Microfluidic template method rare earth-based soil remediation catalyst as well as preparation method and application thereof

Abstract

The invention discloses a micro-fluidic template method rare earth based soil remediation catalyst as well as a preparation method and application thereof. The catalyst takes fly ash nanofiber as a carrier and a composite oxide of cerium oxide and ferroferric oxide as an active component. The catalyst synthesized by the method has the advantages of being good in soil compatibility, high in catalytic efficiency, recyclable and the like, and the target of low-energy-consumption remediation of organic pollutant soil can be achieved.

Description

Technical Field

[0001] The present invention relates to a microfluidic template method rare earth-based soil remediation catalyst and a preparation method and application thereof, belonging to the field of soil pollution remediation. Background Art

[0002] Remediation of soil organic pollution is one of the important topics in the field of environmental protection. With the acceleration of industrialization and urbanization, soil pollution problems are becoming increasingly serious, especially the accumulation and spread of organic pollutants, which pose a great threat to the ecological environment and human health. Organic pollutants mainly come from industrial wastewater, agricultural chemicals (such as pesticides and fertilizers), oil pollution, landfill leakage, etc. Common organic pollutants include polycyclic aromatic hydrocarbons (PAHs), organic chlorides (such as DDT and PCBs), petroleum hydrocarbons, pesticide residues, solvents, etc. They are highly toxic, low in degradability and persistent. They can exist in the soil for a long time and spread through water, air and other channels, affecting the ecosystem. Organic pollutants in the soil not only affect plant growth and reduce soil fertility, but may also affect the health of animals and humans through the food chain. Long-term pollution accumulation may lead to changes in soil microbial communities, thereby affecting the self-purification capacity of the soil.

[0003] Although traditional soil remediation methods such as physical and chemical methods (e.g. soil incineration, chemical oxidation) can remove pollutants, they are costly and may cause secondary pollution to the environment. In addition, many organic pollutants are difficult to completely remove, especially those persistent chemicals. Catalytic removal technology, as an emerging remediation technology, has received widespread attention. The catalytic removal method accelerates the degradation, transformation or mineralization process of organic pollutants through the action of catalysts, and has the characteristics of high efficiency, good selectivity and environmental friendliness. The basic principle of catalytic removal of soil organic matter is to use catalysts to promote oxidation, reduction, cracking and other reactions of pollutants under specific conditions. Catalytic reactions can significantly reduce energy consumption, increase reaction rates and reduce the generation of by-products. Therefore, it is necessary to develop low-cost, non-toxic and efficient nanocatalysts, especially when dealing with complex and diverse organic pollutants, to improve the selectivity and durability of catalysts.

[0004] The development of catalysts is the key to catalytic removal technology. In recent years, researchers have made significant progress in the synthesis, modification, and application of soil remediation catalysts. Noble metal catalysts such as platinum, palladium, and rhodium have been widely studied and have shown excellent catalytic activity in the oxidation and reduction of organic pollutants. Although noble metal catalysts have high activity, their high cost limits their large-scale application. Metal oxide catalysts such as titanium dioxide (TiO2) and manganese dioxide (MnO2) have shown good results in the photocatalytic degradation and oxidation of soil organic pollutants, especially under ultraviolet light, where titanium dioxide has strong photocatalytic activity. In addition, nanomaterials have shown great potential in soil pollution remediation due to their high specific surface area and unique catalytic properties. Nanocatalysts not only improve reaction efficiency but also enhance the adsorption and degradation capacity of pollutants. Therefore, it is of great significance to develop low-cost, non-toxic, and efficient nanoscale soil remediation catalysts, especially in the treatment of complex and diverse organic pollutants, and to improve the selectivity and durability of catalysts. SUMMARY

[0005] The purpose of the present application is to address the current situation and existing problems of existing soil organic pollutant catalytic removal, and to propose a microfluidic template method for rare earth-based soil remediation catalyst and its preparation method and application.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A microfluidic template method for rare earth-based soil remediation catalyst, the catalyst uses fly ash nanofiber as a carrier and a composite oxide of cerium oxide and magnetite as an active component, and is prepared by a microfluidic template-solution polymerization-solvent thermal-microwave assisted calcination combined method. The mass percentage of the active component is 10-50% based on the mass of the carrier, and the mass ratio of cerium oxide to magnetite in the active component is 1:(1-10).

