A chiral gold-modified titanium dioxide composite catalyst for degradation of organophosphorus pesticides, and a preparation method and application thereof

Abstract

The present application relates to a kind of chiral gold modified titanium dioxide composite catalyst for organic phosphorus pesticide degradation and its preparation method and application, belong to the field of nanomaterial pesticide degradation.The method is used to deposit chiral gold on the surface of titanium dioxide by light precipitation to obtain chiral gold modified titanium dioxide composite catalyst, and the photocatalytic effect of D-cys / Au NPs modified titanium dioxide is best, and 1mL is the optimal addition amount.The method can significantly improve the photocatalytic degradation effect of titanium dioxide under visible light;Chiral gold modified titanium dioxide composite catalyst can have good degradation effect on different types of organic phosphorus pesticides such as chlorpyrifos, methyl chlorpyrifos, marathion, parathion and propetofen, at lower addition amount, and the present application has potential application value in nanometer active packaging for fruit and vegetable preservation.

Description

Technical Field

[0001] This invention belongs to the field of pesticide degradation, specifically relating to a chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides, its preparation method, and its application. Background Technology

[0002] Titanium dioxide is a traditional semiconductor material, considered one of the most promising photocatalysts due to its low toxicity, high stability, low cost, recyclability, and high photocatalytic efficiency. Under ultraviolet light excitation, titanium dioxide can form electron-hole pairs, which then react with water or oxygen to produce reactive oxygen species, such as superoxide anions (O2). - Titanium dioxide produces free radicals such as hydroxyl radicals (·OH). These free radicals can oxidize and decompose organic pollutants to produce non-toxic products such as carbon dioxide and water. Furthermore, photogenerated holes can directly oxidize and decompose organic pollutants using their strong oxidizing ability. However, due to the relatively wide band gap of titanium dioxide (approximately 3.3 ± 0.1 eV), it can only absorb ultraviolet light, meaning its utilization rate of sunlight is only 2-3%. Similarly, the high recombination rate of photogenerated carriers in titanium dioxide leads to insufficient photocatalytic performance. Summary of the Invention

[0003] This invention addresses the aforementioned technical problems by providing a chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides and its preparation method.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for preparing a chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides, the method comprising the following steps:

[0006] (1) Preparation of chiral gold nanoparticles: Gold nanoparticles were mixed with cysteine ​​aqueous solution to obtain modified chiral gold nanoparticles.

[0007] (2) The modified chiral gold nanoparticles obtained in step (1) are added to the titanium dioxide dispersion, stirred under ultraviolet light and photodeposited. The precipitate is washed and dried to obtain the chiral gold modified titanium dioxide composite catalyst.

[0008] In the technical solution of this invention: in step (1), the cysteine ​​is selected from D-cysteine ​​or L-cysteine, and the particle size of the gold nanoparticles is 5-20 nm.

[0009] In the technical solution of the present invention: the concentration of cysteine ​​aqueous solution in step (1) is 10-30 mg / mL.

[0010] In the technical solution of this invention: in step (1), the volume of cysteine ​​aqueous solution and gold nanoparticles is 10-20 μL: 1-10 mL.

[0011] In the technical solution of this invention: in step (1), the cysteine ​​aqueous solution is mixed with the gold nanoparticles and shaken at room temperature for 1 to 3 hours.

[0012] In the technical solution of the present invention: the concentration of titanium dioxide dispersion in step (2) is 3-8 mg / mL.

[0013] In the technical solution of this invention: the amount of modified chiral gold nanoparticles added to the 50mL titanium dioxide dispersion in step (2) is 0.01-5mL.

[0014] In the technical solution of this invention: the photodeposition time under ultraviolet light in step (2) is 1 to 2 hours.

[0015] A chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides is prepared by the method described above.

