JP6207302B2 - Oil-water separator manufacturing method and oil-water separator - Google Patents

Description

  The present invention relates to an oil / water separator and its use for separating oil and water from an oil / water mixture.

  The spill of heavy oil into the sea due to a tanker accident causes serious environmental problems. Before spreading heavy oil immediately after the accident occurs, it is required to collect heavy oil as quickly as possible, and highly efficient oil-water separation technology is required.

  As an existing technology, it is known that oil and water can be separated by simply pouring an oil-water mixture into a filter that exhibits water repellency in air or a filter that is hydrophilic in air and exhibits oil repellency in water. ing. For example, the following filters have been proposed as such filters.

  Non-Patent Document 1 describes that the surface of a metal substrate such as nickel, which has a shape like a nano-sized petal, has a super-water-repellent surface, as a thin-layer crystal formed by self-assembly of an alkylphosphonate. Has been.

Non-Patent Document 2 describes that the surface of a stainless steel mesh coated with zinc oxide nanorods exhibits superhydrophobicity and superlipophilicity.
Non-Patent Document 3 discloses that a surface of a stainless steel mesh made of a material containing polytetrafluoroethylene (PTFE) and having a rough unevenness of micrometer size to nanometer size is super-water-repellent and super-parent. It is described that it exhibits oiliness.

Non-Patent Document 4 describes that the surface of a copper mesh grafted with 1-hexadecanethiol after etching with nitric acid exhibits superhydrophobicity and superlipophilicity.
Non-Patent Document 5 describes that the surface of a stainless steel mesh coated with zeolite exhibits super hydrophilicity and super oil repellency in water.

  However, such a conventional filter has a porous surface, and the mechanical strength of the fine porous surface and the adhesion to the substrate are generally weak. In addition, filter clogging due to the adhesion of oil accompanying separation processing is likely to occur.

On the other hand, titanium oxide (TiO ₂ ) is well known as a chemically stable, non-toxic and relatively inexpensive material having a photocatalytic function. Titanium oxide also exhibits amphipathic properties by dramatically changing wettability when irradiated with ultraviolet rays (UV), that is, its contact angle with _{water in air is} smaller than 5 ° (CA _{water / air} It is also known that the contact angle with _{oil in the air is} smaller than 5 ° (CA _{oil / air} <5 °) and exhibits super water repellency in addition to super hydrophilicity (<5 °) (non-patent document) 6). In this way, the flat surface of hydrophilic titanium oxide can be easily manufactured, and has excellent durability and anti-fogging and self-cleaning properties. Mirrors, exterior wall tiles, etc.)

  However, most reports on the wettability of the titanium oxide surface are based on the contact angles of various liquids measured in air, and reports on the contact angle with oil in water (super oil repellency) Never before.

Li et al., J. Mater. Chem., 2007, 17, 4772-4776 Tial et al., Phys. Chem. Chem. Phys., 2011, 13, 14505-14610 Feng et al., Angew. Chem. Int. Ed. 2004, 43, 2012-2014 Wang et al., Applied Materials and Interfaces, 2009, 1 (11), 2613-2617 Wen et al., Chem. Sci., 2013, 4, 591-595 Wang et al., Nature, 1997, 388, 431-432

  As described above, most of the oil / water separators proposed so far need to be made of a member that is brittle on the surface and has a fine porous structure, and considering the practicality as an oil / water separator. In addition, there was room for improvement in terms of durability (mechanical strength, adhesion to the substrate) and prevention of clogging. In addition, such an oil / water separator has a relatively complicated manufacturing process.

  An object of the present invention is to provide a practical oil / water separator that is excellent in durability and prevention of clogging and that can be easily manufactured.

Surprisingly, the inventors of the present invention calculated the measured value of the contact angle with oil in water on the surface of the titanium oxide layer superhydrophilicized by UV irradiation from Young's formula (details will be described later). It was found to be significantly higher than the calculated value, and to exhibit super oil repellency (CA _{oil / water} > 160 °) suitable for use as an _{oil / water} separator. In addition, a relatively simple process of firing a titanium mesh can form a layer made of titanium oxide on its surface, and the titanium oxide layer has excellent mechanical strength and a base (titanium mesh). ) Was found to be highly adhesive. The mesh provided with a superhydrophilic titanium oxide layer on the surface obtained through the baking and ultraviolet irradiation processes as described above can be repeatedly subjected to oil-water separation treatment without causing clogging. It confirmed that it could utilize as an oil-water separator with which it was equipped, and came to complete this invention.

