JP2005021873A - Cleaning method for contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method for contaminated soil where artificial zeolite powder maintaining required performance is dispersed and mixed into water so as to be a cleaning liquid, the liquid is penetrated and diffused into gaps between contaminated soil, and the contaminated soil can easily be purified at a low cost. <P>SOLUTION: This cleaning method for contaminated soil comprises: the survey of the soil of a land to be cleaned; an excavation stage of excavating cleaning liquid injection holes at uniform intervals and a required hole size and a depth on the whole face of the contaminated soil by a boring machine; and a cleaning liquid injection stage where a cleaning liquid is penetrated and diffused into the gaps between the contaminated soil through the insides of the cleaning liquid injection holes under a required injection pressure by using an injection tube. The cleaning method further comprises a backfilling stage where the soil is subjected to backfilling by using the cleaning liquid consisting of the artificial zeolite powder mixed in the weight ratio of 10 to 35% to water, and having a particle diameter of ≤30 μm and a specific surface area of ≥100 m<SP>2</SP>/g, and whose volume (meq/100g) expressed in terms of a base is ≥200 mg, and cleaning packed sand blended with 10 to 35 wt.% artificial zeolite powder based on the excavated and discharged sand through the cleaning liquid injection holes. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

Industrial application fields

  The present invention relates to a contaminated soil purification method capable of purifying contaminated soil simply and inexpensively at the current position.

Conventional technology

  In Japan, the expansion of the industrial scale and the development of the chemical industry have led to remarkable economic growth, but with the expansion of the industrial scale, a large amount of soot and wastewater continues to be discharged, and waste disposal In particular, the entire environment, including the atmosphere and water as well as the soil, has been significantly polluted due to the discharge and disposal of large amounts of chemical substances accompanying the development of the chemical industry, and many health hazards have already been caused. Has reached.

And once soil has been contaminated with chemical substances, the natural purification action does not work unlike air and water, and the accumulation has been gradually increased. Contamination is also frequent.
For this reason, in recent years, the purification of contaminated soil has been raised as an important issue, and guidance on the obligation to purify contaminated soil in land transactions and the evaluation of contaminated land have been reviewed.

  Thus, as a means of remediating contaminated soil, the conventional method is to remediate the vastly contaminated soil, and in the case of a more narrow and highly contaminated contaminated soil, the contaminated soil is excavated and transported and treated with high temperature treatment or chemical treatment. In addition to being able to purify by treatment, it is considered suitable to be re-imported and backfilled.However, since urbanization has further progressed in recent years, even when excavating and transporting temporarily contaminated soil, There is almost no site conditions or space for purifying the contaminated soil, and therefore, it must be carried out to a remote place, cleaned and re-introduced, resulting in enormous labor and cost.

Furthermore, in the in-situ purification method, a suction well is installed in the unsaturated zone above the groundwater surface by boring, and the vapor of the pollutant is sucked by reducing the pressure with a vacuum pump or blower, and the vapor of the pollutant is adsorbed by activated carbon. In addition to soil gas suction method, which is decomposed by ultraviolet rays, or by drilling in multiple circular shapes, solidification / insolubilization methods such as injecting special cement or other insolubilizing / solidifying agent into soil, and contaminated soil such as heavy oil A A soil washing method in which it is washed by flowing it in an aqueous solution of sodium silicate, a reduction stabilization treatment of hexavalent chromium with minerals, and a hexagonal chromium after reduction insolubilization treatment using ferrous sulfate (FeSO ₄ ) as a reducing agent. There are known reduction treatment methods that improve the soil by using them, or electrical separation methods in which electrodes are inserted into the soil and ionic pollutants are transferred and then decomposed.

  However, these publicly known methods not only require a large scale of construction, but also require sophisticated technical skills and machinery and enormous purification costs. As long as it is difficult to apply to the purification of contaminated soil in the general private sector, the effect of the purification has not been fully confirmed.