[0016] The application of the chiral gold-modified titanium dioxide composite catalyst prepared by the above method in the degradation of organophosphorus pesticides; preferably, the amount of chiral gold-modified titanium dioxide photocatalyst added to the organophosphorus pesticide solution is 0.1-3 mg / mL, and the organophosphorus pesticide is selected from chlorpyrifos, methyl chlorpyrifos, malathion, profenofos, or parathion; more preferably, the concentration of the organophosphorus pesticide solution is 0.1-5 μg / mL, and the degradation is carried out under visible light for 0.1-12 h.

[0017] The chiral gold-modified titanium dioxide composite catalyst prepared by the technical solution of this invention exhibits improved photocatalytic performance under visible light. When an appropriate amount of chiral gold is deposited on the titanium dioxide surface, the localized surface plasmon resonance (LSPR) of the noble metal surface absorbs visible light, injecting electrons into the adjacent titanium dioxide matrix. This process also facilitates charge separation and reduces electron-hole pair recombination, thereby enhancing the photocatalytic performance of titanium dioxide under visible light. The presence of cysteine ​​enhances the adsorption of chlorpyrifos onto the nanocomposite material. Therefore, when cysteine ​​is used as a surface modifier, it promotes the diffusion of chlorpyrifos towards the photocatalytic center, further improving the photocatalytic degradation effect of the chiral gold-modified composite photocatalyst.

[0018] The beneficial effects of this invention are:

[0019] (1) Through degradation experiments on chlorpyrifos, a representative organophosphorus pesticide, the results showed that the chiral gold-modified titanium dioxide composite catalyst had better photocatalytic effect than the unmodified titanium dioxide.

[0020] (2) By depositing chiral gold nanoparticles on the surface of titanium dioxide, the catalytic degradation effect of the composite catalyst under visible light can be effectively improved.

[0021] (3) The chiral gold-modified titanium dioxide composite catalyst has different photocatalytic degradation effects on various organophosphorus pesticides such as chlorpyrifos, methyl chlorpyrifos, and malathion. Attached Figure Description

[0022] Figure 1 TEM image of a chiral gold-modified titanium dioxide composite catalyst.

[0023] Figure 2 XPS image of chiral gold-modified titanium dioxide composite catalyst.

[0024] Figure 3 The photocatalytic effect of chiral gold-modified titanium dioxide composite catalyst on different organophosphorus pesticides. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Embodiment 1

[0026] A 15 mg / mL L-cys aqueous solution was prepared. 14 μL of the L-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 1 mL of the prepared L-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water, dried overnight in a 60 °C oven, and ground to obtain a 1-L-cys / Au NPs-modified titanium dioxide composite catalyst.

[0027] Example 2

[0028] A 15 mg / mL D-cys aqueous solution was prepared. 14 μL of the D-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 1 mL of the prepared D-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water, dried overnight in a 60 °C oven, and ground to obtain a 1-D-cys / Au NPs-modified titanium dioxide composite catalyst.

[0029] Blank group

[0030] The chlorpyrifos standard solution (100 μg / mL) was diluted with ultrapure water to 0.5 μg / mL and then left untreated.

[0031] Comparative Example 1

[0032] Place 60 mL of chlorpyrifos solution (0.5 μg / mL) into a beaker and expose it to natural light for 6 hours (stirring continuously during this time).

[0033] Comparative Example 2

[0034] Titanium dioxide alone is used as a comparison.

[0035] Comparative Example 3

[0036] Except for the addition of Au NPs to modify titanium dioxide to obtain Au NPs-modified titanium dioxide, other conditions were the same as in Example 1 to obtain a composite catalyst of 1-Au NPs-modified titanium dioxide.

[0037] Photocatalytic performance test:

[0038] Using chlorpyrifos as a representative organophosphorus pesticide, the photocatalytic effect of the composite photocatalysts prepared in the examples and comparative examples on organophosphorus pesticides was determined. 0.03 g of the photocatalysts prepared in Examples 1-2 and Comparative Examples 2-3 were weighed into a 100 mL beaker, and 60 mL of a chlorpyrifos solution with a concentration of 0.5 μg / mL was added. The mixture was stirred in the dark for 1 h to reach adsorption-desorption equilibrium, and then irradiated under natural light for 12 h (with continuous stirring). After all samples were processed, 0.5 mL of the sample was taken, centrifuged at 6000 rpm for 5 min, and the supernatant was collected. This supernatant was mixed with an equal volume of methanol, filtered through a membrane, transferred to a 200 μL brown bottle, sealed, and stored. The concentration was then determined using ultra-high performance liquid chromatography-tandem mass spectrometry. The photocatalytic performance of the photocatalysts was evaluated by comparing the concentration of chlorpyrifos. The results are shown in the table below.

