Application of phosphorus-iron-aluminum triple-doped carbon material in degradation of organic pollutants

Abstract

According to the application of the phosphorus-iron-aluminum triple-doped carbon material in degradation of the organic pollutants, the phosphorus-iron-aluminum triple-doped carbon material is placed in organic wastewater, oxygen is introduced or degradation reaction is directly carried out in the air, oxidizing agents such as hydrogen peroxide do not need to be added, and the phosphorus-iron-aluminum triple-doped carbon material can be recycled. And degrading organic substances in the wastewater by activating molecular oxygen under non-optical and non-electric conditions. Wherein the phosphorus-iron-aluminum triple-doped carbon material is prepared by mixing biochar with a phosphorus source, an iron source and an aluminum source and carrying out hydrothermal reaction and pyrolysis treatment. Molecular oxygen can be efficiently activated and organic pollutants can be degraded only through the catalytic activity of the material and ventilation, heavy metal ions, the organic pollutants and the like in wastewater are effectively removed, after dissolved oxygen in water captures electrons released by iron phosphide, various reactive oxygen species are generated through electron transfer, oxidative degradation of the organic matters is promoted, and the treatment effect is good. Wide application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and specifically to the application of phosphorus-iron-aluminum triple-doped carbon materials in the degradation of organic pollutants. Background Art

[0002] With the rapid development of industrialization, the types and concentrations of organic pollutants in the environment have increased significantly, posing a serious threat to ecological safety and human health. Traditional wastewater treatment methods, such as adsorption, membrane separation technology, and advanced oxidation processes, can remove organic pollutants to a certain extent, but still have problems such as high cost, low efficiency, and secondary pollution. Especially in advanced oxidation technologies (AOPs), it is generally necessary to add additional oxidants such as hydrogen peroxide, ozone (O 3 ), or persulfate (PMS, PDS).

[0003] Among them, the Fenton reaction (Fe 2+ / H 2 O 2 ) and its improved systems are one of the most common AOPs methods. This system decomposes H 2 O 2 catalyzed by Fe 2+ to generate ·OH to achieve the degradation of organic matter. However, the addition amount of H 2 O 2 directly determines the degradation efficiency. If the dosage is insufficient, the reaction rate is limited; if the dosage is too high, it may lead to the self-decomposition of H 2 O 2 , reducing the utilization rate. In addition, H 2 O 2 is prone to decomposition during storage and transportation, and its instability and additional cost also limit the application scope of the Fenton system.

[0004] To reduce the dependence on external oxidants, some researchers have tried to explore catalytic systems that only rely on dissolved oxygen (O 2 ) in the environment, that is, to activate molecular oxygen through the oxygen reduction reaction (ORR) to generate reactive oxygen species (ROS), such as superoxide anion (O 2 - ·), singlet oxygen ( 1 O 2 ), etc., in order to achieve efficient degradation of organic pollutants. However, such systems often rely on other catalytic conditions to assist in improving the degradation effect. For example, photocatalysts (such as TiO 2 , g-C 3 N 4 ) are used to absorb light energy to excite electrons and reduce O 2Generate O 2 - / ·OH, which requires light of a specific wavelength to excite the catalyst; or use electrocatalysis to drive O 2 to be reduced at the cathode to generate ·OH. Although efficient degradation is achieved, the energy consumption increases.

[0005] In recent years, catalytic technologies based on carbon materials have received extensive attention in the field of organic pollutant degradation due to their advantages such as high efficiency, environmental friendliness, and low cost. Carbon materials (such as activated carbon, carbon nanotubes, graphene, etc.) have characteristics such as a large specific surface area, high chemical stability, and good electrical conductivity, and can be used as catalysts or catalyst carriers to activate molecular oxygen (O 2 ) to generate highly reactive oxygen species (such as hydroxyl radicals ·OH, superoxide radicals ·O 2 - , etc.), thereby efficiently degrading organic pollutants. However, the catalytic activity of existing carbon materials is limited, and the preparation process is complex, making it difficult to apply on a large scale.

