Insolubilizer

Abstract

To enable suppression of elution amounts of fluorine and lead by insolubilization of fluorine and lead included in waste gypsum mixed soils and fly ashes generated from construction demolition sites.SOLUTION: An insolubilizer is an aqueous solution including at least a dihydrogenphosphate salt and is added to carefully selected soils extracted from waste gypsum mixed soils generated from construction demolition sites. By adding this insolubilizer, fluorine and lead are insolubilized to suppress their elution amounts.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an insolubilizer that insolubilizes at least fluorine and lead contained in soil and sand mixed waste and fly ash. [Background technology]

[0002] Various techniques have been proposed for suppressing the elution of soil pollutants contained in contaminated soil or fly ash after the treatment of industrial waste, and for making the environmental standards set by the Ministry of the Environment be met. For example, Patent Document 1 describes a method in which phosphate fertilizer is sprayed or added / mixed into contaminated soil contaminated with heavy metals such as fluorine, mercury, cadmium, etc., thereby converting soluble heavy metals present in the soil into sparingly soluble substances and stabilizing them for a long period of time, and the examples show that the amount of fluorine elution from treated soil meets the environmental standards, even when an elution test specified in Notification No. 46 of the Ministry of the Environment is conducted after 12 months of curing.

[0003] Patent Document 2 proposes a technology for washing contaminated soil by mixing and stirring soil contaminated with pollutants, liquid, and fine particles capable of adsorbing the pollutants, and classifying and removing the fine particles that have adsorbed the pollutants together with soil particles having a predetermined particle size or smaller.

[0004] Patent Document 3 proposes a method for recycling selected soil extracted from soil and sand mixed waste, in which dihydrogen phosphate is added to the selected soil to insolubilize the fluorine in the soil together with hexavalent chromium over the long term.

[0005] Patent Documents 4, 5, and 6 propose technologies in which raw ash, which is the discharged incineration ash, is treated by maintaining a constant temperature for a certain period of time in a low-oxygen space insulated from the outside air, and the generated exhaust gas is detoxified by heating in the presence of a transition metal catalyst, or the generated exhaust gas is mixed with nitrogen gas and the mixed gas is heated and detoxified.

[0006] Patent Document 7 proposes a method for treating fly ash, which is also incineration ash, by adding sodium bicarbonate to the flue to reduce the amount of eluted heavy metals contained in the fly ash generated when treating acidic gas, thereby enabling the fly ash to be buried.

[0007] As described above, various methods have been proposed to suppress the elution of contaminants from soil. However, when using a solid such as fine particles in a treatment method for contaminated soil or solids such as fly ash, the probability of contact with the contaminants decreases, and fine particles may fly into the surroundings, which is a problem, so that it is desirable to develop an insolubilizer that can be applied as an aqueous solution and that maintains its insolubilizing effect for a long period of time. Among these contaminants, it is particularly desirable to develop an insolubilizer that is effective against both fluorine and lead. Furthermore, from the viewpoint of effective use of the insolubilizer, it is desirable to develop a technology for insolubilizing contaminants using an insolubilizer after insolubilizing heavy metals, i.e., an insolubilizer containing heavy metals. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2005-58917 A [Patent Document 2] JP 2013-163158 A [Patent Document 3] JP 2014-35456 A [Patent Document 4] JP 2001-942 A [Patent Document 5] JP 2000-24625 A [Patent Document 6] JP 2000-24624 A [Patent Document 7] JP 2006-110423 A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an insolubilizing agent that can insolubilize and stabilize fluorine and lead contained in refined soil extracted from waste gypsum-containing soil generated at construction and demolition sites, and in fly ash generated during the incineration of industrial waste, and that can suppress the elution of fluorine and lead over a long period of time. [Means for solving the problem]

[0010] As a result of intensive research into achieving the above-mentioned object, the present inventors have developed an insolubilizer that insolubilizes and stabilizes the fluorine and lead contained in selected soil by applying an aqueous solution containing at least dihydrogen phosphate as an insolubilizer for the fluorine and lead contained in the selected soil, in order to recycle selected soil extracted from waste gypsum-mixed soil generated at construction and demolition sites, which contains fluorine and lead, or to stably manage and bury fly ash, and have further developed an insolubilizer that insolubilizes fluorine by using the insolubilizer that insolubilizes lead.

