol solution, dissolve by ultrasonication, and then add a certain amount of crosslinking agent MBAA and benzophenone in sequence, and dissolve by ultrasonication to obtain a mixed solution.

[0046] (5) The modified FeOOH / PVDF base film adsorbed with benzophenone was immersed in the mixed solution and then photo-initiated polymerization was carried out by irradiating the modified FeOOH / PVDF base film immersed in the mixed solution with ultraviolet light. Subsequently, the modified FeOOH / PVDF base film after the reaction was eluted until no gatifloxacin was detected in the eluent. Then, excess acetic acid was washed away with methanol to obtain the modified FeOOH / PVDF molecularly imprinted composite film that can eliminate gatifloxacin.

[0047] The preparation method of the modified FeOOH / PVDF molecularly imprinted composite membrane capable of eliminating gatifloxacin according to the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] Example 1

[0049] (1) Prepare a FeCl3 aqueous solution with a concentration of 1 mol / L, adjust the pH of the FeCl3 aqueous solution to about 12 with 10% NaOH solution, stir magnetically at room temperature for 30 min, and then take the precipitate and place it at 180℃ for 24 h to obtain FeOOH.

[0050] (2) 1.2 g of polyvinylidene fluoride (PVDF) and 0.1 g of FeOOH were added to 15 mL of DMF and heated to dissolve, thus obtaining a casting solution. The solution was stirred in a water bath at 75 °C for 1.5 h and then vacuum dried at 40 °C for 16 h to remove bubbles. The casting solution was coated onto a glass plate using a wet phase inversion method to form a homogeneous liquid film of a certain thickness. After standing in air for 30 s, the glass plate with the homogeneous liquid film was immersed in a deionized water coagulation bath to form a film. After the film automatically peeled off, the residual DMF on the film was thoroughly washed with deionized water, and then dried to obtain a modified FeOOH / PVDF base film.

[0051] (3) The modified FeOOH / PVDF base film was immersed in acetone solution of benzophenone with a volume of 5 mL and a concentration of 0.15 mol / L for 30 min. After immersion, it was taken out and vacuum dried at 40℃ for 30 min.

[0052] (4) Add AMPS to a final concentration of 60 mM in a 0.01 mol / L gatifloxacin methanol solution, sonicate for 30 min, then add MBAA to a final concentration of 300 mM and 10 mmol benzophenone, sonicate for 30 min to obtain a mixed solution.

[0053] (5) The modified FeOOH / PVDF base membrane adsorbed with benzophenone was immersed in a certain amount of mixed solution for 15 min. A 1000W high-pressure mercury lamp was used to directly irradiate the immersed FeOOH / PVDF base membrane with the mixed solution for 15 cycles (1 min interval) to initiate a photo-initiated polymerization reaction. Subsequently, the reacted modified FeOOH / PVDF base membrane was immersed in an eluent (methanol:acetic acid = 95:5) and ultrasonically eluted until no gatifloxacin was detected in the eluent. Excess acetic acid was then washed away with methanol to obtain a modified FeOOH / PVDF molecularly imprinted composite membrane (MIM) with self-cleaning capabilities. The corresponding non-imprinted composite membrane (NIM) was prepared using the same method as above, but without the addition of the template molecule gatifloxacin.

[0054] (6) Determine the photocatalytic efficiency of FeOOH prepared in step (1) for gatifloxacin.

[0055] Refer to Table 1, which shows the photocatalytic efficiency of FeOOH for gatifloxacin (GTFX) under visible and ultraviolet light. Compared with the visible light group, FeOOH showed a higher photocatalytic efficiency under ultraviolet light irradiation, possibly because ultraviolet light has higher energy and the absorption wavelength of FeOOH is closer to that of ultraviolet light. In both the ultraviolet and visible light groups, the photocatalytic efficiency of FeOOH increased after the addition of H2O2 solution, indicating that the photo-Fenton system formed by H2O2 and FeOOH can improve the photocatalytic efficiency of FeOOH.