  That is, this invention provides the oil-water separator which solved the subject mentioned above in one side surface, and also provides the oil-water separator which equip | installed the said oil-water separator. Moreover, this invention provides the oil-water separation method which uses such an oil-water separation material in another side surface. The present invention includes the following matters.

[1] An oil / water separator comprising a mesh having a superhydrophilic titanium oxide layer on its surface.
[2] The oil / water separator according to [1], wherein the superhydrophilic treatment is performed by UV irradiation.

[3] The oil-water separator according to [1] or [2], wherein the mesh is made of titanium, and the titanium oxide layer is formed by firing the titanium mesh.
[4] The oily water according to any one of [1] to [3], wherein a contact angle between the superhydrophilic titanium oxide layer and at least one oil in water is greater than 160 °. Separation material.

[5] An oil / water separator having the oil / water separator according to any one of [1] to [4].
[6] The oil / water mixture is poured into the oil / water separator according to any one of [1] to [4], and water passes through the mesh of the oil / water separator, while oil passes through the mesh of the oil / water separator. The oil-water separation method characterized by including the process of making it not pass.

In the present specification, as in the concept of general terms in the technical field, “superhydrophilic” means that the contact angle with _{water in air is} smaller than 5 ° (CA _{water / air} <5 °). “Super-lipophilic” refers to a physical property having a contact angle with _{oil in the air of} less than 5 ° (CA _{oil / air} <5 °). “Super-oil repellency in water” The angle of contact with oil is greater than 150 ° (CA _{oil / water} <150 °). In the present invention, a relatively small contact angle corresponding to “superhydrophilicity” or “superlipophilicity” is a value calculated by the θ / 2 method, “superoil repellency in water” or “superwater repellency”. A relatively large contact angle corresponding to is defined as a value calculated by the tangent method. The measurement of the contact angle by such a method can be performed using a commercially available general contact angle meter (measurement system).

  Since the surface of the titanium oxide layer subjected to the superhydrophilic treatment exhibits remarkable super oil repellency in water, the mesh provided with such a titanium oxide layer is a member for separating water and oil from the oil-water mixture. High performance can be demonstrated. Moreover, since no oil droplets adhere to the surface of the titanium oxide layer subjected to the superhydrophilic treatment in water, there is no need to worry about clogging of the filter.

  Moreover, a titanium oxide layer can be formed on the surface by a relatively simple process of firing a titanium mesh, and the titanium oxide layer has excellent mechanical strength and high adhesion to the substrate (titanium). . Therefore, the mesh provided with such a titanium oxide layer is expected to maintain an excellent effect as a highly durable oil-water separation filter over a long period of time.

SEM (upper) and AFM (lower) photographed images of samples prepared in Reference Example 1 (left) and 2 (right). The continuous photograph when an oil drop (n-hexadecane, 2 microliters) is made to contact and separate the surface of the sample produced in Reference Example 1 before (left) and after irradiation (right) with UV. Arrows indicate the direction of oil droplet movement. CA _{oil / water} calculated values (black) and measured values (outlined) before and after UV irradiation (upper) and after irradiation (lower) of the samples prepared in Reference Example 1 (left) and 2 (right) . The calculated value is a value calculated from the formula (1) in the specification. An image of the change in wettability in water when UV irradiation is applied to the titanium oxide surface. The schematic diagram and photograph of the oil-water separator provided with the sample (titanium oxide mesh, pore diameter of about 150 μm) produced in the example. n-Hexadecane is dyed red and water is dyed blue (can be visually confirmed in a color photograph).

-Oil / water separator-
The oil / water separator of the present invention is made of a mesh having a super-hydrophilic titanium oxide layer on its surface.

