Composite photocatalytic material, and preparation method and use thereof

Abstract

The disclosure provides a composite photocatalytic material and a preparation method and application thereof, and the preparation method comprises the following steps: S1, respectively dissolving bismuth nitrate and a phosphate into water to obtain a bismuth nitrate solution and a phosphate solution, adding the phosphate solution into the bismuth nitrate solution for first mixing to obtain a suspension containing a BiPO4 precursor; S2, adding melamine into the suspension containing the BiPO4 precursor for second mixing and heating treatment to obtain a first mixed material; S3, centrifugally separating the first mixed material to obtain a solid powder; and calcining the solid powder. The composite photocatalytic material prepared by the method of the disclosure has a good degradation effect on refractory organic dyes.

Description

Technical Field

[0001] This application relates to the field of materials, specifically to a composite photocatalytic material, its preparation method, and its uses. Background Technology

[0002] Semiconductor photocatalysis technology can convert solar energy into chemical energy under mild conditions, completely oxidizing and decomposing organic pollutants, reducing CO2 to fuels or high-value-added chemicals, and even producing hydrogen through water splitting. Therefore, it is considered one of the most promising new technologies capable of simultaneously solving environmental and energy problems. Semiconductor photocatalytic oxidation technology, in particular, can degrade organic matter at room temperature and is a green, advanced oxidation technology that has attracted widespread attention in recent years. However, traditional photocatalysts like TiO2 suffer from low solar energy utilization and high recombination rates of photogenerated electrons and holes, severely limiting their practical application. Solving this problem involves developing novel, highly efficient photocatalysts and, through recombination, preparing heterojunction photocatalysts with visible light response.

[0003] BiPO4 is a novel photocatalyst with excellent performance. Its low valence band position and the photo-excited holes possess extremely strong oxidizing power, making it highly advantageous in degrading recalcitrant organic pollutants. However, it lacks visible light response. C3N4 is an organic semiconductor material with good thermal and chemical stability and can absorb visible light, but it has low hole oxidation capacity and a low electron-hole separation rate. Combining BiPO4 and C3N4 can overcome the shortcomings of both, and the resulting heterojunction facilitates electron-hole separation and migration, thus promising a highly efficient photocatalyst with visible light response.

[0004] The literature (Dramatic Activity of C3N4 / BiPO4 Photocatalyst with Core / Shell Structure Formed by Self-Assembly, Adv. Funct. Mater. 2012, 22, 1518–1524) first reported the preparation and photocatalytic performance of BiPO4 / C3N4, finding that the material's ultraviolet light activity was higher than that of P25 and BiPO4, and it also exhibited visible light activity. The synthesis method of BiPO4 / C3N4 reported in this work is similar to that in Chinese patent literature CN105214707A, both involving the separate synthesis of BiPO4 and C3N4 followed by ultrasonic dispersion to achieve their composite, a method that is time-consuming. Chinese patent literature CN112138700A discloses a method for preparing BiPO4 / C3N4 heterojunctions using ball milling, but this method has drawbacks such as high energy consumption and a long process. Summary of the Invention

[0005] The purpose of this disclosure is to solve the problems of high energy consumption, long process and difficulty in ensuring product uniformity caused by the traditional preparation process of BiPO4 / C3N4 composite materials, which requires the separate synthesis of BiPO4 and C3N4 and then compounding.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a composite photocatalytic material, the method comprising:

[0007] S1. Bismuth nitrate and phosphate are dissolved in water to obtain bismuth nitrate solution and phosphate solution respectively. The phosphate solution is added to the bismuth nitrate solution for a first mixing and stirring to obtain a suspension containing BiPO4 precursor.

[0008] S2. Melamine is added to the suspension containing BiPO4 precursor for a second mixing and heating treatment to obtain a first mixture.

[0009] S3. Centrifuge the first mixture to obtain solid powder; calcine the solid powder.

