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

Abstract

The present application relates to the field of photocatalysis, in particular to a magnetic composite photocatalyst for removing dye, a preparation method and application thereof. The preparation method of the magnetic composite photocatalyst for removing dye comprises the following steps: mixing choline chloride-ethylene glycol, water, a nickel source, a zinc source, an iron source and citric acid and performing a complexation reaction to obtain a sol; adjusting the pH of the sol and heating to form a gel; igniting the gel to obtain a precursor; and calcining the precursor to obtain the magnetic composite photocatalyst for removing dye; and the main components of the magnetic composite photocatalyst include a nickel-zinc ferrite and alpha-Fe2O3. The magnetic composite photocatalyst containing the nickel-zinc ferrite and alpha-Fe2O3 can be prepared by the method, the magnetic composite photocatalyst has a good treatment effect on various dyes, has a high removal rate and a short removal time.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, and more specifically, to a magnetic composite photocatalyst for removing dyes, its preparation method, and its application. Background Technology

[0002] Industrial dyes are widely used in the textile, paper, food, pharmaceutical, and cosmetic industries, generating wastewater that requires effective treatment to avoid harming the environment and human health. In recent years, with the development of science and technology, photocatalytic oxidation technology for degrading pollutants in water has become a novel water treatment technology. Photocatalysts have attracted widespread attention due to their excellent photocatalytic effect and low cost.

[0003] Spinel-type nickel ferrite nanoparticles exhibit stable chemical properties and demonstrate good catalytic performance as catalysts, along with high selectivity. However, pure nickel ferrites possess high magnetic properties, and the magnetic attraction between particles easily reduces their specific surface area, leading to decreased light utilization and affecting dye removal efficiency. Furthermore, the relatively low band gap also limits the quantum yield and catalytic efficiency of NiFe2O4.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing a magnetic composite photocatalyst for removing dyes. This method can produce a magnetic composite photocatalyst containing nickel-zinc ferrite and α-ferric oxide. This magnetic composite photocatalyst has good treatment effects on a variety of dyes, with high removal rates and short removal times.

[0006] The second objective of this invention is to provide a magnetic composite photocatalyst for removing dyes.

[0007] The third objective of this invention is to provide an application of a magnetic composite photocatalyst for removing dyes in photocatalytic dye removal.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] This invention provides a method for preparing a magnetic composite photocatalyst for removing dyes, comprising the following steps:

[0010] Choline chloride-ethylene glycol, water, nickel source, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol;

[0011] The pH of the sol was adjusted and heated to form a gel; the gel was then ignited to obtain the precursor.

[0012] The precursor is calcined to obtain the magnetic composite photocatalyst for removing dyes;

[0013] The main components of the magnetic composite photocatalyst include nickel-zinc ferrite and α-ferric oxide.

[0014] The present invention also provides a magnetic composite photocatalyst for removing dyes, which is mainly prepared by the preparation method of the magnetic composite photocatalyst for removing dyes;

[0015] The main components of the magnetic composite photocatalyst include nickel-zinc ferrite and α-ferric oxide.

[0016] The present invention further provides the application of the magnetic composite photocatalyst for removing dyes in photocatalytic dye removal.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The method for preparing a magnetic composite photocatalyst for removing dyes provided by the present invention can prepare a magnetic composite photocatalyst containing nickel-zinc ferrite and α-ferric oxide. The magnetic composite photocatalyst has a good treatment effect on a variety of dyes, with a high removal rate and a short removal time.

[0019] (2) The magnetic composite photocatalyst for removing dyes prepared by the method of the present invention has magnetic properties, can be recovered and reused multiple times by an external magnetic field, is environmentally friendly and energy-saving, and has high added value.

[0020] (3) The method for preparing the magnetic composite photocatalyst for removing dyes provided by the present invention is easy to operate, suitable for large-scale production, and has low raw material cost.

[0021] (4) The magnetic composite photocatalyst for removing dyes provided by the present invention has a good removal effect on a variety of dyes such as methylene blue, methyl orange, Congo red and malachite green. Attached Figure Description

[0022] 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.

[0023] Figure 1 XRD pattern of the composite photocatalyst prepared in Example 4 of this invention;

[0024] Figure 2The graph shows the change in the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 1 of this invention as a function of treatment time.

