JP2010194451A - Organic halide cleaning agent and cleaning method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve decomposition velocity even if large amounts of water soluble metal salts not are mixed, when the water soluble metal salts are mixed in the decomposition of an organic halide with iron powder. <P>SOLUTION: The organic halide is decomposed and purified for a short time by supplying a mixture of an extremely minute amount of nickel sulfate and/or nickel chloride and a partial alloy powder having a partial alloy phase of iron and nickel inside and/or on a surface of the iron powder to a soil contaminated with the organic halide, wastewater, or underwater. Less than 0.1 wt.% of nickel sulfate and/or nickel chloride to the amount of partial alloy powder is used. It is preferable that the mixed amount of the iron powder is in a scope of 0.1-10 wt.% to the soil. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a detoxifying agent in soil, drainage or groundwater contaminated with an organic halide, and a detoxifying treatment method using the same.

  In recent years, environmental pollution problems due to organic halogen compounds such as TCE (trichloroethylene), PCE (tetrachloroethylene), dichloromethane, PCB (polychlorinated biphenyl) and dioxins have become a major problem, soil contaminated by these organic halides, Detoxification treatment agents such as drainage and groundwater, and purification methods thereof are being studied.

  Conventionally, a soil gas suction method, a soil excavation method, a groundwater pumping method, and the like are known as purification methods for these contaminations. The soil gas suction method is a method for forcibly sucking pollutants, and is a method for collecting and removing the pollutants as soil gas with a pump. The soil excavation method is a method in which contaminated soil is excavated, recovered and removed by drying, heat treatment, and the like. The groundwater pumping method is a method for removing pollutants by pumping contaminated groundwater.

  However, the soil gas suction method groundwater pumping method requires a plurality of suction wells and large ground facilities when a wide range of soil is targeted, and the soil excavation method is costly for heat treatment of the excavated soil. On the other hand, an in-situ purification method using iron has been proposed as a method for directly purifying contaminated soil. However, when iron powder is used alone, there is a problem that it takes a long time to purify the contamination.

  On the other hand, a method of reducing and dechlorinating Ni or Cu, which is a different metal, on iron powder (for example, Non-Patent Document 1), and a method of using a mixture of a water-soluble metal salt simultaneously with iron powder have been proposed. (For example, Patent Documents 1 and 2). Moreover, the method of using the iron powder which comprised the local battery structure in the metal powder particle is proposed (for example, patent documents 3-4). However, it is necessary to add a large amount of different metal elements, and depending on the type of organic halide, the decomposition may take a long time or may not be decomposed, resulting in a problem that a sufficient decomposition rate cannot be obtained. there were.

  On the other hand, a method of improving the decomposition performance with a small amount of dissimilar metals by using a technique called partial alloying when a local battery structure is composed of dissimilar metals and iron has been proposed (see Patent Documents 5 to 12). However, in such a method, when a complete alloy is used, the performance deteriorates with sufficient performance. Therefore, precise control is required for partial alloying. Further, when the content of the different metal is less than 0.1% by weight, there is a problem that the decomposition performance deteriorates (deteriorates) during storage after partial alloying.

JP-A-2005-113112 JP 2004-249223 A JP 2002-309229 A JP 2005-118755 A JP2003-136051A JP 2004-57881 A JP 2004-305235 A JP 2004-305792 A JP 2005-95750 A JP 2006-22166 JP2008-142893 JP 2008-272644 A

Sakizaki et al., Industrial Water, VOL391, (1991), 29.

  It is an object of the present invention to provide a method for decomposing an organic halide in a very short time without requiring a complicated process or apparatus.

  The present inventors have found that a very small amount of nickel sulfate and / or a small amount of nickel sulfate and / or a partial alloy powder having a partial alloy phase of iron and nickel on and / or on the surface of iron powder with respect to soil, drainage or groundwater contaminated with organic halides. Alternatively, the inventors have found that the organic halide can be decomposed in a short time by mixing nickel chloride, and have completed the present invention.

  The present invention will be described in detail below.

  The present invention relates to a partial alloy powder having a partial alloy phase of iron and nickel on the inside and / or surface of iron powder and to a soil, wastewater or groundwater contaminated with an organic halide, and 0. This is a method for purifying organic halides by mixing less than 1% by weight of nickel sulfate and / or nickel chloride.

  The organic halide in the present invention is not particularly limited. For example, unsaturated halogenated carbonization such as tetrachloroethylene, trichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, 1,1-dichloroethylene, vinyl chloride and the like. Saturated halogenated hydrocarbons such as hydrogen, 1,1,2,2-tetrachloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethane, carbon tetrachloride, chloroform, dichloromethane, etc. Can be mentioned.

