JP3592319B2 - Soil modifier - Google Patents
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- JP3592319B2 JP3592319B2 JP2002370497A JP2002370497A JP3592319B2 JP 3592319 B2 JP3592319 B2 JP 3592319B2 JP 2002370497 A JP2002370497 A JP 2002370497A JP 2002370497 A JP2002370497 A JP 2002370497A JP 3592319 B2 JP3592319 B2 JP 3592319B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、汚泥等の高含水土壌や汚染土壌と混合攪拌するだけで、土壌の乾燥安定化および有害物質の不溶化、無害化をすることができる土壌改質材に関するものである。
【０００２】
【従来の技術】
下水処理場やし尿処理場、食品工場、畜産工場等で発生する活性汚泥あるいは港湾、河川、湖沼からの浚渫汚泥などの高含水土壌の処理、またガソリンスタンド跡地等の有機汚染土壌の処理としては、これらの土壌を脱水後、火力乾燥して取り扱いやすい乾燥土壌に改質したり、コンポスト等の発酵乾燥を行うことにより堆肥等に改質することが従来の主たる方法であった。
【０００３】
これらの処理法では、土壌を発生源から処理工場に移動させなければならず、臭気等の二次公害の原因になったり、処理設備の建設に膨大な費用がかかり、また処理に高い運転コストを要する欠点があった。
【０００４】
また土壌に生石灰を混合し、生石灰と土壌中の水分との反応熱を利用して土壌を乾燥する方法もあるが、処理土壌が強アルカリになるために、その後に中和処理が必要であり、非常に困難な作業となっていた。
【０００５】
【発明が解決しようとする課題】
このようなことから、汚泥等の高含水土壌や汚染土壌と混合攪拌するだけで、土壌の乾燥安定化および有害物質の不溶化、無害化をすることができる土壌改質材の開発が望まれていた。
【０００６】
本発明の課題は、汚泥等の高含水土壌や汚染土壌と混合攪拌するだけで、土壌の乾燥安定化および有害物質の不溶化、無害化をすることができ、さらに製造も容易で価格も安価な土壌改質材を提供することである。
【０００７】
【課題を解決するための手段】
上記課題を解決するために、本発明の土壌改質材は、多孔質で吸水性のある粒状粘土鉱物に濃硫酸を滲み込ませると共にその表面を微粉で覆い、さらに該微粉で覆われた粘土鉱物に前記濃硫酸に対し略中和量の生石灰粉末を混合したことを特徴とする。
【０００８】
本発明の土壌改質材は生石灰を含んでいるので、改質材を土壌と混合すると、生石灰が土壌中の水と反応して熱を発生し、
ＣａＯ＋Ｈ２Ｏ→Ｃａ（ＯＨ）２＋１５．２ｋＣａｌ／ｍｏｌ
土壌が８０〜１００℃に加熱され、その熱で土壌中の水が蒸発して土壌が乾燥する。この乾燥により、土壌の水分含有量を約４０％以下にすると、土壌をさらさらな砂状に改質することができる。また土壌が油分や揮発性分等の有機物を含んだ汚染土壌であると、それら有機物が熱で蒸散して土壌中から除去される。
【０００９】
本発明の土壌改質材は粒状粘土鉱物に濃硫酸を含んでいるので、改質材を土壌と混合すると、粒状粘土鉱物表面の微粉で遮蔽されていた濃硫酸と生石灰とが接触して反応し、
Ｈ２ＳＯ４＋ＣａＯ→ＣａＳＯ４＋Ｈ２Ｏ
硫酸カルシウム（ＣａＳＯ４）、つまり石膏が生じて、土壌が有害重金属や有機汚染物質等の汚染物質を含有していると、石膏が汚染物質を単独であるいは土壌ごと包み込んで不溶化を促進し無害化する。
【００１０】
従来の石灰を用いた土壌改質法では、対象土壌のｐＨにもよるが、一般に土壌は強アルカリの状態に処理される。これに対し、本発明の土壌改質材を用いた改質法によれば、土壌改質材が略中和量の硫酸と生石灰を含んでいるので、土壌をｐＨ≒５〜８の弱酸性から弱アルカリ性の状態に処理することができる。
