JP2021151947A - Method for producing inorganic industrial waste recycled product - Google Patents

Abstract

To provide a novel method for producing an inorganic industrial material recycled product with reduced hazardous substances, which is environment-friendly and is capable of significantly reducing landfill disposal of industrial waste as compared with a conventional method.SOLUTION: A method for producing an inorganic industrial recycled waste, comprising the steps: mixing an inorganic industrial waste containing an anionic hazardous substance, a calcium-containing waste, and cement so as to obtain a mixture, and solidifying the resulting mixture. It is preferred, in the step of obtaining the mixture, to additionally mix silica-based particles, which can be crushed stone powders. Preferably, in the step of mixing, a hexavalent chromium reducing agent is additionally mixed. Preferably, a chromate forming compound is further mixed in the mixing step. Preferably, a magnesium compound is further mixed.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method for producing a recycled inorganic industrial waste product. In particular, the present disclosure relates to a method for producing a recycled product obtained by treating an inorganic industrial waste and having a low elution amount of harmful substances such as fluorine, boron, arsenic and hexavalent chromium.

Inorganic industrial waste such as sludge and combustion ash is discharged from various facilities such as factories, treatment plants, and power plants. Hazardous substances such as heavy metals are mixed in such inorganic industrial waste, and when the inorganic industrial waste is landfilled, the harmful substances are fixed by solidifying with cement or the like.

On the other hand, since there is a shortage of final disposal sites for landfill disposal, recycling of inorganic industrial waste is also being considered. In order to recycle inorganic industrial waste, it is necessary to separate and recover harmful substances or immobilize them so that they do not elute.

Japanese Unexamined Patent Publication No. 2015-182057

Hazardous substances of cationic heavy metals can be treated relatively easily by performing base treatment.

On the other hand, harmful anionic substances, such as fluorine (F ^-), boron ^{_{(B (OH) 4 -)}} , arsenic _(AsO ^{4 2-),} and is difficult to process for hexavalent chromium _(CrO ^{4 2-)} Although a method for reducing the amount of hexavalent chromium or the like eluted from the treated ash has been proposed (Patent Document 1), the amount of landfill disposal of industrial waste can still be reduced as compared with the conventional method, and an anionic system is used. An inexpensive and effective treatment method that can reduce the elution amount of harmful substances has not been established.

This disclosure is an environment-friendly manufacturing method that can significantly reduce the landfill disposal of industrial waste compared to the conventional method, and is a new manufacturing of recycled inorganic industrial waste with reduced harmful substances. The purpose is to provide a method.

The present inventors have found that the above problems can be solved by the present disclosure having the following aspects.
<< Aspect 1 >>
Mixing inorganic industrial waste containing anionic hazardous substances, calcium-containing waste, and cement to obtain a mixture, and solidifying the mixture.
A method for manufacturing recycled inorganic industrial waste products, including.
<< Aspect 2 >>
The production method according to aspect 1, wherein in the step of obtaining the mixture, a gap filler which is an inorganic oxide particle is further mixed.
<< Aspect 3 >>
The production method according to aspect 2, wherein the gap filler is silica-based particles.
<< Aspect 4 >>
The production method according to aspect 3, wherein the silica-based particles are crushed stone powder.
<< Aspect 5 >>
The production method according to aspect 2, wherein the gap filler is alumina-based particles or waste glass particles.
<< Aspect 6 >>
The production method according to any one of aspects 1 to 5, wherein the inorganic industrial waste is combustion ash or sludge.
<< Aspect 7 >>
The production method according to any one of aspects 1 to 6, wherein the inorganic industrial waste is combustion ash derived from biomass fuel.
<< Aspect 8 >>
The production method according to any one of aspects 1 to 7, wherein the calcium-containing waste is a waste material of gypsum board or lightweight aerated concrete.
<< Aspect 9 >>
The production method according to any one of aspects 1 to 8, wherein a hexavalent chromium reducing agent is further mixed in the step of obtaining the mixture.
<< Aspect 10 >>
The production method according to any one of aspects 1 to 9, wherein the chromate-forming compound is further mixed in the step of obtaining the mixture.
<< Aspect 11 >>
The production method according to any one of aspects 1 to 10, wherein the magnesium compound is further mixed in the step of obtaining the mixture.
<< Aspect 12 >>
The recycled inorganic industrial waste product is recycled crushed stone, recycled sand, or recycled aggregate. The production method according to any one of aspects 1 to 11.

This disclosure is an environment-friendly manufacturing method that can significantly reduce the landfill disposal of industrial waste compared to the conventional method, and is a new manufacturing of recycled inorganic industrial waste with reduced harmful substances. A method can be provided.

