A magnetic composite photocatalyst for removing tetracycline and a preparation method and application thereof

Abstract

The present application relates to the field of photocatalytic materials and wastewater treatment, in particular to a magnetic composite photocatalyst for removing tetracycline and a preparation method and application thereof. The preparation method comprises the following steps: mixing choline chloride, glycerol, water, a zinc source, an iron source and citric acid, and then performing a complexation reaction to obtain a sol; adjusting the pH of the sol and heating to obtain a gel; igniting the gel to obtain a precursor; calcining the precursor to obtain the magnetic composite photocatalyst; the molar ratio of zinc in the zinc source to iron in the iron source is 1:1.4-2.4; the molar ratio of choline chloride to glycerol is 0.5-1.5:1.5-2.5; and the volume ratio of the sum of choline chloride and glycerol to water is 10-25:2-20. The magnetic composite photocatalyst prepared by the method can effectively remove tetracycline in water, has a high removal rate and a short removal time.

Description

Technical Field

[0001] This invention relates to the fields of photocatalytic materials and wastewater treatment technology, and more specifically, to a magnetic composite photocatalyst for removing tetracycline, its preparation method, and its application. Background Technology

[0002] Antibiotic wastewater mainly originates from hospitals, pharmaceutical industries, livestock farming, and aquaculture. Antibiotics are a new type of pollutant wastewater, exhibiting biotoxicity, environmental persistence, and cumulative effects, posing a potential threat to human health and the ecological environment. According to existing data, only about 10-20% of antibiotics are metabolized by organisms, while the unmetabolized portion is directly or indirectly discharged into the aquatic environment. Therefore, how to effectively remove residual antibiotics has become a research hotspot in recent years, making the removal of trace amounts of antibiotics from water bodies an unresolved problem.

[0003] Tetracycline antibiotics are widely used as broad-spectrum antibiotics. Tetracycline antibiotics share a common chemical matrix and mainly include tetracycline, chlortetracycline, oxytetracycline, and doxycycline. Methods for removing tetracycline antibiotics mainly include advanced oxidation, adsorption, and microbial treatment. Traditional urban wastewater treatment methods primarily focus on removing suspended solids, organic matter, nitrogen, and phosphorus from wastewater, while their removal of trace amounts of drugs and antibiotics is relatively limited.

[0004] Existing methods for removing tetracycline antibiotics from aquatic environments include photocatalytic oxidation technology. Photocatalytic oxidation technology mainly refers to the process where, after a photocatalyst is irradiated by a light source, electrons in the valence band of the semiconductor undergo conduction to the conduction band, forming photogenerated electrons (e electrons). - )-hole(h + Yes, h + It has oxidizing properties and can convert OH groups into hydrogen peroxide. - It is oxidized by H2O to form hydroxyl radicals (·OH); e - It has reducing properties and can react with O2 to generate superoxide radicals (·O2). - );h + ·OH, ·O2 - Various active free radicals can mineralize organic matter such as antibiotics in water. Currently, most studies on photocatalytic degradation use TiO2 and its complexes as photocatalytic materials. However, the fact that TiO2 only responds to ultraviolet light limits its utilization of visible light, which accounts for 48% of the solar spectrum.

[0005] Ferric chloride (FeOCl) is an n-type semiconductor photocatalyst with a stable structure. Its narrow bandgap of 1.6 eV-1.8 eV gives it good visible light response; however, its relatively high eV... - and h +The low recombination rate of FeOCl results in its photocatalytic ability being limited, although it possesses photocatalytic capacity, its photocatalytic activity is not significant. Therefore, FeOCl usually needs to be combined with H2O2 to form a photo-Fenton system for use. As a photo-Fenton catalyst, FeOCl can perform photocatalytic degradation of tetracycline hydrochloride. However, FeOCl has significant shortcomings when used alone as a photocatalyst or a photo-Fenton catalyst, mainly because the core of FeOCl's good catalytic performance lies in the extremely abundant Fe on its surface. 2+ and Fe 3+ Active sites, under illumination, when the irradiation energy exceeds the band gap energy of the semiconductor material, will cause internal electrons to transition from the ground state to an excited state, crossing the band gap to reach the higher energy level of the conduction band, leaving a large number of holes in the valence band. Meanwhile, Fe in the system... 3+ It can also capture photogenerated electrons to form Fe. 2+ And thus Fe 2+ And will continue with ·O 2- The reaction produces ·OH and ·O. 2- and Fe 3+ However, with the increase in the number of transformations, some iron ions will be lost, resulting in a decrease in the electron-hole pair conversion rate. During photo-Fenton catalysis, iron atoms in FeOCl are also prone to efflux and dissolve in the solution, leading to a decrease or loss of overall catalyst activity. The efflux of iron atoms can easily cause catalyst aggregation, which is not conducive to long-term photo-Fenton catalysis and requires continuous replenishment or replacement of the catalyst, which to some extent increases the cost of photo-Fenton catalytic degradation of pollutants. The low separation efficiency of photogenerated electron-hole pairs also limits the catalytic activity of FeOCl as a photo-Fenton catalyst.

