JP2002191972A - Adsorbent and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adsorbent such as active carbon which is excellent in capacity for adsorbing various components such as acidic gases, basic gases, and offensive odors and improved in properties for adsorbing a trace quantity of components and adsorption durability. SOLUTION: At least one kind of gas selected from acidic gases, basic gases, and neutral gases is introduced between a cylindrical external electrode 2 and a cylindrical internal electrode 3 and into an internal electrode space, an electric field is applied across the electrodes, and the gas is converted into plasma and ejected as a plasma jet 4. The plasma jet 4 is contacted with the adsorbent to improve the adsorption capacity of the adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent having excellent adsorption capacity for acidic substances, basic substances, malodorous substances, and the like in a gas, and having a long-term adsorption capacity, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, highly airtight houses are apt to absorb odors and remove basic gases such as tobacco odor, body odor, infant odor, pet odor, etc., ammonia, amines, mercaptan, etc. or odorous gas. At the same time as the demand for wants has been increasing,
The concentration of acid gases such as SO ₂ , NO ₂ , and HCl in the air increases, and these acid gases cause problems such as discoloration of artworks such as paintings and corrosion of components such as communication equipment and electronic computers. . Further, in a semiconductor manufacturing line, it is desired to reduce the concentration of acid gas in the air as much as possible in order to improve the yield of products.

[0003] For this reason, conventionally, an adsorbent made of inorganic or organic fine powder such as activated carbon, zeolite, alumina, silica, synthetic resin having adsorbability or natural substance, fibrous material or honeycomb material has been used in the air. It is widely practiced to adsorb and remove acidic or basic gases or odorous gases. However, the current adsorbent has an amount of adsorption for these basic gases, acid gases, and odorous gases,
It cannot be said that the adsorbing performance for these gases including the adsorbing ability when present in a small amount is sufficiently satisfactory, and that the adsorbing performance of the adsorbent is lost in a short period of time and that the good adsorbing performance is maintained for a long period of time. It was not satisfactory from the aspect. Then, when the amount of the adsorbent adsorbed is saturated, there arises a problem that molecules adsorbed on the adsorbent are desorbed and released again by equilibrium.

In order to cope with this, an alkaline or acidic substance or a metal oxide is impregnated into the adsorbent, and the adsorbent is removed by removing an acidic substance, a basic substance, or a malodorous gas such as methyl mercaptan or trimethylamine. It is well known that it has been used as an agent.

In particular, regarding the impregnation of an alkaline substance of activated carbon, an alkali such as sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate (Na ₂ CO ₃ ), or potassium carbonate (K ₂ CO ₃ ) is used as a main component. There is known a method of impregnating activated chemicals with activated carbon. JP-A-52-6
No. 3882 discloses that an acid or alkali is used in an amount of 0.1 to 20.
Activated carbon impregnated by weight% is described.
Japanese Patent No. 262742 proposes a chemical-carrying activated carbon honeycomb in which an activated carbon honeycomb carries an acid, an alkali, or a weakly acidic chemical such as iron halide.

[0006] Further, with respect to the acid-impregnated activated carbon, JP-A-59-151963 discloses an activated carbon carrying citric acid or an alkali metal salt of citric acid, which is disclosed in JP-A-59-227704. Has proposed an activated carbon carrying 1 to 20% by weight of a phosphoric acid compound.

Further, by using activated carbon to which an alkaline substance is impregnated, an acidic gas such as hydrogen sulfide is removed, and by using activated carbon to which an acid such as phosphoric acid or citric acid is impregnated, a basic gas such as ammonia is removed. It is also known that can be removed.

As a method for producing activated carbon to which the above-mentioned chemicals are impregnated, a method in which activated carbon is immersed in a liquid in which a predetermined amount of a chemical has been dissolved, pulled up, drained from activated carbon, and dried with activated chemicals, Alternatively, there are two methods of immersing activated carbon in a solution in which a chemical is dissolved, forcibly centrifugally dewatering, and then drying. In the former method, the chemicals precipitate on the surface of the activated carbon after drying, and the state becomes as if dusted.Therefore, when the air purifier manufactured by such a method is used, the precipitated chemicals are scattered. Can be seen. For this reason, when the activated carbon produced by the former method is used as an air purifying agent, there is a concern that air may be contaminated by an impregnated substance remaining on the surface of the activated carbon. on the other hand,
In the latter method, dehydration is forcibly performed, so that the amount of chemicals attached is smaller than in the former method, and performance is expected to decrease.