  A mesh provided with a superhydrophilic titanium oxide layer on its surface can be produced by first forming a titanium oxide layer on the surface of the mesh formed of titanium and subjecting it to a superhydrophilic treatment.

  A mesh having a titanium oxide layer on the surface generally heat-treats (fires) the titanium mesh at an appropriate temperature for an appropriate time, and changes the titanium in the surface layer of the titanium mesh to titanium oxide. Can be obtained. Here, the titanium oxide having a photocatalytic function includes those having an anatase type crystal structure and those having a rutile type crystal structure. In general, titanium oxide having an anatase type crystal structure has higher activity as a photocatalyst. In the present invention, titanium oxide having either anatase type or rutile type crystal structure may be used. The temperature, time, and other conditions for forming the titanium oxide layer having these crystal structures can be appropriately adjusted by those skilled in the art while considering the influence on the operational effects of the present invention. In the case of forming a titanium oxide layer having a rutile-type crystal structure, generally, the temperature of the heat treatment is 400 to 800 ° C., and the time is 10 minutes to 4 hours.

The superhydrophilic treatment of the titanium oxide layer is generally performed by irradiating ultraviolet rays having an appropriate intensity. Those skilled in the art can appropriately adjust the irradiation intensity and other conditions for such superhydrophilic treatment, while taking into consideration the influence on the effects of the present invention. In general, the irradiation intensity of ultra-hydrophilic overtreated ultraviolet rays is 1 to 30 mW / cm ² , and the irradiation time is 1 minute to 6 hours.

  However, the production method of the titanium mesh provided with the superhydrophilic titanium oxide layer used in the present invention on the surface is not particularly limited, as long as the effects of the present invention relating to oil-water separation are exhibited. It may be produced by a method other than this method.

The surface of the titanium oxide layer after the superhydrophilic treatment has a higher contact angle (CA _{oil / water} ) with the oil in water than before the superhydrophilic treatment. The contact angle of the surface of the titanium oxide layer after the superhydrophilic treatment with the oil in water is usually larger than 150 ° (that is, exhibits super oil repellency in water), preferably larger than 160 °, more preferably Greater than 165 °. However, the contact angle with oil in water varies depending on the type of oil. In consideration of the use of the oil / water separator of the present invention, it is appropriate that the contact angle with the oil in water satisfies the above conditions in relation to one or more types of oil.

  The type of “oil” to be separated using the oil / water separator is not particularly limited, but is generally liquid under temperature conditions (usually normal temperature) where water is liquid, and is not miscible with water. Oils consisting of a single hydrocarbon and oils consisting of a plurality of hydrocarbons are included. The hydrocarbon constituting such an oil may be any hydrocarbon or alicyclic saturated or unsaturated hydrocarbon having an appropriate number of carbon atoms, for example, 5 to 5 carbon atoms. 19 aliphatic saturated hydrocarbons and alicyclic saturated hydrocarbons having 5 to 8 carbon atoms. Examples of the oil composed of a plurality of hydrocarbons include gasoline, kerosene, light oil (diesel oil), heavy oil, crude oil, and animal or plant-derived oils and fats.

  In other words, the “oil” separated using the oil / water separator has a contact angle in water on the surface of the titanium oxide layer after the superhydrophilization treatment that is at least greater than 150 ° and greater than 160 °. Are preferred, and those greater than 165 ° are more preferred.

  The size or pore size of the mesh (diameter or one side of the gap delimited by the mesh) should be within a range that has appropriate oil-water separation performance, i.e., the water passing through the mesh, taking into account the contact angle with oil in water. It is appropriate to adjust so that the oil-water separation proceeds only by gravity without mixing. The pore diameter is generally 10 to 500 μm, preferably 10 to 200 μm.

-Use of oil / water separator-
The oil / water separator of the present invention can be used by being mounted as an oil / water separator filter on an oil / water separator or other devices requiring an oil / water separator. Various types of oil-water separators are known, and the type of oil-water separator to which the oil-water separator of the present invention is attached is not particularly limited. What is necessary is just to manufacture an oil-water separation material with embodiment adapted to the structure of the oil-water separation apparatus made into the mounting object.

