MOF-based TiO2 / BC composite photocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photocatalysts, in particular to an MOF-based TiO2 / BC composite photocatalyst and a preparation method and application thereof, and the preparation method comprises the following steps: S1, preparing BC from a biomass material; s2, taking BC and a TiO2 precursor to react to obtain TiO2 / BC; s3, putting the MOF precursor and TiO2 / BC into DMF (Dimethyl Formamide), and carrying out reaction and post-treatment to obtain the MOF-based TiO2 / BC composite photocatalyst. The composite photocatalyst provided by the invention preserves the frame structure and pore volume of MOF and overcomes the defects of a traditional MOF material, all the components are closely combined into a whole, so that the stability is improved, the contact with organic pollutants is increased, and the transfer rate of electrons is further improved. A double-metal synergistic poor-rich electron microcell is formed on the surface of the material, so that more reactive oxygen species (ROS) can be generated, and the photocatalytic degradation performance on organic pollutants can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and specifically to a MOF-based TiO 2 / BC composite photocatalyst and its preparation method and application. Background Art

[0002] In recent years, advanced oxidation technologies have achieved good results in the treatment of organic wastewater. In particular, photocatalysis technology has the advantages of simple equipment, easy operation, no secondary pollution, and wide application range, and is considered the most promising "green" water purification technology. Among them, the photocatalyst TiO 2 is widely used due to its low price and small side effects. However, its band gap is about 3.2 eV, and electron-hole pairs are generated only under ultraviolet light, resulting in low light utilization efficiency.

[0003] Metal-organic framework materials (MOFs) are a new type of porous materials formed by the complexation reaction of metal ions and organic ligands, with significant advantages such as high specific surface area, large pore volume, and adjustable structure and function. Using it as a precursor to prepare composite materials can selectively preserve its framework structure, pore volume, and excellent electron transfer rate, which is beneficial to improving the adsorption and photocatalytic removal of organic pollutants.

[0004] Existing photocatalysts that combine TiO 2 and MOF are mostly based on NH 2 -MIL-125(Ti) for improvement. For example, the visible-light photocatalyst of mixed-phase titanium dioxide derived from MOF provided by Chinese patent document CN 112007629 A (application number 200210966474.7) uses NH 2 -MIL-125 as a sacrificial template to synthesize TiO 2 with adjustable morphology and crystal phase. Although its photocatalytic performance is improved to a certain extent, the poor adsorption performance of TiO 2 remains unchanged. This causes the photocatalyst synthesized by this method to be unable to quickly aggregate pollutants in the solution to its surface, thus affecting the removal efficiency of pollutants. Another example is the MOF-derived TiO 2 / porous g-C 3 N 4 composite photocatalyst provided by Chinese patent document CN 113398968 A (application number 202110567409.1). This method first prepares MOF-derived TiO 2 and then porous g-C 3 N 4By simple mixing and calcination, the components of the prepared photocatalyst are not tightly combined, easily fall off, and electron transfer is easily interrupted, thus affecting the photocatalytic effect, and the regeneration effect of the photocatalyst is not ideal. There are also some existing technologies that combine TiO 2 with other MOFs. For example, the journal literature "Wang Kang, He Mengting, Qiu Yunze, etc. Preparation and enhanced photo-Fenton degradation of TC in water by TiO2 / Fe-MOF heterojunction [J]. Environmental Chemistry, 2025, 44(6): 1-11." provides a TiO 2 / NH 2 -MIL-88B(Fe) heterojunction catalyst. Although this catalyst introduces two heavy metal elements and has certain adsorption performance and pollutant degradation performance, it still cannot avoid the inherent disadvantages of MOF materials, such as poor stability, fragile structure, easily affected by environmental factors, and inconvenient recycling, etc. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned existing technologies and provide a MOF-based TiO 2 / BC composite photocatalyst, its preparation method and application. This composite photocatalyst overcomes the disadvantages of traditional MOF materials, makes each component closely combined into one body to improve its own stability and the adsorption ability of organic pollutants, and further improves the electron transfer efficiency. A rich and poor electron micro-region with bimetallic synergy is formed on the material surface, which is beneficial to the generation of more reactive oxygen species (ROS), thereby improving the photocatalytic degradation performance of organic pollutants. To achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] A preparation method of a MOF-based TiO 2 / BC composite photocatalyst, comprising the following steps:

[0007] S1. Immerse the biomass material in an alkali solution, then filter, dry, and pyrolyze to obtain BC (biochar);

[0008] S2. Grind the BC obtained in step S1 and put it into absolute ethanol, then dropwise add tetrabutyl titanate and stir evenly to obtain solution A.

[0009] Mix nitric acid and glacial acetic acid to obtain a mixed acid, and mix the mixed acid, deionized water and absolute ethanol to obtain solution B.

