Preparation method and application of structured molybdenum modified iron-based photo-Fenton catalyst

Abstract

The invention discloses a preparation method and application of a structured molybdenum modified iron-based photo-Fenton catalyst.The preparation method of the structured molybdenum modified iron-based photo-Fenton catalyst.The preparation method of the structured molybdenum modified iron-based photo-Fenton catalyst.The preparation method comprises the following steps that a molybdenum-containing precursor solution is introduced to a metal-based carrier through a vacuum assembly method, and the metal-based carrier is obtained; performing vacuum drying and roasting to obtain a molybdenum modified catalyst; and loading iron oxide on the molybdenum modified catalyst to obtain the structured molybdenum modified iron-based photo-Fenton catalyst, the structured molybdenum modified iron-based photo-Fenton catalyst is simple in preparation process and easy to put into industrial production, the structured plate-shaped catalyst does not need additional separation operation and can be repeatedly used, the industrial cost is reduced, the catalyst can efficiently degrade pollutants such as phenol and chlorophenol in photo-Fenton reaction, and the catalyst has good application prospects. The degradation rate of RhB and 2-CP within 30 min reaches 95%, the degradation rate of 3-CP within 40 min reaches 97.26%, the degradation rate of phenol and 4-CP is slightly lower than that of other pollutants, but the degradation rate within 60 min reaches 95% or above.

Description

Technical Field

[0001] The present invention belongs to the technical fields of photocatalytic materials and wastewater treatment, and particularly relates to a preparation method and application of a structured molybdenum-modified iron-based photo-Fenton catalyst. Background Art

[0002] Refractory organic wastewater has a wide range of sources, complex components, and is difficult to remove by conventional biochemical methods. It has long-term residual and bioaccumulative properties as well as hazards such as carcinogenicity and teratogenicity. Therefore, it is necessary to develop technologies for efficient treatment of refractory organic wastewater. As an environmentally friendly advanced oxidation technology (AOPs), the Fenton reaction rapidly generates hydroxyl radicals (·OH) through Fe 2+ and H2O2, and has advantages such as fast reaction rate, simple operation, and non-selective mineralization of pollutants. However, the practical application of the traditional Fenton reaction is limited by factors such as the need for a strong acidic environment (usually pH = 2-4), the generation of a large amount of iron sludge leading to secondary pollution, and the need for a large amount of externally added H2O2 resulting in an increase in treatment costs.

[0003] To overcome the limitations of the traditional Fenton process, researchers have begun to focus on heterogeneous Fenton-like reactions, using solid catalysts to replace homogeneous Fe 2+ . However, due to the insufficient contact between the active sites on the catalyst surface and the oxidant, its activity is usually lower than that of the homogeneous Fenton reaction. At the same time, there are problems such as slow Fe(III) / Fe(II) cycling rate and poor catalyst stability in the heterogeneous Fenton-like process. Coupling photocatalytic technology with the Fenton reaction, the photo-Fenton technology has emerged. Combining the advantages of both, it uses light irradiation to accelerate and enhance the interaction between the photocatalytic semiconductor and the Fenton catalyst to promote its electron transfer, accelerate the separation of photo-generated electrons and holes, and the cycle of Fe(III) / Fe(II), and improve the catalytic activity. Designing efficient photocatalysts and selecting suitable photo-Fenton oxidants are the keys to the industrial application of photo-Fenton.

[0004] H2O2 and PMS are the most common Fenton-like oxidants at present. Compared with H2O2 and PDS, PMS has an asymmetric molecular structure, making it easier to be activated, and the sulfate radicals (·SO4 - ) generated by activation have a longer lifespan and stronger oxidation ability than hydroxyl radicals (·OH). The activation methods of PMS include thermal activation, catalyst activation, ultraviolet activation, ultrasonic activation, and alkaline condition activation, etc. Among them, thermal activation, ultraviolet activation, and ultrasonic activation are energy transfer processes, while catalyst activation and alkaline condition activation are electron transfer processes. How to construct an efficient photo-Fenton activation PMS system that couples ultraviolet activation and catalyst activation is worthy of in-depth study.

[0005] Patent CN114291864A discloses a method for degrading pollutants in a photo-Fenton system by activating peroxymonosulfate with a MoS2 / BiVO4 photocatalyst. A MoS2 / BiVO4 composite material with a nanoflower structure is added to the wastewater containing pollutants, and peroxymonosulfate (PMS) is added. The reaction is stirred under room temperature, a pH of 3.0 - 9.0, and visible light irradiation conditions. A large amount of reactive oxygen species are rapidly generated in the system, realizing the photo-Fenton oxidation degradation of pollutants. It can resist inorganic anions and organic substances in actual wastewater and has excellent performance and wide applicability. Patent CN109908929A discloses a dual-effect catalyst for synergistically catalyzing visible light / Fenton-like advanced oxidation reactions, its preparation method and application. A composite photocatalyst with Fe3O4 / GO magnetic sheets as the carrier and Ag3PO4 enriched on the surface is prepared. Under the coexistence of visible light and persulfate, it can play a synergistic catalytic role in photocatalysis and Fenton-like reactions. The degradation rate of RhB can reach 97.5% in 20 minutes; the catalyst can be rapidly separated by applying an external magnetic field; the degradation rate is still above 80% after recycling 5 times. Patent CN116440911B discloses the preparation of iron-doped molybdenum oxide as a photocatalytic material and its application in ammonia synthesis. An aqueous solution of ammonium molybdate tetrahydrate and an ethanol solution of CTAB (cetyltrimethylammonium bromide) are mixed. After adjusting the pH with HNO3, FeCl3 is added dropwise to this solution, and then the required catalyst is prepared through a hydrothermal reaction. Iron doping effectively improves the light absorption performance of molybdenum oxide, greatly enhancing its photocatalytic ammonia synthesis activity.

