Algae carbon dot modified composite photocatalyst, preparation method thereof and application of composite photocatalyst in degradation of antibiotics

Abstract

The invention provides a composite photocatalyst modified by algae carbon dots (CDs for short), a preparation method of the composite photocatalyst and application of the composite photocatalyst to degradation of antibiotics, and belongs to the technical field of synthesis of environment multifunctional materials. Common algae in aquaculture are used as raw materials, and the algae CDs with fluorescence characteristics are prepared through a green synthesis method and a one-step hydrothermal method. Terephthalic acid is used as a ligand, tetrabutyl titanate is used as a metal source, the prepared algae CDs are placed in a reaction system for preparing MIL-125 (Ti), a CDs / MIL-125 (Ti) composite photocatalyst is constructed in situ through a solvothermal method, impurities in pore channels are removed through low-temperature roasting, and the CDs / DSMIL-125 (Ti) composite material is obtained. Experimental results show that the 120-minute degradation rate of CDs / DSMIL-125 (Ti) on 20 mg / L tetracycline under simulated sunlight (a full-spectrum xenon lamp light source) reaches 96.22%, and the catalytic activity is still kept to be 90% or above after five times of circulation. According to the invention, high-valued utilization of biomass resources is realized, and a novel high-efficiency photocatalyst is provided for treatment of antibiotic pollution of a water body.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental multifunctional material synthesis, and specifically relates to a composite photocatalyst modified with algae carbon dots, a preparation method thereof, and an application thereof in degrading antibiotics. Background Art

[0002] CDs, as a newly emerging carbon-based photofunctional material in recent years, have attracted extensive attention in the fields of environmental governance and energy conversion due to their excellent water solubility, high biocompatibility, low toxicity, easy functionalization, stable fluorescence performance, wide and continuous excitation spectrum, and continuously adjustable emission spectrum. Biomass CDs are a type of carbon-based nanomaterials prepared from biomass resources (such as plants, crop waste, etc.) through carbonization or other treatment methods. Algae commonly found in aquaculture are used as raw materials, which are rich in polysaccharides, proteins and trace elements. The prepared biomass CDs have good light absorption capacity, rich surface functional groups and high stability. CDs are used in composite photocatalytic materials, which not only have excellent photocatalytic performance, but also can improve compatibility with other materials through surface modification, thereby expanding their application in the field of photocatalysis.

[0003] Metal-organic frameworks (MOFs) are highly ordered porous materials constructed by self-assembly reactions of metal ions and organic ligands. They have large specific surface areas, rich pore structures, adjustable chemical environments, and good electron transport properties, which make MOFs have significant advantages in gas storage, catalytic reactions, and drug release. However, MOFs materials have some limitations in photocatalytic applications, such as rapid recombination of photogenerated carriers, low catalytic activity, and poor photostability. The composite of CDs and MOFs can give full play to the advantages of both and improve the photocatalytic efficiency. On the one hand, CDs have the characteristics of wide absorption peaks, which can broaden the visible light absorption of composite materials, and promote the transmission and separation of electrons through their surface functional groups, thereby enhancing the photocatalytic activity; on the other hand, the pore structure of MOFs helps to provide more reaction sites and promote the diffusion of reactants. The photocatalytic material composited with CDs and MOFs can not only effectively improve the photocatalytic performance, but also enhance the stability and durability of the material, and show good performance in the photocatalytic reaction. Therefore, the research on CDs / MOFs composite photocatalytic materials not only helps promote the development of new environmentally friendly materials, but also provides important technical support for energy conversion and environmental protection. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a composite photocatalyst modified with algal carbon dots, its preparation method and application in degrading antibiotics. The synthesis of CDs has the advantages of being green, environmentally friendly and pollution-free in the synthesis process. The technical problem to be solved by the present invention is to prepare algal biomass CDs by a hydrothermal method, place the CDs in the reaction system for preparing MIL-125(Ti), in-situ synthesize a CDs / MIL-125(Ti) composite structure, and then perform low-temperature calcination on the composite material to remove impurities in the pores to obtain CDs / DSMIL-125(Ti).

[0006] (II) Technical Solution

[0007] To achieve the above object, the present invention provides the following technical solution:

[0008] A composite photocatalyst modified with algal carbon dots, its preparation method and application in degrading antibiotics, comprising the following steps:

[0009] 1) Soak the dried wakame, weigh a certain amount, and add a certain amount of pure water for homogenization treatment.

