Preparation method of modified PAM hydrogel composite photocatalyst

Abstract

The invention discloses a preparation method of a modified PAM hydrogel composite photocatalyst, and belongs to the technical field of photocatalyst preparation. The preparation method comprises the following steps: mixing acrylamide, sodium carboxymethyl cellulose, N, N '-methylene bisacrylamide, g-C3N5, water and an initiator, and carrying out a reaction under a heat preservation condition to obtain a precursor; and calcining the precursor to obtain the modified PAM hydrogel composite photocatalyst. The prepared modified PAM hydrogel composite photocatalyst is used for degrading methylene blue in a water body under visible light and has good degradation performance, and the degradation rate can reach 91.7%.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalyst preparation, and in particular to a method for preparing a modified PAM hydrogel composite photocatalyst. Background Art

[0002] As environmental pollution becomes increasingly serious, it is urgent to develop efficient and sustainable environmental purification technologies. Photocatalytic technology has great potential in the fields of pollutant degradation and photocatalytic water splitting to produce hydrogen because it can use solar energy to drive chemical reactions. At the same time, photocatalytic degradation technology is one of the important technologies for treating organic pollutants in water, and is very promising in treating wastewater containing low-concentration organic dye pollutants. As a new type of material, hydrogel composites have good prospects in various fields. Hydrogel composite photocatalysts combine the unique properties of hydrogels with the photocatalytic activity of photocatalysts and have become a research hotspot. However, the existing hydrogel composite materials have poor degradation effects on organic dye pollutants. It is very necessary to develop hydrogel composite photocatalysts with excellent degradation effects on organic dye pollutants. Summary of the invention

[0003] The purpose of the present invention is to provide a modified PAM hydrogel composite photocatalyst (specifically, carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 A method for preparing a photocatalyst) is provided to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: a method for preparing a modified PAM hydrogel composite photocatalyst, comprising the following steps:

[0006] Acrylamide (PAM), sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5 , water and an initiator are mixed and reacted under heat preservation conditions to obtain a precursor; the precursor is calcined to obtain the modified PAM hydrogel composite photocatalyst.

[0007] Under the condition of heat preservation, the initiator releases free radicals when heated, which initiates the polymerization of monomers to obtain the precursor (loaded gC 3 N 5 Sodium carboxymethyl cellulose modified PAM hydrogel, or uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5Photocatalyst). The precursor is calcined to obtain a modified PAM hydrogel composite photocatalyst. PAM hydrogel has a good network structure. The addition of carboxymethyl cellulose improves its network structure and increases its swelling rate (the carboxylic acid and hydroxyl groups in carboxymethyl cellulose can significantly enhance the hydrophilicity of the PAM hydrogel network and increase its swelling rate). Such a structure can be gC 3 N 5 Provides a large number of anchoring sites, which can bind gC 3 N 5 Evenly dispersed within its network, preventing gC 3 N 5 The particles agglomerate, increase the specific surface area of ​​the photocatalyst, provide more active sites for the photocatalytic reaction, and improve the photocatalytic efficiency; the calcined gel material has the characteristics of high porosity and high specific surface area, so that pollutants are enriched on the surface of the photocatalyst, the adsorption capacity of pollutants is improved, the reaction probability is increased, and the photocatalytic reaction is further promoted. In addition, the modified PAM hydrogel composite photocatalyst of the present invention is also conducive to the separation and transmission of photogenerated carriers (electron-hole pairs), reducing their recombination probability, thereby enhancing the photocatalytic activity and improving the efficiency of the photocatalytic reaction.

[0008] Furthermore, the gC 3 N 5 The mass of the initiator is 0.3-1.8% of the sum of the mass of the acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water.

[0009] Furthermore, taking the sum of the masses of acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water as 100%, the mass percentages of acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water are 5.740-10.860%, 0.700-2.060%, 0.005-0.037%, 0.110-0.280% and 86.763-93.165%, respectively.

[0010] Furthermore, the initiator is ammonium persulfate.

[0011] Furthermore, the insulation temperature is 40-60° C., and the reaction time is 3.5-5.5 h.

[0012] Furthermore, the calcination temperature is 340-420° C. and the calcination time is 1-4 hours.

[0013] Furthermore, the acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5, water and initiator are mixed, and reacted under heat preservation conditions to obtain a precursor comprising: acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5 The mixture is mixed with water, stirred evenly, and then nitrogen is introduced to remove oxygen. The mixture is then preheated under sealed conditions. After preheating to the insulation temperature, an initiator is added, and the mixture is reacted at the insulation temperature to obtain a precursor.

