Composite catalyst and its preparation method and application

Abstract

The present invention relates to the field of catalyst technology, and specifically to a composite catalyst, a preparation method thereof, and an application thereof. The catalyst is prepared by modifying Ce salt and Cu salt solutions in a polyvinyl alcohol dispersion system with glutaraldehyde urea in a staged gradient concentration and a double hydrothermal reaction method to obtain a precursor, which is then calcined under a high-temperature inert atmosphere to achieve heterojunction self-assembly and bandgap width regulation. This structure optimizes energy band matching, promotes electron separation and interfacial charge migration, and strengthens the synergistic redox cycle. It exhibits efficient peroxide activation in Fenton-like reactions and can significantly improve the degradation and mineralization efficiency of organic pollutants such as antibiotics and dyes in water. Overall, the present invention effectively makes up for the defects of existing single metal oxides such as wide bandgap and limited electronic state regulation, and provides a new type of efficient catalytic material and process for the treatment of organic pollution in water bodies.

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, the overuse and discharge of antibiotics, dyes, and phenols in human medicine, animal husbandry, aquaculture, and the pharmaceutical industry have severely polluted the water environment, and the problem of organic pollutants is becoming increasingly serious. Therefore, various methods have been tried to treat antibiotics in water, including physical adsorption, photocatalysis, electrochemistry, and advanced oxidation processes.

[0003] Advanced oxidation treatment (AOT) is a highly efficient and promising wastewater treatment technology, applicable to a wide range of polluted water bodies. Fenton-like processes, one of the most promising approaches for treating organic wastewater, have been extensively studied in recent years. These processes utilize solid-phase catalysts to activate hydrogen peroxide (H2O2), persulfate (PS), and periodate (PI) to generate oxidatively active species, thereby oxidizing and degrading pollutants into small molecules, including carbon dioxide, water, and inorganic salts, achieving wastewater treatment.

[0004] The design and preparation of high-performance catalysts is the key to fully utilize the performance of activated peroxides in the degradation of 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 heterojunctions is a feasible solution to the above problems. The formation of heterojunctions can reduce the intrinsic band gap of CeO2 and lower the energy barrier for electrons to transition from the conduction band to the valence band. At the same time, it can also reconstruct the local electron density of the material and weaken the metal redox conversion (such as CeO2). 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 existing technology, researchers mostly prepare CeO2 and transition metal oxide composites through co-precipitation or sol-gel methods, but such methods have insufficient control over the precursor cross-linking network, making it difficult to achieve a reasonable distribution of metal ions. At the same time, the compatibility of oxidants and pollutant types in conventional processes is poor, and the electronic state of the catalyst surface is difficult to dynamically adjust to adapt to different reaction systems, limiting its practical application range. Therefore, it is urgent to develop a new preparation method that can synergistically optimize metal dispersion, interface 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 and its preparation method and application, which can efficiently activate peroxides, and the catalyst is simple to prepare, economical, and exhibits excellent catalytic degradation effect of organic pollutants.

[0008] The first object of the present invention is to provide a method for preparing a composite catalyst, comprising the following steps:

[0009] S11, precursor preparation: adding a mixed salt solution of Ce salt and Cu salt and modifying liquid A to a polyvinyl alcohol dispersion, stirring and mixing until uniform, and then performing a hydrothermal reaction; then adding a mixed salt solution of Ce salt and Cu salt and modifying liquid B, stirring and mixing until uniform, and then performing a hydrothermal reaction; after centrifugation, washing, and drying, a precursor powder is obtained;

[0010] S12. High-temperature regulation to construct a composite catalyst: Place the precursor powder into a reaction device for a high-temperature reaction for 2-3 hours. The high-temperature reaction temperature 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.

[0011] Centrifugation, washing, and drying of the hydrothermal reaction product are conventional operations, and specific conditions can be selected according to actual conditions. In this application, washing is performed 3-4 times with water and ethanol respectively; the drying temperature is 60-70°C and the drying time is 10-12 hours.

