Preparation method and application of ZnO-TiO2 composite aerogel

Abstract

The present invention discloses a preparation method and application of ZnO-TiO2 composite aerogel. The method comprises the following steps: 1) Dissolve tetrabutyl titanate, silver nitrate, and nitric acid respectively and then mix and stir them to obtain a clear solution; 2) Place the clear solution in an oven and process it to obtain TiO2 wet gel; 3) Add an organic solvent to the TiO2 wet gel and displace it to obtain TiO2 alcohol gel; 4) Perform supercritical drying on the TiO2 alcohol gel to obtain TiO2 aerogel; 5) Place the TiO2 aerogel and Zn powder in the low-temperature zone and high-temperature zone of a two-temperature-zone tube furnace respectively for temperature rise treatment, and continuously introduce a composite atmosphere of O2 and Ar to prepare a black ZnO-TiO2 composite aerogel; 6) Place the black ZnO-TiO2 composite aerogel in a tube furnace and calcine it under a composite atmosphere of H2 and Ar to obtain a hydrogenated modified ZnO-TiO2 composite aerogel. The composite aerogel provided by the present invention is applied in the field of industrial wastewater treatment and has excellent photocatalytic efficiency and antibacterial rate.

Description

Technical Field

[0001] The invention relates to a composite aerogel, and in particular to a preparation method and application of a ZnO-TiO2 composite aerogel. Background Art

[0002] The rise of industrial technology is the driving force of urban development, but the problem that comes with it is the generation of more wastewater and environmental pollution. Due to the high organic content, complex composition, easy breeding of bacteria, and difficulty in degradation of industrial wastewater, traditional treatment methods such as coagulation sedimentation, adsorption and other processes are not ideal for industrial wastewater treatment. Therefore, there is an urgent need to develop efficient and energy-saving industrial wastewater treatment technology. TiO2 aerogel is a mature product of current photocatalytic products. Although it has a high specific surface area and can greatly promote the degradation of wastewater, its absorption and utilization wavelength range of light is narrow, and the separation efficiency of photogenerated carriers and holes is low, which limits the development of TiO2 aerogel in the fields of antibacterial and photocatalysis.

[0003] CN114100602A discloses a method for synthesizing pure phase Zn2Ti3O8 aerogel, which is obtained by sol-gel method and calcination process, solving the problem of less active sites of original TiO2 aerogel and improving its photocatalytic effect. However, Zn2Ti3O8 in this patent is a metastable phase, which is easy to decompose at high temperature, and the bandgap width of TiO2 aerogel prepared by this method is increased, which increases the difficulty of electron transition and increases the energy required for photocatalysis.

[0004] Feng et al. [Heterojunction Structure ZnO / TiO2 Nanorods with Enhanced Photoelectrochemical Properties. Key Engineering Materials. 2017, 726: 333-337.] prepared a ZnO / TiO2 heterojunction by a hydrothermal method and found that the composite of the ZnO / TiO2 heterostructure can improve the surface-to-volume ratio and scattering of incident light. However, the hydrothermal method only produced ZnO / TiO2 nanorods, which is still a long way from application.

[0005] Therefore, it is of great significance to develop TiO2 composite aerogels with improved photocatalytic efficiency and antibacterial rate. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a preparation method and application of ZnO-TiO2 composite aerogel.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a ZnO-TiO2 composite aerogel comprises the following steps:

[0009] 1) Dissolve tetrabutyl titanate, silver nitrate and nitric acid respectively, mix and stir to obtain a clear solution, the molar ratio of the three is 1:(0.001-0.01):(0.1-7);

[0010] 2) placing the clear solution in an oven and reacting at 30-60° C. for 8-20 hours to obtain a TiO2 wet gel;

[0011] 3) adding an organic solvent to the TiO2 wet gel to perform solvent replacement to obtain a TiO2 alcohol gel;

[0012] 4) supercritically drying the obtained TiO2 alcohol gel to obtain white block TiO2 aerogel;

[0013] 5) placing the TiO2 aerogel and Zn powder in the low temperature zone and the high temperature zone of a dual-temperature zone tubular furnace respectively for heating treatment, and continuously introducing a composite atmosphere of O2 and Ar during the treatment process to prepare a black ZnO-TiO2 composite aerogel;

[0014] 6) The black ZnO-TiO2 composite aerogel is placed in a tubular furnace and calcined in a composite atmosphere of H2 and Ar to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0015] As a preferred embodiment, the solvent in step 1) is a mixture of one or more of water, methanol, ethanol and isobutanol.

