A self-template preparation method for FeOCl / Fe2O3 heterojunction catalyst and its application

Abstract

This invention relates to a self-templating preparation method and application of FeOCl / Fe2O3 heterojunction catalysts, belonging to the field of catalyst technology. To address the problems of poor catalytic activity and instability in existing catalysts, this invention provides a self-templating preparation method and application for FeOCl / Fe2O3 heterojunction catalysts. The method includes selecting an iron source, mixing the iron source with a chlorine source for acid leaching to obtain an iron-containing acid leaching solution; adding a self-templating agent to the obtained iron-containing acid leaching solution for complexation to obtain an iron-chlorine-self-templating precursor; and performing calcination heat treatment to obtain the FeOCl / Fe2O3 heterojunction catalyst. This invention can effectively construct a porous structure, thereby increasing the specific surface area of ​​the formed FeOCl / Fe2O3 heterojunction catalyst, exposing more active sites, thus enhancing the mass transfer and adsorption activation capabilities of pollutants, and exhibiting high stability.

Description

Technical Field

[0001] This invention relates to a self-template preparation method and application of FeOCl / Fe2O3 heterojunction catalyst, belonging to the field of catalyst technology. Background Technology

[0002] Advanced oxidation technologies (AOPs), especially those based on sulfate radicals (SO4· ... - The Fenton-like technology, which utilizes hydroxyl radicals (·OH) and hydroxyl radicals, is currently the mainstream technology for treating recalcitrant industrial organic wastewater (such as dyeing, pharmaceutical, and chemical wastewater). Ferric chloride oxide (FeOCl), as a layered crystalline material, exhibits extremely high catalytic activity in Fenton-like reactions due to its unique interlayer structure and highly active Fe(III) sites.

[0003] Existing FeOCl catalysts have the following drawbacks in practical industrial applications:

[0004] Firstly, the preparation cost is high and the process is demanding. Traditional FeOCl is mostly produced by using high-purity anhydrous FeCl3 and Fe2O3 as raw materials, and is produced by a long-term (several days) gas-phase transport (CVT) reaction in a vacuum-sealed quartz tube at high temperature (300℃-400℃), which makes it difficult to achieve industrial-scale mass production.

[0005] Secondly, it has poor stability and its active species are easily lost. FeOCl is highly susceptible to hydrolysis in aqueous solution, leading to the loss of chloride ions (Cl) in its structure. - A large amount of chloride ions are lost, the catalyst is rapidly deactivated, and the lost chloride ions will cause secondary pollution.

[0006] Third, the slow electron transfer means that the reduction process from Fe(III) to Fe(II) in pure FeOCl (the rate-limiting step of the Fenton-like reaction) is slow, which leads to a significant decrease in catalytic efficiency as the reaction time increases.

[0007] Fourth, there is the issue of solid waste disposal. A large amount of scrap iron is generated in industrial production, which is currently mostly recycled as low-end scrap steel with very low added value and lacks ways to utilize it for high value.

[0008] Therefore, it is necessary to seek a Fenton-like catalyst and its preparation method that is low in cost, simple in process, highly stable, and can realize the high-value utilization of solid waste. Summary of the Invention

[0009] This invention addresses the problems existing in the prior art by providing a self-template preparation method and application of FeOCl / Fe2O3 heterojunction catalysts, solving the problem of how to achieve high catalytic activity and high stability.

[0010] One of the objectives of this invention is achieved through the following technical solution: a self-template preparation method for a FeOCl / Fe2O3 heterojunction catalyst, which includes the following steps:

[0011] A. Select an iron source, mix the iron source with a chlorine source, and perform acid leaching to obtain an iron-containing acid leaching solution; the chlorine source contains at least hydrochloric acid.

[0012] B. Add a self-templating agent to the iron-containing acid leaching solution obtained above to perform complexation, adjust the pH value to precipitate the complex, and obtain the iron-chlorine-self-templating precursor; the self-templating agent is selected from macromolecular organic compounds rich in carboxyl groups and / or hydroxyl groups.

[0013] C. The obtained iron-chlorine-self-templating precursor is subjected to calcination heat treatment to obtain FeOCl / Fe2O3 heterojunction catalyst. The calcination heat treatment temperature is 100℃-150℃.

