Bismuth molybdate / polymer photocatalytic porous fiber membrane as well as preparation method and application thereof

Abstract

The invention provides a bismuth molybdate / polymer photocatalytic porous fiber membrane as well as a preparation method and application thereof, and belongs to the technical field of photocatalytic membrane degradation of organic pollutants in a water body. The method aims to overcome the problems of low catalytic efficiency caused by easy agglomeration and precipitation of a powder photocatalyst, high energy consumption in a recycling process and the like. According to the technical scheme, the preparation process of the bismuth molybdate / polymer photocatalytic porous fiber membrane is described in detail and comprises the steps of preparing the porous fiber membrane, loading a photocatalyst, obtaining the bismuth molybdate / polymer photocatalytic porous fiber membrane and the like. The prepared photocatalytic porous fiber membrane shows excellent photocatalytic activity and cycling stability on organic pollutants in a water body, and is easy to reuse. The technology integrates the advantages of photocatalysis and membrane separation, is efficient, economical and environment-friendly, and provides an innovative and practical solution for wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the field of photocatalytic technology and membrane separation technology, in particular to a photocatalytic membrane technology for degradation of organic pollutants, and specifically relates to a bismuth molybdate / polymer photocatalytic porous fiber membrane, a preparation method thereof and an application thereof. Background Art

[0002] In the development of human society, water resources have always played a vital role. However, with the acceleration of industrialization and the continuous growth of population, water resources are facing unprecedented pressure and challenges. Among them, water pollution is particularly prominent, especially the large amount of difficult-to-degrade organic matter contained in industrial wastewater, which has become one of the key factors restricting the sustainable use of water resources. These organic matter not only seriously damages the ecological balance of water bodies, but also may accumulate through the food chain, posing a potential threat to human health. Therefore, it is particularly important to develop new wastewater treatment technologies that are efficient, economical and environmentally friendly.

[0003] At present, as a representative of new water treatment technologies, advanced oxidation technology has attracted widespread attention due to its strong oxidizing properties and high efficiency. It completely mineralizes the refractory organic matter in water into carbon dioxide and water by producing strong oxidizing free radicals (such as hydroxyl radicals). Common advanced oxidation technologies include electrochemical oxidation, Fenton oxidation, photocatalytic oxidation, ozone oxidation, etc. Among them, photocatalytic oxidation technology uses the photogenerated electrons and holes generated by semiconductor photocatalysts under light conditions, and undergoes redox reactions with substances adsorbed on the surface of the catalyst, directly converting light energy into chemical energy, and realizing the rapid degradation of organic pollutants. It has the characteristics of energy saving, environmental protection, and strong sustainability, and has received extensive attention and research in recent years.

[0004] Compared with the low catalytic efficiency of traditional photocatalysts in practical applications, bismuth molybdate, as a new type of photocatalyst, has a narrow bandgap, can absorb visible light, and has a unique layered structure and good electronic structure adjustability, showing high activity in photocatalytic reactions. However, powder catalysts have the disadvantages of easy loss, difficult recovery, and high cost, which are subject to certain limitations in practical applications. Therefore, composite catalytic membranes are studied to replace powder catalysts.

[0005] Polymer membranes have become an excellent separation material in the contemporary chemical industry due to their excellent flexibility, high specific surface area, porosity, and selective separation. Electrospinning technology has been widely used in the field of membrane preparation due to its advantages such as continuous process, simple equipment, high cost performance, and precise control of microstructure and composition. When using electrospinning technology to prepare polymer porous fiber membranes, by adjusting the parameters in the spinning process, such as voltage, solution concentration, receiving distance, etc., the diameter and pore structure of the fiber can be precisely controlled, and submicron or nanometer-level ultrafine fibers can be prepared, so that the polymer porous fiber membrane has extremely high specific surface area and porosity. At the same time, its nanoscale fiber structure also gives the membrane higher flexibility. Combining the membrane with the catalyst and fixing the catalyst on the surface of the polymer porous fiber membrane by the in-situ growth method can obtain a more uniform and finer particle distribution, which not only improves the utilization rate and catalytic efficiency of the catalyst, but also realizes the close combination of the catalyst and the membrane matrix, avoiding the dispersion and secondary recovery of the catalyst.