[0010] Dissolve the surfactant in absolute ethanol to obtain solution C.

[0011] Under stirring at room temperature, dropwise add solution B and solution C to solution A. After the addition is complete, continue stirring for 2 h, let it stand at room temperature for aging for 48 h, and then dry to obtain solid TiO 2 / BC;

[0012] S3. Take FeCl3 ·6H 2 O, 2-aminoterephthalic acid, and the TiO 2 / BC prepared in step S2 are put into DMF (N,N-dimethylformamide) for hydrothermal reaction to obtain an intermediate solid. The intermediate solid is washed with absolute ethanol, dried, and then pyrolyzed to obtain the MOF-based TiO 2 / BC composite photocatalyst.

[0013] Preferably, in step S1, the biomass material is selected from agricultural and forestry solid wastes, and specifically, at least one of corn cob, peanut shell, rice husk, reed, or sunflower straw can be selected.

[0014] Preferably, in step S1, the alkali solution is a KOH solution with a concentration of 2M, and the ratio of the biomass material to the KOH solution is 1g:(3 - 10)mL. Further preferably, the ratio of the biomass material to the KOH solution is 1g:(6 - 10)mL.

[0015] Preferably, in step S1, the pyrolysis conditions are as follows:

[0016] Under the protection of an inert gas, the heating rate is (5 - 10)°C / min, the temperature is raised to 500°C - 800°C, and pyrolysis is carried out at this temperature for 1h - 2h.

[0017] Further preferably, in step S1, the inert gas in the pyrolysis conditions is selected from nitrogen or argon, the heating rate is 5°C / min, the temperature is raised to 600°C, and pyrolysis is carried out at this temperature for 2h.

[0018] Preferably, in step S2, in solution A, the ratio of BC, tetrabutyl titanate, and absolute ethanol is (0.5 - 3)g:(3 - 7)mL:10mL; further preferably, the ratio of BC, tetrabutyl titanate, and absolute ethanol is (1 - 2)g:(5 - 7)mL:10mL.

[0019] Preferably, in step S2, in solution B, the volume ratio of nitric acid to glacial acetic acid in the mixed acid is 1:(1 - 2.5), and the volume ratio of the mixed acid, deionized water, and absolute ethanol is 1:(1 - 2):10; further preferably, the volume ratio of nitric acid to glacial acetic acid in the mixed acid is 1:(2 - 2.5), and the volume ratio of the mixed acid, deionized water, and absolute ethanol is 1:(1 - 1.5):10.

[0020] Preferably, in step S2, in solution C, the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, or Tween, etc.; the ratio of the surfactant to absolute ethanol is (0.02 - 0.05)g:5mL; further preferably, the surfactant is sodium dodecylbenzenesulfonate, and the ratio of the surfactant to absolute ethanol is (0.02 - 0.03)g:5mL.

[0021] Preferably, in step S2, solution B and solution C are simultaneously added dropwise to solution A at a dropping rate of 1 drop / s and a stirring speed of (800 - 1300) rpm; the volume ratio of solution A, solution B, and solution C is (2 - 4):(2 - 3):1; more preferably, the stirring speed is 1000 rpm, and the volume ratio of solution A, solution B, and solution C is (2 - 3.5):(2 - 2.5):1.

[0022] Preferably, in step S3, TiO 2 / BC and FeCl 3 ·6H 2 O are added in a mass ratio of 1:(0.3 - 0.8), the molar ratio of FeCl 3 ·6H 2 O and 2-aminoterephthalic acid is 1:(0.8 - 1.5), and the ratio of TiO 2 / BC and DMF is 1 g:(25 - 60) mL; more preferably, the mass ratio of TiO 2 / BC and FeCl 3 ·6H 2 O is 1:(0.4 - 0.6), the molar ratio of FeCl 3 ·6H 2 O and 2-aminoterephthalic acid is 1:(1 - 1.2), and the ratio of TiO 2 / BC and DMF is 1 g:(30 - 40) mL.

[0023] Preferably, in step S3, the hydrothermal reaction conditions are 120°C - 180°C, and the reaction duration is 8 h - 24 h. More preferably, the hydrothermal reaction temperature is 150°C, and the reaction duration is 24 h; the pyrolysis conditions are in a nitrogen atmosphere furnace, the heating rate is (1 - 10) °C / min, the pyrolysis temperature is 400°C - 600°C, and the pyrolysis duration is 0.5 h - 2 h; more preferably, the pyrolysis temperature is 450°C - 500°C, the heating rate is (2 - 5) °C / min, and the pyrolysis duration is 1 h - 1.5 h.

[0024] The present invention provides an MOF-based TiO 2 / BC composite photocatalyst prepared by the above preparation method.

[0025] The present invention also provides the application of the above MOF-based TiO 2 / BC composite photocatalyst, specifically for the photocatalytic degradation and removal of organic pollutants.

