JP2000202303A - Hollandite type photocatalyst and removal of phenol in water using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove phenol being an internal secretion disturbing material harmful to a human body contained in groundwater, river water, public water and sewage water, industrial waste water, or the like, by converting that to formic acid being a liner chain compound and which is not the internal section disturbing material. SOLUTION: A photocatalyst is expressed by the formula: Ax My N8-y O16 (in the formula, A indicates one or two or more kinds of elements selected from the group consisting of K, Rb, Cs, Ca, Ba and Na, M indicates a divalent or trivalent metallic element, and N indicates a rutile oxide including Ti, Sn and Mn. However, Na element is limited only when M is Cr. (x) and (y) indicate 0.7<x<=2.0 and 0.7<y<=2.0), and comprises a hollandite type crystalline phase, does not support an activated metal, and has capacity of removing phenol by converting selectively phenol being the internal secretion-disturbing material to formic acid which is not an internal secresion-disturbing material under coexistence of dissolved oxygen. Phenol in water is removed by using this photocatalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to groundwater, river water,
Photocatalyst for removing phenol in water, which removes phenol, which is an endocrine disruptor harmful to the human body contained in water and sewage water, industrial wastewater, etc., by converting it into formic acid, a linear compound that is not an endocrine disruptor, and the catalyst The present invention relates to a method for removing phenol in water using phenol.

[0002]

2. Description of the Related Art Phenol is an aromatic compound having a six-membered carbon ring, and is a compound serving as a basic skeleton such as bisphenol A, which is a typical example regarded as a problem as an endocrine disrupting substance. Although phenol itself is listed as an endocrine disruptor, not only is phenol itself considered to have an effect on the human body, but in the catalytic reaction, it is important to know the reactivity of decomposition or removal of aromatic endocrine disruptors. Is a very important model substance.

Conventionally, as a method for removing phenol in water, a method of oxidatively decomposing phenol by an ozone oxidation treatment or a method of decomposing and removing phenol using a microorganism have been considered. Has the problem that a large amount of by-products are generated,
In the latter case, from the technical aspect of dealing with microorganisms,
Due to the processing cost and difficulty of the processing technology, it has not yet been put to practical use.

[0004] Recently, attempts have been made to decompose phenol by using a TiO ₂ -based photocatalyst in order to overcome such problems. However, even if a TiO ₂ -based photocatalyst is used, aromatic compounds such as benzoquinone can be used. Since several types of by-products including group III compounds are generated, a combination of a TiO ₂ -based photocatalyst and an ozone oxidation method is being studied. However, although the generation of by-products is reduced by using this method, the technical advantage of using the photocatalyst impairs the simplicity of the processing, which is a merit of using the ozone oxidation processing technology, while completely reducing the generation of dioxide. There was a problem that by-products other than carbon could not be eliminated.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems. For example, phenol contained in groundwater, river water, water supply and sewage water, industrial wastewater and the like, which is particularly harmful to the human body, is subjected to a trace amount of light energy. To provide a photocatalyst for decomposing phenol in water which is removed by water.

[0006]

Means for Solving the Problems The present inventor has a catalyst capable of removing phenol contained in water from water using a small amount of light energy in the presence of dissolved oxygen, and has excellent durability. a result of continued studies to develop a photocatalyst represented by the general _{formula: a x M y N 8-} y O 16 ( wherein, a represents, K, Rb,
1 selected from the group consisting of Cs, Ca, Ba and Na
Species or two or more elements, M is a divalent or trivalent metal element, and N is an element that forms a rutile oxide such as Ti, Sn, and Mn. However, the Na element is limited only when M is Cr. x and y are 0.7 <x ≦ 2.0
And 0.7 <y ≦ 2.0. ) Has a high ability to selectively convert phenol contained in water to formic acid with a small amount of light energy in the coexistence of dissolved oxygen, and has high durability. Was also found to be excellent.

Namely, the composition of the phenol removal photocatalytic water of the present invention, the general _{formula: A x M y N 8-} y O 16 ( wherein, A represents, K, Rb,
1 selected from the group consisting of Cs, Ca, Ba and Na
Species or two or more elements, M is a divalent or trivalent metal element, and N is an element that forms a rutile oxide such as Ti, Sn, and Mn. However, the Na element is limited only when M is Cr. x and y are 0.7 <x ≦ 2.0
And 0.7 <y ≦ 2.0. ) And must be a catalyst comprising a hollandite-type crystal phase.

