A CeO2 / ZnMn2O4Z-type heterojunction photocatalyst and its preparation method and application

Abstract

The present invention discloses a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst, its preparation method, and application. The CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst is composed of CeO2 and ZnMn2O4, wherein the mass ratio of CeO2 to ZnMn2O4 is 0.25 to 1:1. The CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst is prepared in two steps. First, long strips of ZnMn2O4 are prepared by a coprecipitation-calcination method. Then, a cerium nitrate solution is added to uniformly disperse the ZnMn2O4. A precipitated mixture is obtained by precipitation with ammonia water, and finally, the CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst is obtained by thermal decomposition. The catalyst has a Z-type heterojunction, which promotes the separation of photogenerated carriers and effectively inhibits the recombination process of photogenerated carriers. It has high photocatalytic degradation efficiency and reaction stability for tannic acid under simulated sunlight.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysis, and specifically relates to a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst and a preparation method and application thereof. Background Art

[0002] In the hydrometallurgical zinc smelting process, germanium is a rare associated metal with high recovery value, concentrated in zinc oxide dust. Currently, the primary method for recovering germanium from zinc smelting is to add excess tannic acid to the acid leachate of zinc oxide dust to precipitate it. However, the large amount of excess tannic acid that returns to the leachate after liquid-solid separation increases electrolyte viscosity, reduces electrical efficiency, and in severe cases, can cause cathode zinc to dissolve back and even burn. Industrial methods for removing tannic acid from leachates generally suffer from inadequate degradation, high operating costs, and the potential for secondary pollution. Photocatalysis, as a green and efficient method for degrading organic matter, is gaining increasing favor among researchers.

[0003] Traditional photocatalysts such as TiO2 and ZnO can only absorb high-energy photons due to their wide band gaps. Their use requires high-power ultraviolet radiation, which increases production costs and limits their practical applications. ZnMn2O4, a new spinel photocatalyst, has advantages such as visible light response, good photochemical stability, and excellent catalytic activity. Furthermore, ZnMn2O4 has low solubility in acidic environments, and the dissolved zinc and manganese ions do not cause secondary contamination of the leachate. However, the narrow band gap and low valence band potential of ZnMn2O4 result in a high recombination rate of photogenerated carriers during the photoreaction process, resulting in insufficient hole oxidation capacity, making it difficult to efficiently degrade tannic acid. Summary of the Invention

[0004] In order to solve the technical problems and deficiencies in the prior art, the present invention aims to provide a photocatalyst that can efficiently degrade tannic acid.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst, comprising the following steps:

[0007] (1) Preparation of ZnMn2O4:

[0008] Zinc acetate (CH3COO)2Zn·2H2O and manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution and stirred until completely dissolved to obtain solution A;

[0009] Add oxalic acid H2C2O4·2H2O to ethanol-water solution and stir until completely dissolved to obtain solution B;

[0010] Quickly pour solution A into solution B, heat and stir to obtain a mixed solution, and after the mixed solution is cooled to room temperature, filter, wash and dry to obtain precursor A;

[0011] The precursor A was placed in a tube furnace for high-temperature calcination to obtain ZnMn2O4 with a long strip morphology;

[0012] (2) Preparation of CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst:

[0013] The ZnMn2O4 obtained in step (1) is added to the cerium nitrate solution and stirred thoroughly to be uniformly dispersed in the cerium nitrate solution; then 25% ammonia water is added dropwise, heated and stirred to obtain a precipitated mixture, and after the reaction, the precipitated mixture is cooled to room temperature, filtered, washed and dried to obtain a precursor B, and the precursor B is placed in a tube furnace for high-temperature calcination to obtain a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst.

[0014] Preferably, in step (1), the total metal ion concentration of zinc and manganese in the solution A is 0.02 to 0.16 mol / L.

[0015] Preferably, in step (1), the molar ratio of zinc acetate to manganese acetate is 1:2, and the molar ratio of oxalic acid to zinc acetate is 3 to 3.6:1.

[0016] Preferably, in step (1), the heating and stirring are performed at a temperature of 50 to 60° C., a stirring rate of 500 to 1000 r / min, and a stirring time of 2 to 2.5 h.

