CN116621312A - A confinement-enhanced water treatment method that activates the iron-based Fenton-like process under neutral conditions - Google Patents

Abstract

The invention belongs to the technical field of advanced oxidation water treatment, and discloses a limited-area strengthening water treatment method for activating an iron-based Fenton-like process under a neutral condition. Solvothermal synthesis of a finite field material: the nano iron-based catalyst is controlled to uniformly and densely grow on the pore canal wall surface of the framework material, so that the domain-limiting material is obtained; performing physical and chemical polishing on the outside of the pore canal of the finite field material to remove the residual nano iron-based catalyst; the removal of pollutants in water can be completed by keeping the temperature of the limited-area catalytic reaction at the room temperature of 20-25 ℃. The invention can greatly improve the catalytic performance of the iron-based catalyst under the condition of neutral water quality, and the dynamics strengthening effect can be improved by 2-3 orders of magnitude; the invention can greatly improve the stability of the iron-based catalyst, so that the iron-based catalyst can continuously work for at least 8 hours without activation and regeneration; the invention is suitable for various iron-based catalyst structures, has universality, has no special limit on the material of the finite field framework, and has strong applicability.

Description

A confinement-enhanced water treatment that activates an iron-based Fenton-like process under neutral conditions method

technical field

The invention belongs to the technical field of advanced oxidized water treatment, and relates to a confined and enhanced water treatment method for activating an iron-based Fenton-like process under neutral conditions.

Background technique

Fenton-like advanced oxidation is a commonly used pretreatment or advanced treatment technology for industrial wastewater. It uses iron-based catalysts to contact hydrogen peroxide to rapidly produce hydroxyl radicals (main reaction formula: Fe(II)+H ₂ O ₂ +H ⁺ → Fe(III)+·OH+H ₂ O). Compared with some similar technologies with high power consumption and complicated process combination, the Fenton-like method has the characteristics of simple operation and low cost while retaining the advantages of fast start-up of the traditional Fenton reaction, so it has great development and application value.

Since the iron site is easily hydrolyzed to form a hydroxylated structure, which hinders its contact reaction with H ₂ O ₂ , the current catalysts generally rely on an acidic environment, and the pH range that can work is usually not more than 5 (see "Cai, QQ; Lee, BCY; Ong, SL; Hu, JY Fluidized-Bed Fenton Technologies for Recalcitrant Industrial Wastewater Treatment-Recent Advances, Challenges and Perspective. Water Res 2021, 190, 116692.”). In the case of neutral or near-neutral, the catalyst will be deactivated due to the lack of proton (H ⁺ ) drive. However, the pH of industrial wastewater is usually between 6 and 8, and the application of Fenton-like technology in engineering requires additional acidic agents to maintain (in some cases, additional iron salt additives are required), resulting in high additional operating costs and Secondary iron sludge pollution and other issues.

In order to improve the pH adaptability of the catalyst, the main technology at home and abroad is to modify the structure of iron oxides. On the one hand, the idea is to slow down the combination of Fe and hydroxyl by optimizing and changing the coordination structure of Fe, such as making Fe-Cl coordination bond (see "Yang, XJ; Xu, XM; Xu, J.; Han, YFIron 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 doped with other metal elements (such as Ce, see "Xu, L.; Wang, J. Magnetic Nanoscaled Fe ₃ O ₄ /CeO ₂ Composite as an Efficient Fenton-Like Heterogeneous Catalyst for Degradation of 4-Chlorophenol.Environ.Sci.Technol.2012,46,10145-10153.”); On the other hand, increasing the degree of coordination unsaturation of the iron base increases the probability of its exposure to H ₂ O ₂ , such as manufacturing the surface "Oxygen vacancies" 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 3.2-9.0by Cu Substituted MagneticFe ₃ O ₄ @FeOOH Nanocomposite.Environ.Sci.Technol.2017,51,12699-12706."), or make single-atom iron catalysts (see "Yin,Y .; Shi, L.; Li, W.; Li, X.; Wu, H.; Ao, Z.; Tian, W.; Liu, S.; Wang, S.; Reactions Via Single Atom Fe Catalysis. EnvironSci Technol 2019, 53(19), 11391-11400.”).

