A BiVO4 / γ-Fe2O3-C-Bent composite catalyst, its preparation method and application

Abstract

This invention discloses a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, its preparation method, and its application, belonging to the field of photocatalyst technology. The BiVO4 / γ-Fe2O3-C-Bent composite catalyst is prepared by modifying bentonite with hexadecylpyridine chloride, intercalating it with a polymeric hydroxyl iron columnarizing agent, calcining to obtain a magnetic γ-Fe2O3-C-Bent catalyst, and then loading BiVO4 using a hydrothermal method. The BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared by this invention achieves synergistic enhancement of photocatalysis and heterogeneous photo-Fenton reaction. BiVO4 broadens the visible light response range of the catalyst, while γ-Fe2O3 endows it with photo-Fenton catalytic activity and magnetic recovery performance. This composite catalyst exhibits highly efficient degradation ability of Rhodamine B organic dyes under visible light irradiation and can be rapidly separated and recovered by an external magnetic field, maintaining high catalytic activity even after being reused five times.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of the dyeing and printing industry, a large amount of wastewater containing organic dyes is directly discharged, causing serious pollution to the aquatic ecosystem. Organic pollutants are characterized by high toxicity, difficulty in biodegradation, and deep color. Conventional water treatment technologies are unable to completely degrade and remove them, and their long-term residue in water bodies will seriously threaten the ecological balance and human health.

[0003] Advanced oxidation technologies (AOPs) are effective methods for treating recalcitrant organic wastewater. Among them, the synergistic system combining photo-Fenton and photocatalysis technologies has attracted widespread attention in the water treatment field due to its ability to efficiently generate highly reactive hydroxyl radicals and rapidly degrade organic pollutants. However, existing technologies still have problems in treating such wastewater. For example, γ-Fe2O3-based catalysts are often used in heterogeneous photo-Fenton reactions, but they mainly rely on ultraviolet light excitation, resulting in low utilization of sunlight and a narrow light response range, leading to limited catalytic efficiency. BiVO4, as a novel visible light-responsive semiconductor photocatalyst, has a narrow bandgap (approximately 2.4 eV), is non-toxic, and has excellent chemical stability. It can generate photogenerated electron-hole pairs under visible light irradiation for photocatalytic degradation of organic pollutants. However, pure-phase BiVO4 suffers from problems such as rapid recombination rates of photogenerated electrons and holes, small specific surface area, and difficulty in recovery, which severely limits its practical application potential.

[0004] Bentonite, a natural clay mineral, is characterized by its abundant reserves, low cost, large specific surface area, and strong cation exchange capacity. After organic modification, it can serve as an ideal catalyst support, not only facilitating the uniform dispersion of active components but also significantly improving the catalyst's adsorption and recovery performance. A novel composite catalyst was constructed by co-loading BiVO4 and γ-Fe2O3 onto modified bentonite. This catalyst achieves synergistic effects of photocatalysis and photo-Fenton reaction, broadening the catalyst's light response range and improving the degradation efficiency of organic pollutants. Furthermore, the introduction of γ-Fe2O3 endows the catalyst with good magnetic properties, facilitating rapid separation and recovery of the catalyst through an external magnetic field, effectively overcoming the shortcomings of traditional catalysts.

[0005] Therefore, developing a novel catalyst with excellent visible light response, high catalytic efficiency, good stability, environmental friendliness, and easy recycling for the efficient removal of organic pollutants from wastewater has significant industrial application value. Summary of the Invention

[0006] In view of this, the present invention provides a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, its preparation method and application. This composite catalyst significantly broadens the photoresponse range, improves the separation efficiency of photogenerated carriers, and enhances the generation ability of hydroxyl radicals. It can efficiently degrade organic pollutants in wastewater under visible light irradiation. At the same time, with the help of the magnetic properties of γ-Fe2O3, the catalyst can be rapidly separated and recovered, solving the problems of difficult recovery and easy secondary pollution of traditional catalysts.

