A method for degrading antibiotics in water using a monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst

Abstract

The present invention discloses a method for degrading antibiotics in water using a monolayer of ferric oxyhydroxide / reduced graphene oxide photocatalyst. The method is to perform photo-Fenton degradation of the antibiotics in water using the monolayer of ferric oxyhydroxide / reduced graphene oxide photocatalyst. The monolayer of ferric oxyhydroxide / reduced graphene oxide photocatalyst comprises a monolayer of ferric oxyhydroxide and reduced graphene oxide, wherein the monolayer of ferric oxyhydroxide is nested in the reduced graphene oxide and supported on the surface of the reduced graphene oxide. The method for degrading antibiotics in water using the monolayer of ferric oxyhydroxide / reduced graphene oxide photocatalyst has the advantages of simple process, convenient operation, high treatment efficiency, good degradation effect, low cost, and no secondary pollution. It can achieve efficient and rapid removal of antibiotics from water. It is a method that can be widely adopted and can efficiently and quickly remove antibiotics from water, and has high application value and commercial value.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic treatment and relates to a method for degrading antibiotics, in particular to a method for degrading antibiotics in water by utilizing a single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst. Background Art

[0002] Antibiotics are widely used to treat infectious diseases in humans and animals. However, a large amount of unused antibiotics enters the environment through municipal wastewater, sewage sludge, solid waste, and feces. The concentration of antibiotics in domestic wastewater ranges from 100 ng / L to 6 mg / L. Furthermore, due to their biological activity, stability, and non-biodegradability, antibiotics pose a threat to aquatic organisms when they enter the aquatic environment and also pose a risk of increasing pathogen resistance to antibiotics. Therefore, effectively removing antibiotics from aquatic environments has become a technical challenge that urgently needs to be addressed.

[0003] Currently, methods for removing antibiotics include adsorption, microbial degradation, electrolysis, photocatalysis, and membrane separation. Among these, photocatalysis is considered one of the most promising approaches for antibiotic remediation. Compared to conventional wastewater treatment processes, photocatalysis offers advantages such as low energy consumption, ease of operation, mild reaction conditions, no secondary pollution, and strong oxidative capacity. Consequently, it has been widely used to degrade antibiotics in aquatic environments. Therefore, obtaining a suitable catalyst is crucial for the effective degradation of antibiotics using photocatalytic technology.

[0004] Iron oxyhydroxide is a common iron oxide that is widely present in nature. At the same time, iron oxyhydroxide can be used as a Fenton catalyst in heterogeneous Fenton systems, thereby also achieving the degradation of organic pollutants. However, in the actual application of iron oxyhydroxide, there are still some defects. For example, according to the structural characteristics of iron oxyhydroxide, its surface activity is relatively low due to its small particle size, easy agglomeration, poor dispersibility and other properties, such as low specific surface area and few active sites. Furthermore, according to the optical properties of iron oxyhydroxide, due to the high photogenerated electron-hole pair recombination efficiency and low photogenerated electron mobility of iron oxyhydroxide, it is difficult to show excellent photocatalytic activity, and thus it is difficult to achieve efficient degradation of target pollutants. Obviously, these shortcomings have greatly restricted the widespread application of iron oxyhydroxide in the field of photocatalysis. Based on this, some researchers proposed an α-hydroxy iron oxide loaded graphene-carbon nanotube catalyst, in which α-hydroxy iron oxide was loaded on graphene-carbon nanotubes through a hydrothermal reaction. However, when the heterogeneous photocatalytic system constructed by the α-hydroxy iron oxide loaded graphene-carbon nanotube catalyst as a Fenton catalyst was used to degrade antibiotics, it was still difficult to quickly degrade antibiotics in water, and there was a defect of low degradation efficiency. For example, using 100 mg of catalyst, the degradation rate of tetracycline with an initial concentration of 20 mg / L was only about 90% within 60 minutes. Analysis showed that the reason may be that the α-hydroxy iron oxide prepared by the hydrothermal reaction still has defects such as easy agglomeration, poor dispersibility, small specific surface area, and few active sites, which makes it difficult for the photocatalyst to efficiently degrade antibiotics in water. In addition, the catalyst has poor absorption effect on visible light and can only carry out photocatalytic reaction under ultraviolet light. At the same time, the catalyst also has defects such as high preparation cost, which makes it difficult for the loaded hydroxy iron oxide photocatalyst to be widely used to degrade antibiotics in water. At the same time, the inventors of this application also discovered in their actual research that conventional supported iron oxyhydroxide photocatalysts still suffer from poor stability. Due to structural instability, the iron oxyhydroxide easily falls off during actual use, which not only easily leads to catalyst failure but also may cause secondary pollution, making it difficult to reuse in the treatment of antibiotic wastewater, and the treatment cost remains high. Therefore, how to obtain a supported iron oxyhydroxide photocatalyst with high catalytic activity, good stability, and a wide range of applications is of vital importance for the effective removal of antibiotics from water, and is an urgent need. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for degrading antibiotics in water using a single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst with simple process, convenient operation, high treatment efficiency, good removal effect and environmental friendliness.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A method for degrading antibiotics in water using a single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst. The method comprises performing a photo-Fenton degradation treatment on the antibiotics in water using the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst. The single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst comprises a single-layer iron oxyhydroxide and reduced graphene oxide, wherein the single-layer iron oxyhydroxide is embedded in the reduced graphene oxide and is loaded on the surface of the reduced graphene oxide.

