Amorphous TiO2 modified nanofiber membrane as well as preparation method and application thereof
By modifying amorphous TiO2 on the nanofiber membrane, the problems of poor separation performance and low flux of the nanofiber membrane are solved, and an efficient and self-cleaning oil-water separation effect is achieved, which is adaptable to complex water quality conditions.
Patent Information
- Application Number
- CN202510650601.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-20
- Publication Date
- 2025-09-23
AI Technical Summary
Existing nanofiber membranes used for oil-water separation have technical problems such as poor separation performance, low flux, and membrane fouling. Existing nanofiber membranes used for oil-water separation have technical problems such as poor separation performance, low flux, and membrane fouling in actual applications. Existing nanofiber membranes used for oil-water separation have technical problems such as poor separation performance, low flux, and membrane fouling in actual applications.
Polyacrylonitrile chitosan fiber membranes of uniform size were prepared by electrospinning, and then impregnated with amorphous titanium dioxide coating to form an amorphous TiO2-modified nanofiber membrane. The interaction between chitosan and amorphous TiO2 was utilized to improve the hydrophilicity and self-cleaning ability of the membrane.
It achieves high-throughput and high-efficiency oil-water separation, has super-hydrophilic and self-cleaning effects, can effectively prevent oil and dirt from adhering, adapts to various complex water conditions, and improves separation efficiency.
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Figure CN120679355A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of oil-water separation materials, and in particular to an amorphous TiO2-modified nanofiber membrane and a preparation method and application thereof. Background Art
[0002] Oil-water separation technology plays a crucial role in environmental protection and industrial applications. Efficient oil-water separation technology is particularly crucial when treating oily wastewater. Oily wastewater primarily originates from industries such as petroleum extraction, refining, chemicals, textiles, printing and dyeing, and food processing. It contains large amounts of pollutants such as grease, suspended solids, dissolved organic matter, and inorganic salts. If these pollutants are discharged directly into the environment without treatment, they can cause serious water pollution, impacting ecological balance and human health.
[0003] Traditional oil-water separation methods, such as gravity separation, centrifugal separation, and coalescence separation, have numerous limitations when treating oily wastewater. For example, while gravity separation is simple to operate, it suffers from low separation efficiency, particularly for dispersed oil droplets and emulsified oils. Centrifugal separation consumes significant energy and has high equipment maintenance costs. Coalescing separation is susceptible to water and oil properties and suffers from poor stability. Therefore, developing an efficient, environmentally friendly, and adaptable oil-water separation material is crucial to addressing the challenges of oily wastewater treatment.
[0004] As a new type of material, electrospun nanofiber membranes have shown great potential in the field of oil-water separation. Prepared using electrospinning technology, they possess polymer filaments with nanometer-scale diameters and a microporous structure, resulting in high specific surface area and porosity. This unique structure enables electrospun nanofiber membranes to effectively adsorb and filter oil from oily wastewater, achieving efficient oil-water separation. Furthermore, electrospun nanofiber membranes exhibit excellent mechanical properties and chemical stability, making them adaptable to a variety of complex water quality conditions and treatment environments. Polyacrylonitrile (PAN), as an electrospinning material, possesses hydrophilicity, thermal stability, chemical stability, and a certain degree of mechanical strength. In recent years, PAN membrane materials have been widely used in oil-water separation membranes due to their excellent physicochemical properties. However, in practical applications, they suffer from poor separation performance, low flux, and membrane fouling. Summary of the Invention
[0005] The present invention provides an amorphous TiO2-modified nanofiber membrane, a preparation method and application thereof, which effectively solves the technical problems of poor oil-water separation effect, low flux and easy contamination of existing nanofiber membranes used for oil-water separation. The present invention adopts electrospinning to prepare polyacrylonitrile chitosan fiber membranes with uniform size, and loads an amorphous titanium dioxide coating by impregnating the polyacrylonitrile chitosan fiber membrane to obtain an amorphous TiO2-modified nanofiber membrane with large flux, high separation efficiency, super hydrophilicity and self-cleaning effects.
[0006] The first object of the present invention is to provide a method for preparing an amorphous TiO2-modified nanofiber membrane, comprising the following steps: Chitosan and polyacrylonitrile are used as raw materials to obtain a spinning solution, and polyacrylonitrile / chitosan nanofiber membrane is obtained by electrospinning. Preparation of amorphous TiO2 solution; The polyacrylonitrile / chitosan nanofiber membrane is impregnated with an amorphous TiO2 solution to obtain an amorphous TiO2-modified nanofiber membrane.
