Photocatalyst, and preparation method and application thereof

Abstract

The invention relates to the field of sewage treatment, and discloses a photocatalyst and a preparation method and application thereof, the preparation method comprises the following steps: preparing a first intermediate, namely In2O3 (ZnO) 3, calcining the first intermediate and a tungsten source to obtain a second intermediate, reacting the second intermediate with a carbon nanotube to obtain a photocatalytic carrier, and preparing the photocatalyst. Through heterojunction energy band regulation and control, conductive network construction and a multi-component synergistic activation mechanism, efficient, stable and low-cost pollutant degradation is realized, and an innovative solution is provided for antibiotic pollution treatment in a complex water body.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a photocatalyst, a preparation method of the photocatalyst and application thereof. Background Art

[0002] Antibiotic pollution is a severe challenge to the current water environment management. Among them, tetracycline hydrochloride (TC-HCl) is easy to remain in water for a long time due to its high chemical stability and poor biodegradability, and induces the spread of drug-resistant genes, posing a serious threat to ecological safety and human health. The removal efficiency of tetracycline by traditional biological treatment technology is less than 30%, among which single photocatalysis or persulfate activation technology has significant limitations. The single photocatalytic system is limited by the rapid recombination of carriers and narrow spectral response (such as TiO2 only using ultraviolet light), resulting in low catalytic efficiency, low solar energy utilization efficiency or the need to use special ultraviolet light, etc., while persulfate activation alone (heat, metal ions, etc.) faces problems such as high energy consumption, secondary pollution or pH sensitivity. Summary of the invention

[0003] The purpose of the present invention is to overcome the above technical problems existing in the prior art and provide a photocatalyst, a method for preparing the photocatalyst and its application. The present invention achieves efficient, stable and low-cost pollutant degradation through heterojunction energy band regulation, conductive network construction and multi-component synergistic activation mechanism, and provides an innovative solution for the treatment of antibiotic pollution in complex water bodies.

[0004] In order to achieve the above object, the present invention provides a method for preparing a photocatalyst in a first aspect, wherein the preparation method comprises:

[0005] subjecting a solution containing a zinc salt and an indium salt to a first reaction under alkaline conditions, and subjecting the obtained first product to a first calcination to obtain a first intermediate;

[0006] Dissolving the first intermediate and the tungsten source in solvents to obtain corresponding solutions, mixing the solution containing the first intermediate and the solution containing the tungsten source, and then performing a second reaction, and then performing a second calcination on the obtained second product to obtain a second intermediate;

[0007] The second intermediate and the carbon nanotubes are respectively dissolved in a solvent to obtain corresponding solutions, and then the solution containing the second intermediate and the solution containing the carbon nanotubes are mixed and then subjected to a third reaction to obtain a photocatalyst.

[0008] A second aspect of the present invention provides a photocatalyst, wherein the photocatalyst is prepared according to the preparation method described in the first aspect of the present invention.

[0009] The third aspect of the present invention provides a method for treating sewage containing antibiotics, wherein the method includes: adding the photocatalyst described in the second aspect of the present invention and persulfate to the sewage containing antibiotics, and performing a degradation reaction under the irradiation of a visible light source.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1. The photocatalyst prepared by the present invention is a mixture, including In2O3(ZnO)3, WO3 and CNTs. A heterojunction is formed between In2O3(ZnO)3 and WO3, which can promote the spatial separation of photo-generated electrons (e-) and holes (h+), and at the same time retain the strong oxidation (valence band holes of WO3) and reduction (conduction band electrons of In2O3(ZnO)3) capabilities of the two components, significantly reducing the carrier recombination rate. And carbon nanotubes (CNTs), as highly conductive carriers, accelerate the transfer of electrons from the catalyst surface to persulfate or pollutants, further inhibiting electron-hole recombination and enhancing the photo-quantum efficiency.