[0014] Furthermore, the oxygen exhaust time is 30 minutes.

[0015] Furthermore, the reaction at the insulation temperature is carried out under sealed conditions.

[0016] The second technical solution of the present invention: the modified PAM hydrogel composite photocatalyst prepared by the above-mentioned preparation method.

[0017] The third technical solution of the present invention: Application of the modified PAM hydrogel composite photocatalyst in photocatalytic degradation of organic dyes.

[0018] Furthermore, the organic dye is methylene blue.

[0019] Furthermore, the step of photocatalytically degrading the organic dye comprises:

[0020] The modified PAM hydrogel composite photocatalyst is added into wastewater containing organic dyes to carry out degradation reaction under light conditions.

[0021] The present invention discloses the following technical effects:

[0022] The present invention provides a modified PAM hydrogel composite photocatalyst (i.e., carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The modified PAM hydrogel composite photocatalyst prepared by the method of the present invention is used to degrade methylene blue in water under visible light, and has good degradation performance, and the degradation rate can reach 91.7%.

[0023] The modified PAM hydrogel composite photocatalyst of the present invention is easy to separate and recycle. The composite photocatalyst separated after the photocatalytic degradation reaction can be reused many times after simple cleaning and activation treatment, and the loss of photocatalytic activity is small, which meets the requirements of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (2) of Example 7 3 N 5 Photocatalyst, calcined carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (3) of Example 7 3 N 5 Photocatalyst, the calcined carboxymethyl cellulose modified PAM hydrogel obtained in Comparative Example 2, the carboxymethyl cellulose modified PAM hydrogel obtained in Example 4 (i.e., the uncalcined carboxymethyl cellulose modified PAM hydrogel), and the raw material gC 3 N 5 Infrared spectrum;

[0026] Figure 2 The carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (3) of Example 7 3 N 5 Scanning electron microscope images of the photocatalyst at different magnifications, where the scale bar in (a) is 100 μm, the scale bar in (b) is 20 μm, and the scale bar in (c) is 10 μm;

[0027] Figure 3 As raw material gC 3 N 5 , the calcined carboxymethyl cellulose modified PAM hydrogel obtained in Comparative Example 2 and the calcined carboxymethyl cellulose modified PAM hydrogel obtained in step (3) of Example 7 composite gC 3 N 5 Photoluminescence spectra of photocatalysts. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0031] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0032] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0033] The room temperature or normal temperature involved in the following embodiments and comparative examples of the present invention specifically refers to 20-30°C.

[0034] The “parts” involved in the following examples and comparative examples of the present invention are all “parts by mass”.

[0035] The raw materials used in the following examples and comparative examples of the present invention are all common commercially available products.

[0036] Example 1

[0037] The preparation steps of carboxymethyl cellulose modified PAM hydrogel are as follows:

[0038] (1) According to mass percentage, weigh 8.370% acrylamide, 0.700% sodium carboxymethyl cellulose, 0.210% ammonium persulfate, 90.713% distilled water and 0.007% N,N'-methylenebisacrylamide;

[0039] (2) Acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes. The beaker was sealed with plastic wrap, placed in a water bath and preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for 4 hours. After the reaction was completed, it was cooled to room temperature to obtain carboxymethyl cellulose modified PAM hydrogel.

[0040] Example 2

[0041] The preparation steps of carboxymethyl cellulose modified PAM hydrogel are as follows:

[0042] (1) According to mass percentage, weigh 8.320% acrylamide, 1.390% sodium carboxymethyl cellulose, 0.210% ammonium persulfate, 90.073% distilled water and 0.007% N,N'-methylenebisacrylamide;

[0043] (2) Acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes. The beaker was sealed with plastic wrap, placed in a water bath and preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for 4 hours. After the reaction was completed, it was cooled to room temperature to obtain carboxymethyl cellulose modified PAM hydrogel.

[0044] Example 3

[0045] The preparation steps of carboxymethyl cellulose modified PAM hydrogel are as follows:

[0046] (1) According to mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.290% distilled water and 0.010% N,N'-methylenebisacrylamide;

[0047] (2) Acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes. The beaker was sealed with plastic wrap, placed in a water bath and preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain carboxymethyl cellulose modified PAM hydrogel.

[0048] Example 4

[0049] The preparation steps of carboxymethyl cellulose modified PAM hydrogel are as follows:

[0050] (1) According to mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.282% distilled water and 0.018% N,N'-methylenebisacrylamide;

[0051] (2) Acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes. The beaker was sealed with plastic wrap, placed in a water bath and preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain carboxymethyl cellulose modified PAM hydrogel.