[0008] The above method is further improved, and the preparation method of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst comprises the following steps: mixing a monolayer iron oxyhydroxide, graphene oxide and ascorbic acid, and performing a reduction reaction to obtain a monolayer iron oxyhydroxide-doped reduced graphene oxide photocatalyst.

[0009] The above method is further improved, wherein the mass ratio of the monolayer iron oxyhydroxide to graphene oxide is 5 to 15:1; the mass ratio of the graphene oxide to ascorbic acid is 1:8 to 12; the reduction reaction is carried out at a temperature of 55°C to 65°C; and the reduction reaction time is 3.5h to 4.5h.

[0010] The above method is further improved in that the mass ratio of the monolayer iron oxyhydroxide to graphene oxide is 8-12:1; and the mass ratio of the graphene oxide to ascorbic acid is 1:10.

[0011] The above method is further improved, wherein the preparation method of the monolayer iron oxyhydroxide comprises the following steps:

[0012] S1, removing oxygen from the sodium lauryl phosphate solution;

[0013] S2. Adding the divalent iron salt solution to the sodium lauryl acid solution, adjusting the pH of the system to alkaline, adding the trivalent iron salt solution, stirring under alkaline conditions, and filtering to obtain a precipitate;

[0014] S3, oxidizing the precipitate to obtain iron oxyhydroxide;

[0015] S4. Place the iron oxyhydroxide in an alkaline solution and stir to obtain a monolayer of iron oxyhydroxide.

[0016] The above method is further improved, in step S1, Ar gas is continuously introduced into the sodium dodecanoate solution under stirring conditions to remove oxygen in the sodium dodecanoate solution; the flow rate of the Ar gas is 45 mL / min to 55 mL / min; the continuous introduction time of the Ar gas is 1.5 h to 2.5 h; and the concentration of the sodium dodecanoate solution is 20 mM to 30 mM.

[0017] The above method is further improved, in step S2, a sodium hydroxide solution is used to adjust the pH value of the system to 8±0.5; the concentration of the sodium hydroxide solution is 0.8M~1.2M; the volume ratio of the sodium dodecanoate solution, the divalent iron salt solution and the trivalent iron salt solution is 95:6:7; the divalent iron salt solution is a ferrous sulfate solution; the concentration of the ferrous sulfate solution is 0.5M; the trivalent iron salt solution is a ferrous sulfate solution; the concentration of the ferric sulfate solution is 0.1M; and the pH value of the system is maintained at 8±0.5 during the stirring process.

[0018] The above method is further improved, in step S3, the oxidation treatment is: dispersing the precipitate in oxygen-free water, adjusting the pH value of the system to 8±0.5, and oxidizing the precipitate in the system under stirring conditions; the oxidation time is 10h to 15h.

[0019] The above method is further improved, in step S4, the alkaline solution is a sodium hydroxide solution; the concentration of the sodium hydroxide solution is 0.08M to 0.12M; and the stirring time is 10h to 15h.

[0020] The above method is further improved by using a monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on antibiotics in water, comprising the following steps: mixing the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst with antibiotic wastewater, adding hydrogen peroxide, stirring, and performing a photo-Fenton catalytic reaction under light conditions to complete the degradation of the antibiotics in the wastewater.

[0021] The above method is further improved, wherein the amount of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst added is 12 mg to 20 mg per liter of antibiotic wastewater; and the initial concentration of hydrogen peroxide in the control system during the photo-Fenton catalytic reaction is 0.05 M to 0.2 M.

[0022] The above method is further improved, wherein the initial concentration of the antibiotic in the antibiotic wastewater is 9.8 mg / L to 95 mg / L, the initial pH value of the antibiotic wastewater is 3 to 5; and the antibiotic in the antibiotic wastewater is at least one of ciprofloxacin, norfloxacin, levofloxacin hydrochloride and tetracycline.