[0011] That is, the present invention provides an insolubilizing agent for insolubilizing at least fluorine and lead, the insolubilizing agent being a dihydrogen phosphate, the dihydrogen phosphate including at least one of calcium dihydrogen phosphate and sodium dihydrogen phosphate, The insolubilizer is characterized in that at least one of calcium hydroxide, calcium carbonate, and gypsum is added as a calcium-containing insolubilizer assistant.

[0012] The function of the present invention is to disperse at least calcium dihydrogen phosphate or sodium dihydrogen phosphate as an aqueous solution in the screened soil or fly ash, thereby allowing the active ingredient to act effectively on fluorine and lead. Also, when insolubilizing the fluorine and lead contained in the screened soil or fly ash, the insolubilizer made of the dihydrogen phosphate and the insolubilizer auxiliary containing at least calcium form an insolubilizer, which has the effect of insolubilizing the lead and fluorine.

[0013] The second aspect of the present invention is a lead-containing insolubilizer which insolubilizes lead and further insolubilizes fluorine.

[0014] The effect of the present invention is that the insolubilizer can adsorb lead and then further adsorb fluorine.

[0015] A third aspect of the present invention is a fluorine insolubilizer, which is characterized in that the insolubilizer is a compound comprising at least lead, phosphorus, calcium, and oxygen.

[0016] The effect of this invention is that the insolubilizing agent containing lead acts to more firmly insolubilize fluorine.

[0017] The fourth invention of the present invention is an insolubilizing agent for insolubilizing fluorine, which is a lead-containing insolubilizing agent for fluorine having a molar ratio of lead to phosphorus of 1 / 6 to 1 / 3 moles of lead per mole of phosphorus.

[0018] The effect of the present invention is that the molar ratio of lead to phosphorus is 1 / 6 mol or more and 1 / 3 mol or less, so that fluorine can be effectively insolubilized. Effect of the Invention

[0019] The insolubilizing agent of the present invention, when applied in the form of a solution to water, screened soil, or fly ash, has the effect of insolubilizing and stabilizing the fluorine and lead contained in the water, screened soil, or fly ash. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a conceptual diagram of a presumed chemical reaction related to the action of the insolubilizer of the present invention. [Diagram 2] 1 is a photograph showing the appearance of a product recovered after the action of an insolubilizing agent of the present invention. [Diagram 3] 1 is an electron microscope photograph of a product recovered after the action of the lead-containing insolubilizing agent of the present invention. [Figure 4] 1 shows the results of a component analysis of a product recovered after the action of the lead-containing insolubilizing agent of the present invention. [Diagram 5]FIG. 1 is a diagram summarizing the results of an embodiment of the present invention. [Figure 6] 1 shows the results of analysis of fluorine and lead dissolved from selected soil treated with the insolubilizing agent of the present invention. [Figure 7] 1 shows the results of ion chromatography for investigating the amount of fluorine eluted from fluoroapatite in an aqueous solution. [Figure 8] 1 shows the results of ion chromatography for investigating the amount of fluorine eluted from lead fluoroapatite in an aqueous solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described in more detail with reference to the drawings. The insolubilizer of the present invention is an insolubilizer that insolubilizes fluorine and lead contained in refined soil obtained by separating and classifying waste gypsum-containing soil generated at construction and demolition sites, and in fly ash generated during incineration of industrial waste. This insolubilizer can insolubilize lead and fluorine present in an aqueous solution, thereby reducing the concentrations of these elements in the aqueous solution.

[0022] Here, the waste gypsum-mixed soil generated from construction and demolition sites refers to construction waste generated, for example, from the construction and demolition of buildings, and is a mixture of soil and sand with concrete, rubble, paper, wood chips, plastic, gypsum, etc. This refined soil is soil that has been separated and classified from such waste gypsum-mixed soil generated from construction and demolition sites, and has been selected so that the particle size is 5 mm or less and the content of combustible materials such as paper, wood chips, and plastic is less than 5% by mass (sometimes written as % by weight). Specific sorting methods include, for example, a purification method in which the soil-based mixed waste is purified by dry separation and classification based on the physical properties of the components contained in the soil-based mixed waste. More specifically, the purified soil obtained is sorted using dry separation and classification equipment such as screens, specific gravity separators, wind separators, suction separators, and magnetic separators so that the particle size of the resulting purified soil is 5 mm or less and the content of paper, wood chips, and plastics is less than 5% by weight. This makes it possible to comprehensively select purified soil from the soil-based mixed waste that is 5 mm or less in particle size and has a paper, wood chips, and plastic content of less than 5% by weight.

