CN115634703A

CN115634703A - Catalyst and application thereof

Info

Publication number: CN115634703A
Application number: CN202211122454.7A
Authority: CN
Inventors: 钟理; 汤琳; 刘承斌; 晏智
Original assignee: Guizhou Qianda Ecological Environment And Health Research Institute Co ltd
Current assignee: Guizhou Qianda Ecological Environment And Health Research Institute Co ltd
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2023-01-24

Abstract

The invention relates to a catalyst and application thereof. The catalyst comprises carbon quantum dot-graphite phase carbon nitride and FeOCl loaded on the carbon quantum dot-graphite phase carbon nitride. The catalyst is capable of performing catalysis under a wide range of pH conditions.

Description

Catalyst and application thereof

Technical Field

The invention belongs to the technical field of animal epidemic disease prevention and control, and particularly relates to a catalyst, a preparation method thereof, a method for treating wastewater containing antibiotics by using the catalyst, and application of the catalyst in Fenton reaction and antibiotic degradation.

Background

Antibiotics are a drug widely used worldwide. Due to the current improper treatment of antibiotics, antibiotics inevitably flow into the water environment. In water environment, the antibiotic has high stability, is difficult to degrade in water environment and gradually accumulates.

Even if trace amounts of antibiotics exist in the water environment, serious threats can be caused to the health safety of human beings and the water environment system. The main reason for this is to provide conditions for antibiotic-resistant bacteria and antibiotic resistance genes. Long-term exposure to antibiotic resistance genes may be transmitted to humans, for example by horizontal gene transfer in combination with human pathogens, resulting in human infections. The coexistence of antibiotics and antibiotic resistance genes increases the risk of creating new drug resistance genes, accelerates the spread of antibiotic resistance bacteria in water environment, and finally causes potential fatal threats to the environment and human health.

Tetracycline antibiotics are used to treat protozoal and bacterial infections in aquaculture and, because of their improper disposal, subsequent discharge into the environment, effective measures are required to quickly address this problem.

The Fenton reaction is widely used for treating various organic matters as an effective organic matter treatment technology, and is based on Fe ²⁺ And H ₂ O ₂ The fenton system for generating hydroxyl radicals by combination is carried out under acidic conditions.

Disclosure of Invention

The invention aims to provide a catalyst, a preparation method thereof, a method for treating wastewater containing antibiotics by using the catalyst, and application of the catalyst in Fenton reaction and degradation of antibiotics, wherein the catalyst is used for degrading antibiotics in the environment.

In one aspect, the present disclosure provides a catalyst comprising carbon quantum dot-graphite phase carbon nitride, and FeOCl supported on the carbon quantum dot-graphite phase carbon nitride.

In some embodiments, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to FeOCl is 1; preferably 1.

In some embodiments, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to FeOCl is 1:1.4. in proportion, the catalytic effect of the catalyst is optimal.

In some embodiments, the catalyst has a specific surface area of 8 to 15m ² Per g, pore diameter of

In some embodiments, the catalyst is prepared by grinding and mixing the carbon quantum dot-graphite phase carbon nitride and a precursor of FeOCl, and calcining.

In some embodiments, the precursor is FeCl ₃ 。

In some embodiments, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to the precursor is 3.

In some embodiments, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to the precursor is 1.

In some embodiments, the carbon quantum dot-graphite phase carbon nitride is produced by a hydrothermal process.

In some embodiments, after formamide, citric acid and sodium acetate are uniformly stirred, carrying out hydrothermal reaction for 0.5-1 hour at 20-35 ℃ to obtain a reaction solution containing the carbon quantum dot-graphite phase carbon nitride;

and separating the carbon quantum dot-graphite phase carbon nitride from the reaction solution.

In some embodiments, the carbon quantum dot-graphite phase carbon nitride is washed and dried.

In some embodiments, the solvent used for the washing is absolute ethanol.

In yet another aspect, the present invention provides a process for preparing the above catalyst, the process comprising:

grinding and mixing the carbon quantum dot-graphite phase carbon nitride and a precursor of FeOCl, and calcining for 2-6h at 220-270 ℃ to obtain a mixture containing the catalyst;

separating the catalyst from the mixture.

In some embodiments, the precursor is FeCl ₃ 。

In some embodiments, the separating is washing the mixture with acetone, followed by drying to obtain the catalyst.

In yet another aspect, the present invention provides a method of treating wastewater containing antibiotics, the method comprising the steps of:

adding the catalyst and H into the wastewater ₂ O ₂ 。

The antibiotic in the non-aqueous environment may be dissolved in water to produce the antibiotic-containing wastewater of the present disclosure, which is then treated.

In some embodiments, the catalyst is added in an amount of 0.05 to 0.5g/L, preferably 0.1 to 1g/L, based on the volume of the wastewater.

In some embodiments, the H is based on the volume of the wastewater ₂ O ₂ The amount of (B) is 0.05-0.5g/L, preferably 0.1-0.5g/L.

In some embodiments, the pH of the wastewater is adjusted to 3 to 11. In some embodiments, adjusting the pH of the wastewater can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, or 11.

In some embodiments, the pH of the wastewater is adjusted to 3 to 9.

In some embodiments, the pH of the wastewater is adjusted to 7-9.

In some embodiments, the antibiotic is selected from at least one of a sulfonamide antibiotic, a β -lactam antibiotic, a tetracycline antibiotic, and a fluoroquinolone antibiotic.

In some embodiments, the antibiotic is selected from at least one of sulfamethoxazole, amoxicillin and tetracycline hydrochloride.

In still another aspect, the present invention provides the use of the above catalyst in fenton's reaction.

In some embodiments, the pH of the fenton reaction is between 3 and 11. In some embodiments, the pH of the fenton reaction can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, or 11.

In some embodiments, the pH of the fenton reaction is between 3 and 9.

In some embodiments, the pH of the fenton reaction is between 7 and 9.

In a further aspect, the present invention provides the use of a catalyst as described above for degrading antibiotics.

The catalyst provided by the present disclosure includes carbon quantum dot-graphite phase carbon nitride, and FeOCl supported on the carbon quantum dot-graphite phase carbon nitride. The catalyst is a heterogeneous catalyst.

