JP4531362B2 - Hazardous substance reducing material and method for treating sewage and soil using the same - Google Patents

Description

  The present invention relates to a toxic water reducing material used for sewage and soil contaminated with toxic substances, waste treatment, and the like, and a sewage and soil treatment method.

  In recent years, environmental problems have become apparent. In particular, toxic substances in sewage and soil, such as heavy metals such as chromium, selenium and arsenic, nitrate nitrogen and nitrite nitrogen, fluorine, boron, dioxins, volatile organic compounds such as trichloroethylene and tetrachloroethylene, etc. It is used in various forms in the chemical industry, electrical / electronic industry, medical facilities, various research facilities, etc., and there is a need for safe and easy treatment methods for soil and wastewater containing used hazardous substances.

  These hazardous substances are based on the Basic Environment Law, Environment Agency Notification No. 46 (environmental standards related to soil contamination), Environment Agency Notification No. 59 (environmental standards related to water pollution), Water Pollution Control Act, waste treatment Many environmental standards such as laws and living environment conservation regulations have been established, and it is necessary to maintain a level below this standard value.

  Conventionally, as materials for reducing these harmful substances, methods using activated carbon (see Patent Documents 1 and 2, etc.), methods using zeolites (see Patent Document 3 etc.), hydrotalcites and hydrocalumite are used. Method used (see Patent Documents 4 and 5), method of reducing and decomposing with reductive iron powder (see Patent Document 6 etc.), method using ferrous sulfate (see Patent Document 7 etc.), apatite And the like (see Patent Document 8, etc.), and the method using a heated dehydrated calcium sulfoaluminate hydrate (see Patent Document 9, etc.).

  However, the method using activated carbon simply adsorbs harmful substances, and the adsorbate is easily released into the environment, so that immobilization is not sufficient.

  In addition, the method using zeolite exhibits adsorption and ion exchange reaction and can reduce cadmium, lead, etc., but heavy metals such as chromium, selenium, arsenic, nitrate nitrogen, nitrite nitrogen, fluorine There was a problem that the ability to reduce boron and the like could hardly be expected.

  The method using hydrotalcite and hydrocalumite is a very expensive material itself and not only economically low, but also harmful substances such as hexavalent chromium cannot be sufficiently reduced. There was a problem of being limited.

  The method using reducing iron powder has no immediate effect, and there is a problem that it takes a long time to obtain the effect. Although the method using ferrous sulfate has immediate effect, it adds sulfate ions that it has to the system, and sulfate ions become harmful substances, such as reducing the effects of other harmful substance reducing materials. And the problem is that the target substances are very limited.

  The method using apatite, like zeolite, can reduce cadmium, lead, etc., but it can hardly be expected to reduce heavy metals such as chromium, selenium, arsenic, nitrate nitrogen, nitrite nitrogen, boron, etc. There was a problem.

  As described above, the conventional harmful substance reducing materials have problems such that a sufficient harmful substance reduction effect cannot be obtained depending on the type of the harmful substance, and the effect is reduced when a plurality of harmful substances coexist. Moreover, when using a synthetic product, there also existed the subject that cost became high.

  On the other hand, it is also important to reduce the volume of industrial byproducts and to contribute to solving environmental problems by suppressing the generation of industrial byproducts or effectively using industrial byproducts. As such an industrial by-product, the present inventors paid attention to steelmaking slag generated in large quantities in the process of making pig iron into steel.

  Steelmaking slag is a general term for slag generated in the process of making pig iron into steel, and includes converter slag, various types of hot metal pretreatment slag, refining slag, and the like. Although about 13 million tons of these steelmaking slags are generated annually, the utilization rate is still lower than that of blast furnace slag generated at the stage of obtaining pig iron (see Non-Patent Document 1 etc.). Thus, finding a use of steelmaking slag generated from the steel industry, which can be said to be representative of mass production, is a great social issue.

  A water treatment material and a water treatment method in which converter slag is used in combination with an alkali metal or an alkaline earth metal are known (see, for example, Patent Document 10). The present invention mainly relates to the treatment of phosphoric acid, and it is disclosed that the present invention is also effective in reducing arsenic. However, the harmful substance reducing effect of this water treatment material is not always sufficient. For example, when used in an environment where the concentration of polyvalent anions such as sulfate ion, nitrate ion, carbonate ion is high, the harmful substance reducing effect is not obtained. There was a problem of extremely decreasing.