[0012] In a further embodiment, the molar ratio of the Cu salt to the Ce salt in step S11 is 1:5-5:1.

[0013] In a further embodiment, the mixed salt solution of Ce salt and Cu salt in step S11 is an aqueous solution of chloride, nitrate or sulfate, with a concentration of 0.01-0.21 mol / L. The Ce salt and Cu salt are selected from chloride, nitrate or sulfate soluble in a solvent, wherein the solvent is water or ethanol.

[0014] In a further embodiment, the polyvinyl alcohol dispersion in step S11 is a dispersion formed by dispersing polyvinyl alcohol in water, and its concentration is 0.01-0.1 g / mL.

[0015] In a further embodiment, in step S11, the ratio of the mixed salt solution, the modifying liquid A, the modifying liquid B and the polyvinyl alcohol dispersion is 35 mL:20 mL:20 mL:10 mL.

[0016] In a further embodiment, the preparation method of the modified liquid A or B in step S11 is as follows: urea is added to a glutaraldehyde aqueous solution, the pH is adjusted to 7.5-8 with sodium hydroxide, and stirred for 45 minutes to obtain the modified liquid A or the modified liquid B;

[0017] In a further embodiment, the molar ratio of urea to glutaraldehyde in the raw materials for preparing the modified solution A is 1:0.3-0.5, and the concentration of the glutaraldehyde aqueous solution is 40 wt%.

[0018] In a further embodiment, the molar ratio of urea to glutaraldehyde in the raw materials for preparing the modified solution B is 1:0.05-0.15, and the concentration of the glutaraldehyde aqueous solution is 10 wt %.

[0019] In a further embodiment, the stirring and mixing time in step S11 is 20-40 min, the hydrothermal reaction is carried out in a closed reactor, the hydrothermal reaction temperature is 100-130° C., and the time is 18-24 h.

[0020] In a further embodiment, the high temperature reaction time in step S12 is 2-3 h, and the heating rate is 3-5° C. / min.

[0021] The second object of the present invention is to provide a composite catalyst prepared by the above preparation method.

[0022] The third object of the present invention is to provide an application of the composite catalyst for catalytic degradation of organic pollutants in water.

[0023] In a further embodiment, the composite catalyst is used in a method for catalytically degrading organic pollutants in water, comprising the following steps:

[0024] S21, adding the composite catalyst to the sewage and performing ultrasonic dispersion;

[0025] S22. Add peroxide to carry out catalytic degradation reaction to remove organic pollutants in sewage.

[0026] In a further embodiment, the concentration of organic pollutants in the sewage is 20-100 mg / L;

[0027] Based on the volume of sewage, the added amount of the composite catalyst is 75-750 mg / L, and the added amount of the peroxide is 20-300 mg / L.

[0028] In 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;

[0029] The peroxide is hydrogen peroxide, persulfate or peracetic acid, and the periodate is any one of sodium periodate, potassium periodate or barium periodate;

[0030] 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.

[0031] Furthermore, the composite catalyst prepared in this application can be applied to Fenton-like degradation of other simulated organic pollutant-contaminated water as well as actual organic pollutant-contaminated water. The simulated organic pollutant-contaminated water includes organic pollutant-contaminated water prepared from pure water, tap water, river water, lake water, and river water.

[0032] Compared with the prior art, the composite catalyst provided by the present invention has the following significant advantages:

[0033] First, the present invention combines wide bandgap CeO2 (3.4 eV) with narrow bandgap Cu 2+1 O (1.2~2.2eV). In composite catalysts, the core advantage of heterostructure catalysts formed by the combination of wide bandgap and narrow bandgap materials is the synergistic optimization of the band structures of the two materials. The Fermi level difference between the two materials (such as the Fermi level EF = -0.3 eV of CeO2 vs. Cu 2+1 O EF = +0.2 eV) leads to interfacial charge rearrangement, forming a charge transfer from CeO2 to Cu 2+1 O's built-in electric field is the key to promoting charge separation; at the same time, the chemical bonding at the interface can reduce the charge transfer barrier and improve the interface charge transfer efficiency. 3+ / Ce 4+ With Cu 1+ / Cu 2+ Redox couple formation cycle, CeO2 / Cu 2+1 O degrades tetracycline by activating PI at a rate more than twice that of CeO2 (40%) alone, achieving a synergistic effect. The band gap of the catalyst is indirectly controlled by temperature. A reduction in the band gap increases the probability of electron transitions between the valence band and the conduction band, increasing the electron density on the catalyst surface, thereby promoting the catalyst's enhanced electrostatic adsorption of polar organic molecules and promoting their activation. Therefore, the high-temperature calcined composite catalyst and peroxide in this application constitute a Fenton-like oxidation system, which is used to enhance the activation of peroxide to produce active oxidative species (free radicals and non-free radicals) to degrade and remove organic pollutants in water.

[0034] Secondly, the present invention adopts a gradient concentration glutaraldehyde modification system to form a dense-loose alternating urea immobilization structure through a staged cross-linking reaction. High concentration glutaraldehyde builds a rigid skeleton in the initial stage to limit the migration of metal ions, while the 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 produces differentiated pyrolysis behavior during high temperature calcination. The inner dense area delays the decomposition of urea to maintain a reducing atmosphere, promoting the Cu 2+ Xiang Cu + The outer loose area generates through-holes, which accelerates the 3+ / Ce 4+ valence state cycling, thereby synergistically enhancing redox activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The following drawings, which constitute part of the present invention, are used to assist in understanding the present invention. The contents provided in the drawings and their related descriptions in the present invention may be used to explain the present invention, but do not constitute undue limitations on the present invention. In the drawings:

[0036] Figure 1 CeO2 / Cu prepared in Examples 1, 4, 5 and Comparative Example 1 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+ Scanning electron microscopy images of 1O-pre are shown in Figures c / d / b and a;

[0037] Figure 2 CeO2 / Cu prepared in Examples 1, 4, 5 and Comparative Example 1 of the present invention 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 X-ray diffraction patterns of O-pre, CeO2 / Cu 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+ X-ray diffraction pattern of 1O-pre;

[0038] Figure 3 CeO2 / Cu prepared in Examples 1, 4, 5 and Comparative Example 1 of the present invention 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 O-pre's UV-vis light absorption and diffuse reflection band gap diagram, CeO2 / Cu in the figure 2+1 O-500℃ / 600℃ / 400℃ and CeO2 / Cu 2+1 O-pre;

[0039] Figure 4These are the effects of using the catalysts prepared in Examples 1, 4, and 5 of the present invention to activate PI to degrade tetracycline (TC), Example 2 to activate H2O2 to degrade tetracycline (TC), and Example 3 to activate PI to degrade bisphenol A (BPA).

[0040] Figure 5 This is a diagram showing the effects of activating PI and degrading tetracycline (TC) using the catalysts prepared in Example 1 of the present invention and Comparative Examples 1-6. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to specific examples. However, the essence of the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified, and the materials described are commercially available unless otherwise specified. Those skilled in the art will recognize that any simple modification or substitution based on the essence of the present invention falls within the scope of protection claimed by the present invention.

[0042] Example 1: A CeO2 / Cu 2+1 The preparation method of the bimetallic composite catalyst comprises the following steps:

[0043] (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of a 40 wt% glutaraldehyde aqueous solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A.

[0044] (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of a 10 wt% glutaraldehyde aqueous solution, the pH was adjusted to 7.7 with sodium hydroxide, and the solution was stirred for 30 min to obtain modified solution B.

[0045] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain a precursor powder;

[0046] (4) High temperature control to construct CeO2 / Cu 2+1O bimetallic oxide composite catalyst: The precursor powder is placed in a tubular high-temperature furnace, inert gas is introduced, the temperature is increased at a rate of 3 ~ 5 ° C / min, and the temperature is maintained at 773K for 2 h to obtain CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500℃.

[0047] Example 2: Same as Example 1, except that the oxidant PI is replaced by H2O2 in the degradation test.