[0006] Existing technologies have obtained FeOCl@COF-JLU19 composite materials by combining FeOCl with COFs materials. This composite material significantly improves the photocatalytic activity of tetracycline hydrochloride. However, it still requires a photo-Fenton system formed by H2O2 to achieve a high degradation rate.

[0007] Existing technologies also employ TiO2 and MoS2 to composite with FeOCl, respectively, to form TiO2@FeOCl composite photocatalysts and MoS2@FeOCl composite photocatalysts. Without the addition of H2O2, the degradation rates of Rhodamine B at a concentration of 4 mg / L by TiO2@FeOCl and MoS2@FeOCl composite photocatalysts are nearly double and double that of FeOCl, respectively, with degradation rates of approximately 63% and 98% after 120 min, respectively. However, the multi-component composition of these composite catalysts typically requires multi-step synthesis, which is cumbersome and relatively costly; simultaneously, the smaller particle size makes recovery relatively more difficult.

[0008] Therefore, leveraging the existing advantages of FeOCl, developing novel and highly efficient magnetic FeOCl composite visible light catalysts to improve light energy utilization, reduce the recombination probability of FeOCl photogenerated electron-hole pairs, and utilize its magnetism to achieve its recovery through an external magnetic field is of great significance.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The primary objective of this invention is to provide a method for preparing a magnetic composite photocatalyst for removing tetracycline. This method yields a magnetic composite photocatalyst containing oxyferric chloride, zinc ferrite, and ferric oxide. This magnetic composite photocatalyst can effectively remove tetracycline from water with a high removal rate and short removal time. The preparation method is simple, the recovery of the magnetic composite photocatalyst is easy, and the magnetic composite photocatalyst can achieve a high degradation rate without forming a photo-Fenton system with H2O2.

[0011] The second objective of this invention is to provide a magnetic composite photocatalyst for removing tetracycline. This magnetic composite photocatalyst has a good degradation effect on tetracycline, with a high removal rate, short removal time, and low recovery difficulty. Furthermore, this magnetic composite photocatalyst can achieve a high degradation rate without forming a photo-Fenton system with H2O2.

[0012] A third objective of this invention is to provide the application of a magnetic composite photocatalyst for the removal of tetracycline.

[0013] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0014] This invention first provides a method for preparing a magnetic composite photocatalyst for removing tetracycline, comprising the following steps:

[0015] Choline chloride, glycerol, water, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol; the pH of the sol is adjusted and then heated to obtain a gel; the gel is ignited to obtain a precursor; the precursor is calcined to obtain the magnetic composite photocatalyst for removing tetracycline.

[0016] The molar ratio of zinc in the zinc source to iron in the iron source is 1:1.4 to 2.4.

[0017] The molar ratio of choline chloride to glycerol is 0.5–1.5:1.5–2.5.

[0018] The ratio of the sum of the volumes of choline chloride and glycerol to the volume of water is 10–25:2–20.

[0019] Furthermore, the ratio of the molar amount of citric acid to the sum of the molar amounts of zinc in the zinc source and iron in the iron source is 0.75 to 1.25:1.

[0020] Furthermore, the ratio of the sum of the volumes of the choline chloride, the glycerol, and the water to the molar amount of zinc in the zinc source is 20–100 mL: 1 mol.

[0021] Furthermore, the temperature of the complexation reaction is 40–95°C.

[0022] Furthermore, the pH of the sol is adjusted to 7.5–9.

[0023] Furthermore, the calcination temperature is 500–1000°C.

[0024] Furthermore, the holding time for calcination is ≥40 min.

[0025] Furthermore, the calcination process also includes steps of washing with water and drying.