[0052] Comparative Example 1

[0053] The preparation steps of PAM hydrogel are as follows:

[0054] (1) According to mass percentage, weigh 7.300% acrylamide, 0.180% ammonium persulfate, 92.502% distilled water and 0.018% N,N'-methylenebisacrylamide;

[0055] (2) Acrylamide, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes. The beaker was sealed with plastic wrap, placed in a water bath and preheated to 50°C, then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain PAM hydrogel.

[0056] Test Example 1

[0057] The carboxymethyl cellulose modified PAM hydrogels prepared in Examples 1-4 and the PAM hydrogel prepared in Comparative Example 1 were subjected to a swelling test. The specific method was as follows: the hydrogel samples were placed in distilled water, and the samples were taken out and weighed at regular intervals until the samples reached saturation swelling due to water absorption, and the swelling rate was calculated according to the following formula.

[0058] Swelling rate = (mass of hydrogel after swell to saturation with water absorption - mass of hydrogel before water absorption) / mass of hydrogel before water absorption × 100%

[0059] After testing, the swelling rate of the carboxymethyl cellulose modified PAM hydrogel prepared in Example 1 is 434%, the swelling rate of the carboxymethyl cellulose modified PAM hydrogel prepared in Example 2 is 982%, the swelling rate of the carboxymethyl cellulose modified PAM hydrogel prepared in Example 3 is 1236%, the swelling rate of the carboxymethyl cellulose modified PAM hydrogel prepared in Example 4 is 1473%, and the swelling rate of the PAM hydrogel prepared in Comparative Example 1 is 155%. From the test results, it can be seen that the hydrogel has a good network structure. Under the same conditions, the swelling rate of the hydrogel synthesized by pure acrylamide is only 155%. The addition of carboxymethyl cellulose improves its network structure, so that its swelling rate can reach 1473%. Such a structure can be gC 3 N 5 Provides a large number of anchoring sites, which can bind gC 3 N 5 Evenly dispersed within its network, preventing gC 3 N 5 The particles agglomerate, increase the specific surface area of ​​the photocatalyst, and improve the photocatalytic efficiency. That is, the swelling rate of the hydrogel has an important influence on its loading performance, which in turn affects the hydrogel composite gC prepared based on the hydrogel. 3 N 5 The performance of the photocatalyst, the greater the swelling rate of the hydrogel, the more conducive it is to obtain a high-performance hydrogel composite gC 3 N 5 In Examples 1-4 in which carboxymethyl cellulose was added, the swelling rate of the carboxymethyl cellulose modified PAM hydrogel prepared in Example 4 was the largest. Therefore, based on the preparation conditions of Example 4, the carboxymethyl cellulose modified PAM hydrogel composite was further prepared. 3 N 5 Preparation of photocatalyst (i.e. modified PAM hydrogel composite photocatalyst).

[0060] Example 5

[0061] Modified PAM hydrogel composite photocatalyst (i.e., carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The preparation of photocatalyst) is as follows:

[0062] (1) According to the mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.282% distilled water and 0.018% N,N'-methylenebisacrylamide (the sum is 100%); then weigh 0.6% of the sum of the mass of acrylamide, sodium carboxymethyl cellulose, ammonium persulfate, distilled water and N,N'-methylenebisacrylamide. 3 N 5 ;

[0063] (2) acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5 and distilled water in a beaker, stirred with a glass rod until uniform, then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes, and then the beaker was sealed with plastic wrap, placed in a water bath pot preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added, stirring while adding. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain a precursor (denoted as uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalysts);

[0064] (3) The precursor was calcined at 400 °C for 2 h to obtain a carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalyst (denoted as calcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 photocatalyst).

[0065] Example 6

[0066] Modified PAM hydrogel composite photocatalyst (i.e., carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The preparation of photocatalyst) is as follows:

[0067] (1) According to the mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.282% distilled water and 0.018% N,N'-methylenebisacrylamide (the sum is 100%); then weigh 1.2% of the sum of the mass of acrylamide, sodium carboxymethyl cellulose, ammonium persulfate, distilled water and N,N'-methylenebisacrylamide. 3 N 5 ;

[0068] (2) acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5and distilled water in a beaker, stirred with a glass rod until uniform, then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes, and then the beaker was sealed with plastic wrap, placed in a water bath pot preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added, stirring while adding. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain a precursor (denoted as uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalysts);

[0069] (3) The precursor was calcined at 380 °C for 1 h to obtain a carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalyst (denoted as calcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 photocatalyst).

