Technical Field This invention relates to metal-deposited active carbon having selective adsorption capability for polar contaminants and preparation method thereof. More specifically, this invention relates to copper, nickel or silver-deposited active carbon having selective adsorption capability for NOx and SOx and preparation method thereof.

Background Art More industrialized societies produce sophisticated air pollution and other contaminants. In this regard, interests are increasing in eliminating various contaminants properly and in development and application of active carbon as adsorption materials. Air contaminants include solid types such as dust and coal waste and SO2, S03, S203 (hereinafter referred to as SOx), and Ozone, CO2, volatile hydrocarbon compounds and NO, NO2, N03 (hereinafter referred to as NOx).

Such contaminant as SOx and NOx are yellowish brown colored gas known as one of main factors of causing warm up of earth temperature and photochemical smog and of promoting environmental hormone to harm ecological adaptation. These air contaminants are very polar organic compounds that result from incomplete combustion of automobiles, power stations, incinerators and boilers. Current methods to remove SOx and NOx from exhaust gas are selective catalytic reduction (SCR) and

selective Non-catalytic reduction (SNR), etc.

Active carbon is effective adsorption material due to well-developed specific surface area and pore structure. Therefore, it is used for purifying polluted and wastewater, and for purifying harmful exhaust gas from incinerator and chemical process facilities, and for decolorization and deodorization in food and beverage industry, and for removing small amount of harmful gas at semi-conductor, electronic industry.

However, though active carbon has high specific surface areas and various pore structures, it has not been used for removal of SOx or NOx as efficient materials.

Adsorbing and eliminating technologies of various environmental contaminants with adsorbent having polarity are very much dependent upon physical adsorption of pore structures and chemical characteristics of its surface. Present known technologies to give polarity to the adsorbent surface are impregnation of acid and alkali solutions at room temperature, introducing oxygen functional groups by ozone and oxygen treatments at high temperature, surface treatments by electrolytic process in acid and alkali solutions, oxidizable metal catalyst methods, and so on. But it is not yet reported like this invention to give polarity to the surface of active carbon by electroless plating process of alkalic transition metals of Cu, Ni and Ag.

Existing adsorbent plated with metal ion was used to treat heavy metal-polluted water and waste water from mine and industrial complex areas, but there is limited metal materials which can be used for plating due to surface characteristic of adsorbent itself and is

generally used to adsorption and removal in liquid phases. Moreover, there was disadvantage of ineffective performance as adsorbent due to metal ion.

Disclosure of the invention This invention is based on the fact that adsorptive selectiveness can be improved a lot by various surface treatments of active carbon having high specific surface area and developed pore structure, as the result of continuous research and development on separation and elimination technology of air contaminants of SOx and NOx using activated carbon fiber or active carbon.

This invention is to implement functional groups to the surface of active carbon throughout electroless plating of alkalic transition metals of Cu, Ni and Ag. Therefore, it simultaneously imparts polarity to carbon surface with increased dissociation energy and degree of surface activation. Finally, this invention provides high performing active carbon having selective adsorption capability for main contaminants of SOx and NOx in gas and liquid phase and polar organic and inorganic contaminants, as well.

Hence, this invention is to provide the most effective active carbon to the following products or purposes; eliminating exhaust gas and dust collector of incinerator and boiler, Removing air contaminants of motor vehicles, harmful gas from manufacturing plant of precision equipment, polluted and waste water treatment process, military and industrial masks, air cleaner for office and residential area.

This invention is to provide active carbon having selective adsorption capability to the polar contaminants by electrolessly plating active carbon in the solution of selected alkali transition metals, Cu, Ni, Ag and reducing agent.

Active carbon means not only solid type or powder but activated carbon fiber in this invention. Also activated carbon fiber from this invention can be used as filtration fabrics.

The most suitable aqueous solutions of transition metals is that of CuSo4 NiCl2 or AgNO3. It is desirable to use ethylenediamine triacetate (EDTA) formaldehyde (HCHO) or their compounds for CuSo4, NaH2po.-,.