[0006] In summary, the present application adopts electrospinning and in-situ growth of catalysts to prepare efficient and reliable photocatalytic porous fiber membranes for the degradation of organic pollutants in water bodies, aiming to overcome the problems of low catalytic efficiency caused by the easy agglomeration and precipitation of traditional powder catalysts and secondary recovery of catalysts. Summary of the invention

[0007] This application proposes improvements to the following problems existing in the prior art: First, powder catalysts are prone to particle agglomeration during application, and there are technical bottlenecks such as complex recycling process and low recycling efficiency; second, traditional separation membrane materials lack effective recognition ability for ionic and small molecular pollutants in sewage, which not only easily causes membrane pore blockage, but also makes it difficult to meet the process requirements for specific separation and efficient degradation of pollutants in difficult sewage treatment. Therefore, a bismuth molybdate / polymer photocatalytic porous fiber membrane, its preparation method and its application are proposed. The photocatalytic membrane exhibits excellent photocatalytic activity and cyclic stability for organic pollutants, and is easy to recycle and reuse, which can achieve continuous and efficient degradation of organic pollutants in water.

[0008] To achieve the above-mentioned object, the present invention provides a method for preparing a bismuth molybdate / polymer photocatalytic porous fiber membrane, comprising the following steps.

[0009] (1) The polymer particles were added into a solvent and stirred to dissolve to form a polymer solution with a mass fraction of 12-36 wt%. Subsequently, the polymer solution was electrospinned at a feed rate of 0.5-2.0 mL / h and a spinning voltage of 5-25 kV. Finally, the obtained polymer fiber membrane was hot-pressed at 40-75 °C for 1-20 min to obtain a porous fiber membrane.

[0010] (2) Dissolve 0.121-0.728 g of bismuth nitrate and 0.03-0.182 g of sodium molybdate in 5-7.5 mL of solvent respectively and mix them to obtain a mixed solution. Then, add 25-45 mL of solvent to the mixed solution to obtain a catalyst growth solution. Finally, place the fiber porous membrane obtained in step (1) in the growth solution, and perform in-situ growth of bismuth molybdate catalyst at 80-140° C. for 10-16 h to obtain a bismuth molybdate / polymer photocatalytic porous fiber membrane.

[0011] In this preparation method, electrospinning technology is used to prepare a polymer porous fiber membrane, and then catalyst particles are grown on the surface of the porous fiber membrane through in-situ growth technology. This preparation method is simple and easy to operate, and the obtained photocatalytic fiber porous membrane is stable and has a high catalyst loading.

[0012] Preferably, in step (1), the polymer is at least one of polyvinylidene fluoride, polyetherimide, polysulfone and polyethersulfone, and the solvent is at least one of N-methylpyrrolidone, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide and acetone.

[0013] Preferably, the solvent in step (2) is any one of ethylene glycol, anhydrous ethanol and water.

[0014] The present invention also provides a bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by the method described in any of the above technical solutions.

[0015] Preferably, the bismuth molybdate / polymer photocatalytic porous fiber membrane has a thickness of 50-250 μm and is in the form of a flat membrane. The bismuth molybdate catalyst is in the shape of petals composed of nanosheets and nanocolumns and is evenly, densely and stably connected to the surface of the porous fiber membrane.

[0016] The present invention also provides a method for degrading organic pollutants in water using a bismuth molybdate / polymer photocatalytic porous fiber membrane. The specific implementation steps are as follows: under room temperature conditions, the bismuth molybdate / polymer photocatalytic porous fiber membrane undergoes a photocatalytic reaction on the fiber surface through ultraviolet light and produces strong oxidizing free radicals, thereby photocatalytically oxidizing and degrading organic pollutants in the water.

[0017] Preferably, the organic pollutant is at least one of methyl orange, orange G, Janus green, methylene blue, ciprofloxacin, levofloxacin, sulfamethoxazole and clarithromycin.

[0018] Compared with the prior art, the advantages and positive effects of the present invention lie in the following three aspects.

[0019] 1. The present invention provides a bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by electrospinning and in-situ growth. In the preparation process, the polymer is dissolved and spun, and then the catalyst is grown in-situ on its surface to convert the polymer porous fiber membrane into a bismuth molybdate / polymer photocatalytic porous fiber membrane. The preparation method is simple and easy to operate.

