A TiO 2 @Fe 3 O 4 Preparation of magnetic materials and their application in degradation of potato starch wastewater

Abstract

The invention discloses a preparation method of a TiO2@Fe3O4 magnetic material and its application in the wastewater for degrading potato starch. The preparation method comprises the following steps: dissolving a divalent iron salt and a trivalent iron salt respectively to prepare a solution, carrying out a water bath reaction under protective gas conditions, then heating and adding a surfactant and a precipitant until the reaction is completed, separating, washing, drying and grinding to obtain nano Fe3O4 particles; under strong ultrasonic conditions, dropping tetrabutyl titanate into pure water and adding nano Fe3O4 particles, ultrasonicating, precipitating and washing to obtain a wet gel, and drying the wet gel to obtain a TiO2@Fe3O4 nanocomposite material. The invention adopts the preparation method of the above-mentioned TiO2@Fe3O4 magnetic material and its application in the wastewater for degrading potato starch. The TiO2@Fe3O4 composite catalyst has good catalytic performance and stability at the same time, has a high COD degradation rate for dye wastewater such as methylene blue and potato wastewater, and can be reused many times after recovery, and has important application prospects in the field of potato wastewater removal.

Description

Technical Field

[0001] The invention relates to the technical field of nanocomposite materials, and in particular to the preparation of a TiO2@Fe3O4 magnetic material and its application in degrading potato starch wastewater. Background Art

[0002] Potato starch wastewater is a high-concentration organic wastewater. High-concentration organic wastewater is composed of high-concentration, high-salt, and difficult-to-degrade wastewater. The water quality composition is relatively complex and contains a large amount of organic pollutants. The COD value is generally higher than 1000 mg / L, and even as high as hundreds of thousands of milligrams per liter. This type of wastewater is very harmful to the environment and degrades slowly naturally. If it is not treated scientifically, it will cause irreversible effects on the ecosystem, pollute groundwater, and damage human health.

[0003] Nano-TiO2, as a typical semiconductor material, is one of the most studied photocatalysts in recent years and has been widely used in the field of sewage treatment. At present, nano-TiO2 has shown obvious advantages and potential in the degradation of wastewater, but it generally has disadvantages such as long degradation time, limited degradation capacity, and difficulty in catalyst recovery. Therefore, it is urgent to find an efficient and easily recyclable catalyst. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a TiO2@Fe3O4 magnetic material and its application in degrading potato starch wastewater, so as to solve the problems that the existing nano-titanium dioxide has limited degradation capacity for potato starch wastewater and is difficult to recycle.

[0005] To achieve the above object, the first aspect of the present invention provides a method for preparing a TiO2@Fe3O4 magnetic material, comprising the following steps:

[0006] (1) Preparation of Fe3O4 nanomaterials

[0007] The divalent iron salt and the trivalent iron salt are dissolved separately to prepare a solution, reacted in a water bath under protective gas conditions, then the temperature is increased and a surfactant and a precipitant are added until the reaction is completed, and then separated, washed, dried and ground to obtain nano-Fe3O4 particles;

[0008] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0009] Under strong ultrasonic conditions, tetrabutyl titanate was dropped into pure water and nano-Fe3O4 particles were added, and wet gel was obtained by ultrasonication, precipitation and washing. The wet gel was dried to obtain TiO2@Fe3O4 nanocomposite material.

[0010] Preferably, the molar ratio of the divalent iron salt to the trivalent iron salt in step (1) is 2:3.

[0011] Preferably, the water bath reaction temperature in step (1) is 30°C, the temperature is raised to 50°C, and the reaction time is 30-60 min.

[0012] Preferably, the surfactant in step (1) is PEG-400, the amount of the surfactant added is 6 mL, and the precipitant is NH3·H2O, the amount of the precipitant added is 12 mL.