NH4Cl or their compounds for NiCl2, and formalin for AgNO3 as a reducing agent.

Desirable plating time of electroless plating is 5-60 minutes each. If plating time is less than 5 minutes, there is not sufficient plating to the active carbon, which will lead to less development of surface polarity, so that active carbon has no sufficient capability of selective adsorption continuously. If plating time is more than 60 minutes, there is surplus plating treatment to the metal element, which will lead to reduce adsorption specific surface area and pore structure of active carbon surface.

Also, desired temperature for the plating bath is 20~100C. If the temperature is less than 20C, there is no sufficient reduction reaction by reducing agent and the plating metal can not sufficiently be plated to the active carbon surface, so that there is insufficient constant selective adsorption due to less developed

surface polarity. If more than 100°C, there happens insufficient plating due to decomposition of plating solution by vaporizing of solution.

According to analysis of element of active carbon by electroless plating process of alkalic transition metal, it is desired to have 1-10% amount of each element of metal. If the amount of element of metal is less than 1%, plating metal can not sufficiently be plated to the active carbon surface, so that there is insufficient constant selective adsorption by less developed surface polarity. If more than 10%, there is surplus thick plating, which reduce developed pore structure on the active carbon surface and adsorption surface area.

Usually, element metal for electroless plating is desired to use alkalic transition metal such as Cu, Ni and Ag. These alkalic transition metals tend to have high reducing potential, so that it is well plated to the target object in the ion state by reducing agent. Therefore, there is stable constant selective adsorption by plated element metal.

Precise explanation of this invention depends upon different types of transition metals.

Brief Description of the Drawings Fig. 1 illustrates NOx Conversion rate of active carbon which is plated electrolessly with Cu by this invention.

Fig. 2 illustrates SOx Conversion rate of active carbon which is plated electrolessly with Cu by this

invention.

Fig. 3 illustrates NOx Conversion rate of active carbon which is plated electrolessly with Ni by this invention.

Fig. 4 illustrates SOx Conversion rate of active carbon which is plated electrolessly with Ni by this invention.

Fig. 5 illustrates NOx Conversion rate of active carbon which is plated electrolessly with Ag by this invention.

Fig. 6 illustrates SOx Conversion rate of active carbon which is plated electrolessly with Ag by this invention.

Mode for carrying out this invention According to the following examples for the plating method, about pH 12 alkalic solution is used as an electroless copper plating solution the basic composition of electroless copper plating solution is 1. OM of CuS04 solution with 2: 1 mole ratio of EDTA and HCHO, as a reducing agent respectively. At this time, bipyridyl and tetradiano nickel (II) acid kalium is added 10mg/l to prevent decomposition reaction in the high temperature.

The basic composition of electroless nickel plating solution is 1.0 M of Nicol, solution with 1: 5 mole ratio of NaH2PO2 and NH4Cl as a reducing agent which makes pH 9 alkalic nickel plating solution.

Also, the basic composition of electroless silver plating solution consisting of 0.2 M of AgNO3 and some of ammonia is mixed with 200mQ distilled water and 40mQ formalin as a reducing agent as molar ratio of 5: 1. % is weight percentage in this Specification if not otherwise mentioned.

Example 1 Active carbon for liquid phase treatment (12 x 30mesh size, over 1500m2/g specific surface area produced by Dong-Yang Carbon Co., Ltd. of Korea) is used for electroless copper plating. For electroless copper plating, the basic electroless copper plating solution is 1. 0 M of CuSo4 aqueous solution added by 2: 1 mole ratio of EDTA and HCHO as a reducing agent. Bipyridyl and tetradiano nickel (II) acid kalium is also added by lOmg/1 to prevent decomposition reaction in the high temperature. The solution becomes about pH12.

Active carbon is dipped into copper plating solution for about 5 minutes at 20C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and content of plated copper element.