Although related technologies can properly slow down the deactivation rate of iron-based at near-neutral pH, the problem of H ⁺ scarcity is still an unsolved fundamental problem, which makes it difficult for the improved catalyst to maintain normal operation under neutral conditions. . For example, Wang's research group improved the activity of Fe ₃ O ₄ catalyst at higher pH by doping Ce, but when the pH increased from acidic (2.2) to near-neutral (5.3), the catalytic activity of tetrachlorophenol The removal rate dropped rapidly from 100% (15 minutes) to 21% (120 minutes) (see "Xu, L.; Wang, J. Magnetic Nanoscaled Fe ₃ O ₄ /CeO ₂ 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 Sun's group is much more efficient than iron oxide nanoparticles, but when the pH rises to 6, the single-atom catalyst almost completely loses its 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 SciTechnol 2019, 53(19), 11391-11400.").

Aiming at the current technical defects, the present invention proposes a brand-new nanotechnology capable of activating Fenton-like catalysts under neutral conditions ^. Participation process), the whole process does not need to add acidic agents or chemical additives. This method is inspired by some research conclusions in interdisciplinary fields. When the water molecule is confined in the nanometer space, its own dynamic state and the contact force state with the catalyst surface will change greatly, which will affect its dissociation and the equilibrium state of H ⁺ ( See "Zhang, S.; Hedtke, T.; Zhou, X.; Elimelech, M.; Kim, JH Environmental Applications of Engineered Materials with Nanoconfinement. ACS ES&T Eng. 2021, 1, 706-724."). At the same time, the spatial confinement effect will enhance the surface potential of the catalyst, resulting in the absorption and accumulation of protons on the surface due to the strengthening of electrostatic interaction (see "Wang, L.; Wang, Z.; Patel, SK; 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 effects of "space confinement" and "charge properties of the catalyst", it is expected to form a new nanotechnology to enhance surface protonation.

The specific implementation method of the present invention is to uniformly grow the iron-based catalyst in the skeleton with nanopores, control its reaction space to be kept at about 5 nanometers, and induce a large amount of adsorption and aggregation of H ⁺ on the iron-based surface, thereby controlling the Fenton-like catalyst. Stable and efficient operation at neutral pH. By testing four typical iron-based catalysts (CuFe ₂ O ₄ , Fe ₃ O ₄ , FeOOH, FeOCl), the present invention proves that the developed confinement technology can greatly improve the performance of iron-based catalysts under neutral water quality conditions. Kinetic efficiency (up to 310 times improvement), confinement effect also enhances the ability of the catalyst to work continuously.

Contents of the invention

The technical problem to be solved in the present invention is to finely control the Fenton-like reaction to occur at the nanometer space scale, and use this confined environment to strengthen the protonation process, thereby improving the water treatment efficiency and durability of the iron-based catalyst under neutral conditions. sex.

Technical scheme of the present invention:

A confinement enhanced water treatment method for activating the iron-based Fenton-like process under neutral conditions, the steps are as follows:

(1) Solvothermal synthesis of confinement materials: control the uniform and dense growth of nano-iron-based catalysts on the pore wall of the framework material to obtain confinement materials; among them, control the size of nano-iron-based catalysts so that the surface and the pore wall The maximum distance between them is no more than 10 nanometers; the skeleton material used to support nano-iron-based catalysts has two characteristics: 1) the pore structure is regular; 2) the pore size is between 20-40 nanometers;

(2) Perform physical and chemical polishing outside the pores of the confinement material to remove the residual nano-iron-based catalyst;

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

If the framework material is a membrane structure, _a certain transmembrane pressure needs to be applied to allow water containing both organic pollutants and _H2O2 to enter from one side of the membrane and flow out from the other side, thereby completing the catalytic oxidation reaction.

If the skeleton material is a porous particle, it needs to be maintained: 1) The depth of the hole should not exceed 20 nanometers, otherwise the extra pore space will be useless; 2) The particle is in a stirred suspension state or a fluidized state, so as to ensure its surface Sufficient turbulence of the fluid and sufficient exchange of substances inside and outside the pores.

To completely decompose and remove single organic pollutants containing benzene rings (concentration at the μM level), it is necessary to control the reaction time in the pores not less than 10 seconds, and the concentration of H ₂ O ₂ not less than 20 times the organic concentration.