[0010] Optionally, the concentration of the bismuth nitrate solution is 0.060–0.100 mol / L, preferably 0.070–0.090 mol / L; and the concentration of the phosphate solution is 0.100–0.350 mol / L, preferably 0.150–0.300 mol / L.

[0011] Optionally, the volume ratio of the bismuth nitrate solution to the phosphate solution is 1:0.5 to 1.5; preferably 1:0.8 to 1.2.

[0012] Optionally, the phosphate is at least one of NaH2PO4, Na2HPO4 and Na3PO4, preferably NaH2PO4.

[0013] Optionally, the BiPO4 precursor is bismuth nitrate pentahydrate, and the mass ratio of melamine to bismuth nitrate pentahydrate is 0.10 to 0.70, preferably 0.15 to 0.61.

[0014] Optionally, in step S1, the first mixing includes a first stirring treatment; optionally, the conditions for the first stirring treatment include: a time of 15–45 min; a temperature of 25–30 °C; in step S2, the second mixing includes a second stirring treatment; optionally, the conditions for the second stirring treatment include: a time of 15–45 min; a temperature of 25–30 °C; the conditions for the heating treatment include: a temperature of 90–130 °C, preferably 100–120 °C; a time of 800–1600 min, preferably 900–1500 min; in step S3, the conditions for the centrifugation treatment include: a time of 20–40 min, preferably 25–35 min; a rotation speed of 3000–5000 r / min, preferably 4000–4500 r / min; the conditions for the calcination include: a temperature of 400–600 °C, preferably 500–580 °C; a time of 90–200 min, preferably 100–150 min.

[0015] A second aspect of this disclosure provides a composite photocatalytic material comprising a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots; based on the total weight of the composite photocatalytic material, the weight percentage of the BiPO4 particles is 60-90%, and the weight percentage of the C3N4 quantum dots is 10-40%.

[0016] Optionally, based on the total weight of the composite photocatalytic material, the weight percentage of the BiPO4 core is 60-90%, preferably 65-85%; and the weight percentage of the C3N4 particles is 10-40%, preferably 15-35%.

[0017] A third aspect of this disclosure provides the application of the composite photocatalytic material in the degradation of organic pollutants.

[0018] Optionally, the organic pollutant is a dye in wastewater; alternatively, the dye is methylene blue.

[0019] The above-described technical solution effectively solves the problems of high energy consumption, long process, and difficulty in ensuring product uniformity caused by the traditional preparation process of BiPO4 / C3N4 composite materials, which requires the separate synthesis of BiPO4 and C3N4 before composite formation. The composite photocatalytic material provided in this disclosure has a core-shell structure, and C3N4 exists in the form of quantum dots, which is beneficial for light absorption. This composite photocatalytic material exhibits good degradation effects on recalcitrant organic dyes.

[0020] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 The image shown is a transmission electron microscope (TEM) image of the composite photocatalytic material prepared in Example 1. Detailed Implementation

[0023] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0024] The first aspect of this disclosure provides a method for preparing a composite photocatalytic material, the method comprising:

[0025] S1. Bismuth nitrate and phosphate are dissolved in water to obtain bismuth nitrate solution and phosphate solution respectively. The phosphate solution is added to the bismuth nitrate solution for a first mixing and stirring to obtain a suspension containing BiPO4 precursor.

[0026] S2. Melamine is added to the suspension containing BiPO4 precursor for a second mixing and heating treatment to obtain a first mixture.

[0027] S3. Centrifuge the first mixture to obtain solid powder; calcine the solid powder.

[0028] The method for preparing composite photocatalytic materials disclosed herein effectively solves the problems of high energy consumption, long process, and difficulty in ensuring product uniformity caused by the traditional preparation process of BiPO4 / C3N4 composite materials, which requires the separate synthesis of BiPO4 and C3N4 before composite formation. The composite photocatalytic material prepared by the method disclosed herein has a core-shell structure, with C3N4 attached to the surface of the BiPO4 core in the form of quantum dots. This composite photocatalytic material is more conducive to light absorption and exhibits good degradation effect on recalcitrant organic dyes.