The present invention has been studied in view of such circumstances. Artificial zeolite powder that has a large number of fine pores using industrial waste such as coal ash, has excellent adsorptivity and hygroscopic water absorption, and gives a large base substitution capacity (meq / 100 g). Is suitable for mass production at relatively low cost, and the artificial zeolite powder has a particle size of 30 μm or less, a very large contact surface area, and a large physical adsorption capacity, moisture absorption and water absorption capacity. Therefore, in terms of adsorbing, fixing or decomposing heavy metals and organic compounds which are adsorbed at a specific surface area of at least 100 m ² / g or more, in addition to their inherently retained catalytic action, Since strong base substitution is required, at least 200 mg of artificial zeolite powder is used in the base substitution capacity (meq / 100 g), and this artificial zeolite powder is stored. In order to make effective contact with the heavy metals and organic compounds that are the soil pollutants that are accumulated, they are mixed and dispersed at a rate of 10 to 35% by weight with respect to water to form a cleaning solution, and added to the gaps in the contaminated soil. The inventors of the present invention have found that contamination can be purified easily and inexpensively by pressure injection and osmotic diffusion.

Problems to be solved by the invention

  In the present invention, artificial zeolite powder having the required performance is mixed and dispersed in water to obtain a purification solution, and it is permeated and diffused into the gaps in the contaminated soil, thereby allowing simple, inexpensive and excellent purification. It is to provide a method for purifying contaminated soil that can be realized.

Means for solving the problem

The technical means used by the present invention in order to solve the above-mentioned problems are to drill the appropriate position of the land to be cleaned, investigate the soil contamination state, contamination distribution and soil porosity, and based on this soil survey. A drilling process in which a cleaning liquid injection hole having a required hole diameter and depth is excavated at a uniform interval over the entire contaminated soil with a boring machine, and each cleaning liquid injection hole is provided in a drilling rod for a drilling machine. A purification liquid injection step of infiltrating and diffusing into the contaminated soil gap with a required injection pressure and injection amount from the purification liquid injection port, and bringing the purification liquid into contact with the pollutant, and 10 to 35% by weight with respect to water A purification solution comprising an artificial zeolite powder mixed and dispersed and having a particle size of 30 μm or less, a specific surface area of 100 m ² / g or more, and a base substitution capacity (meq / 100 g) of 200 mg or more; The backfilling step of backfilling with the purified filling soil in which the artificial zeolite powder is mixed in the soil discharged at the time of excavation of the purified solution injection hole in the permeated and diffused purified solution injection hole in a proportion of 10 to 35% by weight. It exists in the composition which consists of.

  Furthermore, in order to further enhance the dispersion of artificial zeolite powder in the cleaning solution and promote the permeation and diffusion into the contaminated soil gap, a cationic surfactant is mixed in the cleaning solution in an amount of 0.5 to 5.0% by weight. In addition to coagulating and peeling off the contaminants firmly attached to fine soils such as rust and clay, and adsorbing and fixing or decomposing them, 0.5 to 5.0% of calcium sulfate is contained in the purification solution. The composition mixed by weight ratio, and the cleaning solution penetrates and diffuses into the contaminated soil gap, and the necessary amount of the cleaning solution is sprayed over the entire contaminated soil surface. And it exists in the structure which aims at compacting of a cleaning liquid injection hole backfill.

Action

Since the present invention uses such a configuration, it has the following effects. In other words, since the soil is surveyed by drilling prior to purification, the contamination, contamination status, contamination distribution, and porosity of the contaminated soil are confirmed, so the mixing ratio and appropriate viscosity of the artificial zeolite powder in the purification solution to be used are determined. The injection pressure and the injection amount can also be discriminated.
Then, a cleaning solution injection hole is drilled over the entire contaminated soil by a boring machine at equal intervals and with the required hole diameter and depth, and is placed at the tip of the boring machine drilling rod in each cleaning solution injection hole. The purifying liquid is injected into the excavated and sealed purifying liquid injection hole at the required injection pressure from the prepared purifying liquid injection port, so that the purifying liquid enters the soil gap in the required radial range around the purifying liquid injection hole. It is intimately contacted with heavy metals and organic compounds that have been permeated and diffused.

  Furthermore, the heavy metals and organic compounds that are in contact with the purification liquid in which the artificial zeolite powder is mixed and dispersed are fine particles, have an extremely large contact surface area ratio, and have a large adsorption capacity, moisture absorption, and water absorption capacity. Actively and efficiently adsorbed or absorbed and absorbed by artificial zeolite powder with a large amount of moisture absorption and water absorption, and the adsorbed heavy metals and organic compounds are essentially retained in their catalytic action and strong base substitution. Heavy metals are strongly adsorbed and fixed, and organic compounds are easily adsorbed and decomposed.