[0014] An acid leaching solution is formed by reacting an iron source with a chlorine source. This solution mainly contains a mixture of FeCl2 and FeCl3. Then, through a self-templating mechanism, using carboxyl and / or hydroxyl groups as templates, the Fe in the acid leaching solution can be effectively leached. 3+ and Fe 2+ The catalyst fully complexes with the carboxyl and hydroxyl groups on the self-templating agent. After adjusting the pH of the system, a complex is formed. In the presence of the selected self-templating agent, calcination is carried out. During the calcination heat treatment, the self-templating agent undergoes partial pyrolysis and releases gas, which can construct porous channels in situ. This effectively constructs a porous structure, thereby increasing the specific surface area of ​​the formed FeOCl / Fe2O3 heterojunction catalyst, exposing more active sites, thus enhancing the mass transfer and adsorption activation capabilities of pollutants, and exhibiting high stability. Its high stability stems from the following: through complexation and in-situ calcination using a self-templating agent, FeOCl and Fe2O3 form a tight heterojunction. The electronic coupling of Fe-O-Fe bonds at the interface enhances the binding energy of Fe-Cl bonds in the structure, effectively anchoring interlayer chloride ions and inhibiting the hydrolysis of FeOCl and chloride ion loss in aqueous solution. Simultaneously, Fe2O3, as a stable framework, provides support and protection for the layered FeOCl, preventing the dissolution of active species during the reaction. This overcomes the shortcomings of traditional FeOCl, such as easy hydrolysis and deactivation, and secondary pollution caused by chloride loss. Furthermore, the self-templating agent, rich in carboxyl and / or hydroxyl groups, forms a tight heterojunction interface between FeOCl and Fe2O3, promoting interfacial electron transfer, accelerating the Fe(III) / Fe(II) cycle, and improving the activation efficiency of PMS, thereby enhancing the degradation performance of organic pollutants.

[0015] In the above-mentioned self-templating preparation method of FeOCl / Fe2O3 heterojunction catalyst, preferably, the iron source in step A is selected from iron salts and / or iron-containing solid waste; the iron-containing waste is selected from one or more of waste iron filings, steel slag, red mud, and acid-containing waste liquid from pickling; the iron-containing waste is pretreated with alkaline solution. Alkaline treatment effectively removes surface oil from the iron-containing waste, which is then washed with clean water and dried before being acid-leached with a chlorine source.

[0016] In the above-mentioned self-template preparation method of FeOCl / Fe2O3 heterojunction catalyst, preferably, the chlorine source in step A is selected from one or more of hydrochloric acid, sodium chloride, ammonium chloride, and chlorine-containing industrial wastewater. Hydrochloric acid provides the acidic environment (H2O) required to dissolve the iron source. + It can also provide the chloride ions (Cl) needed to construct FeOCl. - Sodium chloride, ammonium chloride, or chlorine-containing industrial wastewater are essential components in the system; they cannot directly dissolve the iron source themselves and are mainly used as a supplementary chlorine source. They need to be used in combination with hydrochloric acid to ensure the full dissolution of the iron source while increasing the Cl concentration in the system. - The concentration ensures the stoichiometric ratio of iron to chlorine in the subsequent precursor, which is conducive to the formation of the FeOCl phase.

[0017] In the above-mentioned self-templating method for preparing the FeOCl / Fe2O3 heterojunction catalyst, preferably, the acid leaching temperature in step A is 60°C to 90°C. By controlling the acid leaching at the above temperature, iron can be completely dissolved in the acid leaching process or no more bubbles can be generated, resulting in the presence of Fe in the acid leaching solution. 3+ and Fe 2+ Iron salt components.

[0018] In the above-mentioned self-template preparation method of FeOCl / Fe2O3 heterojunction catalyst, preferably, the macromolecular organic compound rich in carboxyl and / or hydroxyl groups in step B is selected from one or more of humic acid, lignin, cellulose, sodium alginate, citric acid, and polyacrylic acid and their salts. The purpose and function of using the above-mentioned macromolecular organic compound rich in carboxyl and / or hydroxyl groups as a self-template agent is: firstly, the contained carboxyl and hydroxyl functional groups can react with Fe in the acid leaching solution. 3+ Fe 2+ Chelating and complexing occur, allowing iron ions to be uniformly dispersed and fixed on the organic macromolecular framework, resulting in a homogeneous iron-chlorine-self-templating precursor. Secondly, during the calcination heat treatment, the organic compound undergoes partial pyrolysis, releasing gases such as CO2 and H2O, which can create pores in situ within the catalyst, constructing porous channels, increasing the specific surface area, and exposing more active sites. As a further preferred embodiment, the macromolecular organic compound rich in carboxyl and / or hydroxyl groups in step B is selected from humic acid.