[0029] According to this disclosure, the concentration of the bismuth nitrate solution can be 0.060–0.100 mol / L, preferably 0.070–0.090 mol / L; the concentration of the phosphate solution can be 0.100–0.350 mol / L, preferably 0.150–0.300 mol / L.

[0030] According to this disclosure, the volume ratio of the bismuth nitrate solution and the phosphate solution can be 1:0.5 to 1.5; preferably 1:0.8 to 1.2.

[0031] According to this disclosure, the phosphate can be at least one of NaH2PO4, Na2HPO4 and Na3PO4, preferably NaH2PO4.

[0032] According to this disclosure, the BiPO4 precursor can be bismuth nitrate pentahydrate, and the mass ratio of melamine to bismuth nitrate pentahydrate can be 0.10 to 0.70, preferably 0.15 to 0.61.

[0033] According to this disclosure, in step S1, the first mixing may include a first stirring treatment; optionally, the conditions for the first stirring treatment may include: a time of 15–45 min; a temperature of 25–30 °C; in step S2, the second mixing may include a second stirring treatment; optionally, the conditions for the second stirring treatment may include: a time of 15–45 min; a temperature of 25–30 °C; the conditions for the heating treatment may include: a temperature of 90–130 °C, preferably 100–120 °C; a time of 800–1600 min, preferably 900–1500 min; in step S3, the conditions for the centrifugal separation may include: a time of 20–40 min, preferably 25–35 min; a rotation speed of 3000–5000 r / min, preferably 4000–4500 r / min; the conditions for the calcination may include: a temperature of 400–600 °C, preferably 500–580 °C; a time of 90–200 min, preferably 100–150 min.

[0034] A second aspect of this disclosure provides a composite photocatalytic material comprising a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots; based on the total weight of the composite photocatalytic material, the weight percentage of the BiPO4 core is 60-90%, and the weight percentage of the C3N4 particles is 10-40%.

[0035] According to this disclosure, based on the total weight of the composite photocatalytic material, the weight percentage of the BiPO4 core can be 60-90%, preferably 65-85%; the weight percentage of the C3N4 particles can be 10-40%, preferably 15-35%.

[0036] The composite photocatalytic material disclosed herein has a core-shell structure, and C3N4 is attached to the surface of the BiPO4 core in the form of quantum dots. This composite photocatalytic material is more conducive to light absorption and has a good degradation effect on recalcitrant organic dyes.

[0037] A third aspect of this disclosure provides the application of the composite photocatalytic material in the degradation of organic pollutants.

[0038] According to this disclosure, the organic pollutant may be a dye in wastewater; optionally, the dye may be methylene blue.

[0039] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0040] Example 1

[0041] 2.91 g of bismuth nitrate pentahydrate and 2.808 g of sodium dihydrogen phosphate were dissolved in 70 mL of water to obtain bismuth nitrate solution and sodium dihydrogen phosphate solution, respectively. The sodium dihydrogen phosphate solution was added to the bismuth nitrate solution and stirred at 26 °C for 30 min to obtain a suspension containing BiPO4 precursor.

[0042] 1.104 g of melamine was added to a suspension containing BiPO4 precursor, stirred at 26 °C for 30 min, and heated at 160 °C for 24 h in a hydrothermal reactor to obtain the first mixture.

[0043] The first mixture was centrifuged to obtain BiPO4 powder loaded with melamine. The centrifugation time was 30 min and the rotation speed was 4000 r / min.

[0044] BiPO4 powder loaded with melamine was placed in a crucible and calcined in a muffle furnace at 550°C for 2 hours to obtain the composite photocatalytic material of this embodiment.

[0045] In this embodiment, the composite photocatalyst material contains 75% by weight BiPO4 and 25% by weight C3N4. The transmission electron microscope (TEM) image of this embodiment's composite photocatalyst material is shown below. Figure 1 .