[0048] Example 3: Same as Example 1, except that the degradation pollutant TC is replaced by BPA in the degradation test.

[0049] Example 4: The preparation method of Example 1 was followed, except that the temperature was adjusted to 873 K. The catalyst prepared was denoted as CeO2 / Cu 2+1 O-600℃.

[0050] Example 5: The preparation method of Example 1 was followed, except that the temperature was adjusted to 673 K. The catalyst prepared was denoted as CeO2 / Cu 2+1 O-400℃.

[0051] Comparative Example 1: Synthesis of CeO2 / Cu without high temperature treatment 2+1 O catalyst, the steps are:

[0052] (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of a 40 wt% glutaraldehyde aqueous solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A.

[0053] (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of a 10 wt% glutaraldehyde aqueous solution, the pH was adjusted to 7.7 with sodium hydroxide, and the solution was stirred for 30 min to obtain modified solution B.

[0054] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain CeO2 / Cu 2+1 O, recorded as CeO2 / Cu 2+1 O-pre.

[0055] Comparative Example 2: Synthesis of CeO2 / Cu at low temperature 2+1 O catalyst, the steps are:

[0056] (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of a 40 wt% glutaraldehyde aqueous solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A.

[0057] (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of a 10 wt% glutaraldehyde aqueous solution, the pH was adjusted to 7.7 with sodium hydroxide, and the solution was stirred for 30 min to obtain modified solution B.

[0058] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain the precursor powder.

[0059] (4) Construction of CeO2 / Cu 2+1 O catalyst: The precursor powder was placed in a tubular high-temperature furnace and kept at 373 K for 2 h to obtain the catalyst, which was recorded as CeO2 / Cu2+1 O-100℃.

[0060] Comparative Example 3: The preparation method of Example 1 was followed, except that glutaraldehyde was not added to the modified solution A; the steps were:

[0061] (1) Preparation of modified solution A: Add 0.02 mol urea to 20 mL water, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A;

[0062] (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of a 10 wt% glutaraldehyde aqueous solution, the pH was adjusted to 7.7 with sodium hydroxide, and the solution was stirred for 30 min to obtain modified solution B.

[0063] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain the precursor powder.

[0064] (4) High temperature control to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: The precursor powder is placed in a tubular high-temperature furnace, inert gas is introduced, the temperature is increased at a rate of 3 ~ 5 ° C / min, and the temperature is maintained at 773K for 2 h to obtain CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500℃.

[0065] Comparative Example 4: The preparation method of Example 1 was followed, except that glutaraldehyde was not added to the modified solution B; the steps were:

[0066] (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of a 40 wt% glutaraldehyde aqueous solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A.

[0067] (2) Preparation of modified solution B: Add 0.02 mol urea to 20 mL water, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modified solution B;

[0068] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain the precursor powder.

[0069] (4) High temperature control to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: The precursor powder is placed in a tubular high-temperature furnace, inert gas is introduced, the temperature is increased at a rate of 3 ~ 5 ° C / min, and the temperature is maintained at 773K for 2 h to obtain CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500℃.

[0070] Comparative Example 5: The preparation method of Example 1 was followed, except that glutaraldehyde was not added to either the modified solution A or the modified solution B; the steps were:

[0071] (1) Preparation of modified solution A: Add 0.02 mol urea to 20 mL water, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A;

[0072] (2) Preparation of modified solution B: Add 0.02 mol urea to 20 mL water, adjust the pH to 7.7 with sodium hydroxide, and stir for 30 min to obtain modified solution B;

[0073] (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, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution B and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain the precursor powder.

[0074] (2) High temperature control to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: The precursor powder is placed in a tubular high-temperature furnace, inert gas is introduced, the temperature is increased at a rate of 3 ~ 5 ° C / min, and the temperature is maintained at 773K for 2 h to obtain CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500℃.