[0010] 2) Subsequently, put the mixed solution into a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene inner liner and heat it for reaction;

[0011] 3) After the heating reaction is completed, naturally cool it to room temperature, and filter out small molecule impurities with a needle filter;

[0012] 4) Then place it in an oven and dry it to an oily state at a temperature of 40-80 degrees;

[0013] 5) Finally, put it into a vacuum freeze dryer for freeze-drying to obtain brown powder CDs;

[0014] 6) Take a certain amount of wakame CDs and N,N-dimethylformamide to prepare a 1:1 solution;

[0015] 7) Weigh 500 mg of terephthalic acid, add 1 mL of wakame solution, 8 mL of N,N-dimethylformamide, 1 mL of anhydrous methanol and 160 μL of tetrabutyl titanate, and mix evenly;

[0016] 8) Subsequently, put the mixed solution into a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene inner liner and heat it for reaction at 140-180 degrees for 20-24 hours;

[0017] 9) After the heating reaction is completed and naturally cooled to room temperature, rinse the material 2-3 times with N,N-dimethylformamide and anhydrous methanol, and activate the material with anhydrous methanol for 20-24 hours;

[0018] 10) Bake the obtained precipitate at a temperature of 250 - 300 °C for 5 - 8 hours to obtain a light brown CDs / DSMIL-125(Ti) composite material powder.

[0019] Preferably, when the wakame is soaked and rehydrated in step 1), the pure water can be changed several times to fully wash the salt in the wakame; the mass ratio of wakame to pure water is 1:5, and the homogenization treatment time of wakame and pure water is 1 - 2 hours.

[0020] Preferably, in step 2), the mixed solution is heated to 160 - 200 °C in a stainless steel autoclave with a PTFE inner lining for 6 - 10 hours.

[0021] Preferably, in step 5), the sample is dried at a certain temperature of 40 - 80 °C and is in an oily state after drying.

[0022] Preferably, in step 7), the mass ratio of wakame carbon tape to N,N-dimethylformamide is 1:1.

[0023] Preferably, in step 8), the mass of terephthalic acid is 500 mg, the wakame solution is 1 mL, N,N-dimethylformamide is 8 mL, anhydrous methanol is 1 mL, and tetrabutyl titanate is 160 μL.

[0024] Preferably, in step 9), the mixed solution is heated to 140 - 180 °C in a stainless steel autoclave with a PTFE inner lining for 20 - 24 hours.

[0025] Preferably, in step 10), the material is rinsed with N,N-dimethylformamide and anhydrous methanol 2 - 3 times, and the material is activated with anhydrous methanol for 20 - 24 hours.

[0026] Preferably, in step 11), the sample is dried at a temperature of 60 - 100 °C for 5 - 8 hours.

[0027] Preferably, in step 12), the sample is baked at a temperature of 250 - 300 °C for 5 - 8 hours.

[0028] (III) Beneficial effects

[0029] Compared with the prior art, the present invention provides an algae carbon dot-modified composite photocatalyst, its preparation method, and the application of degrading antibiotics. The beneficial effects of the present invention are specifically as follows:

[0030] The CDs synthesized by the hydrothermal method use abundant carbon materials in nature as raw materials and common carbon sources in life to synthesize biomass CDs in a green, convenient and efficient manner. The composite of biomass CDs and MOFs materials can give full play to the advantages of both and improve the photocatalytic efficiency. The composite material improves the photocatalytic performance through the following synergistic mechanisms: (1) Algae, as a precursor, has abundant polysaccharides, proteins and trace elements. The algae-derived CDs have the characteristic of a wide absorption peak, which can broaden the light response range of the photocatalyst; (2) The porous structure of MIL-125(Ti) can provide a high specific surface area and mass transfer channels; (3) Functional groups such as hydroxyl and carboxyl groups on the surface of algae CDs can enhance the interfacial binding with MIL-125(Ti), realizing the interfacial anchoring technology of CDs. Through the Ti-O-C bond, strong coupling is achieved, solving the problem of high recombination rate of photo-generated carriers in MIL-125(Ti); (4) Low-temperature calcination can not only remove impurities in the pores of the metal-organic framework, but also will not damage the structure of MIL-125(Ti) and will not cause the structure of MIL-125(Ti) to collapse.

[0031] From Figure 4 、 Figure 5 and Figure 6 It can be obtained that the photocatalytic degradation efficiency of the CDs / DSMIL-125(Ti) composite material is better than that of the MIL-125(Ti) material, with an increase of about 11%. And after repeated cycling experiments, the photocatalytic degradation effect of the CDs / DSMIL-125(Ti) composite material can still remain above 90%.