Further, the purification solution injection hole into which the purification solution is injected under pressure is backfilled with a purification filling soil in which 10 to 35% by weight of artificial zeolite powder is mixed with the contaminated soil excavated and discharged. Therefore, it is firmly adsorbed and fixed or decomposed by adsorption with the artificial zeolite powder mixed with the heavy metals and organic compounds in the purification packed soil.
In addition, when a cationic surfactant is mixed in the purification solution at a weight ratio of 0.5 to 5.0%, the dispersibility of the artificial zeolite powder in the purification solution increases, so that Osmotic diffusion is significantly promoted, and adsorption and fixation of heavy metals and adsorption and decomposition of organic compounds are remarkably enhanced, or by mixing calcium sulfate in the purification solution in a proportion of 0.5 to 5.0% by weight, Peeling force accompanying cohesion acts on heavy metals and organic compounds that adhere and accumulate in large quantities on fine particles such as soil, clay, and dust, and they are easily adsorbed and fixed or decomposed.

  Further, the purification liquid is injected into the purification liquid injection hole with the required injection pressure and injection volume, and the required amount of the purification liquid is sprayed over the entire contaminated soil surface that has been permeated and diffused into the soil gap and backfilled. Therefore, the artificial zeolite powder is infiltrated and contacted evenly with the pollutant on the contaminated soil surface to perform adsorption fixation and adsorption decomposition and to compact the soil in the backfill portion.

In the following, the embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram of a soil survey method performed prior to the implementation of the purification method of the present invention. Using a suitable excavator 1B, such as an earth auger or a boring machine, at 1A, an excavation hole 1C having a required diameter and depth is excavated, and a soil sample covering the surface layer 1D, the middle layer 10D, or the lower layer 11D is collected. Based on each soil sample, the degree of pollution, pollution distribution and soil porosity are determined for each pollutant.
In such a case, the contamination state for each pollutant is essentially qualitative and quantitative analysis using an analytical instrument such as a gas chromatograph. Currently, a simple analysis method using a reagent for each pollutant, so-called pack test. The method is widespread, and it is convenient to use the pack test method to roughly determine the degree of contamination.

In the soil survey 1, the contamination state, the contamination distribution, and the soil porosity for each pollutant are grasped, and the purification method of the present invention is applied.
That is, FIG. 2 is an explanatory view of a boring machine 2 used in carrying out the purification method of the present invention. The boring machine 2 is provided with a driving device 2B on a base 2A, and the base 2A. A rod 2D, which can move up and down in a required depth direction at one side end and is rotatable so that the purifying solution injection hole 3 can be excavated with a required hole diameter, and a so-called bit 2C attached to the tip of the drill 2C is provided. In addition, the lower end of the rod 2D has a lower end for injecting the cleaning liquid 4 with the required injection pressure and injection amount into the cleaning liquid injection hole 3 drilled to the required hole diameter and depth. Is equipped with a purification liquid injection pipe 2F having a purification liquid injection port 2E.

As a matter of course, the cleaning liquid 4 stored in a required amount in the cleaning liquid tank 40 is injected into the other end 2G of the cleaning liquid injection pipe 2F of the cleaning liquid injection hole 3 of the boring machine 2 with a required injection pressure and injection. A pressure-resistant transfer hose 42 communicated with a pressurizing pump 41 to be transferred by an amount is attached.
Furthermore, the injection pressure of the purification liquid 4 into the purification liquid injection hole 3 excavated by using the boring machine 2 varies depending on the porosity and the injection amount of the soil, but in general soil, about 20 to 40 kgf / It is advantageous to maintain an injection pressure of about cm ² .

The purifying fluid injection hole 3 excavated by the boring machine 2 thus constructed is excavated at equal intervals and with a required hole diameter and depth based on the soil survey. FIG. 3 shows the purifying fluid injection hole according to the present invention. 3 is an explanatory diagram showing the excavation state 3 and a bit 2C is attached to the tip of the rod 2D of the boring machine 2 and moves downward while rotating the rod 2D from an appropriate position of the contaminated soil 1A. By doing so, the purification liquid injection hole 3 having a required depth and hole diameter is excavated.
In this case, the excavation depth of the purification liquid injection hole 3 is determined according to the contamination distribution, and the hole diameter of the purification injection hole 3 is not particularly limited, but the required amount of the purification liquid 4 is reduced to the contaminated soil 1A. Usually, about 50 to 100 mmφ is desirable in order to diffuse and diffuse radially into the gap.

