JP2013188688A - Soil purifying agent for purifying heavy metal-contaminated soil or ground, additive used therefor, and soil purification method - Google Patents

Abstract

The present invention relates to an additive used for a soil purification agent containing a metal oxide as a purification component for purifying soil or ground contaminated with heavy metals, without reducing the processing capacity of the soil purification agent. To provide an additive having a function capable of deeply penetrating into the ground at high speed.
An additive used for a soil purification agent containing a metal oxide as a purification component for purifying soil or ground contaminated with heavy metals, comprising a melamine formaldehyde condensate having a hydrophilic group. An additive for the soil; a soil purification agent using the additive; a soil purification method.
[Selection] Figure 8

Description

  The present invention relates to soil contaminated with heavy metals such as chromium and arsenic, a soil purifier used for purifying (generally insolubilizing, detoxifying or solidifying) these pollutants by injecting them into the ground, and this soil The present invention relates to an additive that is advantageously used as a purification agent, and a soil purification method using the soil purification agent.

  In order to treat harmful substances that adversely affect the human body and the environment, methods such as extraction, detoxification, incineration, melting, solidification, and isolation by a shielding layer have been conventionally used. Hazardous substances containing organic harmful components can be rendered harmless by combustion, ultraviolet irradiation, biodegradation, and the like. On the other hand, when the soil and ground are contaminated with inorganic harmful components, such as heavy metals such as mercury, lead, cadmium, chromium, arsenic, or their compounds, it is difficult to decompose and remove these harmful substances. Therefore, in general, soil and ground are purified by solidification, insolubilization, detoxification or shielding.

  Known methods for purifying soil contaminated with organic halides such as chlorinated hydrocarbons (eg, trichlorethylene), which are harmful organic components, include the soil gas suction method, the groundwater pumping method, and the soil excavation method. Yes. However, these methods are not methods for directly purifying soil, but are methods for purifying contaminated water collected by the soil gas suction method, groundwater pumping method, etc., or contaminated water such as rivers and groundwater. The amount is extremely large, and the treatment often takes a long time. It is also a drawback that the processing steps are often complicated.

  For this reason, Patent Documents 1 and 2 propose a soil purifier containing an iron fine particle slurry in which iron fine particles are dispersed in water as a method for directly and simply purifying soil as a contamination source. By finely pulverizing the iron particles in this way, the surface area of the iron is increased to increase the treatment capacity of pollutants, and by making the particles fine, the rapid penetration of iron into the soil is enabled.

  On the other hand, as a method for purifying soil contaminated with heavy metals such as chromium, for example, soil contaminated with heavy metals is mixed with powder cement, solidified, detoxified, or contaminated soil is excavated and grounded by a plant on the ground. A method of detoxifying by chemical treatment is known. In addition, for example, there is a method of suppressing the elution of chromium by adding cement, lime, gypsum or the like to the soil contaminated with chromium, and a method of mixing fly ash, carbonated aluminate salt material, cement or the like with sludge. However, the above-described method has a disadvantage that a large apparatus or civil engineering equipment is required and the cost is increased.

  In addition, among the heavy metals, soils contaminated with arsenic have been studied for insolubilization and solidification. As a method for treating excavated soil contaminated with arsenic, a technique for insolubilizing arsenic and solidifying the excavated soil is known.For example, iron salt is added to excavated soil containing arsenic, There is known a technique for performing solidification treatment of excavated soil by performing insolubilization treatment of arsenic and adding one or more solidification materials selected from cement-based solidified materials, lime-based solidified materials, and magnesia-based solidified materials (patent) Reference 3). Furthermore, as a technique related to this, a drug containing an iron salt which is an insolubilizing agent for arsenic and magnesium oxide and an alkali metal silicate salt which are solidifying materials is known (Patent Document 4). As a related technique, a technique using a gypsum-based neutral solidifying material is also known.

  For soil contaminated with heavy metals such as chromium and arsenic, there is a need for a method for directly and simply purifying soil, which is a source of contamination, as well as soil contaminated with organic halides, using a slurry soil cleaner. It has been. Patent Document 5 proposes a slurry-like treatment material containing a metal, a metal oxide, and iron hydroxide as a treatment material to be used for insolubilization of heavy metals. With this treatment agent, heavy metals such as selenium and chromium are proposed. Arsenic, cadmium, mercury, tin, etc., particularly selenium and chromium are described as having a high ability to insolubilize.