[0023] The above method is further improved in that the stirring is carried out in the dark; the stirring speed is 300r / min to 400r / min; the stirring time is 1h to 2h; and the photo-Fenton catalytic reaction time is 0.5h to 1h.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] (1) In view of the shortcomings of existing supported ferric hydroxide photocatalysts, such as poor catalytic activity, poor stability, poor visible light absorption capacity, and easy secondary pollution, as well as the resulting difficulty in efficiently degrading antibiotics in water using visible light, the present invention creatively proposes a method for degrading antibiotics in water using a single-layer ferric hydroxide / reduced graphene oxide photocatalyst, wherein the antibiotics in water are subjected to photo-Fenton degradation treatment using a single-layer ferric hydroxide / reduced graphene oxide photocatalyst, wherein the single-layer ferric hydroxide / reduced graphene oxide photocatalyst comprises a single-layer ferric hydroxide and reduced graphene oxide, and the single-layer ferric hydroxide is embedded in the reduced graphene oxide and loaded on the surface of the reduced graphene oxide. In the present invention, the reduced graphene oxide used has the advantages of large specific surface area, high charge carrier mobility, high mechanical strength, etc., which can effectively slow down the recombination of photogenerated electrons and holes in the photocatalytic process. At the same time, the monolayer hydroxyl iron oxide has the advantages of high specific surface area, many active sites (there are a large number of hydroxyl groups on the surface), relatively stable physical and chemical properties, etc., and has good photocatalytic performance. On this basis, by embedding the monolayer hydroxyl iron oxide in the reduced graphene oxide and loading it on the surface of the reduced graphene oxide, the catalytic activity, visible light absorption capacity and physical and chemical stability of the composite material can be significantly enhanced. Specifically: on the one hand, a heterojunction effect can be formed between the monolayer hydroxyl iron oxide and the reduced graphene oxide, thereby effectively improving the high recombination efficiency and low electron mobility of the photogenerated electron-hole pairs of the monolayer hydroxyl iron oxide. The composite material has a low recombination efficiency of photogenerated electron-hole pairs and a high electron mobility, and has good visible light absorption capacity, thereby significantly improving the photocatalytic activity and being a highly efficient catalytic material that can be activated by visible light. On the other hand, reduced graphene oxide can serve as a good dispersant. Therefore, by loading a monolayer of iron oxyhydroxide on the surface of reduced graphene oxide, not only can the monolayer of iron oxyhydroxide be uniformly dispersed on the reduced graphene oxide as uniform, fine nanosheets, thereby overcoming the characteristic of easy agglomeration of iron oxyhydroxide itself, thereby improving the overall catalytic activity of the material, but also by embedding the monolayer of iron oxyhydroxide in the reduced graphene oxide, the iron oxyhydroxide can be effectively fixed to prevent it from falling off, thereby further enhancing the structural stability of the composite material, while avoiding failure and reducing the risk of secondary pollution. In addition, the monolayer of iron oxyhydroxide / reduced graphene oxide photocatalyst used in the present invention can remain stable under high temperature, strong acid and strong base, and has high practicality. The method of the present invention using a single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst to degrade antibiotics in water has the advantages of simple process, convenient operation, high treatment efficiency, good degradation effect, low cost, and no secondary pollution. It can achieve efficient and rapid removal of antibiotics in water. It is a method that can be widely adopted and can efficiently and quickly remove antibiotics from water, and has high application value and commercial value.

[0026] (2) In the preparation method of the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst of the present invention, a monolayer ferric oxyhydroxide and graphene oxide are used as raw materials, and ascorbic acid is used as a reducing agent. The graphene oxide is reduced to reduced graphene oxide through a reduction reaction, and the monolayer ferric oxyhydroxide is embedded in the reduced graphene oxide and loaded on the surface of the reduced graphene oxide, thereby obtaining a monolayer ferric oxyhydroxide-doped reduced graphene oxide photocatalyst with high catalytic activity, physical and chemical stability, and strong visible light absorption capacity. At the same time, the method of preparing the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst of the present invention also has the advantages of simple process and convenient operation, is suitable for large-scale preparation, and is convenient for industrial application. It is of great significance to promote the widespread application of the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst in environmental treatment of antibiotic pollution.

[0027] (3) In the preparation method of the monolayer hydroxyl iron oxide / reduced graphene oxide photocatalyst of the present invention, by optimizing the mass ratio of the monolayer hydroxyl iron oxide to the graphene oxide to be 5 to 15:1, especially when the mass ratio is 8 to 12:1, the monolayer hydroxyl iron oxide can be effectively contacted with the reduced graphene oxide, which is not only beneficial to increase the effective heterojunction interface area between the monolayer hydroxyl iron oxide and the reduced graphene oxide, but also can ensure that the material exhibits excellent visible light absorption ability, thereby making the composite material exhibit more excellent catalytic performance and can more quickly and thoroughly remove antibiotics from water. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0029] Figure 1 These are SEM images of the monolayer iron oxyhydroxide (SSI) and the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, where (a) is SSI and (b) is GS-10.

[0030] Figure 2 TEM images and EDS images of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, where (a), (b), and (c) are TEM images at different magnifications, and (d) is an EDS image.

[0031] Figure 3 This is the XPS spectrum of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, wherein (a) is the XPS measurement spectrum, (b) is the high-resolution C1s spectrum, (c) is the high-resolution O1s spectrum, and (d) is the high-resolution Fe 2p spectrum.

[0032] Figure 4 Figure 1 is a graph showing the light absorption capacity of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, where (a) is the UV-DRS detection graph and (b) is (αhv) 2 Relationship diagram with photon energy (hv).

[0033] Figure 5 This is a diagram showing the degradation effect of tetracycline on the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-5, GS-10, GS-15, GS-20) prepared in Example 1 of the present invention.

[0034] Figure 6 This is a diagram showing the degradation effect of tetracycline on the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) in Example 2 of the present invention in hydrogen peroxide solutions of different concentrations.

[0035] Figure 7 This is a diagram showing the degradation effect of tetracycline on the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) at different pH values in Example 3 of the present invention.

[0036] Figure 8 This is a diagram showing the degradation effect of tetracycline at different initial concentrations by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) in Example 4 of the present invention.