  Moreover, the method of stabilizing the waste containing a heavy metal using steelmaking slag, such as secondary refining slag, hot metal pretreatment slag, and converter slag, is known (refer to patent documents 11 etc.). In this invention, elution of lead, cadmium, and zinc can be suppressed. However, this method requires that the treatment temperature be 60 ° C. or higher, and there is a problem that a sufficient elution suppression effect cannot be obtained at room temperature.

  In addition, a method of stabilizing waste containing chromium using a powder containing calcium aluminate, calcium silicate, calcium aluminosilicate and a powder containing sulfate radicals is known (see Patent Document 12, etc.). This invention discloses that the secondary refining slag and sulfate can be used to suppress elution of chromium and at the same time suppress elution of fluorine. Moreover, it is known that the powder of secondary refining slag containing calcium aluminate is effective in suppressing the elution of fluorine (see Patent Documents 13 to 15). However, the effect varies depending on the type of the toxic substance, and there has been a demand for a toxic substance reducing material that exhibits an excellent reduction effect for any toxic substance.

  Therefore, in view of the effective use of steelmaking slag, which has not been sufficiently advanced in effective use and most of which has been industrial waste, the present inventors have developed a harmful substance reducing material that is economical and excellent in reducing harmful substances. As a result of intensive studies on the development, the present inventors have found that steelmaking slag powder having characteristics such as a specific elemental composition is excellent in reducing many kinds of harmful substances, thereby completing the present invention.

JP 05-076619 A, JP 2002-239347 A JP 2001-238980 Japanese Patent Laid-Open No. 10-128313 JP 2001-252675 A Japanese Unexamined Patent Publication No. 07-108280 Japanese Unexamined Patent Publication No. 09-085224 Japanese Unexamined Patent Publication No. 08-182984 Japanese Patent Laid-Open No. 2001-070926 Japanese Patent Laid-Open No. 2002-086139 JP 2000-037676 JP 2002-059141 A JP 2000-225383 A JP 2000-246267 A JP 2001-259570 Edited by Steel Slag Association, “Steel Slag Production and Utilization in 2002”, [online], [Updated on July 11, 2003], Internet <URL: http: //homepage2.nifty.com/SLG/tokei/ japan / 14 / index.htm>

  In view of the effective use of steelmaking slag, whose effective use has not been sufficiently advanced and most of which has been industrial waste, an economical and harmful substance reducing material that is excellent in reducing various harmful substances is provided.

The present invention has been Al ₂ O ₃ content of 3% or more, and the total amount of Fe ₂ O ₃ and Al ₂ O ₃ content Ri der 15% or more, fluorine, boron, the total amount of sulfur is 2 % Is a hazardous substance reducing material containing steelmaking slag with a Blaine specific surface area of 3,000 cm ² / g or more . Steelmaking slag has a CaO content of 35% or more, free lime content of 15% or less, and SiO ₂ content. It is a method for treating sewage characterized by using the hazardous substance reducing material in an amount of 20% or less, and using the hazardous substance reducing material, and a soil treatment method using the hazardous substance reducing material. is there.

The steelmaking slag used in the present invention is a generic term for slag generated in the steelmaking process among steel slags, and is not particularly limited. Specific examples thereof include various types of hot metal pretreatment slag such as converter slag, desiliconization, decarburization, and dephosphorization, and refining slag. The chemical composition and compound composition of these steelmaking slags vary widely depending on the steelmaking method and process. As the chemical components, for _{example, CaO, SiO 2, Fe 2} O 3, Al 2 O 3, MgO, TiO 2, MnO, Na 2 O, K 2 O, S, P 2 O 5, B 2 O 3 and F etc. are mentioned.

Examples of the compound include calcium aluminoferrite such as 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ and 6CaO · 2Al ₂ O ₃ · Fe ₂ O ₃ and 6CaO · Al ₂ O ₃ · 2Fe ₂ O ₃ ; · Fe ₂ O ₃ and 2CaO · Fe ₂ O ₃ calcium such as ferrite, calcium aluminate such as 12CaO · 7Al ₂ O ₃ and _{12CaO · 7Al 2 O 3 · CaF} 2, 3CaO · Al 2 O 3, gehlenite 2CaO · Al ₂ O ₃ · SiO ₂ and anorthite _{CaO · Al 2 O 3 · 2SiO} 2 and calcium aluminosilicate, Merubinaito 3CaO · MgO · 2SiO ₂ and Akerumanaito 2CaO · MgO · 2SiO ₂ and Monte celite CaO · MgO · SiO _2, etc. calcium magnesium silicate, tri-calcium silicate 3CaO · SiO ₂ or dicalcium silicate 2CaO · SiO ₂ and rankinite night 3CaO · 2SiO ₂ and wollastonite CaO · SiO ₂ such as calcium silicate, Kasupidin 3CaO · 2SiO ₂ · CaF _2, fluoroapatite Or apatite such as hydroxyapatite DOO, wustite FeO, free lime, magnetite Fe ₃ O _4, leucite _{(K 2 O, Na 2 O} ) · Al 2 O 3 · SiO 2 and the like. In steelmaking slag, each of these components exists as crystalline or amorphous.

