Improvement of photocatalytic activity of ferrite-based material under magnetic field

Abstract

To provide a method for improving the photocatalytic ability using a ferrite material composed of easily obtainable elements. The above technical problem is solved by using ferrite particles having a spinel crystal structure, a hexagonal crystal structure, or a garnet crystal structure as a photocatalyst in a magnetic field environment.

Description

Technical Field

[0001] This disclosure relates to improving photocatalytic activity by using ferrite-like materials under a magnetic field. Background Technology

[0002] Ferrite materials are mostly composed of iron and oxygen, making them inexpensive and readily available. As oxides, they also exhibit excellent chemical stability and are resistant to corrosion. Therefore, they are highly preferred materials for practical applications. However, apart from the Bi-type materials shown in Patent Documents 1-4, ferrite materials exhibit low activity as photocatalysts, and have not yet been used in related research.

[0003] Existing technical documents

[0004] Patent documents

[0005] [Patent Document 1] CN104646001 Publication No.

[0006] [Patent Document 2] CN104941662 Publication No.

[0007] [Patent Document 3] CN106807400 Publication

[0008] [Patent Document 4] CN108114736 Publication No. Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] The subject of this disclosure is to provide a non-Bi-based ferrite material that possesses photocatalytic activity.

[0011] [Methods used to solve problems]

[0012] The inventors have discovered that by using a specific ferrite material under a magnetic field, the photocatalytic activity of that material can be improved. This disclosure includes the following invention.

[0013] [1] An application of ferrite particles in a photocatalyst, wherein ferrite particles having a spinel crystal structure, a hexagonal crystal structure or a garnet crystal structure are used as a photocatalyst in a magnetic field.

[0014] [2] [1] The application of the ferrite particles in photocatalysts, wherein the ferrite particles exhibit a saturation magnetization of more than 5 emu / g.

[0015] [3] A magnetic field generating device comprising a magnetic field generating unit capable of generating a magnetic field, wherein a ferrite particle photocatalyst having a spinel crystal structure, a hexagonal crystal structure or a garnet crystal structure is provided on the surface of the magnetic field generating unit.

[0016] [4] An information processing device that outputs at least the following information: photocatalyst information about a photocatalyst, magnetic field correlation information about a magnetic field, and photocatalyst-magnetic field correlation information indicating the relationship between the photocatalyst correlation information and the magnetic field correlation information.

[0017] [5] A method for constructing a photocatalyst, comprising the step of setting a ferrite particle photocatalyst having a spinel-type crystal structure, a hexagonal crystal structure, or a garnet-type crystal structure on the surface of a magnetic field generating unit capable of generating a magnetic field.

[0018] [6] A method for constructing a photocatalyst, comprising: a step of providing a light environment to the object to be constructed; a step of providing a magnetic field environment to the object to be constructed; and a step of setting a ferrite particle photocatalyst having a spinel crystal structure, a hexagonal crystal structure or a garnet crystal structure in the object to be constructed.

[0019] [7] A method for manufacturing a photocatalyst, comprising a quality management process,

[0020] The quality management process includes:

[0021] The steps for preparing a photocatalyst in a magnetic field environment;

[0022] The step of imparting pollutants to the configured photocatalyst;

[0023] The procedure for evaluating the performance of a photocatalyst by irradiating it with light after it has been contaminated with pollutants.

[0024] [8] A photocatalyst recovery device having a magnetic field generating unit.

[0025] The effects of the invention

[0026] According to this disclosure, it is possible to provide ferrite-based materials that can be used as photocatalysts in a magnetic field. Attached Figure Description

[0027]

【 Figure 1 The image shows the XRD pattern of the particles (NiFe2O4) obtained in Example 1.

[0028]

【 Figure 2 The image shows the XRD pattern of the particles (BiFeO3) obtained in Comparative Example 1.

[0029]

【 Figure 3 The image shows a SEM image of the particles (NiFe2O4) obtained in Example 1.

[0030]

【 Figure 4The image shows a SEM image of the particles (BiFeO3) obtained in Comparative Example 1.

[0031]

【 Figure 5 The light absorption spectra of the particles obtained by (a) Example 1 and (b) Comparative Example 1 are shown.