[0039] Table 1. Photocatalytic effects of titanium dioxide modified with different chiral gold materials.

[0040] Example 1 79.61 Example 2 96.65 Blank example 0 Comparative Example 1 27.00 Comparative Example 2 44.05 Comparative Example 3 61.67

[0041] Table 1 shows that the photocatalytic effect of the composite catalysts prepared by modifying titanium dioxide with L-cys / Au NPs and D-cys / Au NPs on chlorpyrifos (Examples 1-2) is higher than that of chlorpyrifos under natural light, pure titanium dioxide, and the composite catalyst prepared by modifying titanium dioxide with Au NPs (Comparative Examples 1-3). This indicates that the photocatalytic degradation effect of the composite catalyst prepared by modifying titanium dioxide with chiral gold on chlorpyrifos is better than that of pure titanium dioxide and the composite photocatalyst prepared by modifying titanium dioxide with Au NPs. Among them, the composite catalyst prepared by modifying titanium dioxide with D-cys / Au NPs has a better photocatalytic effect. Figure 1 and Figure 2The D-cys / Au NPs-modified titanium dioxide composite catalyst obtained in Example 1 was characterized by TEM and XPS, which showed that D-cys / Au NPs were successfully modified on the surface of titanium dioxide.

[0042] 2. Preparation and photocatalytic effect of chiral gold-modified titanium dioxide composite catalysts with different chiral gold addition amounts

[0043] Example 3

[0044] A 15 mg / mL D-cys aqueous solution was prepared. 14 μL of the D-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 0.5 mL of the D-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water and then dried overnight in a 60 °C oven to obtain a 0.5-D-cys / Au NPs-modified titanium dioxide composite catalyst.

[0045] Example 4

[0046] A 15 mg / mL D-cys aqueous solution was prepared. 14 μL of the D-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 2 mL of the D-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water and then dried overnight in a 60 °C oven to obtain a 2-D-cys / Au NPs-modified titanium dioxide composite catalyst.

[0047] Example 5

[0048] A 15 mg / mL D-cys aqueous solution was prepared. 14 μL of the D-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 3 mL of the D-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water and then dried overnight in a 60 °C oven to obtain a 3-D-cys / Au NPs modified titanium dioxide composite catalyst.

[0049] Example 6

[0050] A 15 mg / mL D-cys aqueous solution was prepared. 14 μL of the D-cys aqueous solution was mixed with 5 mL of 10 nm gold nanoparticles and shaken at room temperature for 2 h to obtain a D-cys / Au NPs solution. 0.25 g of titanium dioxide powder was placed in 50 mL of ultrapure water and ultrasonically dispersed to obtain a 5 mg / mL titanium dioxide suspension. 5 mL of the D-cys / Au NPs solution was added, and the mixture was stirred under UV light for 2 h. The resulting precipitate was washed three times with ultrapure water and then dried overnight in a 60 °C oven to obtain a 5-D-cys / Au NPs-modified titanium dioxide composite catalyst.

[0051] Blank group

[0052] The chlorpyrifos standard solution (100 μg / mL) was diluted with ultrapure water to 0.5 μg / mL and then left untreated.

