Surface soil treatment method and surface soil treatment material

Abstract

There was no way to reduce the environmental impact of surface soil generated when demolishing ordinary houses and other buildings. [Solution] When demolishing general houses and other buildings, the surface soil generated is treated with a surface soil treatment material containing at least phosphate, and the surface soil treated with this surface soil treatment material is then treated using a surface soil treatment method to reduce the amount of fluorine and lead that leach out, which have an impact on the environment. Thus, a method and treatment material are provided to insolubilize fluorine, which has an impact on the environment.

Description

Technical Field

[0001] The present invention relates to a surface soil treatment method and a surface soil treatment material including contaminants generated during the demolition of ordinary houses. More specifically, by applying a substance containing phosphoric acid treated to have an effect of reducing the elution amount of fluorine and an effect of reducing the elution amount of lead, the elution amounts of fluorine and lead contained in the surface soil including this contaminant are reduced. The present invention relates to a surface soil treatment method for reducing the elution amounts of fluorine and lead and a surface soil treatment material used in this surface soil treatment method.

Background Art

[0002] Conventionally, various techniques have been proposed to suppress the elution of soil contaminants contained in contaminated soil, solid waste, etc. and to meet the environmental standard values determined by the Ministry of the Environment. For example, Patent Document 1 relates to a resource recovery treatment method for selected soil extracted from earth and sand-based mixed waste and the resource recovery treated selected soil. By using a substance containing phosphoric acid treated to have an effect of reducing the elution amount of fluorine, the elution amount of fluorine contained in the selected soil extracted from earth and sand-based mixed waste is reduced, and the resource recovery treatment method for the selected soil for reducing the elution amount of fluorine and the resource recovery treated selected soil extracted from earth and sand-based mixed waste with the elution amount of fluorine reduced by this resource recovery treatment method are described.

[0003] However, in the implementation of the technique for suppressing the elution of soil contaminants performed in the intermediate treatment facility for waste, it is necessary to bring this contaminated soil into this intermediate treatment facility. If the waste transporter does not bring it in, there is a problem that it cannot be implemented.

[0004] According to the inventors' field research, artificial materials such as wall materials, wood, concrete, and plastic resins used in ordinary houses are properly sorted when these houses are demolished. This sorting is done by hand, but fine artificial materials that are difficult to sort by hand are temporarily left in the topsoil without being collected or sorted. Furthermore, as the heavy machinery used for demolition moves over the topsoil where these artificial materials remain, they are further crushed and compacted into the topsoil, forming a topsoil containing impurities.

[0005] This topsoil containing impurities includes wall materials, wood, concrete, plastics, and other resin materials commonly used in residential buildings. Furthermore, some of the scraps from gypsum board used as insulation become impurities, resulting in topsoil containing these artificial materials.

[0006] The main component of the gypsum used to form this gypsum board is, for example, calcium sulfate (CaSO4) according to Non-Patent Humanities 1, but it has been pointed out that it may contain fluorine during its manufacture.

[0007] Regarding surface soil containing impurities generated during the demolition of ordinary houses, the actual situation was unclear because the surface soil containing impurities is almost always left at the site. Therefore, there was a need to investigate this situation, investigate the types of impurities contained in the surface soil and the substances that affect the environment, and develop technologies to reduce the amount of substances that affect the environment that leach out. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6326246 [Non-patent literature]

[0009] [Non-Patent Document 1] Journal of Geotechnical Engineering, Vol. 4, No. 1, pages 91-98 [Overview of the project] [Problems that the invention aims to solve]

[0010] This invention was made in view of the above problems, and the subject of the investigation was surface soil recovered from the demolition sites of general houses in the suburbs of Tokyo. As part of the actual investigation, the types of impurities contained in this surface soil were identified, and these were classified and investigated according to the type of impurities. As part of the investigation of substances that affect the environment, fluorine leached from the gypsum contained in this surface soil was identified as one of the environmental pollutants because it exceeded the environmental standard. Based on these investigation results, the objective is to provide a surface soil treatment method and a surface soil treatment material that reduces the amount of fluorine leached, and more preferably reduces it to 0.8 mg / L or less, which is the current environmental standard. [Means for solving the problem]

[0011] As a result of diligent research to achieve the above objective, the present inventors have discovered a surface soil treatment method and a surface soil treatment material to be used in this method, which stabilizes surface soil containing impurities containing fluorine and lead by applying a surface soil treatment material containing at least phosphoric acid to the surface soil, thereby reducing the amount of fluorine and lead leaching.

