Preparation of composite ultrafiltration membrane loaded with fe3c and application thereof

Abstract

The application provides a preparation method and application of a composite ultrafiltration membrane loaded with Fe3C and relates to the technical field of ultrafiltration membrane preparation and application. The preparation method is as follows: Fe3C is ultrasonically dissolved in a DMF solution, appropriate amounts of PES and PEG are weighed and placed in the DMF, the mixed solution is placed in an 80 DEG C oil bath, and PES and PEG are uniformly dissolved by stirring to obtain a casting solution; the casting solution is left to stand and deaerated overnight to obtain a blended casting solution; the casting solution is poured on a glass plate at room temperature, spread, left to stand, and then placed in deionized water at room temperature, the casting solution is phase-separated and solidified, the membrane is separated from the glass plate, and a composite ultrafiltration membrane is obtained; the composite ultrafiltration membrane is taken out and soaked in deionized water to obtain the composite ultrafiltration membrane loaded with Fe3C. In the application, the casting solution is prepared by dissolving PES, PEG and Fe3C in an organic solvent DMF, and the composite ultrafiltration membrane loaded with Fe3C is prepared by a one-step non-solvent induced phase separation method. The preparation process is simple, the obtained composite membrane is environmentally friendly, and the composite membrane has the potential for large-scale manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultrafiltration membrane preparation and application, and particularly relates to a preparation method of a composite ultrafiltration membrane loaded with Fe3C and application of the composite ultrafiltration membrane. BACKGROUND

[0002] A membrane bioreactor (MBR) is a new type of sewage treatment system formed by coupling a microfiltration or ultrafiltration membrane assembly in a membrane separation process with a biological reactor in sewage biological treatment. The MBR can effectively retain activated sludge and macromolecular organic matter in the biological reactor by using a membrane separation device, and can significantly improve the treatment efficiency of the MBR. Anaerobic digestion (AD) refers to degradation of biodegradable organic matter by facultative anaerobic bacteria under anaerobic conditions, and conversion of the organic matter into biogas. An MBR is a new technology combining AD with membrane separation, and has advantages of high biomass, complete solid-liquid separation, high water quality, and high resource recovery efficiency. In addition, the AnMBR can efficiently treat sewage in a short hydraulic retention time, and improve the stability of a microbial community in the system, and thus has great potential in anaerobic wastewater treatment. At present, in the field of MBR sewage treatment, organic high-molecular membranes are mainly used. The organic high-molecular membranes have characteristics of simple preparation process, various raw materials, easy modification, low price, and high plasticity, and are widely applied and researched. In the early stage of water treatment, PS, CA, and PP membranes were generally used as membrane materials, and currently, PES and PVDF membranes are mainly used. An ideal membrane material should have high strength and flexibility, and good chemical stability and resistance to acid, alkali, and chlorine. It has been found that the PS membrane has the highest mechanical strength, the PVDF membrane has high strength and flexibility, and the PS / PES membrane can withstand a pH range of 1.5 to 13, has good chemical stability, and has a certain resistance to chlorine.

[0003] It is known that nanoparticles have unique characteristics of stability in electricity, magnetism, light, and heat. Due to some small size effects, a large surface area, and strong activity of the nanoparticles, the nanoparticles can improve the performance of the membrane to some extent. Since a large number of hydroxyl groups exist on the surface of the nanoparticles, the hydrophilicity of the casting solution can be improved, which is beneficial to exchange of the solvent and the non-solvent in the phase inversion process, and thus is beneficial to formation of large pores and improvement of the permeation properties of the membrane. However, the nanoparticles have a large specific surface area, and are prone to agglomeration. In addition, inorganic nanoparticles are not stable in the membrane. SUMMARY

[0004] The present application aims to solve the problem of slow microbial growth in the MBR system, and proposes a preparation method of a composite ultrafiltration membrane loaded with Fe3C, and the treatment efficiency of wastewater in actual use is improved by using the composite ultrafiltration membrane.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] A preparation method of a composite ultrafiltration membrane loaded with Fe3C, comprising the following steps:

[0007] S1: configuring a casting solution: dissolving Fe3C in a DMF solution, then weighing appropriate amounts of PES and PEG in DMF, placing the mixed solution in an 80℃ oil bath, stirring to uniformly dissolve PES and PEG, and obtaining the casting solution; standing and degassing overnight to obtain the blended casting solution;