JP 2005-138107 A JP 2005-270854 A JP 2006-167524 A JP 2007-302885 A JP 2006-205152 A

  However, even if the slurry-like treatment material containing metal, metal oxide and iron hydroxide of Patent Document 5 is poured into soil and ground contaminated with heavy metals, if the viscosity is high, it will penetrate sufficiently into the soil and ground. There are many cases where this is not possible. In order to improve this, when the concentration of the metal oxide particles or the like is lowered, the viscosity can be lowered, but the processing ability of the essential purifier is also lowered, and a desired cleaning effect cannot be obtained.

  Therefore, the present invention is an additive used in a soil purification agent containing a metal oxide as a purification component for purifying soil or ground contaminated with heavy metals, and does not reduce the processing capacity of the soil purification agent. Furthermore, it aims at providing the additive which has a function which can be osmose | permeated deeply in soil and the ground at high speed.

  Further, the present invention is a soil purification agent containing a metal oxide as a purification component for purifying (generally insolubilizing, detoxifying or solidifying, particularly insolubilizing) soil or ground contaminated with heavy metals, An object of the present invention is to provide a soil purification agent that can penetrate deeply into soil and ground without reducing the processing capacity of the purification agent.

  Furthermore, an object of the present invention is to provide a method for purifying contaminated soil or ground that allows the soil purifier to permeate at high speed into soil contaminated with heavy metals or the ground.

  In order to develop a soil purification agent that can penetrate deeply into soil and ground contaminated with heavy metals without degrading the treatment capacity of the purification agent, we focused on additives and examined various additives. I have done it. Among them, the inventors found a particularly effective additive and reached the present invention.

The above object is an additive used in a soil purification agent containing metal iron oxide as a purification component for purifying soil or ground contaminated with heavy metals,
It can be achieved by an additive characterized by containing a melamine formaldehyde condensate having a hydrophilic group.

Preferred embodiments of the additive of the present invention are as follows.
(1) The hydrophilic group is a sulfonic acid group, a sulfonic acid salt group, or a sulfonic acid amide group. Good interaction with the purification component. In particular, a sulfonic acid amide group is preferable. The viscosity of the aqueous dispersion of the soil purification agent can be reduced, and the purification ability of the metal oxide is hardly reduced.
(2) A melamine formaldehyde condensate having a hydrophilic group is a condensate obtained by polycondensation of p-toluenesulfonic acid amide, melamine and formaldehyde (generally a p-toluenesulfonic acid amide-modified melamine formaldehyde condensate). The viscosity of the aqueous dispersion of the soil purification agent can be further reduced, and the purification ability of the metal oxide is hardly reduced.
(3) The metal oxide contains iron oxide. It is particularly effective for insolubilizing arsenic and arsenic compounds.

The above purpose is a soil purification agent for purifying soil or ground contaminated with heavy metals,
This can be achieved by a soil purification agent comprising metal iron oxide as a purification component and a melamine formaldehyde condensate having a hydrophilic group as an additive.

Preferred embodiments of the soil purification agent of the present invention are as follows.
(1) The hydrophilic group is a sulfonic acid group, a sulfonic acid salt group, or a sulfonic acid amide group. Good interaction with the purification component. Particularly preferred is a sulfonic acid amide group. The viscosity of the aqueous dispersion of the soil purification agent can be reduced, and the purification ability of the metal oxide is hardly reduced.
(2) A melamine formaldehyde condensate having a hydrophilic group is a condensate obtained by polycondensation of p-toluenesulfonic acid amide, melamine and formaldehyde (generally a p-toluenesulfonic acid amide-modified melamine formaldehyde condensate). The viscosity of the aqueous dispersion of the soil purification agent can be further reduced, and the purification ability of the metal oxide is hardly reduced.
(3) The purification component contains iron oxide. It is particularly effective for insolubilizing arsenic and arsenic compounds.
(4) The soil purification agent is an aqueous dispersion (slurry), and the additive is generally 0.05 to 5.0% by mass, preferably 0.1 to 3.0% by mass, particularly 0.2 to 2.0%. Contains mass%.
(5) The purification component (particularly iron oxide) is preferably contained in an amount of 5 to 40% by mass, particularly 10 to 30% by mass. Soil cleaners have excellent cleaning ability.
(6) The heavy metal as a pollutant is generally a heavy metal such as mercury, lead, cadmium, chromium, arsenic, or a compound thereof, preferably chromium, arsenic, especially arsenic.

The above purpose is
This can be achieved by a soil purification method in which the soil purification agent (described in any one of claims 6 to 9) is injected into soil and / or ground contaminated with heavy metals. The cleaning agent can be injected efficiently over a wide range.

