Integrated catalytic separation membrane, preparation method thereof and water treatment method and system

Abstract

The invention relates to a water treatment and membrane separation technology, and provides an integrated catalytic separation membrane, a preparation method thereof, and a water treatment method and system. According to the membrane, polyvinylidene fluoride is used as a continuous phase to form a porous matrix, and cerium dioxide is embedded and fixed in a mode of uniform dispersion in a membrane body in a phase inversion membrane forming process; in the presence of illumination and peroxysulfate, active species are generated through in-situ activation on a membrane-water interface, and membrane separation is completed synchronously. The water treatment method comprises the following steps: adding peroxymonosulfate or peroxydisulfate into a water body to be treated, and filtering through the membrane under illumination; the photothermal effect generated by organic matter degradation intermediates in operation inhibits membrane pollution and maintains flux. According to the invention, short-range coupling of active sites and mass transfer channels is realized, the medicament and energy utilization rate is improved, the coating stripping and metal dissolution risk is reduced, and the method is suitable for drinking water pretreatment, reclaimed water deep treatment and treatment of water containing natural organic matters / humic acid.

Description

Technical Field

[0001] This invention relates to the fields of water treatment and membrane separation technology, specifically to a catalytic separation membrane for activating persulfate under light conditions and cooperating with the membrane separation process, its preparation method, and its application in the treatment of water containing natural organic matter / humic acid. In particular, it relates to a cerium dioxide-embedded polyvinylidene fluoride (PVDF) ultrafiltration membrane and its application in in-situ oxidation-antifouling-flux maintenance integrated treatment. Background Technology

[0002] Ultrafiltration membranes are widely used in wastewater treatment and water purification due to their simple operation, low cost, and environmental friendliness. Meanwhile, PVDF ultrafiltration membranes have attracted significant attention due to their excellent chemical stability, low toxicity, and low cost. However, the accumulation of organic pollutants on the membrane surface and in the membrane pores can cause serious membrane fouling problems, affecting the membrane's lifespan, leading to pore blockage, reduced water flux, and low separation efficiency. Peroxymonosulfate oxidation technology is considered an effective means of wastewater treatment. Methods for activating peroxymonosulfate mainly include photocatalysis, transition metals, carbon-based materials, ultrasound, and ultraviolet light. Among these, photocatalytic activation is environmentally friendly and sustainable, making the synergistic treatment of organic pollutants with photocatalysts and peroxymonosulfate a sustainable and environmentally friendly wastewater treatment method.

[0003] Although membrane separation and peroxymonosulfate oxidation each have their own advantages in engineering applications and pollution removal, their synergy still faces multiple bottlenecks: Firstly, the short lifespan and limited diffusion distance of active species mean that the traditional method of activating peroxymonosulfate outside the membrane or far from the membrane interface is prone to the dissipation of free radicals and singlet oxygen during mass transfer, resulting in low reagent utilization. Secondly, powdered or soluble transition metal catalysts pose difficulties in separation and recovery, as well as the risk of potential metal leaching, which is detrimental to sensitive scenarios such as drinking water and reclaimed water. Third, common surface-coated "catalytic films" are prone to coating peeling under cross-flow shear and chemical cleaning conditions, and long-term stability and secondary pollution problems are difficult to completely avoid. Fourth, even with the introduction of advanced oxidation, organic matter may still be redeposited and adhered on the membrane surface, making it difficult to fundamentally alleviate the issues of cleaning frequency and flux decline.

[0004] Overall, existing technologies lack an integrated solution that can generate active species in situ inside the membrane or near the membrane interface, while taking into account material safety and structural stability, and mechanistically suppressing contamination and maintaining flux. Summary of the Invention

[0005] This invention proposes an integrated catalytic separation membrane that works synergistically with persulfate under light conditions, its preparation method, and a water treatment method and system. The catalytic separation membrane uses polyvinylidene fluoride (PVDF) as the continuous phase to form a porous matrix. During the phase transformation and membrane formation process, cerium dioxide particles are embedded and uniformly dispersed within the membrane. In the presence of persulfate and under light irradiation, the target active species are activated in situ at the interface between the membrane and water, simultaneously completing membrane separation. This provides an effective solution to the problems of flux decline and frequent cleaning caused by the accumulation of organic pollutants on the membrane surface and in the pores.