[0012] 2. The band gap of In2O3 in the photocatalyst prepared by the present invention is about 3.6 eV and the band gap of WO3 is about 2.8 eV. The combination of the two broadens the light absorption range, so that the light absorption range of the photocatalyst of the present invention is the ultraviolet-visible light region (300–600 nm), and the introduction of CNTs enhances the visible light capture ability, reduces the dependence on ultraviolet light, adapts to the natural sunlight application scenario, and realizes full-spectrum (400-800 nm) driving.

[0013] 3. The photo-generated electrons in the photocatalyst prepared by the present invention can directly reduce persulfate (S2O8 2- / HSO5 - ) to generate SO4 - ·, while holes oxidize H2O to generate ·OH, forming a SO4 - · / ·OH / O2 - · multi-radical synergistic system, which realizes efficient mineralization of complex pollutants such as tetracyclines.

[0014] 4. The carbon nanotubes (CNTs) used in the present invention have a high specific surface area and can preferentially adsorb pollutant molecules. This local enrichment effect can alleviate the quenching effect of coexisting ions such as Cl- and HCO3- on free radicals, and can improve the adaptability to actual water bodies.

[0015] 5. The present invention replaces precious metals (such as Pt, Au) with inexpensive metals (In, Zn, W), and combines with the large-scale preparation technology of CNTs, significantly reducing the preparation cost. Description of the Drawings

[0016] Figure 1XRD patterns of the prepared photocatalyst, the first intermediate, the second intermediate and WO3;

[0017] Figure 2 Graph of the test results of Test Example 1;

[0018] Figure 3 Graph of the test results of Test Example 2. Detailed implementation manners

[0019] The following describes in detail the specific implementation manners of the present invention with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0020] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0021] The endpoints and any values disclosed in this article are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0022] In addition, the term "and / or" in the specification and claims is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0023] The terms "first", "second", etc. are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are usually of the same type, and the number of objects is not limited. For example, the first object can be one or multiple.

[0024] In a first aspect of the present invention, a method for preparing a photocatalyst is provided, wherein the preparation method includes:

[0025] Carrying out a first reaction on a solution containing a zinc salt and an indium salt under alkaline conditions, and subjecting the obtained first product to a first calcination to obtain a first intermediate;

[0026] Dissolving the first intermediate and a tungsten source in a solvent respectively to obtain corresponding solutions, mixing the solution containing the first intermediate and the solution containing the tungsten source, then carrying out a second reaction, and then subjecting the obtained second product to a second calcination to obtain a second intermediate;

[0027] Dissolving the second intermediate and carbon nanotubes in a solvent respectively to obtain corresponding solutions, then mixing the solution containing the second intermediate and the solution containing the carbon nanotubes, and carrying out a third reaction to obtain the photocatalyst.

[0028] There is no special requirement for the solvent of the solution containing a zinc salt and an indium salt, as long as it can dissolve the zinc salt and the indium salt and does not react with the solute. Generally, water is used as the solvent.

[0029] In the present invention, a zinc salt and an indium salt are used as raw materials to synthesize a first intermediate (In2O3(ZnO)3 solid solution), then the first intermediate is compounded with a tungsten source and calcined to construct a heterojunction. Finally, carbon nanotubes (CNTs) are introduced to form a conductive activation network. The photocatalyst thus prepared promotes the separation of photogenerated carriers through the heterojunction, combines with CNTs to accelerate electron transfer, and synergistically activates persulfate (PMS / PDS) to generate multiple free radicals such as SO4-· and ·OH, thereby enabling the efficient degradation of antibiotics, especially tetracycline hydrochloride.

[0030] There is no special requirement for the solvent in the present invention, as long as it can dissolve the corresponding solute and does not react with the solute. Generally, water is used as the solvent.

[0031] Preferably, the molar ratio of zinc element in the zinc salt to indium element in the indium salt is 2 - 4:1. The molar ratio of zinc element in the zinc salt to indium element in the indium salt can be any value between any two numbers among 2:1, 3:1, and 4:1.