Preferred embodiments of the above method of the present invention are as follows.
(1) The soil purifier is injected by a multi-point injection method with two or more discharge ports. The cleaning agent can be injected efficiently over a wider range.
(2) The multipoint injection method is a displacement control type multipoint injection method. The cleaning agent can be injected over a wider range and more efficiently, and the displacement effect on the structure can be suppressed in the injection immediately below or in the vicinity of the structure.

  The soil purification agent of the present invention contains a metal oxide as a purification component and a melamine formaldehyde condensate having a hydrophilic group as an additive. By using the above-mentioned specific additive for the metal oxide purification agent component, the viscosity of the aqueous dispersion of the soil purification agent can be reduced, and it can penetrate deeply into soil and ground contaminated with heavy metals at high speed. Can be made. At that time, the viscosity can be reduced without reducing the concentration of the purification component. Further, the addition of the additive of the present invention has little adverse effect on the treatment capacity of the soil purification agent, so that the treatment capacity of the soil purification agent can be kept high.

The additive of the present invention can impart the excellent function to the soil purification agent.
Moreover, the purification method of the present invention can perform soil purification with extremely high treatment capacity (high penetration rate of the purification agent, wide penetration range) by using the soil purification agent of the present invention.

FIG. 1 is an example of a super multi-point injection apparatus used for advantageously carrying out the arsenic-contaminated soil and ground purification method of the present invention. FIG. 2 is another example of an injection tube. FIG. 3 is a diagram showing an example of the arrangement of survey holes for confirming contamination of the inlet, soil, and groundwater provided in soil contaminated with arsenic. FIG. 4 is a graph showing the relationship between the ferric oxide concentration (mass%) (slurry concentration) and the viscosity of the soil purification agent not containing an additive. FIG. 5 is a graph showing the effect of reducing the viscosity of the slurry (soil purifier) by adding the additive. FIG. 6 is a graph showing the influence of arsenic insolubilization performance due to the addition of additives. FIG. 7 is a graph showing the relationship between the additive addition rate and the arsenic elution amount of the present invention. FIG. 8 is a graph showing the relationship between the additive addition rate of the present invention and the viscosity of the slurry (soil purifier). FIG. 9 is a schematic view of an apparatus for evaluating the permeability of the soil purification agent to the soil purification agent into the contaminated soil. FIG. 10 is a graph showing the relationship between the pressurization time and the permeation distance of the soil purification agent.

  The additive used in the soil purification agent of the present invention is used in a soil purification agent containing a metal oxide as a purification component for purifying soil or ground contaminated with heavy metals (particularly heavy metals in the Soil Contamination Countermeasures Law). And a melamine formaldehyde condensate having a hydrophilic group. That is, in an aqueous dispersion for soil purification containing a metal oxide as a purification component, the additive of the present invention stabilizes the dispersion of the purification component, lowers the viscosity of the aqueous dispersion, and contaminated soil or ground. It is possible to permeate the aqueous dispersion into the water at a high speed, deeply and over a wide range, and does not reduce the purification ability of the metal oxide.

  Moreover, the soil purification agent of this invention contains the said metal oxide as a purification | cleaning component, and the melamine formaldehyde condensate which has the said hydrophilic group as an additive. Therefore, although the soil purifier of this invention has the said effect, it is especially effective in the soil and ground whose pollutants are arsenic and an arsenic compound. This is because by adding the additive of the present invention to metal oxide fine particles such as iron oxide, aggregation of the metal oxide fine particles is prevented, and the effective contact area of the metal oxide fine particles with heavy metal such as arsenic increases. It is considered that the purification effect is improved.

  The additive used for the additive of the present invention and the soil purification agent of the present invention contains a melamine formaldehyde condensate having a hydrophilic group. Other additives may be included as long as the function of the additive of the present invention is not impaired.

  The hydrophilic group is a polar atomic group having a strong interaction with water. Examples of the ionic polar group include a sulfate group, a sulfonate group, a phosphate group, a carboxylic acid group, and a salt group thereof, and ammonium. Examples of the nonionic hydrophilic group include a hydroxyl group, an oxyethylene group, a carboxylic acid amide group, a sulfonic acid amide group, and a phosphoric acid amide. As the salt, alkali metals (preferably Na, K) are generally preferable.

  As the hydrophilic group, a carboxylate group, a sulfonic acid group, a sulfonate group, a sulfonic acid amide group, and an oxyethylene group are preferable, and in particular, a sulfonic acid group, a sulfonic acid salt group, a sulfonic acid amide group, especially a sulfone group. Acid amide groups are preferred.

