KR102031567B1 - Surface modified activated carbon by high temperature treatment under air condition and its method - Google Patents

Abstract

The present invention relates to a surface-modified activated charcoal acquired by inorganic acid and silica treatment and then, heat treatment at high temperatures of 800°C or higher under a general air atmosphere, and having an excellent adsorption ability to basic gas and aldehyde gas in the air; and a surface-modifying method thereof. The provided surface-modified activated charcoal is acquired by treating activated charcoal with inorganic acid treating the same with silica, doubly coating the surface thereof, and then conducting heat treatment at 800-1,000°C for 1-4 hours under the general air atmosphere. In addition, the surface-modifying method comprises: a step (a) of immersing activated charcoal in an 2-8% of inorganic acid solution for 1-3 hours, dehydrating the same, and drying the same at 300-400°C for 1-4 hours; a step (b) of spraying a 80-90% of silica sol solution to the surface of the dried activated charcoal after being immersed in the inorganic acid solution, maturing the surface with silica sol solution at room temperature for 5-7 hours and then, coating silica on the surface of the activated charcoal; and a step (c) of conducting heat treatment of the silica-coated activated charcoal acquired from the silica coating step at 800-1,000°C for 1-4 hours under the general air atmosphere. Therefore, the surface-modified activated charcoal can be used as an adsorbent for purifying air in air purifying equipment in the form thereof or the form in which a hydrophobic amino acid-based or a vitamin-based impregnating substance is impregnated, and can have an excellent effect of adsorbing base gas and aldehyde gas in the air to remove the same without emission of substances harmful to the human body.

Description

Surface modified activated carbon by high temperature treatment under air condition and its method

 The present invention relates to a surface-modified activated carbon and a method thereof, and more particularly, a surface having excellent adsorptivity to basic gas and aldehyde gas in air obtained by heat treatment at a high temperature of 800 ° C. or higher under a general air atmosphere after treatment with inorganic acid and silica. Modified activated carbon and its surface modification method.

Activated carbon is widely used for the removal of harmful substances in the adsorption tower operating in the workplace, and activated carbon made of coconut, wood, coal, etc. is also used for air cleaner filters to reduce harmful components in the air.

In particular, in recent years, as social awareness about the dangers of harmful gases in the air has spread, air cleaner manufacturers and air pollution prevention facility manufacturers have been able to reduce harmful gaseous components such as volatile organic compounds, acid / base compounds, and aldehyde compounds. We are conducting research for

Activated carbon used in filters generally has a large specific surface area consisting of micropores, which are advantageous for gas phase adsorption. Activated carbons prepared by carbonizing coconuts, wood, coal, etc., and then revitalizing them with water vapor or chemicals are used for activation time and steam input. Specific surface area, pore size and the like vary depending on the activating method of adding phosphoric acid, zinc chloride and the like and the basic characteristics of the raw materials. The pores are usually composed of micropores of less than 1nm, mesopores of 2-40nm, and because of their non-polar surface properties, they have high adsorption capacity for benzene, naphthalene, etc., which are nonpolar materials, and have a high alkalinity of about 10-11. It is known that the adsorption characteristics of acidic gas are excellent.

Activated carbon produced by activating coconut coconut has excellent adsorption capacity of gaseous small molecule materials in the air because the fine pores are developed, and activated carbon made of wood or coal has a high proportion of mesopores, so adsorption and waste water of relatively large molecules It is used for purification and decolorization of sugar, and it is also advantageous for the removal of substances having large molecular weight and high boiling point among harmful gases. However, such activated carbon has a disadvantage that the adsorption capacity of a basic gas such as ammonia is greatly reduced since it has a high pH, and the activity of reacting with a catalyst or a chemical added to remove a gaseous substance of a specific component is reduced. Therefore, activated carbon manufacturers have suggested various methods of manufacturing activated carbon in order to improve the adsorption performance of activated carbon used for air purification, and in particular, the adsorption performance of harmful components through surface modification method of adding metal or organic material to activated carbon. It is trying to increase the concentration of the chemicals and selectively remove the harmful components.

In this regard, U.S. Patent No. 6,789,547 discloses a technique that has a great effect on the removal of harmful substances in the air by adding alkali metal and transition metal materials to various activated carbons in various ways. However, this technology has a problem that it is difficult to use easily because the metal material itself is transferred to the human body during the purification process and may be harmful to the human body.