  In the purification method of the present invention, as the organic halide decomposition treatment agent, a partial alloy powder and a mixture of nickel sulfate and / or nickel chloride of less than 0.1% by weight with respect to the partial alloy powder are used.

  Partial alloy powders have high decomposition performance against organic halides as they are, but when such partial alloy powders are mixed with nickel sulfate and / or nickel chloride, the decomposition performance is further improved by mixing a very small amount. improves. In addition, the partial alloy powder may deteriorate its decomposition performance after long-term storage, but nickel sulfate and / or nickel chloride is mixed with the deteriorated partial alloy powder within the scope of the present invention. However, there is an advantage that high decomposition performance can be obtained.

  The partial alloy powder in which the nickel component is segregated in and / or on the surface of the iron powder is obtained by a mechanical alloying method by strongly pulverizing a mixed powder of iron and nickel. In the case of complete alloying, the decomposition activity is lowered, so that it is preferable to use a partially alloyed (partly non-alloy remains).

  As the partial alloy powder in which the nickel component is segregated in the iron powder and on the surface, it is preferable to use a partial alloy powder obtained by mechanically alloying a mixture composed of 0.01 to 2 parts by weight of nickel with respect to 100 parts by weight of iron.

  As the existence site of the partial alloy of iron and nickel, the alloy part does not occupy the entire surface of the iron particles, and it is preferable that the nickel part and the alloying part exist respectively on the surface of the iron powder. If the alloy covers the entire surface of the iron powder, the local battery action hardly occurs and the organic chlorinated product does not easily decompose. For partial alloying, the alloy layer (nickel diffusion layer) can be confirmed by using EPMA (electron beam microanalyzer) or TEM (transmission electron microscope).

  It is desirable that an alloy part of iron and carbon is further present in the partial alloy powder of the present invention. In general, pure iron, steel, cast iron, pig iron, or the like can be used as the iron powder, but an iron portion existing in the iron powder and an iron-carbon alloy portion such as cementite can also act as active sites. The amount of carbon in the iron powder may be in the range of 2 to 3% when cast iron powder is used, and 0.01 to 0.05% in the case of reduced iron powder.

The shape of the iron powder is not particularly limited, and includes a spherical shape, a dendritic shape, a piece shape, a needle shape, a square shape, a laminated shape, a rod shape, a plate shape, a sponge shape, and the like. When the specific surface area of the iron powder is 0.05 m ² / g or more, preferably 0.2 to 10 m ² / g, the decomposition reaction rate and the contact probability can be improved, which is effective in using coarse particles.

  Also, the particle size of the iron powder is not particularly limited, but if the particle size is less than 53 μm, it is classified as a dangerous substance type 2 if it is 50% by weight or more, and there is a risk such as ignitability. It is preferable that it does not correspond to thing 2nd kind.

  The concentration of nickel sulfate and / or nickel chloride of the present invention is preferably less than 0.1 wt%, particularly preferably in the range of 0.01 to 0.09 wt% with respect to the partial alloy powder.

  In the method using a water-soluble metal salt that has been reported so far, the effect is not exhibited unless a very large amount of the water-soluble metal salt is mixed with the iron powder, but using a large amount of the water-soluble metal salt is not possible. There was a problem in terms of environmental impact. On the other hand, when nickel sulfate and / or nickel chloride is used among water-soluble metal salts, the organic halide can be highly decomposed in a very small amount, ie, less than 0.1% by weight of the iron powder.

  Nickel sulfate and / or nickel chloride may be used in the form of crystals or powder, and may be added to a partial alloy powder or previously added to a slurry of a partial alloy powder after being dissolved in water. . Further, nickel sulfate and / or nickel chloride dissolved in water may be added to and mixed with the iron powder and then used after drying. Since nickel sulfate and / or nickel chloride is used at the same time as the partial alloy powder, most of the nickel precipitates in the partial alloy powder and does not elute as ions, so there is no problem with the environment.

  The mixing amount of the partial alloy powder powder is preferably 0.1 to 10% by weight, particularly 1 to 3% by weight, based on the soil. If the mixing amount is too small, uniform mixing with the soil is difficult, and if the mixing amount is too large, the decomposition rate is saturated at a certain rate and is not economical.

  In the present invention, the partial alloy powder can be used by further mixing iron powder and / or iron oxide not containing nickel.