  The melamine formaldehyde condensate having a hydrophilic group is preferably the melamine formaldehyde condensate having the above hydrophilic group. The melamine formaldehyde condensate is obtained by condensing (or polycondensing) melamine and formaldehyde. The condensate may be a polycondensate.

  The melamine formaldehyde condensate having a hydrophilic group may be a product obtained by directly adding a hydrophilic group to melamine, a product obtained by polycondensing a compound having a hydrophilic group together with melamine and formaldehyde, or both of them.

  As what added a hydrophilic group to melamine directly, the melamine sulfonic-acid formaldehyde condensate and its salt are mentioned. As the production method, melamine sulfonic acid and a salt thereof and formaldehyde are polycondensed, or melamine is reacted with formaldehyde and a sulfonating agent (for example, sodium sulfite) under basic conditions (pH 9-12), Furthermore, the method of polycondensation under acidic conditions (pH 2-6) is mentioned.

  Examples of the compound having a hydrophilic group when the compound having a hydrophilic group is polycondensed with melamine and formaldehyde include, for example, p-toluenesulfonic acid amide, p-toluenesulfonic acid, sodium p-toluenesulfonate, benzene Examples thereof include compounds having a hydrophilic group (generally, aromatic hydrocarbons having a hydrophilic group) such as sulfonic acid amide, naphthalenesulfonic acid, and sodium naphthalenesulfonate.

  Co-condensation of one or more selected from ureas such as urea, thiourea, ethylenethiourea, guanamines such as benzoguanamine, acetoguanamine, formoguanamine, phenylacetoguanamine, CTU guanamine, and other amino compounds May be.

  As the melamine formaldehyde condensate having a hydrophilic group, a melamine sulfonic acid formaldehyde condensate and a sulfonic acid amide-containing (modified) melamine formaldehyde condensate are preferable. Among them, a sulfonic acid amide-containing (modified) melamine formaldehyde condensate is particularly preferable. The sulfonic acid amide-containing melamine formaldehyde condensate is a condensed sulfonic acid amide-containing aromatic hydrocarbon (the aromatic hydrocarbon is preferably benzene or naphthalene which may have a substituent such as an alkyl group) and melamine and formaldehyde. It is a thing. In particular, a p-toluenesulfonic acid amide-modified melamine formaldehyde condensate which is a condensate of p-toluenesulfonic acid amide and melamine with formaldehyde is preferable.

  The melamine formaldehyde condensate having a hydrophilic group may be used in combination with other additives as described above. Other additives include, for example, aromatic sulfonate formaldehyde condensates (eg, naphthalene sulfonate formaldehyde condensates, naphthalene sulfonate formaldehyde condensates and copolymers of olefins and ethylenically unsaturated dicarboxylic acids), Mention may be made of lignin sulfonates.

  The soil purification agent of the present invention containing the additive is generally an aqueous dispersion (slurry), and the additive is generally 0.05 to 5.0% by mass, preferably 0.1 to 3.0% by mass, particularly It is preferable that 0.5-2.0 mass% is included. The total amount of the aqueous dispersion is 100% by mass. If the additive amount of the present invention is too small, the metal oxide fine particles are likely to aggregate, the effective contact area of the metal oxide fine particles with heavy metal such as arsenic is reduced, and the purification effect is reduced. On the other hand, if the amount is too large, the surface of the metal oxide fine particles is covered with the additive, and in this case also, the effective contact area of the metal oxide fine particles with heavy metal such as arsenic is reduced and the purification effect is reduced.

The soil purification agent of the present invention contains a metal oxide as a purification component. The metal oxide of the present invention is preferably an oxide such as iron, magnesium, zinc, titanium, aluminum, or manganese, which is a metal having a reducing action, and these may be used alone or as a mixture of two or more metal oxides. Alternatively, it may be a composite oxide of two or more metals. The metal oxide can be used in various forms such as fine particles, granules, small pieces, etc. The fine particles are preferable because the contact area is large and the reactivity is high. The average particle diameter (50% cumulative diameter by electron microscopy) is preferably in the range of 0.001 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.1 to 3 μm. Furthermore, it is more preferable to use an oxide containing oxygen at a lower ratio than that calculated from the normal valence of the metal component as the metal oxide because the reducing power increases. Examples of such oxides include oxides such as iron, titanium, and manganese. Among metal oxides, iron oxide is particularly preferable. In order to obtain a high reducing power, magnetite Fe ₃ O ₄ (when FeO _x : x = 1.33), overreduced magnetite (FeO _x : 1 <x <1.33), belt ride (FeO _x : 1.33) <X <1.5), lower grade iron oxide such as Fe ₂ O ₃ is particularly preferred.

