Composite catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a composite catalyst and a preparation method and application thereof. According to the catalyst, Ce salt and Cu salt solutions are subjected to staged gradient concentration glutaraldehyde urea modification and a dual hydrothermal reaction method in a polyvinyl alcohol dispersion system to prepare a precursor, and then the precursor is calcined in a high-temperature inert atmosphere to realize heterojunction self-assembly and forbidden bandwidth regulation and control. According to the structure, energy band matching is optimized, electron separation and interface charge migration are promoted, and synergistic redox cycle is enhanced. The catalyst shows efficient peroxide activating capacity in a Fenton-like reaction, and the degradation and mineralization efficiency of organic pollutants such as antibiotics and dyes in water can be remarkably improved. In conclusion, the defects of limited band gap, limited electronic state regulation and control and the like of the existing single metal oxide are effectively overcome, and a novel efficient catalytic material and a novel efficient catalytic process are provided for organic pollution treatment of a water body.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a composite catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, due to the excessive use and discharge of antibiotics, dyes, and phenols in human medicine, animal husbandry, aquaculture, and the pharmaceutical industry, the water environment has been seriously polluted. The problem of organic pollutant pollution is becoming more and more serious. Therefore, people have tried various methods to treat antibiotics in water, including physical adsorption, photocatalysis, electrochemistry, and advanced oxidation processes.

[0003] Among them, advanced oxidation treatment technology, as a highly efficient and promising wastewater treatment technology, can be used to treat a variety of polluted water bodies. Among them, the Fenton-like process, as one of the most promising ways to treat organic wastewater, has been widely studied in recent years. The Fenton-like process activates hydrogen peroxide (H2O2), persulfate (PS), and periodate (PI) through solid-phase catalysts to generate oxidative active species, thereby achieving the purpose of oxidative degradation of pollutants into small molecules and even carbon dioxide, water and inorganic salts, thereby achieving the purpose of sewage treatment.

[0004] Designing and preparing high-performance catalysts is the key to fully exerting the performance of activated peroxides in degrading mineralized pollutants in Fenton-like oxidation technology. Cerium dioxide (CeO2) is a rare earth metal oxide, and Ce 3+ / Ce 4+ The redox pair is the core of catalytic activity expression and determines the activation process and direction of peroxide. 4+ Towards low valence state Ce 3+ The high reaction energy barrier for conversion leads to low intrinsic cycle efficiency of metal redox pairs, which is one of the main factors hindering its development into a high-performance Fenton-like catalyst.

[0005] Introducing transition metal oxides into CeO2 materials to construct heterostructures is a feasible solution to the above problems. Forming a heterojunction can reduce the intrinsic band gap of CeO2 and reduce the energy barrier for electrons to transition from the conduction band to the valence band. It can also reconstruct the local electron density of the material and weaken the metal redox conversion (such as Ce 3+ / Ce 4+ ) activation energy, thereby improving its turnover cycle efficiency and achieving enhanced activation of peroxides to produce more active oxides and degrade organic pollutants.

[0006] In the prior art, researchers mostly prepared CeO2 and transition metal oxide composites through co-precipitation method or sol-gel method. However, such methods have insufficient control over the cross-linked network of precursors and it is difficult to achieve a reasonable distribution of metal ions. At the same time, the compatibility between oxidants and pollutant types in conventional processes is poor, and the surface electronic state of the catalyst is difficult to dynamically adjust to adapt to different reaction systems, which limits its practical application scope. Therefore, there is an urgent need to develop a new preparation method that can synergistically optimize metal dispersion, interfacial electronic structure and pore hierarchy to break through the performance bottleneck of existing catalysts. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a composite catalyst, its preparation method and application. This catalyst can efficiently activate peroxides, and the catalyst preparation is simple and has good economy, showing excellent catalytic degradation effect on organic pollutants.

[0008] The first object of the present invention is to provide a preparation method of a composite catalyst, including the following steps: S11. Preparation of precursor: Add a mixed salt solution of Ce salt and Cu salt and modifier A into a polyvinyl alcohol dispersion, stir and mix evenly, then carry out hydrothermal reaction. Then add a mixed salt solution of Ce salt and Cu salt and modifier B, stir and mix evenly, and then carry out hydrothermal reaction. After centrifugation, washing and drying, a precursor powder is obtained; S12. High-temperature regulation to construct a composite catalyst: Put the precursor powder into a reaction device for high-temperature reaction for 2 - 3 h. The temperature of the high-temperature reaction is 400 - 600 °C, the heating rate is 3 - 5 °C / min, and an inert gas argon atmosphere is used to obtain a composite catalyst.