[0006] According to a first aspect of the present invention, an integrated catalytic separation membrane is provided, comprising: A porous membrane matrix with polyvinylidene fluoride as the continuous phase, and cerium dioxide particles embedded and uniformly dispersed within the membrane. The catalytic separation membrane is suitable for use in water treatment under light conditions and in the presence of persulfate, so that the persulfate is activated to degrade organic pollutants in the water while completing membrane separation.

[0007] In some technical solutions, the cerium dioxide is in the form of nanoparticles, and its addition amount in the casting solution is 1.0 to 3.0 wt%.

[0008] In some technical solutions, the catalytic separation membrane has one or more of the following features: The cross-sectional structure is an asymmetrical porous structure; The water contact angle is minimized when the catalyst content is 2 wt%.

[0009] In some technical solutions, the cerium dioxide is a non-precious metal oxide catalyst, and the catalytic separation membrane does not contain a surface catalytic coating or metal foil layer, with the cerium dioxide fixed in the membrane in an embedded form.

[0010] According to a second aspect of the present invention, a method for preparing the above-described catalytic separation membrane is provided, comprising the following steps: Cerium dioxide particles are dispersed in a polar solvent, and polyvinylidene fluoride membrane material is added, with optional pore-forming agents added to obtain a uniform casting solution; After the casting solution is formed into a film, it is solidified by non-solvent-induced phase separation, so that the cerium dioxide particles are embedded and fixed in the polyvinylidene fluoride membrane during the phase separation process. The catalytic separation membrane was obtained by solvent replacement and drying.

[0011] Some technical solutions must meet at least one of the following process conditions: The polar solvent is N,N-dimethylformamide; The pore-forming agent is polyvinylpyrrolidone, and its average molecular weight is 5000-13800. The casting solution comprises: 12 wt% polyvinylidene fluoride, 1.0–3.0 wt% cerium dioxide, and 3.0 wt% polyvinylpyrrolidone. The cerium dioxide particles were prepared by a hydrothermal method.

[0012] According to a third aspect of the present invention, a water treatment method is provided, comprising the following steps: Persulfate was added to the water to be treated, and the water was filtered through the above-mentioned catalytic separation membrane under light. The persulfate is activated at the inner and outer interfaces of the membrane to generate active species that degrade organic pollutants in the water. During operation, the degradation intermediates of organic pollutants generate a photothermal effect on the membrane surface under light to inhibit membrane fouling and increase or maintain flux.

[0013] Some technical solutions include one or more of the following process implementation conditions: The persulfate is persulfate monosulfate or persulfate disulfate; The concentration of the persulfate added is 0.01–0.05 mM; The wavelength range of the illumination is 200–900 nm, and the irradiation power is 500 W / cm². 2 The irradiation time is 5 hours; The filtration method is cross-flow filtration, and the transmembrane pressure difference is 0.5 bar.

[0014] In some technical solutions, the water to be treated contains natural organic matter and / or humic acid, and under continuous operating conditions, the water flux of the catalytic separation membrane remains or increases.

[0015] According to a fourth aspect of the present invention, a water treatment system is provided for implementing the above-described water treatment method, comprising: The membrane module equipped with the above-mentioned catalytic separation membrane includes a dosing unit for adding persulfate to the feed water and a light source unit for providing light to the membrane module. The outlet of the membrane module is connected to a reflux unit or a discharge unit to achieve continuous or intermittent operation of separation and catalysis in synergy.

