In-situ f-doped feocl layered material, preparation method and application thereof

Abstract

The application discloses an in-situ F-doped FeOCl layered material and a preparation method and application thereof. FeCl3 and a fluorinated salt are calcined in an oxygen-containing gas to obtain the in-situ F-doped FeOCl layered material. The F-doped FeOCl layered material prepared by the application has the advantages of high photo-Fenton activity and good cycle performance, and can efficiently activate H2O2 to degrade organic pollutants in water under light conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental functional materials, and particularly relates to an in-situ F-doped FeOCl layered material, a preparation method and application thereof. BACKGROUND

[0002] Fenton oxidation technology, as a kind of advanced oxidation technology (AOP), can degrade organic pollutants by generating hydroxyl radicals with strong oxidizing properties, and has the advantages of high efficiency and simple operation. However, the traditional homogeneous Fenton system has a narrow pH response range, and the catalyst is difficult to separate and recover, and a large amount of iron sludge is generated during the reaction process, causing secondary pollution. The heterogeneous Fenton technology can effectively overcome the above defects. At present, the iron-based catalyst is mainly used in heterogeneous Fenton catalysts, including metal oxides (Fe2O3, Fe3O4, FeOOH), zero-valent iron, and iron sulfide. However, these heterogeneous Fenton catalysts still have the problems of low H2O2 utilization rate, low Fenton activity, and poor stability.

[0003] FeOCl is a typical layered material, in which each Fe atom is coordinated with 4 O atoms and 2 Cl atoms, forming a cis-[FeO4Cl2] octahedron. The octahedrons are connected by sharing O-O or O-Cl edges to form double layers, and a layer of Cl atoms is further packed outside the double layers. The layers are connected by electrostatic force or van der Waals force. Since van der Waals force is a kind of intermolecular force with weak strength, it provides a rich space for modification. The main Fe element in FeOCl has high environmental abundance, flexible valence change, and is non-toxic and harmless. However, the layered stacking structure of FeOCl cannot fully expose the effective active area, and has the problems of slow Fe(III) / Fe(II) cycle and poor stability.

[0004] Currently, most studies focus on the intercalation modification of FeOCl to improve its Fenton activity. Chinese patent document CN117000303A discloses an FeOCl catalytic material intercalated with organic molecules and a preparation method thereof. The organic molecules are inserted into the layered structure of FeOCl, the interlayer spacing of the obtained catalyst is significantly expanded, and the catalyst exhibits good performance in degrading pollutants by activating H2O2. However, the crystallinity of FeOCl intercalated with alcohol molecules decreases compared with unintercalated FeOCl. Yang Xuejing et al. (Journal of the American Chemical Society. 2022, 144, 4294-4299) introduced potassium ions into the layered structure of FeOCl by KI oxidation-reduction intercalation, realized the precise adjustment of the iron coordination environment, and thus improved the catalytic performance. However, the Fe leakage of the K-ion intercalated FeOCl photo-Fenton system after reaction reached 1.4 ppm. Zhang Wei et al. (Applied Catalysis B: Environmental. 2024, 345, 123701) also embedded hydroxylamine (HA) into the layered structure of FeOCl to reconstruct the twisted two-dimensional surface, and thus improved the activation performance of the catalyst by regulating the electronic structure of the iron site. However, the Fe leakage of the HA-intercalated FeOCl Fenton system after reaction reached 1.12 ppm. Therefore, although the intercalation modification method can effectively improve the catalytic performance of the original FeOCl, the lattice of the intercalated material expands and the unit cell changes, resulting in a decrease in the structural stability of the catalyst. SUMMARY

[0005] The present application aims to overcome the deficiencies in the prior art, and provides an in-situ F-doped FeOCl photocatalyst with high photo-Fenton activity and good stability, a simple preparation method of the F-doped FeOCl photocatalyst, and an application of the F-doped FeOCl photocatalyst in degrading organic pollutants in wastewater.

[0006] The specific technical solutions of the present application are as follows:

[0007] A preparation method of an in-situ F-doped FeOCl layered material, which comprises calcining FeCl3 and a fluorinated salt in an oxygen-containing gas. The method further comprises the steps of washing and drying the calcined product with water.

[0008] The oxygen-containing gas can be oxygen or air.

[0009] The preparation method of the present application preferably uses one or more of FeF3, NH4F and NaF as the fluorinated salt, and more preferably uses FeF3.