[0007] The present invention achieves the above objectives through the following technical solutions: This invention provides a method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, comprising the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Bentonite and hexadecylpyridine chloride were dispersed in deionized water and stirred at a constant temperature of 40-80℃ to obtain an organo-bentonite suspension. While maintaining a constant temperature of 40-80℃, a polymeric hydroxyl iron columnarizing agent was added dropwise to the organo-bentonite suspension with continuous stirring. The stirring was continued for 2-6 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 12-16 hours. After washing, centrifugation, drying, calcination, cooling, and grinding, a magnetic γ-Fe2O3-C-Bent catalyst was obtained. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst The magnetic γ-Fe2O3-C-Bent catalyst prepared in step S1 was dispersed in deionized water and ultrasonically dispersed to obtain a γ-Fe2O3-C-Bent suspension. Bi(NO3)3 solution was added dropwise and stirred until homogeneous. Then Na3VO4 solution was added dropwise and stirred until homogeneous. The mixed solution was subjected to hydrothermal reaction at 160~200℃ for 10~14h. After the reaction was completed, the solution was cooled and the precipitate was washed alternately with deionized water and anhydrous ethanol until neutral. The precipitate was then dried to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0008] Preferably, the preparation method of the polymerized hydroxyl iron columnarizing agent in step S1 includes the following steps: Mix 0.1–0.3 mol / L ferric nitrate solution with 0.4–0.6 mol / L sodium carbonate solution according to Fe 3+ with Na + The mixture is prepared by mixing in a 1:1 molar ratio and aging at 40-80℃ for 20-28 hours.

[0009] Preferably, in step S1, the mass ratio of bentonite to hexadecylpyridine chloride is (3~6):1.

[0010] Preferably, the Fe in the polymerized hydroxyl iron columnarizing agent3+ The ratio of ions to bentonite is (8~12) mmol:1g.

[0011] Preferably, the calcination in step S1 is carried out at 350-450℃ for 2-4 hours.

[0012] Preferably, in step S2, the mass ratio of the magnetic γ-Fe2O3-C-Bent catalyst to deionized water is (1~3):(50~80), the amount of bismuth nitrate added is 5%-15% of the mass of the magnetic γ-Fe2O3-C-Bent catalyst, and the amount of Na3VO4 and the amount of Bi(NO3)3 satisfy the Bi / V molar ratio of 1:1.

[0013] Based on the same inventive concept, the present invention provides a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, which is prepared by the preparation method of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst described in any one of the above claims.

[0014] Based on the same inventive concept, this invention provides the application of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst described above in the visible-field catalytic degradation of organic dye pollutants.

[0015] Preferably, the organic dye pollutant is Rhodamine B.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared in this invention uses CPC-modified bentonite as a support, then loads γ-Fe2O3 via intercalation, and then loads BiVO4 via hydrothermal method. This catalyst achieves synergistic enhancement of photocatalysis and heterogeneous photo-Fenton reaction. BiVO4 effectively broadens the visible light response range of the catalyst, while γ-Fe2O3 endows it with excellent photo-Fenton catalytic activity. The synergistic effect of the two significantly improves the degradation efficiency of organic pollutants. It can achieve efficient degradation of organic pollutants under visible light irradiation without relying on ultraviolet light sources, which greatly reduces the energy consumption and operating costs of sewage treatment.

[0017] 2. Bentonite carrier has a large specific surface area and excellent adsorption performance, which can pre-adsorb organic pollutants in wastewater and enrich them on the catalyst surface, providing sufficient active sites for the degradation reaction of active free radicals, thereby significantly improving the catalytic degradation efficiency. In addition, bentonite is abundant and inexpensive, which effectively reduces the preparation cost of composite catalysts and has good prospects for industrial application.

[0018] 3. The introduction of γ-Fe2O3 gives the composite catalyst good magnetic properties. After the reaction, it can be quickly separated and recovered by an external magnetic field, which effectively solves the problems of difficult recovery and easy secondary pollution of traditional catalysts. Moreover, the recovered catalyst still maintains good catalytic activity and can be reused many times, further reducing the cost of water treatment.

[0019] 4. The preparation process of this invention is simple, the reaction conditions are mild, and all raw materials used are environmentally friendly. No toxic or harmful substances are generated during the preparation process, thus avoiding secondary pollution. It conforms to the concept of green and environmentally friendly development and can be widely used in the treatment of various printing and dyeing wastewater and organic dye wastewater. Attached Figure Description

[0020] Figure 1 This is a SEM image of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared in Example 1 of this invention.