[0046] Example 2

[0047] 2.91 g of bismuth nitrate pentahydrate and 2.808 g of sodium dihydrogen phosphate were dissolved in 70 mL of water to obtain bismuth nitrate solution and sodium dihydrogen phosphate solution, respectively. The sodium dihydrogen phosphate solution was added to the bismuth nitrate solution and stirred at 26 °C for 30 min to obtain a suspension containing BiPO4 precursor.

[0048] 0.442 g of melamine was added to a suspension containing BiPO4 precursor, stirred at 26 °C for 30 min, and heated at 160 °C for 24 h in a hydrothermal reactor to obtain the first mixture.

[0049] The first mixture was centrifuged to obtain BiPO4 powder loaded with melamine. The centrifugation time was 30 min and the rotation speed was 4000 r / min.

[0050] The melamine-loaded BiPO4 powder was placed in a crucible and calcined in a muffle furnace at 550°C for 2 hours to obtain the composite photocatalytic material of this embodiment. In the composite photocatalytic material of this embodiment, the content of BiPO4 is 90% by weight and the content of C3N4 is 10% by weight.

[0051] Example 3

[0052] 2.91 g of bismuth nitrate pentahydrate and 2.808 g of sodium dihydrogen phosphate were dissolved in 70 mL of water to obtain bismuth nitrate solution and sodium dihydrogen phosphate solution, respectively. The sodium dihydrogen phosphate solution was added to the bismuth nitrate solution and stirred at 26 °C for 30 min to obtain a suspension containing BiPO4 precursor.

[0053] 1.766 g of melamine was added to a suspension containing BiPO4 precursor, stirred at 26 °C for 30 min, and heated at 160 °C for 24 h in a hydrothermal reactor to obtain the first mixture.

[0054] The first mixture was centrifuged to obtain BiPO4 powder loaded with melamine. The centrifugation time was 30 min and the rotation speed was 4000 r / min.

[0055] The melamine-loaded BiPO4 powder was placed in a crucible and calcined in a muffle furnace at 550°C for 2 hours to obtain the composite photocatalytic material of this embodiment. In the composite photocatalytic material of this embodiment, the content of BiPO4 is 60% by weight and the content of C3N4 is 40% by weight.

[0056] Comparative Example 1

[0057] 2.91 g of bismuth nitrate pentahydrate and 2.808 g of sodium dihydrogen phosphate were dissolved in 70 mL of water to obtain bismuth nitrate solution and sodium dihydrogen phosphate solution, respectively. The sodium dihydrogen phosphate solution was added to the bismuth nitrate solution, and the mixture was stirred at 26 °C for 30 min to obtain a suspension containing the BiPO4 precursor. The suspension was transferred to a hydrothermal reactor and heated at 160 °C for 24 h. The resulting mixture was centrifuged and dried to obtain BiPO4 powder. The centrifugation time was 30 min at a speed of 4000 r / min, and the drying time was 600 min at a temperature of 105 °C.

[0058] 1.104 g of melamine was weighed and calcined in a muffle furnace at 550 °C for 2 h to obtain C3N4 powder.

[0059] The obtained C3N4 powder was added to an ethanol solution and sonicated for 30 min until the C3N4 powder was completely dispersed. Then, BiPO4 powder was added, and the mixture was stirred in a fume hood for 24 h. After the methanol was completely evaporated, the resulting product was dried at 100 °C to obtain the composite photocatalytic material of this comparative example. In this comparative example, the content of BiPO4 was 75% by weight, and the content of C3N4 was 25% by weight.

[0060] Test Example 1

[0061] This test example illustrates the application of the composite photocatalytic material provided in this disclosure in the degradation of dyes in wastewater.

