Compositions – Reductive bleachant – deoxidant – reductant – or generative
Reexamination Certificate
2001-03-29
2003-07-22
Bos, Steven (Department: 1754)
Compositions
Reductive bleachant, deoxidant, reductant, or generative
C588S253000, C588S253000, C588S249000, C588S253000, C405S128500, C405S128750, C516S095000
Reexamination Certificate
active
06596190
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
Technical Field to Which the Invention Pertains
The present invention relates to a remediation agent for soil contaminated with contaminants such as organic halides and hexavalent chromium, a slurry of fine iron particles suitably employable for the agent and process for the preparation thereof, and a method for the remediation of contaminated soil.
BACKGROUND OF THE INVENTION
Volatile organic halides such as trichloroethylene have been employed in a large amount to industrially wash various machines for removal of stain-containing oils. The use of the organic halides has been increasingly regulated from the consideration of environment pollution. However, a large amount of organic halides already have been employed, and therefore soil and groundwater pollutions have been widely advanced. In more detail, the organic halides such as trichloroethylene are stable and scarcely decomposed by microorganisms, and hence the organic halides abandoned in the soil not only contaminate the soil per se, but also finally do the river or groundwater that is occasionally source for drinking water. Similarly, such environment pollution has also occurred in a site where a factory is removed but hexavalent chromium remains.
Examples of methods for remedying the soil contaminated with volatile organic compounds such as the organic halides include soil-gas sucking method, groundwater pumping-up method, and soil-digging method. The soil-gas sucking method is of coercively sucking aimed substances existed in an unsaturated zone (layer). This method comprises providing wells for suction in the soil (land formation) by boring, reducing the pressure within the wells by a suction pump, collecting the vaporized organic compounds into the wells, and leading the compound to the underground to cause them to be adsorbed by activated carbon for treatment. In the case that the contamination by the organic compounds extends to an aquifer, adopted is a method comprising providing a water pump within the suction wells and pumping up water together with soil-gas to treat them.
The groundwater pumping-up method is performed by providing pumping-up wells within the soil and pumping up contaminated groundwater to treat it. Further, the soil-digging method is done by digging the contaminated soil and subjecting the dug soil to a wind drying and heat treatment to remove and collect the organic compounds.
A method for the remediation of contaminated water that are collected in the above manner or of contaminated groundwater, is disclosed in for example Patent Gazette No. 2636171. The method comprises removing oxygen dissolved in the contaminated water, bringing the water into contact with the surface of metal such as iron, and reducing organic halides contained in the water to remove. Such methods utilizing the reducing action of iron are also described in, for example, JP-A03-106496, JP-A03-30895, JP-A05-501520, JP-A08-257570, JP-A10-263522. Any of these methods have a feature comprising passing the contaminated water through a layer or filter containing iron to treat the water.
As for the soil contaminated with the hexavalent chromium, there is known the method of remedying the soil by the use of a reducing agent such as iron (II) sulfate. However, when the hexavalent chromium is existed in the soil in the form of bulk containing trivalent and hexavalent chromium's such as chromium slag, the iron (II) sulfate is not sufficiently capable of reducing the chromium because it shows reducing action only for short time. Accordingly, there is desire to have a remediation agent showing reducing action for a long-term period.
OBJECT TO BE SOLVED BY THE INVENTION
The object of the present invention is to provide the remediation agent for soil that can directly and effectively render the contaminants such as organic halides, hexavalent chromium in the soil nontoxic through reduction of the contaminants, or render the contaminants nontoxic and remove them; a slurry of fine iron particles suitably employable for the agent and a process for the preparation thereof, and a method for the remediation of contaminated soil by use of the agent.
MEANS TO SOLVE THE OBJECT
Methods for the remediation of contaminated soil with organic halides that have been carried out so far, include those comprising collecting contaminated water from contaminated soil to remedy the water, or comprising collecting contaminated soil to remedy the soil. These methods are not those of directly and effectively remedying the contaminated soil per se.
The present inventors have noted iron having action of reducing and decomposing the organic halides (in other word, dehalogenation) and have studied to develop the above-mentioned process for easily remedying the contaminated soil by utilizing the iron.
The inventors have found by the study the following matter: i.e., the fine iron particles that are employed in the conventional method for the remediation have a relatively large average particle size of several tens to several hundreds &mgr;m and further are unsettled in their shapes; and therefore when the above fine iron particles, for example in the form of their aqueous dispersion, are applied to the contaminated soil, the fine iron particles is not capable of sufficiently penetrating into the soil. The inventors have further studied based on the above findings to solve the above problem by rendering the particles fine to enlarge the surface area, whereby they have attained the invention.
Further, the inventors have found that in addition to increase of disposal capacity of contaminants by increase of the surface area of iron, to render the shape of the iron particle spherical enables the iron particles to rapidly penetrate into the soil. As mentioned above, the conventional fine iron particles used for the remediation have particle size of not less than several tens &mgr;m, whereas the fine iron particles of the invention has particle size of less than 10 &mgr;m, and therefore have remediation capacity two or more times (occasionally ten or more times) that of the conventional fine iron particles. Further in the case that the shape of the particles is spherical, the particles show extremely excellent penetration property compared with the conventional unsettled those.
Hence, the object of the invention is solved by a remediation agent for contaminated soil (agent for remedying contaminated soil), comprising a slurry of fine iron particles in which the fine iron particles (preferably those in the form of sphere) having an average particle size of less than 10 &mgr;m (preferably 0.1 to 6 &mgr;m) are dispersed in water (a first invention).
Moreover, the inventors have studied to enhance the workability when the aqueous suspension containing the above fine iron particles is applied to the soil, by maintaining stable dispersibility and reduced viscosity of the suspension. As a result, they have found that it gives a remediation agent suitable for the above-mentioned simple remediation method to use the fine iron particles that disperses the particles in water via bubbles formed on the periphery of the particles, to attain the present invention. In more detail, such a remediation agent in the form of aqueous suspension can be easily and directly applied to the soil, and can easily penetrate into the soil to bring about rapid remediation.
Further, the reducing agent of the fine iron particles have been found to be effective to contaminants to be reduced, especially hexavalent chromium-containing compounds.
Accordingly, the object of the invention is solved by a remediation agent containing a slurry of fine iron particles (aqueous suspension of fine iron particles) wherein the fine iron particles having an average particle size of less than 10 &mgr;m (preferably 0.1 to 6 &mgr;m) are dispersed via bubbles formed on the periphery of the particles (preferred embodiment of the first invention).
Further, the object of the invention is solved by a method for the remediation of contaminated soil comprising causing the remediation ag
Igawa Junji
Kimura Yasunori
Maeda Terunobu
Bos Steven
Hazama Corp.
Kuhar Anthony
LandOfFree
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