[0021] Figure 2 The image shows the XRD pattern of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared in Example 3 of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0023] The English abbreviation and the full Chinese name used in this invention are as follows: Bentonite and hexadecylpyridine chloride (CPC).

[0024] Preparation Example The preparation method of the polymeric hydroxyl iron columnarizing agent includes the following steps: Mix 0.1 mol / L ferric nitrate solution with 0.4 mol / L sodium carbonate solution according to Fe 3+ with Na + The mixture was prepared by mixing in a 1:1 molar ratio and aging at 40°C for 20 hours. Example

[0025] A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Three parts of bentonite and one part of hexadecylpyridine chloride (CPC) were dispersed in 120 parts of deionized water and stirred at 50°C to obtain an organobentonite suspension. While maintaining a constant temperature of 50°C, 10 parts of the polymerized hydroxyl iron columnar agent prepared in the preparation example were added dropwise to the organobentonite suspension and stirred continuously for 6 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 12 hours. The mixture was washed with deionized water, centrifuged, dried at 70°C, calcined at 450°C for 4 hours, cooled to room temperature, and ground to obtain a magnetic γ-Fe2O3-C-Bent catalyst. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst Two parts of the magnetic γ-Fe₂O₃-C-Bent catalyst prepared in step S1 were dispersed in 80 parts of deionized water and ultrasonically dispersed until the system was homogeneous to obtain a γ-Fe₂O₃-C-Bent suspension. 0.3 parts of bismuth nitrate (Bi(NO₃)₃·5H₂O) were ultrasonically dissolved in 20 parts of deionized water, and the Bi(NO₃)₃ solution was added dropwise to the γ-Fe₂O₃-C-Bent suspension, and magnetically stirred until homogeneous. Then, 0.5 parts of sodium vanadate (Na₃VO₄·12H₂O) were dissolved in 20 parts of deionized water, and the Na₃VO₄ solution was added dropwise, and magnetically stirred until homogeneous, maintaining a Bi / V ratio. The molar ratio was 1:1. The mixed solution was transferred into a hydrothermal reactor and subjected to hydrothermal reaction at 160℃ for 10 h, then naturally cooled to room temperature. The resulting precipitate was washed alternately with deionized water and anhydrous ethanol until neutral, and dried at 50℃ to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0026] Application of a BiVO4 / γ-Fe2O3-C-Bent composite catalyst in the catalytic degradation of organic dye pollutants (Rhodamine B) under visible light: Fifty portions of an aqueous solution of organic dye pollutants with an initial concentration of 20 mg / L were added to a catalytic reactor. 0.1 g / L of the prepared BiVO4 / γ-Fe2O3-C-Bent composite catalyst was added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred for 20 min at room temperature in the dark to allow the composite catalyst and the organic dye pollutant solution to reach adsorption-desorption equilibrium. 5 mmol / L hydrogen peroxide solution was added, and a 200 W (λ≥400 nm) visible light source was turned on. The mixture was magnetically stirred for 1 h to induce a photo-Fenton-photocatalytic synergistic reaction. Samples were extracted every 20 min, centrifuged, and the supernatant was collected. The residual concentration of the organic dye pollutants was measured, and the degradation rate was calculated.

[0027] Testing showed that after 20 minutes, the BiVO4 / γ-Fe2O3-C-Bent composite catalyst achieved a 98.7% degradation rate of Rhodamine B, and after 120 minutes, Rhodamine B was almost completely degraded; the photogenerated carrier separation efficiency was 89.2%; and the hydroxyl radical (OH) free ... · The generation amount is 1.2 × 10 -5 The composite catalyst can be completely separated within 30 seconds under a 0.5T magnetic field. After being reused 5 times, the degradation rate of Rhodamine B still reaches 95.1% after 120 minutes.