[0012] In other words, the first invention of the present invention is a surface soil treatment method for applying a surface soil treatment material to surface soil mixed with foreign matter generated during the demolition of a house, wherein the surface soil treatment material is a substance containing at least phosphoric acid, and the surface soil treatment material is applied to the surface soil in an amount of 0.01% by weight or more and less than 3% by weight as phosphoric acid.

[0013] In this invention, applying a substance containing phosphoric acid to the surface soil as a surface soil treatment material reduces the amount of fluorine and lead leached from impurities.

[0014] The second invention of the present invention is a surface soil treatment method characterized in that the surface soil treatment material is a substance containing phosphoric acid, consisting of at least one selected from superphosphate, heavy superphosphate, magnesium phosphate fertilizer, fused phosphate fertilizer, calcined phosphate fertilizer, coated phosphate fertilizer, liquid phosphate fertilizer, processed phosphate fertilizer, processed slag phosphate fertilizer, humic acid phosphate fertilizer, calcium hydrogen phosphate, calcium phosphate, calcium dihydrogen phosphate, and sodium dihydrogen phosphate.

[0015] This invention relates to a surface soil treatment method, and describes a type of substance containing phosphoric acid, which has the effect of reducing the amount of fluorine and lead leached from impurities contained in the surface soil.

[0016] The third invention of this invention is a method for treating surface soil, wherein the surface soil containing impurities contains at least gypsum.

[0017] The function of this invention is to supply calcium contained in gypsum to the surface soil by including gypsum as an impurity generated when demolishing a typical house.

[0018] The fourth invention of this invention is, This surface soil treatment material is applied to surface soil containing impurities generated during the demolition of a house, and is characterized by being a substance containing at least phosphoric acid.

[0019] This invention, as a treatment material to be applied to surface soil, reduces the amount of environmentally harmful substances leached from surface soil by containing at least phosphoric acid.

[0020] The fifth invention of this invention is, This phosphorus-containing substance is a surface soil treatment material consisting of at least one phosphorus-containing substance selected from superphosphate, double superphosphate, magnesium phosphate fertilizer, fused phosphate fertilizer, calcined phosphate fertilizer, coated phosphate fertilizer, liquid phosphate fertilizer, processed phosphate fertilizer, processed slag phosphate fertilizer, humic acid phosphate fertilizer, calcium hydrogen phosphate, calcium phosphate, calcium dihydrogen phosphate, and sodium dihydrogen phosphate.

[0021] The effect of this invention is not to limit the substance containing phosphoric acid, which is the treatment material applied to the topsoil, and to reduce the elution amounts of fluorine and lead contained in the topsoil.

Effect of the Invention

[0022] According to the topsoil treatment method and the topsoil treatment material of the present invention, there is an effect of reducing the elution amount of fluorine derived from artificial substances contained in the topsoil.

Brief Description of the Drawings

[0023] [Figure 1] It is a representative appearance image of the topsoil used in the examples and comparative examples of the present invention. [Figure 2] It is the result of the fluorine concentration eluted from the topsoil without the topsoil treatment material of the present invention and the topsoil of Example 1 to which the topsoil treatment material was applied. [Figure 3] It is an electron microscope image of the substance generated by the topsoil treatment material collected in Example 8 of the present invention. [Figure 4] It is the result of the component analysis of the substance generated by the topsoil treatment material collected in Example 8 of the present invention. [Figure 5] It is an example of the sorting result of the impurities contained in the topsoil targeted in the present invention.

