JP2012228685A - Injection chemical liquid for preventing diffusion of arsenic, method for preventing diffusion of arsenic in arsenic-contaminated soil, and liquid feeding device for use in the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide injection chemical liquid for preventing diffusion of arsenic in arsenic-contaminated soil and for insolubilizing arsenic in the arsenic-contaminated soil to solidify the soil, wherein the gelation time of the chemical itself is properly long, and insolubilization of the arsenic after the injection and solidification of the soil are quickly performed, and the solidification is achieved with high strength.SOLUTION: This injection chemical liquid injected for preventing diffusion of arsenic in arsenic-contaminated soil or ground and for preventing diffusion of arsenic in arsenic-contaminated soil includes: non-alkali silica sol containing ferric sulfate and/or poly ferric sulfate and an acid containing no phosphorus atom. A method of preventing diffusion of arsenic in arsenic-contaminated soil using the chemical liquid and a liquid feeding device for use in the method are also provided.

Description

  The present invention is an injection chemical solution for preventing diffusion of arsenic by injecting into soil contaminated with arsenic, a method for preventing diffusion of arsenic in arsenic-contaminated soil using this chemical solution, and a method used in this method. The present invention relates to a liquid feeding device.

  Conventionally, methods for extracting harmful substances, detoxifying, incineration, melting, solidifying, and isolating with a shielding layer have been adopted in the treatment of harmful substances that adversely affect the human body and the environment. Hazardous substances containing organic harmful components can be detoxified by combustion, ultraviolet irradiation, biodegradation, etc., but harmful substances containing inorganic harmful components such as heavy metals such as mercury, lead, cadmium and chromium, Alternatively, harmful substances containing arsenic compounds such as arsenic and arsenic compounds are difficult to detoxify and must be solidified, insolubilized or shielded.

  For example, a method in which heavy metal contaminated soil is mixed with powder cement and solidified to make it harmless, or a method in which the contaminated soil is excavated and detoxified by chemical treatment by an above-ground plant 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.

There is also a method of treating toxic heavy metals with a chelating agent alone, but when the chelating agent is subjected to microbial decomposition in the soil, the toxic metal is re-eluted. Furthermore, it is also known to inject the ground injection material into the ground to solidify harmful substances, but the conventional injection material using water glass has poor durability (SiO ₂ leaches out), and is called alkali leaching. There is a concern about secondary pollution, and even if a highly durable injection material is used, it must be a highly permeable injection material. There is no.

  Among the above-mentioned harmful substances, soils contaminated with arsenic are also being 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 1). Furthermore, as a technique related to this, a drug containing an iron salt that is an insolubilizing agent for arsenic and magnesium oxide and an alkali metal silicate salt that are solidifying materials is known (Patent Document 2). As a related technique, a technique using a gypsum-based neutral solidifying material is also known.

  As mentioned above, when cement-based solidified material, lime-based solidified material, magnesia-based solidified material is used as the solidified material, arsenic can be insolubilized and excavated soil can be solidified, but after treatment Since the excavated soil exhibits strong alkalinity (specifically, pH> 9), there arises a problem that, for example, use of the excavated soil after treatment is restricted. In addition, when the treated excavated soil is separately neutralized, the cost increases. Furthermore, when a chemical containing iron salt, magnesium oxide and alkali metal silicate is used, the excavated soil solidifies before the arsenic is sufficiently insolubilized. When the arsenic elution amount is measured for the excavated soil after treatment without being mixed, the elution amount may exceed a predetermined reference value. In addition, when using a gypsum-based neutral solidification material, the excavated soil after treatment will show weak alkalinity or neutrality, but its strength development is low, and the excavated soil is not sufficiently solidified. Become.

  As a method for insolubilizing arsenic to solve the above problem, a method of mixing excavated soil containing arsenic and iron salt and mixing the obtained excavated soil and alkali metal silicate is proposed (Patent Document 3). ). That is, when excavated soil containing arsenic and iron salt are mixed, arsenic contained in the excavated soil reacts with iron ions derived from the iron salt to form poorly soluble iron arsenate. The arsenic contained is insolubilized, and then, when this excavated soil and alkali metal silicate are mixed, the alkali metal silicate reacts with iron ions and hydrogen ions remaining in the excavated soil, and the silicic acid gels. Alternatively, the excavated soil is solidified.

JP 2006-167524 A JP 2007-302885 A JP 2009-166001 A Japanese Patent No. 3776268

  However, in the above method, as the soil containing arsenic is excavated soil, a large amount of contaminated soil cannot be easily insolubilized and solidified, so it cannot be said to be an efficient treatment method.

  The present inventors use the above-described method of injecting a chemical into the ground (soil) to solidify harmful substances, and solidify and insolubilize the soil contaminated with current arsenic without excavation, thereby arsenic. Research has been conducted in order to develop a method for preventing the diffusion of water, and the present invention has been achieved.

