Ag-AgCl particle loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane as well as preparation method and application thereof

Abstract

The invention discloses a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles as well as a preparation method and application of the polyvinylidene fluoride ultrafiltration composite catalytic membrane. The preparation method comprises the following steps: taking a PVDF membrane as a base material, loading nano Cu particles on the PVDF membrane by a CuCl2 solution through a photochemical reduction reaction to obtain a Cu / PVDF ultrafiltration composite membrane, and carrying out a replacement reaction on the Cu / PVDF ultrafiltration composite membrane and a silver nitrate solution to obtain the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. The Ag-AgCl ultrafiltration composite catalytic membrane disclosed by the invention is easy to synthesize, low in energy consumption and easy to recover, and can realize separation and catalysis functions at the same time. In addition, according to the preparation method, copper ions are subjected to photo-reduction firstly, and then silver nitrate with a proper concentration is used for replacement, so that the loading capacity of Ag-AgCl is successfully improved, and the catalytic effect of the prepared Ag-AgCl / PVDF ultrafiltration composite catalytic membrane is remarkably improved; and the waste of silver metal can be reduced, and valuable resources are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, in particular to a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, and a preparation method and application thereof. Background Art

[0002] 4-Nitrophenol (4-NP) is a common nitroaromatic hydrocarbon pollutant found in industrial wastewater. Due to its poor biodegradability, stable physicochemical properties, high toxicity, and easy bioaccumulation, 4-NP accumulates continuously in the surrounding environment, posing a serious threat to human health and well-being. Currently, a widely used and effective method for removing 4-nitrophenol involves converting 4-NP to 4-aminophenol (4-AP) using sodium borohydride (NaBH4) as a reducing agent in the presence of a catalyst. However, this method suffers from difficulties in catalyst recovery and low catalyst reusability. Ultrafiltration (UF) separation technology, as a key membrane separation technique, exhibits broad application prospects due to its low operating pressure, wide applicability, and relatively low cost. With continuous technological advancements and cost reductions, its application in various fields is expanding and deepening. Polyvinylidene fluoride (PVDF), a raw material for ultrafiltration membranes, is a highly valued material with excellent mechanical strength, chemical resistance, and heat resistance, making it a promising material. However, conventional ultrafiltration membranes only have interception and separation functions and cannot remove nitrophenol pollutants. Common methods for doping catalysts into PVDF ultrafiltration membranes include adding a catalyst precursor (such as AgNO3 or AgCl) and a reducing agent to the casting solution or directly mixing ready-made metal nanoparticles into the casting solution, and then preparing a separation membrane doped with metal nanoparticles through a phase inversion method. The disadvantage of these methods is that the prepared ultrafiltration composite membranes are prone to large pores, which seriously reduces the interception performance of the ultrafiltration composite membranes and makes it difficult to produce an ultrafiltration composite catalytic membrane that meets the requirements. Therefore, it is very necessary to develop an ultrafiltration composite catalytic membrane that is easy to synthesize, has low energy consumption, is easy to recycle, and can simultaneously achieve separation and catalytic functions. Summary of the Invention

[0003] The present invention provides a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, as well as its preparation method and application. The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane of the present invention is easy to synthesize, has low energy consumption, is easily recyclable, and simultaneously performs separation and catalytic functions. Furthermore, the present invention's preparation method, which involves photoreduction with copper chloride followed by replacement with an appropriate concentration of silver nitrate, successfully increases the Ag-AgCl loading, resulting in a significantly enhanced catalytic effect of the resulting Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. It also reduces silver metal waste, conserving valuable resources.

[0004] The technical solution of the present invention is a method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles. The method comprises the following steps: using a PVDF membrane as a substrate, loading nano-Cu particles on the PVDF membrane through a photochemical reduction reaction using a CuCl2 solution to obtain a Cu / PVDF ultrafiltration composite membrane; and then performing a replacement reaction with a silver nitrate solution to obtain a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, i.e., an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. The Ag-AgCl loading amount is 0.8-1.2 mg / cm 2 , the percentage of Ag in the Ag-AgCl is 87%-92%.