[0026] Biochar (BC) is a carbon-rich material obtained by the oxygen-limited pyrolysis of biomass such as agricultural and forestry waste and sludge. It has a special porous structure, a high specific surface area, and adsorption capacity, and can be used as a good catalyst support. By loading the photocatalyst on the biochar through an appropriate method, the adsorption performance of the biochar can be utilized to enhance the capture ability of pollutants. At the same time, the conductivity of the carbon material can also reduce the bandgap energy of the photocatalyst, promoting the rapid separation of photo-generated electron-hole pairs, thereby improving the photocatalytic performance of the composite material. From the above aspects, TiO 2 and Fe-MOF are in-situ generated on the surface of biochar and then pyrolyzed to prepare a photocatalytic material, which not only overcomes the disadvantages of traditional MOF materials but also tightly integrates each component to improve its own stability and the adsorption capacity for organic pollutants, further improving the electron transfer efficiency. The formation of electron-rich and electron-poor microdomains with bimetallic synergy on the material surface is conducive to the generation of more reactive oxygen species (ROS), thereby improving the photocatalytic degradation performance of organic pollutants.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The biochar prepared from the agricultural and forestry solid waste used in the present invention has a wide source, is cheap and easily available, can be used on a large scale, and realizes resource utilization to achieve the purpose of "treating pollution with waste".

[0029] (2) In the preparation method provided by the present invention, the preparation process and operation are simple, no special equipment is required, and it is easy to realize industrial production.

[0030] (3) The photocatalytic material prepared by in-situ generating TiO 2 and Fe-MOF on the surface of biochar and then pyrolyzing preserves the framework structure and pore volume of MOF while overcoming the disadvantages of traditional MOF materials. Each component is tightly integrated to improve stability, not only increasing the contact with organic pollutants but also further improving the electron transfer rate. The formation of electron-rich and electron-poor microdomains with bimetallic synergy on the material surface is conducive to the generation of more reactive oxygen species (ROS), thereby improving the photocatalytic degradation performance of organic pollutants.

[0031] (4) The composite photocatalytic material prepared by the present invention is green, non-toxic, environmentally friendly, and can be recycled multiple times. Description of the Drawings

[0032] Figure 1 SEM image of the composite photocatalytic material prepared in Example 1;

[0033] Figure 2 For TiO 2 , Fe-MOF and XRD patterns of the composite photocatalytic material prepared in Example 1. Detailed Embodiments

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] The raw materials and experimental equipment used in each embodiment and comparative example are all commonly used commercially available raw materials and experimental equipment, and their specific sources will not be elaborated here.

[0036] Example 1

[0037] A preparation method of a MOF-based TiO 2 / BC composite photocatalyst is as follows:

[0038] (1) Soak 30 g of peanut shells in 200 mL of 2 M KOH solution for 24 h, then filter, dry, heat up to 600 °C at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyze at this temperature for 2 h to obtain peanut shell biochar (BC-1).

[0039] (2) Add 1.41 g of ground BC-1 to 10 mL of absolute ethanol, and then slowly add 6 mL of tetrabutyl titanate dropwise to the solution. Stir to mix evenly to obtain solution A; Mix 0.3 mL of nitric acid and 0.7 mL of glacial acetic acid, 1.3 mL of deionized water and 10 mL of absolute ethanol evenly to obtain solution B; Dissolve 0.03 g of sodium dodecylbenzenesulfonate in 5 mL of absolute ethanol to obtain solution C. At room temperature, slowly add solution B and solution C dropwise to solution A under continuous magnetic stirring at a dropping rate of 1 drop / s. After dropping, continue to stir for 2 hours at a stirring speed of 1000 rpm, then stand at room temperature for aging for 48 h and dry at 75 °C for 24 h to obtain a solid labeled as TiO 2 / BC-1.

[0040] (3) Put 1.25 g of TiO 2 / BC-1, 0.62 g of FeCl 3 ·6H 2 O, 0.43 g of 2-aminoterephthalic acid into a 150 mL polytetrafluoroethylene autoclave containing 40 mL of N,N-dimethylformamide (DMF), and carry out a hydrothermal reaction at 150 °C for 24 h. After the hydrothermal reaction is completed, the solid is washed with absolute ethanol and dried. The obtained material is heated up to 500 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and kept pyrolyzed for 1 h. After cooling to room temperature, the MOF-based TiO 2 / BC composite photocatalytic material is labeled as Fe-MOF / TiO 2 / BC-1.

[0041] Figure 1 SEM of 2 can clearly show that there are a large number of in-situ generated TiO 2 particles on the surface of the biochar.