[0056] Table 1. Photocatalytic efficiency of FeOOH for gatifloxacin

[0057]

[0058] (7) The obtained FeOOH and modified FeOOH / PVDF base film were subjected to X-ray diffraction analysis.

[0059] See Figure 2 , Figure 2 The image shows a comparison of XRD patterns between FeOOH powder and modified FeOOH / PVDF film. Figure 3 The image shows a comparison of the infrared spectra of the modified FeOOH / PVDF molecularly imprinted composite film before and after photoinitiated polymerization. The characteristic diffraction peaks of the FeOOH powder are at 2θ = 17.90°, 21.20°, 26.46°, 33.34°, 36.76°, 40.08°, 41.28°, 53.34°, 59.12°, and 61.40°, indicating that the FeOOH prepared in step (1) has the crystal form α-FeOOH. The characteristic diffraction peaks of the modified FeOOH / PVDF base film at 2θ = 17.90°, 26.4°, and 36.7° coincide with those of α-FeOOH, therefore, the modified FeOOH / PVDF base film prepared by the wet phase inversion method in step (2) did not change the crystal form of α-FeOOH.

[0060] (8) The modified FeOOH / PVDF base film and the modified FeOOH / PVDF molecularly imprinted film were subjected to infrared spectroscopy analysis.

[0061] See Figure 3 The characteristic absorption peak of the modified FeOOH / PVDF base film is 3021 cm⁻¹. -1 This is the peak of CH saturation stretching vibration, 1401 cm⁻¹. -1 It is the variable-angle vibration peak of δCH2 in PVDF, 1170 cm⁻¹ -1 It is the absorption peak of CF stretching vibration in PVDF, and 974 cm⁻¹ -1 796cm -1 764cm -1 The vibrational absorption peak of the α-crystalline form of PVDF molecules is 839 cm⁻¹. -1 This is the characteristic peak of the β-crystal form of PVDF molecules, 874 cm⁻¹. -1 The absorption peaks are for amorphous PVDF molecules, therefore the PVDF in the modified FeOOH / PVDF film is a semi-crystalline phase composed of α-crystalline, β-crystalline, and amorphous crystalline forms.

[0062] Compared with the modified FeOOH / PVDF base film prepared in step (2), the characteristic absorption peak intensity of PVDF in the modified FeOOH / PVDF molecularly imprinted composite film prepared in step (5) is weakened or even disappears, but a new 1640 cm⁻¹ peak intensity is added. -1 1518cm -1 Two peaks, one at 1640cm -1 It is an amide I bond (carbonyl group), 1518 cm -1 The peaks show amide II bonds (NH bonds), meaning the modified FeOOH / PVDF base membrane exhibits two additional amide bond peaks after polymerization. Since both the functional monomer AMPS and the crosslinking agent MBAA possess amide bonds, the molecularly imprinted polymer was successfully grafted onto the surface of the modified FeOOH / PVDF base membrane via photoinitiated polymerization, resulting in a modified FeOOH / PVDF molecularly imprinted composite membrane. Furthermore, the polymer may have partially covered the surface of the original PVDF microporous filter membrane.

[0063] Example 2

[0064] (1) Prepare a FeCl3 aqueous solution with a concentration of 1 mol / L, adjust the pH of the FeCl3 aqueous solution to about 12 with 10% NaOH solution, stir magnetically at room temperature for 30 min, and then take the precipitate and place it at 180℃ for 24 h to obtain FeOOH.