[0026] The present invention further provides a magnetic composite photocatalyst for removing tetracycline, which is mainly prepared by the preparation method of the magnetic composite photocatalyst for removing tetracycline, wherein the magnetic composite photocatalyst for removing tetracycline includes oxyferric chloride, zinc ferrite and ferric oxide.

[0027] The present invention also provides the application of the magnetic composite photocatalyst for removing tetracycline in the removal of tetracycline.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The magnetic composite photocatalyst for removing tetracycline provided by the present invention contains oxyferric chloride, zinc ferrite and ferric oxide. The magnetic composite photocatalyst has a good degradation effect on tetracycline, with a high removal rate and short removal time. The preparation method is simple, the magnetic composite photocatalyst is easy to recover, and the magnetic composite photocatalyst does not need to form a photo-Fenton system with H2O2 to achieve a high degradation rate.

[0030] (2) The magnetic composite photocatalyst prepared by the method of the present invention for removing tetracycline has magnetic properties, can be recovered by an external magnetic field and reused multiple times, is easy to recover, and is environmentally friendly and energy-saving.

[0031] (3) The method for preparing the magnetic composite photocatalyst for removing tetracycline provided by the present invention is easy to operate, has a short process flow, is suitable for large-scale production, has low raw material cost, and high product added value. The magnetic composite photocatalyst prepared by this method can be widely used in the treatment of tetracycline wastewater. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 XRD pattern of the magnetic composite photocatalyst prepared in Example 1 of this invention;

[0034] Figure 2 The graph shows the change in the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 1 of this invention as a function of treatment time.

[0035] Figure 3 The graph shows the change in the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 2 of this invention as a function of treatment time.

[0036] Figure 4 The graph shows the change in the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 3 of this invention as a function of treatment time.

[0037] Figure 5 The graph shows the change in the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 4 of this invention as a function of treatment time.

[0038] Figure 6 The graph shows a comparison of the removal rates of tetracycline in the first photocatalytic tetracycline solution experiment and the tetracycline removal rate after three repeated recovery experiments using the magnetic composite photocatalyst prepared in Example 3 of this invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] Unless otherwise specified, in this invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0042] Unless otherwise specified, in this invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more.

[0043] In a first aspect, the present invention provides a method for preparing a magnetic composite photocatalyst for removing tetracycline, comprising the following steps:

[0044] Choline chloride, glycerol, water, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol; the pH of the sol is adjusted and then heated to obtain a gel; the gel is ignited to obtain a precursor; the precursor is calcined, cooled and washed with water and dried to obtain the magnetic composite photocatalyst for removing tetracycline.

[0045] Wherein, the molar ratio of zinc in the zinc source to iron in the iron source is 1:

[0046] 1.4 to 2.4; including but not limited to point values ​​of any one of 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, and 1:2.4, or range values ​​between any two.

[0047] The molar ratio of choline chloride to glycerol is 0.5–1.5:1.5–2.5; including but not limited to any one of 0.5:1.5, 1:1.5, 1.5:1.5, 0.5:2, 1:2, 1.5:2, 0.5:2.5, 1:2.5, 1.5:2.5, or any range between the two.

[0048] The ratio of the sum of the volumes of choline chloride and glycerol to the volume of water is 10-25:2-20, including but not limited to any one of 10:20, 15:15, 20:10, 25:5 or any range between the two.

[0049] The magnetic composite photocatalyst for tetracycline removal provided by this invention incorporates a eutectic solvent during its preparation. This eutectic solvent alters the ionic strength and solubility of the reaction system. Furthermore, the eutectic solvent participates in the reaction; choline chloride in the eutectic solvent can act as a chlorine source during calcination, reacting with iron complexes or oxides to generate ferric chloride oxychloride, thus changing the reaction mechanism and pathway. The addition of the eutectic solvent may also affect the reaction rate and kinetics, altering the conditions of the oxidation reaction. These factors influence the composition of the product and cause side reactions. Therefore, the magnetic composite photocatalyst contains ferric chloride oxychloride (FeOCl), zinc ferrite, and ferric oxide. This magnetic composite photocatalyst exhibits good degradation effects on tetracycline, with a high removal rate and short removal time. Moreover, this magnetic composite photocatalyst can achieve a high degradation rate without forming a photo-Fenton system with H2O2.

[0050] Furthermore, this magnetic composite photocatalyst is magnetic, allowing it to be recovered and reused multiple times using an external magnetic field. The recovery process is simple, environmentally friendly, and energy-saving.