[0037] Figure 9 This is a diagram showing the cyclic degradation effect of tetracycline by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) in Example 5 of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0039] Example 1

[0040] A method for degrading antibiotics in water using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, specifically using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on tetracycline wastewater, comprising the following steps:

[0041] 2 mL and 8 mg / mL of single-layer ferric oxyhydroxide / reduced graphene oxide photocatalysts (GS-5, GS-10, GS-15, GS-20) were dispersed in 100 mL of a 50.2 mg / L tetracycline solution (initial pH 4.55), respectively. Hydrogen peroxide was added, and the initial concentration of hydrogen peroxide in the system was 0.1 M. The system was magnetically stirred at a speed of 300 r / min for 1 hour in the dark to reach adsorption equilibrium. The light source was turned on, and the photocatalytic reaction was carried out under simulated sunlight (visible light with λ≥420 nm) for 1 hour to complete the degradation of tetracycline in the water.

[0042] Control group 1: No photocatalyst and hydrogen peroxide solution were used, and other conditions were the same.

[0043] Control group 2: No photocatalyst was used, only hydrogen peroxide solution was used, and other conditions were the same.

[0044] Control group 3: The photocatalyst used was reduced graphene oxide (rGO), and other conditions were the same.

[0045] Control group 4: The photocatalyst used was single-layer iron oxyhydroxide (SSI), and other conditions were the same.

[0046] In this embodiment, the preparation method of reduced graphene oxide (rGO) adopted includes the following steps:

[0047] (1) Mix a certain amount of graphite and concentrated sulfuric acid in an ice bath and stir to mix thoroughly. Weigh a certain amount of potassium permanganate and add it to the mixture and continue stirring. After 1 hour, move it to a 35°C water bath and continue stirring for 30 minutes. Dilute the reaction solution to 800-1000 mL with deionized water (control the temperature below 100°C) and add an appropriate amount of 30% hydrogen peroxide.

[0048] (2) The mixture in step (1) was centrifuged with a 5% hydrochloric acid solution, and then washed with deionized water until the washing solution was nearly neutral.

[0049] (3) The reaction product in step (2) was freeze-dried in a vacuum oven for 48 h to obtain graphene oxide, which was denoted as GO.

[0050] (4) According to the mass ratio of graphene oxide to ascorbic acid being 1:10, the graphene oxide (GO) in step (3) was mixed with ascorbic acid, and stirred at 60° C. for 4 hours to reduce the graphene oxide to reduced graphene oxide.

[0051] (5) The reaction product obtained in step (4) was centrifuged and freeze-dried for 24 hours to obtain reduced graphene oxide, which was recorded as rGO.

[0052] In this embodiment, the method for preparing a single-layer iron oxyhydroxide (SSI) includes the following steps:

[0053] (1) 190 mL of a 25 mM sodium dodecanoate solution was transferred to a 300 mL glass bottle equipped with a rubber septum and bubbling with Ar gas (50 mL / min) for 2 h under magnetic stirring to remove oxygen. 12 mL of a 0.5 M ferrous sulfate solution was slowly added under magnetic stirring and rapidly titrated with a 1 M sodium hydroxide solution to maintain the pH of the solution at 8 ± 0.1. 14 mL of a 0.1 M ferric sulfate solution was then added and a 1 M NaOH solution was added dropwise to maintain the pH of the solution at 8 ± 0.1. The solution was stirred for 12 h to obtain a precipitate. The precipitate was washed three times with deionized water bubbled with Ar gas and then redissolved in oxygen-free water. The resulting solution was neutralized to pH = 8 with a 1 M sodium hydroxide solution. Air was then introduced into the solution by a peristaltic pump and the solution was oxidized under stirring for 12 h.

[0054] (2) The mixture obtained after oxidation in step (1) was centrifuged and filtered, and then the filtrate obtained after centrifugation was redispersed in 200 mL of a 0.1 M NaOH solution, and stirred for 12 hours to achieve stratification of the solution.

[0055] (3) The precipitate obtained after stirring in step (2) was washed three times with an alkaline ethanol / water solution (the volume fraction of ethanol in the solution was 40% v / v and the concentration of sodium hydroxide was 0.1 M), and then dispersed in 200 mL of deionized water, followed by centrifugation and freeze-drying for 24 hours to obtain a monolayer of iron oxyhydroxide, which was recorded as SSI.

[0056] In this embodiment, the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) used includes a single-layer iron oxyhydroxide and reduced graphene oxide. The single-layer iron oxyhydroxide is embedded in the reduced graphene oxide and supported on the surface of the reduced graphene oxide. The single-layer iron oxyhydroxide is in the form of a sheet.

[0057] In this embodiment, the preparation method of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) used includes the following steps:

[0058] (1) The monolayer oxyhydroxide iron (SSI) prepared in the above method was mixed with graphene oxide (GO) at a mass ratio of 10:1 for monolayer oxyhydroxide iron and 1:10 for graphene oxide and ascorbic acid. Ascorbic acid was added and stirred at 60°C for 4 hours to reduce the graphene oxide to reduced graphene oxide and wrap the monolayer oxyhydroxide iron.

[0059] (2) The reaction product obtained in step (1) was centrifuged and freeze-dried for 24 hours to obtain a monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst, which was designated as GS-10.

[0060] At the same time, single-layer iron oxyhydroxide / reduced graphene oxide photocatalysts (GS-5, GS-15, GS-20) were prepared according to the mass ratio of single-layer iron oxyhydroxide to graphene oxide of 5:1, 15:1, and 20:1, respectively. The other conditions were the same as those of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10).