FIG. 1 shows an image of immobilization of harmful substances by cement and strengthening of recycled products by silica-based particles. FIG. 2 shows a comparison between Reference Example 1 and Examples 1 to 3 regarding the amount of fluorine (F) eluted in Experiment 1. FIG. 3 shows a comparison between Reference Example 1 and Examples 1 to 3 regarding the amount of boron (B) eluted in Experiment 1. FIG. 4 shows a comparison between Reference Example 1 and Examples 1 to 3 regarding the amount of arsenic (As) eluted in Experiment 1. FIG. 5 shows a comparison between Reference Example 1 and Examples 1 to 3 regarding the amount of chromium (Cr) eluted in Experiment 1. FIG. 6 shows a comparison between Reference Examples 2 and 3 and Examples 4 to 9 regarding the total amount of chromium (Cr) eluted in Experiment 2. FIG. 7 shows a comparison between Reference Examples 2 and 3 and Examples 4 to 9 regarding the elution amounts of trivalent chromium and hexavalent chromium in Experiment 2. FIG. 8 shows a comparison of Examples 10 to 15 regarding the amount of fluorine (F) eluted in Experiment 3. FIG. 9 shows a comparison of Examples 10 to 15 regarding the amount of boron (B) eluted in Experiment 3. FIG. 10 shows a comparison of Examples 10 to 15 regarding the amount of arsenic (As) eluted in Experiment 3. FIG. 11 shows a comparison of Examples 10 to 15 regarding the amount of chromium (Cr) eluted in Experiment 3. FIG. 12 shows a comparison of Examples 16 to 20 regarding the amount of chromium eluted in Experiment 4. FIG. 13 shows a comparison of Reference Examples 4 to 9 regarding the amount of anionic hazardous substances eluted in Experiment 6.

The present disclosure comprises mixing inorganic industrial waste containing anionic hazardous substances, calcium-containing waste, and cement to obtain a mixture, and solidifying the mixture. Regarding the manufacturing method of.

The present inventors detoxify as waste by mixing calcium-containing waste such as gypsum board and lightweight aerated concrete, which are landfilled as waste, with harmful inorganic industrial waste. It was found that it can be safely used as a product. Without being bound by theory, this is a compound in which anionic toxic substances and calcium are sparingly soluble in water by mixing inorganic industrial waste containing anionic toxic substances with calcium-containing waste. It is thought that this is to form. According to the method of the present disclosure, since both the calcium-containing waste and the inorganic industrial waste that have been landfilled can be used as recycled products, the environmental load can be significantly reduced, which is very advantageous.

Depending on the use of the recycled product of the present disclosure, the method of the present disclosure may include a step of forming the mixture after the step of obtaining the mixture. Further, when the recycled product of the present disclosure is a recycled stone-based material such as recycled crushed stone, recycled sand, and recycled aggregate, the step of solidifying the mixture is followed by the step of crushing the further solidified mixture. Can be done. The step of solidifying may be a so-called curing step. Water can be applied to the mixture in the solidification step.

<Inorganic industrial waste>
The inorganic industrial waste that can be used in the method of the present disclosure means an industrial waste whose main component is an inorganic substance, which is discharged from various facilities such as factories, treatment plants, and power plants.

Examples of the inorganic industrial waste include, but are not limited to, sludge, combustion ash, slag, and soot dust. Among these, sludge or combustion ash can be mentioned in particular. The main raw materials for combustion ash are combustion ash derived from petroleum / coal-based thermal power plants; combustion ash derived from biomass fuel; and coal, wood, wood pellets, coconut shells (PKS), used paper, and waste plastics. Combustion ash derived from solid fuel (RPF) and the like can be mentioned. Among these, combustion ash having high basicity, for example, combustion ash derived from biomass fuel, may elute hexavalent chromium from a chromium-containing refractory combustion furnace such as a stainless steel combustion furnace, and has a hexavalent chromium concentration. May be high. In addition, it is very useful to reuse the combustion ash derived from the thermal power plant to reduce the environmental load.

Inorganic industrial waste contains anionic hazardous substances that can be eluted in water. The anionic hazardous substances, such as fluorine (F ^-), boron ^{_{(B (OH) 4 -)}} , arsenic _(AsO ^{4 2-),} and at least one is content of hexavalent chromium _(CrO ^{4 2-)} Will be done. Fluorine (F ^-), boron ^{_{(B (OH) 4 -)}} , arsenic _(AsO ^{4 2-),} and hexavalent chromium, and calcium, _{respectively, CaF 2, Ca [B (} OH) 4] 2, Ca 3 ( AsO ₄ ) ₂ and CaCrO ₄ can be formed, and since these are poorly soluble inorganic salts in water, they are substantially not eluted from the recycled product.

Inorganic industrial waste before mixing with calcium-containing waste may contain anionic harmful substances above the soil elution amount standard value, that is, inorganic industrial waste contains ^{0 fluorine (F −} ). may contain more than .80Ppm, boron (B _{(OH) 4 ^-)} may contain more than 1.0ppm, and may include arsenic _(AsO ^{4 2-)} of the above 0.01 ppm, and / or hexavalent chromium may be included _(CrO ^{4 2-)} or more 0.05 ppm. Inorganic industrial waste may contain anionic toxic substances below the soil elution amount reference value, and may contain an extremely small amount of anionic toxic substances, for example, before or after the lower limit of detection by analysis.