[0006] Patent CN115212899A discloses a photo-Fenton catalyst comprising molybdenum disulfide and iron oxyhydroxide, wherein the molybdenum disulfide is in the shape of flakes and has both 1T phase and 2H phase; the iron oxyhydroxide is loaded on the molybdenum disulfide. Under light irradiation, the 2H phase of molybdenum disulfide generates photogenerated electrons and holes, and the photogenerated electrons transfer to the 1T phase of molybdenum disulfide, avoiding the recombination of photogenerated electrons and holes. Under the action of photogenerated electrons and holes, Fe 2+ / Fe 3+ 、Mo 4+ / Mo 6+ dual reaction sites are formed, and H2O2 can utilize more sites to provide more free radicals for pollutant degradation, thereby realizing the removal of organic substances in the wastewater to be treated. Patent CN116673056A discloses a preparation method of an Fe-g-C3N4 / MoO 3-x photocatalyst. The preparation process is simple and the oxygen vacancy concentration is controllable. The free radicals generated by photo-Fenton oxidation rapidly degrade humic acid in water.

[0007] The above catalysts are mainly Fe-based catalysts, with the photocatalytic activity of Mo oxides, forming a semiconductor photocatalyst with light response, accelerating the activation of PMS or H2O2, and achieving efficient degradation of pollutants. However, the catalysts produced by the preparation method mainly based on hydrothermal method are mostly in the form of powders or granules, and the problem of catalyst recovery has not been fundamentally solved. In addition, it is difficult to produce catalysts in large quantities to cope with industrial water treatment systems. Therefore, it is necessary to design a simpler production method and a more suitable catalyst form on the basis of ensuring the excellent activity and stability of the catalyst. Summary of the Invention

[0008] Aiming at the problems such as the easy and rapid recombination of photo-generated carriers in the above photocatalytic materials, the unfavorable form of the catalyst itself for coping with industrial water treatment systems, and the unsatisfactory treatment effect of organic matters, the present invention provides a preparation method and application of a structured molybdenum-modified iron-based photo-Fenton catalyst. The preparation process of this catalyst is simple, and it has excellent photo-Fenton oxidation and removal effects on various refractory organic pollutants in industrial wastewater and can be recycled multiple times, providing a certain reference for the industrial preparation of photo-Fenton catalysts and their wide application in the treatment of refractory organic wastewater.

[0009] One of the technical solutions provided by the present invention:

[0010] A preparation method of a structured molybdenum-modified iron-based photo-Fenton catalyst, comprising the following steps: introducing a molybdenum-containing precursor solution onto a metal-based carrier by a vacuum assembly method, and obtaining a molybdenum-modified catalyst through vacuum drying and calcination; loading iron oxide onto the molybdenum-modified catalyst to obtain the structured molybdenum-modified iron-based photo-Fenton catalyst.

[0011] Preferably, the preparation method of the metal-based carrier comprises the following steps: anodizing and calcining an aluminum substrate in sequence to obtain the metal-based carrier.

[0012] More preferably, the conditions for anodization are: the concentration of oxalic acid electrolyte is 0.1 - 0.8 mol / L, the temperature is 20 °C, the current density is 30 A / m 2 , and the oxidation time is 8 - 16 h.

[0013] More preferably, the calcination comprises the following steps: performing a hot hydration reaction after the first calcination, and then performing a second calcination.

[0014] More preferably, the temperature of the first calcination is 350 - 550 °C, and the time is 1 - 3 h; and / or, the temperature of the hot hydration reaction is 30 - 95 °C, and the time is 1 - 2 h; and / or, the temperature of the second calcination is 350 - 550 °C, and the time is 3 - 6 h.

[0015] In the present invention, the aluminum substrate is an aluminum plate with a thickness of 0.3 - 0.6 mm. After anodic oxidation, porous anodic aluminum oxide (AAO) is obtained. AAO undergoes a hydrothermal reaction to obtain boehmite (AlOOH) rich in hydroxyl groups. Through secondary calcination, a metal-based support (γ-Al2O3 / Al) with a dense and ordered porous structure is obtained. The metal-based support with a nano-pore structure prepared in the present invention is an excellent support. Its porous structure is conducive to the subsequent loading of metals, increasing the specific surface area and enhancing the activity.

[0016] Preferably, the concentration of the molybdenum-containing precursor solution is 0.05 - 0.3 M. More preferably, the concentration of the molybdenum-containing precursor solution is 0.3 M.