【００１１】
【発明の実施の形態】
以下、本発明の土壌改質材について詳述する。
【００１２】
本発明の土壌改質材は、多孔質で吸水性のある粒状粘土鉱物に濃硫酸を滲み込ませると共にその表面を微粉で覆い、さらに該微粉で覆われた粘土鉱物に前記濃硫酸に対し略中和量の生石灰粉末を混合してなる。
【００１３】
本発明において、多孔質で吸水性のある粒状粘土鉱物は濃硫酸の担体として使用し、粒状粘土鉱物の多孔質表面の無数にある細孔と膨潤する性質を利用して、濃硫酸を滲み込ませて保持させるものである。濃硫酸の担体として粘土鉱物を使用するのは、粘土鉱物が土壌の構成成分であるので、土壌と混合後に土壌中に残っても問題ないからである。なお、活性炭やガラス質系の火山灰等は多孔質ではあるが吸水性がないので、濃硫酸を滲み込ませることができず用いることはできない。
【００１４】
本発明で用いることができる粒状粘土鉱物としては、鹿沼土、赤玉土、酸性白土、ゼオライト、ベントナイトおよびケイソウ土が挙げられる。これらは単独で使用しても、２種以上を併用してもよい。
【００１５】
粒状粘土鉱物の粒径は約１〜４０ｍｍが好ましい。粒状粘土鉱物の粒径が１ｍｍ未満であると、粒状粘土鉱物の粒が小さすぎて膨潤による吸収量が少ないため、濃硫酸を加える量が適量以下であっても、濃硫酸を粒状粘土鉱物の表面に良好に広げて細孔に浸透させることができず、粒状粘土鉱物と硫酸とがベトベトに混ざった状態になる。粒状粘土鉱物の粒径が４０ｍｍを超えると、単位重量当たりの粒状粘土鉱物の表面積が小さすぎて、一定量の粒状粘土鉱物に保持させることができる濃硫酸の量の減少を無視し得なくなる。
【００１６】
本発明において、粒状粘土鉱物に浸透させる硫酸には濃硫酸を使用する。本発明では、濃度６０％以上の硫酸を濃硫酸と定義する。濃度が６０％以上ならば、使用した廃硫酸を用いることができる。
【００１７】
濃硫酸を使用するのは、粒状粘土鉱物に正味の硫酸、即ち純物質の硫酸をなるべく多量に保持させたいためからであり、濃硫酸の濃度が６０％未満では、粒状粘土鉱物に保持させる純物質の硫酸量が少なすぎて効率的でない。最適な濃硫酸は発煙硫酸ある。発煙硫酸ならば腐食性がないので、濃硫酸を容器内で粒状粘土鉱物に加えて攪拌混合することにより、粒状粘土鉱物に濃硫酸を浸透させる際に、ステンレス製容器等でなく普通の鋼鈑製容器を使用することができ、取り扱いに便利である。
【００１８】
濃硫酸は正味の硫酸の保持量を多くするため、攪拌混合後に粒状粘土鉱物がベトベトにならない範囲でできるだけ多く加えるようにする。その量は粒状粘土鉱物の種類によっても異なるが、一例を挙げれば、粒状粘土鉱物１〜３重量部に対し９８％濃硫酸で概ね３重量部である。
【００１９】
本発明では、濃硫酸を滲み込ませた粒状粘土鉱物は、後で混合する生石灰との濃硫酸の反応を防ぐために、表面を微粉で覆って濃硫酸と生石灰の接触を断つようにする。この微粉は硫酸および生石灰と実質的に反応性がない弱酸性から弱アルカリ性の範囲ならばよい。このような微粉としては、鹿沼土、赤玉土、酸性白土、ゼオライト、ケイソウ土、フライアッシュ、ベントナイト、セピオライトおよび火山灰が挙げられる。これらは単独で使用しても、２種以上を併用してもよい。
【００２０】
微粉の粒径は約１０〜７５μｍが好ましい。微粉の粒径が１０μｍ未満であると、市販品で手に入らず、特殊に微粉加工する必要が生じ、コストが高くなる。微粉の粒径が７５μｍを超えると粒子が大きすぎて、微粉で粒状粘土鉱物の表面を密に覆うのが困難になる。微粉の量は、粒状粘土鉱物および濃硫酸の量によって適宜決めるが、濃硫酸を滲み込ませた粒状粘土鉱物の表面を十分に覆えるように多めに加える。一例を挙げれば、粒状粘土鉱物が１〜３重量部、９８％濃硫酸が３重量部の条件で、微粉が約１〜３重量部である。粒状粘土鉱物の表面を微粉で覆うには、粒状粘土鉱物に濃硫酸を滲み込ませた後微粉を加えて攪拌し、微粉を粒状粘土鉱物に塗せばよい。