The catalyst is capable of performing catalysis under a wide range of pH conditions.

The catalyst expands the pH condition of Fenton reaction.

The catalyst can efficiently remove antibiotics in the environment.

Drawings

FIGS. 1a to 1l are FeOCl and CQDs-g-C, respectively ₃ N ₄ 、CQDs-g-C ₃ N ₄ SEM images and TEM images of/FeOCl. FIG. 1a is an SEM image of FeOCl; FIG. 1b is an enlarged view of FIG. 1 a; FIG. 1C is CQDs-g-C ₃ N ₄ SEM image of/FeOCl; FIG. 1d is CQDs-g-C ₃ N ₄ SEM image of (a); fig. 1e is an enlarged view of fig. 1 d. FIG. 1f is an enlarged view of FIG. 1 c; FIG. 1g is CQDs-g-C ₃ N ₄ TEM image of/FeOCl; FIG. 1h is a TEM image of FeOOL; FIG. 1i is CQDs-g-C ₃ N ₄ A TEM image of (a); FIG. 1j is an HR-TEM image of FeOCl; FIG. 1k and FIG. 1l are CQDs-g-C, respectively ₃ N ₄ HRTEM image of/FeOCl.

FIG. 2 is CQDs-g-C ₃ N ₄ Element map of distribution of respective elements in FeOCl. FIG. 2a is CQDs-g-C ₃ N ₄ Element map of all element distribution of/FeOCl; FIG. 2b is an element map of the distribution of Fe element; FIG. 2c is an element map of the distribution of N elements; fig. 2d is an element map of the distribution of O elements. FIG. 2e is an element map of Cl element distribution; fig. 2f is an element map of the distribution of C elements.

FIG. 3 shows FeOCl and CQDs-g-C ₃ N ₄ 、CQDs-g-C ₃ N ₄ XRD pattern, FT-IR pattern and BET analysis result of/FeOCl. FIG. 3a shows FeOCl and CQDs-g-C ₃ N ₄ 、CQDs-g-C ₃ N ₄ XRD pattern of/FeOCl; FIG. 3b shows FeOCl and CQDs-g-C ₃ N ₄ 、CQDs-g-C ₃ N ₄ FT-IR spectrum of FeOCl; FIG. 3C shows FeOCl and CQDs-g-C ₃ N ₄ 、CQDs-g-C ₃ N ₄ BET analysis result of/FeOCl.

FIG. 4 is CQDs-g-C ₃ N ₄ XPS spectra of/FeOCl before and after catalytic reaction. FIG. 4a is a full spectrum before catalytic reaction; FIG. 4b is C1s before catalytic reaction; FIG. 4c is Cl 2p before catalytic reaction; FIG. 4d is O1s before catalytic reaction; FIG. 4e is N1s before catalytic reaction; FIG. 4f is Fe before catalytic reaction; FIG. 4g is a full spectrum after catalytic reaction; FIG. 4h is C1s after catalytic reaction; FIG. 4i is Cl 2p after catalytic reaction; FIG. 4j is O1s after catalytic reaction; FIG. 4k is N1s after catalytic reaction; FIG. 4l shows Fe2p after catalytic reaction.

FIG. 5 is a graph showing the effect of different reaction conditions on TC-HCl degradation. FIG. 5a shows FeOCl and CQDs-g-C ₃ N ₄ Influence of different doping amounts on TC-HCl degradation; FIG. 5b shows H at different concentrations ₂ O ₂ The effect on TC-HCl degradation; FIG. 5c is a graph of the effect of different pH on TC-HCl degradation; FIG. 5d depicts different quencher pairs CQDs-g-C ₃ N ₄ /FeOCl/H ₂ O ₂ Influence of heterogeneous Fenton reaction System.

FIG. 6 is CQDs-g-C ₃ N ₄ Results of adsorption experiments of TC-HCl by FeOCl. FIG. 6a is CQDs-g-C within 24h ₃ N ₄ The adsorption amount of TC-HCl by FeOCl; FIG. 6b is CQDs-g-C within 24 hours ₃ N ₄ The removal rate of TC-HCl by FeOCl; FIG. 6c is a comparison of adsorption/degradation experiments.

FIG. 7 is CQDs-g-C ₃ N ₄ And the removal result of the antibiotics in the actual surface water sample by the FeOCl. FIG. 7a is CQDs-g-C ₃ N ₄ The result of removing TC-HCl in the actual surface water sample by the FeOCl is obtained; FIG. 7b is CQDs-g-C ₃ N ₄ The removal result of the AM in the actual surface water sample by the FeOCl; FIG. 7c shows different concentrations H ₂ O ₂ (3 mM,5mM,10mM,50mM, 100mM) for CQDs-g-C ₃ N ₄ The effect of FeOCl on the efficiency of removing SMX from the actual surface water sample.

FIG. 8 is CQDs-g-C ₃ N ₄ Results of radical Capture experiments for FeOCl degradation.

Detailed Description

The present invention is further illustrated by the following examples, which should be understood as being merely illustrative of the present invention and not limiting thereof, and all simple modifications thereof which are within the spirit of the invention are intended to be covered by the scope of the claims.

Definition of

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

The expression "about" as used herein is as understood by one of ordinary skill in the art and varies within certain ranges depending on the context in which it is used. If one of ordinary skill in the art would not understand the use of this term based on the context of its use, then "about" would mean that the particular value is at most plus or minus 10%.

As used herein, the term "adduct" refers to the product of two or more different molecules, which are added to each other.

As used herein, the term "heterojunction" refers to an interface or interface junction between different materials, i.e., a crystalline interface formed by the combination of two semiconductor materials having different forbidden band widths.