[0016] The present invention, by employing the above technical solution, has at least the following beneficial effects: 1. In this invention, cerium dioxide is embedded in the polyvinylidene fluoride membrane, with the active sites spatially coinciding with the main mass transfer channel. This activates persulfate at the interface between the membrane and water, significantly shortening the diffusion path of active species and improving their in-situ utilization efficiency. Compared with surface-coated catalytic membranes, the embedded configuration avoids the risk of coating peeling under cross-flow shearing and chemical cleaning, resulting in better long-term stability and resistance to secondary pollution. In the treatment of organic pollutants, especially natural organic matter and humic acid, the degradation intermediates can generate a beneficial photothermal effect on the membrane surface under light irradiation, improving the local interfacial microenvironment and inhibiting organic matter adhesion and redeposition. This enhances the membrane's antifouling performance and its ability to activate persulfate, alleviating membrane fouling problems, extending the service life of the ultrafiltration membrane, and demonstrating promising application prospects. 2. In this invention, cerium dioxide nanoparticles are loaded into a polyvinylidene fluoride (PVDF) membrane. On the one hand, this improves the hydrophilicity of the PVDF ultrafiltration membrane; on the other hand, the PVDF ultrafiltration membrane serves as a catalyst support, solving the problem of difficult photocatalyst recovery during powder degradation; furthermore, cerium dioxide is a non-precious metal oxide catalytic material, and its material safety and full-spectrum light characteristics are suitable for sensitive application scenarios such as drinking water and reclaimed water, reducing concerns about potential metal leaching. 3. In this invention, the casting solution is preferably composed of polyvinylidene fluoride, polyvinylpyrrolidone porogen, and 1.0–3.0 wt% cerium dioxide based on the casting solution. An asymmetric porous structure is obtained through non-solvent-induced phase separation. This structure is beneficial for providing interconnected channels while maintaining mechanical strength, allowing active sites to be more fully exposed to the main hydraulic channels. The embedded distribution of cerium dioxide and the porogen synergistically improve the wettability of the membrane and the hydrophilicity of the interface. At the process level, stable removal and antifouling performance can be obtained under continuous cross-flow conditions by using a light source to drive the process and adding a low dose of persulfate.

[0017] In summary, through the environmental friendliness of material selection, the structural stability of embedded fixation, and the synergistic process enhancement of photo / chemical energy, this invention achieves a significant improvement in overall performance in organic pollution removal, anti-pollution, and flux maintenance, and possesses good engineering feasibility and scalability. Attached Figure Description

[0018] Figure 1 shows the X-ray diffraction (XRD) patterns of the samples prepared in Examples 1-3 and Comparative Example 1; Figure 2 shows a scanning electron microscope (SEM) image of the sample prepared in Example 2; Figure 3 shows the infrared spectra of the samples prepared in Examples 1-3 and Comparative Example 1; Figure 4 shows contact angle photographs of the samples prepared in Examples 1-3 and Comparative Example 1; Figure 5 shows the UV-Vis absorption spectra of the samples prepared in Examples 1-3 and Comparative Example 1; Figure 6 shows the temperature changes of the samples prepared in Examples 1-3 under 808nm infrared laser light. Figure 7 Infrared thermal images of the samples prepared in Examples 1-3 and Comparative Example 1 at different times; Figure 8 shows the humic acid retention performance of the samples prepared in Examples 1-3 and Comparative Example 1. Figures 9-11 show the anti-pollution performance tests of the samples prepared in Examples 1-3 and Comparative Example 1; Figure 12 The self-cleaning performance of the samples prepared in Examples 1-3 and Comparative Example 1 was tested. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of the present invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0020] According to one embodiment of the present invention, an integrated catalytic separation membrane is provided. The membrane is formed with polyvinylidene fluoride as a continuous phase to form a porous membrane substrate, and cerium dioxide is fixed in the membrane substrate in a manner that is embedded and uniformly dispersed within the membrane substrate. The catalytic separation membrane is used for water treatment under light conditions and in the presence of persulfate, so that the persulfate is activated to degrade organic pollutants in the water while completing membrane separation.

[0021] In a preferred embodiment, cerium dioxide is in the form of nanoparticles and is added to the casting solution at an amount of 1.0–3.0 wt%, which enables the catalytic separation membrane to meet at least one or more performance indicators, such as having an asymmetric porous cross-sectional structure and a reduced water contact angle, wherein the water contact angle is minimized when the catalyst amount is 2 wt%. In the specific design, the catalytic separation membrane does not contain a surface catalytic coating or metal foil layer. Cerium dioxide is a non-precious metal oxide catalyst and is fixed in the membrane in an embedded form. Thus, under the operating conditions of light and persulfate coexisting, synergistic activation and separation are achieved at the interface between the catalytic separation membrane and water, improving the in-situ utilization of active species, reducing flux decline caused by surface adhesion, and obtaining more stable operating performance while meeting the above structural and performance indicators.