[0075] Comparative Example 6: The preparation method of Example 1 is the same, except that modifying liquid B is added first and then modifying liquid A in the precursor preparation; the steps are:

[0076] (1) Preparation of modified solution A: Add 0.02 mol of urea to 20 mL of a 40 wt% glutaraldehyde aqueous solution, adjust the pH to 7.8 with sodium hydroxide, and stir for 45 min to obtain modified solution A.

[0077] (2) Preparation of modified solution B: 0.02 mol of urea was added to 20 mL of a 10 wt% glutaraldehyde aqueous solution, the pH was adjusted to 7.7 with sodium hydroxide, and the solution was stirred for 30 min to obtain modified solution B.

[0078] (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 B and 25 mL of solution B were mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, 20 mL of modified solution A and 10 mL of solution B were added, mixed and stirred for 30 min, and then the suspension was transferred to a reactor with a polytetrafluoroethylene substrate, and a hydrothermal reaction was carried out at 120 °C for 24 h. After the reaction was completed, the solid was separated by centrifugation, washed with water and ethanol three times respectively, and dried at 60 °C for 12 h to obtain the precursor powder.

[0079] (2) High temperature control to construct CeO2 / Cu 2+1 O bimetallic oxide composite catalyst: The precursor powder is placed in a tubular high-temperature furnace, inert gas is introduced, the temperature is increased at a rate of 3 ~ 5 ° C / min, and the temperature is maintained at 773K for 2 h to obtain CeO2 / Cu 2+1 O catalyst, denoted as CeO2 / Cu 2+1 O-500℃.

[0080] Test Example 1:

[0081] The present invention is further described below with reference to specific examples. However, the essence of the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified, and the materials described are commercially available unless otherwise specified. Those skilled in the art will recognize that any simple modification or substitution based on the essence of the present invention falls within the scope of protection claimed by the present invention.

[0082] The catalysts prepared in Examples 1-5 or Comparative Examples 1-6 were subjected to relevant performance tests, and the test methods were as follows:

[0083] The morphology of the catalysts was characterized using a FEI-Quanta 200 scanning electron microscope (SEM).

[0084] Use PANalytical X-ray diffractometer to characterize the crystal form and structural characteristics of the material;

[0085] The band gap of the catalyst was characterized using UV-vis light absorption and diffuse reflectance testing;

[0086] An Agilent 1220 high performance liquid chromatograph was used to measure the concentrations of antibiotics in the treated water samples.

[0087] The specific test objects and test results are as follows:

[0088] Test Example 1:

[0089] Figure 1 a is the CeO2 / Cu prepared in Comparative Example 1 of the present invention 2+1 A is the scanning electron microscope image of O-pre, b is the CeO2 / Cu prepared in Example 5 2+1 O-400℃ scanning electron microscope image, c is CeO2 / Cu prepared in Example 1 2+1 O-500℃ scanning electron microscope image, d is CeO2 / Cu prepared in Example 4 2+1 Scanning electron microscope images of 0-600℃. SEM images show pearl-like structures.

[0090] Test Example 2:

[0091] Figure 2 The CeO2 / Cu prepared in Examples 1, 4, and 5 2+1 X-ray diffraction patterns of CeO2 / CuO2 at 500℃ / 600℃ / 400℃, and the X-ray diffraction patterns of CeO2 / CuO2 prepared in Comparative Example 1 2+1 X-ray diffraction pattern of O-pre.

[0092] According to the comparison of PDF standard cards, it can be seen from the XRD patterns that CeO2 / Cu prepared in Examples 1, 4, and 5 2+1 The diffraction peaks of Cerium Dioxide (CeO2) and Cuprous Oxide (Cu 2+1 O) XRD pattern standard card (PDF#05-0667), indicating that the high temperature treatment of Examples 1, 4, and 5 makes the two oxides more crystalline and better composited, and the stronger the diffraction peak is as the temperature rises, the better the crystallinity of the catalyst is. 2+1 The diffraction peak of O-pre is consistent with the diffraction peak of the XRD spectrum standard card of cerium dioxide (CeO2) (PDF#75-0076), indicating that the catalyst prepared in Comparative Example 1 is based on cerium dioxide.