[0032] Preferably, the pH value corresponding to the alkaline condition is 9.5 - 10.5.

[0033] Preferably, the temperature of the first calcination is 1200 - 1400 °C, the time is 3 - 5 h, and the heating rate is 2 - 5 °C / min. The temperature of the first calcination can be any value between any two numbers among 1200 °C, 1300 °C, and 1400 °C, and the time can be any value between any two numbers among 3 h, 4 h, and 5 h.

[0034] Preferably, the step of subjecting the first solution containing a zinc salt and an indium salt to a first reaction under alkaline conditions includes: adding an alkaline solution dropwise to the first solution containing a zinc salt and an indium salt until a preset pH value is reached, then continuing to stir for 1.5 - 2.5 h, then standing for aging for 20 - 25 h, and then performing first centrifugation and first drying to obtain the first product. There are no particular restrictions on the type and concentration of the alkaline solution added dropwise, as long as the pH value can be adjusted to the preset value. For example, a sodium hydroxide solution can be used, and the aging time can be any value between any two of 20 h, 22 h, 24 h, and 25 h.

[0035] Preferably, the temperature of the first drying is 60 - 80 °C and the time is 6 - 12 h.

[0036] Preferably, the ratio of the total molar amount of zinc and indium elements in the first intermediate to the molar amount of tungsten element in the tungsten source is 4 - 6:1. The ratio of the total molar amount of zinc and indium elements in the first intermediate to the molar amount of tungsten element in the tungsten source can be any value between any two of 4:1, 5:1, and 6:1.

[0037] Preferably, the temperature of the second calcination is 400 - 500 °C, the time is 1.5 - 2.5 h, and the heating rate is 3 - 5 °C / min. The temperature of the second calcination can be any value between any two of 400 °C, 450 °C, and 500 °C, and the time can be any value between any two of 1.5 h, 2 h, and 2.5 h.

[0038] Preferably, the step of subjecting the solution containing the first intermediate and the solution containing the tungsten source to a second reaction after mixing includes: adding the solution containing the tungsten source to the solution containing the first intermediate, stirring for 2 - 4 h, and then performing second centrifugation and second drying to obtain the second product.

[0039] Preferably, the temperature of the second drying is 60 - 80 °C and the time is 6 - 12 h.

[0040] Preferably, the mass ratio of the carbon nanotubes to the second intermediate is 0.5 - 2:10. The mass ratio of the carbon nanotubes to the second intermediate can be any value between any two of 0.5:10, 1:10, 1.5:10, and 2:10.

[0041] Preferably, based on the total amount of the solution containing the carbon nanotubes, the mass concentration of the carbon nanotubes is 15 - 25 wt%. Based on the total amount of the solution containing the carbon nanotubes, the mass concentration of the carbon nanotubes can be any value between any two of 15 wt%, 20 wt%, and 25 wt%.

[0042] Preferably, the steps of the third reaction include: reacting under stirring for 1-3 h, followed by third centrifugation and third drying to obtain the photocatalyst.

[0043] Preferably, the temperature of the third drying is 60-80 °C and the time is 6-12 h.

[0044] Preferably, the zinc salt is selected from one or more of zinc nitrate, zinc chloride, zinc acetate, and their respective corresponding hydrates.

[0045] The indium salt includes one or more of indium nitrate, indium chloride, and their respective corresponding hydrates.

[0046] The tungsten source includes tungsten trioxide.

[0047] The second aspect of the present invention provides a photocatalyst, wherein the photocatalyst is prepared according to the preparation method described in the first aspect of the present invention.

[0048] The photocatalyst prepared by the present invention is a mixture, including In2O3(ZnO)3, WO3, and CNTs.

[0049] Preferably, based on the total amount of the photocatalyst, the amount of In2O3(ZnO)3 in the photocatalyst is 60-65 wt.%, the amount of WO3 is 25-30 wt.%, and the amount of CNTs is 9-10 wt.%.