The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Examples

Example 1 carbon Quantum dot-graphite phase carbon nitride (CQDs-g-C) ₃ N ₄ ) Synthesis of (2)

CQDs-g-C in this example ₃ N ₄ The preparation method of the nanosheet takes formamide as a precursor, and g-C is prepared by improving a microwave-assisted hydrothermal method ₃ N ₄ The method of (1). The method comprises the following specific steps:

in this example, formamide was used as a nitrogen source, 10mL of formamide, 0.75g of citric acid, and 0.75g of sodium acetate were stirred for 40min to react sufficiently, and in a slightly alkaline environment (pH = 8.2), the formation of a prepolymer between citric acid and formamide was facilitated. And after stirring uniformly, transferring the reaction solution into a 30mL hydrothermal reaction kettle, heating the reaction solution to 230 ℃ in an oven, carrying out heat preservation reaction for 3 hours, and cooling at room temperature to obtain a brownish black reaction solution. The final reaction solution contains CQDs-g-C ₃ N ₄ And (3) nanosheets, wherein the unreacted reactants are purified by a centrifugal method. Absolute ethanol (500 mL) was first added to the reaction solution to give a large amount of brownish black precipitate which had good water solubility. Washing the precipitate with ethanol for at least three times, and drying the precipitate in a vacuum drying oven at 40 deg.C for 12 hr to obtain final product labeled CQDs-g-C ₃ N ₄ 。

Example 2 Synthesis of FeOCl

The preparation of FeOCl in this example was mainly obtained by a high temperature sintering method. The method comprises the following specific steps:

0.5g FeCl was weighed ₃ ·6H ₂ O was ground thoroughly in an agate mortar to give a yellow powder which was then transferred to a crucible, wrapped with aluminium foil paper and the label transferred to a muffle furnace where it was heated to 250 ℃ at a 2 ℃ ramp rate for 3h. Cooling to room temperature after the reaction is finished, taking out the reaction solution to remove a large amount of unreacted FeCl ₃ ·6H ₂ O, washed to clear with acetone and dried overnight in a vacuum oven at 60 ℃ to afford the subsequent experiments.

Example 3CQDs-g-C ₃ N ₄ Preparation of/FeOCl composite material

CQDs-g-C ₃ N ₄ The preparation scheme of/FeOCl is mainly to add CQDs-g-C3N4 synthesized in example 1 into a precursor for synthesizing FeOCl. The method comprises the following specific steps:

weighing 0.5g of CQDs-g-C ₃ N ₄ And 1.5g FeCl ₃ ·6H ₂ Grinding the mixture in a mortar until the mixture is fully mixed, then transferring the mixture into a crucible, wrapping the mixture by using aluminum foil paper, heating the mixture to 250 ℃ in a muffle furnace at the temperature rise rate of 2 ℃ for heat preservation for 3 hours, taking out the mixture after the reaction is finished, centrifugally washing the mixture for several times by using acetone until the supernatant is clear and transparent, then transferring the precipitate to a vacuum drying oven at the temperature of 60 ℃ for drying overnight for subsequent experiments, and marking the precipitate as CQDs-g-C ₃ N ₄ /FeOCl。

Example 4CQDs-g-C ₃ N ₄ Preparation of/FeOCl composite material

1.5g CQDs-g-C3N4 and 0.5g FeCl were weighed ₃ ·6H ₂ Grinding the mixture in a mortar until the mixture is fully mixed, then transferring the mixture into a crucible, wrapping the mixture by using aluminum foil paper, heating the mixture to 250 ℃ in a muffle furnace at the temperature rise rate of 2 ℃ for heat preservation for 3 hours, taking out the mixture after the reaction is finished, centrifugally washing the mixture for several times by using acetone until the supernatant is clear and transparent, then transferring the precipitate to a vacuum drying oven at the temperature of 60 ℃ for drying overnight for subsequent experiments, and marking the precipitate as CQDs-g-C ₃ N ₄ /FeOCl。

Example 5 FeOCl, CQDs-g-C prepared in examples 1-3 ₃ N ₄ 、CQDs-g-C ₃ N ₄ FeOCl tabulationSign

5.1 this example uses a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), and a High Resolution Transmission Electron Microscope (HRTEM) to study the preparation of FeOCl, CQDs-g-C, respectively, from examples 1-3 ₃ N ₄ 、CQDs-g-C ₃ N ₄ The surface appearance of the/FeOCl three materials. The results of the detection are shown in FIG. 1.

Fig. 1a shows that FeOCl exhibits an irregular layered structure. According to a high-resolution transmission electron microscope (HR-TEM), a significant lattice fringe with a length of 0.23nm is shown in FIG. 1j, and according to the reported literature (Li et al.2020), the (002) crystal plane of FeOCl is shown in FIG. 1 j. CQDs-g-C ₃ N ₄ The SEM image is shown in FIG. 1e, which shows CQDs-g-C ₃ N ₄ Is in an irregular ultrathin bending layered structure. Also, CQDs-g-C can be seen from FIG. 1i ₃ N ₄ The appearance of the CQDs is in an ultra-thin layer structure and the CQDs are loaded on g-C ₃ N ₄ Of (2) is provided. CQDs-g-C ₃ N ₄ SEM and TEM of/FeOCl composites As shown in FIGS. 1C and g, feOCl filled CQDs-g-C ₃ N ₄ In the porous layered structure of (A), CQDs-g-C after compounding ₃ N ₄ And the morphology of FeOCl changes, possibly due to the synthesis of CQDs-g-C ₃ N ₄ CQDs-g-C in FeOCl ₃ N ₄ Incorporation of FeCl ₃ ·6H ₂ The O precursor may undergo a chemical change during the high temperature sintering process. Thus, CQDs-g-C ₃ N ₄ The morphology of/FeOCl is not CQDs-g-C ₃ N ₄ Simple stacking with FeOCl. FIG. 1k also shows CQDs-g-C ₃ N ₄ Existing CQDs-g-C in/FeOCl composite material ₃ N ₄ And also FeOCl. FIG. 1l is CQDs-g-C ₃ N ₄ HRTEM image of/FeOCl showing CQDs-g-C ₃ N ₄ Lattice fringes of FeOCl in FeOCl.

