A confined enhanced water treatment method for activating iron-based fenton process under neutral conditions

Abstract

The application belongs to the technical field of advanced oxidation water treatment, and discloses a confined enhanced water treatment method for activating an iron-based Fenton process under neutral conditions. A confined material is solvent-thermally synthesized: the uniform and dense growth of a nano iron-based catalyst on the pore wall surface of a skeleton material is controlled to obtain the confined material; physical and chemical polishing is performed on the outside of the pores of the confined material to remove residual nano iron-based catalyst; and the temperature of the confined catalytic reaction can be kept at room temperature of 20-25 DEG C to complete the removal of pollutants in water. The application can greatly improve the catalytic performance of the iron-based catalyst under neutral water quality conditions, and the kinetic enhancement effect can be improved by 2-3 orders of magnitude; the application can greatly improve the stability of the iron-based catalyst, so that it can work continuously for at least 8 hours without activation and regeneration; the application is suitable for various structures of iron-based catalysts, has universality, and has no special limitation on the material of the confined skeleton, and has strong applicability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of advanced oxidation water treatment, and relates to a confined enhanced water treatment method for activating an iron-based Fenton process under neutral conditions. BACKGROUND

[0002] Fenton-like advanced oxidation is a common pretreatment or advanced treatment technology for industrial wastewater, which utilizes an iron-based catalyst to contact hydrogen peroxide to rapidly produce hydroxyl radicals (main reaction formula: Fe(II)+H2O2+H + →Fe(III)+·OH+H2O). Compared with some similar technologies with large power consumption and complex process combination, the Fenton-like method has the advantages of simple operation and low cost under the premise of retaining the advantage of fast start-up of the traditional Fenton reaction, and therefore has great development and application value.

[0003] Because the iron site is easy to hydrolyze to form a hydroxylated structure, hindering its contact reaction with H2O2, the current catalyst generally relies on an acidic environment, and the working pH range is usually not more than 5 (see "Cai, Q.Q.; Lee, B.C.Y.; Ong, S.L.; Hu, J.Y. Fluidized-Bed Fenton Technologies for Recalcitrant Industrial Wastewater Treatment-Recent Advances, Challenges and Perspective. Water Res 2021, 190, 116692." for details). In the case of neutral or near-neutral conditions, the catalyst will be deactivated due to the lack of protons (H + ) driving. However, the pH of industrial wastewater is usually between 6 and 8, and the application of the Fenton-like technology in engineering requires the addition of acidic reagents to maintain it (and in some cases, the addition of iron salt aids), thereby generating high additional operating costs and secondary iron sludge pollution and other problems.

[0004] To improve the pH adaptability of catalysts, the main technology at home and abroad is to modify the structure of iron oxides. The idea is to slow down the combination of Fe and hydroxyl group by optimizing the coordination structure of Fe, such as making Fe-Cl coordination bond (see “Yang, X. J.; Xu, X. M.; Xu, J.; Han, Y. F. Iron Oxychloride (FeOCl): An Efficient Fenton-Like Catalyst for Producing Hydroxyl Radicals in Degradation of Organic Contaminants. J Am Chem Soc 2013, 135 (43), 16058-16061.”), or doping other metal elements (such as Ce, see “Xu, L.; Wang, J. Magnetic Nanoscaled Fe3O4 / CeO2 Composite as an Efficient Fenton-Like Heterogeneous Catalyst for Degradation of 4-Chlorophenol. Environ. Sci. Technol. 2012, 46, 10145-10153.”); on the other hand, increase the degree of coordination unsaturation of iron-based, and increase the probability of exposure to H2O2, such as making surface “oxygen vacancy” defects (see “Jin, H.; Tian, X.; Nie, Y.; Zhou, Z.; Yang, C.; Li, Y.; Lu, L., Oxygen Vacancy Promoted Heterogeneous Fenton-like Degradation of Ofloxacin at pH 3.2-9.0 by Cu Substituted Magnetic Fe3O4@FeOOH Nanocomposite. Environ. Sci. Technol. 2017, 51, 12699-12706.”), or making single atom iron catalyst (see “Yin, Y.; Shi, L.; Li, W.; Li, X.; Wu, H.; Ao, Z.; Tian, W.; Liu, S.; Wang, S.; Sun, H. Boosting Fenton-Like Reactions Via Single Atom Fe Catalysis. Environ Sci Technol 2019, 53 (19), 11391-11400.”).