[0019] In the above self-templating method for preparing the FeOCl / Fe2O3 heterojunction catalyst, preferably, the pH value in step B is adjusted to 2.0–4.0. The purpose of controlling the system within this acidic range is to avoid Fe from reacting with excessively high pH values. 3+ Fe 2+ Direct hydrolysis generates Fe(OH)3 and other hydroxide precipitates, leading to chloride ion loss. This ensures that iron mainly precipitates as an iron-chlorine-self-template complex, thus retaining the chloride component in the precursor and facilitating the subsequent formation of the FeOCl phase. As a further preferred option, the stirring time for the complexation in step B is preferably 2–4 hours.

[0020] In the above-mentioned self-templating preparation method of FeOCl / Fe2O3 heterojunction catalyst, preferably, the mass ratio of iron source to self-templating agent in step A is 1:0.1 to 1.0.

[0021] In the above-mentioned self-templating preparation method of FeOCl / Fe2O3 heterojunction catalyst, preferably, the calcination in step C is carried out in an oxygen atmosphere or an air atmosphere, and the calcination temperature is 100℃~150℃. The purpose of controlling the calcination temperature within this range is that it is sufficient to allow the self-templating agent to undergo pyrolysis and vaporization, constructing a porous structure in situ within the catalyst, while also allowing some FeOCl to be controlled and oxidized to Fe2O3, thereby forming a tight heterojunction interface between the FeOCl and Fe2O3 phases. Simultaneously, since FeOCl is prone to further decomposition and significant loss of chlorine components at higher temperatures, controlling the temperature below 150℃ effectively preserves the FeOCl phase and its interlayer chlorine, preventing excessive conversion of FeOCl to Fe2O3, ensuring the two phases coexist in a suitable ratio, and ultimately obtaining a FeOCl / Fe2O3 heterojunction catalyst with high specific surface area, high activity, and high stability. As a further preferred embodiment, the calcination heating rate is 2~10℃ / min. Furthermore, after raising the temperature, the temperature is controlled at 110℃~130℃ and held for 1-4 hours. Even further, the above-mentioned calcination heat treatment includes calcination in a tubular furnace, micro-group calcination, rotary kiln calcination, or fluidized bed calcination.

[0022] The second objective of this invention is achieved through the following technical solution: the application of a FeOCl / Fe2O3 heterojunction catalyst, characterized in that the FeOCl / Fe2O3 heterojunction catalyst obtained by the method described in any one of claims 1-8 degrades organic pollutants by activating persulfate.

[0023] In summary, compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention can construct porous channels in situ, effectively constructing porous structures, thereby increasing the specific surface area of ​​the formed FeOCl / Fe2O3 heterojunction catalyst, exposing more active sites, thereby enhancing the mass transfer and adsorption activation capabilities of pollutants, and exhibiting high stability.

[0025] 2. By utilizing the carboxyl and / or hydroxyl groups of the self-templating agent, a tight heterojunction interface is formed between FeOCl and Fe2O3, which promotes interfacial electron transfer, accelerates the Fe(III) / Fe(II) cycle, improves the activation efficiency of PMS, and thus enhances the degradation performance of organic pollutants. Attached Figure Description

[0026] Figure 1 This is the XRD pattern of the FeOCl / Fe2O3 heterojunction catalyst of the present invention.

[0027] Figure 2 This is a SEM image of the FeOCl / Fe2O3 heterojunction catalyst of the present invention.

[0028] Figure 3 This is a degradation analysis diagram of organic pollutants catalyzed by the FeOCl / Fe2O3 heterojunction catalyst in Example 2 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the present invention is not limited to these embodiments.

[0030] Example 1

[0031] S1: Pretreatment and acid leaching of scrap iron

[0032] Take industrial waste iron filings, wash them with a dilute alkaline solution (such as a dilute sodium hydroxide aqueous solution or a saturated sodium carbonate solution) to remove surface oil, then rinse them with clean water and dry them.