【００２１】
本発明では、濃硫酸を滲み込ませ、表面を微粉で覆った粒状粘土鉱物に最後に生石灰を混合して土壌改質材とする。この生石灰は濃硫酸をほぼ中和する量（当量）で加える。硫酸に対する生石灰の理論中和量は、Ｈ２ＳＯ４／ＣａＯ＝９８／５６≒１．７で、硫酸重量の約１．７倍の量である。ただし、市販品の生石灰は、焼成不完全によりＣａＯ含有量が例えば約４０％と低下しているので、これを換算して生石灰を加える。
【００２２】
なお、処理する土壌が酸性の場合には生石灰が消費され、アルカリ性の場合には硫酸が消費される場合があり、本発明では、処理する土壌のｐＨによって加える生石灰の量を増減するのを禁ずるものではない。
【００２３】
生石灰の粒径は０．１〜５ｍｍ程度がよい。生石灰の粒径が１ｍｍ未満では、加工された粒状粘土鉱物と均質に混合することができず、逆に５ｍｍを超えると水分との反応に時間を要し、土壌を高温に保持することができず、水分蒸発や汚染物質の除去率が向上しない。この生石灰は、表面を微粉で覆った硫酸含有の粒状粘土鉱物に加えて、攪拌混合すればよい。
【００２４】
本発明の土壌改質材は、当量の硫酸と生石灰を含んでいるので、土壌をｐＨ≒５〜８の弱酸性から弱アルカリ性の状態に処理することができる。従来の石灰を用いた土壌改質法では、一般に土壌は強アルカリの状態に処理され、その後に中和する処理が必要とされるが、本発明の土壌改質材ではこのような後処理の問題を生じない。
【００２５】
本発明の土壌改質材を製造するには、攪拌容器に粒状粘土鉱物を入れ、これに濃硫酸を加えて攪拌混合し、濃硫酸の水和による発熱が終了したところで微粉を加えて攪拌混合し、最後に生石灰を加えて攪拌混合すればよい。これにより、濃硫酸が滲み込んだ粒状粘土鉱物の粒と、粒状粘土鉱物の表面に塗された微粉と、生石灰の粒とが混合した、粒状物を含むさらさらした土壌様の中性土壌改質材が得られる。
【００２６】
本発明の土壌改質材は、このように製造が容易であり、また特別高価な材料を使用しないので、安価に製造できることが一つの特徴である。
【００２７】
攪拌容器および攪拌手段としては、簡便にはコンクリートミキサーを使用することができる。濃硫酸を加えるのでミキサーのドラム内面を耐酸塗装して使用するが、発煙硫酸を用いる場合には耐酸処理は不要である。
【００２８】
本発明の改質材は土壌にそのまま加えて処理することができるが、活性汚泥や浚渫汚泥などの高含水汚泥を乾燥処理する場合には、改質材を節約し、改質材の処理効率を向上するために、これらの生汚泥を濾過、圧搾あるいは堆積による自然排水により脱水して脱水汚泥とし、その後改質材による処理を行うようにすることがよい。
【００２９】
また本発明は、改質材により土壌を処理するに当たり、改質材に他の添加剤を加えて処理に供するのを妨げるものではない。例えば汚染土壌が臭気を発する場合には、改質材に過炭酸ソーダ等の酸化剤を混合しておくことにより、土壌の臭気成分を分解して、臭気の発生を抑制するようにしてもよい。また汚染土壌が有害重金属を高濃度に含む場合には、改質材にキレート剤を加えておくことにより、土壌の有害重金属をキレート化して、有害重金属の不溶化により無害化するようにしてもよい。
【００３０】
本発明の改質材による処理法の例の概略を説明すれば、活性汚泥や浚渫汚泥の脱水汚泥に対しては、脱水汚泥堆積上にコンクリートミキサー等の攪拌容器を持ち込んで、攪拌容器中で汚泥と改質材とを混合攪拌して処理すればよい。これにより、汚泥を生石灰の反応発熱で簡単かつ短時間に乾燥させて、中性で取り扱いに都合よいさらさらした土質（水分約４０％以下）に改質することができる。
【００３１】