[0008] S2: preparing a blank ultrafiltration membrane: weighing appropriate amounts of PES and PEG in DMF, placing the mixed solution in an 80℃ oil bath, stirring to uniformly dissolve PES and PEG, and obtaining the casting solution; standing and degassing overnight. At room temperature, pouring the obtained casting solution on a glass plate, spreading it, and then placing it in deionized water at room temperature for phase separation and solidification of the casting solution, after which the membrane is separated from the glass plate to obtain the blank ultrafiltration membrane; taking out the blank ultrafiltration membrane and soaking it in deionized water to remove residual solvents and additives, thereby obtaining the blank ultrafiltration membrane;

[0009] S3: preparing a composite ultrafiltration membrane loaded with Fe3C: at room temperature, pouring the casting solution obtained in step 1 on a glass plate, spreading it, and then placing it in deionized water at room temperature for phase separation and solidification of the casting solution, after which the membrane is separated from the glass plate to obtain the composite ultrafiltration membrane; taking out the composite ultrafiltration membrane and soaking it in deionized water to remove residual solvents and additives, thereby obtaining the composite ultrafiltration membrane loaded with Fe3C.

[0010] Preferably, the addition amount of Fe3C in S1 is 0.3g or 0.5g.

[0011] Preferably, the mass fractions of PES and PEG are 16% and 4%, respectively.

[0012] Preferably, the molecular weight of PEG in S1 is 20000.

[0013] The application also provides a composite ultrafiltration membrane loaded with Fe3C, which is prepared by the above-mentioned preparation method.

[0014] The application also provides an application of the composite ultrafiltration membrane loaded with Fe3C, which is used for efficiently removing nitro pollutants in an MBR system.

[0015] The application also provides a use method of the composite ultrafiltration membrane loaded with Fe3C, which is characterized by comprising the following steps:

[0016] A1: The prepared composite ultrafiltration membrane is put into a MBR reactor to run, and an ultrafiltration membrane coupled anaerobic biological system is constructed;

[0017] A2: The DNCB wastewater is put into the ultrafiltration membrane coupled anaerobic biological system to mix fully;

[0018] A3: In the ultrafiltration membrane coupled anaerobic biological system, sampling is carried out at a specific time, and the sample is analyzed and determined by using high performance liquid chromatography technology, and the running effect of the system is evaluated.

[0019] Preferably, the volume ratio of the DNCB wastewater to the acclimated sludge in A2 is 7:3, and the addition amount of the carbon source is 2 times of the amount required for reducing the corresponding concentration of the DNCB wastewater.

[0020] Preferably, the working conditions of the high performance liquid chromatography in A3 are that the mobile phase is composed of methanol and water (55:45, v / v), the flow rate is 1.0 mL / min, the column temperature is 35℃, and the detection wavelength of DNCB is set to 254 nm.

[0021] Compared with the prior art, in the application, PES, PEG and Fe3C are dissolved in an organic solvent DMF to prepare a casting solution, and a composite ultrafiltration membrane loaded with Fe3C is prepared by a one-step non-solvent induced phase separation method. By changing the addition amount of Fe3C in the casting solution, the separation performance of the composite membrane is realized. The preparation process is simple, the process flow is simple and efficient, the obtained composite membrane is environmentally friendly, and has the potential for large-scale manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a scanning electron microscope image of the blank membrane and the composite ultrafiltration membrane in an embodiment of the application;

[0023] Figure 2 It is a pure water flux graph and a BSA rejection graph of the blank membrane and the composite ultrafiltration membrane in an embodiment of the application;

[0024] Figure 3 It is a DNCB degradation efficiency comparison graph of the blank membrane and the composite ultrafiltration membrane in an embodiment of the application;

[0025] Figure 4 It is a DACB generation rate comparison graph of the blank membrane and the composite ultrafiltration membrane in an embodiment of the application;

[0026] Figure 5 It is a MPD generation rate comparison graph of the blank membrane and the composite ultrafiltration membrane in an embodiment of the application. DETAILED DESCRIPTION

[0027] The application will be further described in detail below in combination with specific embodiments.

[0028] A preparation method of a composite ultrafiltration membrane loaded with Fe3C, comprising the following steps:

[0029] S1: preparing a casting solution.

[0030] In an embodiment, the following steps are included:

[0031] A certain amount of Fe3C is weighed and dissolved in a DMF solution. In an embodiment, the addition amount of Fe3C is 0.3 g and 0.5 g, and preferably, the addition amount of Fe3C is 0.3 g.

[0032] A certain amount of PES and PEG are weighed and placed in DMF, the mass fraction of PES is 16%, and the molecular weight of PEG is 20000, and the mass fraction is 4%.

[0033] The mixed solution is placed in an 80°C oil bath, and stirring is performed to uniformly dissolve the PES and PEG, thereby obtaining a casting solution; and the casting solution is left to stand and degas overnight, thereby obtaining a blended ultrafiltration composite membrane casting solution.