[0017] Preferably, in step (1), the volume ratio of ethanol to water in the ethanol-water solution is 9:1.

[0018] Preferably, in step (2), the concentration of the cerium nitrate solution is 3.0-7.5 mmol / L, the amount of ZnMn2O4 added is 1.25-2 g / L, and the volume ratio of the 25% ammonia solution added to the cerium nitrate solution is 0.01-1:40.

[0019] Preferably, in step (2), the heating and stirring are performed at a temperature of 40 to 50° C., a stirring rate of 500 to 700 r / min, and a stirring time of 2 to 2.5 h.

[0020] Preferably, in step (1) and step (2), the precursor A and the precursor B are respectively heated to 450-550° C. at a heating rate of 2-10° C. / min for calcination, and the calcination holding time is 2-2.5 h.

[0021] The heating rate, calcination temperature and calcination time of step (1) and step (2) are the same.

[0022] In a second aspect, the present invention provides a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst material prepared by the aforementioned preparation method, wherein the mass ratio of CeO2 to ZnMn2O4 is 0.25 to 1:1.

[0023] In a third aspect, the present invention provides the use of the aforementioned CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst material in the photocatalytic degradation of tannic acid.

[0024] The present invention forms a Z-type heterojunction by compounding CeO2 and ZnMn2O4 to enhance the absorption capacity of visible light, effectively inhibit the recombination of photogenerated carriers in the photocatalytic reaction and improve the hole oxidation capacity, and has high photocatalytic degradation efficiency and reaction stability for tannic acid under simulated sunlight.

[0025] Compared with the prior art, the beneficial effects of the technical solution of the present invention include at least:

[0026] (1) The CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst prepared by the present invention using a simple wet chemical-thermal decomposition method has excellent visible light response ability and photocatalytic activity, can efficiently degrade tannic acid, and has better photocatalytic degradation performance than pure CeO2 and ZnMn2O4.

[0027] (2) The CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst prepared by the present invention has good stability and recyclability, and its structure remains stable after being recycled twice ( Figure 1 ), after four cycles of use, the degradation rate of tannic acid can still be maintained at a high level of 65.2%.

[0028] (3) The CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst prepared by the present invention forms a Z-type heterojunction, which effectively separates active oxidative species with stronger oxidation and reduction abilities under the action of the interfacial electric field, inhibits the recombination of photogenerated electrons and holes, and improves the photocatalytic efficiency. It has good practical value and potential application prospects in removing tannic acid in zinc leachate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 are X-ray diffraction patterns, (a) is the X-ray diffraction pattern of the samples prepared in Example 1 and Comparative Example 1; (b) is the X-ray diffraction pattern of the sample prepared in Example 1 before degradation and after two cycles of degradation.

[0030] Figure 2These are field scanning electron microscope photos of CeO2 prepared in Comparative Example 1 and ZnMn2O4 and CeO2 / ZnMn2O4 prepared in Example 1; wherein, a: CeO2, b: ZnMn2O4, c: CeO2 / ZnMn2O4.

[0031] Figure 3 It is the ultraviolet-visible diffuse reflectance spectra of the samples prepared in Comparative Example 1 and Example 1.

[0032] Figure 4 These are the nitrogen adsorption-desorption curves and pore size distribution diagrams of the samples prepared in Comparative Example 1 and Example 1.

[0033] Figure 5 This is the curve of tannic acid concentration changing with time in the photocatalytic degradation reaction of each group of samples in the application example. DETAILED DESCRIPTION

[0034] The following describes in detail the objectives, specific implementation methods and advantages of the present invention, but the present invention is not limited to the following description.

[0035] The present invention compounds CeO2 and ZnMn2O4 to construct a Z-type heterojunction, which accelerates the migration and separation of photogenerated carriers under the action of the interfacial electric field, produces active oxidative species with enhanced oxidizing ability, and thus improves the photocatalytic efficiency. This is of great significance to the application of CeO2 and ZnMn2O4 materials in the field of photocatalysis and the removal of tannic acid in zinc leachate.