Modes for Carrying Out the Invention

[0024] Hereinafter, the present invention will be described in more detail. According to the topsoil treatment method and the topsoil treatment material of the present invention, this topsoil treatment method includes a step of adding a topsoil treatment material containing at least phosphoric acid to the topsoil mixed with artificial substances as impurities generated during the demolition of houses and the like. Here, artificial substances are resin materials such as wall materials, gypsum, wood, paper pieces, concrete, plastics, glass, and asphalt used in ordinary houses.

[0025] The amount of surface soil treatment material to be added to the surface soil will be described in detail. Preferably, the amount of surface soil treatment material to be added is calculated by first measuring the amount of fluorine and lead contained in the surface soil that are the targets for reduction of leaching, and then multiplying this amount by a safety factor and the efficiency of the effect of reducing leaching. However, it can be practically difficult to measure such concentrations at demolition sites. As described in Example 2 below, the inventors estimated the amount of surface soil treatment material to be added based on the amount of fluorine leaching measured for each source of surface soil collected over a period of about 10 years. Preferably, the amount of phosphorus contained in the surface soil treatment material is 3% by weight or less and 0.01% by weight or more relative to the surface soil to be treated, more preferably 2% by weight or less and 0.21% by weight or more, and even more preferably 1% by weight or less and 0.42% by weight or more. Applying 3% by weight or more does not pose any particular problem, but it may increase costs. Also, when the amount is 0.01% by weight or less, the amount applied per unit weight may be small.

[0026] The process of adding this surface soil treatment material to the surface soil preferably involves: spraying the surface soil treatment material as is; spraying a dispersion of the surface soil treatment material in water; or spraying an aqueous solution of the surface soil treatment material dissolved in water. The methods of spraying the surface soil treatment material as is, spraying the dispersion, spraying the aqueous solution, and spraying in combination, or spraying water beforehand followed by each of the above-mentioned spraying methods, are also preferably used. It is also preferable to mix the surface of the surface soil after or in parallel with this addition process. Mixing the surface of the surface soil reduces variations in the concentration of the surface soil treatment material in the depth direction of the surface soil. Furthermore, in the process of mixing the surface of the surface soil, it is preferable to mix it to a depth of 20 centimeters or less from the surface of the surface soil, and more preferably to a depth of 10 centimeters or less. When impurities are mixed into the topsoil, their distribution is often less than 20 centimeters from the surface of the topsoil, so it is preferable to prevent these impurities from mixing into deeper soil. Furthermore, it is preferable to add the above-mentioned topsoil treatment material to the topsoil after the topsoil mixing process, as this may provide a greater reduction in leaching.

[0027] In the surface soil treatment method of the present invention, the curing time after application of the surface soil treatment material is not particularly limited and can be appropriately selected considering temperature, humidity, etc., but for example, 24 to 72 hours is preferred. When surface soil is left outdoors, there is a concern that fluorine may easily leach out due to rainwater, etc. However, the reaction between the leached fluorine and the surface soil treatment agent occurs quickly, reducing the amount of fluorine that leaches out by making it a less soluble substance, which is preferable.

[0028] This section will detail the surface soil treatment material. The surface soil treatment material is preferably one containing phosphoric acid, and more preferably one containing both phosphoric acid and calcium. The phosphoric acid-containing surface soil treatment material is preferably a substance containing phosphoric acid, consisting of at least one selected from superphosphate, superphosphate, magnesium phosphate fertilizer, fused phosphate fertilizer, calcined phosphate fertilizer, coated phosphate fertilizer, liquid phosphate fertilizer, processed phosphate fertilizer, processed slag phosphate fertilizer, humic acid phosphate fertilizer, calcium hydrogen phosphate, calcium phosphate, calcium dihydrogen phosphate, and sodium dihydrogen phosphate. Among these, it is preferable to use a substance containing calcium within its molecule. Furthermore, when using a phosphoric acid-containing compound that does not contain calcium within its molecule as a surface soil treatment material, it is preferable to use it in combination with a calcium-containing compound. When gypsum, used in house walls, is present in the surface soil, the calcium contained in the gypsum can be utilized to reduce the amount of fluorine and lead leaching; therefore, a substance that does not contain calcium can also be preferably used as a surface soil treatment material. Among these calcium-free phosphoric acid-containing compounds, sodium dihydrogen phosphate is particularly preferred.