[0065] (2) 1.2 g of polyvinylidene fluoride (PVDF) and 0.1 g of FeOOH were added to 15 mL of DMF and heated to dissolve, thus obtaining a casting solution. The solution was stirred in a water bath at 75 °C for 1.5 h and then vacuum dried at 40 °C for 16 h to remove bubbles. The casting solution was coated onto a glass plate using a wet phase inversion method to form a homogeneous liquid film of a certain thickness. After standing in air for 30 s, the glass plate with the homogeneous liquid film was immersed in a deionized water coagulation bath to form a film. After the film automatically peeled off, the residual DMF on the film was thoroughly washed with deionized water, and then dried to obtain a modified FeOOH / PVDF base film.

[0066] (3) The modified FeOOH / PVDF base film was immersed in acetone solution of benzophenone with a volume of 5 mL and a concentration of 0.15 mol / L for 30 min. After immersion, it was taken out and vacuum dried at 40℃ for 30 min.

[0067] (4) Add AMPS to a final concentration of 30mM to a 0.01mol / L gatifloxacin methanol solution, sonicate for 30min, then add MBAA to a final concentration of 300mM and 10mmol benzophenone, sonicate for 30min to obtain a mixed solution.

[0068] (5) The modified FeOOH / PVDF base membrane adsorbed with benzophenone was immersed in a certain amount of mixed solution for 15 min. A 1000W high-pressure mercury lamp was used to directly irradiate the immersed FeOOH / PVDF base membrane with the mixed solution for 15 cycles (1 min interval) to initiate a photo-initiated polymerization reaction. Subsequently, the reacted modified FeOOH / PVDF base membrane was immersed in an eluent (methanol:acetic acid = 95:5) and ultrasonically eluted until no gatifloxacin was detected in the eluent. Excess acetic acid was then washed away with methanol to obtain a modified FeOOH / PVDF molecularly imprinted composite membrane (MIM) with self-cleaning membrane capabilities. The corresponding non-imprinted composite membrane (NIM) was prepared using the same method as above, but without the addition of the template molecule gatifloxacin.

[0069] Example 3

[0070] The only difference between this embodiment and Example 2 is that the amount of functional monomer AMPS added in step (4) is replaced with the addition of functional monomer AMPS at a final concentration of 40 mM. All other steps are the same as in Example 2. The corresponding non-imprinted composite membrane (NIM) is prepared in the same way as described above, but without the template molecule gatifloxacin.

[0071] Example 4

[0072] Compared with Example 2, the only difference in this embodiment is that the amount of functional monomer AMPS added in step (4) is replaced with the addition of functional monomer AMPS with a final concentration of 50 mM. The other methods and steps are the same as in Example 2. The corresponding non-imprinted composite membrane (NIM) is prepared in the same way as above, but without the template molecule gatifloxacin.

[0073] Example 5

[0074] The only difference between this embodiment and Example 2 is that the amount of functional monomer AMPS added in step (4) is replaced with the addition of functional monomer AMPS at a final concentration of 70 mM. All other steps are the same as in Example 2. The corresponding non-imprinted composite membrane (NIM) is prepared in the same way as described above, but without the template molecule gatifloxacin.

[0075] Example 6

[0076] The only difference between this embodiment and Example 2 is that the amount of crosslinking agent MBAA added in step (4) is replaced with the addition of functional monomer AMPS at a final concentration of 200 mM. All other steps are the same as in Example 2. The corresponding non-imprinted composite membrane (NIM) is prepared in the same way as described above, but without the template molecule gatifloxacin.

[0077] Example 7

[0078] Compared with Example 2, the only difference in this embodiment is that the amount of crosslinking agent MBAA added in step (4) is replaced with the addition of functional monomer AMPS at a final concentration of 400 mM. The other methods and steps are the same as in Example 2. The corresponding non-imprinted composite membrane (NIM) is prepared in the same way as above, but without the template molecule gatifloxacin.