[0010] The preparation method of the application preferably has a molar ratio of FeCl3 and fluorinated salt of (9.1-9.9):(0.9-0.1), more preferably (9.3-9.7):(0.7-0.3).

[0011] In one specific example of the application, the fluorinated salt is selected from FeF3, and the molar ratio of FeCl3 and FeF3 is 9.7:0.3.

[0012] The preparation method of the application preferably has a calcination temperature of 150-300℃, a heating rate of 10℃ / min, and a calcination time of 0.5-4h.

[0013] In one specific example of the application, the calcination temperature is 220℃, the heating rate is 10℃ / min, and the calcination time is 2h.

[0014] The application also provides an in-situ F-doped FeOCl layered material prepared by the method of the application.

[0015] The application also provides the use of the in-situ F-doped FeOCl layered material as a catalyst for removing organic pollutants in water.

[0016] In one specific application, the in-situ F-doped FeOCl layered material is used as a photo-Fenton catalyst to remove pollutants in water. The organic pollutants are selected from antibiotics, organic dyes, and phenols.

[0017] In the field of water treatment, photo-Fenton technology can be used to treat various organic pollutants and some inorganic pollutants, such as benzene, phenol, dye, pesticide, etc. In particular, in the photo-Fenton process, H2O2 generates hydroxyl radicals, effectively removing pesticides, dyes, drugs, nitrobenzene, and chlorophenol, etc. In addition, Fenton reagent is also widely used in the treatment of industrial wastewater, including oil-containing wastewater, printing and dyeing wastewater, coking wastewater, phenol-containing wastewater, and nitro-containing wastewater.

[0018] The organic pollutants are selected from antibiotics, organic dyes, and phenols, etc. For example, tetracycline, macrolide antibiotics, quinolone antibiotics (such as ciprofloxacin, ofloxacin), methylene blue, rhodamine B, methyl orange, phenol. In one specific example of the application, the organic pollutants are selected from tetracycline, ciprofloxacin, norfloxacin, sulfamethoxazole, 2,4-dichlorophenol, 2,4,6-trichlorophenol, phenol, bisphenol A, and p-fluorophenol.

[0019] The treatment steps are as follows: uniformly dispersing the in-situ F-doped FeOCl layered material in an aqueous solution containing organic pollutants and adding H2O2, and then performing catalytic degradation under light conditions.

[0020] The application has the following beneficial effects:

[0021] 1. The application provides an in-situ strong electronegative atom doped FeOCl photocatalyst, compared with the prior art intercalation modified FeOCl photocatalyst, the strong electronegative atom can directly partially replace Cl in FeOCl, without causing distortion of the layered structure, while regulating the electron density of Fe sites, the original structure is also stable.

[0022] 2. In the application, part of the Cl atoms in the original FeOCl is replaced by F atoms, because F atoms have the strongest electronegativity, the electron density of the iron-oxygen layer can be improved, thereby improving the Fenton-like activity.

[0023] 3. The F doped FeOCl photocatalyst of the application is used for treating organic pollutants, under light conditions, can effectively catalyze and activate H2O2 to degrade pollutants in the solution, has the advantages of high photo-Fenton activity, good recycling performance and the like. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is an XRD graph of F doped FeOCl (3% F-FeOCl) in the embodiment 1 of the application and FeOCl in the comparative example 1.

[0025] Figure 2 It is a scanning electron microscope graph of F doped FeOCl (3% F-FeOCl) in the embodiment 1 of the application.

[0026] Figure 3 It is a transmission electron microscope, high resolution transmission electron microscope and EDS element distribution image of F doped FeOCl (3% F-FeOCl) in the embodiment 1 of the application, wherein (a) is a transmission electron microscope graph, (b) is a high resolution transmission electron microscope graph, and (c) is an EDS element distribution graph.

[0027] Figure 4 It is an XPS graph of F doped FeOCl (3% F-FeOCl) in the embodiment 1 of the application, wherein (a) is a Fe2p fine spectrum, (b) is an O1s fine spectrum, (c) is a F1s fine spectrum, and (d) is a Cl 2p fine spectrum.

[0028] Figure 5 It is a performance graph of F doped FeOCl (1-9% F-FeOCl) photocatalyst in the application example 1 for degrading 4-chlorophenol.

[0029] Figure 6 It is a performance graph of F doped FeOCl (3% F-FeOCl, a-b-3% F-FeOCl) photocatalyst in the application example 2 for degrading 4-chlorophenol.