Further, when an acid or a weakly acidic chemical and an alkali are simultaneously supported on activated carbon, a salt is formed, the functions of the acid and the alkali are not exhibited, and the adsorbing ability for both the nitrogen-containing compound and the sulfur-containing compound is significantly reduced. I do. Therefore, it is necessary to use the acid-carrying activated carbon and the alkali-carrying activated carbon separately. Further, when an alkaline chemical is carried to remove sulfur-containing compounds such as hydrogen sulfide, the flash point is lowered, and there is a practical difficulty. On the other hand, when a flame retardant is added, the adsorption amount per unit specific surface area decreases, and the adsorption efficiency decreases.

As described above, in the impregnated activated carbon, there is a fear that the impregnated substance may be scattered or the performance is reduced in a short period of time. If these substances are simultaneously impregnated with activated carbon, there is a problem that one substance reduces the ability to remove the other substance. For this reason, it has been conventionally difficult to efficiently and efficiently absorb and remove gas to be treated containing a large number of odorous components and harmful substances over a long period of time with one activated carbon.

[0011]

SUMMARY OF THE INVENTION Accordingly, in view of the above problems, it is an object of the present invention to efficiently remove a large number of odor components and harmful substances in a gas to be treated over a long period of time. An object of the present invention is to provide an adsorbent having excellent adsorption performance even when the adsorbent is low. Specifically, an object of the present invention is to provide an adsorbent capable of removing gas components such as acidic, basic, aldehyde, and mercaptans without reducing the adsorption performance of the adsorbent itself for a long period of time. It is in.

[0012]

SUMMARY OF THE INVENTION The present invention relates to an adsorbent treated in the presence of a plasmatized gaseous substance.
The present invention also relates to a method for producing an adsorbent having improved adsorption performance, which comprises contacting the adsorbent with a gaseous substance that has been turned into plasma.

[0013]

In the present invention, since the adsorbent is treated under a gaseous substance converted into plasma, the adsorbent can be treated not only with macropores but also with transitional pores with the gaseous substance. The adsorbing performance of the adsorbent is remarkably improved, and no adhering substance is deposited on the surface of the adsorbent by the conventional adhering method, so that there is no contamination in the air due to scattering of the adhering substance.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. In the present invention, the adsorbent treated with the gasified substance converted into plasma is activated carbon, zeolite, alumina, silica, synthetic resin having adsorptivity, one or more kinds selected from natural substances having adsorbability. Made of material.
Further, the gaseous substance to be turned into plasma is selected from acid gas, basic gas and neutral gas. These gaseous substances are converted into plasma in the state of a mixed gas with an inert neutral gas such as helium, argon, neon, krypton, or nitrogen as required, and contacted with the adsorbent. As a result, a new functional group is introduced to the surface of the adsorbent by the gasified gaseous substance, and the gaseous substance formed by the plasma forms a hydrogen bond, a charge transfer complex or an adsorbed complex with the surface functional group of the adsorbent. Or by ionic bonding,
The adsorption performance is improved.

Specific examples of gaseous substances include, as acidic gaseous substances, oxides such as nitrogen oxides, sulfur oxides, carbon dioxide and oxo acid, hydrogen peroxide, sulfide, bromine, and the like.
Chlorine, chloric acid, gaseous substances of iodine and the like can be mentioned. Examples of the sulfide include hydrogen sulfide (H ₂ S). Examples of the sulfur oxide include:
Sulfur monoxide (SO), sulfur dioxide (SO _2), sulfur trioxide (SO _3), trioxide sulfur (S ₂ O _3), and the like, and heptoxide sulfur (S ₂ O _7). In the present invention, as the acidic gaseous substance to be converted into plasma, sulfur oxide is preferable.

The neutral gaseous substances include hydrogen, helium, neon, argon, krypton, xenon and other rare gases, oxygen, air, nitrogen gas, and metallic hydrogen gas.
Gases composed of metal organic compounds such as metal halide gases and metal alcoholates are exemplified. As the neutral gaseous substance, a mixed gas containing argon and helium or nitrogen and hydrogen is preferable.