[0061] Figure 1 The SEM images of the monolayer iron oxyhydroxide (SSI) and the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, wherein (a) is SSI and (b) is GS-10. Figure 1 It can be seen from the illustration of Figure (a) that the monolayer iron oxyhydroxide (SSI) has an irregular flake morphology and a smooth surface; in Figure (b), the monolayer iron oxyhydroxide (SSI) sheet is tightly embedded in the rGO nanomaterial, proving that under the electrostatic interaction between negatively charged rGO and positively charged SSI, the SSI sheet can be effectively self-assembled onto the rGO nanomaterial.

[0062] Figure 2 TEM images and EDS images of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, wherein (a), (b), and (c) are TEM images at different magnifications, and (d) is an EDS image. Figure 2 (a)(b)(c) show that the SSI nanosheets are embedded in rGO or distributed on the surface of the rGO material without agglomeration, which indicates that the presence of rGO is beneficial to improving the dispersion of the single-layer iron oxyhydroxide (SSI) on its surface; (d) shows that C, O and Fe elements exist in the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10).

[0063] Figure 3This is the XPS spectrum of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, where (a) is the XPS measurement spectrum, (b) is the high-resolution C1s spectrum, (c) is the high-resolution O1s spectrum, and (d) is the high-resolution Fe 2p spectrum. Figure 3(a) shows the presence of C, O, and Fe elements in the GS-10 composite material, with the binding energies of C1s, O 1s, and Fe 2p at 284.8 eV, 530.1 eV, and 710.9 eV, respectively. Figure (b) shows the three deconvolution peaks of the C1s spectrum at 284.2 eV, 285.1 eV, and 287.2 eV, corresponding to the binding energies of the C–C, C–O, and C=O chemical bonds, respectively. (c) The figure shows the three deconvolution peaks of the O1s spectrum, which are at 529.6eV, 530.4eV and 531.3eV, respectively. 529.6eV belongs to the binding energy of the Fe-O bond, 530.4eV belongs to the binding energy of the Fe-O(OH) bond, and 531.3eV belongs to the binding energy of the CO-Fe and Fe-OH bonds. (d) The figure shows the high-resolution spectrum of Fe 2p, where the peaks at 710.6eV and 724.4eV correspond to the binding energy of Fe 2p, respectively. 3 / 2 and Fe 2p 1 / 2 The binding energy.

[0064] Figure 4 Figure 1 is a graph showing the light absorption capacity of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 of the present invention, where (a) is the UV-DRS detection graph and (b) is (αhv) 2 The relationship between the photon energy (hv) and the change of the photon energy (hv). Figure 4 (a) It can be seen that SSI can absorb light from the ultraviolet region to the visible light region, and a significant absorption extension can be observed in the ultraviolet region. The spectrum of GS-10 shows greater absorption than SSI in the visible light range, which is caused by the blackbody properties of rGO in the GS-10 composite material. Due to the expansion of the light absorption range, the GS-10 composite material is expected to achieve more efficient visible light utilization, thereby generating more electron-hole pairs to improve photocatalytic ability. From the inset of (b), it can be estimated that the band gap energies of SSI and GS-10 are approximately 2.27eV and 2.05eV, respectively.

[0065] In addition, during the magnetic stirring and photocatalytic process, 3 mL of sample was taken every 10 minutes and filtered using a 0.2 μm filter head. The absorbance of the filtrate was measured by UV-visible spectrophotometer to determine the concentration of antibiotics, thereby obtaining the photocatalytic degradation efficiency of tetracycline with materials of different mass addition ratios. The results are shown in Figure 2. Figure 5 shown.

[0066] Figure 5 This is a diagram showing the degradation effect of tetracycline on the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-5, GS-10, GS-15, GS-20) prepared in Example 1 of the present invention. Figure 5 The photocatalytic activity of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst of the present invention in the presence of 0.1M hydrogen peroxide is demonstrated. Figure 5 It can be seen that in the absence of photocatalyst and hydrogen peroxide, the degradation rate of tetracycline under simulated light is very low, indicating that the self-photosensitization of tetracycline can be ignored. The combination of hydrogen peroxide and light promotes the decomposition of tetracycline, indicating that indirect photolysis, that is, the generation of hydroxyl radicals to oxidize tetracycline, is the main reason for the decomposition of tetracycline. In addition, Figure 5 It can be seen that compared with GS-20, the single-layer iron oxyhydroxide / reduced graphene oxide photocatalysts of the present invention (GS-5, GS-10, and GS-15) have better degradation effects on tetracycline. In particular, the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared with a mass ratio of GO to SSI of 1:10 has the best degradation efficiency. Among them, after 60 minutes of irradiation with simulated sunlight, about 95.7% of tetracycline was degraded. In addition, the degradation efficiency of GS-5, GS-15, and GS-20 for tetracycline after 60 minutes of reaction was 88.3%, 85.5%, and 76.8%, respectively. It can be seen that the degradation rate of GS-15 and GS-20 is lower than that of GS-10. This may be because further increasing the content of SSI with a large energy band not only reduces visible light absorption, but also reduces the effective heterogeneous interface area between rGO and SSI. Therefore, when the mass ratio of monolayer iron oxyhydroxide to graphene oxide is 8 to 12:1, the prepared monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst exhibits more excellent catalytic performance and can remove antibiotics in water more quickly and thoroughly.

