JPH08132075A - Treatment of aqueous solution containing ammonia and/or ammonium ion - Google Patents

Abstract

PURPOSE: To provide a method for rapidly and efficiently oxidizing an aq. solution containing ammonia and/or ammonium ion. CONSTITUTION: Ammonia and/or ammonium ion is oxidized by allowing the aq. solution containing ammonia and/or ammonium ion to contact with a catalytic body consisting of an adsorbent for adsorbing ammonia and/or ammonium ion and a semiconductor catalyst and irradiating the semiconductor catalyst with light of a wavelength having energy of equal to or above the bandgap thereof.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for treating an aqueous solution containing ammonia and / or ammonium ions. More specifically, the present invention relates to a method for treating an aqueous solution containing ammonia and / or ammonium ions using the photocatalytic function of a semiconductor catalyst.

[0002]

2. Description of the Related Art Domestic wastewater, irrigation wastewater, or industrial wastewater may contain ammonia or ammonium ions. Ammonia and ammonium ions are the causative substances of malodor and causative substances that cause eutrophication of wastewater,
Since it is a causative substance that pollutes waste water, it is necessary to have a means for converting ammonia and ammonium ions into substances with less influence to reduce the amounts of ammonia and ammonium ions.

Further, in the aquarium for breeding aquatic organisms such as fish, shellfish, amphibians, aquatic reptiles and crustaceans, the excrement of aquatic organisms and the concentration of ammonia due to food increase with time. When the concentration of ammonia becomes high, it causes harm to the growth or rearing of aquatic organisms, so there is a need for means for converting ammonia into a less harmful substance to reduce the amount of ammonia.

As a means for reducing ammonia and ammonium ions, the photocatalytic function of a semiconductor catalyst is utilized to convert ammonia and ammonium ions into nitrite ions,
Means to oxidize to nitrate ions have been proposed. (Sol
ar Energy, Vol. 52, No. 6, P45
9-466, 1994, Monatshefte fu
r Chemie, Vol. 123, P333-33
9, 1992, etc.). This means that when a semiconductor catalyst such as titanium oxide is irradiated with light having a wavelength having an energy larger than its band gap, photoexcitation of the semiconductor catalyst produces electrons in the conduction band and holes in the valence band. By utilizing the strong reducing power of the generated electrons and the strong oxidizing power of the holes, ammonia and ammonium ions are oxidized.

[0005]

The above-mentioned means utilizing the photocatalytic function of the semiconductor catalyst has a problem that the oxidation rate of ammonia and ammonium ions is slow and the efficiency is low. In particular, when the pH of the aqueous solution containing ammonia or ammonium ions is 9 or less, the oxidation rate of ammonia or ammonium ions is extremely slow. Therefore, there are problems that a large amount of semiconductor catalyst is required to oxidize ammonia and ammonium ions, and a large-scale semiconductor catalyst treatment tank is required.

[0006]

[Means for Solving the Problems] As a result of various studies on the method of oxidizing ammonia and ammonium ions more rapidly and efficiently, the present inventors focused on the oxidation reaction by the photocatalytic function of the semiconductor catalyst. (1) By using a catalyst body comprising an adsorbent that adsorbs ammonia and / or ammonium ions and a semiconductor catalyst,
The photocatalytic function of the semiconductor catalyst can be effectively utilized. (2) The method of (1) contains ammonia and / or ammonium ions having a pH of 9 or less in which oxidation of ammonia or ammonium ions does not easily occur. The present invention has been completed by finding out that the aqueous solution can be treated rapidly and efficiently.

That is, the present invention relates to ammonia and / or
Or quickly prepare an aqueous solution containing ammonium ions,
In addition, it is to provide a method of efficiently oxidizing.

In the present invention, an aqueous solution containing ammonia and / or ammonium ions is brought into contact with a catalyst body composed of an adsorbent that adsorbs ammonia and / or ammonium ions and a semiconductor catalyst, and the semiconductor catalyst has a band gap of not less than that. The method for treating an aqueous solution containing ammonia and / or ammonium ions is characterized by irradiating light having a wavelength having the energy of 1 to oxidize ammonia and / or ammonium ions.