[0005] Although the related art can properly slow down the deactivation of iron-based catalysts at near-neutral pH, it cannot completely solve the problem of H + The problem of scarcity remains an unsolved fundamental problem, resulting in the improved catalysts still being difficult to maintain normal operation under neutral conditions. For example, the group of Wang improved the activity of Fe3O4 catalyst at higher pH by doping Ce element, but when the pH rose from acidic (2.2) to near-neutral (5.3), the removal rate of the catalyst for tetrachlorophenol dropped rapidly from 100% (15 minutes) to 21% (120 minutes) (see “Xu, L.; Wang, J. Magnetic Nanoscaled Fe3O4 / CeO2 Composite as an Efficient Fenton-Like Heterogeneous Catalyst for Degradation of 4-Chlorophenol. Environ. Sci. Technol. 2012, 46, 10145-10153.”). The single atom Fe catalyst prepared by the group of Sun has much higher efficiency than iron oxide nanoparticles, but when the pH rises to 6, this single atom catalyst almost completely loses activity (see “Yin, Y.; Shi, L.; Li, W.; Li, X.; Wu, H.; Ao, Z.; Tian, W.; Liu, S.; Wang, S.; Sun, H. Boosting Fenton-Like Reactions Via Single Atom Fe Catalysis. Environ Sci Technol 2019, 53 (19), 11391-11400.”).

[0006] In view of the existing technical defects, the present application proposes a new nanotechnology that can activate Fenton-like catalysts under neutral conditions. The idea is to reduce the local pH on the surface of the catalyst (i.e., to strengthen the participation of H + ) by controlling the spatial scale of the catalytic reaction, without the need for additional acidic reagents or chemical aids throughout the process. This method is inspired by some research conclusions in cross-disciplines. When water molecules are confined in a nanoscale space, their own kinetic state and contact stress state with the catalyst surface will change greatly, which will affect their dissociation and the participation of H +equilibrium (see “Zhang, S.; Hedtke, T.; Zhou, X.; Elimelech, M.; Kim, J. H. Environmental Applications of Engineered Materials with Nanoconfinement. ACS ES&T Eng. 2021, 1, 706-724.”). At the same time, the confinement of space will enhance the surface potential of the catalyst, and due to the enhancement of electrostatic effect, the absorption and aggregation of protons on the surface (see “Wang, L.; Wang, Z.; Patel, S. K.; Lin, S.; Elimelech, M. Nanopore-Based Power Generation from Salinity Gradient: Why It Is Not Viable. ACS Nano 2021, 15 (3), 4093-4107.”). Therefore, under the dual action of “spatial confinement” and “charge properties of the catalyst”, it is expected to form a new nanotechnology that enhances the protonation of the surface.

[0007] The specific implementation method of the present application is to grow the iron-based catalyst uniformly in the framework with nanochannels, control the reaction space to be about 5 nanometers, and induce H + adsorbed and aggregated on the iron-based surface, thereby controlling the stable and efficient operation of the Fenton-like process at neutral pH. The present application tests four typical iron-based catalysts (CuFe2O4, Fe3O4, FeOOH, and FeOCl), and confirms that the developed confinement technology can greatly improve the kinetic efficiency of the iron-based catalyst under neutral water quality conditions (up to 310 times improvement), and the confinement effect also enhances the continuous working ability of the catalyst. SUMMARY

[0008] The technical problem to be solved by the present application is to control the Fenton-like reaction in the nanoscale space, use this confined environment to enhance the protonation process, and thereby improve the water treatment efficiency and durability of the iron-based catalyst under neutral conditions.

[0009] Technical scheme of the present application:

[0010] A confined enhancement water treatment method for activating the iron-based Fenton-like process under neutral conditions, comprising the following steps:

[0011] (1) Solvent-thermal synthesis of confined materials: control the uniform and dense growth of nano-iron-based catalysts on the pore wall of the framework material to obtain confined materials; wherein the size of the nano-iron-based catalyst is controlled so that the distance between the surface and the pore wall is not more than 10 nanometers; the framework material used to load the nano-iron-based catalyst has two characteristics: 1) regular pore structure; 2) pore size between 20-40 nanometers;

[0012] (2) Physically and chemically polish the outside of the confined material to remove residual nano-iron-based catalysts;

[0013] (3) The temperature of the confined catalytic reaction can be kept at room temperature of 20-25℃ to complete the removal of pollutants in water.

