Polymer modified titanium dioxide / graphene nano composite material as well as preparation method and application thereof

Abstract

The invention discloses a polymer modified titanium dioxide / graphene nano composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: modifying titanium dioxide nanoparticles with a polymer to obtain polymer modified titanium dioxide nanoparticles, mixing the polymer modified titanium dioxide nanoparticles with graphene, and calcining to obtain the polymer modified titanium dioxide / graphene nanocomposite. The polymer modified titanium dioxide / graphene nanocomposite prepared by the method has excellent photocatalytic activity, and the process is simple, easy to operate and suitable for large-scale application.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic materials, and in particular to a polymer-modified titanium dioxide / graphene nanocomposite material and a preparation method and application thereof. Background Art

[0002] Titanium dioxide (TiO2) is currently the most widely studied photocatalytic material and has been widely used in photocatalytic technologies across a wide range of applications. The anatase phase of TiO2 has a band gap of 3.2 eV at room temperature, and its responsive wavelength range is limited to the ultraviolet region, which accounts for only 3%–5% of the entire solar spectrum. Forming a composite of TiO2 with highly conductive carbon materials is an effective means of improving photocatalytic efficiency. Graphene, among other materials, offers zero band gap, large surface area, high conductivity, and excellent chemical stability. Therefore, combining TiO2 with graphene can broaden the photoresponsive range, promote the separation of photogenerated electron-hole pairs, and enhance photocatalytic efficiency. Recent studies have typically treated the synthesized TiO2 / graphene oxide composite with a reduction process (such as the addition of a reducing agent or thermal reduction under high temperature and high pressure) to obtain the TiO2 / graphene composite, which inevitably increases experimental costs. For example, patent CN108160064B uses a hydrothermal method (requiring high temperature and high pressure) to prepare a graphene / titania composite material with titanium dioxide nanoparticles uniformly dispersed on graphene sheets. The photocatalytic activity can be adjusted by adjusting the weight ratio of graphene to titanium dioxide in the composite material. Patent CN109651860B obtains a graphene / nano-titania composite material by subjecting a graphene oxide / titania composite precursor to high-temperature reduction under an inert atmosphere. However, these methods have lengthy and cumbersome preparation cycles and offer limited performance improvements.

[0003] Introducing polymers during the synthesis process is an important approach to improving the catalytic performance of titanium dioxide. Polymers can also act as stabilizers, preventing particle aggregation and improving the dispersibility of TiO2 particles in solution. Previous studies have shown that incorporating polymers into TiO2 systems can inhibit charge carrier recombination and enhance performance and catalytic stability. For example, Li et al. (Songtao Li et al. Journal of Physics and Chemistry of Solids. 2019, 129, 92-98.) synthesized TiO2 nanoparticles (TiO2@D-PVA) coated with degraded polyvinyl alcohol (PVA). The photocatalytic activity of TiO2@D-PVA under visible light was 25 times that of conventional P25 nanoparticles. However, after high-temperature calcination, the catalyst exhibited some agglomeration, hindering further improvement in photocatalytic performance. Patent CN202011319951.7 invented a sol-gel in situ growth method to prepare TiO2 / reduced graphene oxide (rGO) photocatalytic material, which is then loaded onto chitosan (CS) doped with polyvinyl alcohol (PVA) through electrostatic adsorption and cross-linking. The prepared chitosan-based graphene / TiO2 composite microspheres (TiO2 / rGO@PVA / CS) have both adsorption properties and photocatalytic degradation effects on organic pollutants. However, the reaction process is complex and time-consuming, which is not conducive to commercial applications.

[0004] In summary, current titanium dioxide photocatalysts either have complex preparation methods and harsh conditions, or their photocatalytic performance needs to be improved. Therefore, in this field, there is a need to develop a photocatalyst with simple operation, controllable process, and easy mass production, which has a better photocatalytic effect. Summary of the Invention

[0005] The main purpose of the present invention is to provide a polymer-modified titanium dioxide / graphene nanocomposite material and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include: One aspect of the present invention provides a method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material, which comprises: modifying titanium dioxide nanoparticles with a polymer to obtain polymer-modified titanium dioxide nanoparticles, mixing the polymer-modified titanium dioxide nanoparticles with graphene, and then calcining to obtain the polymer-modified titanium dioxide / graphene nanocomposite material.