[0067] These results demonstrate that the photocatalytic degradation of antibiotics by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst prepared by the present invention increases with increasing light absorption. Furthermore, the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared by the present invention has a wider light absorption range and can more effectively utilize visible light, thereby generating more electron-hole pairs, thereby enhancing photocatalytic activity and effectively degrading antibiotics in water.

[0068] Example 2:

[0069] A method for degrading antibiotics in water using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, specifically using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on tetracycline wastewater, comprising the following steps:

[0070] Four 2 mL, 8 mg / mL portions of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 were taken and added to a 100 mL tetracycline solution (initial pH 4.55) with a concentration of 50.2 mg / L. Hydrogen peroxide solution was added to adjust the initial concentrations of hydrogen peroxide in the system to 0 M, 0.05 M, 0.1 M, 0.15 M, and 0.2 M, respectively. The mixture was magnetically stirred at a speed of 300 r / min for 1 h in the dark to reach adsorption equilibrium. The light source was turned on and the photocatalytic reaction was carried out under simulated sunlight (visible light with λ ≥ 420 nm) for 1 h to complete the degradation of tetracycline in the water.

[0071] During the magnetic stirring and photocatalytic process, 3 mL of sample was taken every 10 minutes and filtered using a 0.2 μm filter head. The filtrate was measured by UV-visible spectrophotometer to determine the antibiotic concentration after adsorption and after illumination, thereby obtaining the photocatalytic degradation efficiency of GS-10 for tetracycline in hydrogen peroxide solutions with different initial concentrations. The results are shown in Figure 2. Figure 6 shown.

[0072] Figure 6 The figure shows the degradation effect of tetracycline by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) in hydrogen peroxide solution with different concentrations in Example 2 of the present invention. Figure 6 It can be seen that in the case of the single-layer hydroxy iron oxide / reduced graphene oxide photocatalyst (GS-10) of the present invention, only 31.3% of tetracycline was degraded after 60 minutes of simulated sunlight irradiation without the addition of hydrogen peroxide H2O2. In contrast, when the initial concentration of H2O2 was 0.1M, tetracycline was almost completely degraded within 60 minutes. When the H2O2 concentration was lower than 0.1M, the tetracycline photodegradation efficiency increased with the increase of H2O2 concentration, but when the H2O2 concentration was greater than 0.1M, the tetracycline photodegradation efficiency decreased with the increase of H2O2 concentration, indicating that the optimal concentration of H2O2 is 0.1M. As the H2O2 concentration increases, the hydroxyl radicals increase, and the degradation efficiency of tetracycline increases accordingly. However, when the H2O2 content in the system is higher than a certain critical value, the degradation efficiency decreases instead. On the one hand, this is because H2O2 can react with hydroxyl radicals to form a weak oxidant HO2 ·- Therefore, when there is an excess of H2O2 in the solution, it will lead to the consumption of hydroxyl radicals. On the other hand, high concentrations of hydroxyl radicals will also self-consume and dimerize to form H2O2. Therefore, when the initial concentration of hydrogen peroxide in the degradation system is 0.05M to 0.2M, it is conducive to the efficient removal of antibiotics in water. In particular, when the initial concentration of hydrogen peroxide in the system is 0.08M to 0.12M, it is more conducive to the efficient removal of antibiotics in water.

[0073] Example 3:

[0074] A method for degrading antibiotics in water using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, specifically using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on tetracycline wastewater, comprising the following steps:

[0075] Five portions of 2 mL, 8 mg / mL of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 were taken and added to tetracycline solutions with pH values of 2.45, 4.55, 6.04, 7.81, and 9.95 (volume 100 mL, concentration 50.2 mg / L) and mixed and dispersed evenly. Hydrogen peroxide was added to make the initial concentration of hydrogen peroxide in the system 0.1 M. Under dark conditions, magnetic stirring was carried out at a speed of 300 r / min for 1 hour to reach adsorption equilibrium. The light source was turned on and the photocatalytic reaction was carried out under simulated sunlight (visible light with λ ≥ 420 nm) for 1 hour to complete the degradation of tetracycline in the water.

[0076] Adsorption equilibrium refers to the state when the concentration of the adsorbate in the solution and the concentration on the adsorbent surface no longer change.

[0077] During the magnetic stirring and photocatalytic process, 3 mL of sample was taken every 10 minutes and filtered using a 0.2 μm filter. The filtrate was measured by UV-visible spectrophotometer to determine the antibiotic concentration, thereby obtaining the photocatalytic degradation effect of GS-10 on tetracycline at different pH values.

