A photosensitive activated type Zn 0.8 Cd 0.2 Preparation method and application of S / PDI composite photocatalyst

Abstract

The application belongs to the technical field of environmental material preparation, and discloses a photosensitive activated type Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, a preparation method and application thereof. The method comprises the following steps: firstly, preparing PDI; adding CTAB into deionized water, stirring until dissolved, and then adding hexamethylenetetramine, monohydrate citric acid, cadmium nitrate tetrahydrate, zinc nitrate hexahydrate, PDI and thioacetamide into the deionized water in sequence, and condensing and refluxing; after stirring for a period of time, cooling to room temperature; and then repeatedly washing the product after reaction with NaCl solution and deionized water, and vacuum drying Zn 0.8 Cd 0.2 S / PDI composite photocatalyst. The application will not cause resource waste and additional pollution, is simple to operate, is a kind of green composite material, realizes complete degradation of decabromodiphenyl ether in water within 2 minutes under focused natural sunlight, and can control the purpose of treating aromatic halides in sewage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental material preparation, and particularly relates to a photosensitive activated type Zn 0.8 Cd 0.2 Preparation method and application of S / PDI composite photocatalyst. BACKGROUND

[0002] With the application of a large number of building materials and the continuous industrialized production of daily necessities, the overuse of flame retardant decabromodiphenyl ether is becoming more and more serious, and the biological toxicity caused by the "escape" of low-bromine products into the environment is increasingly prominent. The pollutants remaining in water and soil are transmitted through the biological chain and accumulated in the human body, thereby forming a potential threat to human health. Therefore, it is urgent to find a green and efficient method for degrading decabromodiphenyl ether.

[0003] At present, the technologies for degrading decabromodiphenyl ether mainly include high-temperature incineration, adsorption, biodegradation, chemical degradation, and photocatalysis technology. Since aromatic halide flame retardants have the properties of high temperature resistance and generation of highly toxic low-bromine products after incineration, the traditional conventional high-temperature incineration technology will cause great pollution to the environment when treating such difficult-to-degrade toxic organic matters; the adsorption technology has the advantages of easy operation, low cost, high efficiency, and no generation of highly toxic by-products, but it has poor mechanical strength stability and is difficult to recycle; the biodegradation method is environmentally friendly, but has high cost and low degradation efficiency, and is difficult to be widely applied; the photocatalysis technology not only has the advantages of simple method, low investment and operation cost, but also has strong reduction capacity and high degradation rate, and is suitable for wide application. In addition, it is crucial to design a high-performance catalyst in the photocatalysis technology.

[0004] Perylene diimide (PDI) as a photosensitive organic semiconductor catalyst provides a promising solution due to its unique planar polycyclic aromatic structure and wide visible light absorption. They enhance the adsorption of polybrominated diphenyl ethers through π-π interactions and expand the light absorption range. However, due to the lack of polar reduction sites and the inertness of X-H covalent bonds, the original PDI as a catalyst faces challenges in direct dehalogenation of aromatic halides, so it is necessary to select a suitable semiconductor to be compounded with PDI to work together in photocatalytic degradation reaction. The dehalogenation efficiency of PDI can be greatly improved by reducing it to PDI radical, but common reducing agents such as triethylamine still pollute the environment, and PDI radical is unstable and easy to be oxidized.

[0005] A self-assembled PDI di-radical (PDI 2-Nanoribbon catalysts, prepared through self-assembly under nitrogen conditions, still exhibit instability in oxygen-containing environments and the time-consuming self-assembly process. Therefore, this study developed a photocatalytic material that can be stably stored in air and rapidly activated by light. PDI was selected as the polymer material for constructing photosensitive smart composite photocatalytic materials. Additionally, Zn... 0.8 Cd 0.2 The addition of S can promote PDI to: PDI 2- In-situ transformation. Activated Zn 0.8 Cd 0.2 S / :PDI 2- The catalyst can fully utilize the solar spectrum, enhance near-infrared absorption, and provide additional free radical reaction sites. It achieves complete dehalogenation of trace amounts of 12 typical aromatic halides, including polybrominated diphenyl ethers, in water within 2 minutes, further optimizing the catalyst's performance and demonstrating good practical application value. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical shortcomings of photocatalysts, such as low dehalogenation efficiency, slow electron transport rate, and high electron-hole recombination rate, by using a chemical synthesis method to prepare Zn. 0.8 Cd 0.2 S / PDI composite photocatalyst was applied to the degradation of aromatic halides in water.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention includes the following steps:

[0008] (1) Preparation of PDI:

[0009] 3,4,9,10-Perylenetetracarboxylic acid dianhydride (PTCDA), imidazole, and β-alanine were mixed and calcined in a tube furnace under nitrogen protection for a period of time. The resulting red solid was dispersed in ethanol, HCl solution was added and stirred overnight, washed with deionized water by centrifugation, and finally dried overnight in a vacuum drying oven to obtain the desired PDI.