[0033] Scrap iron filings were added to concentrated hydrochloric acid, and the reaction temperature was controlled at 80°C. The reaction continued until the iron filings dissolved and no more bubbles were produced. Unreacted impurities were removed by filtration, yielding a high-concentration FeCl₂ solution. x Acid leaching solution (mainly a mixture of FeCl2 and FeCl3).

[0034] S2: Progenitor complex

[0035] The above-obtained FeCl x (The solution is mainly a mixture of FeCl2 and FeCl3.) Add humic acid to the acid leaching solution (the amount added is based on a mass ratio of scrap iron to humic acid of 1:0.5). After the addition is complete, maintain the temperature at room temperature and stir thoroughly for 3 hours to allow the Fe in the acid leaching solution to reach the desired concentration. 3+ Fe2+ The complex is fully complexed with the carboxyl and phenolic hydroxyl groups on humic acid. Then, the pH of the system is adjusted to 3.0 to completely precipitate the complex. The complex is then filtered, washed, dried, and ground to obtain the "iron-chlorine-humic acid" precursor.

[0036] S3: Self-template controlled pyrolysis

[0037] The "iron-chlorine-humic acid" precursor was placed in a tube furnace and heated to 120°C at a heating rate of 5°C / min under a nitrogen atmosphere followed by air. The temperature was then controlled and held for 2 hours. By controlling the temperature range, the humic acid could be pyrolyzed and vaporized to form a porous structure, while some FeOCl could be converted into Fe2O3. After the process was completed, the catalyst was finally cooled to obtain a FeOCl / Fe2O3 heterojunction catalyst with a high specific surface area.

[0038] The FeOCl / Fe2O3 heterojunction catalysts prepared above were characterized, and the specific characterization results are as follows: Figure 1 and Figure 2 shown.

[0039] Depend on Figure 1 The XRD pattern shows that the prepared catalyst has characteristic diffraction peaks of both FeOCl and Fe2O3 phases, and no other impurity phases, proving that the FeOCl / Fe2O3 heterojunction was successfully prepared.

[0040] Depend on Figure 2 The SEM images show that the catalyst exhibits a plate-like morphology, and a heterojunction interface with close contact between FeOCl and Fe2O3 can be observed. The specific surface area test results are 80-150 m² / g.

[0041] Example 2

[0042] This embodiment verifies the catalytic performance of the catalyst of the present invention in activating persulfate to degrade organic pollutants under different pH conditions.

[0043] Weigh 10 mg of the FeOCl / Fe2O3 heterojunction catalyst prepared in Example 1 and place it in a reaction reagent bottle. Add 10 mL of the target organic pollutant solution at 20 ppm. After reaching adsorption equilibrium by sonication or continuous stirring, adjust the pH of the solution to 3.0, 5.0, 7.0, and 9.0 respectively using dilute sulfuric acid or sodium hydroxide. Add 0.4 mM PMS (persulfate) to initiate the reaction and stir the reaction.

[0044] Samples were then taken after different reaction times, quenched with methanol, and immediately filtered through a 0.22 μm filter. The concentration of pollutants in the samples was measured using a UV spectrophotometer, and the degradation rate of organic pollutants was further calculated. The results are shown in [Figure number missing]. Figure 3 .

[0045] As can be seen from the figure, the FeOCl / Fe2O3 heterojunction catalyst of this invention exhibits excellent degradation performance over a wide pH range, and its Fenton-like reaction activity is 3-5 times higher than that of pure FeOCl, indicating that the heterojunction synergistic effect significantly promotes electron transfer and Fe(III) / Fe(II) cycle.

[0046] Example 3

[0047] This embodiment verifies the cycle stability of the catalyst of the present invention.

[0048] The FeOCl / Fe2O3 heterojunction catalyst prepared in Example 1 was used to activate PMS to degrade organic pollutants. After the reaction, the catalyst was recovered by filtration, washed, dried and used for the next cycle reaction. The cycle was repeated 5 times. The pollutant degradation rate was measured after each cycle, and the release of iron and chloride ions in the reaction solution was measured by inductively coupled plasma atomic emission spectrometry (ICP).