[0007] Another aspect of the present application provides a polymer-modified titanium dioxide / graphene nanocomposite prepared by the aforementioned preparation method, which comprises graphene sheets and polymer-modified titanium dioxide nanoparticles distributed on the surface of the graphene sheets.

[0008] Another aspect of the present application also provides an application of the aforementioned polymer-modified titanium dioxide / graphene nanocomposite in photocatalytic degradation of organic matters.

[0009] Compared with the prior art, the present application has at least the following advantages: The polymer-modified titanium dioxide / graphene nanocomposite provided by the present application can be rapidly and batch-synthesized using a simple and green technical route with industrialized titanium dioxide powder (including commercial P25 titanium dioxide and nano-titanium dioxide), polymer and graphene as raw materials, and the reaction conditions are easy to control, which is suitable for large-scale production. The polymer-modified titanium dioxide / graphene nanocomposite provided by the present application has good photocatalytic performance and good stability. Compared with the titanium dioxide / graphene composite material of the prior art which will be stratified after standing in an aqueous solution for several hours, the composite material prepared by the present application can form a uniform dispersion in an aqueous / ethanol medium, and will not be stratified even after long-term storage, and can be used for photocatalytic degradation of organic pollutants in industrial wastewater with high degradation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0011] Figure 1 The scanning electron microscope image (magnification 10.0k) of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 1 of the present application; Figure 2 The scanning electron microscope image (magnification 8.0k) of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 1 of the present application; Figure 3 The scanning electron microscope image (magnification 11.0k) of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 2 of the present application; Figure 4 The scanning electron microscope image (magnification 100k) of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 2 of the present application; Figure 5This is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposites and TiO2 prepared in Examples 1-5 of the present invention; Figure 6 This is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposite material prepared in Example 1 of the present invention, the catalyst material prepared in Comparative Example 1, and TiO2; Figure 7 This is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposite material prepared in Example 1 of the present invention after being irradiated for different times; Figure 8 This is a comparison of the UV absorption spectra of TiO2 after different illumination times; Figure 9 This is a comparison chart of the photocatalytic degradation of methyl orange by the polymer-modified titanium dioxide / graphene nanocomposite material and TiO2 prepared in Example 1 of the present invention; Figure 10 This is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposites and TiO2 prepared in Example 1 and Examples 6-9 of the present invention after ultraviolet light irradiation for 30 minutes. DETAILED DESCRIPTION

[0012] The present invention will be more fully understood by reading the following detailed description. However, it should be understood that the detailed description disclosed below is merely exemplary of the present invention, and that the present invention may be embodied in a variety of forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as a basis for the claims and as a representative basis for teaching those skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.

[0013] As one aspect of the technical solution of the present invention, a method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material is disclosed, comprising: modifying titanium dioxide nanoparticles with a polymer to obtain polymer-modified titanium dioxide nanoparticles; mixing the polymer-modified titanium dioxide nanoparticles with graphene; and then calcining the mixture to obtain a polymer-modified titanium dioxide / graphene nanocomposite material.

[0014] The present invention uses graphene, which is simpler and more convenient to prepare than graphene oxide, thereby simplifying the entire preparation process; at the same time, graphene oxide is easily decomposed when calcined in air, and calcining in an inert atmosphere will increase the preparation cost.

[0015] In some embodiments, the preparation method comprises: Mixing titanium dioxide nanoparticles, a polymer, and water to obtain a polymer-modified titanium dioxide nanoparticle dispersion; dispersing graphene in water to form a graphene dispersion; The graphene dispersion is mixed with the polymer-modified titanium dioxide nanoparticle dispersion to obtain a polymer-modified titanium dioxide / graphene dispersion, which is then calcined to obtain a polymer-modified titanium dioxide / graphene nanocomposite material.