[0030] Figure 7Performance chart of F-doped FeOCl (3%F-FeOCl) in the application example 3 of the present application for the photofenton degradation of 4-chlorophenol.

[0031] Figure 8 Performance chart of F-doped FeOCl (3%F-FeOCl) in the application example 4 of the present application for the photofenton degradation of 4-chlorophenol.

[0032] Figure 9 Performance chart of F-doped FeOCl (3%F-FeOCl) in the application example 5 of the present application for the photofenton degradation of 4-chlorophenol and comparison chart of Fe leakage after the fenton reaction of different FeOCl modified materials, wherein (a) is the performance chart and (b) is the comparison chart of Fe leakage.

[0033] Figure 10 Performance chart of F-doped FeOCl (3%F-FeOCl) in the application example 6 of the present application for the photofenton degradation of different organic pollutants. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The various terms and phrases used in the present application have the general meanings known to those skilled in the art. The materials used in the experiments and the experimental methods are generally or specifically described in the present application. Although many materials and operation methods used to achieve the purpose of the present application are known in the art, the present application still describes them as much as possible. The instruments, reagents, materials and the like involved in the following examples are conventional instruments, reagents, materials and the like in the prior art if not otherwise specified, and are conventional experimental methods, detection methods and the like in the prior art if not otherwise specified. The XPA-7 photochemical reaction instrument is purchased from Nanjing Xujia Machinery Plant.

[0035] Example 1

[0036] (1) 9.7 mmol of FeCl3 and 0.3 mmol of FeF3 were mixed uniformly;

[0037] (2) The mixture was placed in air, heated at a rate of 10 ℃ / min, and kept at 220 ℃ for 2 h. The obtained product was washed with water and dried to obtain the F-doped FeOCl photocatalyst, which was marked as 3%F-FeOCl.

[0038] Example 2

[0039] Example 2 is basically the same as Example 1, except that the molar ratio of FeCl3 and FeF3 is selected as 9.9:0.1, and the remaining steps and raw materials are the same as those in Example 1. The obtained material is marked as 1%F-FeOCl.

[0040] Example 3

[0041] Example 3 is substantially identical to Example 1 except that the molar ratio of FeCl3and FeF3is selected to be 9.5:0.5, and the remaining steps and materials are identical to Example 1. The resulting material is labeled 5% F-FeOCl.

[0042] Example 4

[0043] Example 4 is substantially identical to Example 1 except that the molar ratio of FeCl3and FeF3is selected to be 9.3:0.7, and the remaining steps and materials are identical to Example 1. The resulting material is labeled 7% F-FeOCl.

[0044] Example 5

[0045] Example 5 is substantially identical to Example 1 except that the molar ratio of FeCl3and FeF3is selected to be 9.1:0.9, and the remaining steps and materials are identical to Example 1. The resulting material is labeled 9% F-FeOCl.

[0046] Example 6

[0047] Example 6 is substantially identical to Example 1 except that the fluorinating salt is selected to be NH4F, and the remaining steps and materials are identical to Example 1. The resulting material is labeled a-3%-FeOCl.

[0048] Example 7

[0049] Example 7 is substantially identical to Example 1 except that the fluorinating salt is selected to be NaF, and the remaining steps and materials are identical to Example 1. The resulting material is labeled b-3% F-FeOCl.

[0050] Example 8

[0051] Example 8 is substantially identical to Example 1 except that the calcination temperature is selected to be 150°C, and the remaining steps and materials are identical to Example 1. The resulting material is labeled c-3% F-FeOCl.

[0052] Example 9

[0053] Example 9 is substantially identical to Example 1 except that the calcination temperature is selected to be 260°C, and the remaining steps and materials are identical to Example 1. The resulting material is labeled d-3% F-FeOCl.

[0054] Example 10

[0055] Example 10 is substantially the same as Example 1, except that the calcination temperature is selected to be 300°C, and the remaining steps and raw materials are the same as Example 1, and the resulting material is labeled e-3%F-FeOCl.

[0056] Example 11

[0057] Example 11 is substantially the same as Example 1, except that the calcination time is selected to be 0.5h, and the remaining steps and raw materials are the same as Example 1, and the resulting material is labeled f-3%F-FeOCl.