[0007] As a preferred embodiment, the mass ratio of polyacrylonitrile to chitosan is 1.373:1-2.
[0008] As a preferred embodiment, the preparation method of the amorphous TiO2 solution is: mixing 15 to 20 parts by volume of a titanium source, 4 to 6 parts of hydrochloric acid, 24 to 30 parts of ethanol and 1.6 to 3.2 parts of deionized water, wherein the mass concentration of the above-mentioned titanium source is ≥99%, the mass concentration of hydrochloric acid is 36% to 38%, and the mass concentration of ethanol is ≥99.7%.
[0009] As a preferred embodiment, the titanium source is tetrabutyl titanate, isopropyl titanate, titanyl sulfate, titanium tetrachloride or ethyl titanate; more preferably, the titanium source is tetrabutyl titanate, isopropyl titanate, titanium tetrachloride or ethyl titanate. As a preferred embodiment, the immersion time is 5 min to 20 min.
[0010] As a preferred embodiment, the electrospinning parameters are: 20-30 stainless steel needle; voltage of 10KV~15KV; feed rate of 0.6mL / h~1.0mL / h; electrode distance of 10cm~30cm; ambient temperature of 5℃~40℃; ambient humidity of 30%~50%; receiver speed of 120r / min~200r / min.
[0011] As a preferred embodiment, the solvent of the spinning solution is any one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran and a mixed solvent of dimethylformamide. Before electrospinning, the spinning solution is degassed for 0.5 to 2 hours.
[0012] The second object of the present invention is to provide an amorphous TiO2-modified nanofiber membrane prepared by any of the above-mentioned preparation methods.
[0013] The third object of the present invention is to provide an application of the above-mentioned amorphous TiO2 modified nanofiber membrane in oil-water separation.
[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing an amorphous TiO2-modified nanofiber membrane. The method comprises using chitosan and polyacrylonitrile as raw materials to prepare a spinning solution, and electrospinning to obtain a polyacrylonitrile / chitosan nanofiber membrane. The polyacrylonitrile / chitosan nanofiber membrane is then impregnated with an amorphous TiO2 solution to obtain an amorphous TiO2-modified nanofiber membrane. During the impregnation process, the amorphous TiO2 partially adheres to the surface of the polyacrylonitrile / chitosan nanofiber membrane through physical adsorption. The active hydroxyl and amino groups of chitosan condense with the titanium hydroxyl groups in the amorphous TiO2 solution to form titanyl chitosan. The condensation of the titanyl-titanium network forms hydrated titanium dioxide, which then adheres to the polyacrylonitrile / chitosan nanofiber membrane. The amino groups (-NH2) and hydroxyl groups (-OH) of the chitosan form hydrogen bonds (N / OH···O-Ti) with the Ti-OH groups, and the hydrogen bonds are partially converted to covalent bonds (Ti-OC / N). The present invention adds chitosan to the polyacrylonitrile matrix. The addition of chitosan during electrospinning improves the mechanical properties and hydrophilicity of the polyacrylonitrile membrane. Amorphous titanium dioxide is coated on the polyacrylonitrile / chitosan nanofiber membrane, which produces strong oxidizing properties under ultraviolet light, decomposes oil and organic matter, improves the self-cleaning ability of the separation membrane, reduces pollution, and at the same time gives the membrane surface superhydrophilicity and exhibits superoleophobicity underwater, effectively preventing oil adhesion and improving separation efficiency.
[0015] Compared with other oil-water separation membranes, the amorphous TiO2-modified nanofiber membrane prepared by the present invention has a higher flux and a separation efficiency of more than 99% for kerosene oil-water emulsion, toluene oil-water emulsion, n-hexane oil-water emulsion, and n-dodecyl tributyl phosphate mixed oil nitric acid emulsion (the oil-water volume ratio is 1 / 99). For n-dodecyl tributyl phosphate mixed oil nitric acid emulsion, when the oil-water volume ratio reaches 20 / 80, 30 / 70, and 40 / 60, it also has a high flux and a separation efficiency of more than 96.7%.
[0016] The amorphous TiO2-modified nanofiber membrane prepared by the present invention has the effect of degrading oil-polluted materials under ultraviolet light irradiation and has excellent self-cleaning ability, which is in line with the current development prospects of oil-water separation membranes. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 Figures 1 and 2 are SEM images of the amorphous TiO2-modified nanofiber membrane of Example 1, the polyacrylonitrile fiber membrane of Comparative Example 1, and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2. Figures a1), b1), and c1) are SEM images of PAN, PAN / CS, and PAN / CS / TiO2, respectively. Figures a2), b2), and c2) correspond to their high-magnification SEM images, respectively. Figure d is an EDS scan of the C, O, and Ti elements of the PAN / CS / TiO2 membrane.