[0022] According to another embodiment of the present invention, a method for preparing the above-mentioned catalytic separation membrane is provided, which includes dispersing cerium dioxide particles in a polar solvent, adding polyvinylidene fluoride membrane material and optionally adding a pore-forming agent to obtain a uniform casting solution; after the casting solution is formed into a film, it is solidified by non-solvent-induced phase separation so that the cerium dioxide particles are embedded and fixed in the polyvinylidene fluoride membrane during the phase separation process; and then the catalytic separation membrane is obtained by solvent replacement and drying.

[0023] In a preferred embodiment, at least one of the following process conditions is met: the polar solvent is N,N-dimethylformamide, the pore-forming agent is polyvinylpyrrolidone with an average molecular weight of 5000 to 13800, the casting solution comprises 12 wt% polyvinylidene fluoride, 1.0 to 3.0 wt% cerium dioxide, and 3.0 wt% polyvinylpyrrolidone, and the cerium dioxide particles are obtained by a hydrothermal method.

[0024] In this embodiment, the phase separation and solidification ensures that cerium dioxide is stably fixed inside the membrane in an embedded form, thereby achieving a comprehensive effect of uniform distribution of active sites, intact membrane structure, and operational stability when obtaining the structure and performance indicators of the catalytic separation membrane.

[0025] According to another embodiment of the present invention, a water treatment method is provided, comprising the steps of: adding persulfate to the water to be treated, and filtering the water through the catalytic separation membrane under light, wherein the persulfate is activated at the inner and outer interfaces of the membrane to generate active species that degrade organic pollutants in the water, and during operation, the degradation intermediates of organic pollutants generate a photothermal effect on the membrane surface under light to inhibit membrane fouling and increase or maintain flux.

[0026] In a preferred embodiment, the persulfate is peroxymonosulfate or peroxydisulfate, with a concentration of 0.01–0.05 mM, an illumination wavelength range of 200–900 nm, and an irradiation power of 500 W / cm². 2 The irradiation time was 5 hours, the filtration method was cross-flow filtration, and the transmembrane pressure difference was set to 0.5 bar.

[0027] In the specific design, the water treatment method in this case is applicable to water bodies containing natural organic matter and / or humic acid, and the flux of the catalytic separation membrane is maintained or increased under continuous operation conditions.

[0028] In this embodiment, the active species are generated near the membrane-water interface, and free radicals and singlet oxygen with limited lifespans are more easily consumed by the target pollutants, thus improving reagent utilization. In a complex matrix represented by natural organic matter or humic acid, degradation intermediates generate a usable photothermal effect on the membrane surface under light, thereby improving the membrane's antifouling performance and its ability to activate peroxymonosulfate, alleviating membrane fouling problems, and extending the service life of the ultrafiltration membrane.

[0029] According to another embodiment of the present invention, a water treatment system is provided, comprising: a membrane module equipped with the above-described catalytic separation membrane; a dosing unit for adding persulfate to the feed water; and a light source unit for providing illumination to the membrane module; the effluent end of the membrane module is connected to a reflux unit or a discharge unit to achieve continuous or intermittent operation of separation and catalysis in synergy. In a preferred embodiment, the various units of the system form a compact structure and near-field illumination, enabling simultaneous separation and persulfate activation within the membrane module scale.

[0030] In this embodiment, under the premise of satisfying the above configuration, the system reduces the dissipation of active species in the bulk phase, shortens the mass transfer path and reduces the complexity of equipment links through integrated arrangement. Under the given dosing and illumination conditions, it improves the processing efficiency, slows down the growth of transmembrane pressure difference and reduces the cleaning frequency, thereby obtaining stable continuous or intermittent operation performance.

[0031] To better understand and apply the above solutions and to effectively demonstrate the corresponding benefits, the following detailed embodiments further illustrate the integrated catalytic separation membrane, its preparation method, water treatment method, and system provided by the present invention.

[0032] The integrated catalytic separation membrane prepared in this invention was characterized by the following methods: Structural analysis was performed using a Rigaku D / Max-RB X-ray diffractometer (XRD); UV-Vis diffuse reflectance was measured using a UV-T700 spectrophotometer; the morphology of the sample was analyzed using a HITACHI S-4800 scanning electron microscope (SEM); and the water contact angle (CA) was measured using a JC2000D1 optical contact angle meter.