[0053] Photocatalytic performance test:

[0054] Using chlorpyrifos as a representative organophosphorus pesticide, the photocatalytic effect of the composite photocatalysts prepared in the examples and comparative examples on organophosphorus pesticides was determined. 0.03 g of the photocatalysts prepared in Examples 1-5 were weighed into a 100 mL beaker, and 60 mL of a chlorpyrifos solution with a concentration of 0.5 μg / mL was added. The mixture was stirred in the dark for 1 h to reach adsorption-desorption equilibrium, and then irradiated under natural light for 12 h (with continuous stirring). After all samples were processed, 0.5 mL of the sample was taken, centrifuged at 6000 rpm for 5 min, and the supernatant was collected. This supernatant was mixed with an equal volume of methanol, filtered through a membrane, transferred to a 200 μL brown bottle, sealed, and stored. The concentration was then determined using ultra-high performance liquid chromatography-tandem mass spectrometry. The photocatalytic performance of the photocatalysts was evaluated by comparing the concentration of chlorpyrifos. The results are shown in the table below.

[0055] Table 2. Photocatalytic effects of chiral gold-modified titanium dioxide composite catalysts prepared with different amounts of chiral gold.

[0056] Example 3 67.57 Example 2 96.65 Example 4 77.19 Example 5 75.68 Example 6 68.11 Blank example 0 Comparative Example 1 27.00 Comparative Example 2 44.05

[0057] Table 2 shows that as the amount of chiral gold added increases (Examples 2-6), the photocatalytic effect of the chiral gold-modified titanium dioxide composite catalyst on chlorpyrifos shows a trend of first increasing, then decreasing and then stabilizing. However, the photocatalytic effect of the composite catalysts prepared with different amounts of chiral gold added is higher than that of pure titanium dioxide (Comparative Example 2), and the best photocatalytic efficiency is found in Example 1.

[0058] 3. Photocatalytic effect of chiral gold-modified titanium dioxide composite catalyst on chlorpyrifos with different initial concentrations. Example 7

[0059] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of chlorpyrifos solution with a concentration of 0.5μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0060] Example 8

[0061] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of chlorpyrifos solution with a concentration of 1.0μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0062] Example 9

[0063] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of chlorpyrifos solution with a concentration of 2.0μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (stirring continuously during this period).

[0064] Example 10

[0065] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of chlorpyrifos solution with a concentration of 3.0μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0066] Example 11

[0067] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of chlorpyrifos solution with a concentration of 5.0μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0068] Blank group

[0069] The chlorpyrifos standard solution (100 μg / mL) was diluted with ultrapure water to 0.5, 1.0, 2.0, 3.0, and 5.0 μg / mL, and then no further treatment was performed.

[0070] After all samples were processed, 0.5 mL of sample was taken, centrifuged at 6000 rpm for 5 min, and the supernatant was collected, mixed with an equal volume of methanol, filtered through a membrane, transferred to a 200 μL brown bottle, sealed and stored. The concentration was then determined using ultra-high performance liquid chromatography-tandem mass spectrometry. The results are shown in the table below:

[0071] Table 3. Photocatalytic effects of chiral gold-modified titanium dioxide composite catalysts on chlorpyrifos at different initial concentrations.

[0072] Example 7 96.65 Example 8 86.68 Example 9 75.73 Example 10 69.56 Example 11 47.12 Blank group 0

[0073] Table 3 shows that the photocatalytic degradation of chlorpyrifos solutions with different initial concentrations using chiral gold-modified titanium dioxide composite catalysts (Examples 7-11) showed a gradual decrease in degradation rate as the initial concentration of chlorpyrifos increased, with the best photocatalytic effect observed at the lowest concentration of 0.5 μg / mL.

[0074] 4. Photocatalytic effect of chiral gold-modified titanium dioxide composite catalyst on different organophosphorus pesticides

[0075] Example 12

[0076] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of 0.5μg / mL methyl chlorpyrifos solution, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (stirring continuously during this period).

[0077] Example 13

[0078] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of malathion solution with a concentration of 0.5μg / mL, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0079] Example 14

[0080] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of a 0.5μg / mL solution of propargite, stir for 1h in the dark to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (with continuous stirring during this period).

[0081] Example 15

[0082] Weigh 0.03g of the photocatalyst from Example 2 into a 100mL beaker, add 60mL of a 0.5μg / mL parathion solution, stir in the dark for 1h to reach adsorption-desorption equilibrium, and then irradiate under natural light for 12h (stirring continuously during this period).