US Pat. No. 6,595,218 discloses a technique for attaching 2-aminopropyl silane to silica gel and activated carbon, and the silica gel or activated carbon thus prepared has an advantage of high removal efficiency of HCN, aldehyde and the like in the air. In this technique, the impregnation of activated carbon is more efficient than that of silica gel.However, when impregnated with activated carbon, the impregnated material reacts with hydroxyl groups on the surface of the activated carbon to reduce the active point for gas adsorption. There is a disadvantage that the removal efficiency is lowered.

Korean Patent Publication No. 10-1990-15652 discloses a reagent having an en-diol functional group such as urea, citric acid, glycine, and histidine, which are compounds having high acidity and reacting with an aldehyde in an adsorbent such as activated carbon and zeolite to remove formaldehyde components. Disclosed is a technique for adding a synergy synergy composition. However, the addition of these compositions has the disadvantage that the composition buried on the surface of the activated carbon is vaporized during the air purification process can be transferred to the human body by particulate matter.

In Korean Patent Publication No. 10-1999-16260, activated carbon made from various raw materials is allowed to stand for 60 to 120 minutes in an air atmosphere at 250 to 400 ° C to allow oxygen in the air to react with the surface to attach oxygen-containing functional groups to the surface of the activated carbon. Techniques for increasing the hydrophilic effect are disclosed. In this case, the efficiency of activated carbon can be increased by reducing the amount of activated carbon suspended in the waste water during wastewater purification.However, the activated carbon produced increases the number of functional groups including oxygen, but is less than that of acid-treated samples. The use of activated carbon having a large amount of functional groups and having a large particle size can reduce the amount of activated carbon suspended in water, but there is a problem that does not significantly affect the removal performance of gaseous substances other than wastewater treatment.

As such, when a material such as a metal or an alkali metal is attached to the surface or pores of general activated carbon, the material added to the surface may be inhaled into the human body by an aerosol having a size of 0.1 to 1 μm constituting an air component. In addition, although the reactivity with the aldehyde gas in the filter is known to be strong, there is a problem that the added molecules can be transferred to the human body as an air component even when trimethylamine or the like, which is harmful to the human body, is attached to the adsorbent.

In order to compensate for these disadvantages, methods of modifying the surface of activated carbon with strong acids, strong bases, microwaves, air, and the like are known, and methods of treating activated carbon with strong acids are widely known. In the case of modifying the surface of activated carbon by treating with strong acid, high concentration of strong acid has been generally used because the concentration of strong acid does not introduce a large amount of functional groups on the surface of activated carbon. However, treatment of activated carbon with high concentrations of strong acids can cause problems in commercial manufacturing. Particularly, in the case of treating activated carbon with high concentration of nitric acid, there is an advantage that it is very effective in developing surface functional groups, but it is difficult to commercially manufacture because harmful nitrate gas is generated during the nitric acid treatment and the working environment becomes very poor. In addition, there is a problem that the nitrate gas, which is very harmful to the human body remaining in the pores of activated carbon after nitric acid treatment, is released during the air purification process and can be transferred to the human body, and the specific surface area is reduced due to the high acid concentration, thereby reducing the physical effective adsorption area. There is a problem that is reduced. In addition, the acid-treated activated carbon has a large amount of surface functional groups but is not effective for removing gas phase components, and thus, it is widely used as a pretreatment method for uniformly dispersing metal particles or salts on the surface.

Due to the problem of acid treatment, a method of oxidizing the surface by treating activated carbon under an air atmosphere in which the activated carbon does not ignite is introduced. Although this method is a simple and fast method for surface modification of activated carbon, the surface of activated carbon is introduced. Since there are not more functional groups generated through the reforming than acid treated activated carbon, there is a disadvantage in that the effect is not high for removing harmful components in the air.

Therefore, it does not require an inert gas and accessories to form an oxygen-free atmosphere, thereby significantly lowering the production cost, and performing activated carbon at a high temperature of 800 ° C. or higher, which is higher than the activated carbon ignition temperature under a general air atmosphere, while minimizing the loss of activated carbon. There is a need for a surface modification method. In addition, there is a need for a method for surface modification of activated carbon that is highly hydrophobic and harmless to the human body while having high reactivity with gas molecules and not being detached even under high temperature conditions such as moisture and summer during air purification.

