JP5599061B2 - Neutral solidifying material additive, neutral solidifying material and method for suppressing elution of heavy metals - Google Patents

Neutral solidifying material additive, neutral solidifying material and method for suppressing elution of heavy metals Download PDF

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JP5599061B2
JP5599061B2 JP2010238941A JP2010238941A JP5599061B2 JP 5599061 B2 JP5599061 B2 JP 5599061B2 JP 2010238941 A JP2010238941 A JP 2010238941A JP 2010238941 A JP2010238941 A JP 2010238941A JP 5599061 B2 JP5599061 B2 JP 5599061B2
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祐介 松山
政彦 守屋
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太平洋セメント株式会社
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本発明は、重金属類を含む土壌等を固化して、重金属類の溶出を抑制することができる中性固化材用の添加材、中性固化材および重金属類の溶出抑制方法に関する。   The present invention relates to an additive for a neutral solidifying material that can solidify soil or the like containing heavy metals and suppress elution of heavy metals, a neutral solidifying material, and a method for inhibiting elution of heavy metals.
工場、事業所、廃棄物処理場の跡地等の土壌が、鉛、ヒ素等の重金属やフッ素等により汚染されているという事例が、近年、多数報告されている。
重金属等により土壌が汚染されると、重金属等の汚染域が地下水にまで拡散し、汚染された地下水を経由して最終的には人体や穀物に重金属等が蓄積され、健康を害する事態が生じうる。
また、土壌中の重金属等の濃度が環境基準値を超えると、跡地をそのまま利用できなくなり、土地の有効利用の観点からも問題である。
In recent years, there have been many reports that soils such as sites of factories, offices, and waste disposal sites are contaminated with heavy metals such as lead and arsenic, fluorine, and the like.
When soil is contaminated with heavy metals, the contaminated area of heavy metals diffuses into the groundwater, and eventually the heavy metals are accumulated in the human body and grain via the contaminated groundwater, resulting in a health hazard. sell.
In addition, if the concentration of heavy metals in the soil exceeds the environmental standard value, the site cannot be used as it is, which is also a problem from the viewpoint of effective use of the land.
これらの問題に対処するために、汚染土壌中の重金属等を固化して、重金属等が土壌から溶出するのを防止する手段として、セメント系、石灰系、石膏系およびマグネシア系の固化材が用いられている。   To deal with these problems, cement-based, lime-based, gypsum-based and magnesia-based solidified materials are used as a means to solidify heavy metals in contaminated soil and prevent heavy metals from leaching from the soil. It has been.
しかし、セメント系および石灰系の固化材のスラリーは、pH12程度の高アルカリ性を呈するため、該固化材を用いて汚染土壌を固化した改良土から、アルカリ性条件下で溶解しやすい鉛等の両性金属が溶出するという問題がある。また、改良土を埋立てる場合や盛土等として再利用する場合に、降雨等により改良土や盛土から滲出する液のpHは、排水基準であるpH5.8〜8.6(水道法第4条に基づく水質基準許容値)に適合することが求められている。   However, since the slurry of cement-based and lime-based solidified material exhibits a high alkalinity of about pH 12, amphoteric metals such as lead that are easily dissolved under alkaline conditions from improved soil obtained by solidifying contaminated soil using the solidified material. Has a problem of elution. Moreover, when reclaiming improved soil or reusing it as embankment, etc., the pH of the liquid that exudes from the improved soil or embankment due to rainfall, etc. is pH 5.8 to 8.6 (Article 4 of the Water Supply Law) To meet water quality standard tolerances based on
また、石膏系固化材は、ほぼ中性ではあるが固化強度が低いため、その用途は強度が要求されない分野に限られる。
更に、マグネシア系固化材は、セメント系や石灰系の固化材よりもアルカリ性は低いが、それでもなお、マグネシア系固化材を添加した改良土等から滲出する液のpHは、10程度になるため、前記排水基準のpHを満たすことは難しい。また、その固化強度は石膏系固化材よりも高いとはいえ、まだ十分とはいえない。
In addition, since the gypsum-based solidified material is almost neutral but has a low solidification strength, its use is limited to fields where strength is not required.
Further, the magnesia-based solidified material is less alkaline than the cement-based or lime-based solidified material, but the pH of the liquid exuded from the improved soil or the like to which the magnesia-based solidified material is added is about 10, It is difficult to satisfy the pH of the drainage standard. Further, although its solidification strength is higher than that of the gypsum solidified material, it is still not sufficient.
そこで、マグネシア系固化材においてアルカリ性の低減と固化強度の向上を目的とした中性固化材が、種々提案されている。
例えば、特許文献1には、15〜40重量部の酸化マグネシウムと4〜10重量部の硫酸アルミニウムおよび/または硫酸鉄と、残部がせっこうよりなる含水土壌用固化材が提案されている。該固化材は、酸化マグネシウムのアルカリ性を低減しつつ、固化強度の低下を抑制するために、酸化マグネシウムよりも少ない量の酸性塩(硫酸アルミニウムや硫酸鉄)を混合したものである。しかし、酸性塩は強酸と弱塩基の塩であって弱酸性であるため、強アルカリ性の酸化マグネシウムよりも少ない量の酸性塩の添加では、アルカリ性の低減は十分とはいえず、また、強度発現性の低いせっこうを50重量%以上も含有するため固化強度も不十分である。
Accordingly, various neutral solidification materials have been proposed for the purpose of reducing alkalinity and improving solidification strength in magnesia-based solidification materials.