[0014] If the framework material is a membrane structure, a certain transmembrane pressure needs to be applied to make water containing organic pollutants and H2O2 enter from one side of the membrane and flow out from the other side, thereby completing the catalytic oxidation reaction.

[0015] If the framework material is a porous particle, the following needs to be maintained: 1) the depth of the pores should not exceed 20 nanometers, otherwise the excess pore space will lose its effect; 2) the particles are in a stirred suspension state or a fluidized state, thereby ensuring sufficient turbulence of the surface fluid and sufficient exchange of substances inside and outside the pores.

[0016] If a single organic pollutant containing a benzene ring (concentration at the μM level) is to be completely decomposed and removed, the reaction time in the pores needs to be controlled to be not less than 10 seconds, and the concentration of H2O2 needs to be not less than 20 times the concentration of the organic matter.

[0017] If an organic pollutant (concentration at the μM level) is to be completely mineralized and removed, the reaction time in the pores needs to be controlled to be not less than 2 minutes, and the concentration of H2O2 needs to be not less than 100 times the concentration of the organic matter.

[0018] Advantages of the present application:

[0019] (1) The present application can greatly improve the catalytic performance of iron-based catalysts in neutral water conditions, and the kinetic strengthening effect can be improved by 2-3 orders of magnitude;

[0020] (2) The present application can greatly improve the stability of the iron-based catalyst, so that it can work continuously for at least 8 hours without activation and regeneration;

[0021] (3) The present application is suitable for various iron-based catalyst structures and has universality, and there is no special limitation on the material of the confined framework, and the application is strong. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1are cross-sectional TEM images of "catalyst-AAO", where a is Fe3C>4-AAO, b is FeOOH-AAO, c is CuFe2C>4-AAO, d is FeOCl-AAO, and the scale bar is 100 nm.

[0023] Figure 2 are top-view TEM images of "catalyst-AAO", where a is Fe3C>4-AAO, b is FeOOH-AAO, c is CuFe2C>4-AAO, d is FeOCl-AAO, and the scale bar is 200 nm.

[0024] Figure 3 are XRD diffraction results of "catalyst-AAO", where a is Fe3C>4-AAO (the corresponding standard card in the figure is PDF #19-0629), b is FeOOH-AAO (the corresponding standard card in the figure is PDF #08-0098), c is CuFe2C>4-AAO (the corresponding standard card in the figure is PDF #25-0283), d is FeOCl-AAO (the corresponding standard card in the figure is PDF #72-0619).

[0025] Figure 4 are catalytic effect images of dispersed iron-based catalysts in a stirred reactor (i.e., non-confined catalysis), where a is at pH 3, b is at pH 5, c is at pH 7. Experimental conditions: catalyst dosage, 0.1 g L -1 ; BPA initial concentration, 20 μΜ; H2O2 initial concentration, 2 mM. Error bars represent the results of three parallel tests.

[0026] Figure 5 a is the effect image of BPA concentration change over time, Figure 5 b is the kinetic fitting effect image. Experimental conditions: BPA initial concentration, 20 μΜ; H2O2 initial concentration, 2 mM; solution pH, 7.0. Error bars represent the results of three parallel tests.

[0027] Figure 6 is a confined enhancement effect image after normalizing the surface area of the catalyst. Experimental conditions: BPA initial concentration, 20 μΜ; H2O2 initial concentration, 2 mM; solution pH, 7.0.

[0028] Figure 7 are cross-sectional TEM images of CuFe2C>4-AAO materials with different confinement scales, where a is a 200-300 nm confinement scale, b is a 30 nm confinement scale, c is a 10 nm confinement scale, and d is a 3 nm confinement scale.

[0029] Figure 8are the kinetic enhancement effects of the "catalyst-AAO" system at different confinement scales.