  In the present invention, when the object to be purified is soil, it is necessary that water be present in the soil. The amount of water in the soil is preferably 10 parts by weight or more, particularly preferably in the range of 20 to 60 parts by weight with respect to 100 parts by weight of the soil.

  The purification method of the present invention can be applied to the treatment of contaminated water collected by the groundwater pumping method, river water, etc., but can be particularly preferably applied to the method of pouring into soil or groundwater. The method of the present invention does not require complicated processing steps and equipment, and can easily and directly purify the contamination source.

  The purification method of the present invention can decompose an organic halide in a short time by using a substantially very small amount of nickel sulfate and / or nickel chloride mixed with a partial alloy powder.

It is a figure which shows the decomposition performance improvement of the perchlorethylene by the method of an Example and a comparative example. It is a figure which shows the decomposition performance improvement of the trichlorethylene by the method of an Example and a comparative example. It is a figure which shows the decomposition performance improvement of cis-1, 2- dichloroethylene by the method of an Example and a comparative example. It is a figure which shows the decomposition | disassembly performance of perchlorethylene by the method of a comparative example. It is a figure which shows the decomposition | disassembly performance of the trichlorethylene by the method of a comparative example. It is a figure which shows the decomposition | disassembly performance of cis-1, 2- dichloroethylene by the method of a comparative example.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these.

Example 1
Cast iron powder (containing 2.3% by weight of carbon) is mixed with 0.1% by weight of Ni, and vibration mill (manufactured by Chuo Kako Co., Ltd., trade name: V-MILL, BM-3, 1200 vpm, 6.6L pot) Was used to obtain a partial alloy powder (frequency: 600 vpm, nitrogen gas flow rate: 40 ml / min, grinding time: 2 hours). It was confirmed by EPMA that the obtained powder was a partial alloy.

  Next, an aqueous solution containing 5 mg / L each of perchlorethylene (PCE), trichlorethylene (TCE), and cis-1,2-dichloroethylene (cis-1,2-DCE) was prepared, and 100 mL of the aqueous solution was added to a vial. Sorted into Nickel sulfate was mixed in the range shown in Tables 1 to 3 with respect to the partial alloy powder, and further an equal amount of water was added and left for 5 minutes to prepare a slurry. Ni of 0.02% by weight and 0.035% correspond to 0.053% by weight and 0.092% by weight of nickel sulfate.

  2 g of the slurry was added to a vial bottle from which the organic halide was separated, and the mixture was placed in a constant temperature water bath maintained at 20 ° C., and then rocked at 160 strokes per minute. The remaining slurry was filtered and washed, and the nickel component in the filtrate was quantified by ICP, and nickel was not detected. Further, when the partial alloy powder was analyzed by XPS, nickel oxide was formed on the outermost surface, and the inside was nickel metal.

  The concentration of the organic halide after a certain period of time was measured according to the official method (Ministry of the Environment Notification Nos. 46 and 18).

  Changes in the concentrations of PCE, TCE and cis-1,2-DCE are shown in Tables 1 to 3 and FIGS.

  When the partial alloy powder is treated with a small amount of nickel sulfate, any organic halide is decomposed in a short period of time. PCE takes 6 days, TCE takes 4 days, and cis-1,2-DCE takes 3 days. It became the reference value.

Comparative Example 1
Using the cast iron powder of Example 1 in place of the nickel partial alloy iron powder, the decomposition behavior of the organic halide was measured under the same conditions as in Example 1. Moreover, the density | concentration corresponded to 0.09 weight% as a nickel component was also measured.

  The results are shown in Tables 4-6 and FIGS.

  Compared with Example 1 using the partial alloy powder, when iron powder was used, it took a long time to decompose the organic halide.

Claims (5)

Less than 0.1% by weight with respect to soil, wastewater or groundwater contaminated with organic halides, with partial alloy powder having a partial alloy phase of iron and nickel in and / or on the surface of the iron powder. For purifying organic halides by mixing nickel sulfate and / or nickel chloride. 2. The organic halide purifier according to claim 1, wherein the partial alloy powder has a nickel content of 0.01 to 2 wt% when iron and nickel are partially alloyed by a mechanical alloying method. The purification method according to claim 1, wherein nickel sulfate and / or nickel chloride is mixed with the partial alloy powder in the presence of powder or water. The purification method according to any one of claims 1 to 3, wherein the mixed amount of the partial alloy powder is in the range of 0.1 to 10% by weight with respect to soil, drainage or groundwater. The purification method according to any one of claims 1 to 4, wherein iron powder and / or iron oxide not containing nickel are further mixed.

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