Further, examples of the basic gaseous substance include gaseous substances such as amines, iodides, bromides, dimethylamine and methylamine. These gaseous substances may be used alone or in combination of two or more.

As a method of treating an adsorbent using a gasified substance in the form of plasma, the gaseous substance is converted into plasma by a plasma jet method, a radio frequency plasma method, a microwave plasma method, or the like, and the plasma-converted gas is used. And a method of contacting the adsorbent with the particulate matter.

The plasma jet method is a method in which plasma (particularly, active species of plasma) generated by corona or glow discharge under atmospheric pressure is jetted out to an object to be processed to perform plasma processing. And using an apparatus. The term “atmospheric pressure” as used herein refers to a pressure of 100 to 800 Torr. As the plasma jet method, it is preferable to use an apparatus capable of generating plasma at a pressure in the range of 700 to 780 Torr, which facilitates pressure adjustment and makes the apparatus simple.

The generation of plasma by the plasma jet method according to the present invention will be described with reference to FIG. FIG. 1 schematically shows an example of a cross section at the tip of a plasma jet generator. In FIG. 1, reference numeral 1 denotes a cross section of the tip of the plasma jet generator. 2, 2 are cross sections of the cylindrical outer electrode;
Reference numerals 3 and 3 denote cross sections of the cylindrical inner electrode. Gas is introduced into the space (reaction tube) between the outer electrode 2 and the inner electrode 3 and inside the inner electrode 3. This is a plasma jet to which an AC electric field is applied by an AC power supply 5. By applying an AC electric field between the outer electrode 2 and the inner electrode 3, a corona or glow discharge is generated between the electrodes, and a plasma generating gas is excited by the corona or the glow discharge to generate plasma. Plasma jet 4 from the outlet at the bottom of the reaction tube
And perform plasma processing. FIG. 1 shows an example in which an alternating current is applied between the outer electrode 2 and the inner electrode 3, but a positive voltage is applied to the outer electrode 2,
Further, a negative voltage may be applied to the inner electrode 3.

At this time, an additive gas such as hydrogen or water vapor or an additive such as powder is supplied and mixed from around the jet flow of the plasma jet, or a hole is formed so as to penetrate the electrode 2 or the electrodes 2 and 3. By providing the additional gas or powder from the outside of the electrode through this hole, the additional gas or additive is mixed with the plasma jet, or the powder is added to the plasma generating gas itself. It is also possible to generate plasma every other time.

When the plasma jet method is used, the frequency of the alternating current applied to the outer electrode and the inner electrode is usually set to 1 kHz to 50 GHz. This is because if the frequency of the alternating current is less than 1 kHz, there is a possibility that the discharge in the discharge space cannot be stabilized,
If the frequency of the alternating current exceeds 50 GHz, the plasma temperature in the discharge space may increase significantly.
When the frequency of the alternating current used is less than 10 kHz, the amount of generated radicals is reduced, and the effect of the plasma treatment may be reduced. A preferred AC frequency is 10 kHz to 200 MHz. Further, the outer electrode 2
When an AC electric field is applied to the inner electrode 3 and the inner electrode 3, it is preferable to connect an AC power source to the outer electrode 2 and ground the inner electrode. Thereby, the potential difference between the inner electrode and the activated carbon becomes almost zero, the streamer discharge between the inner electrode and the activated carbon can be suppressed, and the streamer discharge is less likely to be generated.

In the present invention, the power applied to the discharge space between the outer electrode 2 and the inner electrode 3 is 5 W or more.
It is preferably less than 00W. Usually, the applied power is 5
If it is less than W, no effect can be obtained, while if it is more than 300 W, the treatment conditions are too severe, a reaction close to combustion occurs, and it becomes difficult to control the formation of surface functional groups. Usually, the optimum range of the applied power is 10 W or more and 200 W or less.

When a neutral gas is used as the gaseous substance,
Considering the stability and economy of discharge, it is preferable to use argon or helium. However, streamer discharge is easily generated with argon alone, so it is preferable to use a mixed gas obtained by diluting argon with helium.The mixing ratio is closely related to the temperature of the discharge space, but the temperature of the plasma jet is set to 250 ° C. or less. In this case, the content of argon is preferably set to 90% by volume or less. If the amount of argon is larger than this, streamer discharge may easily occur. It is considered that the reason why streamer discharge is likely to occur when the amount of argon is large is that argon has a smaller metastable state energy and life than helium as compared with helium. In particular, as a neutral gas, helium gas has a long metastable life and is convenient and preferable for exciting the processing gas.

