Biomass-based photocatalytic composite membrane material as well as preparation method and application thereof

Abstract

The invention discloses a biomass-based photocatalytic composite membrane material and a preparation method and application thereof, and the preparation method comprises the following steps: uniformly mixing cellulose acetate, a plasticizer and a solvent to obtain a mixed solution I; uniformly mixing the mixed solution I with modified polypyrrole and nano titanium dioxide in sequence to obtain a film forming solution II; performing dry phase conversion on the film forming liquid II to obtain a transparent composite film material; the preparation method comprises the following steps: sequentially immersing a transparent composite membrane material into a Bi (NO3) 3 solution and a (NH4) 2MoO4 solution, uniformly loading bismuth molybdate nanoparticles on the surface and inside of the transparent composite membrane material by using an in-situ coprecipitation method, cleaning after the reaction is finished, and then freeze-drying to obtain a photocatalytic composite membrane material; and carrying out illumination treatment on the photocatalytic composite membrane material under an ultraviolet lamp. According to the material, the utilization efficiency of photons is greatly improved, the photocatalytic activity is enhanced, the process is simple, the operation is convenient and fast, the operation can be carried out at normal temperature, and the energy consumption and the cost are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental functional materials, and particularly relates to a biomass-based photocatalytic composite membrane material, its preparation method and application, which are applicable to fields such as environmental purification. Background Art

[0002] Traditional organic wastewater treatment methods such as physical adsorption and chemical oxidation have problems such as high cost, low efficiency, and easy generation of secondary pollution. Therefore, it is particularly important to develop efficient, environmentally friendly, and sustainable pollution treatment technologies.

[0003] As a green and efficient pollution treatment method, photocatalytic technology has received extensive attention in recent years. Photocatalytic materials can be excited to generate electron-hole pairs under light illumination, and then trigger a series of redox reactions to decompose organic pollutants into harmless small molecule substances. However, traditional photocatalytic materials such as TiO2 have problems such as narrow light absorption range, high recombination rate of photo-generated carriers, and low photocatalytic efficiency, which limit their popularization in practical applications.

[0004] In order to overcome these problems, researchers have begun to explore the preparation of new composite materials with excellent photocatalytic performance by compounding different materials. Among them, biomass-based materials have become ideal choices for preparing photocatalytic composite materials due to their renewable, degradable, and environmentally friendly characteristics. However, the photocatalytic performance and light transmittance of existing biomass-based materials still need to be improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background art, and provide a biomass-based photocatalytic composite membrane material, its preparation method and application. This method can prepare a composite membrane material with excellent photocatalytic performance and light transmittance through simple, efficient, and low-cost steps.

[0006] To solve the above technical problem, the technical solution proposed by the present invention is as follows: A preparation method of a biomass-based photocatalytic composite membrane material, comprising the following steps: (1) Mix cellulose acetate, a plasticizer and a solvent uniformly to obtain a mixed solution I; the plasticizer is selected from at least one of ethylene glycol, diethylene glycol, glycerol, and pentaerythritol; (2) Mix the mixed solution I with modified polypyrrole and nano-titanium dioxide uniformly in sequence to obtain a film-forming solution II; the modified polypyrrole is dopamine-modified polypyrrole; (3) Perform dry phase inversion on the film-forming solution II to obtain a TiO2 / PPy / cellulose acetate transparent composite membrane material; (4) Immerse the transparent composite film material successively into the Bi(NO3)3 solution and the (NH4)2MoO4 solution, and use the in-situ co-precipitation method to uniformly load bismuth molybdate nanoparticles on the surface and inside of the transparent composite film material. After the reaction ends, wash it, and then obtain the photocatalytic composite film material through freeze-drying; (5) Irradiate the photocatalytic composite film material under ultraviolet light to obtain a high-transparency biomass-based Bi2MoO6@TiO2 / PPy photocatalytic composite film material.

[0007] As a further improvement, in the mixture I in step (1), the mass ratio of the cellulose acetate to the plasticizer is 1:0.02 - 0.1.

[0008] As a further improvement, the mass ratio of the cellulose acetate, the modified polypyrrole, and the nano-titanium dioxide is 1:0.001 - 0.008:0.001 - 0.008.

[0009] As a further improvement, the dopamine-modified polypyrrole in step (2) is obtained by the self-polymerization reaction of dopamine on the surface of polypyrrole, and the mass ratio of dopamine to polypyrrole is 1:10 - 50.

[0010] As a further improvement, the titanium dioxide in step (2) is titanium dioxide powder with an average particle size of 20 - 50 nm.

[0011] As a further improvement, the curing temperature of the dry phase inversion in step (3) is 10 - 40 °C, and the humidity is ≤50RH%.

[0012] As a further improvement, the concentration of the Bi(NO3)3 solution in step (4) is 0.03 - 0.25 mol / L, and the concentration of the (NH4)2MoO4 solution is 0.03 - 0.25 mol / L.

[0013] A biomass-based photocatalytic composite film material provided by the present invention is prepared by the described preparation method.

[0014] The present invention also provides an application of the biomass-based photocatalytic composite film material in the degradation of organic pollutants.