Thus, after the rod 2D is rotated to the required depth and hole diameter and excavated, the rotation of the rod 2D is stopped, and the pressure pump 41 of the cleaning liquid 4 is driven to purify the rod 2D. By performing pressure injection from the liquid injection port 2E with a required injection pressure and injection amount, the purification solution 4 injected from the purification solution injection port 2E is permeated and diffused radially into the gap of the contaminated soil 1A. The
Then, the range in which the purifying fluid 4 pressurized and injected into the excavated purifying fluid injection hole 3 is permeated and diffused radially into the gap of the contaminated soil 1A and the other excavated purifying fluid injection hole 3 is pressurized. Due to the range in which the injected cleaning solution 4 is permeated and diffused radially in the gap of the contaminated soil 1A, the entire clearance gap of the contaminated soil 1A is substantially uniformly permeated and diffused by the cleaning solution 4. Then, the respective purifying liquid injection holes 3 may be excavated.

  The range in which the clarified liquid 4 is permeated and diffused into the gap of the contaminated soil 1A and the injection amount vary greatly depending on the viscosity of the clarified liquid 4, the injection pressure, and the porosity of the contaminated soil 1A. The amount of osmotic diffusion of the so-called injection amount is the formula Q = V × n × α = V × λ (where Q = injection amount / kl, V = soil amount to be purified, n = soil porosity%, α = filling rate, (λ−injection rate%), it can be expressed as injection rate λ = soil porosity n × filling rate α.

Thus, the porosity n also varies depending on the soil quality and the degree of compaction of the contaminated soil 1A. In the case of viscous soil, it is approximately 50 in the high pressure dense state, approximately 70 in the low pressure dense state, and further in the case of sandy soil. It is about 30 in the high-pressure dense state, about 50 in the low-pressure dense state, further about 25 in the high-pressure dense state in gravel soil, and about 50 in the low-pressure dense state.
On the other hand, in order to effectively contact the heavy metal or organic compound accumulated in the contaminated soil 1A with the purification solution 4 to adsorb and fix the heavy metal or to adsorb and decompose the organic compound, the purification solution into the gap The filling rate is preferably about 50 to 70% or more.

On the other hand, the purification solution 4 is a mixture of the artificial zeolite powder 4A in a proportion of 10 to 35% by weight with respect to water, but the opportunity for contact with heavy metals and organic compounds accumulated in the contaminated soil 1A. The artificial zeolite powder 4A to be used has a particle size that allows the heavy metals and organic compounds to be adsorbed or absorbed, absorbed and absorbed, and easily penetrated and diffused into the gaps of the fine contaminated soil 1A. Is 30 μm or less, preferably about 1 to 10 μm, and has a large adsorption capacity, moisture absorption, water absorption capacity, so-called large specific surface area for efficiently adsorbing, absorbing, or absorbing heavy metals and organic compounds. at least 100 m ² / g or more preferably those 160 to 200 meters ² / g is used in a specific surface area because it is preferable

  In addition, what is important is that the purifying solution 4 is infiltrated and diffused into the gaps of the contaminated soil 1A to purify it by adsorbing and fixing heavy metals as contaminants and adsorbing and decomposing organic compounds. For this purpose, it is indispensable to impart strong base substitution to the catalytic action inherently retained by the artificial zeolite powder 4A. Therefore, the base substitution capacity (meq / 100 g) is preferably at least 200 mg or more. 240 to 280 mg of artificial zeolite powder 4A is selectively used.

  Thus, the purification solution 4 is formed by mixing the artificial zeolite powder 4A with water at a ratio of 10 to 35% by weight in order to permeate and diffuse into the gaps in the contaminated soil 1A. Infiltrate and diffuse as much artificial zeolite powder 4A as possible into the gaps in the soil 1A, and with its absolute adsorption capacity, adsorbing and fixing heavy metals as contaminants and adsorbing and decomposing organic compounds reliably However, when the artificial zeolite powder 4A is less than 10% by weight, its viscosity is at most several psi (poise), so it is excellent in osmotic diffusion, but it is difficult to achieve sufficient adsorption fixation and adsorption decomposition. When the mixing ratio is 35% or more, the viscosity becomes high viscosity of several hundred psi (poise) or more, and it is difficult to sufficiently permeate and diffuse in the contaminated soil 1A having a small porosity.