[0049] The FeOCl / Fe2O3 heterojunction catalyst of this invention showed no significant decrease in degradation activity after 5 cycles of use, and the loss of iron and chloride ions was lower than the national drinking water standard limit. This indicates that the formation of the heterojunction in the catalyst of this invention effectively enhances the binding energy of the Fe-Cl bond, inhibits chlorine loss, solves the pain points of easy deactivation and secondary pollution of traditional FeOCl, and has excellent chemical stability.

[0050] Example 4

[0051] S1 Scrap Iron Scrap Pretreatment and Acid Leaching

[0052] Take industrial waste iron filings, wash them with a dilute alkaline solution (such as a dilute sodium hydroxide aqueous solution or a saturated sodium carbonate solution) to remove surface oil, then rinse them with clean water and dry them.

[0053] Add scrap iron to concentrated hydrochloric acid. Sodium chloride or ammonium chloride can also be added as chloride ion supplements. Control the reaction temperature at 90℃ and react until the iron scrap dissolves and no more bubbles are produced. Filter to remove unreacted impurities to obtain a high concentration of FeCl₂. x Acid leaching solution (mainly a mixture of FeCl2 and FeCl3).

[0054] S2 precursor complex

[0055] The above-obtained FeCl x (The solution is mainly a mixture of FeCl2 and FeCl3.) Lignin is added to the acid leaching solution (the amount added is based on a mass ratio of scrap iron to lignin of 1:0.8). After addition, the solution is stirred thoroughly at room temperature for 4 hours to allow the Fe in the acid leaching solution to reach the desired concentration.3+ Fe 2+ The complex is fully complexed with the carboxyl group on lignin, and then the pH of the system is adjusted to 2.5 to completely precipitate the complex. Then, it is filtered, washed, dried, and ground to obtain the "iron-chlorine-lignin" precursor.

[0056] S3 self-templating controlled pyrolysis

[0057] The "iron-chlorine-lignin" precursor was placed in a tube furnace and heated to 110°C at a heating rate of 4°C / min under a nitrogen atmosphere followed by air. The temperature was then controlled and held for 3 hours. By controlling the temperature range, lignin could be pyrolyzed and vaporized to form a porous structure, while some FeOCl could be converted into Fe2O3. After the process was completed, the catalyst was finally cooled to obtain a FeOCl / Fe2O3 heterojunction catalyst with a high specific surface area.

[0058] Example 5

[0059] S1 Scrap Iron Scrap Pretreatment and Acid Leaching

[0060] Take industrial waste iron filings, wash them with a dilute alkaline solution (such as a dilute sodium hydroxide aqueous solution or a saturated sodium carbonate solution) to remove surface oil, then rinse them with clean water and dry them.

[0061] Scrap iron filings were added to concentrated hydrochloric acid, and the reaction temperature was controlled at 85°C. The reaction continued until the iron filings dissolved and no more bubbles were produced. The mixture was then filtered to remove unreacted impurities, yielding a high-concentration FeCl₂ solution. x Acid leaching solution (mainly a mixture of FeCl2 and FeCl3).

[0062] S2 precursor complex

[0063] The above-obtained FeCl x (The solution is mainly a mixture of FeCl2 and FeCl3.) Add citric acid to the acid leaching solution (the amount added is based on a 1:1 mass ratio of scrap iron to citric acid). After the addition is complete, maintain the temperature at room temperature and stir thoroughly for 3 hours to allow the Fe in the acid leaching solution to reach the desired concentration. 3+ Fe 2 The complex is fully complexed with the carboxyl group on citric acid, and then the pH of the system is adjusted to 2.0 to completely precipitate the complex. Then, it is filtered, washed, dried, and ground to obtain the "iron-chlorine-citric acid" precursor.

[0064] S3 self-templating controlled pyrolysis

[0065] The "iron-chlorine-citric acid" precursor was placed in a tube furnace and heated to 115°C at a heating rate of 4°C / min under a nitrogen atmosphere followed by air. The temperature was then controlled and held for calcination for 3.5 hours. By controlling the temperature range within this range, citric acid could be pyrolyzed and vaporized to form a porous structure, while some FeOCl could be converted into Fe2O3. After the process was completed, the catalyst was finally cooled to obtain a FeOCl / Fe2O3 heterojunction catalyst with a high specific surface area.

[0066] Example 6

[0067] S1 Scrap Iron Scrap Pretreatment and Acid Leaching

[0068] Take industrial waste steel slag, clean it with a dilute alkaline solution (such as a 5% sodium hydroxide aqueous solution or a saturated sodium carbonate solution) to remove surface oil stains, then rinse it with clean water and dry it.