[0023] The particle size of the selected soil can be confirmed by selecting a sieve that can sift out materials with a particle size of 5 mm or less during screening, and the mass content of wood chips in the total amount of selected soil can be confirmed by sampling an appropriate amount of the selected soil after the screening process, measuring the total amount, subjecting it to heat treatment, burning the paper, wood chips, and plastic in the selected soil, measuring the mass after the heating and burning process, and checking the mass difference before the heating and burning process. In this case, if a material containing crystal water such as gypsum is present, an error will occur due to the water content. In this case, the error can be reduced by preheating the heat treatment to about 150°C to reduce the moisture content.

[0024] The particle size of the selected soil needs to be 5 mm or less, and there is no particular lower limit as long as it passes through a sieve that can separate out materials with a particle size of 5 mm or less. The lower the content of paper, wood chips, and plastics in the total volume of the selected soil, the better, and there is no particular lower limit.

[0025] The concentration of the aqueous solution of the insolubilizer of the present invention is not particularly limited. In the case of calcium dihydrogen phosphate as the dihydrogen phosphate, the content in 100 mL of water is preferably about 1.5 g in view of the solubility. It is also preferable to further dilute it with water before use.

[0026] When the insolubilizer is sodium dihydrogen phosphate, its solubility in water is about 60 g / 100 mL, so it is preferable that the concentration is equal to or less than this value. It is also preferable to further dilute it with water before use.

[0027] It is also preferable to prepare a high-concentration aqueous solution of these dihydrogen phosphates in advance, and then dilute it with water and add it during the process of insolubilizing fluorine and lead.

[0028] The method of adding this insolubilizer to the selected soil is not particularly limited, but preferably used are a method of adding the insolubilizer when the selected soil is granulated in a rotary kiln, a method of dripping the insolubilizer onto the selected soil that is left to stand, and a method of dripping the insolubilizer onto the selected soil that is being transported by a belt conveyor or the like.

[0029] The method of adding the insolubilizing agent to the fly ash is not particularly limited, but preferably used are a method of dropping the insolubilizing agent onto stationary fly ash, a method of dropping the insolubilizing agent onto transported fly ash, and a method of adding the insolubilizing agent to collected fly ash while stirring the fly ash.

[0030] The insolubilizer can be added to the aqueous solution containing lead or fluorine (sometimes referred to as contaminated water) by dropping it into the contaminated water or adding the dihydrogen phosphate as a solid. It is also possible to add the insolubilizer while taking into consideration environmental standards.

[0031] The method of adding the insolubilizing aid to the insolubilizing agent will be described in detail below. When an insolubilizing aid containing at least calcium other than dihydrogen phosphate is added to the insolubilizing agent, the insolubilizing aid can be added before the insolubilizing agent is added to the screened soil or fly ash, or the insolubilizing aid can be added after the insolubilizing agent is added. The insolubilizing aid can be added in the form of an aqueous solution or suspension in water, or further in the form of a powder, similar to the insolubilizing agent.

[0032] The amount of the insolubilizer to be added is not particularly limited, but it is preferable that the amount of fluorine elution is 0.8 mg / L or less and the amount of lead elution is 0.01 mg / L or less according to the elution test specified in Notification No. 46 of the Ministry of the Environment. If the concentration of eluted lead exceeds the environmental standard after the addition of the insolubilizer, further insolubilizer can be added. The amount of the insolubilizer to be added can be appropriately selected taking into consideration the fluorine and lead contents in the screened soil and fly ash, but if the amount added is too large, the cost may increase.

[0033] After adding this insolubilizer to insolubilize lead, fluorine exceeding the environmental standard may leach out from the selected soil, but the lead-containing insolubilizer that insolubilized lead has the effect of insolubilizing fluorine, and since the insolubilization rate of lead and fluorine is faster than that of fluorine, fluorine is gradually insolubilized, so it is effective to determine the amount to be added while observing. On the other hand, the insolubilization effect of fluorine is more effective, that is, the amount of fluorine eluted into an aqueous solution from the lead-containing insolubilizer with the same amount of elements other than lead shown in Figure 8 is 0.2 mg / L, which is about half the amount of fluorine eluted into an aqueous solution from fluoroapatite shown in Figure 7, which is 0.4 mg / L, and it can be confirmed that fluorine can be effectively insolubilized for a long period of time with a small amount of insolubilizer, in other words, with a lead-containing insolubilizer.