  In addition, the oil / water separator of the present invention (particularly the one installed in the oil / water separator) is poured into the oil / water mixture, and the water passes through the mesh of the oil / water separator, while the oil is the oil / water separator. It can be used to carry out an oil / water separation method including a step of preventing the mesh from passing (oil / water separation step). Such an oil-water separation step may be performed a desired number of times by a batch method, or may be performed by a continuous method for a desired time.

  The oil / water separation method described above may include a step of irradiating the titanium oxide layer of the oil / water separator with UV light in order to recover the oil / water separation ability that is lost over time in a dark place. The UV irradiation conditions in this step may be in accordance with the UV irradiation conditions for the superhydrophilic treatment performed when the oil-water separator described above is produced. Therefore, the oil / water separation device may further include a UV irradiation means so that the oil / water separation ability can be recovered by irradiating UV without removing the oil / water separation material (filter) of the present invention.

  Alternatively, when the oil / water separator of the oil / water separator used is weakened, replace it with a newly created or regenerated oil / water separator that retains high oil / water separator by UV irradiation. Is preferred.

  The matters relating to the “titanium oxide layer formed on the glass substrate by the sol-gel method” described as Reference Example 1 below and the matters relating to the “titanium oxide layer formed on the titanium plate” described as Reference Example 2 were carried out. The same applies to the “titanium oxide layer formed on the titanium mesh” described as an example. That is, the surface structure and various contact angles of the titanium oxide layer included in the titanium mesh used in the examples are as shown in FIG. It is estimated that the results are equivalent to the various contact angles shown, and the comparison results between the actual measurement values and the calculated values of the various contact angles shown in FIG. 3 are also the same. In addition, the contact between the titanium oxide layer included in the titanium mesh used in the example (and the titanium oxide layer included in the titanium plate used in Reference Example 2) and the oil droplets was formed on the glass substrate of Reference Example 1. Regarding the contact between the titanium oxide layer and the oil droplets, it is presumed that the contact state shown in FIG. 2 and the model shown in FIG.

[Reference Example 1]
A sample based on a slide glass (thickness 1 mm, Matsunami Glass Industrial Co., Ltd.) and having a layer made of titanium oxide formed on the surface was prepared by the following procedure using dip coating and sol-gel method. . First, the slide glass was immersed in alkoxysilane (NDH-500A, Nippon Soda Co., Ltd.) and pulled up at 2.5 mm / s, and then the alkoxysilane coating film was baked at 500 ° C. for 30 minutes. Next, the obtained slide glass was immersed in titanate tetraisopropoxide (NDH-520C, Nippon Soda Co., Ltd.), pulled up at 2.5 mm / s, and then coated with a tetraisopropoxide titanate coating film. Baked at 30 ° C. for 30 minutes. The prepared sample was stored for several days in the dark.

  FIG. 1 (left) shows an image observed with SEM and AFM. A layer composed of uniform and fine titanium oxide particles (average particle diameter of about 20 to 30 nm) was formed on the surface of the sample of Reference Example 1, and the surface was flat (Ra = 1.09 nm). Moreover, it was confirmed by XRD that the crystal structure of titanium oxide in the sample of Reference Example 1 was anatase type.

[Reference Example 2]
A titanium plate (thickness 5 mm, Niraco Co., Ltd.) was heat-treated at 500 ° C. for 4 hours to prepare a sample having a titanium plate as a base and a layer made of titanium oxide formed on the surface thereof. The prepared sample was stored for several days in the dark.

  FIG. 1 (right) shows images observed with a scanning electron microscope (SEM; JSM-6380A, JEOL Ltd.) and an atomic force microscope (AFM; SPI3800N, Seiko Instruments Inc.). The titanium oxide layer formed on the surface of the sample of Reference Example 2 had minute irregularities, and the surface was relatively rough (Ra = 71.29 nm). Further, it was confirmed by X-ray diffraction (XRD) that the crystal structure of titanium oxide of the sample of Reference Example 2 was a rutile type.