[0018] Figure 2 XRD patterns and FT-IR patterns of the amorphous TiO2-modified nanofiber membrane of Example 1 of the present invention, the polyacrylonitrile fiber membrane of Comparative Example 1, and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2, wherein (a) is the FT-IR pattern and (b) is the XRD pattern.
[0019] Figure 3 These are comparison graphs of emulsion flux and separation efficiency performance of the amorphous TiO2-modified nanofiber membrane of Example 1 of the present invention for four different oil-water emulsions in different concentration ranges, wherein (a) is kerosene oil-water emulsion, (b) is toluene oil-water emulsion, (c) is n-hexane oil-water emulsion, and (d) is n-dodecyl tributyl phosphate mixed oil nitric acid emulsion.
[0020] Figure 4 This is a performance diagram of the separation flux and separation efficiency of the amorphous TiO2 modified nanofiber membrane of Example 1 of the present invention and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2 for high-concentration oil-water emulsion.
[0021] Figure 5 These are UV degradation effect diagrams of the amorphous TiO2-modified nanofiber membrane of Example 1 of the present invention and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2, wherein (a) is Comparative Example 2 and (b) is Example 1. DETAILED DESCRIPTION
[0022] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.
[0023] Existing electrospun nanofiber membranes, polyacrylonitrile membranes, are widely used in oil-water separation membranes due to their excellent physical and chemical properties. However, in practice, they suffer from poor separation performance, low flux, and membrane fouling. To address these technical issues, the present invention provides an amorphous TiO2-modified nanofiber membrane, its preparation method, and its application.
[0024] The technical solution of the present invention is described in detail below.
[0025] The present invention first provides a method for preparing an amorphous TiO2-modified nanofiber membrane, comprising the following steps: Chitosan and polyacrylonitrile are used as raw materials to obtain a spinning solution, and polyacrylonitrile / chitosan nanofiber membrane is obtained by electrospinning.
[0026] Preparation of amorphous TiO2 solution.
[0027] The polyacrylonitrile / chitosan nanofiber membrane is impregnated with an amorphous TiO2 solution to obtain an amorphous TiO2-modified nanofiber membrane.
[0028] In the above technical solution, chitosan is added to the matrix of polyacrylonitrile. The addition of chitosan in electrospinning improves the mechanical properties and hydrophilicity of the polyacrylonitrile membrane. Amorphous titanium dioxide is coated on the polyacrylonitrile / chitosan nanofiber membrane, which produces strong oxidizing properties under ultraviolet light, decomposes oil and organic matter, enhances the self-cleaning ability of the separation membrane, reduces pollution, and simultaneously gives the membrane surface superhydrophilicity and exhibits superoleophobicity underwater, effectively preventing oil from adhering and improving separation efficiency. The amorphous TiO2-modified nanofiber membrane prepared by the present invention has a high flux and a separation efficiency of more than 99% for kerosene oil-water emulsion, toluene oil-water emulsion, n-hexane oil-water emulsion, and tributyl n-dodecyl phosphate mixed oil nitric acid emulsion (the oil-water volume ratio is 1 / 99). For tributyl n-dodecyl phosphate mixed oil nitric acid emulsion, when the oil-water volume ratio reaches 20 / 80, 30 / 70, and 40 / 60, it also has a high flux and a separation efficiency of more than 96.7%.
[0029] To further enhance the mechanical strength and hydrophilicity of the nanofiber membrane, the mass ratio of polyacrylonitrile to chitosan is 1.373:1-2. If the chitosan dosage is too low, the hydrophilicity of the nanofiber membrane is affected, and optimal oil-water separation cannot be achieved. If the chitosan dosage is too high, while the overall mechanical strength of the nanofiber membrane is improved, its oil-water separation performance is also affected.
[0030] The amorphous TiO2 solution used in the present invention is prepared by mixing 15 to 20 parts by volume of a titanium source, 4 to 6 parts of hydrochloric acid, 24 to 30 parts of ethanol, and 1.6 to 3.2 parts of deionized water, wherein the mass concentration of the titanium source is ≥99%, the mass concentration of the hydrochloric acid is 36% to 38%, and the mass concentration of the ethanol is ≥99.7%. The titanium source is tetrabutyl titanate, isopropyl titanate, titanyl sulfate, titanium tetrachloride, or ethyl titanate.