[0008] Further, the mass percentage of the active component is 30-50% based on the mass of the carrier, and the mass ratio of cerium oxide to magnetite in the active component is 1:(1-4).

[0009] A preparation method of the above-mentioned catalyst, the preparation method of the catalyst is as follows:

[0010] (1) Microfluidic template and solution polymerization method for preparing nanohollow fiber template

[0011] Aluminum salt, polyacrylonitrile, and dichloromethane are uniformly mixed to form a spinning solution, and then a syringe is connected to a microfluidic chip, and the spinning solution is introduced through the microfluidic chip channel. The spinning solution in the reaction process is then spun through a microfluidic electrostatic integrated machine to obtain polyacrylonitrile nanofibers loaded with aluminum salt, and the polyacrylonitrile nanofibers are dried and calcined for the first time to obtain alumina nanofibers;

[0012] Acrylonitrile and chloroform are added to alumina nanofibers to form a mixed solution, and then an initiator is added to carry out a chain polymerization reaction. After the reaction is completed, the solution is filtered, washed and dried to obtain a polyacrylonitrile-coated alumina nanofiber material.

[0013] The polyacrylonitrile-coated alumina nanofiber material is added to a dilute hydrochloric acid solution, reacted in a water bath, filtered and dried to obtain a polyacrylonitrile hollow nanofiber template;

[0014] (2) Preparation of fly ash nanofibers by solvent thermal method

[0015] The fly ash is sequentially subjected to acid leaching and alkali leaching, and then the alkali-leached fly ash is dried for the first time, and then hydrochloric acid solution and the polyacrylonitrile nano hollow fiber template prepared in step (1) are added again, and the mixture is evenly mixed and then placed in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, the mixture is filtered, dried for the second time, and calcined to obtain fly ash nanofibers;

[0016] (3) Preparation of catalyst by microwave-assisted calcination

[0017] Weigh cerium salt, iron salt, deionized water and the fly ash nanofibers prepared in step (2), mix them evenly, and then place them in a microwave sintering furnace for microwave-assisted calcination to prepare a rare earth-based soil remediation catalyst.

[0018] In the above preparation method: the preparation conditions of step (1) alumina nanofibers are as follows:

[0019] The aluminum salt is aluminum chloride, and the mass ratio of the aluminum salt, polyacrylonitrile, and dichloromethane is 1:(3-6):(15-30);

[0020] The spinning voltage is 15-25 kV, and the injection rate of the syringe is 0.5-1.5 mL / h;

[0021] The first drying temperature is 60-80°C, and the drying time is 12-24h; the first calcination temperature rise rate is 10-20°C / min, the calcination temperature is 500-800°C, and the calcination time is 4-8h.

[0022] In the above preparation method: the preparation conditions of step (1) polyacrylonitrile-coated alumina nanofiber material are as follows:

[0023] The mass ratio of acrylonitrile, chloroform, aluminum oxide nanofibers and initiator is 1: (5-10): (0.2-0.3): (0.01-0.05), and the initiator is benzoyl peroxide or azobisisobutyronitrile; the polymerization temperature is 50-70° C., and the polymerization time is 4-8 hours.

[0024] In the above preparation method: the preparation conditions of step (1) polyacrylonitrile nano hollow fiber template are as follows:

[0025] The dilute hydrochloric acid solution is a hydrochloric acid solution with a mass fraction of 5 to 10%, and the mass ratio of the polyacrylonitrile-wrapped alumina nanofiber material to the dilute hydrochloric acid solution is 1:(30 to 60); the water bath reaction temperature is 40 to 60° C., and the water bath reaction time is 6 to 12 hours; the drying temperature is 60 to 80° C., and the drying time is 12 to 24 hours.

[0026] In the above preparation method, the acid used in the acid leaching in step (2) is a hydrochloric acid solution with a mass fraction of 5-10%, and the alkali used in the alkali leaching is a sodium hydroxide solution with a mass fraction of 10-20%. The time for the acid leaching and the alkali leaching is 4-8 hours. The conditions for the first and second drying are: the drying temperature is 80-100° C., and the drying time is 6-12 hours.

[0027] During the hydrothermal reaction, the mass ratio of fly ash soaked in alkali, hydrochloric acid solution and polyacrylonitrile nano hollow fiber template is 1: (40-60): (0.3-0.6); the mass concentration of the hydrochloric acid solution is 5-10%;

[0028] The temperature of the hydrothermal reaction is 110-130° C., and the time of the hydrothermal reaction is 12-24 hours; the temperature of the roasting is 600-800° C., and the time of the roasting is 2-4 hours.