For example, Patent Document 1 proposes a solidified material for hydrous soil consisting of 15 to 40 parts by weight of magnesium oxide, 4 to 10 parts by weight of aluminum sulfate and / or iron sulfate, and the balance of gypsum. The solidification material is a mixture of an acid salt (aluminum sulfate or iron sulfate) in an amount smaller than that of magnesium oxide in order to suppress the decrease in solidification strength while reducing the alkalinity of magnesium oxide. However, since the acid salt is a salt of strong acid and weak base and is weakly acidic, the addition of an acid salt in an amount smaller than that of strongly alkaline magnesium oxide does not reduce the alkalinity sufficiently, and also shows strength development. Since it contains 50% by weight or more of low-gypsum gypsum, its solidification strength is insufficient.
特許文献2には、酸化マグネシウムと、硫酸アルミニウム等の固化剤とを含む土壌固化剤が提案されている。また、特許文献3には、酸化マグネシウム100重量部に、10〜100重量部の酸性固化助剤を混合した土壌中性固化材が提案されている。
しかし、特許文献2および3の固化材は、いずれも特許文献1に記載の固化材と同様に、50質量%以下の酸性塩(酸性剤)しか含まないため、アルカリ性の低減は十分とはいえない。
Patent Document 2 proposes a soil solidifying agent containing magnesium oxide and a solidifying agent such as aluminum sulfate. Further, Patent Document 3 proposes a soil neutral solidification material in which 10 to 100 parts by weight of an acidic solidification aid is mixed with 100 parts by weight of magnesium oxide.
However, since the solidifying materials of Patent Documents 2 and 3 both contain only 50% by mass or less of an acidic salt (acidic agent), like the solidified material described in Patent Document 1, the reduction in alkalinity is sufficient. Absent.
特開2000−109829号公報JP 2000-109829 A 特開2000−239660号公報JP 2000-239660 A 特開2002−206090号公報JP 2002-206090 A
そこで、本発明は、固化処理物から滲出する液のpHが排水基準のpH5.8〜8.6を満たし、固化強度が高く、重金属類の溶出を環境基準値以下に抑制することができる中性固化材用の添加材、中性固化材および重金属類の溶出抑制方法を提供することを目的とする。
なお、本発明の中性固化材が溶出抑制の対象とする前記重金属類とは、カドミウム、鉛、六価クロム、ヒ素、総水銀、アルキル水銀、セレン、フッ素、ホウ素およびシアンの第二種特定有害物質、並びに、要監視項目として注意が必要な、ニッケル、モリブデン、アンチモン、硝酸性窒素および亜硝酸性窒素等をいう。
Therefore, the present invention is a solution in which the pH of the liquid exuded from the solidified product satisfies pH 5.8 to 8.6 of the drainage standard, has a high solidification strength, and can suppress elution of heavy metals below the environmental standard value. An object of the present invention is to provide a method for suppressing elution of an additive for a neutral solidifying material, a neutral solidifying material, and heavy metals.
In addition, the said heavy metal which the neutral solidification material of this invention makes the object of elution suppression is cadmium, lead, hexavalent chromium, arsenic, total mercury, alkyl mercury, selenium, fluorine, boron, and cyan | 2nd type identification Toxic substances and nickel, molybdenum, antimony, nitrate nitrogen, nitrite nitrogen, etc. that require attention as items to be monitored.
本発明者は、上記課題を解決するために鋭意検討した結果、特定量の酸性硫酸塩および特定量の炭酸カルシウム含有物を含む中性固化材用の添加材と、特定量の軽焼マグネシアまたは軽焼マグネシア部分水和物とを含有する中性固化材は、前記本発明の目的を達成できることを見出し、本発明を完成した。   As a result of intensive studies to solve the above problems, the present inventor has found that a specific amount of an acid sulfate and a specific amount of calcium carbonate-containing additive for a neutral solidifying material and a specific amount of light-burned magnesia or The present inventors have found that a neutral solidified material containing light-burned magnesia partial hydrate can achieve the object of the present invention, and completed the present invention.
すなわち、本発明は、以下の[1]〜[3]を提供する。
[1]酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を、炭酸カルシウム換算で3〜42質量部含む中性固化材用の添加材。
[2]前記[1]に記載の中性固化材用の添加材と、軽焼マグネシアまたは軽焼マグネシア部分水和物とを含有する中性固化材であって、前記[1]に記載の酸性硫酸塩100質量部に対し、前記軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部含有する中性固化材。
[3]処理対象物100質量部に対し、前記[2]に記載の中性固化材を1〜40質量部添加し混合する重金属類の溶出抑制方法。
That is, the present invention provides the following [1] to [3].