[0034] S2: preparing a blank ultrafiltration membrane:

[0035] In an embodiment, the specific steps are as follows:

[0036] A certain amount of PES and PEG are weighed and placed in DMF, the mass fraction of PES is 16%, and the molecular weight of PEG is 20000, and the mass fraction is 4%.

[0037] The mixed solution is placed in an 80°C oil bath, and stirring is performed to uniformly dissolve the PES and PEG, thereby obtaining a casting solution; and the casting solution is left to stand and degas overnight, thereby obtaining a blended blank casting solution.

[0038] At room temperature, the blended casting solution obtained in S2 is poured onto a glass plate, spread, and then placed in deionized water at room temperature to allow the casting solution to phase separate and solidify.

[0039] The solidified casting solution is separated from the glass plate, thereby obtaining a blank ultrafiltration membrane.

[0040] After the blank ultrafiltration membrane is taken out, it is soaked in deionized water to remove residual solvents and additives, thereby obtaining a blank ultrafiltration membrane.

[0041] S3: preparing a composite ultrafiltration membrane loaded with Fe3C:

[0042] In an embodiment, the specific steps are as follows:

[0043] At room temperature, the blended casting solution obtained in S1 is poured onto a glass plate, spread, and then placed in deionized water at room temperature to allow the casting solution to phase separate and solidify.

[0044] Separating the solidified casting solution from the glass plate to obtain a composite ultrafiltration membrane;

[0045] After taking out the composite ultrafiltration membrane, soaking it in deionized water to remove residual solvents and additives, thereby obtaining a composite ultrafiltration membrane loaded with Fe3C.

[0046] The application also provides a new application of the composite ultrafiltration membrane loaded with Fe3C, which is used for efficient removal of nitro pollutants in an MBR system.

[0047] The application also provides a method for using the composite ultrafiltration membrane loaded with Fe3C, which comprises the following steps:

[0048] A1: Putting the prepared composite ultrafiltration membrane into an MBR reactor for operation, constructing an ultrafiltration membrane coupled anaerobic biological system,

[0049] A2: Putting DNCB wastewater into the ultrafiltration membrane coupled anaerobic biological system for sufficient mixing and reaction;

[0050] In an embodiment, the volume ratio of DNCB wastewater to acclimated sludge is 7:3, and the amount of carbon source added is twice the amount required to reduce the corresponding concentration of DNCB wastewater;

[0051] A3: In the ultrafiltration membrane coupled anaerobic biological system, sampling at a specific time, using high performance liquid chromatography to analyze and determine the sample, and evaluating the operation effect of the system.

[0052] In an embodiment, the working conditions of the high performance liquid chromatography are as follows: the mobile phase is composed of methanol and water (55:45, v / v), the flow rate is 1.0 mL / min, the column temperature is 35℃, and the detection wavelength of DNCB is set to 254 nm.

[0053] The composite ultrafiltration membrane loaded with Fe3C prepared by the application is verified by the following specific examples:

[0054] Example 1: Preparation of the composite ultrafiltration membrane loaded with Fe3C:

[0055] S1: Preparation of casting solution

[0056] In an embodiment, the following steps are included

[0057] Weigh 0.3g of Fe3C and ultrasonically dissolve it in a DMF solution, the mass fraction of Fe3C being 0.3%. Weigh an appropriate amount of PES and PEG and place them in DMF, wherein the mass fraction of PES is 16% and the molecular weight of PEG is 20000, the mass fraction being 4%.

[0058] The mixed solution is placed in an 80℃ oil bath, and the PES and PEG are stirred to dissolve uniformly to obtain a casting solution; the casting solution is left to stand and deaerated overnight to obtain a blended casting solution;

[0059] S2: Preparation of a blank ultrafiltration membrane

[0060] In an embodiment, the specific steps are as follows:

[0061] An appropriate amount of PES and PEG are weighed and dissolved in DMF, the mass fraction of the PES being 16%, and the mass fraction of the PEG being 4% and the molecular weight of the PEG being 20000.

[0062] The mixed solution is placed in an 80℃ oil bath, and the PES and PEG are stirred to dissolve uniformly to obtain a casting solution; the casting solution is left to stand and deaerated overnight to obtain a blended blank casting solution;

[0063] The blended casting solution obtained above is poured onto a glass plate at room temperature, spread, left to stand, and then placed in deionized water at room temperature to allow the casting solution to phase separate and solidify;

[0064] The solidified casting solution is separated from the glass plate to obtain a blank ultrafiltration membrane;

[0065] After the blank ultrafiltration membrane is taken out, it is soaked in deionized water to remove residual solvents and additives, thereby obtaining a blank ultrafiltration membrane.