[0016] As a preferred embodiment, in step 1), the mixing and stirring time of tetrabutyl titanate, silver nitrate and nitric acid is 15 to 20 minutes, and the stirring speed is 200 to 500 r / min.

[0017] As a preferred embodiment, the organic solvent in step 3) is one or more of ethanol, methanol, isopropanol, acetone, and isopropyl alcohol;

[0018] Preferably, in step 3), the organic solvent is replaced 2 to 6 times, and each replacement takes 12 to 48 hours.

[0019] The so-called solvent replacement in the present invention is to remove the original solvent in the wet gel by soaking in an organic solvent to obtain an alcohol gel.

[0020] As a preferred embodiment, the supercritical drying method in step 4) is one of ethanol supercritical or carbon dioxide supercritical methods.

[0021] The process conditions for supercritical drying of ethanol can be: the kettle pressure is controlled at 7-11 MPa, the temperature is 200-275°C, the reaction time is 10-15 hours, and the protective gas is N2. The process conditions for supercritical drying of CO2 can be: the kettle pressure is controlled at 8-12 MPa, the reaction temperature is 45-55°C, and the reaction time is 8-15 hours.

[0022] As a preferred embodiment, in step 5), the mass ratio of TiO2 aerogel to Zn powder is 1:(0.01-0.6);

[0023] Preferably, the Zn powder is 400-1000 mesh Zn powder.

[0024] As a preferred embodiment, the temperature of the low temperature zone of the double temperature zone tubular furnace is 200-400°C, the temperature of the high temperature zone is 400-800°C, and the treatment time in the furnace is 1-3h.

[0025] As a preferred embodiment, in the composite atmosphere of step 5), the volume ratio of O2 to Ar is 0.01-0.05:1, and the flow rate of the composite atmosphere is 10-100 sccm.

[0026] In the embodiment of the present invention, Zn powder and TiO2 gel are vapor-deposited in a dual-temperature zone tubular furnace to generate a composite aerogel in which ZnO is coated on the surface of TiO2, wherein the oxygen part of ZnO formed in a weak oxygen atmosphere comes from TiO2, so that a large number of oxygen defects are formed on its surface, which can improve the separation and transmission rate of electron-hole pairs and greatly improve the photocatalytic effect of TiO2 itself. In addition, the composite aerogel structure in which ZnO is coated on the surface of TiO2 has a higher photocatalytic efficiency than traditional TiO2 aerogel.

[0027] The advantage of the present invention over existing TiO2 aerogels is that after vapor deposition, the color of the composite aerogel turns black, which can more effectively absorb thermal energy in light, thereby providing energy for electron transition and improving photocatalytic efficiency.

[0028] As a preferred embodiment, in step 6), the calcination temperature in the tube furnace is 300-700° C., and the calcination time is 1-3 hours.

[0029] As a preferred embodiment, in the composite atmosphere of step 6), the volume ratio of H2 to Ar is 0.01-0.2:1, and the composite atmosphere flow rate is 10-100 sccm. Hydrogenation modification can significantly increase the light absorption wavelength of the composite aerogel, narrow the band gap, and reduce the electron transition energy level.

[0030] The present invention also provides an application of the ZnO-TiO2 composite aerogel prepared by the method described above in the field of industrial wastewater treatment.

[0031] The present invention combines the gel method with the vapor deposition method to prepare the ZnO-TiO2 composite aerogel, wherein the inner and outer layers between ZnO and TiO2 are arranged in order to form a regular heterojunction, which can limit the electron-hole recombination behavior and extend the carrier life, and has the advantages of high photocatalytic efficiency and good antibacterial property. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the EDS spectrum of the ZnO-TiO2 composite aerogel prepared in Example 1.