[0017] The vacuum pressure induction method is beneficial to overcoming the problem that in the impregnation method, due to the surface tension of the solution, it is difficult for metal salts in the solution to enter the micropores of the support in the later stage of loading, resulting in the active metal only accumulating on the outer surface of the support.

[0018] The present invention uses ammonium heptamolybdate ((NH4)6Mo7O 24 ·4H2O) solution as the molybdenum-containing precursor solution. When introducing Mo compounds onto the γ-Al2O3 / Al support by the ordinary impregnation method, when the concentration of ammonium molybdate is 0.3 M, the pH of the solution is 5.36, which is higher than the isoelectric point of the γ-Al2O3 / Al support (PZC = 4). Due to electrostatic repulsion, the anion Mo7O 24 6- is difficult to adsorb onto the equally negatively charged γ-Al2O3 / Al support. Therefore, the present invention proposes to assemble as many molybdenum compounds as possible into the micropores of the γ-Al2O3 / Al support in a short time through the vacuum pressure induction method, making the active component Mo more evenly distributed on the surface of the support, modifying the support, and improving the photocatalytic activity of the catalyst.

[0019] Preferably, the temperature of the vacuum drying is 60 °C and the time is 12 h; and / or, the temperature of the calcination is 500 °C and the time is 4 h.

[0020] Preferably, the specific operation of loading the iron compound on the molybdenum-modified catalyst includes: impregnating the molybdenum-modified catalyst in a ferric nitrate solution and then performing secondary calcination.

[0021] More preferably, the concentration of the ferric nitrate solution is 0.05 mol / L, the impregnation time is 12 h, and the impregnation temperature is 25 °C; and / or, the temperature of the secondary calcination is 500 °C and the time is 4 h.

[0022] The second technical solution provided by the present invention:

[0023] A structured molybdenum-modified iron-based photo-Fenton catalyst prepared by the above preparation method.

[0024] The structure of the structured molybdenum-modified iron-based Fenton catalyst prepared by the present invention is plate-shaped, and its color is reddish-brown. It can be folded or cut into an ideal shape according to the shape of the reactor.

[0025] The third technical solution provided by the present invention:

[0026] An application of the above-mentioned structured molybdenum-modified iron-based Fenton catalyst in the treatment of refractory organic wastewater.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The present invention can quickly introduce a large number of MoO3 crystals into the channels and the surface of the monolithic γ-Al2O3 by means of vacuum pressure induction, realizing the molybdenum doping modification of the carrier and improving the light response activity of the catalyst. Then, an iron component is introduced. Iron is a transition metal commonly used to activate PMS. A molybdenum-modified iron-based catalyst for degrading industrial wastewater in the photo-Fenton reaction is prepared. This catalyst has stable properties and makes the reaction proceed in a direction favorable for the degradation of organic matter by utilizing the synergistic effect of photocatalytic reaction and Fenton reaction. In addition, the inactivated catalyst can be regenerated only by simple calcination operation.

[0029] The preparation process of the structured molybdenum-modified iron-based Fenton catalyst of the present invention is simple and easy to be put into industrial production. The structured plate-shaped catalyst does not require additional separation operations, can be reused, reduces industrial costs, and the catalyst can efficiently degrade pollutants such as phenol and chlorophenol in the photo-Fenton reaction. The degradation rate of RhB and 2-CP reaches 95% within 30 min, the degradation rate of 3-CP reaches 97.26% within 40 min, and the degradation rates of phenol and 4-CP are slightly slower than those of other pollutants, but the degradation rates all reach more than 95% within 60 min. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is the preparation flow chart of the structured molybdenum-modified iron-based Fenton catalyst in Embodiment 1 of the present invention;

[0032] Figure 2 It is the schematic diagram of the reaction device and the catalyst model in Performance Test Experiment 1;

[0033] Figure 3Figures (a) and (b) are scanning electron microscope (SEM) images of the catalysts prepared in Comparative Example 3 at different sizes (500 nm and 200 nm), and figures (c) and (d) are scanning electron microscope (SEM) images of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1 at different sizes (500 nm and 200 nm);

[0034] Figure 4 This is the ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) diagram of the catalysts prepared in Example 1 and Comparative Example 3 of the present invention;

[0035] Figure 5 This is the X-ray diffraction pattern of the catalysts prepared in Example 1 and Comparative Example 3;

[0036] Figure 6 This is the specific surface area (a) and pore size distribution diagram (b) of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1 and the metal-based support (γ-Al2O3 / Al) prepared in step (1) of Example 1;

[0037] Figure 7 This is the comparison diagram of the degradation effect of c / c0 over time in the system of Performance Test Experiments 1-4 for 2-chlorophenol wastewater;

[0038] Figure 8 This is the comparison diagram of the degradation effect of c / c0 over time for 2-chlorophenol wastewater at different reaction pH values;

[0039] Figure 9 This is the comparison diagram of the degradation effect of c / c0 over time for 2-chlorophenol wastewater under the oxidation of different oxidants;

[0040] Figure 10 This is the comparison diagram of the degradation effect of c / c0 over time for wastewater with different pollutants;

[0041] Figure 11 This is the cyclic stability test result of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1. Detailed Description of the Invention

[0042] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the present invention.