[0016] In some preferred embodiments, the preparation method comprises: uniformly dispersing titanium dioxide nanoparticles in water to obtain a titanium dioxide nanoparticle dispersion; then adding a polymer and uniformly dispersing the dispersion to form the polymer-modified titanium dioxide nanoparticle dispersion. While water is used as the dispersion liquid in the present invention, replacing it with an ethanol solution may result in the formation of other substances, such as beads, with the polymer used later.

[0017] In some more preferred embodiments, the mass concentration of the titanium dioxide nanoparticle dispersion is 0.5 wt % to 5.0 wt %.

[0018] In some more preferred embodiments, the mass of the polymer is 1% to 20% of the mass of the titanium dioxide nanoparticles.

[0019] In some more preferred embodiments, the dispersion method includes ultrasonic dispersion, but is not limited thereto, and the ultrasonic dispersion time is 0.5 to 2 h.

[0020] In some preferred embodiments, the titanium dioxide nanoparticles are titanium dioxide nanoparticles containing a single rutile crystal form, titanium dioxide nanoparticles containing a single anatase crystal form, or titanium dioxide nanoparticles containing both anatase and rutile crystal forms, and the particle size of the titanium dioxide nanoparticles is 20 to 400 nm. When the nanoparticle size is too small, the nanoparticles easily agglomerate. When the nanoparticle size is too large, the specific surface area is small, resulting in fewer active sites. Therefore, a nanoparticle size of 20 to 400 nm is a suitable range. The ratio of anatase to rutile crystal forms in the titanium dioxide used in the present invention can be 85%:15%, and the type of crystal form has no significant effect on the morphology of the synthesized composite.

[0021] In some preferred embodiments, the polymer includes any one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinyl pyrrolidone, and sodium polystyrene sulfonate.

[0022] In some preferred embodiments, the weight average molecular weight of the polymer is 10,000-3,000,000.

[0023] In some preferred embodiments, the mass concentration of the graphene dispersion is 0.1 wt% to 2.0 wt%.

[0024] In some preferred embodiments, the graphene can be purchased powder or prepared in-house; the graphene flake size is 0.1-5 μm, and its thickness is ≤10 nm. When the graphene is smaller in size, the resulting composite material has higher photocatalytic performance.

[0025] In some preferred embodiments, the dispersion method includes ultrasonic dispersion, but is not limited thereto, and the ultrasonic dispersion time is 0.5 to 2 h.

[0026] In some preferred embodiments, the preparation method includes: mixing a graphene dispersion with the polymer-modified titanium dioxide nanoparticle dispersion, and obtaining a polymer-modified titanium dioxide / graphene dispersion after ultrasonic treatment; filtering, drying, and grinding the polymer-modified titanium dioxide / graphene dispersion to obtain a polymer-modified titanium dioxide / graphene composite, and then calcining to obtain the polymer-modified titanium dioxide / graphene nanocomposite material.

[0027] In some more preferred embodiments, the ultrasonic treatment time is 1 to 3 hours.

[0028] In some more preferred embodiments, the drying temperature is 60-80° C., and the drying time is 2-3 h.

[0029] In some embodiments, the mass ratio of the titanium dioxide nanoparticles to graphene is 100:1 to 2000:1.

[0030] In some embodiments, the calcination process conditions include: heating to 300-500° C. at a heating rate of 1-3° C. / min and calcining for 1-5 h.