[0034] The lead content of the lead-containing insolubilizer is preferably 1 / 6 to 1 / 3 per mole of phosphorus, more preferably 1 / 5.5 to less than 1 / 3 per mole of phosphorus, and even more preferably 1 / 5.5 to less than 1 / 5 per mole of phosphorus. From the results of the component analysis described below, it was confirmed that the lead-containing insolubilizer, which has a fluorine insolubilizing effect, contains about 1 / 5 (19%) of lead per mole of phosphorus.

[0035] The presumed chemical reaction formulae for the insolubilization of fluorine and lead by this insolubilizing agent are shown in Formulae 1 to 5. Fig. 1 is a diagram showing Formulae 1 to 5 in schematic form. Ca(H2PO4)2+ Ca 2+ → Complex of dihydrogen phosphate and calcium (Ca5(PO4)3OH) (Equation 1) Ca5(PO4)3OH + F - → Ca5(PO4)3F + OH - (Formula 2) Ca5(PO4)3OH + Pb 2+ → PbCa4(PO4)3OH + Ca 2+ (Formula 3) Ca5(PO4)3F + Pb 2+ → PbCa4(PO4)3F + Ca2+ (Formula 4) PbCa4(PO4)3OH + F - → PbCa4(PO4)3F + OH - (Formula 5) In the insolubilizer of the present invention, lead, which is a cation in an aqueous solution, and fluorine, which is also an anion in an aqueous solution, can be bonded in the same molecule. When the reaction product of the insolubilizer produced in the screened soil or fly ash is an apatite-like substance, the product of insolubilization of lead and fluorine becomes lead fluoroapatite.

[0036] In FIG. 1, the regions are divided into A, B, C, and D. Region A shows (Reaction 1) shown in (Formula 1). The reaction from region A to region B is the process of insolubilizing fluoride ions, and shows (Reaction 2) shown in (Formula 2). The reaction from region A to region C is the process of insolubilizing lead ions, and shows the production reaction (Reaction 3) of a lead-containing insolubilizing agent shown in (Formula 3). This lead-containing insolubilizing agent preferably contains 1 / 3 of lead per mole of phosphorus contained in the lead-containing insolubilizing agent, more preferably contains less than 1 / 3 of lead per mole of phosphorus, and even more preferably contains 1 / 5 or less of lead per mole of phosphorus. The reaction from region B to region D in FIG. 1 is a process in which the insolubilizer that has insolubilized fluorine further insolubilizes lead ions, and shows (reaction 4) shown in (formula 4). The reaction from region C to region D is a process in which the insolubilizer that has insolubilized lead (sometimes referred to as lead-containing insolubilizer) further insolubilizes fluorine ions, and shows (reaction 5) shown in (formula 5). FIG. 2 shows an external photograph of product 1 recovered when fluorine is insolubilized by this lead-containing insolubilizer. FIG. 3 shows an electron microscope photograph of this product 1, and FIG. 4 shows the results of a component analysis of the product in this electron microscope photograph, in other words, the lead-containing insolubilizer containing fluorine produced by insolubilizing fluorine with the lead-containing insolubilizer. This component analysis was measured using an electron beam microanalyzer EPMA-1610 manufactured by Shimadzu Corporation. The preparation of this lead-containing insolubilizer will be described later.

[0037] Figure 4 also shows the results of the component analysis, which confirmed that the sample contained 17.6 moles of phosphorus, 3.4 moles of lead, and 9.5 moles of fluorine. This result was consistent with the results of the high fluorine insolubilization effect of the lead-containing insolubilizer in the ion chromatography shown above. Furthermore, the insolubilization rate of 0.53 moles of fluorine per mole of phosphoric acid calculated from this result indicates the high insolubilization rate of fluorine of the lead-containing insolubilizer of the present invention.