[0042] Figure 2 XRD of Example 1 shows that the characteristic peaks of TiO 2 can be seen in the composite material, indicating that the crystal structure of TiO 2 has not changed significantly. However, the characteristic peaks of Fe-MOF were not observed significantly in the composite material. This is because during the preparation process, the crystal configuration of Fe-MOF has changed significantly, retaining both the biological framework structure of Fe-MOF to enhance the structural strength of the composite and having a large pore volume and excellent electron transfer rate, thereby improving the adsorption and photocatalytic removal of organic pollutants.

[0043] Example 2

[0044] A preparation method of a MOF-based TiO 2 / BC composite photocatalyst is as follows:

[0045] (1) Soak 30 g of corncobs in 250 mL of 2 M KOH solution for 24 h, then filter, dry, heat up to 600 °C at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyze at this temperature for 2 h to obtain peanut shell biochar (BC-2).

[0046] (2) Add 1.76 g of ground BC-2 to 10 mL of absolute ethanol, and then slowly add 5 mL of tetrabutyl titanate dropwise to the solution. Stir and mix evenly to obtain solution A; mix 0.3 mL of nitric acid and 0.7 mL of glacial acetic acid, 1.3 mL of deionized water and 10 mL of absolute ethanol evenly to obtain solution B; dissolve 0.04 g of sodium dodecylbenzenesulfonate in 5 mL of absolute ethanol to obtain solution C. At room temperature, slowly add solution B and solution C dropwise to solution A under continuous magnetic stirring. After the addition is complete, continue to stir for 2 hours, then let it stand at room temperature for aging for 48 h and dry at 75 °C for 24 h to obtain a solid labeled as TiO 2 / BC-2.

[0047] (3) Put 1.25 g of TiO 2 / BC-2, 0.75 g of FeCl 3 ·6H 2 O, 0.52 g of 2-aminoterephthalic acid into a 150 mL polytetrafluoroethylene autoclave containing 50 mL of N,N-dimethylformamide (DMF), and carry out a hydrothermal reaction at 150 °C for 24 h. After the hydrothermal reaction is completed, the solid is washed with absolute ethanol and dried. The obtained material is heated up to 450 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and kept pyrolyzed for 1 h. After cooling to room temperature, the MOF-based TiO 2 / BC composite photocatalytic material is labeled as Fe-MOF / TiO2 / BC-2。

[0048] Example 3

[0049] A preparation method of a MOF-based TiO 2 / BC composite photocatalyst is as follows:

[0050] (1) Soak 30 g of rice husks in 200 mL of 2 M KOH solution for 24 h, then filter, dry, heat up to 600 °C at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyze at this temperature for 2 h to obtain peanut shell biochar (BC-3).

[0051] (2) Add 1.41 g of ground BC-2 to 10 mL of absolute ethanol, and then slowly add 7 mL of tetrabutyl titanate dropwise to the solution. Stir and mix evenly to obtain solution A; Mix a mixed acid composed of 0.3 mL of nitric acid and 0.75 mL of glacial acetic acid, 1.5 mL of deionized water and 10 mL of absolute ethanol evenly to obtain solution B; Dissolve 0.03 g of sodium dodecylbenzenesulfonate in 5 mL of absolute ethanol to obtain solution C. At room temperature, slowly add solution B and solution C dropwise to solution A under continuous magnetic stirring. After the addition is completed, continue to stir for 2 hours, then let it stand at room temperature for aging for 48 h, and then dry at 75 °C for 24 h to obtain a solid labeled as TiO 2 / BC-3。

[0052] (3) Put 1.5 g of TiO 2 / BC-2, 0.75 g of FeCl 3 ·6H 2 O, 0.62 g of 2-aminoterephthalic acid into a 150 mL polytetrafluoroethylene autoclave containing 60 mL of N,N-dimethylformamide (DMF), and carry out a hydrothermal reaction at 150 °C for 24 h. After the hydrothermal reaction is completed, the solid is washed with absolute ethanol and dried. The obtained material is heated up to 450 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and kept pyrolyzed for 1.5 h. After cooling to room temperature, the MOF-based TiO 2 / BC composite photocatalytic material is labeled as Fe-MOF / TiO 2 / BC-3。

[0053] Comparative Example 1

[0054] (1) Soak 30 g of peanut shells in 200 mL of 2 M KOH solution for 24 h, then filter, dry, and pyrolyze in an atmosphere furnace to obtain peanut shell biochar (BC-4).

[0055] (2) Add 1.41 g of ground BC-4 to 10 mL of anhydrous ethanol, and then slowly add 6 mL of tetrabutyl titanate dropwise to the solution. Mix well under stirring to obtain solution A; mix a mixed acid composed of 0.3 mL of nitric acid and 0.7 mL of glacial acetic acid, 1.3 mL of deionized water and 10 mL of anhydrous ethanol uniformly to obtain solution B; dissolve 0.03 g of sodium dodecylbenzenesulfonate in 5 mL of anhydrous ethanol to obtain solution C. At room temperature, slowly add solution B and solution C dropwise to solution A under continuous magnetic stirring. After the addition is complete, continue stirring for 2 hours, then let it stand at room temperature for aging for 48 h, and then dry at 75 °C for 24 h to obtain a solid labeled as TiO 2 / BC-4.