[0005] In the above-mentioned preparation method of the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, the loading amount of the Ag-AgCl is 1.0 mg / cm 2 , the percentage of Ag in the Ag-AgCl is 91.34%.

[0006] The preparation method of the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane comprises the following steps: A. Place a PVDF flat membrane as the substrate with the filter side facing down on the surface of the ethanol solution containing CuCl2 / benzophenone, allowing the solution to fully wet the substrate. Cover and seal to form a closed reaction system. B. Place the closed reaction system under ultraviolet light for 30-120 minutes. The photoinitiator benzophenone absorbs ultraviolet light and reacts with the co-initiator ethanol to produce active free radicals that reduce the Cu ions in the solution into Cu nanoparticles, which are loaded on the surface and between the pores of the PVDF membrane. C. Rinse the excess reaction solution on the PVDF membrane loaded with Cu nanoparticles to obtain a Cu / PVDF ultrafiltration composite membrane; D. Place the Cu / PVDF ultrafiltration composite membrane in an ethanol solution of silver nitrate to allow a sufficient replacement reaction to occur, thereby obtaining an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane.

[0007] In the preparation method of the polyvinylidene fluoride ultrafiltration composite catalytic membrane of above-mentioned load Ag-AgCl particle, in steps A, described CuCl concentration is 0.015-0.1mol / L, and the concentration of described benzophenone is 0.03-0.2mol / L.Described reactant concentration can accurately control the size, morphology and distribution of copper nanoparticles, thereby realizes the controlled synthesis to copper nanoparticles.Simultaneously, described CuCl concentration can make Ag-AgCl / PVDF ultrafiltration composite catalytic membrane be mixed with a small amount of chlorine element, thereby significantly improve the catalytic activity of Ag-AgCl / PVDF ultrafiltration composite catalytic membrane.

[0008] In the above-mentioned method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, in step A, the concentration of CuCl2 is 0.08 mol / L, and the concentration of benzophenone is 0.16 mol / L. These reactant concentrations enable the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane to have good separation catalytic performance.

[0009] In the above-mentioned method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, in step B, the closed reaction system is evacuated to a pressure of 10-30 kPa. Under this vacuum, the size, morphology, and distribution of the copper nanoparticles can be accurately controlled, thereby achieving controllable synthesis of the copper nanoparticles.

[0010] In the above-mentioned method for preparing the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane, in step B, a tempered glass cover plate is used for sealing.

[0011] In the above-mentioned method for preparing the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane, in step B, the illumination time is 90 minutes. The illumination time can make the copper nanoparticles in the synthesized intermediate Cu / PVDF have a better size, morphology and distribution form.

[0012] In the above-mentioned method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, in step B, the power of the ultraviolet light source is 12 W, and the wavelength of the ultraviolet light is 365 nm. These illumination conditions can ensure that the copper nanoparticles in the synthesized intermediate Cu / PVDF have a preferred size, morphology, and distribution.

[0013] In the above-mentioned method for preparing the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane, in step C, the excess reaction solution on the Cu nanoparticle-loaded PVDF membrane is rinsed clean with ethanol and deionized water respectively to obtain a Cu / PVDF ultrafiltration composite catalytic membrane.

[0014] In the above-mentioned method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, in step D, the concentration of the silver nitrate ethanol solution is 0.015-0.1 mol / L. The concentration of the reactants ensures effective replacement while incorporating a very small amount of chlorine into the product, thereby significantly improving the catalytic activity of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane.

[0015] In the above-mentioned method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, in step D, the concentration of the silver nitrate ethanol solution is 0.08 mol / L. This reactant concentration enables the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane to have good separation catalytic performance.

[0016] In the above-mentioned method for preparing a polyvinylidene fluoride nanofiltration composite catalytic membrane loaded with Ag-AgCl particles, the molar ratio of CuCl2 to AgNO3 in the CuCl2 solution and the silver nitrate solution is 1:2. This molar ratio allows silver to be loaded onto the membrane via a replacement reaction without causing waste.