[0051] Specifically, this invention uses a mixed solution of choline chloride, glycerol, and water as a solvent. The electrostatic interaction between the anions and cations in this mixture during the formation of the sol and gel allows the metal complexes formed by the iron salt and divalent metal salt with the complexing agent to be more stable and uniformly dispersed in the sol and gel. This is beneficial for the nanoparticles in the precursor to be small and uniform, and for the metal ions to be more uniformly dispersed. This results in a more regular spatial arrangement of the gel during its formation, thereby increasing the specific surface area of ​​the product, the dispersion uniformity of each component in the product, and the interaction between each component in the product. This, in turn, enhances the photocatalytic performance and magnetic recyclability of the magnetic composite photocatalyst.

[0052] By adjusting the pH of the sol, the formation and stability of the sol, the morphology and structure of the gel, and the stability of metal ions can be controlled, thereby controlling the microstructure and properties of the material.

[0053] Before the precursor forms, it is ignited in its gel state, allowing the nitrates within to react fully, thereby accelerating the reaction rate, shortening the reaction time, and optimizing the preparation process. Compared to heating the gel, igniting the gel at room temperature is simpler and consumes less energy. The addition of metal ions during the preparation of the magnetic composite catalyst increases the ferromagnetism of the photocatalyst, facilitating its separation and recycling.

[0054] Furthermore, the method for preparing a magnetic composite photocatalyst for removing tetracycline provided by this invention is simple to operate, has a short process, is suitable for large-scale production, has low raw material costs, and high product added value. The magnetic composite photocatalyst prepared by this method can be widely used in antibiotic wastewater treatment.

[0055] In some specific embodiments, the preparation method of the magnetic composite photocatalyst for removing tetracycline includes: first, mixing choline chloride, glycerol and water evenly, then adding a zinc source and an iron source, stirring for a period of time, then adding citric acid to carry out a complexation reaction, and after reacting for a period of time, adding an alkaline solution such as an ammonia solution to adjust the pH of the reaction system to obtain a sol; heating the sol to gradually form a gel, and then igniting the gel to obtain a precursor; calcining the precursor and cooling it to obtain the magnetic composite photocatalyst.

[0056] In some specific embodiments, the zinc source includes, but is not limited to, zinc-containing compounds such as zinc nitrate.

[0057] In some specific embodiments, the iron source includes iron-containing compounds, such as ferric nitrate, but is not limited thereto.

[0058] To further improve the degradation effect of magnetic composite photocatalyst on tetracycline, increase the removal rate, and shorten the removal time, the present invention has optimized the following parameters, including the amount of citric acid, the pH value during the reaction process, and the temperature and time during the preparation process.

[0059] In some specific embodiments, the ratio of the molar amount of citric acid to the sum of the molar amounts of zinc in the zinc source and iron in the iron source is 0.75 to 1.25:1, including but not limited to any one of 0.75:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.25:1 or any range between two of them.

[0060] In some specific embodiments, the ratio of the sum of the volumes of choline chloride, glycerol, and water to the molar amount of zinc in the zinc source is 20–100 mL (including but not limited to any one of 20 mL, 30 mL, 50 mL, 60 mL, 80 mL, and 100 mL, or any range between two): 1 mol.

[0061] In some specific embodiments, the temperature of the complexation reaction is 40 to 95°C, including but not limited to any one of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 95°C, or any range between two of them.

[0062] In some specific embodiments, the reaction time of the complexation reaction is ≥20 min, including but not limited to any one of 20 min, 30 min, 40 min, 50 min, 60 min, 120 min, 180 min, 240 min, and 300 min, or any range between two of them.

[0063] In some specific embodiments, the pH of the sol is adjusted to a pH of 7.5 to 9, including but not limited to any one of 7.5, 8, 8.5, and 9, or any range between two of them.

[0064] In some specific embodiments, the calcination temperature is 500 to 1000°C, including but not limited to any one of 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, and 1000°C, or a range between any two.

[0065] In some specific embodiments, the calcination holding time is ≥40 min, including but not limited to any one of 40 min, 1 h, 2 h, 3 h, 4 h, 6 h, 8 h, 10 h, 12 h, 15 h, 20 h, 24 h, or any range between two of them.

[0066] In some specific embodiments, the calcination process further includes washing and drying steps.