When using the metal oxide, particularly iron oxide, iron hydroxide may be used in combination. As iron hydroxide, in addition to normal iron hydroxide such as ferrous hydroxide (Fe (OH) ₂ ) and ferric hydroxide (Fe (OH) ₃ ), iron oxyhydroxide (FeO (OH )), Hydrated iron oxide or hydrous iron oxide (FeO.H ₂ O, Fe ₂ O ₃ .H ₂ O) can also be used. These may be used singly or as a mixture. It is more preferable that the iron hydroxide contains an amorphous component because the adsorption ability is further increased. The properties of iron hydroxide may be fine particles, granules, pellets, wet cakes, or the like. When the specific surface area of iron hydroxide is at least 100 m ² / g, the adsorption capacity of heavy metals such as arsenic and chromium is excellent, and the heavy metals once adsorbed hardly re-elute and can be insolubilized over a long period of time. When the specific surface area (according to the BET method) is smaller than 100 m ² / g, not only the adsorptive power is lowered but also the heavy metal once adsorbed is easily re-eluting. The specific surface area is more preferably 150 to 300 m ² / g.

  When using the above metal oxide, particularly iron oxide, iron fine particles may be used in combination. The average particle size of the iron fine particles is less than 10 μm, preferably 0.1 to 6 μm, particularly preferably 0.1 to 3 μm.

  It is preferable that the metal oxide as the purification component is contained in the aqueous dispersion at 5 to 50% by mass, further 10 to 30% by mass, and particularly 10 to 25% by mass. Thereby, the soil purification agent shows the outstanding purification capability.

  The iron hydroxide is preferably used by adding to the iron oxide, and the blending amount is appropriately set according to the amount of heavy metals such as arsenic and chromium contained in the object to be treated, but generally the total amount of metal oxides The range of 0.01 to 20 parts by weight of iron hydroxide is preferable with respect to 1 part by weight. A more preferable range is 0.1 to 15 parts by weight.

  The soil purification agent of the present invention comprises, if necessary, an adsorbent (activated carbon, zeolite, chelate resin, etc.); clay mineral (bentonite, talc, clay, etc.); organic polymer (anionic organic polymer (polyacrylic acid soda)) Acrylic acid-acrylic acid ester copolymer, sodium acrylate-acrylamide copolymer, carboxymethylcellulose soda salt, starch-acrylic acid-sodium acrylate copolymer, vinyl acetate-sodium maleate copolymer, etc.); Ionic organic polymers (polyacrylamide, alkyl cellulose, polyethylene oxide, etc.); (d) solidifying materials (cement, lime, gypsum, etc.); (e) neutralizers (aluminum sulfate, calcium carbonate, etc.); (f ) A flocculant or the like may be contained in the treatment material.

  For iron oxide and iron hydroxide, the use of the product obtained by neutralizing waste sulfuric acid containing iron components generated in the manufacturing process of sulfuric acid method titanium oxide, the cleaning process of steel materials, etc., makes the present invention low cost. Can be constructed with. Similarly, gypsum is low in cost if by-products such as a sulfuric acid-process titanium oxide production process, a washing process of steel materials, and by-product gypsum such as phosphate gypsum and desulfurized gypsum are used. When waste sulfuric acid generated from the manufacturing process of sulfuric acid method titanium oxide is neutralized with basic calcium compounds such as calcium hydroxide and calcium carbonate, a mixture of gypsum and iron oxide or iron hydroxide is obtained. You can also.

  The object to be treated in the present invention is soil and ground contaminated with heavy metals, but sludge incineration ash, general waste incineration ash, industrial waste incineration ash, exhaust gas dust ash, solid waste such as coal ash, various waste water and It can be used for water in the environment such as rivers, lakes, oceans, and groundwater, residual soil generated by construction work, excavation work, dredging work, and soil in the environment. Further, even if a plurality of heavy metals such as arsenic, chromium, selenium, cadmium, mercury and tin are contained, they can be detoxified and insolubilized together. The method of the present invention is effective for purifying chromium and arsenic, and particularly effective for arsenic.

  The purification method by detoxification or insolubilization of pollutants in the soil (or ground) contaminated with heavy metal pollutants of the present invention, the soil purifier of the present invention is applied to the soil or ground contaminated with pollutants. This can be done by injection. The purification method of the present invention is preferably carried out by a multi-point injection method, particularly a super multi-point injection method.