U.S. Patent No. 6,789,547 U.S. Patent No. 6,595,218 Republic of Korea Patent Publication No. 10-1990-15652 Republic of Korea Patent Publication No. 10-1999-16260

It is an object of the present invention to provide a method for surface modification of activated carbon that can be heat-treated at a high temperature of 800 ° C. or higher in a general air atmosphere without forming an oxygen-free atmosphere, and to provide such surface modified activated carbon.

An object of the present invention is to provide an activated carbon having excellent adsorption capacity to specific gaseous components, particularly basic gas and aldehyde gas by hydrophobizing the surface of activated carbon by heat treatment at a high temperature of 800 ° C. or higher in a general air atmosphere.

In order to achieve the above object, in the present invention,

(a) immersing activated carbon in an aqueous solution of 2-8% inorganic acid for 1 to 3 hours and then dehydrating and drying for 1 to 4 hours at 300 to 400 ° C;

(b) spraying an 80-90% silica sol solution on the surface of the dried activated carbon obtained by immersing the inorganic acid aqueous solution obtained in the above step, and then aging at room temperature for 5-7 hours to coat silica on the surface of the activated carbon; And

(c) providing a method for surface modification of activated carbon comprising the step of heat-treating the silica-coated activated carbon obtained in the step of coating the silica at 800 to 1,000 ℃ for 1 to 4 hours under normal air conditions.

In the manufacturing method, the step of coating the silica is preferably coated with 2 to 4% by weight of silica based on the weight of the dried activated carbon.

In the above production method, the inorganic acid is preferably at least one selected from phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, hypochlorous acid and hydrofluoric acid, and particularly preferably phosphoric acid.

In the preparation method, prior to the step (a), it may further comprise a step of dehydrating after reacting for 5 to 7 hours at 60 ~ 80 ℃ by immersing activated carbon in 1-5% organic acid aqueous solution. The organic acid is preferably at least one selected from citric acid, acetic acid, oxalic acid, tartaric acid and benzoic acid.

The manufacturing method may further include a step of attaching a hydrophobic amino acid series or vitamin-based adherent material to the surface-modified activated carbon after the heat treatment.

In the present invention,

The activated carbon is treated with silica after inorganic acid treatment to provide a surface-modified activated carbon obtained by subjecting the surface to double coating and heat-treating at 800 to 1,000 ° C. for 1 to 4 hours in a general air atmosphere.

The inorganic acid is preferably at least one selected from phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, hypochlorous acid, and hydrofluoric acid, and particularly preferably phosphoric acid.

The surface-modified activated carbon is preferably treated with an organic acid before the inorganic acid treatment. The organic acid is preferably at least one selected from citric acid, acetic acid, oxalic acid, tartaric acid and benzoic acid.

In one embodiment of the present invention, the surface-modified activated carbon is impregnated with an impregnated material of hydrophobic amino acid series or vitamin series after the heat treatment.

In the present invention, a double coating film is formed on the surface of the activated carbon by inorganic acid treatment and silica treatment to solve the problem that the activated carbon reacts with oxygen during the heat treatment at 800 ° C. or higher, and a high temperature heat treatment of 800 ° C. or higher is possible under a general air atmosphere. Lose. Therefore, it is economical by reforming the activated carbon by heat treatment at a high temperature of 800 ° C. or higher in a general air atmosphere without forming an oxygen free atmosphere.

In addition, since the surface of the activated carbon is hydrophobized by the high temperature heat treatment, it is possible to minimize the reduction of the active point of the hydrophobic amino acid series or the vitamin-based adherent, and thus it is used as a precursor for attaching the hydrophobic amino acid or vitamin-based adherent. Very suitable.

When the surface-modified activated carbon is attached with a hydrophobic amino acid or vitamin-based impregnated substance, it is possible to remove basic gas and aldehyde gas in the air very effectively without releasing harmful substances in the air purification process.