[0029] Preferably used calcium-containing compounds include gypsum, lime, and calcium hydroxide.

[0030] The reaction mechanism currently considered to be responsible for the effect of the surface soil treatment material is described below. The reaction between a phosphate-containing compound and fluorine is shown in Equation 1 below. Ca5(PO4)3OH + F - → Ca5(PO4)3F + OH - (Formula 1) Phosphate (PO4) 3- Calcium (Ca) reacts with hydroxyapatite (Ca5(PO4)3OH) in the surface soil. This hydroxyapatite then reacts with free fluorine to form fluoroapatite (Ca5(PO4)3F), a poorly soluble substance, which is thought to reduce the amount of fluorine released.

[0031] The present invention will be described in more detail below with reference to examples and experimental examples, but the present invention is not limited to the following examples.

[0032] (Experimental Example 1) Recovery of topsoil: First, we collected topsoil generated when a house located in northern Tokyo was demolished, through the demolition company. Figure 1 shows an image of this topsoil. In Experimental Example 1 of the present invention, 28 different topsoil samples from different sites where the soil was collected were used as specimens from June to August 2023.

[0033] Results of sorting of impurities contained in the topsoil: To measure the types and approximate amounts of impurities in the recovered topsoil, 100g samples of topsoil were visually and manually sorted for impurities. The weight of each impurity is shown in Figure 5. The types of impurities sorted were wood chips, plastic, gypsum, charcoal, ceramics, metal, asphalt, concrete, stone, and glass. On average, wood accounted for 1.18% by weight, plastic for 0.08% by weight, gypsum for 2.45% by weight, charcoal for 0.01% or less by weight, ceramic for 0.41% by weight, metal for 0.07% by weight, asphalt for 1.29% by weight, concrete for 8.75% by weight, stone for 1.48% by weight, and glass for 1.31% by weight. Furthermore, these distributions were consistent with the sorting results obtained by the inventors in the past.

[0034] (Experimental Example 2) Figure 2 shows the results of a leaching test conducted on 30 topsoil samples collected from June to August 2023, as shown in Experimental Example 1. The test was performed using water at a concentration of 1:10 in proportion to the weight of the topsoil, as stipulated in Ministry of the Environment Notification No. 46. In Figure 2, the topsoil is labeled as "mixed soil" because it contains impurities. The leaching test revealed fluorine leaching from all topsoil samples. The average concentration of leached fluorine was 1.66 mg / L, exceeding the environmental standard of 0.8 mg / L in all samples. Additionally, arsenic (As) leached at a concentration of 0.02 mg / L in the topsoil sample taken on July 4th. Hexavalent chromium (Cr(VI)) leaching of approximately 0.05 mg / L was confirmed in 11 samples.

[0035] (Experimental Example 3) In Experimental Example 2, fluorine leaching exceeding environmental standards was observed from the topsoil, so the causative substance of fluorine leaching was investigated. Using gypsum collected from the topsoil, similar to Experimental Example 1, the same leaching test was conducted while adjusting the amount of gypsum. A positive correlation was found between the amount of gypsum and the amount of fluorine leached. From the results of Experimental Example 3, gypsum, an impurity, was considered to be one of the causative substances of fluorine leaching.

