阅读说明：本技术 一种铋/钨酸铋/四氧化三铁复合光催化剂的制备方法 (Preparation method of bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst ) 是由 李靖 杨华美 李响 窦艳 李昭 王鹏 董黎明 堵锡华 吉顺育 于 2021-02-20 设计创作，主要内容包括：本发明公开了自制Fe-3O-4/C磁微球、聚乙二醇(PEG)作为分散剂,通过溶剂热合成法,控制调节Bi-2WO-6和Fe-3O-4/C磁微球的质量比例,合成高活性、高稳定性、易回收的铋/钨酸铋/四氧化三铁复合光催化剂,Bi-2WO-6呈纳米片状包裹在Fe-3O-4/C磁微球表面,形成多层壳核包裹结构。本申请公开的Bi/Bi-2WO-6/Fe-3O-4复合光催化剂在可见光照射下能够催化还原Cr(VI),其中,Fe-3O-4/C磁微球含量30％的Bi/Bi-2WO-6/Fe-3O-4-30的光催化效率最高,约是Bi-2WO-6的2.8倍、Fe-3O-4/C磁微球的4.2倍,本发明公开的制备方法便于推广,效果优异,制备的Bi/Bi-2WO-6/Fe-3O-4复合光催化剂具备较好的应用前景。(The invention discloses self-made Fe 3 O 4 the/C magnetic microsphere and polyethylene glycol (PEG) are used as dispersing agents, and Bi is controlled and adjusted through a solvent thermal synthesis method 2 WO 6 And Fe 3 O 4 The mass ratio of the/C magnetic microspheres is used for synthesizing a bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst which has high activity, high stability and easy recovery, and Bi 2 WO 6 Is wrapped in Fe in nano-sheet shape 3 O 4 And forming a multi-layer shell-core packaging structure on the surface of the/C magnetic microsphere. Bi/Bi disclosed in the present application 2 WO 6 /Fe 3 O 4 The composite photocatalyst can catalyze and reduce Cr (VI) under the irradiation of visible light, wherein Fe 3 O 4 Magnetic/magneticBi/Bi with 30% of microsphere content 2 WO 6 /Fe 3 O 4 The photocatalytic efficiency of-30 is highest, about Bi 2 WO 6 2.8 times of that of Fe 3 O 4 4.2 times of the magnetic microsphere/C, the preparation method disclosed by the invention is convenient to popularize, the effect is excellent, and the prepared Bi/Bi 2 WO 6 /Fe 3 O 4 The composite photocatalyst has better application prospect.)

1. A preparation method of a bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst is characterized in that the preparation method of the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst comprises the following steps:

s1: a certain amount of Fe₃O₄Sufficiently grinding a certain amount of glucose to obtain a mixture, adding a certain amount of polyethylene glycol into the mixture, and continuously grinding;

s2: dissolving the mixture obtained in the step S1 in deionized water, carrying out ultrasonic treatment, taking out, mechanically stirring, and repeating the operation for multiple times;

s3: transferring the mixed solution obtained in the step S2 to a stainless steel reaction kettle, heating in a drying oven at constant temperature, cooling to room temperature after heating, obtaining a product through centrifugal separation and water washing, drying the cleaned product in the drying oven, grinding, and performing magnetic separation to obtain Fe₃O₄C microspheres.

S4: weighing a certain amount of Bi (NO)₃)₃·5H₂O and a certain amount of Na₂WO₄·2H₂O, grinding to be uniform to obtain a precursor, and weighing the Fe obtained in the step S3₃O₄Adding the/C magnetic microspheres into the precursor, grinding until the mixture is uniform, mixing the mixture with ethylene glycol, transferring the mixture into a stainless steel reaction kettle, keeping the temperature constant, cooling the reaction to room temperature, cleaning, drying the obtained product, grinding, and performing magnetic separation to obtain the magnetic microsphere.

2. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein Fe in the step S1₃O₄Glucose and polyethylene glycol in a molar ratio of 2.5:25: 1.

3. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein Fe in the step S1₃O₄And the grinding time of glucose is 30min, and the grinding time after adding polyethylene glycol in the step S1 is 30 min.

4. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein the polyethylene glycol in the step S1 is polyethylene glycol 6000.

5. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein in the step S2, ultrasonic treatment is performed for 5min, the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst is taken out and mechanically stirred for 5min, and the operation is repeated three times.

6. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein a polytetrafluoroethylene lining is contained in the stainless steel reaction kettle in the step S3.

7. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein in the step S3, the reaction temperature is 180 ℃, and the heating is carried out for 12 hours; drying the cleaned product at 80 deg.C for 6h, grinding, and magnetically separating to obtain Fe₃O₄Magnetic microsphere/C.

8. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein in the step S4, Bi (NO) is added₃)₃·5H₂O and Na₂WO₄·2H₂The molar ratio of O is 2: 1.

9. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein in the step S4, the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst is preparedBi(NO₃)₃·5H₂O and Na₂WO₄·2H₂Grinding for 30min, adding Fe₃O₄And the post-grinding time of the/C magnetic microspheres is 20 min.

10. The method for preparing the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst as claimed in claim 1, wherein in the step S4, the reaction temperature is 180 ℃, and the heating is carried out for 12 hours; the drying temperature of the obtained product is 80 ℃, and the drying time is 6 h.

Technical Field

The invention relates to the field of preparation of composite photocatalysts, in particular to a preparation method of a visible light driven bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst.

Background

Cr (VI) has stronger mobility and toxicity in water and is one of the priority control pollutants in the global scope. The industrial waste water generated in the production and use of chromium-containing compounds contains a large amount of chromiumCr (VI) and chromium-containing industrial wastewater which is not treated or does not reach the standard can seriously affect the ecological environment. Of note is the low toxicity of Cr (III), which has a low oxidation number, and the tendency to precipitate out of water (K)^θ _sp(Cr(OH)₃)＝6.3×10^–31)). Therefore, conversion of Cr (VI) to Cr (III) has become a common method for treating chromium-containing wastewater. In the process of treating chromium-containing wastewater by using a chemical reduction method, a large amount of chemical reagents are consumed, secondary pollution is possibly caused, and a green and economic Cr (VI) reduction method still needs to be developed. The semiconductor photocatalysis technology utilizes photo-generated electrons and holes generated by the semiconductor catalyst absorbing the light energy of sunlight to drive the oxidation-reduction reaction, has wide application in the aspects of photocatalytic hydrogen production, carbon dioxide reduction, organic pollutant degradation and hexavalent chromium reduction, and has the advantages of low consumption, economy, recyclability and the like. Therefore, the photocatalytic reduction technology has potential application prospect in treating the chromium-containing wastewater. However, according to the current application of the photocatalytic technology, the currently used catalyst has low visible light activity, poor stability, difficulty in separation from a solution, and the like, which hinders the practical application of the photocatalytic reduction method. Therefore, the research on the high-activity high-stability visible light driven semiconductor catalyst has important significance for the popularization and application of the photocatalytic technology.

Bi₂WO₆The semiconductor is a novel narrow-band-gap semiconductor (2.6-2.8 eV), has a similar layered perovskite structure, and compared with oxide and sulfide photocatalysts, layers of the layered structure can be used as an active region of photocatalytic reaction, and meanwhile, the layered structure is beneficial to separating photoproduction electrons and holes, so that the photocatalytic efficiency is greatly improved. The separation of photon-generated carriers can be further promoted by methods such as noble metal deposition, non-metal doping, heterojunction construction and the like, so that the Bi content is improved₂WO₆Photocatalytic activity of (1). Since Bi₂WO₆The hydrophilic property of (B) is such that it is difficult to make Bi into a form which does not use a method such as centrifugation₂WO₆Separating from the aqueous solution.

Fe₃O₄Is a cheap and environment-friendly magnetic n-type semiconductor material, has a narrow band gap (1.4eV) and has strong visibilityLight absorption properties while Fe₃O₄Has strong magnetism, and can recover the catalyst from the photocatalytic reaction solution by using a magnet. But also due to Fe₃O₄The band gap of the photocatalyst is narrow, the photocatalytic activity of the photocatalyst is poor due to the high recombination rate of photo-generated electrons and holes, and the photocatalyst is rarely used as a photocatalyst alone and is often used as a magnetic carrier of other semiconductor photocatalysts. Research reports that Xu obtains three-dimensional Bi through a hydrothermal method₂WO₆/Fe₃O₄The composite material has higher degradation efficiency on RhB. Liu et al prepared Bi by template-free hydrothermal method₂WO₆/Fe₃O₄And the performance of the visible light photocatalytic degradation 17b-Estradiol is researched. In the synthesized composite material, due to Fe₃O₄Fe in (1)²⁺Is easily oxidized into Fe in air³⁺Resulting in a decrease in magnetic properties of the synthesized composite material, and therefore it is required to wrap Fe with a stable, high specific surface area support₃O₄。

Disclosure of Invention

In view of the above, the invention aims to provide a preparation method of a bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst, which is prepared by preparing Fe₃O₄the/C magnetic microspheres and polyethylene glycol (PEG) are used as dispersing agents to control and regulate Bi₂WO₆And Fe₃O₄The mass ratio of the/C magnetic microspheres to synthesize Bi/Bi with high activity, high stability and easy recovery₂WO₆/Fe₃O₄The composite photocatalyst has better catalytic activity of treating Cr (VI) by visible light catalysis.