[0029] In the above preparation method: the cerium salt described in step (3) is cerium nitrate hexahydrate or cerium chloride, the iron salt is ferric nitrate nonahydrate or ferric chloride hexahydrate, the microwave power of the microwave-assisted calcination is 1000-1500W, and the microwave-assisted calcination time is 0.5-1h.

[0030] In the technical solution of the present invention, the catalyst is used in the catalytic removal of organic pollutants in the field of soil remediation.

[0031] In some preferred technical solutions, the organic pollutants are chlorobenzene and o-xylene.

[0032] The thermal desorption experimental conditions and results of the present invention are as follows: 50g of soil containing 5% chlorobenzene or 5% o-xylene is loaded into a catalyst performance evaluation reaction device, the inner diameter of the quartz tube in the evaluation reaction device is 10mm, the soil heating temperature and the hot air temperature are 100°C, the amount of catalyst used is 5g, and the desorption effect of chlorobenzene and o-xylene can reach 100% after thermal desorption at 100°C for 20 minutes.

[0033] Beneficial effects:

[0034] (1) The present invention utilizes the compatibility of aluminum chloride and dichloromethane to first prepare blue-loaded polyacrylonitrile nanofibers, then calcines to obtain aluminum oxide nanofibers, then utilizes solution polymerization to grow and wrap the polyacrylonitrile fibers on the surface of the aluminum oxide fibers, and finally utilizes dilute hydrochloric acid to react and dissolve the aluminum oxide nanofibers to obtain polyacrylonitrile nano hollow fiber templates. This method can avoid the difficulty in preparing uniform metal oxide nanofibers due to the insolubility of conventional metal salts in organic solvents, and can also utilize the volatility of dichloromethane as a solvent to facilitate the preparation of fibers. In addition, the present invention can also utilize only existing conventional methods to prepare nano hollow fibers, providing the necessary conditions for the subsequent preparation of fly ash nanofibers. Finally, raw materials such as aluminum chloride can be reused in the preparation process, and industrial-scale preparation is easy.

[0035] (2) In the present invention, fly ash is first subjected to acid leaching and alkaline leaching using hydrochloric acid and sodium hydroxide to remove impurities, and then the purified fly ash is reacted with dilute hydrochloric acid in a hydrothermal reactor for a long time, so that the fly ash can grow in the pores and outer surface of the polyacrylonitrile nano hollow fiber, thereby preparing fly ash nanofibers;

[0036] (3) The present invention utilizes a microwave-assisted calcination method to load the active components onto the surface of fly ash nanofibers. Microwave-assisted calcination can reach the required temperature in a short time, effectively avoiding strong interactions between the active components that lead to agglomeration on the fiber surface, thereby preparing active component nanoparticles, promoting more uniform growth of the active components, and ultimately improving catalytic activity.

[0037] (4) The catalyst prepared in the present invention uses cerium oxide and ferroferric oxide as active components, and the content of the active components is relatively high. It can utilize the excellent redox properties of cerium oxide and the electron transport properties of ferroferric oxide to ensure that the catalyst can catalytically remove organic matter in the soil at low temperatures. At the same time, after use, the magnetic properties of ferroferric oxide can be utilized to easily separate the catalyst from the soil, thereby avoiding the catalyst remaining in the soil.

[0038] (5) In the present invention, fly ash nanofibers are used as a carrier, and a composite oxide of cerium oxide and ferroferric oxide is used as an active component. Even if a small amount of catalyst remains in the soil after separation from the soil by magnetic means, since fly ash can improve soil properties and cerium oxide and ferroferric oxide do not have heavy metal toxicity, secondary pollution of the soil will not occur.

[0039] Therefore, the catalyst prepared by the present invention not only has excellent low-temperature catalytic removal of chlorobenzene and o-xylene performance, but also has good soil compatibility. Moreover, the catalyst component is environmentally friendly, the preparation process is simple, and it has strong application and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the SEM image of the catalyst prepared in Example 1;

[0041] Figure 2 This is a graph showing the chlorobenzene removal rate of the catalysts prepared in Examples 1-3 and Comparative Example 1;

[0042] Figure 3 This is a graph showing the o-xylene removal rate of the catalysts prepared in Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the following examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating processes. However, the protection scope of the present invention is not limited to the following examples.

