A method for preparing semiconductor titanium dioxide

Abstract

A method for preparing semiconductor titanium dioxide is provided. The method does not require complex pretreatment and can be simply prepared using general equipment. The method comprises: a first soaking step of soaking a titanium-containing substrate in a hydrogen peroxide aqueous solution at 70 to 90°C for 1 to 28 hours; and a second soaking step; the second soaking step comprising: soaking the substrate after the first soaking step in room temperature water at 10 to 30°C for 24 to 48 hours; and finally, soaking the substrate after the room temperature water soaking step in warm water at 70 to 90°C for 24 to 96 hours.

Description

Technical Field

[0001] The invention relates to a method for preparing semiconductor titanium dioxide. Background Art

[0002] It is well known that semiconductor titanium dioxide, as a photocatalyst, possesses properties such as the ability to oxidize and decompose organic matter and a super-hydrophilic property. This oxidative decomposition ability can be used for antibacterial and deodorizing purposes, while the super-hydrophilic property can be used, for example, for antifouling. Such semiconductor titanium dioxide can be prepared, for example, by the methods described in Patent Documents 1 and 2.

[0003] In addition, a method for preparing a titanium dioxide film including a treatment step with hydrogen peroxide and a treatment step with water (e.g., Patent Document 3) and a method for crystallizing amorphous titanium dioxide into anatase by treating with hydrogen peroxide, room temperature water, and warm water are also known (e.g., Non-Patent Document 1).

[0004] Related technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-271493

[0007] Patent Document 2: Japanese Patent No. 3795515

[0008] Patent Document 3: Chinese Patent No. 1252310

[0009] Non-patent literature

[0010] Non-patent literature 1: Jin-Ming WU, et al., Crystallization of Anatase from Amorphous Titania in Hot Water and In Vitro Biomineralization, Journal of theCeramic Society of Japan, 110[2],78-80(2002) Summary of the Invention

[0011] Problems to be solved by the invention

[0012] In the method for preparing a photocatalytic material described in Patent Document 1, anodized titanium metal is calcined at 500° C. in air. However, the pretreatment process is complicated and not practical.

[0013] In the method for preparing a semiconductor photoelectrochemical cell described in Patent Document 2, a substrate composed of titanium or a titanium alloy is calcined in air at 700 to 1000°C at a heating rate of 5°C / second or higher to form a titanium dioxide layer on the surface. The substrate is then quenched in cold water below 10°C, thereby producing a semiconductor photoelectrochemical cell (semiconductor titanium dioxide) with excellent photocatalytic activity without the need for anodization. However, calcination at 700 to 1000°C requires relatively large-scale equipment and is very expensive. Furthermore, people have been seeking semiconductor titanium dioxide with even better photocatalytic activity.

[0014] Patent Document 3 describes the formation of anatase-like titanium dioxide films on titanium surfaces by immersing titanium in a 12-30% by mass aqueous hydrogen peroxide solution at a temperature of 60-90°C for 2-72 hours, followed by holding the solution in 80°C water for 0-72 hours. However, Patent Document 3 does not describe the step of treating the titanium dioxide with room-temperature water prior to the warm water treatment. Furthermore, Patent Document 3 only generally states that the titanium dioxide films can be used in the field of photocatalysis, without addressing whether the titanium dioxide films obtained using the preparation method described in Patent Document 3 possess photocatalytic activity.

[0015] The aforementioned Non-Patent Document 1 states that titanium and titanium alloys are widely used as implant materials in orthopedics and dentistry due to their low specific gravity, excellent wear resistance, corrosion resistance, excellent biocompatibility, and long fatigue life. However, the document does not discuss photocatalysis at all. This Non-Patent Document 1 discloses that an excellent crystalline anatase layer is obtained by immersing a titanium sheet in a 30% by mass H₂O₂ solution for 8 hours, then immersing it in room temperature water for 12 hours, and then immersing it in 80°C water for 3 days. However, the document does not describe any specific method, process, or conditions for achieving good photocatalysis, which would be considered a technical concept. Furthermore, the inventors discovered that sufficient photocatalysis was clearly not achieved under the processing conditions described in Non-Patent Document 1. In other words, this Non-Patent Document 1 merely discloses titanium materials as implant materials in orthopedics and dentistry, without any disclosure of photocatalysis or the relationship between immersion time and photocatalysis.