[1] An additive for a neutral solidifying material containing 3 to 42 parts by mass of calcium carbonate-containing material in terms of calcium carbonate with respect to 100 parts by mass of acidic sulfate.
[2] A neutral solidified material containing the additive for a neutral solidified material according to [1] and light-burned magnesia or light-burned magnesia partial hydrate, according to [1] The neutral solidification material which contains 7-98 mass parts of said light-burning magnesia or light-burning magnesia partial hydrate in conversion of magnesium oxide with respect to 100 mass parts of acidic sulfates.
[3] A method for suppressing elution of heavy metals, wherein 1 to 40 parts by mass of the neutral solidifying material according to [2] is added to and mixed with 100 parts by mass of the processing object.
本発明の中性固化材等によれば、固化処理物から滲出する液のpHが排水基準のpH5.8〜8.6を満たし、固化強度が高く、重金属類の溶出を環境基準値以下に抑制することができる。   According to the neutral solidifying material and the like of the present invention, the pH of the liquid exuded from the solidified product satisfies the drainage standard pH 5.8 to 8.6, the solidification strength is high, and the elution of heavy metals is below the environmental standard value. Can be suppressed.
本発明は、中性固化材用の添加材、これを含む中性固化材および該中性固化材を用いた重金属類の溶出抑制方法である。   The present invention relates to an additive for a neutral solidifying material, a neutral solidifying material containing the additive, and a method for suppressing elution of heavy metals using the neutral solidifying material.
中性固化材用の添加材について、以下に説明する。
本発明の中性固化材用の添加材は、酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を、炭酸カルシウム換算で3〜42質量部含むものである。
The additive for the neutral solidifying material will be described below.
The additive for a neutral solidifying material of the present invention contains a calcium carbonate-containing material in an amount of 3 to 42 parts by mass in terms of calcium carbonate with respect to 100 parts by mass of the acidic sulfate.
前記酸性硫酸塩は、硫酸と弱塩基の塩であり、水溶液にした場合に酸性を呈する塩である。従って、該酸性硫酸塩には、pHが約7である半水石膏や二水石膏およびpHが約11である無水石膏は含まれない。
該酸性硫酸塩としては、例えば、硫酸アルミニウム、硫酸第一鉄等およびこれらの水和物から選ばれる1種または2種以上が挙げられる。該酸性硫酸塩は、アルカリ性を呈するマグネシア系固化材のpHを中性域にまで低減することができる。
The acidic sulfate is a salt of sulfuric acid and a weak base, and is an acidic salt when made into an aqueous solution. Accordingly, the acidic sulfate does not include hemihydrate or dihydrate gypsum having a pH of about 7 and anhydrous gypsum having a pH of about 11.
Examples of the acidic sulfate include one or more selected from aluminum sulfate, ferrous sulfate, and the like and hydrates thereof. The acidic sulfate can reduce the pH of the magnesia-based solidified material exhibiting alkalinity to a neutral range.
また、前記炭酸カルシウム含有物は、炭酸カルシウムを80質量%以上含むものが好ましく、85質量%以上含むものがより好ましく、90質量%以上含むものが更に好ましい。該炭酸カルシウム含有物としては、例えば、工業用炭酸カルシウム粉末、試薬の炭酸カルシウム粉末、石灰石粉末、炭酸カルシウムを主成分とする貝殻の粉砕物またはサンゴの粉砕物等が挙げられる。その中でも、石灰石粉末は低コストであるため好適である。   The calcium carbonate-containing material preferably contains 80% by mass or more of calcium carbonate, more preferably 85% by mass or more, and still more preferably 90% by mass or more. Examples of the calcium carbonate-containing material include industrial calcium carbonate powder, reagent calcium carbonate powder, limestone powder, ground shells of calcium carbonate, coral grounds, and the like. Among them, limestone powder is preferable because of its low cost.
炭酸カルシウム含有物のブレーン比表面積は、3000〜7000cm/gが好ましく、4000〜6800cm/gがより好ましい。該値が3000cm/g未満であると、後述する酸性硫酸塩との反応性が低いため二水石膏の生成が十分ではなく、該値が7000cm/gを超えると、粉砕に手間がかかり粉砕コストが高くなる。 Blaine specific surface area of the calcium carbonate-containing material is preferably 3000~7000cm 2 / g, 4000~6800cm 2 / g is more preferable. When the value is less than 3000 cm 2 / g, the production of dihydrate gypsum is not sufficient due to low reactivity with acidic sulfate described later, and when the value exceeds 7000 cm 2 / g, it takes time and effort to grind. The grinding cost is increased.