[0015] The described application includes: dispersing the biomass-based photocatalytic composite film material in a solution containing organic pollutants and degrading it under light irradiation.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The present invention uses cellulose acetate, a biomass-based material, as the substrate, and synergistically combines the conductive polymer modified polypyrrole, nano-titanium dioxide (Nano-TiO2), and bismuth molybdate (Bi2MoO6) as organic and inorganic fillers, which can significantly expand the spectral response range of the high-transparency composite film material, increase the utilization of visible light by the high-transparency composite film material, and also reduce the recombination of photo-generated electron-hole pairs, accelerating the degradation of pollutants in water. At the same time, the use of the film material form is conducive to separation and recycling during use. In addition, the high transparency of the cellulose acetate film ensures that light can effectively penetrate to the surface of the catalyst, enabling the catalysts on both the surface and in the bulk phase of the photocatalytic composite film material to photocatalytically degrade pollutants, greatly improving the utilization efficiency of photons and thus enhancing the photocatalytic activity.

[0017] The present invention has the following advantages and effects compared with the existing powder photocatalyst technology: (1) Structural advantages and performance improvement: The high-transparency composite film material prepared by the dry phase inversion technology in the present invention has a large specific surface area, a rich pore structure, and high transparency, significantly increasing the contact area between the photocatalyst and the reactants, greatly improving the utilization efficiency of photons, and thus enhancing the photocatalytic activity. In addition, the introduction of nano-TiO2 and modified polypyrrole (PPy), as well as the uniform loading of Bi2MoO6 nanoparticles, further improves the conductivity, stability, and photocatalytic performance of the composite material; (2) Innovation and high efficiency of the preparation process: The one-step or multi-step dry phase inversion method and in-situ co-precipitation method are adopted, with simple process, convenient operation, and can be carried out at room temperature, reducing energy consumption and cost. By precisely controlling the film-forming conditions, precise regulation of the morphology and performance of the film material is achieved, improving the uniformity and repeatability of the product; (3) Environmental protection and sustainable development: Using biomass-based cellulose acetate as the substrate and combining with environmentally friendly materials, the prepared photocatalytic composite transparent film material has good biocompatibility and degradability, meeting the requirements of green chemistry and sustainable development.

[0018] In summary, the high-transparency biomass-based photocatalytic composite film material of the present invention, through its unique porous structure, excellent performance, and innovative preparation process, not only significantly improves the photocatalytic efficiency, but also reduces production costs and environmental pollution, showing broad application prospects and market potential, bringing new breakthroughs to the preparation and application fields of photocatalysts. Brief Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 is the photocatalytic degradation result of the photocatalytic composite membrane material prepared in Example 1; Figure 2 is the appearance diagram of the photocatalytic composite membrane material prepared in Example 1; Figure 3 is the microscopic diagram of the photocatalytic composite membrane material prepared in Example 1; Figure 4 is the cross-sectional scanning electron microscope diagram of the photocatalytic composite membrane material prepared in Example 1; Figure 5 is the EDS energy spectrum analysis (Bi, Mo, Ti) of the photocatalytic composite membrane material prepared in Example 1. Detailed implementation manners

[0021] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0022] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0023] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0024] In some specific implementation manners, the preparation method of the biomass-based photocatalytic composite membrane material of the present invention includes the following steps: (1) Mix cellulose acetate, a plasticizer, and a solvent evenly to obtain a mixed solution I.

[0025] In some embodiments, the mass ratio of the cellulose acetate, the plasticizer, and the solvent in the mixed solution I is 1:0.02 - 0.1:5 - 10.

[0026] In some embodiments, the plasticizer is selected from at least one of ethylene glycol, diethylene glycol, glycerol, and pentaerythritol. More preferably, the plasticizer is glycerol.

[0027] In some embodiments, the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and tetrahydrofuran.

[0028] In some embodiments, the mixing is carried out in the presence of stirring, the speed of the stirring is 500 - 800 rpm, the temperature of the mixing is 10 - 30 °C, and the time of the mixing is 3 - 6 h.

[0029] (2) Mix the mixed solution I with modified polypyrrole (PPy) and nano-titanium dioxide (Nano-TiO2) in sequence and uniformly to obtain a film-forming solution II.

[0030] In some embodiments, first mix the mixed solution I with modified polypyrrole (PPy), stir and dissolve for 60 - 120 min, then mix the obtained product with nano-titanium dioxide (Nano-TiO2), stir for 60 - 120 min, and then let the obtained mixed solution stand for 2 - 5 h to defoam, so as to obtain a film-forming solution II.

[0031] In some embodiments, the mass ratio of the dosages of the cellulose acetate, modified polypyrrole, and nano-titanium dioxide is 1:0.001 - 0.008:0.001 - 0.008.

[0032] In some embodiments, the modified polypyrrole is dopamine-modified polypyrrole, which is obtained by the self-polymerization reaction of dopamine on the surface of polypyrrole, and the mass ratio of the dosages of dopamine and polypyrrole is 1:10 - 50. For example, it can be obtained by carrying out a polymerization reaction by adding ammonium persulfate to a pyrrole and dopamine solution under the reaction conditions of pH 8 - 9 and temperature 5 - 10 °C.