[0020] 2. The bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by the above method has the "three high characteristics" of high loading, high stability and high catalytic activity. The coupling of photocatalytic technology and membrane separation technology can not only achieve the effective degradation of organic pollutants, but also the immobilization of photocatalysts by polymer membranes avoids the secondary separation and recovery of catalysts and the discontinuous operation of the degradation process, so that the entire degradation process can be operated continuously until the organic pollutants are completely degraded, which has great potential in practical applications.

[0021] 3. This process significantly improves the structural stability of the material while simplifying the preparation process through the chemical bonding of nanocatalysts and fiber matrix. The prepared photocatalytic film can not only achieve continuous cyclic degradation of organic pollutants (removal rate can reach 95.2%), but also overcome the defects of traditional powder catalysts that are easy to agglomerate and difficult to recycle, and can effectively maintain a catalytic efficiency of more than 92% after 10 cycles. It provides an effective method for industrial wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an electron microscope photograph of polyetherimide porous fiber membrane.

[0023] Figure 2 This is an electron microscope photograph of a polyetherimide photocatalytic porous fiber membrane loaded with nano-pillar petal-shaped bismuth molybdate.

[0024] Figure 3 This is an electron microscope photograph of a polyetherimide photocatalytic porous fiber membrane loaded with nano-petal-shaped bismuth molybdate. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] An embodiment of the present invention provides a method for preparing a bismuth molybdate / polymer photocatalytic porous fiber membrane, comprising the following steps.

[0027] (1) The polymer particles were added into a solvent and stirred to dissolve to form a polymer solution with a mass fraction of 12-36 wt%. Subsequently, the polymer solution was electrospinned at a feed rate of 0.5-2.0 mL / h and a spinning voltage of 5-25 kV. Finally, the obtained polymer fiber membrane was hot-pressed at 40-75 °C for 1-20 min to obtain a porous fiber membrane.

[0028] (2) Dissolve 0.121-0.728 g of bismuth nitrate and 0.03-0.182 g of sodium molybdate in 5-7.5 mL of solvent respectively and mix them to obtain a mixed solution. Then, add 25-45 mL of solvent to the mixed solution to obtain a catalyst growth solution. Finally, place the fiber porous membrane obtained in step (1) in the growth solution, and perform in-situ growth of bismuth molybdate catalyst at 80-140° C. for 10-16 h to obtain a bismuth molybdate / polymer photocatalytic porous fiber membrane.

[0029] The main features of the preparation method provided in the above example are: the polymer porous fiber membrane is prepared by electrospinning technology, and then bismuth molybdate nanofiltration particles are loaded on the surface of the polymer porous fiber membrane by in-situ growth, and finally a bismuth molybdate / polymer photocatalytic porous fiber membrane is obtained. Specifically, before starting spinning, it is necessary to set appropriate spinning parameters according to the properties of the spinning solution and the characteristics of the target fiber, including voltage, solution flow, receiving distance, etc. These parameters have a significant effect on the diameter, porosity and uniformity of the fiber. When the high-voltage power supply is turned on, the spinning solution forms a Taylor cone under the action of the high-voltage electric field. When the electric field force exceeds the surface tension, the spinning solution ejects a thin stream from the tip of the Taylor cone. During the injection process, the solvent gradually evaporates, the fiber gradually solidifies and is finally deposited on the receiving device to form a porous fiber membrane. The polymer porous fiber membrane obtained by spinning is subjected to hot pressing treatment, cut into a certain size, and immersed in bismuth nitrate, sodium molybdate / ethylene glycol, ethanol, and an aqueous solution. The hydrothermal reaction is carried out by setting appropriate temperature and time to load the catalyst particles onto the surface of the fiber membrane to obtain a bismuth molybdate / polymer photocatalytic porous fiber membrane.

[0030] In the above steps, the bismuth molybdate / polymer photocatalytic porous fiber membrane prepared based on the electrospinning process and in-situ growth technology achieved a breakthrough improvement in material performance through the nanoscale composite structure. The catalyst was evenly anchored on the fiber surface by the in-situ growth method, which effectively overcame the common catalyst agglomeration problem in traditional loading methods and achieved efficient dispersion and stable binding of the catalyst. The nanofibers with high specific surface area and uniformly distributed active sites significantly improved the pollutant degradation efficiency, and the catalyst immobilization strategy realized the continuous recycling of the material.