[0010] (2) Photosensitive activated Zn 0.8 Cd 0.2 Preparation of S / PDI composite photocatalyst:

[0011] Add CTAB to deionized water and stir until dissolved. Then add hexamethylenetetramine, citric acid monohydrate, cadmium nitrate tetrahydrate, zinc nitrate hexahydrate, and PDI prepared in step (1) in sequence. Heat the mixture and finally add thioacetamide. After reflux and stirring for a period of time, cool to room temperature. Centrifuge the product and wash it repeatedly with NaCl solution and deionized water. Finally, vacuum dry the product to obtain the final product, photosensitive activated Zn. 0.8 Cd0.2 S / PDI composite photocatalyst.

[0012] Preferably, in step (1), the molar ratio of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), imidazole and beta-alanine is 1:50:5; the concentration of the HCl solution is 2 mol / L.

[0013] Preferably, in step (1), the calcination temperature is 100-120℃, and the calcination time is 4-5h.

[0014] Preferably, in step (1), the temperature of vacuum drying is 60-70℃, and the time is 10-12h.

[0015] Preferably, in step (2), the amount ratio of CTAB, hexamethylenetetramine, citric acid monohydrate, cadmium nitrate tetrahydrate, zinc nitrate hexahydrate, PDI and thioacetamide is 0.86g:0.327g:0.243g:0.283g:1.093g:0.025-3.75g:0.345g.

[0016] Preferably, in step (2), the heating temperature is 80-85℃, and the time is 5-6h.

[0017] Preferably, in step (2), the concentration of the NaCl solution is 0.3%.

[0018] Preferably, in step (2), the temperature of vacuum drying is 60-70℃, and the time is 10-12h.

[0019] Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, wherein the mole percentage of PDI in Zn 0.8 Cd 0.2 S is 1%-15%.

[0020] Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, applied to degrade polybrominated diphenyl ethers in wastewater.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The present application uses ordinary chemical synthesis method to synthesize Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, compared with conventional PDI, saves the time needed for self-assembly and eliminates harsh solvent and atmosphere conditions.

[0023] (2) The catalyst synthesized by the scheme can be stored under normal temperature and pressure in air, and the activation process does not require hydrazine hydrate or triethylamine and other strong reducing agents which are not environmentally friendly. Only light is needed to convert it into a free radical form.

[0024] (3) The present application composites PDI with Zn 0.8 Cd 0.2 S, because PDI molecules contain a perylene core structure, have strong electron-withdrawing properties, and under photoexcitation, the conduction band of Zn 0.8 Cd 0.2 S nanoparticles can conduct two electrons to each PDI molecule, and PDI is activated to PDI 2- , the catalyst in the free radical state increases the separation of electron-hole pairs, thereby improving the photocatalytic performance of the composite material;

[0025] (4) After light irradiation, Zn 0.8 Cd 0.2 S / PDI is converted to Zn 0.8 Cd 0.2 S / :PDI 2- , which changes from inverse KIE to positive KIE, and realizes efficient dehalogenation of aromatic halides through a double free radical attack pathway. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the XRD graph of PDI, Zn 0.8 Cd 0.2 S and different proportions of Zn 0.8 Cd 0.2 S / PDI composite photocatalyst.

[0027] Figure 2 A is the SEM graph of Zn 0.8 Cd 0.2 S, B is the SEM graph of PDI, C and D are the SEM graphs of 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, E is the Mapping graph of 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst.

[0028] Figure 3 It is the PL graph of PDI, Zn 0.8 Cd 0.2 S, 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst before light irradiation and 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst after light irradiation.

[0029] Figure 4 For PDI, Zn 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 UV-Vis absorption spectrum of S / PDI composite photocatalyst.