[0006] To improve the catalytic performance of carbon materials, researchers usually use the method of element doping to regulate the electronic structure and surface properties of carbon materials by introducing heteroatoms (such as nitrogen, phosphorus, sulfur, etc.) or metal elements (such as iron, cobalt, manganese, etc.), thereby enhancing their catalytic activity. However, in existing technologies, chemical reagents are mostly used as carbon sources and doping sources, which not only have a high cost but may also cause secondary pollution to the environment. In addition, carbon materials doped with a single element still have deficiencies in catalytic activity and stability, making it difficult to meet the requirements of practical applications. Summary of the Invention

[0007] The purpose of the present invention is to provide an application of a phosphorus-iron-aluminum triple-doped carbon material in degrading organic pollutants in view of the deficiencies of the prior art.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] Place the phosphorus-iron-aluminum triple-doped carbon material in organic wastewater, introduce oxygen or directly carry out a degradation reaction in air, and degrade the organic substances in the wastewater by activating molecular oxygen;

[0010] Among them, the phosphorus-iron-aluminum triple-doped carbon material is prepared by the following method:

[0011] Step (1): Clean, dry, crush the carbon source and then sieve it to obtain biochar;

[0012] Step (2): Mix the biochar with a phosphorus source, an iron source, and an aluminum source, add hydrochloric acid, stir evenly, and then carry out a hydrothermal reaction;

[0013] Step (3), after the hydrothermal reaction is completed, the reaction system is placed under an inert gas atmosphere for pyrolysis treatment to obtain the phosphorus-iron-aluminum triple-doped carbon material.

[0014] Preferably, the time of the degradation reaction is 10 to 180 min, more preferably 30 to 60 min.

[0015] Preferably, the dosage of the phosphorus-iron-aluminum triple-doped carbon material relative to the organic wastewater is 0.8 to 1 g / L.

[0016] Preferably, the mentioned carbon sources include at least one of the following: agricultural and forestry wastes, animal wastes, fruit shells; the selection range of the phosphorus source covers: phosphate rock, struvite, hydroxyapatite; the selection range of the iron source covers: iron sludge, iron ore, ferric chloride, ferrous chloride, ferrous sulfate; and the aluminum source can be: kaolin, feldspar, alumina, aluminum chloride. Such a selection provides a diverse raw material source for the preparation process, taking into account both cost-effectiveness and the sustainable utilization of resources.

[0017] Preferably, in step one, the particle size of the biochar is 50 - 200 mesh.

[0018] Preferably, in step two, the hydrochloric acid concentration is 1 - 10 M; the mass ratio of the biochar to the phosphorus source is 5:1 - 1:5; the mass ratio of the phosphorus source to the iron source is 3:1 - 1:3; the mass ratio of the iron source to the aluminum source is 5:1 - 1:2.

[0019] Preferably, in step three, the temperature of the hydrothermal reaction is 50 - 250 °C, and the reaction time is 18 - 48 h.

[0020] Preferably, the inert gas in step four can be either nitrogen or argon, the pyrolysis temperature is 600 - 1000 °C, and the reaction time is 0.5 - 5 h.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The present invention can efficiently activate molecular oxygen (O 2 / air) and degrade organic pollutants only through the catalytic activity of the material itself and aeration (O 2 ). Among them, iron and aluminum, as active components, can undergo redox reactions, complexation reactions, etc. with pollutants, effectively removing heavy metal ions, organic pollutants, etc. in the wastewater. When the reaction is carried out, it can efficiently activate molecular oxygen. After the dissolved oxygen in water captures the electrons released by iron phosphide, a variety of reactive oxygen species are generated through electron transfer, promoting the oxidative degradation of organic matter. There is no need to add chemical agents such as hydrogen peroxide, which helps to save costs, thereby realizing the efficient degradation of organic pollutants by the catalyst.

[0023] In addition, the present invention introduces a phosphorus source, which can not only adjust the surface charge and acid-base properties of the material, but also remove heavy metal ions in wastewater through ion exchange. The formed iron phosphide has lower electron transfer resistance, better stability and a wider pH value range.

[0024] The present invention uses natural source materials as carbon and doping sources, turning waste into treasure, with low cost and environmental friendliness. Description of the Drawings

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, where:

[0026] Figure 1 It is the SEM electron micrograph of the catalyst prepared in Example 1 of the present invention. Detailed Embodiments

[0027] The present invention will be further described below through specific embodiments, but the protection scope of the present invention is not limited thereto. The test materials and reagents used in the following embodiments can all be obtained through commercial channels.