[0009] Centrifugation, washing and drying of the hydrothermal reaction product are all existing conventional operations, and the specific conditions can be selected according to the actual situation. In this application, washing is carried out 3 - 4 times with water and ethanol respectively; the drying temperature is 60 - 70 °C and the time is 10 - 12 h.

[0010] Further, in step S11, the molar ratio of Cu salt to Ce salt is 1:5 - 5:1.

[0011] Further, in step S11, the mixed salt solution of Ce salt and Cu salt is an aqueous solution of chloride, nitrate or sulfate, and its concentration is 0.01 - 0.21 mol / L. Ce salt and Cu salt are selected from chlorides, nitrates or sulfates that are soluble in solvents, where the solvent is water or ethanol.

[0012] Further, in step S11, the polyvinyl alcohol dispersion is a dispersion formed by dispersing polyvinyl alcohol in water, and its concentration is 0.01 - 0.1 g / mL.

[0013] For a further embodiment, in step S11, the dosage ratio of the mixed salt solution, modifier solution A, modifier solution B and polyvinyl alcohol dispersion is 35 mL: 20 mL: 20 mL: 10 mL.

[0014] For a further embodiment, the preparation method of modifier solution A or B in step S11 is as follows: Add urea to the aqueous glutaraldehyde solution, adjust the pH to 7.5 - 8 with sodium hydroxide, and stir for 45 min to obtain modifier solution A or modifier solution B; For a further embodiment, in the preparation raw materials of the modifier solution A, the molar ratio of urea to glutaraldehyde is 1: 0.3 - 0.5, and the concentration of the aqueous glutaraldehyde solution is 40 wt%.

[0015] For a further embodiment, in the preparation raw materials of the modifier solution B, the molar ratio of urea to glutaraldehyde is 1: 0.05 - 0.15, and the concentration of the aqueous glutaraldehyde solution is 10 wt%.

[0016] For a further embodiment, in step S11, the stirring and mixing time is 20 - 40 min, the hydrothermal reaction is carried out in a sealed reaction kettle, the temperature of the hydrothermal reaction is 100 - 130 °C, and the time is 18 - 24 h.

[0017] For a further embodiment, in step S12, the high-temperature reaction time is 2 - 3 h, and the heating rate is 3 - 5 °C / min.

[0018] The second object of the present invention is to provide a composite catalyst prepared by the above preparation method.

[0019] The third object of the present invention is to provide the application of the above composite catalyst, which is used for catalytic degradation of organic pollutants in water.

[0020] For a further embodiment, the method for using the composite catalyst to catalytically degrade organic pollutants in water includes the following steps: S21. Add the composite catalyst into the sewage and disperse it by ultrasonic wave; S22. Add peroxide and carry out a catalytic degradation reaction to remove organic pollutants in the sewage.

[0021] For a further embodiment, the concentration of organic pollutants in the sewage is 20 - 100 mg / L; Based on the volume of the sewage, the dosage of the composite catalyst is 75 - 750 mg / L, and the dosage of peroxide is 20 - 300 mg / L.

[0022] For a further embodiment, the organic pollutants in the sewage include at least one of tetracycline, oxytetracycline hydrochloride, sulfadiazine, chlortetracycline hydrochloride, doxycycline, methylene blue, bisphenol A and its derivatives; The peroxide is hydrogen peroxide, persulfate or peracetic acid, and the periodate is any one of sodium periodate, potassium periodate or barium periodate; In a further embodiment, in step S22, the catalytic degradation reaction is carried out under stirring at 300 - 600 rpm / min, and the reaction time is 30 - 90 min.

[0023] In a further embodiment, the composite catalyst prepared in this application can be applied to the Fenton-like degradation of other simulated organic pollutant-contaminated water and actual organic pollutant-contaminated water. The simulated organic pollutant-contaminated water includes organic pollutant-contaminated water prepared with pure water, tap water, river water, lake water, and river water.