[0056] (3) Place 0.62 g of FeCl 3 ·6H 2 O and 0.42 g of 2-aminoterephthalic acid in a 150 mL polytetrafluoroethylene autoclave containing 40 mL of N,N-dimethylformamide (DMF), and carry out a hydrothermal reaction at 150 °C for 24 h. After the hydrothermal reaction is completed, the solid material obtained after washing with anhydrous ethanol and drying is heated to a temperature of 500 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyzed for 1 h. After cooling to room temperature, the MOF-based material can be obtained. Mix this material with 1.25 g of TiO 2 / BC-3 uniformly by grinding to obtain the MOF-based TiO 2 / BC-3 composite material, labeled as Fe-MOF / TiO 2 / BC-4

[0057] Comparative Example 2

[0058] (1) Soak 30 g of peanut shells in 200 mL of 2 M KOH solution for 24 h, then filter, dry, and pyrolyze in an atmosphere furnace to obtain peanut shell biochar (BC-5).

[0059] (2) Add 6 mL of tetrabutyl titanate dropwise to 10 mL of anhydrous ethanol under stirring to obtain a uniform solution A; mix a mixed acid composed of 0.3 mL of nitric acid and 0.7 mL of glacial acetic acid, 1.3 mL of deionized water and 10 mL of anhydrous ethanol uniformly to obtain solution B; dissolve 0.03 g of sodium dodecylbenzenesulfonate in 5 mL of anhydrous ethanol to obtain solution C. At room temperature, slowly add solution B and solution C dropwise to solution A under continuous magnetic stirring. After the addition is complete, continue stirring for 2 hours, then let it stand at room temperature for aging for 48 h, and then dry at 75 °C for 24 h and grind to obtain a solid. Mix the obtained solid with 1.41 g of ground BC-5 uniformly to obtain a mixed solid labeled as TiO 2 / BC-5.

[0060] (3) Add 1.25 g of TiO 2 / BC-1, 0.62 g of FeCl 3 ·6H 2 O, 0.42 g of 2-aminoterephthalic acid were placed in a 150 mL polytetrafluoroethylene autoclave containing 40 mL of N,N-dimethylformamide (DMF), and a hydrothermal reaction was carried out at 150 °C for 24 h. After the hydrothermal reaction was completed, the solid material obtained after washing with absolute ethanol and drying was heated to 500 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyzed for 1 h. After cooling to room temperature, the MOF-based TiO 2 / BC-5 composite photocatalytic material was labeled as Fe-MOF / TiO 2 / BC-5.

[0061] Comparative Example 3

[0062] (1) 6 mL of tetrabutyl titanate was added dropwise to 10 mL of absolute ethanol under stirring to obtain a homogeneous solution A; a mixed acid composed of 0.3 mL of nitric acid and 0.7 mL of glacial acetic acid, 1.3 mL of deionized water and 10 mL of absolute ethanol were mixed evenly to obtain solution B; 0.03 g of sodium dodecylbenzenesulfonate was dissolved in 5 mL of absolute ethanol to obtain solution C. At room temperature, solution B and solution C were slowly added dropwise to solution A under continuous magnetic stirring. After the addition was completed, stirring was continued for 2 hours, and then it was left to age at room temperature for 48 h and dried at 75 °C for 24 h to obtain solid TiO 2 .

[0063] (2) 1.25 g of TiO 2 , 0.62 g of FeCl 3 ·6H 2 O, 0.43 g of 2-aminoterephthalic acid were placed in a 150 mL polytetrafluoroethylene autoclave containing 40 mL of N,N-dimethylformamide (DMF), and a hydrothermal reaction was carried out at 150 °C for 24 h. After the hydrothermal reaction was completed, the solid obtained after washing the solid with absolute ethanol and drying was heated to 500 °C again at a rate of 5 °C / min in a nitrogen atmosphere furnace and pyrolyzed for 1 h. After cooling to room temperature, pyrolysis was carried out to obtain the MOF-based TiO 2 composite photocatalytic material labeled as Fe-MOF / TiO 2 .

[0064] Comparative Example 4

[0065] The difference between this comparative example and Example 1 is that: there is no addition of MOF in step (3), and the material is the solid finally prepared in step (2), labeled as TiO 2 / BC-6.

[0066] Comparative Example 5

[0067] The difference between this comparative example and Example 1 is that: the amount of biochar (BC-6) added in step (2) is 0.7 g, and the finally obtained material is labeled as Fe-MOF / TiO 2 / BC-7.