[0032]

【 Figure 6 The evaluation of the photocatalytic ability of the particles obtained by (a) Example 1 and (b) Comparative Example 1 under the presence and absence of a magnetic field is shown.

[0033]

【 Figure 7 (a) is the Ni particle used as a reference, (b) is the NiFe2O4 particle obtained in Example 1, and (c) is the JH curve of the BiFeO3 particle obtained in Comparative Example 1. Detailed Implementation

[0034] (Photocatalyst particles)

[0035] One embodiment involves ferrite materials that are ferrite particles having a spinel-type crystal structure, a hexagonal crystal structure, or a garnet-type crystal structure. Specifically, the crystal structure of the ferrite particles consists of MFe₂O₄, MFe₂O₄, and MFe₂O₃. 12 O 19 and RFe5O 12 The elements are selected from the group consisting of Fe, Ni, and Co (where M includes at least one element selected from the group consisting of Ba, Sr, and Pb, M' includes at least one element selected from the group consisting of Ba, Sr, and Pb, and R includes rare earth elements).

[0036] Ferrite particles can have either a single-crystal or polycrystalline structure. In the case of polycrystalline ferrite, grain boundaries exist between the grains. The presence of grain boundaries can be visually determined in SEM images.

[0037] (Grain shape)

[0038] The shape of the grains is not particularly limited. For example, they can be spherical, rod-shaped, plate-shaped, flower-shaped, amorphous, etc. In the case of polycrystalline grains, they can also contain any combination of two or more of these shapes.

[0039] (Grain size, average grain size)

[0040] The grain size is the arithmetic mean of the major and minor diameters of the grain in the SEM image.

[0041] The average grain size is the arithmetic mean of the grain sizes of more than 100 grains.

[0042] In the case of single crystals, the average particle size is not particularly limited; for example, it can be 1 nm to 1000 nm.

[0043] In the case of polycrystalline grains, the average grain size is not particularly limited; for example, it can be 1 to 1000 nm.

[0044] The grain size of the secondary particles (aggregates) is not particularly limited; for example, it can be above 1 μm or below 10 μm.

[0045] (Supported co-catalyst)

[0046] Ferrite particles can also have metallic particles supported on the grain surface. The metal in the metallic particles can be any one of the group consisting of Au, Pd, Ag, and Pt, or an alloy of any combination thereof. The surface of the metallic particles can also be covered with oxides such as silicon dioxide. Such a structure is called a core-shell structure. Examples of core-shell metallic particles are Au core-silica shell particles and Ag core-silica shell particles.

[0047] There is no limit to the average particle size of the metal particles; it can be set to 1–1000 nm. The particle size of the metal particles is the arithmetic mean of the major and minor axes of the particle in the SEM image. The average particle size of the metal particles is the arithmetic mean of the particle sizes of more than 100 particles.

[0048] There is no particular limitation on the loading of metal particles as co-catalysts. For example, the loading of metal particles can be set to 0.2 to 10 mass relative to the total mass of ferrite particles and metal particles.

[0049] (Ferromagnetism of ferrite particles)

[0050] The ferrite particles involved in this embodiment are preferably ferromagnetic. Ferromagnetism refers to the presence of a hysteresis loop in the JH curve (magnetization-external magnetic field curve) obtained by VSM measurements, etc. The saturation magnetization of the polycrystalline particles can be 3 emu / g or more, 5 emu / g or more, or 10 emu / g or more.

[0051] (band gap)

[0052] The band gap width of the ferrite particles involved in this embodiment can be 1.0 to 3.5 eV.

[0053] (Mechanism of action)

[0054] The ferrite particles in this embodiment are used in a magnetic field. A magnetic field refers to a magnetic field environment stronger than the conventional geomagnetic field (tens of μT) in atmospheric conditions. For example, it could be 1 mT or more, 10 mT or more, 100 mT or more, 0.5 T or more, or 1 T or more. When the ferrite particles are irradiated with ultraviolet or visible light in a magnetic field, excitation substances such as OH free radicals are generated, which can decompose harmful substances such as organic compounds that are components of dirt.

[0055] The ferrite particles involved in this embodiment can be fixed on the surface of substrates such as metal, ceramic tile, enamel, cement, concrete, glass, fiber, wood, paper, and plastic for photocatalytic reaction.