[0030] Figure 9 are the enhancement effects of CuFe2O4-AAO confinement system on the durability of the catalyst, where a is the control experiment, i.e. CuFe2O4 catalyst particles (2 g) are intercepted outside the AAO skeleton, and the durability of the catalyst in a non-confined state is investigated by continuous through-type reaction; b is the effect comparison chart, which investigates the relationship between BPA removal rate and continuous reaction time. Reaction conditions: BPA concentration, 20 μM; H2O2 concentration, 2 mM; pH of the influent solution, 7.0; flow rate, 1 mL min -1 Error bars represent the results of three parallel experiments. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and technical solutions.

[0032] The examples involved in the present application all use anodic aluminum oxide film (AAO) as the skeleton material for confinement. First, the iron-based catalyst is uniformly grown in the form of nanoparticles on the AAO pore wall through a solvothermal reaction, and the distance between the catalyst surface and the AAO wall (i.e. the confinement scale) is controlled as needed.

[0033] In the confinement reaction test part, the "catalyst-AAO" membrane is first fixed in the membrane module device, and the mixed solution containing organic pollutants and H2O2 is pushed through the membrane in the form of "one-way filtration", thereby triggering the Fenton-like reaction in the pores of the membrane and completing the confined water treatment process.

[0034] The test of the control experiment is to stir the iron-based catalyst particles in a glass reactor (the reactor is pre-configured with a mixed solution containing organic pollutants and H2O2), sample according to the specified time, remove the solids by high-speed centrifugation, and then analyze the residual organic matter concentration in the solution.

[0035] Example 1. Preparation method of four confinement materials and four control materials

[0036] Confinement material 1: a preparation method of a confinement structure containing Fe3O4 (Fe3O4-AAO), which is as follows:

[0037] FeCl2·4H2O (purity ≥99.0%) and 0.06M sodium citrate (anhydrous, purity >99.0%) were dissolved in ethylene glycol (anhydrous, purity >99.8%) and sonicated for 1 hour. AAO was then immersed in the solution and sonicated for 10 minutes. The alumina-containing solution was then transferred to a hydrothermal reactor (maintained at 180°C for 6 hours, with the temperature rising at 5°C per minute). The catalyst-grown film was then immersed in ethanol and rapidly sonicated for 10-20 seconds (ultrasonic frequency of 40kHz) to remove excess catalyst from the membrane. High-purity water was then injected into the nanopores for cleaning and allowed to dry for later use.

[0038] Material 1 (Comparative Example): Synthesis of Dispersed Fe3O4 Particles (Non-confined Catalysis)

[0039] 0.18 M FeCl2·4H2O (purity ≥99.0%) and 0.12 M sodium citrate (purity ≥99.0%) were dissolved in 30 mL of high-purity water by ultrasonic vibration. The solution was then transferred to a hydrothermal reactor and treated at 200°C for 10 hours (temperature increase controlled at 5°C / min). The resulting particles were washed three times with high-purity water and dried for later use.

[0040] Confined material 2: A method for preparing a confined structure containing FeOOH (FeOOH-AAO), as follows:

[0041] Prepare a 1M butylamine solution and adjust the pH to between 4.5 and 5.0 with acetic acid. Immerse the anodized aluminum oxide in the solution for 1 hour, take it out and dry it at room temperature for 1 hour, then place it in a furnace filled with N2 and keep it at 135°C for 1 hour. The resulting aluminum oxide film is placed in a FeSO4 solution (1-octanol as solvent) and ultrasonically treated for 10 minutes. Then the entire solid-liquid system is placed in a hydrothermal reactor and treated at 110°C for 0.5 hours (the temperature is controlled to rise by 5°C per minute). The obtained material is quickly swept on the outer surface of the membrane using a soft fine brush dipped in a dilute acid solution (1mM HCl dissolved in ethanol solution). After each sweep of about 2 seconds, rinse it with high-purity water to prevent the acid from penetrating into the membrane pores. Repeat this process several times to complete the polishing. Vacuum dry it and set it aside for use.

[0042] Material 2 (Comparative Example): Synthesis of Dispersed FeOOH Particles (Non-confined Catalysis)

[0043] Dissolve 0.15 M of FeS04-7H20 (purity > 99.0%) and 0.002 M of EDTA-Na (purity > 99.0%) in 100 mL of high purity water and adjust the pH of the solution to be between 6.3-7.5 with 0.1 M of NaOH. As the color of the solution changes from light green to brown, remove the precipitate and wash with high purity water three times. Dry under vacuum and use.