前記中性固化材用の添加材は、水中または湿潤状態において、酸性硫酸塩由来の硫酸イオンと炭酸カルシウム含有物由来のカルシウムイオンが反応して、二水石膏を生成する。該二水石膏は、それ本来の、固化処理物の初期強度を高めるという作用に加え、二水石膏の生成過程で、結晶水として化合物(二水石膏)内に水を結合するため、固化処理物の含水量が減少する。この結果、本発明の添加材を含有する固化材は、二水石膏の形態で石膏を含有する固化材と比べ、更に固化強度が増大する。   The additive for the neutral solidifying material reacts with sulfate ions derived from acidic sulfates and calcium ions derived from calcium carbonate-containing materials in water or in a wet state to form dihydrate gypsum. In addition to its original effect of increasing the initial strength of the solidified product, the dihydrate gypsum binds water into the compound (dihydrate gypsum) as crystal water in the formation process of the dihydrate gypsum. The water content of the object is reduced. As a result, the solidification material containing the additive of the present invention has a further increased solidification strength as compared with the solidification material containing gypsum in the form of dihydrate gypsum.
上述した通り、本発明の中性固化材用の添加材は、酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を、炭酸カルシウム換算で3〜42質量部含むものであり、5〜40質量部含むものが好ましく、10〜30質量部含むものがより好ましい。該含有量が3質量部未満では固化強度の増大効果が低く、該含有量が42質量部を超えると、酸性硫酸塩が炭酸カルシウムとの反応により消費されすぎて、固化材のpH低減効果が低下する。   As described above, the additive for a neutral solidifying material of the present invention contains 3 to 42 parts by mass of calcium carbonate-containing material in terms of calcium carbonate with respect to 100 parts by mass of acidic sulfate, and 5 to 40 masses. Those containing parts are preferred, and those containing 10 to 30 parts by mass are more preferred. When the content is less than 3 parts by mass, the effect of increasing the solidification strength is low, and when the content exceeds 42 parts by mass, the acidic sulfate is excessively consumed by the reaction with calcium carbonate, and the effect of reducing the pH of the solidification material is obtained. descend.
次に、本発明の中性固化材について説明する。
本発明の中性固化材は、前記中性固化材用の添加材と、軽焼マグネシアまたは軽焼マグネシア部分水和物とを含有するものであって、酸性硫酸塩100質量部に対し、軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部含有する中性固化材である。
Next, the neutral solidifying material of the present invention will be described.
The neutral solidification material of the present invention contains the additive for the neutral solidification material and light-burned magnesia or light-burned magnesia partial hydrate. It is a neutral solidified material containing 7 to 98 parts by mass of calcined magnesia or light calcined magnesia partial hydrate in terms of magnesium oxide.
前記軽焼マグネシアは、例えば、炭酸マグネシウムおよび/または水酸化マグネシウムを含む固形物を、650〜1300℃で焼成することによって得ることができる。   The light-burned magnesia can be obtained, for example, by firing a solid containing magnesium carbonate and / or magnesium hydroxide at 650 to 1300 ° C.
前記固形物中の炭酸マグネシウムおよび/または水酸化マグネシウムの含有率は80質量%以上であり、85質量%以上が好ましく、90質量%以上がより好ましい。該含有率が80質量%未満では、軽焼マグネシアに含まれる酸化マグネシウム成分が少なく、固化強度や重金属類の溶出抑制効果が低下する傾向がある。
前記固形物としては、マグネサイト、ドロマイト、ブルーサイトまたは海水中のマグネシウム成分を消石灰等のアルカリで沈殿させて得た水酸化マグネシウム等の、塊状物または粉粒状物が挙げられる。
The content of magnesium carbonate and / or magnesium hydroxide in the solid is 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more. When the content is less than 80% by mass, the magnesium oxide component contained in the light-burned magnesia is small, and the solidification strength and the elution suppressing effect of heavy metals tend to decrease.
Examples of the solid material include lump or powdery particles such as magnesite, dolomite, brucite, or magnesium hydroxide obtained by precipitating a magnesium component in seawater with an alkali such as slaked lime.
前記固形物の焼成温度は、通常、650〜1300℃であり、750〜950℃が好ましく、800〜900℃がより好ましい。該焼成温度が650℃未満では、軽焼マグネシアが生成し難く、該焼成温度が1300℃を超えると、固化強度や重金属類の溶出抑制効果が低下する虞がある。前記固形物の焼成時間は、固形物の仕込み量や粒径等にもよるが、通常、30分〜5時間である。   The baking temperature of the solid is usually 650 to 1300 ° C, preferably 750 to 950 ° C, and more preferably 800 to 900 ° C. When the firing temperature is less than 650 ° C., light-burned magnesia is difficult to generate, and when the firing temperature exceeds 1300 ° C., the solidification strength and the effect of suppressing the elution of heavy metals may be reduced. The firing time of the solid is usually 30 minutes to 5 hours, although it depends on the amount of solids charged and the particle size.
前記軽焼マグネシアに代えて使用する軽焼マグネシア部分水和物は、前記軽焼マグネシアを粉砕した後、該粉砕物に水を添加して撹拌し混合するか、または、該粉砕物を相対湿度80%以上の雰囲気下に1週間以上保持することにより得られる。   The light-burned magnesia partial hydrate to be used in place of the light-burned magnesia is obtained by pulverizing the light-burned magnesia and then adding water to the pulverized product and stirring or mixing the mixture, It can be obtained by keeping it in an atmosphere of 80% or more for 1 week or more.
