Fe-C micro-electrolysis photocatalytic composite catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a Fe-C micro-electrolysis photocatalytic composite catalyst as well as a preparation method and application thereof. According to the preparation method, oxides of main active elements such as platinum, titanium, vanadium and iron are kneaded with carbon nitride, meanwhile, the efficient catalyst can be obtained only through simple mixing and roasting, precious metal platinum has a plasma resonance effect, structural optimization of a catalytic material is achieved by changing electron distribution in a system, the absorption and utilization rate of visible light can be increased, and the catalytic efficiency is improved. The photocatalytic efficiency of the catalyst is obviously improved, and the catalyst has the advantages of good stability, strong anti-toxicity capability, environment-friendly preparation process and the like. The catalyst has a wide industrialization prospect, and is especially suitable for catalyzing and activating persulfate to carry out advanced oxidation treatment on sewage with relatively high organic matter content. The preparation method of the catalyst is simple and low in cost, and the prepared catalyst is environmentally friendly and has long service life.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and specifically relates to a Fe-C micro-electrolysis photocatalytic composite catalyst and a preparation method and application thereof, and is particularly suitable for catalyzing PDS and PMS advanced oxidation treatment of sewage with a high organic matter content. Background Art

[0002] With the gradual improvement of the level of industrialization, the amount of industrial organic wastewater, especially pharmaceutical wastewater, is increasing. At present, the commonly used methods for treating organic wastewater mainly include physical method, biological method, chemical method and photocatalytic method. Among them, the photocatalytic persulfate (peroxymonosulfate (PMS) or peroxydisulfate (PDS)) produces sulfate radicals with high reactivity, which can treat a variety of organic and inorganic wastewater. Compared with the Fenton method, it does not produce iron mud and does not require the use of hydrogen peroxide. It has the advantages of low energy consumption, cleanliness, and no secondary pollution.

[0003] Although traditional photocatalysts have achieved certain results in sewage treatment and chemical synthesis, they still have problems such as narrow light absorption range, high recombination rate of photogenerated electron-hole pairs, low catalytic efficiency and poor stability. In recent years, the use of metal oxide catalysis has become one of the efficient and easy-to-operate activation methods. The catalytic performance directly affects the effect of oxidation technology, so the selection of catalytic activators has become a core influencing factor in persulfate technology.

[0004] Based on this, the present invention proposes a new type of multi-component synergistic photocatalyst, aiming to improve the photocatalytic activity and stability and broaden its application range by optimizing the catalyst composition and structure. Summary of the invention

[0005] The purpose of the present invention is to provide a Fe-C micro-electrolysis photocatalytic composite catalyst suitable for a variety of sewage treatment scenarios. By compounding the oxides of the main active elements titanium, vanadium, iron, etc. with carbon nitride (g-C3N4), and adding precious metals such as platinum, palladium, rhodium, ruthenium, etc., the application range and decontamination ability of the catalyst are further increased. The catalyst has the advantages of high photocatalytic efficiency, good stability, strong anti-toxicity and environmentally friendly preparation process, and is particularly suitable for sewage treatment with a high organic matter content.

[0006] Furthermore, the present invention also provides a method for preparing the Fe-C micro-electrolysis photocatalytic composite catalyst.

[0007] Furthermore, the present invention also provides the use of the Fe-C micro-electrolysis photocatalytic composite catalyst in catalytic degradation of water pollutants.

[0008] Based on the above purpose, the present invention adopts the following technical solutions:

[0009] A method for preparing a Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0010] 1) mixing a certain amount of water-soluble salt of titanium, water-soluble salt of vanadium, water-soluble salt of iron and water-soluble salt of precious metal elements to prepare an aqueous solution of a certain concentration;

[0011] 2) mixing the aqueous solution in step 1) and graphite phase carbon nitride (g-C3N4), and then dehydrating (or not dehydrating) under reduced pressure or normal pressure to obtain a mixture (the purpose of dehydration is to make the mixture viscous and slightly fluid to facilitate catalyst calcination and molding); and then calcining the mixture in a muffle furnace to obtain a block solid;

[0012] 3) The blocky solid obtained in step 2) is crushed and granulated to obtain a photocatalytic composite catalyst with a particle size of 0.1-5 mm.