[0033] In some embodiments, the modified polypyrrole is a modified polypyrrole powder with an average particle size of 50 - 100 nm.

[0034] The core advantage of dopamine-modified polypyrrole is that through the adhesiveness and chemical activity of dopamine, it significantly improves the interfacial bonding strength between polypyrrole and the substrate material (such as cellulose acetate membrane). Unmodified polypyrrole is prone to uneven distribution due to surface hydrophobicity and aggregation problems, while the introduction of dopamine can enhance the dispersibility of polypyrrole through π-π stacking and hydrogen bond interactions. At the same time, the rich amino and hydroxyl functional groups can promote the separation of photo-generated electron-hole pairs, thereby enhancing conductivity and photocatalytic activity. In addition, the antioxidant property of dopamine can also delay the degradation of polypyrrole during long-term use and enhance the stability of the composite material.

[0035] In some embodiments, the titanium dioxide is a titanium dioxide powder with an average particle size of 20 - 50 nm. Preferably, the titanium dioxide is selected from at least one of rutile, P25, and anatase; more preferably, the titanium dioxide is anatase type.

[0036] (3) Carry out dry phase inversion on the film-forming solution II to obtain a TiO2 / PPy / cellulose acetate transparent composite membrane material.

[0037] In some embodiments, the dry phase inversion method is a room-temperature dry phase inversion method. Pour the film-forming solution II onto a glass plate, use a glass rod to evenly push the film, and then perform a curing treatment to completely evaporate the solvent. Preferably, the conditions of the curing treatment at least satisfy: the atmosphere is an air atmosphere, the temperature is 10 - 40 °C, the humidity is ≤50RH%, and the time is 1 - 3 h. Excessive humidity will cause the collapse of the pore structure in the film or a decrease in connectivity, reducing the light transmittance of the film and further weakening the efficiency of the photocatalytic reaction.

[0038] In dry phase inversion, as the solvent evaporates, the polymer solution gradually concentrates, and the dynamic equilibrium between the solvent and the non-solvent (plasticizer) is broken, forming a continuous polymer-rich phase and a solvent-rich phase. Eventually, after the solvent volatilizes, a uniform porous structure is left. This pore structure not only enhances the mass transfer efficiency of the reactants but also retains the overall light transmittance of the film, and the two cooperate to improve the photocatalytic performance. In addition, by adjusting the addition amount of the plasticizer, a certain balance can be achieved between the pore structure and transparency, so that the film has both a pore structure and high light transmittance.

[0039] The cellulose acetate membrane material prepared by dry phase inversion has high transparency, and by controlling the temperature and humidity conditions, the solvent evaporation rate can be controlled, and the pore distribution and pore size in the film can be precisely regulated to form a more uniform and stable porous structure. Therefore, the dry method is more controllable and applicable in the preparation of composite membrane materials with high porosity and high light transmittance, especially suitable for scenarios with high requirements for mass transfer and light utilization efficiency such as photocatalytic membrane reactors.

[0040] (4) Immerse the transparent composite membrane material successively in Bi(NO3)3 solution and (NH4)2MoO4 solution, and use the in-situ co-precipitation method to uniformly load bismuth molybdate nanoparticles on the surface and inside of the transparent composite membrane material. After the reaction ends, wash it, and then obtain the photocatalytic composite membrane material through freeze-drying.

[0041] In some embodiments, first immerse the transparent composite membrane material in Bi(NO3)3 solution for 1 - 3 h, and then immerse the obtained product in (NH4)2MoO4 solution for 10 - 60 min for contact reaction.

[0042] In some embodiments, the contact with Bi(NO3)3 solution is carried out in the presence of ultrasonic waves, and the ultrasonic frequency is 20 - 50 KHz to enable the surface and inside of the composite membrane material to uniformly contact the Bi(NO3)3 solution.

[0043] In some embodiments, the concentration of the Bi(NO3)3 solution is 0.03 - 0.25 mol / L, and the concentration of the (NH4)2MoO4 solution is 0.03 - 0.25 mol / L; more preferably, the concentration of the Bi(NO3)3 solution is 0.05 - 0.15 mol / L, and the concentration of the (NH4)2MoO4 solution is 0.05 - 0.12 mol / L. High-concentration salt solutions tend to result in the formation of large-sized particles rather than uniformly dispersed active sites, affecting the catalytic performance.

[0044] Under the above conditions, bismuth molybdate nanoparticles can be prepared and uniformly loaded on the surface and inside of the transparent composite film material.

[0045] In some embodiments, the solvent for cleaning is deionized water, the temperature for freeze-drying is -55°C to -35°C, and the time for freeze-drying is 6 - 12 h. Compared with other drying methods, freeze-drying can keep the composite film material from being damaged.

[0046] (5) Subject the dried photocatalytic composite film material to light irradiation under an ultraviolet lamp to obtain a highly transparent biomass-based Bi2MoO6@TiO2 / PPy photocatalytic composite film material.

[0047] In some embodiments, the time for light irradiation treatment is 30 - 90 min.