[0024] Compared with the prior art, the composite catalyst provided by the present invention has the following significant advantages: First of all, in the present invention, by combining wide-bandgap CeO2 (3.4 eV) with narrow-bandgap Cu 2+1 O (1.2 - 2.2 eV), in the composite catalyst, the heterostructure catalyst formed by the combination of wide-bandgap and narrow-bandgap materials has the core advantage of realizing the synergistic optimization of the energy band structures of the two. The Fermi level difference between the two materials (such as the Fermi level EF of CeO2 = -0.3 eV vs. Cu 2+1 O's EF = +0.2 eV) leads to interfacial charge rearrangement, forming a built-in electric field pointing from CeO2 to Cu 2+1 O, which is the key to promoting charge separation; at the same time, the chemical bond energy at the interface reduces the charge transfer barrier and improves the interfacial charge transfer efficiency. Ce 3+ / Ce 4+ and Cu 1+ / Cu 2+ redox pairs form a cycle. The degradation rate of tetracycline by CeO2 / Cu 2+1 O through the activation of PI is more than twice that of pure CeO2 (40%), thus achieving a synergistic effect. By indirectly regulating the bandgap of the catalyst through temperature, the decrease in the bandgap will increase the transition probability of electrons between the valence band and the conduction band, increase the surface electron density of the catalyst, promote the catalyst to enhance the electrostatic adsorption of polar organic molecules and promote their activation. Therefore, in this application, the composite catalyst calcined at high temperature and peroxide form a Fenton-like oxidation system for enhancing the activation of peroxide to generate reactive oxygen species (free radicals and non-free radicals) to degrade and remove organic pollutants in water.

[0025] Secondly, the present invention adopts a glutaraldehyde modification system with gradient concentrations, and forms a dense-loose alternating urea immobilization structure through staged cross-linking reactions. High-concentration glutaraldehyde constructs a rigid framework in the initial stage, restricting the migration of metal ions, while subsequent low-concentration cross-linking induces the growth of a secondary network, forming a urea concentration gradient from the inside to the outside. This structure exhibits differential pyrolysis behavior during high-temperature calcination. The inner dense region delays the decomposition of urea to maintain a reducing atmosphere, promoting the progressive reduction of Cu 2+ to Cu + ; the outer loose region generates through-pores, accelerating the Ce 3+ / Ce 4+ valence cycle, thereby synergistically enhancing the redox activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following drawings, which form a part of the present invention, are used to assist in understanding the present invention. The content provided in the drawings and the related descriptions in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention. In the drawings: Figure 1 Scanning electron microscope images of CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+ 1O-pre prepared in Example 1, 4, 5 and Comparative Example 1 are respectively c / d / b and a in the figure; Figure 2 X-ray diffraction patterns of CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 O-pre prepared in Example 1, 4, 5 and Comparative Example 1 of the present invention are respectively the X-ray diffraction patterns of CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+ 1O-pre in the figure; Figure 3 UV-vis diffuse reflectance band gap diagrams of CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 O-pre prepared in Example 1, 4, 5 and Comparative Example 1 of the present invention are respectively the UV-vis diffuse reflectance band gap diagrams of CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 O-pre in the figure; Figure 4 Effect diagrams of the catalysts prepared in Example 1, 4, 5 of the present invention for activating PI to degrade tetracycline (TC), Example 2 for activating H2O2 to degrade tetracycline (TC), and Example 3 for activating PI to degrade bisphenol A (BPA).

[0027] Figure 5 The figure shows the effect of the catalysts prepared in Example 1 and Comparative Examples 1-6 of the present invention on activating PI to degrade tetracycline (TC). Detailed implementation manners

[0028] The present invention will be further described below in conjunction with specific embodiments, but the substantial content of the present invention is not limited to the following embodiments. The methods are conventional methods unless otherwise specified, and the materials can be obtained from public commercial channels unless otherwise specified. Those skilled in the art should know that any simple transformation or substitution based on the substantial content of the present invention belongs to the protection scope required by the present invention.