汚染土壌については、汚染土壌の現場で土壌の汚染部分に土壌改質材を散布し、バックホーやスタビライザー、深層攪拌混合機等で汚染土壌を地面から攪拌混合する（なお、土壌の掻上げ送り機構、放出機構および薬剤混合タンク等を備えたキャタピラ式の自走土壌改良機が市販されており、これを使用すれば、汚染土壌を掻き取り、改質した土壌を地面に敷設することができる）。これにより、汚染土壌を生石灰の反応発熱により乾燥させて、土壌を中性のさらさらした土質に改質すると共に、硫酸と生石灰の反応による石膏で土壌中の汚染物質を包み込ませ、汚染物質の不溶化を促進して無害化することができる。
【００３２】
【実施例】
本発明の実施例について説明する。
【００３３】
実施例１
コンクリートミキサーのドラム（内面は耐酸塗装した）に粒状粘土鉱物として粒径３〜５ｍｍの鹿沼土１２５ｋｇを入れ、これに９８％のＨ２ＳＯ４を１２５ｋｇ加えて２０分攪拌混合し、発熱が終了して約温度６０℃になったところで、粒径１０〜５０μｍのフライアッシュを５０ｋｇ加えて攪拌混合し、最後に粒径０．１〜２ｍｍの生石灰（ＣａＯ含有量約４０％）を２００ｋｇ加えて攪拌混合し、本発明の土壌改質材Ａを５００ｋｇ製造した。
【００３４】
この土壌改質材Ａの各材料の重量比は、粒状粘土鉱物：硫酸：微粉：生石灰＝５：５：２：８である。
【００３５】
油分（四塩化炭素抽出物質）の含有量を表１に示すように異ならせた土壌を原土壌として、これを別なコンクリートミキサーのドラムに入れ、原土壌に改質材Ａを１５％の割合で加えて攪拌混合し、原土壌を改質して改質土壌を得た。改質土壌の油分含有量および油分の減少量を表１に示す。油分（四塩化炭素抽出物質）の分析には、ＪＩＳ Ｋ０１０２を使用した。
【００３６】
【表１】
実施例２
粒状粘土鉱物と微粉末を酸性白土に代えた以外は改質材Ａと同様にして土壌改質材Ｂを製造した。同様に、原土壌（１種類）に改質材Ｂを加えて攪拌混合し、原土壌を改質して改質土壌を得た。改質土壌の油分含有量および油分の減少量を同様に表１に示す。
【００３８】
土壌改質材Ｂの各材料の重量比は、粒状粘土鉱物：硫酸：微粉：生石灰＝５：５：２：８である。
【００３９】
表１に示されるように、本発明の土壌改質材によればいずれも、油分（四塩化炭素抽出物質）を高効率で除去することができた。
【００４０】
実施例３
実施例１で使用した土壌改質材Ａを用い、これを原土壌に加える量を異ならせて、原土壌の油分（ノルマルヘキサン抽出物質）および水分の除去を行った。原土壌および改質土壌Ｎｏ．１、２、３、４の油分含有量および含水率を表２に示す。
【００４１】
改質土壌Ｎｏ．１は原土壌１０００ｋｇに改質材Ａを１００ｋｇ、Ｎｏ．２は２００ｋｇ、Ｎｏ．３は２５０ｋｇを加えた。ｎ−ヘキサン抽出物質はＪＩＳ Ｋ０１０２の重量法（定量限界２５０ｍｇ／ｋｇ）、含水率（乾燥減量）は１０５℃加熱重量法（昭和６３年環水管第１２７号ＩＩ−３）で測定した。
【００４２】
【表２】
表２に示されるように、本発明の土壌改質材によれば、原土壌が含有する油分（ｎ−ヘキサン抽出物質）および水分量（含水率）を大きく低減できた。
【００４４】
【発明の効果】
以上の説明から明らかなように、本発明の土壌改質材は、多孔質で吸水性のある粒状粘土鉱物に濃硫酸を滲み込ませると共にその表面を微粉で覆い、さらに該微粉で覆われた粘土鉱物に前記濃硫酸に対し略中和量の生石灰粉末を混合してなるので、汚泥等の高含水土壌や汚染土壌と混合攪拌するだけで、土壌の乾燥安定化および有害物質の不溶化、無害化をすることができ、さらに製造も容易で価格も安価である。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a soil modifying material capable of stabilizing drying of soil and insolubilizing and detoxifying harmful substances only by mixing and stirring with highly water-containing soil such as sludge or contaminated soil.