[0048] As a biomass-based raw material, cellulose acetate is a renewable, degradable, and environmentally friendly green material. As a film-forming matrix, a highly transparent film with a transparency >90% can be obtained by dry phase inversion through the casting method, but its pore structure is not rich. Therefore, a certain amount of plasticizer can be used to regulate the balance between transparency and pore structure. Loading a photocatalyst (which must be nanoscale, only nanoscale will have light diffraction, thus reducing the impact on transparency) in the film. Since the film has both pore structure and high transparency, it ensures that light can penetrate the film layer efficiently and act on the catalyst, thereby achieving high light utilization efficiency in the photocatalytic process and solving the problem of low light utilization efficiency of the films prepared by wet phase inversion in the past due to their opacity.

[0049] In the biomass-based Bi2MoO6@TiO2 / PPy photocatalytic composite film material of the present invention, the introduction of modified polypyrrole can improve the conductivity of the material and promote the separation and transport of photo-generated carriers. Loading bismuth molybdate (Bi2MoO6) nanoparticles with excellent photocatalytic performance can further expand the light absorption range of the material and improve the photocatalytic efficiency.

[0050] The present invention adopts the combined technology of dry phase inversion and in-situ co-precipitation. Through phase inversion, a highly transparent cellulose acetate-based membrane is formed and a PPy-TiO2 conductive catalytic layer is synchronously embedded, and then Bi2MoO6 is in-situ deposited to construct a gradient heterojunction. By regulating the synergistic effect of the membrane light transmittance (>85%) and porosity, the photoexcitation of the catalyst in the whole film layer and the mass transfer of reactants are optimized. The removal efficiency of the transparent membrane material for refractory organic pollutants under visible light is better than that of traditional non-transparent membrane materials, and the activity decay is <8% after continuous operation for 120 h, solving the problem of inactivation of internal catalysts caused by poor light transmittance of traditional photocatalytic membranes.

[0051] The present invention prepares a highly transparent biomass-based Bi2MoO6@TiO2 / PPy multi-component photocatalytic composite membrane material by constructing a multi-scale composite of a Bi2MoO6-TiO2 heterojunction system and a PPy conductive network in a cellulose acetate matrix. This method can not only broaden the light response range of the photocatalyst, improve the quantum efficiency, but also endow the material with good biocompatibility and degradability. At the same time, this method is of great significance for promoting the application of photocatalytic technology in the fields of environmental purification, biomedicine, etc.

[0052] The preparation method of dopamine-modified polypyrrole in the following examples and comparative examples is as follows: 0.05 g of pyrrole (Py) monomer is added to 25 mL of Tris solution and stirred for 10 min. After the system is homogeneous, different amounts of dopamine (DA) are added. After adding DA, it is stirred for 2 h. The reaction solution is placed in a low-temperature bath to maintain the reaction temperature at 8°C and continuously stirred. After 2 h, 0.5 g of ammonium persulfate (APS) is dissolved in 5 mL of Tris solution and added dropwise to the Py / DA solution, and continuously stirred under low-temperature conditions for 24 h. Then, the PDA-PPy particle precipitate generated in the reaction is collected after centrifugation and washing with deionized water. Finally, the precipitate collected by centrifugation is dried at -54°C in freeze-drying for 24 h, and the dried solid is ground in an agate mortar and collected for standby.

[0053] Example 1 Cellulose acetate (accounting for 1 / 7 of the total mass of mixture I), glycerol as a plasticizer (accounting for 0.02 / 7 of the total mass), and tetrahydrofuran solvent were mixed in proportion. Under a stirring speed of 500 rpm, it was stirred at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mixture I was mixed and stirred with polypyrrole modified by dopamine (the mass ratio of dopamine to polypyrrole was 1:20) for 60 minutes, and then anatase-type nano-titanium dioxide with an average particle size of 50 nm was added. Stirring was continued for 90 minutes and then left standing for 3 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide was 1:0.003:0.003. The prepared film-forming solution was left standing to defoam, and then poured onto a glass plate respectively, and a glass rod was used to evenly push the film. It was placed in a fume hood for 2 h, with a temperature of 25 °C and a humidity of 45RH%. After the solvent was completely evaporated, the film was taken off from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, the composite film was successively immersed in a 0.1 mol / L Bi(NO3)3 solution and a 0.1 mol / L (NH4)2MoO4 solution, and soaked for 1 hour and 40 minutes respectively for in-situ coprecipitation reaction, where the soaking in the Bi(NO3)3 solution was carried out under 35KHz ultrasonic waves. After the reaction, the composite film material was thoroughly washed with deionized water and subjected to freeze-drying treatment at -55 °C for 8 hours. Finally, the dried composite film material was irradiated under an ultraviolet lamp for 60 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and organic pollutant degradation of the prepared film material are shown in Table 1.

[0054] Figure 2 It is the apparent diagram of the photocatalytic composite film material prepared in Example 1. It can be seen that the composite film material has high transparency. Figure 3 It is the micrograph of the photocatalytic composite film material prepared in Example 1; Figure 4 It is the scanning electron microscope cross-section diagram of the photocatalytic composite film material prepared in Example 1; Figure 5 It is the EDS energy spectrum analysis (Bi, Mo, Ti) of the photocatalytic composite film material prepared in Example 1.