[0044] Confinement material 3: A method for preparing a confinement structure containing CuFe204(CuFe204-AAO) is as follows:

[0045] Dissolve 0.38 M of FeCl2(purity 98.0%), 0.06 M of CuCl2(purity > 99.9%) and 0.025 mM of sodium citrate (purity > 99.9%) in 20 mL of ethylene glycol solution and continuously sonicate for 1 hour. Soak the AAO in the mixture and sonicate for 10 minutes, then transfer to a hydrothermal reactor and treat at 180 °C for 4 hours (control the temperature increase to 5 °C per minute). Use a soft brush to quickly brush the outer surface of the film with a dilute acid solution (1 mM HCl dissolved in ethanol) for about 2 seconds each time, then rinse with high purity water to avoid the acid penetrating into the pores of the film. Repeat several times to complete the polishing. Dry under vacuum and use.

[0046] Material 3 (comparative example): A method for synthesizing dispersed CuFe204particles (non-confined catalyst)

[0047] Dissolve 0.38 M of FeCl2(purity > 99.0%), 0.06 M of Cu(NO3)2-3H2O (purity > 99.9%) and 0.025 M of sodium citrate (purity > 99.0%) in 20 mL of ethylene glycol solution and continuously sonicate for 1 hour. Then transfer the solution to a hydrothermal reactor and treat at 180 °C for 4 hours (control the temperature increase to 5 °C per minute). Wash the obtained particles with high purity water three times and dry.

[0048] Confinement material 4: A method for preparing a confinement structure containing FeOCl (FeOCl-AAO) is as follows:

[0049] Dissolve 1.0 g mL -1FeCl3-6H2O (purity > 99.0%) was dissolved in anhydrous ethanol and the alumina film was put into the mixture. The whole system was treated under ultrasonic for 0.5 hour and shaken for 24 hours (rotation speed 160 rpm). Then the wet alumina film was taken out, clamped by polished silicon sheet on both sides and put into the muffle furnace for treatment at 220 °C for 1 hour (temperature rising controlled at 10 °C per minute). The obtained material was polished by using a soft brush dipped in dilute acid solution (1 mM HCl dissolved in ethanol solution) for about 2 seconds each time and then washed by high purity water to avoid the acid solution from penetrating into the film pores. The polishing was repeated for several times and then vacuum dried for use.

[0050] Material 4 (comparative example): synthesis of dispersed FeOCl particles (non-confined catalyst)

[0051] A certain amount of FeCl3-6H2O (purity > 99.0%) powder was laid on the bottom of a quartz boat, which was sealed to isolate air, and then the quartz boat was put into the muffle furnace for treatment at 220 °C for 1 hour (temperature rising controlled at 10 °C per minute). The obtained particles were washed by high purity water for three times and dried for use.

[0052] Characterization of four confined "catalyst-AAO" materials

[0053] The effect of the "catalyst-AAO" film structure synthesized in Example 1 is shown in Figure 1 and Figure 2 wherein Figure 1 is a cross-sectional electron micrograph, Figure 2 is a top-view electron micrograph. It can be seen that the four typical iron-based catalyst nanoparticles (Fe3O4, FeOOH, CuFe2O4, FeOCl) are uniformly grown in the array pores of AAO (the pore size of AAO skeleton is about 20 nm). Since the particles themselves occupy a certain space, the space available for the solution is the distance between the particle surface and the AAO wall (we regard this distance as the "confined scale" for subsequent discussion). It can be seen that our synthesis method can basically realize the control of the four iron-based catalysts working at similar confined scales (about 5 nm).

[0054] The XRD characterization results of the four "catalyst-AAO" materials are shown in Figure 2 . The AAO skeleton itself is an amorphous structure, so there is no characteristic diffraction peak; after loading different iron-based catalysts, it shows different diffraction peaks. By comparing the standard card, it is confirmed that the corresponding catalyst structures on the four "catalyst-AAO" materials are Fe3O4 Figure 3 a), FeOOH Figure 3 b), CuFe2O4 Figure 3c) FeOCl( Figure 3 d).