  In addition, although a large base substitution capacity (meq / 100 g) is desired for adsorption fixation and adsorption decomposition, when the base substitution capacity (meq / 100 g) exceeds 200 mg, the dispersibility in water tends to deteriorate. . Therefore, as a countermeasure against such a problem, it is preferable to improve the dispersibility by mixing 0.5 to 5.0% of the cationic surfactant with respect to the total amount of the cleaning liquid 4. The cationic surfactant in such a case is not particularly limited, and specific examples thereof include alkyltrimethylammonium chloride and alkyldimethylbenzolammonium.

  In addition, the contaminated soil 1A often has a large amount of contaminants deposited and accumulated on fine particulate matter such as dust, corrosive soil or clay in the soil. In order to achieve adsorption fixation or adsorption decomposition, it is advantageous to peel off contaminants from these fine particles by utilizing the agglomeration action. It is proposed to mix in a 5 to 5.0% weight ratio.

FIG. 4 is an explanatory view of the pressure injection construction of the purification liquid in the present invention. In the present invention, the purification liquid injection hole 3 excavated by the boring machine 2 has a required depth position corresponding to the contamination distribution. The purification solution 4 is injected under pressure and injected into the gap between the contaminated soil 1A with the injection pressure and the injection amount, and the artificial zeolite powder 4A is 15% due to many inventors' background. The average radiation osmosis diffusion range 4B when the injection pressure is 30 kgf / cm ² and injected into the contaminated soil 1A having an average porosity of 50% using the purification liquid 4 mixed and dispersed in the weight ratio is the purification liquid injection. It is understood that the distance is about 2.1 to 2.8 m around the entrance 2E. Thus when the pollution distribution over a high range, the gap of the contaminated soil 1A the required injection pressure and injection rate of the rod 2D tip of the boring machine 2 after purification liquid 4 coordination on the level of L ₁ as shown infiltrated diffused within and Thus by pulling coordinated to the level of the distal end L ₂ of the rod 2D, it is injected under pressure drives out the required injection pressure and injection volume cleaning solution 4 again, contamination in the vertical direction soil Permeate and diffuse into the entire 1A gap.

  FIG. 5 is an explanatory diagram showing the state of water spray penetration of the cleaning liquid, and the cleaning liquid injection holes 3 are excavated at equal intervals and at the required hole diameter and depth over the entire contaminated soil 1A. After the purifying liquid 4 is infiltrated and diffused into the gap of the contaminated soil 1A with the required injection pressure and injection amount into the liquid injection hole 3, it is applied to the excavated discharge soil 10A accompanying the excavation of the purification liquid injection hole 3. Then, the purification liquid injection hole 3 is backfilled with the purification filling soil 5 in which the artificial zeolite powder 4A is mixed at a weight ratio of 10 to 35%.

However, in the pressure injection means based on the required injection pressure and the injection amount of the purification liquid 4 in the purification liquid injection hole 3, the discharge occurs everywhere in the vicinity of the surface of the contaminated soil 1A due to the high injection pressure, and the contaminated soil. Not only the penetration and diffusion into the gap near the surface of 1A cannot be sufficiently achieved, but also the backfilling with the clarified filling soil 5 does not lead to a sufficiently filled and solidified state.
Accordingly, by purifying the surface of the contaminated soil 1A and compacting the backfill portion by spraying the required amount of the cleaning solution 4 over the entire surface of the contaminated soil 1A that has been backfilled.
In such a case, the sprinkling permeation 6 of the purification liquid 4 can be easily achieved by simply connecting an appropriate watering tool 6A and a pressurization pump 41 for pressurizing the purification liquid 4 with an appropriate hose 6B. In this case, about 20 to 40 l per 1 m ² is sufficient as the amount of water permeation of the purification liquid 4 slightly depending on the mixing ratio of the artificial zeolite powder 4A.