The content of Fe ₂ O ₃ and Al ₂ O ₃ in steelmaking slag is extremely important because it is related to the effect of reducing harmful substances. In the present invention, the content of Al ₂ O ₃ is 3% or more, and the total content of Fe ₂ O ₃ and Al ₂ O ₃ is 15% or more, and the content of Fe ₂ O ₃ and Al ₂ O ₃ The total amount is preferably 20% or more. If the content of Al ₂ O ₃ is less than 3% or the total content of Fe ₂ O ₃ and Al ₂ O ₃ is less than 15%, the harmful substance reducing effect is low, and heating is performed when reducing harmful substances. Therefore, the harmful substances may be evaporated or scattered by heating during the reduction process of the harmful substances.

Here, the iron oxide may contain iron in the form of Fe ₂ O ₃ forming calcium ferrite or calcium aluminoferrite, as well as iron in the form of wustite FeO or magnetite Fe ₃ O _4. is there. Wustite FeO, magnetite Fe ₃ O _{4 and the} like are known as reducing agents, and have the effect of reducing or decomposing harmful substances, but in the present invention, the iron content forming calcium ferrite, calcium aluminoferrite, etc. A high content is preferable. Further, these iron components may exist in any form of crystalline or amorphous.

In addition, the existence form of Fe ₂ O ₃ and Al ₂ O ₃ in steelmaking slag is not particularly limited, but heavy metals such as lead, cadmium, chromium, arsenic, selenium, nitrate nitrogen, nitrite nitrogen, boron, phosphorus, In applications that reduce dioxins, volatile organic compounds such as trichlorethylene and tetrachlorethylene, the content of Fe ₂ O ₃ and Al ₂ O ₃ in steelmaking slag is important. That is, even if just adding a compound containing Fe ₂ O _3, Al ₂ O _3, or the steelmaking slag content is less of Fe ₂ O _3, Al ₂ O _3, or the, same effect as the present invention is not obtained. Although its action mechanism is not clear, it is considered that the effects of the present invention can be obtained by the interaction of each component in the steelmaking slag and Fe ₂ O ₃ and Al ₂ O ₃ .

The CaO content in steelmaking slag is also important. The CaO content is preferably 35% or more, and more preferably 40% or more. In this case, free lime is often present, but the presence of free lime also has a preferable aspect from the viewpoint of reducing phosphoric acid and the like, specifically, a range that does not substantially hinder the object of the present invention, specifically If it is within 15%, there is no problem. In addition, the content of SiO ₂ is preferably 20% or less, more preferably 15% or less, from the viewpoint of ensuring a high content of Fe ₂ O ₃ , Al ₂ O ₃ , and CaO.

On the other hand, the content of fluorine, boron, and sulfur in the harmful substance reducing material is preferably low, and the total content of these elements is preferably 2% or less. If the total amount exceeds 2%, the effect of reducing harmful substances may not be sufficient. For example, 12CaO · 7Al ₂ O ₃ · CaF ₂ , caspidine 3CaO · 2SiO ₂ · CaF ₂ , fluorine apatite and the like, which are fluorine-containing compounds, inhibit the effects of the present invention, so the content of these compounds is small. Is preferred. The same is true for compounds containing boron or sulfur.

The particle size of the steel slag of the invention, but are not particularly limited, is preferably 3,000~9,000cm ^{2 /} g in Blaine specific surface area value, 4,000~6,000cm ^{2 /} g is more preferable. If it is less than 3,000 cm ² / g, the effect of reducing harmful substances may not be sufficient, and it is uneconomical to grind it to exceed 9,000 cm ² / g.