The hollandite type crystal is a compound having a one-dimensional tunnel structure. As tunnel ions,
There are alkali metal ions such as K or alkaline earth metal ions such as Ba. In the case of Na, a hollandite type crystal structure can be obtained only when used in combination with Cr, but when combined with other elements,
The tunnel structure is lost, resulting in a Freudenbergite-type crystal structure or the like, which is not preferable.

The values of x and y are respectively 0.7 <x
≦ 2.0 and 0.7 <y ≦ 2.0,
Above or below this range, oxides or carbonates of alkali metals, oxides or carbonates of alkaline earth metals, oxides of divalent or trivalent metals and oxides of Ti precipitate, and the activity of Is not preferred because it is significantly reduced. In addition, when Ba is used, it is preferable that y = x if M = 2 and y = 2x if M = 3 from the electrical neutral condition in the compound.

When the alkali metal and the alkaline earth metal are combined, for the same reason, 0.7 <x <
1.2 is preferred.

As the divalent or trivalent metal element used in the photocatalyst of the present invention, Al, Ga, Cr, Mg or the like is preferable for forming a hollandite type crystal structure.

Further, in the method for removing phenol in water using a photocatalyst according to the present invention, the hollandite-type compound and phenol are brought into contact with each other in water in the coexistence of dissolved oxygen under light irradiation, whereby endocrine disruption in water is achieved. It is possible to remove phenol, which is an aromatic compound, by converting it efficiently to linear formic acid which is not an endocrine disrupting substance. As the wavelength of the light to be irradiated, light having a wavelength longer than that of ultraviolet light may be used, and a fluorescent lamp or sunlight may be used.
It is effective to use light near m.

Further, such a photocatalytic reaction proceeds when phenol and dissolved oxygen dissolved in water react on the surface of the catalyst at room temperature, and oxygen is introduced into the water by bubbling of oxygen or the like, whereby the oxygen is dissolved. Improving the contact between the catalyst and the catalyst surface and improving the stirring efficiency are also effective for improving the reaction efficiency.

The emission standard of phenol in water is 10
ppm, and the stoichiometric amount of oxygen required to remove this concentration of phenol will necessarily be of the same order. Therefore, when it is feared that the amount of dissolved oxygen is insufficient in view of the concentration of the phenol to be treated, the reaction can be smoothly performed by bubbling oxygen as described above.

There is no particular limitation on the concentration of phenol in water which is the object of the present invention, but it is practically preferable to use the phenol in a region where the content in water is 10 ppm or less, based on the saturated dissolved amount of coexisting oxygen.

The hollandite type catalyst according to the present invention can be used as a photocatalyst by supporting a photocatalytically active metal such as platinum or an oxide such as ruthenium oxide as required.

There is no particular limitation on the light irradiation method in the present invention.
Light irradiation can be performed from the outside as needed.

This catalyst is used as a powder.
In addition, porous catalyst carriers, quartz glass tubes, quartz glass substrates
TiO as the top or representative photocatalyst_TwoMade fibrous
TiO _TwoFiber and this TiO_TwoWeave fiber two-dimensionally
Cloth sample or TiO_TwoThe fiber is formed three-dimensionally
Hollandite type catalyst is coated on the surface of
And use it as a film of hollandite type crystal phase
Can be.

[0019] When used as films, porous catalyst support or a quartz glass tube of the aqueous or non-aqueous dispersed therein hollandite type catalyst, TiO ₂ fibers or the TiO ₂ is a quartz glass substrate or representative photocatalysts 2 fibers
A method of forming a film by soaking a three-dimensionally molded cloth-shaped sample or a three-dimensionally molded TiO ₂ fiber or the like is adopted.

[0020] General _{formula: A x M y N 8-} y O 16 ( in the formula, A
Is one or more elements selected from the group consisting of K, Rb, Cs, Ca, Ba and Na, M is a divalent or trivalent metal element, N is Ti, Sn, Mn, The elements that form the rutile-type oxide are shown below. Where N
The element a is limited to the case where M is Cr. x and y are 0.
7 <x ≦ 2.0 and 0.7 <y ≦ 2.0. The method for producing the hollandite-type catalyst constituting the photocatalyst of the present invention represented by the formula (1) is not particularly limited.