[0043] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0044] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0045] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0046] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0047] The room temperature in the present invention refers to 25 ± 2 °C.

[0048] The embodiment of the present invention provides a preparation method of a structured molybdenum-modified iron-based photo-Fenton catalyst, including the following steps: subjecting an anodized aluminum substrate to a first calcination, then performing a hydrothermal reaction, and then performing a second calcination to obtain a metal-based support; assembling molybdenum oxide crystals onto the surface and pores of the support by a vacuum pressure induction method to obtain a molybdenum-modified catalyst, and then loading iron oxide onto the molybdenum-modified catalyst to obtain a structured molybdenum-modified iron-based photo-Fenton catalyst.

[0049] Wherein, the vacuum pressure induction method specifically includes: placing the support in a vacuum container, continuously evacuating and maintaining a vacuum negative pressure environment for 20 min, and then inducing the ammonium molybdate precursor solution to assemble into the surface and pores of the support through a pressure difference. After drying the excess residues on the surface with absorbent paper, drying in vacuum and then calcining to obtain a modified catalyst. The concentration of the precursor solution is 0.3 M, the temperature is 25 °C; the assembly time is 15 min; the vacuum drying temperature is 60 °C, the vacuum drying time is 12 h; the calcination temperature is 500 °C, and the calcination time is 4 h.

[0050] In some embodiments of the invention, the aluminum substrate is an aluminum plate.

[0051] In some embodiments of the invention, the aluminum substrate needs to be pretreated before use; the pretreatment method is: successively performing alkali washing and acid washing on it for 1 to 5 minutes; the alkali solution is a 5 to 15 wt% sodium hydroxide solution, and the acid solution is a 5 to 15 wt% nitric acid solution.

[0052] In some embodiments of the invention, the anodic oxidation specifically includes: placing the pretreated aluminum plate in an oxalic acid electrolyte for anodic oxidation and then naturally drying it, performing hot hydration after one calcination and then performing a second calcination. The concentration of the oxalic acid electrolyte is 0.1 to 0.8 M, the anodic oxidation conditions are a temperature of 20 °C, an oxidation time of 8 to 16 h, and a current density of 30 A / m 2 ; the temperature of the first calcination is 350 °C and the time is 1 h; the temperature of the hot hydration is 30 to 95 °C and the time is 1 to 2 h; the temperature of the second calcination is 500 °C and the time is 4 h.

[0053] In some embodiments of the invention, the conditions for loading iron oxide are: 0.05 M ferric nitrate solution, an impregnation solution temperature of 25 °C, a time of 8 to 16 h, a calcination temperature of 500 °C, and a time of 4 h.

[0054] The embodiments of the invention also provide a structured molybdenum-modified iron-based photo-Fenton catalyst prepared by the above preparation method.

[0055] The embodiments of the invention also provide the application of the above structured molybdenum-modified iron-based photo-Fenton catalyst in the treatment of refractory organic wastewater.

[0056] The present invention uses PMS as an oxidant, avoiding the transportation problem of hydrogen peroxide or the harsh in-situ production requirements (pH 2 to 3). By means of vacuum pressure induction, MoO3 crystals with photocatalytic activity are introduced onto the surface and in the pores of the γ-Al2O3 / Al support, and then metal iron oxide is loaded, improving the light absorption ability of the catalyst, inhibiting the recombination of photo-generated carriers, efficiently activating PMS, and achieving the removal of refractory organic matter in wastewater.

[0057] In the embodiment of the present invention, the specific operations of the molybdenum doping modification step include: (i) Assembly system setup: Two plate-shaped γ-Al2O3 / Al carriers with dimensions of 2.8 cm * 7 cm are stacked crosswise and placed in a three-necked vacuum reactor padded with a rubber tube. The reactor is respectively connected to a vacuum system (ultimate vacuum degree ≤ 10 Pa), a feeding unit (including an in-built diversion funnel), and a digital display vacuum gauge through standard ground joints to construct a closed impregnation system; (ii) Establishment of negative pressure field: Close the feeding valve, start the vacuum pump, and make the absolute pressure of the system stable at 100 kPa (gauge pressure -0.1 MPa) and maintain it for 20 min to fully remove the physically adsorbed substances on the carrier surface and the gas retained in the pores; (iii) Preparation of precursor solution: At a constant temperature of 25 °C, prepare an impregnation solution with an ammonium heptamolybdate concentration of 0.05 - 0.3 mol / L, and the solution volume is 50 - 100 mL; (iv) Vacuum assembly: Quantitatively transfer the precursor solution into the reactor through an airtight syringe, and use the pressure difference drive to achieve instantaneous atomization and spraying of the solution under the vacuum state to ensure the rapid diffusion-adsorption of the active components inside the pores on the carrier surface; (v) Aging treatment: After impregnation, continue to evacuate for 15 min to promote the chemical bonding between the active components and the hydroxyl sites on the carrier; (vi) Drying and forming: Transfer the loaded precursor to a vacuum drying oven, and vacuum dry to remove the physically adsorbed water; (vii) High-temperature calcination to obtain the molybdenum-modified catalyst.