5.2 this example also addresses CQDs-g-C ₃ N ₄ The elements of the/FeOCl composite material are analyzed (by using a scanning electron microscope and a British edax apollo XL energy spectrometer, a backscattering image is shot by using a JSM-7800F type thermal field emission scanning electron microscope, the voltage is 20eV, the current is 10nA, the beam spot is 1 mu m, and 20mgCQDs-g-C is taken ₃ N ₄ /FeOCl for tablet carbon spray). The results of the detection are shown in FIG. 2.

FIGS. 2a-f show the Mapping images (Mapping) of each element, where Fe, O, cl, N, C are distributed on CQDs-g-C ₃ N ₄ On a/FeOCl composite material. Wherein the mapping of Fe, O and Cl elements can be attributed to FeOCl; the mapping of C, N can be attributed to CQDs-g-C ₃ N ₄ A compound is provided.

5.3 this example utilizes X-ray diffraction (XRD) analysis of examples 1-3 to prepare FeOCl, CQDs-g-C, respectively ₃ N ₄ 、CQDs-g-C ₃ N ₄ Purity and crystalline phase of/FeOCl three materials. The results are shown in FIG. 3 a.

CQDs-g-C as shown in FIG. 3a ₃ N ₄ Is determined by two diffraction peaks of 13.3 DEG and 27.4 DEG (JCPDS No. 87-1526), wherein the diffraction peak of 13.3 DEG appears corresponding to CQDs-g-C ₃ N ₄ Structural stacking of planar repeating tri-s-triazine units, a characteristic strong peak at 27.4 ° is caused by a graphite-like interlayer structural motif; three diffraction peaks at 24.8 °,26.8 °,28.2 ° were shown, indicating CQDs-g-C ₃ N ₄ There are different types of layered structures in the crystal due to planar stacking and interlayer stacking of the aromatic segments. CQDs doped g-C ₃ N ₄ Corresponding diffraction peaks of (A) and reported pure phase g-C ₃ N ₄ The diffraction peaks are basically consistent, which indicates that CQDs do not influence g-C ₃ N ₄ The structure of (1). In addition, since the CQDs content is low and the crystallinity is low, no diffraction peak of CQDs is found. All diffraction peaks of pure phase FeOCl can match the standard card for FeOCl (JCPDS card No. 24-1005); for CQDs-g-C ₃ N ₄ the/FeOCl composite material is formed by CQDs-g-C ₃ N ₄ Has a low content of CQDs-g-C ₃ N ₄ CQDs-g-C in XRD pattern of/FeOCl composite material ₃ N ₄ The diffraction peak of (A) is unclear, possibly due to excessive FeOCl wrapping CQDs-g-C ₃ N ₄ Covering up CQDs-g-C ₃ N ₄ And the diffraction peak of Fe is relatively strong, so that CQDs-g-C can be covered up ₃ N ₄ A diffraction peak of CQDs-g-C, thereby ₃ N ₄ the/FeOCl composite material is mainly characterized in thatShowing diffraction peaks for FeOCl.

5.4 this example was analyzed by Fourier transform infrared spectroscopy (FT-IR) in order to determine the functional groups and chemical bonds present in the catalyst. The results are shown in FIG. 3 b.

As shown in FIG. 3b, at 3387cm ^-1 The broad peak appears nearby and is designated as the surface absorption H of the three compounds ₂ Stretching mode of the O-H group of the O molecule; for FeOCl, the Fe-O group was 499.87cm ^-1 A distinct absorption band, 1625cm ^-1 Stretching vibration of Fe-Cl occurred nearby. For pure phase CQDs-g-C ₃ N ₄ Compound 1394-1625cm ^-1 Corresponds to a tensile vibration of the C = N, C-N bond, 798.3cm ^-1 The vicinity is due to CQDs-g-C ₃ N ₄ And 483.6cm ^-1 The absorption edge is present in relation to the energy gap; in the preparation of CQDs-g-C ₃ N ₄ 1625cm in the FeOCl system ^-1 The absorption bands at (A) are assigned to C = O and-CH ₂ (ii) a After FeOCl is doped, the corresponding peak is not shifted, but the characteristic peak of the compound is weaker than that of pure-phase FeOCl, CQDs-g-C ₃ N ₄ Also proves CQDs-g-C ₃ N ₄ CQDs-g-C present in/FeOCl ₃ N ₄ And FeOCl.

5.5 this example also analyzes the specific surface area of the prepared material using a full automatic specific surface and porosity analyzer (BET). The results are shown in FIG. 3 c.

CQDs-g-C as shown in FIG. 3C ₃ N ₄ Having H ₃ Type IV isotherms of type hysteresis loops, which indicate the presence of significant mesoporosity, feOCl and CQDs-g-C ₃ N ₄ The isotherm of/FeOCl conforms to the type I isotherm, which indicates that it is a microporous structure, feOCl, CQDs-g-C ₃ N ₄ 、CQDs-g-C ₃ N ₄ The specific surface area of/FeOCl was 9.2854m2/g, 58.4287m2/g, and 9.1073m2/g, respectively. However, when CQDs-g-C ₃ N ₄ In which FeOCl material, CQDs-g-C, is doped ₃ N ₄ The surface area of the CQDs-g-C is reduced, which indicates that the FeOCl particles are opposite to the CQDs-g-C ₃ N ₄ The active site of the/FeOCl has an occupying effect. In general terms, the term "a" or "an" is used to describe a device that is capable of generating a signalThe microporous structure can provide more active centers for the enrichment of contaminants. Indicating that the specific surface area influences CQDs-g-C ₃ N ₄ Important parameter for the FeOCl activity. Thus, with pure phase FeOCl and CQDs-g-C ₃ N ₄ CQDs-g-C ₃ N ₄ /FeOCl(9.1073m ² The specific surface area per gram) substantially corresponds to that of FeOCl (9.2854m2/g).