[0016] The invention provides a method for preparing semiconductor titanium dioxide. The method does not require complicated pretreatment and can simply prepare semiconductor titanium dioxide with excellent photocatalytic effect by using general equipment.

[0017] Solutions for solving problems

[0018] The present invention provides a method for preparing semiconductor titanium dioxide, comprising: a first soaking step of soaking a titanium-containing substrate in a hydrogen peroxide aqueous solution at 70 to 90° C. for 1 to 28 hours; and a second soaking step of soaking the substrate after the first soaking step in water for 24 to 96 hours.

[0019] In one aspect of the present invention, the temperature of water in the second soaking step is 70-90°C.

[0020] The present invention also provides a method for preparing semiconductor titanium dioxide, comprising:

[0021] A first soaking step of soaking the titanium-containing substrate in a hydrogen peroxide solution at 70 to 90° C. for 1 to 28 hours; and

[0022] Second soaking process;

[0023] The second soaking process includes: soaking the substrate after the first soaking process in room temperature water of 10 to 30° C. for 24 to 48 hours; and soaking the substrate after the room temperature water soaking process in warm water of 70 to 90° C. for 24 to 96 hours.

[0024] In one aspect of the present invention, the concentration of hydrogen peroxide in the aqueous hydrogen peroxide solution is 20 to 45% by mass.

[0025] In one aspect of the present invention, the semiconductor titanium dioxide has a photocatalytic effect.

[0026] Effects of the Invention

[0027] The method for preparing the semiconductor titanium dioxide of the present invention does not require complicated pretreatment, and semiconductor titanium dioxide with excellent photocatalytic effect can be simply prepared using general equipment. DETAILED DESCRIPTION

[0028] The method for preparing semiconducting titanium dioxide according to this embodiment includes a first soaking step of soaking a titanium-containing substrate in a hydrogen peroxide solution at 70-90°C for 1-28 hours, and a second soaking step of soaking the substrate after the first soaking step in water for 24-96 hours. This method for preparing semiconducting titanium dioxide according to this embodiment does not require complex pretreatment and can simply produce semiconducting titanium dioxide with excellent photocatalytic properties using common equipment.

[0029] <First Soaking Step>

[0030] The first immersion step is a step of immersing the titanium-containing substrate in a hydrogen peroxide aqueous solution at 70 to 90° C. for 1 to 28 hours.

[0031] The substrate contains titanium. From the perspective of obtaining a semiconductor titanium dioxide having excellent photocatalytic activity, the substrate is preferably composed of titanium or a titanium alloy. The shape of the substrate is not particularly limited, and can be selected appropriately depending on the intended use, such as a plate, rod, or block.

[0032] Preferably, the substrate is pre-cleaned with water or an organic solvent. The organic solvent used to clean the substrate is not particularly limited, and may be, for example, acetone or methanol. The substrate may be surface-polished as needed.

[0033] From the perspective of obtaining semiconductor titanium dioxide having excellent photocatalytic activity, the temperature of the aqueous hydrogen peroxide solution in which the substrate is immersed is 70° C. or higher, preferably 75° C. or higher. From the perspective of production efficiency, the temperature of the aqueous hydrogen peroxide solution in which the substrate is immersed is 90° C. or lower, preferably 85° C. or lower.

[0034] From the perspective of obtaining semiconductor titanium dioxide having excellent photocatalytic activity, the concentration of the aqueous hydrogen peroxide solution used in the first immersion step is preferably 15% by mass or greater, more preferably 20% by mass or greater, and even more preferably 25% by mass or greater. From the same perspective, the concentration of the aqueous hydrogen peroxide solution used in the first immersion step is preferably 45% by mass or less, more preferably 40% by mass or less.