[0070] Example 7

[0071] Modified PAM hydrogel composite photocatalyst (i.e., carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The preparation of photocatalyst) is as follows:

[0072] (1) According to the mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.282% distilled water and 0.018% N,N'-methylenebisacrylamide (the sum is 100%); then weigh 1.2% of the sum of the mass of acrylamide, sodium carboxymethyl cellulose, ammonium persulfate, distilled water and N,N'-methylenebisacrylamide. 3 N 5 ;

[0073] (2) acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, gC 3 N 5 and distilled water in a beaker, stirred with a glass rod until uniform, then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes, and then the beaker was sealed with plastic wrap, placed in a water bath pot preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added, stirring while adding. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain a precursor recorded as uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalysts);

[0074] (3) The precursor was calcined at 380 °C for 2 h to obtain a carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 Photocatalyst (denoted as calcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 photocatalyst).

[0075] Comparative Example 2

[0076] The preparation steps of calcined carboxymethyl cellulose modified PAM hydrogel are as follows:

[0077] (1) According to mass percentage, weigh 7.300% acrylamide, 1.220% sodium carboxymethyl cellulose, 0.180% ammonium persulfate, 91.282% distilled water and 0.018% N,N'-methylenebisacrylamide;

[0078] (2) acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide and distilled water were mixed in a beaker, stirred with a glass rod until uniform, and then stirred with a magnetic stirrer for 30 minutes, and nitrogen was introduced to remove oxygen for 30 minutes, and then the beaker was sealed with plastic wrap, placed in a water bath pot and preheated to 50°C, and then the plastic wrap was removed and the initiator ammonium persulfate was added while stirring. After the addition was completed, the beaker was sealed with plastic wrap again and kept at 50°C for reaction for 4.5 hours. After the reaction was completed, it was cooled to room temperature to obtain a carboxymethyl cellulose modified PAM hydrogel;

[0079] (3) The carboxymethyl cellulose modified PAM hydrogel is calcined at 380° C. for 2 h to obtain a calcined carboxymethyl cellulose modified PAM hydrogel.

[0080] Test Example 2

[0081] Structure and performance characterization

[0082] (1) Infrared spectroscopy analysis

[0083] Figure 1 The uncalcined carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (2) of Example 7 3 N 5 Photocatalyst, calcined carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (3) of Example 7 3 N 5 Photocatalyst, the calcined carboxymethyl cellulose modified PAM hydrogel obtained in Comparative Example 2, the carboxymethyl cellulose modified PAM hydrogel obtained in Example 4 (i.e., the uncalcined carboxymethyl cellulose modified PAM hydrogel), and the raw material gC 3 N 5 Infrared spectrum. 808cm -1 The peak is gC3 N 5 Stretching vibration absorption peak of triazine unit in NN, 1200-1260cm -1 The absorption peaks in the range belong to the CN / C=N heterocyclic characteristic absorption peaks of the CN unit. It can be observed in the figure that there are obvious differences between the calcined and uncalcined composite materials. 3 N 5 The existence of interaction with the gel material indicates that the composite material was successfully synthesized.

[0084] (2) Electron microscopy analysis

[0085] Figure 2 The carboxymethyl cellulose modified PAM hydrogel composite gC obtained in step (3) of Example 7 3 N 5 Scanning electron microscope images of the photocatalyst at different magnifications, where the scale bar of (a) is 100 μm, the scale bar of (b) is 20 μm, and the scale bar of (c) is 10 μm. It can be observed from the figure that gC 3 N 5 It is relatively evenly attached to the surface of the calcined gel carbon material, and can exhibit the dual effects of rapid adsorption and photocatalysis under the synergistic effect of adsorption-photocatalysis.

[0086] (3) Photoluminescence spectroscopy analysis

[0087] Photoluminescence (PL) spectroscopy is used to characterize the difference in electron-hole recombination rates. The lower the PL peak intensity, the lower the recombination rate of electron-hole pairs on the photocatalyst surface. 3 N 5 , the calcined carboxymethyl cellulose modified PAM hydrogel obtained in Comparative Example 2 and the calcined carboxymethyl cellulose modified PAM hydrogel obtained in step (3) of Example 7 composite gC 3 N 5 The photocatalyst is excited to obtain the PL spectrum, such as Figure 3 As shown in the figure, there is a strong emission peak at around 521nm, and the calcined carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The PL intensity of the photocatalyst is higher than that of pure gC 3 N 5 , calcined carboxymethyl cellulose modified PAM hydrogel has greater inhibition on photoinduced carriers.

