JP2000262891A - Offensive gas adsorbing agent and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an adsorbent which can adsorb offensive odors in a living space efficiently without deteriorating the performance of a porous substance itself by making at least titanium dioxide and an inorganic acid adhere to the porous substance. SOLUTION: An odorous gas adsorbing agent is formed by making titanium dioxide and an inorganic acid adhere to a porous substance. Titanium dioxide of anatase-type crystal structure is preferably used as the titanium dioxide. A mineral acid such as hydrochloric acid, phosphoric acid, and sulfuric acid can be used as the inorganic acid. Active carbon, hydrophobic zeolite, silica, and others can be used as the porous substance. In the production, titanium dioxide and the inorganic acid are dispersed/mixed in water to prepare a mixed liquid. Next, the pH of the mixed liquid is adjusted at 7 or below at room temperature by the inorganic acid, and the mixed liquid is sprayed to the porous substance, or the porous substance is immersed in the mixed liquid. Subsequently, the porous substance is dried at a necessary temperature for a necessary time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an odor gas adsorbent and a method for producing the same. More specifically, the present invention relates to a malodor gas adsorbent obtained by impregnating at least titanium dioxide and an inorganic acid to a porous substance, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the diversification of living environments, odors such as ammonia, mercaptan, and aldehyde often occur from facilities such as domestic wastewater, human waste, industrial wastewater, and garbage disposal plants. These foul odors, although in a trace amount, drift in the living space, causing unpleasant odors.
Environmental pollution by harmful substances such as Ox and SOx is becoming a serious problem. Activated carbon is a non-polar adsorbent, and is excellent in adsorbing almost all offensive odor gases. Therefore, activated carbon is frequently used as a deodorant in order to maintain a comfortable living environment. However, odors are becoming more complicated year by year, and the development of adsorbents having high adsorption performance is desired.

[0003] In recent years, attention has been paid to the photocatalytic function of titanium oxide by visible light and near ultraviolet light, and it has been studied to further improve the deodorizing function of an adsorbent made of a porous substance such as activated carbon using titanium oxide. For example, JP
JP-A-235637 discloses an adsorbent in which at least one kind of metal salt or oxide such as titanium is attached to a porous substance such as activated carbon, and JP-A-8-196903 discloses that the surface of a porous body is made of titanium oxide. A porous photocatalyst coated with a membrane is disclosed. Japanese Patent Application Laid-Open No. 9-948 discloses that an aqueous dispersion slurry of inorganic particles such as titanium oxide containing a wetting agent such as alcohol is applied to an activated carbon substrate, or the activated carbon substrate is immersed in the slurry and dried. A method for supporting inorganic particles is disclosed, and Japanese Patent Application Laid-Open No. 9-206602 discloses a method for fixing a photocatalyst such as titanium oxide, which is fixed on activated carbon or the like, and then aggregated by a coagulant to be supported on a carrier. ing.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No.
The adsorbent disclosed in Japanese Patent No. 235637 is obtained by dissolving a metal salt or oxide in water or an organic solvent, immersing activated carbon or the like in this and drying it, and according to this method, titanium oxide is activated carbon. However, the rate of attachment to the surface is low, and it cannot be said that this is a method with good production efficiency. In addition, kneading using a binder, granulation, a manufacturing method of drying after molding is also disclosed, but the adsorbent manufactured by this method, because titanium oxide present inside does not participate in the reaction, This is an uneconomical manufacturing method in which titanium oxide is not used effectively.

[0005] The porous photocatalyst disclosed in JP-A-8-196903 can be obtained by adding polyethylene glycol or polyethylene oxide to a titania sol, coating the surface of the porous body, and then firing by heating. Since the firing is performed at a high temperature, the adsorption performance may be reduced. In addition, in the method for supporting inorganic particles disclosed in Japanese Patent Application Laid-Open No. 9-948, since a wetting agent is used, the wetting agent such as alcohols and ketones remains on the activated carbon, and the adsorption performance tends to deteriorate. is there.

Further, in the method for fixing a photocatalyst disclosed in Japanese Patent Application Laid-Open No. 9-206602,
As in the case of 235637, the titanium oxide present inside does not participate in the reaction, so that the titanium oxide is not used effectively, which can be said to be an uneconomical production method. Therefore, an object of the present invention is to provide an adsorbent to which titanium oxide is efficiently attached without deteriorating the performance of activated carbon itself and which is excellent in adsorption of malodorous gas and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have intensively studied the effects of inorganic acids, and have achieved the above object by adjusting the pH of a preparation solution used for impregnating a porous substance. They have found that they can do so and arrived at the present invention. That is, the present invention is a malodorous gas adsorbent obtained by adhering at least titanium dioxide and an inorganic acid to a porous substance. Another invention of the present invention is a method for producing a malodorous gas adsorbent, characterized by impregnating a porous substance with a mixed solution of titanium dioxide and an inorganic acid dispersed in water and having a pH of 7 or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The odorous gas adsorbent of the present invention is obtained by impregnating a porous substance with titanium dioxide and an inorganic acid. As the titanium dioxide, a titanium dioxide having an anatase type crystal structure is used. The effects of the present invention are well exhibited and are preferred. Particle diameter of titanium dioxide, from the viewpoint of dispersibility, 0.001 ~ 0.3μm, more preferably 0.005 ~ 0.1μm
It is desirable to use those.