[0028] As described above, the present invention provides the application of a phosphorus-iron-aluminum triple-doped carbon material in activating molecular oxygen to degrade organic pollutants, specifically:

[0029] Place the phosphorus-iron-aluminum triple-doped carbon material in organic wastewater, introduce oxygen or directly carry out the degradation reaction in air, and degrade the organic substances in the wastewater by activating molecular oxygen.

[0030] In some embodiments, the reaction duration is 10 to 180 min, for example: 10 min, 60 min, 90 min, 120 min, 180 min, or other values within the range, which can be selected according to actual needs and are not limited herein.

[0031] In some embodiments, the dosage of the phosphorus-iron-aluminum triple-doped carbon material relative to the organic wastewater is 0.8 to 1 g / L, for example, it can be selected from 0.8 g / L, 0.85 g / L, 0.9 g / L, 0.95 g / L or 1 g / L, or other values within the range, which can be selected according to actual needs and are not limited herein.

[0032] The phosphorus-iron-aluminum triple-doped carbon material described in the present invention is prepared by the following method:

[0033] First, the carbon source is pretreated to reach a certain particle size, and then the carbon source, phosphorus source, iron source and aluminum source are mixed with acid and stirred evenly. Hydrothermal reaction is carried out at a set initial temperature and time to obtain a primary mixture. The primary mixture is placed under an inert atmosphere for pyrolysis treatment to finally obtain a natural source phosphorus / iron / aluminum triple-doped carbon material.

[0034] The above carbon source, phosphorus source and iron source raw materials are all selected from industrial or agroforestry wastes. The raw materials are easily available, which not only reduces the cost of materials, but also provides a treatment method for zero discharge of industrial and agroforestry wastes, and has very good application prospects. Specifically, the mentioned carbon source includes but is not limited to: agroforestry wastes, animal wastes, fruit shells; the phosphorus source includes but is not limited to: phosphate rock, struvite, hydroxyapatite; the iron source includes but is not limited to: iron sludge, iron ore (such as magnetite Fe 3 O 4 , hematite Fe 2 O 3 , siderite FeCO 3 ), ferric chloride, ferrous chloride, ferrous sulfate; the aluminum source includes but is not limited to: kaolin, feldspar, alumina, aluminum chloride.

[0035] According to the embodiment of the present invention, after the carbon source is pretreated, it is mixed with the phosphorus source, iron source and aluminum source in a certain proportion, stirred evenly with hydrochloric acid, and a hydrothermal reaction is carried out at a set initial temperature and time to obtain a primary mixture. Among them, the particle size of the biochar is 50-200 mesh, the hydrochloric acid concentration is 1-10M, and it is dried at 50-250°C to obtain the primary mixture.

[0036] In the embodiment of the present invention, the particle size of the biochar can be any one of 50-200 mesh, such as 50 mesh, 80 mesh, 100 mesh, 140 mesh, 200 mesh; the hydrochloric acid concentration can be any one of 1-10M, such as 1M, 3M, 5M, 10M; the drying temperature can be any one of 50-250°C, such as 50°C, 100°C, 200°C, 250°C; the hydrothermal reaction time can be any one of 18-48h, such as 18h, 24h, 36h, 48h, or other values within the range, which can be selected according to actual needs and are not limited here.

[0037] In the embodiment of the present invention, the mass ratio of biochar to phosphorus source in the above initial mixture is 5:1-1:5, for example, it can be any one of the following mass ratios: 5:1, 4:2, 3:3, 1:5; the mass ratio of the above phosphorus source to iron source is 3:1-1:3, for example, it can be any one of the following mass ratios: 3:1, 2:2, 1:3; the mass ratio of the above iron source to the above aluminum source is 5:1-1:2, for example, it can be any one of the following mass ratios: 5:1, 4:1, 2:3, 1:2, or other values within the range, which can be selected according to actual needs and are not limited here.

[0038] According to an embodiment of the present invention, after the primary mixture is formed and dried, it is pyrolyzed in an inert atmosphere to obtain a phosphorus / iron / aluminum triple-doped carbon material, which includes: after the primary mixture is formed and dried, it is carbonized in an inert atmosphere at 600-1000 °C for 0.5-5 h to obtain a natural-source phosphorus / iron / aluminum triple-doped carbon material.