[0030] Figure 5 A represents PDI and 10% Zn. 0.8 Cd 0.2 C1s spectrum of S / PDI composite photocatalyst, where B represents PDI and 10% Zn. 0.8 Cd 0.2 N1s spectrum of S / PDI composite photocatalyst, where C represents PDI and 10% Zn. 0.8 Cd 0.2 The O1s spectrum of the S / PDI composite photocatalyst, where D represents Zn. 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 The S2p spectrum of the S / PDI composite photocatalyst, where E represents Zn. 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 Cd3d spectrum of S / PDI composite photocatalyst, where F represents Zn. 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 Zn2p spectrum of S / PDI composite photocatalyst.

[0031] Figure 6 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst in AM 1.5 and xenon lamp (1000mW·cm) -2 The performance of degrading decabromodiphenyl ether under light irradiation.

[0032] Figure 7 Zn 0.8 Cd 0.2 Flowchart for photoactivation of S / PDI composite photocatalyst. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the invention and should not be considered as specific limitations thereof. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods.

[0034] The 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), imidazole, beta-alanine, cetyltrimethylammonium bromide (CTAB), hexamethylenetetramine, citric acid monohydrate, cadmium nitrate tetrahydrate, zinc nitrate hexahydrate and thioacetamide used in the present application are all analytical pure and purchased from Aldrich (Shanghai) Biochemical Science and Technology Co., Ltd.

[0035] The photocatalytic activity of the photocatalyst prepared in the present application is evaluated in a DW-01 type photochemical reaction instrument (purchased from Yangzhou University City Technology Co., Ltd.), under irradiation of visible light and focused natural sunlight. 10 mL of decabromobiphenyl ether simulated wastewater with a concentration of 10 - 5 mol / L (the solution composition is volume ratio of tetrahydrofuran: ethanol: deionized water = 1:9:99) is added to the reactor and its initial value (A0) is determined, then the prepared photocatalyst is added, magnetically stirred and the aeration device is opened to introduce nitrogen to keep the solution in an anaerobic state. During the light irradiation process, samples are taken at intervals of 5 s to 1 h for analysis. After centrifugal separation, the supernatant is taken and subjected to determination of substrate concentration (A i ) in high performance liquid chromatography, determination of bromide ion concentration (c i ) in ion chromatography, and calculation of degradation rate by the formula: Dr = [1-A i / A0] x 100%, and calculation of degradation efficiency by the formula Y = (c i / 10 -4 ) x 100%. Wherein A0 is the concentration of decabromobiphenyl ether solution when adsorption equilibrium is reached, A i is the concentration of decabromobiphenyl ether solution determined by sampling at regular intervals, and c i is the bromide ion concentration of decabromobiphenyl ether solution determined by sampling at regular intervals.

[0036] Example 1:

[0037] (1) Preparation of PDI: 1.376 g of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 18 g of imidazole and 2.5 g of beta-alanine were mixed, and then calcined at 120°C for 5 h under nitrogen protection using a tube furnace. The obtained red solid was dispersed in 100 mL of ethanol, 600 mL of 2M HCl solution was added and stirred overnight. After centrifugation, the product was washed with deionized water until neutral, and finally dried in a vacuum drying oven at 60°C overnight to obtain PDI.

[0038] (2) Preparation of Zn 0.8 Cd 0.2Preparation of S / PDI composite photocatalyst: 0.86 g of CTAB was weighed into 100 mL of deionized water, heated to 30°C and stirred until dissolved, 0.327 g of methenamine, 0.243 g of citric acid monohydrate, 0.283 g of cadmium nitrate tetrahydrate, 1.093 g of zinc nitrate hexahydrate and 0.025 g of PDI were added in turn, stirred for 15 min, heated to 85°C and then 0.345 g of thioacetamide was added, and the condensation reflux reaction was carried out for 5 h. After cooling to room temperature, the product was centrifuged and washed repeatedly with 0.3% NaCl solution and deionized water, and finally vacuum dried at 60°C to obtain the final product photosensitive activated type 1% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst;

[0039] (3) The sample in (2) was subjected to photocatalytic degradation test under visible light lamp in a photochemical reaction instrument, and the degradation efficiency of the photocatalyst for decabromodiphenyl ether was measured to be 16.9% within 1 h, which could not completely degrade decabromodiphenyl ether.