[0031] In order to further control the loading amount of amorphous TiO2 on the nanofiber membrane, thereby improving the super-hydrophilicity and self-cleaning properties of the nanofiber membrane, the immersion time is 5 min to 20 min.
[0032] It should be noted that the electrospinning parameters used in the present invention are: 20-30 stainless steel needle; voltage of 10KV~15KV; feed rate of 0.6mL / h~1.0mL / h; electrode distance of 10cm~30cm; ambient temperature of 5℃~40℃; ambient humidity of 30%~50%; receiver speed of 120r / min~200r / min.
[0033] It should be noted that the solvent used in the preparation of the spinning solution of the present invention is any one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran and a mixed solvent of dimethylformamide. Before electrospinning, the spinning solution is degassed for 0.5 to 2 hours to avoid the influence of bubbles in the spinning solution on the structure and properties of the polyacrylonitrile / chitosan nanofiber membrane.
[0034] The present invention will be described in detail below through the following examples and comparative examples.
[0035] Example 1 A method for preparing an amorphous TiO2-modified nanofiber membrane comprises the following steps: S1, 0.856 g of polyacrylonitrile powder (PAN) and 0.623 g of chitosan powder (CS) were dissolved in 10 mL of DMF solution, and then stirred at room temperature for 12 h to obtain a spinning solution after dissolution. Then, electrospinning was performed, and the spinning solution was placed in a plastic syringe, and the syringe was placed in a syringe pump. A 22-gauge metal needle was used during the spinning process, the speed was maintained at 0.6 mL / h, the voltage was set to 10 KV, and a metal drum collector wrapped with aluminum foil was used. The speed was set to 120 r / min. After spinning for 8 h, the aluminum foil loaded with the fiber film was removed and dried in an oven at 80°C for 12 h to obtain a polyacrylonitrile / chitosan nanofiber membrane, recorded as PAN / CS fiber membrane.
[0036] S2. Preparation of amorphous titanium dioxide solution: 24 mL of ethanol (mass concentration ≥ 99.7%), 1.6 mL of deionized water, 4 mL of hydrochloric acid (mass concentration 37%), and 15 mL of tetrabutyl titanate were mixed and ultrasonically stirred to obtain an amorphous titanium dioxide solution.
[0037] S3, preparation of composite membrane: immerse the polyacrylonitrile / chitosan nanofiber membrane in an amorphous titanium dioxide solution for 10 min, rinse with deionized water, and dry in an oven at 80° C. to obtain an amorphous TiO2-modified nanofiber membrane, which is designated as PAN / CS / TiO2 composite membrane.
[0038] Example 2 A method for preparing an amorphous TiO2-modified nanofiber membrane comprises the following steps: S1, 0.856 g of polyacrylonitrile powder (PAN) and 0.935 g of chitosan powder (CS) were dissolved in 10 mL of DMF solution, and then stirred at room temperature for 12 h to obtain a spinning solution after dissolution. Then, electrospinning was performed, and the spinning solution was placed in a plastic syringe, and the syringe was placed in a syringe pump. A 22-gauge metal needle was used during the spinning process, the speed was maintained at 1 mL / h, the voltage was set to 10 KV, and a metal drum collector wrapped with aluminum foil was used. The speed was set to 120 r / min. After spinning for 8 h, the aluminum foil loaded with the fiber film was removed and dried in an oven at 80°C for 12 h to obtain a polyacrylonitrile / chitosan nanofiber membrane, recorded as PAN / CS fiber membrane.
[0039] S2, preparation of an amorphous titanium dioxide solution: 24 mL of ethanol (mass concentration ≥ 99.7%), 1.6 mL of deionized water, 4 mL of hydrochloric acid (mass concentration 37%), and 15 mL of tetrabutyl titanate were mixed and ultrasonically stirred to obtain an amorphous titanium dioxide solution.
[0040] S3, preparation of composite membrane: immerse the polyacrylonitrile / chitosan nanofiber membrane in an amorphous titanium dioxide solution for 10 min, rinse with deionized water, and dry in an oven at 80° C. to obtain an amorphous TiO2-modified nanofiber membrane, which is designated as PAN / CS / TiO2 composite membrane.