[0028] Figure 1 This is a SEM image of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared in this embodiment. The image clearly shows that the composite catalyst has a loose and porous network microstructure. The BiVO4 nanoparticles and γ-Fe2O3 particles do not show obvious agglomeration and are uniformly dispersed on the surface of the CPC-modified bentonite support, confirming that the active component and the support are effectively combined. The porous structure can increase the specific surface area and provide more catalytic active sites. Example

[0029] A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Five parts of bentonite and one part of hexadecylpyridine chloride (CPC) were dispersed in 80 parts of deionized water and stirred at a constant temperature of 40°C to obtain an organobentonite suspension. While maintaining a constant temperature of 40°C, 30 parts of the polymerized hydroxyl iron columnar agent prepared in the preparation example were added dropwise to the organobentonite suspension and stirred continuously for 2 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 16 hours. The mixture was washed with deionized water, centrifuged, dried at 50°C, calcined at 350°C for 2 hours, cooled to room temperature, and ground to obtain a magnetic γ-Fe2O3-C-Bent catalyst. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst One part of the magnetic γ-Fe₂O₃-C-Bent catalyst prepared in step S1 was dispersed in 50 parts of deionized water and ultrasonically dispersed until the system was homogeneous, resulting in a γ-Fe₂O₃-C-Bent suspension. 0.1 parts of bismuth nitrate (Bi(NO₃)₃·5H₂O) was ultrasonically dissolved in 10 parts of deionized water, and the Bi(NO₃)₃ solution was added dropwise to the γ-Fe₂O₃-C-Bent suspension, with magnetic stirring until homogeneous. Then, 0.1 parts of sodium vanadate (Na₃VO₄·12H₂O) was dissolved in 10 parts of deionized water, and the Na₃VO₄ solution was added dropwise, with magnetic stirring continued until homogeneous, maintaining a Bi / V ratio. The molar ratio was 1:1. The mixed solution was transferred into a hydrothermal reactor and subjected to hydrothermal reaction at 200℃ for 14 h, followed by natural cooling to room temperature. The resulting precipitate was washed alternately with deionized water and anhydrous ethanol until neutral, and then dried at 70℃ to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0030] Application of a BiVO4 / γ-Fe2O3-C-Bent composite catalyst in the catalytic degradation of organic dye pollutants (Rhodamine B) under visible light: One hundred portions of an aqueous solution of organic dye pollutants with an initial concentration of 30 mg / L were added to a catalytic reactor. 0.3 g / L of the prepared BiVO4 / γ-Fe2O3-C-Bent composite catalyst was added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred for 40 min at room temperature in the dark to allow the composite catalyst and the organic dye pollutant solution to reach adsorption-desorption equilibrium. 15 mmol / L hydrogen peroxide solution was added, and a 400 W (λ≥400 nm) visible light source was turned on. The mixture was magnetically stirred for 1 h to induce a photo-Fenton-photocatalytic synergistic reaction. Samples were extracted every 20 min, centrifuged, and the supernatant was collected. The residual concentration of the organic dye pollutants was measured, and the degradation rate was calculated.

[0031] Testing showed that after 20 minutes, the BiVO4 / γ-Fe2O3-C-Bent composite catalyst achieved a 97.5% degradation rate of Rhodamine B, and after 120 minutes, Rhodamine B was almost completely degraded; the photogenerated carrier separation efficiency was 86.4%; and the hydroxyl radical (OH) fraction was... · The generation amount is 1.1 × 10 -5 The composite catalyst can be completely separated within 35 seconds under a 0.5T magnetic field. After being reused 5 times, the degradation rate of Rhodamine B still reaches 95.7% after 120 minutes. Example