Therefore, the surface-modified activated carbon of the present invention can be usefully used as an adsorbent in air cleaners, adsorption towers, etc. by themselves or in the form of impregnated with hydrophobic amino acid or vitamin-based additives. In particular, it is used as an adsorbent in an air cleaner to remove ammonia, acetaldehyde, acetic acid, formaldehyde and toluene, and is particularly suitable for the removal of acetaldehyde, and has a very good removal effect.

1 is a photograph of raw activated carbon.
2 is a photograph of the surface modified activated carbon of Example 1.
3 is a photograph of the surface modified activated carbon of Example 2.
4 is a photograph of the surface modified activated carbon of Example 3.
5 is a photograph comparing raw activated carbon with surface modified activated carbon of Examples 1 to 3. FIG.
6 is a photograph comparing the size of the raw activated carbon and the surface-modified activated carbon of Examples 1 to 3.
7 is a pore distribution curve derived from the BET analysis of the raw activated carbon and the surface modified activated carbon of Examples 1 to 3. FIG.

The surface modification method of the activated carbon of the present invention,

(a) immersing activated carbon in an aqueous solution of 2-8% inorganic acid for 1 to 3 hours and then dehydrating and drying for 1 to 4 hours at 300 to 400 ° C;

(b) spraying an 80-90% silica sol solution on the surface of the dried activated carbon obtained by immersing the inorganic acid aqueous solution obtained in the above step, and then aging at room temperature for 5-7 hours to coat silica on the surface of the activated carbon; And

(c) heat-treating the silica-coated activated carbon obtained in the step of coating the silica at 800 to 1,000 ° C. for 1 to 4 hours under normal air conditions.

Preferably, prior to the step (a), by immersing activated carbon in an aqueous solution of 1 ~ 5% organic acid and reacting for 5 to 7 hours at 60 ~ 80 ℃ may further comprise a step of dehydration.

In addition, the method may further include a step of attaching a hydrophobic amino acid or vitamin-based additive to the surface-modified activated carbon after the heat treatment as necessary.

Hereinafter, the present invention will be described in more detail with each configuration and step.

1. Activated Carbon

Activated carbon, which is a raw material, may use activated carbon manufactured using various materials including palm coconut, wood, and coal. In addition, activated carbon prepared by steam or chemical reactivation according to known methods, and activated carbon treated by various known methods such as treatment of activated carbon with hydrochloric acid or sodium chloride to remove impurities and metals can be used.

2. Removal of impurities by organic acid treatment

In order to remove impurities in activated carbon which is a raw material, it is preferable to immerse activated carbon in an aqueous organic acid solution at a concentration of 1 to 5% and react for 5 to 7 hours at 60 to 80 ° C. By treatment with an organic acid, impurities such as calcium and sodium remaining in the activated carbon can be removed. After the reaction, the activated carbon is dehydrated, and at this time, it is more preferable to dehydrate under conditions of pH 8 or less.

It is preferable to select and use at least one of citric acid, acetic acid, oxalic acid, tartaric acid and benzoic acid for food addition as the organic acid. This is because the organic acid remaining in the activated carbon after treatment may volatilize and affect the human body. It is more preferable to use a low boiling point food additive organic acid.

3. inorganic acid treatment

Activated carbon is treated with an inorganic acid to form a coating film on the surface of the activated carbon.

Activated carbon is immersed in an aqueous inorganic acid solution of 2-8% concentration for 1 to 3 hours, then dehydrated and dried at 300 to 400 ° C. for 1 to 4 hours. In this case, the activated carbon is preferably dehydrated activated carbon after the organic acid treatment.

The inorganic acid may be phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, hypochlorous acid, hydrofluoric acid, and the like, and one or more of them may be selected and used. Preferably, an inorganic acid for food addition is used, and particularly preferably phosphoric acid is used. Phosphoric acid is a material harmless to human body that can be used for food additives, which can ensure the safety of workers when it is manufactured, and is converted into pyrophosphoric acid or metaphosphoric acid that does not sublime when heat treated at 300 ° C or higher to form a coating film on the surface of activated carbon. This is because the coating film is a stable material that does not affect the human body even when used as a material for air purification. In addition, the coating film formed on the surface of the activated carbon by converting phosphoric acid into pyrophosphoric acid or metaphosphoric acid serves to protect the activated carbon from disappearing at a high temperature heat treatment of 800 ° C. or higher.