前記軽焼マグネシア部分水和物は、酸化マグネシウムを65〜96.5質量%および水酸化マグネシウムを3.5〜30質量%含有するものが好ましく、酸化マグネシウムを70〜95質量%および水酸化マグネシウムを5〜20質量%含有するものがより好ましく、酸化マグネシウムを75〜90質量%および水酸化マグネシウムを7〜17質量%含有するものが更に好ましい。該値を好ましい範囲とすれば、固化強度や重金属類の溶出抑制効果をより高めることができる。   The light-burned magnesia partial hydrate preferably contains 65 to 96.5% by mass of magnesium oxide and 3.5 to 30% by mass of magnesium hydroxide, 70 to 95% by mass of magnesium oxide and magnesium hydroxide. Is more preferable, and what contains 75-90 mass% magnesium oxide and 7-17 mass% magnesium hydroxide is still more preferable. If the value is within a preferable range, the solidification strength and the elution suppressing effect of heavy metals can be further enhanced.
軽焼マグネシアまたは軽焼マグネシア部分水和物は、前記の成分の他、酸化カルシウムおよび/または水酸化カルシウムを含有してもよい。軽焼マグネシアまたは軽焼マグネシア部分水和物中の酸化カルシウムおよび/または水酸化カルシウムの合計の含有率は、酸化物換算で、3.0質量%以下が好ましく、2.5質量%以下がより好ましく、2.0質量%以下が更に好ましい。該含有率が3.0質量%を超えると、重金属類による汚染の程度の高い処理対象物に使用した場合、重金属類の溶出抑制効果が低下することがある。   The light-burned magnesia or light-burned magnesia partial hydrate may contain calcium oxide and / or calcium hydroxide in addition to the above components. The total content of calcium oxide and / or calcium hydroxide in light-burned magnesia or light-burned magnesia partial hydrate is preferably 3.0% by mass or less, more preferably 2.5% by mass or less in terms of oxide. Preferably, it is 2.0 mass% or less. When the content exceeds 3.0% by mass, the effect of suppressing the elution of heavy metals may be reduced when used for a processing object having a high degree of contamination by heavy metals.
なお、軽焼マグネシアまたは軽焼マグネシア部分水和物は、前記成分(酸化マグネシウム、水酸化マグネシウム、酸化カルシウム、水酸化カルシウム)以外の成分(例えば、シリカ、酸化鉄等の夾雑物)を、好ましくは4.0質量%以下で含むことができる。該含有率が4.0質量%を超えると、重金属類による汚染の程度の高い処理対象物に使用した場合、固化強度や重金属類の溶出抑制効果が低下することがある。   The light-burned magnesia or light-burned magnesia partial hydrate is preferably a component other than the above components (magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide) (for example, impurities such as silica and iron oxide). May be included at 4.0 mass% or less. When the content exceeds 4.0% by mass, the solidification strength and the elution suppression effect of heavy metals may be reduced when used for a processing object having a high degree of contamination with heavy metals.
軽焼マグネシアまたは軽焼マグネシア部分水和物のブレーン比表面積は、3000〜15000cm/gが好ましく、4000〜10000cm/gがより好ましく、4500〜7000cm/gが特に好ましい。該値が3000〜15000cm/gの範囲であると、重金属類の溶出抑制効果は増大する。 Blaine specific surface area of the light burned magnesia or light burned magnesia partially hydrate is preferably 3000~15000cm 2 / g, more preferably 4000~10000cm 2 / g, 4500~7000cm 2 / g is particularly preferred. When the value is in the range of 3000 to 15000 cm 2 / g, the elution suppressing effect of heavy metals increases.
本発明の中性固化材は、上述した通り、中性固化材用の添加材と、軽焼マグネシアまたは軽焼マグネシア部分水和物とを含有するものであって、酸性硫酸塩100質量部に対し、通常、軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部含有するものであり、10〜90質量部が好ましく、20〜80質量部がより好ましく、30〜70質量部が更に好ましい。
該含有量が7質量部未満では、固化強度や重金属類の溶出抑制効果が十分でなく、98質量部を超えると、固化材のpHを中性域へ調整することが困難になる虞がある。
As described above, the neutral solidified material of the present invention contains an additive for a neutral solidified material and light-burned magnesia or light-burned magnesia partial hydrate. On the other hand, usually it contains 7 to 98 parts by mass of light-burned magnesia or light-burned magnesia partial hydrate in terms of magnesium oxide, preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight. -70 mass parts is still more preferable.
If the content is less than 7 parts by mass, the solidification strength and the elution suppressing effect of heavy metals are not sufficient, and if it exceeds 98 parts by mass, it may be difficult to adjust the pH of the solidified material to a neutral range. .
次に、本発明の重金属類の溶出抑制方法について説明する。
本発明の重金属類の溶出抑制方法は、以下の(1)粉体添加方法と(2)スラリー添加方法がある。
Next, the method for suppressing elution of heavy metals according to the present invention will be described.