The technical scheme is as follows:

a preparation method of a bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst is characterized in that the preparation method of the bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst comprises the following steps:

s1: a certain amount of Fe₃O₄Sufficiently grinding a certain amount of glucose to obtain a mixture, adding a certain amount of polyethylene glycol into the mixture, and continuously grinding;

s2: dissolving the mixture obtained in the step S1 in deionized water, carrying out ultrasonic treatment, taking out, mechanically stirring, and repeating the operation for multiple times;

s3: transferring the mixed solution obtained in the step S2 to a stainless steel reaction kettle, heating in a drying oven at constant temperature, cooling to room temperature after heating, obtaining a product through centrifugal separation and water washing, drying the cleaned product in the drying oven, grinding, and performing magnetic separation to obtain Fe₃O₄C, microspheres;

s4: weighing a certain amount of Bi (NO)₃)₃·5H₂O and a certain amount of Na₂WO₄·2H₂O, grinding to be uniform to obtain a precursor, and weighing the Fe obtained in the step S3₃O₄Adding the/C magnetic microspheres into the precursor, grinding until the mixture is uniform, mixing the mixture with ethylene glycol, transferring the mixture into a stainless steel reaction kettle, keeping the temperature constant, cooling the reaction to room temperature, cleaning, drying the obtained product, grinding, and performing magnetic separation to obtain the magnetic microsphere.

Preferably, Fe in step S1₃O₄Glucose and polyethylene glycol in a molar ratio of 2.5:25: 1.

Preferably, Fe in step S1₃O₄And the grinding time of glucose is 30min, and the grinding time after adding polyethylene glycol in the step S1 is 30 min.

Preferably, the polyethylene glycol in step S1 is polyethylene glycol 6000.

Preferably, the ultrasonic treatment in the step S2 is performed for 5min, the mechanical stirring is taken out for 5min, and the operation is repeated three times.

Preferably, the stainless steel reaction kettle in the step S3 contains a polytetrafluoroethylene lining;

preferably, the reaction temperature in the step S3 is 180 ℃, and the heating is carried out for 12 h; drying the cleaned product at 80 deg.C for 6h, grinding, and magnetically separating to obtain Fe₃O₄Magnetic microsphere/C.

Preferably, Bi (NO) is used in the step S4₃)₃·5H₂O and Na₂WO₄·2H₂The molar ratio of O is 2: 1.

Preferably, Bi (NO) is used in the step S4₃)₃·5H₂O and Na₂WO₄·2H₂Grinding for 30min, adding Fe₃O₄And the post-grinding time of the/C magnetic microspheres is 20 min.

Preferably, the reaction temperature in the step S4 is 180 ℃, and the heating is carried out for 12 h; the drying temperature of the obtained product is 80 ℃, and the drying time is 6 h.

Has the advantages that:

the invention has the beneficial effects that:

the invention discloses self-made Fe₃O₄the/C magnetic microsphere and polyethylene glycol (PEG) are used as dispersing agents, and Bi is controlled and adjusted through a solvent thermal synthesis method₂WO₆And Fe₃O₄The mass ratio of the/C magnetic microspheres is used for synthesizing a bismuth/bismuth tungstate/ferroferric oxide composite photocatalyst which has high activity, high stability and easy recovery, and Bi₂WO₆Nano sheet coated on Fe₃O₄The surface of the/C magnetic microsphere forms a multi-layer shell-core packaging structure. Bi/Bi disclosed in the present application₂WO₆/Fe₃O₄The composite photocatalyst can catalyze and reduce Cr (VI) under the irradiation of visible light, wherein Fe₃O₄Bi/Bi with 30 percent of/C magnetic microsphere content₂WO₆/Fe₃O₄The highest catalytic efficiency of-30, about Bi₂WO₆2.8 times of that of Fe₃O₄4.2 times of the magnetic microsphere/C, the preparation method disclosed by the invention is convenient to popularize, the effect is excellent, and the prepared Bi/Bi₂WO₆/Fe₃O₄The composite photocatalyst has better application prospect.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 shows Fe in the examples of the present application₃O₄/C、Bi/Bi₂WO₆、BiFe-20XRD pattern of (a);