It is preferable to use the said inorganic acid in the density | concentration of 2-8%. Typically, treatment of activated carbon with inorganic acids results in a slight increase in surface functional groups. High concentrations of acid were used for the development of conventional surface functional groups. However, the use of high concentration of acid decreases the specific surface area, which decreases the physical effective adsorption area, and in the process of processing activated carbon, steam containing acid due to exothermic reaction can be generated, which makes the working environment very poor. In the case of using as an impregnated support, there is a disadvantage in that the impingement material is prevented from penetrating into activated carbon. Therefore, it is very important to use a low concentration of inorganic acid. However, if the concentration of the inorganic acid is less than 2%, hydrogen ions are not sufficiently introduced during the high temperature heat treatment, and the surface treatment effect of the activated carbon is lowered. Decreases the supporting effect of the impregnated substance and decreases the gas adsorption capacity.

By the inorganic acid treatment, the carbon ring structure constituting the activated carbon is oxidized to neutralize or remove the hydrophilic functional groups present on the surface of the activated carbon such as carboxyl, carbonyl and phenolic hydroxyl groups. . In addition, when heated to 300 ° C or more, the inorganic acid forms a coating film on the surface of the activated carbon to cover and protect the surface of the activated carbon, thereby blocking oxygen in the subsequent heat treatment.

The heat treatment of the activated carbon may be carried out in a rotary kiln or batch reactor, and other known means may be used if necessary.

4. Silica treatment

After the inorganic acid treatment, dehydrated activated carbon is treated with silica to form a coating film on the surface of the activated carbon. Following the inorganic acid treatment, this treatment with silica forms a double coating on the surface of the activated carbon.

After the inorganic acid treatment, a silica sol solution containing silica of 80 to 90% concentration is sprayed on the surface of the dehydrated activated carbon. After spraying the silica sol solution on the surface of the activated carbon is aged at room temperature for 5-7 hours to form a coating film by coating 2 to 4% by weight of silica per weight of activated carbon on the surface of the activated carbon.

If the weight of the coated silica is less than 2%, there is no uniform coating on the surface of the activated carbon, and the effect of oxygen blocking is reduced in the heat treatment process, resulting in burning of activated carbon.If the weight of the coated silica is 4% or more, activated carbon It is preferable to coat 2-4% by weight of silica per weight of activated carbon because pore clogging can be significantly increased. When an appropriate amount of silica is coated on the surface of activated carbon, the amount of oxidized carbon fine powder generated during the heat treatment is small, so that the working environment is not deteriorated and the yield reduction rate of the activated carbon during the heat treatment is low.

 When silica is coated on activated carbon, a coating film is formed to prevent oxygen from moving to the surface of activated carbon under a high temperature general air atmosphere, and thus heat treatment may be performed at a high temperature of 800 ° C. or higher in a general air atmosphere. By coating with silica and heat treatment in a normal air atmosphere to hydrophobize the surface of activated carbon, it is possible to obtain surface-modified activated carbon having excellent adsorption capacity for basic gas and aldehyde gas without releasing harmful substances to human body during air purification process. .

5. Hydrophobicity of Surface by High Temperature Heat Treatment

The activated carbon coated by the silica treatment is heat treated at 800 to 1,000 ° C. for 1 to 4 hours under general air conditions to hydrophobize the surface of the activated carbon.

The reforming of activated carbon requires a high temperature heat treatment of 800 to 1,000 ° C. In the prior art, such high temperature treatment should be performed under anoxic conditions (nitrogen atmosphere) because activated carbon burns in the presence of oxygen. However, in the present invention, since the surface is modified by inorganic acid treatment and silica treatment to block oxygen, high temperature heat treatment of 800 to 1,000 ° C. is possible under general air conditions in which oxygen is present.

Hydrogen ions introduced from the inorganic acid during the high temperature heat treatment process are chemically bonded to a functional group containing oxygen on the surface of the activated carbon to reduce the surface, thereby changing to a hydrophobized surface made of carbon and hydrogen. In addition, the added inorganic acid chemically reacts with the carbon having the activity of the surface constituting the activated carbon to expand the size of the existing pores to generate a pore distribution consisting of more than the mesopores. The enlarged pores in the activated carbon provide favorable conditions for the penetration and deposition of the adherent material after heat treatment.