[0035] From the perspective of obtaining semiconductor titanium dioxide having excellent photocatalytic activity, the substrate is immersed in the aqueous hydrogen peroxide solution for at least one hour, preferably at least four hours, in the first immersion step. From the perspective of production efficiency, the substrate is immersed in the aqueous hydrogen peroxide solution for at least 28 hours, more preferably at most 12 hours, in the first immersion step.

[0036] <Second Soaking Step>

[0037] The second immersion step is a step of immersing the substrate after the first immersion step in water for 24 to 96 hours.

[0038] The water used to soak the substrate in the second soaking step may be, for example, distilled water, deionized water, purified water, tap water, industrial water, etc. From the perspective of easy availability, distilled water or deionized water is preferred.

[0039] From the perspective of obtaining semiconductor titanium dioxide having excellent photocatalytic activity, the substrate is immersed in water for a period of 24 hours or longer, preferably 36 hours or longer, in the second immersion step. From the perspective of production efficiency, the substrate is immersed in water for a period of 96 hours or shorter, in the second immersion step.

[0040] From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the water used in the second soaking process is preferably above 70°C, more preferably above 75°C. From the perspective of preparation efficiency, warm water is preferably below 90°C, more preferably below 85°C.

[0041] In the second immersion step, the substrate may be immersed in water at room temperature (hereinafter referred to as "room temperature water") before being immersed in the warm water. In other words, the second immersion step may include a room temperature water immersion step in which the substrate is immersed in room temperature water, and a warm water immersion step in which the substrate is immersed in the warm water after the room temperature water immersion step.

[0042] From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the time for immersing the substrate in the normal temperature water during the normal temperature water immersion step is preferably 12 hours or longer, more preferably 17 hours or longer. Furthermore, from the perspective of obtaining semiconductor titanium dioxide with even better photocatalytic activity, the time for immersing the substrate in the normal temperature water is more preferably 24 hours or longer. From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the time for immersing the substrate in the normal temperature water is preferably 48 hours or shorter, and may be 24 hours or shorter.

[0043] From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the temperature of the room-temperature water used in the room-temperature water immersion step is preferably 10°C or higher, more preferably 13°C or higher. From the perspective of production efficiency, the temperature of the room-temperature water used in the room-temperature water immersion step is preferably 30°C or lower, more preferably 25°C or lower.

[0044] From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the time for immersing the substrate in warm water during the warm water immersion step is preferably 24 hours or longer. Furthermore, from the perspective of obtaining semiconductor titanium dioxide with even better photocatalytic activity, the time for immersing the substrate in warm water during the warm water immersion step is more preferably 48 hours or longer. From the perspective of obtaining semiconductor titanium dioxide with excellent photocatalytic activity, the time for immersing the substrate in warm water during the warm water immersion step is preferably 96 hours or shorter, and more preferably 72 hours or shorter.

[0045] The semiconducting titanium dioxide prepared by the method for preparing semiconducting titanium dioxide according to this embodiment exhibits excellent photocatalytic activity. One indicator of photocatalytic activity is the acetic acid decomposition evaluation described in the Examples. In this acetic acid decomposition evaluation, a greater amount of carbon dioxide produced indicates a stronger photocatalytic activity. The semiconducting titanium dioxide of the present invention can be used in a wide range of fields and is particularly suitable for applications requiring a high photocatalytic effect.

[0046] Example

[0047] <Preparation of Evaluation Samples>

[0048] [Example 1]

[0049] A rod-shaped substrate composed of pure titanium (99.5% by mass) with a diameter of approximately 3 mm and a length of approximately 80 mm was washed with distilled water and acetone, dried, and then immersed in a 30% by mass aqueous hydrogen peroxide solution at approximately 80°C in a 250 mL polypropylene container for one hour. The substrate was then immersed in water at room temperature (approximately 15°C) for 24 hours, and then in water at approximately 80°C for 48 hours, to obtain the evaluation sample of Example 1.

[0050] [Examples 2-5, Comparative Examples 1 and 2, Reference Examples 2-5]

[0051] The evaluation samples of Examples 2-5, Comparative Examples 1 and 2, and Reference Examples 2-5 were obtained in the same manner as in Example 1, except that the soaking steps were changed to those described in Table 1.