[0068] Comparative Example 6

[0069] The difference between this comparative example and Example 1 is that: 0.31 g of FeCl 3 ·6H 2 O and 0.22 g of 2-aminoterephthalic acid were added in step (3), and the finally obtained material is labeled as Fe-MOF / TiO 2 / BC-8.

[0070] Experimental Example 1

[0071] The final composite photocatalytic materials obtained in Examples 1-3 and Comparative Examples 1-5 were applied to the photocatalytic degradation of antibiotics in sewage, and the specific steps are as follows:

[0072] Weigh 5 mg of the above photocatalytic materials and place them in a quartz tube containing 50 mL of 30 mg / L tetracycline hydrochloride (TC) solution in a 150 mL volume, and then put it into a photoreactor. Stir for 60 min under dark conditions to reach the adsorption equilibrium. React under simulated sunlight (500 w xenon lamp). Samples were taken at 1 h of illumination for each group, and the absorbance value at 276 nm was detected using a UV spectrophotometer, so as to calculate the removal rate (R TC ) of tetracycline hydrochloride. The calculation formula is:

[0073] R TC =(C TC0 -C TCt ) / C TC0 ×100% Formula Ⅰ

[0074] In Formula Ⅰ, C TC0 is the initial concentration of TC in the reaction solution, and C TCt is the concentration of TC in the reaction solution at the reaction time t.

[0075] The experimental results are statistically as follows:

[0076] Table 1 Results of Experimental Example 1

[0077] Group TC Removal Rate Example 1 99.6％ Example 2 98.4％ Example 3 98.8％ Comparative Example 1 72.5％ Comparative Example 2 64.7％ Comparative Example 3 48.9％ Comparative Example 4 62.8％ Comparative Example 5 68.6％ Comparative Example 6 76.4％

[0078] The composite photocatalytic materials prepared in Examples 1-3 showed excellent performance in the photocatalytic degradation and removal of tetracycline hydrochloride. At 1 h of illumination time, the removal rate of tetracycline hydrochloride was above 98%.

[0079] In Comparative Example 1, due to the preparation of MOF by pyrolysis and then combined with TiO 2In the composite material prepared by grinding and mixing with BC-3, the combination between components is not tight, which affects the electron transfer during the photocatalytic degradation process, resulting in a removal rate of only 72.5% for tetracycline hydrochloride;

[0080] In the composite material prepared in Comparative Example 2, TiO 2 and BC-5 are only mechanically mixed by grinding, rather than in-situ generated as in the examples. Similarly, it causes the combination between components in the composite material to be not tight, affects the electron transfer during the photocatalytic degradation process, and results in a low removal rate of only 64.7% for tetracycline hydrochloride;

[0081] In the composite material prepared in Comparative Example 3, no biochar is added, resulting in a decrease in the adsorption capacity of the material and an inability to quickly aggregate tetracycline hydrochloride in the solution onto the surface of the composite material, leading to a removal rate of only 48.9% for tetracycline hydrochloride;

[0082] In the composite material prepared in Comparative Example 4, no MOF is added, resulting in a change in the structure of the material, affecting the adsorption performance of the material and the electron transfer during the photocatalytic process, and an inability to form a rich and poor electron micro-region with bimetallic synergy, thus leading to a removal rate of only 62.8% for tetracycline hydrochloride;

[0083] In Comparative Example 5 and Comparative Example 6, the proportions of biochar (Comparative Example 5) and MOF (Comparative Example 6) are changed respectively. The results show that the removal rates of the prepared materials for tetracycline hydrochloride both decrease, being 68.6% and 76.4% respectively.

[0084] The above results show that the preparation method of this application can enable each material species to play a synergistic role, optimize the surface structure of the material, enhance the adsorption performance of the material, greatly improve the absorption and utilization of visible light by the composite photocatalytic material and the transfer and separation efficiency of electron-hole pairs during the photocatalytic process, thereby improving the photocatalytic activity for tetracycline hydrochloride.

[0085] Experimental Example 2

[0086] The final composite photocatalytic materials obtained in Examples 1-3 and Comparative Examples 1-5 were applied to the photocatalytic degradation of organic pigments in sewage. The specific steps are as follows:

[0087] Weigh 5 mg of the above photocatalytic materials and place them in 150 mL quartz tubes containing 50 mL of 10 mg / L methyl orange (MO) solution respectively, and put them into the photoreactor. Stir for 60 min under dark conditions to reach the adsorption equilibrium. React under simulated sunlight (500 w xenon lamp). Samples are taken at 2 h of illumination for each group, and the absorbance value at 463 nm is detected using an ultraviolet spectrophotometer to calculate the removal rate (R MO ), and the calculation formula is:

[0088] RMO = (C MO0 - C MOt ) / C MO0 × 100% Formula II

[0089] In Formula II, C MO0 is the initial concentration of MO in the reaction solution, and C MO t is the concentration of MO in the reaction solution at reaction time t.