The heavy metal elution suppression method of the present invention includes the following (1) powder addition method and (2) slurry addition method.
(1)粉体添加方法
該方法は、処理対象物100質量部に対し、中性固化材を1〜40質量部添加し混合する方法である。該添加量が1質量部未満では、処理対象物と中性固化材を均質に混合することが困難であるうえ、固化強度が低く、また、重金属類の溶出抑制効果は十分でない。該添加量が40質量部を超えると、固化強度の増加は飽和する傾向にあり、むしろコスト高になる。
ここで、処理対象物は、中性固化材との混合(混練)や、軽焼マグネシアの水和および酸性硫酸塩等の溶解に必要な水量を含むことが望ましい。処理対象物中の含水量は、含水比(処理対象物中の固形分に対する、処理対象物中の水の質量比)で0.2〜2.0が好ましく、0.3〜1.5がより好ましく、0.4〜1.0が特に好ましい。該含水比が0.2未満では処理対象物と中性固化材の混合等が困難になり、2.0を超えると固化強度が十分でない。該含水比が小さい場合は、予め処理対象物に水を添加して、前記含水比の範囲に調製する必要がある。
(1) Powder addition method This method is a method of adding 1 to 40 parts by mass of a neutral solidifying material to 100 parts by mass of the object to be processed and mixing them. When the addition amount is less than 1 part by mass, it is difficult to uniformly mix the object to be treated and the neutral solidifying material, and the solidification strength is low, and the elution suppressing effect of heavy metals is not sufficient. When the added amount exceeds 40 parts by mass, the increase in solidification strength tends to be saturated, and the cost is rather increased.
Here, it is desirable that the object to be treated includes an amount of water necessary for mixing (kneading) with a neutral solidifying material, hydration of light-burned magnesia, and dissolution of acidic sulfate. The water content in the treatment object is preferably 0.2 to 2.0, preferably 0.3 to 1.5 in terms of the water content ratio (mass ratio of water in the treatment object to the solid content in the treatment object). More preferred is 0.4 to 1.0. If the water content is less than 0.2, it becomes difficult to mix the object to be treated and the neutral solidified material, and if it exceeds 2.0, the solidification strength is not sufficient. When the water content ratio is small, it is necessary to add water to the object to be treated in advance and prepare it within the range of the water content ratio.
(2)スラリー添加方法
該方法は、以下の(i)および(ii)の方法を含むものである。
(i)酸性硫酸塩の水溶液(A)と、該酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を、炭酸カルシウム換算で3〜42質量部、および、軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部含有するスラリー(B)とを混合した後、(A)と(B)の混合液を処理対象物に添加し混合する方法。
(ii)酸性硫酸塩の水溶液に、該酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を炭酸カルシウム換算で3〜42質量部、および、軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部、粉体のままで添加し混合してスラリーを調製した後、該スラリーを処理対象物に添加し混合する方法。
(2) Slurry addition method This method includes the following methods (i) and (ii).
(I) An aqueous solution of acidic sulfate (A) and 100 parts by mass of the acidic sulfate, calcium carbonate-containing material, 3 to 42 parts by mass in terms of calcium carbonate, and light calcined magnesia or light calcined magnesia partial water A method of mixing a slurry (B) containing 7 to 98 parts by mass of a Japanese product in terms of magnesium oxide, and then adding and mixing the mixture of (A) and (B) to the object to be treated.
(Ii) An aqueous solution of acidic sulfate, with respect to 100 parts by mass of the acidic sulfate, 3 to 42 parts by mass of calcium carbonate-containing material in terms of calcium carbonate, and light-burned magnesia or light-burned magnesia partial hydrate, A method in which 7 to 98 parts by mass in terms of magnesium oxide is added as powder and mixed to prepare a slurry, and then the slurry is added to the object to be treated and mixed.
以下、本発明を実施例により具体的に説明するが、本発明はこれら実施例に限定されるものではない。
1.固化材の各成分の調製等
(1)軽焼マグネシア粉砕物(M1)および軽焼マグネシア部分水和物(W1)
炭酸マグネシウムを97質量%含むマグネサイトを、850℃で30分間、電気炉(中外エンジニアリング社製、型式:KSL−2)で焼成して軽焼マグネシアを得た。次に、該軽焼マグネシアを粉砕して、ブレーン比表面積6500cm/gの軽焼マグネシア粉砕物(M1)を得た。更に、該粉砕物を温度20℃、相対湿度100%の恒温恒湿槽に10日間放置し、軽焼マグネシアの一部を水和させて、ブレーン比表面積6500cm/gの軽焼マグネシア部分水和物(W1)を得た。
軽焼マグネシア部分水和物(W1)は、酸化マグネシウムを88.0質量%および水酸化マグネシウムを8.5質量%含有するものであった。
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
1. Preparation of each component of solidified material, etc. (1) Light-burned magnesia pulverized product (M1) and light-burned magnesia partial hydrate (W1)
Magnesite containing 97% by mass of magnesium carbonate was fired at 850 ° C. for 30 minutes in an electric furnace (manufactured by Chugai Engineering Co., Ltd., model: KSL-2) to obtain light-burned magnesia. Next, the light-burned magnesia was pulverized to obtain a pulverized light-burned magnesia (M1) having a Blaine specific surface area of 6500 cm 2 / g. Further, the pulverized product is left in a constant temperature and humidity chamber at a temperature of 20 ° C. and a relative humidity of 100% for 10 days to hydrate part of the light-burned magnesia, and light-burned magnesia partial water having a Blaine specific surface area of 6500 cm 2 / g. A Japanese product (W1) was obtained.