[0093] Test Example 3:

[0094] Figure 3 The band gap width of the catalyst was characterized by using UV-vis light absorption diffuse reflection test. Example 1, Example 4, Example 5 and Comparative Example 1 were characterized respectively, and the band gap width was calculated by Tauc plot method ( E g) values, as shown in Table 1. The data in Table 1 show that at different treatment temperatures, the bandgap decreases as the temperature increases. However, when the temperature reaches 600°C, the bandgap increases again. Therefore, in this application, the temperature range is around 500°C, and the treatment time is 2-3 hours.

[0095] Table 1 Bandgap widths of the catalysts prepared in Example 1, Example 4, Example 5 and Comparative Example 1

[0096]

[0097] Test Example 2:

[0098] Using TC as a pollutant, the degradation effects of the catalysts prepared in Examples 1, 2, 4, 5 and Comparative Examples 1-6 on TC were tested.

[0099] Using BPA as a pollutant, the degradation effect of the catalyst of Example 3 on BPA was tested.

[0100] The specific operations are as follows:

[0101] Prepare a TC aqueous solution with a TC concentration of 20 mg / L, denoted as C0; then divide it into ten equal portions of 50 mL each, as test water samples;

[0102] Prepare a BPA aqueous solution with a BPA concentration of 20 mg / L, denoted as C1; then prepare a 50 mL portion as the test water sample;

[0103] 7.5 mg of each of the catalysts prepared in Examples 1, 2, 4, 5 and Comparative Examples 1-6 were weighed and added to a test water sample (C0) respectively. The catalysts were fully dispersed by ultrasonication to obtain ten treated samples.

[0104] 7.5 mg of the catalyst prepared in Example 3 was weighed and added to a test water sample (C1), and the catalyst was fully dispersed by ultrasonication to obtain a treated sample;

[0105] Each treated sample was placed on a stirring platform. 1 mM PI was added to Examples 1, 3, 4, 5, and Comparative Examples 1-6, and 0.1 mL of 30% H₂O₂ was added to Example 2. The mixture was stirred at 350 rpm / min and subjected to catalytic degradation at 25°C (the pH of the mixed solution was approximately 6.4 at this point, requiring no additional adjustment). Water samples were collected at 0, 2, 5, 10, 20, and 30 minutes into the degradation reaction and measured for TC concentration using an Agilent 1220 HPLC. This concentration is recorded as C.

[0106] Test Example 4:

[0107] The degradation test results of the above treatment samples are as follows: Figure 4 and Figure 5 As shown in the figure, Examples 1-5 are respectively marked as CeCu-1 to CeCu-5, and Example 1 and Comparative Examples 1-6 are marked as CeCu-1 and CeCu-6 to CeCu-11 in the figure. The vertical axis 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; conversely, the larger the value of C / C0, the lower the removal rate of TC.

[0108] from Figure 4 and Figure 5 It can be seen that the CeO2 / Cu prepared in Example 1 2+1 O-500℃ had the best degradation effect, with a degradation rate of 98.2%; while the CeO2 / Cu 2+1 O-pre had the worst degradation effect, with a degradation rate of only about 41%; the degradation effects of Examples 2 and 3 were 88.3% and 71.5% respectively; the degradation efficiencies of Examples 4 and 5 were about 70% and 80% respectively; the CeO2 / Cu prepared in Comparative Example 2 was 2+1 The degradation effect of CeO2 / Cu ... 2+1 The degradation effects at 0-500℃ were lower than those in Example 1.

[0109] This indicates 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 CeO2 / Cu 2+1 The band gap width of the O catalyst is reduced. A reduction in the band gap width increases the probability of electron transitions between the valence band and the conduction band, increases the electron density on the catalyst surface, promotes the electrostatic adsorption of polar molecules on the catalyst surface, and promotes their activation. The two metal pairs promote the redox efficiency of the metal oxide. At the same time, the two metal oxides with different band gap widths in the material can be combined to reduce the band gap width and play a synergistic role, further improving the removal efficiency of pollutants. Therefore, the temperature of the high-temperature treatment in this application is preferably 400-500 ° C.