(Cross cut test)
The adhesion between the substrate and the titanium oxide layer formed on the surface thereof was evaluated according to ISO 2409 (cross cut test). The titanium oxide layer was cut into a grid pattern with a stainless steel cutter, attached with adhesive tape, and peeled off with almost constant force. As a result, no peeling was observed at all for the sample of Reference Example 1 (glass substrate) and the sample of Reference Example 2 (titanium substrate), and the evaluation was excellent (Excellent level).

(Pencil scratch test)
The mechanical strength of the titanium oxide layer formed on the surface of the substrate was evaluated according to ISO15184 (pencil scratching test). The pencil was fixed at 45 ° with respect to the surface of the titanium oxide layer and moved while applying a constant force vertically. The pencil hardness is tested in order from the softer one (9B) to the harder one (9H), and the hardest hardness without scratching the titanium oxide layer is the evaluation result. As a result, it was evaluated that the mechanical strength of the titanium oxide layer of the sample of Reference Example 1 corresponds to 3H of pencil hardness, and the mechanical strength of the titanium oxide layer of the sample of Reference Example 2 corresponds to 6H of pencil hardness.

  From the above two test results, it can be seen that the titanium oxide layer has practically sufficient mechanical strength and adhesion to the substrate, and it is expected to maintain an excellent effect as a highly durable separation membrane over a long period of time. .

(Measurement of contact angle)
Each of the sample of Reference Example 1 and the sample of Reference Example 2 was irradiated with UV in order to change the wettability of the titanium oxide film, and the contact angle with water in the air before and after that (CA _{water / air} ) The contact angle with _{oil in the air} (CA _{oil / air} ) and the contact angle with _{oil in water} (CA _{oil / water} ) were measured. As an oil model, n-heptane (Wako Pure Chemical Industries, Ltd.), dodecane (Wako Pure Chemical Industries, Ltd.) and n-hexadecane (Wako Pure Chemical Industries, Ltd.) were used. A 300 W xenon lamp was used as the UV light source, the irradiation intensity was about 15 mW / cm ² , and the irradiation time was 3 hours. The contact angle is measured with an automatic contact angle meter (Drop Master 300, Kyowa Interface Science Co., Ltd.) on a 2 μL droplet at room temperature, and the contact angle with _{water in water} (CA _{water / air} ) and The contact angle with _{oil in the air} (CA _{oil / air} ) was calculated by the θ / 2 method, and the contact angle with _{oil in water} (CA _{oil / water} ) was calculated by the tangent method. When measuring the contact angle (CA _{oil / water} ) with _oil in water, deionized water is used as the water, and when no oil droplets adhere to the surface (CA _{oil / water} > 165 °), it is suppressed with a needle. It was. The contact angle was measured at least at five locations for one sample.

Table 1 shows the measurement results of the contact angle. By UV irradiation, the surface of the calcined titanium plate is amphiphilic, ie, super hydrophilic (CA _{water / air} <5 °) and super lipophilic (CA _{oil / air} <5 °), and any of the three types of oils. Also showed remarkable super oil repellency (CA _{oil / water} > 165 °) in _water . From this result, it can be seen that the surface of titanium oxide irradiated with UV repels oil significantly in water.

(Observation of contact between titanium oxide layer and oil droplets)
In FIG. 2, a mode when n-hexadecane (2 microliters) is made to contact the surface of the sample of the reference example 1 as an oil droplet is shown. When the spherical oil droplet at the tip of the needle is brought into contact with the surface of the titanium oxide layer before the UV irradiation (CA _{hexadecane / water} = 139.2 ± 5.8 °), it will be deformed when the needle is released. Residually adhered to the surface. On the other hand, the surface of the titanium oxide layer after UV irradiation (CA _{hexadecane / water} = 169.5 ± 2.7 °) does not adhere to the surface even if the spherical oil droplet at the tip of the needle is strongly pressed. When the needle was released, the oil droplets were easily removed from the surface without deformation and did not remain at all.

(Comparison of actual and calculated CA _{oil / water} values)
The contact angle (CA _{oil / water} ) with _{oil in water} is expressed by the following formula (1) (Young's formula), the contact angle with _{water in water} (CA _{water / air} ), and the oil in air. It can be calculated by substituting literature values for the actual measured value and surface tension of the contact angle (CA _{oil / air} ).