[0038] The insolubilizing aid added to the insolubilizing agent will be described in detail. The insolubilizing aid is made of a compound containing at least calcium, and contains at least one selected from calcium hydroxide, calcium carbonate, and gypsum. The insolubilizing agent and the insolubilizing aid cause (Reaction 1) shown in (Formula 1) in area A in FIG. 1. When the amount of gypsum in the selected soil to be insolubilized is large, or when the amount of calcium in the selected soil is large, the lead and fluorine may be below the environmental standard values ​​stipulated in Notification No. 46 of the Ministry of the Environment even without adding the insolubilizing aid, but when this is not met, it is also preferable to add the insolubilizing aid.

[0039] Regarding the amount of the insolubilizing aid to be added, when dihydrogen phosphate is used as the insolubilizing agent, it is preferable to add it so that the molar ratio of calcium to phosphorus in the insolubilizing agent is 5 / 3 or more.

[0040] The insolubilizing agent of the present invention is also capable of insolubilizing lead and fluorine in an aqueous solution, and therefore, when the aqueous solution does not contain calcium, the addition of this insolubilizing aid is particularly effective in insolubilizing these contaminants. EXAMPLES

[0041] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0042] In these examples and comparative examples, the lead concentration was measured using an inductively coupled plasma analyzer. The fluorine concentration was analyzed using an ion chromatograph. The humus in the soil was analyzed using the Kumada method. The humus is a type of organic matter that gives soil a black color, and may react with phosphoric acid, etc., so the analysis results are shown.

[0043] Example 1 First, in order to verify the effect of the insolubilizer of the present invention, an aqueous solution was prepared using sodium dihydrogen phosphate as an insolubilizer. Lead nitrate was added to this aqueous solution so that the concentration of lead ions was 1 mg / L. Since there was no calcium in the aqueous solution, calcium hydroxide was added so that the concentration of calcium contained in the insolubilizer assistant was 5 / 3 times the molar ratio of the concentration of phosphorus contained in the insolubilizer. Thereafter, the supernatant of the aqueous solution was collected, and the concentration of lead contained in this aqueous solution was measured. As a result, the concentration of lead was below the environmental standard of 0.01 mg / L, and a good result was obtained. In addition, this enabled the preparation of a lead-containing insolubilizer. When the insolubilizing effect of fluorine in an aqueous solution with a fluorine ion concentration of 1 mg / L was confirmed using the lead-containing insolubilizer prepared in Example 1, the fluorine ion concentration was 0.8 mg / L or less, and it was confirmed that fluorine was insolubilized. At this time, the concentration of lead was below the environmental standard of 0.01 mg / L. The insolubilization of fluorine was also carried out in Example 5 described later.

[0044] Example 2 An aqueous solution was prepared using calcium dihydrogen phosphate as an insolubilizing agent. Lead nitrate was added to this aqueous solution so that the lead ion concentration was 1 mg / L. Taking into consideration the concentration of calcium dihydrogen phosphate, calcium hydroxide was added as an insolubilizing aid so that the calcium concentration was 5 / 3 times the molar ratio of the phosphorus concentration contained in the insolubilizing agent. Thereafter, the supernatant of the aqueous solution was collected, and the lead concentration contained in this aqueous solution was measured. As a result, the lead concentration was below the environmental standard of 0.01 mg / L, and a good result was obtained. In addition, a lead-containing insolubilizing agent was prepared by this. When the insolubilizing effect of fluorine in an aqueous solution with a fluorine ion concentration of 1 mg / L was confirmed using the lead-containing insolubilizing agent prepared in Example 2, the fluorine ion concentration was 0.8 mg / L or less, and it was confirmed that fluorine was insolubilized. At this time, the lead concentration was below the environmental standard of 0.01 mg / L. The insolubilization of fluorine was also carried out in Example 6 described later.

[0045] Example 3 As in Example 1, an aqueous solution was prepared using sodium dihydrogen phosphate as an insolubilizer. Lead nitrate was added to this aqueous solution so that the concentration of lead ions was 1 mg / L. Since there was no calcium in the aqueous solution, calcium carbonate was added so that the concentration of calcium contained in the insolubilizer was 5 / 3 times the molar ratio of the concentration of phosphorus contained in the insolubilizer. Thereafter, the supernatant of the aqueous solution was collected, and the concentration of lead contained in this aqueous solution was measured. As a result, the concentration of lead was below the environmental standard of 0.01 mg / L, and a good result was obtained. In addition, a lead-containing insolubilizer was prepared by this. When the insolubilizing effect of fluorine in an aqueous solution with a fluorine ion concentration of 1 mg / L was confirmed using the lead-containing insolubilizer prepared in Example 3, the fluorine ion concentration was 0.8 mg / L or less, and it was confirmed that fluorine was insolubilized. At this time, the concentration of lead was below the environmental standard of 0.01 mg / L. The insolubilization of fluorine was also carried out in Example 7 described later.