In a mixed gas of a neutral gas and an acidic gas or an alkaline gas, or a mixed gas of a neutral gas, an acidic gas and an alkaline gas, an acidic gas or an alkaline gas or a mixed gas of an acidic gas and an alkaline gas to a neutral gas Is 20% by volume or less based on the neutral gas,
Preferably it is in the range of 0.1 to 10% by volume. When the addition amount of the acidic gas or the alkaline gas or the mixed gas of the acidic gas and the alkaline gas is less than 0.1% by volume, the treatment effect is reduced, and when the addition amount of the reaction gas exceeds 20% by volume, the reaction gas If the flow rate is too large, the temperature of the plasma decreases, the reactive gas is not efficiently activated, and it becomes difficult to generate uniform discharge plasma even when a voltage is applied. Further, the discharge may be unstable. The ratio of these gas mixtures is determined by the type of gas used.

When the plasma jet method is used, not only is an acidic gas or an alkaline gas or a mixed gas of an acidic gas and an alkaline gas turned into plasma and sprayed onto an adsorbent such as activated carbon, but also the adsorbent and the treated gas are simultaneously treated. The treatment gas and the adsorbent can be simultaneously turned into plasma by being introduced into a plasma jet. In this case, if the adsorbent is activated carbon, impurities adhering to the activated carbon can be subjected to high-temperature treatment and oxidation treatment by plasma, so that the activated carbon can be more efficiently treated with the treatment gas.

The distance between the electrodes 2 and 3 is appropriately determined by the thickness of the metal constituting the electrodes, the thickness of the solid dielectric, the thickness of the porous body, the magnitude of the applied voltage, the flow rate of the mixed gas, and the like. However, it is preferably 1 to 30 mm. If it is less than 1 mm, the gas to be used is wasted, which is not appropriate. On the other hand, if it exceeds 30 mm, it is difficult to generate uniform discharge plasma.

The discharge plasma is generated between the electrodes.
This is performed by applying a voltage. The voltage is decided appropriately
When applied, the electric field strength is 1 to 40 kV / cm
It is preferable that Less than 1 kV / cm
If it is, processing takes too much time and exceeds 40 kV / cm
This is because an arc discharge occurs. For the above voltage application
The required power supply is not particularly limited, but as described above,
It is preferable that the AC power supply has a wave number of 10 to 200 kHz.
New In addition, the above discharge plasma treatment can be performed at room temperature.
However, it may be performed by heating or cooling the processing gas.
No.

The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage and the mixed gas used. Radicals and peroxide groups can be formed by short-time treatment. In the case of a helium gas atmosphere, radicals and peroxide groups are formed by the treatment for 15 seconds.

FIG. 2 shows an example of another apparatus used for the plasma treatment of the adsorbent of the present invention. In FIG. 2, 6 is a microwave oscillator, 7 is a waveguide, and 8 is a quartz glass reaction tube. The pressure in the reaction tube 8 is reduced 9 to reduce the internal pressure. The pressure reduction mentioned here is 10 ⁻⁶ To
It means rr or more and less than 1 atm. In the apparatus shown in FIG. 2, plasma is generated in the reaction tube 8 by irradiation of microwaves oscillated from the microwave oscillating unit 6. Microwave frequency is about 1GHz ~ 1000GHz, usually 1GHz ~
10 GHz is preferred.

The adsorbent used in the plasma treatment of the present invention is activated carbon, zeolite, alumina, silica, an adsorbent synthetic resin or a natural substance, which has been conventionally used as an adsorbent. In the present invention, activated carbon is particularly preferred as the adsorbent. The type of activated carbon used is not particularly limited.For example, activated carbon produced by a conventional method using charcoal, coke, coconut shell, natural fiber, polyacrylonitrile, rayon, synthetic resin such as phenolic resin, pitch, etc. as raw materials Can be used. The form of the activated carbon may be, for example, any of powder, granule, pellet, macaroni, fiber, honeycomb, and the like. Of activated carbon, pellet form,
Fibrous or honeycomb activated carbon is preferred, and honeycomb activated carbon is particularly preferred because of its low pressure loss and large contact surface area with the gas to be treated.