[0025] Figure 3 The graph shows the change in the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 2 of this invention as a function of treatment time.

[0026] Figure 4 The graph shows the change in the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 3 of this invention as a function of treatment time.

[0027] Figure 5 The graph shows the change in the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 5 of this invention as a function of treatment time.

[0028] Figure 6 The graph shows the change in the removal rate of methyl orange solution by the magnetic composite photocatalyst prepared in Example 4 of this invention as a function of treatment time.

[0029] Figure 7 The graph shows the change in the removal rate of Congo red solution by the magnetic composite photocatalyst prepared in Example 4 of this invention as a function of treatment time.

[0030] Figure 8 The graph shows the change in the removal rate of malachite green solution by the magnetic composite photocatalyst prepared in Example 4 of this invention as a function of treatment time.

[0031] Figure 9 A comparison of the removal rates of methylene blue in the first photocatalytic methylene blue test and the removal rates in three repeated recovery experiments using the magnetic composite photocatalyst provided in Example 4 of this invention.

[0032] Figure 10 A schematic diagram of the magnetic composite photocatalyst provided in Example 4 of this invention during the third recovery;

[0033] Figure 11 Hysteresis loop diagram of the magnetic composite photocatalyst prepared in Example 4 of this invention. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In a first aspect, the present invention provides a method for preparing a magnetic composite photocatalyst for removing dyes, comprising the following steps:

[0039] Choline chloride-ethylene glycol, water, nickel source, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol.

[0040] In this process, choline chloride-ethylene glycol is used as a eutectic solvent, and water is used to mix with the eutectic solvent to form a certain amount of eutectic solvent.

[0041] Deep eutectic solvents (DESs) are systems with a eutectic point lower than the melting point of each component. Due to their advantages such as mild synthesis conditions, environmental friendliness, high solubility, and controllable structure, DESs have shown significant advantages in the synthesis of inorganic materials and catalytic materials.

[0042] In this invention, the main functions of DESs include: (1) acting as a solvent, reactant, and template agent in the synthesis of magnetic composite photocatalysts; (2) the large number of hydrogen bond networks in DESs gives them good solubility for metal oxides and the like, and significantly reduces the influence of the formation of gel spatial network due to the precipitation of metal oxides and the like under alkaline conditions; (3) participating in the formation of gel spatial network makes the metal ions in the precursor more uniformly dispersed and the particles finer; (4) the fineness of the precursor particles and the decomposition and heat release of DESs during the precursor calcination process will accelerate the generation rate of the composite photocatalyst of the calcination product and reduce the particle size of the composite photocatalyst; (5) the one-pot synthesis of composite photocatalysts enhances the interaction between the components nickel-zinc ferrite and α-ferric oxide and forms a heterojunction structure, thereby reducing the recombination probability of photogenerated carriers and improving the catalytic activity of the composite photocatalyst.

[0043] In the sol-gel self-propagating process, the role of citric acid can be viewed from two aspects: First, its buffering effect. Citric acid acts as a buffer in aqueous solution, helping to regulate the pH of the reaction system, thereby promoting sol formation and gel stability. Second, citric acid also has a coordination complexing effect. Its carboxyl groups can undergo coordination complexation reactions with metal ions to form stable complexes. This complexation helps stabilize metal ions in the spatial network, thereby controlling gel formation and regulating particle size and distribution. Overall, the role of citric acid in the sol-gel self-propagating process is mainly achieved through its role as a buffer and complexing agent, regulating reaction conditions, stabilizing the sol and gel formation process, and influencing the microstructure and properties of the material.

[0044] The pH of the sol is then adjusted and heated to allow it to form a gel.

[0045] 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 in the sol-gel self-propagating method can be controlled, thereby controlling the microstructure and properties of the material.

[0046] The gel was ignited with a small amount of ethanol to obtain the precursor.

[0047] Compared to heating the gel, simply igniting the gel at room temperature is simpler and consumes less energy.

[0048] The precursor is calcined to obtain the magnetic composite photocatalyst for removing dyes.

[0049] The main components of the magnetic composite photocatalyst include nickel-zinc ferrite and α-ferric oxide.