[0013] Furthermore, the water-soluble titanium salt in step 1) is one or more of titanium tetrachloride, titanium tetraiodide, and titanium tetrabromide. In the final catalyst, titanium exists in the form of titanium dioxide, and its mass accounts for 1 to 30 wt%, preferably 5 to 10 wt%.

[0014] Furthermore, the water-soluble salt of vanadium in step 1) is one or more of metavanadate, pyrovanadate, orthovanadate, polyvanadate, and decavanadate. In the final formed catalyst, vanadium exists in the form of vanadium pentoxide, and its mass proportion is 1 to 15 wt%, preferably 3 to 10 wt%.

[0015] Furthermore, the water-soluble iron salt in step 1) is one or more of ferric chloride, ferric sulfate, and ferric nitrate. In the final catalyst, the iron exists in the form of iron oxide, and its mass accounts for 1 to 30 wt%, preferably 5 to 15 wt%.

[0016] Furthermore, the precious metal described in step 1) is one or more of platinum, palladium, rhodium, and ruthenium, and its water-soluble salts are mainly chlorides, nitrates, etc., and the precious metal content is 0.01 to 3.0 wt% of the total mass of the catalyst, preferably 0.1 to 0.5 wt%.

[0017] Furthermore, in step 1), the concentration of the aqueous solution made of the water-soluble salt of titanium, the water-soluble salt of vanadium, the water-soluble salt of iron or the water-soluble salt of a precious metal element is set to vary from 0.1 to 50 wt% according to the solubility of the material. When the water-soluble salt of titanium, the water-soluble salt of vanadium, the water-soluble salt of iron or the water-soluble salt of a precious metal element is made into an aqueous solution, the aqueous solutions can be prepared separately and then mixed, or the individual water-soluble salts can be mixed and then water can be added to form a mixed solution.

[0018] Furthermore, in step 2), the mass ratio of the aqueous solution to the graphite-phase carbon nitride is 0.5:1 to 10:1; preferably 1:1 to 3:1.

[0019] Furthermore, the graphite phase carbon nitride (g-C3N4) described in step 2) can be a commercial product, or it can be prepared by the polymerization of succinic acid and urea or cyanamide, dicyandiamide, or melamine, and dehydrated to an overall viscous and slightly fluid state to facilitate catalyst calcination and molding.

[0020] Furthermore, in step 2), the calcination temperature is 350-650° C., preferably 450-550° C., and the calcination time is 1-10 h, preferably 2-5 h.

[0021] Furthermore, in step 2), calcination is carried out in an air environment or an oxygen environment, and the heating rate during calcination is 0.5 to 5°C / min.

[0022] Furthermore, in step 3), the calcined product is crushed using a ball mill; during granulation, 5 to 10% of the total weight of the crushed solid water glass or water can be added as a binder.

[0023] Furthermore, the present invention also provides a Fe-C micro-electrolysis photocatalytic composite catalyst prepared by the above method, and the photocatalytic composite catalyst can be used as a persulfate activator for catalytic degradation of organic pollutants or inorganic pollutants in water.

[0024] Furthermore, based on a general inventive concept, the present invention also provides the use of the Fe-C micro-electrolysis photocatalytic composite catalyst as a persulfate activator in catalytic degradation of water pollutants.

[0025] Furthermore, based on a general inventive concept, the present invention also provides the use of the Fe-C micro-electrolysis photocatalytic composite catalyst as a persulfate activator in improving sewage quality.

[0026] Furthermore, based on a general inventive concept, the present invention also provides the use of the Fe-C micro-electrolysis photocatalytic composite catalyst as a persulfate activator in improving the COD removal rate of sewage.

[0027] Specifically, the persulfate is peroxymonosulfate (PMS) or peroxydisulfate (PDS).

[0028] Specifically, the water body is domestic sewage, industrial sewage, agricultural sewage, lake water, river water or aquaculture water.

[0029] Specifically, the pollutants are one or more of steroid hormone raw materials, organic chemical raw materials and dyes.

[0030] Specifically, the steroid hormone raw materials include triethylamine, propionic acid, acetone, dihydroxide, DMF, n-butyraldehyde, isobutyric anhydride, pyridine, dichloromethane, sodium formate, etc.

[0031] Specifically, the organic chemical raw materials include polytetrahydrofuran, chloroacetic acid ethanol, etc.

