HK1201812B

HK1201812B - Insolubilizing agent for specific toxic substances, method for insolubilizing specific toxic substances using same, and soil improvement method

Info

Publication number: HK1201812B
Application number: HK15102437.0A
Authority: HK
Inventors: 山口雅人; 三浦真一; 市野佑介; 石井三郎; 橘田一臣
Original assignee: 吉野石膏株式会社
Priority date: 2012-03-30
Filing date: 2013-03-28
Publication date: 2018-02-02

Description

Insolubilizing material for specific harmful substance, insolubilizing method for specific harmful substance using same, and soil improvement method

Technical Field

The present invention relates to an economically excellent insolubilizing material for a specific harmful substance (hereinafter, also referred to as "heavy metal or the like"). More specifically, the first invention of the present invention relates to an insolubilizing material capable of insolubilizing a specific harmful substance (heavy metal or the like) contained in soil such as soil of old factory land or soil for landfill and suppressing re-dissolution of the specific harmful substance (heavy metal or the like) from a treated matter, and a method for insolubilizing a specific harmful substance (heavy metal or the like) using the insolubilizing material, and the second invention of the present invention relates to an insolubilizing material for a specific harmful substance (heavy metal or the like) containing gypsum as an essential component, and a method for improving soil using the insolubilizing material, the insolubilized material of the specific harmful substance (heavy metal or the like) is particularly useful for the treatment of soil to which fluidity is imparted by adding soil or water, and functions as a solidified material capable of imparting strength to the treated material at a level at which the treated material can be easily transported and buried.

Background

For example, in old factories or the like operated from an age when health hazards due to heavy metals or the like have not been recognized, there are cases where contaminated soil contaminated with heavy metals or the like exists. Further, due to this, the landfill soil may contain heavy metals and the like. In recent years, it has been known that heavy metals contained in these soils are eluted, and the substances enter groundwater or the like, and thus, a situation that threatens human health occurs, and the importance of a technique for stably immobilizing heavy metals or the like in soils or the like has been recognized. In addition, for example, in a shield method performed at a construction site, alkaline soil mixed with mortar or the like is frequently discharged, and therefore, spoil used for landfill is often alkaline. On the other hand, the soil to be buried is expected to be neutral due to environmental concerns. Moreover, spoil used for landfill also often is soil with high water content such as a large amount of sludge generated in drainage treatment, cement-containing soil such as construction spoil, and when these are used for landfill, it is also often necessary to solidify the soil. In japan where volcanoes are abundant and the surroundings are surrounded by the sea, heavy metals and the like may be contained in natural ground layers and soil, and soil near living spaces such as residential areas and water sources may require insolubilization of heavy metals and the like.

As described above, since it is considered necessary to prevent elution of heavy metals and the like from soil such as old plant soil or soil buried in spoil, conventionally, various insolubilizing materials for heavy metals and the like have been used in order to suppress elution of heavy metals and the like, and the effect thereof has been confirmed. The "heavy metal and the like" in the present invention means "heavy metal and the like as specific harmful substances" (2 nd specific harmful substances) specified in article 2 of the soil pollution countermeasure law executed in 2003, and specifically means the following substances.

Cadmium and compounds thereof

Hexavalent chromium compounds

Cyanide compounds

Mercury and its compounds (including alkyl mercury)

Selenium and compounds thereof

Lead and compounds thereof

Arsenic and compounds thereof

Fluorine and compounds thereof

Boron and compounds thereof

However, in the case of a conventional insolubilized material such as a heavy metal, the treated material after the insolubilization treatment may be difficult to handle during transportation and filling, and a separate curing treatment (strength application) may be required. On the other hand, in the soil solidification treatment, cement-based or lime-based solidified materials are generally used, but there is a problem that the soil after the treatment is alkaline due to the use of these solidified materials. That is, considering that these treated materials are used in landfills and the like, it is desired to develop a curing material in which the treated soil (treated material) is neutral from the viewpoint of environmental concerns.

Here, as one method of soil hardening with neutrality, a method of using a neutral gypsum-based hardening material is used, but there is a problem that the strength of the treated product is poor. In order to solve this problem, it has been proposed to increase the strength of a treated product by adding an aluminum compound and a calcium compound to generate ettringite when mixed with soil (see patent document 1). In order to promote recycling of building materials, it has been also studied to use recycled gypsum separated and recovered from waste gypsum boards as construction waste, recycled gypsum derived from old gypsum molds, or the like (hereinafter simply referred to as "waste gypsum") as a raw material of gypsum-based setting materials. However, the waste gypsum may contain heavy metals such as fluorine and lead derived from the waste gypsum itself or other dismantling building materials mixed with the waste gypsum. Therefore, even when a gypsum-based cured material using waste gypsum is used, there is a concern that the amount of released heavy metals or the like may exceed the environmental standard. The biggest technical problem with insolubilizing materials such as heavy metals is to suppress elution of heavy metals and the like in the soil to be treated more effectively and to reduce the amount of elution, and therefore, even in the presence of heavy metals and the like derived from waste gypsum, it is necessary to avoid such a situation from occurring, and development of insolubilizing materials for heavy metals and the like having higher effects is desired.

Under the circumstances, as a technique for insolubilizing/stabilizing fluorine in, for example, fluorine-contaminated soil, a method of insolubilizing/stabilizing fluorine by producing fluorapatite and ettringite using a material containing gypsum, lime, iron sulfate and a phosphoric acid compound has been proposed (see patent document 2). The present applicant has proposed a gypsum-based insolubilization/solidification agent for heavy metals and the like, which is added to and mixed with soil such as sludge generated in drainage treatment or construction waste, and which can neutralize the treated material, insolubilize and solidify heavy metals and the like contained in the soil, and impart strength to the soil, thereby providing excellent handleability (see patent document 3). Specifically, an insolubilized and solidified material of heavy metal or the like is proposed, which contains an aluminum compound selected from aluminum hydroxide or the like and a neutralizing agent containing a calcium or magnesium component in plaster of paris.

In view of the above, development of new materials different from conventional cement-based, lime-based, and gypsum-based setting materials has been also proceeding. For example, proposed are: as a neutral hardening material for hydrous soil suitable for hardening hydrous soil such as dredging sludge and construction sludge, hydraulic alumina produced by heating and oxidizing an aluminum compound containing amorphous aluminum hydroxide as a main component by-produced by neutralization/aggregation in an aluminum anodizing treatment step is used (see patent documents 4 and 5). In these documents, the hydraulic alumina is added with a curing aid (curing strength-enhancing material) such as lithium carbonate or calcium carbonate, whereby the hydrous soil can be cured in a neutral state to have sufficient strength. In addition, elution of heavy metals such as hexavalent chromium and lead can be prevented.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-51910

Patent document 2: japanese laid-open patent publication No. 2007-330884

Patent document 3: japanese patent laid-open publication No. 2010-207659

Patent document 4: japanese patent No. 4690729

Patent document 5: japanese patent No. 4680549

Disclosure of Invention

Problems to be solved by the invention

However, the technique described in patent document 1 is not intended to insolubilize heavy metals and the like, and since the generation of ettringite, which is advantageous for improving the strength of the treated product, occurs in a strongly alkaline range, even if it is assumed that heavy metals and the like can be immobilized in the generated ettringite, ettringite is decomposed under acidic conditions such as acid rain, and heavy metals and the like may be eluted again.

Similarly, in the technique described in patent document 2, fluorine is insolubilized/stabilized by the formation of ettringite, and therefore, it is necessary to maintain the pH thereof to be alkaline, and there is a problem that the treated product cannot be made neutral. In addition, the method of mixing and using an acidic material and a basic material as described in patent document 2 has another problem that the composition of an insolubilizing material needs to be adjusted according to the pH of the soil.

In addition, although the techniques described in patent documents 3 to 5 can obtain a neutral treated product, the main purpose thereof is to solidify the soil, and there is room for improvement in terms of achieving more effective insolubilization of various heavy metals and the like and stable fixation over a long period of time. For example, patent document 3 has a problem in that although inexpensive gypsum is used as a raw material, an aluminum compound and a neutralizing agent containing a calcium or magnesium component are required, and a more inexpensive and reliable treatment method is provided.

In addition, in the techniques described in patent documents 4 and 5, although the raw material for obtaining hydraulic alumina is amorphous aluminum hydroxide which is by-produced by neutralization and aggregation in the aluminum anodizing treatment step, it is necessary to heat and oxidize the amorphous aluminum hydroxide, and there is a great problem from the viewpoint of economy in which a large amount of soil is treated more reliably by a cheaper method. Further, it is developed as a solidifying material, and it is difficult to say that it is sufficient for insolubilizing a heavy metal, and there is room for improvement.