[0040] Example 2:

[0041] (1) Preparation of PDI: 1.376 g of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 18 g of imidazole and 2.5 g of β-alanine were mixed, and then calcined at 120°C for 5 h under nitrogen protection in a tube furnace. The obtained red solid was dispersed in 100 mL of ethanol, 600 mL of 2M HCl solution was added and stirred overnight, washed with deionized water until neutral by centrifugation, and finally dried in a vacuum drying oven at 60°C overnight to obtain PDI;

[0042] (2) Zn 0.8 Cd 0.2 Preparation of S / PDI composite photocatalyst: 0.86 g of CTAB was weighed into 100 mL of deionized water, heated to 30°C and stirred until dissolved, 0.327 g of methenamine, 0.243 g of citric acid monohydrate, 0.283 g of cadmium nitrate tetrahydrate, 1.093 g of zinc nitrate hexahydrate and 0.025 g of PDI were added in turn, stirred for 15 min, heated to 85°C and then 0.345 g of thioacetamide was added, and the condensation reflux reaction was carried out for 5 h. After cooling to room temperature, the product was centrifuged and washed repeatedly with 0.3% NaCl solution and deionized water, and finally vacuum dried at 60°C to obtain the final product photosensitive activated type 1% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst;

[0043] (3) Take the sample in (2) in the photochemical reactor under visible light lamp for photocatalytic degradation test, and it is found that the degradation efficiency of the photocatalyst decabromodiphenyl ether reaches 25.0% within 1 h, which cannot completely degrade decabromodiphenyl ether.

[0044] Example 3:

[0045] (1) Preparation of PDI: 1.376 g of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 18 g of imidazole and 2.5 g of β-alanine were mixed, and then calcined at 120°C for 5 h under nitrogen protection by using a tube furnace. The obtained red solid was dispersed in 100 mL of ethanol, 600 mL of 2M HCl solution was added and stirred overnight. After centrifugation, deionized water was used for washing until neutral, and finally dried in a vacuum drying oven at 60°C overnight to obtain PDI;

[0046] (2) Zn 0.8 Cd 0.2 Preparation of S / PDI composite photocatalyst: 0.86 g of CTAB was added to 100 mL of deionized water, heated to 30°C and stirred until dissolved. 0.327 g of methenamine, 0.243 g of citric acid monohydrate, 0.283 g of cadmium nitrate tetrahydrate, 1.093 g of zinc nitrate hexahydrate and 0.25 g of PDI were added in sequence, stirred for 15 minutes, heated to 85°C and then 0.345 g of thioacetamide was added. The condensation reflux reaction was carried out for 5 h. After cooling to room temperature, the obtained product was centrifuged and washed repeatedly with 0.3% NaCl solution and deionized water, respectively. Finally, vacuum drying was carried out at 60°C to obtain the final product of photosensitive activated type 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst;

[0047] (3) Take the sample in (2) in the photochemical reactor under visible light lamp for photocatalytic degradation test, and it is found that the degradation efficiency of the photocatalyst decabromodiphenyl ether reaches 46.3% within 1 h, and reaches 98% degradation rate within 6 h, realizing the complete degradation of decabromodiphenyl ether.

[0048] Example 4:

[0049] (1) Preparation of PDI: 1.376 g of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 18 g of imidazole and 2.5 g of β-alanine were mixed, and then calcined at 120°C for 5 h under nitrogen protection by using a tube furnace. The obtained red solid was dispersed in 100 mL of ethanol, 600 mL of 2M HCl solution was added and stirred overnight. After centrifugation, deionized water was used for washing until neutral, and finally dried in a vacuum drying oven at 60°C overnight to obtain PDI;

[0050] (2) Zn 0.8 Cd0.2 Preparation of S / PDI composite photocatalyst: 0.86 g of CTAB was weighed into 100 mL of deionized water, heated to 30°C and stirred until dissolved, 0.327 g of hexamethylenetetramine, 0.243 g of citric acid monohydrate, 0.283 g of cadmium nitrate tetrahydrate, 1.093 g of zinc nitrate hexahydrate and 0.375 g of PDI were added in turn, stirred for 15 minutes, heated to 85°C and then 0.345 g of thioacetamide was added, and the condensation reflux reaction was carried out for 5 h. After cooling to room temperature, the product was centrifuged and washed repeatedly with 0.3% NaCl solution and deionized water, and finally vacuum dried at 60°C to obtain the final product photosensitive activated type 15% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst;

[0051] (3) The sample in (2) was subjected to photocatalytic degradation test under visible light in a photochemical reaction instrument, and the degradation efficiency of the photocatalyst for decabromodiphenyl ether was measured to be 25.0% within 1 h, which could not completely degrade decabromodiphenyl ether.