  FIG. 1 shows an example of a super multi-point injection apparatus that is advantageously used for carrying out the method for detoxifying and insolubilizing pollutants in contaminated soil of the present invention. The insolubilization method when the contaminant in the contaminated soil of the present invention using the super multi-point injection device is arsenic will be described below.

  In the purification method of the present invention, for example, as shown in FIG. 1, an injection pipe 1 having many discharge ports 4 is inserted into contaminated soil (ground) 15, and the soil purification of the present invention is inserted into this injection pipe 1. It is performed by feeding the agent and injecting it into the soil from the discharge port 4. In the super multi-point injection method (particularly the displacement control type multi-point injection method), a large number of such injection tubes 1 are inserted, and the injection amount, injection speed, and injection pressure are controlled.

  Then, the installation of the injection pipe 1 in the soil and the supply and injection of the soil purification agent are carried out through the pressure passage 16 by means of a pressure detector and a flow rate detector, respectively, stored in the detection box 8. Pressure, flow rate, and detection are performed, and data on each pressure and flow rate in the detection tube 8 is sent to the controller 10 by an electric signal, and injection is performed in each injection capillary 3 constituting the injection tube.

  These injection tubules 3 are also connected to a unit pump 12 of a multi-stacked multiple series, as disclosed in Japanese Patent Application Laid-Open No. 11-21296. The soil purifier is uniformly introduced into the soil 15 from the discharge port 4 provided by shifting the position in the length direction of the injection thin tubes 3 of the injection tubes 1 that are pressure-fed through 16 and inserted into the predetermined ground 15. 14 can be injected three-dimensionally into the ground 15 in a vast area through low pressure penetration.

  As an injection tube used in the present invention, for example, as shown in FIG. As shown in FIG. 2, it may be composed of the core tube 2 and the injection thin tube 3, and has a large number of discharge ports, and can discharge the injection chemical solution at a low pressure and control the discharge amount and the like. That's fine.

  The injection tube 1 in FIG. 2 has a core tube 2 made of metal or hard synthetic resin at the center thereof, and a predetermined number of injection thin tubes 3 around the core tube 2 as shown in FIG. Alternatively, it is provided around the entire periphery via an adhesive or the like.

  The injection tube 1 is preferably a bundle of the same number of injection thin tubes 3 as the discharge ports. For example, as shown in FIG. 1, the longest injection tubule is arranged at the end, and an injection tubule having a gradually shorter length is arranged in parallel with this, or the longest injection tubule is arranged at the center, and its periphery It is preferable that an injection tubule with a gradually shorter length is disposed at the end. The diameter of the injection capillary is preferably 0.6 to 0.8 cm, and the length is generally preferably 1 to 80 m and 1 to 50 m.

  In the super multi-point injection method, a necessary number of injection pipes 1 used for contaminated soil are installed based on the result of a preliminary survey described later, and diffusion prevention processing is performed. At that time, if necessary, the detection tube 8, the controller 10, and the like are added to control the injection amount, the injection speed, and the injection pressure.

  The injection tube 1 is preferably provided at intervals of 1 to 5 m, particularly at intervals of 2 to 3 m on the horizontal plane. Moreover, it is preferable that the injection tube 1 has the discharge ports 4 at intervals of 0.3 to 1.5 m in the vertical direction. The injection tube 1 is generally composed of an injection capillary, and since the injection capillary has only one discharge port, the number of injection tubes necessary for the number of discharge ports is required.

  The number of discharge ports (generally the number of injection capillaries) provided in each injection tube is generally 2 to 100, preferably 2 to 60. The discharge port provided in the injection tube is appropriately set so that the drug solution can be uniformly injected. For example, it is preferable that the longest injection tube is installed at the center, and the short injection tube is gradually left around the periphery so that the discharge port is located outside the bundle. Further, the injection amount from each discharge port is preferably 0.1 to 4 L (liter) / min, particularly preferably 0.2 to 1 L / min. The injection pressure is preferably 0.1 to 0.3 MPa.

  A preliminary survey is performed to determine the placement of the injection tube. As an investigation hole for that purpose, for example, as shown in FIG. 3, from the inlet (position of the injection pipe) provided in the soil contaminated with arsenic, for example, at a radius (r) 1 m, 2 m, 3 m, for example, Survey holes for confirming soil contamination (AB2, AC2, BC2), survey holes for confirming groundwater contamination (A1, A2, A3, C1, C2, C3), survey for confirming groundwater contamination Survey holes (all other symbols, B1, B2, B3...) Are installed to confirm the contamination of the holes and soil. Then, a pre-investigation of the degree of contamination is performed in this way, and the arrangement (number, interval, etc.) of the injection tube is determined. An injection tube (generally a plurality) as shown in FIG. 1 is provided at a position to be arranged, and an injection chemical solution is directly injected into an arsenic-contaminated area by a super multi-point injection method to perform diffusion prevention processing.