[0055] From Figure 3 and Figure 4 it can be seen that there are uniform and stable pore structures on the surface and cross-section of the composite film, and they are very abundant. The presence of pores does not overly affect the light transmittance of the film, and it can adsorb organic pollutant molecules during the photocatalytic process, indicating that during the photocatalytic reaction, not only can the surface degrade organic pollutants, but the pores in the bulk phase can also adsorb organic pollutants for degradation through their existence, thereby improving the catalytic efficiency of the composite film material.

[0056] Combined with the analysis of the transparency of the film and the EDS energy spectrum results, bismuth molybdate is a nano-sized particle with good dispersibility because there is no agglomeration on the film surface and the transparency is high.

[0057] Example 2 Cellulose acetate (accounting for 1 / 7 of the total mass of the mixed solution I), ethylene glycol as a plasticizer (accounting for 0.05 / 7 of the total mass), and N,N-dimethylformamide solvent were mixed in proportion. Under a stirring speed of 600 rpm, it was stirred at 15 °C for 4 hours to obtain a uniform mixed solution I. Subsequently, the mixed solution I was mixed and stirred with polypyrrole modified with dopamine (the mass ratio of dopamine to polypyrrole was 1:30), and then anatase-type nano-titanium dioxide with an average particle size of 20 nm was added. Stirring continued for 120 minutes and then left standing for 4 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide was 1:0.002:0.002. The prepared film-forming solution was left standing to defoam, and then poured onto glass plates respectively, and a glass rod was used to evenly push the film. It was placed in a fume hood for 2.5 h, with a temperature of 40 °C and a humidity of 10 RH%. After the solvent completely evaporated, the film was taken off from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, the composite film was successively immersed in a 0.08 mol / L Bi(NO3)3 solution and a 0.08 mol / L (NH4)2MoO4 solution, and soaked for 1.5 hours and 30 minutes respectively for in-situ coprecipitation reaction. The soaking in the Bi(NO3)3 solution was carried out under 32 KHz ultrasonic waves. After the reaction, the composite film material was thoroughly washed with deionized water and subjected to freeze-drying treatment at -45 °C for 10 hours. Finally, the dried composite film material was subjected to light treatment under an ultraviolet lamp for 45 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and organic pollutant degradation of the prepared film material are shown in Table 1.

[0058] Example 3 Cellulose acetate (accounting for 1 / 7 of the total mass of mixture I), diethylene glycol as a plasticizer (accounting for 0.08 / 7 of the total mass), and acetone solvent are mixed in proportion. Stir at a speed of 700 rpm at 25 °C for 5 hours to obtain a uniform mixture I. Subsequently, mix mixture I with polypyrrole modified with dopamine (the mass ratio of dopamine to polypyrrole is 1:40) and stir for 120 minutes. Then add anatase-type nano-titanium dioxide with an average particle size of 40 nm, continue to stir for 60 minutes and let it stand for 5 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide is 1:0.008:0.008. Let the prepared film-forming solution stand to defoam, and then pour it on a glass plate respectively, and use a glass rod to evenly push the film. Place it in a fume hood for 3 h, with a temperature of 10 °C and a humidity of 35RH%. After the solvent has completely evaporated, remove the film from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, immerse the composite film successively in 0.12 mol / L Bi(NO3)3 solution and 0.12 mol / L (NH4)2MoO4 solution, and soak for 2.5 hours and 50 minutes respectively for in-situ coprecipitation reaction, where the immersion in Bi(NO3)3 solution is carried out under 38 KHz ultrasonic waves. After the reaction, thoroughly wash the composite film material with deionized water and perform freeze-drying treatment at -35 °C for 12 hours. Finally, perform light treatment on the dried composite film material under an ultraviolet lamp for 75 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and organic pollutant degradation of the prepared film material are shown in Table 1.

[0059] Example 4 Cellulose acetate (accounting for 1 / 10 of the total mass of mixture I), pentaerythritol as a plasticizer (accounting for 0.1 / 10 of the total mass), and N,N-dimethylacetamide solvent were mixed in proportion. Under a stirring speed of 800 rpm, it was stirred at 10 °C for 6 hours to obtain a uniform mixture I. Subsequently, mixture I was mixed and stirred with polypyrrole modified with dopamine (mass ratio of dopamine to polypyrrole was 1:50) for 60 minutes, then anatase-type nano-titanium dioxide with an average particle size of 20 nm was added, and stirring was continued for 90 minutes and then left to stand for 2 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide was 1:0.001:0.001. The prepared film-forming solution was left to stand to remove bubbles, and then poured onto glass plates respectively, and a glass rod was used to evenly push the film. It was placed in a fume hood for 3 h, with a temperature of 40 °C and a humidity of 20RH%. After the solvent completely evaporated, the film was taken off from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, the composite film was successively immersed in 0.15 mol / L Bi(NO3)3 solution and 0.15 mol / L (NH4)2MoO4 solution, and soaked for 3 hours and 60 minutes respectively for in-situ co-precipitation reaction, where the immersion in Bi(NO3)3 solution was carried out under 40KHz ultrasonic wave. After the reaction, the composite film material was thoroughly washed with deionized water and subjected to freeze-drying treatment at -55 °C for 6 hours. Finally, the dried composite film material was subjected to light treatment under an ultraviolet lamp for 90 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency of the prepared film material and the degradation of organic pollutants are shown in Table 1.