[0090] Table 2 Results of Experimental Example 2

[0091]

[0092]

[0093] The composite photocatalytic materials prepared in Examples 1 - 3 showed excellent performance in the photocatalytic degradation and removal of methyl orange. At a light irradiation time of 2 h, the removal rates of tetracycline hydrochloride were all above 96%.

[0094] In Comparative Example 1, after preparing MOF by pyrolysis and then grinding and mixing it with TiO 2 / BC - 3, the components in the prepared composite material were not tightly combined, which affected the electron transfer during the photocatalytic degradation, resulting in a removal rate of methyl orange of only 65.8%;

[0095] For the composite material prepared in Comparative Example 2, TiO 2 and BC - 5 were only mechanically mixed by grinding, rather than in - situ generated as in the examples. Similarly, the components in the composite material were not tightly combined, which affected the electron transfer during the photocatalytic degradation, resulting in a low removal rate of methyl orange of only 64%;

[0096] The composite material prepared in Comparative Example 3 did not add biochar, resulting in a decrease in the adsorption capacity of the material and an inability to quickly aggregate methyl orange in the solution onto the surface of the composite material, affecting the removal rate of methyl orange to only 40.3%;

[0097] The composite material prepared in Comparative Example 4 did not add MOF, resulting in a change in the structure of the material, affecting the adsorption performance of the material and the electron transfer during the photocatalytic process, and an inability to form a rich - poor electron micro - region with bimetallic synergy, thus resulting in a removal rate of methyl orange of only 58.9%;

[0098] In Comparative Examples 5 and 6, the ratios of biochar (Comparative Example 5) and MOF (Comparative Example 6) were changed respectively. The results showed that the removal rates of methyl orange of the prepared materials both decreased, to 66.2% and 75% respectively.

[0099] The above results show that the preparation method provided by the present application can enable various material species to work together synergistically, optimize the surface structure of the material, increase the adsorption effect on methyl orange, greatly improve the visible light absorption utilization rate of the composite photocatalytic material and the transfer and separation efficiency of electron-hole pairs, and improve the photocatalytic activity. The degradation efficiency of methyl orange is greatly improved through adsorption, photocatalysis and synergistic Fenton reaction.

[0100] Experimental Example 3

[0101] At present, most photocatalysts have problems such as difficult recycling and poor recyclability, which significantly reduce the economic benefits of photocatalysts and hinder further popularization and use. In this experimental example, the recovery rate of the materials and the removal rate of TC of the composite photocatalytic materials prepared in Examples 1-3 and Comparative Examples 1-6 after being recycled 3 times were studied, as shown in Table 3. The specific steps were as follows: after the experiment of Experimental Example 1 was completed, the composite photocatalytic material was washed thoroughly with deionized water and dried, and then the next cycle experiment was carried out. The material recovery rate after three cycles and the TC removal rate in the third cycle (under illumination for 1 h) were counted.

[0102] Table 3 Results of Experimental Example 3

[0103] Group Material Recovery Rate (%) TC Removal Rate (%) Example 1 96.5％ 99.1％ Example 2 96％ 98％ Example 3 96.3％ 98.3％ Comparative Example 1 68.6％ 48.5％ Comparative Example 2 73.9％ 40.9％ Comparative Example 3 80.5％ 37.6％ Comparative Example 4 83.9％ 49.5％ Comparative Example 5 85.8％ 60.2％ Comparative Example 6 87.1％ 71.7％

[0104] The results showed that after the composite photocatalytic materials prepared in Examples 1-3 were recycled 3 times, the recovery rate of the materials was above 96%, and the removal rate of TC basically remained unchanged. This indicates that the materials prepared by the preparation method provided by the present application have good regeneration and recyclability, have good economy in practical applications, and can be popularized and applied. After the composite photocatalytic materials prepared in Comparative Examples 1-6 were recycled 3 times, both the recovery rate of the materials and the removal rate of TC decreased significantly. This is because the changes in the preparation method and component ratio affected the final structure and properties of the composite material, and the components in the material were not tightly combined, resulting in some components being easily detached during use, reducing the recovery rate of the material. At the same time, the change in structure affected the absorption and utilization of visible light by the material and the electron transport during the photocatalytic process, thus leading to a decrease in the removal rate of TC.