[0036] (Example 1) For a sample of topsoil collected on June 28, a topsoil treatment agent was added to the topsoil at a concentration of 0.25% by weight (0.2% by weight as phosphorus). After mixing with the topsoil using a shovel, the agent was cured for about two weeks, and the results of the leaching test are shown in Figure 2. Here, 0.25% by weight relative to the topsoil was used as the standard amount of topsoil treatment agent. In addition, a double amount of 0.5% by weight (0.4% by weight as phosphorus) was used, and the leaching test was conducted in the same manner. In this Example 1, calcium dihydrogen phosphate was used as the topsoil treatment agent. The solubility of calcium dihydrogen phosphate in water is approximately 1.8 g / 100 mL, which is relatively low. Against a fluorine leaching amount of 1.92 mg / L, the leaching amount when the standard amount of topsoil treatment agent was added was 1.0 mg / L, and when double the amount was added it was 0.18 mg / L, meaning that the double amount fell below the environmental standard. The reduced fluorine leaching amount was 0.92 mg / L at a surface soil treatment material addition rate of 0.25% by weight and 1.74 mg / L at a rate of 0.5% by weight, indicating favorable results. This represents one embodiment of the present invention using a surface soil treatment material with moderate solubility.

[0037] (Example 2) For a sample of surface soil collected on June 29, treatment was carried out in the same manner as in Example 1, except that sodium dihydrogen phosphate was used as the surface soil treatment material. The solubility of sodium dihydrogen phosphate in water was approximately 91 g / 100 mL, which is relatively high. When the standard amount of surface soil treatment material was added, the amount of fluorine leached out was 0.7 mg / L compared to 1.21 mg / L, and when twice the amount was added, it was 0.65 mg / L, which was below the environmental standard at the standard amount. The reduced amount of fluorine leached out was 0.51 mg / L at an addition amount of 0.25% by weight (0.2% by weight as phosphoric acid) and 0.56 mg / L at an addition amount of 0.5% by weight (0.4% by weight as phosphoric acid), which were good results. This is one embodiment of the present invention using a readily soluble surface soil treatment material.

[0038] (Example 3) For a sample of surface soil collected on June 30, treatment was carried out in the same manner as in Example 1, except that calcium phosphate was used as the surface soil treatment material. The solubility of calcium phosphate in water was approximately 0.02 g / 100 mL, indicating very low solubility. Compared to a fluorine elution amount of 1.28 mg / L, the fluorine elution amount was 0.7 mg / L when 0.25% by weight (0.14% by weight as phosphoric acid) of the surface soil treatment material was added as the standard amount, and 0.3 mg / L when 0.5% by weight (0.28% by weight as phosphoric acid) of the surface soil treatment material was added, both of which were below the environmental standard at the standard amount. The reduced fluorine elution amount was 0.58 mg / L at an added amount of 0.25% by weight of the surface soil treatment material and 0.98 mg / L at an added amount of 0.5% by weight, showing good results. This is one embodiment of the present invention using a poorly soluble surface soil treatment material.

[0039] From the results of these [Examples 1] to [Examples 3], it was confirmed that using a phosphate-containing compound as a surface soil treatment material can reduce the amount of fluorine leached from the surface soil.

[0040] (Example 4) For surface soil samples collected from July 1st to August 1st, the same method as in Example 1 was used, except that sodium dihydrogen phosphate was used as the surface soil treatment material. Except for the standard amount for July 5th, which exceeded the fluorine leaching amount when no surface soil treatment material was added, the surface soil treatment material was found to reduce fluorine leaching. For the surface soil sample from July 5th, it was thought that the amount of gypsum in the surface soil treated with the standard amount of 0.25% by weight (0.2% by weight as phosphoric acid) was greater than the amount of gypsum in the surface soil sample collected for the surface soil-only test. On the other hand, for the surface soil sample from July 5th, applying twice the amount of surface soil treatment material resulted in a fluorine leaching amount of 0.32 mg / L, which is below the environmental standard, and a good result was obtained.

[0041] (Example 5) In summary, the fluorine leaching amount in the topsoil (labeled as mixed soil in Figure 2) was an average of 1.66 mg / L. However, by adding 0.25% by weight (0.2% by weight as phosphoric acid) of the topsoil treatment agent to the topsoil, the fluorine leaching amount decreased to an average of 0.47 mg / L. Furthermore, when 0.5% by weight (0.4% by weight as phosphoric acid) of the topsoil treatment agent was added to the topsoil, the fluorine leaching amount decreased to an average of 0.16% by weight, which was also below the environmental standard, indicating favorable results.