The BET specific surface area of the activated carbon is usually 2
00 to 4000 m ² / g, preferably 400 to 3500
m ² / g, particularly preferably 500~3000m ² / g. The BET specific surface area of the honeycomb activated carbon is usually 30
0 to 3000 m ² / g, preferably 400 to 2500 m ²
/ G. When activated carbon having such a specific surface area is used, the adsorption capacity can be increased.

[0033]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to the following examples. Example 1 As a plasma generation gas, a mixed gas of neutral gas of oxygen, helium, and argon and acid gas of sulfur dioxide was used, and the flow rate of helium was 3 liter / min.
The mixed gas was adjusted so that the flow rate of argon was 5 liters / minute, the flow rate of sulfur dioxide was 1 liter / minute, and the flow rate of oxygen was 1 liter / minute, and the inner electrode of the plasma jet generator shown in FIG. A high frequency (frequency: 13.56 MHz, applied power: 250 W) is applied to the outer electrode 2 while the ground 3 is grounded, a plasma is generated under a pressure of 760 Torr, and a plasma jet 4 blown out from a blowing port is introduced into the reaction tube. Then, 10 g of granular activated carbon made of Kuraray Chemical having a specific surface area of 800 m ² in the reaction tube was brought into contact with a plasma jet for 15 minutes while stirring to obtain activated carbon as an adsorbent. The specific surface area of the obtained activated carbon was evaluated, the humidity was 50% RH, and the SV value was 60000.
such that h ^-1, at 15 l / min flow rate, 50p
The target gas of ammonia having a pm concentration of ammonia is passed through the obtained activated carbon, and the concentration of ammonia in the passed target gas is measured with a detection tube manufactured by Gastech Co., Ltd., and the 50% breakthrough time of the ammonia removal efficiency is measured. Thus, the ammonia adsorption ability of the adsorbent was obtained. The specific surface area was about 1100 m ² / g, while the ammonia adsorption capacity was 11 hr.

Example 2 As a plasma generating gas, helium or neutral gas, which is a neutral gas, was used.
Of argon and argon with acid gas sulfur dioxide
Gas is sealed in the reaction tube 8 of the microwave plasma apparatus of FIG.
And the microwave generated by the microwave generator 6
(Frequency 2.45 GHz, applied power 300 W)
To generate a microwave, and into the reaction tube 8.
Enclosed average pore diameter 18 Å
Diameter distribution 10-50 Å), pore volume 0.
5cc / g, specific surface area 1000m ^Two/ G manufactured by Ador
1 g of fibrous activated carbon is applied to this plasma under reduced pressure (30 Torr).
r) contact for 2 minutes while stirring in
I got charcoal. Fiber contacted with this plasma gas
Example 1 Specific Surface Area and Ammonia Adsorption Capacity of Granular Activated Carbon
The specific surface area was about 1100 m
^Two/ G, while the ammonia adsorption capacity is 10 hr.
Was.

EXAMPLE 3 A mixture of hydrogen and nitrogen in a ratio of 1: 2 was added to a reaction tube 8 of the microwave plasma apparatus shown in FIG.
Microwave generator 6 introduced at a flow rate of 5 liters / minute
Microwave (frequency 2.45 GHz)
z, an applied power of 300 W) to generate microwaves, and 1 g of granular activated carbon manufactured by Kuraray Chemical Co., Ltd., having a specific surface area of 800 m ² / g, previously sealed in the reaction tube 8, is decompressed to this plasma. Bottom (30 Torr
The mixture was brought into contact for 2 minutes with stirring in r) to obtain activated carbon which had been subjected to gas plasma treatment as an adsorbent. The specific surface area and gas adsorption capacity of the obtained activated carbon were measured. The measurement was performed in the same manner as in Example 1 except that a 50 ppm concentration of hydrogen sulfide-containing gas was used as the target gas instead of the 50 ppm concentration of ammonia-containing gas. Specific surface area is about 1000m ²
/ G, while the ability to adsorb hydrogen sulfide was 13 hr.