[0033] Figure 2 This is the SEM photograph of the ZnO-TiO2 composite aerogel prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0035] Unless otherwise specified, the raw materials involved in the following examples of the present invention were purchased from commercial sources. Among them, Zn powder had a mesh size of 600 mesh and was purchased from Aladdin.

[0036] The main test methods involved in the following embodiments of the present invention are as follows:

[0037] (1) The pore structure of aerogels was measured using a BET surface analyzer.

[0038] (2) The antibacterial property of aerogel was tested by natural colony method: the aerogel was ground into powder in a mortar and pestle, diluted with water to 100 ppm, 9 ml of aerogel was sterilized by irradiation under a 20 W ultraviolet lamp for 24 h, and then diluted with 10 3 The strain was multiplied by 100 μL and placed in a constant temperature shaker for 24 hours. The temperature was set to 37°C and the speed was 250 rpm. After culturing, 100 μL of the mixture was evenly spread on the sterilized agar medium using a pipette and cultured in a 37°C incubator for 24 hours. The number of colonies was determined by counting method, and the blank sample without aerogel was used as the control group. The sterilization rate (W) of aerogel was determined by the following formula.

[0039] W=(N0-N) / N0×100%

[0040] Where N0 is the number of viable bacteria in the test group without antibacterial materials, and N is the number of viable bacteria in the test group with antibacterial materials.

[0041] (3) Photocatalytic degradation performance of aerogel: The aerogel sample (100 mg) was mixed with methyl orange solution (100 mL, 0.1 mol / L), stirred in the dark for 30 min to reach adsorption equilibrium, and then irradiated with a 300 W Hg lamp. In order to avoid interference from solvent evaporation, the solution was cooled with a water circulation jacket of the reactor. The concentration of the methyl orange aqueous solution was measured at 464 nm using a UV-visible spectrophotometer, and its degradation rate was calculated.

[0042] [Example 1]

[0043] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.002:5, and stirred at 400 r / min for 20 minutes to obtain a clear solution.

[0044] The solution was placed in a 40°C oven for constant temperature reaction for 16 hours to obtain TiO2 wet gel.

[0045] Anhydrous ethanol sufficient to immerse the wet TiO2 gel was added, aged for 48 hours, filtered, and the operation was repeated 5 times to separate the solid to obtain the TiO2 alcohol gel.

[0046] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using the ethanol supercritical method, wherein the pressure in the autoclave was controlled at 10 MPa and the temperature was 220°C. The sample was dried for 10 h in a N2 atmosphere to obtain white TiO2 aerogel.

[0047] A mixed atmosphere of O2 and Ar in a volume ratio of 0.03:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 10 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.3, the temperature in the low-temperature zone was 300°C, and the temperature in the high-temperature zone was 600°C. After vapor deposition treatment for 1.5 hours, a black ZnO-TiO2 composite aerogel was obtained.

[0048] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar in a volume ratio of 0.1:1 was introduced into the tubular furnace at a flow rate of 30 sccm. The mixture was calcined at 500°C for 1.5 h to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0049] [Example 2]

[0050] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.008:6, and stirred at 400 r / min for 20 minutes to obtain a clear solution.

[0051] The solution was placed in a 55°C oven for constant temperature reaction for 18 hours to obtain TiO2 wet gel.

[0052] Anhydrous methanol was added to the TiO2 wet gel to submerge it, and the gel was aged for 24 hours. After filtering, the operation was repeated three times to separate the solid and obtain the TiO2 alcohol gel.

[0053] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using an ethanol supercritical method, wherein the pressure in the autoclave was controlled at 10 MPa and the temperature was 270°C. The sample was dried for 12 hours to obtain a white TiO2 aerogel.

[0054] A mixed atmosphere of O2 and Ar in a volume ratio of 0.05:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 30 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.6, the temperature in the low-temperature zone was 350°C, and the temperature in the high-temperature zone was 700°C. After vapor deposition treatment for 1 hour, black ZnO-TiO2 composite aerogel was obtained.