Therefore, the present invention is an infusion chemical solution for insolubilizing arsenic in arsenic-contaminated soil and solidifying the soil, the gelation time of the drug itself is reasonably long, and insolubilization of arsenic after infusion, solidification of soil It is an object of the present invention to provide an infusion solution for preventing arsenic diffusion in arsenic-contaminated soil, which can be realized quickly and further solidified with high strength.
Another object of the present invention is to provide a method for preventing arsenic diffusion in arsenic-contaminated soil, in which arsenic in arsenic-contaminated soil is insolubilized and solidified by using the above-mentioned injection solution for preventing arsenic diffusion.
Furthermore, an object of this invention is to provide the liquid feeding apparatus used advantageously in the said method.

  As described above, cement, water glass, and the like are known as the caking agent to be injected into the soil or the ground, but the present inventor has dealt with a dealkalized silica sol (for example, a patent) having almost no elution risk after solidification. (Refered to literature 4 etc.), and a method for preventing arsenic diffusion in soil or ground contaminated with arsenic has been studied using this. Patent Document 4 discloses a chemical solution for preventing liquefaction of the ground made of non-alkaline silica sol containing water glass, phosphoric acid, and acidic water-soluble aluminum.

  As a result of investigating a combination of dealkalized silica sol and an acid having a function of a curing agent and a pH adjuster in order to insolubilize arsenic in arsenic-contaminated soil and solidify the soil, Patent Literature It was found that when a solution containing phosphoric acid as described in 4 was used, the arsenic elution amount increased. And when sulfuric acid was used as an acid, for example, it discovered that the elution amount of arsenic could be suppressed.

  As a result of further studies, for example, the gelation time of an injecting agent containing dealkalized silica sol, ferric sulfate and sulfuric acid is affected by the pH of the injecting agent, and the gelling time is usually appropriate (about 12 hours). It is necessary to adjust the pH to a low level (the closer the pH is to neutrality, the shorter the gelation time), but the insolubilization and solidification of arsenic will be improved as the pH of the injection becomes closer to neutrality. It was. As a result of further studies based on these findings, the present invention has been achieved.

The above purpose is
An infusion solution for preventing arsenic diffusion in arsenic contaminated soil, which is injected to prevent arsenic diffusion in soil or ground contaminated with arsenic,
This can be achieved by an injectable solution for preventing arsenic diffusion in arsenic-contaminated soil containing ferric sulfate and / or polyferric sulfate, an acid containing no phosphorus atom, and a non-alkali silica sol.

Preferred embodiments of the present invention are as follows.
(1) The concentration of silica is 3 to 12% by mass. It is possible to achieve both strength and economic efficiency after soil solidification.
(2) The acid containing no phosphorus atom is sulfuric acid. It is particularly advantageous for achieving both gelling time suitability and insolubilization of arsenic, and is excellent in economic efficiency. The use of phosphoric acid conventionally used is advantageous in that point because the gel concentration time is less dependent on the acid concentration, but the effect of arsenic insolubilization cannot be obtained.
(3) The pH is 3.5 to 4.5. This is particularly advantageous for achieving both gelling time suitability, insolubilization and solidification of arsenic.
(4) Further contains sodium silicate. It is possible to achieve both strength and economic efficiency after soil solidification.
(5) It consists of a first liquid containing a non-alkali silica sol containing ferric sulfate and / or polyferric sulfate and an acid containing no phosphorus atom, and a second liquid containing sodium silicate. The stability of the liquid containing non-alkaline silica sol containing ferric sulfate and / or polyferric sulfate and an acid containing no phosphorus atom is increased. The first liquid is an acid not containing a phosphorus atom such as sulfuric acid, ferric sulfate and / or polyferric sulfate (especially polyferric sulfate; both ferric sulfate and polyferric sulfate). In the case of putting them, the order may be either, or they may be put at the same time), and it is preferable to add them in the order of non-alkali silica sol and mix each time.
(6) When sodium silicate is used, the non-alkali silica sol accounts for at least 8% by mass of the total silica with respect to the total mass of the non-alkali silica sol and sodium silicate. The strength after solidification of the soil and the prevention of elution are possible, and the economy is excellent.

The above purpose is
This can be achieved by a method for preventing arsenic diffusion in arsenic-contaminated soil, characterized by injecting the arsenic diffusion preventing infusion solution into soil or ground contaminated with arsenic.