[0032] Furthermore, the photocatalytic composite catalyst can be reused as a persulfate activator when catalytically degrading pollutants in water, and the number of reuses is 7 times.

[0033] Further, based on a general inventive concept, the present invention also provides a method for utilizing the Fe-C micro-electrolysis photocatalytic composite catalyst to catalytically activate persulfate to degrade pollutants in water and improve the COD removal rate of sewage, comprising the following steps:

[0034] Add an oxidant to the water containing pollutants, then add the photocatalytic composite catalyst, mix evenly, activate with light, and then react at room temperature for 1 to 15 hours, so as to achieve the degradation of pollutants below 50,000 mg / L in the water.

[0035] Specifically, the oxidant is peroxymonosulfate (PMS) or peroxydisulfate (PDS).

[0036] Specifically, the mass ratio of water to the photocatalytic composite catalyst is (5-15):1, preferably 10:1.

[0037] Specifically, the mass ratio of the oxidant to the photocatalytic composite catalyst is 1:(10-15), preferably 1:12.5.

[0038] Specifically, the light irradiation is visible light irradiation and / or ultraviolet light irradiation, the wavelength of visible light is 240nm, and the wavelength of ultraviolet light is 253nm.

[0039] Further, based on a general inventive concept, the present invention also provides an activation and regeneration method for the Fe-C micro-electrolysis photocatalytic composite catalyst, which specifically comprises the following steps:

[0040] The deactivated or less active photocatalytic composite catalyst is first heated to 120-150°C at a rate of 0.5-2°C / min, kept warm for 45-60 minutes, then continued to be heated to 350-380°C at a rate of 0.5-1°C / min, kept warm for 1-2 hours, then heated to 850-950°C at a rate of 1-2°C / min, kept warm for 1-2 hours, and then naturally cooled to room temperature.

[0041] The Fe-C micro-electrolysis photocatalytic composite catalyst prepared by the present invention can perform catalytic degradation in a variety of sewage treatment scenarios. During the degradation process, it is activated by visible light and ultraviolet light irradiation, catalyzing the degradation of peroxymonosulfate (PMS) or peroxydisulfate (PDS) to treat sewage, and has high catalyst activity.

[0042] The present invention introduces a variety of active substances on the basis of photocatalysis to further increase the anti-toxicity of the catalyst, especially introduces precious metals, so that the catalyst increases the absorption and utilization of visible light. It has the advantages of high photocatalytic efficiency, good stability, strong anti-toxicity ability and environmentally friendly preparation process, and is particularly suitable for sewage treatment with a high organic matter content.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The present invention kneads the oxides of the main active elements platinum, titanium, vanadium, iron, etc. with carbon nitride by a simple method, and obtains a high-efficiency catalyst by simple mixing and calcination. The precious metal platinum has a plasma resonance effect, and the structure of the catalytic material is optimized by changing the electron distribution in the system, which can enhance the absorption and utilization rate of visible light, significantly improve the photocatalytic efficiency of the catalyst, and has the advantages of good stability, strong anti-toxicity and environmentally friendly preparation process. The catalyst can have a one-way service life of more than 5 years if it is cleaned every year, and can be regenerated more than 3 times. The cost of sewage treatment per ton is lower than the currently commonly used sewage treatment process, and the industrialization prospect is broad. It is particularly suitable for catalytic activation of persulfate advanced oxidation to treat sewage with high organic content.

[0045] 2. The Fe-C micro-electrolysis photocatalytic composite catalyst prepared by the present invention can perform catalytic degradation in a variety of sewage treatment scenarios. During the degradation process, it is activated by visible light and ultraviolet light, catalyzing the degradation of peroxymonosulfate (PMS) or peroxydisulfate (PDS) to treat sewage, and has a high catalyst activity.

[0046] 3. The preparation method of the catalyst of the present invention is simple and low-cost, and the prepared catalyst is not only environmentally friendly but also has a long service life. DETAILED DESCRIPTION

[0047] In order to make the technical purpose, technical scheme and beneficial effects of the present invention clearer, the technical scheme of the present invention is further described below in conjunction with specific embodiments. However, the embodiments are intended to explain the present invention and cannot be understood as limiting the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0048] The raw materials used in the examples are all conventional reagents, water is laboratory-made deionized water, and graphite phase carbon nitride (g-C3N4) is purchased from Guangdong Hongjiang Chemical Reagent Co., Ltd.