[0036] The technical solution of the present invention is described below in conjunction with specific embodiments:

[0037] Comparative Example 1:

[0038] The preparation of pure CeO2 includes the following steps:

[0039] Add 100 mg of cerium nitrate to 40 mL of deionized water and stir until completely dissolved; then add 0.8 mL of 25% ammonia water dropwise and stir at 40°C and 700 r / min for 2 hours. After cooling to room temperature, filter and collect the precipitate, wash it three times with deionized water and ethanol, and then dry it in an oven at 60°C overnight. Finally, place the obtained precursor in a tubular furnace and keep it at 450°C for 2 hours at a heating rate of 2°C / min to finally obtain CeO2 monomer material.

[0040] Example 1:

[0041] A CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst is prepared by the following preparation steps:

[0042] (1) Preparation of ZnMn2O4:

[0043] 0.220 g of zinc acetate (CH3COO)2Zn·2H2O and 0.490 g of manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution (45 mL + 5 mL) and stirred until completely dissolved to obtain solution A with a total zinc and manganese metal ion concentration of 0.02 mol / L. Similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (90 mL + 10 mL) and stirred until completely dissolved to obtain solution B. Solution A was then quickly poured into solution B and stirred at 60°C and 1000 r / min for 2 h to obtain a mixed solution. After the mixed solution was cooled to room temperature, it was filtered, washed and dried to obtain a precursor sample. Finally, the dried precursor was placed in a tubular furnace and calcined at 450°C for 2 h at a heating rate of 2°C / min to finally obtain ZnMn2O4 with a long strip morphology.

[0044] (2) Preparation of CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst:

[0045] 100 mg of cerium nitrate was added to 40 mL of deionized water and stirred until completely dissolved; then 60 mg of ZnMn2O4 obtained in step (1) was added to the above cerium nitrate solution and stirred thoroughly to uniformly disperse it in the cerium nitrate solution; then 0.8 mL of 25% ammonia water was added dropwise, and stirred at 40°C and 700 r / min for 2 h. After cooling to room temperature, the mixed precipitate was collected by filtration, washed with deionized water and ethanol three times, and then dried in a 60°C oven overnight; finally, the dried precursor was placed in a tube furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst.

[0046] The X-ray diffraction patterns of the samples obtained in Example 1 and Comparative Example 1 of the present invention are shown in detail. Figure 1 ,Depend on Figure 1 It can be seen that all diffraction peaks of pure CeO2 can match those of CeO2 (JCPD card number 34-0394), indicating that it has high purity and good crystallinity. For pure ZnMn2O4, all diffraction peaks correspond to ZnMn2O4 (JCPD card number 24-1133). The X-ray diffraction pattern of the CeO2 / ZnMn2O4 composite material contains all the characteristic peaks of CeO2 and ZnMn2O4. Compared with pure CeO2, the peak position of the CeO2 / ZnMn2O4 composite material is basically not shifted, indicating that the compound of CeO2 has no effect on the lattice of ZnMn2O4. At the same time, no other obvious impurity phases were observed, which means that the CeO2 / ZnMn2O4 composite material has a high degree of crystallinity.

[0047] The field scanning electron microscope photos of the samples obtained in Example 1 of the present invention and Comparative Example 1 are shown in detail. Figure 2 ,Depend on Figure 2-a, it can be seen that CeO2 presents an irregular block morphology with a diameter of about 10 to 20 μm. Figure 2 -b zinc manganate ZnMn2O4 is in the form of long strips with a diameter of about 300nm and a length between 4 and 5μm. Figure 2 -c CeO2 / ZnMn2O4 composite material maintains the bulk of CeO2 as a whole, and the surface is covered with short rod-shaped ZnMn2O4.

[0048] The UV-visible diffuse reflectance spectra of the samples prepared in Example 1 and Comparative Example 1 of the present invention are shown in detail. Figure 3 ,Depend on Figure 3 Pure CeO2 exhibits strong absorption in the ultraviolet region around 300nm, while ZnMn2O4 has strong absorption in the visible light spectrum around 400nm. Compared with pure ZnMn2O4, the absorption edge of the CeO2 / ZnMn2O4 composite exhibits a red shift, showing an enhanced visible light response, which can be attributed to the synergistic effect of ZnMn2O4 and CeO2. These results show that the CeO2 / ZnMn2O4 composite exhibits a broadened light absorption range and enhanced visible light absorption capacity, which is beneficial for photocatalytic reactions.