[0031] In a preferred embodiment, the mass fraction of the polymer in the polymer solution is 12% to 36%. The mass fraction of the polymer in the polymer solution is limited in this embodiment because when the mass fraction is lower than 12%, the viscosity of the spinning solution is too low, so that the jet is prone to uneven force during the stretching process and cannot form fibers with uniform diameters; when the mass fraction is higher than 36%, the polymer molecular chains are tightly entangled, and the molecular chains entangled with each other under the same electric field tension cannot whip freely in the radial direction of the jet, resulting in serious fiber adhesion. It is understandable that the mass fraction of the polymer in the polymer solution can also be any point value within the above range, and those skilled in the art can adjust it according to the actual reaction situation. In addition, the choice of solvent in step (1) of the embodiment is not limited to N-methylpyrrolidone, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, and acetone, and can also be other substances that are reasonably selected and adjusted by those skilled in the art in the art according to common sense in the field. Finally, in the preparation process of the porous fiber membrane, the spinning voltage is 5-25 kV, the feed rate is 0.5-1.5 mL / h, the hot pressing temperature is 40-75 ° C, and the hot pressing time is 1-20 min. In this example, the spinning voltage, feed rate, hot pressing temperature and hot pressing time of the fiber membrane are limited. The reason is that when the spinning voltage is lower than 5 kV and the feed rate is lower than 0.5 mL / h, the spinning liquid jet is unevenly stressed during the stretching process and the solvent volatilization rate is insufficient to form fibers with uniform diameters; when the spinning voltage is higher than 25 kV and the feed rate is higher than 1.5 mL / h, the speed of the spinning jet is accelerated, which shortens the time required for the jet to reach the receiving roller, and the instability increases. At the same time, the too short time makes it impossible for the solvent in the jet to completely volatilize, and the residual solvent causes the fibers that are not completely solidified on the roller to adhere to each other, or even adhere to sheets, without fiber structure. When the hot pressing temperature is lower than 40°C and the hot pressing time is lower than 1 minute, the mechanical strength of the membrane is not greatly improved, and the fiber diameter and membrane thickness are almost unaffected; when the hot pressing temperature is higher than 75°C and the hot pressing time is higher than 20 minutes, the fiber membrane will be damaged, the fibers will be melted and bonded, and the porosity will be reduced. It is understandable that the above-mentioned spinning voltage, feed rate, hot pressing temperature, and hot pressing time can be any point value within the above-mentioned range, and those skilled in the art can adjust them according to the actual reaction situation.

[0032] In a preferred embodiment, the mass of bismuth nitrate is 0.121-0.728 g, the mass of sodium molybdate is 0.03-0.182 g, the total volume of the solvent is 30-52.5 mL, the solvent is at least one of ethylene glycol, ethanol, and water, the in-situ growth time is 10-16 h, and the in-situ growth temperature is 80-140° C. In the present embodiment, the solute mass, solvent volume, solvent type, temperature and time of in-situ growth are defined, because when the mass of bismuth nitrate is less than 0.121g, the mass of sodium molybdate is less than 0.03g, the solvent volume is less than 30mL, the solvent is not at least one of the above-mentioned ethylene glycol, ethanol, and water, the hydrothermal reaction temperature is less than 80°C, and the hydrothermal reaction time is less than 10h, the solute cannot be dissolved and the bismuth molybdate catalyst cannot be generated; when the mass of bismuth nitrate is higher than 0.728g, the mass of sodium molybdate is higher than 0.182g, the solvent volume is higher than 52.5mL, the hydrothermal reaction temperature is higher than 140°C, and the hydrothermal reaction time is higher than 16h, the ion concentration and reaction temperature are high, the growth time is too long, and the catalyst will be closely stacked on the fiber membrane, and even cause the fiber to melt, so that the effective area of ​​the catalyst is reduced, and the catalytic efficiency is reduced. It can be understood that the mass of bismuth nitrate and sodium molybdate, the volume of solvent, the in-situ growth temperature, and the growth time can also be any point value within the above range, and those skilled in the art can adjust according to the actual reaction situation.