[0060] Example 5 Cellulose acetate (accounting for 1 / 6.5 of the total mass of mixture I), glycerol as a plasticizer (accounting for 0.03 / 6.5 of the total mass), and tetrahydrofuran solvent are mixed in proportion. Stir at a speed of 550 rpm at 15 °C for 3.5 hours to obtain a uniform mixture I. Subsequently, mix mixture I with polypyrrole modified with dopamine (mass ratio of dopamine to polypyrrole is 1:25) and stir for 75 minutes. Then add anatase-type nano-titanium dioxide with an average particle size of 50 nm, continue to stir for 105 minutes and let it stand for 3.5 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide is 1:0.004:0.004. Let the prepared film-forming solution stand to defoam, then pour it onto a glass plate respectively, and use a glass rod to evenly spread the film. Place it in a fume hood for 2.2 h at a temperature of 25 °C and a humidity of 45RH%. After the solvent has completely evaporated, remove the film from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, immerse the composite film successively in 0.07 mol / L Bi(NO3)3 solution and 0.07 mol / L (NH4)2MoO4 solution, and soak for 2 hours and 10 minutes respectively for in-situ coprecipitation reaction, where the soaking in Bi(NO3)3 solution is carried out under 35KHz ultrasonic wave. After the reaction, thoroughly wash the composite film material with deionized water and perform freeze-drying treatment at -50 °C for 9 hours. Finally, perform light treatment on the dried composite film material under an ultraviolet lamp for 50 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and degradation of organic pollutants of the prepared film material are shown in Table 1.

[0061] Comparative Example 1 Cellulose acetate (accounting for 1 / 7 of the total mass of mixture I), glycerol as a plasticizer (accounting for 0.02 / 7 of the total mass), and tetrahydrofuran solvent are mixed in proportion. Stir at a speed of 500 rpm at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mix mixture I with polypyrrole modified with dopamine (the mass ratio of dopamine to polypyrrole is 1:20) and stir for 60 minutes. Then add anatase-type nano-titanium dioxide with an average particle size of 50 nm, continue to stir for 90 minutes and let it stand for 3 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide is 1:0.003:0.003. Let the prepared film-forming solution stand to defoam, then pour it on a glass plate respectively, and use a glass rod to evenly push the film. Place it in a fume hood for 2 h, with a temperature of 25 °C and a humidity of 90 RH%. After the solvent has completely evaporated, remove the film from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, immerse the composite film successively in 0.3 mol / L Bi(NO3)3 solution and 0.3 mol / L (NH4)2MoO4 solution, and soak for 2 hours and 50 minutes respectively for in-situ coprecipitation reaction, where the immersion in Bi(NO3)3 solution is carried out under 35 KHz ultrasonic waves. After the reaction, thoroughly wash the composite film material with deionized water and perform freeze-drying treatment at -55 °C for 8 hours. Finally, perform light treatment on the dried composite film material under an ultraviolet lamp for 60 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and degradation of organic pollutants of the prepared film material are shown in Table 1.

[0062] Comparative Example 2 (using polylactic acid to replace cellulose acetate) Mix polylactic acid (with a proportion of 1 / 7 of the total mass), glycerol as a plasticizer (with a proportion of 0.02 / 7 of the total mass) and tetrahydrofuran solvent in proportion, and stir at a stirring speed of 500 rpm at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mix mixture I with polypyrrole modified with dopamine (the mass ratio of dopamine to polypyrrole is 1:20), stir for 60 minutes, then add anatase-type nano-titanium dioxide with an average particle size of 50 nm, continue to stir for 90 minutes and let stand for 3 hours to obtain a film-forming solution II. The mass ratio of polylactic acid, modified polypyrrole and nano-titanium dioxide is 1:0.003:0.003. Let the prepared film-forming solution stand to defoam, then pour it on a glass plate respectively, and use a glass rod to uniformly push the film. Place it in a fume hood for 2 h, with a temperature of 25 °C and a humidity of 45RH%, and take the film off the glass plate after the solvent has completely evaporated to obtain a TiO2 / PPy / polylactic acid composite film. Then, immerse the composite film in a 0.1 mol / L Bi(NO3)3 solution and a 0.1 mol / L (NH4)2MoO4 solution successively, and soak for 1 hour and 40 minutes respectively to carry out an in-situ co-precipitation reaction, where the soaking in the Bi(NO3)3 solution is carried out under 35 KHz ultrasonic waves. After the reaction, thoroughly wash the composite film reactor with deionized water and perform freeze-drying treatment at -55 °C for 8 hours. Finally, perform a light treatment on the dried composite film reactor under an ultraviolet lamp for 60 minutes to obtain the final high-transparency biomass-based photocatalytic composite film reactor. The transparency and organic pollutant degradation of the prepared film reactor are shown in Table 1.