[0042] (Example 6) In summary, the fluorine leaching amount from the topsoil (labeled as mixed soil in Figure 2) was an average of 1.66 mg / L. However, by adding 0.25 wt% of the topsoil treatment material (0.14 wt% to 0.2 wt% as phosphoric acid) to the topsoil, the fluorine leaching amount averaged 0.47 mg / L. Based on this, the amount of topsoil treatment material needed to reduce the fluorine leaching amount per unit weight of topsoil to 1.7 mg / L, which is below the environmental standard of 0.8 mg / L. Since 0.25 wt% of the topsoil treatment material (0.14 wt% as phosphoric acid) can reduce the fluorine leaching amount by approximately 1.2 mg / L, it was estimated that 1 wt% of the topsoil treatment material (0.52 wt% as phosphoric acid) is effective in reducing fluorine by 4.8 mg / L. These results confirmed that adding 0.19 wt% (0.1 wt% as phosphoric acid) of surface soil treatment material to the surface soil could reduce the amount of fluorine leached to below environmental standards. When using fluorine as the standard, it was found that adding 0.21 wt% of surface soil treatment material (0.12 wt% as phosphoric acid) per 1 mg / L of fluorine is preferable. Furthermore, when the amount of fluorine leached from the surface soil was the lowest at 0.84 mg / L, the amount of surface soil treatment material to be applied was estimated to be 0.01 wt% (0.006 wt% as phosphoric acid).

[0043] (Example 7) In Examples 1 and 2, a yellow product was observed in the surface soil where the amount of fluorine leached after application of the surface soil treatment material was reduced. Crystal analysis of these products confirmed that the yellow product is a substance similar to hydroxyapatite and fluoroapatite. Since hydroxyapatite and fluoroapatite contain calcium, phosphorus, oxygen, hydrogen, and fluorine in their structure, it was thought that hydroxyapatite was generated by adding a phosphate-containing compound as a surface soil treatment material, and that fluoroapatite was generated by reacting with fluorine. In Example 2, sodium dihydrogen phosphate was used as the surface soil treatment material, so calcium was not added, but it was thought that apatite was formed by utilizing the calcium contained in the surface soil.

[0044] (Experimental Example 4) To investigate apatite formation by sodium dihydrogen phosphate, an experiment was conducted in which sodium dihydrogen phosphate and calcium hydroxide were added to an aqueous solution adjusted to a fluorine concentration of 2 mg / L to reduce the amount of fluorine eluted. As a result, a white product precipitated in this aqueous solution, and the amount of fluorine eluted was below the environmental standard of 0.8 mg / L. Crystal analysis of this white product was performed as in Example 7, and it was confirmed that it was a crystal similar to hydroxyapatite and fluoroapatite.

[0045] (Example 8) The specific chemical formulas of the crystalline substances similar to the hydroxyapatite and fluoroapatite produced in Experimental Example 4 are presumed to be Ca5(PO4)3OH for hydroxyapatite and Ca5(PO4)3F for fluoroapatite. Lead present in the surface soil dissolves into Pb 2+If it enters the human body, it will be exchanged with calcium (Ca) that makes up the bone and will remain in the bone for a long period of time. To investigate whether it has the effect of reducing the amount of lead that is a concern when wiring etc. is present in the surface soil, the surface soil treatment material of the present invention was applied and its effect was investigated. Except for using surface soil to which 5% by weight of waste gypsum was added to the test soil containing lead ions, the treatment to reduce the amount of leaching was carried out in the same manner as in Example 2. The resulting yellow crystals were collected on filter paper, washed three times with pure water, and dried. An electron microscope image of these crystals is shown in Figure 3. The results of the component analysis of these crystals are also shown in Figure 4. It was confirmed that these crystals contain at least calcium (Ca), phosphorus (P), oxygen (O), fluorine (F), and lead (Pb). From this, it was confirmed that the surface soil treatment material and surface soil treatment method of the present invention can reduce the amount of fluorine and lead that leach out of the surface soil.