[0017] The invention discloses a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, wherein the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles for catalytic reduction of 4-nitrophenol is prepared by the preparation method of the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles for catalytic reduction of 4-nitrophenol.

[0018] Application of Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane in the catalytic reduction of 4-nitrophenol compounds.

[0019] In the above application, the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles is used for the catalytic reduction of wastewater containing 4-nitrophenol.

[0020] Compared with the prior art, the present invention constructs the intermediate Cu / PVDF through a simple, green and environmentally friendly photochemical reduction method, and then obtains the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane through a replacement method. The method of first synthesizing the intermediate and then replacing the product in the present invention can increase the loading amount of Ag-AgCl in the ultrafiltration composite catalytic membrane. Under the premise of not destroying the basic chemical structure and performance of the PVDF ultrafiltration membrane, the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane prepared by the present invention is obtained by doping a very small amount of chlorine element into the photochemical reduction substrate copper chloride solution, and the Ag-AgCl load is uniform, dense and stable. Compared with silver nanoparticles, the Ag-AgCl group can significantly improve the catalytic activity at the same loading amount. The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane improves its catalytic degradation performance of 4-NP while retaining the membrane separation performance, has good cyclic catalytic stability, good pure water flux, and a small increase in the retention rate of HA. The present invention first photoreduces copper nanoparticles and then replaces them with silver nitrate solution of appropriate concentration, which can reduce the waste of Ag metal and save precious resources. The present invention takes into account economic practicality while improving the catalytic reduction performance. The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane of the present invention is easy to synthesize, has low energy consumption, is easy to recycle, and can simultaneously achieve separation and catalytic functions. In addition, the preparation method of the present invention of first photoreducing copper ions and then replacing them with silver nitrate of appropriate concentration successfully increases the loading amount of Ag-AgCl, and the catalytic effect of the obtained Ag-AgCl / PVDF ultrafiltration composite catalytic membrane is significantly improved; it can also reduce the waste of silver metal and save precious resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Surface SEM images of PVDF and Ag-AgCl / PVDF ultrafiltration composite catalytic membranes according to the present invention; Figure 2 1 is a cross-sectional SEM image of PVDF and Ag-AgCl / PVDF ultrafiltration composite catalytic membranes in an embodiment of the present invention; Figure 3 This is an EDS-Mapping image of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane surface in an embodiment of the present invention; Figure 4 This is an EDS-Mapping diagram of the cross section of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane in an embodiment of the present invention; Figure 5 This is the 4-nitrophenol catalytic reaction device in the experimental example of the present invention, and the marks in the figure are: 1-peristaltic pump, 2-membrane device, 3-pressure gauge, 4-pressure regulator. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0023] Example 1. Preparation of PVDF ultrafiltration membrane The substrate used in ultrafiltration membrane production is PET non-woven fabric. To ensure the membrane's performance, the substrate must be clean and unobstructed. Therefore, pretreatment is performed before use. First, ultrasonic cleaning with an appropriate concentration of hydrochloric acid removes residual impurities. Then, ultrasonic cleaning with an appropriate concentration of acetone removes oil. Finally, thorough rinsing with anhydrous ethanol and ultrapure water is performed. After cleaning, the membrane is dried and stored in a 50°C oven.

[0024] PVDF ultrafiltration membranes are prepared using a phase inversion method. The casting solution is prepared using the formula in Table 1. Once the casting solution is fully blended and ready for use, the membrane solution is applied to the substrate using a scraper. The coated PVDF ultrafiltration membrane is then soaked in tap water for 24 hours to stabilize. It is then treated with a sodium chlorate solution of appropriate concentration to clean the PVDF membrane without affecting its functionality. The membrane is then soaked in 60°C hot water, dried naturally, and stored for later use.