[0013] Preferably, after the reaction in step (1) is completed, ultrasonic dispersion is performed for 5 minutes, cooled to room temperature, and the nano-Fe3O4 particles are separated from the liquid with the aid of a magnet, then filtered and separated, washed with pure water and anhydrous ethanol, and dried at 60°C for 48 hours.

[0014] Preferably, the strong ultrasound conditions in step (2) are: power 120 W, time 5-7 h.

[0015] The raw materials for preparing nanocomposites, TiO2 and Fe3O4 nanoparticles, are easy to agglomerate, which is not conducive to the uniform loading of TiO2 on Fe3O4. Strong ultrasound can better disperse the nanoparticles, and the ultrasound temperature can reach 60-70°C at most, which can reduce the oxidation of Fe3O4. TiO2 is evenly loaded on Fe3O4, and the surface area for generating electrons-holes is larger, and the degradation efficiency of the prepared TiO2@Fe3O4 nanocomposites is higher. By fixing the amount of TiO2 and changing the doping amount of Fe3O4, the composite photocatalytic material with the best degradation rate is studied.

[0016] The present invention prepares the composite material under ultrasonic conditions with a power of 120W. Too low a power may result in insufficient dispersion, and TiO2 and Fe3O4 nanoparticles cannot be uniformly loaded on the Fe3O4 magnetic material due to their own agglomeration, resulting in low degradation efficiency of the TiO2@Fe3O4 magnetic material. Too high a power may cause the TiO2 to be unable to be successfully loaded on the Fe3O4 due to the strong cavitation effect of the ultrasound.

[0017] Preferably, in step (2), the ratio of the volume of tetrabutyl titanate to the mass of ferrosoferric oxide is 10 mL: 0.2-1 g.

[0018] Preferably, the vacuum drying temperature of the wet gel in step (2) is 60-80° C. and the drying time is 8-12 h.

[0019] The second aspect of the present invention provides a TiO2@Fe3O4 magnetic material prepared by the above-mentioned preparation method.

[0020] The third aspect of the present invention provides an application of a TiO2@Fe3O4 magnetic material, and the application of the TiO2@Fe3O4 magnetic material in degrading potato starch wastewater.

[0021] Therefore, the present invention adopts the preparation of a TiO2@Fe3O4 magnetic material with the above structure and its application in the degradation of potato starch wastewater, which has the following beneficial effects:

[0022] (1) In the TiO2@Fe3O4 composite catalyst prepared by the present invention, TiO2 nanoparticles are successfully coated on the surface of Fe3O4 particles, and the doped Fe3O4 enables it to have high catalytic efficiency and good magnetic separation performance.

[0023] (2) The TiO2@Fe3O4 composite catalyst can be stably applied to methylene blue and potato wastewater, and can degrade the COD, total carbon and total nitrogen in the wastewater, and has broad application prospects in anti-pollution environments.

[0024] (3) The TiO2@Fe3O4 composite catalyst prepared by the present invention is used as a magnetic material for photocatalytic degradation of potato starch wastewater and has good stability after being recycled and used three times.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD characterization diagrams of Fe3O4, TiO2, and TiO2@Fe3O4;

[0027] Figure 2 FT-IR images of Fe3O4 (red), TiO2 (black), and TiO2@Fe3O4 (blue);

[0028] Figure 3 TEM image, EDX spectrum and surface scanning mapping analysis diagram of TiO2@Fe3O4 nanocomposite materials;

[0029] Figure 4 MH curve of TiO2@Fe3O4 nanocomposite;

[0030] Figure 5 It is the ultraviolet absorption curve of catalytic degradation with different Fe3O4 doping amounts;

[0031] Figure 6 The degradation rate histogram of catalytic degradation with different Fe3O4 doping amounts;

[0032] Figure 7 It is a curve diagram of catalytic degradation rate with different catalyst dosages;

[0033] Figure 8 The histogram of COD, TOC and TN degradation rate of potato wastewater by visible light catalytic degradation of composite catalyst under different illumination time;