[0031] In some more specific embodiments, the method for preparing the polymer-modified titanium dioxide / graphene nanocomposite material comprises the following steps: (1) Titanium dioxide nanoparticles are dispersed in water and uniformly dispersed by ultrasonication to form a titanium dioxide nanoparticle dispersion; a certain amount of polymer is then added and ultrasonicated for 0.5 to 2 h to obtain a polymer-modified titanium dioxide nanoparticle dispersion; (2) Graphene powder is dispersed in water and ultrasonically treated for 0.5 to 2 h to form a graphene dispersion; (3) mixing the polymer-modified titanium dioxide nanoparticle dispersion obtained in step (1) and the graphene dispersion obtained in step (2), and ultrasonically treating them for 1 to 3 hours to obtain a polymer-modified titanium dioxide / graphene dispersion; then filtering and drying them at 60 to 80° C. for 2 to 3 hours, and then fully grinding them to obtain a polymer-modified titanium dioxide / graphene composite; (4) The composite particles (polymer-modified titanium dioxide / graphene composite) in step (3) are heated to 300-500°C at a rate of 1-3°C / min in a static air atmosphere and calcined at a constant temperature for 1-5 h to obtain a polymer-modified titanium dioxide / graphene nanocomposite material.

[0032] As another aspect of the technical solution of the present invention, the polymer-modified titanium dioxide / graphene nanocomposite material prepared by the aforementioned preparation method comprises graphene sheets and polymer-modified titanium dioxide nanoparticles distributed on the surface of the graphene sheets.

[0033] As another aspect of the technical solution of the present invention, it involves the application of the aforementioned polymer-modified titanium dioxide / graphene nanocomposite material in the photocatalytic degradation of organic matter.

[0034] In some embodiments, the organic matter includes but is not limited to any one or a combination of two or more of methyl orange, rhodamine B, methylene blue, acid orange 7, and Congo red.

[0035] In summary, the present invention utilizes titanium dioxide, a polymer, and graphene as raw materials, and produces a polymer-modified titanium dioxide / graphene nanocomposite through a series of processes, including ultrasonic mixing, drying, and sintering. This composite material can be used in applications such as photocatalytic treatment of organic matter in industrial wastewater. Organic dyes found in wastewater include methyl orange, rhodamine B, methylene blue, acid orange 7, and Congo red. The preparation method of the present invention is simple, easy to operate, and readily applicable on a large scale.

[0036] The present invention is further illustrated by way of examples below, but the invention is not limited to the scope of the examples. The reagents and raw materials used in the following examples are commercially available, and the experimental methods where specific conditions are not specified are generally carried out under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0037] Example 1 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material comprises the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w= 105000) and ultrasonicated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite powder sample.

[0038] like Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 The scanning electron microscope images of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 1 at different angles show that titanium dioxide nanoparticles are distributed on both sides of the graphene sheet. Due to the small size of the graphene used and the complete distribution of titanium dioxide nanoparticles on the graphene surface, it is difficult to observe individual graphene sheets.

[0039] Example 2 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the mass ratio of titanium dioxide powder to graphene is different, and the size of graphene is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w = 105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flakes were 5 μm in size and 5 nm in thickness). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 100:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite powder sample.

[0040] like Figure 3 andFigure 4 As shown, Figure 3 and Figure 4 These are scanning electron microscope images of the polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite material obtained in Example 2 at different angles. Large-sized graphene was used in the experiment, and it can be clearly observed that titanium dioxide nanoparticles are distributed on both sides of the graphene sheet.

[0041] Example 3 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the mass ratio of titanium dioxide powder to graphene is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w = 105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 200:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite powder sample.

[0042] Example 4 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the mass ratio of titanium dioxide powder to graphene is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w= 105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 500:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite powder sample.

[0043] Example 5 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the mass ratio of titanium dioxide powder to graphene is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w = 105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 2000:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl alcohol-modified titanium dioxide / graphene nanocomposite powder sample.

[0044] The polymer modified titanium dioxide / graphene nanocomposite catalyst and TiO2 in Examples 1-5 were tested by UV-visible absorption spectra. Figure 5 As shown. Figure 5 It can be seen that the ultraviolet-visible light absorption intensity of the catalysts in Examples 1-5 is significantly greater than that of single TiO2, indicating that the combination of polymer-modified titanium dioxide and graphene is beneficial to improving the light absorption intensity, and the light absorption intensity can be adjusted by adjusting the mass ratio of titanium dioxide to graphene.