[0029] Example 1: A preparation method of a CeO2 / Cu 2+1 O bimetallic composite catalyst, comprising the following steps: (1) Preparation of modification liquid A: Add 0.02 mol of urea to 20 mL of a 40wt% aqueous glutaraldehyde solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modification liquid A; (2) Preparation of modification liquid B: Add 0.02 mol of urea to 20 mL of a 10wt% aqueous glutaraldehyde solution, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modification liquid B; (3) Preparation of precursor: Dissolve 10 g of polyvinyl alcohol in 200 mL of water to obtain solution A, dissolve 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 in 35 mL of water to obtain solution B. Mix 10 mL of solution A, 20 mL of modification liquid A and 25 mL of solution B and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out hydrothermal reaction at 120°C for 24 h. After the reaction is completed, add 20 mL of modification liquid B and 10 mL of solution B, mix and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out hydrothermal reaction at 120°C for 24 h. After the reaction is completed, centrifuge to separate out the solid, wash it 3 times with water and 6 times with ethanol respectively, and dry it at 60°C for 12 h to obtain precursor powder; (4) High-temperature regulation to construct a CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: Place the precursor powder in a tubular high-temperature furnace, introduce a protective inert gas, heat at a rate of 3 - 5°C / min, and maintain at 773K for 2 h to obtain the CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500°C.

[0030] Example 2: Identical to Example 1, except that in the degradation test, the oxidant PI was replaced with H2O2.

[0031] Example 3: Identical to Example 1, except that in the degradation test, the degradation pollutant TC was replaced with BPA.

[0032] Example 4: According to the preparation method of Example 1, except that the temperature was adjusted to 873K, and the prepared catalyst was denoted as CeO2 / Cu 2+1 O-600 °C.

[0033] Example 5: According to the preparation method of Example 1, except that the temperature was adjusted to 673K, and the prepared catalyst was denoted as CeO2 / Cu 2+1 O-400 °C.

[0034] Comparative Example 1: CeO2 / Cu 2+1 O catalyst was synthesized without high-temperature treatment, and the steps were as follows: (1) Preparation of modification solution A: Add 0.02 mol of urea to 20 mL of a 40wt% aqueous glutaraldehyde solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modification solution A; (2) Preparation of modification solution B: Add 0.02 mol of urea to 20 mL of a 10wt% aqueous glutaraldehyde solution, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modification solution B; (3) Preparation of the precursor: Dissolve 10g of polyvinyl alcohol in 200 mL of water to obtain solution A, dissolve 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 in 35 mL of water to obtain solution B, mix 10 mL of solution A, 20 mL of modification solution A and 25 mL of solution B and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, add 20 mL of modification solution B and 10 mL of solution B, mix and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, centrifuge to separate the solid, wash it 3 times with water and 6 times with ethanol respectively, and dry it at 60 °C for 12 h to obtain CeO2 / Cu 2+1 O, denoted as CeO2 / Cu 2+1 O-pre.

[0035] Comparative Example 2: CeO2 / Cu 2+1 O catalyst was synthesized at low temperature, and the steps were as follows: (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of glutaraldehyde aqueous solution with a concentration of 40 wt%, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A; (2) Preparation of modified solution B: Add 0.02 mol of urea to 20 mL of glutaraldehyde aqueous solution with a concentration of 10 wt%, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modified solution B; (3) Preparation of precursor: Dissolve 10 g of polyvinyl alcohol in 200 mL of water to obtain solution A, dissolve 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 in 35 mL of water to obtain solution B. Mix 10 mL of solution A, 20 mL of modified solution A and 25 mL of solution B and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, and carry out hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, add 20 mL of modified solution B and 10 mL of solution B, mix and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, and carry out hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, centrifuge to separate the solid, wash it 3 times with water and 6 times with ethanol respectively, and dry it at 60 °C for 12 h to obtain precursor powder (4) Construction of CeO2 / Cu 2+1 O catalyst: Place the precursor powder in a tubular high-temperature furnace and keep it at 373 K for 2 h to obtain the catalyst, denoted as CeO2 / Cu 2+1 O-100 °C.