Further, as described below, the above-described various techniques have room for improvement in the following respects: in addition to effectively insolubilizing various heavy metals and the like, the present invention can more reliably realize the fixation of heavy metals immobilized in a treated object for a long period of time in the treated object placed in various natural environments for landfill or the like. That is, according to the studies of the present inventors, even if heavy metals and the like contained in the soil can be insolubilized and solidified as necessary to impart strength to the soil, it is difficult to say that the current state of the art can be achieved sufficiently reliably in the aspect that the heavy metals and the like which are further desired to be insolubilized in the treated material are not re-eluted to the acid rain and are stably maintained in an insolubilized state.

In addition, in particular, in the vicinity of the surface of soil in contaminated old plants and the like, it is considered that heavy metals and the like are present in large amounts, and it is extremely useful to develop a simple insolubilizing material for heavy metals and the like which can immobilize heavy metals and the like by merely being applied by scattering on the surface of soil.

Accordingly, an object of the present invention is to provide a high-performance insolubilizing material for a specific harmful substance (heavy metal or the like) which solves the above-mentioned problems of the conventional techniques. That is, an object of the present invention is to provide an economical insolubilizing material for a specific hazardous substance, which is capable of using an inexpensive raw material in an insolubilizing treatment by adding and mixing the insolubilizing material to soil or in an insolubilizing treatment by scattering the insolubilizing material to a soil surface, can effectively insolubilize and immobilize heavy metals and the like that affect health in soil and in the vicinity of a soil surface, is an environmentally friendly neutral material capable of reusing a treated object, and is highly practical, in which heavy metals and the like are not eluted even when the treated object is exposed to an acidic condition such as a neutral condition or acid rain. In particular, it is extremely useful if waste whose disposal has been a problem in the past can be used as a raw material, and an object of the present invention is to provide an insolubilizing material for a specific harmful substance which is extremely useful in terms of economy.

In addition, the second invention provides an insolubilizing agent for a specific harmful substance, which is highly practical, and which can easily impart strength to the treated material in addition to the above-described effects in the treatment of soil.

Means for solving the problems

[ first invention of the invention ]

The above object is achieved by the following invention. That is, the first invention of the present invention provides an insolubilizing agent for a specific hazardous substance, which is used for soil in a state not to be in a strongly alkaline range of pH11 or more, the insolubilizing agent for a specific hazardous substance containing an amorphous aluminum compound or a derivative thereof as a main component; alternatively, as another means, there is provided an insolubilizing agent for a specific hazardous substance, which is used for soil in a state not to be in a strongly alkaline range of pH11 or more, and which contains an amorphous aluminum compound or a derivative thereof as a main component and further contains a calcium component exhibiting acidity, neutrality or weak alkalinity lower than pH11 when contacting with water contained in soil.

In addition, as a preferred embodiment of the first invention of the present invention, there are mentioned: the amorphous aluminum compound is amorphous aluminum hydroxide; the amorphous aluminum compound or a derivative thereof is a substance derived from aluminum sludge, which is used as it is, or a substance obtained by dehydrating and drying a substance derived from aluminum sludge without changing the properties thereof; the specific harmful substance is at least one selected from the group consisting of cadmium and compounds thereof, hexavalent chromium compounds, cyanides, mercury and compounds thereof (including alkyl mercury), selenium and compounds thereof, lead and compounds thereof, arsenic and compounds thereof, fluorine and compounds thereof, and boron and compounds thereof; the calcium component is any one selected from the group consisting of dihydrate gypsum, calcium carbonate, calcium peroxide, calcium fluoride, calcium iodide, calcium phosphate, calcium chloride, calcium nitrate, calcium acetate, calcium citrate, calcium gluconate, calcium malate, and calcium lactate.

Further, another embodiment of the first invention of the present invention provides a method for insolubilizing a specific hazardous substance, characterized in that an insolubilizing agent for mixing or dispersing the specific hazardous substance is added to soil, and the soil is treated in a state not being in a strongly alkaline range of pH11 or more, thereby insolubilizing the specific hazardous substance.

Preferred embodiments thereof include: adding an amorphous aluminum compound or a derivative thereof as a main component of an insolubilizing agent for the specific harmful substance to the soil in an amount of 0.5 to 50g per 1kg of dry mass of the soil; more preferably, the amorphous aluminum compound or a derivative thereof, which is a main component of the insolubilizing agent for the specific harmful substance, is added to the soil in an amount of 10 to 40g per 1kg of dry mass of the soil. The insolubilized specific hazardous substance is derived from the soil or a constituent derived from the insolubilizing material; the insoluble material contains calcium as a constituent component. In the above description, the dry mass means the mass of soil dried in a drying oven at 110 ℃. + -. 5 ℃ to a constant mass according to "soil moisture ratio test method JIS A1203".

[ second invention of the invention ]

The above object is achieved by the following invention. That is, the second invention of the present invention provides an insolubilizing material for a specific hazardous substance, which contains plaster of Paris, and which also functions as a plaster of Paris-containing solidifying material used for soil containing a specific hazardous substance in a state that it does not have a strong alkaline range of pH11 or more, and which is characterized in that an amorphous aluminum compound or a derivative thereof is added and mixed in an amount of 0.5 to 60 parts by mass per 100 parts by mass of plaster of Paris.

In addition, as a preferred embodiment of the second invention of the present invention, the following embodiment can be cited. Comprises the following steps: the amorphous aluminum compound is amorphous aluminum hydroxide; the amorphous aluminum compound or a derivative thereof is a substance derived from aluminum sludge, which is used as it is, or a substance obtained by dehydrating and drying a substance derived from aluminum sludge without changing the properties thereof; an amorphous aluminum compound or a derivative thereof is added and mixed in an amount of 15 to 50 parts by mass based on 100 parts by mass of the plaster of paris; the specific harmful substance is at least one selected from the group consisting of cadmium and compounds thereof, hexavalent chromium compounds, cyanides, mercury and compounds thereof (including alkyl mercury), selenium and compounds thereof, lead and compounds thereof, arsenic and compounds thereof, fluorine and compounds thereof, and boron and compounds thereof.

Further, another embodiment of the second invention of the present invention provides a method for improving soil, characterized in that an insolubilizing agent for a specific harmful substance having a constitution that also functions as a solidifying agent is added and mixed to soil containing the specific harmful substance, and the soil is treated in a state that the insolubilizing agent does not fall within a strongly alkaline range of pH11 or more. In addition, asPreferred embodiments thereof include: in soil containing specific harmful substances every 1m³In the above range, 30 to 200kg of an insolubilizing agent for mixing the specific harmful substance is added.

ADVANTAGEOUS EFFECTS OF INVENTION

[ first invention of the invention ]

According to the first aspect of the present invention, there is provided an excellent insolubilizing material for a specific harmful substance, which is capable of effectively insolubilizing heavy metals and the like present in soil and in the vicinity of the soil surface and forming a treated product in which re-elution of the insolubilized heavy metals and the like under neutral conditions and under acidic conditions is suppressed, when the insolubilizing material for a specific harmful substance of the present invention is used in a state not being in a strongly alkaline range of pH11 or more, that is, in a pH range in which ettringite is not generated. The insolubilizing agent for a specific harmful substance according to the first aspect of the present invention is not only a simple material that exhibits the above-described effects when added to and mixed with soil for treatment, but also exhibits the above-described effects only by scattering on the soil surface. Further, the treated product is a neutral substance in consideration of the influence on the environment when used for landfill or the like. In addition, according to the present invention, as an amorphous aluminum compound which characterizes the present invention, aluminum sludge generated in an anodized aluminum plant and an aluminum alloy window frame plant, which are mostly regarded as waste, can be effectively utilized, and thus an environmentally friendly product can be provided.

[ second invention of the invention ]

According to the second aspect of the present invention, there is provided an excellent insolubilizing material for a specific harmful substance, which is effectively insolubilized to heavy metals and the like in soil and soil under a condition that the insolubilizing material does not fall within a strongly alkaline range of pH11 or more, forms a treated material in which re-elution of the insolubilized heavy metals and the like in the treated material under neutral conditions and acidic conditions is effectively suppressed, and functions as a curing material in which the treated material is in a state having a curing strength that facilitates handling during transportation and landfill. In particular, a treated product obtained by curing the insolubilizing agent of the specific harmful substance is a neutral substance in consideration of the influence on the environment when the treated product is directly used for landfill or the like. Further, according to the second aspect of the present invention, as the amorphous aluminum compound characterizing the present invention, aluminum sludge generated in an anodized aluminum plant and an aluminum alloy window frame plant, which are mostly regarded as wastes, can be effectively utilized, and a gypsum raw material can be also utilized by calcining waste gypsum, which contributes to solving the problem of recycling of construction waste, and a further environment-friendly product can be provided.