[0110] The gradient concentration design of glutaraldehyde in the modifying liquid A / B in the glutaraldehyde modification system may achieve a directional immobilization effect by regulating the urea cross-linking density in stages. In the initial stage, high-concentration glutaraldehyde (modifying liquid A) preferentially fixes urea molecules through the Schiff base reaction of aldehyde groups and amino groups to build the basis of the macromolecular skeleton; the subsequent addition of low-concentration modifying liquid B grafts a secondary network on the existing skeleton through a weaker cross-linking effect, forming a concentration gradient field of urea distribution. This hierarchical cross-linking system makes the urea molecules present a decreasing immobilization density from the core to the surface, and produces a gradient pyrolysis behavior during the subsequent high-temperature calcination process - the dense area delays the decomposition of urea to produce a continuous reducing atmosphere, which promotes Cu 2+ The gradual reduction of Cu + , while the surface loose area generates a mesoporous structure, which is beneficial to Ce 3+ / Ce 4+ The data from Comparative Examples 3-6 confirm that the lack of this gradient system leads to instantaneous and massive decomposition of urea (Comparative Example 5) or the formation of a disordered pore structure (Comparative Example 6), significantly reducing the efficiency of electron cooperative transport between active components.

[0111] Finally, it should be noted that the above embodiments are merely preferred implementations of the present invention and are intended only to explain the present invention, not to limit the present invention. Those skilled in the art will appreciate that they may modify the technical solutions described in the above embodiments or substitute equivalent features for some of the technical features. Any changes, substitutions, and modifications made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite catalyst, characterized in that: The following steps are involved: S11, precursor preparation: adding a mixed salt solution of Ce salt and Cu salt and modifying liquid A to a polyvinyl alcohol dispersion, stirring and mixing until uniform, and then performing a hydrothermal reaction; then adding a mixed salt solution of Ce salt and Cu salt and modifying liquid B, stirring and mixing until uniform, and then performing a hydrothermal reaction; after centrifugation, washing, and drying, a precursor powder is obtained; S12, high-temperature construction of a composite catalyst: placing the precursor powder in a high-temperature reaction for 1-3 hours at a temperature of 400-600° C. in an inert gas argon atmosphere to obtain a composite catalyst; The preparation method of the modified liquid A or B is as follows: adding urea to a glutaraldehyde aqueous solution, adjusting the pH to 7.5-8 with sodium hydroxide, and stirring for 45 minutes to obtain the modified liquid A or the modified liquid B; The molar ratio of urea to glutaraldehyde in the raw materials for preparing the modified liquid A is 1:0.3-0.5, and the concentration of the glutaraldehyde aqueous solution is 40 wt %. The molar ratio of urea to glutaraldehyde in the raw materials for preparing the modified liquid B is 1:0.05-0.15, and the concentration of the glutaraldehyde aqueous solution is 10 wt %.

2. The method for preparing the composite catalyst according to claim 1, wherein In step S11, the molar ratio of the Cu salt to the Ce salt is 1:5-5:

1.

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

4. The method for preparing the composite catalyst according to claim 1, wherein: The polyvinyl alcohol dispersion in step S11 is a dispersion formed by dispersing polyvinyl alcohol in water, and its concentration is 0.1-3 mol / L.

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

6. The method for preparing the composite catalyst according to claim 1, wherein The stirring and mixing time in step S11 is 20-40 minutes, and the temperature of the hydrothermal reaction is 100-200° C. and the time is 18-24 hours.

7. The method for preparing the composite catalyst according to claim 1, wherein The high temperature reaction time in step S12 is 2-3 h, and the heating rate is 3-5° C. / min.

8. A composite catalyst obtained by the preparation method of the composite catalyst according to any one of claims 1 to 7.

9. Use of the composite catalyst according to claim 8, characterized in that: Used for catalytic degradation of organic pollutants in water.

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