[0058] In the embodiment of the present invention, all raw materials and reagents required are obtained by purchasing commercially.

[0059] In the embodiment of the present invention, an aqueous solution of ammonium heptamolybdate ((NH4)6Mo7O 24 ·4H2O) is used as the ammonium molybdate precursor solution.

[0060] Example 1

[0061] A preparation method of a structured molybdenum-modified iron-based photo-Fenton catalyst

[0062] (1) Preparation of metal-based carrier: First, soak an aluminum plate (14 cm * 12 cm * 5 mm) in a 10 wt% NaOH solution for 4 min for alkali treatment, take it out and then soak it in a 10 wt% HNO3 aqueous solution for 2 min for acid treatment. Place the pretreated aluminum plate in an oxalic acid solution with a temperature of 20 °C, a current density of 30 A / m 2 ^2 and an electrolyte of 0.4 mol / L for anodic oxidation for 12 h, take it out and air-dry naturally, and then perform high-temperature calcination at 350 °C for 1 h to obtain anodic aluminum oxide; Place the obtained anodic aluminum oxide in deionized water at 80 °C for a hot hydration reaction for 60 min, dry it at room temperature to obtain boehmite (AlOOH) rich in hydroxyl groups, and then perform high-temperature calcination at 500 °C for 4 h to obtain a metal-based carrier (γ-Al2O3 / Al);

[0063] (2) Molybdenum doping modification: Place the metal support prepared in step (1) in a vacuum assembly container, maintain a vacuum environment for 20 min, and assemble the ammonium molybdate precursor solution at a temperature of 25 °C and a concentration of 0.3 M into the surface and pores of the support through vacuum pressure induction. Continue to evacuate and wait for 15 min. After blotting the excess residue on the surface with absorbent paper, dry it in vacuo (60 °C, 12 h), then place it in a muffle furnace and calcine it at 500 °C for 4 h to obtain a molybdenum-modified catalyst (Mo / γ-Al2O3 / Al);

[0064] (3) Iron compound loading: Immerse the molybdenum-modified catalyst prepared in step (2) in a 0.05 mol / L iron nitrate solution for 12 h at an impregnation temperature of 25 °C. After taking it out, let it dry naturally, then place it in a muffle furnace and calcine it at 500 °C for 4 h to prepare a structured molybdenum-modified iron-based photo-Fenton catalyst (Mo 7.08 Fe / γ-Al2O3 / Al).

[0065] Figure 1 This is the preparation flow chart of the structured molybdenum-modified iron-based photo-Fenton catalyst of Example 1 of the present invention.

[0066] Example 2

[0067] Same as Example 1, the only difference is that in step (2), the concentration of the ammonium molybdate precursor solution is 0.05 M.

[0068] Example 3

[0069] Same as Example 1, the only difference is that in step (2), the concentration of the ammonium molybdate precursor solution is 0.1 M.

[0070] Example 4

[0071] Same as Example 1, the only difference is that in step (2), the concentration of the ammonium molybdate precursor solution is 0.2 M.

[0072] Comparative Example 1

[0073] Same as Example 1, the only difference is that in step (2), the molybdenum doping modification method is: Place the metal support prepared in step (1) in a 0.3 M ammonium molybdate precursor solution, immerse it at 25 °C for 15 min, then take it out and let it dry naturally, and then place it in a muffle furnace and calcine it at 500 °C for 4 h.

[0074] Comparative Example 2

[0075] Same as Example 1, except that in step (2), the molybdenum doping modification method is as follows: Place the metal support prepared in step (1) in a 0.3 M ammonium molybdate precursor solution, impregnate it at 25 °C for 15 min, then take it out and place it in a vacuum container, evacuate for 20 min, take it out and place it in a muffle furnace, and calcine it at 500 °C for 4 h.

[0076] Determine the Mo content in the catalysts prepared in Examples 1-4 and Comparative Examples 1-2, and the determination results are shown in Table 1.

[0077] Table 1

[0078]

[0079] Comparative Example 3

[0080] Same as Example 1, except that there are only steps (1) and (2), and Fe is not loaded subsequently, to obtain Mo 7.08 / γ-Al2O3 / Al.

[0081] Figure 3 Figures (a) and (b) are scanning electron microscope (SEM) images of the catalyst prepared in Comparative Example 3 at different sizes (500 nm and 200 nm), and figures (c) and (d) are scanning electron microscope (SEM) images of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1 at different sizes (500 nm and 200 nm). It can be seen from Figure 3 that the MoO3 loaded on the carrier surface is mainly in the form of nanosheets. The length of the nanosheets can reach several micrometers, and the thickness is about 200 nanometers, forming a regular two-dimensional layered structure. The surface of the sheet structure is rough and the edges are clear. Under the calcination condition of 500 °C, most of the sheet structures are broken, forming dispersed elliptical nanoparticles. When the Fe component is further loaded on it, the Mo 7.08 Fe / γ-Al2O3 / Al catalyst is obtained. The nanosheet structure disappears, and the surface of the catalyst turns up in a fish scale shape. The Fe component is dispersed in the MoO3 nanolayer in the form of small particles.