[0083] Blank group

[0084] Different organophosphorus pesticide standard solutions (chlorpyrifos, methyl chlorpyrifos, malathion, profenofos, parathion, 100 μg / mL) were diluted with ultrapure water to 0.5 μg / mL and then left untreated.

[0085] After all samples were processed, 0.5 mL of sample was taken, centrifuged at 6000 rpm for 5 min, and the supernatant was collected, mixed with an equal volume of methanol, filtered through a membrane, transferred to a 200 μL brown bottle, sealed and stored. The concentration was then determined using ultra-high performance liquid chromatography-tandem mass spectrometry. The results are shown in the table below:

[0086] Table 4. Photocatalytic effects of chiral gold-modified titanium dioxide composite catalysts on different organophosphorus pesticides.

[0087] Example 7 96.65 Example 12 56.91 Example 13 42.57 Example 14 83.72 Example 15 49.19 Blank group 0

[0088] Table 4 shows that the chiral gold-modified titanium dioxide composite catalyst exhibits different photocatalytic degradation effects on various organophosphorus pesticides. The best photocatalytic degradation effects are observed for chlorpyrifos and profenofos (Examples 7 and 14), followed by methyl chlorpyrifos and parathion (Examples 12 and 15), while malathion shows the worst photocatalytic degradation effect (Example 13). Figure 3 The changes in degradation rate of Examples 7 and 12-15 under different illumination times are shown.

Claims

1. A method for preparing a chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides, characterized in that: The method includes the following steps: (1) Preparation of chiral gold nanoparticles: Gold nanoparticles were mixed with cysteine ​​aqueous solution to obtain modified chiral gold nanoparticles. In step (1), D-cysteine ​​is selected as the cysteine, and the volume ratio of the cysteine ​​aqueous solution to the gold nanoparticles in step (1) is 10~20μL:1~10mL. (2) The modified chiral gold nanoparticles obtained in step (1) are added to the titanium dioxide dispersion, stirred under ultraviolet light and photodeposited. The precipitate is washed and dried to obtain the chiral gold modified titanium dioxide composite catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the particle size of the gold nanoparticles is 5~20nm.

3. The preparation method according to claim 1, characterized in that: In step (1), the concentration of cysteine ​​aqueous solution is 10~30 mg / mL.

4. The method for preparing the chiral gold-modified titanium dioxide composite catalyst for organophosphorus pesticide degradation according to claim 1, characterized in that: In step (1), the cysteine ​​aqueous solution is mixed with the gold nanoparticles and shaken at room temperature for 1-3 hours.

5. The method for preparing the chiral gold-modified titanium dioxide composite catalyst for organophosphorus pesticide degradation according to claim 1, characterized in that: In step (2), the concentration of titanium dioxide dispersion is 3~8 mg / mL.

6. The method for preparing the chiral gold-modified titanium dioxide composite catalyst for organophosphorus pesticide degradation according to claim 1, characterized in that: In step (2), the amount of modified chiral gold nanoparticles added to the 50 mL titanium dioxide dispersion is 0.01~5 mL.

7. The method for preparing the chiral gold-modified titanium dioxide composite catalyst for organophosphorus pesticide degradation according to claim 1, characterized in that: In step (2), the photodeposition time under ultraviolet light is 1~2 h.

8. A chiral gold-modified titanium dioxide composite catalyst for the degradation of organophosphorus pesticides, characterized in that: The catalyst is prepared by the method described in any one of claims 1 to 7.

9. The application of the chiral gold-modified titanium dioxide composite catalyst according to claim 8 in the degradation of organophosphorus pesticides.

10. The application according to claim 9, characterized in that, The amount of chiral gold-modified titanium dioxide photocatalyst added to the organophosphorus pesticide solution is 0.1~3 mg / mL. The organophosphorus pesticides selected are chlorpyrifos, methyl chlorpyrifos, malathion, profenofos, or parathion.

11. The application according to claim 10, characterized in that, The concentration of organophosphorus pesticide solution was 0.1~5 μg / mL, and the degradation was carried out under visible light for 0.1~12 h.

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