Preferred embodiments of the above method of the present invention are as follows.
(1) The drug is injected by the super multi-point injection method. The drug can be injected efficiently over a wide range.
(2) Each material of the injection chemical solution for preventing arsenic diffusion is sent to a static mixer (static mixer) with a screw pump (preferably Mono pump) or screw pump, mixed with a static mixer, and the resulting injection chemical solution is buffer tank And then inject. It is possible to efficiently produce and inject drugs.
(3) Each material of the injection chemical solution for preventing arsenic diffusion is sent to the first static mixer (static mixer) with a screw pump (preferably a Mono pump) or a screw pump, and mixed with the first static mixer, Send to the first buffer tank, detect pH and temperature and check if they are within the prescribed range, if they are within the range, send them to the second buffer tank, otherwise they will be mixed The necessary material for adjusting the pH of the material (chemical solution) is sent to the second static mixer via the screw pump or screw pump and mixed, and this is sent to the first buffer tank to adjust the pH. After adjustment, send to the second buffer tank for injection. The drug can be manufactured and injected more efficiently.

  A preferred embodiment of the arsenic diffusion preventing infusion solution can also be applied to the above method.

Furthermore, the above purpose is
Screw pumps (preferably Mono pumps) or screw pumps for pumping each material of the arsenic diffusion preventing infusion chemical solution,
Static mixer (static mixer) for mixing each material sent from each MONO pump
A buffer tank for storing the mixed material (chemical solution) sent from the static mixer, and a device for detecting the pH and temperature of the mixed material provided between the static mixer and the buffer tank,
an automatic control device that operates a screw pump or a screw pump to pump the necessary material for adjusting the pH of the mixed material (chemical solution) when the pH and temperature are outside the predetermined range;
An arsenic diffusion preventing infusion chemical solution feeding apparatus; and each screw pump or screw pump for pumping each material of the arsenic diffusion preventing infusion solution,
A first static mixer for mixing each screw pump or each material sent from the screw pump;
The first buffer tank for storing the mixed material (chemical solution) sent from the first static mixer, and the pH of the mixed material provided between the first static mixer and the first buffer tank And temperature detecting equipment,
an automatic control device that operates a screw pump or a screw pump to pump the necessary material for adjusting the pH of the mixed material (chemical solution) when the pH and temperature are outside the predetermined range;
a second static mixer that mixes each screw pump or each material sent from the screw pump to adjust the pH and sends it to a first buffer tank;
The second buffer tank for storing the mixed material, the pH and temperature of which are adjusted within a predetermined range, sent from the first buffer tank;
A liquid delivery device for an infusion chemical solution for preventing arsenic diffusion,
Can be achieved.

  A preferred embodiment of the method can also be applied to the apparatus.

  According to the present invention, as an infusion solution for preventing arsenic diffusion, ferric sulfate and / or polyferric sulfate as an arsenic insolubilizing agent, non-alkali silica sol as a soil solidifying agent, and curing for solidifying the non-alkali silica sol By using an acid that does not contain a phosphorus atom as an acid having a function of an agent and a pH adjuster, it is possible to appropriately lengthen the gelation time of the chemical solution itself, and to make arsenic insoluble and solidify the soil after injection. It can be carried out promptly and solidification can be achieved with high strength. And the injection chemical | medical solution of this invention can prevent the spreading | diffusion prevention of the arsenic of a wide range of contaminated soil by inject | pouring into the soil or the ground contaminated with arsenic.

  In addition, the liquid delivery device of the present invention is particularly useful in order to advantageously prevent such diffusion of arsenic.

FIG. 1 is an example of a super multi-point injection apparatus used to advantageously carry out the method for preventing arsenic diffusion in arsenic contaminated soil 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 an example of a liquid delivery device used to advantageously carry out the method for preventing arsenic diffusion in arsenic-contaminated soil of the present invention. FIG. 5 is another example of a liquid delivery device used to advantageously carry out the method for preventing arsenic diffusion in arsenic-contaminated soil of the present invention. FIG. 6 shows the amount of polyferric sulfate and the amount of arsenic elution when using polyferric sulfate as an injecting solution and using non-alkali silica sol to which sulfuric acid and polyferric sulfate are added. It is a graph which shows the relationship.

  The injected chemical solution of the present invention is an injected chemical solution for preventing arsenic diffusion in arsenic-contaminated soil, which is injected to prevent arsenic diffusion in soil or ground contaminated with arsenic. This injection chemical solution contains, as a basic structure, ferric sulfate and / or polyferric sulfate, an acid containing no phosphorus atom, and a non-alkali silica sol.

  The injection chemical solution for preventing arsenic diffusion of the present invention uses ferric sulfate and / or polyferric sulfate as an arsenic insolubilizer, uses a non-alkali silica sol as a soil solidifying agent, and cures to solidify the non-alkali silica sol As an acid having a function of an agent and a pH adjuster, an acid containing no phosphorus atom is used. And in the system containing non-alkali silica sol and ferric sulfate, the gelation time of the drug itself can be reduced by using an acid that does not contain a phosphorus atom in an optimum amount (particularly so as to have a pH of 3.5 to 4.5). It can be made moderately long, and arsenic insolubilization and soil solidification can be promptly performed after injection. Further, this solidification of the soil can be realized with high strength. Therefore, by simply injecting the injection chemical solution of the present invention into soil or ground contaminated with arsenic, it is possible to prevent diffusion of arsenic in soil contaminated with arsenic over a wide area.