[0036] Comparative example 3: According to the preparation method of Example 1, the difference is only that no glutaraldehyde is added to the modified solution A; the steps are as follows: (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of water, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A; (2) Preparation of modified solution B: Add 0.02 mol of urea to 20 mL of glutaraldehyde aqueous solution with a concentration of 10 wt%, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modified solution B; (3) Preparation of precursor: 10 g of polyvinyl alcohol was dissolved in 200 mL of water to obtain solution A. 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 were dissolved in 35 mL of water to obtain solution B. 10 mL of solution A, 20 mL of modified solution A and 25 mL of solution B were mixed and stirred for 30 min, then the suspension was transferred to a reaction kettle with a polytetrafluoroethylene substrate. Hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction ended, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, then the suspension was transferred to a reaction kettle with a polytetrafluoroethylene substrate. Hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction ended, the solid was separated by centrifugation, washed 3 times with water and 6 times with ethanol respectively, and dried at 60 °C for 12 h to obtain the precursor powder (4) High-temperature regulation to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: The precursor powder was placed in a tubular high-temperature furnace, an inert protective gas was introduced, the heating rate was 3 - 5 °C / min, and it was maintained at 773 K for 2 h to obtain the CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500 °C.

[0037] Comparative Example 4: According to the preparation method of Example 1, the only difference is that glutaraldehyde was not added to the modified solution B; the steps are as follows: (1) Preparation of modified solution A: 0.02 mol of urea was added to 20 mL of an aqueous solution of glutaraldehyde with a concentration of 40 wt%, and the pH was adjusted to 7.8 with sodium hydroxide, and stirred for 45 min to obtain modified solution A; (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of water, and the pH was adjusted to 7.7 with sodium hydroxide, and stirred for 30 min to obtain modified solution B; (3) Preparation of precursor: 10 g of polyvinyl alcohol was dissolved in 200 mL of water to obtain solution A. 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 were dissolved in 35 mL of water to obtain solution B. 10 mL of solution A, 20 mL of modified solution A and 25 mL of solution B were mixed and stirred for 30 min, then the suspension was transferred to a reaction kettle with a polytetrafluoroethylene substrate. Hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction ended, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, then the suspension was transferred to a reaction kettle with a polytetrafluoroethylene substrate. Hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction ended, the solid was separated by centrifugation, washed 3 times with water and 6 times with ethanol respectively, and dried at 60 °C for 12 h to obtain the precursor powder (4) High-temperature regulation to construct CeO2 / Cu2+1 O Double-metal oxide composite catalyst: Place the precursor powder in a tubular high-temperature furnace, introduce a protective inert gas, heat at a rate of 3 - 5 °C / min, and hold at 773 K for 2 h to obtain the CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O - 500 °C.

[0038] Comparative Example 5: According to the preparation method of Example 1, the only difference is that glutaraldehyde is not added to both Modifying Solution A and Modifying Solution B; the steps are as follows: (1) Preparation of Modifying Solution A: Add 0.02 mol of urea to 20 mL of water, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain Modifying Solution A; (2) Preparation of Modifying Solution B: Add 0.02 mol of urea to 20 mL of water, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain Modifying Solution B; (3) Preparation of the precursor: Dissolve 10 g of polyvinyl alcohol in 200 mL of water to obtain Solution A, dissolve 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 in 35 mL of water to obtain Solution B. Mix 10 mL of Solution A, 20 mL of Modifying Solution A and 25 mL of Solution B and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out a hydrothermal reaction at 120 °C for 24 h. After the reaction ends, add 20 mL of Modifying Solution B and 10 mL of Solution B, mix and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene lining, carry out a hydrothermal reaction at 120 °C for 24 h. After the reaction ends, centrifuge to separate out the solid, wash it 3 times with water and 6 times with ethanol respectively, and dry it at 60 °C for 12 h to obtain the precursor powder (2) High-temperature regulation to construct CeO2 / Cu 2+1 O Double-metal oxide composite catalyst: Place the precursor powder in a tubular high-temperature furnace, introduce a protective inert gas, heat at a rate of 3 - 5 °C / min, and hold at 773 K for 2 h to obtain the CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O - 500 °C.