As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 1% of the treated active carbon. Figure 1 and 2 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 35% and that of SO by over 130% 7 hours after treated active carbon is placed in the air, respectively.

Example 2 For electroless copper plating, the basic electroless copper plating solution is same as Example 1.

Active carbon is dipped into the solution for about 15 minutes at 40C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and amount of plated copper element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 3% of the treated active carbon. Figure 1 and 2 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 210% and that of SO by over 210% 7 hours after treated active carbon is placed in the air, respectively.

Example 3 For electroless copper plating, the basic electroless copper plating solution is same as Example 1.

Active carbon is dipped into the solution for about 30 minutes at 60C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and amount of plated copper element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 5% of the treated active carbon. Figure 1 and 2 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 280% and that of SO by over 280% 7 hours after treated active carbon is placed in the air, respectively.

Example 4 For electroless copper plating, the basic electroless copper plating solution is same as Example 1.

Active carbon is dipped into the solution for about 45 minutes at 80C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and amount of plated copper element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 7% of the treated active carbon. Figure 1 and 2 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 520% and that of SO by over 440% 7 hours after treated active carbon is placed in the air, respectively.

Example 5 For electroless copper plating, the basic electroless copper plating solution is same as Example 1.

Active carbon is dipped into the solution for about 60 minutes at 100C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and amount of plated copper element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 10% of the treated active carbon. Figure 1 and 2 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 490% and that of SO by over 370% 7 hours after treated active carbon is placed in the air, respectively.

Example 6 Active carbon for gas phase treatment (4 x 8mesh size, over 1000 m'/g specific surface area produced by Dong-Yang Carbon Co., Ltd. of Korea) is used for electroless nickel plating. For electroless copper plating, the basic electroless copper plating solution is 1.0 M of NiCl2 and is added by 1: 5 mole ratio of NaH2PO2 and NH4CI to be pH 9. Active carbon is dipped into the nickel plating solution for about 5 minutes at 20C. Table 1 illustrates specific surface area and iodine adsorption amount according to treated active carbon and amount of plated nickel element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 1% of the treated active carbon. Figure 3 and 4 show conversion rate of SO and NO in the air, respectively.

It shows that conversion rate of NO is increased by over 10% and that of SO by over 150% 10 hours after the treated active carbon is placed in the air, respectively.

Example 7 The basic plating solution for electroless nickel plating is same as Example 6. Active carbon is dipped into the solution and plated for about 15 minutes at 40C.

Table 1 illustrates specific surface area and iodine adsorption amount of treated active carbon and contents of plated nickel element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 3% of the treated active carbon. Figure 3 and 4 show conversion rate of SO and NO in the air, respectively. It shows

that conversion rate of NO is increased by over 50% and that of SO by over 320% 10 hours after the treated active carbon is placed in the air, respectively.

Example 8 The basic plating solution for electroless nickel plating is same as Example 6. Active carbon is dipped into the solution and plated for about 30 minutes at 60C.

Table 1 illustrates specific surface area and iodine adsorption amount of treated active carbon and contents of plated nickel element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase but the amount of copper of treated active carbon is about 5% of the treated active carbon. Figure 3 and 4 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 100% and that of SO by over 500% 10 hours after the treated active carbon is placed in the air, respectively.

Example 9 The basic plating solution for electroless nickel plating is same as Example 6. Active carbon is dipped into the solution and plated for about 45 minutes at 80C.

Table 1 illustrates specific surface area and iodine adsorption amount of treated active carbon and contents of plated nickel element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 7% of the treated active carbon. Figure 3 and 4 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 340% and

that of SO by over 610% 10 hours after the treated active carbon is placed in the air, respectively.

Example 10 The basic plating solution for electroless nickel plating is same as Example 6. Active carbon is dipped into the solution and plated for about 60 minutes at 100C. Table 1 illustrates specific surface area and iodine adsorption amount of treated active carbon and contents of plated nickel element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 10% of the treated active carbon. Figure 3 and 4 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 160% and that of SO by over 560% 10 hours after the treated active carbon is placed in the air, respectively.