The non-alkali silica sol of the present invention is colloidal silica, in which SiO ₂ or a hydrate thereof is dispersed in water. The chemical formula is generally represented by SiO ₂ .xH ₂ O (x: 5.0 to 200.0, preferably 5.0 to 163.6). The concentration is generally 2-40% by mass (preferably 4-30% by mass), the particle size of the colloidal particles is generally 2-200 nm (preferably 10-100 nm), and the pH is 7-12 (preferably 8-11). Such non-alkali silica sol is commercially available, for example, under the trade names of ASF silica-30, -20, -6, and -4 (manufactured by Reinforced Earth Engineering Co., Ltd.), and can be preferably used.

  The non-alkali silica sol is generally obtained by subjecting water glass to dealkalization. For example, a dealkalized silica sol can be obtained by a method in which an ion exchange resin is packed in a tower and a water glass diluted with water is passed through the column to conduct dealkalization treatment.

The injection chemical solution for preventing arsenic diffusion of the present invention can further contain sodium silicate (water glass). Sodium silicate is represented by Na ₂ O.nSiO ₂ (n: 2.0 to 5.0, preferably 2.1 to 3.7) as a component, and its chemical formula is generally Na ₂ O.nSiO _2. xH ₂ O (n: 2.0 to 5.0, preferably 2.1 to 3.7, x: 8.0 to 50.0, preferably 8.7 to 32.6). For example, it is commercially available under the trade name of PR silica (manufactured by Reinforced Earth Engineering Co., Ltd.) and can be preferably used. The concentration of the component Na ₂ O · nSiO ₂ is generally 7 to 55% by mass.

  The silica concentration in the arsenic diffusion preventing injectable chemical solution of the present invention is preferably 3 to 12% by mass, more preferably 3.5 to 10% by mass, and particularly preferably 4 to 8% by mass. The concentration of silica represents the silica concentration when only non-alkali silica sol is used, and the total silica concentration when both non-alkali silica sol and sodium silicate are used. When the amount is less than 3% by mass, the solidification strength is insufficient, or there is a disadvantage that the amount of silica to be eluted increases, and when it exceeds 12% by mass, the economic efficiency is deteriorated.

  When both non-alkali silica sol and sodium silicate are used, it is preferable that the non-alkali silica sol occupies at least 8 mass%, further 10 mass%, particularly 12 mass% of the total silica. When the amount is less than 8% by mass, there is a disadvantage that the solidification strength is insufficient or the amount of silica to be eluted increases.

  Furthermore, containing sodium silicate is advantageous in achieving both strength and economic efficiency after solidifying the soil.

  In the present invention, an acid containing no phosphorus atom is used as an acid having a function of a curing agent and a pH adjusting agent for solidifying the non-alkali silica sol (and sodium silicate). Examples of such acids include inorganic acids such as sulfuric acid, nitric acid and hydrochloric acid, and organic acids such as formic acid and acetic acid. Sulfuric acid is preferred because pH can be controlled with a small amount of addition, and it is economical. In general, sulfuric acid having a concentration of 5 to 98% is used, but 30 to 70% is preferable in terms of workability.

  Sulfuric acid is particularly advantageous in achieving both gelling time optimization and insolubilization of arsenic, and is excellent in economic efficiency. The use of phosphoric acid is advantageous in this respect because the gel concentration time is less dependent on the acid concentration, but the effect of arsenic insolubilization cannot be obtained.

  The acid of the present invention is also used for adjusting the pH of the arsenic diffusion preventing injectable drug solution of the present invention. The acid is preferably added so that the pH is 3.5 to 4.5. Thereby, it is excellent in coexistence of optimization of gelation time and insolubilization of arsenic.

In the present invention, ferric sulfate and / or polyferric sulfate is used as an arsenic insolubilizer. Polyferric sulfate is generally represented by [Fe ₂ (OH) _n (SO ₄ ) _{3 -n / 2} ] _m . The ferric sulfate and / or polyferric sulfate is preferably used in an amount of 1 to 5% by mass, particularly 2 to 4% by mass, based on the total mass of the non-alkali silica sol and sodium silicate. When the upper limit is exceeded, an insoluble effect is hardly obtained with respect to the added amount, and when it is less than the lower limit, the insoluble effect is insufficient.

  The infusion solution for preventing arsenic diffusion of the present invention is preferably used in the pH range of 3.5 to 4.5 as described above, but the adjustment method is generally ferric sulfate and / or poly Ferric sulfate, acid containing no phosphorus atom, non-alkali silica sol and water, or ferric sulfate and / or polyferric sulfate, acid containing no phosphorus atom, non-alkali silica sol, sodium silicate and water The amount of the acid is adjusted in advance so that the pH becomes 3.5 to 4.5, and each material is mixed based on the blending. And when the obtained mixture does not show predetermined | prescribed pH, it adjusts so that it may become predetermined | prescribed pH by adding an acid, a silica (a non-alkali silica sol and / or sodium silicate), water, etc.