[0045] Example 6 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the polymer is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyethylene glycol (molecular weight M w = 10000) and ultrasonicated for 30 minutes to obtain a polyethylene glycol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyethylene glycol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and ultrasonicated for 1 hour to obtain a polyethylene glycol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyethylene glycol-modified titanium dioxide / graphene nanocomposite powder sample.

[0046] Example 7 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the polymer is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyacrylamide (molecular weight M w = 3000000) and ultrasonicated for 30 minutes to obtain a polyacrylamide-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyacrylamide-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and ultrasonicated for 1 hour to obtain a polyacrylamide-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyacrylamide-modified titanium dioxide / graphene nanocomposite powder sample.

[0047] Example 8 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the polymer is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl pyrrolidone (molecular weight M w =1300000) and ultrasonicated for 30 minutes to obtain a polyvinyl pyrrolidone-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl pyrrolidone-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and ultrasonicated for 1 hour to obtain a polyvinyl pyrrolidone-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a polyvinyl pyrrolidone-modified titanium dioxide / graphene nanocomposite powder sample.

[0048] Example 9 A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material (compared with Example 1, the polymer is different), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of sodium polystyrene sulfonate (molecular weight M w =70000) and ultrasonicated for 30 minutes to obtain a sodium polystyrene sulfonate-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The sodium polystyrene sulfonate-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and ultrasonicated for 1 hour to obtain a sodium polystyrene sulfonate-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a sodium polystyrene sulfonate-modified titanium dioxide / graphene nanocomposite powder sample.

[0049] Example 10 Compared with Example 1, the difference is that the temperature is increased to 300° C. at a rate of 1° C. / min and calcined at a constant temperature for 1 h in a static air atmosphere.

[0050] Example 11 Compared with Example 1, the difference is that the temperature is increased to 500° C. at a rate of 3° C. / min and calcined at a constant temperature for 5 h in a static air atmosphere.

[0051] Comparative Example 1 A method for preparing a catalyst material (compared with Example 1, without calcination), comprising the following steps: 1 g of titanium dioxide powder was dispersed in 200 mL of water and sonicated for 30 minutes to achieve uniform dispersion, forming a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (PVA) was then added and sonicated for 30 minutes to obtain a PVA-modified titanium dioxide aqueous solution. 1 g of graphene powder was dispersed in 100 mL of water and sonicated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flakes were 0.5 μm in size and 5 nm in thickness). The PVA-modified titanium dioxide dispersion and the graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 1000:1) and sonicated for 1 hour to obtain a PVA-modified titanium dioxide / graphene dispersion. The mixture was then filtered, dried at 60°C for 2 hours, and thoroughly ground to obtain a PVA-modified titanium dioxide / graphene powder sample.

[0052] like Figure 6 As shown, Figure 6 The UV absorption spectra of the polyvinyl alcohol modified titanium dioxide / graphene nanocomposite material (400°C for 3 h) in Example 1, the catalyst material (uncalcined) in Comparative Example 1, and TiO2 are compared. Figure 6 It can be seen that after the polyvinyl alcohol modified titanium dioxide / graphene powder sample is calcined at a certain temperature, the absorption intensity of ultraviolet-visible light increases significantly, which shows that the calcination process can enhance the interaction between titanium dioxide and graphene, which is beneficial to improving the photocatalytic efficiency.

[0053] Comparative Example 2 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w= 105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 50:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a composite powder sample.