[0033] The evaluation process for the retention performance of the integrated catalytic separation membrane described in this embodiment of the invention is as follows: A self-built circulating cross-flow filtration device was used to fix the effective filtration area of ​​the membrane sample at 28.26 cm². 2 The sample was fixed in a membrane filtration unit, and the membrane sample was pre-pressurized with ultrapure water at a pressure of 1 bar for 30 min to achieve a stable water flux. The filtration pressure was set to 0.5 bar. Simultaneously, the ultrapure water in the feed tank was replaced with a 10 mg / L humic acid solution (solution A), and the filtered solution in the filtrate tank (solution B) was collected. The absorbance of solutions A and B was measured at 254 nm using a liquid chromatography-ultraviolet spectrophotometer and converted to concentration. The rejection rate was then calculated. R The calculation formula is:

[0034] C: Concentration of the solution filtered out in the filtrate tank; C0: Concentration of the humic acid solution in the feed tank.

[0035] The weight (volume) of the water filtered by the membrane sample was recorded in real time every 3 minutes using an electronic balance. The water flux of the sample membrane was calculated using the following formula:

[0036] J Water flux (L / m) 2 V: Volume of the permeate solution (L), A: Effective area of ​​the membrane sample filtered (m²) 2 T: Filtration time (h), P: Transmembrane pressure difference (bar).

[0037] Example 1 Prepare an integrated catalytic separation membrane using the following steps: Step 1: Preparation of CeO2 photocatalyst At room temperature, 4.0 g of cerium nitrate hexahydrate was weighed and dissolved in 4 mL of ultrapure water. The mixture was stirred for 10 minutes and labeled as solution A. In another beaker, 4 mL of glacial acetic acid and 104 mL of ethylene glycol were added and stirred for 10 minutes until the solution was homogeneous. This solution was labeled as solution B. Then, solution A was slowly added dropwise to solution B, and the mixture was stirred at room temperature for 30 minutes. Finally, the obtained solution was transferred to a 200 mL stainless steel hydrothermal reactor and reacted in a 180 °C drying oven for 200 minutes. After cooling to room temperature, the solution was centrifuged, washed three times with ultrapure water and anhydrous ethanol, and vacuum dried at 80 °C for 12 h to obtain a light purple solid. This solid was ground into powder and placed in a 50 mL crucible. The powder was heated in a muffle furnace for 2 h at 500 °C at a heating rate of 2 °C / min. The resulting light yellow powder was the CeO2 photocatalyst.

[0038] Step 2: Preparation of CeO2 / PVDF ultrafiltration membrane The prepared CeO2 catalyst was mixed with DMF (N,N-dimethylformamide) in a certain proportion, and after sonication for 30 minutes, PVP and PVDF membrane material were added. The mixture was stirred at 60 °C for 12 hours, and the homogenized casting solution was placed in a vacuum drying oven at 60 °C for 4 hours to remove bubbles. Then, the casting solution was poured onto a glass plate, and an automatic coating machine was used to coat the membrane with a doctor blade height of 0.25 mm. The membrane and glass plate were immersed together in deionized water to solidify and detach the membrane, which was then stored in deionized water to obtain the CeO2 / PVDF ultrafiltration membrane.

[0039] Step 3: Construction of the membrane separation system A CeO2 / PVDF ultrafiltration membrane was installed in a self-built membrane separation device to retain a simulated organic pollutant humic acid (HA) solution. A certain mass of persulfate was added to the solution, and the device was run under light conditions for 5 hours. During the reaction, the persulfate and photocatalysis worked synergistically to continuously generate reactive oxygen species. The pollutant intermediates generated during the degradation of HA could induce a photothermal effect on the membrane surface, thereby further improving the membrane's permeability and antifouling performance.

[0040] In the above embodiments, preferably, the molecular weight of PVP in the casting solution is 8000 and the addition amount is 3 wt%; the addition amount of PVDF in the casting solution is 12 wt%; the addition amount of CeO2 in the casting solution is 2 wt%; and the concentration of PMS is 0.02 mM.

[0041] Example 2 The steps in this embodiment are basically the same as those in Embodiment 1, except that the CeO2 content is 1 wt%.

[0042] Example 3 The steps in this embodiment are basically the same as those in Embodiment 1, except that the CeO2 content is 3 wt%.

[0043] Comparative Example 1 The steps in this comparative example are the same as those in Example 1, except that no CeO2 catalyst was added to obtain the PVDF membrane.