[0079] Example of effect 1

[0080] Static adsorption tests of gatifloxacin were performed on the MIM and NIM prepared in Examples 1-7: A certain amount of modified FeOOH / PVDF molecularly imprinted composite membrane was added to the corresponding test solution, and the membrane was left to stand in a constant temperature water bath. After a certain period of time, the amount of binding on the membrane was measured. If the area of ​​the membrane is S (cm²), the adsorption capacity is determined by the amount of binding on the membrane. 2 The volume of the test solution is V (mL), the initial concentration of gatifloxacin is C0 (mg / mL), and its concentration after a certain time is C (mg / mL). Then, the membrane binding capacity is Q (mg / cm³). 2 )=(C0-C)V / S.

[0081] See Figure 4 , Figure 4 The graph shows the gatifloxacin binding amounts of MIM and NIM prepared in Examples 1-5. As the concentration of the functional monomer AMPS added in preparation step (4) increases, the binding amount of MIM increases. This may be because when the amount of AMPS added is small, the covalent or non-covalent interaction between AMPS and the functional groups of the template molecule gatifloxacin is weak, failing to form a sufficient functional monomer-template molecule complex, and ultimately failing to form sufficient recognition sites. However, when the AMPS concentration exceeds 60 mM, the binding amount of MIM decreases, possibly because excessive AMPS leads to self-polymerization between AMPS, reducing the number of recognition sites. When the AMPS concentration is 60 mM, the specificity factor β(Q)... MIM / Q NIM Therefore, the optimal preparation condition for MIM is to add AMPS at a final concentration of 60 mM.

[0082] See Figure 5 , Figure 5 The graph shows the gatifloxacin binding amounts of MIM and NIM prepared in Examples 1, 6, and 7. As the concentration of the crosslinking agent MBAA added in preparation step (4) increases, the binding amount of MIM increases. This may be because a low amount of MBAA will result in low rigidity of the molecularly imprinted layer recognition site structure, leading to fewer or unstable recognition sites. However, when the MBAA concentration exceeds a certain level, the binding amount of MIM decreases. This may be because excessive MBAA will reduce the flexibility of the molecularly imprinted layer, hindering the mass transfer of the target substance. At an MBAA concentration of 300 mM, the specificity factor β(Q)... MIM / Q NIMTherefore, the optimal preparation condition for MIM is to add an MBAA concentration of 300 mM.

[0083] The static adsorption test results of gatifloxacin on the MIM and NIM prepared in Examples 1 to 7 showed that Example 1 was the best example, and the MIM prepared in Example 1 had the highest binding amount of gatifloxacin. Therefore, the MIM prepared in Example 1 was used for subsequent experiments.

[0084] Example 2

[0085] The MIM prepared in Example 1 was placed in 3 mL of methanol solutions of gatifloxacin with different initial concentrations (120 ppm, 150 ppm, 180 ppm, 210 ppm, 240 ppm, 270 ppm and 300 ppm), and allowed to stand for 4 h. The binding amount of MIM was then measured.

[0086] See Figure 6 At low concentrations of gatifloxacin, the binding amount of MIM is low, indicating that the number of MIM recognition sites binding to gatifloxacin has not yet reached saturation. As the concentration increases, the binding amount of MIM increases. However, when the concentration increases further, the binding amount of MIM decreases. This may be because at higher concentrations, the number of template molecules bound to the recognition sites rapidly approaches saturation, making it easier for template molecules to clog the pores inside the imprinted layer, affecting further mass transfer. Furthermore, steric hindrance also reduces the stability of recognition at the recognition sites, leading to a decrease in binding amount. Therefore, MIM works best in a methanol solution of gatifloxacin with an initial concentration of 150 ppm.

[0087] Example 3

[0088] Several portions of the MIM prepared in Example 1 were placed in a methanol solution of gatifloxacin with an initial concentration of 300 ppm. The supernatant was taken at intervals (10 min, 20 min, 40 min, 60 min, 80 min, and 100 min). The supernatant was filtered through a 0.45 μm nylon microporous membrane (organic system) to obtain the filtrate. The concentration of gatifloxacin in the filtrate was measured by HPLC.