[0067] Secondly, the present invention provides a magnetic composite photocatalyst for removing tetracycline, which is mainly prepared by the method for preparing the magnetic composite photocatalyst for removing tetracycline, wherein the magnetic composite photocatalyst for removing tetracycline includes oxyferric chloride, zinc ferrite and ferric oxide.

[0068] This magnetic composite photocatalyst exhibits good degradation effect on tetracycline, with high removal rate, short removal time, and low recovery difficulty.

[0069] Furthermore, this magnetic composite photocatalyst is magnetic, allowing it to be recovered and reused multiple times using an external magnetic field, making it environmentally friendly and energy-saving.

[0070] Thirdly, the present invention provides the application of the magnetic composite photocatalyst for removing tetracycline in the removal of tetracycline.

[0071] Magnetic composite photocatalysts have a good degradation effect on tetracycline, with a high removal rate and short removal time. They can also be recycled and reused with a high reuse removal rate, and can be widely used in tetracycline wastewater treatment.

[0072] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0073] Example 1

[0074] The preparation method of the magnetic composite photocatalyst for tetracycline removal provided in this embodiment includes the following steps: Choline chloride and glycerol are mixed at a molar ratio of 1:2 to prepare a choline chloride-glycerol mixture. This choline chloride-glycerol mixture is then mixed with water at a volume ratio of 18:12 to obtain a choline chloride-glycerol-water mixed solution. 1 mol of zinc nitrate and 2 mol of ferric nitrate, weighed in advance, are added to a 30 mL volume of the choline chloride-glycerol-water mixed solution and stirred until homogeneous. Then, 3 mol of citric acid is added, and a complexation reaction is carried out at 60 °C to obtain a sol. The pH of the sol is then adjusted to 7.5 with ammonia water, and the mixture is continuously heated to form a gel. After drying the gel, a small amount of ethanol is added and ignited. After the combustion reaction is complete, a precursor is obtained. The precursor is calcined at 750 °C for 2 h, cooled, washed with water, and dried to obtain the magnetic composite photocatalyst for tetracycline removal.

[0075] like Figure 1 The image shown is the XRD pattern of the magnetic composite photocatalyst prepared in this embodiment. Figure 1 It can be seen that the main components of the magnetic composite photocatalyst prepared in this embodiment are oxyferric chloride, zinc ferrite and ferric oxide.

[0076] Example 2

[0077] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1. The difference is that choline chloride and glycerol are mixed at a molar ratio of 1:1.5 to prepare a choline chloride-glycerol mixture, and the choline chloride-glycerol mixture is mixed with water at a volume ratio of 20:10 to obtain a choline chloride-glycerol-water mixed solution.

[0078] Example 3

[0079] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1, except that the pH value of the sol is adjusted to 8.5 with ammonia.

[0080] Example 4

[0081] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1. The difference is that the pH value of the sol is adjusted to 8 with ammonia water, and the calcination temperature of the precursor is replaced with 550°C and the holding time is replaced with 6h.

[0082] Example 5

[0083] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1, except that the heat preservation time of the precursor calcination is replaced with 4 hours.

[0084] Example 6

[0085] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1, except that the molar amount of zinc nitrate is replaced with 1 mol and the molar amount of ferric nitrate is replaced with 2.4 mol.

[0086] Example 7

[0087] The preparation method of the magnetic composite photocatalyst for removing tetracycline provided in this embodiment is basically the same as that in Example 1, except that the complexation reaction is carried out at 80°C.

[0088] Comparative Example 1

[0089] The preparation method of the photocatalyst provided in this comparative example is basically the same as that in Example 1, except that glycerol is replaced with an equimolar amount of choline chloride, that is, glycerol is not added during the preparation process.

[0090] Comparative Example 2

[0091] The preparation method of the photocatalyst provided in this comparative example is basically the same as that in Example 1, except that choline chloride is replaced with an equimolar amount of glycerol, that is, no choline chloride is added during the preparation process.

[0092] Comparative Example 3

[0093] The preparation method of the photocatalyst provided in this comparative example is basically the same as that in Example 1, except that the mixed solution of choline chloride-glycerol-water is replaced with an equal volume of water, that is, choline chloride and glycerol are not added during the preparation process.

[0094] Comparative Example 4

[0095] The photocatalyst provided in this comparative example is ferric oxide.

[0096] Comparative Example 5

[0097] The photocatalyst provided in this comparative example is ferric chloride with oxygen.

[0098] Comparative Example 6

[0099] The photocatalyst provided in this comparative example is zinc ferrite.

