An AC / CeO2 / ZnMn2O4 composite photocatalyst and its preparation method and application

Abstract

The present invention discloses an AC / CeO2 / ZnMn2O4 composite photocatalyst, its preparation method, and application. The AC / CeO2 / ZnMn2O4 composite photocatalyst is composed of AC, CeO2, and ZnMn2O4, wherein the mass ratio of CeO2 to ZnMn2O4 is 0.25 to 1:1, and the mass ratio of AC to CeO2 / ZnMn2O4 is 0.1:1 to 0.5:1. The AC / CeO2 / ZnMn2O4 composite photocatalyst is prepared in three 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; and then, a precipitated mixture is obtained by precipitation with ammonia water. CeO2 / ZnMn2O4 is thermally decomposed to obtain the precipitated mixture. Finally, AC and CeO2 / ZnMn2O4 are combined by ultrasonic treatment to obtain the AC / CeO2 / ZnMn2O4 composite photocatalyst. The composite photocatalyst combines traditional adsorption and photocatalytic processes to achieve 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 in particular relates to an AC / CeO2 / ZnMn2O4 composite photocatalyst and a preparation method and application thereof. Background Art

[0002] Numerous adsorbents, such as activated carbon, zeolite, bentonite, and silica, have been used to remove many pollutants, including heavy metals and organic compounds from industrial wastewater. Adsorption has attracted numerous researchers to develop this technology due to its simplicity, low toxicity, cost-effectiveness, and ease of integration with other methods. For example, excess tannic acid used to recover germanium in the hydrometallurgical zinc smelting process is removed by activated carbon adsorption. However, this method can only adsorb a certain amount of tannic acid, failing to degrade and reuse it, and can even easily cause secondary pollution after use. In recent years, photocatalytic technology has attracted the attention of increasing numbers of researchers due to its clean and efficient advantages in organic matter degradation. Summary of the Invention

[0003] In order to solve the technical problems and deficiencies in the prior art, the object of the present invention is to provide a composite photocatalyst that can efficiently degrade tannic acid and has recycling capabilities.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing an AC / CeO2 / ZnMn2O4 composite photocatalyst, comprising the following steps:

[0006] (1) Preparation of ZnMn2O4:

[0007] 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;

[0008] Add oxalic acid H2C2O4·2H2O to ethanol-water solution and stir until completely dissolved to obtain solution B;

[0009] 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;

[0010] The precursor A was placed in a tube furnace for high-temperature calcination to obtain ZnMn2O4 with a long strip morphology;

[0011] (2) Preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst:

[0012] The ZnMn2O4 obtained in step (1) is added to a 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 heterojunction photocatalyst;

[0013] (3) Preparation of AC / CeO2 / ZnMn2O4 composite photocatalyst:

[0014] Activating activated carbon using alkaline solution;

[0015] The CeO2 / ZnMn2O4 heterojunction photocatalyst obtained in step (2) is added to deionized water and fully stirred and dispersed, and then alkali-activated activated carbon AC is added and fully stirred, and the mixed solution is ultrasonically treated at 35-45 kHz and an ultrasonic power of 150-180 W for 1-1.5 hours, and the ultrasonically treated suspension is filtered, washed, and dried to obtain an AC / CeO2 / ZnMn2O4 composite photocatalyst; wherein the mass ratio of alkali-activated activated carbon AC to CeO2 / ZnMn2O4 heterojunction photocatalyst is 0.1:1-0.5:1.

[0016] Preferably, in step (1), the volume ratio of ethanol to water in the ethanol-water solution is 9:1.

[0017] The volume ratio of ethanol to water in the precipitation medium plays a key role in the change in the aspect ratio of the ZnMn2O4 particles. By adopting the preferred embodiment of step (1) above, long strips of porous ZnMn2O4 with a large specific surface area and pore volume can be prepared. This facilitates sufficient contact between the photocatalyst and the degradation target, provides more mass transfer channels and reaction active sites, reduces the recombination rate of photogenerated electrons and holes, and improves the photocatalytic degradation efficiency.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The heating rate, calcination temperature and calcination time of step (1) and step (2) are the same.

[0023] 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.

[0024] 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.

[0025] Preferably, in step (3), the mass volume ratio (g / mL) of the activated carbon and the alkaline solution is 1:5 to 1:4, and the alkaline solution is a KOH solution with a concentration of 1% to 5% (w / w).