Drawings

FIG. 1 is an X-ray diffraction measurement (CuK) of dehydrated/dried aluminum sludge_αRay) results.

FIG. 2 is a graph showing X-ray diffraction measurements (CuK) of samples taken from soil alone, aged for 1 week and aged for 1 month (CuK) in the case where the insolubilizing agent for a specific hazardous substance of the present invention is mixed with soil in a state not being in a strongly alkaline range of pH11 or more_αRay) results.

Fig. 3 is a graph showing the results of an elution test under neutral conditions and acidic conditions for each treatment using the insolubilizing agent for a specific harmful substance of the present invention and the cement-based curing material of comparative example.

Detailed Description

Hereinafter, the present invention will be described in further detail by way of examples of preferred embodiments. In order to solve the above problems of the prior art, the present inventors have made detailed studies on the reason why elution of heavy metals and the like contained in soil cannot be sufficiently prevented in the treatment of soil containing heavy metals and the like, and the reason why solidification performance is unstable when a solidification function is provided.

As a result of the studies by the present inventors, it has been found that the conventional insolubilizing materials used for the insolubilization treatment of heavy metals in soil or soil as described above have a problem that the reactivity with heavy metals is insufficient and the amount thereof to be used becomes large for complete insolubilization, and that the insolubilized materials cannot be stably immobilized in an insolubilized state even when they are insolubilized during the treatment, and that the heavy metals are sometimes eluted again when they are used for landfill after the treatment. As described above, conventional insolubilizing materials and curing materials used in combination therewith tend to be alkaline in themselves and are not sufficient in terms of environmental friendliness, which also causes a large factor that makes it difficult to utilize the treated product. Further, the present inventors have recognized that the treatment product has the following problems: in particular, when a treated material is exposed to an acidic condition such as acid rain, the insoluble heavy metal or the like is re-eluted from the treated material, and this problem is significant when the treated material is alkaline. It has been also confirmed that the problem of re-elution of the heavy metal and the like may similarly occur in an insolubilizing material of a specific harmful substance which also functions as a curing material. Furthermore, in particular, in the vicinity of the surface of soil in contaminated old factories and the like, it is considered that heavy metals and the like are present in large amounts, and it is extremely useful to develop an insolubilizing material which can be applied to a specific economically excellent harmful substance, such as heavy metals, and the like, and which can be immobilized reliably and stably only by scattering on the surface of soil. However, such an insolubilized material is not known.

[ first invention of the invention ]

The present inventors have further studied in detail based on the above findings, and as a result, have reached the first invention of the present invention. That is, it has been found that when an aluminum compound, particularly an amorphous aluminum compound or a derivative thereof (hereinafter referred to as an amorphous aluminum compound) is added to or dispersed in soil, heavy metals and the like can be insolubilized more reliably and stably, and even when the treated material is exposed to acidic conditions such as acid rain, the heavy metals and the like are not eluted again and are stably maintained in an immobilized state, and the treated material can be provided as an insolubilized material such as a neutral heavy metal, and the present invention has been completed. The amorphous aluminum compound or a derivative thereof may be any aluminum compound as long as it is confirmed to be in an amorphous state by X-ray diffraction. As will be described later, the amorphous aluminum compound used in the present invention can be used as it is in the state of being usually discarded and disposed of in an anodized aluminum plant, an aluminum alloy window frame plant, or the like, or in the state of being simply dehydrated and air-dried, and therefore, the insolubilizing material for a specific hazardous substance of the present invention is extremely economical in terms of its material constitution.

Hereinafter, each material constituting the insolubilizing material for a specific harmful substance according to the first aspect of the present invention will be described.

(amorphous aluminum Compound)

The inventors of the present invention have considered, based on the examination results described below, that the reason why the amorphous aluminum compound, which is characterized by the insolubilizing material of the specific hazardous substance according to the first invention of the present invention, functions as an excellent insolubilizing chemical conversion agent distribution, which can effectively immobilize a heavy metal or the like in a treated object and can effectively suppress re-dissolution of the immobilized heavy metal or the like from the treated object under both neutral conditions and acidic conditions, is as follows. Consider that: when the insolubilizing agent of the specific harmful substance of the present invention is used for soil in a state not being in a strongly alkaline range of pH11 or more, that is, in a pH range not generating ettringite, a mineral other than ettringite is generated from aluminum in the amorphous aluminum compound, a silica component and a calcium component contained in the soil to be treated, and components such as heavy metals contained in the soil and the insolubilizing agent itself, and as a result, the heavy metals and the like in the soil are immobilized as constituent components of the mineral, and the excellent effect of the first invention of the present invention is achieved.

According to the detailed studies of the present inventors, since an amorphous aluminum compound is superior in the adsorption ability of heavy metals and the like to a crystalline substance, when the amorphous aluminum compound is added to soil or the surface of soil, heavy metals and the like contained in soil, the surface of soil, or an insolubilizing material itself are easily adsorbed. Further, it is considered that the adsorbed heavy metals and the like, the silica component and the calcium component contained in the soil are captured and mineralized in the soil or in the process of the amorphous aluminum compound changing to a crystalline state, and as a result, the heavy metals and the like can be stably insolubilized. According to the studies of the present inventors, the amorphous aluminum compound characterized by the first invention of the present invention has a function of insolubilizing a specific harmful substance contained in soil, for example, heavy metals such as arsenic, selenium, cadmium, mercury, cyanide, lead and hexavalent chromium, and inorganic substances such as fluorine and boron to stably immobilize the substance to be treated.

In order to confirm the above functions of the amorphous aluminum compound, the present inventors have mixed and aged an amorphous aluminum compound with soil in a state not being in a strongly alkaline range of pH11 or more, and examined the properties of the cured product after aging. Specifically, X-ray diffraction was measured for each of the soil-only samples, the samples aged for 1 week, and the samples aged for 1 month used in the above tests. The results of the obtained X-ray diffraction are shown in fig. 2. In the figure, 1 is an X-ray diffraction of a sample of only soil, 2 is an X-ray diffraction of a sample aged for 1 week, and 3 is an X-ray diffraction of a sample aged for 1 month. In the above test, the calcined gypsum was used in combination with the amorphous aluminum compound for the following reasons. As a result of the study, calcium, silica and aluminum are essential components in the insolubilization technique of the present invention, and among these components, the calcium component supplied from the soil is extremely small as compared with the silica component supplied from the soil without being positively added and the amorphous aluminum compound is positively added. On the other hand, since gypsum is a neutral material, it does not come into a strongly alkaline range when mixed with soil, and the treatment range can be surely set to a state in which calcium is abundantly present, and therefore, it is added in the above test. Therefore, the first invention of the present invention is also preferably configured as follows: the amorphous aluminum compound is used as a main component, and the amorphous aluminum compound also contains a calcium component such as gypsum which shows acidity, neutrality or alkalescence lower than pH11 when contacting with water contained in soil. The calcium component used in this case may be at least one selected from the group consisting of calcium carbonate, calcium peroxide, calcium fluoride, calcium iodide, calcium phosphate, calcium chloride, calcium nitrate, calcium acetate, calcium citrate, calcium gluconate, calcium malate, and calcium lactate, in addition to the gypsum. When the soil is an acid soil (soil having a pH of 4 or less), calcium oxide or calcium hydroxide may be used. The gypsum is not particularly limited, and is preferably dihydrate gypsum that can be used without being subjected to a baking treatment. In addition, even when there is a fear of the presence of heavy metals or the like derived from gypsum itself, such as waste gypsum, these heavy metals are stably fixed in the treated object and can be used.

As shown in fig. 2, it was confirmed that a peak apparently not attributable to the insoluble material, the gypsum used in combination, and the constituent components of the soil appeared in the vicinity of 28.5 ° 2 θ in the sample aged for 1 week and further in the sample aged for 1 month. When the results for the sample aged for 1 week were compared with the results for the sample aged for 1 month, a peak near 28.5 ° 2 θ appeared in the sample aged for 1 month grew as compared with the peak of the sample aged for 1 week. This indicates that a certain crystalline compound (mineral) is formed in the treated product by the above treatment. From the results shown in fig. 2, it was also confirmed that characteristic peaks corresponding to ettringite were not present (2 θ ═ 9.1 ° and 15.8 °).