[0050] The third aspect of the present invention provides a method for treating sewage containing antibiotics, wherein the method includes: adding the photocatalyst described in the second aspect of the present invention and persulfate to the sewage containing antibiotics, and carrying out a degradation reaction under the irradiation of a visible light source.

[0051] Preferably, the antibiotic is a tetracycline antibiotic, and the concentration of the tetracycline antibiotic in the sewage containing antibiotics is 5-100 mg / L. The photocatalyst prepared by the present invention has a good degradation effect on tetracycline antibiotics, especially tetracycline hydrochloride, and still has a high degradation rate for tetracycline hydrochloride with a concentration of up to 100 mg / L in the sewage.

[0052] Preferably, the light wavelength emitted by the visible light source is 400-800 nm, and the intensity is 50-200 mW / cm 2 . The catalytic light source wavelength that can be used in the present invention can be 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, etc., and the intensity can be 50 mW / cm 2 , 100 mW / cm 2 , 150 mW / cm 2 , 200 mW / cm 2 Any value between any two numbers.

[0053] Preferably, based on the total amount of the antibiotic-containing sewage, the concentration of the photocatalyst is 0.1 - 1.5 g / L. The dosage of the photocatalyst in the present invention is relatively small, and its concentration can be any value between any two of 0.1 g / L, 0.5 g / L, 1 g / L, and 1.5 g / L.

[0054] Preferably, the concentration of the persulfate is 0.2 - 10.0 mM, and the mass ratio of the persulfate to the photocatalyst is (1 - 10):(5 - 1). The concentration of the persulfate can be any value between any two of 0.2 mM, 1 mM, 3 mM, 5 mM, 7 mM, and 10 mM. The mass ratio of the persulfate to the photocatalyst can be any value between any two of 1:1, 1:5, 1:3, 3:1, 5:1, 5:3, 10:3, 10:1, 10:3, and 10:5.

[0055] Preferably, the persulfate is peroxymonosulfate and / or peroxydisulfate.

[0056] In the following examples and comparative examples, unless otherwise specified, for reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained by commercial purchase. For those not specifying specific conditions in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer.

[0057] Carbon nanotubes (CNTs) were purchased from Nanjing Xianfeng Nano Material Technology Co., Ltd., with a specific surface area of 150 m 2 / g.

[0058] Example 1

[0059] I. Preparation of the first intermediate In2O 3( ZnO)3

[0060] S1, Weigh 3 mol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1 mol of indium nitrate pentahydrate (In(NO3)3·4.5H2O), dissolve them in 100 mL of distilled water, and stir magnetically for 30 minutes until completely dissolved.

[0061] S2, Dropwise add 0.5 mol / L NaOH solution to adjust the pH to 10.0, continue stirring and reacting for 2 hours, then stand for aging for 24 hours, centrifuge to obtain a precipitate, and alternately wash it with ethanol and distilled water by centrifugation 3 times to remove impurity ions. Then place the centrifuged product in a drying oven at 70 °C and dry it for 10 hours to obtain the first product, and grind it into powder with a mortar.

[0062] S3. Place the obtained powder in a muffle furnace, heat it to 1300 °C at a rate of 5 °C / min, calcine for 4 hours, and then cool it naturally to obtain the first intermediate, denoted as In2O3(ZnO)3.

[0063] II. Preparation of the second intermediate In2O3(ZnO)3 / WO3

[0064] S4. Take 1 mol of the first intermediate and disperse it in 50 mL of distilled water, and perform ultrasonic treatment for 30 minutes to obtain a solution containing the first intermediate.