[0062] The degradation process is as follows: Accurately weigh 25 mg of the composite photocatalyst material and add it to 50 mL of a solution with a concentration of 2 × 10⁻⁶ mg / mL. -5 In a mol / L methylene blue solution, the mixture was stirred for 30 min to reach adsorption equilibrium. A xenon lamp was then turned on and a timer started. After 2 hours, the illumination was stopped, and 3 mL of the suspension was collected and centrifuged to obtain the supernatant for later use. The concentration of methylene blue in the solution before and after adsorption was measured using a Hitachi U-3010 UV-Vis spectrophotometer. The removal rate of methylene blue was calculated based on the concentration difference before and after the reaction. The results are listed in Table 1.

[0063] Table 1

[0064] Example Methylene blue removal rate (%) Example 1 98％ Example 2 82％ Example 3 88％ Comparative Example 61％

[0065] As shown in Table 1, the composite photocatalyst prepared by the method of this disclosure has a higher removal rate of methylene blue, reaching 98%. Therefore, the composite photocatalyst of this disclosure has a good degradation effect on recalcitrant organic dyes.

[0066] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0067] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0068] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a composite photocatalytic material, characterized in that, The preparation method includes: S1. Bismuth nitrate pentahydrate and phosphate are dissolved in water to obtain bismuth nitrate solution and phosphate solution, respectively. The phosphate solution is added to the bismuth nitrate solution for a first mixing to obtain a suspension containing BiPO4 precursor. S2. Melamine is added to the suspension containing the BiPO4 precursor for a second mixing and then heated in a hydrothermal reactor to obtain a first mixture. The heating conditions include: temperature of 90~130℃ and time of 800~1600min. S3. Centrifuge the first mixture to obtain solid powder; calcine the solid powder. The mass ratio of melamine to bismuth nitrate pentahydrate is 0.15~0.61; The concentration of the bismuth nitrate solution is 0.060~0.100 mol / L; the concentration of the phosphate solution is 0.100~0.350 mol / L.

2. The preparation method according to claim 1, wherein, The concentration of the bismuth nitrate solution is 0.070~0.090 mol / L; the concentration of the phosphate solution is 0.150~0.300 mol / L.

3. The preparation method according to claim 1, wherein, The volume ratio of the bismuth nitrate solution to the phosphate solution is 1:0.5~1.

5.

4. The preparation method according to claim 3, wherein, The volume ratio of the bismuth nitrate solution to the phosphate solution is 1:0.8~1.

2.

5. The preparation method according to claim 1, wherein, The phosphate is at least one of NaH2PO4, Na2HPO4 and Na3PO4.

6. The preparation method according to claim 5, wherein, The phosphate is NaH2PO4.

7. The preparation method according to claim 1, wherein, In step S1, the first mixing includes a first stirring process; the conditions for the first stirring process include: a time of 15 to 45 minutes and a temperature of 25 to 30 degrees Celsius. In step S2, the second mixing includes a second stirring treatment; the conditions for the second stirring treatment include: a time of 15-45 min and a temperature of 25-30°C; the conditions for the heating treatment include: a temperature of 100-120°C and a time of 900-1500 min. In step S3, the centrifugal separation conditions include: a time of 20-40 min and a rotation speed of 3000-5000 r / min; the calcination conditions include: a temperature of 400-600℃ and a time of 90-200 min.

8. The preparation method according to claim 7, wherein, In step S3, the centrifugal separation conditions include: a time of 25-35 min and a rotation speed of 4000-4500 r / min; the calcination conditions include: a temperature of 500-580℃ and a time of 100-150 min.

9. A composite photocatalytic material prepared by the method for preparing the composite photocatalytic material according to any one of claims 1-8, characterized in that, The composite photocatalytic material includes a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots; based on the total weight of the composite photocatalytic material, the weight percentage of the BiPO4 core is 65-85%, and the weight percentage of the C3N4 particles is 15-35%.

10. The application of the composite photocatalytic material according to claim 9 in the degradation of organic pollutants, The organic pollutant is a dye in the wastewater; the dye is methylene blue.

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