[0044] Example 1

[0045] (1) Preparation of nano hollow fiber templates by combining microfluidic templates and solution polymerization

[0046] 5.0 g of aluminum chloride, 15.0 g of polyacrylonitrile, and 75.0 g of dichloromethane were weighed and mixed evenly to form a spinning solution. The syringe was then connected to the microfluidic chip, and the spinning solution was introduced through the microfluidic chip channel. The spinning solution in the reaction process was spun by a microfluidic electrostatic integrated machine (spinning voltage was 15 kV, and the injection rate of the syringe was 0.5 mL / h) to obtain polyacrylonitrile nanofibers loaded with aluminum salt. The polyacrylonitrile nanofibers were dried at 60 ° C for 24 h and then placed in a muffle furnace and rapidly heated to 500 ° C at a rate of 10 ° C / min and calcined for 8 h to obtain alumina nanofibers.

[0047] Then 7.5 g of acrylonitrile, 37.5 g of chloroform and 1.5 g of alumina nanofiber were weighed and mixed to form a mixed solution, and 75 mg of benzoyl peroxide was added during continuous stirring in a 50°C water bath for 8 h of chain polymerization reaction. After the reaction was completed, the product was filtered, washed with anhydrous ethanol and dried at 60°C for 24 h to obtain a polyacrylonitrile-coated alumina nanofiber material;

[0048] Then 5.0 g of the polyacrylonitrile-coated alumina nanofiber material was added to 150.0 g of a 5% mass fraction dilute hydrochloric acid solution, and after 12 h of reaction in a 40°C water bath, the product was filtered and dried at 60°C for 24 h to obtain a polyacrylonitrile nanohollow fiber template;

[0049] (2) Solvothermal preparation of fly ash nanofiber

[0050] 20.0 g of fly ash was weighed and added to 800.0 g of a 5% mass fraction dilute hydrochloric acid solution for 8 h of acid leaching. After filtration, 400.0 g of a 10% mass fraction sodium hydroxide solution was added for 8 h of alkali leaching. After filtration and drying at 80°C for 12 h, 10.0 g of the alkali-leached fly ash was weighed and added again to 400.0 g of a 5% mass fraction dilute hydrochloric acid solution and 3.0 g of the polyacrylonitrile nanohollow fiber template prepared in step (1). The mixture was uniformly mixed and placed in a hydrothermal reaction kettle for 24 h of low-temperature hydrothermal reaction at 110°C. After the reaction was completed, the product was filtered and dried at 80°C for 12 h, and then calcined at 600°C for 4 h to obtain a fly ash nanofiber;

[0051] (3) Preparation of catalyst by microwave-assisted calcination

[0052] 1.892 g of cerium nitrate hexahydrate, 3.926 g of iron nitrate nonahydrate, 151.360 g of deionized water and 5.0 g of the fly ash nanofiber prepared in step (2) were uniformly mixed, and then placed in a microwave sintering furnace for 1 h of microwave-assisted calcination at a microwave power of 1000 W to obtain a rare earth-based soil remediation catalyst (the mass percentage content of the active component was 30% based on the mass of the carrier, and the mass ratio of cerium oxide to magnetite in the active component was 1:1, and the SEM image of the catalyst is shown in Figure 1 );

[0053] (4) Catalytic activity test

[0054] 50 g of soil containing 5% chlorobenzene and 5% o-xylene was respectively taken and loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm, the soil heating temperature and hot air temperature were 100°C, the amount of catalyst used was 5 g, and after 20 min of thermal desorption at 100°C, the desorption effect of chlorobenzene and o-xylene could reach 100%.

[0055] Example 2

[0056] (1) Preparation of nano hollow fiber templates by combining microfluidic templates and solution polymerization

[0057] 5.0 g of aluminum chloride, 20.0 g of polyacrylonitrile, and 100.0 g of dichloromethane were weighed and mixed evenly to form a spinning solution. The syringe was then connected to the microfluidic chip, and the spinning solution was introduced through the microfluidic chip channel. The spinning solution in the reaction process was spun by a microfluidic electrostatic integrated machine (spinning voltage was 20 kV, and the injection rate of the syringe was 1.0 mL / h) to obtain polyacrylonitrile nanofibers loaded with aluminum salt. The polyacrylonitrile nanofibers were dried at 70 ° C for 16 h and then placed in a muffle furnace and rapidly heated to 700 ° C at a rate of 15 ° C / min and calcined for 6 h to obtain alumina nanofibers.