[0055] Example 2

[0056] A confined enhanced water treatment method for activating an iron-based Fenton-like process under neutral conditions

[0057] First, a mixture containing organic pollutants and H2O2 was prepared, where the concentration of organic pollutants was controlled at 20μM and the concentration of H2O2 was controlled at 2mM. The "catalyst-AAO" material was fixed in the membrane assembly and the membrane assembly was sealed so that water could only flow out in one direction through the membrane pores. A micro pump was used to push the mixed solution through the membrane assembly, achieving a confined catalytic reaction inside the membrane pores. At a specific flow rate (flow rate range 0.6-4mL min -1 ). Since the residence time of the mixed solution within the membrane pores is inversely proportional to the water volume of the membrane pores, the residence time within the membrane can be flexibly controlled by controlling the water flow rate of the micropump as needed, provided the membrane pore water volume is known in advance, thereby completing the evaluation of reaction kinetics. The water that passes through the membrane after the reaction is directly collected in a liquid phase vial and rapidly analyzed by liquid chromatography. The confinement material is CuFe2O4, Fe3O4, FeOOH, and FeOCl prepared in Example 1, and the framework material is a membrane structure.

[0058] For the non-confined reaction of the comparative example (i.e., using dispersed catalyst particles), 100 mL of a mixed solution containing 20 μM organic pollutant concentration and 2 mM H2O2 concentration was prepared in advance, and the pH value of the solution was adjusted to 3, 5, and 7 respectively with dilute hydrochloric acid as needed, and then 0.1 g L -1 The catalyst is added and the reaction time is calculated. At a specific sampling time, a certain volume of water sample is quickly removed with a pipette and placed into a 1.5 mL centrifuge tube. The sample is then rapidly centrifuged using a high-speed centrifugal pump to remove solid particles. The resulting liquid is then analyzed by liquid chromatography.

[0059] Analysis of Fenton-like effect in confined area enhancement

[0060] The water treatment capabilities of the same catalyst were compared under confined (i.e., using "catalyst-AAO") and non-confined (i.e., using dispersed catalyst particles) conditions. Bisphenol A (BPA), a typical organic pollutant, was used as an indicator.

[0061] First, the effect of non-confined catalytic reaction was tested (such as Figure 4 As shown in Figure 2, with the gradual increase of solution pH (from 3 to 7), the catalytic degradation effect of the four iron-based catalysts on BPA decreased sharply. When the pH reached 7, the four catalysts almost completely lost their activity (the corresponding pseudo-first-order kinetic constant decreased to 10-6 s -1 level).

[0062] This result is in sharp contrast to the confined reaction state. Figure 5 As shown in Figure a, all four catalysts were able to completely remove the same concentration of BPA in less than 10 seconds in the "catalyst-AAO" test, with corresponding pseudo-first-order kinetic constants ranging from 0.36 to 1.77 s. -1 (See Figure 5 b), which is much higher than that of the non-confined case. Specifically, Fe3O4-AAO improves 2.1×10 5 times, FeOOH-AAO increased by 6.4×10 5 times, CuFe2O4-AAO increased by 7.6×10 5 times, FeOCl-AAO increased by 8.3×10 5 times.

[0063] It is important to emphasize that the surface area concentration of the catalyst exposed per unit volume of solution affects the kinetics. We eliminated the difference in "concentration" between confined and unconfined conditions and normalized the effect of confinement on the kinetics, obtaining the improvement factor E for the performance of iron-based catalysts at the same surface area. SVR .like Figure 6 As shown in the figure, after normalization, the four iron-based catalysts in the confined state still showed a huge kinetic improvement effect, and the order of the improvement effect was CuFe2O4-AAO (E SVR =310)>FeOCl-AAO(E SVR =198)>FeOOH-AAO(E SVR =158)>Fe3O4-AAO(E SVR =105). This indicates that the confinement of the nanospace has resulted in a significant protonation enhancement effect.

[0064] Example 3

[0065] A confined enhanced water treatment method for activating an iron-based Fenton-like process under neutral conditions

[0066] Taking the CuFe2O4-AAO confined reaction system as an example, we first synthesized CuFe2O4-AAO materials with different pore sizes, whose confinement scales were 200-300 nanometers ( Figure 7 a), 30 nanometers ( Figure 7 b), 10 nanometers ( Figure 7 c), 5 nanometers ( Figure 1 c) and 3 nm ( Figure 7d) The synthesis procedure and conditions of the materials are described in Example 1 for confined material 3, with the exception that in some cases AAO templates with different pore sizes were used, as follows: for the 200-300 nm CuFe2O4-AAO material, the AAO template used was 200-300 nm pore size, for the 30 nm CuFe2O4-AAO material, the AAO template used was 40-70 nm pore size, and for the rest of the CuFe2O4-AAO materials (including 10 nm, 5 nm and 3 nm), the AAO template used was <20 nm pore size. The operation of the confined catalytic reaction process and the test conditions were the same as described in Example 2 for the confined reaction.