In equation (1), γ _OA is the oil / air interface tension, θ _OA is CA _{oil / air} , γ _WA is the water / air interface tension, θ _WA is CA _{water / air} , γ _OW is the water / oil interfacial tension.

From the comparison between the measured value of CA _{oil / water} measured as described above and the calculated value calculated from Equation (1), the wettability of titanium oxide can be considered as follows.
When the surface of the substrate (titanium oxide) and oil droplets are in uniform contact at the interface, the measured value of CA _{oil / water} agrees well with the calculated value. However, when water is trapped between the surface of the porous substrate (titanium oxide) and the oil droplets, the measured value of CA _{oil / water} is larger than the calculated value.

  Such a complex wet state can be described by the following equation (2) based on the Cassue-Baxter model.

In formula (2), f is an area fraction of the substrate (titanium oxide), θ _OW is CA _{oil / water} on the smooth substrate surface, and θ ′ _OW is CA _{oil on the} porous substrate surface. _{oil / water} . The area ratio of f in this experiment excludes the area of the entire surface of the titanium oxide that does not come into contact with the oil droplets by being covered with water, and can contact with the oil droplets without being covered with water. It represents the ratio of the area of the characteristic part.

FIG. 3 shows measured values and calculated values of the contact angle (CA _{oil / water} ) with _{oil in water} . As for the sample of Reference Example 1, the measured value of CA _{oil / water} is higher than the calculated value even before UV irradiation, so that even if the surface of the titanium oxide layer is smooth, some water is still on the surface and oil droplets. It was suggested that it was trapped in between. Moreover, after UV irradiation, CA _{oil / water} becomes remarkably high for all three types of oil, and the amount of water trapped between the surface of the titanium oxide layer and the oil droplets is increased by UV irradiation. It has been suggested. This is considered to be because the pollutant adhering to the titanium oxide surface was decomposed by the photocatalytic function by UV irradiation, and water preferentially covered the titanium oxide surface. The change in wettability due to UV irradiation as described above is schematically shown in FIG.

On the other hand, for the sample of Reference Example 2, the measured value of CA _{oil / water} was higher than the calculated value before UV irradiation, but the difference was even greater than that for the sample of Reference Example 1. This is presumably because the surface of the titanium oxide layer of the sample of Reference Example 2 is relatively rough and can trap more water. The difference between the measured value and the calculated value of CA _{oil / water} after UV irradiation was the same as or slightly smaller than the difference of the sample of Reference Example 1, but the measured value of CA _{oil / water} was almost the same as the sample of Reference Example 1 Met.

Here, as the reason why CA _{oil / water} increases after UV irradiation, as described above, the effect of decomposing contaminants originally attached to the titanium oxide surface by the photocatalytic function by UV irradiation (first effect) In addition to this, the effect of the fact that water molecules are strongly attracted to defects in Ti ³⁺ caused by UV irradiation, and a layer composed of such water molecules is formed between the surface of the titanium oxide layer and the oil droplets (first step). 2 effects) are also conceivable. Therefore, which effect contributed mainly was verified as follows.

First, the sample of Reference Example 1 was washed with a UV-O ₃ cleaner (PC440, Meiwa Forsys, Inc.), and contaminants originally attached to this sample were removed (cleaning treatment). The super-hydrophilic treatment of titanium oxide is also performed by the UV irradiation during the cleaning treatment. Subsequently, the sample was immersed in an n-hexadecane solution to which oleic acid (Wako Pure Chemical Industries, Ltd., 0.5% by volume) was added as a contaminant, pulled up at 9.9 mm / s, and at 50 ° C. for 20 minutes. Dried (contamination treatment). Thereafter, the CA _{water / air} and CA _{hexadecane / water} of the sample were measured. As a result, although the contamination treatment was performed immediately after the washing treatment (superhydrophilic treatment), the contamination treatment caused superhydrophilicity and It was found that the super oil repellency was lost. If, due to the second effect, a layer made of water molecules is formed on the surface of the titanium oxide layer after the cleaning treatment, the oil (n-hexadecane) and the contaminant (oleic acid) are also oxidized by the contamination treatment. It does not adhere to the surface and should not lose its super hydrophilicity and super oil repellency in water. From this, it is surmised that the second effect hardly contributes to the operational effect of the present invention, and that the first effect mainly contributes.