[0082] Figure 4 This is the ultraviolet-visible diffuse reflectance spectrum (UV-vis DRS) diagram of the catalysts prepared in Example 1 and Comparative Example 3 of the present invention. It can be known from Figure 4 that Mo 7.08 Fe / γ-Al2O3 / Al has strong light absorption ability, especially in the range of 400-760 nm (visible light range), and still has obvious absorption. While Mo 7.08 / γ-Al2O3 / Al has poor visible light absorption ability. Its absorption edge is located near 460 nm, indicating that the vast majority of light cannot be absorbed by Mo 7.08Utilization of / γ-Al2O3 / Al. However, when Fe oxide is combined with MoO3, Mo 7.08 The absorption edge of the Fe / γ-Al2O3 / Al heterojunction is significantly redshifted to around 710 nm. This indicates that the introduction of Fe broadens the visible light absorption range of MoO3 and improves the utilization rate of sunlight.

[0083] Figure 5 X-ray diffraction patterns of the catalysts prepared in Example 1 and Comparative Example 3. As can be seen from Figure 5 it, after assembling Mo and calcining, obvious MoO3 crystal form (JCPDS NO. 05-05087) appears on the catalyst surface, and the strongest diffraction peaks are at (110) and (021) crystal planes with 2θ = 23.3° and 27.3° respectively. After loading the Fe component thereon, the diffraction peaks of MoO3 are covered, and no obvious diffraction peaks of iron oxide and molybdenum iron compound can be observed, which is attributed to the high dispersion of Fe on the catalyst surface.

[0084] Figure 6 Specific surface area (a) and pore size distribution diagram (b) of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1 and the metal-based support (γ-Al2O3 / Al) prepared in step (1) of Example 1. As can be seen from Figure 6 it, both the support and the catalyst are mesoporous structures, with average pore sizes of 4.35 nm and 3.88 nm respectively, and the pore size of the support decreases after loading the active component. They are both type IV isotherms, where the support shows an H2(b) type hysteresis loop and the catalyst shows an H3 type hysteresis loop. This shows that after loading the active component, the pore structure of γ-Al2O3 / Al becomes irregular. After loading the active component, the specific surface area of the catalyst increases (from 86.76 cm 2 / g to 95.76 cm 2 / g), which is more conducive to the adsorption of pollutant molecules.

[0085] Comparative Example 4

[0086] Same as Example 1, except that without going through step (2), iron oxide is directly loaded on the metal-based support prepared in step (1) to obtain Fe / γ-Al2O3 / Al.

[0087] Performance test experiment 1

[0088] Add 250 mL of 2-chlorophenol wastewater to the photoreactor. The concentration of 2-chlorophenol in it, c0, is measured by ultraviolet spectrophotometry to be 10 mg / L. Fix the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 through a polytetrafluoroethylene electrode clamp. The size of the catalyst is 2.8 cm * 7 cm. The reaction temperature is 25 °C. Do not adjust the initial pH of the reaction. Set the concentration of potassium persulfate (PMS) to 2 mM. Use two UV365 light sources with a power of 10 W to irradiate the photoreactor on both sides of the catalyst respectively. Set the solution rotation speed to 400 rpm to ensure that the plate-shaped catalyst rotates continuously during the reaction, and both the front and back sides of the catalyst are always covered by ultraviolet light. Measure the concentration c of 2-chlorophenol in the wastewater every 10 minutes.

[0089] Figure 2 It is a schematic diagram of the reaction device and catalyst model in Performance Test Experiment 1.

[0090] Performance Test Experiment 2

[0091] Same as the system in Example 1 of Performance Test Experiment 1, the only difference is that no oxidant (PMS) is added to the system.

[0092] Performance Test Experiment 3

[0093] Same as the system in Example 1 of Performance Test Experiment 1, the only difference is that the UV365 light source is not introduced into the system.

[0094] Performance Test Experiment 4

[0095] Same as the system in Example 1 of Performance Test Experiment 1, the only difference is that no catalyst is introduced into the system.