It is known that the hollandite type crystal phase can be synthesized by various methods. For example, as a solid phase synthesis method, a method in which a carbonate of an alkali metal or an alkaline earth metal, titanium oxide, and an oxide of a divalent or trivalent metal element are mixed and then fired at a temperature of 1200 to 1500 ° C. As a liquid phase method, an aqueous solution of an inorganic salt such as a nitrate of an alkali metal or an alkaline earth metal, titanium chloride and a nitrate of a divalent or trivalent metal element is used, and the mixed solution is mixed with aqueous ammonia or aqueous ammonia. The solution was dropped into an aqueous solution of ammonium acid to obtain a precipitate, and the precipitate was washed with water, filtered and dried.
As a coprecipitation method and an alkoxide method of firing at a temperature of 0 ° C. or lower, alkoxides such as alkoxides such as alkali metal or alkaline earth metal elements and divalent or trivalent metal elements such as methoxide, ethoxide and butoxide are mixed in a non-aqueous solution, After hydrolysis and drying, it can be obtained by firing at a temperature of 800 ° C. or more and 1200 ° C. or less.

Regarding the calcination temperature, a hollandite-type crystal structure is stably formed even at a calcination temperature of 1500 ° C. or higher, but calcination at a high temperature causes a decrease in the specific surface area of the catalyst, and is not preferred. Further, the firing time is not preferable because the specific surface area decreases even if the firing time is too long.

The specific surface area of the hollandite type catalyst is 1 m
If it is about ² / g or more, phenol in water can be removed in the presence of dissolved oxygen. The phenol removal efficiency of this catalyst increases as the specific surface area increases, and in particular, in the case of a continuous flow type processing apparatus having a large amount of treated water, the larger the specific surface area is, the more preferable. The porous structure also has an important effect on the phenol removal efficiency, and it is particularly effective to use a porous body having a pore distribution in the mesopore region.

[0024]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

Example 1 Composition K_1.7A1_1.7Ti_6.3O₁₆Oxidation
Titanium (made by Kishida Chemical Co., Ltd.), aluminum oxide
(Manufactured by Kishida Chemical Co., Ltd.) and potassium carbonate (Kishida
(Manufactured by Kagaku Co., Ltd.) and mixed in an agate mortar for 30 minutes.
After firing for 2 hours at 1200 ° C,
Nite type K_1.7A1_1.7Ti_6.3O ₁₆Of single phase powder
Done.

The X-ray diffraction pattern of the catalyst thus obtained is shown in FIG.
Shown in The catalyst activity evaluation test was performed using a batch-type reactor. That is, 1 g of the catalyst was placed in 1 liter of distilled water containing 10 ppm of phenol, irradiated with 15 W, 360 nm ultraviolet rays with stirring, and analyzed for phenol and by-product concentrations in the aqueous solution at regular intervals. did. The test results are shown in Tables 1 to 3.

However, the phenol conversion rate, formic acid formation rate, benzoquinone formation rate, maleic acid formation rate, and glyoxylic acid formation rate in water were calculated by the formulas (1) to (5).

[0028] Phenol conversion _{(%) = {(Ph 0} -Ph t) / Ph 0} × 100 (1 type) formic acid production rate (%) = {formic acid _t / formic acid _calc.} × 100 (2 expression) benzoquinone production rate _{(%) = {Bz t /} Bz calc.} × 100 (3 type) maleate production rate _{(%) = {MA t /} MA calc.} × 100 (4 type) glyoxylic acid production rate (%) = ｛GA _t / GA _calc. ｝ × 100 (5 equations) where Ph ₀ : initial concentration of phenol (ppm) Ph _t : phenol concentration after t hours (ppm) Formic acid _t : formic acid concentration after t hours (ppm) ) Formic acid _calc : Amount when all phenols are converted to formic acid (ppm) Bz _t : Benzoquinone concentration after t hours (ppm) Bz _calc : Amount when all phenols are converted to benzoquinone (ppm) MA _t: t time after the maleic acid concentration (ppm) MA _calc:. generation amount when phenol is changed all maleic acid (ppm) GA _t: t time after glyoxylic Concentration (ppm) GA _calc:. Generation amount when phenol is changed to all glyoxylic acid (ppm) The concentration of each compound was determined by high performance liquid chromatography.

As can be seen from the results of Tables 1 to 3, phenol was adsorbed on the catalyst surface at the beginning of the reaction,
After the apparent conversion occurred, it was confirmed by high-performance liquid chromatography that it did not change to carbon dioxide but converted to formic acid, which is a partial oxidation product of phenol. In addition, it was confirmed that phenol was removed from water with this partial oxidation reaction (reaction for inserting oxygen into phenol molecules).

Example 2 Gallium oxide (manufactured by Kishida Chemical Co., Ltd.), tin oxide (manufactured by Kishida Chemical Co., Ltd.) and potassium carbonate (manufactured by Kishida Chemical Co., Ltd.) so that the composition becomes K _2.0 Ga _2.0 Sn _6.0 O _16. Weighed and mixed for 30 minutes in an agate mortar,
By baking at 200 ° C. for 2 hours, a single-phase powder of hollandite type K _2.0 Ga _2.0 Sn _6.0 O ₁₆ was synthesized.