Claims

1. A method for preparing a MOF-based TiO2 / BC composite photocatalyst, characterized in that: The steps include: S1. Soak the biomass material in alkali solution, filter, dry and pyrolyze to obtain BC; S2. Grind the BC obtained in step S1 and add anhydrous ethanol, then drop tetrabutyl titanate and stir to obtain solution A. Nitric acid and glacial acetic acid are mixed to obtain a mixed acid, and the mixed acid, deionized water and anhydrous ethanol are mixed to obtain a solution B. Take the surfactant and dissolve it in anhydrous ethanol to obtain solution C. Under stirring at room temperature, solution B and solution C were added dropwise to solution A. After the addition was completed, stirring was continued for 2 hours. After standing at room temperature for 48 hours, solid TiO2 / BC was obtained by drying. S3. FeCl3·6H2O, 2-aminoterephthalic acid and the TiO2 / BC prepared in step S2 are put into DMF for hydrothermal reaction to obtain an intermediate solid. The intermediate solid is washed with anhydrous ethanol, dried and then pyrolyzed to obtain a MOF-based TiO2 / BC composite photocatalyst.

2. The preparation method according to claim 1, characterized in that In step S1, the biomass material is agricultural and forestry solid waste, the alkali solution is a 2M KOH solution, and the ratio of the biomass material to the KOH solution is 1 g: (3-10) mL; Preferably, the biomass material is at least one of corn cobs, peanut shells, rice husks, reeds or sunflower stalks; the ratio of the biomass material to the KOH solution is 1 g: (6-10) mL.

3. The preparation method according to claim 1, characterized in that: In step S1, the pyrolysis conditions are: Under the protection of inert gas, the temperature is raised to 500-800°C at a rate of (5-10)°C / min and pyrolyzed at this temperature for 1h-2h; Preferably, the pyrolysis conditions are: Under nitrogen or argon protection, the temperature was raised to 600°C at a rate of 5°C / min and pyrolyzed at this temperature for 2 h.

4. The preparation method according to claim 1, characterized in that: In step S2, in solution A, the ratio of BC, tetrabutyl titanate and anhydrous ethanol is (0.5-3) g:(3-7) mL:10 mL; in solution B, the volume ratio of nitric acid and glacial acetic acid in the mixed acid is 1:(1-2.5), and the volume ratio of the mixed acid, deionized water and anhydrous ethanol is 1:(1-2):10; Further preferably, in solution A, the ratio of BC, tetrabutyl titanate and anhydrous ethanol is (1-2) g:(5-7) mL:10 mL; the volume ratio of nitric acid and glacial acetic acid in the mixed acid is 1:(2-2.5), and the volume ratio of the mixed acid, deionized water and anhydrous ethanol is 1:(1-1.5):

10.

5. The preparation method according to claim 1, characterized in that: In step S2, in solution C, the surfactant is selected from at least one of sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide or Tween; the ratio of the surfactant to anhydrous ethanol is (0.02-0.05) g:5 mL; further preferably, the surfactant is sodium dodecylbenzene sulfonate, and the ratio of the surfactant to anhydrous ethanol is (0.02-0.03) g:5 mL.

6. The preparation method according to claim 1, characterized in that: In step S2, solution B and solution C are simultaneously added dropwise to solution A, the dropping rate is 1 drop / s, and the stirring speed is (800-1300) rpm; the volume ratio of solution A, solution B and solution C is (2-4):(2-3):1; further preferably, the stirring speed is 1000 rpm, and the volume ratio of solution A, solution B and solution C is (2-3.5):(2-2.5):

1.

7. The preparation method according to claim 1, characterized in that: In step S3, the mass ratio of the addition amount of TiO2 / BC and FeCl3·6H2O is 1:(0.3-0.8), the molar ratio of the addition amount of FeCl3·6H2O and 2-aminoterephthalic acid is 1:(0.8-1.5), and the ratio of TiO2 / BC and DMF is 1g:(25-60)mL; further preferably, the mass ratio of the addition amount of TiO2 / BC and FeCl3·6H2O is 1:(0.4-0.6), the molar ratio of the addition amount of FeCl3·6H2O and 2-aminoterephthalic acid is 1:(1-1.2), and the ratio of TiO2 / BC and DMF is 1g:(30-40)mL.

8. The preparation method according to claim 1, characterized in that: In step S3, the hydrothermal reaction conditions are 120°C-180°C, the reaction time is 8h-24h, and the further preferred hydrothermal reaction temperature is 150°C, and the reaction time is 24h; the pyrolysis conditions are in a nitrogen atmosphere furnace, the heating rate is (1-10)°C / min, the pyrolysis temperature is 400°C-600°C, and the pyrolysis time is 0.5h-2h; further preferably, the pyrolysis temperature is 450°C-500°C, the heating rate is (2-5)°C / min, and the pyrolysis time is 1h-1.5h.

9. A MOF-based TiO2 / BC composite photocatalyst prepared by the preparation method according to any one of claims 1 to 8.

10. An application of a MOF-based TiO2 / BC composite photocatalyst, characterized in that: Used for photocatalytic degradation and removal of organic pollutants, the MOF-based TiO2 / BC composite photocatalyst is prepared by the preparation method described in any one of claims 1-8.

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