[0058] Example 12

[0059] Example 12 is substantially the same as Example 1, except that the calcination time is selected to be 4h, and the remaining steps and raw materials are the same as Example 1, and the resulting material is labeled g-3%F-FeOCl.

[0060] Example 13

[0061] Example 13 is substantially the same as Example 1, except that the calcination time is selected to be 8h, and the remaining steps and raw materials are the same as Example 1, and the resulting material is labeled h-3%F-FeOCl.

[0062] Comparative Example 1

[0063] A FeOCl photocatalyst is prepared by the following steps:

[0064] (1) 10mM FeCl3 is ground to be uniform;

[0065] (2) It is placed in air, and heated at a rate of 10°C / min, and kept at 220°C for 2h, and the resulting product is washed with water and vacuum dried, to obtain a FeOCl photocatalyst, labeled FeOCl.

[0066] The XRD pattern of the F-doped FeOCl (3%F-FeOCl) in Example 1 of the present application and the FeOCl in Comparative Example 1 is shown in Figure 1 From Figure 1 it can be seen that the diffraction peak position and intensity of the 3%F-FeOCl do not change compared with the FeOCl, indicating that the method of replacing Cl atoms with F atoms does not destroy the original crystal structure of the FeOCl.

[0067] The scanning electron microscope pattern of the F-doped FeOCl (3%F-FeOCl) in Example 1 of the present application is shown in Figure 2 From Figure 2 it can be seen that the 3%F-FeOCl is in a rod-like structure.

[0068] The TEM, high-resolution TEM and EDS elemental mapping images of F-doped FeOCl (3% F-FeOCl) in Example 1 of the present application are shown in Figure 3 . Figure 3 a shows that 3% F-FeOCl presents a rod-like structure, from Figure 3 b the iron-oxygen layer structure can be clearly observed, which proves that FeOCl is successfully synthesized and F doping does not destroy the original layered structure. Figure 3 c the uniform distribution of each element confirms the successful doping of F.

[0069] The XPS chart of F-doped FeOCl (3% F-FeOCl) in Example 1 of the present application is shown in Figure 4 . Figure 4 a is the Fe2p fine spectrum, and it can be observed that iron exists in the form of divalent iron and trivalent iron at the same time; Figure 4 b is the O1s fine spectrum, and the diffraction peak attributed to M-O is observed at 529.77 eV; Figure 4 c is the F1s fine spectrum, which indicates the successful doping of F element; Figure 4 d is the Cl 2p fine spectrum, and the diffraction peaks attributed to M-Cl are observed at 198.32 eV and 199.91 eV.

[0070] Application Example 1

[0071] The photocatalysts obtained in Examples 1-5 were used to degrade 4-chlorophenol. The specific experimental conditions were as follows: 10 mg of the catalyst was placed in 50 mL of a 0.1 mM 4-chlorophenol solution, and after 30 min, adsorption-desorption equilibrium was reached, then 50 μL of H2O2 solution (3 mM) was added, and the xenon lamp was turned on to perform the photo-Fenton reaction. The results are shown in Figure 5 . The results show that with the increase of the F doping concentration, the removal performance of the photo-Fenton system of different catalysts on 4-chlorophenol first increases and then decreases, and 3% F-FeOCl exhibits the most excellent catalytic performance, with a removal rate of 100% at 30 min.

[0072] Application Example 2

[0073] The photocatalysts obtained in Examples 1, 6-7 were used to degrade 4-chlorophenol. The specific experimental conditions were as follows: 10 mg of the catalyst was placed in 50 mL of a 0.1 mM 4-chlorophenol solution, and after 30 min, adsorption-desorption equilibrium was reached, then 50 μL of H2O2 solution (3 mM) was added, and the xenon lamp was turned on to perform the photo-Fenton reaction. The results are shown in Figure 6 . The results show that the photo-Fenton activities of the catalysts prepared using different F precursors are significantly different, and among them, 3% F-FeOCl prepared using FeF3 as the precursor exhibits the most excellent catalytic performance.

[0074] Application Example 3

[0075] The photocatalysts obtained in Examples 1, 8-10 were used to degrade 4-chlorophenol. The specific experimental conditions were as follows: 10 mg of the catalyst was placed in 50 mL of a 0.1 mM 4-chlorophenol solution, and after 30 min of adsorption-desorption equilibrium, 50 μL of a H2O2 solution (3 mM) was added, and the photofenton reaction was carried out with a xenon lamp. The results are shown in Table 2. Figure 7 The results show that as the calcination temperature increased from 150°C to 300°C, the catalytic activity of the prepared 3% F-FeOCl first increased and then decreased, and thus the calcination temperature is preferably 220°C.