[0032] A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Six parts of bentonite and one part of hexadecylpyridine chloride (CPC) were dispersed in 90 parts of deionized water and stirred at 80°C to obtain an organobentonite suspension. While maintaining a constant temperature of 80°C, 20 parts of the polymerized hydroxyl iron columnar agent prepared in the preparation example were added dropwise to the organobentonite suspension and stirred continuously for 4 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 13 hours. The mixture was washed with deionized water, centrifuged, dried at 60°C, calcined at 400°C for 3 hours, cooled to room temperature, and ground to obtain a magnetic γ-Fe2O3-C-Bent catalyst. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst Two parts of the magnetic γ-Fe₂O₃-C-Bent catalyst prepared in step S1 were dispersed in 60 parts of deionized water and ultrasonically dispersed until the system was homogeneous to obtain a γ-Fe₂O₃-C-Bent suspension. 0.2 parts of bismuth nitrate (Bi(NO₃)₃·5H₂O) were ultrasonically dissolved in 15 parts of deionized water. The Bi(NO₃)₃ solution was added dropwise to the γ-Fe₂O₃-C-Bent suspension, and the mixture was magnetically stirred until homogeneous. Then, 0.2 parts of sodium vanadate (Na₃VO₄·12H₂O) were dissolved in 15 parts of deionized water. The Na₃VO₄ solution was added dropwise, and the mixture was magnetically stirred until homogeneous, maintaining a Bi / V ratio. The molar ratio was 1:1. The mixed solution was transferred into a hydrothermal reactor and subjected to hydrothermal reaction at 180℃ for 12 h, followed by natural cooling to room temperature. The resulting precipitate was washed alternately with deionized water and anhydrous ethanol until neutral, and then dried at 60℃ to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0033] Application of a BiVO4 / γ-Fe2O3-C-Bent composite catalyst in the catalytic degradation of organic dye pollutants (Rhodamine B) under visible light: Seventy portions of an aqueous solution of organic dye pollutants with an initial concentration of 10 mg / L were added to a catalytic reactor. 0.2 g / L of the prepared BiVO4 / γ-Fe2O3-C-Bent composite catalyst was added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred for 30 min at room temperature in the dark to allow the composite catalyst and the organic dye pollutant solution to reach adsorption-desorption equilibrium. 10 mmol / L hydrogen peroxide solution was added, and a 300 W (λ≥400 nm) visible light source was turned on. The mixture was magnetically stirred for 1 h to induce a photo-Fenton-photocatalytic synergistic reaction. Samples were extracted every 20 min, centrifuged, and the supernatant was collected. The residual concentration of the organic dye pollutants was measured, and the degradation rate was calculated.

[0034] Testing showed that after 20 minutes, the BiVO4 / γ-Fe2O3-C-Bent composite catalyst achieved a 95.2% degradation rate of Rhodamine B, and after 120 minutes, Rhodamine B was almost completely degraded; the photogenerated carrier separation efficiency was 82.7%; and the hydroxyl radical (OH) fraction was... · The generation amount is 0.95 × 10 -5 The composite catalyst can be completely separated within 40 seconds under a 0.5T magnetic field. After being reused 5 times, the degradation rate of Rhodamine B still reached 93.2% after 120 minutes.

[0035] Figure 2 The XRD pattern of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst prepared in this embodiment is shown. The figure shows the characteristic diffraction peaks of BiVO4 (2θ=18.9°, 28.8°), γ-Fe2O3 (2θ=30.1°, 35.4°) and bentonite, respectively. The peaks are sharp and free of impurities, which proves that the composite catalyst has a pure phase and good crystallinity. Example

[0036] A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Three parts of bentonite and 0.5 parts of hexadecylpyridine chloride (CPC) were dispersed in 110 parts of deionized water and stirred at a constant temperature of 70°C to obtain an organobentonite suspension. While maintaining a constant temperature of 70°C, 25 parts of the polymerized hydroxyl iron columnarizing agent prepared in the preparation example were added dropwise to the organobentonite suspension and stirred continuously for 5 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 13 hours. The mixture was washed with deionized water, centrifuged, dried at 55°C, calcined at 350°C for 2 hours, cooled to room temperature, and ground to obtain a magnetic γ-Fe2O3-C-Bent catalyst. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst One part of the magnetic γ-Fe₂O₃-C-Bent catalyst prepared in step S1 was dispersed in 75 parts of deionized water and ultrasonically dispersed until the system was homogeneous to obtain a γ-Fe₂O₃-C-Bent suspension. 0.15 parts of bismuth nitrate (Bi(NO₃)₃·5H₂O) was ultrasonically dissolved in 15 parts of deionized water, and the Bi(NO₃)₃ solution was added dropwise to the γ-Fe₂O₃-C-Bent suspension, and magnetically stirred until homogeneous. Then, 0.4 parts of sodium vanadate (Na₃VO₄·12H₂O) was dissolved in 12 parts of deionized water, and the Na₃VO₄ solution was added dropwise, and magnetically stirred until homogeneous, maintaining a Bi / V ratio. The molar ratio was 1:1; the mixed solution was transferred into a hydrothermal reactor and subjected to hydrothermal reaction at 190℃ for 13 h, and then naturally cooled to room temperature; the obtained precipitate was washed alternately with deionized water and anhydrous ethanol until neutral, and dried at 55℃ to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0037] Application of a BiVO4 / γ-Fe2O3-C-Bent composite catalyst in the catalytic degradation of organic dye pollutants (Rhodamine B) under visible light: Fifty-five portions of an aqueous solution of organic dye pollutants with an initial concentration of 25 mg / L were added to a catalytic reactor. 0.1 g / L of the prepared BiVO4 / γ-Fe2O3-C-Bent composite catalyst was added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred for 25 min at room temperature in the dark to allow the composite catalyst and the organic dye pollutant solution to reach adsorption-desorption equilibrium. 5 mmol / L hydrogen peroxide solution was added, and a 250 W (λ≥400 nm) visible light source was turned on. The mixture was magnetically stirred for 1 h to induce a photo-Fenton-photocatalytic synergistic reaction. Samples were extracted every 20 min, centrifuged, and the supernatant was collected to determine the residual concentration of the organic dye pollutants and calculate the degradation rate.