[0050] The magnetic composite photocatalyst for dye removal provided by this invention incorporates a eutectic solvent during its preparation. This eutectic solvent can alter the ionic strength and solubility of the reaction system, and may also participate in the reaction, thus changing the reaction mechanism and pathway. The addition of the eutectic solvent may also affect the reaction rate and kinetics, changing the conditions of the oxidation reaction. These factors influence the composition of the product and cause side reactions. Therefore, in addition to nickel-zinc ferrite, the magnetic composite photocatalyst also contains α-ferric oxide. The preparation method of the magnetic composite photocatalyst for dye removal provided by this invention can produce a magnetic composite photocatalyst whose main components include nickel-zinc ferrite and α-ferric oxide. This magnetic composite photocatalyst exhibits good degradation effects on various dyes, with high removal rates and short removal times.

[0051] 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.

[0052] Furthermore, the method for preparing the magnetic composite photocatalyst for removing dyes provided by this invention is easy to operate, 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 the treatment of colored dye wastewater.

[0053] In some specific embodiments, the preparation method of the magnetic composite photocatalyst for removing dyes specifically includes: first, mixing choline chloride and ethylene glycol evenly, then adding water and mixing evenly, then adding a nickel source, 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 ammonia to adjust the pH value of the reaction system to obtain a sol; then 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.

[0054] In some specific implementations, the nickel source includes, but is not limited to, nickel-containing compounds such as nickel nitrate.

[0055] In some specific implementations, the zinc source includes, but is not limited to, nickel-containing compounds such as zinc nitrate.

[0056] In some specific implementations, the iron source includes iron-containing compounds, such as ferric nitrate, but is not limited to these.

[0057] To further improve the degradation effect of magnetic composite photocatalyst on dyes, increase the removal rate, and shorten the removal time, this invention has optimized the following parameters: the ratio of choline chloride, ethylene glycol, and water; the ratio of metal elements; the pH value during the reaction process; the amount of citric acid used; and the temperature and time during the preparation process.

[0058] In some specific embodiments, during the mixing process, the molar ratio of zinc in the zinc source, nickel in the nickel source, and iron in the iron source is x:1 to x:1.9 to 2.8, where 0.2 ≤ x ≤ 0.8. The molar ratios x:1 to x:1.9 to 2.8 include, but are not limited to, 0.25:0.75:1.9, 0.3:0.7:1.9, 0.4:0.6:1.9, 0.5:0.5:1.9, 0.6:0.4:1.9, 0.7:0.3:1.9, 0.75:0.25:1.9, 0.25:0.75:2.2, 0.3:0.7:2.2, 0.4:0.6:2.2, 0.5:0.5:2.2, 0.6:0.4:2.2, 0.7:0.3:2.2, and 0.75:0.25:2. The point value of any one of the following: 0.2, 0.25:0.75:2.5, 0.3:0.7:2.5, 0.4:0.6:2.5, 0.5:0.5:2.5, 0.6:0.4:2.5, 0.7:0.3:2.5, 0.75:0.25:2.5, 0.25:0.75:2.8, 0.3:0.7:2.8, 0.4:0.6:2.8, 0.5:0.5:2.8, 0.6:0.4:2.8, 0.7:0.3:2.8, or 0.75:0.25:2.8, or the range value between any two.

[0059] In some specific embodiments, during the mixing process, the molar ratio of choline chloride to ethylene glycol 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 two of them.

[0060] In some specific embodiments, during the mixing process, the ratio of the sum of the volumes of choline chloride and ethylene glycol to the volume of water is 18-27:3-12, including but not limited to any one of the following values ​​or any range between two: 18:3, 20:3, 22:3, 25:3, 27:3, 18:5, 20:5, 22:5, 25:5, 27:5, 18:8, 20:8, 22:8, 25:8, 27:8, 18:10, 20:10, 22:10, 25:10, 27:10, 18:12, 20:12, 22:12, 25:12, and 27:12.

[0061] 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, nickel in the nickel source, and iron in the iron source is 1 to 1.5:1, including but not limited to the point value of any one of 1:1, 1.2:1, 1.4:1, and 1.5:1 or the range between any two.