[0058] Then, 6.0 g of acrylonitrile and 42.0 g of chloroform were weighed and added to 1.5 g of alumina nanofibers to form a mixed solution. 180 mg of azobisisobutyronitrile was added while stirring in a water bath at 60°C for 6 h to carry out a chain polymerization reaction. After the reaction, the solution was filtered, washed with anhydrous ethanol, and dried at 70°C for 16 h to obtain a polyacrylonitrile-coated alumina nanofiber material.

[0059] Then, 6.0 g of polyacrylonitrile-coated alumina nanofiber material was added to 240.0 g of 7% dilute hydrochloric acid solution, reacted in a water bath at 50°C for 8 h, filtered, and dried at 70°C for 16 h to obtain a polyacrylonitrile hollow nanofiber template;

[0060] (2) Preparation of fly ash nanofibers by solvent thermal method

[0061] Weigh 20.0g of fly ash, add 1600.0g of 10% by mass dilute hydrochloric acid solution to acid leaching for 4h, filter and add 800.0g of 20% by mass sodium hydroxide solution to alkali leaching for 4h, filter and dry at 100℃ for 6h, then weigh 5.0g of fly ash after alkali leaching, add 300.0g of 10% by mass dilute hydrochloric acid solution and 3.0g of polyacrylonitrile nano hollow fiber template prepared in step (1), mix well and place in a hydrothermal reactor for low-temperature hydrothermal reaction at 130℃ for 12h, filter and dry at 100℃ for 6h after the reaction, and then calcine at 800℃ for 2h to obtain fly ash nanofibers;

[0062] (3) Preparation of catalyst by microwave-assisted calcination

[0063] 1.345 g of cerium nitrate hexahydrate, 3.737 g of ferric chloride hexahydrate, 134.500 g of deionized water and 4.0 g of the fly ash nanofibers obtained in step (2) were weighed and mixed evenly, and then placed in a microwave sintering furnace for microwave-assisted calcination at a microwave power of 1200 W for 40 min to prepare a rare earth-based soil remediation catalyst (based on the mass of the carrier, the mass percentage of the active component is 40%, and the mass ratio of cerium oxide to ferrosoferric oxide in the active component is 1:2);

[0064] (4) Catalytic activity test

[0065] 50g of soil containing 5% chlorobenzene and 5% o-xylene were respectively taken and loaded into the catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, the soil heating temperature and the hot air temperature were 100℃, the amount of catalyst used was 5g, and the desorption effect of chlorobenzene and o-xylene could reach 100% after thermal desorption at 100℃ for 20 minutes.

[0066] Example 3

[0067] (1) Preparation of nano hollow fiber templates by combining microfluidic templates and solution polymerization

[0068] 5.0 g of aluminum chloride, 30.0 g of polyacrylonitrile, and 150.0 g of dichloromethane were weighed and mixed evenly to form a spinning solution. The syringe was then connected to the microfluidic chip, and the spinning solution was introduced through the microfluidic chip channel. The spinning solution in the reaction process was spun by a microfluidic electrostatic integrated machine (spinning voltage was 25 kV, and the injection rate of the syringe was 1.5 mL / h) to obtain polyacrylonitrile nanofibers loaded with aluminum salt. The polyacrylonitrile nanofibers were dried at 80 ° C for 12 h and then placed in a muffle furnace and rapidly heated to 800 ° C at a rate of 20 ° C / min and calcined for 4 h to obtain alumina nanofibers.

[0069] Then, 5.0 g of acrylonitrile and 50.0 g of chloroform were weighed and 1.5 g of alumina nanofibers were added to form a mixed solution. 250 mg of azobisisobutyronitrile was added while stirring in a water bath at 70° C. for 4 h to carry out a chain polymerization reaction. After the reaction, the mixture was filtered, washed with anhydrous ethanol, and dried at 80° C. for 12 h to obtain a polyacrylonitrile-coated alumina nanofiber material. Then, 6.0 g of the polyacrylonitrile-coated alumina nanofiber material was added to 360.0 g of a 10% dilute hydrochloric acid solution by mass, reacted in a water bath at 60° C. for 6 h, filtered, and dried at 80° C. for 12 h to obtain a polyacrylonitrile hollow nanofiber template.