  As a method for injecting an injectable chemical solution by the super multi-point injection method, for example, a soil purifier is alternately discharged from every other outlet in the height direction, and this is similarly applied to each inlet; or There can be mentioned, for example, a method in which soil purifiers are alternately discharged from the outlets divided into several groups in the height direction, and the same number of groups are simultaneously discharged to each inlet. .

    As described above, the soil purification agent can be injected over a wide range efficiently by injecting the soil purification agent by the super multi-point injection method.

  Although the super multi-point injection method has been described above, it is also preferable to employ a displacement control type multi-point injection method (DCI multi-point injection method) immediately below or in the vicinity of the structure. The displacement control type multi-point injection method is a more managed system of the super multi-point injection method, and is performed by slowly permeating and simultaneously injecting from multiple points to a unit volume to suppress displacement.

  For example, in FIG. 1, a plurality of (for example, four) detection tubes 8 are provided, and a plurality of injection tubes 1 are connected from each detection tube 8, and data on each pressure and flow rate is managed by the controller 10 with electrical signals. Each flow rate is managed and controlled. At that time, the injection is performed while controlling the displacement in the vicinity of the structure or the vicinity of the line by the application technique of the penetration theory. Not only can displacement be minimized, but also an excellent penetration effect and a shorter construction period can be realized. As a result, 32 points can be injected simultaneously in one unit, high quality and uniform improvement can be achieved with pump discharge without pulsation, and variable discharge control that controls flow and pressure steplessly is possible. Performance Flow rate: 0.5 to 10 L / min), all injection points can be monitored and controlled at once by a computer. In addition, the optimum injection specifications can be determined by conducting soil surveys and water injection tests, and the measurement data of the displacement meter installed in the structure etc. can be linked with the injection management system in real time, and injection can be performed while controlling the displacement. It can be carried out.

[Examples and Comparative Examples]
(1) Viscosity of soil cleaner (slurry) The following soil cleaner was prepared.
[Soil Cleaner (A)] (Example)
Ferric oxide (Fe ₂ O ₃ ) (average particle size: about 1 μm) 20 parts by weight Water 78.5 parts by weight Additive A (p-toluenesulfonic acid amide-modified melamine formaldehyde condensate; Danby filler admixture C, 1.5 parts by mass

The following soil purification agents (B) to (E) (these are comparative examples) were prepared in the same manner except that the additive A was changed as follows.
Soil purification agent (B): Sodium lignin sulfonate (NJ powder, manufactured by Ryokan Co., Ltd.) (Additive B)
Soil purification agent (C): carboxylic acid-containing methacrylic acid ester copolymer (Polyty MX300, manufactured by Lion Corporation) (additive C)
Soil purification agent (D): sodium polycarboxylate (Telflow soil, manufactured by Ternite Co., Ltd.) (Additive D)
Soil purification agent (E): polycarboxylic acid polymer aqueous solution (Rheoflow A-1000, manufactured by Lion Corporation) (additive E)

  The viscosity of the obtained soil purifier was measured using a B-type viscometer (No. 1 rotor, 60 rpm, 20 ° C.). The amount of the additive was also measured for 0.5 parts by mass and 1.0 part by mass, and the effect of reducing the viscosity of the slurry (soil purifier) by adding the additive was observed. In addition, the quantity of water was adjusted so that the whole might be 100 mass parts with the change of an additive. The results are shown in FIG. For reference, FIG. 4 shows the relationship between the ferric oxide concentration (mass%) and the viscosity of the soil purification agent not containing an additive. The viscosity of 20 mass% ferric oxide of the soil purification agent not containing an additive is 400 to 500 mPa · s.

  From the results shown in FIG. 5, the soil purification agent (A) of the example by adding 1.5 parts by mass of the additive A has an extremely low viscosity (10 mPa · 10) that is expected to allow good penetration of the purification agent into the soil. s or less). Therefore, it turns out that the additive A used for the soil purifier (A) shows the outstanding viscosity reduction effect. Although the soil purification agent (C) of the comparative example also showed low viscosity, it was found that a large amount of foam was generated in the obtained purification agent, and there was a problem in workability.