[0063] Comparative Example 3 (using wet phase inversion) Cellulose acetate (accounting for 1 / 7 of the total mass), glycerol as a plasticizer (accounting for 0.02 / 7 of the total mass), and tetrahydrofuran solvent were mixed in proportion. Under a stirring speed of 500 rpm, the mixture was stirred at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mixture I was mixed and stirred with polypyrrole modified with dopamine (mass ratio of dopamine to polypyrrole was 1:20) for 60 minutes. Then, anatase-type nano-titanium dioxide with an average particle size of 50 nm was added, and stirring continued for 90 minutes followed by standing for 3 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, modified polypyrrole, and nano-titanium dioxide was 1:0.003:0.003. The prepared film-forming solution was allowed to stand to remove bubbles and then poured onto glass plates respectively, and a glass rod was used to evenly spread the film. Subsequently, the spread film was immersed in normal-temperature water for wet phase inversion film formation. After the solvent and water exchange was complete, the film was taken off the glass plate and dried to obtain a TiO2 / PPy / cellulose acetate composite film. Then, the composite film was successively immersed in 0.1 mol / L Bi(NO3)3 solution and 0.1 mol / L (NH4)2MoO4 solution, and soaked for 1 hour and 40 minutes respectively for in-situ co-precipitation reaction, where the soaking in Bi(NO3)3 solution was carried out under 35 KHz ultrasonic waves. After the reaction, the composite film reactor was thoroughly washed with deionized water and subjected to freeze-drying treatment at -55 °C for 8 hours. Finally, the dried composite film reactor was subjected to light treatment under an ultraviolet lamp for 60 minutes to obtain the final biomass-based photocatalytic composite film reactor. The transparency of the prepared film reactor and the degradation of organic pollutants are shown in Table 1.

[0064] Comparative Example 4 (without conductive polymer polypyrrole PPy) Cellulose acetate (accounting for 1 / 7 of the total mass), glycerol as a plasticizer (accounting for 0.02 / 7 of the total mass), and tetrahydrofuran solvent are mixed in proportion. Stir at a speed of 500 rpm at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mix mixture I with anatase-type nano-titanium dioxide with an average particle size of 50 nm, stir for 90 minutes and let it stand for 3 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate to nano-titanium dioxide is 1:0.003. Let the prepared film-forming solution stand to defoam, then pour it onto a glass plate respectively, and use a glass rod to evenly push the film. Place it in a fume hood for 2 h, with a temperature of 25 °C and a humidity of 45RH%. After the solvent has completely evaporated, remove the film from the glass plate to obtain a TiO2 / cellulose acetate composite film. Then, immerse the composite film successively in a 0.1 mol / L Bi(NO3)3 solution and a 0.1 mol / L (NH4)2MoO4 solution, and soak for 1 hour and 40 minutes respectively to carry out an in-situ co-precipitation reaction, where the immersion in the Bi(NO3)3 solution is carried out under 35 KHz ultrasonic waves. After the reaction, thoroughly wash the composite film reactor with deionized water and perform freeze-drying treatment at -55 °C for 8 hours. Finally, irradiate the dried composite film reactor under an ultraviolet lamp for 60 minutes to obtain the final high-transparency biomass-based photocatalytic composite film reactor. The transparency of the prepared film reactor and the degradation of organic pollutants are shown in Table 1.

[0065] Comparative Example 5 (polypyrrole not modified) Cellulose acetate (accounting for 1 / 7 of the total mass of mixture I), glycerol as a plasticizer (accounting for 0.02 / 7 of the total mass), and tetrahydrofuran solvent were mixed in proportion. Under a stirring speed of 500 rpm, it was stirred at 20 °C for 3 hours to obtain a uniform mixture I. Subsequently, mixture I was mixed and stirred with polypyrrole for 60 minutes, then anatase-type nano-titanium dioxide with an average particle size of 50 nm was added, and stirring was continued for 90 minutes and then left standing for 3 hours to obtain a film-forming solution II. The mass ratio of cellulose acetate, polypyrrole, and nano-titanium dioxide was 1:0.003:0.003. The prepared film-forming solution was left standing to defoam, and then poured onto a glass plate respectively, and a glass rod was used to uniformly push the film. It was placed in a fume hood for 2 h, with a temperature of 25 °C and a humidity of 45RH%. After the solvent was completely evaporated, the film was taken off from the glass plate to obtain a TiO2 / PPy / cellulose acetate composite film. Then, the composite film was successively immersed in 0.1 mol / L Bi(NO3)3 solution and 0.1 mol / L (NH4)2MoO4 solution, and soaked for 1 hour and 40 minutes respectively for in-situ co-precipitation reaction, and the soaking in Bi(NO3)3 solution was carried out under 35 KHz ultrasonic waves. After the reaction, the composite film material was thoroughly washed with deionized water and freeze-dried at -55 °C for 8 hours. Finally, the dried composite film material was irradiated under an ultraviolet lamp for 60 minutes to obtain the final high-transparency biomass-based photocatalytic composite film material. The transparency and degradation of organic pollutants of the prepared film material are shown in Table 1.