To completely mineralize and remove organic pollutants (concentration at the μM level), it is necessary to control the reaction time in the pores not less than 2 minutes, and the concentration of H ₂ O ₂ not less than 100 times the concentration of organic matter.

Beneficial effects of the present invention:

(1) The present invention can greatly improve the catalytic performance of iron-based catalysts under neutral water quality conditions, and its kinetic strengthening effect can be improved by 2-3 orders of magnitude;

(2) The present invention can greatly improve the stability of the iron-based catalyst, making it work continuously for at least 8 hours without activation and regeneration;

(3) The present invention is applicable to various iron-based catalyst structures, has universal applicability, and has no special restrictions on the material of the confined framework, and has strong applicability.

Description of drawings

Figure 1 is a cross-sectional electron microscope image of "catalyst-AAO", where a is Fe ₃ O ₄ -AAO, b is FeOOH-AAO, c is CuFe ₂ O ₄ -AAO, d is FeOCl-AAO, and the scale bar is 100nm.

Figure 2 is an electron micrograph of "catalyst-AAO" viewed from above, where a is Fe ₃ O ₄ -AAO, b is FeOOH-AAO, c is CuFe ₂ O ₄ -AAO, d is FeOCl-AAO, and the scale bar is 200nm.

Figure 3 is the XRD diffraction result of "Catalyst-AAO", where a is Fe ₃ O 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 CuFe ₂ O 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).

Figure 4 is a diagram of the catalytic effect of the dispersed iron-based catalyst in a stirred reactor (that is, unconfined catalysis), where a is at pH 3, b is at pH 5, and c is at pH 7. Experimental conditions: catalyst dosage, 0.1g L ^-1 ; BPA initial concentration, 20μM; H ₂ O ₂ initial concentration, 2mM. Error bars represent the results of triplicate tests.

Figure 5a is an effect diagram of BPA concentration changing with time, and Figure 5b is an effect diagram of kinetic fitting. Experimental conditions: initial concentration of BPA, 20 μM; initial concentration of H ₂ O ₂ , 2 mM; solution pH, 7.0. Error bars represent the results of triplicate tests.

Fig. 6 is a diagram of the confinement strengthening effect after normalizing the surface area of the catalyst. Experimental conditions: initial concentration of BPA, 20 μM; initial concentration of H ₂ O ₂ , 2 mM; solution pH, 7.0.

Figure 7 is a cross-sectional electron microscope image corresponding to CuFe ₂ O ₄ -AAO materials with different confinement scales, where a is the confinement scale of 200-300 nm, b is the confinement scale of 30 nm, and c is the confinement scale of 10 nm. d is the confinement scale of 3 nm.

Figure 8 shows the corresponding kinetic enhancement effect of the "catalyst-AAO" system at different confinement scales.

Figure 9 is to investigate the improvement effect of CuFe ₂ O ₄ -AAO confinement system on catalyst durability, where a is a comparative example, that is, CuFe ₂ O ₄ catalyst particles (2g) are intercepted outside the AAO framework, and the reaction is carried out through continuous permeation , to investigate the persistence of the catalyst in the unconfined state; b is the effect comparison chart, which examines the relationship between the BPA removal rate and the continuous reaction time. Reaction conditions: BPA concentration, 20 μM; H ₂ O ₂ concentration, 2 mM; pH of the feed solution, 7.0; flow rate, 1 mL min ^-1 . Error bars represent the results of three parallel experiments.

Detailed ways

The specific implementation manners of the present invention will be further described below in conjunction with the accompanying drawings and technical solutions.

The embodiments involved in the present invention all use anodic aluminum oxide film (AAO) as the framework material for confinement, and first grow the iron-based catalyst uniformly in the form of nanoparticles on the AAO pore wall through solvothermal reaction, and control the The distance between the catalyst surface and the AAO wall (ie, the confinement scale).

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 H ₂ O ₂ is pushed through the membrane in the form of "one-way filtration", so that the The Fenton-like reaction is triggered in the pores to complete the confined water treatment process.