In the following adsorption experiments, pure phase FeOCl and CQDs-g-C ₃ N ₄ Does not have better effect on the adsorption of the target antibiotic tetracycline hydrochloride. Surprisingly, CQDs-g-C ₃ N ₄ Although the specific surface area of the/FeOCl is small, the adsorption effect on tetracycline is very good (FIGS. 6a and b), and the experimental result further proves that the microporous structure is formed to provide more active centers. Also described are binary systems CQDs-g-C ₃ N ₄ The enhanced catalytic activity of/FeOCl is attributed to its formation of a heterojunction structure, i.e., feOCl exhibits excellent catalytic performance as a Fenton catalyst due to the narrow band gap (about 1.9 eV) and appropriate band structure of FeOCl, which allows for its use with other semiconductors such as CQDs-g-C ₃ N ₄ A heterojunction is formed.

5.6 to further explore CQDs-g-C ₃ N ₄ The chemical morphology of the/FeOCl composite material, in this example, was also analyzed in detail by X-ray photoelectron spectroscopy (XPS). The results of the detection are shown in FIG. 4.

FIG. 4a is a full spectrum showing CQDs-g-C ₃ N ₄ Elements in the/FeOCl composite material. The results of fig. 4a confirm the presence of Fe, O, cl, C, N in the composite material.

CQDs-g-C in FIG. 4b ₃ N ₄ The element C exists in the/FeOCl composite material. 284.8eV, 288.2eV, and 286.5eV correspond to CQDs-g-C, respectively ₃ N ₄ C-C, N-C = N, peak of C-O-C bond in (1).

Typical spectra for Cl 2p are shown in FIG. 4c, with characteristic peaks for Cl 2p at 197.6eV and 199.3eV corresponding to Fe-Cl bonds, respectively.

Fig. 4d shows the spectrum of O1 s: 529.19eV to 530.82eV match the Fe-O bond phase of the metal oxide in the FeOCl lattice; 532.78eV is attributed to surface water molecules.

In the N1s spectrum shown in fig. 4e, 398.6eV and 399.7eV are assigned to the C-N = C bond and N (N- (C) respectively ₃ ) A bond); 397.8eV to the Fe-N bond.

Fig. 4f shows the spectrum of Fe2 p: the peaks at 711.2eV and 725.17eV correspond to Fe ³⁺ Peaks at 2p3/2 and 2p 1/2; the peaks at 710.26eV and 723.45eV are assigned to Fe ²⁺ 2p3/2 and 2p1/2, and at the same time, two satellite peaks at 713.39eV and 717.38eV, these findings all confirmed CQDs-g-C ₃ N ₄ Successful synthesis of/FeOCl, and in CQDs-g-C ₃ N ₄ In FeOCl, feOCl and CQDs-g-C ₃ N ₄ There is an interaction. Furthermore, from the reacted CQDs-g-C ₃ N ₄ In XPS of the/FeOCl composite material, fe-N groups disappear and are possibly consumed in the reaction process of catalyzing and degrading TC-HCl, and other groups are basically kept unchanged, which shows that CQDs-g-C ₃ N ₄ the/FeOCl has certain stability as a catalyst.

Example 6CQDs-g-C ₃ N ₄ Evaluation of catalytic Performance of/FeOCl as catalyst

The heterogeneous Fenton reaction of this example was performed in a 100ml reaction flask for TC-HCl degradation. The specific experimental steps are as follows:

40ml of TC-HCl solution is filled in an experimental reaction bottle, the initial pH of the TC-HCl solution is adjusted by 1M HCl or NaOH, the catalyst is put into the reaction bottle filled with the TC-HCl solution at room temperature, and H is added ₂ O ₂ The reaction was initiated and at predetermined time intervals (2min, 4min,6min,8min,10min or 1h,2h,4h,6h,12h, 24h) 1.6ml of sample was taken from the reaction flask, quenched immediately by addition of 300. Mu.L of t-butanol, filtered through a 0.22 μm filter for further analysis, and the results were averaged over three runs. After the experiment, the sample was refrigerated in a refrigerator at 4 ℃ for HPLC testing.

The concentration of TC-HCl solution was determined by high performance liquid chromatography (Agilent-1260) equipped with UV detector, and the chromatography was performed by reverse phase C18 chromatography. The mobile phase of TC-HCl consists of 65 percent of sodium dihydrogen phosphate and 35 percent of acetonitrile, the elution flow rate is 1ml/min, the sample injection amount is 20 mu L, the detection wavelength is 360nm, and the column temperature is 25 ℃.

Liquid chromatography-mass spectrometer (HPLC-MS, thermo Fisher Scientific): mobile phase selection in positive ion mode: a-0.1% formic acid aqueous solution, B-0.1% formic acid-acetonitrile aqueous solution; selection of mobile phase in negative ion mode: a-0.03% ammonia solution; b-0.03% ammonia water-acetonitrile solution.

6.1FeOCl and CQDs-g-C ₃ N ₄ Influence of doping amount

The removal of tetracycline hydrochloride (TC-HCl) was evaluated in different systems. For the formation of. OH, the Fe content had a significant effect on the removal of contaminants.

(40 ml of TC-HCl solution is filled in an experimental reaction bottle, the initial pH of the TC-HCl solution is adjusted by 1M HCl or NaOH, the catalyst is put into the reaction bottle filled with the TC-HCl solution at room temperature, and H is added ₂ O ₂ The reaction was initiated and at predetermined time intervals (2min, 4min,6min,8min,10min or 1h,2h,4h,6h,12h, 24h), 1.6ml of sample was taken from the reaction flask, quenched by immediately adding 300. Mu.L of t-butanol, filtered through a 0.22. Mu.m filter for further analysis, and the results were averaged for three runs per set. Samples obtained after the experiment were refrigerated in a refrigerator at 4 ℃ for HPLC testing). Experimental conditions, [ TC] _Initial =20ppm CQDs-g-C prepared in example 1 ₃ N ₄ FeOCl prepared in example 2, and CQDs-g-C prepared in examples 3 and 4 ₃ N ₄ /FeOCl＝0.2g/L，[H ₂ O ₂ ]＝0.3mM，[pH] _{Initiation of} =3.5. See figure 5a for results. FIG. 5a shows FeOCl and CQDs-g-C ₃ N ₄ Influence of different doping amounts on the degradation of TC-HCl.