[0039] In the embodiment of the present invention, in an inert atmosphere, it can be any one of the following gases: N 2 or Ar; the pyrolysis temperature includes 600-1000 °C, for example, it can be any one of the following temperatures: 600 °C, 700 °C, 800 °C, 1000 °C; the pyrolysis time includes 0.5-5 h, for example, it can be any one of the following times: 0.5 h, 1 h, 2 h, 4 h, 5 h, and finally a natural-source phosphorus / iron / aluminum triple-doped carbon material is obtained.

[0040] In the embodiment of the present invention, the natural-source phosphorus / iron triple-doped carbon material belongs to an iron-carbon internal electrolysis material, which does not require an external power source, has excellent stability, and most of the raw materials are waste. The currently widely used iron-carbon internal electrolysis material uses zero-valent iron as the active center, but zero-valent iron is easily oxidized by oxygen in the air and gradually lost during the wastewater treatment process, resulting in a decrease in activity. In contrast, the triple-doped carbon material of the present invention uses iron phosphide as the active ingredient, and a variety of free radicals and singlet oxygen participate in the degradation of pollutants. The special structure of iron phosphide can effectively prevent the loss of zero-valent iron, thereby maintaining its activity for a long time and reducing the generation of iron mud. In addition, the phosphorus element in the material hardly leaks, which not only reduces the generation of red mud during the industrial wastewater treatment process but also avoids introducing phosphorus pollution into the wastewater. At the same time, the natural biochar carrier in the material enhances the adsorption and capture ability of organic matter, which helps the reactive oxygen species generated on the material surface to selectively degrade pollutants.

[0041] In the embodiment of the present invention, the above natural-source phosphorus / iron / aluminum triple-doped carbon material has a strong adsorption capacity for organic matter. Iron phosphide can form a metallic state due to the alloying of iron and phosphorus, so it has a high electron transfer ability and also has good acid resistance and stability. Secondly, iron combines with aluminum metal nanoparticles to form an infinite primary battery, which promotes the corrosion of Fe 0 such that molecular oxygen obtains electrons from the catalyst surface, resulting in the weakening of the O-O bond. After this bond obtains sufficient energy, it breaks to form two reactive oxygen species (O * ), and then the reactive oxygen species migrate on the catalyst surface to find reactant molecules. The iron and aluminum bimetals can provide different active sites to promote the migration and stabilization of oxygen species. Finally, loading the material in situ onto mesoporous biochar can further improve its stability and reactivity, thereby promoting the selective and efficient removal of organic matter in industrial wastewater.

[0042] The present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] In this example, torreya grandis shell is used as the carbon source, hydroxyapatite as the phosphorus source, hematite as the iron source, and alumina as the aluminum source; the preparation method is as follows:

[0045] Step 1: Pretreat the torreya grandis shell and select torreya grandis shell powder with a particle size of 100 mesh.

[0046] Step 2: Take 5 g of torreya grandis shell powder, 5 g of hydroxyapatite, 5 g of hematite and 1.5 g of alumina, add 80 mL of 3 M hydrochloric acid, and stir evenly.

[0047] Step 3: Heat and dry the above mixture on a heating plate at 200 °C to form an initial mixture.

[0048] Step 4: Place the above primary mixture under a tube furnace and carry out a pyrolysis reaction at 800 °C in an N 2 atmosphere for 2 h, then naturally cool and grind into powder to obtain a natural source phosphorus / iron / aluminum triple-doped carbon material (BC-Fe x PAl), and its SEM electron micrograph is as Figure 1 shown.

[0049] Comparative Example 1

[0050] A natural source phosphorus / iron double-doped carbon material (BC-Fe x P). The difference between this Comparative Example 1 and Example 1 is that: the mass ratio of the iron source to the aluminum source in Step 2 is 1:0 (specifically 5 g of hematite and 0 g of alumina). Other steps and parameters are the same as those in Example 1.

[0051] Comparative Example 2

[0052] A natural source phosphorus / aluminum double-doped carbon material (BC-P-Al). The difference between this Comparative Example 2 and Example 1 is that: the mass ratio of the iron source to the aluminum source in Step 2 is 0:1 (specifically 0 g of hematite and 5 g of alumina). Other steps and parameters are the same as those in Example 1.

