DE2335297C3 - Process for enhancing the chemisorption capacity of carbon towards gases - Google Patents

Description

In industry, adsorption is used to a great extent in a wide variety of processes physical adsorption more common. Chemical adsorption or chemisorption is more specific than physical adsorption. A large area of application for chemisorption is the use of Activated carbon in gas masks.

To increase the sorption capacity, especially the chemisorption of activated carbon in gas masks and air filters, it is already known to treat these active carbon with heavy metals such as copper, chromium, silver, zinc, Impregnate cobalt, manganese and molybdenum.

When a toxic substance is caught by an impregnated carbon filter, the following can occur:

1. Physical sorption, with chloropicrin as a typical example;

2. Chemisorption, for which as a typical example Phosgene, cyanochloride and hydrocyanic acid should be mentioned; and

3. Catalytic reaction, a typical example of which Is arsine.

The capacity of a filter for toxic gases is determined by saturating a standard amount with one Air flow measured, which contains a certain concentration of a poisonous gas. The penetration time (min) is a measure of the capacity and can be expressed as min / mi, i.e. H. in minutes per milliliter Filter mass, are expressed.

It is common practice to use cyanochloride for this test. The retention of cyanide through Impregnated activated carbon is a typical chemisorption process. The absorption capacity of carbon against this gas gives a measure of its power to hold on to other poisonous gases, e.g. B. from Hydrocyanic acid, by chemisorption.

For qualification testing for filters to be used in air-raid shelters (Dräger room ^r ilter), following typical conditions are applied:

\ dsorption of cyan chloride. 0.3 kg / 25 l carbon;
Adsorption of hydrogen cyanide: 0.3 kg / 25 l carbon.

This corresponds to 12 mg / n carbon for each of these gases. In the method according to the invention result according to table 2, experiment no. 1: 0.18 min / m corresponding to 13 mg / ml carbon.

Among these poisonous gases, typical war gases are removed by chemisorption, such as cyanochloride, chloropicrin, phosgene, hydrogen cyanide, mustard gai and arsine, as well as the nerve gases "sarin" and "taburine". Some of these gases are also found in industrial waste gases, from which SO ₂ , NO 2 and the like are also removed by chemisorption

The invention of SO ₂ by sorption on activated carbon has been known for a long time. As a result of the stringent requirements for the removal of SO 2 which have been established in many countries in recent years, the importance of sorption has increased, as methods such as the use of gas scrubbers are commonly used are not very effective at low concentrations of less than 100 ppm. In those cases in which regeneration means higher costs or special difficulties, sorption without regeneration can definitely be an advantage. In this case, the strengthening of the original sorption capacity would be particularly important.

The use of chemisorption is of course not limited to the removal of toxic gases, but it can also be used for gas separation, and due to its high selectivity even for gases, soft are not considered poisonous.

Regarding the composition of the impregnation materials and the impregnation process are only extreme Sparing information is available, as it is often within the framework of industrial or military secrecy fall.

In German Auslegeschrift 10 87 579, the following mixture is used for impregnating 100 kg Coal grains suggested:

Basic copper carbonate 6 kg Ammonium carbonate 5 kg Ammonia (25%) 101 Potassium dichromate 3 kg Silver rite 0.17 kg water 59.51

Activated carbon impregnated with such a mixture provides particularly good protection against poisonous substances Gases such as hydrogen cyanide and cyanochloride.

From French patent specification 15 75 501 it is already known that by impregnation of activated carbon with copper chromate in the presence of ethylenediamine and pyridine a very high sorption capacity for cyanochloride is achieved. Be in the patent specification Cited copper and chromium contents of 1.9 and 1.3%, respectively.

It is also known that the properties of solids can be changed by very strong irradiation. For example, in the Zeitschrift für physical Chemie (Frankfurt), 72 (No. 1-3-1970), p. 44, it is shown that the irradiation of a catalyst such as that used for the hydrogenation of carbon monoxide in the Fischer-Tropsch process is reduced its efficiency with a Co ⁶⁰ gamma radiation source. The process known from US Pat. No. 32 17 032, in which activated carbon is used in the production of vinyl esters, which for the purpose of activation with high-energy radiation (electron beams, gamma rays), also belongs in this context.

radiation) and then impregnated with metal compounds. That also the chemisorption carbon already impregnated with metal compounds can be improved by gamma radiation can not be derived from these known measures derive.