  Furthermore, the characteristics of the wettability change due to UV irradiation of the titanium oxide layer were examined by the following method. First, in the same manner as described above, an n-hexadecane solution to which oleic acid was added as a contaminant was brought into contact with the sample of Reference Example 1 to lose the super hydrophilicity and super oil repellency in water of the sample. Next, when the sample in such a state was irradiated with UV, the lost super hydrophilicity and the super oil repellency in water were recovered. Even when such treatment was repeated at least three times, recovery of super hydrophilicity and super oil repellency in water was observed. Similar results were obtained for the sample of Reference Example 2. Therefore, it was found that the wettability of the surface of the titanium oxide layer was reproducible without causing damage even after several changes.

[Example]
A sample (titanium oxide mesh sample) in which a titanium mesh (100 mesh, pore diameter of about 150 μm, Nilaco Co., Ltd.) was heat-treated under the same conditions as in Reference Example 2 to form a layer made of titanium oxide on the surface was produced.

  Using the sample, an oil-water separation test was performed as shown in FIG. First, the titanium oxide mesh sample is irradiated with UV (UV irradiation conditions are as described above in Reference Example 2), immersed in deionized water to form a water film on the surface, and then placed under the glass funnel. Attached to. Next, oil (n-hexadecane) colored red with Sudan IV (Tokyo Chemical Industry Co., Ltd.) and water colored blue with methylene blue (Kanto Chemical Co., Ltd.) (oil: water = 8 mL: 8 mL) with a whole pipette Poured from above. As a result, only water quickly passed through the titanium oxide mesh sample and dropped into the lower beaker, while the oil remained on the titanium oxide mesh sample. At this time, no external force was applied and only gravity worked.

  On the other hand, when the titanium oxide mesh sample was used without irradiating UV, separation of water and oil as described above could not be performed. The appearance of oil droplets entering the water layer on the titanium oxide layer was observed, thereby causing the oil to pass through the titanium oxide mesh sample.

  From the above results, it became clear that a mesh provided with a titanium oxide layer superhydrophilicized by UV irradiation can be used as a filter for oil-water separation. This excellent oil / water separation ability was based on the remarkable super oil repellency of the titanium oxide layer in water, and almost no oil droplets were attached to the titanium oxide mesh sample.

  Moreover, the titanium oxide mesh can repeatedly exhibit oil / water separation ability, and is considered to be robust and stable due to its dense surface structure. The super oil repellency of titanium oxide mesh in water is lost when placed in a dark place for several hours after UV irradiation, but can be recovered by UV irradiation. Therefore, the titanium oxide mesh can be used as a filter for oil / water separation having both high oil / water separation ability, durability and oil contamination resistance, and easy reusability.

Claims (4)

  In the method for producing an oil / water separator comprising a mesh provided with a superhydrophilic titanium oxide layer on the surface,
  A baking step of forming the titanium oxide layer by baking a titanium mesh;
  A superhydrophilization treatment step for increasing the contact angle of the titanium oxide layer with at least one kind of oil in water by performing UV irradiation on the titanium oxide layer;
The manufacturing method of the oil-water separation material characterized by having.   In the superhydrophilic treatment step, the irradiation intensity of the UV irradiation is 1 to 30 mW / cm. ² The method according to claim 1, wherein the irradiation time is 1 minute to 6 hours.   The method for producing an oil / water separator according to claim 1 or 2, wherein the firing step is performed at a firing temperature of 400 to 800 ° C and a firing time of 10 minutes to 4 hours. An oil / water mixture is poured into the oil / water separator produced by the production method according to claim 1 , and water passes through the mesh of the oil / water separator, while oil is a mesh of the oil / water separator. The oil-water separation method characterized by including the process which makes it not pass through.