Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2003-06-26
2004-11-02
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S248000, C510S508000
Reexamination Certificate
active
06812197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an iron-based powder useful for cleaning materials (particularly soil, underground water, etc.) contaminated with organic halides.
2. Description of the Related Art
Volatile organic chlorine compounds, such as trichloroethylene, have widely been used not only as degreasing detergents in semiconductor factories and metal working factories, but also as detergents in dry cleaning. However, those organic chlorine compounds have often been discharged and discarded in the past. Because the organic chlorine compounds are hard to decompose in the natural world, they are gradually accumulated in and contaminate the soil and the underground water, thus resulting in a social problem.
Known treatment methods for rendering contaminants in the soil and the underground water harmless include, for example, a pyrolysis method comprising the steps of excavating contaminated soil and removing the contaminants with combustion using a rotary kiln or the like, a soil vapor extraction method comprising the steps of sucking contaminants dissolved in the underground water with a vacuum pump and recovering the contaminants for removal, a pumping treatment method comprising the steps of pumping up the underground water and extracting contaminants for removal, and a microbial method utilizing the microbe ability of decomposing contaminants.
Those treatment methods, however, have disadvantages as follows. The pyrolysis method needs large-scaled equipment for excavating the soil and requires a high cost when the soil after the heat treatment is utilized for refilling. The soil vapor extraction method is able to recover only vaporized contaminants and raises the necessity of decomposing the contaminants after the recovery. The pumping treatment method is able to recover only contaminants dissolved in water and requires decomposition of the contaminants after the recovery. The microbial method cannot be applied to some cases depending on soil conditions. Further, because the microbial method relies on the decomposing reaction caused by microbes, there is a disadvantage that a longer treatment period than the other methods is needed in the case of high-concentration contamination, or the decomposing reaction proceeds just halfway in some cases.
A method of reducing and decomposing organic chlorine compounds using iron powder has been proposed as a method that requires neither large-scaled equipment nor the decomposing process after the recovery and can render the organic chlorine compounds harmless with stability. The proposed method utilizes electrons generated upon oxidization of the iron powder and decomposes the organic chlorine compounds while reducing them. However, the decomposition efficiency of the organic chlorine compounds with the iron powder is not so high because of the specific property, and hence a variety of methods are proposed for more satisfactory practical use.
For example, Japanese Examined Patent Application Publication No. 2-49158 proposes a method for decomposing hydrocarbon halides by adding iron powder to water, which is to be treated and contains hard-to-decompose hydrocarbon halides, and by shaking a mixture, the method comprising the steps of removing dissolved oxygen from the treated water in advance and adjusting the treated water to the pH range of 6.5 to 9.5. However, this method requires complicated operations, such as removal of the dissolved oxygen and the pH adjustment, and hence has a difficulty in application to field treatment in the contaminated site.
Japanese Patent Publication (by PCT Application) No. 6-506631 proposes a method for decomposing contaminated water containing organic chlorine compounds to render it harmless by passing the contaminated water through filings of iron and steel, the method comprising the steps of mixing the filings of iron and steel with activated coal, and passing the contaminated water through a mixture layer. However, this method necessitates the use of expensive activated coal and increases a treatment cost.
Recently, methods for increasing reactivity of iron powder itself without requiring pretreatment of contaminated soil and water or without employing activated coal have also been proposed. For example, Japanese Unexamined Patent Application Publication No. 11-235577 discloses a method comprising the steps of mixing soil with iron powder having a carbon content of not less than 0.1 weight % and a specific surface area of not less than 500 cm
2
/g, and decomposing organic chlorine compounds in the soil. The iron powder having a large specific surface area is provided as iron powder obtained by reducing iron ore (i.e., sponge-shaped ore-reduced iron powder). However, iron powder other than the sponge-shaped ore-reduced iron powder cannot be practically used because reactivity lowers when the iron powder has a smaller specific surface area.
Also, Japanese Unexamined Patent Application Publication No. 2001-9475 proposes the use of iron powder containing copper in consideration of that metallic copper noticeably promotes the reaction of decomposing organic halogen compounds, which is caused by metallic iron. However, copper has a high material cost. Further, when producing the iron powder containing copper, the proposal requires a complicated production process of mixing iron powder in a copper ion solution, such as an aqueous solution of copper sulfate, and recovering an obtained precipitate, whereby the production cost is increased.
In addition to the sponge-shaped iron powder mentioned above, atomized iron powder is also known. The atomized iron powder is produced by atomizing molten steel into powder. The as-atomized powder is called black powder because the powder surface is oxidized to become black. The black powder is perfectly reduced, as required, into a reduced powder. The reduced powder is called white powder in contrast with the black powder. The white powder is coated with a resin, which serves as a binder, over the powder surface, and is employed in the field of powder metallurgy. There is also proposed a method of utilizing the iron powder for powder metallurgy (i.e., the atomized iron powder) instead of the sponge-shaped iron powder for the purpose of cleaning soil.
For example, Japanese Unexamined Patent Application Publication No. 2002-20806 suggests a proposal of containing 0.01 to 4.0 mass % of Ni in the iron powder for powder metallurgy in consideration of that hydrogen produced on Ni surfaces promotes the decomposing reaction (including the reducing reaction of organic halogen contaminants and the oxidizing reaction of metals). However, this Publication states that reactivity of the cleaning reaction lowers when oxides are formed on powder surfaces.
SUMMARY OF THE INVENTION
In view of the state of the art described above, it is an object of the present invention to provide an iron-based cleaning powder capable of efficiently decomposing organic halides even when oxides are formed on powder surfaces.
Another object of the present invention is to provide an iron-based cleaning powder which is capable of decomposing organic halides at higher efficiency than the so-called white powder and can be produced in a more simple process than the white powder.
As a result of conducting intensive studies to achieve the above objects, the inventors discovered that, if the oxides formed on the powder surfaces are ones formed during atomization, even iron powder having those oxides is able to efficiently decompose organic halides on the contrary to the suggestion stated in the above-cited Japanese Unexamined Patent Application Publication No. 2002-20806, and then found that iron powder (black powder) obtained with the atomization process can be used for the purpose of cleaning materials (such as soil and underground water) contaminated with organic halides. Also, the inventors found that the effective use of the black powder eliminates the necessity of reducing the black powder to the white powder and enables cleaning iron powder to be provided w
Kawai Kenji
Matsubara Masaaki
Sakuma Hitoshi
Seki Yoshikazu
Yakou Yasuko
(Kobe Steel, Ltd.)
Ogden Necholus
LandOfFree
Iron-based cleaning powder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Iron-based cleaning powder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Iron-based cleaning powder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3358748