Electron irradiation of ZnO and MgO catalysts after heat treatment results in a higher Co2 sorption capacity for ZnO, but not for MgO (see Izv. Akad. Nauk, Kaz. SSR, Ser, Fiz-Mat 2 [No. 2-1971] p. 56).

From British patent specification 12 30950 it is known _{to adsorb O2 on SiO 2} and bentonite while the material is being irradiated.

The neutron irradiation of a material containing carbon, sets the adsorption capacity for benzene at 2O ⁰ C down (see Fig. Constr. Mater. Ons. Grafita No. 5-1970).

The invention now has the task of specifying a method by means of which the chemisorption capacity of carbon with respect to gases can be increased, in which the carbon is impregnated with one or more metal compounds for the purpose of adsorbing toxic gases and industrial waste gases.

To solve this problem, the invention proposes essentially, the impregnated activated carbon before To irradiate chemisorption with gamma rays to an intensity of at least 1 Mrad.

Experiments have shown that an irradiation of impregnated activated carbon for gas masks with gamma rays a much higher chcmisorptive capacity (min / ml filter mass) results, which is quite surprising is. The ability to retain chloropicrin, which is typical for physical adsorption, increased but not because the sorption capacity of carbon for chloropicrin was the same as before Irradiation.

According to a special feature of the invention, the carbon is irradiated in a nitrogen atmosphere. For reasons as yet unknown, it appears that in order to achieve increased chemisorption by irradiating carbon nitrogen is required.

Most of the experiments conducted within the scope of the invention have impregnated carbon of the type »ASC-12 χ 30, Pittsburg Activated Carbon«, a product from Chemviron. Carbons have been used in various amounts contained of impregnating substances, which are hereinafter referred to as type A and type B. The Type A kept in an open drum for two or three years, while Type B dated Manufactured fresh in a sealed container.

In both cases the impregnating agents consisted of basic copper carbonate, silver nitrate and chromium oxides in addition to ammonia.

An analysis of these impregnating substances showed that type A was somewhat less productive than type B, see Table!.

Table 1

Type a

Type B

To. % Total
"r,% total

5.4 to 7.0
2.0 to 2.1

6.2 to 7.8
2.4 to 2.6

A more detailed explanation of the invention emerges from the following description of some exemplary embodiments.

example 1

Type A activated carbon impregnated with 7.0% Cu, 2.1% Cr and 0.05% Ag was irradiated with gamma rays for 50 hours, resulting in a radiation amount of 43 megarads (Mrad) or a radiation amount of 725 kilorads / h. A sealed polyethylene bottle of 150 m! Granules of this carbon were placed in the radiation field. Their distance from the radiation source was 6 cm. Dry air was used as the irradiation atmosphere, specifically at a temperature of about 20 ^° C. The grain size of the granules corresponded to 0.59 mm (78%) and 0.42 mm (21 ^° Jo) (between 50 and 35 meshes). Cobalt 60 was used as the radiation source. Two gamma quanta with energies of 1.33 Mev and 1.17 Mev resulted from decay.

At the beginning of the experiment, the activity of the radiation source was 32,300 Curie. It consisted of seven cylindrical rods each 20 cm long, which were arranged horizontally. The amount of radiation was checked with a Friecke dosimeter.

After the irradiation, the carbon was stored in a polyethylene container for about 48 hours before being has been tested for cyanochloride sorbability.

The irradiated granulate (76 ml) was filled into a filter container. Cyan chloride gas was then introduced into the filter in an amount of 72 ± 3 mg of gas in 301 dry air / min. This mixture was thermostatically controlled ^{to 18 ± 0.5 ° C.} The penetration time (min) for cyan chloride is a measure of filter performance or filter capacity. The permeation time is referred to herein as the time elapsed from the moment cyanochloride was added to the filter inlet to the moment the gas could be detected at the filter outlet.

In the present case, the penetration time was measured to be 20.5 minutes. The filter capacity can be expressed as Define the penetration time per unit volume of the filter material. For the amount irradiated, this would be mean a value of 0.27 min / ml. The sorption capacity of the original non-irradiated product was measured to be 0.18 min / ml.