[0065] S5. Weigh 1 mol of WO3 and dissolve it in 50 mL of distilled water to obtain a solution containing WO3. Slowly add the solution containing WO3 to the solution containing the first intermediate (added within 30 min), stir magnetically for 3 hours, then centrifuge to separate the precipitate, and then dry it at 70 °C for 10 hours to obtain the second product. Grind it with a mortar and place it in a muffle furnace, heat it to 450 °C at a rate of 5 °C / min, and keep it warm for 2 hours to obtain the second intermediate, denoted as In2O3(ZnO)3 / WO3. This second intermediate is a composite of In2O3(ZnO)3 and WO3.

[0066] III. Preparation of the photocatalyst In2O3(ZnO)3 / WO3 / CNTs

[0067] S6. Disperse 0.1 g of the second intermediate in 50 mL of distilled water and perform ultrasonic treatment for 30 minutes to obtain a solution containing the second intermediate.

[0068] Weigh an appropriate amount of CNTs and disperse them in 50 mL of distilled water to obtain a solution containing carbon nanotubes, and its mass concentration is 20 wt%.

[0069] S7. Add the solution containing carbon nanotubes to the solution containing the second intermediate, and the addition amount is such that the mass ratio of CNTs to the second intermediate is 1:10. Stir magnetically for 2 hours, then centrifuge to collect the solid, and dry it at 70 °C for 12 hours to obtain the photocatalyst, denoted as In2O3(ZnO)3 / WO3 / CNTs. The prepared photocatalyst simultaneously includes In2O3(ZnO)3, WO3, and CNTs. A heterojunction is formed between In2O3(ZnO)3 and WO3. Among them, In2O3(ZnO)3 is 62.9 wt.%, WO3 is 27.9 wt.%, and CNTs is 9.2 wt.%.

[0070] Perform XPD scanning on the photocatalyst (denoted as In2O3(ZnO)3 / WO3 / CNT) prepared in this example, the first intermediate (denoted as IZO3), the second intermediate (denoted as IZO3 / WO3), and one of the raw materials WO3, and the results are as Figure 1 shown.

[0071] Comparing the above spectrum with the standard spectrum of standard products Zn3In2O6 and WO3 (provided by the image library), it can be seen that the first intermediate prepared by the present invention is Zn3In2O6, the second intermediate is a complex of Zn3In2O6 and WO3, and the final photocatalyst is a complex of In2O3(ZnO)3, WO3 and CNTs. In the final photocatalyst, In2O3(ZnO)3 and WO3 coexist with no impurity peaks, indicating that a heterojunction is formed between the two.

[0072] Test Example 1

[0073] The photocatalyst, the first intermediate and the second intermediate prepared in Example 1 were subjected to an antibiotic degradation test as follows:

[0074] Three 100 mL tetracycline hydrochloride solutions with a concentration of 20 mg / L (wastewater to be treated) were prepared, and 50 mg of the photocatalyst prepared by the present invention (IZO / WO3 / CNTs, concentration of 0.5 g / L), the first intermediate (IZO, concentration of 0.5 g / L), and the second intermediate (IZO / WO3, concentration of 0.5 g / L) were added to each wastewater to be treated, and they were adsorbed in the dark state (without light source) for 30 min to adsorption-desorption equilibrium, and then 0.03 g of persulfate (permonosulfate PMS, active ingredient KHSO5, concentration of 2 mM) was added. At this time, the natural pH value of the reaction system was about 6.5, the temperature was 30°C, and a xenon lamp light source was turned on. The light source was equipped with a 420 nm cutoff filter, a wavelength range of 400-800 nm, and an intensity of 100 mW / cm 2 5 mL of the sample was taken every 20 minutes, filtered through a 0.22 μm filter membrane, and then the TC-HCl concentration was determined by high performance liquid chromatography (HPLC) to calculate the degradation rate. Figure 2 As shown in the figure, it can be seen that the photocatalyst prepared by the present invention has the highest degradation rate of tetracycline hydrochloride. At 10 minutes, the degradation rate is not less than 80%, and at 60 minutes, the degradation rate is as high as 91%.