The test of the comparative example is to stir the iron-based catalyst particles in a glass reactor (the mixed solution containing organic pollutants and H ₂ O ₂ is configured in the reactor in advance), and the sample is sampled according to the specified time. First, the sample is passed through high-speed centrifugation to remove solids and then analyze the concentration of residual organic matter in solution.

Example 1. Preparation methods of four kinds of confined materials and four kinds of contrast materials

Confinement material 1: a method for preparing a confinement structure containing Fe ₃ O ₄ (Fe ₃ O ₄ -AAO), as follows:

FeCl ₂ ·4H ₂ O (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. The AAO was then soaked in the solution, sonicated for 10 min, and then the alumina-containing solution was transferred to a hydrothermal reactor (reaction was maintained at 180 °C for 6 hours, and the temperature increase was controlled at 5 °C per minute). Then soak the catalyst-grown film in ethanol for 10-20 seconds of rapid ultrasonic vibration (ultrasonic frequency is 40kHz) to remove excess catalyst outside the film. Then inject high-purity water into the nanopore to clean, and place it to dry for use.

Material 1 (Comparative Example): Synthesis of Dispersed Fe ₃ O ₄ Particles (Unconfined Catalysis)

0.18M FeCl ₂ ·4H ₂ O (purity ≥ 99.0%) and 0.12M sodium citrate (purity ≥ 99.0%) were dissolved in 30 mL of high-purity water by ultrasonic vibration, and then the solution was transferred to a hydrothermal reaction kettle at 200 ℃ for 10 hours (temperature rise is controlled at 5 ℃ per minute). The obtained particles were repeatedly washed three times with high-purity water, and dried for later use.

Confinement material 2: a method for preparing a confinement structure containing FeOOH (FeOOH-AAO), as follows:

Prepare 1M butylamine solution and adjust the pH to 4.5-5.0 with acetic acid. The anodized aluminum was immersed in the solution for 1 hour, taken out to dry at room temperature for 1 hour, and then placed in a furnace filled with _N2 and kept at 135 °C for 1 hour. The obtained aluminum oxide thin film is put into FeSO ₄ solution (1-octanol is solvent), ultrasonic treatment is 10 minutes, then whole solid-liquid system is put into hydrothermal reactor and is processed at 110 ℃ for 0.5 hour (temperature rising is controlled at every Minutes rise 5°C). The obtained material uses a soft fine brush to quickly sweep the outer surface of the membrane with a dilute acid solution (ethanol solution in which 1mM HCl is dissolved), and rinses it once with high-purity water after each sweep for about 2 seconds to avoid acid infiltration Into the film hole, so repeated several times to complete the polishing. Vacuum dried before use.

Material 2 (comparative example): Synthesis method of dispersed FeOOH particles (unconfined catalysis)

Dissolve 0.15M FeSO ₄ ·7H ₂ O (purity≥99.0%) and 0.002M EDTA-Na (purity>99.0%) in 100mL of high-purity water, and adjust the pH value of the solution at 6.3 with 0.1M sodium hydroxide Between -7.5. As the color of the solution changed from light green to brown, the precipitate was taken out, washed three times with high-purity water, and dried in vacuum before use.

Confinement material 3: a method for preparing a confinement structure containing CuFe ₂ O ₄ (CuFe ₂ O ₄ -AAO), as follows:

Dissolve 0.38M FeCl ₂ (purity 98.0%), 0.06M CuCl ₂ (purity ≥ 99.9%) and 0.025mM sodium citrate (purity ≥ 99.9%) in 20mL of ethylene glycol solution and oscillate continuously for 1 Hour. Soak the AAO in the mixed solution for 10 minutes of sonication, and then transfer it to a hydrothermal reactor for treatment at 180°C for 4 hours (control the temperature increase at 5°C per minute). The obtained material is quickly brushed with a soft fine brush dipped in a dilute acid solution (ethanol solution in which 1mM HCl is dissolved) on the outer surface of the film, and rinsed once with high-purity water after each sweep for about 2 seconds to avoid acid infiltration Into the film hole, so repeated several times to complete the polishing. Vacuum dried for use.