[0044] The prepared CeO2 / PVDF ultrafiltration membrane was subjected to the following tests: XRD structure analysis, solid UV-Vis diffuse reflectance testing, infrared and SEM morphology analysis, contact angle test; retention rate test, antifouling performance test, and photothermal performance test. The test results are as follows: Figure 1 shows the X-ray diffraction (XRD) patterns of samples from Examples 1-3 and Comparative Example 1. The samples prepared in Examples 1-3 have characteristic diffraction peaks of CeO2, and the samples prepared in Examples 1-3 show the same characteristic diffraction peaks as Comparative Example 1, proving that CeO2 / PVDF photocatalytic ultrafiltration membranes were successfully prepared.

[0045] Combination Figure 2 As shown, Figure 2 is a cross-sectional scanning electron microscope (SEM) image of the sample prepared in Example 2, and Figures 2b and 2c are magnified partial images of Figure 2a. As shown, the sample prepared in Example 2 has a porous asymmetric structure, with CeO2 firmly loaded within the membrane's pores. Figure 2d is a cross-sectional scanning electron microscope (SEM) image of the sample prepared in Comparative Example 1. The comparison shows that the addition of the catalyst in the sample prepared in Example 2 did not disrupt the structure of the separation membrane itself.

[0046] Figure 3 shows the Fourier Transform Infrared (FTIR) spectra of the samples prepared in Examples 1-3 and Comparative Example 1. Comparative Example 1 consists of α, β, and γ phases. Furthermore, the samples prepared in Examples 1-3 exhibit spectra similar to those of Comparative Example 1. Therefore, it can be demonstrated that loading the catalyst into the membrane structure via phase inversion does not significantly alter the chemical properties of the membrane.

[0047] Figure 4 shows contact angle photographs of samples prepared in Examples 1-3 and Comparative Example 1, indicating that the original PVDF membrane has a smaller contact angle after being loaded with CeO2, and its hydrophilicity is improved, which is beneficial to improving its antifouling performance.

[0048] Figure 5 shows the UV-Vis absorption spectra of the samples prepared in Examples 1-3 and Comparative Example 1. It indicates that the samples prepared in Examples 1-3 significantly enhanced their light absorption capacity and improved their light energy utilization compared to Comparative Example 1, thus promoting the enhancement of photocatalytic activity.

[0049] Combination Figure 6 The figures show the temperature changes of the samples prepared in Examples 1-3 under 808 nm infrared light irradiation. Figure 6 This indicates that the dry film after PMS activation exhibits a strong photothermal effect, which is beneficial to improving antifouling performance. Example 2, which did not undergo PMS activation, did not show a significant photothermal effect. This suggests that under light conditions, PMS is activated by the catalytic membrane to degrade humic acid, and the degradation products adhere to the membrane surface, inducing the generation of a photothermal effect, thereby enhancing the membrane's antifouling performance.

[0050] Combination Figure 7 The images shown are infrared thermal images and temperature changes of Examples 1-3 and Comparative Example 1, respectively. In Examples 1-3, the membrane surface temperature rose rapidly under illumination, while the dry membrane surface temperature of Comparative Example 1 remained unchanged. This demonstrates that persulfate promotes the self-transformation of pollutants, induces the generation of photothermal effects on the membrane surface, and improves the antifouling performance of the ultrafiltration membrane.

[0051] Figure 8 shows the humic acid retention performance of the samples prepared in Examples 1-3 and Comparative Example 1, respectively. It indicates that after loading CeO2, the original PVDF membrane has a more uniform pore size due to the uniform dispersion of nanoparticles, which enriches the pore size distribution of the membrane. Therefore, the retention rate of humic acid is further improved.

[0052] Figures 9-11 show the antifouling performance of samples prepared in Examples 1-3 and Comparative Example 1, respectively. The results indicate that under simulated sunlight irradiation, the addition of PMS facilitates the degradation and transformation of pollutants, promotes the adhesion of pollutant intermediates to the membrane surface, induces photothermal effects on the membrane surface under light conditions, increases the water flux of the ultrafiltration membrane, and improves the membrane's antifouling performance, enabling more effective pollutant degradation while maintaining a stable water flux.