[0056] As a fixation method, conventional methods such as sintering the photocatalyst or using a binder can be used. Alternatively, a binder can be mixed into the photocatalyst particles as needed to form them into flat, corrugated, honeycomb, spherical, or curved shapes for use in the photocatalytic reaction.

[0057] (Method for manufacturing ferrite particles)

[0058] A manufacturing method relating to one embodiment of the above-mentioned ferrite particles will be described.

[0059] As for the synthesis of ferrite particles involved in this embodiment, decomposition processes that mechanically crush large particles or clumps to obtain small particles and synthesis processes that obtain them from raw materials through physical and chemical reactions can be used.

[0060] For decomposition processes, equipment such as air jet mills, ball mills, planetary mills, and bead mills can be used. For synthesis processes, methods such as gas-phase synthesis, liquid-phase synthesis, and solid-phase synthesis can be used.

[0061] As a gas-phase method, it includes chemical vapor deposition (CVD) methods such as thermal CVD, plasma CVD, and flame CVD, as well as physical vapor deposition (PVD). As a liquid-phase method, it includes physical energy irradiation methods such as spray pyrolysis, laser decomposition, and ultrasonic methods, as well as sol-gel methods, liquid-phase reduction methods, and solvothermal methods. As a solid-phase method, solid-phase thermal decomposition is an example. Among these, the solvothermal method is preferred.

[0062] As a solvent in the solvothermal method, water, ethylene glycol, etc. can be used under high temperature, high pressure or supercritical conditions.

[0063] (Supported co-catalyst)

[0064] Depending on the requirements, metal particles or metal oxide particles with co-catalytic function can be loaded onto the surface of the obtained ferrite particles.

[0065] When metal particles are loaded onto the surface of ferrite particles, for example, the ferrite particles can be dispersed in a solvent containing a dissolved metal salt, and then a reducing agent can be added to the solution to cause the metal particles to precipitate onto the surface of the ferrite particles. Examples of reducing agents include ethanol.

[0066] When metal oxide particles are loaded onto the surface of ferrite particles, for example, the ferrite particles are dispersed in a solvent containing organometallic compounds such as TEOS, and then the metal oxide particles are precipitated on the surface of the ferrite particles by adjusting the pH of the solution and heating and drying.

[0067] The ferrite particles involved in this embodiment are ferromagnetic and can be separated by magnetic adsorption. Compared to photocatalyst particles such as titanium dioxide, they are easier to recover from photocatalytic waste.

[0068] The ferrite particles described in this embodiment can also be used simultaneously with the binder resin of the coating in a magnetic field. Alternatively, they can be provided as a composite of ferrite particles and resin, or as a composition in which ferrite particles and resin are dissolved or dispersed in a solvent.

[0069] (Magnetic field generating device)

[0070] As another embodiment, a magnetic field generating device is provided, which includes a magnetic field generating unit capable of generating a magnetic field, and ferrite particle photocatalyst is provided on the surface of the magnetic field generating unit.

[0071] As a magnetic field generating unit, any unit capable of generating a magnetic field can be used, such as an electromagnet, a permanent magnet, or a Helmholtz coil, but it is not limited to these. Examples of magnetic field generating devices equipped with a magnetic field generating unit include scrap metal cranes with electromagnets or the like at the front end of a crane, and medical devices that generate magnetic fields, such as MRI machines.

[0072] (Information processing device)

[0073] As another embodiment, an information processing device can be provided that outputs at least: photocatalyst information about the photocatalyst, magnetic field correlation information about the magnetic field, and photocatalyst-magnetic field correlation information indicating the relationship between the photocatalyst correlation information and the magnetic field correlation information.

[0074] Photocatalyst information may include the composition and physical properties of the photocatalyst, such as crystal structure, light absorption characteristics, and photocatalytic activity, but is not limited to these. Magnetic field correlation information may include the unit or method of generating the magnetic field, the strength of the magnetic field, etc., but is not limited to these. As an information processing device that outputs photocatalyst-magnetic field correlation information representing the relationship between this photocatalyst correlation information and the magnetic field correlation information, examples include web servers and database servers.

[0075] (Application method of photocatalyst)

[0076] As another embodiment, a method for constructing a photocatalyst can be described, which includes the step of setting ferrite particle photocatalysts on the surface of a magnetic field generating unit.