[0034] Fig. 9 The UV absorption curves of the composite catalyst for visible light catalytic degradation of potato wastewater under different illumination times;

[0035] Fig.10 To study the effect of repeated use of the composite catalyst three times on the photocatalytic degradation of MG;

[0036] Fig.11 The effect of the scavenger on the photocatalytic degradation of MG. DETAILED DESCRIPTION

[0037] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0038] Example 1

[0039] A method for preparing a TiO2@Fe3O4 magnetic material comprises the following steps:

[0040] (1) Preparation of Fe3O4 nanomaterials

[0041] Weigh 6.1g of divalent iron salt (FeCl2·4H2O) and 4.8g of trivalent iron salt (FeCl3·6H2O) and dissolve them to make 50mL solution, add them to a 250mL three-necked flask under N2 protection for reaction, the water bath temperature is 30℃, the mechanical stirring speed is 300r / min, adjust the water bath temperature to 50℃ after 5min, drop 6mL of surfactant PEG-400 and 12mL of precipitant NH3·H2O into the reaction system, and terminate the reaction time for 50min. The final sample solution needs to be ultrasonically dispersed for 5min and naturally cooled at room temperature for 1h, and finally separated from the solution with the help of a magnet, then filtered under reduced pressure, washed with pure water and anhydrous ethanol 3 times, placed at 60℃ and dried for 48h, and ground to obtain nano-Fe3O4 particles.

[0042] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0043] Under strong ultrasonic conditions of 120W, 10ml of tetrabutyl titanate was slowly dripped into ultrapure water to dissolve, and 0.2g of ferroferric oxide was added. After ultrasonic treatment for 6h, the brown precipitate was collected and washed with ethanol and pure water several times. Then, the wet gel was vacuum dried at 70℃ for 10h to obtain the TiO2@Fe3O4 composite material, which was recorded as TF-0.2.

[0044] Example 2

[0045] A method for preparing a TiO2@Fe3O4 magnetic material comprises the following steps:

[0046] (1) Preparation of Fe3O4 nanomaterials

[0047] The specific steps are the same as those in Example 1.

[0048] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0049] Under strong ultrasound conditions of 120W, 10ml of tetrabutyl titanate was slowly dripped into ultrapure water to dissolve, and 0.4g of ferroferric oxide was added. After ultrasound for 6h, the brown precipitate was collected and washed several times with ethanol and pure water. Then, the wet gel was vacuum dried at 70℃ for 10h to obtain the TiO2@Fe3O4 composite material, which was recorded as TF-0.4.

[0050] Example 3

[0051] A method for preparing a TiO2@Fe3O4 magnetic material comprises the following steps:

[0052] (1) Preparation of Fe3O4 nanomaterials

[0053] The specific steps are the same as those in Example 1.

[0054] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0055] Under strong ultrasound conditions of 120W, 10ml of tetrabutyl titanate was slowly dripped into ultrapure water to dissolve, and 0.6g of ferrosoferric oxide was added. After ultrasound for 6h, the brown precipitate was collected and washed several times with ethanol and pure water. Then, the wet gel was vacuum dried at 70℃ for 10h to obtain the TiO2@Fe3O4 composite material, which was recorded as TF-0.6.

[0056] Example 4

[0057] A method for preparing a TiO2@Fe3O4 magnetic material comprises the following steps:

[0058] (1) Preparation of Fe3O4 nanomaterials

[0059] The specific steps are the same as those in Example 1.

[0060] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0061] Under strong ultrasound conditions of 120W, 10ml of tetrabutyl titanate was slowly dripped into ultrapure water to dissolve, and 0.8g of ferroferric oxide was added. After ultrasound for 6h, the brown precipitate was collected and washed several times with ethanol and pure water. Then, the wet gel was vacuum dried at 70℃ for 10h to obtain the TiO2@Fe3O4 composite material, which was recorded as TF-0.8.