[0039] Comparative Example 6: According to the preparation method of Example 1, the only difference is that in the preparation of the precursor, Modifying Solution B is added first, and then Modifying Solution A; the steps are as follows: (1) Preparation of Modifying Solution A: Add 0.02 mol of urea to 20 mL of an aqueous solution of glutaraldehyde with a concentration of 40 wt%, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain Modifying Solution A; (2) Preparation of modified liquid B: Add 0.02 mol of urea to 20 mL of an aqueous glutaraldehyde solution with a concentration of 10 wt%, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modified liquid B; (3) Preparation of precursor: Dissolve 10 g of polyvinyl alcohol in 200 mL of water to obtain solution A. Dissolve 0.005 mol of Cu(NO3)2 and 0.005 mol of Ce(NO3)2 in 35 mL of water to obtain solution B. Mix 10 mL of solution A, 20 mL of modified liquid B, and 25 mL of solution B, stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene liner, and carry out a hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, add 20 mL of modified liquid A and 10 mL of solution B, mix and stir for 30 min, then transfer the suspension to a reaction kettle with a polytetrafluoroethylene liner, and carry out a hydrothermal reaction at 120 °C for 24 h. After the reaction is completed, centrifuge to separate the solid, wash it 3 times with water and 6 times with ethanol, and dry it at 60 °C for 12 h to obtain precursor powder (2) High-temperature regulation to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: Place the precursor powder in a tubular high-temperature furnace, introduce a protective inert gas, heat it at a heating rate of 3 - 5 °C / min, and hold it at 773 K for 2 h to obtain the CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500 °C.

[0040] Test Example 1: The following further elaborates on the present invention in combination with specific embodiments, but the substantial content of the present invention is not limited to the following embodiments. The methods are all conventional methods unless otherwise specified, and the materials can all be obtained from public commercial channels unless otherwise specified. Those skilled in the art should know that any simple transformation or substitution based on the substantial content of the present invention belongs to the protection scope required by the present invention.

[0041] Perform relevant performance tests on the catalysts prepared in the above Examples 1-5 or Comparative Examples 1-6. The test methods are as follows: Use a FEI-Quanta 200 type scanning electron microscope (SEM) to characterize the morphology of the catalyst; Use a PANalytical X-ray diffractometer to characterize the crystal form and structural characteristics of the material; Use UV-vis diffuse reflectance spectroscopy to characterize the band gap of the catalyst; Use an Agilent 1220 type high performance liquid chromatography to detect the concentration of antibiotics in the treated water sample.

[0042] The specific test objects and test results are as follows: Detection Example 1: Figure 1 where a is the CeO2 / Cu prepared in Comparative Example 1 of the present invention 2+1 Scanning electron micrograph of O-pre, b is the scanning electron micrograph of CeO2 / Cu prepared in Example 5 2+1 Scanning electron micrograph of O-400°C, c is the scanning electron micrograph of CeO2 / Cu prepared in Example 1 2+1 Scanning electron micrograph of O-500°C, d is the scanning electron micrograph of CeO2 / Cu prepared in Example 4 2+1 Scanning electron micrograph of O-600°C. The SEM images all show a pearl-like structure.

[0043] Detection Example 2: Figure 2 where are the X-ray diffraction patterns of CeO2 / Cu prepared in Examples 1, 4, and 5 2+1 O-500°C / 600°C / 400°C, and the X-ray diffraction pattern of CeO2 / Cu prepared in Comparative Example 1 2+1 O-pre.

[0044] According to the comparison with the PDF standard card, it can be seen from the XRD pattern that the diffraction peaks of CeO2 / Cu prepared in Examples 1, 4, and 5 2+1 O-500°C / 600°C / 400°C show the diffraction peaks of the XRD pattern standard card (PDF#75-0076) of cerium dioxide (CeO2) and the diffraction peaks of the XRD pattern standard card (PDF#05-0667) of copper oxide and cuprous oxide (Cu 2+1 O), indicating that after high-temperature treatment in Examples 1, 4, and 5, the crystallinity of the two oxides is stronger and better composite is obtained, and the diffraction peak becomes stronger with the increase of temperature, that is, a catalyst with good crystallinity is formed. While in Comparative Example 1, the diffraction peak of CeO2 / Cu 2+1 O-pre is consistent with the diffraction peak of the XRD pattern standard card (PDF#75-0076) of cerium dioxide (CeO2), indicating that the catalyst prepared in Comparative Example 1 is based on cerium dioxide.

[0045] Detection Example 3: Figure 3 The band gaps of the catalysts were characterized by UV-vis diffuse reflectance spectroscopy for Examples 1, 4, 5, and Comparative Example 1 respectively, and their band gap values ( E g ) were calculated by the Tauc plot method. The results are shown in Table 1. The data in Table 1 show that under different temperature treatments, the band gap decreases with the increase of temperature. However, when the temperature is raised to 600°C, the band gap increases again. Therefore, in this application, the temperature range is around 500°C and the treatment time is 2 - 3 hours.