[0066] S3: Preparation of a composite ultrafiltration membrane loaded with Fe3C

[0067] In an embodiment, the specific steps are as follows: the blended casting solution obtained in S1 is poured onto a glass plate at room temperature, spread, left to stand, and then placed in deionized water at room temperature to allow the casting solution to phase separate and solidify; the solidified casting solution is separated from the glass plate to obtain a composite ultrafiltration membrane; after the composite ultrafiltration membrane is taken out, it is soaked in deionized water to remove residual solvents and additives, thereby obtaining a composite ultrafiltration membrane loaded with Fe3C.

[0068] Example 2: Preparation of a composite ultrafiltration membrane loaded with Fe3C: This example is basically the same as Example 1, except that in this example, 0.5g of Fe3C is added, and a composite ultrafiltration membrane loaded with Fe3C is prepared.

[0069] Verification Experiment 1: Comparison of surface morphology of blank membrane and composite ultrafiltration membrane

[0070] Please refer to Figure 1 , Figure 1 for the membrane surface morphology of the blank membrane and the composite ultrafiltration membrane respectively magnified by 50000 times and 100000 times. From Figure 1It can be seen that, compared with the blank membrane, the surface morphology of the membrane remains unchanged and the structure is uniform with the addition of Fe3C material. The composite membrane has more pores on its surface, which will help improve the membrane flux.

[0071] In general, inorganic nanomaterials and polymers in organic-inorganic blend membranes tend to aggregate due to their poor affinity, often leading to defects or voids in the mixed matrix membrane and reduced membrane retention performance. However, the interaction between the hydrophilic additive and the polymer matrix ensures that Fe3C is uniformly dispersed in the membrane, resulting in a membrane surface free of macroporous defects.

[0072] Verification Experiment 2: Comparison of Permeability and Retention Rate

[0073] The blank membrane, Fe3C-loaded composite ultrafiltration membrane A, and Fe3C-loaded composite ultrafiltration membrane B were subjected to pure water flux testing and protein retention testing (the above experiments have been disclosed in the prior art, so they will not be elaborated on here).

[0074] The results are as follows Figure 2 As shown, Figure 2 This diagram shows the pure water flux and bovine serum albumin (BSA) retention rates of different composite ultrafiltration membranes. The permeation performance of the membrane is influenced by various factors, including its hydrophilicity, average pore size, volumetric porosity, and morphological structure. Figure 2 It is evident that the pure water flux of the composite membrane is higher than that of the blank membrane, and the addition of Fe3C can increase the pure water flux of the membrane. During membrane separation, the highly hydrophilic membrane surface readily adsorbs water molecules, forming a hydration layer on the membrane surface. This facilitates the preferential entry and permeation of water molecules into the membrane matrix, thus increasing the membrane's water flux. Simultaneously, the low-resistance membrane pore structure formed by the addition of Fe3C, as well as the increased number and size of surface pores, are another reason for the increased membrane flux. Generally, increased pore size increases membrane flux while decreasing the membrane rejection rate. When the Fe3C dosage is 0.3g, the pure water flux reaches its maximum value, increasing from 337.47 L / m³ to 1421.98 L / m³. 2 The per-h-bar ratio is 1.89 times that of the blank membrane. It is noteworthy that when the Fe3C dosage is increased to 0.5 g, the pure water flux of the composite ultrafiltration membrane decreases, but this flux is still higher than that of the blank membrane. This may be due to excessive Fe3C causing membrane pore blockage and reducing water flux.

[0075] Based on the preceding analysis, compared to the blank ultrafiltration membrane, the composite ultrafiltration membrane has a larger surface pore structure. Figure 2It can be seen that the retention rate of bovine serum albumin (BSA) gradually increases with the addition of Fe3C. When the Fe3C dosage is 0.3g, the BSA retention rate reaches 96.56%, indicating that the composite ultrafiltration membrane can effectively retain BSA macromolecules. When the Fe3C dosage is 0.5g, the BSA retention rate decreases to 93.33%. In summary, the membrane exhibits optimal flux and retention performance when the Fe3C dosage is 0.3g.

[0076] Validation Experiment 3: Validating the application of ultrafiltration membranes in the efficient removal of nitro pollutants in MBR systems.