[0055] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar in a volume ratio of 0.1:1 was introduced into the tubular furnace at a flow rate of 20 sccm. The mixture was calcined at 600°C for 2h to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0056] [Example 3]

[0057] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.005:2, and stirred at 300 r / min for 15 minutes to obtain a clear solution.

[0058] The solution was placed in a 50°C oven for constant temperature reaction for 10 hours to obtain TiO2 wet gel.

[0059] Anhydrous methanol was added to the TiO2 wet gel to submerge it, and the gel was aged for 10 h. After filtering, the operation was repeated 4 times to separate the solid and obtain the TiO2 alcohol gel.

[0060] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using the ethanol supercritical method, wherein the pressure in the autoclave was controlled at 10 MPa, the temperature was 250°C, and it was dried for 12 hours under a N2 atmosphere to obtain white TiO2 aerogel.

[0061] A mixed atmosphere of O2 and Ar in a volume ratio of 0.01:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 80 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.1, the temperature in the low-temperature zone was 280°C, and the temperature in the high-temperature zone was 680°C. After vapor deposition treatment for 2 hours, a black ZnO-TiO2 composite aerogel was obtained.

[0062] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar with a volume ratio of 0.15:1 was introduced into the tubular furnace at a flow rate of 70 sccm. The mixture was calcined at 450°C for 1 hour to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0063] [Example 4]

[0064] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.004:3, and stirred at 500 r / min for 15 minutes to obtain a clear solution.

[0065] The solution was placed in a 50°C oven for constant temperature reaction for 12 hours to obtain TiO2 wet gel.

[0066] Anhydrous ethanol sufficient to immerse the wet TiO2 gel was added, aged for 36 hours, filtered, and the operation was repeated twice to separate the solid to obtain the TiO2 alcohol gel.

[0067] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using the ethanol supercritical method. The pressure in the autoclave was controlled at 10 MPa and the temperature was 255°C. It was dried for 13 hours under a N2 atmosphere to obtain white TiO2 aerogel.

[0068] A mixed atmosphere of O2 and Ar in a volume ratio of 0.02:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 40 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.5, the temperature in the low-temperature zone was 280°C, and the temperature in the high-temperature zone was 530°C. The vapor deposition treatment was carried out for 1.5 hours to obtain a black ZnO-TiO2 composite aerogel.

[0069] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar with a volume ratio of 0.05:1 was introduced into the tubular furnace at a flow rate of 40 sccm. The mixture was calcined at 400°C for 2.5 hours to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0070] [Example 5]

[0071] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.002:3, and stirred at 350 r / min for 20 minutes to obtain a clear solution.

[0072] The solution was placed in a 45°C oven for constant temperature reaction for 15 hours to obtain TiO2 wet gel.

[0073] Anhydrous methanol was added to the TiO2 wet gel to submerge it, and the gel was aged for 20 h. After filtering, the operation was repeated three times to separate the solid and obtain the TiO2 alcohol gel.

[0074] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using a supercritical carbon dioxide method, wherein the pressure in the autoclave was controlled at 10 MPa and the temperature was 50°C. The sample was dried for 10 h in a CO2 atmosphere to obtain a white TiO2 aerogel.

[0075] A mixed atmosphere of O2 and Ar in a volume ratio of 0.03:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 30 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.2, the temperature in the low-temperature zone was 300°C, and the temperature in the high-temperature zone was 580°C. The vapor deposition treatment was carried out for 1.5 hours to obtain a black ZnO-TiO2 composite aerogel.

[0076] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar in a volume ratio of 0.1:1 was introduced into the tubular furnace at a flow rate of 30 sccm. The mixture was calcined at 550°C for 1.5 h to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0077] [Example 6]

[0078] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed with an aqueous solution of silver nitrate and nitric acid in a molar ratio of 1:0.005:2, and stirred at 500 r / min for 15 minutes to obtain a clear solution.

[0079] The solution was placed in a 30°C oven for constant temperature reaction for 18 hours to obtain TiO2 wet gel.