[0032] The above description is only an overview of the technical solution of this application. In order to be able to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following specifically gives the specific implementation manners of this application. Brief Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the present disclosure or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0034] Figure 1 It is the X-ray diffraction pattern of CDs;

[0035] Figure 2X-ray diffraction patterns of MIL-125(Ti), DSMIL-125(Ti), CDs / MIL-125(Ti) and CDs / DSMIL-125(Ti). Comparison with Simulated MIL-125(Ti) revealed the successful preparation of these four materials. Whether CDs were added or not, the structure of the materials remained unchanged, and no structural collapse occurred in the low-temperature calcined DSMIL-125(Ti) and CDs / DSMIL-125(Ti);

[0036] Figure 3 UV-visible absorption spectra of MIL-125(Ti), DSMIL-125(Ti), CDs / MIL-125(Ti) and CDs / DSMIL-125(Ti) nanocomposites; It can be seen that after the materials were treated, the visible light response intensity of the composite materials was significantly improved, especially for the CDs / DSMIL-125(Ti) composite material. This result indicates that the CDs / DSMIL-125(Ti) composite material has a higher utilization efficiency of visible light under visible light conditions, which is conducive to promoting the separation of photogenerated electron-hole pairs, thereby more efficiently degrading tetracycline;

[0037] Figure 4 Efficiencies of photocatalytic degradation of tetracycline (20 mg / mL) by MIL-125(Ti), DSMIL-125(Ti), CDs / MIL-125(Ti) and CDs / DSMIL-125(Ti) nanocomposites. When the dosage of the photocatalyst was 10 mg, the concentration of tetracycline was 20 mg / L (50 mL of water sample was taken), and the light irradiation was 120 min, the photocatalytic degradation efficiency of tetracycline by MIL-125(Ti) was 85.76%; the photocatalytic degradation efficiency of DSMIL-125(Ti) was 89.80%; the photocatalytic degradation efficiency of CDs / MIL-125(Ti) was 87.75%; the photocatalytic degradation efficiency of CDs / DSMIL-125(Ti) was 91.60%. It can be seen that whether compounded with CDs or calcined at low temperature, the photocatalytic degradation efficiency was significantly improved compared with MIL-125(Ti), especially for the CDs / DSMIL-125(Ti) composite material, with an efficiency increase of about 6%;

[0038] Figure 5 Experiment on the dosage of CDs / DSMIL-125(Ti) nanocomposite. When the concentration of tetracycline was 20 mg / L (50 mL of water sample was taken), with the increase of the dosage of CDs / DSMIL-125(Ti) composite material, the photocatalytic degradation efficiency of tetracycline increased from 91.60% to 96.22%, with an increase in the catalytic degradation efficiency of about 5%;

[0039] Figure 6Cyclic experiment of CDs / DSMIL-125(Ti) nanocomposites. After 5 cycles, the catalytic activity of the composites remained above 90%, indicating strong stability of the materials. Detailed implementation mode

[0040] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] Example 1:

[0042] 1) Weigh a certain amount of dried wakame after soaking it, and add a certain amount of pure water for homogenization. The mass ratio of wakame to pure water is 1:5, and the time for homogenization of wakame and pure water is 30 - 60 minutes;

[0043] 2) Subsequently, put the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene liner for heating reaction. Heat it to 160 - 200 degrees, and the reaction time is 6 - 10 hours;

[0044] 3) After the heating reaction is completed, naturally cool it to room temperature, and filter out small molecule impurities with a needle filter;

[0045] 4) Then place it in an oven to dry it into an oily state at a temperature of 40 - 80 degrees;

[0046] 5) Finally, put it into a vacuum freeze dryer for freeze drying to obtain brown powder CDs;

[0047] 6) Take a certain amount of wakame CDs (Q-CDs) and configure it into a 1:1 solution with N,N-dimethylformamide;

[0048] 7) Weigh 500 mg of terephthalic acid, add 1 mL of wakame solution, 8 mL of N,N-dimethylformamide, 1 mL of anhydrous methanol and 160 μL of tetrabutyl titanate, and mix them evenly;

[0049] 8) Subsequently, put the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene liner for heating reaction at 140 - 180 degrees, and the reaction time is 20 - 24 hours;

[0050] 9) After the heating reaction is completed and naturally cooled to room temperature, rinse the material 2 - 3 times with N,N-dimethylformamide and anhydrous methanol, and activate the material with anhydrous methanol for 20 - 24 hours;

[0051] 10) The obtained precipitate is calcined at a temperature of 250 - 300 °C for 5 - 8 hours to obtain a light brown QCDs / DSMIL-125(Ti) composite material powder.