(2) Soil cleaning agent purification (insolubilization) test The above soil cleaning agents (A), (D), (E) and additive-free soil cleaning agents, each of which was contaminated with arsenic (Ministry of the Environment) Elution amount in accordance with Notification No. 18: 0.272 mg / L (27.2 times the environmental standard), added to 1 m ³ of soil at an injection amount of 10 kg (in solids), mixed, arsenic after curing for 2 days The amount of leaching of arsenic was observed, and the effect of the additive on the arsenic insolubilization performance was observed.
The result is shown in FIG.

  When the amount of ferric oxide was small, the soil purification agent (A) of the example did not reach the additive-free addition, but when increased, the arsenic elution amount was lower than the additive-free addition.

Arsenic after injecting no soil additive into the soil contaminated with arsenic, and after injecting 10 kg of solid matter (A) (3 concentrations of additives) into 1 m ³ of soil contaminated with arsenic The elution amount was observed, and the relationship between the additive addition rate and the arsenic elution amount is shown in FIG. The soil purification agent (A) showed a lower arsenic elution amount than when no additive was added when the concentration of the additive was low.
From the above results, only the soil purification agent (A) showed excellent characteristics in both permeability and purification.

  Viscosity of soil purification agent (A) (ferric oxide concentration of 20% by mass) and soil purification agent in which the ferric oxide concentration of soil purification agent (A) was changed to 15% by mass, the amount of additive A added The change is shown in FIG. It has been found that at both ferric oxide concentrations, a very low viscosity (less than 10 mPa · s) where good penetration of the cleaner into the soil is expected can be achieved.

(3) Pressurization injection test of soil purification agent In order to evaluate the permeability of the soil purification agent to the soil purification agent into the contaminated soil, the soil purification agent (A) (however, using the apparatus shown in FIG. , Fe ₂ O _{3 (} 15 parts by mass, additive 0.5 parts by mass). A column having a length of 1055 mm and an inner diameter of 50 mm in which a filter material is disposed was packed with No. 7 cinnabar sand and compacted (water permeability coefficient 3 × 10 ⁻³ cm / sec). The soil purification agent was introduced into an injection device equipped with a stirrer and pressure (applying device), and the soil purification agent was fed in the direction of the arrow at 0.2 MPa, and injected into No. 7 cinnabar in the column. It penetrated 1000 mm in 290 seconds. A graph of the relationship between the permeation distance and the pressurization time is shown in FIG. As can be seen from the graph, no significant decrease in permeation rate was observed. Moreover, it was confirmed by the visual inspection of the column after the test that the soil purification agent penetrates evenly. In addition, in the soil purifier which does not contain an additive, it penetrated only to 100 mm.

DESCRIPTION OF SYMBOLS 1 Injection pipe 2 Core pipe 3 Injection thin tube 4 Discharge port 8 Detection box 10 Controller 12 Unit pump 13 Tank for injection chemical liquid 14 Injection chemical liquid 15 Contaminated ground 16 Pressure feed passage

Claims (12)

An additive used in a soil purification agent containing a metal oxide as a purification component for purifying soil or ground contaminated with heavy metals,
An additive comprising a melamine formaldehyde condensate having a hydrophilic group.   The additive according to claim 1, wherein the hydrophilic group is a sulfonic acid group, a sulfonic acid salt group, or a sulfonic acid amide group.   The additive according to claim 1 or 2, wherein the hydrophilic group is a sulfonic acid amide group.   The additive according to any one of claims 1 to 3, wherein the melamine formaldehyde condensate having a hydrophilic group is a condensate obtained by polycondensation of p-toluenesulfonic acid amide, melamine and formaldehyde.   The additive according to any one of claims 1 to 4, wherein the metal oxide is iron oxide. A soil purification agent for purifying soil or ground contaminated with heavy metals,
A soil purification agent comprising a metal oxide and the additive according to any one of claims 1 to 5.   The soil purification agent according to claim 6, wherein the soil purification agent is an aqueous dispersion and contains 0.2 to 2.0 mass% of the additive.   The soil purifier of Claim 6 or 7 containing 10-30 mass% of metal oxides.   The soil purification agent according to any one of claims 6 to 8, wherein the heavy metal is arsenic.   The soil purification method which inject | pours the soil purification agent of any one of Claims 6-9 to the soil and / or the ground which were contaminated with the heavy metal.   The purification method according to claim 10, wherein the soil purification agent is injected by a multi-point injection method with two or more discharge ports.   The purification method according to claim 11, wherein the multipoint injection method is a displacement control type multipoint injection method.

Images