Example 4 As a plasma generating gas, a mixture of hydrogen and nitrogen in a ratio of 1: 2 was used.
Using gas, the inner power of the plasma jet
With the pole 3 grounded, a high frequency (frequency
10 MHz, an applied power of 250 W) and a pressure of 76
Generates plasma under 0 Torr, and
The plasma jet 4 blown out is introduced into the reaction tube,
Average pore diameter of 18 Å in the reaction tube
Diameter distribution 10-50 Å), pore volume 0.
5cc / g, specific surface area 1000m ^Two/ G manufactured by Ador
10 g of fibrous activated carbon is contacted for 15 minutes while stirring.
Activated carbon was obtained as an adsorbent. This plasma gas
Table as in Example 3 for fibrous activated carbon contacted with
When the area and hydrogen sulfide adsorption capacity were determined, the specific surface area was
About 1100m^Two/ G, while the ability to adsorb hydrogen sulfide is 15
hr.

Comparative Example 1 1 liter / minute of sulfur dioxide and 3 liter / minute of helium were passed through 10 g of granular activated carbon manufactured by Kuraray Chemical Co., Ltd. having a specific surface area of 800 g / m ² for 15 minutes to obtain activated carbon. When the specific surface area was measured, it was about 800 g / m ² . Further, the ammonia adsorption ability was 0.5 hr.

Comparative Example 2 Sodium hydroxide was impregnated into 10 g of granular activated carbon manufactured by Kuraray Chemical Co., Ltd. having a specific surface area of 800 g / m ² to obtain activated carbon as an adsorbent. When the specific surface area of this impregnated activated carbon was measured, it was about 400 g / m ² . In addition, the hydrogen sulfide adsorption ability was 9 hours.

[0039]

As described in detail above, in the present invention, an inorganic or organic adsorbent such as activated carbon, zeolite, alumina, silica, synthetic resin having an adsorbent property or a natural substance is used in an acidic gas, an alkaline gas, a neutral gas or a neutral gas. The characteristics of the adsorbent are improved by bringing the gas into contact with the gas that has been converted into plasma, and the amount of adsorption to acidic gases, basic gases, odorous substances, etc. is large. It has a remarkable effect that it is possible to obtain an adsorbent that exhibits performance and can maintain adsorption performance for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tip portion of a plasma jet generator for carrying out a method of the present invention.

FIG. 2 is an explanatory diagram of a microwave plasma device for performing the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front end of plasma jet generator 2 Outer electrode 3 Inner electrode 4 Plasma jet 5 AC power supply 6 Microwave generator 7 Waveguide 8 Reaction tube 9 Decompression

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 20/20 B01J 20/20 D 20/24 20/24 A 20/26 20/26 A C01B 31/10 C01B 31/10 (72) Inventor Kazuo Sugiyama 5-8-2 Oizumi-cho, Nerima-ku, Tokyo (72) Inventor Nobuyuki 2-28-8 Honkomagome, Bunkyo-ku, Tokyo Clariant Japan Co., Ltd. F-term (Reference) 4G046 HA00 HC08 HC10 HC11 HC12 4G066 AA05B AA12A AA12B AA20B AA22B AA61B BA23 BA25 BA26 BA36 CA24 CA29 DA01 FA17 FA31 FA33 FA40 4G075 AA22 AA42 BA02 BD14 CA16 CA18 CA25 CA26 CA47 CA65 DA01EB02 EC21

Claims (8)

[Claims] An adsorbent treated in the presence of a gasified gaseous substance. 2. The adsorbent according to claim 1, wherein the gaseous substance is at least one selected from an acidic gas, a basic gas, and a neutral gas. 3. The adsorbent according to claim 1, wherein said gaseous substance is a gaseous substance containing sulfur oxide. 4. The adsorbent according to claim 1, wherein said gaseous substance is a gaseous substance containing hydrogen and nitrogen. 5. An adsorbent, wherein the adsorbent is activated carbon. 6. An adsorbent, wherein the adsorbent is zeolite, alumina or silica. 7. An adsorbent, wherein the adsorbent is selected from synthetic resins having adsorption properties or natural substances. 8. A method for producing an adsorbent having improved adsorption performance, which comprises contacting the adsorbent with a gaseous substance that has been turned into plasma.