[0046] (Example 9) When the crystals formed by carrying out the above Examples 1 to 7 were subjected to the same component analysis as in Example 8, calcium, phosphorus, and fluorine were identified.

[0047] (Example 10) An aqueous solution was prepared using sodium dihydrogen phosphate as a surface soil treatment material. Lead nitrate was added to this aqueous solution to achieve a lead ion concentration of 1 mg / L. Since there was no calcium in the aqueous solution, gypsum was added so that the calcium concentration was 20 / 3 times the molar ratio of the phosphorus concentration contained in the surface soil treatment material. After thorough stirring, the supernatant of the aqueous solution was collected, and the lead concentration contained in this solution was measured. As a result, the lead concentration was below the environmental standard of 0.01 mg / L, which was a good result. In this Example 10, the effect of reducing the amount of fluorine leached in an aqueous solution with a fluoride ion concentration of 1 mg / L was confirmed using the surface soil treatment material that reduced the amount of lead leaching. The fluoride ion concentration was 0.8 mg / L or less, confirming that the amount of fluorine leaching was reduced. At this time, the lead concentration was below the environmental standard of 0.01 mg / L.

[0048] (Example 11) An aqueous solution was prepared using calcium dihydrogen phosphate as a surface soil treatment material. Lead nitrate was added to this aqueous solution to achieve a lead ion concentration of 1 mg / L. Considering the concentration of calcium dihydrogen phosphate, gypsum was added so that the calcium concentration was 20 / 3 times the molar ratio of the phosphorus concentration contained in the surface soil treatment material. After thorough stirring, the supernatant of the aqueous solution was collected, and the lead concentration contained in this solution was measured. As a result, the lead concentration was below the environmental standard of 0.01 mg / L, which was a good result. When the effect of reducing the amount of fluorine leached in an aqueous solution with a fluoride ion concentration of 1 mg / L was confirmed using the surface soil treatment material used in this Example 11, the fluoride ion concentration became 0.8 mg / L or less, confirming that the amount of fluorine leached was reduced. At this time, the lead concentration was below the environmental standard of 0.01 mg / L.

[0049] Although embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the invention. [Industrial applicability]

[0050] The surface soil treatment method and surface soil treatment material of the present invention can reduce the amount of fluorine leached that exceeds the environmental standard to 0.8 mg / L or less, thus having high industrial applicability.

Claims

1. A surface soil treatment method comprising applying a surface soil treatment material to surface soil mixed with foreign matter generated during the demolition of a house, wherein the surface soil treatment material is a substance containing at least phosphoric acid, and the surface soil treatment material is applied to the surface soil in an amount of 0.01% by weight or more and less than 3% by weight as phosphoric acid.

2. The surface soil treatment method according to claim 1, characterized in that the surface soil treatment material is a substance containing phosphoric acid, consisting of at least one selected from superphosphate, double superphosphate, magnesium phosphate fertilizer, fused phosphate fertilizer, calcined phosphate fertilizer, coated phosphate fertilizer, liquid phosphate fertilizer, processed phosphate fertilizer, processed slag phosphate fertilizer, humic acid phosphate fertilizer, calcium hydrogen phosphate, calcium phosphate, calcium dihydrogen phosphate, and sodium dihydrogen phosphate.

3. The surface soil treatment method according to claims 1 and 2, wherein the surface soil mixed with impurities contains at least gypsum.

4. A surface soil treatment material for use on surface soil containing impurities generated during the demolition of a house, characterized in that it is a substance containing at least phosphoric acid.

5. The surface soil treatment material according to claim 4, characterized in that the substance containing phosphoric acid is a substance containing phosphoric acid, consisting of at least one selected from superphosphate, double superphosphate, magnesium phosphate fertilizer, fused phosphate fertilizer, calcined phosphate fertilizer, coated phosphate fertilizer, liquid phosphate fertilizer, processed phosphate fertilizer, processed slag phosphate fertilizer, humic acid phosphate fertilizer, calcium hydrogen phosphate, calcium phosphate, calcium dihydrogen phosphate, and sodium dihydrogen phosphate.

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