  Alternatively, a liquid containing non-alkali silica sol containing ferric sulfate and / or polyferric sulfate is adjusted to a higher pH in advance by adding an acid containing no phosphorus atom, and then a liquid containing sodium silicate is added thereto. You may do it. Also in this case, when the obtained mixture does not show a predetermined pH, it is adjusted to have a predetermined pH by adding acid, silica (non-alkali silica sol and / or sodium silicate), water or the like. Thereby, the stability of the liquid containing the non-alkaline silica sol containing ferric sulfate and / or polyferric sulfate and an acid containing no phosphorus atom is increased.

  The method for preventing arsenic diffusion in arsenic-contaminated soil of the present invention can be carried out by injecting the above arsenic diffusion preventing infusion solution into soil or ground contaminated with arsenic.

  An example of a super multi-point injection apparatus that is advantageously used to carry out the method for preventing arsenic diffusion in arsenic-contaminated soil of the present invention is shown in FIG. The method for preventing arsenic diffusion in the arsenic-contaminated soil of the present invention using the super multi-point injection device will be described below.

  In the arsenic diffusion preventing method of the present invention, for example, as shown in FIG. 1, an injection tube 1 having a large number of discharge ports 4 is inserted into soil (ground) 15 contaminated with arsenic. The injection chemical solution for preventing arsenic diffusion of the invention is sent in and injected into the soil from the discharge port 4.

  Then, the installation of the injection tube 1 in the soil and the supply and injection of the injected chemical solution are carried out through the pressure supply passage 16, and the pressure of each of the pressure supply passages by the pressure detector and the flow rate detector respectively housed in the detection box 8. The flow rate and the detection are performed, and the data of each pressure and flow rate in the detection tube 8 are sent to the controller 10 by an electric signal, and the injection of each injection capillary 3 constituting the injection tube is controlled.

  These injection tubules 3 are also connected to the unit pump 12 of the multi-stacked multiple series as disclosed in Japanese Patent Application Laid-Open No. 11-21296, and the injection chemical solution 14 in the injection chemical solution tank 13 for preventing arsenic diffusion is used. Uniformly injected into the soil 15 from the discharge port 4 provided by shifting the position in the length direction of each injection tube 3 of each injection tube 1 that is pumped through the pressure passage 16 and inserted into the predetermined ground 15. The chemical solution 14 can be injected three-dimensionally into the ground 15 in a vast area by penetrating the chemical solution 14 at a low pressure.

  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.

  A necessary number of injection pipes 1 used in the super multi-point injection method are installed on the contaminated soil based on the results of a preliminary survey described later, and a diffusion prevention process is performed.

  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 of injecting an injecting drug solution by the super multi-point injection method, for example, a drug solution is discharged alternately from every other outlet in the height direction, and this is similarly performed for each inlet; Examples include a method in which the drug solution is alternately discharged from the discharge ports divided into several groups in the vertical direction by the number of groups divided at the same time, and this is similarly performed for each injection port.

  As described above, the injection of the injected drug can be efficiently performed over a wide range by performing the super multi-point injection method.

  The arsenic diffusion prevention injection chemical solution to the arsenic diffusion prevention injection solution tank (buffer tank) 13 and the like is sent to the static mixer by the mono pump and mixed with the static mixer. Thus, by sending the obtained injecting drug solution to the buffer tank, the drug can be manufactured and injected efficiently.

  In addition, each material of the arsenic diffusion prevention infusion chemical solution is sent to the first static mixer by the Mono pump, mixed by the first static mixer, sent to the first buffer tank, and the pH and temperature are detected and determined. If it is within the range, it is sent to the second buffer tank. If it is outside the range, the necessary material for adjusting the pH of the mixed material (chemical solution) is sent to the MONO pump. It is also possible to send to the second static mixer via the mixer, mix it, send it to the first buffer tank to adjust the pH, and then send it to the second buffer tank for injection. Thereby, manufacture and injection | pouring of a chemical | medical agent can be performed still more efficiently.

  For example, the injection and injection of the arsenic diffusion preventing infusion chemical liquid into the arsenic diffusion prevention infusion chemical liquid tank (buffer tank; for example, 13) is performed using the liquid feeding apparatus shown in FIG. 4 or FIG. Can do.