[0067] Effect of the confinement scale

[0068] As shown in Figure 8 , as the confinement scale gradually decreases from 200-300 nm to about 3 nm, the kinetic enhancement effect (i.e. E SVR ) of the CuFe2O4-AAO system correspondingly increases, especially when the confinement scale is less than 10 nm, E SVR rapidly increases and can be as high as about 300. This huge increase is due to the fact that a smaller confinement system can enhance the concentration of H + to a greater extent, and on the other hand, nanoscale confinement can greatly enhance the heterogeneous distribution of H + , so that H + has a higher concentration and activity on the surface of the catalyst. Therefore, the confinement scale suggested by the present patent technology should be controlled within 10 nm.

[0069] Example 4

[0070] A confined enhanced water treatment method for activating an iron-based Fenton process under neutral conditions

[0071] Taking CuFe2O4 catalyst as an example, a flow-through reaction without confinement was designed as a comparative example. In the comparative example, 2 g of CuFe2O4 catalyst particles were adhered to the outside of the AAO template by suction filtration (as shown in Figure 9 a), a peristaltic pump was used to provide a certain water power (the water flow rate was controlled at 1 mL min -1 ), and a mixture containing 20 μM of BPA and 2 mM of H2O2 was continuously passed through the CuFe2O4 catalyst particle layer, liquid phase vials were used to collect the effluent, and liquid chromatography was performed rapidly. The operation process and test conditions of the confined reaction experiment were the same as described in Example 2 for the confined reaction.

[0072] Confinement structure enhances the stability of iron-based catalysts

[0073] The results are shown inFigure 9 As shown in Fig. 2b, in the case of flow-through reaction without confinement, the removal rate of BPA by CuFe2O4 catalyst particles decreased from the initial 100% to less than 80% in 15 minutes, and completely lost the reaction activity (no removal effect on BPA) in less than 1 hour, which indicates that the iron-based catalyst quickly loses the water treatment ability in the non-confined neutral water environment. In contrast, the CuFe2O4-AAO confined system can maintain a very high removal efficiency of BPA (see details in Figure 5 ) and can remove 100% of BPA for at least 8 hours without activation or cleaning treatment. It is directly proved that the confined catalytic system can greatly extend the service life of the catalyst.

Claims

1. A confined enhanced water treatment method for activating an iron-based Fenton-like process under neutral conditions, characterized in that: Here are the steps: (1) Solvothermal synthesis of confined materials: Control the uniform and dense growth of nano-iron-based catalysts on the pore walls of the framework material to obtain confined materials. The size of the nano-iron-based catalysts is controlled so that the maximum distance between their surface and the pore walls does not exceed 10 nanometers. The framework material used to support the nano-iron-based catalysts has two characteristics: 1) a regular pore structure; 2) a pore size between 20 and 40 nanometers. (2) Physical and chemical polishing is performed on the outside of the pores of the confined material to remove the residual nano-iron-based catalyst; (3) The temperature of the confined catalytic reaction is kept at room temperature of 20-25°C to complete the removal of pollutants in water.

2. The confined enhanced water treatment method according to claim 1, characterized in that: The skeleton material is a membrane structure. By applying transmembrane pressure, water containing both organic pollutants and H2O2 enters from one side of the membrane and flows out from the other side, thereby completing the catalytic oxidation reaction.

3. The confined enhanced water treatment method according to claim 1, characterized in that: The skeleton material is a porous particle, 1) the pore depth shall not exceed 20 nanometers; 2) the particles are in a stirred suspension state or a fluidized state.

4. The confined enhanced water treatment method according to claim 1, characterized in that: The reaction time in the control channel is not less than 10 seconds, and the H2O2 concentration is not less than 20 times the organic matter concentration.

5. The confined enhanced water treatment method according to claim 1, characterized in that: The reaction time in the pores is controlled to be no less than 2 minutes, and the H2O2 concentration is no less than 100 times the organic matter concentration.

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