However, the catalyst activity was evaluated in accordance with Example 1. The results are shown in Tables 1 to 3.
As in Example 1, phenol was adsorbed on the catalyst surface at the beginning of the reaction, resulting in an apparent conversion rate.
It was confirmed by high performance liquid chromatography that it did not change to carbon dioxide but was converted to formic acid, a partial oxidation product of phenol. In addition, it was confirmed that phenol was removed from water with this partial oxidation reaction (reaction for inserting oxygen into phenol molecules).

Example 3 Potassium butoxide (manufactured by Tri-Chemical Research Laboratories), gallium butoxide (manufactured by Tri-Chemical Research Laboratories) and tin ethoxide (manufactured by Tri-Chemical Research Laboratories) were used so that the composition became K _1.8 Ga _1.8 Sn _6.2 O _16. After weighing and dissolving in dehydrated 2-methoxyethanol, mixing was performed to prepare a sol solution. Thereafter, hydrolysis water was added dropwise to this solution to perform hydrolysis. The hydrolyzed gel was dried and pulverized and then calcined at 1100 ° C. for 3 hours to synthesize a single-phase powder having a hollandite-type crystal structure.

The obtained catalyst has a specific surface area of 30 m ² / g.
Was a porous mesopore material. However, the catalytic activity evaluation
Performed according to Example 1. The results are shown in Tables 1 to 3. In the case of Example 3, as in the case of Examples 1 and 2, phenol does not undergo a process of being converted into carbon dioxide by a simple oxidation reaction with dissolved oxygen, but is a partial oxidation product of phenol. It was confirmed by high performance liquid chromatography that it was selectively converted to certain formic acid. In addition, it was confirmed that phenol was removed from water with this partial oxidation reaction (reaction for inserting oxygen into methanol molecules).

[0034] As Example 4 composition becomes _{K 1.4 Ga 1.4 Sn 6.6 O 16} , potassium butoxide (manufactured by Tri Chemical Laboratories), gallium butoxide (manufactured by Tri Chemical Laboratories) and Suzuetokishido (manufactured by Tri Chemical Laboratories) It was weighed, and a single-phase powder having a hollandite-type crystal structure was synthesized according to the method of Example 3. The resulting catalyst has a specific surface area of 38 m ² /
g of mesopore porous body. In addition, catalyst activity evaluation,
Performed according to Example 1. The results are shown in Tables 1 to 3. It was confirmed by high performance liquid chromatography that the phenol was converted to formic acid, which is a partial oxidation product, as in the above example. In addition, it was confirmed that phenol was removed from water with this partial oxidation reaction (reaction for inserting oxygen into phenol molecules).

[0035] As Example 5 composition is _{K 1.8 Ga 1.8 Mn 6.2 O 16} , potassium butoxide (manufactured by Tri Chemical Laboratories), gallium butoxide (manufactured by Tri Chemical Laboratories) and manganese ethoxide (Tri Chemical Laboratories Ltd. ) Was weighed, and a single-phase powder having a hollandite-type crystal structure was synthesized according to the method of Example 3. The resulting catalyst has a specific surface area of 30 m.
^{It was a 2} / g porous mesopore. The evaluation of the catalyst activity was performed in accordance with Example 1. The results are shown in Tables 1 to 3.
It is shown along with

In the same manner as in the above example, it was confirmed by high performance liquid chromatography that the phenol was converted into formic acid which is a partial oxidation product. In addition, with this partial oxidation reaction (reaction to insert oxygen into phenol molecules),
Phenol was confirmed to be removed from the water.

Example 6 Sodium butoxide (manufactured by Tri-Chemical Research Laboratories), chromium butoxide (manufactured by Tri-Chemical Research Laboratories) and tin ethoxide (manufactured by Tri-Chemical Research Laboratories) were used so that the composition became Na _1.8 Cr _1.8 Sn _6.2 O _16. Weighed, Example 3
A single-phase powder having a hollandite-type crystal structure was synthesized according to the method described in (1). The resulting catalyst has a specific surface area of 20
It was a m ² / g mesopore porous body. The evaluation of the catalyst activity was performed in accordance with Example 1. The results are shown in Tables 1 to 3.

In the same manner as in the above Examples, it was confirmed by high performance liquid chromatography that the phenol was converted into formic acid, which is a partial oxidation product. In addition, with this partial oxidation reaction (reaction to insert oxygen into phenol molecules),
Phenol was confirmed to be removed from the water.