<Calcium-containing waste>
In the method of the present disclosure, calcium-containing waste can be used as a calcium source. Calcium-containing waste is a type of waste different from the above-mentioned inorganic industrial waste, and contains calcium in an element ratio of 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, and 30% by mass. % Or more or 40% by mass or more.

Examples of calcium-containing waste include cinders containing calcium and construction waste materials, and examples of construction waste materials include gypsum (dihydrate gypsum) or concrete waste materials, specifically gypsum board or high temperature. Examples of waste materials of lightweight cellular concrete (ALC) cured by high pressure steam can be mentioned. The cinders are incinerator ash generated from a cleaning plant or the like, ash such as coal husks generated from a coal-fired power plant, and / or burnt residue, and are required to be reused as civil engineering materials. Nisui gypsum (CaSO ₄・ H ₂ O) is used in large quantities as a building material for the walls of houses, etc., and is also discharged in large quantities as a by-product from thermal power plants, so reuse is required. ing. ALC is made of silica stone, cement, slaked lime, aluminum powder, etc., and its main components are silicon and calcium. ALC is used for the outer walls of buildings and the like, and reuse is required.

The calcium-containing waste may contain anionic toxic substances in an amount equal to or higher than the soil elution amount reference value, or may contain substantially no anionic toxic substances. For example, the content of anionic hazardous substances in calcium-containing waste may be, for example, fluorine (F ⁻ ) less than 0.80 ppm and boron (B (OH) ₄ ⁻ ) less than 1.0 ppm. at best, arsenic _(AsO ^{4 2-)} may be less than 0.01 ppm, and / or hexavalent chromium _(CrO ^{4 2-)} may be less than 0.05 ppm.

The amount of calcium-containing waste that can be used in the method of the present disclosure depends on the amount of calcium in the calcium-containing waste and the amount of harmful substances in the inorganic industrial waste, but is, for example, 100 parts by mass of the inorganic industrial waste. On the other hand, it may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, or 20 parts by mass or more, 100 parts by mass or less, 70 parts by mass or less, 50 parts by mass or less, 30 parts. It may be less than a part by mass or less than 20 parts by mass. For example, the amount of calcium-containing waste is 1 part by mass or more and 100 parts by mass or less, 3 parts by mass or more and 50 parts by mass or less, or 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of inorganic industrial waste. There may be.

<cement>
The type of cement that can be used in the method of the present disclosure is not particularly limited as long as it can be used as a recycled product by solidifying inorganic industrial waste and calcium-containing waste.

Cement can immobilize at least one of the harmful substances. FIG. 1 shows an image of immobilization of harmful substances by cement. Without being bound by theory, cement, the internal and / or external CaO by reacting with water, cement hydrate and ettringite a _{(3CaO · Al 2 O 3 ·} 3CaSO 4 · 32H 2 O) It is considered that the hydrate formed and produced takes in harmful substances due to its agglomeration, and ettringite fixes anionic harmful substances by the ion exchange effect and suppresses elution.

For example, cements that can be used in the present disclosure include Portland cement (for example, ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, low heat Portland cement, sulfate-resistant Portland cement), and mixed cement ( For example, blast furnace cement, fly ash cement, silica cement), alumina cement, eco-cement and the like can be mentioned.

The amount of cement that can be used in the method of the present disclosure depends on the use of the recycled product, but for example, 5 parts by mass or more and 10 parts by mass or more with respect to 100 parts by mass in total of inorganic industrial waste and calcium-containing waste. , 15 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more, 100 parts by mass or less, 70 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less. May be good. For example, the amount of cement is 5 parts by mass or more and 100 parts by mass or less, 10 parts by mass or more and 50 parts by mass or less, or 15 parts by mass or more and 40 parts by mass with respect to a total of 100 parts by mass of inorganic industrial waste and calcium-containing waste. It may be less than a part by mass.

<Gap filling material>
In the method of the present disclosure, a gap filler which is an inorganic oxide particle can be further mixed in the step of obtaining the mixture.

According to the study by the present inventors, it was found that the strength of the recycled product can be increased by using the gap filler. FIG. 1 shows an image of strengthening a recycled product by using crushed stone powder as a gap filling material. Although not bound by theory, when the recycled product is solidified by cement, the gap filler enters the gaps of the cement hydrate, which increases the density of the recycled product and strengthens the recycled product. Conceivable. Further, the gap filler is useful because the inorganic oxide usually has an adsorption effect on the anionic toxic substance, so that the elution amount of the anionic toxic substance can be reduced. Further, the interstitial filler is useful because the inorganic oxide can usually accelerate the hydration reaction of the cement and densify the structure of the cement, so that the elution amount of anionic harmful substances can be reduced. be.