The catalyst body composed of an adsorbent that adsorbs ammonia and / or ammonium ions and a semiconductor catalyst maintains the state in which the adsorbent and the semiconductor catalyst are at least partially in contact with each other. The semiconductor catalyst is loaded on the surface of the semiconductor catalyst, the adsorbent is mixed with the semiconductor catalyst, the semiconductor catalyst is inserted into the layers or the pores of the adsorbent, or the semiconductor catalyst is loaded on the surface of the adsorbent. Or you can get it. In the present invention, since it is possible to easily obtain a catalyst body that can efficiently utilize the photocatalytic function,
Is preferred.

In the present invention, as the adsorbent, a substance having a cation exchange ability, for example, zeolites such as aluminosilicate, metallosilicate, aluminophosphate, oxides of metals such as silicon, tungsten and niobium, hydrous oxide or Hydroxide, silicon oxide
Aluminum oxide, metal oxide such as aluminum oxide-titanium oxide, heteropolyacid such as molybdophosphoric acid or its salt, phosphate such as hydroxyapatite, smectite, clay mineral such as montmorillonite, vermiculite and mica, titanic acid. Salt, niobate,
An inorganic ion exchanger such as an inorganic layered compound such as a phosphate or an organic ion exchanger such as an ion exchange resin can be used. In the present invention, an adsorbent having a suitable adsorbing power for ammonia and ammonium ions and having a fast ion exchange rate is preferable, and as such an adsorbent, a clay mineral, a metal oxide, a hydrous oxide or Examples thereof include hydroxides and metal complex oxides. In the present invention, montmorillonite and silicon oxide are particularly preferable as the adsorbent. In the present invention, the silicon oxide includes not only silicon oxide but also silicon hydrous oxide and silicon hydroxide.

As the semiconductor catalyst, titanium oxide,
Known semiconductors such as zinc oxide, tungsten oxide, iron oxide, strontium titanate, molybdenum sulfide, and cadmium sulfide can be used alone or in combination of two or more kinds. Further, in order to improve the photocatalytic function of the semiconductor catalyst, a metal such as platinum, gold, silver, copper, palladium, rhodium, ruthenium, iron, vanadium, or a compound of those metals is formed on or inside the surface of the semiconductor catalyst. May be supported or contained. In the present invention, titanium oxide, which has a high photocatalytic function, is chemically stable, and is harmless, is preferable. The titanium oxide includes, in addition to titanium oxide, those generally called hydrous titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide and the like, and their crystal forms are not limited.

In the present invention, in order to carry an adsorbent which adsorbs ammonia and / or ammonium ions on the surface of the semiconductor catalyst, a fine particle adsorbent is added to the dispersion liquid of the semiconductor catalyst, or a substance serving as the adsorbent is added. A preferred method is to add, neutralize or hydrolyze as necessary, then filter, wash if necessary, and dry or calcinate. As the adsorbent supported on the surface of the semiconductor catalyst, a substance having a low cation exchange ability and a low isoelectric point, for example, a metal oxide such as silicon, tungsten or niobium, a hydrous oxide or hydroxide, or a silicon oxide. -Aluminum oxide, aluminum oxide-Titanium oxide and other metal composite oxides are preferred. In particular, silicon oxide is most preferable as the adsorbent. The amount of the adsorbent supported can be appropriately set depending on the usage of the catalyst body, but the amount of the adsorbent with respect to the total amount of the adsorbent and the semiconductor catalyst is preferably 0.1 to 10.
70% by weight, more preferably 1 to 50% by weight, still more preferably 1 to 40% by weight. If the supported amount of the adsorbent is less than 0.1% by weight, it may be difficult to adsorb a large amount of ammonia and / or ammonium ions, and if it is greater than 70% by weight, the ammonia by the semiconductor catalyst may be insufficient. And / or the oxidation of ammonium ions may be difficult to proceed, which is not preferable.
In the present invention, carrying means that an adsorbent is present on the surface of the semiconductor catalyst, and includes expressions such as surface treatment, coating, adhering, and adsorbing.