As shown in FIG. 5a, in the presence of H ₂ O ₂ The removal rate of TC-HCl solution after FeOCl in 10min can reach 78.5%, and pure phase CQDs-g-C is added ₃ N ₄ The tetracycline solution in 10min was only removed by 27.0%. From CQDs-g-C ₃ N ₄ CQDs-g-C prepared by taking the mass ratio of CQDs to FeOCl as 1 ₃ N ₄ /FeOCl (prepared in example 3)Prepared) has obviously improved degradation activity to TC-HCl solution, the reaction time is only 8min, and the removal rate of tetracycline hydrochloride can reach 100%. However, from CQDs-g-C ₃ N ₄ And CQDs-g-C prepared by FeOCl with the mass ratio of 3 ₃ N ₄ the/FeOCl (prepared in example 4) degradation activity on TC-HCl solution was not as high as FeOCl. The reason may be that, due to CQDs-g-C ₃ N ₄ Blocking the Fe active center in FeOCl, and illustrating CQDs-g-C ₃ N ₄ Is not the primary active center. The experimental result shows that CQDs-g-C ₃ N ₄ The catalytic activity of the/FeOCl is higher than that of FeOCl and CQDs-g-C ₃ N ₄ Indicating the formation of CQDs-g-C ₃ N ₄ The FeOCl improves the FeOCl and the CQDs-g-C ₃ N ₄ The catalytic performance of (2).

6.2 different H ₂ O ₂ Effect on TC-HCl degradation

H ₂ O ₂ The concentration problem of (A) is also an important problem in heterogeneous Fenton reaction, if H ₂ O ₂ At a lower concentration, the amount of OH produced is insufficient to successfully initiate the fenton reaction; if H is ₂ O ₂ Too high a concentration of H ₂ O ₂ Not only will rob OH generated in the solution to reduce the catalytic efficiency, but also will cause reagent waste and increase the catalytic cost. In view of this, H ₂ O ₂ Is also one of the investigated ranges, therefore the CQDs-g-C prepared in example 3 was investigated ₃ N ₄ H in heterogeneous Fenton degradation system by FeOCl ₂ O ₂ The addition concentrations are respectively 0.05mM, 0.1mM, 0.3mM, 0.6mM and 1mM, and the influence on TC-HCl degradation is achieved. Experimental conditions, [ TC-HCl ]] _{Initiation of} ＝20ppm，CQDs-g-C ₃ N ₄ /FeOCl＝0.2g/L，[H ₂ O ₂ ]＝0.05mM、0.1mM、0.3mM、0.6mM、1mM，[pH] _Initial =3.5. The results are shown in FIG. 5 b. FIG. 5b shows a difference H ₂ O ₂ Effect of concentration on TC-HCl degradation.

As shown in FIG. 5b, TC-HCl removal efficiency vs. H ₂ O ₂ The degradation efficiency of TC-HCl gradually increases with the increase of the H2O2 concentration. Wherein H ₂ O ₂ At a concentration of 0.6-1mM, inWhen the reaction is carried out for 4min, the removal rate of TC-HCl almost reaches 100 percent and is far higher than that of H ₂ O ₂ The removal rate of TC-HCl at a concentration of 0.05-0.3 mM.

6.3 Effect of different pH on TC degradation

The existing Fenton reaction is carried out in a narrow pH range, usually the pH is 3-4, and the application of the Fenton reaction in a practical water sample is limited. And in the heterogeneous Fenton reaction pH influences the properties of the catalyst, the dissociation of the antibiotic and H ₂ O ₂ Has a certain influence.

This example is to explore H ₂ O ₂ In the whole reaction system, the influence of initial pH values of TC-HCl solutions of 3.0, 5.0, 7.0, 9.0 and 11.0 on TC-HCl degradation experiments is set. The results are shown in FIG. 5 c.

As can be seen in FIG. 5c, the pH of the initial solution affects catalyst/H ₂ O ₂ Key factors in the catalytic performance of the system. CQDs-g-C ₃ N ₄ /FeOCl/H ₂ O ₂ The initial pH of the solution in the removal system has a significant effect on tetracycline hydrochloride. In the pH range of 3-9, the removal of TC is promoted. Especially, the TC-HCl removal rate is up to 100 percent when the reaction is carried out for 2min within the pH range of 7-9. At a pH of 11, in addition to CQDs-g-C ₃ N ₄ When the/FeOCl has certain adsorption effect on TC-HCl, the removal rate of TC-HCl and the removal rate of TC-HCl under other pH conditions are reduced from 100% to 60% along with the increase of degradation time, thereby indicating that H ₂ O ₂ More easily generate a large amount of hydroxyl radicals under acidic, neutral and alkalescent conditions. At lower pH, the amine group of TC-HCl is protonated and at pH > 7 is converted to the anion by deprotonation under basic conditions. Therefore, at different pH values, TC-HCl has two forms of protonation and deprotonation, and the pH value plays an important role in removing TC-HCl. From the view of the reaction speed, the TC-HCl removal rate under the neutral condition with the optimal pH value of 7.00 can also reach 100 percent, and the removal efficiency can be seriously influenced under the condition of strong acid or strong alkali. CQDs-g-C has also been shown ₃ N ₄ The excellent catalytic performance of the/FeOCl is still maintained in a wide pH range. CQDs-g-C are also disclosed ₃ N ₄ The FeOCl can effectively make up for the shortage of the homogeneous Fenton pH range without introducing light, and is more beneficial to being applied to the actual water environment.

6.4 this example also investigated other references to compare TC-HCl removal, as shown in Table 1.

TABLE 1 catalytic Performance of different catalysts for degradation of TC-HCl in Fenton's reaction

As can be seen from Table 1, CQDs-g-C are compared with catalysts and their catalytic performances reported in other literatures ₃ N ₄ the/FeOCl has the characteristics of no need of introducing illumination and H ₂ O ₂ The catalyst has the advantages of small dosage, short catalysis time, suitability for a reaction system with pH of 3-11 and wide pH range. Thus, CQDs-g-C ₃ N ₄ the/FeOCl has certain practical value in the field of antibiotic degradation.