The gap filler is an inorganic oxide particle, and the type thereof is not particularly limited. For example, silica-based particles, alumina-based particles, titania-based particles, ferritic particles, zirconia-based particles, or their inorganic oxides. Combination particles can be mentioned. Here, the "system particles" refer to particles containing the substance in a molar ratio of 50% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

The average particle size D50 of the gap filler is 3000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, 200 μm or less, 100 μm or less when measured with a laser diffraction type particle size distribution measuring device (SALD-7000, Shimadzu Corporation). , 50 μm or less, 30 μm or less, or 20 μm or less, and may be 1 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, 30 μm or more, 50 μm or more, 100 μm or more, or 150 μm or more. For example, the average particle size D50 of the gap filler may be 1 μm or more and 3000 μm or less, 5 μm or more and 500 μm or less, and 10 μm or more and 300 μm or less.

The amount of the gap filler that can be used in the method of the present disclosure depends on the use of the recycled product, but for example, 50 parts by mass or more, 100 parts by mass or more, 150 parts by mass or more, and 200 parts by mass with respect to 100 parts by mass of cement. It may be more than or equal to 300 parts by mass or more, and may be 1000 parts by mass or less, 700 parts by mass or less, 500 parts by mass or less, 400 parts by mass or less, or 300 parts by mass or less. For example, the amount of the gap filler may be 50 parts by mass or more and 1000 parts by mass or less, 100 parts by mass or more and 500 parts by mass or less, or 150 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of cement.

The silica-based particles are particles containing silica, and may further contain alumina and the like. For example, silica-based particles can contain 50% or more of silicon oxide in terms of molar ratio, and can further contain 10% or more of aluminum oxide. The silica-based particles can be, for example, SiO ₂ , NaAlSi ₃ O ₈ or a combination thereof. When the recycled product is a recycled stone-based material such as recycled crushed stone, it is very useful to use silica-based particles because it is easy to obtain sufficient strength. In addition, such silica-based particles usually have an adsorption effect on anionic harmful substances, and by solidifying the mixture containing the silica-based particles, the anionic harmful substances are eluted from the recycled product. It is useful because the amount can be reduced.

As the silica-based particles, crushed stone powder can be preferably used. The crushed stone powder is a very fine stone powder generated as a by-product when crushed stone or crushed sand is produced from rock, and has an average particle size as described above. Crushed stone powder is also disposed of in large quantities as industrial waste, and its economic and environmental burdens are large, so it is required to reuse it as a building material.

In particular, when crushed stone powder is used, the average particle size D50 of silica-based particles is 100 μm or less, 50 μm or less, and 30 μm or less when measured with a laser diffraction type particle size distribution measuring device (SALD-7000, Shimadzu Corporation). , 20 μm or less, 1 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more. For example, the average particle size D50 may be 1 μm or more and 100 μm or less, 5 μm or more and 50 μm or less, or 10 μm or more and 30 μm or less.

Further, glass particles can be used as the silica-based particles. Further, as the glass particles, waste glass, for example, particles derived from glass for a solar panel can be used. Waste glass is also disposed of in large quantities as industrial waste, and its economic load and environmental load are large, so that it is required to be reused as a building material or the like. In particular, glass for solar panels is expected to be discarded in large quantities in the future, and it is industrially very advantageous to recycle this into a useful recycled product. On the other hand, since the waste glass may contain a large amount of sodium, the amount of waste glass particles used can be limited when sodium becomes a problem.

When the glass for a solar panel is used, a cover glass obtained by removing an aluminum frame, a solar cell portion necessary for power generation, etc. from the solar panel can be used. By using this cover glass, crushing it by a crushing means such as a ball mill, and classifying it by sieving or the like, waste glass particles having a desired particle size can be obtained. The balls for the ball mill preferably have high hardness, and examples thereof include zirconia balls and alumina balls.

In particular, when glass particles are used, the average particle size D50 of the glass particles is 3000 μm or less, 2000 μm or less, 1000 μm or less when measured with a laser diffraction type particle size distribution measuring device (SALD-7000, Shimadzu Corporation). It may be 500 μm or less, 300 μm or less, or 200 μm or less, and may be 10 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, or 200 μm or more. For example, the average particle size D50 may be 10 μm or more and 3000 μm or less, 50 μm or more and 2000 μm or less, and 100 μm or more and 1000 μm or less. The glass particles contain a large amount of silicate components, which may react with calcium, but if the particle size of the glass particles is in this range, the reaction with calcium affects the final recycled product. It is suitable because it does not exist. Further, if the particle size of the glass particles is in such a range, the strength of the recycled product can be made very high.

Alumina particles can also be suitably used as a gap filler. It is considered that the addition of alumina-based particles can cause an early hydration reaction of cement and promote the production of monocarbonate. Further, it is considered that the smaller the particle size of the alumina-based particles, the faster the reaction proceeds and the structure of the cement becomes denser, whereby the elution of anionic harmful substances is suppressed. In particular, it has been found that it is useful to use alumina-based particles when it is particularly desired to remove fluorine as an anionic harmful substance.

The average particle size D50 of alumina-based particles is 500 μm or less, 300 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm when measured with a laser diffraction type particle size distribution measuring device (SALD-7000, Shimadzu Corporation). It may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more. For example, the average particle size D50 may be 0.1 μm or more and 500 μm or less, 0.5 μm or more and 300 μm or less, or 1 μm or more and 30 μm or less.