In order to detect the penetration of cyan chloride, V _{6 of} the air flow was passed over a trough which contained an indicator solution. The vertical distance between the filter outlet and the trough was 2 cm. The trough contained 0.5 ml of fresh Dimedon solution, which was prepared as follows: 1 mg of dimethyldehydroresorcinal was dissolved in 90 ml of pyridine and then 10 ml of distilled water was added. The indicator consisted of 0.5 ml of this solution. The penetration of cyan chloride colored this solution scarlet. The penetration time was determined by the moment at which this staining had occurred in 20 seconds, the color intensity then being identical to the scarlet color of a standard solution. This standard solution contains 0.15 mg of "Sudan" red and 0.12 mg of parrot toner, dissolved in 100 ml of pyridine.

Example 2

A number of tests were carried out under the same general test conditions as in Example 1

performed, with the exception that the radiation dosage changed from 1 to 100 Mrad. The terms and results are in below Table 2 laid down

Table 2

Cyan chloride sorption capacity of gamma-irradiated »ASC activated carbon, type A«

Experi dosage Irradiation Relative Filter volume Permeable capacity Capacity ment the gamma the atmosphere humidity life time profit*) Irradiation No. (Mrad) (%) (O / o) (min) (min / ml) (%) 1 0 0 61 11.0 0.180 2 1 air 0 68 14.0 0.205 6.2 3 5 air 0 72 16.0 0.223 15.5 4th 10 air 0 65 15.5 0.239 23.8 5 43 air 0 76 20.5 0.270 40.0 6th 100 air 0 65 18.0 0.277 43.5

Capacity gain compared to non-irradiated material, experiment no. 1.

Example 3

Experiments analogous to those according to Example 1 and 2 were with impregnated carbon with something higher Cu-Cr content carried out in percentages

Table 3

the impregnation mixture corresponded to type B carbon, Table 1. The conditions were im otherwise the same as in Example 2. The precise conditions and results are shown in the table below 3.

Cyan chloride sorption capacity of gamma-irradiated »ASC activated carbon, type B«

Experi dosage Irradiation Relative Filter volume Permeable capacity Capacity ment the gamma the atmosphere humidity life time profit*) Irradiation No. (Mrad) (%) (%) (min) (min / ml) (O / o)

1 0 air 0 65 11.5 I. 0.238 0 2 20th . air 0 68 16.5 0.242 1.6 3 40 air 0 70 18.0 0.256 7.5 4th 43 air 0 76 24.0 0.316 32.8 5 75 air 0 68 26.0 0.384 61.2 6th 100 air 0 67 27.0 0.400 68.2 *) Cape: Equal to not irradiated Material. Attempt no. acity gain in Ve

Example 4

Gas mask filter with a volume of 180 ml in the manufacturer's packaging and through aluminum foil isolated, were irradiated with a Co ^ radiation source.

The filters were impregnated activated carbon. The impregnation material contained Cu 4.9%, Cr 3.3%, Ag 0.04%.

Table 4

Following the irradiation, the filters were tested for cyanochloride sorption capacity. The test conditions were the same as in Example 1 with Except that the moisture content was kept at 75% room humidity. Table below 4 shows the test conditions and results as well as the results with non-irradiated filters.

experiment

dosage
of gamma irradiation
(Mrad)

Irradiation atmosphere

Relative
humidity

(o / o)

Filter volume

Permeability time

(min)

capacity
(min / ml)

Capacity gain *)

(o / o)

1 0 air 75 180 72 0.400 0 2 50 air 75 180 79 0.439 9.7 3 100 air 75 180 84 0.466 16.6

Kiipa / .itiitspcwinn compared / um iinbcsirahltcn Oiu'iiüiliiliur. Kxnerimcni No. 1.

Example 5

Table 5 shows how the atmosphere at the irradiation stage increases the cyanochloride sorbability of the impregnated carbon influenced (min / ml filter mass). All samples were irradiated with a radiation dose of M) Mrad. Before the irradiation

Table 5

all samples were flushed with the gas in question for 0.5 h.

As the table below shows, he ;; starting with the irradiation of carbon in a nitrogen atmosphere the adsorption of cyan chloride has the greatest capacity gain.

Experi dosage Irradiation Relative Filter volume Permeable capacity Capacity ment the gamma the atmosphere humidity life time profit*) Irradiation No. (Mrad) (%) (%) (min) (min / ml) (%) 1 0 air 0 61 11th 0.18 0 2 50 Hey 0 65 11th 0.17 0 3 50 Ο2 0 69 12.5 0.18 0 4th 50 air 0 68 17.5 0.25 38.9 5 50 N2 0 72 19.5 0.27 50

*) Capacity gain compared to / u unirradiated material. Experiment no.