[0026] As an exemplary illustration, step (3) is specifically performed as follows:

[0027] Commercial activated carbon is added to a potassium hydroxide (KOH) solution of a certain volume concentration, stirred and mixed at room temperature for a period of time, and then filtered. The activated carbon filtrate is continuously washed with dilute hydrochloric acid and distilled water to make the pH of the activated carbon filtrate neutral, and then dried overnight to obtain alkali-activated AC; the CeO2 / ZnMn2O4 heterojunction photocatalyst in step (2) is added to deionized water (mass volume ratio is 0.1:30 to 0.1:20) and stirred and dispersed for 10 to 20 minutes, and then alkali-activated AC with a mass ratio of 0.1 to 1:2 to the CeO2 / ZnMn2O4 heterojunction photocatalyst is added and stirred for 20 to 30 minutes, and mixed with the above CeO2 / ZnMn2O4 suspension. Next, the mixed solution is ultrasonically treated at 35 to 45 kHz and an ultrasonic power of 150 to 180 W for 1 to 1.5 hours. Finally, the ultrasonically treated suspension is filtered, washed, and dried to obtain an AC / CeO2 / ZnMn2O4 composite photocatalyst.

[0028] In a second aspect, the present invention provides an AC / CeO2 / ZnMn2O4 composite photocatalyst material prepared by the aforementioned preparation method, wherein the mass ratio of CeO2 and ZnMn2O4 is 0.25 to 1:1, and the mass ratio of AC and CeO2 / ZnMn2O4 is 0.1:1 to 0.5:1.

[0029] In a third aspect, the present invention provides the use of the aforementioned AC / CeO2 / ZnMn2O4 composite photocatalyst material in photocatalytic degradation of tannic acid.

[0030] Compared with the prior art, the beneficial effects of the technical solution of the present invention include at least:

[0031] (1) The AC / CeO2 / ZnMn2O4 composite photocatalyst prepared by the present invention has a large specific surface area, excellent visible light response ability and photocatalytic activity, can efficiently adsorb and photodegrade tannic acid, and has better photocatalytic degradation performance than pure ZnMn2O4 and CeO2 / ZnMn2O4 photocatalysts.

[0032] (2) The AC / CeO2 / ZnMn2O4 composite photocatalyst prepared by the present invention has good stability and recyclability.

[0033] (3) The AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in this invention exhibits a highly efficient removal rate for tannic acid through a combined adsorption and photocatalytic reaction process. AC plays a key role as a charge carrier transfer pathway and a "bridge" between tannic acid and the catalyst. This composite photocatalyst has considerable practical value and potential application prospects for removing tannic acid from zinc leachate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 These are the field scanning electron microscope photograph (a), SEM diagram (b), C, Mn, Ce, and Zn element distribution diagram (cf), and X-ray diffraction patterns (g) of AC, CeO2 / ZnMn2O4, and AC / CeO2 / ZnMn2O4 of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1.

[0035] Figure 2 This is a field scanning electron microscope photograph of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1.

[0036] Figure 3 This is the UV-visible diffuse reflectance spectrum of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1.

[0037] Figure 4 1 is the nitrogen adsorption-desorption curve and pore size distribution diagram of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1.

[0038] Figure 5 This is a curve showing the change of tannic acid concentration over time in the photocatalytic degradation reaction of the samples prepared in Examples 1 to 3.

[0039] Figure 6This is a bar chart of the cyclic stability of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0040] 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.

[0041] The present invention composites AC and CeO2 / ZnMn2O4 heterojunction photocatalysts to construct an AC / CeO2 / ZnMn2O4 composite photocatalyst. The material exhibits enhanced visible light absorption capacity and photogenerated electron-hole separation efficiency, improves the photocatalytic efficiency of tannic acid, and has excellent recycling performance, which is of great significance for the application of photocatalytic removal of tannic acid in zinc leachate.

[0042] The technical solution of the present invention is described below in conjunction with specific embodiments:

[0043] Comparative Example 1:

[0044] The preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst includes the following steps:

[0045] (1) Preparation of ZnMn2O4:

[0046] 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 (90 mL + 10 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (45 mL + 5 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.

[0047] (2) Preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst:

[0048] 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 tubular furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 heterojunction photocatalyst.