[0089] like Figure 7 As shown, the adsorption kinetic constant of gatifloxacin by MIM is relatively large, and it can reach adsorption saturation in a short time. If the binding amount of MIM at 60 min in the figure is taken as the saturation binding amount, MIM reaches 86.36% of the saturation binding amount within the first 20 min, indicating that the recognition sites distributed on the surface of MIM can rapidly bind to the template molecule gatifloxacin and tend to saturate.

[0090] Example of effect 4

[0091] The MIM that had adsorbed gatifloxacin was washed with eluent (methanol:acetic acid = 95:5) until no gatifloxacin was detected in the eluent. The eluent on the membrane was then washed off with methanol. The eluted MIM was then used again for adsorption experiments, and the data were measured. The measurements were repeated 5 times.

[0092] See Figure 8 The loss rates of MIM reused twice and three times were low, both not exceeding 0.5%. When MIM was reused five times, the loss rate reached 23.23%, indicating that the prepared MIM has a certain degree of reusability. Therefore, MIM can be used as a pretreatment method for gatifloxacin detection, and the content of gatifloxacin in the sample can be calculated by detecting the content of gatifloxacin in the eluent.

[0093] Example 5

[0094] The modified FeOOH / PVDF molecularly imprinted composite membrane was used to remove gatifloxacin from milk: a certain amount of commercially available milk sample was taken, and a certain amount of gatifloxacin methanol standard solution was added to make the concentration after spiking 100 ppm. The MIM was directly placed in the solution and allowed to stand for 1 h. The recovery rate of gatifloxacin in milk by the MIM was then detected.

[0095] Referring to Table 2, the recovery rate of gatifloxacin in milk by MIM was 77.0%, and the bound amount was 1.9736 mg / cm³. 2 The RSD is 2.0%.

[0096] Example 6

[0097] The modified FeOOH / PVDF molecularly imprinted composite membrane was used for the removal of gatifloxacin from Pearl River water: A certain amount of Pearl River water sample was taken, and scum was filtered out. A certain amount of gatifloxacin methanol standard solution was added to the Pearl River water sample to make the concentration 100 ppm after spiking. The MIM was placed in 3 mL of the spiked solution, allowed to stand for 1 h, and the recovery rate of gatifloxacin in Pearl River water by the MIM was detected.

[0098] Referring to Table 2, the recovery rate of gatifloxacin in the Pearl River water by MIM was 80.1%, and the binding amount was 2.0793 mg / cm³. 2 The RSD is 0.8%.

[0099] Table 2. Spiked recoveries of gatifloxacin in actual samples

[0100]

[0101] Examples 5 and 6 show that the prepared MIM can effectively separate gatifloxacin from milk and Pearl River water. However, the recovery rate of MIM in milk is low, which may be because milk contains a lot of macromolecular components such as proteins, making the MIM's reaction environment more complex and resulting in a weaker adsorption effect.

[0102] Comparative Example 1

[0103] (1) 1.2 g of PVDF was added to 15 mL of DMF and heated to dissolve, thus obtaining a casting solution. The solution was stirred in a water bath at 75 °C for 1.5 h and then vacuum dried at 40 °C for 16 h to remove bubbles. The casting solution was coated onto a glass plate using a wet phase inversion method to form a homogeneous liquid film of a certain thickness. After standing in air for 30 s, the glass plate with the homogeneous liquid film was immersed in a deionized water coagulation bath to form a film. After the film peeled off automatically, the residual DMF on the film was thoroughly washed with deionized water, and then dried to obtain a PVDF base film.

[0104] (2) The PVDF base film was immersed in an acetone solution of benzophenone with a volume of 5 mL and a concentration of 0.15 mol / L for 30 min, and then removed and vacuum dried at 40 °C for 30 min to obtain the modified PVDF base film.