[0041] Example 3 A method for preparing an amorphous TiO2-modified nanofiber membrane comprises the following steps: S1, 0.856 g of polyacrylonitrile powder (PAN) and 1.246 g of chitosan powder (CS) were dissolved in 10 mL of DMF solution, and then stirred at room temperature for 12 h to dissolve to obtain a spinning solution, which was then electrospun. The spinning solution was placed in a plastic syringe, and the syringe was placed in a syringe pump. A 22-gauge metal needle was used during the spinning process, the speed was maintained at 0.6 mL / h, the voltage was set to 15 KV, and a metal drum collector wrapped with aluminum foil was used. The speed was set to 120 r / min. After spinning for 8 h, the aluminum foil loaded with the fiber film was removed and dried in an oven at 80°C for 12 h to obtain a polyacrylonitrile / chitosan nanofiber membrane, recorded as PAN / CS fiber membrane.
[0042] S2, preparation of an amorphous titanium dioxide solution: 24 mL of ethanol (mass concentration ≥ 99.7%), 1.6 mL of deionized water, 4 mL of hydrochloric acid (mass concentration 37%), and 15 mL of tetrabutyl titanate were mixed and ultrasonically stirred to obtain an amorphous titanium dioxide solution.
[0043] S3, preparation of composite membrane: immerse the polyacrylonitrile / chitosan nanofiber membrane in an amorphous titanium dioxide solution for 10 min, rinse with deionized water, and dry in an oven at 80° C. to obtain an amorphous TiO2-modified nanofiber membrane, which is designated as PAN / CS / TiO2 composite membrane.
[0044] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, as follows: Comparative Example 1 Compared with Example 1, the difference is that only polyacrylonitrile fiber membrane is prepared.
[0045] A method for preparing a polyacrylonitrile fiber membrane comprises the following steps: 0.856 g of polyacrylonitrile powder (PAN) was dissolved in 10 mL of DMF solution, and then stirred at room temperature for 12 hours to obtain a spinning solution after dissolution. Electrospinning was then performed, and the spinning solution was placed in a plastic syringe, and the syringe was placed in a syringe pump. A 22-gauge metal needle was used during the spinning process, the speed was maintained at 0.6 mL / h, the voltage was set to 10KV, and a metal drum collector wrapped with aluminum foil was used. The speed was set to 120 r / min. After spinning for 8 hours, the aluminum foil loaded with the fiber film was removed and dried in an oven at 80°C for 12 hours to obtain a polyacrylonitrile fiber membrane, which was recorded as a PAN fiber membrane.
[0046] Comparative Example 2 Compared with Example 1, the difference is that only polyacrylonitrile / chitosan nanofiber membrane is prepared.
[0047] A method for preparing a polyacrylonitrile / chitosan nanofiber membrane comprises the following steps: 0.856 g of polyacrylonitrile powder (PAN) and 0.623 g of chitosan powder (CS) were dissolved in 10 mL of DMF solution and then stirred at room temperature for 12 h to obtain a spinning solution. Electrospinning was then performed, and the spinning solution was placed in a plastic syringe, and the syringe was placed in a syringe pump. A 22-gauge metal needle was used during the spinning process, the speed was maintained at 0.6 mL / h, the voltage was set to 10 KV, and a metal drum collector wrapped with aluminum foil was used. The speed was set to 120 r / min. After spinning for 8 h, the aluminum foil loaded with the fiber film was removed and dried in an oven at 80°C for 12 h to obtain a polyacrylonitrile / chitosan nanofiber membrane, recorded as PAN / CS fiber membrane.
[0048] The fiber membranes prepared in the above examples and comparative examples were characterized as follows.
[0049] Figure 1 The following are SEM images of the amorphous TiO2-modified nanofiber membrane of Example 1 of the present invention, the polyacrylonitrile fiber membrane of Comparative Example 1, and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2. Figures a1), b1), and c1 are SEM images of PAN, PAN / CS, and PAN / CS / TiO2, respectively. Figures a2), b2), and c2 correspond to their high-magnification SEM images, respectively. Figure d is an EDS scanning image of C, O, and Ti elements of the PAN / CS / TiO2 membrane. Figure 1 It can be seen that the morphological characteristics of PAN, PANCS and PANCSTiO2 electrospun membranes at different magnifications were observed using field emission scanning electron microscopy (FESEM). Figure 1 As shown, Figure 1 Figures a1) and a2) show that the original PAN nanofiber membrane has uniform fiber distribution and a smooth surface. The addition of chitosan did not significantly change the appearance or fiber diameter of the PANCS membrane. Figure 1 However, due to the fiber pairing adhesion, which may be caused by the mixing of heterogeneous polymer solutions, an increase in fiber density was observed. The PANCS fiber membrane was immersed in an amorphous TiO2 solution, as shown in Figure 1b1) and Figure 1b2). Figure 1 In Figures c1) and c2), the fibers are thicker and significantly larger than those of the PAN and PANCS membranes. TiO2 and its precursors are observed to coat the membrane surface and rough cracks, uniformly penetrating the entire width of the PANCS membrane nanofibers. This process enhances the distribution and permeability of the PANCS nanofibers. Figure 1 Figure d) also confirms the uniform distribution of C, O, and Ti elements on the film, indicating that the TiO2 coating was successfully applied.