[0066] The performance of the biomass-based Bi2MoO6@TiO2 / PPy photocatalytic composite film materials prepared in Examples 1-5 and Comparative Examples 1-5 was tested, and the test methods are as follows: At room temperature, using a 500 W xenon lamp as a light source, 500 mg of the photocatalytic composite transparent film material was uniformly dispersed in 150 mL of an organic pollutant solution (rhodamine B, methyl orange, phenol or tetracycline) with a concentration of 10 mg / L. The solution was kept uniform by magnetic stirring, and samples were taken every 1 hour. The absorbance of the solution was measured using a UV-visible spectrophotometer to monitor the degradation process, and the reaction continued for 8 hours. The test results are shown in Table 1. Figure 1 It is the photocatalytic degradation result of the photocatalytic composite film material prepared in Example 1.

[0067] According to GB / T2410-2008, at a wavelength of 650 nm, its transmittance and haze were measured using a 721 spectrophotometer.

[0068] Table 1: Transparency (%) of the photocatalytic film materials prepared in Examples 1-6 and results of catalytic degradation of different pollutants (degradation rate / %=(1-C / C0)×100%, C is the concentration, C0 is the initial concentration)

[0069] It can be seen that from Example 1 to Example 4, as the plasticizer addition ratio increases, the film transparency decreases. The optimal mass ratio of the dosage of cellulose acetate to the plasticizer is 1:0.02 - 0.05. When it is lower than 0.02, although the transparency is high, the pores are not abundant. When it is higher than 0.05, the pore structure is abundant but the transparency is not high. Between 0.02 and 0.05, the transparency and the pore structure are integrated.

[0070] The main reason for the low photocatalytic efficiency in Comparative Example 1 is that it uses high-concentration Bi(NO3)3 and (NH4)2MoO4 solutions for in-situ coprecipitation reaction. High-concentration salt solutions are likely to cause the generated Bi2MoO6 nanoparticles to rapidly agglomerate on the film surface, forming large-sized particles instead of uniformly dispersed active sites, thereby reducing the effective catalytic area and hindering mass transfer. In addition, the 90% high-humidity environment during the experiment may delay the solvent evaporation rate, making the phase separation process insufficient, resulting in the collapse or decreased connectivity of the pore structure in the film, making the film turn white and thus reducing the light transmittance of the film, further weakening the efficiency of the photocatalytic reaction.

[0071] In Comparative Example 4, the transparency will be a little higher due to the addition of one less substance, and the photocatalytic effect will be reduced. In Comparative Example 5, the non-modification of polypyrrole will result in poor dispersibility, affecting the film transparency, and the photocatalytic effect will also be slightly weakened.

[0072] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope protected by the technical solution of the present invention.

Claims

1. A method for preparing a biomass-based photocatalytic composite film material, characterized in that: The steps include: (1) uniformly mixing cellulose acetate, a plasticizer and a solvent to obtain a mixed solution I; the plasticizer is at least one selected from ethylene glycol, diethylene glycol, glycerol and pentaerythritol; (2) uniformly mixing the mixed solution I with modified polypyrrole and nano-titanium dioxide in sequence to obtain a film-forming solution II; the modified polypyrrole is dopamine-modified polypyrrole; (3) performing dry phase conversion on the film-forming solution II to obtain a TiO2 / PPy / cellulose acetate transparent composite film material; (4) immersing the transparent composite film material in Bi(NO3)3 solution and (NH4)2MoO4 solution in turn, using an in-situ co-precipitation method to uniformly load bismuth molybdate nanoparticles on the surface and inside of the transparent composite film material, washing after the reaction, and then freeze-drying to obtain a photocatalytic composite film material; (5) The photocatalytic composite film material is subjected to light treatment under ultraviolet light to obtain a highly light-transmitting biomass-based Bi2MoO6@TiO2 / PPy photocatalytic composite film material.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the cellulose acetate to the plasticizer in the mixed solution I of step (1) is 1:0.02-0.

1.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the cellulose acetate, the modified polypyrrole and the nano-titanium dioxide is 1:0.001-0.008:0.001-0.

008.

4. The preparation method according to claim 1, characterized in that: The dopamine-modified polypyrrole in step (2) is obtained by self-polymerization of dopamine on the surface of polypyrrole, and the mass ratio of dopamine to polypyrrole is 1:10-50.

5. The preparation method according to claim 1, characterized in that The titanium dioxide in step (2) is titanium dioxide powder with an average particle size of 20-50 nm.

6. The preparation method according to any one of claims 1 to 5, characterized in that The curing temperature of the dry phase conversion in step (3) is 10-40° C. and the humidity is ≤50RH%.

7. The preparation method according to any one of claims 1 to 5, characterized in that In step (4), the concentration of the Bi(NO3)3 solution is 0.03-0.25 mol / L, and the concentration of the (NH4)2MoO4 solution is 0.03-0.25 mol / L.

8. A biomass-based photocatalytic composite film material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the biomass-based photocatalytic composite membrane material according to claim 8 in degrading organic pollutants.

10. The use according to claim 9, characterized in that: include: The biomass-based photocatalytic composite film material is dispersed in a solution containing organic pollutants and degraded under light.

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