The heat treatment temperature is preferably 800 ~ 1000 ℃, if the heat treatment temperature is less than 800 ℃, the reaction rate and reaction amount of the functional group pyrolysis on the surface of the activated carbon is lowered, the hydrophobization surface treatment effect is reduced, the heat treatment temperature exceeds 1000 ℃ In the case of activated carbon surface treatment effect is no problem, but the production yield is drastically reduced.

The heat treatment of activated carbon may be carried out in a rotary kiln or a batch reactor, and other known means may be used if necessary.

6. Impregnation

The surface-modified activated carbon of the present invention can be used by itself or as an activated carbon precursor for depositing hydrophobic amino acid or vitamin-based additives. As a method of attaching the adhesive substance, methods known in the art may be used.

The surface-modified activated carbon of the present invention has a lower specific surface area than raw activated carbon, but has a large size and quantity of produced pores and changes to mesoporosity, thereby adsorbing gaseous substances such as benzene or toluene having a relatively high molecular weight. The performance is excellent.

In addition, since the specific surface area is reduced but the pore size and amount are increased and a hydrophobic surface is provided, it can be usefully applied to the adhesion of relatively high molecular weight of the hydrophobic amino acid series or vitamin series.

When the surface-modified activated carbon of the present invention is impregnated with a hydrophobic amino acid or vitamin-based impregnated substance, the hydrophobicity of the surface of the activated carbon increases, so that the adsorption ability of basic gas such as gaseous ammonia and aldehyde gas component such as acetaldehyde is higher. Is raised.

Therefore, the surface-modified activated carbon of the present invention can be widely used for the purpose of adsorbing gaseous harmful substances, including filters for air purification. When the surface-modified activated carbon of the present invention is added to an air purifying filter as an adsorbent, gaseous components such as basic gases, aldehyde gases, easily condensed acid gases, and volatile organic compounds, which are harmful substances contained in air, are adsorbed and removed. The ability to do it is very good. In particular, ammonia, acetaldehyde, acetic acid, formaldehyde and toluene can be effectively removed, and the removal efficiency to acetaldehyde is particularly excellent.

Hereinafter, the present invention will be described in more detail with reference to the following examples. These examples are illustrative of the invention and the scope of the invention is not limited thereto.

<Example 1>

As a raw material activated carbon, pellet activated carbon having an average diameter of 3 mm prepared from a coconut shell raw material by a steam activating method was used. The photograph of the raw activated carbon used is shown in FIG.

The activated carbon was immersed in a 3% citric acid aqueous solution at a temperature of 70 ℃ and then reacted for 6 hours and dehydrated.

The dehydrated activated carbon was immersed in 4% aqueous phosphoric acid solution, dehydrated, and dried in a rotary kiln equipment. At this time, the inside of the kiln was maintained at 300 ° C. under a general air atmosphere, and activated carbon was allowed to stay in the kiln for 1 hour.

After uniformly spraying the silica sol containing 90% silica in the treated activated carbon and aged for 6 hours at room temperature. At this time, silica was distributed on the surface of activated carbon at 2 to 4% by weight based on the weight of activated carbon.

Aged activated carbon was continuously heat-treated in rotary kiln equipment. In this case, the inside of the kiln was maintained at 900 ° C. under a general air atmosphere, and the activated carbon remained in the kiln for 4 hours to obtain surface modified activated carbon.

The photograph of the obtained surface modified activated carbon is shown in FIG.

< Comparative example  1>

Activated carbon was obtained in the same manner as in Example 1 except that the phosphoric acid treatment step was omitted.

The photograph of the obtained surface modified activated carbon is shown in FIG.

< Comparative example  2>

Activated carbon was obtained in the same manner as in Example 1, except that the silica sol treatment step was omitted.

The photograph of the obtained surface modified activated carbon is shown in FIG.

< Comparative example  3>

Activated carbon was obtained in the same manner as in Example 1, except that citric acid, phosphoric acid, and silica sol treatment steps were omitted.