[0077] In this application, the degradation analysis of 2,4-dinitrochlorobenzene (DNCB) with an initial concentration of 100 mg / L was performed using a blank ultrafiltration membrane group (Blank), a composite ultrafiltration membrane group (0.3), and an anaerobic control system. Samples were taken and analyzed at specific time points, and the test results are as follows: Figure 3 , 4 As shown in Figure 5. From Figure 3 It can be seen that the removal rate of DNCB was 100% after 9 hours. The degradation effect of Blank and 0.3 groups on DNCB was much better than that of the Control system group, indicating that the added membrane material can effectively promote the degradation rate of DNCB in the MBR system. Figure 4 and Figure 5 The results showed that 4-chloro-1,3-phenylenediamine (DACB) and m-phenylenediamine (MPD) were generated in the product. During the DNCB reduction process, the maximum formation rates of DAB and MPD were 19.33% and 0.224%, respectively, indicating that DAB was the main intermediate. The detection of MPD in the effluent of the DNCB reduction system demonstrated that dechlorination could be achieved under the action of this membrane.

[0078] This invention employs a one-step solvent-inducible phase separation method, blending Fe3C and PEG as additives in a PES casting solution. This not only optimizes the membrane surface properties by modifying the membrane matrix through coordination interactions, but also promotes the transfer of PEG from the casting solution to the phase separation solution during the phase separation process. This allows for the control of the membrane phase separation process and ultimately optimizes key membrane performance parameters such as pore size, pore density, and selective layer thickness. The resulting Fe3C-loaded composite ultrafiltration membrane significantly improves water flux and retention rate, thereby enhancing wastewater treatment efficiency.

[0079] In summary: the application is prepared by dissolving PES, PEG and Fe3C in organic solvent DMF to prepare casting solution, and through one-step non-solvent induced phase separation method, a composite ultrafiltration membrane loaded with Fe3C is prepared, by changing the addition amount of Fe3C in the casting solution, the separation performance of the composite membrane is realized, the preparation process is simple, the process flow is simple and efficient, the obtained composite membrane is environment-friendly, and has the potential for large-scale manufacturing.

Claims

1. A method of using a composite ultrafiltration membrane loaded with Fe3C, characterized in that: The Fe3C-loaded composite ultrafiltration membrane was prepared by the following steps: S1: Preparation of casting solution: Dissolve Fe3C in DMF solution by ultrasonication, then weigh appropriate amounts of PES and PEG and place them in DMF. Place the mixed solution in an 80℃ oil bath and stir to dissolve PES and PEG evenly to obtain the casting solution; let it stand overnight to remove bubbles to obtain the blended casting solution. S2: Preparation of Fe3C-loaded composite ultrafiltration membrane: Under room temperature conditions, the casting solution obtained in step 1 is poured onto a glass plate, spread out, and placed in deionized water at room temperature. The casting solution is phase-separated and solidified, and then the membrane is separated from the glass plate to obtain a composite ultrafiltration membrane. After the composite ultrafiltration membrane is taken out, it is soaked in deionized water to remove residual solvents and additives, thus obtaining a composite ultrafiltration membrane loaded with Fe3C. The method of using the Fe3C-loaded composite ultrafiltration membrane includes the following steps: A1: The prepared composite ultrafiltration membrane was put into operation in an MBR reactor to construct an ultrafiltration membrane coupled with an anaerobic biological system. A2: The DNCB wastewater is fed into an ultrafiltration membrane coupled with an anaerobic biological system for thorough mixing and reaction; A3: In an ultrafiltration membrane coupled anaerobic biological system, samples are taken at specific times, and high-performance liquid chromatography is used to analyze and determine the samples to evaluate the system's operational effectiveness.

2. The method of using the Fe3C-loaded composite ultrafiltration membrane according to claim 1, characterized in that: The amount of Fe3C added in S1 is 0.3g or 0.5g.

3. The method of using the composite ultrafiltration membrane loaded with Fe3C according to claim 1, characterized in that: The mass fractions of PES and PEG were 16% and 4%, respectively.

4. The method of using a composite ultrafiltration membrane loaded with Fe3C according to claim 1, characterized in that: The molecular weight of PEG in S1 is 20000.

5. The method of using a composite ultrafiltration membrane loaded with Fe3C according to claim 1, characterized in that: In A2, the volume ratio of DNCB wastewater to acclimatized sludge is 7:3, and the amount of carbon source added is twice the amount required to reduce the corresponding concentration of DNCB wastewater.

6. The method of using a composite ultrafiltration membrane loaded with Fe3C according to claim 1, characterized in that: The high-performance liquid chromatography (HPLC) operating conditions described in A3 are as follows: the mobile phase consists of methanol and water in a volume ratio of 55:45, the flow rate is 1.0 mL / min, the column temperature is 35 °C, and the detection wavelength of DNCB is set to 254 nm.

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