[0096] Figure 7 It is a comparative chart of the degradation effect of c / c0 of 2-chlorophenol wastewater over time in the systems of Performance Test Experiments 1-4 above. As can be seen from Figure 7 it, in this photo-Fenton reaction system, ultraviolet light, oxidant, and catalyst show a synergistic effect. The degradation effect of a single photocatalytic reaction (Performance Test Experiment 2), a single Fenton reaction (Performance Test Experiment 3), or a single ultraviolet light-activated PMS (Performance Test Experiment 4) on 2-CP is very weak. The photo-Fenton systems jointly constructed by ultraviolet light, oxidant, and different catalysts (Example 1, Comparative Examples 3-4) all have a better degradation effect than the aforementioned single systems. When using the Mo 7.08 / γ-Al2O3 / Al catalyst, the degradation rate of 2-chlorophenol within 60 minutes is 38.52%, which is better than that of a single ultraviolet light-activated PMS system (22.21%); when using Fe / γ-Al2O3 / Al as the catalyst, the reaction activity is further increased to 75.34%; when using a composite photocatalyst of iron oxide and molybdenum oxide Mo7.08 When oxidizing 2-chlorophenol with Fe / γ-Al2O3 / Al, the degradation rate reaches as high as 94.20% in 30 min, and it is basically completely oxidized in 60 min. This is attributed to the synergistic oxidation effect of the composite catalyst, and the energy level matching between the composite photocatalysts inhibits the recombination of photogenerated electrons and holes; the catalyst and ultraviolet light synergistically activate persulfate to generate a large amount of strongly oxidizing ·SO4 - and ·OH free radicals. By comparing the catalysts prepared from different ammonium molybdate precursor solutions (Examples 1-4), it is found that the higher the concentration of ammonium molybdate, the better the catalytic activity. As can be seen from Figure 7 the Mo 7.08 Fe / γ-Al2O3 / Al catalyst (Example 1) has the best effect on degrading 2-CP, which is better than Mo 5.37 Fe / γ-Al2O3 / Al (Example 4), better than Mo 4.59 Fe / γ-Al2O3 / Al (Example 3), better than Mo 3.48 Fe / γ-Al2O3 / Al (Example 2). This is because increasing the concentration of the precursor for vacuum assembly is beneficial to improving the Mo loading. In addition, by comparing the catalytic activities of the catalysts loaded with Mo on the γ-Al2O3 / Al support by the vacuum assembly method in the present invention and other methods (Example 1 and Comparative Examples 1-2), it can be found that the vacuum assembly method of the present invention is better than ordinary impregnation followed by vacuum pumping for 15 min (Comparative Example 2), and better than the ordinary impregnation method (Comparative Example 1).

[0097] Performance test experiment 5

[0098] Add 250 mL of 2-chlorophenol wastewater to the photoreactor, and the concentration of 2-chlorophenol in it, c0 = 10 mg / L, is measured by ultraviolet spectrophotometry. Fix the Mo 7.08 Fe / γ-Al2O3 / Al catalyst prepared in Example 1 with a polytetrafluoroethylene electrode clip. The size of the catalyst is 2.8 cm * 7 cm, the reaction temperature is 25 °C, and the initial pH of the reaction is adjusted to 3, 5.7, 7, 9 with H2SO4 and NaOH (where pH = 5.7 is the initial pH of 10 mg / L 2-CP). Set the concentration of potassium hydrogen persulfate (PMS) to 2 mM, and irradiate the photoreactor with two UV365 light sources with a power of 10 W on both sides of the catalyst. Set the solution rotation speed to 400 rpm to ensure that the plate-shaped catalyst rotates continuously during the reaction, and both sides of the catalyst are always covered by ultraviolet light. Measure the concentration c of 2-chlorophenol in the wastewater every 10 min.

[0099] Figure 8 is a comparison chart of the degradation effect of c / c0 of 2-chlorophenol wastewater over time at different reaction pH values. As can be seen from Figure 8It can be seen that the prepared photo-Fenton catalyst shows excellent treatment effects on 2-CP wastewater in a wide pH range, and the degradation rate can reach over 95% within 40 min. The degradation is the fastest without adjusting the initial pH of the reaction, which greatly facilitates practical industrial applications.

[0100] Performance test experiment 6

[0101] Add 250 mL of 2-chlorophenol wastewater to the photoreactor. The concentration of 2-chlorophenol in it, c0, is measured by ultraviolet spectrophotometry to be 10 mg / L. Fix the Mo 7.08 Fe / γ-Al2O3 / Al catalyst prepared in Example 1 through a polytetrafluoroethylene electrode clamp. The size of the catalyst is 2.8 cm * 7 cm, the reaction temperature is 25 °C, without adjusting the initial pH of the reaction. The concentrations of potassium persulfate (PMS) in the wastewater are set to be 2 mM, the concentration of H2O2 is 1200 ppm, and the active chlorine content of NaClO is 0.018 - 0.02%. Use two UV365 light sources with a power of 10 W to irradiate the photoreactor on both sides of the catalyst respectively. Set the solution rotation speed to 400 rpm to ensure that the plate-shaped catalyst rotates continuously during the reaction, and both sides of the catalyst are always covered by ultraviolet light. Measure the concentration c of 2-chlorophenol in the wastewater every 10 min.

[0102] Figure 9 It is a comparative diagram of the degradation effect of c / c0 of 2-chlorophenol wastewater with time under the oxidation of different oxidants; Figure 9 It can be seen that in addition to PMS as an oxidant, sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2) can also be used as oxidants to catalytically degrade 2-chlorophenol. This indicates that the catalyst can activate various types of Fenton oxidants. The strong oxidizing property of NaClO benefits from the easy cleavage of the O-Cl bond at room temperature.