[0075] Test Example 2

[0076] The photocatalyst, the first intermediate and the second intermediate prepared in Example 1 were subjected to an antibiotic degradation test (without adding persulfate), and the method was as follows:

[0077] Prepare three 100 mL solutions of tetracycline hydrochloride with a concentration of 20 mg / L (sewage to be treated). Add 50 mg of the photocatalyst prepared in the present invention (IZO / WO3 / CNTs, with a concentration of 0.5 g / L), the first intermediate (IZO, with a concentration of 0.5 g / L), and the second intermediate (IZO / WO3, with a concentration of 0.5 g / L) to each sewage to be treated respectively. Adsorb them in the dark state (without a light source) for 30 min until adsorption-desorption equilibrium is reached. At this time, the system temperature is 30 °C and the natural pH value is 6.5 (the natural pH value means the pH formed naturally in the system without pH adjustment). Turn on the xenon lamp light source with a wavelength range of 400 - 800 nm and an intensity of 100 mW / cm 2 , Take 5 mL of samples every 20 minutes, filter them through a 0.22 μm filter membrane, and then measure the concentration of TC-HCl by high performance liquid chromatography (HPLC) to calculate the degradation rate. The results are as Figure 3 shown.

[0078] Comparison Figure 2 and Figure 3 , It can be seen that when persulfate is not added, the degradation rates of IZO / WO3 / CNTs, IZO, and IZO / WO3 for tetracycline hydrochloride are significantly lower than those when persulfate is added. In the two test examples, the degradation rate of IZO / WO3 / CNTs is significantly higher than the other two. When persulfate is not added, at 120 min, the degradation rate of IZO / WO3 / CNTs for tetracycline hydrochloride is about 70%, while after adding persulfate, the degradation rate of IZO / WO3 / CNTs for tetracycline hydrochloride can reach as high as 91% at 60 min. Moreover, the photocatalyst prepared in the present invention does not require a specific light source, has a high solar energy utilization efficiency, and is not sensitive to environmental temperature, pH value, etc.

[0079] Example 2

[0080] I. Preparation of the first intermediate

[0081] S1, Weigh 2 mol of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and 1 mol of indium chloride pentahydrate (InCl3·4.5H2O), dissolve them in 100 mL of distilled water, and stir magnetically for 30 minutes until completely dissolved.

[0082] S2, Slowly add 0.5 mol / L NaOH solution dropwise to adjust the pH to 10.5, continue stirring and reacting for 2.5 hours, then let it stand and age for 20 hours, centrifuge to obtain a precipitate, wash it alternately with ethanol and distilled water by centrifugation 3 times to remove impurity ions, then place the centrifuged product in a drying oven at 70 °C for 10 hours, and grind it into powder with a mortar.

[0083] S3. Place the obtained powder in a muffle furnace, heat it to 1200 °C at a rate of 2 °C / min, calcine for 5 hours, and obtain the first intermediate after natural cooling.

[0084] II. Preparation of the second intermediate

[0085] S4. Take 1 mol of the first intermediate and disperse it in 50 mL of distilled water, and perform ultrasonic treatment for 30 minutes to obtain a solution containing the first intermediate.

[0086] S5. Weigh 0.85 mol of WO3 and dissolve it in 50 mL of distilled water to obtain a solution containing WO3. Slowly add the solution containing WO3 to the solution containing the first intermediate (add it up within 30 min), magnetically stir for 4 hours, then centrifuge to separate the precipitate, dry it at 70 °C for 10 hours, grind it with a mortar, and place it in a muffle furnace. Heat it to 500 °C at a rate of 4 °C / min, and keep it warm for 1.5 hours to obtain the second intermediate.

[0087] III. Preparation of the photocatalyst

[0088] S6. Disperse 0.1 g of the second intermediate in 50 mL of distilled water, and perform ultrasonic treatment for 30 minutes to obtain a solution containing the second intermediate.