Example 6

Active charcoal granules of type A, Table 1, were irradiated at 50 Mrad in a steel container. The container with the activated carbon was previously evacuated to about 0.1 mm Hg pressure at room temperature for about 20 minutes, after which pure nitrogen gas (99.9%) was poured into the container to bring the pressure back to one atmosphere. The container was then ^{exposed to gamma irradiation (CO 60} ) in the manner described in Example 1. The temperature during this irradiation was about 2O ⁰ C. After the irradiation, the activated carbon in a polyethylene bottle in Stickstoffatmo sphere was transferred and long maintained there for about three days before they re cyanide gas was tested for its adsorption capacity.

A 79 ml sample of the irradiated granulate (12 × 30 mesh) was placed in a filter container with an area of 30 cm ² . Air was introduced into this filter at a rate of 30 l / min. The concentration of hydrogen cyanide in this air was 1.38 mg / l. The relative humidity was about 75%, corresponding to a dosage of 340 to 360 mg H ₂ 0 / min. This gas mixture was kept at 18 ± 0.5 ° C by thermostatic control. The penetration time was determined as in Example 1

In the present case, the measured penetration time was 33 minutes than the retention capacity through chemisorption of hydrocyanic acid (mg) per unit volume of the filter mass determine. This leads to 173 mg HCN / mL The capacity in relation to the irradiated original product was measured in the same way, and the result was a value of 16 mg HCN / nd, what means that the irradiation of the granulate increased the adsorption capacity by 8.1%.

The determination of the permeability of the pitcher with respect to hydrogen cyanide was carried out in the manner that the gas escaping from the filter was passed on to filter paper tires, which were previously with A solution was moistened, which is the same Vohanenteflen 0.28% Knpferacetat and Benädmazetat contained, colored hydrocyanic acid escaping from the filter the filter paper blue.

The concentration of hydrogen cyanide in the gas stream is measured by the fact that the gas stream before the Filtering was passed through an absorption tower containing one liter of a solution of 54 g of HgCb and Contained 72 g of KBr in distilled water. This solution was 1 ml of 0.2% methyl red in 60% ethanol and 3 ml 0.1% bromocresol green in 20% ethanol added. In addition, a few ml of 0.1 normal soda lye were used added. This complex mixture would be colored wine-red by hydrogen cyanide gas. Once this occurred, a stopwatch was switched on while at the same time a certain amount N of 0.1 normal Soda lye was added. The stopwatch was stopped as soon as the staining turned wine red again turned over and read the stopped time.

The hydrogen cyanide concentration C (mg / m ³ of gas) is calculated using the following formula:

_ NH-27000,. ₃ .
C = γ- (mg / m ³ ).

H = concentration of soda lye (mol / 1),
N = volume of the soda lye (ml),
V = air speed (l / min),
t = time (min).

The measurements of the hydrogen cyanide concentration were taken before and after the filter capacity was checked accomplished. The mentioned concentration of 1.38 mg / ml was therefore the average value of both Measurements.

Example 7

Activated carbon impregnated with potassium carbonate accordingly a potassium content of about 14% was with a gamma radiation in an amount of 40 Megarad irradiates Die Radstrahlungscjueile and the Amounts were the same as in Example 1. Jane 40 ml sample of this charcoal granulate was made into one Nitrogen atmosphere in a polyethylene ash at a temperature of about 20 ° C

The grain size of the granulate, which was the type "Dräger E 90G" for use in gas masks, corresponded to 1.2 mm (50% by volume) and Ij «in {50% by volume).

After irradiation, the charcoal was about 72 Ii in

709 614/237

ft

left in a nitrogen atmosphere in the container. It was then checked for its ability to adsorb SO _2.

The granules (40 ml) were poured into a filter glass container under thermostatic control. The: layer was 6.6 cm high and the filter cross-section was 6.0 cm ² . _{103.4 mg of SO 2} gas mixed with 151 of dry nitrogen gas (99.9% purity) were introduced into the filter every minute. This corresponds to an SO ₂ concentration of 0.25% by volume. This is a typical amount of pollution in gaseous emissions or exhaust gases. For example, the SO ₂ concentration in exhaust gases in coal-fired power stations is between 0.05 and 0.3 percent by volume. The gas mixture was thermostatically controlled ^{to 15 ± 0.5 ° C. with the filter.}

By determining the permeability (min) for SO2, a measure of the filter capacity was obtained. This permeability time was determined analogously to Example 1 as the time span which had elapsed between the inflow of SO ₂ at the filter inlet and the detection of the gas at the filter outlet. In the present case the permeability time was 11.25 min, corresponding to a capacity of 0.281 min / ml filter material. The unirradiated original product gave a filter capacity of 0.257 min / ml. The latter number was the average of five measurements with a relative standard deviation of ± 2.5%. The permeability of the filter for SO ₂ was in the

Table 6

Example stated that 'Z ₁₅ of the gas stream was passed through ei indication tube of the type "Dräger SO _2, 20 / a number 242nd The tube was filled with a yellow salt which turned white upon passage of SO white. The pipe was divided into concentration zones of 20 ppm to 200 ppm (1 _ppm =, _{mg SO2} / _{kg G} as. The permeability time was determined for the moment in which the 20 _PP m / zone had been colored completely white The capacity gain in the present case was 9.3%.

Example 8
Under generally the same conditions as

ZrcllTu ^were carried out ^{a number of} tempter, except that the irradiation

Since? ° w ^e _u ^r rH ^ng κ " ⁰ f ^Atmos P" * re have been changed. Dabe, _in experiments 2 to 5 the

ExnlriJ ^Un f '\ ^LU u ^{ft by} S ^ef "hrt. While ^{a nitrogen atmosphere was used with the torsion 5 blS 10} D, the relative humidity was 0% and the gas pressure during the irradiation 1 kg / cm-'.

as well as showing the results

that after irradiation in a greater increase in capacity

BeMen both u u · ^{that a higher} dosage results in higher capacity.

_{t welcbe}

Experiment dosage of the irradiation filter volume η Z, '"

Si? ™. '. atmosphere "itervolume dura _{| ility} . capacity

(min / ml)

1
2
3
4th
5
6th
7th
8th
9
10

gamma

Irradiation

(Mrad)

atmosphere _zejf

W (min)

0
20th
40
75

100
20th
40
50
75

100

air

air

air

air

N ₂

N ₂

N ₂

N ₂

N ₂

40.4 41.0 40.0 41.0 40.0 41.0 40.0 40.0 43.0 41.0

10.35

10.75

11.00

11.25

11.75

10.75

11.25

11.25

12.81

12.75 0.257 **)

0.262

0.268 ***)

0.274

0.294

0.262

0.281

0.281

0.296

0311

Increase in capacity compared to unirradiated material Experiment M 1
*** l £ ^apa , ^ZIti "i ¹ " * original material. Average of 5 measurements IW c '
***) Average of 2 measurements. Measurements. Relative standard deviation + 2 5%

****) Average of 3 measurements. ~

Capacity gain *)

1.9

4.2

6.6
14.3

1.9

9.3

9.3

14.9 ****)
21.0

One

Example 9 ⁵⁵

In general, carbon impregnated with Cu, Cr and Ag does not absorb gaseous CO and is therefore not included in the same Weist SchatzmaskeH provided for this purpose. Filled into protective masks against 60. Each GO gas, a sorbent called Mixture of mmg Hopcaüt is used. This is an oxide-Perosad mixture of the metals CU, Mn, Co and Ag. This mixture oxidizes Co to CO ₂ . It therefore seems quite important that the aforementioned absorption 6s of poisonous gases, and the CO absorption in the same consisted of; Combine type of sorbent together to form selenium dioxide. In order to check this possibility, it was dealt with.

kstoifet
50 Mrad irradiated

^{in the}

this . _ " _Ul ^ _w
nig) OO and 2750 ml pure »
central from «mÄ * ^ * ¹

^Dfe

a

I ■ - : - - ■■ -

H

Color change for the indicator mass from white to brownish green result. The indicator tube had concentration zones from 10 to 300 ppm (1 ppm CO = 1.17 mgCO / m ³ gas). The permeability time was determined for the moment at which the 50 ppm zone was colored completely brown, analogously to Example 7.

The permeability time was found to be 5.0 min, which corresponds to a capacity of 0.125 min / ml filter mass or approximately (6.25-0.125) = 0.78 mg CO / ml Filter mass corresponds. When the original product was not irradiated, the result was a capacity of 0.107 min / ml corresponding to 0.67 mg CO / ml filter mass. The latter capacity value was an average of five measurements with a relative standard deviation of ± 4.2%. The capacity gain was here 16.8%.

Example 10

In general, under the same conditions as in Example 9, a series of experiments were carried out, although the dose of irradiation and the atmosphere were dependent on the conditions de; Example 9 deviated. Thus, Experiment No. 2 was carried out with irradiation in air, while the irradiation atmosphere in Experiments 3 and 4 was nitrogen. The relative humidity was 0% and the gas pressure was 1 kg / cm ² . The other conditions and the results are recorded in Table 7 below.

Table 7

CO sorption capacity of gamma-irradiated activated carbon, type B.

experiment Dosage of the Irradiation Pilter volume Permeability capacity Capacity Gamma- the atmosphere time profit*) Irradiation No. (Mrad) (Ο / α) (min) (min / ml) (%) 1 40 4.35 0.107 **) 2 50 air 41 4.37 0.106 0 3 50 N2 40 5.00 0.125 ***) 16.8 4th 100 N2 40 7.25 0.181 ****) 69.0

Capacity gain compared to non-irradiated material. Experiment * No. 1.

Original material capacity. Average of 5 measurements. Relative standard deviation ± 4.5%. Average capacity of 4 measurements. * ·· * ') Average capacity of 3 measurements.

Example 11

In this example, a "Pittsburg" activated carbon of the BPL type was used as the impregnated sorbent used. This is a typical sorption carbon for gas.

The BPL carbon was impregnated with a solution of 100 g of copper chloride CuCl in 1 l of a 25% strength ammonia solution. A total of 250 ml of the granules were treated with this solution for 3 hours. The solution was then separated from the coal, which was then dried by being treated with nitrogen, namely 5 min at room temperature, then for 5 hours was carried out at 7O ⁰ C and finally 2 hours at 120 ⁰ C. The impregnated coal by Analyzed atomic absorption method for copper and shows 4.7% Cu or 7.25% CuCl. The charcoal was irradiated in nitrogen at a dosage of 40 Mrad.

A sample of 40 ml of the impregnated granulate was examined with regard to the CO holding capacity as in Example 9 and the penetration time for CO gas was determined in an analogous manner using the same type of indicator tube. The penetration time was 8 ^ min corresponding to a capacity of 0.212 rorin / ml recorded Unirradiated charcoal impregnated with CuQ gave values of 7.5 min and 0.187 niin / ml. The increase in capacity was 133%. Measurements carried out for comparison purposes showed a width of 44 min or 0.166 min / mL for irradiated and non-impregnated BPL-ReMeäa

Example 12

»Pittburg« BPL activated carbon was impregnated with 7.5% potassium fluoride. A total of 250 ml of this impregnated carbon was irradiated in nitrogen at a dosage of 50 Mrad. A sample of 18.5 g of this irradiated sorbent was placed in a glass filter container. The filter volume was 43 cm ³ with a layer thickness of 7 cm. Nitrogen gas containing 1.34% by volume of Xe was passed over the impregnated coal until a sorption equilibrium was achieved between the gas phase and the sorbent material, which was 85 min

50 required.

The temperature was kept at 21 ° C. To analyze the Xe, a radioactive indicator Xe ^{133 was added to} the gas at 0.5 μCi / cm ³ . Xe ¹³³ emits gamma rays with a characteristic energy of 0.08 MeV and a half-value of 5.65 days. A measurement of the gas phase concentration of Xe can be achieved by measuring the Xe ^{133 beam.} The total amount of Xe in the system was 4.4 ml. In the present case, an amount of 233% Xe was retained in the sorbent material. This corresponds to a gain of 37 % over the unpunished KF-impregnated sorbent.

Example 13

The following experiment was performed in essentially the same manner as Example 12 carried out using BPL-KoMe, which was impregnated with sodium fluoride {23% NaF).

it

The irradiation took place in air and in nitrogen with Dosages of 50 Mrad. The other conditions were the same as in Example 12. The percentage Sorption gain (retention of Xe in the sorbent compared to non-irradiated, NaF-impregnated Sorbent) was 40.0% for air and 51.5% for nitrogen.

Example 14

In this example, Kr was used as the sorbent gas and Kr ⁸⁵ as the radioactive indicator. The gas contained a total of 1.059% krypton, the remainder being nitrogen. A total of 0.19 ml of krypton and an indicator concentration ^{corresponding to 0.5 μCi Kr 8 Vcm 3 were} used in the system. The coal is of the same type as in Example 12. The material was: irradiated with a dosage of 50 Mrad in nitrogen. There was a sorption gain of 13.4% compared to unirradiated material.

Surprisingly, it was found that an increase in the chemisorption capacity was achieved by increasing the nitrogen pressure with constant gamma irradiation. Table 1 shows, inter alia, that the irradiation of impregnated carbon with a dosage of about 26 Mrad at 15 kg / cm ² N ₂ pressure resulted in a gain in capacity which was greater than that obtained with 50 Mrad irradiation at one N. ₂ -pressure of 1 kg / cm ² achieved wuide. This of course reduces the irradiation costs, since these depend on the dosage.

According to a special feature of the invention, therefore, is a method for enhancing the chemisorption capacity of carbon which has been impregnated with one or more metal compounds toxic gases or industrial exhaust gases in which the impregnated carbon prior to chemisorption with a dosage of at least 1 Mrad gamma irradiated, characterized in that the Irradiation is carried out under a partial pressure of nitrogen, which is greater than the partial pressure of nitrogen in air at atmospheric pressure.

This peculiarity of the invention is to be explained in more detail in the following examples:

Example 15

Granulated activated carbon of type A according to Example 1 was irradiated in a steel container with a dosage of 27 Mrad. Before the irradiation, the container with the activated charcoal was evacuated to 0.1 mm Hg pressure for about 20 minutes. Then pure nitrogen gas (99.99%) was filled into the container in order to achieve a pressure of 15 kg / cm ² . The container was then exposed to a gamma radiation source (Co ⁶⁰ ) in the manner described in Example 1. After the irradiation, the carbon was stored in a polyethylene container in a nitrogen atmosphere before its sorption capacity for cyan chloride was tested.

For this purpose, a 75 ml sample of the irradiated granulate was poured into a filter container. the Capacity with respect to cyan chloride was measured in the same manner as in Example 1. In the present case the permeation time was recorded as 23 minutes, giving a capacity of 0.306 minutes / ml. the Average capacity with 8 measurements and with the unirradiated original product was 0.197 min / ml. the Capacity gain was 55.2% compared to the original capacity.

Example 16

Under generally the same general conditions as in Example 15, a series of prior experiments were carried out, with the exception of the dosage of the irradiation, which was kept at 50 Mrad and with respect to the nitrogen pressure during the irradiation, which was within the range of 0.1 bi; 15 kg / cm ^{2 was} changed. The test conditions and the results are given in Table f below.

Table 8

Cyan chloride sorption capacity of gamma-irradiated ASC activated carbon, type A in the presence of nitrogen gas

Experi
ment dosage
the Irradiating
lung N 2 pressure
while I iller-
volume Permeable
life time capacity Capacity
profit*) Bern. Gamma- atmo- the Be Irradiate sphere radiation No. lung
(Mrad) (kg / cm ^) (cm') (min) (min / ml) (%) 1 0 - - 75 14.8 0.197 **) _ Original material 2 50 air 0.75 68 17.5 0.257 30.4 Exp.Table 5 3 50 N ² 1 72 19.5 0.270 37.1 Pat Aram. 24S2 / 72 4th 50 N2 3 75 20.6 * »*) 0.274 * · *) 39.1 5 26th N2 ! 5 75 23 0306 55.3

"J Capacity gain compared to unirradiated original flight. Experiment no. 1

**} Capacity with original product not irradiated. Average of 8 trials, relative standard deviation ± 8.7% ***} © nrcBschtÄ of 2 attempts.

^{elSP> e} 65 container with the activated charcoal for 20 minutes on one

Aktjykohiengranulat of the type A according to example 1 pressure of 0.1 ram Wg evacuated trad then with travel «

was placed in a fine container with a dosage of nitrogen gas (9939%) to a pressure of 5 kg / eni

50 Mrad besetanlL Before the irradiation, the container was found. The container was then a Garama-Steah

k

lenqueUe (Co ») in the same way as in Example 1 exposed to ^H

The charcoal was then tested for its hydrocyanic acid kajratät as in Example 6. In this example, a penetration time of 35 min resulted, which means a capacity of 18.5 mg HCN / ml or a capacity gain of 16.2%. The unirradiated original material had a capacity of 16 mg HCN / mL

Example 18

Further tests were carried out under generally the same spraying conditions as in Example 17, with the exception of the nitrogen pressure during the irradiation, which was varied within a range from 1 to 15 kg / cm ² . The test conditions and the results are summarized in Table 9 below

Table 9 Hydrocyanic acid sorption capacity of gamma-irradiated ASC activated carbon, type A.

Experi- Dosing irradiation of the lung

Gamma-

Irradiation
(Mrad)

atmo-

Sphere radiation

S ^ a ^Fll , ^ter ' ^ReL HCN-Kon- by- HCN-

moving volume moisture concentration casual ^{capacity the} wedge time did

(kg / cm *) (ml)

(mg / 1)

(min) (mg / ml)

Capacity gain *)

0
50
50
50
50

air

N.2

N ₂

N2

15th

75 75 1.43 28 16 0 78 75 1.39 27 14.4 0 (-1O) 79 75 1.38 35 17.3 + 8.1 76 75 1.32 35 18.6 + 16.2 75 75 1.25 45 22.4 +40

*) Capacity gain compared to non-irradiated material.

Example 19

A 43 ml sample of gas mask carbon impregnated with potassium carbonate of the type "Dräger 900" according to Example 7 was irradiated in a steel container with a dosage of 40 Mrad. The container was filled with nitrogen to a pressure of 15 kg / cm ^2. After the irradiation, the coal was tested for its sorption capacity or capacity with respect to SO ² , in the same way as in the example! 7. The permeation time was 12.5 min, which means a capacity of 0.291 min / ml. This gives a capacity gain of 13.4% compared to the original product, where it was 0.257 min / ml.

Example 20

A series of experiments were carried out under generally the same conditions as in Example 19 performed with the exception of a change in nitrogen pressure. The test conditions and results are shown in Table 10 below.

Table 10

SO2 sorption capacity of impregnated activated carbon, irradiated with gamma rays at different nitrogen pressures

Experi dosage Punishment N2 printing Filter volume Permeable capacity Capacity ment the gamma the atmosphere during the life time profit*) irradiation Irradiation No. (Mrad) (kg / cm ') (cm3) (min) (min / ml) (Vo) 1 0 _ 40.4 *) 10.35 *) 0.257 **) _ 2 40 air 0.75 41 11th 0.268 4.2 ···) 3 40 N2 1 40 11.25 0.281 9.3 4th 40 N2 15th 43 12.5 0.291 13.4

*) Increase in capacity compared to unirradiated original material.

**) Capacity of the original material. Average of 5 measurements, relative standard deviation ± 2.5%. ***) Average of 2 measurements.

example

Under generally the same conditions as in Example 10, measurements were made on the Influence of the pressure on the holding capacity of carbon monoxide carried out. Table 4 shows the Results for a nitrogen irradiation atmosphere and a filter volume of 40 ml.

Table 11

Carbon monoxide sorption capacity of gamma-irradiated activated carbon, type B

Experiment Dosing Pressure Permeable Capacity Capacity

the gamma gain during the time *)

Irradiation irradiation

No. (Mrad) (kg / cm ^) (min) (min / ml) (%)

1 50 1 5.00 0.125 16.8 2 50 15th 5.50 0.138 30.2 *) 3 100 1 7.25 0.181 69.0

*) Capacity gain compared to non-irradiated material.

Average of 2 measurements.

Claims (3)

Patent claims: ; 1. Process for enhancing chemisorption capacity of activated carbon versus gases, in which the activated carbon is more toxic for the purpose of adsorption Gases and industrial exhaust gases are impregnated with one or more metal compounds, characterized in that the impregnated activated carbon before chemisorption with Gamma rays irradiated to an intensity of at least 1 Mrad: is 2. The method according to claim 1, characterized in that the irradiation of the activated carbon is carried out in a nitrogen atmosphere 3. The method according to claim 2, characterized in that the irradiation is carried out under a partial pressure of nitrogen and this is greater than the partial pressure of nitrogen in air at atmospheric pressure.