[0062] Example 5

[0063] A method for preparing a TiO2@Fe3O4 magnetic material comprises the following steps:

[0064] (1) Preparation of Fe3O4 nanomaterials

[0065] The specific steps are the same as those in Example 1.

[0066] (2) Preparation of TiO2@Fe3O4 nanocomposites

[0067] Under strong ultrasonic conditions of 120W, 10ml of tetrabutyl titanate was slowly dripped into ultrapure water to dissolve, and 1g of ferroferric oxide was added. After ultrasonic treatment for 6h, the brown precipitate was collected and washed several times with ethanol and pure water. Then, the wet gel was vacuum dried at 70℃ for 10h to obtain the TiO2@Fe3O4 composite material, which was recorded as TF-1.

[0068] Comparative Example 1

[0069] The difference from Example 2 is that step (2) is omitted and Fe3O4 nanomaterial is directly obtained, which is denoted as F.

[0070] Comparative Example 2

[0071] The difference from Example 2 is that step (1) is omitted, and no ferroferric oxide is added in step (2), and TiO2 material is directly obtained. It is denoted as T.

[0072] Test Example 1

[0073] The structure of the TiO2@Fe3O4 composite material prepared in Example 2 was characterized.

[0074] (1) X-ray diffraction (XRD) analysis

[0075] X-ray diffraction (XRD) was used to analyze the crystal structure and phase of TiO2, Fe3O4, and TiO2@Fe3O4 composite catalysts. Figure 1As shown. At the (220), (311), (400), (511) and (440) diffraction planes, the corresponding 2θ peak characteristic peaks of Fe3O4 are 30.2°, 35.6°, 43.1°, 56.9° and 62.9°, respectively, confirming the formation of Fe3O4 material. The 2θ peaks of anatase nano-TiO2 appear at 25.5°, 37.9°, 48.1°, 54.2°, 62.8° and 69.1°, and the corresponding crystal plane indices are (101), (004), (200), (211), (204) and (116). As the doping amount of Fe3O4 in the TiO2@Fe3O4 composite catalyst gradually increases, the diffraction peak of Fe3O4 gradually weakens, indicating that the loading amount of TiO2 on Fe3O4 gradually increases.

[0076] (2) Infrared spectroscopy analysis

[0077] Figure 2 Infrared spectra of TiO2, Fe3O4 and TiO2@Fe3O4 composite catalysts. 3400 cm -1 The peak at 1635 cm belongs to the stretching vibration peak of water and OH group. -1 The peak at 400~700cm is the bending vibration peak of the OH group. The high OH stretching frequency indicates that the surface hydroxide strength is high, which is conducive to the dispersion of Fe3O4 nanoparticles and also enhances the affinity between Fe3O4 nanoparticles and TiO2. -1 The bands at 569 cm are attributed to the stretching vibrations of Ti-O and Ti-O-Ti. -1 The absorption peak belongs to the stretching vibration peak of Fe-O in Fe3O4. By comparing the spectrum of TiO2@Fe3O4 composite materials, it is found that with the decrease of Fe3O4 doping amount in the composite catalyst, the stretching vibration peak of Fe-O in Fe3O4 gradually becomes smaller, which may be due to the gradual increase of the loading amount of TiO2 on Fe3O4, and TiO2 wraps the Fe3O4 nanoparticles. And it can be noted that the Ti-O peak overlaps with the Fe-O peak, indicating that the TiO2@Fe3O4 nanocomposite material has been successfully prepared. However, the crystal form and coating state of TiO2 should be confirmed by XRD and TEM detection.