[0046] Example 4 As in Example 2, an aqueous solution was prepared using calcium dihydrogen phosphate as an insolubilizer. Lead nitrate was added to this aqueous solution so that the lead ion concentration was 10 mg / L. Taking into account the concentration of calcium dihydrogen phosphate, calcium carbonate was added as an insolubilizer aid so that the calcium concentration was 5 / 3 times the molar ratio of the phosphorus concentration contained in the insolubilizer. Thereafter, the aqueous solution was collected and the lead concentration contained in this aqueous solution was measured. As a result, the lead concentration was below the environmental standard of 0.01 mg / L, and a good result was obtained. In addition, a lead-containing insolubilizer was prepared by this. When the insolubilizing effect of fluorine in an aqueous solution with a fluorine ion concentration of 1 mg / L was confirmed using the lead-containing insolubilizer prepared in Example 4, the fluorine ion concentration was 0.8 mg / L or less, and it was confirmed that fluorine was insolubilized. At this time, the lead concentration was below the environmental standard of 0.01 mg / L. Fluorine insolubilization was also carried out in Example 8 described later.

[0047] Example 5 An aqueous sodium fluoride solution was added to the solution in which lead was insolubilized in Example 1 so that the fluoride ion concentration was 1 mg / L. After stirring and leaving to stand, the concentrations of fluorine and lead were measured, and it was found that the fluorine concentration was below the environmental standard of 0.8 mg / L and the lead concentration was below the environmental standard of 0.01 mg / L.

[0048] (Examples 6 to 8) In Example 6, an aqueous sodium fluoride solution was added to the solution of Example 2, in Example 7 to the solution of Example 3, and in Example 8 to the solution of Example 4, in the same manner as in Example 5, so that the fluorine ion concentration was 1 mg / L. The fluorine and lead concentrations of each solution were measured, and in all Examples, the fluorine concentration was below the environmental standard of 0.8 mg / L, and the lead concentration was below the environmental standard of 0.01 mg / L.

[0049] Example 9 The effect of the insolubilizer was verified using an aqueous solution containing lead and fluorine, which contained 1 mg / L of lead ions and 1 mg / L of fluorine ions. As insolubilizers, calcium dihydrogen phosphate and sodium dihydrogen phosphate were added to aqueous solutions containing lead and fluorine, which were prepared separately, and calcium hydroxide was added as an insolubilizer so that the molar ratio of calcium was 5 / 3 times the phosphorus concentration in each solution. When the lead concentration was measured 30 minutes after the insolubilizer was added, it was below the environmental standard of 0.01 mg / L. On the other hand, the fluorine concentration measured 30 minutes after the insolubilizer was 0.9 mg / L, which exceeded the environmental standard. After leaving the solution to stand for 3 hours, the lead and fluorine concentrations were measured again, and both were below the environmental standard. When sodium dihydrogen phosphate was used as the insolubilizer, the amount of fluoride eluted after 3 hours was 0.7 mg / L, and when calcium dihydrogen phosphate was used as the insolubilizer, the amount of fluoride eluted was 0.6 mg / L. From the results of Example 9, when the reaction rates of (Reaction 2) and (Reaction 3) were compared, it was considered that the reaction rate of (Reaction 3) was higher than that of (Reaction 2). It was also considered that the fluoride insolubilizing effect of calcium dihydrogen phosphate was higher than that of sodium dihydrogen phosphate.