[0025] Table 1 Ratio of reagents in PVDF casting solution Reagents Proportion PVDF 16 wt% DMAc 78 wt% PEG400 6 wt% Example 2. Preparation of Ag-AgCl / PVDF ultrafiltration composite catalytic membrane Take a piece of PVDF base film with a size of 8cm×6cm, with the filter surface facing up, and place it on the surface of an ethanol solution containing CuCl2 / benzophenone (CuCl2 concentration is 0.08mol / L, benzophenone concentration is 0.16mol / L), cover and seal it with a tempered glass cover plate to form a closed reaction system, evacuate to 20kPa, and place the closed reaction system under ultraviolet light for illumination. The light source is a 12W ultraviolet lamp with a wavelength of 365nm. The illumination time is 1.5 hours. Benzophenone and ethanol A bimolecular reaction occurs, generating active free radicals that reduce copper ions to copper nanoparticles, which are loaded on the surface and between the pores of the PVDF flat membrane. The copper-loaded PVDF flat membrane, after illumination, is then placed in ethanol and deionized water for multiple cleanings to remove the surface solution to obtain a Cu / PVDF ultrafiltration composite membrane. Finally, a sufficient replacement reaction occurs with a 0.16 mol / L silver nitrate solution (the replacement reaction time is 5 minutes) to obtain an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. After being fully cleaned, it is stored in deionized water. In the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane, the Ag-AgCl loading is 1.00 mg / cm 2 , the percentage of Ag in the Ag-AgCl is 91.34%.

[0026] Example 3. Application of Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane in the catalytic reduction of 4-nitrophenol compounds The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane prepared in the example was used for catalytic reduction treatment of wastewater containing 4-nitrophenol.

[0027] Experimental Example 1. Morphology Analysis of Ag-AgCl / PVDF Ultrafiltration Composite Catalytic Membrane The PVDF base membrane and Ag-AgCl / PVDF ultrafiltration composite catalytic membrane in the embodiment were scanned by SEM. The results are as follows: Figure 1 (where a and c are PVDF ultrafiltration membranes, b and d are Ag-AgCl / PVDF ultrafiltration composite catalytic membranes) and Figure 2 (a is a PVDF ultrafiltration membrane, b, c, and d are Ag-AgCl / PVDF ultrafiltration composite catalytic membranes) The structures of the two are essentially identical, with no significant changes, indicating that the photochemical reduction and replacement reactions did not alter the structure of the PVDF-based membrane. Compared to the PVDF-based membrane, the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane has a load both near the surface and within its pores.

[0028] EDS-Mapping analysis was performed on the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. The results are as follows: Figure 3 and Figure 4 As shown, the load near the surface and in the inner pores of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane is Ag-AgCl. The Ag-AgCl is evenly distributed on the surface and in the inner pores of the composite catalytic membrane. The Ag content is much higher than the Cl content, with the Cl content being approximately 2%. Thermogravimetric analysis shows that the mass fraction of Ag-AgCl nanoparticles in the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane is 6.2%.

[0029] Experimental Example 2. Chemical Composition Analysis of Ag-AgCl / PVDF Ultrafiltration Composite Catalytic Membrane ATR-FTIR analysis was performed on the PVDF base membrane and Ag-AgCl / PVDF ultrafiltration composite catalytic membrane in the embodiment. During the test, the scanning accuracy was set to 2 cm. -1, with 64 scans. The characteristic peaks of the two membranes are essentially identical, with similar peak heights. This indicates that the loading of Ag-AgCl nanoparticles after photochemical reduction and replacement does not damage the chemical structure of the PVDF ultrafiltration membrane and does not alter the composition of the PVDF base membrane. The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane was subjected to X-ray diffraction (XRD) testing (the sample was tested in the range of 0-85°). According to the standard cards PDF#31-1238 and PDF#87-0597, the diffraction peaks at 38.1°, 44.2°, 64.4° and 77.4° at 2θ corresponded to the nanosilver crystal planes (111), (200), (220) and (311), respectively, and the diffraction peaks at 27.8°, 32.1° and 46.3° at 2θ corresponded to the nanosilver chloride planes (111), (200) and (220), indicating that AgCl and Ag were successfully loaded on the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane.