FIG. 2 is an XRD pattern of a BiFe-10-40 sample in an example of the present application;

FIG. 3 shows Fe in the examples of the present application₃O₄、Fe₃O₄The infrared spectra of the/C magnetic microspheres and the BiFe-30 samples;

FIG. 4 shows Fe in the examples of the present application₃O₄FESEM image of (B);

FIG. 5 shows Fe in the examples of the present application₃O₄FESEM image of/C;

FIG. 6 shows Bi/Bi in the present embodiment₂WO₆FESEM image of (B);

FIG. 7 is a FESEM image of BiFe-40 in an example of the present application;

FIG. 8 is a FESEM image of BiFe-30 in an example of the present application;

FIG. 9 is a FESEM image of BiFe-20 in an example of the present application;

FIG. 10 is a FESEM image of BiFe-10 in an example of the present application;

FIG. 11 is a TEM image of BiFe-30 in the example of the present application;

FIG. 12 shows Fe in the examples of the present application₃O₄Magnetic microsphere/C and Bi/Bi₂WO₆BiFe-30 sample N₂An adsorption curve;

FIG. 13 shows Bi/Bi in the present embodiment₂WO₆/Fe₃O₄Ultraviolet-visible diffuse reflectance spectrogram;

FIG. 14 shows Bi/Bi in the present embodiment₂WO₆/Fe₃O₄Visible light catalytic reduction Cr (VI) diagram.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1: Bi/Bi₂WO₆/Fe₃O₄Preparation of composite photocatalyst

1、Fe₃O₄Magnetic microsphere/CPreparation of

0.4630g (2mmol) Fe₃O₄And 3.6030g (20mmol) of glucose (Glc) were thoroughly ground in an agate mortar for 30min, 0.5g (0.8mmol) of polyethylene glycol 6000(PEG6000) was added to the mixture and the grinding was continued for 30 min.

Dissolving the mixture in 20mL of deionized water, carrying out ultrasonic treatment for 5min, taking out, mechanically stirring for 5min, and repeating the operation for three times. Transferring the mixed solution into a polytetrafluoroethylene lining, sealing the polytetrafluoroethylene lining into a stainless steel reaction kettle, and heating the stainless steel reaction kettle in an oven at the constant temperature of 180 ℃ for 12 hours. Cooling to room temperature, centrifuging, washing with water to obtain product, oven drying at 80 deg.C for 6 hr, grinding, and magnetically separating to obtain Fe₃O₄C microspheres.

2、Bi/Bi₂WO₆/Fe₃O₄Preparation of composite photocatalyst

Weighing 5mmol (0.2425g) of Bi (NO)₃)₃·5H₂O and 2.5mmol (0.8243g) Na₂WO₄·2H₂And O, grinding in an agate mortar for 30min until the mixture is uniform. Respectively weighing 10%, 20%, 30% and 40%) of Fe₃O₄Adding the/C magnetic microspheres into the precursor, grinding for 20min to be uniform, transferring the mixture to a polytetrafluoroethylene lining filled with 30mL of Ethylene Glycol (EG), and sealing in a stainless steel reaction kettle. Keeping the temperature at 180 ℃ for 12 h. Cooling the reaction to room temperature, ultracentrifuging and cleaning with ethanol and deionized water, drying the product at 80 deg.C for 6 hr, grinding, and magnetic separating. For convenience of presentation, in terms of Fe₃O₄The adding mass of the/C magnetic microspheres is respectively marked as BiFe-10, BiFe-20, BiFe-30 and BiFe-40.