[0050] Figure 2 The XRD and FT-IR patterns of the amorphous TiO2-modified nanofiber membrane of Example 1 of the present invention, the polyacrylonitrile fiber membrane of Comparative Example 1, and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2 are shown, wherein (a) is the FT-IR pattern and (b) is the XRD pattern. Figure 2 It can be seen that the functional groups of PAN, PAN / CS and PAN / CS / TiO2 nanofiber membranes were detected by FTIR analysis, e.g. Figure 2 As shown in Figure (a). The FTIR spectrum of pure PAN is at 2244 cm -1 The butyl group shows a unique absorption band at 1451 cm, which is attributed to the stretching vibration of the nitrile group (-CN). In PANCS, the butyl group intensity is reduced and the CH -1 and 815 cm -1 At 2936 cm -1 and 3643 cm -1 The characteristic peaks of NH, CN and OH vibrations are observed at 3000-3600 cm -1 There is a broad and strong absorption peak in the range of 480-750 cm-1, which corresponds to the abundant OH groups produced by hydrolysis of amorphous TiO2 suspension. -1 There are a lot of TiO2 vibration mode absorption peaks, among which 1632 cm -1 There is an obvious TiO2 absorption peak at , indicating that TiO2 is successfully coated on the PAN / CS nanofibers.
[0051] Figure 2 Figure (b) shows the XRD of PAN film and its composite film, in which PAN / CS / TiO2 has no fixed peak. Figure 2 SEM showed that the TiO2 coating on the surface of PAN / CS film existed on the surface of PAN / CS fiber in the form of amorphous TiO2.
[0052] In order to test the separation performance of the amorphous TiO2-modified nanofiber membrane of Example 1, the polyacrylonitrile fiber membrane of Comparative Example 1, and the polyacrylonitrile / chitosan nanofiber membrane of Comparative Example 2 for oil-water emulsions, 1 mL of oil components (kerosene, toluene, n-hexane) was mixed with 99 mL of deionized water to prepare an oil-water emulsion without surfactant. 1 mL of a mixed oil of n-dodecane tributyl phosphate (wherein the volume ratio of n-dodecane to tributyl phosphate oil was 7 / 3) was mixed with 2 mol of nitric acid emulsion (99 mL of nitric acid emulsion) to prepare an emulsion without surfactant to simulate nuclear industry oily wastewater. The mixture was stirred at 500 r / min for 5 h and ultrasonically treated to produce a stable oil-in-water emulsion. Using an effective filtration area of 12.56 cm 2 The filtration device separates all the oil-in-water emulsions. The separation flux and separation efficiency are calculated according to the following formula:
[0053] Separation flux = (emulsion volume) / time × filtration area Separation efficiency = (1 - (concentration before separation / concentration after separation)) × 100% When using membrane materials to separate oily wastewater, flux and separation efficiency tests can be performed on emulsions of varying concentrations to comprehensively evaluate membrane performance. First, separation efficiency can be examined by testing oily wastewater with varying concentrations to assess the membrane's separation capabilities under varying contaminant loads. For example, a membrane may easily achieve high separation efficiency with low-concentration oily wastewater, but this efficiency may decrease as the oil concentration increases. Second, the change in membrane flux, a key performance indicator, must be determined. Membrane flux can vary significantly when treating oily wastewater with varying concentrations. Higher concentrations may cause oil to clog the membrane pores more quickly, leading to a more significant reduction in flux. By measuring membrane flux at different concentrations, a flux-concentration curve can be constructed, providing a visual representation of the membrane's anti-fouling and mass transfer capabilities. Finally, membrane service life must be assessed. High-concentration oily wastewater may lead to more severe fouling and damage to the membrane material. Long-term testing at varying concentrations simulates the complex operating conditions of the membrane, thereby predicting its service life.