[0030] Experimental Example 3. Basic Performance Test of Ag-AgCl / PVDF Ultrafiltration Composite Catalytic Membrane Pure Water Flux Test: After rinsing the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane sample in the example with pure water, the membrane was placed in a three-way high-pressure flat-plate membrane test apparatus for flux testing. To ensure stable performance of the composite membrane, the sample was pre-pressurized at 0.1 MPa and 0.6 MPa for 15 minutes before each test to achieve flux stability. During the experiment, a certain volume V of liquid was collected in a clean conical flask, and the time ∆t required was recorded with a stopwatch. The permeate pure water flux was calculated. The results were averaged from three tests. The measured pure water flux of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane was 120.36 L·m -2 ·h -1 .

[0031] Determination of separation function: The test solution is 50 mg·L -1A humic acid (HA) aqueous solution was prepared. The Ag-AgCl / PVDF ultrafiltration composite catalytic membrane from this example was first pre-pressurized in a triple high-pressure flat-plate membrane pilot plant for 10-15 minutes to achieve stable flux. During the test, a certain volume V of permeate was collected, and the required time ∆t was recorded using a stopwatch. During the experiment, the pressure was maintained at 0.1 MPa, the temperature was approximately 25°C, and the circulation flow rate was 5 LPM. The filtration flux J of the membrane sample was measured. The HA solution concentration was determined by measuring the absorbance of the permeate and feed solution at a wavelength of 254 nm using ultrapure water as a reference using a UV spectrophotometer. The corresponding HA concentration was then calculated. Finally, the target molecule retention rate (R) was calculated, and the results were averaged from three replicate experiments. The retention rate of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane from this example was found to be 98.55%, approximately 1.5% higher than that of the PVDF-based membrane from this example.

[0032] Experimental Example 4. Catalytic Performance Test of Ag-AgCl / PVDF Ultrafiltration Composite Catalytic Membrane In the presence of NaBH4, the catalytic reaction can reduce 4-NP to 4-AP. This experimental example will verify the catalytic performance of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane by using the catalytic conversion of 4-NP to 4-AP.

[0033] With 4-nitrophenol catalytic reaction device (said reaction device as Figure 5 The catalytic performance of an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane was measured. The membrane sample to be tested was placed in membrane device 2 and secured within the membrane device to prevent liquid from escaping from the sides. A 4-nitrophenol solution was pumped into membrane device 2 via peristaltic pump 1. The filtrate was collected every 15 minutes and the 4-nitrophenol removal efficiency was measured.

[0034] In this experiment, the concentration of NaBH4 was 0.906 g·L -1 , flux size is 120-140 L·m −2 ·h −1 ·bar under the condition of treating 10mg·L -1 The total reaction time was 1.5 hours. The removal efficiency of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane exceeded 97.5%. During the uninterrupted catalytic process, freshly prepared feed solution was used each time. After eight cycles, the catalytic removal efficiency of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane remained above 96%. In contrast, the removal efficiency of a PVDF ultrafiltration membrane with the same silver nanoparticle loading was 39.76%.

[0035] These results demonstrate that the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane can efficiently remove 4-nitrophenol while maintaining a high rejection rate and exhibiting good stability. Compared to silver nanoparticles, the Ag-AgCl group significantly improves catalytic activity at the same loading level.

[0036] Experimental Example 5. Stability Test of Ag-AgCl / PVDF Ultrafiltration Composite Catalytic Membrane A static immersion test was used to test the stability of the silver nanoparticles loaded on the surface and inner pores of the Ag-AgCl / PVDF ultrafiltration composite catalytic membrane in the embodiment. The composite membrane sample was cut into appropriate sizes and placed in a certain volume of ultrapure water. 5 mL of the sample was taken out from the membrane with a pipette at regular intervals and then placed in a colorimetric tube. The sample was dissolved in nitric acid solution and allowed to stand for 30 minutes. The Ag content was determined by spectrophotometry (using water as a reference and a measurement wavelength of 570 nm). + The silver concentration was determined according to the above method.