[0105] (3) Add 60 mM AMPS to a 0.01 mol / L gatifloxacin methanol solution, sonicate for 30 min, then add 300 mM MBAA and 10 mmol benzophenone, sonicate for 30 min to obtain a mixed solution.

[0106] (4) The modified PVDF base film was immersed in a certain amount of mixed solution for 15 min, and then the modified PVDF base film immersed in the mixed solution was directly irradiated with a 1000W high-pressure mercury lamp for 15 cycles (1 min interval) to carry out the polymerization reaction. Subsequently, the modified PVDF base film after the reaction was immersed in the eluent (methanol:acetic acid = 95:5), and ultrasonically eluted until no gatifloxacin was detected in the eluent. Then, excess acetic acid was washed away with methanol to obtain the modified PVDF molecularly imprinted composite membrane (B-MIM).

[0107] (5) Test the reusability of MIM and B-MIM.

[0108] The MIM that has adsorbed gatifloxacin and the B-MIM that has adsorbed gatifloxacin were placed in 3 mL of 1% H2O2 solution and irradiated with ultraviolet light (365 nm) for 1 h. Then the MIM was placed in 300 ppm of gatifloxacin standard solution to measure its binding amount. The measurement was repeated.

[0109] See Figure 9 After four reuses, the loss rate of MIM was only 41.76%, and its binding amount was still 1.23 mg / cm³. 2The loss rate of B-MIM reached 85.24%, and the binding amount was only 0.9333 mg / cm³. 2 This data successfully demonstrates that MIMs prepared with FeOOH / PVDF as the base film exhibit a certain degree of self-cleaning ability in H2O2 solution through photocatalytic degradation of template molecules at recognition sites or within the pores of the imprinted layer via a photo-Fenton system. B-MIMs with PVDF as the base film, however, lack this self-cleaning capability. However, because the ·OH generated by the photo-Fenton system indiscriminately oxidizes and degrades organic compounds, the photocatalytic degradation of the molecularly imprinted layer increases the loss rate of the MIM. Therefore, compared to Example 4, direct elution with organic solvents has a smaller impact on the loss of MIM recognition sites, while the self-cleaning MIM using the photo-Fenton system results in a higher loss rate, slightly reducing the number of times it can be reused.

[0110] Compared with the prior art, the present invention has the following advantages:

[0111] 1. This invention utilizes a wet phase inversion method to prepare a modified FeOOH / PVDF base membrane. A molecularly imprinted layer is then applied to the surface of the modified FeOOH / PVDF base membrane via photo-initiated polymerization to create a modified FeOOH / PVDF molecularly imprinted composite membrane. The preparation process is simple, eliminating the complex steps of grinding and centrifugation required in traditional molecularly imprinted membrane preparation. This method is characterized by its greenness, high efficiency, stability, and specific adsorption of organic pollutants used as template molecules. The modified FeOOH / PVDF molecularly imprinted composite membrane exhibits excellent reusability. Furthermore, the addition of FeOOH endows the membrane with photocatalytic properties and self-cleaning capabilities. Therefore, compared to traditional methods of reusing imprinted membranes by eluting template molecules with organic solvents, this molecularly imprinted composite membrane can achieve specific enrichment and complete elimination of template molecules through photocatalytic FeOOH degradation of template molecules, enabling reusability without the need for large amounts of organic solvents.

[0112] 2. The modified FeOOH / PVDF molecularly imprinted composite membrane of the present invention can be used as a pretreatment method for the detection of organic pollutants. After enriching the organic pollutants as template molecules, the organic pollutants are eluted with organic solvents and the content of organic pollutants in the organic solvent is detected. The modified FeOOH / PVDF molecularly imprinted composite membrane can also be used to remove organic pollutants from water. The membrane can be used to filter water or placed in water for static treatment. Then the membrane can be removed and the organic pollutants can be degraded by photocatalysis of FeOOH to achieve reuse. In addition, by changing the template molecules in the membrane preparation process, the membrane can achieve specific enrichment, separation and elimination of a variety of different organic pollutants.