[0078] (3) Microstructure analysis

[0079] In order to further study the microstructure of TiO2@Fe3O4 composite catalyst, TEM was used to characterize and analyze TF-0.4. Figure 3(a) It can be clearly seen that the dark area is Fe3O4, and the light area is TiO2. It can be seen that TiO2 is successfully coated on the Fe3O4 particles. At the same time, Fe3O4 shows a certain agglomeration phenomenon due to the attraction between magnetic powders. Figure 3 In (b), it can be clearly seen that Fe3O4 is the core, the TiO2 coating layer is clearly visible, and the coating is very uniform. Figure 3 (c) is the EDX characterization spectrum of the composite catalyst, in which the diffraction peaks of Ti, Fe, and O appear, with mass percentages of 27.24%, 3.52%, and 12.93%, respectively. This value is consistent with the theoretical value of the relevant elements in the catalyst. The element mapping of TiO2@Fe3O4 is shown in Figure 2. Figure 3 As shown in (d), red, orange, and yellow are the element distributions of Ti, Fe, and O, respectively. It can be seen that the constituent elements of the TiO2@Fe3O4 nanocomposite are Ti, Fe, and O. This is consistent with the results of XRD, FT-IR, and TEM, indicating that the TiO2@Fe3O4 nanocomposite was successfully prepared.

[0080] (4) Magnetic properties (VSM) analysis

[0081] like Figure 4 MH curve of TiO2@Fe3O4 composite material. No hysteresis loop is observed in the figure, indicating that the composite material has superparamagnetism at room temperature. The saturation magnetization of TF-0.2, TF-0.4, TF-0.6, TF-0.8 and TF-1 are 3.9, 6.1, 9.3, 11.3 and 15.4 emu g respectively. This is because the magnetic properties of Fe3O4 are related to particle size and content. It can be seen from the figure that with the increase of Fe3O4 doping amount, the relative content of Fe3O4 nanoparticles in TiO2@Fe3O4 composite material increases, thereby enhancing the magnetism of TiO2@Fe3O4 composite material.

[0082] Test Example 2

[0083] The photodegradation performance of the TiO2@Fe3O4 composite catalyst prepared in Examples 1-5 on methylene blue was tested.

[0084] The test process is as follows: the photocatalytic performance of the TiO2@Fe3O4 composite catalyst synthesized in Examples 1-5 is measured in a weighing bottle, the methylene blue solution is treated with visible light catalysis, and the catalytic degradation effect of the catalyst is evaluated by the ultraviolet degradation rate of the methylene blue solution. The light source is a xenon lamp, and the filter provides 400-780nm visible light. 25mL of 5mg / L methylene blue solution and 10mg of the composite catalyst sample are mixed evenly in the reaction system, the light source is turned on, the reaction is continued for a predetermined time of 3h, the catalyst is removed by magnetic separation, the absorbance of the filtrate is measured by an ultraviolet visible spectrophotometer, and the ultraviolet absorbance degradation rate of methylene blue by the photocatalytic degradation technology is calculated.

[0085] Figure 5 The figure is the ultraviolet absorption curve of the catalytic degradation of the composite catalyst with different Fe3O4 doping amounts. It can be seen that with the increase of the Fe3O4 doping amount, the removal rate of methylene blue by the TiO2@Fe3O4 composite material gradually decreases, and the maximum absorption peak of its ultraviolet absorption curve also gradually increases. Figure 6 The degradation rate histogram of the catalytic degradation of the composite catalyst with different Fe3O4 doping amounts shows that the photocatalytic degradation rate of pure TiO2 for methylene blue solution is 66.6%, and the degradation rates of methylene blue in Examples 1-5 are 61.7%, 56.7%, 49.9%, 41.5%, and 31.5%, respectively. As the Fe3O4 doping amount in the catalyst decreases, the catalytic efficiency decreases. When the Fe3O4 doping amount in the TiO2@Fe3O4 composite catalyst is 0.2g, the catalytic degradation rate is the highest, reaching 61.7%. However, according to Figure 4 The VSM magnetic curve analysis of the TiO2@Fe3O4 composite catalyst with different Fe3O4 doping amounts shows that TF-0.2 has the smallest magnetization intensity and cannot achieve the expected magnetic separation effect. Compared with other materials, TF-0.4 has good magnetic separation effect and the best photocatalytic performance, and the catalytic degradation rate is only 5.0% lower than that when the doping amount is 0.2g. Therefore, the magnetic TiO2@Fe3O4 nanocomposite material doped with 0.4gFe3O4 is the best composite photocatalyst and is used for the photocatalytic degradation of potato starch processing wastewater in subsequent experiments.