In the liquid delivery device of FIG. 4, each Mohno pump M _a for pumping water a, acid b, ferric sulfate c and silica d, which are the materials of the arsenic diffusion preventing infusion chemical solution, to the static mixer S. , M _b , M _c , M _d are provided. Water a and acid b merge before entering the static mixer S. Each material sent from each of the MONO pumps M _a , M _b , M _c , and M _d is mixed by the static mixer S, and the mixed material (chemical solution) is supplied to the buffer tank T. A device (pH / temperature sensor) for detecting the pH and temperature of the mixed material is provided in the middle of the static mixer S and the buffer tank T (pipe). When the measured values of pH and temperature are within predetermined ranges, the chemical solution is sent to the flow unit Flow via the pump unit P and injected. The flow rate or the like to be injected is detected by the flow unit Flow, and the flow rate is finely adjusted by the control PC. In the flow section Flow, the pressure, flow rate, and pressure of each pressure feed passage are detected by the pressure detector and the flow rate detector, and the data of each pressure and flow rate are sent to the control PC as electrical signals.

  When the measured values of pH and temperature are not within the predetermined ranges, the MONO pump can increase the amount of necessary material (for example, acid when pH is too low) by a control PC (automatic control device). Adjust. The gel time of the drug solution can be adjusted by adjusting the pH.

  Therefore, in the liquid delivery apparatus of FIG. 4, each material is continuously mixed with the static mixer S, the pH and temperature are monitored, and the amount of acid added is automatically adjusted so that it is within the predetermined value. Can be obtained. If the pH deviates from the predetermined value, mixing is automatically stopped.

  In the liquid delivery device of FIG. 5, a separate buffer tank for adjusting pH (gel time) is provided in front of the buffer tank, and even when the pH deviates from a predetermined value, a nonstandard liquid is injected. Can be prevented.

Monono pumps M _a , M for pumping water a, acid b, ferric sulfate c, and silica d, which are each material of the above-described injection chemical solution for preventing arsenic diffusion, to the first static mixer S (A) _{b 1} , M _c , M _d are provided. Water a and acid b merge before entering the first static mixer S (A). The respective materials sent from the respective Mono pumps M _a , M _b , M _c and M _d are mixed by the first static mixer S (A), and the mixed material (chemical solution) is supplied to the first buffer tank T1. . A device (pH / temperature sensor) pH for detecting the pH and temperature of the mixed material is provided in the middle (the pipe) of the first static mixer S (A) and the first buffer tank T1. When the measured values of pH and temperature are within the predetermined ranges, this chemical solution is sent to the second buffer tank T2, and then sent to the injection unit Flow via the pump unit P and injected. . The injection amount is adjusted by a control PC (automatic control device).

When the pH and temperature are out of the predetermined range, each MONO pump M _a , M _b , M _c , M _d and the first static mixer S (A) are stopped, and the opening direction of the valve V of each MONO pump is changed. Each of the mono pumps M _a , M _b , M _c , M _d and the static mixer S (B) that receives the material sent therefrom is operated. For example, when the pH is less than a predetermined range, the mono pump M _{b for the} acid _b And the acid b is sent from the static mixer S (B) to the first buffer tank T1, and the obtained chemical solution is sent to the second buffer tank T2 to the flow section Flow via the pump unit P. Sent and injected. When the pH exceeds a predetermined range, for example, the silica d is sent from the static mixer S (B) to the first buffer tank T1 by operating the silica pump Md pump M _d . It is sent to the buffer tank T2, sent to the flow section Flow via the pump unit P, and injected. This adjustment is performed by the control PC.

Equipment for detecting pH and temperature (pH / temperature sensor) The pH is also provided in the first buffer tank T1 and in the first buffer tank T1 (it may not be present). M _a , M _b , M _c , M _d and the first static mixer S (A) are stopped, and the necessary mono pumps and static mixers S (B) for each of the mono pumps M _a , M _b , M _c and M _d are turned on. Adjusted by operating.

  Although the MONO pump is used for feeding each material, a screw pump or screw pump other than the MONO pump can be used.

  The device of the present invention is capable of injecting an infusion chemical solution at a predetermined pH stably and continuously into soil, but each material is fed by a screw pump (preferably a Mono pump) or a screw pump. This is also characterized in that the mixing is performed by a static mixer. For this reason, since each material can be easily transferred without alteration, the above apparatus is excellent in productivity.

  In the apparatus of the present invention, a screw pump other than the MONO pump or a screw pump can be used for feeding each material, but the MONO pump is preferable. As the MONO pump, for example, a HAISHIN MONO pump (preferably, NY type or CY type) manufactured by Hyojin Equipment Co., Ltd. can be used, and as a static mixer (static mixer), for example, Nippon Flow Control Co., Ltd. A static mixer (preferably, a stator type) manufactured by the manufacturer can be used.

[Preliminary experiment]
(1)
Soil contaminated with arsenic (elution amount according to Ministry of the Environment Notification No. 18: 0.099 mg / L (9.9 times the environmental standard)) solution type active silica grout (registered trademark: Permalock ASF-IIα, fortification) adding the soil engineering Co., Ltd.) silica concentration of 4 mass%, 6 mass%, in the injection rate 40.5 percent injected drug solution was adjusted to 8 wt% (405L in soil 1 m ^3), were mixed, two days aging Later, the elution amount of arsenic was measured.