As a result of the above, the present inventors have carried out synthesis of crystalline compounds having various compositional formulas in consideration of the constituent components of the insolubilizing agent for a specific harmful substance of the present invention and the components of the soil to which the insolubilizing agent is added, and measured X-ray diffraction with respect to the obtained compounds. As a result, it was found that the obtained compound having a peak near 2 θ of 28.5 ° was CaAl₂Si₆O₁₆·6H₂O、Ca(Si，Al)₁₆O₃₂·13H₂O、CaAl₂Si₇O₁₈·5.5H₂O、Ca₁₂Al₂Si₁₈O₅₁·18H₂O、CaAl₂Si₁₀O₂₄·7H₂O、(Ca，Na₂，K₂)Al₂Si₁₀O₂₄·7H₂O、CaAl₂Si₇O₁₈·6H₂O、CaAl₂Si₆O₁₆·4H₂O、Ca₃Al₂(SiO₄)(OH)₈、Ca₃Al₂Si₃O₁₂Any of the above. It is considered that since the chemical compositions of these mineral species are consistent, a certain crystalline compound (mineral) is generated by treatment with the insolubilizing material of the specific harmful substance of the present invention, and as a result, a peak appears in the vicinity of 28.5 ° 2 θ in X-ray diffraction.

As a result of the above-described studies, it has been found that calcium, silica and aluminum are essential components in the insolubilization technique of the present invention, and the calcium component is extremely small as compared with the silica component supplied from the soil as described above, and therefore, it is preferable to further use the calcium component in combination with the amorphous aluminum compound as the insolubilization material for the specific hazardous substance of the first invention of the present invention. In the present invention, the specific substance of the calcium component used in combination with the amorphous aluminum compound may be any substance as long as it is a calcium component which is acidic, neutral or weakly basic at a pH of below 11 when it comes into contact with the moisture contained in the soil as exemplified above. The reason for this is that, if the calcium component used in combination is a substance which does not become pH11 or more (strongly alkaline) when it comes into contact with the water contained in the soil as described above, insolubilization treatment of heavy metals or the like can be performed in a state where the pH of the soil does not become 11 or more, that is, ettringite is not generated when it is used. In addition, even when a heavy metal or the like derived from the calcium component itself used is present or there is a fear of the presence of a heavy metal or the like, when the insolubilizing material of the specific harmful substance of the first invention of the present invention is used, these heavy metals are stably immobilized in the treated object.

[ amorphous aluminum hydroxide ]

According to further studies by the present inventors, in order to highly achieve the object of the first invention of the present invention, amorphous aluminum hydroxide is particularly preferably used as the amorphous aluminum compound. Examples of such substances include volcanic ash, aluminum sludge produced in an anodized aluminum plant and an aluminum alloy window frame plant. Further, it has been found that, surprisingly, in the present invention, the remarkable effects of the present invention can be obtained by using the aluminum sludge as it is or by using a material obtained by dehydrating and drying the aluminum sludge without changing the properties. According to the studies of the present inventors, the aluminum sludge generated in an anodized aluminum plant or an aluminum alloy window frame plant differs in properties depending on the process and the like, and it is difficult to specify the properties, but it contains at least a large amount of amorphous aluminum hydroxide. The present inventors have found that the insolubilizing material of the first invention of the present invention can be effectively used as long as it contains a large amount of amorphous aluminum hydroxide, and has an effect of insolubilizing heavy metals and the like and stably suppressing elution of heavy metals and the like including re-elution thereafter.

Specifically, the treated product is a neutral substance while the elution of heavy metals and the like is effectively inhibited only by adding and mixing a large amount of aluminum sludge containing the amorphous aluminum hydroxide in soil or scattering the aluminum sludge on the soil surface, and it goes without saying that when the treated product is exposed to neutral conditions, the fixed heavy metals and the like are not eluted from the treated product again even if the treated product is exposed to acidic conditions such as acid rain. In the present invention, particularly as the amorphous aluminum compound characterizing the first invention of the present invention, it is preferable to use the aluminum sludge containing amorphous aluminum hydroxide as it is or to dehydrate and dry it without changing its properties. If such a material is used, more economical processing becomes possible. Unlike the techniques described in patent documents 3 and 4, the first invention of the present invention needs to be used so as not to oxidize amorphous aluminum hydroxide contained in aluminum sludge. As the means for preventing the amorphous aluminum hydroxide from being oxidized, any conventionally used means can be suitably used. The results of the X-ray diffraction measurement of the dehydrated/dried aluminum sludge are shown in fig. 1.

As described above, although the details of the insolubilizing material for a specific harmful substance according to the first aspect of the present invention having the above-described configuration are not clear, it is considered that the amorphous aluminum compound adsorbs heavy metals and the like contained in soil, on the surface of soil, or in the insolubilizing material itself, and then the heavy metals and the like are captured and mineralized, whereby the heavy metals can be stably insolubilized, and as a result, the significant effect of the first aspect of the present invention can be obtained. The remarkable results of the present invention can be confirmed by performing a dissolution test under neutral conditions or acidic conditions as described later. It is also understood that the amorphous aluminum compound used in the first invention of the present invention is insoluble in water, but slowly reacts with an alkali and can function as a neutralizing agent. Therefore, many soils and the like produced on site exhibit alkalinity, but it was confirmed that: when the insoluble material of the specific harmful substance according to the first aspect of the present invention is used for the treatment, a treated product in which the pH is effectively kept neutral can be obtained.

The insolubilizing agent for a specific harmful substance according to the first aspect of the present invention can be effectively used by being added to and mixed with soil, but the effect of the first aspect of the present invention can be obtained by dispersing the insolubilizing agent in the vicinity of the surface of soil, and the insolubilizing agent can be used easily.

Next, a preferred embodiment of the method for insolubilizing a specific harmful substance according to the first aspect of the present invention will be described. The method for insolubilizing a specific hazardous substance of the present invention is characterized in that the insolubilizing agent for a specific hazardous substance of the first invention of the present invention is added, mixed or dispersed in soil to perform treatment, and the addition, mixing or dispersion of the insolubilizing agent at this time is preferably performed in accordance with the following criteria. Thus, the effects of the first aspect of the present invention can be sufficiently obtained, and economical processing becomes possible. That is, the amount of the insolubilizing agent for a specific hazardous substance according to the first aspect of the present invention added to the soil may be such that the amount of the amorphous aluminum compound or its derivative as a main component of the insolubilizing agent for a specific hazardous substance is in the range of 0.5 to 50g, and more preferably 10 to 40g, per 1kg of the dry mass of the soil, and the amorphous aluminum compound or its derivative is added, mixed or dispersed. If the amount of the amorphous aluminum compound or its derivative added, mixed or dispersed is less than 0.5g, the amount is too small, and it is difficult to uniformly disperse these compounds in the soil, which is not preferable. On the other hand, even if more than 50g of the amorphous aluminum compound or the derivative thereof is added, mixed or dispersed, it is difficult to obtain further effects, and the cost becomes high, which is uneconomical. In addition, when the insolubilizing agent for a specific harmful substance according to the first aspect of the present invention is added to and mixed with soil, an appropriate amount of water may be added to the soil as necessary to facilitate the mixing operation. In view of the fact that the treated material is used for landfill, it is preferable that the pH of the treated soil is in the range of 5.6 to 8.6 in addition to the above, but if the insoluble material of the specific harmful substance of the present invention is added and mixed as described above, the pH value in the above range can be achieved without particularly adjusting the pH thereafter. As a result, for example, in the case of performing an elution test of heavy metals or the like in soil buried with a treatment substance, elution of heavy metals or the like can be more reliably suppressed.

[ second invention of the invention ]

Next, an insolubilizing material (hereinafter, also referred to as "insolubilizing material such as the second heavy metal of the present invention") of a specific harmful substance of the second invention of the present invention, which is the second invention of the present invention and also functions as a curing material, will be described.