[0070] (2) Preparation of fly ash nanofibers by solvent thermal method

[0071] Weigh 20.0g of fly ash, add 1600.0g of 10% by mass dilute hydrochloric acid solution to acid leaching for 4h, filter and add 800.0g of 20% by mass sodium hydroxide solution to alkali leaching for 4h, filter and dry at 100℃ for 6h, then weigh 5.0g of fly ash after alkali leaching, add 300.0g of 10% by mass dilute hydrochloric acid solution and 3.0g of polyacrylonitrile nano hollow fiber template prepared in step (1), mix well and place in a hydrothermal reactor for low-temperature hydrothermal reaction at 130℃ for 12h, filter and dry at 100℃ for 6h after the reaction, and then calcine at 800℃ for 2h to obtain fly ash nanofibers;

[0072] (3) Preparation of catalyst by microwave-assisted calcination

[0073] 0.573 g of cerium chloride, 5.604 g of ferric chloride hexahydrate, 85.950 g of deionized water, and 4.0 g of the fly ash nanofibers obtained in step (2) were weighed and mixed evenly, and then placed in a microwave sintering furnace for microwave-assisted calcination at a microwave power of 1500 W for 0.5 h to obtain a rare earth-based soil remediation catalyst (based on the mass of the carrier, the mass percentage of the active component was 50%, and the mass ratio of cerium oxide to ferrosoferric oxide in the active component was 1:4);

[0074] (4) Catalytic activity test

[0075] 50g of soil containing 5% chlorobenzene and 5% o-xylene were respectively taken and loaded into the catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, the soil heating temperature and the hot air temperature were 100℃, the amount of catalyst used was 5g, and the desorption effect of chlorobenzene and o-xylene could reach 100% after thermal desorption at 100℃ for 20 minutes.

[0076] Comparative Example 1

[0077] (1) Catalyst preparation

[0078] Except that aluminum salt was not used in the catalyst preparation, other conditions were the same as those in Example 1;

[0079] (2) Catalytic activity test

[0080] 50g of soil containing 5% chlorobenzene and 5% o-xylene were respectively loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10mm, the soil heating temperature and the hot air temperature were 100℃, and the amount of catalyst used was 5g. After thermal desorption at 100℃ for 20 minutes, the removal rate of chlorobenzene was 63.8%, and the removal rate of o-xylene was 43.6%%;

[0081] (3) Contrast effect

[0082] Compared with Example 1, if aluminum salt is not used in the preparation of the catalyst, polyacrylonitrile nanofibers loaded with aluminum salt cannot be prepared, and alumina nanofibers and polyacrylonitrile nano hollow fiber templates cannot be prepared. Therefore, nanofibers cannot be prepared from fly ash, that is, only a catalyst in which cerium-iron composite oxide is loaded on conventional fly ash particles can be prepared. The fly ash obtained by the conventional method is micron-sized agglomerated particles, resulting in a significant decrease in its catalytic activity.

Claims

1. A rare earth-based soil remediation catalyst using a microfluidic template method, characterized by: The catalyst uses fly ash nanofibers as a carrier and a composite oxide of cerium oxide and ferroferric oxide as an active component, and is prepared by a combined method of microfluidic template-solution polymerization-solvent thermal-microwave-assisted calcination. The mass percentage of the active component is 10-50% based on the mass of the carrier, and the mass ratio of cerium oxide to ferroferric oxide in the active component is 1:(1-10).

2. The microfluidic template method rare earth-based soil remediation catalyst according to claim 1, characterized in that: Based on the mass of the carrier, the mass percentage of the active component is 30-50%, and the mass ratio of cerium oxide to ferrosoferric oxide in the active component is 1:(1-4).