The inorganic acids include mineral acids such as hydrochloric acid, phosphoric acid and sulfuric acid. Hydrochloric acid is preferred in terms of the effect of adsorbing offensive odor gas, but it is more preferred to impregnate hydrochloric acid and phosphoric acid. Examples of the porous substance include activated carbon, hydrophobic zeolite, silica and the like. Among them, activated carbon is preferred as the porous substance used in the present invention. Activated carbon activated by a known method can be used, and those having a particle size of 0.1 mm to 5 mm are easy to handle and are preferable in terms of moldability.

The most important feature of the present invention is that an inorganic acid is used to impregnate the porous material with titanium dioxide. In order to produce the adsorbent of the present invention, first, titanium dioxide and an inorganic acid are dispersed and mixed in water to prepare a mixed solution. Hydrochloric acid is preferred as the inorganic acid used to prepare the mixture. The mixing ratio of these components is usually 0.3 to 20 parts by weight of titanium dioxide and 100 parts by weight of water, and the inorganic acid is used in a small amount so as to have a predetermined pH.

The pH of the mixed solution is adjusted to 7 or less, preferably 5 or less at room temperature with an inorganic acid, and sprinkled on a separately prepared porous material or the porous material is immersed in the mixed solution. The immersion time is not particularly limited, and is usually 30 minutes.
It takes about a minute to an hour. In preparing the mixture, the order of mixing water, titanium dioxide and the inorganic acid is not particularly limited, but it is better to dissolve titanium dioxide in water in advance and then add the inorganic acid to adjust the pH of the mixture. Is easy and preferable. Thereafter, drying is performed at a temperature of 80 to 130 ° C. for about 2 to 5 hours.

It is preferable to use phosphoric acid to which phosphoric acid is preliminarily impregnated, since the adhesion of titanium dioxide is improved and the effect of adsorbing odorous gas is increased. Activated carbon is preferred as the porous substance. The amount of titanium dioxide impregnated in the adsorbent depends on the particle size of the adsorbent. However, if the amount is too small, the effect is small, and if it is too large, the effect corresponding thereto is not exhibited.
The amount of titanium dioxide impregnated can be confirmed by elemental analysis of ash by fluorescent X-ray, and the acid is extracted with water,
It can be confirmed by analyzing with an ion chromatograph. Note that a polysaccharide such as carboxymethyl cellulose can be added to the dispersion water in order to improve the adhesion between the porous substance and titanium dioxide.

Although the reason why the adsorbent of the present invention is excellent in adsorbing odorous gas cannot always be clearly explained,
The interface potential (ζ potential) of activated carbon with water is negative over almost the entire pH range, and the interface potential of titanium oxide (の potential)
Is positive when pH is 6.1 or less (anatase type),
In a dispersion containing an inorganic acid such as hydrochloric acid, the resilience of the titanium oxide particles enhances the dispersibility, suppresses the aggregation of the titanium oxide particles, enables attachment by fine particles, and enhances the activity of the titanium oxide. Can be considered. Further, at the time of impregnation, an electrostatic attraction acts between the activated carbon and the titanium oxide, so that an increase in the impregnated amount is expected. Further, the attached inorganic acid has a synergistic effect of improving the adsorption performance of a basic gas such as ammonia.

Since the removal rate of the odorous gas is slow only by the photocatalytic function, the removal rate is reduced at a high air flow rate. Immediately after the reaction of the basic gas is completed, the performance suddenly decreases, but the adsorbent of the present invention can also solve these problems. The adsorbent of the present invention may be used standing in a room or the like, or may be molded into a sheet or the like, but used in a well-dispersed state in order to sufficiently exhibit the function as a photocatalyst. It is desirable. Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to these.

[0015]

Example 1 A mixture was prepared by dispersing 2 parts by weight of titanium dioxide in 30 parts by weight of water and adjusting the pH to 1 with hydrochloric acid. 20 to
100 parts by weight of coconut shell activated carbon sized to 40 mesh was sprinkled and dried at 120 ° C. for 2 hours to obtain an adsorbent. The adsorbent is impregnated with 1.8% by weight of titanium dioxide by elemental analysis of ash with fluorescent X-rays. The adsorbent is extracted with water and analyzed by ion chromatography to obtain an acid. It was confirmed that it was also attached.