[0086] Test Example 3

[0087] The photodegradation performance of the TiO2@Fe3O4 composite catalyst prepared in Example 2 on potato starch wastewater was tested.

[0088] The test process is as follows: The photocatalytic performance of the TiO2@Fe3O4 composite catalyst synthesized in Example 2 is measured in a weighing bottle, and the potato starch processing wastewater is treated with visible light catalysis, and the catalytic degradation effect of the catalyst is evaluated by the removal rate of tail water COD, TOC, and TN. The light source is a xenon lamp, and the filter provides 400-780nm visible light. 50mL of potato starch processing wastewater diluted 50 times and the composite catalyst sample are mixed evenly in the reaction system, the light source is turned on, the reaction is continued for a predetermined time, the catalyst is removed by magnetic separation, the absorbance of the filtrate is measured by an ultraviolet visible spectrophotometer, the COD value of the sample is measured by a COD measuring instrument, the removal rate of tail water COD by the photocatalytic degradation technology is calculated, the total carbon and total nitrogen value of the sample is measured by a total organic carbon / nitrogen analyzer, and the removal rate of the total carbon and total nitrogen of the wastewater by the photocatalytic degradation technology is calculated.

[0089] The photocatalytic performance of the TiO2@Fe3O4 composite catalyst of Example 2 was specifically tested under different amounts of composite catalyst and different reaction times. The parameters and results of the test process are shown in Table 1.

[0090]

[0091] From Table 1, we can see that different dosages of TiO2@Fe3O4 composite catalyst are used to catalyze potato wastewater for 3h. The dosage of catalyst ranges from 10mg to 50mg. As the dosage of catalyst increases, the catalytic efficiency gradually increases, and the COD, TOC, and TN degradation rates of potato wastewater reach the highest, which are 25.88%, 15.89%, and 5.10%, respectively. However, when the dosage of catalyst exceeds 50mg / 50mL, the catalytic efficiency is significantly reduced. This may be due to the excessive concentration of catalyst particles, which produces a strong scattering effect on the incident light, affecting the full utilization of light, thereby reducing the catalytic efficiency. Therefore, the optimal catalyst dosage is 50mg / 50mL. Figure 8 It shows the photocatalytic degradation of potato wastewater under different illumination times under the condition of catalyst dosage of 50mg / 50mL. It can be seen that the degradation rates of COD, TOC and TN in potato wastewater gradually increase with the increase of catalytic time. When the catalyst time is 9h, the degradation rates of COD, TOC and TN can reach 62.84%, 40.71% and 20.00%.

[0092] Fig. 9 The figure shows the UV absorption curve of the photocatalytic degradation of potato wastewater under different illumination times. The maximum absorption peak gradually decreases, indicating that the organic matter in the potato wastewater is degraded.

[0093] Test Example 4

[0094] The reusability of TiO2@Fe3O4 nanocomposite catalyst was studied.

[0095] In order to investigate the reusability of the catalytic material, a recycling experiment was conducted. Using 10 mg of TiO2@Fe3O4 composite catalyst and 25 ml of methylene blue aqueous solution with an initial concentration of 1 mg / L as raw materials, the recyclability of the composite catalyst was studied. Fig.10 As shown in the figure, after three cycles, the catalytic efficiency of the composite material TiO2@Fe3O4 decreased from 79.8% to 76.9%, but it still had a high catalytic activity. This shows that the prepared TiO2@Fe3O4 has good stability.

[0096] Test Example 5

[0097] The photocatalytic mechanism of TiO2@Fe3O4 nanocomposite catalyst was studied.