[0089] Weigh an appropriate amount of CNTs and disperse them in 50 mL of distilled water to obtain a solution containing carbon nanotubes, and its mass concentration is 25 wt%.

[0090] S7. Add the solution containing carbon nanotubes to the solution containing the second intermediate, and the addition amount is such that the mass ratio of CNTs to the second intermediate is 2:10. Magnetically stir for 3 hours, then centrifuge to collect the solid, and dry it at 70 °C for 12 hours to obtain the photocatalyst.

[0091] Example 3

[0092] I. Preparation of the first intermediate

[0093] S1. Weigh 4 mol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1 mol of indium nitrate pentahydrate (In(NO3)3·4.5H2O), dissolve them in 100 mL of distilled water, and magnetically stir for 30 minutes until completely dissolved.

[0094] S2. Dropwise add 0.5 mol / L NaOH solution to adjust the pH to 9.5, continue stirring and reacting for 1.5 hours, then let it stand for aging for 22 hours, centrifuge to obtain the precipitate, wash it alternately with ethanol and distilled water by centrifugation 3 times to remove impurity ions, then place the centrifuged product in a drying oven at 70 °C and dry it for 10 hours, and grind it into powder with a mortar.

[0095] S3. Place the obtained powder in a muffle furnace, heat it to 1400 °C at a rate of 3 °C / min, calcine for 3 hours, and obtain the first intermediate after natural cooling.

[0096] II. Preparation of the second intermediate

[0097] S4. Take 1 mol of the first intermediate and disperse it in 50 mL of distilled water, and perform ultrasonic treatment for 30 minutes to obtain a solution containing the first intermediate;

[0098] S5. Weigh 1.25 mol of WO3 and dissolve it in 50 mL of distilled water to obtain a solution containing WO3. Slowly add the solution containing WO3 to the solution containing the first intermediate (add it up within 30 min), magnetically stir for 2 hours, then centrifuge to separate the precipitate, and then dry it at 70 °C for 10 hours. Grind it with a mortar and place it in a muffle furnace, heat it to 400 °C at a rate of 3 °C / min, and keep it warm for 2.5 hours to obtain the second intermediate.

[0099] III. Preparation of the photocatalyst

[0100] S6. Disperse 0.1 g of the second intermediate in 50 mL of distilled water and perform ultrasonic treatment for 30 minutes to obtain a solution containing the second intermediate;

[0101] Weigh an appropriate amount of CNTs and disperse them in 50 mL of distilled water to obtain a solution containing carbon nanotubes, and its mass concentration is 15 wt%.

[0102] S7. Add the solution containing carbon nanotubes to the solution containing the second intermediate, and the addition amount is such that the mass ratio of CNTs to the second intermediate is 0.5:10. Magnetically stir for 1.5 hours, then centrifuge to collect the solid, and dry it at 70 °C for 12 hours to obtain the photocatalyst.

[0103] Perform two tests on the catalyst prepared in 1 - 3 according to Test Example 1. The only difference between the two tests is that the concentrations of the tetracycline hydrochloride solutions are 20 mg / L and 100 mg / L respectively, and the degradation rates at 60 min are shown in Table 1.

[0104] Table 1 Test results of degradation rate

[0105]

[0106] As can be seen from Table 1, the present invention has a very good degradation effect on low - concentration tetracycline hydrochloride solutions. Even for a tetracycline hydrochloride solution with a concentration as high as 100 mg / L, the degradation rate is as high as over 70% at 60 min.

[0107] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any suitable combination of each specific technical feature. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. However, these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A preparation method of a photocatalyst, characterized in that, The preparation method includes: Performing a first reaction on a solution containing a zinc salt and an indium salt under alkaline conditions, and subjecting the obtained first product to first calcination to obtain a first intermediate; Dissolving the first intermediate and a tungsten source in solvents respectively to obtain corresponding solutions, then mixing the solution containing the first intermediate and the solution containing the tungsten source and performing a second reaction, and subjecting the obtained second product to second calcination to obtain a second intermediate; Dissolving the second intermediate and carbon nanotubes in solvents respectively to obtain corresponding solutions, then mixing the solution containing the second intermediate and the solution containing the carbon nanotubes and performing a third reaction to obtain a photocatalyst.