[0037] Ag shedding was tested at different storage times. The results showed that on days 3 and 7, the amount of Ag accumulated in the water was very low, with almost no shedding. By day 28, the amount released into the water was also relatively low, at only 2.14%, fully meeting the relevant national standards. The amount of Ag shedding in the water confirms the good stability and high catalytic activity of the composite catalytic membrane.

[0038] The catalytic removal of 4-NP by an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane was tested at different storage times (7, 14, 21, and 28 days). The test results showed that while the 4-NP removal rate decreased with increasing storage time, the decrease was not significant. Furthermore, after 28 days of storage, the ultrafiltration composite catalytic membrane maintained relatively high catalytic activity, reaching a catalytic removal rate of 93.07%. This further demonstrates the excellent catalytic ability and stability of the composite catalytic membrane.

[0039] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, characterized in that: The PVDF membrane is used as the substrate, and CuCl2 solution is used to load nano-Cu particles on the PVDF membrane through a photochemical reduction reaction to obtain a Cu / PVDF ultrafiltration composite membrane. Then, a replacement reaction is carried out with a silver nitrate solution to obtain a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, namely, an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane. The Ag-AgCl loading amount is 0.8-1.2 mg / cm 2 , the percentage of Ag in the Ag-AgCl is 87%-92%.

2. The method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 1, wherein: The following steps are included: A. Use PVDF flat membrane as substrate, with the filter side facing up, and then add ethanol solution containing CuCl2 / benzophenone to fully wet the substrate. Cover and seal to form a closed reaction system; B. Place the closed reaction system under ultraviolet light for 30-120 minutes. The photoinitiator benzophenone absorbs ultraviolet light and reacts with the co-initiator ethanol to produce active free radicals that reduce the Cu ions in the solution into Cu nanoparticles, which are loaded on the surface and between the pores of the PVDF membrane. C. Rinse the excess reaction solution on the PVDF membrane loaded with Cu nanoparticles to obtain a Cu / PVDF ultrafiltration composite membrane; D. Place the Cu / PVDF ultrafiltration composite membrane in an ethanol solution of silver nitrate to allow a sufficient replacement reaction to occur, thereby obtaining an Ag-AgCl / PVDF ultrafiltration composite catalytic membrane.

3. The method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 2, wherein: In step A, the concentration of CuCl2 is 0.015-0.1 mol / L, and the concentration of benzophenone is 0.03-0.2 mol / L.

4. The method for preparing a polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 3, wherein: In step A, the concentration of CuCl2 is 0.08 mol / L, and the concentration of benzophenone is 0.16 mol / L.

5. The method for preparing the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 2, wherein: In step B, the closed reaction system is evacuated to 10-30 kPa.

6. The method for preparing the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 2, wherein: In step B, the power of the ultraviolet light source is 12W, and the wavelength of the ultraviolet light is 365nm.

7. The method for preparing the polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles according to claim 2, wherein: In step D, the concentration of the silver nitrate ethanol solution is 0.015-0.1 mol / L.

8. The method for preparing the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane according to claim 7, wherein: In step D, the concentration of the silver nitrate ethanol solution is 0.08 mol / L.

9. A polyvinylidene fluoride ultrafiltration composite catalytic membrane loaded with Ag-AgCl particles, characterized in that: The Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane for catalytic reduction of 4-nitrophenol is prepared by the preparation method of the Ag-AgCl particle-loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane for catalytic reduction of 4-nitrophenol according to any one of claims 1 to 9.

10. Application of Ag-AgCl particle loaded polyvinylidene fluoride ultrafiltration composite catalytic membrane in the catalytic reduction of 4-nitrophenol compounds.

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