6.5CQDs-g-C ₃ N ₄ Adsorption of TC-HCl by FeOCl

During the catalytic experiment, it was found that the degradation process was accompanied by the adsorption process, and thus CQDs-g-C was performed ₃ N ₄ Adsorption experiment of TC-HCl by FeOCl to evaluate CQDs-g-C ₃ N ₄ Adsorption by FeOCl. The adsorption and degradation experiments are carried out simultaneously, the steps and conditions of the adsorption and degradation experiments are the same, and the difference is that H is not added in the adsorption experiments ₂ O ₂ And the reaction flask was on a constant temperature stirrer, 25 ℃,150rpm. The experimental conditions are as follows: [ TC-HCl ]] _Initial ＝20ppm、CQDs-g-C ₃ N ₄ /FeOCl＝0.2g/L、[H ₂ O ₂ ]＝0.3mM、[pH] _{Initiation of} ＝3.5。

As shown in FIG. 6a, CQDs-g-C were observed within 24 hours ₃ N ₄ /FeOClThe adsorption capacity to TC-HCl can reach 105.2632mg/g.

As can be seen from FIG. 6b, CQDs-g-C were observed at an adsorption time of 1 hour ₃ N ₄ The adsorption capacity of the/FeOCl to TC-HCl is higher, and the TC-HCl is completely adsorbed with the increase of time until 24h.

As shown in FIG. 6c, the TC-HCl removal rate in the adsorption experiment within 10min is only 53.33%, while H is added ₂ O ₂ When the reaction time in the degradation experiment of (2) was only 4min, TC-HCl was completely removed, which indicates that adsorption and degradation proceeded simultaneously, and H ₂ O ₂ The removal efficiency of TC-HCl is accelerated, and the heterogeneous Fenton system provided by the invention has potential huge value in the aspect of removing antibiotics, particularly organic pollutants such as TC-HCl and the like.

Example 7 validation of CQDs-g-C ₃ N ₄ Removal effect on antibiotics in actual water environment

This example demonstrates CQDs-g-C prepared in example 3 ₃ N ₄ The removal effect of FeOCl on different antibiotics. The water sample used in this example was obtained from the southern Ming river in south Ming district, guiyang City, guizhou province.

The specific experimental steps are as follows: 40ml of TC-HCl/river water solution is filled in an experimental reaction bottle, the initial pH of the TC-HCl solution is adjusted by 1MHCl or NaOH, the catalyst is put into the reaction bottle filled with the TC-HCl solution at room temperature, and H is added ₂ O ₂ The reaction was initiated and at predetermined time intervals (2min, 6min,10min or 10min,20min,40min,50min, 60min), 1.6ml of sample was taken in the reaction flask, 300. Mu.L of t-butanol was immediately added to quench the reaction, and filtration was performed with a 0.22 μm filter for further analysis, and the results were averaged for three times for each set of experiments. After the experiment, the sample was refrigerated in a refrigerator at 4 ℃ for HPLC testing.

The concentration of antibiotics TC-HCl, SMX and AM was determined by high performance liquid chromatography (Agilent-1260) equipped with UV detector, and reversed phase C18 column was used for chromatographic separation.

The mobile phase of TC-HCl consists of 65 percent of sodium dihydrogen phosphate and 35 percent of acetonitrile, the elution flow rate is 1ml/min, the sample injection amount is 20 mu L, the detection wavelength is 360nm, and the column temperature is 25 ℃.

The mobile phase of Amoxicillin (AM) is 70% potassium dihydrogen phosphate and 30% methanol, the elution flow rate is 0.6ml/min, and the sample injection amount is 20 μ L. The detection wavelength was 240nm and the column temperature was 30 ℃.

Mobile phase of Sulfamethoxazole (SMX) by 65% H ₂ O (containing 0.1% glacial acetic acid) and 35% methanol, the elution flow rate is 0.8ml/min, the sample injection amount is 20 mu L, the detection wavelength is 270nm, and the column temperature is 30 ℃.

7.1 in practical Water environments, various inorganic ions in the Water affect the catalyst CQDs-g-C in many ways ₃ N ₄ The properties of/FeOCl, including adjusting pH, trapping OH, and affecting H ₂ O ₂ The decomposition rate of (c). The influence of the actual water environment on tetracycline hydrochloride cannot be ignored, so that a related experiment for simulating the removal of TC-HCl with different concentrations is carried out in order to explore the influence of the actual water sample on the degradation of TC-HCl. The experimental conditions are as follows: [ TC-HCl ]]＝20、40、60ppm、[H ₂ O ₂ ]＝0.3mM、[CQDs-g-C ₃ N ₄ /FeOCl]=0.2g/L, pH =3.5. The results are shown in FIG. 7 a.

As can be seen from the results shown in FIG. 7a, the surface water environment had no significant effect on TC degradation, even at higher TC-HCl concentrations (60 ppm), CQDs-g-C ₃ N ₄ The removal rate of TC-HCl by the/FeOCl can still reach 95.9 percent. Visible, CQDs-g-C ₃ N ₄ the/FeOCl composite material has stronger adaptability to complex water environment.

7.2 this example is to demonstrate CQDs-g-C ₃ N ₄ the/FeOCl has universal applicability and also verifies CQDs-g-C ₃ N ₄ The removal effect of/FeOCl on the other two antibiotics, amoxicillin (AM) and Sulfamethoxazole (SMX), respectively. Experimental conditions for AM removal: [ AM ]]＝20ppm、[H ₂ O ₂ ]＝3mM、[CQDs-g-C ₃ N ₄ /FeOCl]=0.2g/L, pH =3.5. Experimental conditions for removal of SMX: [ SMX ]]＝20ppm、[H ₂ O ₂ ]＝3mM,10mM,50mM,100mM、[CQDs-g-C ₃ N ₄ /FeOCl]＝0.2g/L、pH＝3.5。

The result of removing AM is shown in fig. 7 b. As can be seen from FIG. 7b, CQDs-g-C ₃ N ₄ The degradation efficiency of the/FeOCl to AM within 1h reaches more than 90 percent.