Material 3 (Comparative Example): Synthesis of Dispersed CuFe ₂ O ₄ Particles (Unconfined Catalysis)

Dissolve 0.38M FeCl ₂ (purity ≥99.0%), 0.06M Cu(NO ₃ ) ₂ ·3H ₂ O (purity ≥99.9%) and 0.025M sodium citrate (purity ≥99.0%) in 20 mL of B Diol solution and continuous ultrasonic vibration for 1 hour. Then the solution was transferred to a hydrothermal reactor and treated at 180° C. for 4 hours (the temperature rise was controlled at 5° C. per minute). The obtained particles were repeatedly washed three times with high-purity water, and dried for later use.

Confinement material 4: a method for preparing a confinement structure containing FeOCl (FeOCl-AAO), as follows:

Dissolve 1.0g mL ^-1 FeCl ₃ ·6H ₂ O (purity ≥ 99.0%) in absolute ethanol and put the aluminum oxide film in, and the whole mixed system is treated continuously under ultrasound for 0.5 hours and shaken for 24 hours (rotating speed 160rpm ). Then the wetted aluminum oxide flakes were taken out, clamped on both sides with polished silicon wafers, and placed in a muffle furnace for 1 hour at 220°C (temperature rise was controlled at 10°C per minute). The obtained material is quickly brushed with a soft fine brush dipped in a dilute acid solution (ethanol solution in which 1mM HCl is dissolved) on the outer surface of the film, and rinsed once with high-purity water after each sweep for about 2 seconds to avoid acid infiltration Into the film hole, so repeated several times to complete the polishing. Vacuum dried before use.

Material 4 (comparative example): Synthesis method of dispersed FeOCl particles (unconfined catalysis)

Spread a certain amount of FeCl ₃ 6H ₂ O (purity ≥ 99.0%) powder on the bottom of the quartz boat, seal the top to insulate the air, then place the quartz boat in a muffle furnace, and treat it at 220°C for 1 hour (The temperature rise is controlled at 10°C per minute). The obtained particles were repeatedly washed three times with high-purity water, and dried for later use.

Characterization of Four Confined "Catalyst-AAO" Materials

The structural effect of the "catalyst-AAO" thin film synthesized in Example 1 is shown in Figure 1 and Figure 2, wherein Figure 1 is a section electron microscope image, and Figure 2 is a top view electron microscope image. It can be seen that four typical iron-based catalyst nanoparticles (ie, Fe ₃ O ₄ , FeOOH, CuFe ₂ O ₄ , FeOCl) are grown uniformly in the array channels of AAO (the channel size of the AAO framework is about 20 nanometers). . Since the particle itself occupies a certain space, the space that the solution can pass through is the distance between the surface of the particle and the wall of the AAO (we will regard this distance as the "limitation scale" for subsequent discussions). It can be seen that our synthesis method can basically realize the control of four iron-based catalysts to work at a similar confinement scale (≈5 nanometers).

The XRD characterization results of the four "catalyst-AAO" materials are shown in Fig. 2 . The AAO framework itself is an amorphous structure, so it has no characteristic diffraction peaks; but after loading different iron-based catalysts, it presents different diffraction peaks. By comparing the standard cards, it was confirmed that the corresponding catalyst structures on these four "catalyst-AAO" materials were Fe ₃ O ₄ (Fig. 3a), FeOOH (Fig. 3b), CuFe ₂ O ₄ (Fig. 3c), FeOCl (Fig. 3d).

Example 2

A confinement-enhanced water treatment method that activates the iron-based Fenton-like process under neutral conditions

First, prepare a mixed solution containing organic pollutants and H ₂ O ₂ , wherein the concentration of organic pollutants is controlled at 20 μM, and the concentration of H ₂ O ₂ is controlled at 2 mM. The "catalyst-AAO" material is fixed in the membrane module, and the membrane module is sealed so that the water flow can only be discharged through the membrane channel in one direction. A micropump is used to push the mixed liquid through the membrane module to realize the 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 in the membrane pore is inversely proportional to the water-filled volume of the membrane pore, it is possible to know the water-filled volume of the membrane pore in advance, According to the need to control the water flow of the micropump to flexibly control the residence time in the membrane, so as to complete the evaluation of the reaction kinetics. The membrane-passed water after the reaction was directly collected in a liquid phase vial, and quickly analyzed by liquid chromatography. The confinement material is CuFe ₂ O ₄ , Fe ₃ O ₄ , FeOOH, FeOCl prepared in Example 1, and the framework material is a membrane structure.