Formulation of the above-mentioned solution type active silica grout (Permalock ASF-IIα) (in the case of silica concentration of 6% by mass) [Liquid A (200 L (liter))]
Permalock ASF silica-30 (solid content 30% by mass) 9.5 L
ASF Actor MS 9.8L
Water 180.7L
[Liquid B (200L)]
Permalock PR silica 60.0L
Water 140.0L

  Said A liquid and B liquid were mixed just before injection | pouring, and it was set as the injection chemical | medical solution. The silica concentrations of 4% by mass and 8% by mass were increased or decreased so that ASF silica-30 / PR silica maintained the above ratio.

  The results are shown in Table 1.

  As apparent from Table 1, the higher the silica concentration, the greater the arsenic elution amount and the lower the soil pH.

(2)
For the purpose of keeping the pH of the soil neutral, a mixed solution of phosphoric acid and sulfuric acid (ASF Actor MS) as an acid having the functions of a curing agent and a pH adjusting agent, the same normal formulation as the above-mentioned solution type active silica grout, The same experiment as (1) was performed by reducing the usual blending to 85%, 75%, and 50% by weight. Further, an experiment was also conducted in which sulfuric acid was added instead of ASF Actor MS. The results are shown in Table 2.

  When a mixed solution of phosphoric acid and sulfuric acid (ASF Actor MS) was used, the pH of the soil could be maintained in a neutral range, but the arsenic elution amount did not decrease. On the other hand, when sulfuric acid was used as the acid having the functions of a curing agent and a pH adjuster, the amount of arsenic elution was drastically reduced although it did not meet the environmental standards.

  The composition of the ASF Actor MS 100% by mass infusion solution is shown below.

[Liquid A (200L (liter))]
Permalock ASF silica-30 (solid content 30% by mass) 6.4L
ASF Actor MS 6.5L
Water 187.1L
[Liquid B (200L)]
Permalock PR silica (solid content 35% by mass) 40.0L
Water 160.0L

    Said A liquid and B liquid were mixed just before injection | pouring, and it was set as the injection chemical | medical solution.

[Example 1]
Poly ferric sulfate: (solid content 11 wt%) infusion liquid medicine comprising only when added at a rate of ^{2L / m 3, 5L / m} 3, 10L / m 3 with respect to the soil, also solution-type activity In silica grout, an infusion solution (polysulfuric acid 2) prepared by adding polyferric sulfate and adjusting the pH to 4.2 using sulfuric acid instead of ASF Actor MS as an acid having the functions of a curing agent and a pH adjusting agent. Soil contaminated with the same arsenic as in (1) (preparation of chemicals with different concentrations so that iron is 2 L / m ³ , 5 L / m ³ , 10 L / m ³ ) Elution amount in accordance with No .: 0.099 mg / L (9.9 times the environmental standard) and mixing.After 2 days of curing, the elution amount of arsenic was measured. Shown in

  As is apparent from FIG. 6, arsenic insolubilization effect is markedly greater in the solution type active silica grout added with sulfuric acid and polyferric sulfate than in the case of the injection solution of ferric sulfate alone. It was excellent. In addition, in the case of an infusion solution containing ferric iron alone, the arsenic elution amount was not improved even when the amount was increased from 5 L.

[Example 2]
In the solution type active silica grout of Example 1, sulfuric acid was used instead of ASF Actor MS, poly ferric sulfate was added in an amount corresponding to 5 L / m ³ to the soil, and the amount of sulfuric acid was changed. The pH of the injected drug solution was adjusted, and the gel time of the injected drug solution and the insolubilizing effect of arsenic were measured. The results are shown in Table 3.

  As is apparent from Table 3, the insolubilization effect tends to decrease as the pH of the injected drug solution decreases, and the gel time decreases as the pH increases.

No. showing the above excellent results. The formulation of 2 injectable drug solutions is shown below.
[Liquid A (200 L (liter))] (silica concentration: 4% by mass)
Permalock ASF silica-30 (solid content 30% by mass) 6.4L
Polyferric sulfate 5.0L
Sulfuric acid 2.22L
Water 186.5L
[Liquid B (200L)]
Permalock PR silica 40.0L
Water 160.0L

  Said A liquid and B liquid were mixed just before injection | pouring, and it was set as the injection chemical | medical solution. No. No. 1 and 3-6 infusion solutions were No. Only the amount of sulfuric acid with the blend of 2 was changed. At this time, the blending order of the liquid A was blended in the order of sulfuric acid, polyferric sulfate, and silica-30. When blended in this order, the gel time became stable, but in other orders, the gel time became unstable.