[0080] Anhydrous ethanol sufficient to immerse the wet TiO2 gel was added, aged for 24 hours, filtered, and the operation was repeated three times to separate the solid to obtain the TiO2 alcohol gel.

[0081] The TiO2 alcohol gel was placed in an autoclave and the sample was dried using a supercritical carbon dioxide method, wherein the pressure in the autoclave was controlled at 10 MPa and the temperature was 45°C. The sample was dried for 13 hours in a CO2 atmosphere to obtain a white TiO2 aerogel.

[0082] A mixed atmosphere of O2 and Ar in a volume ratio of 0.02:1 was introduced into a double-temperature zone tubular furnace at a flow rate of 30 sccm, and the TiO2 aerogel was placed in the low-temperature zone of the double-temperature zone tubular furnace, and the zinc powder was placed in the high-temperature zone. The mass ratio of TiO2 aerogel to zinc powder was 1:0.3, the temperature in the low-temperature zone was 300°C, and the temperature in the high-temperature zone was 700°C. After vapor deposition treatment for 1 hour, black ZnO-TiO2 composite aerogel was obtained.

[0083] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar with a volume ratio of 0.05:1 was introduced into the tubular furnace at a flow rate of 30 sccm. The mixture was calcined at 500°C for 1 hour to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0084] [Comparative Example 1]

[0085] The hydrogenated modified ZnO-TiO2 composite aerogel was prepared by gel method:

[0086] After tetrabutyl titanate is dissolved in anhydrous ethanol, it is mixed and stirred with aqueous solutions of silver nitrate, zinc nitrate and nitric acid in a molar ratio of 1:0.002:0.5:5, and stirred at 400 r / min for 20 minutes to obtain a clear solution.

[0087] The solution was placed in a 40°C oven for constant temperature reaction for 16 hours to obtain ZnO-TiO2 wet gel.

[0088] Anhydrous ethanol sufficient to immerse the ZnO-TiO2 wet gel was added, aged for 48 hours, filtered, and the operation was repeated 5 times to separate the solid to obtain the ZnO-TiO2 alcohol gel.

[0089] The ZnO-TiO2 alcohol gel was placed in an autoclave and the sample was dried using the ethanol supercritical method. The pressure in the autoclave was controlled at 10 MPa and the temperature was 220°C. The sample was dried for 10 h in a N2 atmosphere to obtain a white ZnO-TiO2 aerogel.

[0090] The composite aerogel was placed in a tubular furnace, and a mixed atmosphere of H2 and Ar in a volume ratio of 0.1:1 was introduced into the tubular furnace at a flow rate of 30 sccm. The mixture was calcined at 500°C for 1.5 h to obtain a hydrogenated modified ZnO-TiO2 composite aerogel.

[0091] [Comparative Example 2]

[0092] The hydrogenated modified ZnO-TiO2 composite aerogel was prepared in a method substantially the same as that in Example 1, except that the mixed atmosphere introduced into the dual-temperature zone tubular furnace was O2 and Ar in a volume ratio of 1:1.

[0093] [Comparative Example 3]

[0094] The hydrogenated ZnO-TiO2 composite aerogel was prepared in a method substantially the same as that in Example 1, except that the black ZnO-TiO2 composite aerogel prepared in the dual-temperature zone tubular furnace was not hydrogenated.

[0095] [Comparative Example 4]

[0096] The hydrogenated modified ZnO-TiO2 composite aerogel was prepared in a method substantially the same as that in Example 1, except that when the TiO2 aerogel was treated in a dual-temperature zone tubular furnace, zinc powder was not placed in the high temperature zone.

[0097] The specific surface area, porosity and density of the aerogels prepared in each embodiment and comparative example were tested, and the results are shown in Table 1. In addition, the EDS spectrum and SEM photos of the composite aerogel prepared in Example 1 are shown in Table 1. Figure 1 , Figure 2 shown.