In the present invention, in order to mix the adsorbent that adsorbs ammonia and / or ammonium ions and the semiconductor catalyst, the adsorbent and the semiconductor catalyst are mixed in a dry or wet manner, and if necessary, molded or The obtained mixture or molded product is fired if necessary. In the present invention, it is preferable to use a method in which the adsorbent and the semiconductor catalyst are each made into a dispersion, which is then mixed, then filtered, washed if necessary, and dried or calcined. As the adsorbent mixed with the semiconductor catalyst, a substance having a cation exchange ability, for example, clay minerals such as smectite and montmorillonite, metal oxides such as silicon, tungsten and niobium, hydrous oxides or hydroxides, and silicon oxides. Preferred are metal complex oxides such as aluminum oxide and aluminum oxide-titanium oxide. In particular, montmorillonite or silicon oxide is most preferable as the adsorbent. The mixing ratio of the adsorbent and the semiconductor catalyst can be appropriately set according to the usage of the catalyst body, but the amount of the adsorbent with respect to the total amount of the adsorbent and the semiconductor catalyst is preferably 10 to 90% by weight, more preferably Is 10 to 70% by weight
Is. The mixing ratio of the adsorbent, which is different from the amount of the adsorbent supported, may be unfavorable if it is less than 10% by weight because it is difficult to adsorb a large amount of ammonia and / or ammonium ions, and is more than 90% by weight. In some cases, it may be difficult for the semiconductor catalyst to oxidize ammonia and / or ammonium ions, which is not preferable.

In the present invention, the catalyst body is brought into contact with an aqueous solution containing ammonia and / or ammonium ions, and the semiconductor catalyst contained in the catalyst body is irradiated with light having a wavelength of energy greater than the band gap. To do.

In the present invention, the aqueous solution containing ammonia and / or ammonium ion is an aqueous solution in which compounds such as ammonia, ammonium hydroxide, ammonia complex salt (ammine complex salt), ammonium salt and quaternary ammonium compound are dissolved. . The light with which the semiconductor catalyst is irradiated may be any light that includes light having a wavelength having energy greater than the known band gap of the semiconductor catalyst.
For example, when titanium oxide is used as a semiconductor catalyst, the band gap of titanium oxide is about 3.0 eV, and therefore energy of 3.0 eV or more, that is, about 400 eV.
Light having a wavelength of nm or less is used. For such light,
Light such as sunlight, fluorescent lamp, black light, xenon lamp, mercury lamp, germicidal lamp, etc. can be used. In the present invention, the amount of light with which the semiconductor catalyst is irradiated, the irradiation time, and the like can be appropriately set depending on the content concentration of ammonia and ammonium ions, the amount of treatment aqueous solution, and the like. The present invention
It can be applied to an aqueous solution containing ammonia and / or ammonium ions in any pH range, but is particularly difficult to oxidize in a pH range of 9 or less, and further in a pH range of 5 to 5.
Suitable for aqueous solutions in the range of 9.

[0016]

【Example】

Example 1 Using titanium oxide having a specific surface area of 308 m ² / g, 1
A sodium hydroxide aqueous solution was added to the titanium oxide slurry adjusted to 100% by weight to adjust the pH of the titanium oxide slurry.
Was adjusted to 10. Next, after heating the titanium oxide slurry to 75 ° C., water glass was added under stirring while maintaining the temperature. The addition amount of the water glass, the water glass in terms of SiO _2, and SiO ₂ with respect to the total amount of TiO ₂ of the titanium oxide was 1 wt%. Subsequently, the titanium oxide slurry was heated to a temperature of 85 ° C., and then aged for 30 minutes while maintaining the temperature. After that, an aqueous nitric acid solution was added to the titanium oxide slurry to adjust the pH of the titanium oxide slurry to 4.5, and then filtered, washed, and dried to carry an adsorbent (silicon hydroxide) on the semiconductor catalyst. A catalyst body (Sample A) made of (titanium oxide) was obtained.

Example 2 In Example 1, the water glass was converted to SiO ₂ to obtain 10
A catalyst body (sample B) made of a semiconductor catalyst (titanium oxide) carrying an adsorbent (silicon hydroxide) was obtained by performing the same treatment as in Example 1 except that the addition was performed by weight.

Example 3 In Example 1, the water glass was converted into SiO ₂ and converted to 20
A catalyst body (sample C) made of a semiconductor catalyst (titanium oxide) carrying an adsorbent (silicon hydroxide) was obtained by performing the same treatment as in Example 1 except that the addition was performed by weight.

Example 4 In Example 1, the water glass was converted to SiO ₂ and converted to 40
A catalyst body (Sample D) made of a semiconductor catalyst (titanium oxide) carrying an adsorbent (silicon hydroxide) was obtained in the same manner as in Example 1 except that the addition was performed by weight.

Comparative Example 1 In Example 1, except that water glass was not added.
Comparative sample E was obtained by treating in the same manner as in Example 1.