[0049] Example 1:

[0050] An AC / CeO2 / ZnMn2O4 composite photocatalyst is prepared by the following preparation steps:

[0051] (1) Preparation of ZnMn2O4:

[0052] 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 (90 mL + 10 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (45 mL + 5 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.

[0053] (2) Preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst:

[0054] 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 tubular furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 heterojunction photocatalyst.

[0055] (3) AC / CeO2 / ZnMn2O4 composite photocatalyst

[0056] 25g of AC was added to 100mL of a 1% KOH solution and stirred continuously at room temperature for 24 hours. The mixture was then filtered and washed repeatedly with dilute hydrochloric acid and distilled water until the pH of the AC filtrate was neutral. The mixture was then dried overnight to obtain an alkali-activated AC. 0.10g of the CeO2 / ZnMn2O4 heterojunction photocatalyst was added to 20mL of deionized water and stirred thoroughly for 10-20 minutes. 0.03g of the alkali-activated AC was then added and stirred continuously for 20-30 minutes before mixing with the CeO2 / ZnMn2O4 suspension. The mixed solution was then sonicated at 45kHz and 180W of ultrasonic power for 1 hour. Finally, the sonicated suspension was filtered, washed, and dried to obtain the AC / CeO2 / ZnMn2O4 composite photocatalyst.

[0057] The X-ray diffraction patterns and EDX elemental analysis scans of the samples obtained in Example 1 of the present invention and Comparative Example 1 are shown in FIG. Figure 1 . X-ray diffraction patterns show that both the CeO2 / ZnMn2O4 composite material and the AC / CeO2 / ZnMn2O4 composite photocatalyst have obvious characteristic peaks of CeO2 and ZnMn2O4; EDX elemental analysis scanning patterns show that the middle layer of the long block AC / CeO2 / ZnMn2O4 composite photocatalyst only shows C and O elements, and Ce, Zn and Mn elements are evenly distributed on the surface of the AC / CeO2 / ZnMn2O4 composite photocatalyst, indicating that CeO2 / ZnMn2O4 particles are relatively evenly distributed on the AC surface. In summary, Example 1 of the present invention prepared an AC / CeO2 / ZnMn2O4 composite photocatalyst with higher purity.

[0058] The field scanning electron microscope photo of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1 of the present invention is shown in detail. Figure 2 ,Depend on Figure 2 It can be seen that a large number of tiny spherical CeO2 / ZnMn2O4 particles are gathered on the surface of the AC / CeO2 / ZnMn2O4 composite photocatalyst. The distribution of CeO2 / ZnMn2O4 photocatalyst particles on the surface of the AC / CeO2 / ZnMn2O4 composite photocatalyst produces more pore structures and provides more active sites, thereby improving the adsorption and photocatalytic ability and effectively removing tannic acid.

[0059] The UV-visible diffuse reflectance spectrum of the sample prepared in Example 1 of the present invention is shown in detail. Figure 3 ,Depend on Figure 3It can be seen that the AC / CeO2 / ZnMn2O4 composite photocatalyst has significantly enhanced absorption in the visible light range of 400-800nm ​​compared with ZnMn2O4 and CeO2 / ZnMn2O4 heterojunction photocatalysts, which is beneficial to the photocatalytic reaction under visible light.

[0060] The nitrogen adsorption and desorption curve of the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Example 1 of the present invention is shown in detail. Figure 4 ,Depend on Figure 4 It can be seen that the adsorption-desorption curve of AC / CeO2 / ZnMn2O4 composite material is a type IV isotherm, and the adsorption hysteresis loop belongs to H3 type, indicating that the sample has a mesoporous structure. AC / CeO2 / ZnMn2O4 has a large specific surface area and pore volume, which are 111.842m 2 ·g -1 and 0.176cm 3 ·g -1 , providing a large number of surface active sites for photocatalytic reactions, which is beneficial to the improvement of adsorption and photocatalytic efficiency.

[0061] Example 2:

[0062] An AC / CeO2 / ZnMn2O4 composite photocatalyst is prepared by the following preparation steps:

[0063] (1) Preparation of ZnMn2O4:

[0064] 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 (90 mL + 10 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (45 mL + 5 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.

[0065] (2) Preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst:

[0066] 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 tubular furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 heterojunction photocatalyst.