<Hexavalent chromium reducing agent>
In the method of the present disclosure, a hexavalent chromium reducing agent that reduces hexavalent chromium to trivalent chromium can be further mixed in the step of obtaining the mixture. When hexavalent chromium is reduced to trivalent chromium, trivalent chromium is basically harmless and is sparingly soluble in water with sulfate ions contained in cement and / or other materials (eg dihydrate gypsum). It is very advantageous because it forms the sulfate of.

Examples of the hexavalent chromium reducing agent include iron divalent compounds, for example, iron (II) hydroxide, iron (II) chloride, iron (II) fluoride, iron (II) bromide, iron sulfate ( II), iron nitrate (II), iron lactate (II), sodium ferrous citrate, ferrous gluconate, ferrous pyrophosphate, ferrous fumarate and the like can be mentioned. When such a reducing agent is used, hexavalent chromium can be reduced to trivalent chromium, and / or even when the basicity of inorganic industrial waste is particularly high, it suppresses the carbonation of calcium. Hexavalent chromium is converted to calcium chromate and can be easily fixed to recycled products.

The amount of the hexavalent chromium reducing agent that can be used in the method of the present disclosure depends on the amount of hexavalent chromium contained in the inorganic industrial waste, etc., but for example, the total mass of the inorganic industrial waste and the calcium-containing waste is 100 mass. It may be 0.1 part by mass or more, 0.3 part by mass or more, 0.5 part by mass or more, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more, and 30 parts by mass. Hereinafter, it may be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less. For example, the amount of hexavalent chromium reducing agent is 0.1 part by mass or more and 30 parts by mass or less, and 0.3 parts by mass or more and 10 parts by mass with respect to 100 parts by mass in total of inorganic industrial waste and calcium-containing waste. The following, or 0.5 parts by mass or more and 5 parts by mass or less may be used.

<Chromate-forming compound>
In the method of the present disclosure, a chromate-forming compound that further reacts with hexavalent chromium to form a water-insoluble chromate can be mixed in the step of obtaining the mixture. Such compounds are very useful because they prevent the elution of hexavalent chromium from the resulting recycled product. In addition, in this specification, insoluble in water means that it dissolves in 100 grams of water at 20 degreeC by 3.0 grams or less, 1.0 grams or less, or 0.1 grams or less.

According to the study by the present inventors, even when a large amount of hexavalent chromium is contained in the inorganic industrial waste and / or the basicity of the inorganic industrial waste is particularly high, the chromate salt is used. It has been found that the amount of elution can be significantly reduced by using the forming compound. For example, when the inorganic industrial waste is combustion ash derived from biomass fuel, it is highly basic and / or may contain a large amount of hexavalent chromium, so that a chromate-forming compound may be used. Very advantageous.

Examples of such chromate-forming compounds include _{barium compounds that form barium chromate (BaCrO 4} ), such as barium hydroxide, barium chloride, barium fluoride, barium bromide, barium sulfate, barium nitrate, and the like; zinc chromate. Zinc compounds forming (ZnCrO ₄ ), such as zinc hydroxide, zinc chloride, zinc fluoride, zinc bromide, zinc sulfate, zinc nitrate, etc .; _{copper compounds forming copper chromate (CuCrO 4} ), such as copper hydroxide , Copper chloride, copper fluoride, copper bromide, copper sulfate, copper nitrate and the like; _{lead compounds forming lead chromate (PbCrO 4} ), for example, lead hydroxide, lead chloride, lead nitrate and the like can be mentioned.

The amount of the chromate-forming compound depends on the amount of hexavalent chromium contained in the inorganic industrial waste and the amount of sulfate ions contained in the mixture, but for example, the inorganic industrial waste and the calcium-containing waste. For a total of 100 parts by mass, it may be 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more, and 20 parts by mass or less. It may be 15 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less. For example, the amount of the chromate-forming compound is 0.1 parts by mass or more and 20 parts by mass or less, and 0.3 parts by mass or more and 15 parts by mass with respect to 100 parts by mass in total of the inorganic industrial waste and the calcium-containing waste. The following, or 0.5 parts by mass or more and 10 parts by mass or less may be used. The chromate-forming compound may produce not only chromate but also sulfate, and in that case, sulfate may be produced preferentially over chromate, so this point should also be taken into consideration. Then, the amount of addition can be determined.

<Magnesium compound>
In the method of the present disclosure, a magnesium compound can be further mixed in the step of obtaining the mixture. When calcium is exposed to water and / or air for a long period of time even after forming an anionic harmful substance and a poorly soluble inorganic salt in water, calcium carbonate is generated and the anionic harmful substance is eluted. Magnesium is more easily carbonated than calcium, and it is possible to prevent calcium from becoming calcium carbonate by becoming magnesium carbonate itself. Therefore, by using the magnesium compound, the detoxifying effect of calcium on anionic harmful substances can be maintained for a long period of time.