[0050] Example 10 Soil containing gypsum waste generated from construction demolition sites was separated and classified to have a particle size of 5 mm or less and a content of paper, wood chips, and plastic of less than 5% by mass. This was used as the selected soil, and an experiment was conducted to insolubilize and stabilize the fluorine and lead in the selected soil. The gypsum contained in the selected soil has the chemical formula CaSO4 and exists as a hydrate. The content of gypsum in the selected soil was determined from the results of an X-ray diffraction experiment on the selected soil, and it was confirmed to be 10 to 20% by weight. The selected soil was used in 26 samples from July 1st to August 4th, and each sample was treated by adding sodium dihydrogen phosphate as an aqueous solution to verify the effect of the insolubilizer. The gypsum in the selected soil was used as an insolubilizer. The aqueous solution containing the insolubilizer was sprayed onto the selected soil introduced into a rotary kiln and mixed while stirring. The selected soil was granulated to a particle size of about 10 mm by this treatment. After curing for a certain period of time, the selected soil was subjected to an elution test as specified by the Ministry of the Environment. The concentrations of humic substances, lead (Pb), arsenic (As), and fluorine (F) contained in the selected soil are shown in FIG. 6. The results of measuring lead and arsenic are shown on the 7th day of curing. As a result, it was confirmed that lead and arsenic do not elute from the selected soil. In addition, although the amount of fluorine exceeded the environmental standard on the 7th day of curing, the amount of elution decreased as the number of curing days increased, and after 30 days of curing, the amount of fluorine elution fell below the environmental standard of 0.8 mg / L. From this, the insolubilizing effect of the insolubilizing agent on the selected soil was confirmed. The verification results of the insolubilizing effect on the selected soil were not inconsistent with the results in the aqueous solutions of Examples 1 to 9.

[0051] Example 11 Fly ash containing lead was obtained and added to an aqueous solution, after which the lead concentration was adjusted to 1000mg / L. Calcium dihydrogen phosphate was added to this aqueous solution of lead containing fly ash as an insolubilizer, and the lead concentration was checked, which was found to have decreased to 50mg / L. As this exceeded the environmental standard, sodium dihydrogen phosphate was further added to equalize the amount of phosphorus, and the lead concentration was found to be below the environmental standard of 0.01mg / L.

[0052] Example 12 The calcium dihydrogen phosphate of the present invention was added to water to prepare an aqueous solution, and calcium hydroxide was added to the phosphorus added as calcium in a molar ratio of 5 / 3. The resulting white solid was collected, and an aqueous solution of lead nitrate was added to the solid in small amounts. The addition of the aqueous solution of lead nitrate was continued until the lead concentration did not decrease, to obtain a lead-containing insolubilizer. The lead-containing insolubilizer was collected, and the fluorine concentration was measured by adding the lead-containing insolubilizer to an aqueous solution adjusted to a fluorine ion concentration of 1 mg / L. As a result, the fluorine concentration was below the environmental standard of 0.8 mg / L.

[0053] (Example 13, Comparative Example 1) Lead fluoroapatite was prepared by adding an aqueous lead nitrate solution to fluoroapatite purchased as a reagent. This lead fluoroapatite and this fluoroapatite were used, and then the fluorine and phosphate eluted from each substance were measured after placing them in water. In this case, the case where only this fluoroapatite was used was set as Comparative Example 1. The results of Comparative Example 1 and Example 13 are shown in FIG. 7 and FIG. 8, respectively. The horizontal axis of FIG. 7 and FIG. 8 is time, and the vertical axis is electrical conductivity. The fluorine and phosphate, which are the measurement objects that passed through the column, passed through the column in about 3.1 minutes for fluorine and about 9.4 minutes for phosphoric acid, and were observed as electrical conductivity by a detector. The higher the concentration of the measurement object, the higher the electrical conductivity tends to be. The amount of fluorine eluted from the lead fluoroapatite shown in FIG. 8 was 0.2 mg / L in the aqueous solution. The amount of fluorine eluted from the fluoroapatite shown in FIG. 7 was 0.4 mg / L. Furthermore, while phosphoric acid was eluted from the fluoroapatite shown in FIG. 7, almost no phosphoric acid was eluted from the lead fluoroapatite shown in FIG. 8. From this result, it was confirmed that the amount of fluorine and phosphoric acid eluted from the lead fluoroapatite was lower than that from the fluoroapatite, and that the lead fluoroapatite, in other words, the lead-containing insolubilizer, has a higher insolubilizing effect on fluorine than that of fluoroapatite. When comparing the insolubilizing speed of lead and fluorine in this insolubilizer, the insolubilizing speed of lead is higher than that of fluorine, so it was confirmed that after the lead-containing insolubilizer is generated, this lead-containing insolubilizer insolubilizes fluorine. Note that the nitric acid used in the preparation of this lead fluoroapatite remained in the aqueous solution, and its presence was confirmed by ion chromatography.