[0053] Combination Figure 12 The figures show the self-cleaning performance of samples prepared in Examples 1-3 and Comparative Example 1, respectively. Comparing the self-cleaning performance of Example 2 and Comparative Example 1, under light irradiation, the synergistic effect of photocatalysis and PMS effectively degrades the organic pollutants enriched in the pores, greatly improving the antifouling performance of the catalytic membrane. However, the self-cleaning performance of the pure PVDF membrane is not significantly improved, because it cannot activate peroxymonosulfate. Comparing the self-cleaning ability of Examples 1-3, Example 2 exhibits the best self-cleaning performance, because Example 2 has a suitable catalyst content, which can maximize the activation of peroxymonosulfate.

[0054] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An integrated catalytic separation membrane, characterized in that, include: A porous membrane matrix with polyvinylidene fluoride as the continuous phase, and cerium dioxide particles embedded and uniformly dispersed within the membrane. The catalytic separation membrane is suitable for use in water treatment under light conditions and in the presence of persulfate, so that the persulfate is activated to degrade organic pollutants in the water while completing membrane separation.

2. The catalytic separation membrane according to claim 1, characterized in that, The cerium dioxide is in the form of nanoparticles, and its addition amount in the casting solution is 1.0 to 3.0 wt%.

3. The catalytic separation membrane according to claim 1 or 2, characterized in that, The catalytic separation membrane has one or more of the following characteristics: The cross-sectional structure is an asymmetrical porous structure; The water contact angle is minimized when the catalyst content is 2 wt%.

4. The catalytic separation membrane according to claim 1, characterized in that, The cerium dioxide is a non-precious metal oxide catalyst, and the catalytic separation membrane does not contain a surface catalytic coating or metal foil layer. The cerium dioxide is fixed in the membrane in an embedded form.

5. A method for preparing the catalytic separation membrane according to any one of claims 1 to 4, characterized in that, Includes the following steps: Cerium dioxide particles are dispersed in a polar solvent, and polyvinylidene fluoride membrane material is added, with optional pore-forming agents added to obtain a uniform casting solution; After the casting solution is formed into a film, it is solidified by non-solvent-induced phase separation, so that the cerium dioxide particles are embedded and fixed in the polyvinylidene fluoride membrane during the phase separation process. The catalytic separation membrane was obtained by solvent replacement and drying.

6. The preparation method according to claim 5, characterized in that, At least one of the following process conditions must be met: The polar solvent is N,N-dimethylformamide; The pore-forming agent is polyvinylpyrrolidone, and its average molecular weight is 5000-13800. The casting solution includes Composition: Polyvinylidene fluoride 12 wt%, Cerium dioxide 1.0–3.0 wt%, Polyvinylpyrrolidone 3.0 wt%; The cerium dioxide particles were prepared by a hydrothermal method.

7. A water treatment method, characterized in that, Includes the following steps: Persulfate is added to the water to be treated, and the water is filtered under light through the catalytic separation membrane described in any one of claims 1 to 4 or the catalytic separation membrane prepared by any one of claims 5 to 6. The persulfate is activated at the inner and outer interfaces of the membrane to generate active species that degrade organic pollutants in the water. During operation, the degradation intermediates of organic pollutants generate a photothermal effect on the membrane surface under light to inhibit membrane fouling and increase or maintain flux.

8. The water treatment method according to claim 7, characterized in that, Includes one or more of the following process implementation conditions: The persulfate is persulfate monosulfate or persulfate disulfate; The concentration of the persulfate added is 0.01–0.05 mM; The wavelength range of the illumination is 200–900 nm, and the irradiation power is 500 W / cm². 2 The irradiation time is 5 hours; The filtration method is cross-flow filtration, and the transmembrane pressure difference is 0.5 bar.

9. The water treatment method according to claim 7, characterized in that, The water to be treated contains natural organic matter and / or humic acid, and under continuous operating conditions, the water flux of the catalytic separation membrane remains or increases.

10. A water treatment system, characterized in that, For implementing the water treatment method according to any one of claims 7 to 9, comprising: A membrane module equipped with a catalytic separation membrane according to any one of claims 1 to 4 or a catalytic separation membrane prepared by any one of claims 5 to 6, a dosing unit for adding persulfate to feed water, and a light source unit for providing light to the membrane module; The outlet of the membrane module is connected to a reflux unit or a discharge unit to achieve continuous or intermittent operation of separation and catalysis in synergy.

Images