[0062] In some specific embodiments, during the complexation reaction, the temperature of the mixture is 40 to 90°C; including but not limited to any one of 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C, or any range between two of them.

[0063] 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.

[0064] In some specific embodiments, the pH of the sol is adjusted to pH = 7 to 11, including but not limited to any one of 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11 or any range between two of them.

[0065] In some specific embodiments, the calcination temperature is 450 to 850°C; including but not limited to any one of 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, and 850°C, or a range between any two.

[0066] In some specific embodiments, the calcination time is ≥1h, including but not limited to any one of 1h, 2h, 3h, 4h, 6h, 8h, 10h, 12h, 15h, 20h, and 24h, or any range between two of them.

[0067] Secondly, the present invention provides a magnetic composite photocatalyst for removing dyes, which is mainly prepared by the method for preparing the magnetic composite photocatalyst for removing dyes.

[0068] The main components of the magnetic composite photocatalyst include nickel-zinc ferrite and α-ferric oxide.

[0069] The magnetic composite photocatalyst for removing dyes provided by this invention has a good treatment effect on dyes, with a high removal rate and short removal time, and can be recycled and reused after use.

[0070] Thirdly, the present invention provides the application of the magnetic composite photocatalyst for removing dyes as described above in the photocatalytic removal of dyes.

[0071] The magnetic composite photocatalyst for removing dyes provided by this invention has a good degradation effect on a variety of dyes, such as methylene blue, methyl orange, Congo red, malachite green, etc., but is not limited to these.

[0072] In some specific embodiments, the magnetic composite photocatalyst has a removal rate of ≥70% for methylene blue solutions with a concentration ≤20mg / L; including but not limited to point values ​​of any one of 70%, 75%, 80%, 85%, 90%, 95%, and 99%, or a range between any two.

[0073] In some specific embodiments, the magnetic composite photocatalyst has a removal rate of ≥85% for methyl orange solutions with a concentration ≤10mg / L, including but not limited to point values ​​of any one of 85%, 88%, 90%, 92%, 95%, 98%, and 100%, or a range between any two.

[0074] In some specific embodiments, the magnetic composite photocatalyst has a removal rate of ≥70% for Congo red solutions with a concentration ≤140mg / L, including but not limited to point values ​​or ranges between any one of 70%, 75%, 80%, 85%, 88%, 90%, 92%, 95%, 98%, and 100%.

[0075] In some specific embodiments, the magnetic composite photocatalyst has a removal rate of ≥88% for malachite green solutions with a concentration ≤10mg / L, including but not limited to point values ​​of any one of 88%, 90%, 92%, 95%, 98%, and 100%, or a range between any two.

[0076] 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.

[0077] Example 1

[0078] The method for preparing the magnetic composite photocatalyst for removing dyes provided in this embodiment includes the following steps:

[0079] Choline chloride and ethylene glycol were mixed at a molar ratio of 1:2 and magnetically stirred to obtain a choline chloride-ethylene glycol solution. The choline chloride-ethylene glycol solution was then mixed with water at a volume ratio of 18:12 and magnetically stirred to obtain a mixed solvent. 2 mol of ferric nitrate, 0.5 mol of nickel nitrate, and 0.5 mol of zinc nitrate, weighed beforehand, were added to a 30 mL volume of the mixed solvent and stirred until homogeneous. Then, 3 mol of citric acid was added, and a complexation reaction was carried out at 60 °C to obtain a sol. The pH of the sol was then adjusted to 7 with ammonia water, and the resulting sol was continuously heated to form a gel. After drying the gel, a small amount of ethanol was added and ignited. After the combustion reaction was complete, a precursor was obtained. The precursor was calcined at 450 °C for 2 h, cooled, washed with water, and dried to obtain a magnetic composite photocatalyst.

[0080] Example 2

[0081] The preparation method of the magnetic composite photocatalyst for removing dyes provided in this embodiment is basically the same as that in Example 1, except that the volume ratio of choline chloride-ethylene glycol solution to water is replaced with 22.5:7.5.

[0082] Example 3

[0083] The preparation method of the magnetic composite photocatalyst for removing dyes provided in this embodiment is basically the same as that in Example 2, except that the pH value of the sol is adjusted to 8 using ammonia.