Experimental Example 1

Yield measurement by surface modification

For the surface modified activated carbon obtained in Example 1 and Comparative Examples 1 to 3, the yield of the final surface modified activated carbon discharged relative to the weight of activated carbon injected into the rotary kiln was calculated according to Equation 1 below and the results are shown in Table 1 below. Indicated.

sample Weight (g) yield(%) Before reforming After modification Example 1 100 70 70 Comparative Example 1 100 80 80 Comparative Example 2 100 40 40 Comparative Example 3 100 5 5

In the results of Table 1, in the case of Comparative Example 3, the burnt phenomenon of the discharged activated carbon occurs in a whitened shape, so that the yield is drastically reduced, and processing conditions including the silica treatment step (Example 1, Comparative Example 1 ), The yield is 70% or more, but if the silicon treatment step is omitted (Comparative Examples 2, 3) it can be confirmed that the yield is 40% or less. This may be because the silica film formed on the surface of the activated carbon effectively blocked the access of oxygen in the air. In Comparative Example 2, which was not treated with silica, the coated phosphoric acid was converted to pyrophosphoric acid or metaphosphoric acid to partially block the contact of oxygen in the air, but the blocking effect was low, and the yield of the product was significantly reduced.

Experimental Example 2

Measurement of pH value change before and after activated carbon reforming

After treating the activated carbon having an average pH value of 10 to 11 by the method of Example 1 and Comparative Examples 1 to 3, the change in pH value was confirmed and the results are shown in Table 2 below.

sample pH value Before reforming After modification Example 1 10-11 4 ~ 5 Comparative Example 1 10-11 7-8 Comparative Example 2 10-11 4 ~ 5 Comparative Example 3 10-11 10-11

As a result, in Example 1 and Comparative Example 2, the pH value was weakly acidic, Comparative Example 1 was neutral, and Comparative Example 3 was not changed. This result shows that the surface modified activated carbon (Example 1, Comparative Example 2) including the step of treating with phosphoric acid seems to be influenced by the residual phosphoric acid by neutralizing or removing the basic substance of the raw activated carbon, and simply treated with silica alone. In the case of (Comparative Example 1), it appears that the raw activated carbon was neutralized in the treatment with citric acid.

Experimental Example 3

BET analysis

The BET analysis of surface modified activated carbon and raw activated carbon of Example 1 and Comparative Examples 1 and 2 was carried out to confirm the change in physical properties, and the results are shown in Table 3 below.

sample Specific surface area (m ² / g) Pore volume (cc / g) Average pore size (nm) Raw Material Activated Carbon 832 0.32 1.55 Example 1 810 0.54 2.98 Comparative Example 1 831 0.45 1.64 Comparative Example 2 802 0.52 2.92

In the results of Table 3, the surface-modified activated carbon can be seen that the specific surface area is slightly reduced compared to the raw activated carbon, but the pore volume is increased and the pore size is enlarged.

The pore distribution curve derived from the BET analysis result is shown in FIG. 7. In the graph of Figure 7, it can be confirmed that more than 2nm mesopores are developed through the heat treatment step according to the embodiment.

Experimental Example 4

Gas adsorption performance test

The gas adsorption performance of the raw activated carbon and the surface modified activated carbon were tested as follows.

The raw material activated carbon, the surface modified activated carbon of Example 1, Comparative Examples 1 and 2, the amino acid-impregnated raw activated carbon, and the amino acid-impregnated activated carbon of Example 1, Comparative Examples 1 and 2 were used. The adsorption performance of the gas was confirmed by three gas removal performance tests in which ammonia, acetaldehyde and acetic acid were simultaneously present in an acrylic chamber having a volume of 4 m ³ .

The amino acid-impregnated raw activated carbon and the amino acid-impregnated activated carbon of Example 1, Comparative Examples 1 and 2 were prepared as follows. 1 kg of activated carbon was immersed in 2 L of an aqueous solution containing 10% of aminobenozic acid, an amino acid series of 80 ° C., and dehydrated. After dehydration, the dried activated oven was dried at 110 ° C. for 12 hours to obtain impregnated activated carbon.

190 g of each sample was mounted in a deodorizing filter housing for an air cleaner, and then tested. First, three kinds of gas generated by bubbling using the bubbling port are injected into the chamber, and then, the fan is mounted in the chamber for 5 minutes to reflux the air to distribute the gas uniformly. Was analyzed. Thereafter, the air cleaner was operated for 30 minutes to remove the gas in the chamber, and after standing for 2 minutes, the final concentration was analyzed using a detection tube. Chamber test conditions were carried out in a laboratory in which constant temperature and humidity were maintained, and the temperature was maintained at 20 ° C. and the relative humidity was 50-60%.