[0077] Another example is a method for constructing a photocatalyst, which includes: a step of providing the object with a light environment; a step of providing the object with a magnetic field environment; and a step of setting ferrite particle photocatalysts in the object.

[0078] There are no particular restrictions on the methods used to apply ferrite particle photocatalysts to the surface of the magnetic field generating unit or the object being constructed. Furthermore, regarding the steps for obtaining the light environment, the object can be exposed to sunlight (natural light), or it can be illuminated using lighting such as LED lighting.

[0079] (Methods for manufacturing photocatalysts)

[0080] As another embodiment, a method for manufacturing a photocatalyst that includes a quality management process can be cited. The quality management process includes: a step of preparing the photocatalyst in a magnetic field environment; a step of imparting a contaminant to the prepared photocatalyst; and a step of evaluating the performance of the photocatalyst by irradiating the photocatalyst with the contaminant.

[0081] Quality management processes are used to ensure the manufacturing of photocatalysts, and one example is conducting performance tests on the photocatalysts.

[0082] (Photocatalyst recovery device)

[0083] As another embodiment, a photocatalyst recovery device including a magnetic field generating unit can be provided. An electromagnet or similar device can be used as the magnetic field generating unit to recover ferrite particle photocatalysts. The specific configuration of the recovery device is not particularly limited, as long as it includes a magnetic field generating unit.

[0084]

Example

[0085] (Use of medicine)

[0086] Bismuth nitrate (Bi(NO3)3·5H2O, ≥98%), ferric nitrate (Fe(NO3)3·9H2O, ≥98%), nickel sulfate (NiSO4·6H2O, ≥98%), nitric acid (HNO3, 65%), and malachite green oxalate (MG, ≥90%) were all sourced from Sigma-Aldrich. Potassium hydroxide (KOH, 85%) and urea (99.5%) were purchased from Kanto Chemical Co., Ltd. All reagents were used directly, with deionized water (Milipore System, 18.2Ω) used as the solvent.

[0087] (Example 1) Preparation of NiFe2O4 polycrystalline particles

[0088] 0.005 mol of NiSO4·6H2O, 0.01 mol of Fe(NO3)3·9H2O, 1 g of urea, 2 mL of HNO3, and 18 mL of deionized water were mixed. This mixture was then added to 30 mL of 14 M KOH aqueous solution. The resulting mixture was transferred to an autoclave reactor with a polytetrafluoroethylene (PTFE) inner coating and heated at 180 °C for 24 hours. After cooling to room temperature, the product was centrifuged, washed with ethanol and deionized water, and finally dried in an oven at 80 °C. The sample was then placed in a muffle furnace and heated at 700 °C for 2 hours to obtain the particles of Example 1.

[0089] (Comparative Example 1) Preparation of BiFeO3 polycrystalline particles

[0090] 0.005 mol of Bi(NO3)3·5H2O, 0.005 mol of Fe(NO3)3·9H2O, 0.05 mol of urea, and 2 mL of HNO3 were mixed, and deionized water was added to bring the volume to 20 mL. The mixture was stirred continuously until all the chemicals were completely dissolved. Next, the homogenized solution was mixed with 60 mL of 14 M KOH aqueous solution. The resulting mixture was transferred to an autoclave reactor with a polytetrafluoroethylene (PTFE) inner coating and heated at 180 °C for 24 hours. After cooling to room temperature, the product was centrifuged, washed with ethanol and deionized water, and finally dried in an oven at 80 °C to obtain the particles of Comparative Example 1.

[0091] [XRD Test]

[0092] Figure 1 as well as Figure 2 The XRD patterns were obtained by performing XRD tests on the particles (NiFe2O4) obtained in Example 1 and (BiFeO3) obtained in Comparative Example 1 under the following test conditions.

[0093] Machine used: MiniFlex manufactured by Rigaku Corporation

[0094] Method: 2θ-θ reflection method

[0095] Using X-rays: Cu-Kα rays

[0096] Scanning speed: 1.00° / min

[0097] Sampling interval: 0.10°

[0098] Slit width: DS: (variable), SS: 4.2°, RS: 0.3mm

[0099] from Figure 1 The XRD pattern confirms that the synthesized particles in Example 1 are NiFe2O4.