Example 5 Using titanium oxide having a specific surface area of 308 m ² / g, 1
A titanium oxide slurry adjusted to 00% by weight and a 40% by weight montmorillonite (manufactured by Hanai Chemical Co., Ltd.) slurry were mixed. The addition amount of montmorillonite is 1 with respect to the total amount of montmorillonite and titanium oxide converted into TiO _2.
It was set to 0% by weight. Subsequently, the mixed slurry was filtered and then calcined at a temperature of 200 ° C. for 3 hours to obtain a catalyst body (sample F) obtained by mixing the adsorbent (montmorillonite) and the semiconductor catalyst (titanium oxide).

Example 6 The procedure of Example 5 was repeated except that 20% by weight of montmorillonite was added, and the adsorbent (montmorillonite) and the semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample G) was obtained.

Example 7 The procedure of Example 5 was repeated except that 30% by weight of montmorillonite was added, and the adsorbent (montmorillonite) and the semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample H) was obtained.

Comparative Example 2 Comparative Example I was obtained by the same procedure as in Example 5 except that montmorillonite was not added.

Example 8 Using titanium oxide having a specific surface area of 308 m ² / g, 1
A titanium oxide slurry adjusted to 00% by weight and a slurry of 40% by weight of colloidal silica (AEROSIL 200, manufactured by Nippon Aerosil Co., Ltd.) were mixed. Colloidal silica is added by adding Ti of colloidal silica and titanium oxide.
It was set to 20% by weight based on the total amount of O ₂ conversion. Subsequently, the mixed slurry is filtered and then calcined at a temperature of 500 ° C. for 3 hours to mix an adsorbent (colloidal silica) and a semiconductor catalyst (titanium oxide) (sample J).
I got

Example 9 The procedure of Example 8 was repeated except that 30% by weight of colloidal silica was added, and the adsorbent (colloidal silica) and the semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample K) was obtained.

Example 10 The procedure of Example 8 was repeated, except that 50% by weight of colloidal silica was added, and the adsorbent (colloidal silica) and the semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample L) was obtained.

Example 11 The same procedure as in Example 8 was carried out except that 70% by weight of colloidal silica was added, and an adsorbent (colloidal silica) and a semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample M) was obtained.

Comparative Example 3 A comparative sample N was obtained in the same manner as in Example 8 except that colloidal silica was not added.

Example 12 The same procedure as in Example 8 was carried out except that the firing temperature was changed to 200 ° C., and the adsorbent (colloidal silica) and the semiconductor catalyst (titanium oxide) were mixed. A catalyst body (Sample O) was obtained.

Comparative Example 4 A comparative sample P was obtained by the same procedure as in Example 8 except that the colloidal silica was not added and the firing temperature was 200 ° C.

Samples (A) obtained in the above-mentioned Examples and Comparative Examples
~ P) aqueous solution containing ammonia and / or ammonium ion was tested. That is, NH
1 g of the catalyst sample was put into 250 ml of a liquid (pH = 7.0) having a total concentration of ₄ ⁺ and NH ₃ of 1.67 mmol / l and dispersed. Next, the semiconductor catalyst contained in the catalyst body was irradiated with ultraviolet rays emitted from a 100 W high-pressure mercury lamp, and the semiconductor catalyst was irradiated with light having a wavelength having an energy not less than the band gap. The irradiation area is 137.4.
cm ^2, and also, the average amount of light applied to the semiconductor catalyst was 41mW / cm ^2. The amount of NO ₃ ⁻ produced after irradiation with ultraviolet rays for 5 hours was measured to compare the activities of the catalyst bodies.

The results are shown in Tables 1 and 2. As is clear from Table 1 and Table 2, the present invention using a catalyst body composed of an adsorbent that adsorbs ammonia and / or ammonium ions and a semiconductor catalyst has a remarkably high oxidation rate of ammonia and ammonium ions. This is because ammonia or ammonium ions are captured by the adsorbent, and the adsorbed ammonia or ammonium ions move to the surface of the semiconductor catalyst with the concentration gradient as a driving force, and are oxidized by the photocatalytic function of the semiconductor catalyst. It is speculated that this happens more efficiently.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