The light-burned magnesia partial hydrate (W1) contained 88.0% by mass of magnesium oxide and 8.5% by mass of magnesium hydroxide.
(2)酸性硫酸塩
酸性硫酸塩は、無水硫酸アルミニウム(試薬1級、関東化学社製)と硫酸第一鉄1水塩(試薬1級、関東化学社製)を用いた。
(2) Acid Sulfate As the acid sulfate, anhydrous aluminum sulfate (reagent grade 1, manufactured by Kanto Chemical Co.) and ferrous sulfate monohydrate (reagent grade 1, manufactured by Kanto Chemical Co., Ltd.) were used.
(3)炭酸カルシウム含有物
炭酸カルシウムを92質量%含む粒状の石灰石を粉砕し、ブレーン比表面積が5500cm/gの炭酸カルシウム含有物を得た。
(4)二水石膏
二水石膏は、排煙脱硫二水石膏(中部電力社 碧南火力発電所産、ブレーン比表面積が6000cm/g)を用いた。
(3) Calcium carbonate-containing material Granular limestone containing 92% by mass of calcium carbonate was pulverized to obtain a calcium carbonate-containing material having a Blaine specific surface area of 5500 cm 2 / g.
(4) Dihydrate gypsum As the dihydrate gypsum, flue gas desulfurization dihydrate gypsum (manufactured by Chubu Electric Power Company Shonan Thermal Power Plant, Blaine specific surface area of 6000 cm 2 / g) was used.
2.固化処理土のpHと固化強度、および、重金属類の溶出試験
[供試体の作成]
表1の配合に従い固化材を調製した。次に、鉛、ヒ素およびフッ素を含有する粘性土(含水比0.5)100質量部に対し、該固化材を20質量部添加し、ホバートミキサを用いて混合して混合物を調製した。また、比較のため、前記粘性土100質量部に対し、表1の配合2の固化材を0.5質量部および50質量部添加し混合して混合物を調製した。
前記混合物を用いて、JGS0821−2009「安定処理土の締固めをしない供試体作製方法」に準拠して供試体を作製した。
2. PH and solidification strength of solidified soil and elution test of heavy metals [Preparation of specimen]
A solidified material was prepared according to the formulation shown in Table 1. Next, 20 parts by mass of the solidified material was added to 100 parts by mass of the viscous soil (water content ratio 0.5) containing lead, arsenic, and fluorine, and mixed using a Hobart mixer to prepare a mixture. For comparison, 0.5 parts by mass and 50 parts by mass of the solidified material of Formulation 2 in Table 1 were added to 100 parts by mass of the clay and mixed to prepare a mixture.
Using the mixture, a specimen was prepared according to JGS0821-2009 “Method for preparing specimen without compaction of stabilized soil”.
[pH測定]
作製した供試体を20℃の恒温室にて湿空養生した後、材齢1日の供試体のpHを、地盤工学会基準JGS0211−2009に準拠して測定した。ちなみに、排水基準のpHは5.8〜8.6である。
[PH measurement]
The prepared specimen was wet-cured in a thermostatic chamber at 20 ° C., and then the pH of the specimen one day old was measured in accordance with JGS0211-2009. By the way, the pH of the drainage standard is 5.8 to 8.6.
[重金属類の溶出試験]
該供試体からの重金属類の溶出試験は、鉛では環境省告示46号およびJIS K 0120−2008 5.4「ICP質量分析法」に準拠して、ヒ素では環境省告示46号法およびJIS K 0120−2008 61.4「ICP質量分析法」に準拠して、フッ素では環境省告示46号および昭和46年12月環境庁告示第59号付表6「イオンクロマトグラフ法」に準拠して行なった。ちなみに、重金属類の環境基準値は、鉛およびヒ素では0.01mg/L、フッ素では0.8mg/Lである。
[Elution test of heavy metals]
The elution test for heavy metals from the specimen was conducted in accordance with Ministry of the Environment Notification No. 46 and JIS K 0120-2008 5.4 “ICP Mass Spectrometry” for lead, and for Ministry of the Environment Notification No. 46 and JIS K for arsenic. In accordance with 0120-2008 61.4 “ICP Mass Spectrometry”, fluorine was carried out in accordance with Ministry of the Environment Notification No. 46 and Annex 6 of the Environment Agency Notification No. 59 in December 1971, “Ion Chromatograph Method”. . Incidentally, the environmental standard value of heavy metals is 0.01 mg / L for lead and arsenic, and 0.8 mg / L for fluorine.