[0100] from Figure 2 The XRD pattern confirms that the synthesized particles in Comparative Example 1 are BiFeO3.

[0101] [SEM Observation]

[0102] Figure 3 and Figure 4 The images shown are SEM images of the particles obtained by Example 1 and Comparative Example 1. It was confirmed that the sample synthesized in Example 1 consisted of polycrystalline particles with a secondary particle size of 1–10 μm, which are nanoparticles with a grain size of 1–1,000 nm. It was also confirmed that the sample synthesized in Comparative Example 1 consisted of polycrystalline particles with a secondary particle size of 1–10 μm, which are nanoparticles with a grain size of 1–1,000 nm.

[0103] [Optical Absorption Spectroscopy Measurement]

[0104] Figure 5 The images shown are the optical absorption spectra of the particles obtained from Example 1 and Comparative Example 1. The band gap of the sample synthesized in Example 1 was confirmed to be 1.8–2.7 V. The band gap of the sample synthesized in Comparative Example 1 was confirmed to be 2.0–2.5 V.

[0105] (Verification of photocatalytic activity)

[0106] To evaluate the photocatalytic performance of malachite green (MG) under visible light in its photodecomposition, MG was used as the test contaminant. In a typical procedure, 30 mg of the sample was immersed in a quartz tube containing 20 mL of MG aqueous solution (20 μM). After standing in the dark for 120 minutes to reach adsorption-desorption equilibrium, the reaction solution was tested using an output power of 500 mW / cm². 2 The reaction solution was irradiated with white light using a xenon lamp (LCS-100, 94011A, Newport) and photodecomposition experiments were conducted with and without a samarium magnet (saturation magnetization 0T~0T). Specifically, a magnetic field environment was created by placing a stir bar made of samarium magnets into a quartz tube impregnated with the sample and stirring the aqueous solution. 0.2 mL of the reaction solution was drawn at specified time intervals and centrifuged to remove all solid particles dispersed in the solution. The absorbance of the reaction solution at λ=664 nm was obtained using a UV-Vis spectrometer (PD-3000UVe, Apel) to determine the concentration of MB in the reaction solution.

[0107] Figure 6 To plot the first-order reaction curves of Example 1 (NiFe2O4) and Comparative Example 1 (BiFeO3) under the presence and absence of a samarium magnet (magnetic field), with sampling time as the x-axis and malachite green decolorization ability as the y-axis, respectively.

[0108] (Magnetic property test of particles)

[0109] The magnetic properties of the particles were evaluated using a vibrating sample magnetometer (VSM). Specifically, a TM-VSM1530-HGC-D manufactured by Tamagawa Corporation was used, and measurements were performed at 23°C. The scan rate was 200 Oe / s, and the scan range was 1.5 T.

[0110] 0.10g (NiFe2O4) and 0.07g (BiFeO3) particles were placed on a φ5mm epoxy resin sample stage for VSM evaluation.

[0111] Figure 7 (a) is a Ni particle used as a reference, (b) is a NiFe2O4 particle from Example 1, and (c) is a BiFeO particle from Comparative Example 1. 39 JH curves of the particles. Similar to (a), hysteresis loops were also observed in (b), confirming ferromagnetism.

[0112] [Postscript] • Goal 9: "Building Industrial Innovation and Infrastructure"

[0113] The photocatalyst particles disclosed herein possess excellent photocatalytic activity in a magnetic field, which can contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs).

Claims

1. An application of ferrite particles in a photocatalyst, wherein ferrite particles having a spinel-type crystal structure, a hexagonal crystal structure, or a garnet-type crystal structure are used as a photocatalyst in a magnetic field.

2. The application of the ferrite particles according to claim 1 in a photocatalyst, wherein the ferrite particles exhibit a saturation magnetization of 5 emu / g or higher.

3. A magnetic field generating device, comprising a magnetic field generating unit capable of generating a magnetic field. The surface of the magnetic field generating unit is provided with ferrite particle photocatalysts having spinel-type crystal structure, hexagonal crystal structure or garnet-type crystal structure.

4. An information processing apparatus that outputs at least the following information: Information about photocatalysts Information about magnetic field correlations, and Photocatalyst-magnetic field association information indicates the relationship between the photocatalyst association information and the magnetic field association information.

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