[0038] Testing showed that after 20 minutes, the BiVO4 / γ-Fe2O3-C-Bent composite catalyst achieved a 93.2% degradation rate of Rhodamine B, and after 120 minutes, Rhodamine B was almost completely degraded; the photogenerated carrier separation efficiency was 79.3%; and the hydroxyl radical (OH) fraction was... · The generation amount is 0.85 × 10 -5 The composite catalyst can be completely separated within 45 seconds under a 0.5T magnetic field at mol / L. After being reused 5 times, the degradation rate of Rhodamine B still reaches 91% after 120 minutes. Example

[0039] A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Six parts of bentonite and one part of hexadecylpyridine chloride (CPC) were dispersed in 100 parts of deionized water and stirred at a constant temperature of 60°C to obtain an organobentonite suspension. While maintaining a constant temperature of 60°C, 15 parts of the polymerized hydroxyl iron columnar agent prepared in the preparation example were added dropwise to the organobentonite suspension under continuous stirring. The intercalation reaction was carried out by continuous stirring for 3.5 h. After the reaction was completed, the mixture was allowed to stand for 15 h. The mixture was washed with deionized water, centrifuged, dried at 65°C, calcined at 400°C for 3.5 h, cooled to room temperature, and ground to obtain a magnetic γ-Fe2O3-C-Bent catalyst. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst Three parts of the magnetic γ-Fe₂O₃-C-Bent catalyst prepared in step S1 were dispersed in 70 parts of deionized water and ultrasonically dispersed until the system was homogeneous to obtain a γ-Fe₂O₃-C-Bent suspension. 0.3 parts of bismuth nitrate (Bi(NO₃)₃·5H₂O) were ultrasonically dissolved in 10 parts of deionized water, and the Bi(NO₃)₃ solution was added dropwise to the γ-Fe₂O₃-C-Bent suspension, and magnetically stirred until homogeneous. Then, 0.3 parts of sodium vanadate (Na₃VO₄·12H₂O) were dissolved in 10 parts of deionized water, and the Na₃VO₄ solution was added dropwise, and magnetically stirred until homogeneous, maintaining a Bi / V ratio. The molar ratio was 1:1. The mixed solution was transferred into a hydrothermal reactor and subjected to hydrothermal reaction at 160℃ for 10 h, then naturally cooled to room temperature. The resulting precipitate was washed alternately with deionized water and anhydrous ethanol until neutral, and dried at 55℃ to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

[0040] Application of a BiVO4 / γ-Fe2O3-C-Bent composite catalyst in the catalytic degradation of organic dye pollutants (Rhodamine B) under visible light: Ninety portions of an aqueous solution of organic dye pollutants with an initial concentration of 25 mg / L were added to a catalytic reactor. 0.2 g / L of the prepared BiVO4 / γ-Fe2O3-C-Bent composite catalyst was added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred for 40 min at room temperature in the dark to allow the composite catalyst and the organic dye pollutant solution to reach adsorption-desorption equilibrium. 15 mmol / L hydrogen peroxide solution was added, and a 350 W (λ≥400 nm) visible light source was turned on. The mixture was magnetically stirred for 1 h to induce a photo-Fenton-photocatalytic synergistic reaction. Samples were extracted every 20 min, centrifuged, and the supernatant was collected. The residual concentration of the organic dye pollutants was measured, and the degradation rate was calculated.