[0049] The nitrogen adsorption and desorption curves of the samples prepared in Example 1 and Comparative Example 1 of the present invention are shown in detail. Figure 4 ,Depend on Figure 4 It can be seen that ZnMn2O4, CeO2 and CeO2 / ZnMn2O4 composite materials show H3 type adsorption hysteresis loop and IV type characteristic isotherm of mesoporous materials. The specific surface area of ​​CeO2 / ZnMn2O4 composite materials (95.483m 2 ·g -1 ) are greater than ZnMn2O4(62.550m 2 ·g -1 ) and CeO2(86.935m 2 ·g -1 In addition, the pore volume of CeO2 / ZnMn2O4 composite material is the largest among the three, which is 0.242 cm 3 ·g -1 The pore volumes of ZnMn2O4 and CeO2 are 0.180 and 0.197 cm 3 ·g -1The results show that compared with ZnMn2O4 and CeO2, the CeO2 / ZnMn2O4 composite material has a larger specific surface area and pore volume, providing more active sites for the photocatalytic reaction, a shorter bulk diffusion length and a wider mass transfer channel, and is conducive to simultaneously enhancing the adsorption performance and photocatalytic efficiency.

[0050] Example 2:

[0051] A CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst, which differs from Example 1 in that the total metal ion concentration of zinc and manganese is controlled to 0.04 mol / L, the water bath temperature is 50°C, the stirring rate is 500 r / min, the stirring time is 2.5 h, the calcination temperature is 500°C, the heating rate is 5°C / min, and the calcination holding time is 2.5 h, is prepared by the following preparation steps:

[0052] (1) Preparation of ZnMn2O4:

[0053] 0.440 g of zinc acetate (CH3COO)2Zn·2H2O and 0.980 g of manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution (45 mL + 5 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.756 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (90 mL + 10 mL) and stirred until completely dissolved to obtain solution B. Solution A was then quickly poured into solution B and stirred at 50°C and 500 r / min for 2.5 h to obtain a mixed solution. After the mixed solution was cooled to room temperature, it was filtered, washed and dried to obtain a precursor sample. Finally, the dried precursor was placed in a tubular furnace and calcined at 500°C for 2.5 h at a heating rate of 5°C / min to finally obtain ZnMn2O4 with a long strip morphology.

[0054] (2) Preparation of CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst:

[0055] 80 mg of cerium nitrate was added to 40 mL of deionized water and stirred until completely dissolved; then 70 mg of ZnMn2O4 obtained in step (1) was added to the above cerium nitrate solution and stirred thoroughly to uniformly disperse it in the cerium nitrate solution; then 0.6 mL of 25% ammonia water was added dropwise, and stirred at 50°C and 500 r / min for 2.5 h. After cooling to room temperature, the mixed precipitate was collected by filtration, washed with deionized water and ethanol three times, and then dried in a 60°C oven overnight; finally, the dried precursor was placed in a tube furnace and kept at 500°C for 2.5 h at a heating rate of 5°C / min to obtain a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst.

[0056] Example 3:

[0057] A CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst, which differs from Example 1 in that the molar ratio of oxalic acid to zinc acetate is controlled to 3.6, the concentration of the cerium nitrate solution is 7.5 mmol / L, and the amount of ZnMn2O4 added is 1.25 g / L, is prepared by the following preparation steps:

[0058] (1) Preparation of ZnMn2O4:

[0059] 0.220 g of zinc acetate (CH3COO)2Zn·2H2O and 0.490 g of manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution (45 mL + 5 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.454 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (90 mL + 10 mL) and stirred until completely dissolved to obtain solution B. Solution A was then quickly poured into solution B and stirred at 60°C and 1000 r / min for 2 h to obtain a mixed solution. After the mixed solution was cooled to room temperature, it was filtered, washed and dried to obtain a precursor sample. Finally, the dried precursor was placed in a tubular furnace and calcined at 450°C for 2 h at a heating rate of 2°C / min to finally obtain ZnMn2O4 with a long strip morphology.