[0033] The embodiment of the present invention also provides a bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by the method described in the above embodiment.

[0034] In a preferred embodiment, the bismuth molybdate / polymer photocatalytic porous fiber membrane has a thickness of 50-250 μm and is in the form of a flat membrane, such as Figure 2 and Figure 3 As shown. In this embodiment, the thickness of the bismuth molybdate / polymer photocatalytic porous fiber membrane is measured by a thickness gauge. It is understandable that the thickness of the bismuth molybdate / polymer photocatalytic porous fiber membrane can also be any point value within the above range. The reason why the present invention limits the thickness of the bismuth molybdate / polymer photocatalytic porous fiber membrane is that when the thickness of the bismuth molybdate / polymer photocatalytic porous fiber membrane is less than 50μm, the residence time of organic pollutants passing through the membrane during the catalytic process is short, and the catalytic efficiency is low; when the thickness of the bismuth molybdate / polymer photocatalytic porous fiber membrane is higher than 250μm, the membrane resistance increases, and the flux of the organic pollutant solution passing through the membrane decreases, which is not conducive to the large-scale treatment of sewage and reduces the amount of sewage treated.

[0035] An embodiment of the present invention also provides a method for catalytically degrading organic pollutants in wastewater using the bismuth molybdate / polymer photocatalytic porous fiber membrane described in the above embodiment. The specific implementation steps are as follows: under room temperature conditions, the bismuth molybdate / polymer photocatalytic porous fiber membrane undergoes a photocatalytic reaction on the fiber surface through ultraviolet light and produces strong oxidizing free radicals, thereby photocatalytically oxidizing and degrading organic pollutants in the water.

[0036] In a preferred embodiment, the organic pollutant is at least one of methyl orange, orange yellow G, Janus green, methylene blue, ciprofloxacin, levofloxacin, sulfamethoxazole, and clarithromycin. In this embodiment, there are many types of organic pollutants that can be degraded. The above only lists the more common organic pollutants, but does not exclude the diversity of applicable types.

[0037] In order to more clearly and in detail introduce the bismuth molybdate / polymer photocatalytic porous fiber membrane, its preparation method and application provided by the embodiments of the present invention, they will be described below in conjunction with specific embodiments.

[0038] Example 1

[0039] The polyetherimide nanofiber membrane was prepared by electrospinning technology. Specifically, 5g of dried polyetherimide polymer was dissolved in a solvent of 12g of N-methylpyrrolidone and 3g of tetrahydrofuran, stirred at 60°C for 12h, and a uniform and clear polyetherimide spinning solution was obtained after standing. Subsequently, electrospinning was performed at a voltage of 10kV, with a feed rate of 0.6mL / h, a spinning distance of 20cm, a spinning ambient temperature of 25°C, and an ambient humidity of 40%. The collected fiber membrane was placed in a hot press and hot pressed at 50°C for 15min to obtain a polyetherimide nanofiber membrane.

[0040] The bismuth molybdate / polymer photocatalytic porous fiber membrane was prepared by the in-situ growth method. Specifically, 0.364g of bismuth nitrate was weighed and dissolved in 7.5mL of ethylene glycol to obtain a 12.5mmol / L bismuth nitrate / ethylene glycol solution, and 0.091g of sodium molybdate was weighed and dissolved in 7.5mL of ethylene glycol to obtain a 6.3mmol / L sodium molybdate / ethylene glycol solution, which was fully stirred and then 45mL of ethanol was added to obtain a growth solution. Subsequently, the polyetherimide fiber membrane obtained above was cut into a size of 7×7cm, placed in the above solution, and reacted at 120°C for 12 hours. After the reaction was completed, the membrane was taken out, washed alternately with deionized water and anhydrous ethanol 3 times, and then dried at 60°C for 12 hours to obtain a bismuth molybdate / polymer photocatalytic porous fiber membrane.

[0041] The obtained bismuth molybdate / polymer photocatalytic porous fiber membrane was placed in 30 mL, 10 mg / L methyl orange solution for photocatalytic reaction.