[0067] (3) AC / CeO2 / ZnMn2O4 composite photocatalyst

[0068] 25g of AC was added to 100mL of a 1% KOH solution and stirred continuously at room temperature for 24 hours. The mixture was then filtered and washed repeatedly with dilute hydrochloric acid and distilled water until the pH of the AC filtrate was neutral. The mixture was then dried overnight to obtain an alkali-activated AC. 0.10g of the CeO2 / ZnMn2O4 heterojunction photocatalyst was added to 20mL of deionized water and stirred thoroughly for 10-20 minutes. Then, 0.01g of the alkali-activated AC was added and stirred continuously for 20-30 minutes before mixing with the CeO2 / ZnMn2O4 suspension. The mixed solution was then sonicated at 45kHz and 180W of ultrasonic power for 1 hour. Finally, the sonicated suspension was filtered, washed, and dried to obtain the AC / CeO2 / ZnMn2O4 composite photocatalyst.

[0069] Example 3:

[0070] An AC / CeO2 / ZnMn2O4 composite photocatalyst is prepared by the following preparation steps:

[0071] (1) Preparation of ZnMn2O4:

[0072] 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 (90 mL + 10 mL) and stirred until completely dissolved to obtain solution A. Similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (45 mL + 5 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 porcelain boat and calcined in a tube furnace. It was kept at 450°C for 2 h at a heating rate of 2°C / min to finally obtain ZnMn2O4 with a long strip morphology.

[0073] (2) Preparation of CeO2 / ZnMn2O4 heterojunction photocatalyst:

[0074] 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 tubular furnace and kept at 450°C for 2 h at a heating rate of 2°C / min to obtain a CeO2 / ZnMn2O4 heterojunction photocatalyst.

[0075] (3) AC / CeO2 / ZnMn2O4 composite photocatalyst

[0076] 25g of AC was added to 100mL of a 1% KOH solution and stirred continuously at room temperature for 24 hours. The mixture was then filtered and washed repeatedly with dilute hydrochloric acid and distilled water until the pH of the AC filtrate was neutral. The mixture was then dried overnight to obtain an alkali-activated AC. 0.10g of the CeO2 / ZnMn2O4 heterojunction photocatalyst was added to 20mL of deionized water and stirred thoroughly for 10-20 minutes. Then, 0.05g of the alkali-activated AC was added and stirred continuously for 20-30 minutes before mixing with the CeO2 / ZnMn2O4 suspension. The mixed solution was then ultrasonically treated at 45kHz and 180W of power for 1 hour. Finally, the ultrasonically treated suspension was filtered, washed, and dried to obtain the AC / CeO2 / ZnMn2O4 composite photocatalyst.

[0077] Application examples:

[0078] The CeO2 / ZnMn2O4 heterojunction photocatalyst prepared in Comparative Example 1 and the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Examples 1 to 3 were used to catalytically degrade tannic acid under simulated sunlight.

[0079] The specific operations are as follows:

[0080] (1) Control group: Without adding any catalyst, 50 mL of 200 mg·L -1 The samples were treated in dark with tannic acid solution for 30 minutes and then irradiated under a xenon lamp for 150 minutes.

[0081] (2) CeO2 / ZnMn2O4 group: 20 mg of the CeO2 / ZnMn2O4 heterojunction photocatalyst prepared in Comparative Example 1 was weighed and added to a quartz test tube, and then 50 mL of 200 mg·L -1The 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.

[0082] (3) AC / CeO2 / ZnMn2O4 group: 20 mg of the AC / CeO2 / 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.

[0083] Application Example 1:

[0084] Tannic acid was photocatalytically degraded under simulated sunlight using a tannic acid solution without any catalyst (control), ZnMn2O4, the CeO2 / ZnMn2O4 heterojunction photocatalyst prepared in Comparative Example 1, and the AC / CeO2 / ZnMn2O4 composite photocatalyst prepared in Examples 1 to 3.

[0085] Weigh 20 mg of the sample to be tested and add it to a quartz test tube, then measure 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 500W xenon lamp was then used to conduct the photocatalytic reaction under simulated sunlight. 2mL of the reaction solution was sampled at regular intervals and filtered through a 0.22μm filter membrane. The absorbance was measured using a colorimetric method to determine the residual tannic acid concentration and calculate the reduction rate (see Table 1).