[0054] Example 14 Example 14 was carried out in order to confirm the fluorine insolubilizing effect and lead content of the lead-containing insolubilizing agent of the present invention. First, a lead nitrate aqueous solution was prepared so that the lead concentration was 1000 mg / L. 10 mL of this lead aqueous solution was taken into each of three containers. 0.1 g of fluoroapatite, sodium dihydrogen phosphate, and calcium dihydrogen phosphate were added to each lead aqueous solution and stirred so that the molar concentration of phosphorus was the same. Calcium hydroxide was further added to the lead aqueous solution to which sodium dihydrogen phosphate and calcium dihydrogen phosphate were added. After further stirring, each lead aqueous solution was left to stand for 3 hours, and the supernatant was taken without involving the precipitated white crystals, and the lead concentration was measured. As a result, the lead content was about 50 mg / L in the lead solution treated with fluoroapatite, and 50 mg / L and 50 mg / L in the case of calcium dihydrogen phosphate and sodium dihydrogen phosphate, respectively, which were almost the same. A simple colorimetric analysis method was used to measure the lead concentration in this example. Furthermore, as a result of these, when the number of moles of phosphorus contained in the insolubilizer is used as a standard, the molar ratio of insolubilized lead, i.e., the lead content in the insolubilizer, to 1 mole of phosphorus was calculated to be about 20%. In each of these lead aqueous solutions, elution of fluorine was not observed. Furthermore, a precipitate was collected from the lead aqueous solution, washed three times with pure water, and dried, i.e., the lead-containing insolubilizer of the present invention, and an aqueous sodium fluoride solution adjusted to 10 mg / L of fluorine was added to insolubilize the fluorine. The amount of eluted fluorine was 0.6 mg / L. Furthermore, the lead-containing insolubilizer after insolubilizing the fluorine was collected, washed three times with pure water, and then dried. Each of these dried products was photographed under an electron microscope and quantitatively measured using an electron beam microanalyzer. Part of the results of the electron beam microanalyzer are shown in FIG. 4. As a result, it was confirmed that the lead-containing insolubilizer insolubilized fluorine.

[0055] This electron beam microanalyzer is an analytical device that observes the characteristic X-rays observed when an electron beam is irradiated onto an object to be measured, for each wavelength of this characteristic X-ray. The electron beam microanalyzer, the results of which are shown in Figure 4, is equipped with four types of dispersing crystals that disperse different wavelength regions. Since these characteristic X-rays are observed as different waves for each element, it is possible to determine the type of element contained in the object to be measured from the peak position where the characteristic X-rays are observed, and the content of this element from the intensity of this peak. Note that Figure 4 contains four graphs, each of which corresponds to one of the four types of dispersing crystals.

[0056] The results of Examples 1 to 9, Examples 11 to 13, and Comparative Example 1 are shown in Fig. 5. The results of Example 10 are shown in Fig. 6.

[0057] Although the embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and it goes without saying that various modifications can be made without departing from the gist of the present invention. [Industrial Applicability]

[0058] INDUSTRIAL APPLICABILITY The present invention relates to an insolubilizing agent that is used for environmental sanitation and can further be used for safe waste management, and therefore has high industrial applicability. [Explanation of symbols]

[0059] 1:Product

Claims

1. An insolubilizing agent that insolubilizes at least fluorine and lead, the insolubilizing agent being a dihydrogen phosphate, the dihydrogen phosphate including at least one of calcium dihydrogen phosphate and sodium dihydrogen phosphate; 1. An insolubilizer comprising at least one of calcium hydroxide, calcium carbonate, and gypsum as a calcium-containing insolubilizer assistant.

2. 2. The insolubilizer according to claim 1, wherein a substance produced from at least the insolubilizer, the insolubilizer assistant, fluorine, and lead is lead fluoroapatite.

3. A lead-containing insolubilizing agent for fluorine, which is an insolubilizing agent for insolubilizing fluorine, characterized in that the insolubilizing agent is a compound comprising at least lead, phosphorus, calcium and oxygen.

4. 4. The insolubilizing agent for insolubilizing fluorine containing lead according to claim 3, wherein the molar ratio of lead to phosphorus is 1 / 6 to 1 / 3 moles of lead per mole of phosphorus.

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