The present inventors have further studied in detail based on the above findings, and as a result, they have found that it is effective to use plaster of paris for imparting curing performance to insolubilized materials of specific harmful substances. Further, it has been found that when a mixed aluminum compound, particularly an amorphous aluminum compound or a derivative thereof (amorphous aluminum compound) is added to plaster of paris, elution of heavy metals and the like can be efficiently reduced, and the treated material can be stably immobilized without elution of heavy metals and the like even when exposed to acidic conditions such as acid rain, and further, a specific harmful substance insolubilized and solidified material in which the treated material is neutral can be provided, and thus, the second invention of the present invention has been completed. The amorphous aluminum compound or a derivative thereof may be any aluminum compound as long as it is in an amorphous state when observed by X-ray diffraction. In order to obtain the excellent effects of the second invention of the present invention, it is particularly preferable to add the amorphous aluminum compound in a range of 0.5 to 60 parts by mass, and further in a range of 15 to 50 parts by mass, to 100 parts by mass of plaster of paris. As described later, the amorphous aluminum compound used in the present invention can be used as it is in the state of being easily dehydrated and air-dried or in the state of being largely discarded aluminum sludge generated in an anodized aluminum plant, an aluminum alloy window frame plant, or the like. Further, since waste gypsum, which is concerned about the presence of heavy metals and the like originating from the material itself, can be effectively used as the material, the insolubilizing material for a specific harmful substance according to the second aspect of the present invention is extremely economical in terms of the material composition.

Further, the insolubilizing agent for a specific harmful substance of the second aspect of the present invention having the above-mentioned configuration is obtained by mixing plaster of paris and an amorphous aluminum compound or a derivative thereof in a homogeneous state, and therefore, when it is used, the efficiency of the treatment operation can be remarkably improved.

Hereinafter, each material constituting the insolubilizing material for a specific harmful substance according to the second aspect of the present invention will be described.

(Gypsum)

The gypsum used for the insolubilizing material such as the second heavy metal of the present invention is plaster of Paris which is excellent in soil solidification performance. The plaster of Paris refers to 1/2 hydrate of calcium sulfate (CaSO)₄·1/2H₂O]And anhydrate [ CaSO₄]The setting performance of the insolubilizing agent of the second specific harmful substance of the present invention can be further improved by using plaster of Paris, that is, plaster of Paris chemically reacted with water in the soil to be easily converted into dihydrate Gypsum, and therefore the soil treated with the plaster of Paris is cured to have strength, examples of plaster of Paris β type hemihydrate, α type hemihydrate Gypsum, type II anhydrite, type III anhydrite, and mixtures thereof can be used arbitrarily, type II anhydrite gypsum and type III anhydrite gypsum can be used arbitrarilyOther plaster of paris hydrate at a slower rate than it does, but can be used. As the gypsum used as the raw material of the plaster of paris, natural products, gypsum as a by-product or waste gypsum can be used. Among these, natural products and gypsum by-produced are also inexpensive materials and are preferable, but waste gypsum is more preferable as a raw material in view of higher economy and efficient use of resources. As described above, when the insolubilized material of the second specific harmful substance of the present invention is used, even when there is a fear of existence of heavy metals and the like derived from the material itself like waste gypsum, these heavy metals are stably immobilized in the treated object.

(amorphous aluminum Compound)

The inventors of the present invention have considered, based on the results of the verification described below, that the reason why the amorphous aluminum compound constituting the insolubilizing material for a specific hazardous substance according to the second aspect of the present invention functions as an excellent insolubilizing component distribution, which can effectively immobilize a heavy metal or the like in a treated object and effectively suppress re-elution of the immobilized heavy metal or the like under both neutral conditions and acidic conditions, is as follows. That is, it is considered that when the insolubilizing agent of the specific harmful substance according to the second invention of the present invention is used for soil containing heavy metals or the like under the condition that it does not fall within the strongly alkaline range of pH11 or more, minerals other than ettringite are generated from aluminum in the amorphous aluminum compound, calcium in gypsum, a calcium component contained in the soil to be treated, a silica component, the soil, metals contained in the insolubilizing agent itself, and the like, and as a result, heavy metals or the like in the soil are immobilized as constituent components of the minerals, and as a result, the excellent effects of the second invention of the present invention can be achieved. According to the detailed studies of the present inventors, since an amorphous aluminum compound is superior in the adsorption ability of heavy metals and the like to a crystalline aluminum compound, when the amorphous aluminum compound is added to soil, heavy metals and the like contained in gypsum materials, which are constituent components of a solidified material, and in soil are easily adsorbed. Further, it is considered that these adsorbed heavy metals and the like are captured and mineralized in the soil or in the process of converting the amorphous aluminum compound into a crystal, and as a result, the heavy metals and the like can be stably insolubilized. According to the studies of the present inventors, the amorphous aluminum compound having the characteristics of the present invention has a function of insolubilizing a specific harmful substance contained in soil, for example, heavy metals such as arsenic, selenium, cadmium, mercury, lead and hexavalent chromium, and inorganic substances such as fluorine and boron to stably fix the substance to a treated object.

In order to confirm the above functions of the amorphous aluminum compound, the present inventors mixed and aged plaster, an amorphous aluminum compound, and soil under conditions that do not fall within a strongly alkaline range of pH11 or more, and examined the properties of the cured product after aging. Specifically, X-ray diffraction was measured for each of the soil-only samples, the samples aged for 1 week, and the samples aged for 1 month used in the above tests. The results of the obtained X-ray diffraction are shown in fig. 2. In the figure, 1 is an X-ray diffraction of a sample of only soil, 2 is an X-ray diffraction of a sample aged for 1 week, and 3 is an X-ray diffraction of a sample aged for 1 month.

As shown in fig. 2, it was confirmed that a peak apparently not attributable to the insoluble material and the constituent components of soil appeared in the vicinity of 28.5 ° 2 θ in the sample aged for 1 week and further in the sample aged for 1 month. When the results for the sample aged for 1 week were compared with the results for the sample aged for 1 month, a peak near 28.5 ° 2 θ appeared in the sample aged for 1 month grew as compared with the peak of the sample aged for 1 week. This indicates that a certain crystalline compound (mineral) is formed in the treated product by the above treatment. From the results shown in fig. 2, it was also confirmed that characteristic peaks corresponding to ettringite were not present (2 θ ═ 9.1 ° and 15.8 °).

As a result of the above, the present inventors have carried out synthesis of crystalline compounds having various compositional formulas in consideration of the constituent components of the insolubilizing agent of the specific harmful substance of the second invention of the present invention and the components of the soil to which the insolubilizing agent is added, and have carried out X-ray diffraction with respect to the obtained compounds. As a result, it was found that the compound having a peak near 2 θ of 28.5 ° was CaAl₂Si₆O₁₆·6H₂O、Ca(Si，Al)₁₆O₃₂·13H₂O、CaAl₂Si₇O₁₈·5.5H₂O、Ca₁₂Al₂Si₁₈O₅₁·18H₂O、CaAl₂Si₁₀O₂₄·7H₂O、(Ca，Na₂，K₂)Al₂Si₁₀O₂₄·7H₂O、CaAl₂Si₇O₁₈·6H₂O、CaAl₂Si₆O₁₆·4H₂O、Ca₃Al₂(SiO₄)(OH)₈、Ca₃Al₂Si₃O₁₂Any of them. It is considered that since the chemical compositions of these mineral species are identical, a certain crystalline compound (mineral) is produced by treatment with an insolubilizing material of a specific harmful substance according to the second aspect of the present invention, and as a result, a peak derived from the mineral appears in the vicinity of 2 θ ═ 28.5 ° in X-ray diffraction.

[ amorphous aluminum hydroxide ]

As a result of further studies by the present inventors, it has been found that amorphous aluminum hydroxide is particularly preferably used as the amorphous aluminum compound in order to highly achieve the object of the second invention of the present invention. Examples of such substances include aluminum components contained in volcanic ash, aluminum sludge generated in an anodized aluminum plant and an aluminum alloy window frame plant. Further, surprisingly, the second invention of the present invention can obtain the remarkable effect of the second invention of the present invention by using the aluminum sludge as it is in combination with the gypsum or by using the aluminum sludge dehydrated and dried without changing its properties in combination with the gypsum to prepare the solidified material. According to the studies of the present inventors, the aluminum sludge generated in an anodized aluminum plant or an aluminum alloy window frame plant differs in properties depending on the process and the like, and it is difficult to specify the properties, but it contains at least a large amount of amorphous aluminum hydroxide. The present inventors have found that the insolubilizing material for a specific harmful substance according to the second aspect of the present invention is effective as long as it contains a large amount of amorphous aluminum hydroxide, and has an effect of insolubilizing a heavy metal or the like and stably suppressing elution of the heavy metal or the like including re-elution thereafter.