[0049] Example 1

[0050] This embodiment prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing V, Ti, and Fe elements;

[0051] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0052] Weigh 15.15 g of ferric nitrate, 16.62 g of titanium tetrachloride, and 2.56 g of sodium pyrovanadate, add them into 90 g of water and stir to completely dissolve them, then add 78 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0053] Then the solid was crushed and granulated by adding 5% water glass of the total mass of the crushed solid, and finally a catalyst 1 with a diameter of about 1 mm was obtained, which was recorded as 5% V2O5 / 7% TiO2 / 10% Fe2O3-C.

[0054] Example 2

[0055] This example prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing Pt, V, Ti, and Fe elements;

[0056] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0057] Weigh 0.81 g of chloroplatinic acid hexahydrate (platinum content 37 wt%), 15.15 g of ferric nitrate, 16.62 g of titanium tetrachloride, and 2.56 g of sodium pyrovanadate, add them into 90 g of water and stir to completely dissolve them, then add 78 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0058] Then the solid was crushed and granulated by adding 5% water glass of the total mass of the crushed solid, and finally a catalyst 2 with a diameter of about 1 mm was obtained, which was recorded as 0.3% Pt-5% V2O5 / 7% TiO2 / 10% Fe2O3-C.

[0059] Example 3

[0060] This example prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing Pt, Ti, and Fe elements;

[0061] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0062] Weigh 0.81 g of chloroplatinic acid hexahydrate (platinum content 37 wt%), 15.15 g of ferric nitrate, and 16.62 g of titanium tetrachloride, add them into 90 g of water and stir to completely dissolve them, then add 83 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0063] Then the solid was crushed and granulated by adding 5% water glass as the total weight of the crushed solid to obtain catalyst 3 with a diameter of about 1 mm, which was recorded as 0.3% Pt-7% TiO2 / 10% Fe2O3-C.

[0064] Performance Test 1

[0065] The catalysts obtained in Examples 1 to 3 were evaluated by taking 1 kg of sewage, adding 8 g of peroxydisulfate (PDS), adding 100 g of catalyst, irradiating with visible light (240 nm) and ultraviolet light (253 nm) for activation, and oxidizing for 15 h. The comparison results are shown in Table 1 below:

[0066] Table 1

[0067]

[0068] It can be concluded from Table 1 that the catalytic system formed by adding a catalyst containing precious metal platinum and peroxydisulfate (PDS) can significantly improve the removal rate of various pollutants, and the addition of vanadium to the catalyst can effectively enhance the synergistic effect with the precious metal. Finally, Example 2 was selected as the optimal preparation process for the catalyst.

[0069] Example 4

[0070] This example prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing Pd, V, Ti, and Fe elements;

[0071] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0072] Weigh 0.50 g of palladium chloride (palladium content 59.5 wt%), 15.15 g of ferric nitrate, 16.62 g of titanium tetrachloride, and 2.56 g of sodium pyrovanadate, add them into 90 g of water and stir to completely dissolve them, then add 78 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0073] Then it was crushed and granulated by adding 5% water glass of the total mass of the crushed solid to obtain catalyst 4 with a diameter of about 1 mm, which was recorded as 0.3% Pd-5% V2O5 / 7% TiO2 / 10% Fe2O3-C.

[0074] Example 5

[0075] This embodiment prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing Ru, V, Ti, and Fe elements;

[0076] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0077] Weigh 0.81 g of ruthenium trichloride (ruthenium content 37 wt%), 15.15 g of ferric nitrate, 16.62 g of titanium tetrachloride, and 2.56 g of sodium pyrovanadate, add them into 90 g of water and stir to completely dissolve them, then add 78 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0078] Then the solid was crushed and granulated by adding 5% water glass as the total weight of the crushed solid to obtain a catalyst 5 with a diameter of about 1 mm, which was recorded as 0.3% Ru-5% V2O5 / 7% TiO2 / 10% Fe2O3-C.