Examples of such magnesium compounds include magnesium oxide, magnesium sulfide, magnesium peroxide, magnesium hydroxide, magnesium chloride, magnesium bromide, magnesium sulfate, magnesium nitrate and the like.

The amount of the magnesium compound depends on the amount of hexavalent chromium contained in the inorganic industrial waste, etc., but for example, 0.1 part by mass with respect to 100 parts by mass of the total of the inorganic industrial waste and the calcium-containing waste. It may be 0.3 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more, 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, and 5 parts by mass. It may be less than 3 parts by mass or less than 3 parts by mass. For example, the amount of the magnesium compound is 0.1 part by mass or more and 20 parts by mass or less, 0.3 parts by mass or more and 15 parts by mass or less, or 100 parts by mass or less, based on 100 parts by mass of the total of inorganic industrial waste and calcium-containing waste. It may be 0.5 parts by mass or more and 10 parts by mass or less.

<Use>
Examples of the recycled product obtained by the method of the present disclosure include recycled stone materials such as recycled crushed stone, recycled sand, and recycled aggregate. In addition, an interlocking block can be mentioned as a recycled product obtained by the method of the present disclosure. Among these, the recycled product of the present disclosure is particularly effective when it is a recycled stone-based material such as recycled crushed stone and is used in a place where it is difficult to come into contact with air and / or rainwater. When the recycled product of the present disclosure is used in a place where it is difficult to come into contact with air and / or rainwater, for example, an embankment material for civil engineering work, a roadbed under the road, etc., the strength can be increased and the anionic harmful substance becomes long. It is particularly useful because it can maintain a non-eluting state over a period of time.

Experiment 1: Examination of suppression of elution of anionic harmful substances in biomass combustion ash In a 100 ml polyethylene bottle, combustion ash derived from biomass fuel, crushed stone powder with an average particle size D50 of 19.7 μm, Portland cement, and lightweight cellular concrete. (ALC) and dihydrate gypsum were mixed in the amounts shown in Table 1. Further, to this mixture, anionic harmful substances (that is, salts of fluorine (F), boron (B), arsenic (As), and chromium (Cr)) were added in equal amounts in each example and mixed. The mixture was stirred for 30 minutes, then transferred to a petri dish and allowed to air dry for 48 hours.

8 grams of the dried mixture and 80 grams of water were placed in a 100 ml polyethylene bottle, shaken for 6 hours, and then centrifuged at 3000 rpm for 20 minutes to collect the supernatant. The supernatant was filtered through a 5C filter paper and then further filtered through a 0.20 μm membrane filter. Regarding the filtrate, fluorine (F) is measured by ion chromatography, boron (B) and chromium (Cr) are measured by ICP-MS, and arsenic (As) is measured by an atomic absorption spectrophotometer. By doing so, the amount of elution was quantified. The measurement was performed according to JIS K 0102. The pH of water was also measured.

The results are shown in Table 1 below. Further, FIGS. 2 to 5 show a comparison of the elution amount of each harmful substance according to Reference Example 1 and Examples 1 to 3. The dotted lines in FIGS. 2 to 5 indicate the environmental standard values of each harmful substance.

As can be seen from FIGS. 2 and 3, for fluorine (F) and boron (B), a sufficient elution suppressing effect can be obtained simply by adding combustion ash, crushed stone powder, cement, ALC and / or dihydrate gypsum. , The amount of these elutions could be suppressed to below the environmental standard value.

As can be seen from FIG. 4, for arsenic (As), the elution suppressing effect was obtained only by adding combustion ash, crushed stone powder, cement, ALC and / or dihydrate gypsum, but the elution amount was set to the environmental standard value. It could not be suppressed to the following.

As can be seen from FIG. 5, the elution amount of chromium (Cr) could not be reduced even if they were used.

Experiment 2: Examination of suppression of chromium elution in combustion ash using a hexavalent chromium reducing agent Ferrous chloride tetrahydrate (FeCl ₂ ) was added as a hexavalent chromium reducing agent, and the amounts of each component were shown in Table 2. In the same manner as in Experiment 1, the elution amount of trivalent chromium (Cr (III)), the elution amount of hexavalent chromium (Cr (VI)), and the elution amount of total chromium (Cr) were the same as in Experiment 1. We examined how it would change. The elution amount of total chromium was measured by ICP-MS, and the elution amount of hexavalent chromium was measured using a spectrophotometer (Packtest Multi SP). The elution amount of trivalent chromium was the difference between the elution amount of total chromium and the elution amount of hexavalent chromium.

The results are shown in Table 2 below. In addition, FIGS. 6 and 7 show a comparison of reference examples 2 to 3 and examples 4 to 9 in the amount of chromium elution.