[0052] The photocatalytic degradation efficiency of MIL-125(Ti) for tetracycline is 85.76%; the photocatalytic degradation efficiency of QCDs / DSMIL-125(Ti) is 91.60%. It can be seen that the photocatalytic degradation efficiency of the QCDs / DSMIL-125(Ti) composite material is significantly higher than that of pure MIL-125(Ti), with an increase of about 6% in efficiency. By appropriately increasing the dosage of the QCDs / DSMIL-125(Ti) photocatalyst, the photocatalytic degradation efficiency can reach more than 96%.

[0053] Example 2:

[0054] 1) After soaking and expanding the dried laver, a certain amount is weighed and a certain amount of pure water is added for homogenization treatment. The mass ratio of laver to pure water is 1:5, and the homogenization treatment time of the laver and pure water is 30 - 60 minutes;

[0055] 2) Subsequently, the mixed solution is placed in a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene inner liner and heated for reaction at 160 - 200 °C for 6 - 10 hours;

[0056] 3) After the heating reaction is completed, it is naturally cooled to room temperature, and small molecule impurities are removed by filtration with a needle filter;

[0057] 4) Then it is placed in an oven and dried to an oily state at a temperature of 40 - 80 °C;

[0058] 5) Finally, it is freeze-dried in a vacuum freeze dryer to obtain brown powder CDs;

[0059] 6) A certain amount of laver CDs (Z-CDs) and N,N-dimethylformamide are configured into a 1:1 solution;

[0060] 7) Weigh 500 mg of terephthalic acid, add 1 mL of laver solution, 8 mL of N,N-dimethylformamide, 1 mL of anhydrous methanol, and 160 μL of tetrabutyl titanate and mix evenly;

[0061] 8) Subsequently, the mixed solution is placed in a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene inner liner and heated for reaction at 140 - 180 °C for 20 - 24 hours;

[0062] 9) After the heating reaction is completed and naturally cooled to room temperature, the material is rinsed 2 - 3 times with N,N-dimethylformamide and anhydrous methanol, and the material is activated with anhydrous methanol for 20 - 24 hours;

[0063] 10) The obtained precipitate is calcined at a temperature of 250 - 300 °C for 5 - 8 hours to obtain a light brown ZCDs / DSMIL-125(Ti) composite powder.

[0064] The photocatalytic degradation efficiency of the ZCDs / DSMIL-125(Ti) composite is significantly improved compared to that of pure MIL-125(Ti), with an efficiency increase of approximately 5%.

[0065] Example 3:

[0066] 1) After soaking and swelling the dried kelp, a certain amount is weighed and a certain amount of pure water is added for homogenization treatment. The mass ratio of kelp to pure water is 1:5, and the homogenization treatment time of the kelp and pure water is 30 - 60 minutes;

[0067] 2) Subsequently, the mixed solution is placed in a stainless steel autoclave with a polytetrafluoroethylene liner and heated for reaction at 160 - 200 °C for 6 - 10 hours;

[0068] 3) After the heating reaction is completed, it is naturally cooled to room temperature, and small molecule impurities are removed by filtration with a needle filter;

[0069] 4) Then it is placed in an oven and dried to an oily state at a temperature of 40 - 80 °C;

[0070] 5) Finally, it is freeze-dried in a vacuum freeze dryer to obtain a brown powder CDs;

[0071] 6) A certain amount of kelp CDs (H-CDs) and N,N-dimethylformamide are configured into a 1:1 solution;

[0072] 7) Weigh 500 mg of terephthalic acid, add 1 mL of kelp solution, 8 mL of N,N-dimethylformamide, 1 mL of anhydrous methanol, and 160 μL of tetrabutyl titanate and mix evenly;

[0073] 8) Subsequently, the mixed solution is placed in a stainless steel autoclave with a polytetrafluoroethylene liner and heated for reaction at 140 - 180 °C for 20 - 24 hours;

[0074] 9) After the heating reaction is completed and naturally cooled to room temperature, the material is rinsed 2 - 3 times with N,N-dimethylformamide and anhydrous methanol, and the material is activated with anhydrous methanol for 20 - 24 hours;

[0075] 10) The obtained precipitate is calcined at a temperature of 250 - 300 °C for 5 - 8 hours to obtain a light brown HCDs / DSMIL-125(Ti) composite powder.

[0076] The photocatalytic degradation efficiency of the HCDs / DSMIL-125(Ti) composite material is significantly improved compared to that of pure MIL-125(Ti), with an efficiency increase of approximately 4%.