[0060] (2) Preparation of CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst:

[0061] 130 mg of cerium nitrate was added to 40 mL of deionized water and stirred until completely dissolved; then 50 mg of ZnMn2O4 obtained in step (1) was added to the above cerium nitrate solution and stirred thoroughly to uniformly disperse it in the cerium nitrate solution; then 1 mL of 25% ammonia water was added dropwise, stirred at 40°C and 700 r / min for 2 h, cooled to room temperature, filtered and collected the mixed precipitate, washed with deionized water and ethanol three times, and dried in a 60°C oven overnight; finally, the dried precursor was placed in a tube furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst.

[0062] Application examples:

[0063] The CeO2 prepared in Comparative Example 1, the ZnMn2O4 prepared in Example 1, and the CeO2 / ZnMn2O4 Z-type heterojunction photocatalysts were used to catalytically degrade tannic acid under simulated sunlight.

[0064] The specific operations are as follows:

[0065] (1) Control group: 50 mL of 200 mg·L -1After dark treatment with tannic acid solution for 30 minutes, the samples were irradiated under a xenon lamp for 150 minutes.

[0066] (2) CeO2 group: 20 mg of CeO2 photocatalyst prepared in Comparative Example 1 was weighed and added to a quartz test tube, and then 50 mL of 200 mg·L -1 The tannic acid solution was poured into a quartz test tube containing the catalyst. After ultrasonic dispersion for 5 minutes, the solution was darkened for 30 minutes to allow the catalyst to reach adsorption equilibrium. A xenon lamp was then turned on to conduct a photocatalytic reaction under simulated sunlight. Every 30 minutes, 2 mL of the reaction solution was sampled and filtered through a 0.22 μm filter membrane. The absorbance was measured using a colorimetric method to determine the residual tannic acid concentration and calculate the reduction rate.

[0067] (3) ZnMn2O4 group: 20 mg of the ZnMn2O4 photocatalyst prepared in Example 1 was weighed and added to a quartz test tube, and then 50 mL of 200 mg·L -1 The tannic acid solution was poured into a quartz test tube containing the catalyst. After ultrasonic dispersion for 5 minutes, the solution was darkened for 30 minutes to allow the catalyst to reach adsorption equilibrium. A xenon lamp was then turned on to conduct a photocatalytic reaction under simulated sunlight. Every 30 minutes, 2 mL of the reaction solution was sampled and filtered through a 0.22 μm filter membrane. The absorbance was measured using a colorimetric method to determine the residual tannic acid concentration and calculate the reduction rate.

[0068] (4) CeO2 / ZnMn2O4 group: 20 mg of CeO2 / ZnMn2O4 photocatalyst prepared in Examples 1-3 were weighed and added to a quartz test tube, and then 50 mL of 200 mg·L -1 The tannic acid solution was poured into a quartz test tube containing the catalyst. After ultrasonic dispersion for 5 minutes, the solution was darkened for 30 minutes to allow the catalyst to reach adsorption equilibrium. A xenon lamp was then turned on to conduct a photocatalytic reaction under simulated sunlight. Every 30 minutes, 2 mL of the reaction solution was sampled and filtered through a 0.22 μm filter membrane. The absorbance was measured using a colorimetric method to determine the residual tannic acid concentration and calculate the reduction rate.

[0069] Depend on Figure 5It can be seen that within 30 minutes of dark treatment, the CeO2 / ZnMn2O4 composite materials prepared in Examples 1-3 all showed better adsorption rates for tannic acid than the control group, the pure CeO2 group, and the ZnMn2O4 group, which is related to their larger specific surface areas and pore volumes. Photodegradation results show that in the presence of pure CeO2 and ZnMn2O4, 51.3% and 89.3% of tannic acid were decomposed within 150 minutes of illumination, respectively. However, the CeO2 / ZnMn2O4 composite material prepared in Example 1 completely photodegraded tannic acid within only 90 minutes. The CeO2 / ZnMn2O4 prepared in Examples 2 and 3 also achieved photocatalytic removal rates of 99.5% and 95.1% for tannic acid within 150 minutes, respectively. The photocatalytic degradation efficiency of CeO2 / ZnMn2O4 composite materials is significantly improved because the Z-type heterojunction formed by CeO2 and ZnMn2O4 is conducive to the rapid transfer of photogenerated carriers, inhibits the combination of photogenerated electron-hole pairs, and generates active oxidative species with enhanced oxidation ability.