For the non-confined reaction of the comparative example (i.e. using dispersed catalyst particles), 100 mL of a mixed solution containing an organic pollutant concentration of 20 μM and a H ₂ O ₂ concentration of 2 mM was prepared in advance, and the pH values of the solutions were adjusted to 3 with dilute hydrochloric acid as required. , 5, 7, then add 0.1g L ^-1 catalyst in the solution and start to count the reaction time. At a specific sampling time, a certain volume of water sample was quickly taken out with a pipette gun and put into a 1.5mL centrifuge tube. The solid particles were removed by rapid centrifugation with a high-speed centrifugal pump, and the liquid obtained after centrifugation was analyzed by liquid chromatography.

Analysis of the Fenton-like Effect of Boundary Reinforcement

The water treatment capabilities of the same catalyst were compared under confined (ie using "Catalyst-AAO") and unconfined (ie using dispersed catalyst particles) conditions. The typical organic pollutant bisphenol A (BPA for short) was selected as the indicator.

First, the unconfined catalytic reaction effect was tested (as shown in Figure 4). As the pH of the solution gradually increased (from 3 to 7), the catalytic degradation effects of the four iron-based catalysts on BPA decreased sharply. When the pH reached 7 When , the four catalysts almost completely lost their activity (the corresponding pseudo-first-order kinetic constants decreased to the level of 10 ^-6 s ^-1 ).

This result is in stark contrast to that in the confinement response state. As shown in Figure 5a, the four catalysts can completely remove the same concentration of BPA in less than 10 seconds in the "catalyst-AAO" test, and the corresponding pseudo-first-order kinetic constants range from 0.36 to 1.77s ^-1 (see Fig. 5b), which is much higher than the unconfined case. Specifically, Fe ₃ O ₄ -AAO increased by 2.1×10 ⁵ times, FeOOH-AAO increased by 6.4×10 ⁵ times, CuFe ₂ O ₄ -AAO increased by 7.6×10 ⁵ times, and FeOCl-AAO increased by 8.3× 10 ⁵ times.

It should be emphasized that the surface area concentration of exposed catalyst per unit volume of solution affects the kinetics. We eliminated the difference between this "concentration" under confined and unconfined conditions, and performed a After normalization, the improvement factor E _SVR of the performance of iron-based catalysts under the same surface area is obtained. As shown in Figure 6, after normalization treatment, the iron-based catalysts in the four confinement states still showed a huge kinetic improvement effect, and the order of the improvement effect was CuFe ₂ O ₄ -AAO( _ESVR = 310) > FeOCl-AAO ( _ESVR = 198) > FeOOH-AAO ( _ESVR = 158) > Fe ₃ O ₄ -AAO ( _ESVR = 105). This shows that the confinement of the nanometer space has caused a more obvious effect of protonation strengthening.

Example 3

A confinement-enhanced water treatment method that activates the iron-based Fenton-like process under neutral conditions

Take CuFe ₂ O ₄ -AAO confined reaction system as an example. First, CuFe ₂ O ₄ -AAO materials with different pore sizes were synthesized, and the confinement scales were 200-300 nm (Fig. 7a), 30 nm (Fig. 7b), 10 nm (Fig. 7c), 5 nm (Fig. 1c) and 3 nm (Fig. 7d). The synthesis steps and conditions of the material are detailed in the confinement material 3 in Example 1. The slight difference is that in some cases AAO frameworks with different pore sizes are used, specifically as follows: 200-300 nm CuFe ₂ O ₄ - The AAO skeleton selected by the AAO material is 200-300 nanometer aperture, the AAO skeleton selected by the 30 nanometer CuFe ₂ O ₄ -AAO material is 40-70 nanometer aperture, and the rest of the CuFe ₂ O ₄ -AAO material (including 10 nanometer, 5 nanometer and 3 nanometers) the selected AAO frameworks are all <20 nanometers in diameter. The operation and test conditions of the confinement catalytic reaction process are identical to the description of the confinement reaction in Example 2.