Industrial Applicability According to the present invention, an aqueous solution containing ammonia and / or ammonium ions is brought into contact with a catalyst body composed of an adsorbent that adsorbs ammonia and / or ammonium ions and the semiconductor catalyst, and the band is applied to the semiconductor catalyst. A method for treating an aqueous solution containing ammonia and / or ammonium ions, which comprises irradiating light having a wavelength having an energy equal to or greater than a gap to oxidize ammonia and / or ammonium ions, wherein the ammonia and ammonium ions are rapidly and Since it can be efficiently oxidized, it is useful for purification of various wastewater such as domestic wastewater, irrigation wastewater, and industrial wastewater, water in aquariums for breeding aquatic organisms, pool water, and other aqueous solutions containing ammonia and ammonium ions. . In particular, the present invention is suitable for treating an aqueous solution containing ammonia and / or ammonium ions having a pH of 9 or less, and not only for industrial applications but also for general household use of aqueous solutions containing ammonia and / or ammonium ions. Useful for purification.

In the present invention, as the form of the above-mentioned catalyst body, the one in which the adsorbent is carried on the surface of the semiconductor catalyst or the one in which the adsorbent and the semiconductor catalyst are mixed are used, and ammonia and ammonium ions are more rapidly and Particularly preferred, because it can be more efficiently oxidized, purification of various wastewater,
It is suitable for advanced treatment of water in aquariums for breeding aquatic organisms and pool water.

Further, in the present invention, montmorillonite or silicon oxide as the adsorbent has a large adsorption capacity for ammonia and ammonium ions and has a high adsorption rate, so that ammonia and / or ammonium ions can be adsorbed more quickly. Moreover, it can be more efficiently oxidized, and is suitable for purification of various drainages and advanced treatment of water in aquariums for breeding aquatic organisms, pool water, and the like.

In a particularly preferred embodiment of the present invention, a silicon oxide is used as an adsorbent for adsorbing ammonia and / or ammonium ions, and a catalyst body having the silicon oxide supported on the surface of a semiconductor catalyst is used. A treatment method of an aqueous solution containing ammonia and / or ammonium ions can be mentioned. In a particularly preferred embodiment of the present invention, montmorillonite or silicon oxide is used as an adsorbent that adsorbs ammonia and / or ammonium ions, and a catalyst body obtained by mixing these adsorbents with a semiconductor catalyst is used.
A treatment method of an aqueous solution containing ammonia and / or ammonium ions can be mentioned. In these preferred embodiments, ammonia and / or ammonium ions can be oxidized more quickly and more efficiently, so that various wastewater such as domestic wastewater, irrigation wastewater, industrial wastewater, and aquariums for breeding aquatic organisms can be used. It is most suitable for purifying aqueous solutions containing ammonia and ammonium ions such as water and pool water. In particular, it is most suitable for treating an aqueous solution containing ammonia and / or ammonium ions having a pH of 9 or less, and is suitable for not only industrial applications but also purification of aqueous solutions containing ammonia and / or ammonium ions for general household use. is there.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 35/02 J (72) Inventor Shoichi Chiba 2-3-3 Nishishibukawa, Kusatsu City, Shiga Ishihara Central Research Institute of Industry Co., Ltd.

Claims (5)

[Claims] 1. A catalyst body comprising an adsorbent that adsorbs ammonia and / or ammonium ions and a semiconductor catalyst is brought into contact with an aqueous solution containing ammonia and / or ammonium ions, and the semiconductor catalyst has energy of a band gap or more. A method for treating an aqueous solution containing ammonia and / or ammonium ions, which comprises irradiating with light having a wavelength of 1 to oxidize ammonia and / or ammonium ions. 2. The aqueous solution containing ammonia and / or ammonium ions according to claim 1, wherein the catalyst body is a catalyst body in which an adsorbent that adsorbs ammonia and / or ammonium ions is carried on the surface of a semiconductor catalyst. Processing method. 3. The aqueous solution containing ammonia and / or ammonium ions according to claim 1, wherein the catalyst body is a catalyst body obtained by mixing an adsorbent that adsorbs ammonia and / or ammonium ions with a semiconductor catalyst. Processing method. 4. The method for treating an aqueous solution containing ammonia and / or ammonium ions according to claim 1, wherein the pH of the aqueous solution containing ammonia and / or ammonium ions is in the range of 9 or less. 5. The method for treating an aqueous solution containing ammonia and / or ammonium ions according to claim 1, wherein the adsorbent is montmorillonite or silicon oxide.