[0077] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0078] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite photocatalyst modified by algal carbon dots, its preparation method and application in degrading antibiotics, characterized in that, Algal CDs modify MIL-125(Ti) in the following ways: (1) Coordination of carboxyl groups with titanium-oxygen clusters; (2) π-π stacking interaction with ligand aromatic rings; (3) Hydrogen bonding of surface hydroxyl groups with the pores of MIL-125(Ti). The specific experimental process includes the following steps: 1) Soak dried wakame seaweed until it swells, weigh a certain amount, and add a certain amount of pure water for homogenization treatment. 2) Subsequently, place the mixed solution in a stainless-steel autoclave with a Teflon liner and heat it for reaction. 3) After the heating reaction ends, naturally cool it to room temperature, and filter out small-molecule impurities with a needle filter. 4) Then place it in an oven to dry it into an oily state at a temperature of 40 - 80 °C. 5) Finally, put it into a vacuum freeze dryer to freeze-dry and obtain brown powder CDs. 6) Take a certain amount of wakame seaweed CDs and N,N-dimethylformamide to prepare a 1:1 solution. 7) Weigh 500 mg of terephthalic acid, add 1 mL of wakame seaweed solution, 8 mL of N,N-dimethylformamide, 1 mL of anhydrous methanol, and 160 μL of tetrabutyl titanate, and mix them evenly. 8) Subsequently, place the mixed solution in a stainless-steel autoclave with a Teflon liner and heat it for reaction at 140 - 180 °C for 20 - 24 hours. 9) After the heating reaction ends and it is naturally cooled to room temperature, rinse the material 2 - 3 times with N,N-dimethylformamide and anhydrous methanol, and activate the material with anhydrous methanol for 20 - 24 hours. 10) Calcine the obtained precipitate at a temperature of 250 - 300 °C for 5 - 8 hours to obtain a light brown CDs / DSMIL-125(Ti) composite powder.

2. The composite photocatalyst modified by algal carbon dots, its preparation method and application in degrading antibiotics according to claim 1, wherein, In step 1), when soaking wakame seaweed, the pure water can be changed several times to fully wash the salt in the wakame seaweed. The mass ratio of wakame seaweed to pure water is 1:5, and the homogenization treatment time of wakame seaweed and pure water is 1 - 2 hours.

3. A composite photocatalyst modified with algal carbon dots, its preparation method, and application in degrading antibiotics according to claim 1, characterized in that, In step 2), heat the mixed solution in a stainless-steel autoclave with a Teflon liner to 160 - 200 °C, and the reaction time is 6 - 10 hours.

4. A composite photocatalyst modified with algal carbon dots, its preparation method, and application in degrading antibiotics according to claim 1, characterized in that, In step 5), the certain temperature for sample drying is 40 - 80 °C, and it is dried into an oily state.

5. A composite photocatalyst modified with algal carbon dots, its preparation method, and its application in degrading antibiotics according to claim 1, characterized in that, In step 7), the mass ratio of wakame seaweed carbon tape to N,N-dimethylformamide is 1:

1.

6. The composite photocatalyst modified with algal carbon dots, its preparation method and application for degrading antibiotics according to claim 1, characterized in that, In step 8), the mass of terephthalic acid is 500 mg, the wakame seaweed solution is 1 mL, N,N-dimethylformamide is 8 mL, anhydrous methanol is 1 mL, and tetrabutyl titanate is 160 μL.

7. A composite photocatalyst modified with algal carbon dots, its preparation method, and its application in degrading antibiotics according to claim 1, characterized in that, In step 9), heat the mixed solution in a stainless-steel autoclave with a Teflon liner to 140 - 180 °C, and the reaction time is 20 - 24 hours.

8. A composite photocatalyst modified with algal carbon dots, its preparation method and application in degrading antibiotics according to claim 1, characterized in that, In step 10), rinse the material 2 - 3 times with N,N-dimethylformamide and anhydrous methanol, and activate the material with anhydrous methanol for 20 - 24 hours.

9. A composite photocatalyst modified with algal carbon dots, its preparation method and application in degrading antibiotics according to claim 1, characterized in that, In step 11), the drying temperature of the sample is 60 - 100 °C for 5 - 8 hours.

10. A composite photocatalyst modified with algal carbon dots, its preparation method and application for degrading antibiotics according to claim 1, characterized in that, In step 12), the calcination temperature of the sample is 250 - 300 °C for 5 - 8 hours.

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