The influence of bounding scale

As shown in Fig. 8, as the confinement scale gradually decreases from 200-300 nm to about 3 nm, the corresponding kinetic strengthening effect (ie _ESVR ) of the CuFe ₂ O ₄ -AAO system increases correspondingly, especially when the confinement When the scale is smaller than 10nm, the _ESVR increases rapidly and can be as high as about 300. This huge improvement effect, on the one hand, is due to the fact that the smaller confinement system can enhance the concentration of H ⁺ to a greater extent; on the other hand, the nanoscale confinement will greatly enhance the heterogeneous distribution of H ⁺ state, so that H ⁺ has a higher concentration and activity on the surface of the catalyst. Therefore, the confinement scale suggested by this patent technology should be controlled within 10 nanometers.

Example 4

A confinement-enhanced water treatment method that activates the iron-based Fenton-like process under neutral conditions

Taking CuFe ₂ O ₄ catalyst as a case, a flow-through reaction without confinement was designed as a comparative example. In the comparative example, 2g of CuFe ₂ O ₄ catalyst particles were adhered to the outside of the AAO skeleton by suction filtration (as shown in Figure 9a), and a peristaltic pump was used to provide a certain hydrodynamic force (the water flow rate was controlled at 1mL min ^-1 ), The mixed solution containing 20 μM BPA and 2 mM H ₂ O ₂ was controlled to pass through the CuFe ₂ O ₄ catalyst particle layer continuously, and the water was collected by a liquid phase vial, and quickly analyzed by liquid chromatography. The operating process and test conditions for the confinement reaction experiment are the same as those described for the confinement reaction in Example 2.

Confined structures enhance the stability of iron-based catalysts

The results are shown in Figure 9b. In the case of flow-through reaction without confinement, the removal rate of BPA by CuFe ₂ O ₄ catalyst particles decreased from the initial 100% to below 80% when the reaction lasted for 15 minutes. By 1 hour, the reaction activity was completely lost (no removal effect on BPA), which indicated that the iron-based catalyst quickly lost its ability to treat water in an unconfined neutral water environment. In contrast, the CuFe ₂ O ₄ -AAO confinement system can maintain a 100% BPA removal state for at least 8 hours while maintaining a very high removal efficiency for BPA (see Figure 5 for details), without activation throughout the process or cleaning. It directly proves that the confined catalytic system can greatly prolong the service life of the catalyst.

Claims (5)

1. a method for confinement strengthening water treatment of activating iron-based Fenton process under neutral conditions, is characterized in that, the steps are as follows: (1) Solvothermal synthesis of confinement materials: control the uniform and dense growth of nano-iron-based catalysts on the pore wall of the framework material to obtain confinement materials; among them, control the size of nano-iron-based catalysts so that the surface and the pore wall The maximum distance between them is no more than 10 nanometers; the skeleton material used to support nano-iron-based catalysts has two characteristics: 1) the pore structure is regular; 2) the pore size is between 20-40 nanometers; (2) Perform physical and chemical polishing outside the pores of the confinement material to remove the residual nano-iron-based catalyst; (3) The temperature of the confined catalytic reaction can be kept at room temperature of 20-25°C to complete the removal of pollutants in water. 2. The confinement-enhanced water treatment method according to claim 1, characterized in that, if the skeleton material is a membrane structure, transmembrane pressure needs to be applied so that the water containing organic pollutants and H ₂ O ₂ flows from the membrane One side enters and the other side flows out, thus completing the catalytic oxidation reaction. 3. The confinement-enhanced water treatment method according to claim 1, wherein, if the framework material is a porous particle, it is required: 1) the depth of the hole must not exceed 20 nanometers; 2) the particle is in a state of stirring suspension or fluidized state. 4. The confining enhanced water treatment method according to claim 1, characterized in that, to completely decompose and remove a single organic pollutant containing a benzene ring, the concentration is at the μM level, and the reaction time in the channel needs to be controlled not less than 10 Seconds, the H ₂ O ₂ concentration is not lower than 20 times the organic matter concentration. 5. The confining and intensified water treatment method according to claim 1, characterized in that, if the organic pollutants are to be completely mineralized and removed, the concentration is at the μM level, and the reaction time in the pores needs to be controlled to not be less than 2 minutes, and the H ₂ The _O2 concentration is not lower than 100 times the organic matter concentration.