[0042] Example 2

[0043] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 1, except that the hydrothermal reaction temperature is 140°C.

[0044] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0045] Example 3

[0046] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 1, except that the hydrothermal reaction temperature is 100°C.

[0047] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0048] Example 4

[0049] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 1, except that the hydrothermal reaction temperature is 80°C.

[0050] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0051] Example 5

[0052] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 2, except that the bismuth ion concentration used is 28.6 mmol / L, the molybdenum particle concentration is 14.3 mmol / L, and the polymer used is polyvinylidene fluoride.

[0053] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0054] Example 6

[0055] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 2, except that the bismuth ion concentration used is 25.01 mmol / L and the molybdenum particle concentration is 12.53 mmol / L.

[0056] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0057] Example 7

[0058] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 2, except that the bismuth ion concentration used is 6.25 mmol / L and the molybdenum particle concentration is 3.13 mmol / L.

[0059] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0060] Example 8

[0061] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 2, except that the bismuth ion concentration used is 4.16 mmol / L and the molybdenum particle concentration is 2.08 mmol / L.

[0062] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0063] Example 9

[0064] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 5, except that the solvents used are ethylene glycol and water, and the polymer used is polyethersulfone.

[0065] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0066] Example 10

[0067] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 5, except that the solvent used is water.

[0068] The method for degrading methyl orange using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0069] Embodiment 11

[0070] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that of Example 1, except that the polymer used is polysulfone.

[0071] The method for degrading organic pollutants using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1, except that the target degradation product is orange G.

[0072] Example 12

[0073] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0074] The method for degrading organic pollutants using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1, except that the target degradation product is Janus Green B.

[0075] Embodiment 13

[0076] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0077] The method for degrading organic pollutants using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1, except that the target degradation product is methylene blue.

[0078] Embodiment 14

[0079] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0080] The method for degrading organic pollutants using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1, except that the target degradation product is ciprofloxacin.

[0081] Embodiment 15

[0082] The preparation method of bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1.

[0083] The method for degrading organic pollutants using bismuth molybdate / polymer photocatalytic porous fiber membrane is the same as that in Example 1, except that the target degradation product is levofloxacin.

[0084] Comparative Example 1

[0085] The preparation method of the polyetherimide porous fiber membrane is the same as that in Example 1.

[0086] The method for degrading methyl orange by the polyetherimide porous fiber membrane is the same as that in Example 1.

[0087] Comparative Example 2

[0088] The preparation method of the polyetherimide porous fiber membrane is the same as that in Example 1.

[0089] The degradation method of ciprofloxacin by the polyetherimide porous fiber membrane is the same as that in Example 1.

[0090] Performance Testing

[0091] 1. Catalytic performance

[0092] The relevant performance test data of catalytic degradation of organic pollutants by the catalytic membranes prepared in Examples 1-15 of the present invention and Comparative Examples 1-2 are shown in Table 1.

[0093] The analytical method for organic degradation adopted in the present invention is absorbance method. Specifically, dyes such as methyl orange and orange yellow G have maximum absorbance in the visible light region and are proportional to their content, so colorimetry is used to measure the content of different degradation stages. In addition, antibiotics such as ciprofloxacin and levofloxacin are determined by high performance liquid chromatography.

[0094] The calculation formula for the degradation rate of organic pollutants is as follows.

[0095] Degradation rate (%) = (mass of degraded organic matter / mass of initial organic matter) × 100%.

[0096] Table 1 Relevant performance test data of catalytic degradation of organic pollutants by catalytic membrane Degradation time Final degradation rate Example 1 25min 93% Example 2 35min 94.4% Example 3 45min 99.8% Example 4 55min 92.1% Example 5 45min 93.3% Example 6 40min 93.3% Example 7 35min 92.9% Example 8 45min 92.9% Example 9 60min 93% Example 10 60min 95% Embodiment 11 20min 85.8% Example 12 95min 89.7% Embodiment 13 70min 97.2% Embodiment 14 180min 87.5% Embodiment 15 160min 80.9% Comparative Example 1 24h 0 Comparative Example 2 24h 0

[0097] From the results in Table 1, it can be seen that the bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by the embodiment of the present invention has excellent catalytic performance for both dyes and antibiotics, and the catalytic membrane avoids the secondary separation of the catalyst, thereby reducing the cost. The bismuth molybdate / polymer photocatalytic porous fiber membranes prepared by different solvent types, reaction temperatures, and solute concentrations all have excellent catalytic performance.