In the second invention of the present invention, specifically, by using a large amount of aluminum sludge containing amorphous aluminum hydroxide in combination with plaster of paris, elution of heavy metals and the like can be effectively suppressed in the treated product by merely adding and mixing them to the soil, and the treated product is neutral, and when the treated product is neutral, it is needless to say that the fixed heavy metals and the like are not eluted from the treated product even if the treated product is exposed to an acidic condition such as acid rain, and the soil has a strength of a level that can be solidified to facilitate handling at the time of transportation and landfill even when the soil is sludge generated in drainage treatment or soil such as construction waste. In the present invention, particularly, as the amorphous aluminum compound constituting the second invention of the present invention, an aluminum sludge containing amorphous aluminum hydroxide can be used as it is or dehydrated and dried without changing its properties, and thus, economical treatment can be performed with respect to the material used. This means that, unlike the techniques of patent documents 1 and 2, the second invention of the present invention needs to be used so as not to oxidize amorphous aluminum hydroxide contained in aluminum sludge. As means for preventing the amorphous aluminum hydroxide from being oxidized, any conventionally used means can be suitably used. The results of the X-ray diffraction measurement of the dehydrated/dried aluminum sludge are shown in fig. 1.

The insolubilizing agent for a specific harmful substance according to the second aspect of the present invention is obtained by externally adding the above-mentioned amorphous aluminum compound in an amount within a range of 0.5 to 60 parts by mass to 100 parts by mass of plaster of paris. That is, when the amount of the amorphous aluminum compound added is less than 0.5 parts by mass per 100 parts by mass of plaster of paris, the effect of insolubilizing heavy metals and the like cannot be sufficiently obtained when the compound is mixed in soil as a solidifying material, while when the amount is more than 60 parts by mass, the material cost becomes high, which is uneconomical. More preferably, the amorphous aluminum compound is added to 100 parts by mass of plaster of paris in an amount within a range of 15 to 50 parts by mass.

The insolubilizing agent of a specific harmful substance, which also functions as a curing agent, of the second aspect of the present invention having the above-described configuration is particularly preferably used when the insolubilizing agent is added to and mixed with clay to perform a curing treatment, and the significant effects of the present invention as described above can be obtained. As described above, although the details are not clear, it is considered that the amorphous aluminum compound contained together with gypsum such as plaster of paris can adsorb heavy metals and the like in the soil and then mineralize these heavy metals and the like in the soil, thereby stably insolubilizing the heavy metals. The remarkable results of the second invention of the present invention obtained by using an insolubilizing material to which a specific harmful substance such as an amorphous aluminum compound is added to gypsum in a ratio to be blended as described above can be confirmed by performing a dissolution test under neutral conditions or acidic conditions. It is also understood that the amorphous aluminum compound used in the second invention of the present invention is insoluble in water, but slowly reacts with an alkali and can function as a neutralizing agent. Therefore, although many of soils and the like generated on site exhibit alkalinity, when the insoluble material of the second specific harmful substance of the present invention is cured, a treated matter which effectively keeps the pH neutral can be obtained.

Next, a preferred embodiment of the soil improvement method of the present invention using the insolubilizing agent for a specific harmful substance that also functions as a solidifying agent of the second invention of the present invention will be described. The soil improvement method of the second aspect of the present invention is characterized in that the insolubilizing agent of the second specific harmful substance of the present invention is added to and mixed with the soil, and the soil is subjected to solidification treatment while insolubilizing the heavy metal or the like. The addition and mixing of the insolubilized curable material at this time are preferably performed in accordance with the following criteria. Thus, the effects of the present invention can be sufficiently obtained, and economical processing becomes possible. That is, the amount of the insolubilizing agent for a second specific harmful substance of the present invention to be added to soil depends on the water content of soil and the required strength of solidification of the treated soil, but it is preferable that the insolubilizing agent for a specific harmful substance is added to soil containing the specific harmful substance per 1m³Adding and mixing 30-200 kg of insoluble material of the specific harmful substanceAnd (5) feeding. Thus, elution of heavy metals and the like is suppressed, and the cone index when the soil is uniformly mixed with the solidifying material of the present invention, solidified and aged for one day is 100kN/m²Above, preferably 150kN/m²Above, more preferably 200kN/m²The above. Considering that the treated material is used for landfill or the like, it is preferable that the pH of the solidified soil is in the range of 5.6 to 8.6 in addition to the above, and the addition and mixing can be performed by adjusting the amount of the insolubilizing agent of the second specific harmful substance of the present invention as described above. As a result, elution of heavy metals and the like from the soil can be more reliably suppressed at the site where the treatment object is used for landfill.

In the method for improving soil according to the second aspect of the present invention, water is dispersed in the soil in advance to impart a certain level of fluidity to the soil, and then the insoluble material mixed with the second specific harmful substance according to the present invention is added, whereby the mixing operation becomes easy. Since the insolubilizing agent of the second specific harmful substance of the present invention has a soil-hardening property, even when the soil is treated after fluidity is imparted thereto by dispersing water as described above, the treated material is hardened to a level at which handling at the time of transportation and landfill is easy. Therefore, when the soil improvement method according to the second aspect of the present invention is applied to soil such as sludge generated in wastewater treatment or construction waste, the soil may be treated by adding an insolubilizing agent obtained by mixing the second specific harmful substance according to the present invention thereto without dewatering or the like.

[ test method used in the present invention ]

The measurement of each value was carried out by the following method according to each test method shown below.

(1) Water ratio test: according to "test method for soil moisture ratio JIS A1203". The water content w (%) is calculated by the following equation.

w＝(m_a-m_b)×100/(m_b-m_c)

m_a: mass of sample and container: (g)

m_b: mass (g) of oven-dried sample and container

m_c: mass of container (g)

(2) Dissolution test method No. 18 of 2003 Environment Notification (hereinafter, also referred to as "test No. 18")

The soil to be tested was dried and passed through a 2mm sieve, and then water was used as a solvent, and water in an amount 10 times that of the dried soil after passing was added to prepare a test sample. Continuously vibrating and mixing the mixture for 6 hours at 200 times per minute with the amplitude of 4-5 cm. Then, the filtrate obtained by centrifugal separation and filtration was used as a sample for measurement. The metal analysis in the sample was performed by a method in accordance with each metal analysis method standardized by JIS.

(3) Long term stabilization test

A dissolution test under acidic conditions was performed in the same manner as described above except that the solvent water was replaced with a 0.769mmol/L aqueous sulfuric acid solution (measured pH was 2.9). The reason why the dissolution test is carried out under the above conditions using a sulfuric acid solution as the solvent is that acid rain generated in nature is assumed in which the treated material is left to stand. Specifically, the above conditions are calculated in the case where the treated material is exposed to a pH of 4.0 for 100 years at an annual rainfall of 2000mm [ relative evaluation method for stability against pH change of insolubilized soil such as heavy metal (hereinafter also referred to as "acid addition dissolution test") ] according to the technical standards of the center of soil environment ].

(4) And (3) pH test: according to the 'pH test method of soil suspension JGS 0211'.

The sample was placed in a beaker and water was added so that the mass ratio of water (including water in the sample) to the dry mass of the sample was 5. The sample is suspended by a stirring rod, left to stand for 30 minutes to 3 hours, and the liquid left to stand is used as a sample liquid for measurement. The sample solution in the beaker was stirred and then measured with a glass electrode pH meter.

(5) Cone index test: according to "Cone index test of compacted soil JIS A1228".

First, a sample of soil passed through a 9.5mm sieve was placed in a mold having an inner diameter of 10cm according to JIS A1210, and 3 layers of soil were tamped with a 2.5 kg-mass rammer 25 times per 1 layer. Then, the cone penetration gauge was vertically erected at the center of the upper end face of the object to be measured, and penetrated at a speed of 1 cm/sec, and the penetration resistance was obtained from the readings of the load gauges at the time when the tip of the cone penetrated 5cm, 7.5cm, and 10cm from the end face of the object to be measured. Conic index q_c(kN/m²) From the average penetration resistance Q_c(N) and the base area A (cm) of the conical tip²) And calculated by the following equation.

q_c＝Q_c×10/A

Examples

The present invention will be described in detail below with reference to examples and comparative examples of the present invention.

[ first invention of the invention ]

< preparation of evaluation sample >

Soil was prepared to be dried to a constant quality in a drying oven at 110 ℃. + -. 5 ℃. Then, arsenic and fluorine were added to the soil to prepare a simulated contaminated soil so that the elution amount of arsenic was 0.1mg/L and the elution amount of fluorine was 2.5 mg/L.