[0088] Test Example 3

[0089] Photocatalytic performance test

[0090] (1) Degradation performance test of methylene blue by different photocatalysts

[0091] The photocatalytic activity of the sample was evaluated using the degradation rate of methylene blue by the photocatalyst as an indicator. The experiment was carried out in a photocatalytic device, and the reaction was carried out under the premise of effectively preventing the entry of external light sources. A 500W xenon lamp was used to simulate a solar light source, the light source was about 5cm away from the surface of the solution, and it was operated at room temperature. 40mg of the photocatalyst sample was added to 40mL of methylene blue (concentration of 40mg / L) solution, and the suspension was continuously stirred in the dark for 0.5h to reach adsorption-desorption equilibrium. A 500W xenon lamp (filter 420nm) was then used for photocatalytic reaction. When the photocatalytic degradation process began, about 4mL of solution was taken out at a given time interval (15min), and the photodegradation rate was calculated by monitoring the ultraviolet absorbance of the solution after removing the catalyst and comparing the ultraviolet absorbance of the original solution. The photocatalysts of Examples 5-7 and Comparative Example 2 and pure gC 3 N 5 The degradation rate after the photocatalytic degradation reaction was carried out for 90 min is shown in Table 1.

[0092] Table 1

[0093] Degradation rate (%) Example 5 77.6 Example 6 84.5 Example 7 91.7 Comparative Example 2 37.7 <![CDATA[Pure g-C 3 N 5 > 26.7

[0094] As shown in Table 1, the modified PAM hydrogel composite photocatalyst prepared by the method of the present invention is more 3 N 5 The photocatalyst has a greatly improved degradation effect on methylene blue.

[0095] (2) Degradation performance test of modified PAM hydrogel composite photocatalyst on rhodamine B

[0096] The methylene blue (concentration of 40 mg / L) solution in the above degradation performance test of methylene blue was replaced with a rhodamine B (concentration of 40 mg / L) solution, and other operating conditions remained unchanged, and the degradation performance of the modified PAM hydrogel composite photocatalyst on rhodamine B was tested. The test results show that the modified PAM hydrogel composite photocatalyst (i.e., the carboxymethyl cellulose modified PAM hydrogel composite gC 3 N 5 The degradation rate of rhodamine B by photocatalyst) within 90 minutes was only 35.5%, which shows that its degradation effect on methylene blue was significantly better than that on rhodamine B.

[0097] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a modified PAM hydrogel composite photocatalyst, characterized in that: The following steps are involved: Acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, g-C3N5, water and an initiator are mixed and reacted under heat preservation conditions to obtain a precursor; the precursor is calcined to obtain the modified PAM hydrogel composite photocatalyst.

2. The preparation method according to claim 1, characterized in that The mass of the g-C3N5 is 0.3-1.8% of the sum of the mass of the acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water.

3. The preparation method according to claim 1, characterized in that: Taking the sum of the masses of acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water as 100%, the mass percentages of acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, initiator and water are 5.740-10.860%, 0.700-2.060%, 0.005-0.037%, 0.110-0.280% and 86.763-93.165%, respectively.

4. The preparation method according to claim 1, characterized in that: The initiator is ammonium persulfate.

5. The preparation method according to claim 1, characterized in that: The insulation temperature is 40-60° C., and the reaction time is 3.5-5.5 h.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 340-420° C. and the calcination time is 1-4 hours.

7. The preparation method according to claim 1, characterized in that: The method comprises mixing acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, g-C3N5, water and an initiator, and reacting the mixture under heat preservation conditions to obtain a precursor, comprising: mixing acrylamide, sodium carboxymethyl cellulose, N,N'-methylenebisacrylamide, g-C3N5 and water, stirring the mixture evenly, introducing nitrogen to remove oxygen, and then preheating the mixture under sealing conditions, adding an initiator after preheating to a heat preservation temperature, and reacting the mixture at the heat preservation temperature to obtain a precursor.

8. The modified PAM hydrogel composite photocatalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified PAM hydrogel composite photocatalyst as claimed in claim 8 in photocatalytic degradation of organic dyes.

10. The use according to claim 9, characterized in that The step of photocatalytic degradation of organic dyes comprises: The modified PAM hydrogel composite photocatalyst is added into wastewater containing organic dyes to carry out degradation reaction under light conditions.

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