[0076] Application Example 4

[0077] The photocatalysts obtained in Examples 1, 11-13 were used to degrade 4-chlorophenol. The specific experimental conditions were as follows: 10 mg of the catalyst was placed in 50 mL of a 0.1 mM 4-chlorophenol solution, and after 30 min of adsorption-desorption equilibrium, 50 μL of a H2O2 solution (3 mM) was added, and the photofenton reaction was carried out with a xenon lamp. The results are shown in Table 4. Figure 8 The results show that as the calcination time increased, the catalytic activity of the prepared 3% F-FeOCl first increased and then decreased, and thus the calcination time is preferably 2 h.

[0078] Application Example 5

[0079] This example aims to characterize the recycling stability of the catalyst.

[0080] Taking the F-doped FeOCl photocatalyst (3% F-FeOCl) prepared in Example 1 as an example, its stability was investigated through a recycling experiment, and the degradation experimental conditions were the same as in Application Example 1. After the catalyst in the photofenton reaction was filtered and dried, the next cycle of degradation experiment was carried out under the same reaction conditions, and this was repeated 5 times. The results are shown in Table 5. Figure 9 The results show that after 5 cycles, the removal rate of 4-chlorophenol in the 3% F-FeOCl photofenton system after 40 min was still 100%, indicating that the 3% F-FeOCl has good stability.

[0081] Further referring to the method disclosed in the literature (Journal of the American Chemical Society. 2022, 144, 4294-4299), the Fe leakage amount after F-doped FeOCl Fenton reaction was detected and compared with K-FeOCl (Journal of the American Chemical Society. 2022, 144, 4294-4299) and HA-FeOCl (Applied Catalysis B: Environmental. 2024, 345, 123701), and the results are shown in Figure 9 b. The results show that the Fe leakage amount after F-doped FeOCl Fenton reaction is only 0.38 ppm, which is much lower than that of K-FeOCl (Fe leakage amount is 1.4 ppm) and HA-FeOCl (Fe leakage amount is 1.12 ppm), indicating that the in-situ substitution strategy of strong electronegative atoms can effectively solve the problem of structural stability decline of FeOCl intercalation modified materials.

[0082] Application Example 6

[0083] This example aims to characterize the degradation effect of the catalyst on different phenolic pollutants.

[0084] Taking the F-doped FeOCl (3% F-FeOCl) prepared in Example 1 as an example, the degradation effect of different organic pollutants was investigated, and the degradation experiment conditions were the same as in Application Example 1, except that any one of tetracycline (TC), ciprofloxacin (CIP), norfloxacin (NFX), sulfamethoxazole (SMZ), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), phenol (Phenol), bisphenol A (BPA), and p-fluorophenol (4-FP) was used as the pollutant. The results are shown in Figure 10 The results show that the degradation rate of F-doped FeOCl (3% F-FeOCl) on various organic pollutants (tetracycline, ciprofloxacin, norfloxacin, sulfamethoxazole, 2,4-dichlorophenol, 2,4,6-trichlorophenol, phenol, bisphenol A, and p-fluorophenol) is higher than 99% after 40 min of photo-Fenton reaction, showing good broad-spectrum performance.

Claims

1. A method for the preparation of an in situ F-doped FeOCl layered material, characterized in that FeCl3 and a fluorinated salt selected from FeF3 are calcined in an oxygen-containing gas, the molar ratio of FeCl3 and the fluorinated salt is (9.1-9.9):(0.9-0.1), the calcination temperature is 220℃, the heating rate is 10℃ / min, and the calcination time is 2h.

2. An in situ F-doped FeOCl layered material characterized by The in-situ F-doped FeOCl layered material is prepared by the method of claim 1.

3. Use of the in-situ F-doped FeOCl layered material of claim 2 as a catalyst for removing organic pollutants in water.

4. Use according to claim 3, characterized in that The treatment procedure is as follows: the in-situ F-doped FeOCl layered material is uniformly dispersed in an aqueous solution containing organic pollutants and H2O2 is added, and the catalytic degradation is carried out under light conditions.

5. Use according to claim 4, characterized in that The organic pollutants are selected from antibiotics, organic dyes, and phenols.

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