The invention's effect

As described above, the present invention bores the appropriate position of the land to be cleaned in advance and grasps the soil contamination state, the contamination distribution, and the soil porosity, so that the cleaning solution injection hole to which the cleaning solution should be injected The depth, excavation interval, mixed dispersion concentration of the cleaning liquid, injection pressure, injection amount, and permeation diffusion range can also be determined, and an accurate construction plan can be easily created.
In addition, a bit is attached to the tip of the rod, and a cleaning liquid injection pipe inside the rod, a boring machine having a cleaning liquid injection port at the tip, a purification liquid tank at the other end of the cleaning liquid injection pipe of the boring machine, and By connecting the pressurizing pump, the cleaning solution injection hole with a very small hole diameter can be easily excavated, and the tip of the rod is arranged at the required level position, and the cleaning solution is supplied with the required injection pressure and injection volume. By repeating the injection, the osmotic diffusion is carried out throughout the gap of the contaminated soil, so that the contaminated soil can be diffused and accumulated in the contaminated soil in an extremely simple and efficient manner. The cleaning liquid can be contacted.

In addition, the purification solution that comes into contact with the pollutant has a base substitution capacity (meq / 100 g) of 200 mg or more in addition to the catalytic action that the particle size is 30 μm or less and the specific surface area is 100 m ² / g or more and is inherently retained. Since the artificial zeolite powder having extremely strong base substitution property is mixed and dispersed at a ratio of 10 to 35% by weight with respect to water, not only can it easily permeate and diffuse even in contaminated soil gaps with low porosity, but also artificial zeolite powder. Combined with the extremely large surface area of the powder, the specific surface area, and the amount of mixing and dispersion, the absolute adsorption capacity, moisture absorption, and water absorption capacity are enormous, so heavy metals and organic compounds are aggressive. Adsorbed or absorbed and absorbed efficiently, heavy metals are strongly adsorbed and fixed, and organic compounds are adsorbed and decomposed. This is a groundbreaking method for the purification of contaminated soil.

  It is explanatory drawing of a soil investigation method.   It is explanatory drawing of a boring machine.   It is explanatory drawing of the excavation state of a purification liquid injection hole.   It is explanatory drawing of purification liquid pressurization injection construction.   It is explanatory drawing which shows the state of purification liquid sprinkling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soil investigation 1A Contaminated soil 10A Excavation discharge soil 1B Excavator 1C Excavation hole 2 Boring machine 2A Base 2B Drive device 2C Bit 2D Rod 2E Purification liquid inlet 2F Purification liquid injection pipe 2G The other end of the purification liquid injection pipe 3 Purification liquid Injection hole 4 Purification liquid 4A Artificial zeolite powder 4B Radiation penetration diffusion range 40 Purification liquid tank 41 Pressure pump 42 Pressure-resistant transfer hose 5 Purification filling soil 6 Sprinkling penetration 6A Sprinkling tool 6B hose

Claims (4)

Boring the appropriate position of the land to be cleaned, soil survey to determine the soil contamination status, contamination distribution and soil porosity, and based on the soil survey, even intervals and required pore size and depth over the entire contaminated soil The excavation process of excavating the purification liquid injection hole with a boring machine, and the soil with the required injection pressure and injection amount from the purification liquid injection hole arranged in the boring machine excavation rod in each purification liquid injection hole A purification liquid injection step for permeating and diffusing into the gap, and a mixture of 10 to 35% by weight with respect to water, the particle size of which is 30 μm or less, the specific surface area is 100 m ² / g or more, and the base substitution capacity (meq / 100 g ) Is 200 mg or more of the purified zeolite powder, and the artificial zeolite powder is 1 to the soil excavated and discharged into the purified solution injection hole into which the purified solution is permeated and diffused. A method for purifying contaminated soil, comprising a backfilling step of backfilling with a cleansing filled soil blended at a ratio of 0 to 35% by weight.   2. The method for purifying contaminated soil according to claim 1, wherein a cationic surfactant is mixed in the purification solution in an amount of 0.5 to 5.0% by weight.   The method for purifying contaminated soil according to claim 1, wherein calcium sulfate is mixed in the purification solution at a weight ratio of 0.5 to 5.0%.   4. The method for purifying contaminated soil according to claim 1, wherein a necessary amount of the purifying liquid is sprayed and permeated over the entire contaminated soil surface in which the purifying liquid has been permeated and diffused, and the soil surface is purified and compacted. .

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