[0054] Comparative Example 3 1 g of titanium dioxide powder was dispersed in 200 mL of water and ultrasonicated for 30 min to form a titanium dioxide dispersion. 0.05 g of polyvinyl alcohol (molecular weight M w =105000) and ultrasonically treated for 30 minutes to obtain a polyvinyl alcohol-modified titanium dioxide aqueous dispersion. 1 g of graphene powder was dispersed in 100 mL of water and ultrasonically treated for 30 minutes to form a 1% (mass fraction) graphene dispersion (graphene flake size was 0.5 μm and thickness was 5 nm). The polyvinyl alcohol-modified titanium dioxide dispersion and graphene dispersion were mixed (mass ratio of titanium dioxide powder to graphene was 2500:1) and ultrasonicated for 1 hour to obtain a polyvinyl alcohol-modified titanium dioxide / graphene dispersion. The mixture was then filtered and dried at 60°C for 2 hours. After thorough grinding, the mixture was heated to 400°C in a static air atmosphere at a rate of 2°C / min and calcined for 3 hours to obtain a composite powder sample.

[0055] Experimental testing The polymer-modified titanium dioxide / graphene nanocomposites and TiO2 described in Examples 1 and 6-9 were tested for photocatalytic degradation of methyl orange. The specific testing method is as follows: Photocatalytic performance testing was conducted in a darkroom using a 100W LED light (365 nm wavelength) as the light source. A 10 mg / L methyl orange solution was used as the simulated wastewater. 50 mL of the methyl orange solution and 50 mg of the prepared photocatalyst (10 mg / mL) were added to a 100 mL beaker. Ultrasonication was performed at room temperature for 3 minutes in the dark to establish adsorption-desorption equilibrium. The light source was then turned on and the distance from the light source was adjusted to 10 cm for illumination. Samples were collected at regular intervals during the test, centrifuged, and the supernatant was collected for UV absorption spectroscopy within the 200-800 nm range. The photocatalytic methyl orange removal efficiency (δ%) was calculated using the following formula.

[0056] ; wherein: δ is the removal rate (%) of the methyl orange solution; A 0 is the absorbance of the initial methyl orange solution at 464 nm; A x is the absorbance of the methyl orange solution at 464 nm at the time of sampling; x

[0057] As shown in Figure 7 to Figure 9 , Figure 7 is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 1 after different times of illumination, Figure 8 is a comparison chart of the ultraviolet absorption spectra of TiO2 after different times of illumination, Figure 9 is a comparison chart of the photocatalytic degradation of methyl orange by the polymer-modified titanium dioxide / graphene nanocomposite prepared in Example 1 and TiO2; as shown in Figure 7 to Figure 9 It can be seen that the efficiency of the polyvinyl alcohol-modified titanium dioxide and graphene composite in degrading methyl orange is significantly improved. The degradation rate of methyl orange by Example 1 reached 96.45% after 30 min of illumination, showing good photocatalytic effect, while the degradation rate of methyl orange by single TiO2 was 84.69% in 30 min.

[0058] As shown in Figure 10 , Figure 10 is a comparison chart of the ultraviolet absorption spectra of the polymer-modified titanium dioxide / graphene nanocomposites prepared in Example 1, Example 6-9 and TiO2 after 30 min of ultraviolet illumination. Figure 10 The results show that the degradation rates of the polyvinyl alcohol-modified titanium dioxide / graphene, polyethylene glycol-modified titanium dioxide / graphene, polyacrylamide-modified titanium dioxide / graphene, polyvinylpyrrolidone-modified titanium dioxide / graphene and sodium polystyrene sulfonate-modified titanium dioxide / graphene after 30 min of ultraviolet illumination were 96.45%, 92.47%, 97.95%, 89.79% and 86.78%, respectively, all of which were greater than the photocatalytic efficiency of TiO2 (84.69%). These results show that the polymer-modified titanium dioxide / graphene nanocomposite provided by the present application is an excellent photocatalyst. In addition, the composite materials prepared in Comparative Example 2 and Comparative Example 3 were subjected to photocatalytic tests, and the degradation rates of methyl orange after 30 min of ultraviolet illumination were less than that of single TiO2, indicating that too much or too little graphene is not conducive to improving the photocatalytic performance.

[0059] ​In addition, the inventors of the present application also refer to the foregoing examples, and test other raw materials, process operations and process conditions described in the specification, and all obtain relatively ideal results.