[0098] 2. Stability of bismuth molybdate / polymer photocatalytic porous fiber membrane

[0099] In order to further investigate the stability of the bismuth molybdate / polymer photocatalytic porous fiber membrane, the organic matter degradation rate of the stability of the bismuth molybdate / polymer photocatalytic porous fiber membrane under different reaction times was monitored. The results are shown in Table 2.

[0100] Table 2 Stability data of bismuth molybdate / polymer photocatalytic porous fiber membrane Reaction times Example 1 Embodiment 13 1 93% 87.5% 2 92.9% 87.4% 3 92.9% 87.4% 4 92.8% 87.3% 5 92.7% 87.2% 6 92.7% 87.3% 7 92.6% 87.2% 8 92.7% 87.2% 9 92.6% 87.1% 10 92.7% 87.1%

[0101] It can be seen from the results in Table 2 that the bismuth molybdate / polymer photocatalytic porous fiber membrane prepared by the embodiment of the present invention still maintains a high catalytic efficiency after 10 cycles of catalytic degradation, and has good stability and reusability.

Claims

1. A method for preparing a bismuth molybdate / polymer photocatalytic porous fiber membrane, characterized in that: The method is prepared by the following steps: (1) adding polymer particles to a solvent and stirring and dissolving the polymer particles to form a polymer solution with a mass fraction of 12-36 wt%, and then spinning the polymer fiber membrane by an electrospinning method at a feed rate of 0.5-2.0 mL / h and a spinning voltage of 5-25 kV. Finally, hot pressing the obtained polymer fiber membrane at 40-75° C. for 1-20 min to obtain a porous fiber membrane; (2) dissolving 0.121-0.728 g of bismuth nitrate and 0.03-0.182 g of sodium molybdate in 5-7.5 mL of solvent respectively and then mixing the mixture to obtain a mixed solution. Then, adding 25-45 mL of solvent to the mixed solution to obtain a catalyst growth solution. Finally, placing the fiber porous membrane obtained in step (1) in the growth solution, and performing in-situ growth of bismuth molybdate catalyst at 80-140° C. for 10-16 h to obtain a bismuth molybdate / polymer photocatalytic porous fiber membrane.

2. The method for preparing a bismuth molybdate / polymer photocatalytic porous fiber membrane according to claim 1, characterized in that: In step (1), the polymer is at least one of polyvinylidene fluoride, polyetherimide, polysulfone, and polyethersulfone, and the solvent is at least one of N-methylpyrrolidone, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, and acetone; and in step (2), the solvent is any one of ethylene glycol, anhydrous ethanol, and water.

3. A bismuth molybdate / polymer photocatalytic porous fiber membrane, characterized in that: The bismuth molybdate / polymer photocatalytic porous fiber membrane is prepared by the preparation method of any one of claims 1-2.

4. A bismuth molybdate / polymer photocatalytic porous fiber membrane as claimed in claim 3, characterized in that: The bismuth molybdate / polymer photocatalytic porous fiber membrane has a thickness of 50-250 μm and is in the form of a flat membrane. The bismuth molybdate catalyst is in the shape of petals composed of nanosheets and nanocolumns and is evenly, densely and stably connected to the surface of the porous fiber membrane.

5. An application of the bismuth molybdate / polymer photocatalytic porous fiber membrane as claimed in claim 3, characterized in that: Applied to degrading organic pollutants in water, the degradation method mainly includes the following steps: under room temperature conditions, bismuth molybdate / polymer photocatalytic porous fiber membrane undergoes photocatalytic reaction on the fiber surface through ultraviolet light and produces strong oxidizing free radicals, thereby photocatalytically oxidizing and degrading organic pollutants in water.

6. An application of the bismuth molybdate / polymer photocatalytic porous fiber membrane as claimed in claim 5, characterized in that: The organic pollutant is at least one of methyl orange, orange G, Janus green, methylene blue, ciprofloxacin, levofloxacin, sulfamethoxazole and clarithromycin.

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