Component for deodorizing air and other gases

A component for deodorizing air or gas having a coexist compound as a deodorizing element, said coexist compound comprising a metal and a reaction product of the metal and an acid, wherein the metal is selected from at least one of Fe, Mn, Cr, Ni, Zn, Al and Cu, and the acid is selected from at least one of ascorbic acid, gluconic acid, citric acid, tartaric acid, tannic acid, gallic acid, EDTA and malic acid, wherein clean air or gas is passed through the deodorizing element to restore its deodorizing effect after a period of time sufficient for the deodorizing element to lose its deodorizing power.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a component for deodorizing air and other 
gases. 
2. Background Information 
There are known a number of components for deodorizing air or other gases, 
including those containing active carbon which absorbs odorous substances, 
and those containing a chemical agent which emits a fragrance to conceal 
the existing odor. However, these deodorants cannot destroy the existing 
odorous substance and the deodorizing effect is saturated or diminished 
within in a short period of time. 
Japanese Patent Application No. 59-132937 relates to a powdered complex 
having a deodorizing effect. This application discloses a powdered complex 
mixture obtained by drying a solution produced by reacting an L-ascorbic 
acid solution with a ferrous salt solution such as FeSO.sub.4 FeCl.sub.2 
Fe(NO.sub.3).sub.2 solution. This powdered complex mixture reacts with an 
odorous substance to change its chemical structure. However, the powdered 
complex mixture simultaneously undergoes chemical changes in this 
reaction, and loses its odorizing power in a short period of time. 
Clearly, a deodorizing component in which the deodorizing agent can be 
revitalized easily and simply whenever its deodorizing effect is 
diminished would be advantageous, as that would reduce the troublesome 
procedure of replacing the deodorizing agent. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a component 
for deodorizing air or other gases having a powerful deodorizing element 
and an easy means to revitalize the deodorizing power of the element so 
that the component can be used for a much longer period of time than any 
known component without the need to replace the deodorizing element. 
According to the present invention, a coexist compound containing a 
particular metal and the reaction product of the particular metal and a 
particular acid solution is used as the deodorizing element. The metal is 
selected from Fe, Mn, Cr, Ni, Zn, and Al and the acid solution is selected 
from ascorbic acid, gluconic acid, citric acid, tartaric acid, tannic 
acid, gallic acid, EDTA and malic acid. The metal and the acid solution 
are contacted with each other and react chemically with each other. 
Using this process, the coexist compound containing a particular metal and 
a reaction product of the particular metal and the particular acid can be 
obtained. The coexist compound of the present invention differs from the 
composition of the powdered complex shown in Japanese Patent Application 
No. 59-132937 described above in that the coexist compound of the present 
invention contains unreacted metal in its composition. The coexist 
compound of the present invention has a deodorizing effect similar to 
those of the powdered complexes of the prior art. However, in contrast to 
the powdered complex of the prior art, the deodorizing effect of the 
coexist compound of the present invention can be revitalized easily when 
the deodorizing power is decreased or lost with use over a long period of 
time. In the coexist compound of the present invention, the revitalization 
of the deodorizing effect can be achieved in a short period of time by 
passing clean air or another gas through the deodorizing element. 
The deodorizing power of the element in treating H.sub.2 S containing gas, 
for example, can be strengthened by incorporating a basic salt into the 
coexist compound. Examples of basic salts which can be used include CaO, 
MgO, Ca(OH).sub.2, Mg(OH).sub.2, CaCO.sub.2, MgCO.sub.3 and Na.sub.2 
CO.sub.3. An ordinary deodorizing compound containing active carbon can be 
used together with the deodorizing element of the present invention. In 
producing the deodorizing element of the present invention, it is 
preferable to use as the metal a porous metal block obtained by sintering 
and having numerous pores passing through it. An electric resistance 
heater or an electromagnetic induction heater can be used to heat the 
deodorizing element during revitalization.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present inventors used an iron powder and a porous block of urethane 
foam to produce a porous block of iron. A slurry was prepared by mixing 
iron powder with a paste liquid. The urethane block was placed into the 
slurry and then removed. By this process, all the skeleton composing the 
urethane foam was covered with the slurry. Then the urethane block was 
heated and sintered. By this heating and sintering, the urethane was 
decomposed and eliminated, leaving a porous block of sintered iron. This 
porous block of sintered iron was then immersed in an ascorbic acid 
solution, and the surface of the sintered iron was reacted with the 
ascorbic acid. Then the porous block was removed from the solution and 
dried. By this process, all iron skeleton composing pores of the sintered 
iron was covered by the reaction product of the iron and ascorbic acid. 
The coexist compound of iron and the reaction product of iron and ascorbic 
acid, thus obtained, was used as a deodorizing element in the following 
experiment. 
In examining the deodorizing effect of this new element, it was found that 
this coexist compound has a powerful deodorizing effect similar to those 
of the powdered complex shown in Japanese Patent Application No. 
59-132937, and that this coexist compound can destroy harmful gases 
including SO.sub.x, NO.sub.x, CO, CO.sub.2 and acetaldehyde. It was also 
found that, although this new element gradually loses its deodorizing 
effect when it is used for a long period of time, it regains the 
deodorizing effect by simply exposing it to flowing air for a short period 
of time or, more simply, by leaving it alone in the ordinary atmosphere 
for several days. 
In an experiment, the inventors used a test assembly as illustrated in FIG. 
2, where container 9 was filled with a deodorant, and air containing 
NH.sub.3 at a concentration of 100 ppm was blown out of gas cylinder 5. 
Arrows 4 show the flow direction of the gas, the amount, temperature and 
moisture of which were controlled by elements 6,7 and 8 respectively. The 
NH.sub.3 concentration of the air after passing it through the container 9 
was then measured. Treated gas was sampled via pipe 10. 
FIG. 1(A) illustrates a result of the experiment on the powdered complex 
described in the above-cited Japanese Patent Application. As is apparent 
from FIG. 1(A), the known deodorant was highly effective for the first 15 
days of use, but thereafter rapidly lost its effect, becoming almost 
ineffective in 25 days. After having been used for 25 days, the deodorant 
was removed from the container and exposed to fresh air for 5 days. Then 
the deodorant was placed back in the container and the same experiment was 
performed again. However, as shown in FIG. 1(A), the known deodorant never 
regained its deodorizing effect, thus showing its limited service life. 
FIG. 1(B) shows the deodorizing effect of the deodorizing element of the 
present invention. As in the case of FIG. 1(A), the deodorizing element 
gradually loses its effect after the first 15 days of service. The 
inventors removed the deodorizing element from the container after it had 
been used for 25 days and exposed it to fresh air for 5 days. The 
deodorizing element was then put to use again, as in the case of FIG. 
1(A). As shown in FIG. 1(B), exposure to the fresh air restored the 
deodorizing effect of the element, which was almost as effective as it had 
been in the initial stage of use. However, it is considered that a period 
of 5 days to regain its deodorizing effect is too long and thus the 
deodorizing element is not adequate for use in a continuously operating 
apparatus. 
FIG. 1(C) shows another aspect of the deodorizing effect of the deodorizing 
element of the present invention. In FIG. 1(C), after the element had been 
used for 25 days, the gas cylinder 5 of FIG. 2 was removed and fresh air 
was passed through the container for 5 minutes. It was found that the 
deodorizing effect was restored almost to the initial level in this case. 
Thus, this revitalizing method to restore the deodorizing effect is very 
suitable for the deodorizing element in a continuously operating 
apparatus, as a 5 minute period of time necessary to regain its effect is 
not expected to cause a serious problem in a continuous operation. 
FIG. 1(D) shows still another aspect of the deodorizing effect of the 
present invention. In this case, after it had been used for 25 days, steam 
having a temperature of approximately 80.degree. C. was passed through the 
container for several minutes. It was found that the deodorizing effect 
was almost fully restored. Thus, heating and/or moistening of the 
deodorizing element of the present invention is a very suitable method to 
restore its deodorizing effect. 
FIG. 1(E) shows yet another aspect of the deodorizing effect of the present 
invention. In this case, steam was periodically passed through the 
container once in every 15 days. The deodorizing effect did not 
significantly decline in 15 days and therefore the deodorizing element of 
the present invention regained its effect with a very short exposure to 
steam. Thus, periodic exposure to steam can greatly extend the service 
life of the deodorizing element. 
The inventors conducted similar experiments substituting H.sub.2 S, 
SO.sub.x, NO.sub.x, CO, CO.sub.2, acetaldehyde and other gases for NH, 
gas, and found that the coexist compound of the present invention has a 
strong deodorizing effect on these gases and can regain its air cleaning 
effect quickly by passing fresh air through the coexist compound, and 
optionally heating and/or moistening the coexist compound. 
The inventors have also prepared a coexist compound containing metallic Mn 
and a reaction product of Mn and ascorbic acid using powdered Mn in place 
of iron powder. The deodorizing effect of the coexist compound was also 
examined and it was proved that this coexist compound was as effective for 
ammonia gas as the iron type coexist compound, and more effective for 
hydrogen sulfide gas than the iron type coexist compound. When the Mn type 
coexist compound partially loses its deodorizing effect after a long 
period of use, it can be revitalized for a short period of time by 
treatment with fresh air, hot air and moistened air or by moistening or 
heating the coexist compound in the same way as for the iron type coexist 
compound. 
By conducting a similar experiment using Cr, Ni, Zn, Al and Cu in place of 
Fe and Mn, the inventors found that a coexist compound containing Al or Ni 
is as effective as one containing iron, and that a coexist compound 
containing Cr, Zn or Cu is not as effective as one containing iron. Also 
the inventors found that the deodorizing effect of all of these coexist 
compounds can be restored in the same manner as for the iron type coexist 
compound. 
The inventors also conducted experiments using various acids including 
gluconic acid, citric acid, tartaric acid, tannic acid, gallic acid, EDTA 
and malic acid in place of ascorbic acid. As a result of the experiments, 
it was found that gluconic acid, citric acid, tartaric acid, tannic acid 
and gallic acid are as effective as ascorbic acid in producing an 
excellent coexist compound that can be fully revitalized in a similar 
manner as in the case of an ascorbic acid type coexit compound, while EDTA 
and malic acid are not as effective in that sense and can be fully 
revitalized in a similar manner. 
The Fe, Mn, Cr, Ni, Zn, Al and Cu used in producing the deodorizing element 
need not be in a pure metal form. Metals containing the usual impure 
elements can be used. Also a mixture or an alloy of these metals can be 
used. 
The metal used for producing the deodorizing element is not necessarily in 
the form of a porous block. A metal other than a porous block, for 
example, a pebble-sized metal or a grain-sized metal can also be used for 
this purpose. However, a porous metal block having numerous pores passing 
through it in random directions is preferred, because a coexist compound 
prepared from this porous metal block is in a porous shape which enables 
air and gas to contact closely with the deodorizing compound and pass 
easily through the deodorizing elements. This porous metal block can 
easily be obtained by sintering process, as described above. 
Ascorbic acid, gluconic acid, citric acid, tartaric acid, tannic acid, 
gallic acid, EDTA and malic acid, as referred to in this specification, 
are meant to include acids having a concentration and purity sufficient to 
form a reaction product with the above-identified metals. Therefore an 
acid having the usual concentration and usual purity can be used. 
Clean air or gas, as referred to in this specification, are meant to 
include air or gas which is clean enough to restore the deodorizing effect 
of the deodorizing element. 
The inventors also found that the power to decompose H.sub.2 S gas can be 
enhanced remarkably by incorporating a basic salt in the coexist compound 
of the present invention. One or more than one basic salt selected from 
CaO, Mgo, Ca(OH).sub.2, Mg(OH).sub.2, CaCO.sub.2, MGCO.sub.3 and Na.sub.2 
CO.sub.3 can be used for this purpose. 
The inventors have provided an emulsion by mixing a powder of the basic 
salt and organic solvent, and this emulsion was sprayed on the surface of 
the coexist compound. Using this process, the deodorizing effect of the 
coexist compound in destroying the odorous substance of H.sub.2 S has been 
improved remarkably. 
A typical process of preparing a deodorizing element according to the 
present invention is described below. 
A powdered iron having a size smaller than 10 .mu.m was obtained by 
crushing pig iron in a wet process. The powdered iron was mixed with a 
binding solution containing carboxylmethylcellulose to obtain a slurry. A 
porous block of urethane foam was provided. The slurry was placed onto the 
skeleton of the urethane foam. Then the urethane block was heated. By this 
heating, the urethane was eliminated, the slurry was sintered, and a 
porous block of sintered iron having numerous pores passing through it was 
obtained. This iron block was immersed in an ascorbic acid solution having 
a concentration of 1 mol for 30 minutes. Then the iron block was removed 
and dried to produce a porous block of a deodorizing element in which a 
reaction product of iron and ascorbic acid coexisted with the iron. While 
this deodorizing element may be used without further treatment, its 
deodorizing effect can be strengthened by incorporating into its surface a 
basic salt. 
In this deodorizing element, the gas flows through the numerous pores of 
the porous block and, since the reaction product of iron and ascorbic acid 
are placed on the surface of the pore, the gas is brought into sufficient 
contact with the reaction product so that the odor component of the gas 
may be fully eliminated. 
In the present invention, clean or heated or moistened air or gas is 
supplied or the deodorizing element is heated or moistened for a short 
period of time regularly or periodically or whenever necessary. By this 
process, the deodorizing power of the element is revitalized regularly or 
periodically or whenever necessary during the operation. 
When the apparatus is used to process a massive amount of gas containing 
odorous substances at a high concentration, the deodorant will be rapidly 
consumed. Therefore, in such a case, it is preferable to perform a 
revitalizing treatment regularly or periodically at short intervals. 
On the other hand, when the apparatus is used to process a small amount of 
gas containing an odorous substance at a low concentration, the deodorant 
will not be consumed for a long time. Therefore, in this case, it is 
preferable to perform a revitalizing treatment whenever necessary. 
When the deodorizing element is moistened, the moisture should be supplied 
carefully so that the moisture will not form dew drops and fall down from 
the element. In the present invention, odorous substance contained in air 
or gas are chemically decomposed by the reaction product of the metal and 
the metal and acid, and the reaction product is water soluble. Therefore, 
when too much moisture is supplied and dew drops form, the reaction 
product will dissolve in the dew drops and be lost as they fall from the 
deodorizing element. 
Since the deodorizing element of the present invention contains free metal 
as a component, the deodorizing element can be heated using an electric 
resistance heater, an electromagnetic induction heater or similar electric 
heating means. 
FIGS. 3(A) through 3(C) illustrate examples of arrangements for moistening 
and heating the deodorizing element. Numeral 1 denotes a deodorizing 
element, 2 an ultrasonic humidifier, 3 a heater-steam generator, 11 a 
heater for heating a deodorizing element. Odorous gas flows and passes 
through the deodorizing element in the direction indicated by arrow 4. 
When an ultrasonic humidifier or a heater-steam generator is arranged at 
the inlet side and air containing water particles less than 100 .mu.m in 
diameter is supplied to the deodorizing element, as in the case of FIG. 
3(A) and FIG. 3(B), the deodorizing element will be evenly moistened with 
no problems. FIG. 3(C) shows an arrangement where moistening and heating 
are conducted simultaneously. FIG. 3(D) illustrates a case where only 
clean air, shown as numeral 12, is supplied to revitalize the deodorizing 
element, without heating or moistening. 
In contrast to the powdered complex shown in Japanese Patent Application 
59-132937 where the deodorizing effect cannot be revitalized, the 
deodorizing effect of the deodorizing element of the present invention can 
be revitalized easily. Although the exact reasons for this difference are 
not entirely clear, some explanation can be made. 
The deodorizing element of the present invention comprises a metal and its 
reaction product. The reaction product in the present invention is 
believed to have similar characteristics to that of the powdered complex 
of the prior art. Therefore the reaction product of the present invention 
may react with odorous substances in a similar manner as the powdered 
complex of the prior art and may produce a similar resultant chemical 
substance as that of the powdered complex of the prior art. In this 
reaction with an odorous substance, the reaction product of the present 
invention as well as the powdered complex of the prior art may be equally 
consumed and the deodorizing effect may equally decrease. 
The deodorizing effect of the resultant chemical substance as described 
above cannot be revitalized by merely introducing fresh air or heating or 
moistening. However, the resultant chemical substance may be revitalized 
when it is contacted with a free metal. Therefore, in the case of the 
deodorizing element of the present invention which contains free metal, 
the deodorizing effect can be revitalized. However, in the case of the 
powdered complex of the prior art which does not contain any free metal, 
the deodorizing effect cannot be revitalized. 
In the present invention, the deodorizing effect can be revitalized in a 
much shorter period of time by heating or moistening, rather than simply 
exposing the deodorizing element to the atmosphere. The exact reasons for 
this difference are not entirely clear. However, it is the inventors' 
belief that the contact of the resultant chemical substance described 
above with the metal is accelerated by heating or moistening, and the 
chemical reaction necessary to revitalize the deodorizing effect is 
achieved in a shorter period of time by heating or moistening. 
The component of the present invention may comprise a deodorizing compound 
of active carbon, along with the coexist compound previously described. 
The deodorizing compound of active carbon includes an absorption active 
carbon such as a powdered active carbon, a fibrous active carbon and 
active carbon prepared from coconut shell. 
The active carbon compound can be used as an independent deodorizing 
element. It can also be mixed with the coexist compound. There are odorous 
substances such as trichloroethylene and other organic chlorides that 
cannot be removed by chemical reaction with a deodorant. By including an 
active carbon compound with the coexist compound, the scope of the use of 
the deodorizing apparatus can be extended remarkably. In addition, with 
such a combination, ammonia and hydrogen sulphide absorbed in the active 
carbon compound can be processed further by the coexist compound. Thus, 
with the combined use of an active carbon compound, the deodorizing 
efficiency and the life of the active carbon compound can also be 
improved. 
Another embodiment of the present invention is described below. Powdered 
iron and powdered manganese having an average particle size of 10 .mu.m 
were mixed at a ratio of Fe:Mn=80:20 by weight, and a slurry was prepared 
from the mixture using a carboxymethylcellulose aqueous solution. The 
slurry was then applied to the surface of a porous block of urethane foam 
having dimensions of 200 mm.times.200 mm.times.10 mm and an average pore 
diameter of about 1 mm. The block of urethane foam was then subjected to 
heating at about 1200.degree. C., by which urethane was burnt and 
dissipated, leaving a porous block of sintered iron having numerous pores 
passing through it in random directions. The porous sintered block was 
then immersed in a 1 mol L-ascorbic aid solution for 30 minutes to produce 
a coexist compound of the present invention. The coexist compound was then 
basically treated by spraying an emulsion of Na.sub.2 CO.sub.3 and 
methylalcohol to obtain the deodorizing element of the present invention. 
The deodorizing element was set in a component or unit and the component 
was arranged in a lavatory to observe its performance. Line 13 of FIG. 4 
shows its performance when no treatment for revitalizing the deodorizing 
element was performed. Line 14 of FIG. 4 shows its performance when wet 
fresh air at a temperature of 80.degree. C. was supplied to the 
deodorizing element periodically for 1 minute in every 24 hours. Line 15 
of FIG. 5 shows its performance when the deodorizing element was heated 
periodically at 80.degree. C. for 1 minute in every 24 hours. As shown in 
line 13 of FIG. 4, the component loses its deodorizing effect 
significantly in the long run when the deodorizing element is not treated 
for revitalizing. However, as shown by line 14 and line 15 of FIG. 4, it 
can maintain its effect at a high level when it is periodically subjected 
to a treatment for revitalizing the deodorizing element. 
Still another embodiment of the present invention is described below. A 
porous block of sintered iron was prepared using powdered iron with an 
average particle size of 5 .mu.m in a similar manner as described above. 
The obtained porous block was then immersed in a solution containing 
L-ascorbic acid at a concentration of 0.5 mol/l and gluconic acid at a 
concentration of 0.5 mol/l at a temperature of 60.degree. C. for 15 
minutes and dried in the atmosphere. An emulsion of Ca(OH).sub.2 and 
ethanol was then sprayed on its surface. The deodorizing elements of the 
present invention, thus obtained, were set in an apparatus. The component 
was set in a small room, where more than 20 cigarettes were smoked every 
day. A tentilator was arranged so that clean air was supplied to the 
deodorizing element for 3 minutes following every ventilating operation. 
During the 2 years in which the experiment was conducted, the air was 
always kept clean and the content of the substances contained in the air 
was as follows: H.sub.2 S:0.1 ppm, NH.sub.3 :0.1 ppm, 50x:1 ppm, NO.sub.2 
:0 ppm, CO.sub.2 :50 ppm, CO:3 ppm, acetaldehyde:0 ppm. As is apparent 
from the above description, the component of the present invention can 
maintain its deodorizing effect at its initial level over a long period of 
use without the need to replace its deodorizing element.