[0113] 3. The modified FeOOH / PVDF molecularly imprinted composite membrane of this invention, which can eliminate gatifloxacin, has a certain ability to efficiently separate and enrich gatifloxacin in complex environmental systems. It can be applied to the separation and enrichment of gatifloxacin in actual samples: the recovery rate of gatifloxacin in milk is 77.0%, and the recovery rate of GTFX in Pearl River water is 80.1%, with the MIM binding amount being 1.9–2.0 mg / cm³. 2 The levels were all below 3%, with RSDs all less than 3%.

[0114] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a modified FeOOH / PVDF molecularly imprinted composite film, characterized in that, Includes the following steps: (1) FeOOH was synthesized by hydrothermal method using water-soluble iron salts as the iron source; (2) PVDF and FeOOH are dispersed in DMF and fully dissolved to obtain a casting solution. After degassing the casting solution, a wet phase inversion method is used to form a film. The film is washed and dried to obtain a modified FeOOH / PVDF base film. (3) The modified FeOOH / PVDF base film was immersed in a photoinitiator solution and then dried. (4) Mix template molecules and functional monomers to obtain template molecule-functional monomer complexes; (5) The modified FeOOH / PVDF base film with adsorbed photoinitiator is immersed in a mixture containing template molecule-functional monomer complex, crosslinking agent and photoinitiator. Photoinitiated polymerization is carried out by ultraviolet light irradiation, so that the template molecule-functional monomer complex undergoes crosslinking polymerization reaction on the base film surface to form molecularly imprinted polymer. At the same time, the photoinitiator grafts the molecularly imprinted polymer onto the base film surface, so that there are molecularly imprinted specific recognition sites and recognition channels in the imprinted layer on the base film surface. Finally, the template molecules are eluted to obtain the modified FeOOH / PVDF molecularly imprinted composite film that can specifically adsorb template molecules. The template molecule is an organic pollutant selected from one of quinolone antibiotics, β-lactam antibiotics, macrolides, and aminoglycoside antibiotics, and the photoinitiator is benzophenone.

2. The preparation method according to claim 1, characterized in that, The soaking time in step (5) is 15 min, and the polymerization initiation includes 15 cycles of direct irradiation of the modified FeOOH / PVDF base film immersed in the mixed solution by a 1000 W high-pressure mercury lamp.

3. The preparation method according to claim 2, characterized in that, The soaking time in step (2) is 30 min, and the concentration of the photoinitiator is 0.15 mol / L.

4. The preparation method according to claim 1, characterized in that, The mass ratio of FeOOH to PVDF is 1:12, and the degassing treatment specifically involves heating and stirring at 75°C for 1.5 h, followed by vacuum drying at 40°C for 16 h.

5. The preparation method according to claim 4, characterized in that, The preparation method of FeOOH includes adjusting the pH of a 1 mol / L FeCl3 aqueous solution to about 12 with a 10% NaOH solution, stirring at room temperature for 30 min, and then taking the precipitate and reacting it at 180℃ for 24 h to obtain FeOOH.

6. The preparation method according to claim 5, characterized in that, The template molecule-functional monomer complex in step (4) is obtained by mixing the template molecule and the functional monomer. The template molecule is gatifloxacin, the functional monomer is AMPS, and the crosslinking agent is MBAA.

7. The preparation method according to claim 6, characterized in that, The concentration of the template molecule is 5-15 mM, the concentration of the functional monomer is 30-70 mM, and the concentration of the crosslinking agent is 200-400 mM.

8. A modified FeOOH / PVDF molecularly imprinted composite membrane prepared by any one of claims 1 to 7.

9. The application of the modified FeOOH / PVDF molecularly imprinted composite membrane as described in claim 8 in the selective adsorption and elimination of organic pollutants.

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