2. The preparation method according to claim 1, wherein The molar ratio of zinc element in the zinc salt to indium element in the indium salt is 2 - 4:1; And / or, the pH value corresponding to the alkaline conditions is 9.5 - 10.5; And / or, the temperature of the first calcination is 1200 - 1400 °C, the time is 3 - 5 h, and the heating rate is 2 - 5 °C / min; And / or, the step of performing the first reaction on the first solution containing a zinc salt and an indium salt under alkaline conditions includes: dropping an alkaline solution into the first solution containing a zinc salt and an indium salt to a preset pH value, then stirring for 1.5 - 2.5 h, standing for aging for 20 - 25 h, and then performing first centrifugation and first drying to obtain the first product; Preferably, the temperature of the first drying is 60 - 80 °C, and the time is 6 - 12 h.

3. The preparation method according to claim 1 or 2, wherein The molar ratio of the total molar amount of zinc element and indium element in the first intermediate to the molar amount of tungsten element in the tungsten source is 4 - 6:1; And / or, the temperature of the second calcination is 400 - 500 °C, the time is 1.5 - 2.5 h, and the heating rate is 3 - 5 °C / min; And / or, the step of mixing the solution containing the first intermediate and the solution containing the tungsten source and performing a second reaction includes: adding the solution containing the tungsten source to the solution containing the first intermediate, stirring for 2 - 4 h, and then performing second centrifugation and second drying to obtain the second product; Preferably, the temperature of the second drying is 60 - 80 °C, and the time is 6 - 12 h.

4. The preparation method according to claim 3, wherein, The mass ratio of the carbon nanotubes to the second intermediate is 0.5 - 2:10; And / or, based on the total amount of the solution containing the carbon nanotubes, the mass concentration of the carbon nanotubes is 15 - 25 wt%; And / or, the step of the third reaction includes: reacting under stirring for 1 - 3 h, and then performing third centrifugation and third drying to obtain the photocatalyst; Preferably, the temperature of the third drying is 60 - 80 °C, and the time is 6 - 12 h.

5. The preparation method according to claim 4, wherein, The zinc salt is selected from one or more of zinc nitrate, zinc chloride, zinc acetate and their respective corresponding hydrates; The indium salt includes one or more of indium nitrate, indium chloride and their respective corresponding hydrates; The tungsten source includes trioxides.

6. A photocatalyst, characterized in that, The photocatalyst is prepared by the preparation method according to any one of claims 1 - 5.

7. A sewage treatment method containing antibiotics, characterized in that, The method includes: adding the photocatalyst according to claim 6 and persulfate to sewage containing antibiotics, and performing a degradation reaction under the irradiation of a visible light source.

8. The method according to claim 7, wherein The antibiotic is a tetracycline antibiotic, and the concentration of the tetracycline antibiotic in the sewage containing the antibiotic is 5 - 100 mg / L; And / or, the light emitted by the visible light source has a wavelength of 400 - 800 nm and an intensity of 50 - 200 mW / cm 2 .

9. The method according to claim 7 or 8, wherein, Based on the total amount of the sewage containing the antibiotic, the concentration of the photocatalyst is 0.1 - 1.5 g / L; And / or, the concentration of the persulfate is 0.2 - 10.0 mM, and the mass ratio of the persulfate to the photocatalyst is (1 - 10):(5 - 1); And / or, the persulfate is peroxymonosulfate and / or peroxydisulfate.

10. The method according to claim 9, wherein, The time of the degradation reaction is 10 - 180 min, preferably 10 - 120 min; And / or, the pH value of the degradation reaction is 3 - 10, and the temperature is 25 - 50 °C.

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