Example 11 Active carbon fiber with specific surface area over 2500 mVg is made by carbonizing PAN (Polyacrylonitrile) produced by Tae-Kwang Industrial Co., Ltd. of Korea, at 1000C under the atmosphere of N2 and activation at 900 C under CO2 atmosphere and is then silver plated by electroless plating. For the electroless silver plating, the basic silver plating solution consisting of 0.2 M of AgNO3 and proper amount of ammonia is added by formalin solution consisting of 200mu distilled water and 40mQ formalin as reducing agent on the volume ratio 5: 1 of the basic silver plating solution to the formalin solution. Active carbon is dipped into silver plating solution for about 5 minutes at 20C. Table 1

illustrates specific surface area and iodine adsorption amount according to plated activated carbon fiber and amount of plated silver element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 1% of the treated active carbon. Figure 5 and 6 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 100% and that of SO by over 80% 20 hours after the activated carbon fiber is paced in the air, respectively.

Example 12 The basic plating solution is same as Example 11.

Active carbon is dipped into and plated for about 15 minutes at 40C. Table 1 illustrates specific surface area and iodine adsorption amount according to plated activated carbon fiber and amount of plated silver element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 3% of the treated active carbon. Figure 5 and 6 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 140% and that of SO by over 200% 20 hours after the plated fiber is placed in the air, respectively.

Example 13 The basic plating solution is same as Examplell.

Active carbon is dipped into and plated for about 30 minutes at 60C. Table 1 illustrates specific surface area and iodine adsorption amount according to plated

activated carbon fiber and amount of plated silver element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 5% of the treated active carbon.

Figure 5 and 6 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 230% and that of SO by over 320% 20 hours after the plated fiber is placed in the air, respectively.

Example 14 The basic plating solution is same as Examplell.

Active carbon is dipped into and plated for about 45 minutes at 80C. Table 1 illustrates specific surface area and iodine adsorption amount according to plated activated carbon fiber and amount of plated silver element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 7% of the treated active carbon.

Figure 5 and 6 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 510% and that of SO by over 450% 20 hours after the plated fiber is placed in the air, respectively.

Example 15 The basic plating solution is same as Example 11.

Active carbon is dipped into and plated for about 60 minutes at 100C. Table 1 illustrates specific surface area and iodine adsorption amount according to plated activated carbon fiber and amount of plated silver

element. As a result, there is no significant change of BET specific surface area and iodine adsorption amount in liquid phase, but the amount of copper of treated active carbon is about 10% of the treated active carbon.

Figure 5 and 6 show conversion rate of SO and NO in the air, respectively. It shows that conversion rate of NO is increased by over 360% and that of SO by over 370% 20 hours after the plated fiber is placed in the air, respectively.

Every electroless-plated active carbon is used after it was washed 2-3times with distilled water and dried over 12 hours in the 100 C oven. The following table shows specific surface area, iodine adsorption capability and content of plated metal element for plated active carbon in above examples and untreated active carbon.

Measurement of BET specific surface area : The amount of adsorption according to concentration increase is measured with nitrogen as adsorptive gas by taking about 0.2g specimen under-196C of liquid nitrogen and P/Po (P; partial pressure, Po; saturated vapor pressure) shows linear against partial pressure in the range of From this, specific surface area of BET and volume of micro pore are measured.

Measurement of iodine adsorption capability According to ASTM D4607, residual concentration of iodine within the solution and amount of adsorptive iodine at each of weight specimen are measured. From this, the adsorptive capability is decided as iodine adsorption amount when residual concentration is 0.02 N. Before the above measurement, 5 wt% HC1 solution, 0.100N sodium thiosulfate solution, 0.1000. 001 N standard

iodine solution and 0.100 N iodine acid kalium solution is prepared and used after standardization. 0.1,0.3, 0.5 and 1.0 g of specimens are put into triangle flask, 10ml of 5 wt% HC1 solution is added into same flask, heated for 30 seconds slowly and then 50ml of standard iodine solution is added into same flask. Filtrate solution is titrated by 0.100 N sodium thiosulfate, after shaking for 15-20miniutes in the room temperature.