[0052] Figure 1 PDI, Zn 0.8 Cd 0.2 S and different proportions of Zn 0.8 Cd 0.2 XRD pattern of S / PDI composite photocatalyst; the figure clearly shows the characteristic peaks of PDI and Zn 0.8 Cd 0.2 S, Zn 0.8 Cd 0.2 S / PDI composite photocatalyst has been detected PDI and Zn 0.8 Cd 0.2 S, and the intensity of the characteristic peak of PDI is different with different proportions, in addition, we found that photosensitive Zn 0.8 Cd 0.2 S / PDI composite photocatalyst does not change the crystal structure of PDI and Zn 0.8 Cd 0.2 S.

[0053] Figure 2 A is Zn 0.8 Cd 0.2 SEM of S, B is SEM of PDI, C and D are 10% Zn 0.8 Cd 0.2 SEM of S / PDI composite photocatalyst, E is 10% Zn 0.8 Cd 0.2 Mapping of S / PDI composite photocatalyst; from the C, D and E figures, it can be seen that the morphology of Zn is spherical 0.8 Cd0.2 S particles (A) were evenly dispersed on PDI (B) with long sheet-like morphology, indicating that 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst has been successfully synthesized.

[0054] Figure 3 PDI, Zn 0.8 Cd 0.2 S, 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst and 10% Zn 0.8 Cd 0.2 PL spectra of S / PDI composite photocatalyst; strong emission peaks of PDI are shown at 550, 590 and 705 nm, after adding Zn 0.8 Cd 0.2 S, 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst, indicating that 10% Zn 0.8 Cd 0.2 S / PDI composite material can be efficiently transferred at the heterojunction interface, and has higher photocatalytic activity than PDI, Zn 0.8 Cd 0.2 S; at the same time, the fluorescence intensity decreases and slightly blue shifts after light irradiation, indicating that 10% Zn 0.8 Cd 0.2 S / PDI composite material structure has changed and it is verified that the material has better performance under simulated sunlight.

[0055] Figure 4 PDI, Zn 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 UV-Vis absorption spectra of S / PDI composite photocatalyst, indicating that the incorporation of Zn 0.8 Cd 0.2 S into PDI can greatly expand the visible light absorption region and enhance the photocatalytic efficiency.

[0056] Figure 5 PDI, Zn 0.8 Cd 0.2 S and 10% Zn 0.8 Cd 0.2 XPS spectra of S / PDI composite photocatalyst, indicating that 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst and PDI, Zn 0.8 Cd0.2 Differences in the crystal structure of S.

[0057] Figure 6 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst under AM1.5 and xenon lamp irradiation (1000mW·cm) -2 The degradation performance of decabromodiphenyl ether was found to be higher under simulated sunlight than under xenon lamp irradiation, which verifies that the material enhances ultraviolet absorption and is more conducive to the practical application of the catalyst.

[0058] Figure 7 Zn 0.8 Cd 0.2 Flowchart for photoactivation of S / PDI composite photocatalyst.

[0059] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. The photosensitive activated Zn 0.8 Cd 0.2 Use of S / PDI composite photocatalyst for degrading polybrominated diphenyl ethers in wastewater, characterized in that, The photosensitive activated Zn 0.8 Cd 0.2 The S / PDI composite photocatalyst is prepared by the following steps: (1) Preparation of PDI: 1.376 g of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 18 g of imidazole and 2.5 g of β-alanine were weighed and mixed, and then calcined at 120°C for 5 h under nitrogen protection in a tube furnace. The obtained red solid was dispersed in 100 mL of ethanol, 600 mL of 2M HCl solution was added and stirred overnight. After centrifugation, it was washed with deionized water until neutral, and finally dried in a vacuum drying oven at 60°C overnight to obtain PDI; (2) Zn 0.8 Cd 0.2 Preparation of S / PDI composite photocatalyst: 0.86 g of CTAB was weighed into 100 mL of deionized water, heated to 30°C and stirred until dissolved, 0.327 g of hexamethylenetetramine, 0.243 g of citric acid monohydrate, 0.283 g of cadmium nitrate tetrahydrate, 1.093 g of zinc nitrate hexahydrate and 0.25 g of PDI were added in turn, stirred for 15 min, heated to 85°C and then 0.345 g of thioacetamide was added, and the condensation reflux reaction was carried out for 5 h, cooled to room temperature, the product was centrifuged, washed repeatedly with 0.3% NaCl solution and deionized water, and finally vacuum dried at 60°C to obtain the final product photosensitive activated type 10% Zn 0.8 Cd 0.2 S / PDI composite photocatalyst.

Images