[0098] In order to explore the possible photocatalytic mechanism of TiO2@Fe3O4 composite catalyst and determine the main active substances in the photocatalytic degradation system, an active free radical capture experiment was carried out. Using 10 mg of TiO2@Fe3O4 composite catalyst and 25 ml of methylene blue aqueous solution with an initial concentration of 1 mg / L as raw materials, 1 mM isopropanol (i-PrOH), 1 mM ascorbic acid, and 1 mM potassium iodide (KI) were introduced into the catalytic degradation system as capture agents to capture ·OH, ·O 2- 、h + The catalytic activity of the composite catalyst on simulated methylene blue wastewater was determined. Fig.11 As shown in the figure, without any capture agent, the degradation rate of simulated wastewater by TiO2@Fe3O4 composite catalyst was almost 100% within 2 h; when KI and i-PrOH were added, the addition of i-PrOH had a significant inhibitory effect on the catalytic degradation rate, indicating that h + ·OH is the main active substance in the visible light catalytic degradation process of TiO2@Fe3O4 composite catalyst, which plays a decisive role in its catalytic activity. After adding 1mM ascorbic acid into the catalytic degradation system, the degradation rate is reduced to a certain extent, indicating that a small amount of ·O 2- The above results show that the addition of three scavengers inhibited the degradation rate of MG. + ·OH is the main active substance of TiO2@Fe3O4 composite catalyst, which directly oxidizes and degrades organic matter in the photocatalytic process. + OH - , and O 2- The contributions to the MG degradation rate were 50%, 39.3% and 8.5%, respectively.

[0099] Therefore, the present invention adopts the preparation of a TiO2@Fe3O4 magnetic material with the above structure and its application in the degradation of potato starch wastewater. The TiO2@Fe3O4 composite catalyst has both good catalytic performance and stability, and has a high COD degradation rate for dye wastewater such as methylene blue and potato wastewater, and can be reused many times after recovery, which has important application prospects in the field of potato wastewater removal.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Application of TiO2@Fe3O4 magnetic material in the degradation of potato starch wastewater, characterized in that: 50 mg TiO2@Fe3O4 magnetic material was added to 50 mL of potato wastewater diluted 50 times and treated with visible light catalysis for 9 h; The preparation method of TiO2@Fe3O4 magnetic material comprises the following steps: (1) Preparation of Fe3O4 nanomaterials Dissolve the divalent iron salt and the trivalent iron salt separately to prepare a solution, the molar ratio of the divalent iron salt to the trivalent iron salt is 2:3, react in a water bath under protective gas conditions, then heat up and add a surfactant and a precipitant until the reaction is complete, separate, wash, dry and grind to obtain nano-Fe3O4 particles; the surfactant is PEG-400; (2) Preparation of TiO2@Fe3O4 magnetic materials Under strong ultrasonic conditions, the strong ultrasonic conditions are: power 120W, time 5-7h, tetrabutyl titanate is dropped into pure water and nano-Fe3O4 particles are added, the volume ratio of tetrabutyl titanate to the mass ratio of ferrosoferric oxide is 10mL:0.4g, ultrasonication, precipitation and washing are performed to obtain wet gel, and the wet gel is dried to obtain TiO2@Fe3O4 magnetic material.

2. The use according to claim 1, characterized in that: The water bath reaction temperature in step (1) is 30°C, which is raised to 50°C, and the reaction time is 30-60min.

3. The use according to claim 2, characterized in that: In step (1), the amount of surfactant added is 6 mL, the precipitant is NH3·H2O, and the amount of precipitant added is 12 mL.

4. The use according to claim 3, characterized in that: After the reaction in step (1) is completed, ultrasonic dispersion is performed for 5 minutes, cooled to room temperature, and the nano-Fe3O4 particles are separated from the liquid with the help of a magnet, then filtered and separated, washed with pure water and anhydrous ethanol, and placed at 60°C to dry for 48 hours.

5. The use according to claim 4, characterized in that: The vacuum drying temperature of the wet gel in step (2) is 60-80° C. and the time is 8-12 h.

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