[0053] Comparative Example 3

[0054] A natural source iron / aluminum double-doped carbon material (BC-Fe-Al). The difference between this Comparative Example 3 and Example 1 is that: no phosphorus source, that is, hydroxyapatite, is added in Step 2. Other steps and parameters are the same as those in Example 1.

[0055] Example 2

[0056] In order to more clearly illustrate the present invention, the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention were subjected to the detection of wastewater degradation.

[0057] The detection process is as follows:

[0058] (1) Take pharmaceutical wastewater as the experimental wastewater source, which mainly contains organic pollutants such as flavonoids (such as quercetin) and anthraquinones (such as emodin); the initial concentration of COD (Chemical Oxygen Demand) in the wastewater is 3185 mg / L, and the initial concentration of TOC (Total Organic Carbon) is 1176 mg / L.

[0059] (2) Divide the experimental wastewater source into four equal parts, put the catalysts prepared in Example 1 and Comparative Examples 1-3 respectively, then stir evenly. The mass concentration of the catalyst is 1 g / L, and then mark each wastewater source. The reaction is carried out directly under air conditions during the experimental process.

[0060] (3) Start timing when the catalyst is poured into the wastewater. Sampling is carried out at fixed time intervals to detect the COD concentration and TOC concentration in the wastewater source, which are respectively recorded as the COD degradation concentration and TOC degradation concentration. Then calculate the degradation percentage according to the formula:

[0061] COD degradation rate (%) = (COD initial concentration - COD degradation concentration) / COD initial concentration × 100%;

[0062] TOC degradation rate (%) = (TOC initial concentration - TOC degradation concentration) / TOC initial concentration × 100%.

[0063] The detection results are shown in Table 1:

[0064] Table 1 Efficiency performance of the catalyst in degrading wastewater

[0065]

[0066] (5) Filter and collect the catalyst after the wastewater treatment. After soaking it in ethanol and ultrasonicating for 0.5 h respectively, dry it and then put it into use again. After repeating the use 5 times in the manner of step (2), detect the COD and TOC degradation efficiency of the wastewater again at 60 min. The detection results are shown in Table 2:

[0067] Table 2 Recycling performance of the catalyst

[0068] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 COD degradation rate 93.0％ 86.0％ 78.8％ 75.4％ TOC degradation rate 89.0％ 80.9％ 78.9％ 78.1％

[0069] The results prove that, as can be seen from Table 1, when the catalyst prepared in Example 1 of the present invention is used to degrade wastewater, no hydrogen peroxide needs to be added. The degradation rate of COD reaches 75.1% at 30 min, 94.4% at 60 min, and 95.5% at 90 min. The degradation rate of TOC reaches 77.1% at 30 min, 90.3% at 60 min, and 92.1% at 90 min. This shows that the catalyst prepared in Example 1 of the present invention has very good degradation effect and is superior to the performance of other comparative examples. And as can be seen from Table 2, the catalyst prepared in Example 1 of the present invention can still maintain a high COD and TOC degradation rate after being reused 5 times, indicating that it has strong reusability, is not easily deactivated, and has a long service life.

[0070] Example 3

[0071] Perform performance tests on the catalysts prepared in Example 1 and Comparative Examples 1-3. The content of the performance test is the yield of ·OH.

[0072] Test method for the yield of ·OH:

[0073] (1) Add 0.01 mol of dimethyl sulfoxide (DMSO) and 0.05 mol of anhydrous sodium sulfate (Na 2 SO 4 ) to 1 L of water, and adjust the pH of the solution to 3 with dilute sulfuric acid.

[0074] (2) Take four conical flasks, all add an equal amount of the prepared solution, and respectively put the catalysts prepared in Example 1 and Comparative Examples 1-3, and then stir evenly. The mass concentration of the catalyst is 1 g / L.

[0075] (3) During the reaction, take 1 mL of sample every 5 minutes, filter the sampled solution to remove catalyst particles, and obtain a clear liquid.