[0054] For kerosene water emulsion, such as Figure 3 As shown in Figure (a), the separation flux and efficiency of kerosene emulsions with different concentrations were evaluated. It is worth noting that when the volume ratio of kerosene to water changes from 1:20 to 1:99, the flux increases from 3722 L·m -1 ·h -1 Reduced to 3149 L·m -1 ·h -1However, the separation efficiency remained relatively stable, consistently exceeding 99%. Even at a concentration of 1 / 20, its performance was still commendable. This suggests that the membrane has the potential to separate oil-water emulsions at higher concentrations.
[0055] For toluene water emulsion, Figure 3 As shown in Figure (b), the flux of toluene emulsion increased from 3771 L·m -1 ·h -1 Down to 3257 L·m -1 ·h -1 Despite the high separation efficiency, the membrane consistently exceeded 99.4%. Compared to the higher concentration of kerosene emulsion, the separation flux and efficiency of the toluene emulsion were significantly higher. This can be attributed to the complexity and viscosity of the oil. Performance remained high for the toluene emulsion at a concentration of 1 / 20. This demonstrates the membrane's potential for separating oil-water emulsions at higher concentrations.
[0056] For n-hexane water emulsion, such as Figure 3 As shown in Figure (c), the flux of n-hexane emulsion increased from 3674 L·m -1 ·h -1 Reduced to 3149 L·m -1 ·h -1 Despite the high flux and separation efficiency, the PAN / CS / TiO2 membrane maintained a separation efficiency exceeding 99%. The membrane demonstrated excellent flux and separation efficiency for oil-water emulsions across a wide concentration range. Even at a concentration of 1 / 20, its performance remained commendable. This demonstrates the membrane's potential for separating oil-water emulsions at higher concentrations.
[0057] As for the emulsion composed of a mixture of n-dodecyl tributyl phosphate oil and 2 mol of nitric acid, Figure 3 As shown in Figure (d), the separation efficiency exceeds 99%, comparable to that of the other emulsions. The decreased separation flux compared to the other three emulsion systems is attributed to the complexity and viscosity of the oil. In summary, the amorphous TiO2-modified nanofibrous membrane (PAN / CS / TiO2 composite membrane) exhibits excellent flux and separation efficiency for oil-water emulsions across a wide concentration range. Even at a concentration of 1 / 20, its performance remains commendable. This demonstrates the potential of this membrane for separating oil-water emulsions at higher concentrations.
[0058] Membrane separation technology has been considered as a potential strategy for treating oily wastewater. However, membrane fouling limits its practical application, especially for high-concentration and high-viscosity oil-water emulsions. Oil droplets and emulsifiers in high-concentration oil-water emulsions are easily adsorbed on the membrane surface or clog the membrane pores, resulting in a decrease in flux. When treating high-concentration oil-water emulsions for a long time, the membrane material may be subject to chemical erosion and physical wear, affecting its service life. Figure 5As shown in Figure 2, n-dodecane and tributyl phosphate (TBP) were mixed with a 2 mol nitric acid solution at a ratio of 7:3 (V0 / V) to simulate an oily wastewater emulsion. When used to separate a high-concentration emulsion (volume ratio of 1 / 20), no oil contamination was observed on the membrane surface, and high flux and separation efficiency were achieved, as shown in Figure 2. Figure 4 It has potential application value in treating high-concentration oil-water emulsions. PAN / CS / TiO2 films were tested at oil concentrations of 20%, 30%, and 40%. Under gravity conditions, the flux at 20% concentration was 2398 L·m -1 ·h -1 , the separation efficiency is 97%. When the concentration is 30% and 40%, the separation efficiency is 96%, and the flow rate exceeds 2123L·m -1 · h -1 . When PAN / CS / TiO2 membrane is used to treat high-concentration, high-viscosity oil-water emulsions. This study proposes an effective method for the continuous separation and recovery of high-viscosity, high-concentration oil-in-water emulsions. The reasons why PAN / CS / TiO2 can efficiently separate high-concentration oil-water emulsions are: First, the superhydrophilic / superhydrophobic properties. The superhydrophilic part is conducive to the passage of the aqueous phase. This hydrophilic / hydrophobic difference enables the membrane to efficiently treat high-concentration oil-water emulsions. Second, the synergistic effect of the separation mechanism: on the one hand, the membrane material separates oil and water by physical screening during the treatment process; on the other hand, the membrane material separates oil and water by physical screening. During the separation process, on the one hand, the pore size is used to intercept oil droplets through the physical screening effect; on the other hand, the functional groups on the membrane surface can adsorb oil droplets or water droplets. This synergistic effect of physical screening and adsorption is particularly important when treating high-concentration oil-water emulsions.