3. A method for preparing the catalyst according to claim 1, characterized in that: The preparation method of the catalyst is as follows: (1) Preparation of nano hollow fiber templates by combining microfluidic templates and solution polymerization Aluminum salt, polyacrylonitrile, and dichloromethane are uniformly mixed to form a spinning solution, and then a syringe is connected to a microfluidic chip, and the spinning solution is introduced through the microfluidic chip channel. The spinning solution in the reaction process is then spun through a microfluidic electrostatic integrated machine to obtain polyacrylonitrile nanofibers loaded with aluminum salt, and the polyacrylonitrile nanofibers are dried and calcined for the first time to obtain alumina nanofibers; Acrylonitrile and chloroform are added to alumina nanofibers to form a mixed solution, and then an initiator is added to carry out a chain polymerization reaction. After the reaction is completed, the solution is filtered, washed and dried to obtain a polyacrylonitrile-coated alumina nanofiber material. The polyacrylonitrile-coated alumina nanofiber material is added to a dilute hydrochloric acid solution, reacted in a water bath, filtered and dried to obtain a polyacrylonitrile hollow nanofiber template; (2) Preparation of fly ash nanofibers by solvent thermal method The fly ash is sequentially subjected to acid leaching and alkali leaching, and then the alkali-leached fly ash is dried for the first time, and then hydrochloric acid solution and the polyacrylonitrile nano hollow fiber template prepared in step (1) are added again, and the mixture is evenly mixed and then placed in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, the mixture is filtered, dried for the second time, and calcined to obtain fly ash nanofibers; (3) Preparation of catalyst by microwave-assisted calcination Weigh cerium salt, iron salt, deionized water and the fly ash nanofibers prepared in step (2), mix them evenly, and then place them in a microwave sintering furnace for microwave-assisted calcination to prepare a rare earth-based soil remediation catalyst.

4. The preparation method according to claim 3, wherein: The preparation conditions of the alumina nanofibers in step (1) are as follows: The aluminum salt is aluminum chloride, and the mass ratio of the aluminum salt, polyacrylonitrile, and dichloromethane is 1:(3-6):(15-30); The spinning voltage is 15-25 kV, and the injection rate of the syringe is 0.5-1.5 mL / h; The first drying temperature is 60-80°C, and the drying time is 12-24h; the first calcination temperature is 10-20°C / min, the calcination temperature is 500-800°C, and the calcination time is 4-8h.

5. The preparation method according to claim 3, wherein: The preparation conditions of the polyacrylonitrile-coated alumina nanofiber material in step (1) are as follows: The mass ratio of acrylonitrile, chloroform, aluminum oxide nanofibers and initiator is 1: (5-10): (0.2-0.3): (0.01-0.05), and the initiator is benzoyl peroxide or azobisisobutyronitrile; the polymerization temperature is 50-70° C., and the polymerization time is 4-8 hours.

6. The preparation method according to claim 3, wherein: The preparation conditions of the polyacrylonitrile nano hollow fiber template in step (1) are as follows: The dilute hydrochloric acid solution is a hydrochloric acid solution with a mass fraction of 5 to 10%, and the mass ratio of the polyacrylonitrile-wrapped alumina nanofiber material to the dilute hydrochloric acid solution is 1:(30 to 60); the water bath reaction temperature is 40 to 60° C., and the water bath reaction time is 6 to 12 hours; the drying temperature is 60 to 80° C., and the drying time is 12 to 24 hours.

7. The preparation method according to claim 3, wherein: The acid used in the acid leaching in step (2) is a hydrochloric acid solution with a mass fraction of 5-10%, and the alkali used in the alkali leaching is a sodium hydroxide solution with a mass fraction of 10-20%. The time for the acid leaching and the alkali leaching is 4-8 hours. The conditions for the first and second drying are: the drying temperature is 80-100° C., and the drying time is 6-12 hours. During the hydrothermal reaction, the mass ratio of fly ash soaked in alkali, hydrochloric acid solution, and polyacrylonitrile hollow nanofiber template is 1:(40-60):(0.3-0.6); The mass concentration of the hydrochloric acid solution is 5-10%; The temperature of the hydrothermal reaction is 110-130° C., and the time of the hydrothermal reaction is 12-24 hours; the temperature of the roasting is 600-800° C., and the time of the roasting is 2-4 hours.

8. The preparation method according to claim 3, wherein: The cerium salt described in step (3) is cerium nitrate hexahydrate or cerium chloride, the iron salt is ferric nitrate nonahydrate or ferric chloride hexahydrate, the microwave power of the microwave-assisted calcination is 1000-1500W, and the microwave-assisted calcination time is 0.5-1h.

9. Use of the catalyst according to claim 1 in the catalytic removal of organic pollutants in the field of soil remediation.

10. The use according to claim 9, characterized in that The organic pollutants are chlorobenzene and o-xylene.

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