The result of removing SMX is shown in fig. 7 c. As can be seen from FIG. 7C, CQDs-g-C ₃ N ₄ the/FeOCl also has a strong removing effect on SMX. At the same time react on different H ₂ O ₂ Degradation of SMX under concentration conditions when H ₂ O ₂ When the concentration reaches 10mM, the SMX degradation efficiency can reach more than 96%.

In conclusion, the CQDs-g-C of the present invention ₃ N ₄ the/FeOCl has higher catalytic activity to different types of antibiotics.

Example 8 catalytic degradation mechanism

The experimental procedure and experimental conditions of this example were the same as those of example 6.

8.1 active species analysis

8.1.1 quenching of hydroxyl radicals by Tert-Butanol and p-benzoquinone

To gain an insight into CQDs-g-C ₃ N ₄ The degradation mechanism of/FeOCl, the free radical trapping experiment, was performed in this example to study CQDs-g-C ₃ N ₄ The efficiency of degradation of TC-HCl by FeOCl in this study, we selected different quenchers, including t-Butanol (TBA) and p-benzoquinone, to quench OH and superoxide such as O, respectively ₂ · ^- Or HO ₂ · ^- . The results of the experiment are shown in FIG. 5 d.

FIG. 5d shows that the degradation efficiency of TC-HCl is 64.95% and 100% respectively within 10min, compared with the degradation experiment without TBA, after TBA is added, the degradation reaction is inhibited, one group of degradation experiments with p-benzoquinone is not inhibiting the reaction rate, and TC-HCl can be completely degraded, indicating that the whole reaction system OH plays a dominant role rather than HO ₂ · ^- 。

8.1.2DMPO Capture of hydroxyl radical

To further investigate CQDs-g-C of the heterogeneous Fenton System ₃ N ₄ CQDs-g-C, the catalytic mechanism of the major active species component in FeOCl composites ₃ N ₄ /FeOCl/H ₂ O ₂ Various reactive species such as hydroxyl radical, superoxide radical, etc. may be generated from the system, and in order to identify the main reactive species in the heterogeneous fenton reaction, electron Spin Resonance (ESR) spectroscopy was performed using 5, 5-dimethyl-1-pyrroline nitroxide (DMPO) as a nitrocopper spin trap for trapping radicals.

As a comparison, during the experiment, the first group was controlled without addition of H, still with TC-HCl as substrate ₂ O ₂ The second set of pure DMPO blank experiments of (1) was TC-HCl + H ₂ O ₂ + DMPO (100 mM) assay, third TC-HCl + H ₂ O ₂ +DMPO(100mM)+CQDs-g-C ₃ N ₄ Experiments with/FeOCl. The results of three experiments are shown in FIG. 8, at TC-HCl + H ₂ O ₂ No significant signal was found in the + DMPO (100 mM) experiment. Interestingly, in the third group TC-HCl + H ₂ O ₂ +DMPO(100mM)+CQDs-g-C ₃ N ₄ The typical fourfold characteristic peak of the DMPO-OH stable adduct with an intensity ratio of 1 ₃ N ₄ /FeOCl/H ₂ O ₂ Is prepared by the steps of (1).

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention can be made, and the same should be considered as the disclosure of the present invention as long as the idea of the present invention is not violated.

Claims

1. A catalyst, comprising carbon quantum dot-graphite phase carbon nitride, and FeOCl supported on the carbon quantum dot-graphite phase carbon nitride.

2. The catalyst according to claim 1, wherein the mass ratio of the carbon quantum dot-graphite phase carbon nitride to FeOCl is 1; preferably 1.

3. The catalyst of claim 1, wherein the catalyst has a two-dimensional layered structure and wherein Fe-N bonds are present in the catalyst.

4. The catalyst according to claim 1, wherein the specific surface area of the catalyst is 8 to 15m ² Per g, pore diameter of

5. The catalyst according to claim 1, wherein the catalyst is prepared by grinding and mixing the carbon quantum dot-graphite phase carbon nitride and a precursor of FeOCl, and calcining the mixture;

preferably, the precursor is FeCl ₃ ；

Preferably, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to the precursor is 3.

6. The catalyst of claim 1, wherein the carbon quantum dot-graphite phase carbon nitride is prepared by a hydrothermal method;

preferably, after uniformly stirring formamide, citric acid and sodium acetate, carrying out hydrothermal reaction for 0.5-1 hour at 20-35 ℃ to obtain a reaction solution containing the carbon quantum dot-graphite phase carbon nitride;

separating the carbon quantum dot-graphite phase carbon nitride from the reaction solution;

more preferably, the carbon quantum dot-graphite phase carbon nitride is washed and dried;

more preferably, the solvent used for the washing is absolute ethanol.

7. A process for preparing the catalyst of any one of claims 1 to 6, comprising:

separating the catalyst from the mixture;

preferably, the mass ratio of the carbon quantum dot-graphite phase carbon nitride to the precursor is 3;

preferably, the precursor is FeCl ₃ ；

Preferably, the separation is washing the mixture with acetone, followed by drying to obtain the catalyst.

8. A method of treating wastewater containing antibiotics, the method comprising the steps of:

adding the catalyst of claims 1-6 and H to the wastewater ₂ O ₂ ；

Preferably, the dosage of the catalyst is 0.05-0.5g/L, preferably 0.1-1g/L, based on the volume of the wastewater;

preferably, said H is based on the volume of said wastewater ₂ O ₂ The adding amount of (A) is 0.05-0.5g/L, preferably 0.1-0.5g/L;

preferably, the pH of the wastewater is adjusted to 3 to 11, preferably 3 to 9, more preferably 7 to 9;

preferably, the antibiotic is selected from at least one of sulfonamide antibiotics, beta-lactam antibiotics, tetracycline antibiotics, and fluoroquinolone antibiotics;

more preferably, the antibiotic is selected from at least one of sulfamethoxazole, amoxicillin and tetracycline hydrochloride.

9. Use of the catalyst of any one of claims 1 to 6 in a fenton reaction;

preferably, the pH of the fenton reaction is between 3 and 11, preferably between 3 and 9, more preferably between 7 and 9.

10. Use of a catalyst according to any one of claims 1 to 6 for degrading antibiotics;