[一軸圧縮強さ試験]
前記混合物を、内径50mm、長さ100mmの型枠に入れて、20℃で3日間、密閉養生して供試体を作成した後、該供試体の一軸圧縮強さを自動一軸圧縮試験装置(win土質2007、テスコ社製)を用いて測定した。
以上の結果を表2に示す。
なお、比較例7では、中性固化材用の添加材に代えて二水石膏を用いた。また、参考例では、粘性土のみを用いた。
[Uniaxial compressive strength test]
The mixture was put in a mold having an inner diameter of 50 mm and a length of 100 mm, and hermetically cured at 20 ° C. for 3 days to prepare a specimen, and then the uniaxial compression strength of the specimen was measured by an automatic uniaxial compression test apparatus (win Measured using Soil 2007 (manufactured by Tesco).
The results are shown in Table 2.
In Comparative Example 7, dihydrate gypsum was used instead of the additive for the neutral solidifying material. In the reference example, only viscous soil was used.
表2に示すように、本発明の中性固化材(実施例1〜14)を用いた固化処理物から滲出した液のpHは、5.9〜8.5であるから、すべてにおいて排水基準のpH5.8〜8.6を満たしている。
また、該浸出液中の鉛、ヒ素およびフッ素の濃度は、すべてにおいて環境基準値未満である。
As shown in Table 2, since the pH of the liquid exuded from the solidified product using the neutral solidifying material of the present invention (Examples 1 to 14) is 5.9 to 8.5, the drainage standard is used in all cases. Of 5.8 to 8.6.
In addition, the concentrations of lead, arsenic and fluorine in the leachate are all below the environmental standard value.
さらに、固化処理物の一軸圧縮強さについて、硫酸塩と炭酸カルシウムを合計で120質量部含む実施例2、5、7および8では、270〜298kN/mであるのに対し、二水石膏を同じ120質量部含む比較例7では、179kN/mである。従って、本発明の添加材を含有する中性固化材を用いた場合は、当初から二水石膏を含有する固化材を用いた場合と比べ、固化処理物の一軸圧縮強さは格段に高い。
また、固化処理物から滲出した液のpHは、前記中性固化材(実施例2、5、7および8)を用いた場合では、7.4(実施例8)〜7.8(実施例2)と中性域にあるのに対し、当初から二水石膏を含有する固化材を用いた場合では、10.4である。従って、本発明の中性固化材の添加材は、二水石膏と比べpHの低減効果も格段に高い。
Furthermore, the uniaxial compressive strength of the solidified product was 270 to 298 kN / m 2 in Examples 2, 5, 7 and 8 containing 120 parts by mass of sulfate and calcium carbonate in total, whereas dihydrate gypsum In Comparative Example 7 containing the same 120 parts by mass, 179 kN / m 2 . Therefore, when the neutral solidified material containing the additive of the present invention is used, the uniaxial compressive strength of the solidified product is remarkably high compared to the case of using the solidified material containing dihydrate gypsum from the beginning.
Moreover, the pH of the liquid exuded from the solidified product is 7.4 (Example 8) to 7.8 (Example) when the neutral solidified material (Examples 2, 5, 7, and 8) is used. 2) and in the neutral range, it is 10.4 when using a solidifying material containing dihydrate gypsum from the beginning. Therefore, the neutralizing material additive of the present invention has a much higher pH reduction effect than dihydrate gypsum.

Claims (3)

  1. 酸性硫酸塩100質量部に対し、炭酸カルシウム含有物を、炭酸カルシウム換算で3〜42質量部含むことを特徴とする中性固化材用の添加材。   An additive for a neutral solidifying material, comprising 3 to 42 parts by mass of calcium carbonate-containing material in terms of calcium carbonate with respect to 100 parts by mass of acidic sulfate.
  2. 請求項1に記載の中性固化材用の添加材と、軽焼マグネシアまたは軽焼マグネシア部分水和物とを含有する中性固化材であって、請求項1に記載の酸性硫酸塩100質量部に対し、前記軽焼マグネシアまたは軽焼マグネシア部分水和物を、酸化マグネシウム換算で7〜98質量部含有することを特徴とする中性固化材。 A neutral solidified material comprising the additive for a neutral solidified material according to claim 1 and light-burned magnesia or light-burned magnesia partial hydrate, wherein 100 mass of acidic sulfate according to claim 1 7 to 98 parts by mass of the light calcined magnesia or the light calcined magnesia partial hydrate in terms of magnesium oxide is contained with respect to parts.
  3. 処理対象物100質量部に対し、請求項2に記載の中性固化材を1〜40質量部添加し混合することを特徴とする重金属類の溶出抑制方法。   A method for suppressing elution of heavy metals, comprising adding 1 to 40 parts by mass of the neutral solidifying material according to claim 2 and mixing with respect to 100 parts by mass of the object to be treated.
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