Amount of absorptive iodine mg is measured to be titrated until yellow color of iodine is disappeared.

Measurement of conversion rate of SOx and NOx : For measuring conversion rate of SOx and NOx, specimens are put into quartz tube of 4mm inner diameter to reach 10 mm high and heated for 30 minutes at 300C. After that, gas concentration of SO2 and NO2 which emitted and passed at the speed of 60cm3/min inside of tube at the atmosphere state, is measured by SOx/NOx meter (EcomS A plus, ECOM America Ltd). At this time, each emitted gas concentration is measured by conversion rate of SOx and NOx.

[Table 1] BET Iodine Alkalic NOx SOx Specif Adsorpt Transitio Conversi Conversi ic ion n metal's on Rate on Rate Surfac Capabil element (at (at e area @ity content 20hrs) [m2/g] [%][%][%] Untreated Active carbon for 1560 1644 0 7.5 8.3 (examples examples 1.0 Example 1 1556 1675 10.0 19.8 (Cu/C) 2.9 Example 2 1548 1573 19.3 30.0 (Cu/C) 4.9 Example 3 1546 39.730.1 (Cu/C) 6.9 Example 4 1545 1562 55.3 59.1 (Cu/C) 9.8 Example 5 1441 43.348.3 (Cu/C) Untreated active carbon for 1050 1087 0 6. 3 10. 1 gas phase (examples 6#10) 1.0 Example 6 1000 1077 11.3 17.4 (Ni/C) 3.1 Example 7 995 1072 21.2 33.7 (Ni/C) 4.9 Example 8 990 1065 44.5 (Ni/C) 7.0 Example 9 990 1058 79.3 64.1 (Ni/C) 9.9 Example 10 880 947 44.8 53.8 (Ni/C) Untreated active carbon fiber 2533 2522 0 8.3 12.3 (examples11# 15) 1.0 Example 11 2523 2567 18.7 24.1 (Ag/C) 2.9 Example 12 2512 2565 36.4 (Ag/C) 4.9 Example 13 2505 2561 30.8 50.7 (Ag/C) 6.9 Example 14 2491 2505 54.5 64.9 (Ag/C) 9.9 Example 15 2350 2387 58.2 (Ag/C) Table shows average of measurements in each Example.

Industrial Applicability When we compare active carbon of this invention with non-treated active carbon, there is no significant physical change in pore structure and adsorption specific surface area. As a result, there is no significant change of iodine adsorptive capability in liquid phase. But, it is proved that conversion rate against NOx and SOx is highly improved by outstanding development of surface polarity by the plated metal element. Among the examples, electroless-copper-plated active carbon according to increase of content of copper element shows that conversion rate of NO is increased by minimum 1.3 to maximum 6.2 times and the conversion rate of SO is increased by the minimum 2.3 to maximum 5.4 times than non-treated active carbon after 7 hours passed. Electroless nickel plated active carbon shows conversion rate of NO is increased by minimum 1.1 to maximum 4.4 times and the conversion rate of SO is increased by the minimum 2.5 to maximum 7.1 times than non-treated active carbon after 10 hours passed. Electroless silver plated active carbon shows conversion rate of NO is increased by minimum of 2.0 to maximum of 6.1 times and the conversion rate of SO is increased by minimum of 1.8 to maximum of 5.5 times than non-treated active carbon after 20 hours passed. From above invention, high functionality active carbon with having selective adsorption capability by electroless plating of alkalic transition metal is manufactured, without changing capability of adsorption for the contaminants of SOx and NOx at gas phase which have comparative polarity. It is possible to set up far better economical process because electroless-plating method in the present invention does not need electricity unlike an electrolytic plating method.