  The harmful substance in the present invention is not particularly limited. For example, heavy metals such as chromium, selenium, arsenic, cadmium, lead and mercury, all cyan, nitrate nitrogen, Nitrite nitrogen, fluorine, boron, phosphorus, and organic substances include dioxins, volatile organic compounds such as trichlorethylene and tetrachloroethylene, PCB, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1 -Dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, benzene, organic phosphorus and the like. In addition, examples of harmful substances for which environmental standards are not defined include copper, zinc, molybdenum, amine compounds, various environmental hormones, endocrine disrupting substances, and the like.

  In the present invention, calcium ferrite, calcium aluminate, calcium aluminoferrite, various portland cements, filler cement mixed with limestone powder, etc., and environmentally friendly cement manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials, Powders such as so-called eco-cement, granulated blast furnace slag, fly ash, etc., all hydrates produced from these hydraulic materials, latent hydraulic substances and pozzolanic substances, calcium oxide, blast furnace chilled slag, magnesium oxide and hydroxide Magnesium compounds such as magnesium, dolomite and hydrotalcite, carbonaceous materials such as activated carbon, bentonites which are layered compounds represented by montmorillonite and kaolinite, zeolites, phosphoric acids such as sepiolite, apatite and zirconium phosphate Antimonates such as antimony trioxide and antimony pentoxide, activated carbon, sulfur compounds such as polysulfides, sulfides, thiosulfates, sulfites and thioureas, amalgam, reduced iron powder, ferrous sulfate and chloride One or more of the group consisting of iron compounds such as ferrous iron, water-soluble polymers such as celluloses, polyvinyl alcohol and chitosan, dialkyldithiocarbamic acids, quinoline compounds, polyamines, saccharides, etc. They can be used in combination as long as the purpose is not substantially inhibited.

  The above materials may be used in combination with the hazardous substance reducing material of the present invention, or may be used separately. For example, after the primary treatment is performed with the hazardous substance reducing material of the present invention, the secondary treatment can be performed with the above materials. It is preferable to carry out such double or more harmful substance reduction treatment from the viewpoint of reducing harmful substances in a multifaceted manner.

  The method of using the hazardous substance reducing material of the present invention is not particularly limited. For example, when used for sewage treatment, it is used by adding it to sewage in the form of powder or granules, followed by solid-liquid separation. Alternatively, it may be processed into pellets, columns, filters or the like and passed through treated water.

  As a method for producing pellets and filters, for example, a method of pressure-molding the hazardous substance reducing material of the present invention, or a method of molding by curing with a small amount of hydraulic material, such as various Portland cements or alumina cement, etc. good.

  In the case of using for soil, a method of using the harmful substance reducing material of the present invention by mixing and stirring with soil, a method of spraying and using, a method of injecting into the soil in a slurry form, and the like can be mentioned. At this time, it can be used in combination with various cements.

Further, the mixing ratio of the soil and the hazardous substance reducing material of the present invention is not particularly limited, but the hazardous substance reducing material is preferably 100 to 300 kg per 1 m ^{3 of} soil. Adverse mixing ratio of the material reducing material may be insufficient toxic substances reducing effect is less than 100kg against soil 1 m ^3, may not toxic substances reducing effect can be obtained further be greater than 300 kg.

The hazardous substance reducing material of the present invention can reduce many kinds of harmful substances, and has such effects as little inhibitory effect due to coexisting substances and very high reduction ability.

Various steelmaking slags having the compositions shown in Table 1 were pulverized to a brain specific surface area of 5,000 cm ² / g to obtain hazardous substance reducing materials. 1 g of the hazardous substance reducing material was added to 50 ml of a solution containing the harmful substances shown in Table 2, and the mixture was stirred for 3 hours, and then separated into solid and liquid. And the density | concentration of the harmful | toxic substance which remains in a liquid phase was measured, and the reduction rate (henceforth "reduction rate") of a harmful | toxic substance was calculated | required. Moreover, the same experiment was conducted when a commercially available harmful substance reducing material was used. The results are also shown in Table 2.

<Materials used>
Steelmaking slag (1): Converter slag, CaO contains 10.7% free lime and does not contain calcium aluminate.
Steelmaking slag (2): Hot metal pretreatment slag, CaO contains 0.8% free lime and does not contain calcium aluminate.
Steelmaking slag (3): Refined slag, CaO free lime content 8.3%, calcium aluminate not included.
Steelmaking slag (4): Dephosphorized slag CaO contains 8.9% free lime and does not contain calcium aluminate.
Steelmaking slag (5): Hot metal pretreatment slag, CaO contains 0.8% free lime and does not contain calcium aluminate.
Steelmaking slag (6): Hot metal pretreatment slag, CaO contains 0.8% free lime and does not contain calcium aluminate.