Comparative Example 1 Titanium oxide (manufactured by Kishida Chemical Co., Ltd.), aluminum oxide (manufactured by Kishida Chemical Co., Ltd.) and potassium carbonate (manufactured by Kishida Chemical Co., Ltd.) so that the composition becomes K _2.5 Al _2.5 Ti _5.5 O _16. Was weighed, mixed for 30 minutes in an agate mortar, and baked at 1200 ° C. for 2 hours to obtain a powder. The obtained powder was a mixed phase composed of a trace amount of a hollandite-type crystal phase and potassium hexatitanate and aluminum oxide. The activity evaluation of the catalyst was performed according to Example 1.
The results are shown in Tables 1 to 3.

Comparative Example 2 Tin oxide (manufactured by Kishida Chemical Co., Ltd.), gallium oxide (manufactured by Kishida Chemical Co., Ltd.) and potassium carbonate (manufactured by Kishida Chemical Co., Ltd.) so that the composition becomes K _0.3 Ga _0.3 Sn _7.7 O _16. Weighed and mixed for 30 minutes in an agate mortar,
The powder was fired at 200 ° C. for 2 hours to obtain a powder. The obtained powder was a mixed phase comprising a trace amount of a hollandite type crystal phase and tin oxide and gallium oxide. The activity evaluation of the catalyst was performed according to Example 1. The results are shown in Tables 1 to 3. The powders of the compositions of Comparative Examples 1 and 2 had a small phenol removing function even after 100 hours of light irradiation.

[0041] As Comparative Example 3 composition becomes _{K 0.01 Ga 0.01 Ti 7.99 O 16} , potassium butoxide (manufactured by Tri Chemical Laboratories), gallium butoxide (manufactured by Tri Chemical Laboratories) and titanium ethoxide (Tri Chemical Laboratories Ltd. ) Was weighed and dissolved in dehydrated 2-methoxyethanol, and each solution was mixed to prepare a starting sol solution. Thereafter, hydrolysis water was added dropwise to this solution to perform hydrolysis. The hydrolyzed gel was dried and pulverized and calcined at 1100 ° C. for 3 hours. The obtained catalyst was a mixture mainly composed of a rutile phase and a small amount of gallium oxide, and had a specific surface area of 20 m ² / g.

The catalyst activity was evaluated in accordance with Example 1. The results are shown in Tables 1 to 3. As is clear from Tables 1 to 3, the results are significantly different from those of the examples, and phenol is not converted to formic acid, and aromatic compounds such as benzoquinone, as well as by-products such as maleic acid and glyoxylic acid are produced. Conversion to material was observed. Since the phenol, which is an aromatic compound, was converted to benzoquinone, which is the same aromatic compound, the usefulness of the composition of Comparative Example 3 in terms of the environmental purification function was considered to be extremely low.

In Tables 1 to 3, a portion where the sum of the by-product formation rates of Comparative Example 3 did not match the phenol removal rate was observed, but it is presumed that the difference was converted to carbon dioxide. Was done.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a catalyst prepared in Example 1.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 23/34 B01J 23/34 M C02F 1/32 C02F 1/32 1/58 1/58 F 1/72 101 1/72 101 (72) Inventor Kenjiro Fujimoto 1-1-1, Namiki, Tsukuba-shi, Ibaraki Pref. BB16 4D050 AA02 AA13 AB15 BB01 BC06 BC09 BD08 4G069 AA02 AA08 BA36A BA48A BB06A BB06B BC02A BC03A BC03B BC05A BC06A BC09A BC13A BC16B BC17B BC22A BC22B BC50A BC50B BC58B BC62A BC62E CA13 EA07CA05

Claims (2)

[Claims] 1. A general _{formula: A x M y N 8-} y O 16 ( in the formula, A
Is one or more elements selected from the group consisting of K, Rb, Cs, Ca, Ba and Na, M is a divalent or trivalent metal element, N is Ti, Sn, Mn, The elements that form the rutile-type oxide are shown below. Where N
The element a is limited to the case where M is Cr. x and y are 0.
7 <x ≦ 2.0 and 0.7 <y ≦ 2.0. ), Which consists of a hollandite-type crystal phase, does not carry active metals, and removes phenol by selectively converting phenol, an endocrine disruptor, to formic acid, which is not an endocrine disrupter, in the presence of dissolved oxygen. A photocatalyst for removing phenol in water, which has the ability to perform. 2. The hollandite-type compound and phenol are brought into contact with each other in water in the presence of dissolved oxygen under light irradiation to convert phenol, which is an endocrine disrupting substance, into formic acid, which is not an endocrine disrupting substance. A method for removing phenol in water, wherein the method removes phenol from water.