[0078] Figure 7 The figure shows the degradation effect of tetracycline by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) at different pH values in Example 3 of the present invention. Figure 7 It can be seen that when the solution pH is 4.55, the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) has the best degradation performance for tetracycline. At this time, the material has the fastest photocatalytic degradation rate and the highest degradation rate for tetracycline. However, when the pH increases to 9.95, the degradation rate decreases significantly. This is because HO2 ·- The anion exists as the conjugate base of H2O2 under strong alkaline conditions. ·- The proportion of anions increases with the increase of pH value. ·- Anions can react with H2O2 and OH respectively. In the above process, H2O2 at high pH level, OH － To a certain extent, it promotes the decomposition of H2O2 itself, and the main decomposition product is O2 with low oxidizing ability. This process reduces the reaction rate and efficiency of the catalytic oxidation of tetracycline. In addition, due to the acidification of the solution by hydrochloric acid, under strong acidic conditions, Cl－ Can react with hydroxyl radicals to produce inorganic radical ions ClO － However, in the catalytic reaction, the activity of these inorganic radical anions is much lower than that of OH, which is why the degradation rate and degradation rate of tetracycline are low at pH = 2.45. － There is a fierce competition between tetracycline and hydroxyl radical in the reaction with ·OH, thus weakening the degradation effect of tetracycline.

[0079] Example 4:

[0080] A method for degrading antibiotics in water using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, specifically using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on tetracycline wastewater, comprising the following steps:

[0081] Take 5 portions of 2 mL and 8 mg / mL of the monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 and add them to 5 portions of tetracycline solutions with initial concentrations of 9.8 mg / L, 24.4 mg / L, 50.2 mg / L, 74.6 mg / L and 95 mg / L, respectively (volume 100 mL, initial pH value 4.55) and mix and disperse evenly. Hydrogen peroxide is added to make the initial concentration of hydrogen peroxide in the system 0.1 M. The mixture is magnetically stirred at a speed of 300 r / min for 1 h in dark conditions to reach adsorption equilibrium. The light source is turned on and the photocatalytic reaction is carried out under simulated sunlight (visible light with λ ≥ 420 nm) for 1 h to complete the degradation of tetracycline in the water.

[0082] During the magnetic stirring and photocatalytic process, 3 mL of sample was taken every 10 minutes and filtered using a 0.2 μm filter. The filtrate was measured by UV-visible spectrophotometer to determine the antibiotic concentration, thereby obtaining the photocatalytic degradation effect of GS-10 on tetracycline at different concentrations.

[0083] Figure 8 The figure shows the degradation effect of tetracycline at different initial concentrations by the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) in Example 4 of the present invention. Figure 8As can be seen, the degradation rate decreases with increasing initial tetracycline concentration. The results indicate that the initial tetracycline concentration plays a significant role in the photocatalytic process. When the tetracycline concentrations were 24.4 mg / L, 50.2 mg / L, 74.6 mg / L, and 95 mg / L, the tetracycline removal rates after 60 minutes of photocatalysis were 97.2%, 95.7%, 77.1%, and 61.8%, respectively. This may be due to the fact that more tetracycline molecules and their derivatives compete with H2O2 molecules in the solution for active sites on the surface of the GS-10 composite material, resulting in a decrease in the decomposition of H2O2 on the catalyst surface, thereby reducing the generation of hydroxyl radicals. This may also be due to the fact that the increase in the initial tetracycline concentration offsets the constant dosage of the catalyst and H2O2. The experimental results show that GS-10 has a better degradation effect on a lower initial tetracycline concentration (9.8 mg / L), removing all tetracycline within 30 minutes. The material still has high removal efficiency when treating low concentrations of target pollutants, which is very important in practical applications.

[0084] Example 5:

[0085] A method for degrading antibiotics in water using a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, specifically comprising repeatedly performing photo-Fenton degradation treatment on tetracycline wastewater using the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst, comprising the following steps:

[0086] (1) 2 mL, 8 mg / mL of the single-layer ferric oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) prepared in Example 1 was dispersed in 100 mL of tetracycline wastewater with a concentration of 50.2 mg / L (initial pH value of 4.55), and hydrogen peroxide was added to make the initial concentration of hydrogen peroxide in the system 0.1 M. The mixture was magnetically stirred at a speed of 300 r / min under dark conditions for 1 h to reach adsorption equilibrium, and then the light source was turned on and the photocatalytic reaction was carried out under simulated sunlight (visible light with λ≥420 nm) for 1 h to complete the degradation of tetracycline in the water.

[0087] (2) Recovering the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) after the degradation reaction in step (1) is completed, and continuing to use the catalyst to treat tetracycline wastewater, repeating the treatment 4 times.

[0088] During the magnetic stirring and photocatalytic process, 3 mL of sample was taken every 10 minutes and filtered using a 0.2 μm filter head. The filtrate was measured by UV-visible spectrophotometer to determine the antibiotic concentration, thereby obtaining the cyclic experimental effect of GS-10 photocatalytic degradation of tetracycline.

[0089] Figure 9The figure shows the effect of the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst (GS-10) on the cyclic degradation of tetracycline in Example 5 of the present invention. Photocatalytic efficiency and stability are important factors in measuring catalyst performance. During the photocatalytic process, photocorrosion or photolysis may usually occur on the surface of the photocatalyst, so the stability of the catalyst is crucial for its recycling. Figure 9 As shown, after four cycles, GS-10 still achieved a tetracycline degradation efficiency of 84.5%. Compared to the 95.7% degradation efficiency achieved in the first cycle, GS-10's photocatalytic degradation performance declined only slightly, demonstrating the stability of GS-10 during the photocatalytic reaction. Furthermore, the slight decrease in photocatalytic activity can largely be attributed to the inevitable loss of the photocatalyst during the recovery process (washing and centrifugation).