[0098] Table 1. Aerogel properties

[0099] <![CDATA[Specific surface area m 2 / g]]> Aperture nm <![CDATA[Pore volume cm 3 / g]]> Example 1 210 13.1 0.71 Example 2 204 12.5 0.68 Example 3 222 14.3 0.84 Example 4 189 15.3 0.64 Example 5 206 11.4 0.66 Example 6 186 10.8 0.55 Comparative Example 1 179 11.8 0.58 Comparative Example 2 202 12.0 0.67 Comparative Example 3 210 13.1 0.71 Comparative Example 4 224 17.2 0.83

[0100] The aerogels prepared in each embodiment and comparative example were respectively subjected to antibacterial test and photocatalytic degradation performance test, and the test results are shown in Table 2.

[0101] Table 2. Performance test results

[0102]

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a ZnO-TiO2 composite aerogel, characterized in that: The following steps are involved: 1) Dissolve tetrabutyl titanate, silver nitrate and nitric acid respectively, mix and stir to obtain a clear solution, wherein the molar ratio of the three is 1:(0.001-0.01):(0.1-7); 2) placing the clear solution in an oven and reacting at 30-60° C. for 8-20 hours to obtain a TiO2 wet gel; 3) adding an organic solvent to the TiO2 wet gel to perform solvent replacement to obtain a TiO2 alcohol gel; 4) supercritically drying the obtained TiO2 alcohol gel to obtain white block TiO2 aerogel; 5) The TiO2 aerogel and Zn powder are placed in the low temperature zone and the high temperature zone of a double temperature zone tubular furnace respectively for heating treatment, and a composite atmosphere of O2 and Ar is continuously introduced during the treatment process to prepare a black ZnO-TiO2 composite aerogel; in the composite atmosphere, the volume ratio of O2 and Ar is 0.01-0.05:1; the temperature of the low temperature zone of the double temperature zone tubular furnace is 200-400°C, and the temperature of the high temperature zone is 400-800°C; 6) placing the black ZnO-TiO2 composite aerogel in a tubular furnace and calcining it in a composite atmosphere of H2 and Ar to obtain a hydrogenated modified ZnO-TiO2 composite aerogel; the calcination temperature in the tubular furnace is 300-700°C.

2. The method for preparing the ZnO-TiO2 composite aerogel according to claim 1, characterized in that: In step 1), the solvent is a mixture of one or more of water, methanol, ethanol and isobutanol.

3. The method for preparing the ZnO-TiO2 composite aerogel according to claim 1 or 2, characterized in that: In step 1), the mixing and stirring time of tetrabutyl titanate, silver nitrate and nitric acid is 15 to 20 minutes, and the stirring speed is 200 to 500 r / min.

4. The method for preparing the ZnO-TiO2 composite aerogel according to any one of claims 1 to 3, characterized in that: In step 3), the organic solvent is one or more of ethanol, methanol, isopropanol, acetone and isopropyl ketone.

5. The method for preparing the ZnO-TiO2 composite aerogel according to claim 4, characterized in that: In step 3), the organic solvent is replaced 2 to 6 times, and the time for each replacement is 12 to 48 hours.

6. The method for preparing the ZnO-TiO2 composite aerogel according to any one of claims 1 to 3, characterized in that: In step 5), the mass ratio of TiO2 aerogel to Zn powder is 1:(0.01-0.6).

7. The method for preparing the ZnO-TiO2 composite aerogel according to claim 6, characterized in that: The treatment time in the double-temperature zone tubular furnace is 1 to 3 hours.

8. The method for preparing the ZnO-TiO2 composite aerogel according to claim 7, characterized in that: Step 5) The flow rate of the composite atmosphere is 10 to 100 sccm.

9. The method for preparing the ZnO-TiO2 composite aerogel according to any one of claims 1 to 3, characterized in that: In step 6), the calcination time in the tubular furnace is 1 to 3 hours.

10. The method for preparing the ZnO-TiO2 composite aerogel according to claim 9, characterized in that: In the composite atmosphere of step 6), the volume ratio of H2 to Ar is 0.01-0.2:1, and the composite atmosphere flow rate is 10-100 sccm.

11. Use of the ZnO-TiO2 composite aerogel prepared according to the method according to any one of claims 1 to 10 in the field of industrial wastewater treatment.

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