[0084] Example 4

[0085] The preparation method of the magnetic composite photocatalyst for removing dyes provided in this embodiment is basically the same as that in Example 3, except that the calcination temperature of the precursor is replaced with 700°C.

[0086] like Figure 1 The image shown is the XRD pattern of the composite photocatalyst prepared in this embodiment. Figure 1 It can be seen that the main components of the composite photocatalyst prepared in this embodiment are nickel-zinc ferrite and α-ferric oxide.

[0087] The BET data of the composite photocatalyst were measured using a Micromeritics 3020 fully automated specific surface area and porosity analyzer, and the average particle size was found to be 34 nm.

[0088] Example 5

[0089] The preparation method of the magnetic composite photocatalyst for removing dyes provided in this embodiment is basically the same as that in Example 4, except that the molar amount of nickel nitrate is replaced with 0.8 mol and the molar amount of zinc nitrate is replaced with 0.2 mol.

[0090] Comparative Example 1

[0091] The preparation method of the magnetic composite photocatalyst for removing dyes provided in this embodiment is basically the same as that in Example 4, except that ethylene glycol is replaced with an equal volume of choline chloride, that is, the raw materials for synthesis do not contain ethylene glycol.

[0092] Comparative Example 2

[0093] The preparation method of the photocatalyst provided in this comparative example is basically the same as that in Example 4, except that choline chloride is replaced with an equal volume of ethylene glycol, that is, the raw materials do not contain choline chloride.

[0094] Comparative Example 3

[0095] The preparation method of the photocatalyst provided in this comparative example is basically the same as that in Example 4, except that choline chloride-ethylene glycol is replaced with an equal volume of water, that is, the raw materials do not contain choline chloride and ethylene glycol.

[0096] The BET data of the composite photocatalyst were measured using a Micromeritics 3020 fully automated surface area and porosity analyzer, and the average particle size was found to be 824 nm.

[0097] Comparative Example 4

[0098] The photocatalyst provided in this comparative example is α-ferric oxide.

[0099] Experimental Example

[0100] The magnetic composite photocatalysts prepared in the above embodiments and the photocatalysts prepared in the comparative examples were used to carry out dye degradation experiments. After the dye degradation experiments were completed, the photocatalysts were recovered, and the removal rate and recovery rate of each group of photocatalysts for each dye were calculated. The results are shown in Table 1.

[0101] The dye degradation test method is as follows: 100 ml of methylene blue solution, 100 ml of methyl orange solution, 100 ml of Congo red solution, and 100 ml of malachite green solution of a certain concentration were respectively transferred to each dye solution. The initial concentration of each dye solution was measured. The weighed photocatalyst (100 mg) was added to each dye solution respectively. Irradiation (40 W visible light) was started and the mixture was stirred. Timing was started. Every 30 min, 5 ml of dye solution was taken, centrifuged, and magnetically separated. The concentration of the supernatant was measured, and its change over time was investigated. When the dye removal reached equilibrium, the removal rate of each photocatalyst on the dye solution was calculated. The magnetic composite photocatalyst was separated by a magnet. Then, the magnetic composite photocatalyst was recovered and regenerated by alternate washing with anhydrous ethanol and distilled water. The recovery rate of the magnetic composite photocatalyst was calculated.

[0102] Table 1. Removal rate and recovery rate of dye solution by various magnetic composite photocatalysts

[0103]

[0104] The curve showing the change in the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 1 over treatment time is shown below. Figure 2 As shown in the figure. The curve of the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 2 as a function of treatment time is shown in the figure. Figure 3 As shown in the figure. The curve of the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 3 as a function of treatment time is shown in the figure. Figure 4 As shown in the figure. The curve of the removal rate of methylene blue solution by the magnetic composite photocatalyst prepared in Example 5 as a function of treatment time is shown in the figure. Figure 5 As shown in the figure. The curve of the removal rate of methyl orange solution by the magnetic composite photocatalyst prepared in Example 4 as a function of treatment time is shown in the figure. Figure 6 As shown in the figure. The curve of the removal rate of Congo red solution by the magnetic composite photocatalyst prepared in Example 4 as a function of treatment time is shown in the figure. Figure 7 As shown in the figure. The curve of the removal rate of malachite green solution by the magnetic composite photocatalyst prepared in Example 4 as a function of treatment time is shown in the figure. Figure 8 As shown.