[0100] Experimental Example

[0101] The magnetic composite photocatalysts prepared in the above embodiments and the photocatalysts prepared in the comparative examples were used to carry out tetracycline degradation tests. After the tetracycline degradation test was completed, the photocatalysts were recovered, and the removal rate and recovery rate of tetracycline by each group of photocatalysts were calculated. The results are shown in Table 1.

[0102] The test method for tetracycline degradation is as follows: 100 ml of 10 mg / L tetracycline solution was transferred to the reactor, and the initial absorbance of the tetracycline solution was measured using a UV-Vis spectrophotometer. 100 mg of the weighed photocatalyst was added to the tetracycline solution, and the reactor was irradiated (40 W visible light) and stirred. Timing was started. Every 30 minutes, 5 ml of tetracycline solution was taken, centrifuged, and magnetically separated. The absorbance of the supernatant was measured using a UV-Vis spectrophotometer to observe its change over time. When the absorbance of the supernatant did not change over time, it indicated that the reaction had reached equilibrium. The removal rate of tetracycline solution by each photocatalyst was calculated. The magnetic composite photocatalyst was separated using a magnet, then washed alternately with anhydrous ethanol and distilled water, and dried in an oven. The dried magnetic composite photocatalyst was reused in the photocatalytic degradation of tetracycline, and the antibiotic removal rate of each photocatalytic experiment was calculated.

[0103] Table 1. Removal rate of tetracycline solution by various photocatalysts

[0104] Group Removal rate of tetracycline solution / % Example 1 90 Example 2 95 Example 3 99.5 Example 4 87 Example 5 85 Example 6 92 Example 7 93 Comparative Example 1 27.1 Comparative Example 2 52.1 Comparative Example 3 35 Comparative Example 4 25 Comparative Example 5 41 Comparative Example 6 30.8

[0105] As can be seen from Table 1, the magnetic composite photocatalysts prepared in each embodiment have a high removal rate of tetracycline, and the removal rate is ≥85%, especially Example 3, which has a removal rate as high as 99.5%.

[0106] The change curve of the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 1 with treatment time is shown below. Figure 2 As shown in the figure. The change curve of the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 2 with treatment time is shown in the figure. Figure 3 As shown in the figure. The change curve of the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 3 with treatment time is shown in the figure. Figure 4 As shown in the figure. The change curve of the removal rate of tetracycline solution by the magnetic composite photocatalyst prepared in Example 4 with treatment time is shown in the figure. Figure 5 As shown in the figure. The comparison of the tetracycline removal rate of the magnetic composite photocatalyst prepared in Example 3 during the first photocatalytic tetracycline solution experiment and after three repeated recovery experiments is shown in the figure. Figure 6 As shown.

[0107] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a magnetic composite photocatalyst for removing tetracycline, characterized in that, Includes the following steps: Choline chloride, glycerol, water, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol; the pH of the sol is adjusted and then heated to obtain a gel; the gel is ignited to obtain a precursor; the precursor is calcined to obtain the magnetic composite photocatalyst for removing tetracycline. The molar ratio of zinc in the zinc source to iron in the iron source is 1:1.4 to 2.

4. The molar ratio of choline chloride to glycerol is 0.5–1.5:1.5–2.5; The ratio of the sum of the volumes of choline chloride and glycerol to the volume of water is 10–25:2–20.

2. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The ratio of the molar amount of citric acid to the sum of the molar amounts of zinc in the zinc source and iron in the iron source is 0.75 to 1.25:

1.

3. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The ratio of the sum of the volumes of choline chloride, glycerol, and water to the molar amount of zinc in the zinc source is 20–100 mL: 1 mol.

4. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The temperature of the complexation reaction is 40–95°C.

5. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The pH of the sol is adjusted to 7.5-9.

6. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The calcination temperature is 500–1000℃.

7. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The holding time for calcination is ≥40 min.

8. The method for preparing the magnetic composite photocatalyst for removing tetracycline according to claim 1, characterized in that, The calcination process also includes washing and drying steps.

9. A magnetic composite photocatalyst for removing tetracycline, characterized in that, It is mainly prepared by the method of preparing a magnetic composite photocatalyst for removing tetracycline as described in any one of claims 1 to 8, wherein the magnetic composite photocatalyst for removing tetracycline includes ferric chloride, zinc ferrite and ferric oxide.

10. The application of the magnetic composite photocatalyst for removing tetracycline as described in claim 9 in the removal of tetracycline.

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