[0052] [Comparative Example 3]

[0053] A substrate consisting of rod-shaped pure titanium (99.5% by mass) with a diameter of approximately 3 mm and a length of approximately 80 mm was pre-washed with a hydrofluoric acid solution and dried, then heated and calcined in air at 800°C for 4 minutes in an electric furnace at a heating rate of 7°C / second, and then quenched with cold water at approximately 10°C to obtain an evaluation sample of Comparative Example 3.

[0054] <Assessment>

[0055] [Acetic acid decomposition evaluation]

[0056] [Examples 1-5, Comparative Examples 1-3, Reference Examples 2-5]

[0057] Four evaluation samples from each of Examples 1-5, Comparative Examples 1-3, and Reference Examples 2-5 were placed in a 20 mm diameter test tube, and 15 ml of water containing 100 μmol of acetic acid was added to the test tube. To further promote the decomposition of acetic acid, oxygen was bubbled into the liquid phase of each test tube for 20 minutes and into the gas phase for 10 minutes using a bubbling device connected to a gas cylinder and polyethylene tubing. Simultaneously, the samples were irradiated with 6 W light at a wavelength of 368 nm for 24 hours in a dark room under a black light, with the heat generated by the black light not affecting the temperature. The amount of carbon dioxide produced by the photocatalytic decomposition of acetic acid in each evaluation sample was measured by gas chromatography.

[0058] [Comparative Example 4]

[0059] The acetic acid decomposition evaluation was conducted in the same manner as in Example 1, except that a substrate composed of pure titanium (99.5% by mass) in the form of a rod having a diameter of approximately 3 mm and a length of approximately 80 mm, which had not been treated in Example 1, was used.

[0060] [Reference Example 1]

[0061] The acetic acid decomposition evaluation was performed without immersing the evaluation sample in acetic acid.

[0062] The measurement results are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] The evaluation samples of Examples 1-5, which are within the scope of the claims of the present application, produced more carbon dioxide than the evaluation samples of Comparative Examples 1-4, which are outside the scope of the claims of the present application, and had excellent acetic acid decomposition effects, and therefore it can be seen that they had excellent photocatalytic effects. In addition, the preparation process of the evaluation sample of Reference Example 2 was the same as that of Example 2, except that there was no room temperature water immersion process. Compared with Example 2, which underwent both room temperature water immersion and warm water immersion processes, it can be seen that the photocatalytic effect of Reference Example 2 was poor. In addition, the preparation process of the evaluation sample of Reference Example 3 was the same as that of Example 2, except that there was no warm water immersion process. Compared with Example 2, the amount of carbon dioxide generated in Reference Example 3 was less than half, and it can be seen that the photocatalytic effect was poor. It can be seen that the amount of carbon dioxide generated under the treatment conditions shown in Reference Examples 4 and 5 was small, and sufficient photocatalytic effect could not be obtained.

[0067] Industrial Applicability

[0068] The semiconductor titanium dioxide of the present invention has a photocatalytic effect and can be widely used in the fields of food industry, chemical industry, medical industry, environmental equipment industry and the like.

Claims

1. A method for preparing semiconductor titanium dioxide, comprising: A first soaking step of soaking the titanium-containing substrate in a hydrogen peroxide solution at 70 to 90° C. for 1 to 28 hours; as well as, Second soaking process; The second soaking process comprises: A step of soaking the substrate after the first soaking step in water at room temperature of 10 to 30° C. for 24 to 48 hours; and a warm water soaking step of soaking the substrate after the normal temperature water soaking step in warm water at 70 to 90° C. for 24 to 96 hours; Wherein, the titanium-containing substrate is composed of titanium or titanium alloy.

2. The method for preparing semiconductor titanium dioxide according to claim 1, wherein The concentration of hydrogen peroxide in the aqueous hydrogen peroxide solution is 20 to 45% by mass.

3. The method for preparing semiconductor titanium dioxide according to claim 1 or 2, wherein: The semiconductor titanium dioxide has a photocatalytic effect.

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