[0059] When treating wastewater containing oil and dyes, membranes are susceptible to both reversible and irreversible contaminants. These contaminants can alter the wettability of the membrane surface, reducing adsorption sites. Therefore, developing self-cleaning membranes with durable performance is crucial.
[0060] like Figure 5 As shown in the experimental data, the PAN / CS / TiO2 composite membrane can effectively photocatalytically degrade Sudan red oil emulsion under ultraviolet irradiation. These results indicate that the dyed PAN / CS / TiO2 composite membrane can be effectively cleaned under ultraviolet irradiation and has excellent antifouling properties. After ultraviolet irradiation, the PAN / CS / TiO2 composite membrane turns white and the original dye stains are also removed. The excellent light-induced self-cleaning performance of the PAN / CS / TiO2 nanofiber membrane is due to the excellent photocatalytic properties of TiO2. Under ultraviolet irradiation, electrons (e - ) are excited from the valence band of titanium dioxide to the conduction band, while the electron hole (h + ) are generated in the valence band. - ) and electron holes (h+ ) may reduce the overall efficiency of the photocatalytic process. The carriers escaping from the charge annihilation reaction then migrate to the titanium dioxide surface. In this stage, the photoexcited electrons catalytically reduce atmospheric oxygen to produce superoxide radicals, while the holes in the valence band oxidize the surface-adsorbed water or OH - , generating hydroxyl radicals (OH - ). These reactive oxygen species (ROS) interact with organic pollutants, destroying their chemical structure and gradually degrading them into smaller molecular compounds, ultimately turning them into CO2 and H2O. The specific light-induced self-cleaning process can be expressed as follows:
[0061] TiO2+ hv → e - + h + e - + h + → energy h + + H2O → OH + h + e - + O2 → ·O － 2 O － 2+ H2O → ·OH - O － 2 / OH + organic pollutants → H2O + CO2 Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.
Claims
1. A method for preparing amorphous TiO2-modified nanofiber membrane, characterized in that: The following steps are involved: Chitosan and polyacrylonitrile are used as raw materials to obtain a spinning solution, and polyacrylonitrile / chitosan nanofiber membrane is obtained by electrospinning. Preparation of amorphous TiO2 solution; The polyacrylonitrile / chitosan nanofiber membrane is impregnated with an amorphous TiO2 solution, and the amorphous TiO2 is attached to the surface of the polyacrylonitrile / chitosan nanofiber membrane through physical adsorption, chemical condensation and hydrogen bonding to obtain an amorphous TiO2 modified nanofiber membrane.
2. The preparation method according to claim 1, characterized in that The mass ratio of the polyacrylonitrile to chitosan is 1.373:1-2.
3. The preparation method according to claim 1, characterized in that The amorphous TiO2 solution is prepared by mixing 15 to 20 parts by volume of a titanium source, 4 to 6 parts by volume of hydrochloric acid, 24 to 30 parts by volume of ethanol, and 1.6 to 3.2 parts by volume of deionized water; the mass concentration of the titanium source is ≥99%, the mass concentration of the hydrochloric acid is 36% to 38%, and the mass concentration of the ethanol is ≥99.7%.
4. The preparation method according to claim 3, characterized in that The titanium source is tetrabutyl titanate, isopropyl titanate, titanyl sulfate, titanium tetrachloride or ethyl titanate.
5. The preparation method according to claim 1, characterized in that The dipping time is 5 min to 20 min.
6. The preparation method according to claim 1, characterized in that The electrospinning parameters are: 20-30 stainless steel needle; voltage of 10KV to 15KV; feed rate of 0.6 mL / h to 1.0 mL / h; electrode distance of 10 cm to 30 cm; ambient temperature of 5°C to 40°C; ambient humidity of 30% to 50%; and receiver speed of 120 r / min to 200 r / min.
7. The preparation method according to claim 1, characterized in that The solvent of the spinning solution is any one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran and a mixed solvent of dimethylformamide. Before electrospinning, the spinning solution is allowed to stand for 0.5 to 2 hours.
8. Amorphous TiO2 modified nanofiber membrane, characterized in that, The preparation method according to any one of claims 1 to 7 is used to prepare the compound.
9. Use of the amorphous TiO2 modified nanofiber membrane according to claim 8 in oil-water separation.