[0046] Table 1 Band gaps of the catalysts prepared in Example 1, Example 4, Example 5 and Comparative Example 1

[0047] Test Example 2: Using TC as a pollutant, the degradation effects of the catalysts prepared in Example 1, 2, 4, 5 and Comparative Examples 1-6 on TC were detected.

[0048] Using BPA as a pollutant, the degradation effect of the catalyst of Example 3 on BPA was detected.

[0049] The specific operation is as follows: Prepare an aqueous TC solution with a TC concentration of 20 mg / L in the aqueous TC solution, denoted as C0; then divide it into ten equal parts, each of 50 mL, as the detection water sample; Prepare an aqueous BPA solution with a BPA concentration of 20 mg / L in the aqueous BPA solution, denoted as C1; then take one portion of 50 mL as the detection water sample; Weigh 7.5 mg of each of the catalysts prepared in Example 1, 2, 4, 5 and Comparative Examples 1-6, and add them to a detection water sample (C0) respectively. Ultrasonic to fully disperse the catalyst to obtain ten treated samples; Weigh 7.5 mg of the catalyst prepared in Example 3, add it to a detection water sample (C1), and ultrasonically disperse the catalyst to obtain a treated sample; Place each treated sample on a magnetic stirrer. Add 1 mM of PI to Examples 1, 3, 4, 5 and Comparative Examples 1-6, and add 0.1 mL of H2O2 (30%) to Example 2. Stir at a speed of 350 rpm / min and carry out the catalytic degradation reaction at 25 °C (at this time, the pH of the mixed solution is about 6.4, no additional adjustment is required). And take water samples at the 0th, 2nd, 5th, 10th, 20th, and 30th minutes during the degradation reaction, and use an Agilent 1220 high performance liquid chromatography to detect the TC concentration in the water sample, denoted as C.

[0050] Detection Example 4: Then the degradation experimental results of the above-mentioned treated samples are respectively as Figure 4 and Figure 5 shown. Examples 1-5 are respectively denoted as CeCu-1 ~ CeCu-5 in the figure, and Examples 1 and Comparative Examples 1-6 are marked as CeCu-1 and CeCu-6~ CeCu-11 in the figure. The ordinate C / C0 in the figure represents the removal rate of TC. Specifically, the smaller the value of C / C0, the greater the removal rate (or degradation rate) of TC; on the contrary, the larger the value of C / C0, the smaller the removal rate of TC.

[0051] From Figure 4 and Figure 5 It can be seen that the CeO2 / Cu prepared in Example 1 2+1 O-500 °C has the best degradation effect, and the degradation rate reaches 98.2%; while the CeO2 / Cu in Comparative Example 1 2+1 O-pre has the worst degradation effect, and the degradation rate is only about 41%; the degradation effects of Examples 2 and 3 are 88.3% and 71.5% respectively; the degradation efficiencies of Examples 4 and 5 are about 70% and about 80% respectively; the CeO2 / Cu prepared in Comparative Example 2 2+1 O-100 °C has a better degradation effect than Comparative Example 1, and the CeO2 / Cu prepared in Comparative Examples 3-6 2+1 O-500 °C has a lower degradation effect than Example 1.

[0052] It shows that the synergistic effect of high-temperature heat treatment and glutaraldehyde modification system may be the key mechanism to improve catalytic performance. High-temperature heat treatment indirectly regulates the band gap of the CeO2 / Cu 2+1 O catalyst by controlling the appropriate temperature. The decrease of the band gap will increase the transition probability of electrons between the valence band and the conduction band, increase the surface electron density of the catalyst, promote the electrostatic adsorption of polar molecules on the catalyst surface and promote their activation. The two metals promote the oxidation-reduction efficiency of metal oxides for valence state cycling. At the same time, the composite of two metal oxides with different band gaps in the material can reduce the band gap and play a synergistic role to further improve the removal efficiency of pollutants. Therefore, the temperature of high-temperature treatment in this application is preferably 400-500 °C.