[0103] Performance test experiment 7

[0104] Add 250 mL of wastewater containing different pollutants (RhB, phenol, 2-CP, 3-CP, 4-CP) to the photoreactor. The concentration of the pollutants in it, c0, is measured by ultraviolet spectrophotometry to be 10 mg / L. Fix the Mo 7.08 Fe / γ-Al2O3 / Al catalyst prepared in Example 1 through a polytetrafluoroethylene electrode clamp. The size of the catalyst is 2.8 cm * 7 cm, the reaction temperature is 25 °C, without adjusting the initial pH of the reaction. Set the concentration of potassium persulfate (PMS) to be 2 mM, and use two UV365 light sources with a power of 10 W to irradiate the photoreactor on both sides of the catalyst respectively. Set the solution rotation speed to 400 rpm to ensure that the plate-shaped catalyst rotates continuously during the reaction, and both sides of the catalyst are always covered by ultraviolet light. Measure the concentration c of the pollutants in the wastewater every 10 min.

[0105] Figure 10 It is a comparison chart of the degradation effect of c / c0 of wastewater with different pollutants over time. As Figure 10 shown, the Mo 7.08 Fe / γ-Al2O3 / Al photo-Fenton catalyst prepared in Example 1 has good degradation performance for different pollutants and has universality for dealing with actual industrial wastewater.

[0106] Performance test experiment 8

[0107] Add 250 mL of 2-chlorophenol wastewater to the photoreactor. The concentration of 2-chlorophenol c0 in it is measured by ultraviolet spectrophotometry to be 10 mg / L. Fix the Mo 7.08 Fe / γ-Al2O3 / Al photo-Fenton catalyst through a polytetrafluoroethylene electrode clip. The size of the catalyst is 2.8 cm * 7 cm, the reaction temperature is 25 °C, the initial pH of the reaction is not adjusted, the concentration of potassium persulfate (PMS) is set to 2 mM, and two UV365 light sources with a power of 10 W are used to irradiate the photoreactor on both sides of the catalyst respectively. The solution rotation speed is set to 400 rpm to ensure that the plate-shaped catalyst rotates continuously during the reaction, and both the front and back sides of the catalyst are always covered by ultraviolet light. The concentration c of 2-chlorophenol in the wastewater is measured every 10 min, and the one-time treatment time is 60 min. After the reaction, the catalyst is rinsed clean and dried, the solution is reconfigured, the catalyst is fixed, PMS is added, and the light is turned on, and this cycle is repeated 12 times. After the 10th cycle, the catalyst is rinsed clean and dried, then calcined at 500 °C for 1 h and then put into use.

[0108] Figure 11 It is the test result of the cyclic stability of the structured molybdenum-modified iron-based photo-Fenton catalyst prepared in Example 1. From Figure 11 it can be seen that the catalyst prepared in the present invention has excellent stability. After 8 cycles, the degradation rate of 2-chlorophenol can still be maintained at 96%. Although there is an obvious decrease starting from the 9th time, the activity is 68.5% at the 10th time. However, only through a simple high-temperature calcination operation, the activity of the catalyst can be restored. This is because the active sites of the catalyst are occupied by partially adsorbed organic substances or intermediates, and these active sites can be released again after calcination to achieve regeneration. This characteristic is beneficial to the long-term degradation of wastewater by the catalyst in actual industrial applications.

[0109] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a structured molybdenum-modified iron-based photo-Fenton catalyst, characterized in that, It includes the following steps: Introduce a molybdenum-containing precursor solution onto a metal-based support by vacuum assembly method, and obtain a molybdenum-modified catalyst through vacuum drying and calcination; Load iron oxide onto the molybdenum-modified catalyst to obtain the structured molybdenum-modified iron-based Fenton catalyst.

2. The preparation method according to claim 1, characterized in that, The preparation method of the metal-based support includes the following steps: subject an aluminum substrate to anodic oxidation and calcination in sequence to obtain the metal-based support.

3. The preparation method according to claim 2, characterized in that, The conditions for anodic oxidation are as follows: the concentration of the oxalic acid electrolyte is 0.1 - 0.8 mol / L, the temperature is 20 °C, and the current density is 30 A / m 2 , and the oxidation time is 8 - 16 h.

4. The preparation method according to claim 2, characterized in that, The calcination includes the following steps: perform a hot hydration reaction after the first calcination, and then perform a second calcination.

5. The preparation method according to claim 4, wherein The temperature of the first calcination is 350 - 550 °C, and the time is 1 - 3 h; and / or, the temperature of the hot hydration reaction is 30 - 95 °C, and the time is 1 - 2 h; and / or, the temperature of the second calcination is 350 - 550 °C, and the time is 3 - 6 h.

6. The preparation method according to claim 1, characterized in that, The concentration of the molybdenum-containing precursor solution is 0.05 - 0.3 M.

7. The preparation method according to claim 1, characterized in that, The specific operation of loading iron compound onto the molybdenum-modified catalyst includes: place the molybdenum-modified catalyst in a ferric nitrate solution, and perform re-calcination after impregnation.

8. The preparation method according to claim 7, characterized in that, The concentration of the ferric nitrate solution is 0.05 mol / L, the impregnation time is 12 h, and the impregnation temperature is 25 °C; and / or, the temperature of the re-calcination is 500 °C, and the time is 4 h.

9. A structured molybdenum-modified iron-based Fenton catalyst prepared by the preparation method according to any one of claims 1 - 8.

10. An application of the structured molybdenum-modified iron-based Fenton catalyst according to claim 9 in the treatment of refractory organic wastewater.

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