[0079] Example 6

[0080] This example prepares a Fe-C micro-electrolysis photocatalytic composite catalyst containing Rh, V, Ti, and Fe elements;

[0081] The preparation method of the Fe-C micro-electrolysis photocatalytic composite catalyst comprises the following steps:

[0082] Weigh 1.75 g of sodium hexachlororhodiumate (rhodium content 17.1 wt%), 15.15 g of ferric nitrate, 16.62 g of titanium tetrachloride, and 2.56 g of sodium pyrovanadate, add them into 90 g of water and stir to completely dissolve them, then add 78 g of graphite phase carbon nitride (g-C3N4), mix well and place in a muffle furnace, heat to 550°C at a rate of 1°C / min in an air environment, keep warm and roast for 3 hours, then cool naturally to room temperature to obtain a block solid;

[0083] Then the solid was crushed and granulated by adding 5% water glass to the total mass of the crushed solid to obtain a catalyst 6 with a diameter of about 1 mm, which was recorded as 0.3% Rh-5% V2O5 / 7% TiO2 / 10% Fe2O3-C.

[0084] Performance Test 2

[0085] The catalysts obtained in Examples 4 to 6 were compared with the catalyst in Example 2 under the same conditions using the method in Performance Test 1. The comparison results are summarized in Table 2 below.

[0086] Table 2

[0087]

[0088]

[0089] It can be concluded from Table 2 that the performance of the catalyst prepared using metallic rhodium in Example 6 is substantially equivalent to that of the catalyst prepared using metallic platinum in Example 2. Considering that rhodium is relatively expensive and difficult to recover, the catalyst using metallic platinum in Example 2 is preferred in the present invention.

[0090] Embodiments 7 to 9

[0091] Using the same preparation method as in Example 2, the content (mass percentage) of the precious metal platinum was adjusted to 0.1%, 0.5%, and 0.7%, to obtain the catalysts of Example 7, Example 8, and Example 9, respectively, and recorded as 0.1% Pt-5% V2O5 / 7% TiO2 / 10% Fe2O3-C, 0.5% Pt-5% V2O5 / 7% TiO2 / 10% Fe2O3-C, and 0.7% Pt-5% V2O5 / 7% TiO2 / 10% Fe2O3-C, respectively.

[0092] Performance Test 3

[0093] The catalysts obtained in Examples 7 to 9 were compared with the catalyst in Example 2 under the same conditions using the method in Performance Test 1. The comparison results are summarized in Table 3 below.

[0094] Table 3

[0095]

[0096]

[0097] It can be concluded from Table 3 that among the prepared catalysts, the effects of catalysts with a platinum content of 0.3% or more are not very different. Considering the economic efficiency, the present invention selects a catalyst with a platinum content of 0.3% as the best choice.

[0098] Catalyst application test

[0099] (I) In order to prove that the catalyst of the present invention is suitable for various wastewater treatment scenarios, the present invention tests the catalyst of Example 2 in treating different types of wastewater generated by multiple projects, and uses the method in Performance Test 1 to compare under the same conditions. The comparison results are summarized in the following Table 4. The steroid hormone APIs in Table 4 are the same as those in Table 1, Table 2, and Table 3.

[0100] Table 4

[0101]

[0102]

[0103] It can be concluded from Table 4 that the catalyst of the present invention has achieved good results in treating wastewater produced by polytetrahydrofuran, dodecanol and chloroacetic acid ethanol by replacing Fenton method, ordinary micro-electrolysis method and ozone oxidation method.

[0104] (ii) The present invention further evaluates the life and performance of the prepared catalyst (the catalyst described in Example 2).

[0105] The specific method is: the COD of the wastewater generated by the steroid hormone raw material is increased to four times the normal feed, a catalyst (the catalyst described in Example 2) of 10% (mass fraction) of the wastewater is added, and the COD changes at the inlet and outlet are monitored. When the COD removal rate is lower than 85% of the COD removal rate of the catalyst described in the present invention, an ultrasonic ozone combined cleaning technology is used to wash away the sludge, salt, scale and organic matter adhering to the catalyst.

[0106] If the performance of the new catalyst can only be restored to 90% or less, the catalyst needs to be regenerated. The regeneration conditions are: first increase the temperature to 120°C at a rate of 0.5°C / min, keep warm for 60 minutes, then continue to increase the temperature to 350°C at a rate of 1°C / min, keep warm for 2 hours, then increase the temperature to 900°C at a rate of 1°C / min, keep warm for 2 hours, and then naturally drop to room temperature.