[0053] The gradient concentration design of glutaraldehyde in the modification liquid A / B in the glutaraldehyde modification system may achieve a directional immobilization effect by regulating the urea crosslinking density in stages. In the initial stage, high-concentration glutaraldehyde (modification liquid A) preferentially immobilizes urea molecules through the Schiff base reaction between aldehyde groups and amino groups to construct the basis of the macromolecular framework; then the addition of low-concentration modification liquid B grafts a secondary network on the existing framework through a weaker crosslinking effect to form a concentration gradient field of urea distribution. This hierarchical crosslinking system makes the immobilization density of urea molecules decrease from the core to the surface layer, and produces a gradient pyrolysis behavior during the subsequent high-temperature calcination process - the dense region delays the decomposition of urea to generate a continuous reducing atmosphere, promoting the progressive reduction of Cu 2+ to Cu + , while the loose surface layer forms a mesoporous structure, which is beneficial to the rapid cycle of the Ce 3+ / Ce 4+ redox pair. The data of Comparative Examples 3-6 confirm that the lack of this gradient system will lead to a large amount of instantaneous decomposition of urea (Comparative Example 5) or the formation of a disordered pore structure (Comparative Example 6), significantly reducing the electron co-transport efficiency between active components.

[0054] Finally, it should be noted that the above embodiments are only the preferred embodiments of the present invention, which are only used to explain the present invention and do not limit the present invention. For those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or equivalently replace some of the technical features. Any changes, replacements, and modifications made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite catalyst, characterized in that, It includes the following steps: S11. Preparation of precursor: A mixed salt solution of Ce salt and Cu salt and modifier A are added to a polyvinyl alcohol dispersion liquid. After stirring and mixing evenly, a hydrothermal reaction is carried out. Then, a mixed salt solution of Ce salt and Cu salt and modifier B are added. After stirring and mixing evenly, a hydrothermal reaction is carried out. After centrifugation, washing, and drying, precursor powder is obtained; S12. High-temperature construction of composite catalyst: The precursor powder is put into a high-temperature reaction for 1 - 3 h. The temperature of the high-temperature reaction is 400 - 600 °C, and an inert gas argon atmosphere is used to obtain a composite catalyst; The preparation method of the modifier A or B is as follows: Urea is added to an aqueous glutaraldehyde solution, and the pH is adjusted to 7.5 - 8 with sodium hydroxide, and stirred for 45 min to obtain modifier A or modifier B.

2. The preparation method of the composite catalyst according to claim 1, characterized in that, In the step S11, the molar ratio of Cu salt to Ce salt is 1:5 - 5:

1.

3. The preparation method of the composite catalyst according to claim 1, characterized in that, In the step S11, the mixed salt solution of Ce salt and Cu salt is an aqueous solution of chloride, nitrate, or sulfate, and its concentration is 0.01 - 0.21 mol / L.

4. The preparation method of the composite catalyst according to claim 1, characterized in that: In the step S11, the polyvinyl alcohol dispersion liquid is a dispersion liquid formed by dispersing polyvinyl alcohol in water, and its concentration is 0.1 - 3 mol / L.

5. The preparation method of the composite catalyst according to claim 1, characterized in that, In the preparation raw materials of the modifier A, the molar ratio of urea to glutaraldehyde is 1:0.3 - 0.5, and the concentration of the aqueous glutaraldehyde solution is 40 wt%; in the preparation raw materials of the modifier B, the molar ratio of urea to glutaraldehyde is 1:0.05 - 0.15, and the concentration of the aqueous glutaraldehyde solution is 10 wt%.

6. The preparation method of the composite catalyst according to claim 1, wherein, In the step S11, the dosage ratio of the mixed salt solution, modifier A, modifier B, and polyvinyl alcohol dispersion liquid is 35 mL:20 mL:20 mL:10 mL.

7. The preparation method of the composite catalyst according to claim 1, characterized in that, In the step S11, the stirring and mixing time is 20 - 40 min, the temperature of the hydrothermal reaction is 100 - 200 °C, and the time is 18 - 24 h.

8. The preparation method of the composite catalyst according to claim 1, characterized in that, In the step S12, the time of the high-temperature reaction is 2 - 3 h, and the heating rate is 3 - 5 °C / min.

9. A composite catalyst is obtained by the preparation method of the composite catalyst according to any one of claims 1 - 8.

10. Use of the composite catalyst according to claim 9, characterized in that, It is used for catalytic degradation of organic pollutants in water.

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