Preparation of Bi/Bi as described above₂WO₆/Fe₃O₄Experimental procedure for composite materials without addition of Fe₃O₄The product prepared from the/C magnetic microspheres is marked as Bi/Bi₂WO₆。

Example 2: Bi/Bi₂WO₆/Fe₃O₄Performance evaluation of composite photocatalyst

1、Bi/Bi₂WO₆/Fe₃O₄Analysis of photocatalytic Activity

At 50 mg.L^-1Potassium dichromate (K)₂Cr₂O₇) Investigation of the resulting Bi/Bi₂WO₆/Fe₃O₄Photocatalytic activity of (1). Stirring 300mL of pollutant solution and 300mg of catalyst in a dark place until adsorption-desorption balance is achieved; and then, opening a 200W Xe lamp to perform visible light catalytic activity analysis, taking 5mL of liquid to be detected at fixed illumination intervals in the illumination process, obtaining supernatant through centrifugal separation, and determining the concentration of pollutants in the supernatant by spectrophotometry. Wherein the concentration of Cr (VI) is detected by national standard diphenyl carbonyl dihydrazide spectrophotometry (lambda)_max540 nm). The measured absorbance was converted into the content C% of Cr (VI) using the formula (1). Wherein A is₀The absorbance of the solution at the time of illumination for 0min (i.e., at dark adsorption-desorption equilibrium), A_tIs the absorbance of the solution at the moment of illumination t min

2、Bi/Bi₂WO₆/Fe₃O₄XRD spectrum analysis of

FIG. 1 and FIG. 2 are Fe₃O₄Magnetic microsphere/C and Bi/Bi₂WO₆And XRD patterns of BiFe-10-40 samples. From FIG. 1, Fe can be seen₃O₄the/C magnetic microsphere has obvious diffraction peaks at 18.29 degrees, 30.08 degrees, 35.44 degrees, 43.07 degrees, 53.47 degrees, 56.96 degrees and 62.54 degrees, and has obvious diffraction peaks with Fe₃O₄Standard diffraction cards (JCPDS No.74-0748) were matched and respectively corresponded to orthorhombic Fe₃O₄The (111), (220), (311), (400), (422), (333) and (440) crystal planes of the Fe-Fe alloy have weaker round-coating peaks between 15.00 and 25.00 degrees, which indicates the existence of simple substance carbon and indicates that Fe is obtained₃O₄Magnetic microsphere/C.

According to FIG. 1 showing the absence of Fe₃O₄The XRD pattern of the sample synthesized by the/C magnetic microsphere has stronger diffraction peaks at 28.29 degrees, 32.67 degrees, 47.13 degrees, 55.99 degrees, 58.6 degrees and 68.8 degrees, and is matched with Bi₂WO₆Standard diffraction cards (JCPDS No.39-0256) matched with the corresponding orthorhombic system Bi₂WO₆The (131), (002), (202), (133), (262) and (400) crystal planes of (a). Meanwhile, diffraction peaks exist at 27.16 degrees, 37.95 degrees, 39.62 degrees and 48.70 degrees, and are matched with a simple substance Bi standard diffraction card (JCPDS No.85-1329), and corresponding crystal faces (012), (104), (110) and (202) of trigonal Bi indicate that the simple substance Bi is deposited on the synthesized Bi₂WO₆On a sample of (2). Fe is simultaneously observed in a sample of BiFe-10-40₃O₄Magnetic microsphere/C and Bi₂WO₆Characteristic diffraction peak of Bi, which shows that Bi/Bi is obtained₂WO₆/Fe₃O₄Composite material, and with Fe in the composite sample₃O₄The content of the/C magnetic microspheres is increased, the crystallinity of the composite sample is weakened, and the deposition amount of Bi is increased.

3、Bi/Bi₂WO₆/Fe₃O₄FTIR spectrum analysis of

FIG. 3 shows Fe₃O₄、Fe₃O₄Magnetic microsphere/C and Bi/Bi₂WO₆/Fe₃O₄-30 characteristic infrared peak, all samples at 1632cm^-1And an absorption peak is nearby, which is probably a hydroxyl group stretching vibration absorption peak of the water adsorbed on the surface of the material. 2371cm^-1Is caused by the adsorption of carbon dioxide molecules in the air on the surface of the sample. In Fe₃O₄And Fe₃O₄584cm in infrared characteristic peak of/C magnetic microsphere^-1Is the telescopic vibration peak of Fe-O-Fe, 1632cm^-1And 1590cm^-1The doublet of (2) is a stretching vibration peak of C ═ O, C ═ C double bond. 730cm^-1And 584cm^-1The infrared characteristic peak is attributed to the stretching vibration peak of Bi-O and W-O.