[0107] During the test, the catalyst used (the catalyst described in Example 2) was washed 6 times and regenerated once under this test. The evaluation results are shown in Table 5 below:

[0108] Table 5

[0109] Running time / d Early COD removal rate / % Late COD removal rate / % Catalyst treatment 123 53.87 46.38 One wash 118 53.11 46.22 Secondary washing 116 52.79 46.05 Three washes 110 52.32 45.84 Four washes 98 50.20 46.03 Five washes 91 49.56 45.96 Six washes 76 47.84 / Seven wash / regeneration times 116 53.03 46.15

[0110] From Table 5, it can be concluded that the performance of the catalyst used (the catalyst described in Example 2) is generally stable, and most of the activity can be restored after 6 washings. However, the performance will drop sharply in the later stage of operation, and more than 98% of the activity can be restored again by regeneration after washing. Therefore, it can be judged that the service life of this catalyst is relatively long. According to estimates, it can be used for more than 5 years if it is washed with a solvent every year, and it can be regenerated for more than 3 times.

[0111] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for preparing a Fe-C micro-electrolysis photocatalytic composite catalyst, characterized in that: The steps include: 1) Mix a certain amount of water-soluble salt of titanium, water-soluble salt of vanadium, water-soluble salt of iron and water-soluble salt of precious metal elements to prepare an aqueous solution of a certain concentration; 2) mixing the aqueous solution in step 1) and graphite phase carbon nitride to obtain a mixture; and then calcining the mixture to obtain a block solid; 3) The blocky solid obtained in step 2) is crushed and granulated to obtain a photocatalytic composite catalyst with a particle size of 0.1-5 mm.

2. The preparation method according to claim 1, characterized in that: Step 1) The water-soluble titanium salt is one or more of titanium tetrachloride, titanium tetraiodide, and titanium tetrabromide. In the final catalyst, titanium exists in the form of titanium dioxide, and its mass proportion is 1 to 30 wt%; Step 1) the water-soluble salt of vanadium is one or more of metavanadate, pyrovanadate, orthovanadate, polyvanadate, and decavanadate, and in the final formed catalyst, vanadium exists in the form of vanadium pentoxide, and its mass proportion is 1 to 15 wt %; Step 1) The water-soluble iron salt is one or more of ferric chloride, ferric sulfate, and ferric nitrate. In the final catalyst, the iron exists in the form of iron oxide, and its mass accounts for 1 to 30 wt %; The noble metal in step 1) is one or more of platinum, palladium, rhodium and ruthenium, and its content is 0.01 to 3.0 wt % of the total mass of the catalyst, calculated as the noble metal element.

3. The preparation method according to claim 1, characterized in that: In step 2), the mass ratio of the aqueous solution to the graphite phase carbon nitride is 0.5:1 to 10:

1.

4. The preparation method according to claim 1, characterized in that: In step 2), the calcination temperature is 350-650° C., and the calcination time is 1-10 hours; in step 2), the calcination is carried out in an air environment or an oxygen environment, and the heating rate during calcination is 0.5-5° C. / min.

5. The Fe-C micro-electrolysis photocatalytic composite catalyst prepared by the method according to any one of claims 1 to 4.

6. Use of the Fe-C micro-electrolysis photocatalytic composite catalyst according to claim 5 as a persulfate activator in catalytic degradation of water pollutants.

7. Use of the Fe-C micro-electrolysis photocatalytic composite catalyst as claimed in claim 5 as a persulfate activator in improving the COD removal rate of sewage.

8. The use according to claim 6 or 7, characterized in that: The persulfate is peroxymonosulfate or peroxydisulfate; the pollutant is one or more of steroid hormone raw materials, organic chemical raw materials and dyes.

9. A method for utilizing the Fe-C micro-electrolysis photocatalytic composite catalyst of claim 5 to catalytically activate persulfate to degrade pollutants in water and improve the COD removal rate of sewage, characterized in that: The steps include: Add an oxidant to the water containing pollutants, then add the photocatalytic composite catalyst, mix them evenly, activate them with light, and then react at room temperature for 1 to 15 hours to achieve the degradation of pollutants in the water.

10. The method according to claim 9, characterized in that The mass ratio of water to the photocatalytic composite catalyst is (5-15):1; the mass ratio of oxidant to the photocatalytic composite catalyst is 1:(10-15).

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