< evaluation 1>

The simulated contaminated soil obtained as described above was adjusted to have a water content of 40%, and the amount of each of the amorphous aluminum hydroxide added was changed as shown in table 1, and the soil was mixed with the adjusted simulated contaminated soil, thereby carrying out the insolubilization of arsenic and fluorine in the soil using the insolubilization material for a specific hazardous substance according to the first invention of the present invention as examples 1-1 to 1-4. Further, an example in which amorphous aluminum hydroxide was not used was defined as comparative example 1-1, and examples in which aluminum hydroxide and aluminum chloride were used instead of amorphous aluminum hydroxide used in examples, respectively, and 10g of these compounds were added and mixed to 1kg of the above-described simulated contaminated soil after drying, were defined as comparative examples 1-2 and 1-3.

TABLE 1 sample preparation

	Species of	Added amount (g)
			Examples 1 to 1	Amorphous aluminum hydroxide	0.5
Examples 1 to 2	Amorphous aluminum hydroxide	10
			Examples 1 to 3	Amorphous aluminum hydroxide	40
Examples 1 to 4	Amorphous aluminum hydroxide	50
			Comparative example 1-1	Without adding	-
Comparative examples 1 to 2	Aluminum hydroxide	10
			Comparative examples 1 to 3	Alumina oxide	10

Specifically, the insolubilizing treatment was performed by adding the insolubilizing agent for each specific harmful substance of the examples and comparative examples described above to the simulated soil to be treated in a desired amount and sufficiently kneading the mixture. After the treatment, the amount of arsenic and fluorine eluted from the treated soil and the pH of the treated soil were measured after 1 day of aging. The measurement at this time was performed by the method described above. The obtained results are shown in table 2. As shown in Table 2, it was confirmed that elution of arsenic and fluorine was suppressed in all cases where the insolubilizing agent of the specific harmful substance of the example was used. Further, the treated product was confirmed to be neutral. In addition, in the case of the insolubilized material using the specific harmful substance according to the example of the first invention of the present invention, the treated material subjected to the above treatment was left for 6 months, and the elution amounts of arsenic and fluorine were measured in the same manner as described above, and it was confirmed that the measured values shown in table 2 were maintained.

TABLE 2 dissolution test results

< evaluation 2>

Further, the following heavy metals were subjected to an insolubilization treatment using amorphous aluminum hydroxide, which is an insolubilizing material for a specific hazardous substance in example, in the same manner as in example 1-2, and the resultant treated material was subjected to an elution test to evaluate. Specifically, a simulated contaminated soil was prepared in which lead, hexavalent chromium, and selenium were added and the amount of lead released was adjusted to 0.1mg/L, the amount of hexavalent chromium released was adjusted to 0.5mg/L, and the amount of selenium released was adjusted to 0.1mg/L, and the water content was adjusted to 40%. Then, the soil was added with an insolubilizing agent for a specific harmful substance and kneaded in the same manner as in example 1-2 of evaluation 1, and then subjected to a dissolution test. The same treatments as in example 1-2 were carried out using the compounds used in comparative examples 1-1 to 1-3. As a result, it was confirmed that the insolubilization effect was remarkably obtained in any of the metals when the insolubilizing agent for the specific harmful substance of example 1-2 was used, as compared with the comparative example.

TABLE 3 dissolution test results

< examples 1 to 5 and comparative examples 1 to 4>

To 25 parts by mass of aluminum sludge containing a large amount of amorphous aluminum hydroxide as an amorphous aluminum compound, 100 parts by mass of plaster of paris was added for the purpose of adding a calcium component and imparting a curing function, and an insolubilizing agent for the specific harmful substance of the first invention of examples 1 to 5 was produced. For comparison, a test for elution of heavy metals after treatment was carried out using a commercially available cement-based curing material. Using each material, 1600kg (1 m) of simulated soil for the treatment object³) After adding 100kg of each material, the mixture was sufficiently kneaded and processed. Then aging for 60 days. Samples on the first day, the 30 th day and the 60 th day were collected, and the test No. 18 and the acid addition dissolution test were performed. The obtained test results are shown in fig. 3.

As is apparent from FIG. 3, it was confirmed that the elution amounts of the insolubilizing agents for specific harmful substances of examples 1 to 5 of the first invention were significantly different from those of the cured materials of comparative examples 1 to 4, and that the elution amounts of fluorine were significantly less when the insolubilizing agents for specific harmful substances of examples 1 to 5 were used than those of the cured materials of comparative examples 1 to 4. In addition, when the insolubilized materials of the specific harmful substances of examples 1 to 5 were used, the results of the test using the sulfuric acid solution as the solvent were conversely less eluted in the initial stage after the treatment, as compared with the case of using the elution with water. On the other hand, it was revealed that when the cured materials of comparative examples 1 to 4 were used, the elution amount was significantly larger than that when water was used as a solvent under acidic conditions using a sulfuric acid solution, and there was a problem that, in particular, immobilized heavy metals and the like were redissolved.

< examples 1 to 6>

To 25 parts by mass of aluminum sludge containing a large amount of amorphous aluminum hydroxide as an amorphous aluminum compound, 100 parts by mass of plaster of paris, which was observed to contain fluorine and was made of waste gypsum, was added for the purpose of adding a calcium component and imparting a curing function, and an insolubilizing agent for the specific harmful substances of examples 1 to 6 was produced. Spread on the soil surface and ripen for 60 days. On the first day and the 60 th day, the insoluble material portion was sampled from the surface of the soil in the scattered portion, and the same dissolution test as in examples 1 to 5 was performed. As a result, it was confirmed that the elution amount of the sample on day 60 was significantly reduced as compared with the elution amount of the sample on day one.

[ second invention of the invention ]

Next, the present invention will be specifically described by referring to examples of the second invention of the present invention and comparative examples. In the following description, "part" is based on mass unless otherwise specified.

< preparation of evaluation samples of examples 2-1 to 2-4 and comparative example 2-1 >

Specific harmful substance-insolubilizing materials of examples and comparative examples of the formulation shown in table 4 were prepared using plaster of paris and an amorphous aluminum compound. As the calcined gypsum, those obtained by pulverizing and calcining waste gypsum are used, respectively. In addition, amorphous aluminum hydroxide (reagent) is used as the amorphous aluminum compound.

TABLE 4 sample preparation

< evaluation 1>

Evaluation was carried out using a simulated contaminated soil having a water content of 40%, in which arsenic and fluorine were added and the amount of arsenic eluted was adjusted to 0.1mg/L and the amount of fluorine eluted was adjusted to 2.5 mg/L. Then, the insoluble materials of the specific hazardous substances of examples 2-1 to 2-4 and the cured material of comparative example 2-1 containing no amorphous aluminum hydroxide, which were added to gypsum in respective amounts by changing the amount of amorphous aluminum hydroxide according to the formulation shown in Table 4, were used to perform the respective operations of insolubilizing arsenic and fluorine in the simulated clay.

Specifically, a simulated soil 1m for a treatment object³100kg of each insolubilizing agent for the specific hazardous substance of example and 100kg of the curing agent of comparative example were added, and then sufficiently kneaded to conduct insolubilization. After the treatment, the amount of arsenic and fluorine eluted from the soil and the solidification strength (cone index) thereof were measured in test No. 18 after aging for 1 day. The measurement at this time was performed by the method described above. The obtained results are shown in table 5.

As shown in table 5, it was confirmed from the results of the dissolution test of the treated object when the insolubilizing material for a specific harmful substance of the example of the second invention of the present invention was used that the dissolution of arsenic and fluorine was suppressed by using the insolubilizing material for a specific harmful substance of the example, and that it was useful as an insolubilizing material for a specific harmful substance. Furthermore, it was confirmed that the insolubilizing agent for the second specific harmful substance of the present invention is also useful as a curing agent. More specifically, it is known that: the cured strength (cone index) of the treated product was at a level at which handling was easy, and the treated product had a strength in a state of being easily reused. This means that the insolubilizing agent of the second specific harmful substance of the present invention using an amorphous aluminum compound is also more useful as a curing agent than the conventional gypsum-based material. The treated product thus treated was left for 6 months, and the elution amounts of arsenic and fluorine in test No. 18 were measured in the same manner as described above. As a result, it was confirmed that the treated material obtained by using the cured material according to the example of the second invention of the present invention maintained the measurement values shown in table 5, and that elution of heavy metals and the like can be effectively suppressed when the treated material is used for landfill or the like. Further, the pH of the treated product is in the neutral range, and therefore, landfill treatment is possible in consideration of environmental protection.