 Degassing average performance was calculated by the air purifier performance test method conducted by the Air Cleaners Association as shown in Equation 2 below.

In addition, the removal efficiency (%) for each gas was calculated as in Equation 3 below.

The results are shown in Table 4 below.

sample Test gas removal efficiency (%) Degassing
Average performance (%) ammonia Acetaldehyde Acetic acid Before sticking Raw Material Activated Carbon 50 40 100 57.5 Example 1 100 50 98 74.5 Comparative Example 1 50 40 100 57.5 Comparative Example 2 100 50 95 73.75 After impregnation Raw Material Activated Carbon 50 70 95 71.25 Example 1 (adhesion) 100 95 95 96.25 Comparative Example 1 (Adhesion) 80 80 95 83.75 Comparative Example 2 (Adhesion) 100 95 95 96.25

In the results of Table 4, when the amino acid reagent is not impregnated, the ammonia removal performance in Example 1 and Comparative Example 2 is sharply increased and the removal performance is slightly increased in the case of acetaldehyde, but the difference is insignificant. The performance decreased, which seems to be due to the phosphoric acid treatment step.

In the case of the raw activated carbon impregnated with the amino acid reagent, the acetaldehyde removal performance was improved by the impregnated amino acid reagent, but the ammonia removal performance was not changed, even though the added amino acid reagent was a reagent having both acidic and basic activity. This may be due to the fact that acidic activity was consumed.

On the other hand, in the case of surface-modified activated carbon impregnated with an amino acid reagent, acetaldehyde removal performance was improved. In particular, in Example 1 and Comparative Example 2 including a phosphate treatment step, acetaldehyde adsorption performance was significantly increased with ammonia. This seems to be because the surface modified activated carbon plays a role in maintaining the activity of the amino acid reagent having acidic / basic amphoteric properties.

In the case of the activated carbon of Comparative Example 1, the adsorption performance of ammonia and acetaldehyde gas increased at the same time after the addition of the amino acid reagent. It is presumed that this is due to the progress of the oxidation process, which can be judged as the result of the neutralization and hydrophobicization of activated carbon surface.

Claims (12)

(a) immersing activated carbon in an aqueous solution of 1-5% organic acid, reacting at 60-80 ° C. for 5-7 hours, and then dehydrating to remove impurities in activated carbon;
(b) immersing the activated carbon in which the impurities are removed in an aqueous solution of 2-8% phosphoric acid for 1 to 3 hours, then dehydrating and drying for 1 to 4 hours at 300 to 400 ° C. to form a coating film on the surface of the activated carbon;
(c) spraying a silica sol solution containing 80 to 90% silica on the surface of the activated carbon on which the coating film is formed, and then aged at room temperature for 5 to 7 hours to coat silica on the surface of the activated carbon to form a double coating film. Making; And
(d) heat treating the activated carbon having the double coating film formed at 800 to 1,000 ° C. for 1 to 4 hours under general air conditions, and hydrophobizing the surface. The method of claim 1,
The coating of the silica is characterized in that for coating 2 to 4% by weight of silica based on the weight of the dried activated carbon, surface modification method of activated carbon. delete delete delete The method of claim 1,
The organic acid is a surface modification method of activated carbon, characterized in that at least one selected from citric acid, acetic acid, oxalic acid, tartaric acid and benzoic acid. The method according to any one of claims 1, 2 and 6,
After the heat treatment, the surface-modified activated carbon further comprises the step of attaching a hydrophobic amino acid series or vitamin-based adherent material, characterized in that the surface modified method of activated carbon. The organic carbon is treated with activated carbon to remove impurities, the surface is treated with phosphoric acid to form a coating film, and silica is coated to form a double coating film, which is obtained by heat treatment at 800 to 1,000 ° C. for 1 to 4 hours in a general air atmosphere. Surface modified activated carbon. delete delete delete The method of claim 8,
Surface-modified activated carbon, characterized in that the impregnated with a hydrophobic amino acid or vitamin-based impregnated material after the heat treatment.