[0086] Table 1. Photodegradation rates of tannic acid in Examples 1-3

[0087] Time (min) comparison <![CDATA[ZnMn2O4]]> Comparative Example 1 Example 1 Example 2 Example 3 -30 (dark reaction) 0％ 0％ 0％ 0％ 0％ 0％ 0 0.1％ 46.7％ 62.4％ 68.1％ 70.0％ 64.8％ 15 0.3％ 55.8％ 80.3％ 89.9％ 82.8％ 84.18％ 30 0.4％ 64.4％ 89.1％ 96.0％ 95.6％ 97.18％ 45 0.5％ 70.8％ 98.4％ 98.2％ 98.2％ 98.7％ 60 0.6％ 76.7％ 99.0％ 100％ 99.6％ 99.3％

[0088] Depend on Figure 5It can be seen that the photocatalytic removal rate of tannic acid by the CeO2 / ZnMn2O4 heterojunction photocatalyst prepared in Comparative Example 1 during the dark adsorption process is 99% within 60 minutes, and the photocatalytic removal rates of tannic acid by the AC / CeO2 / ZnMn2O4 composite photocatalysts prepared in Examples 1 to 3 can reach 100%, 99.6% and 99.3% respectively within 60 minutes, indicating that the AC / CeO2 / ZnMn2O4 composite photocatalysis combined with the adsorption and photocatalytic reaction process shows an efficient removal rate of tannic acid, among which AC plays a key role as a transfer path for charge carriers and a "bridge" between tannic acid and the catalyst.

[0089] Application Example 2:

[0090] The AC / CeO2 / ZnMn2O4 composite photocatalyst of the first photoreaction in Application Example 1 was centrifuged and dried to obtain the AC / CeO2 / ZnMn2O4 composite photocatalyst of the first cycle. The AC / CeO2 / ZnMn2O4 composite photocatalyst of the first cycle was then added to 50 mL of 200 mg·L -1 The tannic acid solution was poured into a quartz test tube containing the catalyst, and ultrasonically dispersed for 5 minutes and then dark treated for 30 minutes to allow the catalyst to reach adsorption equilibrium. Then a 500W xenon lamp was turned on and the photocatalytic reaction was carried out under simulated sunlight for 60 minutes. The reduction rate was calculated as the first cycle degradation rate. This was repeated four times. The degradation rate of each cycle was as follows: Figure 6 As shown. Figure 6 It can be seen that after four cycles, the degradation rate of tannic acid by AC / CeO2 / ZnMn2O4 composite photocatalyst is still 86.6%, indicating that it has good cyclic stability.

[0091] 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 an AC / CeO2 / ZnMn2O4 composite 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 heterojunction photocatalyst: The ZnMn2O4 obtained in step (1) is added to a 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 heterojunction photocatalyst; (3) Preparation of AC / CeO2 / ZnMn2O4 composite photocatalyst: Activating activated carbon using alkaline solution; The CeO2 / ZnMn2O4 heterojunction photocatalyst obtained in step (2) Add deionized water and stir thoroughly to disperse, then add alkali-activated activated carbon AC and stir thoroughly, ultrasonicate the mixed solution at 35-45 kHz and 150-180 W ultrasonic power for 1-1.5 hours, filter, wash and dry the ultrasonicated suspension to obtain AC / CeO2 / ZnMn2O4 composite photocatalyst; Wherein, the mass ratio of alkali-activated activated carbon AC and CeO2 / ZnMn2O4 composite material is 0.1:1-0.5:

1.

2. 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.

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 metal ion concentration in the solution A is 0.02 to 0.16 mol / L.

5. 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.

6. The preparation method according to claim 1, 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.

7. 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.

8. 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.

9. The preparation method according to claim 1, characterized in that In step (3), the mass volume ratio (g / mL) of the activated carbon and the alkaline solution is 1:5 to 1:4, and the alkaline solution is a KOH solution with a concentration of 1% to 5% (w / w).

10. An AC / CeO2 / ZnMn2O4 composite photocatalyst material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9, wherein the mass ratio of CeO2 and ZnMn2O4 is 0.25 to 1:1, and the mass ratio of AC and CeO2 / ZnMn2O4 is 0.1:1 to 0.5:

1.

11. Use of the AC / CeO2 / ZnMn2O4 composite photocatalyst material according to claim 10 in photocatalytic degradation of tannic acid.

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