Hazardous substance reducing material A: Commercial zeolite harmful substance reducing material B: Commercial activated carbon harmful substance reducing material C: Commercial hydrotalcite harmful substance Cr: Hexavalent chromium standard solution, hexavalent chromium concentration 1,000 mg / liter solution, Kanto Chemical Hazardous Substance Se: Selenium Standard Solution, Selenium Concentration 1,000mg / L Solution, Kanto Chemical Hazardous Substance As: Arsenic Standard Solution, Arsenous Acid Concentration 1,000mg / L Solution, Kanto Chemical Hazardous Substance F: Sodium Fluoride, Powdered, reagent grade 1, Wako Pure Chemical Hazardous Substance B: boric acid, powder, reagent grade 1, Wako Pure Chemical Hazardous Substance NO ₃ : Sodium nitrate, reagent grade 1, Wako Pure Chemical Hazardous Substance P: Ortholine Sodium acid (Na ₃ PO ₃ ), powder, reagent grade 1, Wako Pure Chemical's hazardous substance TCE (trichloroethylene): reagent grade 1, Wako Pure Chemical

<Measurement method>
Hazardous substance concentration: Measured according to Environmental Agency Notification No. 46.
Hazardous substance reduction rate (reduction rate): Calculated by the following formula based on the concentration of harmful substances measured based on Environmental Agency Notification No. 46.
Hazardous substance reduction rate (%) = C / C ₀ × 100
However, C ₀ : Total amount of hazardous substance elution when no hazardous substance reducing material is added
C: Total amount of toxic substance elution when toxic substance reducing material is added.

注：「F+B+S」は、各製鋼スラグ中のフッ素、ホウ素、及びイオウの含有量の合計。

Note: “F + B + S” is the total content of fluorine, boron, and sulfur in each steelmaking slag.

注：TCEはトリクロロエチレン。

Note: TCE is trichlorethylene.

The same procedure as in Example 1 was carried out except that the bulk slag used as a raw material for the steelmaking slag (1) was used, the crushing strength was changed, and a harmful substance reducing material having a brain specific surface area as shown in Table 3 was prepared. The results are also shown in Table 3.

注：TCEはトリクロロエチレン。

Note: TCE is trichlorethylene.

For soil that uses steelmaking slag (1) as a hazardous substance reducing material, contains chromium, selenium, and arsenic, and as a result of an elution test based on the Environmental Agency Notification No. 46, the amount of elution of heavy metals exceeds the environmental standard value. The soil treatment effect was confirmed. 150 kg of hazardous substance reducing material was added to 1 m ^{3 of} soil, mixed well, and the soil was treated. The elution test based on the Environmental Agency Notification No. 46 method was performed again using the treated soil. The results are shown in Table 4. For comparison, the results of the same operation using ordinary Portland cement are also shown.

<Materials used>
Soil: Kanto loam soil added with toxic metal compounds. The concentrations of hexavalent chromium, selenium, and arsenic were adjusted to 30 mg / liter, 5 mg / liter, and 5 mg / liter, respectively.
Ordinary Portland cement (OPC): Uses a mixture of three commercial products in equal amounts.

注：OPCは普通ポルトランドセメント

Note: OPC is ordinary Portland cement

The material for reducing harmful substances according to the present invention contributes to reducing the volume of steelmaking slag as industrial waste by making effective use of steelmaking slag that has not been fully utilized and is mostly industrial waste. Because it is economical, it can reduce many types of harmful substances, has no inhibition by coexisting substances, and has a large ability to reduce each harmful substance, chemical industry, electrical / electronic industry, Suitable for reducing harmful substances contained in soil and drainage contaminated by harmful substances generated from medical facilities and various research facilities.

Claims (4)

A is Al ₂ O ₃ content of 3% or more, and, Fe ₂ O ₃ and Al ₂ O ₃ Ri der total more than 15% of the content of fluorine, boron, in a total amount of sulfur of 2% or less, Hazardous material reducing material containing steelmaking slag with a specific surface area of Blaine of 3,000 cm ² / g or more . Steelmaking slag, CaO content 35% or more, free lime content 15% or less, SiO ₂ The hazardous substance reducing material according to claim 1, wherein the content is 20% or less. Method of processing sewage, which comprises using a harmful substance reducing material according to one of claims 1-2. Processing method of soil, which comprises using a hazardous substance reducing material according to one of claims 1-2.