[0105] As can be seen from Table 1, the magnetic composite photocatalysts prepared in each embodiment have higher removal rates for each dye, while the photocatalysts prepared in each comparative embodiment have lower removal rates for the dye solution.

[0106] Furthermore, the magnetic composite photocatalysts prepared in each embodiment have a high recovery rate and can be reused.

[0107] Furthermore, the magnetic composite photocatalyst recovered in Example 4 was used to continue the photocatalytic methylene blue test, and the recovery was repeated twice. A comparison chart of the methylene blue removal rate of the magnetic composite photocatalyst provided in Example 4 during the first photocatalytic methylene blue test and after three repeated recovery tests is available. Figure 9 As shown in the diagram, the third recovery of the magnetic composite photocatalyst is as follows: Figure 10 As shown. By Figure 9 It can be seen that even after the third recovery, the magnetic composite photocatalyst still exhibits a high removal rate of methylene blue. Figure 10 It can be seen that the recovery rate of the magnetic composite photocatalyst in the third recovery is still relatively high.

[0108] Furthermore, the hysteresis loop diagram of the magnetic composite photocatalyst prepared in Example 4 can be found in [reference needed]. Figure 11 As shown. By Figure 11 It can be seen that the magnetic composite photocatalyst prepared in Example 4 has high coercivity and high saturation magnetization, which is beneficial for recycling and reuse.

[0109] In summary, the magnetic composite photocatalyst prepared by the method provided by this invention has a significant effect on the degradation of dyes, with a high initial concentration and high removal rate of methylene blue dye solution. Furthermore, the magnetic composite photocatalyst exhibits excellent magnetic separation and recovery performance (within 10 hours, the removal rate was 99.8% in the first photocatalytic experiment, 99.1% in the first recycling, 99.5% in the second recycling, and 97.1% in the third recycling). The removal rate remains essentially unchanged during repeated use.

[0110] The method for preparing the magnetic composite photocatalyst provided by this invention is simple to operate, low in cost, energy-saving, and can be widely used in the degradation treatment of dyes.

[0111] 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 dyes, characterized in that, Includes the following steps: Choline chloride-ethylene glycol, water, nickel source, zinc source, iron source and citric acid are mixed and subjected to a complexation reaction to obtain a sol; The pH of the sol was adjusted to 7-11 and heated to form a gel; the gel was then ignited to obtain the precursor. The precursor is calcined at 450~850℃ to obtain the magnetic composite photocatalyst for removing dyes. Wherein, the molar ratio of zinc in the zinc source, nickel in the nickel source, and iron in the iron source is x:1-x:1.9~2.8, where 0.2≤x≤0.8; The main components of the magnetic composite photocatalyst include nickel-zinc ferrite and α-ferric oxide; During the mixing process, the molar ratio of choline chloride to ethylene glycol is 0.5~1.5:1.5~2.5; During the mixing process, the ratio of the sum of the volumes of choline chloride and ethylene glycol to the volume of water is 18~27:3~12; The ratio of the molar amount of citric acid to the sum of the molar amounts of zinc in the zinc source, nickel in the nickel source, and iron in the iron source is 1 to 1.5:

1. The temperature of the complexation reaction is 40~90℃.

2. The application of the magnetic composite photocatalyst for removing dye prepared by the method described in claim 1 in the photocatalytic removal of dye.

3. The application according to claim 2, characterized in that, It includes at least one of the following features (1) to (4): (1) The magnetic composite photocatalyst has a removal rate of ≥70% for methylene blue solutions with a concentration ≤20 mg / L; (2) The magnetic composite photocatalyst achieves a removal rate of ≥85% for methyl orange solutions with a concentration ≤10 mg / L; (3) The magnetic composite photocatalyst achieves a removal rate of ≥70% for Congo red solutions with a concentration ≤140 mg / L; (4) The magnetic composite photocatalyst has a removal rate of ≥88% for malachite green solution with a concentration ≤10mg / L.

Images