[0069] Industrial waste steel slag was added to concentrated hydrochloric acid, and the reaction temperature was controlled at 90℃. The reaction continued until the steel slag dissolved and no more bubbles were produced. Unreacted impurities were removed by filtration, yielding a high-concentration FeCl₂-containing solution. x Acid leaching solution (mainly a mixture of FeCl2 and FeCl3).

[0070] S2 precursor complex

[0071] The above-obtained FeCl x Polyacrylic acid (mainly a mixture of FeCl2 and FeCl3) is added to the acid leaching solution (the amount added is based on a 1:1 mass ratio of waste steel slag to polyacrylic acid). After the addition is complete, the solution is stirred thoroughly at room temperature for 3 hours to allow the Fe in the acid leaching solution to reach a certain concentration. 3+ Fe 2+ The complex is fully complexed with the carboxyl groups on polyacrylic acid, and then the pH of the system is adjusted to 2.0 to allow the formed complex to precipitate completely. Then, it is filtered, washed, dried, and ground to obtain the "iron-chlorine-citric acid" precursor.

[0072] S3 self-templating controlled pyrolysis

[0073] The "iron-chlorine-polyacrylic acid" precursor was placed in a tube furnace and heated to 115°C at a heating rate of 4°C / min under a nitrogen atmosphere followed by air. The temperature was then controlled and held for calcination for 3.5 hours. By controlling the temperature range, the polyacrylic acid could be pyrolyzed and vaporized to form a porous structure, while some FeOCl could be converted into Fe2O3. After the process was completed, the catalyst was finally cooled to obtain a FeOCl / Fe2O3 heterojunction catalyst with a high specific surface area.

[0074] The specific embodiments described in this invention are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0075] Although the present invention has been described in detail and specific embodiments have been cited, it will be apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A self-template preparation method for a FeOCl / Fe2O3 heterojunction catalyst, characterized in that, The method includes the following steps: A. Select an iron source, mix the iron source with a chlorine source, and perform acid leaching to obtain an iron-containing acid leaching solution; the chlorine source contains at least hydrochloric acid. B. Add a self-templating agent to the iron-containing acid leaching solution obtained above to perform complexation, adjust the pH value to precipitate the complex, and obtain the iron-chlorine-self-templating precursor; the self-templating agent is selected from macromolecular organic compounds rich in carboxyl groups and / or hydroxyl groups. C. The obtained iron-chlorine-self-template precursor is subjected to calcination heat treatment to obtain FeOCl / Fe2O3 heterojunction catalyst. The calcination heat treatment temperature is 100℃~150℃.

2. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, characterized in that, The iron source in step A is selected from iron salts and / or iron-containing solid waste; the iron-containing waste is selected from one or more of the following: scrap iron, steel slag, red mud, and acidic pickling waste liquid; the iron-containing waste is pretreated with alkaline solution.

3. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, characterized in that, The chlorine source mentioned in step A is selected from one or more of hydrochloric acid, sodium chloride, ammonium chloride, and chlorine-containing industrial wastewater.

4. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, characterized in that, The acid leaching temperature in step A is 60℃~90℃.

5. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, 2, 3, or 4, characterized in that, The macromolecular organic compounds rich in carboxyl and / or hydroxyl groups mentioned in step B are selected from one or more of humic acid, lignin, cellulose, sodium alginate, citric acid, and polyacrylic acid and their salts.

6. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, 2, 3, or 4, characterized in that, The pH value mentioned in step B is adjusted to 2.0-4.

0.

7. The self-templating method for preparing the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, 2, 3, or 4, characterized in that, The mass ratio of the iron source to the self-tempering agent in step A is 1:0.1 to 1.

0.

8. The self-templating preparation method of the FeOCl / Fe2O3 heterojunction catalyst according to claim 1, 2, 3, or 4, characterized in that, The calcination in step C is carried out in an oxygen atmosphere or an air atmosphere, and the calcination temperature is 110℃~130℃.

9. The application of a FeOCl / Fe2O3 heterojunction catalyst, characterized in that, The FeOCl / Fe2O3 heterojunction catalyst obtained by the method described in any one of claims 1-8 degrades organic pollutants by activating persulfate.

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