[0060] The above-described examples only express several embodiments of the present application, which are described in a more specific and detailed manner, but cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method for preparing a polymer-modified titanium dioxide / graphene nanocomposite material, characterized in that: include: Titanium dioxide nanoparticles are modified with a polymer to obtain polymer-modified titanium dioxide nanoparticles, and the polymer-modified titanium dioxide nanoparticles are mixed with graphene, followed by calcination to obtain a polymer-modified titanium dioxide / graphene nanocomposite material.

2. The preparation method according to claim 1, characterized in that include: mixing titanium dioxide nanoparticles, a polymer, and water to obtain a polymer-modified titanium dioxide nanoparticle dispersion; dispersing graphene in water to form a graphene dispersion; The graphene dispersion is mixed with the polymer-modified titanium dioxide nanoparticle dispersion to obtain a polymer-modified titanium dioxide / graphene dispersion, which is then calcined to obtain a polymer-modified titanium dioxide / graphene nanocomposite material.

3. The preparation method according to claim 2, characterized in that include: uniformly dispersing titanium dioxide nanoparticles in water to obtain a titanium dioxide nanoparticle dispersion, and then adding a polymer and uniformly dispersing the polymer to form the polymer-modified titanium dioxide nanoparticle dispersion; Preferably, the mass concentration of the titanium dioxide nanoparticle dispersion is 0.5wt%~5.0wt%; Preferably, the mass of the polymer is 1% to 20% of the mass of the titanium dioxide nanoparticles; Preferably, the dispersion method includes ultrasonic dispersion, and the ultrasonic dispersion time is 0.5 to 2 hours.

4. The preparation method according to claim 2, characterized in that The titanium dioxide nanoparticles are titanium dioxide nanoparticles containing a single rutile crystal form, titanium dioxide nanoparticles containing a single anatase crystal form, or titanium dioxide nanoparticles containing both anatase and rutile crystal forms, and the particle size of the titanium dioxide nanoparticles is 20 to 400 nm; And / or, the polymer includes any one or a combination of two or more of polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinyl pyrrolidone, and sodium polystyrene sulfonate; And / or, the weight average molecular weight of the polymer is 10,000-3,000,000.

5. The preparation method according to claim 2, characterized in that The mass concentration of the graphene dispersion is 0.1wt%~2.0wt%; And / or, the graphene sheet size is 0.1-5 μm and the thickness is ≤10 nm; And / or, the dispersion method includes ultrasonic dispersion, and the ultrasonic dispersion time is 0.5 to 2 hours.

6. The preparation method according to claim 2, characterized in that include: The graphene dispersion is mixed with the polymer-modified titanium dioxide nanoparticle dispersion, and subjected to ultrasonic treatment to obtain a polymer-modified titanium dioxide / graphene dispersion; the polymer-modified titanium dioxide / graphene dispersion is filtered, dried, and ground to obtain a polymer-modified titanium dioxide / graphene composite, which is then calcined to obtain the polymer-modified titanium dioxide / graphene nanocomposite material; Preferably, the ultrasonic treatment time is 1 to 3 hours; Preferably, the drying temperature is 60-80° C., and the drying time is 2-3 h.

7. The preparation method according to claim 1, characterized in that The mass ratio of the titanium dioxide nanoparticles to the graphene is 100:1 to 2000:

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8. The preparation method according to claim 1, characterized in that The calcination process conditions include: heating to 300-500° C. at a heating rate of 1-3° C. / min and calcining for 1-5 hours.

9. The polymer-modified titanium dioxide / graphene nanocomposite material prepared by the preparation method according to any one of claims 1 to 8, comprising a graphene sheet and polymer-modified titanium dioxide nanoparticles distributed on the surface of the graphene sheet.

10. Use of the polymer-modified titanium dioxide / graphene nanocomposite material according to claim 9 in photocatalytic degradation of organic matter; Preferably, the organic matter includes any one or a combination of two or more of methyl orange, rhodamine B, methylene blue, acid orange 7, and Congo red.

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