  From the above results, the injection solution for arsenic diffusion prevention of the present invention exhibits excellent arsenic insolubilization effect and soil solidification effect, and also has excellent workability because the gel time of the drug itself is reasonably long. I understand that there is.

1 injection tube 2 core tube 3 injection capillary 4 ejection ports 8 detection box 10 Controller 12 unit pump 13 infusion liquid chemical tank 14 injecting liquid medicine 15 contaminated ground 16 pumping passage _{M a, M b, M c} , M d mono pump S Static Mixer S (A) First static mixer S (B) Second static mixer

Claims (14)

An infusion solution for preventing arsenic diffusion in arsenic contaminated soil, which is injected to prevent arsenic diffusion in soil or ground contaminated with arsenic,
An infusate solution for preventing arsenic diffusion in arsenic-contaminated soil containing non-alkaline silica sol containing ferric sulfate and / or polyferric sulfate and an acid containing no phosphorus atom.   The infusion chemical solution for preventing arsenic diffusion according to claim 1, wherein the concentration of silica is 3 to 12% by mass.   The injectable liquid for preventing arsenic diffusion according to claim 1 or 2, wherein the acid containing no phosphorus atom is sulfuric acid.   The injectable drug solution for preventing arsenic diffusion according to any one of claims 1 to 3, which has a pH of 3.5 to 4.5.   Furthermore, the injection chemical | medical solution for arsenic diffusion prevention of any one of Claims 1-4 containing sodium silicate.   6. The method according to claim 1, comprising a first liquid containing a non-alkali silica sol containing ferric sulfate and / or polyferric sulfate and an acid containing no phosphorus atom, and a second liquid containing sodium silicate. The injectable drug solution for preventing arsenic diffusion according to Item 1.   The first liquid is obtained by adding an acid containing no phosphorus atom, ferric sulfate and / or polyferric sulfate, and a non-alkali silica sol in this order, and mixing each time. 6. An infusion chemical solution for preventing arsenic diffusion according to 6.   The injectable solution for preventing arsenic diffusion according to any one of claims 5 to 7, wherein the non-alkali silica sol accounts for at least 8 mass% of the total silica with respect to the total mass of the non-alkali silica sol and sodium silicate.   A method for preventing diffusion of arsenic in arsenic-contaminated soil, characterized by injecting the arsenic diffusion-preventing injectable chemical solution according to any one of claims 1 to 8 into soil or ground contaminated with arsenic.   The arsenic diffusion prevention method according to claim 9, wherein the drug is injected by a super multi-point injection method.   10. Each material of an injection chemical solution for preventing arsenic diffusion is sent to a static mixer by a screw pump or a screw pump, mixed by a static mixer, and the obtained injection chemical solution is sent to a buffer tank and then injected. Or the arsenic diffusion prevention method of 10.   Each material of the injection solution for preventing arsenic diffusion is sent to the first static mixer with a screw pump or screw pump, mixed with the first static mixer, sent to the first buffer tank, and the pH and temperature are adjusted. Detect and investigate whether they are within the predetermined range, and if they are within the range, send them to the second buffer tank, and if they are outside the range, adjust the pH of the mixed material (chemical solution) The necessary materials are sent to the second static mixer via the screw pump or the screw pump and mixed, and this is sent to the first buffer tank to adjust the pH, and then sent to the second buffer tank. The method for preventing arsenic diffusion according to any one of claims 9 to 11, which is injected. Each screw pump or screw pump for pumping each material of the injection chemical solution for preventing arsenic diffusion according to any one of claims 1 to 8,
Static mixer for mixing each material sent from each MONO pump,
A buffer tank for storing the mixed material (chemical solution) sent from the static mixer, and a device for detecting the pH and temperature of the mixed material provided between the static mixer and the buffer tank,
an automatic control device that operates a screw pump or a screw pump to pump the necessary material for adjusting the pH of the mixed material (chemical solution) when the pH and temperature are outside the predetermined range;
A liquid delivery device for an infusion chemical solution for preventing arsenic diffusion. Each screw pump or screw pump for pumping each material of the injection chemical solution for preventing arsenic diffusion according to any one of claims 1 to 8,
A first static mixer for mixing each screw pump or each material sent from the screw pump;
The first buffer tank for storing the mixed material (chemical solution) sent from the first static mixer, and the pH of the mixed material provided between the first static mixer and the first buffer tank And temperature detecting equipment,
an automatic control device that operates a screw pump or a screw pump to pump the necessary material for adjusting the pH of the mixed material (chemical solution) when the pH and temperature are outside the predetermined range;
a second static mixer that mixes each screw pump or each material sent from the screw pump to adjust the pH and sends it to a first buffer tank;
The second buffer tank for storing the mixed material, the pH and temperature of which are adjusted within a predetermined range, sent from the first buffer tank;
A liquid delivery device for an infusion chemical solution for preventing arsenic diffusion.

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