[0090] Based on the above results, it can be seen that the single-layer ferric oxyhydroxide / reduced graphene oxide photocatalyst prepared by the present invention has the advantages of high catalytic activity, strong visible light absorption ability, stable physical and chemical properties, and environmental friendliness. It can also remain stable under high temperature, strong acid and strong alkali, and has high practicality. Therefore, the method of the present invention using a single-layer ferric oxyhydroxide / reduced graphene oxide photocatalyst to degrade antibiotics in water has the advantages of simple process, convenient operation, high treatment efficiency, good degradation effect, low cost, and no secondary pollution. It can achieve efficient and rapid removal of antibiotics in water, is a method that can be widely adopted and can efficiently and quickly remove antibiotics in water, and has high application value and commercial value.

[0091] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for degrading antibiotics in water using a monolayer iron oxyhydroxide / reduced graphene oxide photocatalyst, characterized in that: The method utilizes a single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst to perform photo-Fenton degradation treatment on antibiotics in water. The single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst comprises a single-layer iron oxyhydroxide and reduced graphene oxide, wherein the single-layer iron oxyhydroxide is embedded in the reduced graphene oxide and supported on the surface of the reduced graphene oxide. The preparation method of the single-layer iron oxyhydroxide comprises the following steps: S1, removing oxygen from the sodium lauryl phosphate solution; S2. Adding the divalent iron salt solution to the sodium lauryl acid solution, adjusting the pH of the system to alkaline, adding the trivalent iron salt solution, stirring under alkaline conditions, and filtering to obtain a precipitate; S3, oxidizing the precipitate to obtain iron oxyhydroxide; S4. Place the iron oxyhydroxide in an alkaline solution and stir to obtain a monolayer of iron oxyhydroxide.

2. The method according to claim 1, characterized in that The preparation method of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst comprises the following steps: mixing the single-layer iron oxyhydroxide, graphene oxide and ascorbic acid, and performing a reduction reaction to obtain the single-layer iron oxyhydroxide-doped reduced graphene oxide photocatalyst.

3. The method according to claim 2, characterized in that The mass ratio of the monolayer iron oxyhydroxide to graphene oxide is 5-15:1; the mass ratio of the graphene oxide to ascorbic acid is 1:8-12; the reduction reaction is carried out at a temperature of 55°C to 65°C; and the reduction reaction time is 3.5h to 4.5h.

4. The method according to claim 3, characterized in that The mass ratio of the monolayer iron oxyhydroxide to graphene oxide is 8-12:1; the mass ratio of the graphene oxide to ascorbic acid is 1:

10.

5. The method according to claim 4, wherein In step S1, Ar gas is continuously introduced into the sodium dodecanoate solution under stirring to remove oxygen in the sodium dodecanoate solution; the flow rate of the Ar gas is 45 mL / min to 55 mL / min; the continuous introduction time of the Ar gas is 1.5 h to 2.5 h; the concentration of the sodium dodecanoate solution is 20 mM to 30 mM; In step S2, a sodium hydroxide solution is used to adjust the pH value of the system to 8±0.5; the concentration of the sodium hydroxide solution is 0.8M to 1.2M; the volume ratio of the sodium dodecanoate solution, the divalent iron salt solution, and the trivalent iron salt solution is 95:6:7; the divalent iron salt solution is a ferrous sulfate solution; The concentration of the ferrous sulfate solution is 0.5M; the ferric salt solution is a ferric sulfate solution; the concentration of the ferric sulfate solution is 0.1M; the pH value of the system is maintained at 8±0.5 during the stirring process; In step S3, the oxidation treatment is as follows: dispersing the precipitate in oxygen-free water, adjusting the pH value of the system to 8±0.5, and oxidizing the precipitate in the system under stirring conditions; the oxidation time is 10h to 15h; In step S4, the alkaline solution is a sodium hydroxide solution; the concentration of the sodium hydroxide solution is 0.08 M to 0.12 M; and the stirring time is 10 h to 15 h.

6. The method according to any one of claims 1 to 5, characterized in that The invention utilizes a monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst to carry out photo-Fenton degradation treatment of antibiotics in water, comprising the following steps: mixing the monolayer ferric oxyhydroxide / reduced graphene oxide photocatalyst with antibiotic wastewater, adding hydrogen peroxide, stirring, and carrying out a photo-Fenton catalytic reaction under light conditions to complete the degradation of the antibiotics in the wastewater.

7. The method according to claim 6, characterized in that The addition amount of the single-layer iron oxyhydroxide / reduced graphene oxide photocatalyst is 12 mg to 20 mg per liter of antibiotic wastewater; during the photo-Fenton catalytic reaction, the initial concentration of hydrogen peroxide in the control system is 0.05 M to 0.2 M.

8. The method according to claim 7, characterized in that The initial concentration of the antibiotic in the antibiotic wastewater is 9.8 mg / L to 95 mg / L, and the initial pH value of the antibiotic wastewater is 3 to 5; the antibiotic in the antibiotic wastewater is at least one of ciprofloxacin, norfloxacin, levofloxacin hydrochloride and tetracycline.

9. The method according to claim 8, characterized in that The stirring is carried out in the dark; the stirring speed is 300 r / min to 400 r / min; the stirring time is 1 h to 2 h; and the photo-Fenton catalytic reaction time is 0.5 h to 1 h.

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