[0070] Table 1. Photodegradation rate of tannic acid by materials in each experimental group

[0071] Time (min) comparison <![CDATA[ZnMn2O4]]> <![CDATA[CeO2]]> Example 1 Example 2 Example 3 -30 (dark reaction) 0％ 0％ 0％ 0％ 0％ 0％ 0 0.1％ 46.7％ 35.9％ 62.4％ 75.9％ 51.9％ 30 0.4％ 64.4％ 40.7％ 89.1％ 94.3％ 86.5％ 60 0.6％ 76.7％ 46.8％ 99.0％ 97.8％ 93.3％ 90 0.7％ 84.7％ 48.0％ 100.0％ 98.0％ 93.8％ 120 0.8％ 89.1％ 50.1％ 100.0％ 98.8％ 94.5％ 150 0.9％ 89.3％ 51.3％ 100.0％ 99.5％ 95.1％

[0072] The above examples merely illustrate several preferred embodiments of the present invention, and the detailed descriptions should not be construed as limiting the scope of the present invention. Any variations and equivalent modifications made in accordance with the present invention, without departing from the technical concepts and features of the present invention, fall within the scope of protection of the present invention.

Claims

1. A method for preparing a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst, characterized in that: The following steps are involved: (1) Preparation of ZnMn2O4: Zinc acetate (CH3COO)2Zn·2H2O and manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution and stirred until completely dissolved to obtain solution A; Add oxalic acid H2C2O4·2H2O to ethanol-water solution and stir until completely dissolved to obtain solution B; Quickly pour solution A into solution B, heat and stir to obtain a mixed solution, and after the mixed solution is cooled to room temperature, filter, wash and dry to obtain precursor A; The precursor A is calcined to obtain ZnMn2O4 with a long strip morphology; (2) Preparation of CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst: The ZnMn2O4 obtained in step (1) is added to the cerium nitrate solution and stirred thoroughly to be uniformly dispersed in the cerium nitrate solution; then 25% ammonia water is added dropwise, heated and stirred to obtain a precipitated mixture, and after the reaction, the precipitated mixture is cooled to room temperature, filtered, washed and dried to obtain a precursor B, and the precursor B is calcined to obtain a CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst.

2. The preparation method according to claim 1, characterized in that In step (1), the total metal ion concentration in the solution A is 0.02 to 0.16 mol / L.

3. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of zinc acetate to manganese acetate is 1:2, and the molar ratio of oxalic acid to zinc acetate is 3 to 3.6:

1.

4. The preparation method according to claim 1, characterized in that In step (1), the heating and stirring are performed at a temperature of 50 to 60° C., a stirring rate of 500 to 1000 r / min, and a stirring time of 2 to 2.5 h.

5. The preparation method according to claim 1, characterized in that In step (1), the volume ratio of ethanol to water in the ethanol-water solution is 9:

1.

6. The preparation method according to claim 1, characterized in that In step (2), the concentration of the cerium nitrate solution is 3.0-7.5 mmol / L, the amount of ZnMn2O4 added is 1.25-2 g / L, and the volume ratio of the 25% ammonia solution added dropwise to the cerium nitrate solution is 0.01-1:

40.

7. The preparation method according to claim 1, characterized in that In step (2), the heating and stirring are performed at a temperature of 40 to 50° C., a stirring rate of 500 to 700 r / min, and a stirring time of 2 to 2.5 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that In step (1) and step (2), the precursor A and the precursor B are respectively heated to 450-550° C. at a heating rate of 2-10° C. / min for calcination, and the calcination holding time is 2-2.5 hours.

9. A CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8, wherein the mass ratio of CeO2 to ZnMn2O4 is 0.25 to 1:

1.

10. Use of the CeO2 / ZnMn2O4 Z-type heterojunction photocatalyst material according to claim 9 in photocatalytic degradation of tannic acid.

Images