[0041] Testing showed that after 20 minutes, the BiVO4 / γ-Fe2O3-C-Bent composite catalyst achieved a 93.2% degradation rate of Rhodamine B, and after 120 minutes, Rhodamine B was almost completely degraded; the photogenerated carrier separation efficiency was 72.5%; and the hydroxyl radical (OH) fraction was... · The generation amount is 0.65 × 10 -5 The composite catalyst can be completely separated within 60 seconds under a 0.5T magnetic field. After being reused 5 times, the degradation rate of Rhodamine B is still over 92.2% after 120 minutes.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst, characterized in that, Includes the following steps: S1. Preparation of magnetic γ-Fe2O3-C-Bent catalyst Bentonite and hexadecylpyridine chloride were dispersed in deionized water and stirred at a constant temperature of 40-80℃ to obtain an organo-bentonite suspension. While maintaining a constant temperature of 40-80℃, a polymeric hydroxyl iron columnarizing agent was added dropwise to the organo-bentonite suspension with continuous stirring. The stirring was continued for 2-6 hours to carry out the intercalation reaction. After the reaction was completed, the mixture was allowed to stand for 12-16 hours. After washing, centrifugation, drying, calcination, cooling, and grinding, a magnetic γ-Fe2O3-C-Bent catalyst was obtained. S2. Preparation of BiVO4 / γ-Fe2O3-C-Bent composite catalyst The magnetic γ-Fe2O3-C-Bent catalyst prepared in step S1 was dispersed in deionized water and ultrasonically dispersed to obtain a γ-Fe2O3-C-Bent suspension. Bi(NO3)3 solution was added dropwise and stirred until homogeneous. Then Na3VO4 solution was added dropwise and stirred until homogeneous. The mixed solution was subjected to hydrothermal reaction at 160~200℃ for 10~14h. After the reaction was completed, the solution was cooled and the precipitate was washed alternately with deionized water and anhydrous ethanol until neutral. The precipitate was then dried to obtain the BiVO4 / γ-Fe2O3-C-Bent composite catalyst.

2. The preparation method of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to claim 1, characterized in that, The preparation method of the polymerized hydroxyl iron columnarizing agent in step S1 includes the following steps: Mix 0.1–0.3 mol / L ferric nitrate solution with 0.4–0.6 mol / L sodium carbonate solution according to Fe 3+ with Na + The mixture is prepared by mixing in a 1:1 molar ratio and aging at 40-80℃ for 20-28 hours.

3. The method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to claim 1, characterized in that, In step S1, the mass ratio of bentonite to hexadecylpyridine chloride is (3~6):

1.

4. The preparation method of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to claim 2, characterized in that, Fe in the polymerized hydroxyl iron columnarizing agent 3+ The ratio of ions to bentonite is (8~12) mmol:1g.

5. The preparation method of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to claim 1, characterized in that, In step S1, the roasting is carried out at 350-450℃ for 2-4 hours.

6. The method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to claim 1, characterized in that, In step S2, the mass ratio of magnetic γ-Fe2O3-C-Bent catalyst to deionized water is (1~3):(50~80), the amount of bismuth nitrate added is 5%-15% of the mass of magnetic γ-Fe2O3-C-Bent catalyst, and the amount of Na3VO4 and Bi(NO3)3 used satisfies the molar ratio of Bi / V of 1:

1.

7. A BiVO4 / γ-Fe2O3-C-Bent composite catalyst, characterized in that, It is prepared by the method for preparing a BiVO4 / γ-Fe2O3-C-Bent composite catalyst according to any one of claims 1-6.

8. The application of the BiVO4 / γ-Fe2O3-C-Bent composite catalyst as described in claim 7 in the visible-field catalytic degradation of organic dye pollutants.

9. The application according to claim 8, wherein the organic dye contaminant is Rhodamine B.

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