[0076] (4) Next, perform concentration determination by high performance liquid chromatography. The detection conditions are that the ratio of water to methanol is 40:60, the detection wavelength is 355 nm, the flow rate is set to 0.8 mL min-1, and the peak emergence time is 5.2 minutes. The detection results are shown in Table 3:

[0077] Table 3 Performance of the yield of ·OH of the catalyst

[0078] <![CDATA[Yield of HO· (μM·L -1 )]]> Example 1 101.2 Comparative Example 1 79.7 Comparative Example 2 72.4 Comparative Example 3 82.1

[0079] The results prove that it is found that the yield of hydroxyl radicals of the catalyst prepared in Example 1 is as high as 101.2 μM·L -1 , which is much higher than the yields of other catalysts.

[0080] Example 4

[0081] To more clearly illustrate the present invention, Example 1 of the present invention is used to detect active molecular oxygen.

[0082] The detection process is as follows:

[0083] The difference between this Example 4 and Example 2 is that Example 1 is detected under the conditions of passing oxygen / passing nitrogen / direct exposure to air respectively.

[0084] The detection results are shown in Table 4:

[0085] Table 4 Efficiency performance of the catalyst for wastewater degradation

[0086]

[0087] The results prove that as can be seen from Table 4, when the catalyst prepared in Example 1 of the present invention degrades wastewater, under the condition of passing oxygen, the degradation rates of COD and TOC are the highest. At 60 minutes, the degradation rate of COD reaches 98.1%, and the degradation rate of TOC reaches 94.5%. Under the condition of passing nitrogen, due to the lack of molecular oxygen, its degradation efficiency is the lowest. And the degradation rate of direct exposure to air is between the two. Therefore, it can be shown that the catalyst of the present invention can effectively activate molecular oxygen (O 2 ), generate reactive oxygen species (such as hydroxyl radicals), thereby significantly improving the degradation efficiency of organic pollutants in sewage. Especially under the condition of high-concentration oxygen, the degradation performance of the catalyst reaches the optimal, further verifying that the activation of molecular oxygen is the key mechanism for the efficient degradation of the catalyst.

[0088] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the present invention.

Claims

1. Application of phosphorus-iron-aluminum tri-doped carbon material in degradation of organic pollutants, characterized in that: Specifically: The phosphorus-iron-aluminum tri-doped carbon material is placed in organic wastewater, oxygen is introduced or degradation reaction is directly carried out in the air, and organic substances in the wastewater are degraded by activating molecular oxygen; Wherein, the phosphorus-iron-aluminum tri-doped carbon material is prepared by the following method: Step (1), washing, drying, crushing and sieving the carbon source to obtain biochar; Step (2), mixing the biochar with a phosphorus source, an iron source, and an aluminum source, adding hydrochloric acid, stirring evenly, and then performing a hydrothermal reaction; Step (3), after the hydrothermal reaction is completed, the reaction system is placed in an inert gas atmosphere for pyrolysis treatment to obtain the phosphorus-iron-aluminum tri-doped carbon material.

2. The use according to claim 1, characterized in that: The degradation reaction time is 10 to 180 minutes.

3. The use according to claim 1, characterized in that: The dosage of phosphorus-iron-aluminum tri-doped carbon material relative to organic wastewater is 0.8-1 g / L.

4. The use according to claim 1, characterized in that: The carbon source is selected from one of agricultural and forestry wastes, animal wastes or fruit shells; the phosphorus source is selected from one of phosphate rock, struvite or hydroxyapatite; the iron source is selected from one of iron mud, iron ore, ferric chloride, ferrous chloride or ferrous sulfate; the aluminum source is selected from one of kaolin, feldspar, alumina or aluminum chloride.

5. The use according to claim 1, characterized in that: The particle size of the biochar is 50-200 meshes.

6. The use according to claim 1, characterized in that: The concentration of the hydrochloric acid is 1-10M.

7. The use according to claim 1, characterized in that: The mass ratio of biochar to phosphorus source is 5:1 to 1:

5.

8. The use according to claim 7, characterized in that: The mass ratio of the phosphorus source to the iron source is 3:1 to 1:3, and the mass ratio of the iron source to the aluminum source is 5:1 to 1:

2.

9. The use according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 50-250° C., and the reaction time is 18-48 hours.

10. The use according to claim 1, characterized in that: The temperature of the pyrolysis treatment is 600-1000° C., and the reaction time is 0.5-5 h.

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