2 ml (about 0.8 g) of the adsorbent is used
mm, 300 mm long stainless steel column,
In order to exhibit the photocatalytic function of titanium dioxide, 254
A UV lamp of 10 nm was fixed at a position 15 mm above the column and lit. 10 liters (L) of air containing 100 ppm of acetaldehyde gas at room temperature and normal humidity
The mixture was circulated at a flow rate of 00 ml / min, and the concentration of acetaldehyde gas was measured every 5 minutes by a detector tube to determine the acetaldehyde gas removal rate. Table 1 shows the results.

In the same manner, 2 ml of the adsorbent (about 0.
8 g) was packed in a stainless steel column having an inner diameter of 60 mm and a length of 300 mm, and 10 L of air containing 100 ppm of ammonia gas was circulated at 200 ml / min without using an ultraviolet lamp and under the same other conditions. One hour after the start of circulation, the ammonia gas removal rate was 80%.

[0018]

[Table 1]

Example 2 An adsorbent was prepared in the same manner as in Example 1 except that 4 parts by weight of titanium dioxide was dispersed in 30 parts by weight of water. White powder of titanium dioxide was found on the surface of the activated carbon. 2m of the adsorbent
1 (about 0.8 g), and the removal rate of acetaldehyde was determined in the same manner as in Example 1. Table 2 shows the results. When a test for removing ammonia gas was performed on the adsorbent in the same manner as in Example 1, the ammonia gas removal rate one hour after the start of circulation was 80%.

[0020]

[Table 2]

Example 3 4 parts by weight of phosphoric acid was sprinkled on 100 parts by weight of coconut shell activated carbon sized to 20 to 40 mesh to make phosphoric acid impregnated carbon, and immersed in a mixture prepared in the same manner as in Example 2. 120 ° C
For 2 hours to obtain an adsorbent. About the adsorbent,
An acetaldehyde gas removal test was performed in the same manner as in Example 1. Table 3 shows the results.

[0022]

[Table 3]

2 ml (about 0.8 g) of the adsorbent prepared above
Was packed in a stainless steel column having an inner diameter of 60 mm and a length of 300 mm, and 10 liters (L) of air containing 100 ppm of ammonia gas was circulated at 200 ml / min at room temperature and normal humidity without using an ultraviolet lamp. One hour after the start of the circulation, the ammonia gas removal rate was 100%.

Comparative Example 1 Titanium dioxide (2 parts by weight) was dispersed in water (30 parts by weight) to prepare a mixed solution. The pH of the mixture was 7.5. The mixture was sprinkled on 100 parts by weight of coconut shell activated carbon sized to 20 to 40 mesh and dried at 120 ° C. for 2 hours to obtain an adsorbent. Example 1 was used using 2 ml (about 0.8 g) of the adsorbent.
The removal rate of acetaldehyde gas was determined in the same manner as described above.
Table 4 shows the results. When an ammonia gas removal test was performed in the same manner as in Example 1, the ammonia gas removal rate one hour after the start of circulation was 20%.

[0025]

[Table 4]

Comparative Example 2 4 parts by weight of phosphoric acid was sprinkled on 100 parts by weight of coconut shell activated carbon sized to 20 to 40 mesh and dried at 120 ° C. for 2 hours to obtain an adsorbent. Using 2 ml (about 0.8 g) of the adsorbent, the removal rate of acetaldehyde gas was measured in the same manner as in Example 1. Table 5 shows the results. When the removal rate of ammonia gas was measured in the same manner as in Example 1, the removal rate of ammonia gas after one hour from the start of circulation was 1
00%.

[0027]

[Table 5]

[0028]

According to the present invention, it is possible to provide an adsorbent to which activated carbon itself is not impaired in performance and to which titanium oxide is efficiently attached and which is excellent in adsorbing odorous gas and a method for producing the same. According to the adsorbent of the present invention, since it is excellent in the adsorption of malodorous gas such as acetaldehyde, it can be suitably used as a deodorant for malodorous gas generated from the living environment,
A comfortable living environment can be maintained.

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Claims (9)

[Claims] 1. An odorous gas adsorbent obtained by adhering at least titanium dioxide and an inorganic acid to a porous substance. 2. The odorous gas adsorbent according to claim 1, wherein said titanium dioxide is titanium dioxide having an anatase type crystal structure. 3. The method of claim 1, wherein said inorganic acid is hydrochloric acid.
The odorous gas adsorbent as described. 4. The odorous gas adsorbent according to claim 1, wherein said inorganic acid is hydrochloric acid or phosphoric acid. 5. The method according to claim 1, wherein said porous substance is activated carbon.
4. Any offensive odor gas adsorbents. 6. A method for producing an offensive odor gas adsorbent, comprising adhering a mixture of titanium dioxide and an inorganic acid dispersed in water and having a pH of 7 or less to water to a porous substance. 7. The method according to claim 6, wherein the inorganic acid is hydrochloric acid. 8. The method according to claim 6, wherein the porous substance is a porous substance to which phosphoric acid is impregnated. 9. The porous material is activated carbon.
8. The method for producing any of the offensive odor gas adsorbents.