As can be seen from FIGS. 6 and 7, by using ferrous chloride as a hexavalent chromium reducing agent, the elution amount of hexavalent chromium, which could not be reduced only by cement and calcium-containing waste, was significantly increased. Was able to be reduced to. This, Fe ₂ ⁺ is itself is reduced to hexavalent chromium trivalent chromium while being oxidized to Fe ₃ ^+, trivalent chromium and SO ₄ ^2-, to form a salt sparingly soluble in water, elution Is thought to have been suppressed. Change in elution concentration of trivalent chromium of not believed to be because of the reaction by SO ₄ ^2-and minute that hexavalent chromium is reduced.

Experiment 3: Examination of suppression of elution of anionic harmful substances in combustion ash using barium chloride as a chromate-forming compound Magnesium oxide (MgO) as a magnesium compound and barium chloride dihydrate as a chromate-forming compound ( Except for the addition of BaCl ₂ ) and the mixing of each component in the amounts shown in Table 3, the elution amount of anionic harmful substances was examined in the same manner as in Experiment 1.

The results are shown in Table 3 below. In addition, FIGS. 8 to 11 show a comparison of the elution amounts of each harmful substance according to Examples 10 to 15.

As can be seen from FIGS. 8 and 9, for fluorine (F) and boron (B), magnesium oxide and barium chloride may be added in addition to combustion ash, crushed stone powder, cement, ALC, and dihydrate gypsum. A sufficient elution suppressing effect was obtained, and the amount of these elutions could be suppressed to below the environmental standard value.

As can be seen from FIG. 10, for arsenic (As), a sufficient elution suppressing effect can be obtained by adding magnesium oxide and barium chloride in addition to combustion ash, crushed stone powder, cement, ALC, and dihydrate gypsum. Was done. In particular, by increasing the amount of barium chloride, the amount of elution could be suppressed to below the environmental standard value. It is considered that this is because barium and arsenic _{produce Ba 3} (AsO ₄ ) ₂ , which is a salt sparingly soluble in water, and therefore, a larger amount of barium chloride is more effective in suppressing elution.

As can be seen from FIG. 11, with respect to chromium (Cr), the amount of chromium eluted could be significantly reduced by using barium chloride, which is a chromate-forming compound. Also, by increasing the amount of barium chloride, the elution of chromium was almost undetectable. This is believed to be due to generated the BaCrO ₄ is a sparingly soluble salt in water.

Experiment 4: Examination of suppression of chromium elution in combustion ash using various chromate-forming compounds Various substances were mixed as chromate-forming compounds in the amounts shown in Table 4, and anionic harmful substances were added. Except for the fact that this was not done, how the total amount of chromium (Cr) eluted changed was examined in the same manner as in Experiment 1.

The results are shown in Table 4 below. Further, FIG. 12 shows a comparison of Examples 16 to 20 regarding the amount of chromium eluted.

As can be seen from FIG. 12, various chromate-forming compounds could be used to reduce the amount of chromium elution. Of these, barium was the most effective. Among zinc (Zn), copper (Cu), and lead (Pb), zinc (Zn) had the highest effect. This is considered to be for generating ZnCrO ₄ is a sparingly soluble salt in water. Of barium chloride and zinc chloride, zinc chloride is also very advantageous because zinc chloride is more cost effective.

Experiment 5: Examination of elution suppression of anionic harmful substances using alumina particles as the gap filler Three types of alumina particles with an average particle size D50 of 2 μm, 20 μm, and 200 μm were used instead of the crushed stone powder as the gap filler. Got ready. They had a substantially single particle size distribution and composition.

7 grams of each alumina particle was placed in a 100 ml polyethylene bottle, and a fluorine (F) salt as an anionic harmful substance was added dropwise so as to elute at a maximum of 10 ppm after the elution test. There, 3 grams of Portland cement, a calcium source (Ca (OH) ₂ ), a magnesium compound (MgCl ₂ ), and a hexavalent chromium reducing agent (FeSO ₄ ) were mixed. The mixture was stirred for 30 minutes, then transferred to a petri dish and allowed to air dry for 48 hours.

Then, the dissolution test was carried out according to the factory wastewater test method JIS K 0102, and the fluorine (F) concentration was measured by ion chromatography.

As a result, those having a smaller particle size of the alumina particles used showed a higher elution suppressing effect. The addition of alumina particles causes an early hydration reaction in the cement and promotes the production of monocarbonate. It is considered that the smaller the particle size of the alumina particles and the higher the reactivity, the more the reaction proceeded and the densification of the cement structure suppressed the elution. In addition to the effect of particle size, it was also clarified that the reactivity with anionic harmful substances and reagents such as magnesium compounds and hexavalent chromium reducing agents is also related. In the case of alumina particles, they showed reactivity with fluorine, and an elution reduction effect that was thought to be due to adsorption was observed.

Experiment 6: Examination of elution suppression of anionic harmful substances using waste glass particles as a gap filler We also examined waste glass such as solar panel glass as a gap filler. Here, the cover glass (white plate tempered glass) on the surface of the crystalline solar cell was used. JIS standards have been established for the glass surface of this solar cell, and even if a steel ball weighing 227 grams and having a diameter of 38 mm is dropped from a height of 1 m or a twist of 2 mm per 100 mm diagonal is applied, significant abnormalities occur. It is stipulated that there is no such thing and that the electrical performance is satisfied. Further, this glass has a property that when it breaks, it breaks into a spider web shape of 3 to 5 mm square, but does not shatter. In this glass, after heating the plate glass to about 650 to 700 ° C., air is blown onto the glass surface and the glass surface is cooled rapidly to form a compressive stress layer on the surface, and a stress field is formed due to the density difference from the inside. , It is necessary to devise for crushing.