4、Fe₃O₄、Fe₃O₄/C、Bi/Bi₂WO₆/Fe₃O₄SEM and TEM analysis of

Fe shown in FIG. 4₃O₄In SEM picture, Fe with octahedral structure₃O₄The grain diameter is 100 nm-380 nm, and the dispersion is uniform without obvious agglomeration.FIG. 5 is Fe₃O₄SEM image of/C magnetic microsphere, as seen from the section of single microsphere, the inside is solid lamellar structure, Fe₃O₄the/C magnetic microspheres have a main particle size of about 5 mu m. FIG. 6 shows Bi/Bi₂WO₆The SEM image shows that the shape of the nano-sheet is stacked in a large nano-sheet shape, the stacking degree is loose, and multiple layers of Bi can be observed₂WO₆And (4) a sheet layer. FIGS. 7-10 are SEM images of BiFe-40-10 samples, in which the microspheres are all in irregular multi-layer shell-core wrapped structure, and the shell of BiFe-40 in FIG. 7 is covered with larger Bi₂WO₆Nanosheet, outer layer Bi of the shell-core structure of BiFe-30 in FIG. 8₂WO₆Is in the shape of a nano-flake and is uniformly distributed on the surface of the microsphere, and the picture of FIG. 9 is an SEM picture of a BiFe-20 sample, Fe₃O₄Bi on shell layer of/C magnetic microsphere₂WO₆Mostly bird's nest-shaped, FIG. 10 is an SEM image of BiFe-10 sample, and Bi can be observed₂WO₆The particles are in the form of fine particles and flakes and cover the Fe as a shell₃O₄The surface of the/C magnetic microsphere is porous and loose.

FIG. 11 is a TEM image of a BiFe-30 sample, in which a distinct shell-core interface structure and flaky Bi are observed₂WO₆Uniformly coated with Fe₃O₄the/C magnetic microsphere surface.

5、Bi/Bi₂WO₆/Fe₃O₄N of (A)₂Adsorption Curve analysis

By N₂Fe is obtained by testing an adsorption-desorption isothermal curve₃O₄Magnetic microsphere/C and Bi/Bi₂WO₆And the adsorption-desorption isothermal curve type of BiFe-30. FIG. 12 shows Fe₃O₄The adsorption-desorption isothermal curve of the/C magnetic microspheres presents a weaker hysteresis loop; bi₂WO₆And the adsorption-desorption isothermal curves of the BiFe-30 are III-type hysteresis loops and have mesoporous structures. The UV-visible diffuse reflectance absorption spectrum shown in FIG. 13 shows Bi/Bi₂WO₆/Fe₃O₄Bi is₂WO₆Has enhanced visible light absorption performance, and can drive photocatalytic reaction by using visible light.

6、Bi/Bi₂WO₆/Fe₃O₄Catalytic activity of photocatalytic treatment of Cr (VI)

FIG. 14 shows Bi/Bi₂WO₆/Fe₃O₄The order of strong to weak adsorption performance of each catalyst on Cr (VI) from experimental data of adsorption-desorption of the catalytic activity of the photocatalytic treatment Cr (VI) is BiFe-30>Bi/Bi₂WO₆>BiFe-40>Fe₃O₄Magnetic microsphere/C. All Bi/Bi during irradiation with visible light₂WO₆/Fe₃O₄The composite catalysts all had better catalytic activity than the single catalyst, in which BiFe-30 having the largest adsorption had the highest Cr (VI) reduction rate (85%), Bi₂WO₆And Fe₃O₄The visible light reduction efficiency of the/C magnetic microspheres to Cr (VI) is 30% and 20%, respectively.

In conclusion, the invention discloses self-made Fe₃O₄the/C magnetic microsphere and polyethylene glycol (PEG) are used as dispersing agents, and Bi is controlled and adjusted through a solvent thermal synthesis method₂WO₆And Fe₃O₄The mass ratio of the/C magnetic microspheres to synthesize Bi/Bi with high activity, high stability and easy recovery₂WO₆/Fe₃O₄Composite photocatalyst, Bi₂WO₆Is wrapped in Fe in nano-sheet shape₃O₄And forming a multi-layer shell-core packaging structure on the surface of the/C magnetic microsphere. Bi/Bi disclosed in the present application₂WO₆/Fe₃O₄The composite photocatalyst can catalyze and reduce Cr (VI) under the irradiation of visible light, wherein Fe₃O₄Bi/Bi with 30 percent of/C magnetic microsphere content₂WO₆/Fe₃O₄The highest catalytic efficiency of-30, about Bi₂WO₆2.8 times of that of Fe₃O₄4.2 times of the magnetic microsphere/C, the preparation method disclosed by the invention is convenient to popularize, the effect is excellent, and the prepared Bi/Bi₂WO₆/Fe₃O₄The composite photocatalyst has better application prospect.

Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention.