U.S. patent application number 10/539563 was filed with the patent office on 2006-06-15 for material for treating harmful substance and method for treating harmful substance using the same.
Invention is credited to Kaoru Sakurai, Ken-ichi Sasaki.
Application Number | 20060129019 10/539563 |
Document ID | / |
Family ID | 32684198 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060129019 |
Kind Code |
A1 |
Sasaki; Ken-ichi ; et
al. |
June 15, 2006 |
Material for treating harmful substance and method for treating
harmful substance using the same
Abstract
The present invention relates to a harmful material remediating
agent comprising a metal oxide and a reducing material, and it can
remediate environmental pollutants such as harmful organic
compounds and nitrate or nitrite nitrogen-containing compounds
efficiently and at low cost.
Inventors: |
Sasaki; Ken-ichi;
(Yokkaichi, JP) ; Sakurai; Kaoru; (Yokkaichi,
JP) |
Correspondence
Address: |
MANELLI DENISON & SELTER
2000 M STREET NW SUITE 700
WASHINGTON
DC
20036-3307
US
|
Family ID: |
32684198 |
Appl. No.: |
10/539563 |
Filed: |
December 18, 2003 |
PCT Filed: |
December 18, 2003 |
PCT NO: |
PCT/JP03/16257 |
371 Date: |
June 17, 2005 |
Current U.S.
Class: |
588/313 |
Current CPC
Class: |
A62D 2101/47 20130101;
B01J 23/745 20130101; A62D 2101/26 20130101; A62D 2101/45 20130101;
B09C 1/08 20130101; A62D 2101/22 20130101; C09K 15/02 20130101;
A62D 3/37 20130101; C02F 2101/30 20130101; A62D 2101/28 20130101;
A62D 2101/20 20130101; C02F 1/705 20130101; C09K 15/06 20130101;
Y10S 588/901 20130101 |
Class at
Publication: |
588/313 |
International
Class: |
A62D 3/00 20060101
A62D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2002 |
JP |
2002-370564 |
Dec 27, 2002 |
JP |
2002-379598 |
Claims
1. A harmful material remediating agent comprising a metal oxide
and a reducing material.
2. A harmful material remediating agent according to claim 1,
wherein the reducing material is a metal and the harmful material
to be remediated is an organic compound.
3. A harmful material remediating agent according to claim 2,
wherein the metal oxide is iron oxide and/or titanium oxide.
4. A harmful material remediating agent according to claim 2,
wherein the metal oxide is a suboxide.
5. A harmful material remediating agent according to claim 2,
wherein the metal is at least one metal selected from the group
consisting of iron, aluminum, zinc, copper and magnesium.
6. A harmful material remediating agent according to claim 2,
wherein the metal is iron and the metal oxide is iron oxide.
7. A harmful material remediating agent according to claim 3,
wherein the iron oxide is at least one iron oxide selected from the
group consisting of magnetite, hyper-reduced magnetite and
berthollide.
8. A harmful material remediating agent according to claim 2,
wherein the mixing ratio of the metal and the metal oxide is in the
range of 0.02:1-9:1 in weight ratio.
9. A harmful material remediating agent according to claim 1,
wherein the harmful material to be remediated is a nitrate and
nitrite nitrogen-containing compound and the remediating agent is
used under normal pressure.
10. A harmful material remediating agent according to claim 9,
wherein the reducing material is a metal and/or a reducing
agent.
11. A harmful material remediating agent according to claim 9,
wherein the metal oxide is iron oxide and/or titanium oxide.
12. A harmful material remediating agent according to claim 9,
wherein the metal oxide is a suboxide.
13. A harmful material remediating agent according to claim 11,
wherein the iron oxide is magnetite, hyper-reduced magnetite and/or
berthollide.
14. A harmful material remediating agent according to claim 11,
wherein the titanium oxide is a titanium oxide having a
non-stoichiometric composition.
15. A harmful material remediating agent according to claim 9,
wherein the reducing material is iron and the metal oxide is iron
oxide.
16. A harmful material remediating agent according to claim 9,
wherein the reducing material is at least one reducing agent
selected from the group consisting of metal sulfites, metal
hydrogensulfites, metal thiosulfates, metal dithionites,
phosphorous acid and metal salts thereof, and hypophosphorous acid
and metal salts thereof.
17. A harmful material remediating agent according to claim 9,
wherein the reducing material is a reducing agent and the mixing
ratio of the reducing agent and the metal oxide is in the range of
0.1:1-5:1 in weight ratio.
18. A harmful material remediating agent according to claim 9,
wherein the reducing material is at least one metal selected from
the group consisting of iron, aluminum, zinc, copper and
magnesium.
19. A harmful material remediating agent according to claim 9,
wherein the reducing material is a metal and the mixing ratio of
the metal and the metal oxide is in the range of 0.001:1-3:1 in
weight ratio.
20. A method for remediating harmful materials which comprises
introducing the harmful material remediating agent of claim 1 into
soil to decompose the harmful materials in the soil.
21. A method for remediating harmful materials which comprises
introducing the harmful material remediating agent of claim 1 into
water to decompose the harmful materials in the water, and then
separating the remediating agent by solid-liquid separation.
Description
TECHNICAL FIELD
[0001] The present invention relates to a harmful material
remediating agent which can remediate environmental pollutants such
as harmful organic compounds and nitrate and nitrite
nitrogen-containing compounds at low cost and high efficiency.
BACKGROUND ART
[0002] Highly volatile organic compounds, e.g., halogenated
hydrocarbons such as trichloroethylene and tetrachloroethylene,
aromatic compounds such as benzene, xylene and toluene, and
aldehydes such as acetaldehyde and formaldehyde are industrially
widely used as solvents, detergents, etc., and organic agricultural
chemicals such as organic chlorine compounds and organic phosphorus
compounds are used as insecticides, fungicides and herbicides in
agricultural fields. Some of these organic compounds have toxicity
or carcinogenicity for men or cause inhibition of growth and
induction of malformation for animals and plants, and preparation,
use and disposition of them are severely regulated. However, many
of the above organic compounds are hardly decomposable, and those
which have been abandoned or leaked under no severe control or
those which have been used before issuance of regulations, such as
DDT and BHC, remain in the environment. These compounds have
polluted soil or underground water over a long period of time, and,
furthermore, highly volatile matters discharged into atmosphere
have polluted the atmosphere, which have caused serious social
problems. Furthermore, recently, it has been reported that a part
of organic compounds act as so-called endocrine disturbing
substances (or environmental hormones) which inhibit generative
power of animals and plants.
[0003] On the other hand, since nitrate and nitrite
nitrogen-containing compounds have carcinogenicity, recently,
discharge of them is severely controlled as water pollutants, and
chemical industries and fertilizer industries are demanded to cope
with the problems. Moreover, in agriculture, organic nitrogen
compounds contained in fertilizers produce nitrate and nitrite
nitrogen-containing compounds by biodegradation or oxidative
decomposition in the fertilized soil, which not only pollute
underground water and agricultural waste water, but also cause
formation of acidic soil to inhibit rearing of crops. These are
also serious problems.
[0004] As a method for remediating organic compounds in soil, it
has been known to carry out the airlation of soil and collect
gaseous components, followed by carrying out reduction
decomposition using hydrogen as a reducing agent and platinum or
palladium as a catalyst (for example, Isao Joko, "Environmental
Catalyst Handbook", (p. 134-138, the first edition, published from
NTS Co., on Nov. 20, 2001, hereinafter referred to as "Non-Patent
Document 1"). Moreover, there is known a method of directly
introducing reducing agent or oxidizing agent into polluted soil to
carry out reduction decomposition or oxidation decomposition of
organic compounds, which is so-called in-situ remediation method.
According to this method, metallic iron (e.g., U.S. Pat. No.
3,079,109 (pages 1-2), hereinafter referred to as "Patent Document
1") or a composite compound of magnetite and metallic iron (e.g.,
JP-A-2002-317202 (page 1), hereinafter referred to as "Patent
Document 2") is used as a reducing agent, and potassium
permanganate or hydrogen peroxide (e.g., JP-A-7-75772 (page 1),
hereinafter referred to as "Patent Document 3") is used as an
oxidizing agent.
[0005] For remediating nitrate or nitrite nitrogen-containing
compounds in waste water, there are known a method of reducing with
hydrogen as in the treatment of the organic compounds, ion exchange
method, reverse osmosis method, electrodialysis method, and
biodegradation method using bacteria (e.g., pages 89-91 of
Non-Patent Document 1). Furthermore, there is known a method of
remediating nitrate nitrogen contained in waste water using a solid
catalyst containing a metal compound such as titanium oxide or iron
oxide and a noble metal catalyst such as platinum, palladium or
nickel in the presence of a reducing agent with keeping waste water
in liquid phase at a temperature of 120-370.degree. C. under a
pressure at which the waste water keeps liquid phase (e.g.,
JP-A-9-70589 (pages 1-8), hereinafter referred to as "Patent
Document 4"). In the case of remediating nitrate or nitrite
nitrogen-containing compounds in soil, the above in-situ
remediation method is also applied, and metallic iron or sulfide is
used as the reducing agent introduced into soil.
DISCLOSURE OF INVENTION
[0006] However, the hydrogen reduction method requires too much
cost for treatment of organic compounds because a noble metal is
used as the catalyst. The so-called in-situ remediation method is
low in cost, but the metallic iron disclosed in Patent Document 1
brings about a phenomenon of underground water being colored red,
which is called red water, and, moreover, metallic iron or the
composite compound disclosed in Patent Document 2 is insufficient
in decomposing ability for organic compounds. The oxidizing agent
disclosed in Patent Document 3 is too strong in oxidizing power and
oxidizes nitrogen compounds and minerals in soil, which causes a
problem of changing the properties of soil.
[0007] As the method for remediating nitrate or nitrite
nitrogen-containing compounds, the hydrogen reduction method
requires high cost, the ion exchange method, reverse osmosis method
and electrodialysis method remove inorganic ions in water to result
in change of water properties, and biodegradation method requires
high cost and sometimes adversely affect the ecosystem. The method
disclosed in Patent Document 4 uses expensive noble metal catalysts
like the hydrogen reduction method and besides carries out the
treatment at high temperatures and high pressures. Thus, this
method needs a large-scaled apparatus. The in-situ remediation
method has the problem of red water caused by metallic iron used as
a reducing agent, and sulfides may generate harmful hydrogen
sulfide.
[0008] As a result of intensive research conducted by the inventors
in an attempt to solve these problems, it has been found that a
harmful material remediating agent containing a metal having
reducibility and a metal oxide has conspicuously high decomposing
ability for organic compounds and a harmful material remediating
agent containing a reducing material such as reducing agent or
metal and a metal oxide has conspicuously high remediating ability
for nitrate and nitrite nitrogen-containing compounds even when
used under normal pressure, namely, harmful material remediating
agents containing a reducing material and a metal oxide are
conspicuously high in remediating ability for harmful materials
such as organic compounds and nitrate or nitrite
nitrogen-containing compounds. Thus, the present invention has been
accomplished.
[0009] That is, the present invention relates to a harmful material
remediating agent comprising a reducing material and a metal
oxide.
[0010] Furthermore, the present invention relates to a remediating
agent for organic compounds harmful to environment which contains a
metal having reducibility and a metal oxide.
[0011] Moreover, the present invention relates to a remediating
agent for nitrate and nitrite nitrogen-containing compounds harmful
to environment for using under normal pressure which contains a
reducing material and a metal oxide.
[0012] In addition, the present invention relates to a method for
remediating harmful materials in soil and water which uses the
above remediating agent.
[0013] The harmful material remediating agent of the present
invention, particularly, a remediating agent for organic compounds
harmful to environment which contains a metal having reducibility
and a metal oxide, is excellent in decomposing ability for harmful
organic compounds, a remediating agent for nitrate and nitrite
nitrogen-containing compounds harmful to environment for using
under normal pressure which contains a reducing material and a
metal oxide is excellent in remediating ability for these compounds
under normal pressure. These remediating agents hardly cause
secondary environmental pollution and soil deterioration, and,
furthermore, are low in cost because a reducing material such as a
reducing agent or metal and a metal oxide are used.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] The present invention relates to a harmful material
remediating agent comprising a reducing material and a metal oxide.
It is presumed that the reducing material and the metal oxide used
in the present invention are not high in ability for remediating
environmental pollutants such as organic compounds and nitrate and
nitrite nitrogen-containing compounds when they are singly
contacted with environmental pollutants, but when they are used in
admixture, the metal oxide exerts a certain catalytic action to
develop markedly superior remediating ability. Therefore, the
reducing material and metal oxide, each of which alone is low in
reaction activity, show high remediating ability when they are used
in admixture and give gentle decomposition reaction, and thus it is
considered that the nature of soil hardly changes.
[0015] The reducing materials used in the present invention are not
particularly limited so long as they are non-toxic, and known
reducing agents or metals can be used. When the present invention
is applied to water treatment, the reducing materials are
preferably solid and hardly water-soluble reducing agents or metals
since separation of them can be easily performed.
[0016] The reducing agents can be used each alone or in admixture
of two or more, and may be liquid, solid, gel and the like.
Specific examples thereof are metal sulfites, metal
hydrogensulfites, metal thiosulfates, metal dithionites,
phosphorous acid (H.sub.2PHO.sub.3) and metal salts thereof,
hypophosphorous acid (HPH.sub.2O.sub.2) and metal salts thereof,
and the like. The metal sulfites, the metal hydrogensulfites, the
metal thiosulfates, the metal dithionites, and the metal salts of
phosphorous acid and hypophosphorous acid include, for example,
alkali metal salts and alkaline earth metal salts. Among them,
sodium sulfite (Na.sub.2SO.sub.3), sodium hydrogensulfite
(NaHSO.sub.3), sodium thiosulfate (Na.sub.2S.sub.2O.sub.3), sodium
dithionite (Na.sub.2S.sub.2O.sub.4), sodium phosphite
(Na.sub.2PHO.sub.3) and sodium hypophosphite (NaPH.sub.2O.sub.2)
are high in remediating ability and preferred. As solid and hardly
water-soluble reducing agents, mention may be made of sodium
sulfite, metal salts of phosphorous acid excluding alkali metal
salts, alkaline earth metal salts of hypophosphorous acid, and the
like, which are preferred for application to water treatment.
[0017] The metals may be those which per se act as reducing agents,
and include, for example, iron, aluminum, zinc, copper, magnesium,
and the like, and these may be used each alone or in admixture of
two or more, or as alloys. The form of the metals is not
particularly limited and may be fine powders, particles, small
pieces, and the like, and the fine powders are preferred because
the area of contact with environmental pollutants to be remediated
is larger.
[0018] As the metal oxides, there may be used oxides of iron,
titanium, aluminum, zinc, manganese, and the like, and these may be
used each alone or in admixture of two or more or as composite
oxides thereof. Here, the metal oxides include metal hydrated
oxides and metal hydroxides in addition to usual metal oxides. The
metal oxides may be in any forms of fine powders, particles, small
pieces, and the like, and the fine powders are preferred because
the area of contact with environmental pollutants to be remediated
is larger and the reactivity is high. As the metal oxides, iron
oxide and/or titanium oxide are preferred because of their high
remediating ability. The iron oxides are compounds represented by
the general formula FeO.sub.x (1.ltoreq.x.ltoreq.1.5) and include
specifically ferrous oxide FeO (x=1), ferric oxide Fe.sub.2O.sub.3
(x=1.5), magnetite Fe.sub.3O.sub.4 (x=1.33) and hyper-reduced
magnetite FeO.sub.x (1<x<1.33) and berthollide FeO.sub.x
(1.33<x<1.5). As the iron oxides, there may also be used
those which are obtained by neutralizing waste sulfuric acid
containing iron components produced during production of titanium
oxide by sulfate process or acid washing of iron materials. The
titanium oxides are compounds represented by the general formula
TiO.sub.x (1.ltoreq.x.ltoreq.2) and include specifically titanium
monoxide TiO (x=1), dititanium trioxide Ti.sub.2O.sub.3 (x=1.5),
titanium dioxide TiO.sub.2 (x=2) and titanium oxides having
non-stoichiometric composition (1<x<1.5 or
1.5<x<2).
[0019] Furthermore, when metal oxides having oxygen at a ratio
lower than that calculated from normal valence of the metal
component, so-called suboxides, are used in the present invention,
the remediating ability is enhanced due to the synergistic effect
of the reducibility of the metal suboxides and the reducing
material, which is preferred. The suboxides include those of iron,
titanium, manganese, and the like. Among them, magnetite,
hyper-reduced magnetite, berthollide and titanium oxide having
non-stoichiometric composition are preferred metal suboxides
because of their superior remediating ability.
[0020] In the case of using a metal as the reducing material, this
metal and the metal element constituting the metal oxide may be the
same or different. The reducing material and the metal oxide may be
merely mixed, but in order to improve the operability, they may be
formed into particles or pellets with addition of clay minerals
such as bentonite, talc and clay as a binder. Furthermore, metal
powders can be dispersed in water with addition of optional
dispersant or adjustment of pH, followed by mixing with the metal
oxide to prepare a slurry. In addition, for the purpose of
increasing the effect of the present invention, an adsorbent such
as active carbon or zeolite and a reducing agent such as sodium
sulfite may be added or an oxidizing agent such as hydrogen
peroxide can be added so long as the effect of the present
invention is not damaged.
[0021] In case a water-soluble solid reducing agent is used as the
reducing material, an aqueous solution thereof is mixed with the
metal oxide and a slurry prepared from the mixture can be used. In
case a hardly water-soluble or water-insoluble solid reducing agent
is used, the reducing agent can be dispersed in water with addition
of optional dispersant or adjustment of pH, followed by mixing with
the metal oxide to prepare a slurry. In addition, for the purpose
of increasing the effect of the present invention, an adsorbent
such as active carbon or zeolite and a reducing agent such as
sodium sulfite may be added or an oxidizing agent such as hydrogen
peroxide may be added so long as the effect of the present
invention is not damaged.
[0022] When the harmful material remediating agent of the present
invention is used as a remediating agent for organic compounds
harmful to environment, a metal is used as the reducing agent.
Particularly, use of metallic iron and iron oxide or metallic iron
and titanium oxide as the remediating agent is high in effect and
preferred, and use of metallic iron and iron oxide is more
preferred. Mixing ratio of the metal and the metal oxide
(metal:metal oxide) is preferably 0.02:1-9:1 in weight ratio, and
if the ratio of the metal is higher or lower than the above range,
the desired effect can hardly be obtained. Particularly, when
metallic iron and iron oxide are used, when the mixing ratio is
within the above range, production of red water may be prevented
although metallic iron is contained. More preferred range is
0.05:1-4:1.
[0023] The organic compounds which can be decomposed in the present
invention are not particularly limited, and the present invention
can also be applied to highly volatile organic compounds, organic
agricultural chemicals, dioxin, PCB, nonylphenol, bisphenol A,
4-nitrotoluene, and the like. The highly volatile organic compounds
include, for example, halogenated hydrocarbons such as
trichloroethylene, tetrachloroethylene, perchloroethylene,
trichloroethane, tetrachloroethane, chlorobenzene, dichloromethane
and trichloroethane, aromatic compounds such as benzene, xylene,
toluene and acetone, and aldehydes such as acetaldehyde and
formaldehyde. The organic agricultural chemicals include, for
example, organic chlorine compounds such as DDT, BHC, endrin,
dierdrin, aldrin, heptachlor, chlordane, pentachlorobenzyl alcohol,
atrazine, hexachlorobenzene, hexachlorocyclohexane, methoxychlor
and pentachlorophenol; organic phosphorus compounds such as
parathion, TEPP and malathion; carbamate compounds such as
methomyl; synthetic pyrethroid compounds such as permethrin;
phenoxy compounds such as 2,4-dichlorophenoxyacetic acid and
2,4,5-trichlorophenoxyacetic acid; and dibromochloropropane,
tributyltin chloride and 2,4-D. The remediating agents of the
present invention have especially high effect on DDT and BHC.
[0024] When the remediating agents of the present invention are
used for remediation of nitrate and nitrite nitrogen-containing
compounds harmful to environment, they can reduce nitrate nitrogen
and nitrite nitrogen to harmless nitrogen gas or ammonia even under
normal pressure. Either of reducing agent and metal can be used as
the reducing material, and when metal is used, use of metallic iron
and iron oxide or metallic iron and titanium oxide as the
remediating agent is high in effect and preferred, and use of
metallic iron and iron oxide is further preferred. In the case of
using reducing agent as the reducing material, the mixing ratio of
the reducing agent and the metal oxide (reducing agent:metal oxide)
is preferably 0.1:1-5:1 in weight ratio, and in the case of using
metal as the reducing material, the mixing ratio of the metal and
the metal oxide (metal:metal oxide) is preferably 0.001:1-3:1 in
weight ratio. If the ratio of each reducing material is higher or
lower than the above range, the desired effect can hardly be
obtained. Particularly, when metallic iron and iron oxide are used
in combination within the above range, generation of red water can
be prevented although metallic iron is contained in the remediating
agent. More preferred ranges are 0.5:1-2:1 and 0.005:1-2:1,
respectively.
[0025] As the nitrate nitrogen-containing compounds which can be
remediated by the present invention, mention may be made of
ammonium nitrate (NH.sub.4NO.sub.3), Chile nitre (NaNO.sub.3),
calcium nitrate (Ca(NO.sub.3).sub.2), potassium nitrate
(KNO.sub.3), ammonium sulfate-nitrate (a mixture of
NH.sub.4NO.sub.3 and (NH.sub.4).sub.2SO.sub.4), Nitro-chalk (a
mixture of NH.sub.4NO.sub.3 and CaCO.sub.3), Calurea
(Ca(NO.sub.3).sub.2.4CO(NH.sub.2).sub.2), and compositions
containing the above compounds, such as nitrogenous fertilizers,
and as nitrite nitrogen-containing compounds, mention may be made
of reduction products of the above nitrate nitrogen-containing
compounds.
[0026] The harmful material remediating agents of the present
invention can be used for water treatment and soil treatment by
known methods. For example, for water treatment, the remediating
agent of the present invention is introduced into various waste
waters such as industrial waste water, agricultural waste water and
living waste water, and underground water pumped up, followed by
stirring to remediate the environmental pollutants such as organic
compounds and the nitrate and nitrite nitrogen-containing compounds
and then the remediating agents may be filtered off or can be used
by supporting on adsorbents such as active carbon and zeolite and
packing in a reaction column. The remediated water is recycled into
environments such as seas, rivers, lakes and underground water. In
the case of remediation of underground water, for example, the
present invention can be applied to so-called permeation barrier
method according to which a layer containing the remediating agent
of the present invention is formed in soil to remediate
environmental pollutants contained in the underground water during
permeation of the underground water through the layer.
[0027] For soil treatment, when environmental pollutants are highly
volatile organic compounds, the soil is subjected to deaeration and
gaseous components containing the volatilized organic compounds are
collected, followed by allowing the gaseous components to contact
with the remediating agent. Alternatively, the remediating agent
can be applied to the in-situ remediation method by introducing the
remediating agent into soil. The in-situ remediation method is
especially preferred because it does not need special equipments
such as reaction column and can remediate soil at low cost, and can
be employed for remediation of, particularly, low volatile organic
compounds such as organic agricultural chemicals, PCB and dioxin or
nitrate and nitrite nitrogen-containing compounds. The method for
introduction into soil is not particularly limited and can be
optionally selected depending on nature of soil and configuration
of the ground, and, for example, in the case of solid remediating
agent, the soil is dug up and the soil is mixed with the
remediating agent, followed by returning the soil or the
remediating agent is made to a slurry and poured into soil.
EXAMPLES
[0028] The examples of the present invention will be explained
below, which do not limit the present invention in any manner.
Examples 1-3
[0029] Metallic iron (electrolytic metallic iron powder having an
average particle diameter of about 5.0 .mu.m: special grade
chemical manufactured by Kanto Kagaku Co., Ltd.) as a reducing
material and iron oxide (berthollide (FeO.sub.1.447) powder having
an average particle diameter of about 0.1 .mu.m) as a metal oxide
were mixed at a weight ratio of 3:1, 1:1 and 0.33:1 to obtain
harmful material remediating agents of the present invention
(samples A-C). These are referred to as remediating agents of
Examples 1-3.
Examples 4-7
[0030] Metallic iron used in Example 1 as a reducing material and
iron oxide obtained by neutralizing and oxidizing iron-containing
waste sulfuric acid (berthollide (FeO.sub.1.39) powder having an
average particle diameter of about 0.07 .mu.m) as a metal oxide
were mixed at a weight ratio of 3:1, 1:1, 0.33:1 and 0.1:1 to
obtain harmful material remediating agents of the present invention
(samples D-G). These are referred to as remediating agents of
Examples 4-7.
Examples 8-10
[0031] Sodium hydrogensulfite as a reducing material was mixed with
berthollide powder used in Example 1, magnetite powder
(FeO.sub.1.333) having an average particle diameter of about 0.1
.mu.m and titanium oxide powder (TiO1.82) having an average
particle diameter of about 0.2 .mu.m as metal oxides at a weight
ratio of 1:1, respectively, to obtain harmful material remediating
agents of the present invention (samples H-J). These are referred
to as remediating agents of Examples 8-10.
Examples 11-17
[0032] Colloidal metallic iron powder having an average particle
diameter of about 0.5 .mu.m as a reducing material and the
berthollide powder used in Examples 4-7 as a metal oxide were mixed
at a weight ratio of 1:1, 0.2:1, 0.1:1, 0.05:1, 0.03:1, 0.02:1 and
0.01:1 to obtain harmful material remediating agents of the present
invention (samples K-Q). These are referred to as remediating
agents of Examples 11-17.
Comparative Examples 1-7
[0033] The electrolytic metallic iron powder used in Examples 1-7,
the berthollide powder used in Examples 1-17, the berthollide
powder used in Examples 4-7 and 11-17, the magnetite powder,
titanium oxide powder and sodium hydrogensulfite used in Examples
8-10, and the colloidal metallic iron powder used in Examples 11-17
were used as comparative samples. (Samples R-X).
Evaluation 1
[0034] Each of the samples A-C, R and S of Examples 1-3 and
Comparative Examples 1 and 2 was added to a 3 ppm aqueous
trichloroethylene solution in an amount of 25 g/liter and the
solution was charged in a vial, which was stoppered tightly,
followed by stirring with shaking for 24 hours to carry out the
treatment. The concentration of trichloroethylene in the aqueous
solution after lapse of 1 day and 7 days from the treatment was
measured by GC-MS head space method. Furthermore, color of the
aqueous solution after the treatment was visually judged.
[0035] The results of the evaluation are shown in Table 1. It was
found that when the metallic iron and the iron oxide were used each
alone, the decomposing ability for organic compounds was small
while the environmental remediating agents of the present invention
obtained by mixing them were high in decomposing ability for
trichloroethylene and useful as remediating agents for organic
compounds harmful to environment and besides they caused no
coloration of the aqueous solution after the treatment.
TABLE-US-00001 TABLE 1 Remediating Concentration of agent
trichloroethylene Metallic iron (ppm) Color of powder:Iron after
after remediated Example Sample oxide 1 day 7 days water Example 1
A 3:1 1.8 0.8 Colorless Example 2 B 1:1 1.5 0.0 '' Example 3 C
0.33:1 1.5 0.1 '' Comparative R 1:0 3.0 3.0 Red Example 1
Comparative S 0:1 2.6 3.0 Colorless Example 2
Evaluation 2
[0036] A test solution in an amount of 100 ml was prepared by
adding .gamma.-BHC to distilled water so that the concentration of
.gamma.-BHC reached 1 ppm. To this test solution was added 10 g of
each of samples D-G of Examples 4-7 and samples R and T of
Comparative Examples 1 and 3, and the solution was charged in a 15
vial, which was stoppered tightly, followed by stirring with
shaking for 24 hours to carry out the treatment. The test solution
to which no sample was added was referred to as Comparative Example
8. Then, each of the test solution was charged in a separating
funnel of 100 ml and 10 ml of methylene chloride was added thereto,
followed by mixing for 10 minutes. Then, the lower layer (methylene
chloride layer) was collected and the extract was subjected to
spontaneous filtration. To the remaining upper layer (aqueous
layer) was further added 10 ml of methylene chloride, followed by
mixing for 10 minutes. Then, the lower layer (methylene chloride
layer) was collected and the extract was subjected to spontaneous
filtration and combined with the first extract. To the resulting
extract was added 2 g of anhydrous sodium sulfate to adsorb water
for 10 minutes, and, thereafter, anhydrous sodium sulfate was
separated by spontaneous filtration. The concentration of BHC
contained in the extracted methylene chloride was measured by GC-MS
head space method.
[0037] The results are shown in Table 2. It was found that the
harmful material remediating agents of the present invention were
also high in decomposing ability for BHC as remediating agents for
organic compounds harmful to environment. TABLE-US-00002 TABLE 2
Concentration Remediating agent of BHC Example Sample Metallic
iron:Iron oxide (ppm) Example 4 D 3:1 0.12 Example 5 E 1:1 Less
than measurement limit Example 6 F 0.33:1 Less than measurement
limit Example 7 G 0.1:1 0.07 Comparative R 1:0 0.84 Example 1
Comparative T 0:1 0.94 Example 3 Comparative -- --:-- 0.95 Example
8
Evaluation 3
[0038] Each of the samples (H-J, S, U-W) obtained in Examples 8-10
and Comparative Examples 2 and 4-6 was added in an amount of 150
g/liter to an aqueous potassium nitrate solution of 10 ppm in
concentration and charged in a vial, which was stoppered tightly,
followed by stirring with shaking for 24 hours to carry out the
treatment. The concentration of nitrate ion contained in the
aqueous solution after the treatment was measured by ion
chromatograph method. Since the decomposition reaction of nitrate
ion is affected by pH, some of the samples were optionally adjusted
to pH 6.5-7.5 before the treatment. For example, in Example 8, pH
was adjusted using an aqueous sodium hydroxide solution.
[0039] The results of the evaluation are shown in Table 3. It was
found that when the metal oxide and the reducing agent were used
each alone, the decomposing ability for nitrate ion was small while
the harmful material remediating agents of the present invention
obtained by mixing them were high in decomposing ability for
nitrate ion even under normal pressure and useful as remediating
agents for nitrate nitrogen-containing compounds harmful to
environment. TABLE-US-00003 TABLE 3 Concentration of nitrate ion
Example Sample Remediating agent (ppm) Example 8 H Sodium
hydrogensulfite + 0.1 or less Berthollide Example 9 I Sodium
hydrogensulfite + 0.1 or less Magnetite Example 10 J Sodium
hydrogensulfite + 0.1 or less Titanium oxide Comparative S
Berthollide 9.8 Example 2 Comparative U Magnetite 9.6 Example 4
Comparative V Titanium oxide 9.0 Example 5 Comparative W Sodium
hydrogensulfite 10.0 Example 6
Evaluation 4
[0040] Each of the samples (K-Q, T, X) obtained in Examples 11-17
and Comparative Examples 3 and 7 was added in an amount of 100
g/liter to an aqueous potassium nitrate solution of 230 ppm in
concentration of nitrate ion. The solution to which no remediating
agent was added is referred to as Comparative Example 9. These were
remediated in the same manner as in evaluation 3, and the nitrate
ion concentration was measured and simultaneously ammonium ion
concentration was also measured. Conversion rate to ammonia was
calculated from the formula: {concentration of ammonium ion in
terms of nitrogen (ppm)/52 (concentration of nitrate ion in terms
of nitrogen in Comparative Example 9: ppm)}.times.100. Furthermore,
color of the aqueous solution after treatment was visually
judged.
[0041] The results of the evaluation are shown in Table 4. It was
found that the harmful material remediating agents of the present
invention obtained by mixing the metal oxide and the metallic iron
were high in decomposing ability for nitrate ion even under normal
pressure and the remediated nitrate ion was efficiently converted
to harmless ammonium ion when they were used as remediating agents
for nitrate nitrogen-containing compounds harmful to environment.
It was also found that the aqueous solution was not colored even
after the treatment. TABLE-US-00004 TABLE 4 Concentration
Remediating Concentration Concentration of ammonium agent of
nitrate of ammonium ion in terms Conversion Color of Metallic iron
ion ion of nitrogen rate remediated Example Sample powder:Iron
oxide (ppm) (ppm) (ppm) (%) water Example 11 K 1:1 47 31 25 48
Colorless Example 12 L 0.2:1 0 44 36 69 '' Example 13 M 0.1:1 0 52
43 83 '' Example 14 N 0.05:1 2 56 46 89 '' Example 15 O 0.03:1 1 50
41 79 '' Example 16 P 0.02:1 2 47 39 75 '' Example 17 Q 0.01:1 46
43 36 69 '' Comparative T 0:1 230 1 1 2 '' Example 3 Comparative X
1:0 182 16 13 25 Red Example 7 Comparative -- 0:0 230 0 0 0
Colorless Example 9
Evaluation 5
[0042] The remediating agent (sample M) obtained in Example 13 was
added in an amount of 100 g/liter to a polluted water containing a
nitrate and nitrite nitrogen-containing compound and the polluted
water was charged in a vial, which was stoppered tightly, followed
by stirring with shaking for 24 hours to carry out the treatment.
The polluted water to which the remediating agent was not added is
referred to as Comparative Example 10. The concentration of nitrate
ion and nitrite ion contained in the aqueous solution after the
treatment were measured by ion chromatograph method.
[0043] The results of the evaluation are shown in Table 5. It was
found that the harmful material remediating agent of the present
invention was also useful as a remediating agent for nitrite
nitrogen-containing compound. TABLE-US-00005 TABLE 5 Concentration
Concentration Metallic iron of nitrate of nitrite powder:Iron ion
ion Sample oxide (ppm) (ppm) Example 13 M 0.1:1 0 0.1 or less
Comparative -- 0:0 162 0.8 Example 10
INDUSTRIAL APPLICABILITY
[0044] The present invention is useful for remediation of
underground water or soil containing harmful organic compounds or
nitrate and nitrite nitrogen-containing compounds.
* * * * *