TABLE 5 results of evaluation 1 (dissolution test result-1)

< evaluation 2>

Furthermore, the insolubilizing agent for a specific harmful substance of example 2-2 and the curing agent of comparative example 2-1 were used to conduct an elution test for a representative heavy metal and evaluated. Specifically, a simulated contaminated soil was prepared in which lead, hexavalent chromium and selenium were added and the amount of elution of lead was adjusted to 0.1mg/L, the amount of elution of hexavalent chromium was adjusted to 0.5mg/L, and the amount of elution of selenium was adjusted to 0.1mg/L, and the simulated soil was kneaded with an insolubilized material or a solidified material of a specific harmful substance in the same manner as in evaluation 1, and then subjected to an elution test. The results are shown in table 6, which shows that: the insolubilizing agent for the specific harmful substance of example 2-2 was used for any of the metals, and the effect of insolubilizing these metals was clearly exhibited as compared with the case of using the cured material of comparative example 2-1.

TABLE 6 results of evaluation 2 (dissolution test result-2)

< examples 2 to 5 and comparative examples 2 to 2>

The insolubilizing agents for specific harmful substances of examples 2 to 5 were produced in a ratio of 100 parts by mass of plaster of paris and 25 parts by mass of aluminum sludge containing a large amount of amorphous aluminum hydroxide as an amorphous aluminum compound. For comparison, a heavy metal elution test was performed using a commercially available cement-based curing material. Using these materials, 100kg of a curing material was added to a simulated soil 1m3 as a treatment target, and then sufficiently kneaded to conduct insolubilization treatment. Then, the mixture was aged for 60 days. Samples on the first day, the 30 th day and the 60 th day were collected, and the test No. 18 and the acid addition dissolution test were performed. The obtained test results are shown in fig. 3.

As is apparent from FIG. 3, it was confirmed that the elution amount of the insolubilizing agent for a specific harmful substance in example 2-5 was significantly different from that of the cured material in comparative example 2-2, and that the elution amount of fluorine was significantly smaller when the insolubilizing agent for a specific harmful substance in example 2-5 was used than when the cured material in comparative example 2-2 was used. In addition, when the insolubilized materials of the specific harmful substances of examples 2 to 5 were used, the results of the test using the sulfuric acid solution as the solvent were conversely less eluted in the initial stage after the treatment as compared with the case of using the elution with water. On the other hand, it was revealed that when the cured material of comparative example 2-2 was used, the elution amount was significantly larger than that when water was used as a solvent under acidic conditions using a sulfuric acid solution, and there was a problem that, in particular, immobilized heavy metals and the like were redissolved.

Industrial applicability

[ first invention of the invention ]

Examples of the use of the present invention include: an insolubilizing material for a specific harmful substance which can reliably insolubilize heavy metals and the like contained in soil or in the vicinity of the soil surface, does not re-elute from a treated material even when the treated material is exposed to rain, acid rain, and the like thereafter, can stably insolubilize heavy metals and the like by components contained in soil, and can stably render the treated material neutral and suitable for soil treatment. As a practical example of the present invention, there is also mentioned an insolubilizing material which is economically excellent and capable of effectively utilizing waste gypsum and aluminum sludge which are mostly wastes, and a treatment method using the insolubilizing material is extremely simple, and therefore, its utilization is expected.

[ second invention of the invention ]

Examples of the use of the present invention include: the insolubilizing material for a specific harmful substance, which can reliably insolubilize heavy metals and the like contained in soil, does not re-dissolve from the treated material even when the treated material is exposed to rain, acid rain and the like, can stably insolubilize heavy metals and the like contained in soil, can impart strength to soil by solidification, and can stably render the treated material neutral, and is suitable for soil improvement. As an example of the application of the present invention, there is also mentioned an insolubilized material of a specific harmful substance which is economically excellent and can effectively utilize waste gypsum and aluminum sludge which are mostly wastes, and the utilization thereof is expected.

Claims

1. An insolubilizing agent for a specific hazardous substance, which is used for soil in a state not being in a strongly alkaline range of pH11 or more, characterized in that it comprises an amorphous aluminum compound or a derivative thereof as a main component,

the amorphous aluminum compound or a derivative thereof is amorphous aluminum hydroxide or a derivative thereof.

2. An insolubilizing agent for a specific hazardous substance, which is used for soil in a state not being in a strongly alkaline range of pH11 or more, characterized in that it comprises an amorphous aluminum compound or a derivative thereof as a main component,

the insolubilizing material of the specific harmful substance further comprises a calcium component exhibiting acidity, neutrality or weak alkalinity lower than pH11 when in contact with moisture contained in soil.

3. An insolubilizing agent for a specific hazardous substance, which is used for a soil containing the specific hazardous substance in a state not to be brought into a strongly alkaline range of pH11 or more, characterized in that the insolubilizing agent for the specific hazardous substance contains an amorphous aluminum compound or a derivative thereof as a main component,

the insolubilizing material for a specific harmful substance further contains plaster of paris,

the amorphous aluminum compound or a derivative thereof is added and mixed in an amount of 0.5 to 60 parts by mass per 100 parts by mass of the plaster of paris.

4. The insolubilizing material for specific harmful substances according to claim 2 or 3, wherein the amorphous aluminum compound is amorphous aluminum hydroxide.

5. The specific hazardous substance insolubilizing material according to any one of claims 1 to 3, wherein the amorphous aluminum compound or a derivative thereof, or the amorphous aluminum hydroxide or a derivative thereof is a substance derived from aluminum sludge, which is used as it is, or a substance obtained by dehydrating and drying a substance derived from aluminum sludge without changing its properties.

6. The insolubilizing material for specific harmful substances according to any one of claims 1 to 3, wherein the specific harmful substance is at least one selected from the group consisting of cadmium and its compounds, hexavalent chromium compounds, cyanides, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds.

7. The insolubilizing material for specific harmful substances according to claim 6, wherein the mercury compound comprises alkyl mercury.

8. The insolubilizing material for specific harmful substances according to claim 2, wherein the calcium component is at least one selected from the group consisting of dihydrate gypsum, calcium carbonate, calcium peroxide, calcium fluoride, calcium iodide, calcium phosphate, calcium chloride, calcium nitrate, calcium acetate, calcium citrate, calcium gluconate, calcium malate, and calcium lactate.

9. The insolubilizing agent for specific harmful substances according to claim 3, wherein an amorphous aluminum compound or a derivative thereof is added and mixed in an amount of 15 to 50 parts by mass based on 100 parts by mass of the plaster of paris.

10. A method for insolubilizing a specific hazardous substance, characterized by adding an insolubilizing agent for mixing or dispersing the specific hazardous substance according to claim 1 or 2 to soil, and treating the soil so as not to have a strong alkaline range of pH11 or more, thereby insolubilizing the specific hazardous substance.

11. The method for insolubilizing a specific hazardous substance according to claim 10, wherein the amorphous aluminum compound or a derivative thereof or the amorphous aluminum hydroxide or a derivative thereof as a main component of the insolubilizing agent for the specific hazardous substance is added to or dispersed in an amount of 0.5 to 50g per 1kg of dry mass of the soil.

12. The method for insolubilizing a specific hazardous substance according to claim 10, wherein the amorphous aluminum compound or a derivative thereof or the amorphous aluminum hydroxide or a derivative thereof as a main component of the insolubilizing material for a specific hazardous substance is added to or dispersed in an amount of 10 to 40g per 1kg of dry mass of the soil.

13. The method for insolubilizing a specific hazardous substance according to any one of claims 10 to 12, wherein the specific hazardous substance to be insolubilized is derived from the soil or a constituent component of the insolubilized material.

14. The method for insolubilizing specific hazardous substance according to claim 13, wherein the constituent component of the insolubilized material is a calcium component.

15. A method for improving soil, characterized in that the soil containing a specific harmful substance is treated in a state where an insolubilizing agent of the specific harmful substance according to claim 3 is added and mixed thereto so as not to be in a strongly alkaline range of pH11 or more, and the insolubilizing agent of the specific harmful substance also functions as a solidifying agent.

16. The method for improving soil according to claim 15, wherein the soil containing the specific harmful material is 1m per one soil³In the above step (b), an insolubilizing agent for mixing the specific harmful substance is added in an amount of 30 to 200 kg.