Therefore, a panel glass of about 3 mm square, which was roughly divided by removing the aluminum frame, the solar cell portion necessary for power generation, etc. from the solar panel, was crushed by a ball mill. At the time of pulverization, 1800 grams of zirconia balls were added to 90 grams of waste glass, and the mixture was pulverized for 60 minutes. Then, it was separated into waste glass particles having a particle size of 0.2 to 1 mm and waste glass particles having a particle size of 0.2 mm or less by sieving. When the zirconia ball was changed to an iron ball, the surface of the iron ball was scraped and the obtained powder became gray, which was unsuitable. When the zirconia balls were changed to alumina balls, they needed to be hung for a longer time than the zirconia balls, but they could be crushed.

In a 100 ml polyethylene bottle, crushed stone powder or waste glass particles, Portoland cement, calcium source (Ca (OH) ₂ ), magnesium compound (MgCl ₂ ), hexavalent chromium reducing agent (FeSO ₄ ) or chromate The forming compound (BaCl ₂ ) was mixed in the amounts shown in Table 5. Further, to this mixture, anionic harmful substances (that is, salts of fluorine (F), boron (B), arsenic (As), and chromium (Cr)) were added in equal amounts in each example and mixed. The mixture was stirred for 30 minutes, then transferred to a petri dish and allowed to air dry for 48 hours.

5 grams of the dried mixture and 50 grams of water were placed in a 100 ml polyethylene bottle, shaken for 6 hours, and then centrifuged at 3000 rpm for 20 minutes to collect the supernatant. The supernatant was filtered through a 5C filter paper and then further filtered through a 0.20 μm membrane filter. Regarding the filtrate, fluorine (F) is measured by ion chromatography, boron (B) and chromium (Cr) are measured by ICP-MS, and arsenic (As) is measured by an atomic absorption spectrophotometer. By doing so, the amount of elution was quantified. The measurement was performed according to JIS K 0102 for the industrial wastewater test method. The pH of water was also measured.

The results are shown in Table 5 below. Further, FIG. 13 shows a comparison of the elution amount of each harmful substance according to Reference Examples 4 to 9.

As can be seen from Table 5 and FIG. 13, the waste glass particles have the same effect as the crushed stone powder. On the other hand, the average particle size of the crushed stone powder is about 20 μm, and the particle size of the waste glass particles includes particles larger than that, so it cannot be said that they are exactly the same.

In the example using waste glass particles, the reason why the elution concentrations of arsenic and boron are slightly high is that the crushed stone powder also contains a relatively large amount of calcium, which has an elution-suppressing effect, whereas the waste glass contains a relatively large amount of calcium. , It is considered that the silicic acid component reacts with calcium. Based on this premise, the smaller the particle size of the waste glass particles, the higher the reactivity with calcium. Therefore, it is considered that waste glass particles having a larger size (for example, 0.2 to 1 mm in particle size) are desirable.

This disclosure is an environment-friendly manufacturing method that can significantly reduce the landfill disposal of industrial waste compared to the conventional method, and is a new manufacturing of recycled inorganic industrial waste with reduced harmful substances. It has very high industrial utility because it can provide a method.

Claims (12)

Mixing inorganic industrial waste containing anionic hazardous substances, calcium-containing waste, and cement to obtain a mixture, and solidifying the mixture.
A method for manufacturing recycled inorganic industrial waste products, including. The production method according to claim 1, wherein in the step of obtaining the mixture, a gap filler which is an inorganic oxide particle is further mixed. The production method according to claim 2, wherein the gap filler is silica-based particles. The production method according to claim 3, wherein the silica-based particles are crushed stone powder. The production method according to claim 2, wherein the gap filler is alumina-based particles or waste glass particles. The production method according to any one of claims 1 to 5, wherein the inorganic industrial waste is combustion ash or sludge. The production method according to any one of claims 1 to 6, wherein the inorganic industrial waste is combustion ash derived from biomass fuel. The production method according to any one of claims 1 to 7, wherein the calcium-containing waste is a waste material of gypsum board or lightweight cellular concrete. The production method according to any one of claims 1 to 8, wherein a hexavalent chromium reducing agent is further mixed in the step of obtaining the mixture. The production method according to any one of claims 1 to 9, wherein the chromate-forming compound is further mixed in the step of obtaining the mixture. The production method according to any one of claims 1 to 10, wherein the magnesium compound is further mixed in the step of obtaining the mixture. The recycled inorganic industrial waste product is recycled crushed stone, recycled sand, or recycled aggregate. The manufacturing method according to any one of claims 1 to 11.

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