[0002]
[Prior art]
Treatment of activated sludge generated in sewage treatment plants and human waste treatment plants, food factories, livestock factories, etc. or highly water-containing soil such as dredged sludge from harbors, rivers, lakes and marshes, and treatment of organic contaminated soil such as gas station sites Conventionally, these soils have been conventionally dehydrated and then thermally dried to reform them into dry soils which can be easily handled, or fermented and dried with compost or the like to convert them into compost or the like.
[0003]
In these treatment methods, the soil must be moved from the source to the treatment plant, causing secondary pollution such as odors, enormous costs for construction of treatment facilities, and high operating costs for treatment. There was a disadvantage that required.
[0004]
There is also a method of mixing quicklime with soil and drying the soil using the heat of reaction between quicklime and moisture in the soil.However, since the treated soil becomes strongly alkaline, a neutralization process is required afterwards. Had been a very difficult task.
[0005]
[Problems to be solved by the invention]
For this reason, there is a need for the development of a soil modifying material that can stabilize the drying of soil and insolubilize and detoxify harmful substances simply by mixing and stirring with highly hydrous soil or contaminated soil such as sludge. Was.
[0006]
An object of the present invention is to stabilize the drying of soil and insolubilize and detoxify harmful substances by simply mixing and stirring with high water content soil or contaminated soil such as sludge, and furthermore, the production is easy and the price is low. It is to provide a soil modifying material.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the soil modifying material of the present invention impregnates porous sulfuric acid-containing granular clay minerals with concentrated sulfuric acid and covers the surface with fine powder, and further comprises a clay covered with the fine powder. It is characterized in that the mineral is mixed with quick lime powder in a substantially neutralized amount to the concentrated sulfuric acid.
[0008]
Since the soil modifier of the present invention contains quicklime, when the modifier is mixed with soil, quicklime reacts with water in the soil to generate heat,
CaO + H 2 O → Ca (OH) 2 +15.2 kCal / mol
The soil is heated to 80 to 100 ° C, and the heat evaporates water in the soil to dry the soil. By this drying, when the moisture content of the soil is reduced to about 40% or less, the soil can be modified into a smooth sandy state. Further, when the soil is a contaminated soil containing organic matter such as oil and volatile matter, the organic matter evaporates by heat and is removed from the soil.
[0009]
Since the soil modifier of the present invention contains concentrated sulfuric acid in the granular clay mineral, when the modifier is mixed with the soil, the concentrated sulfuric acid and quicklime, which are shielded by the fine powder on the surface of the granular clay mineral, come into contact and react. And
H 2 SO 4 + CaO → CaSO 4 + H 2 O
If calcium sulfate (CaSO 4 ), that is, gypsum is generated and the soil contains contaminants such as harmful heavy metals and organic pollutants, the gypsum singly or wraps the contaminant together with the soil to promote insolubilization and detoxification. I do.
[0010]
In the conventional soil modification method using lime, the soil is generally treated in a strongly alkaline state, depending on the pH of the target soil. On the other hand, according to the reforming method using the soil modifying material of the present invention, since the soil modifying material contains sulfuric acid and quick lime in a substantially neutralized amount, the soil is weakly acidified at pH ≒ 5-8. To a weakly alkaline state.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the soil modifying material of the present invention will be described in detail.
[0012]
The soil modifier of the present invention impregnates porous sulfuric acid granular clay mineral with concentrated sulfuric acid and covers the surface with fine powder. It is made by mixing a neutralized amount of quicklime powder.
[0013]
In the present invention, the porous and water-absorbing granular clay mineral is used as a carrier for concentrated sulfuric acid, and impregnated with concentrated sulfuric acid by utilizing the innumerable pores and swelling properties of the porous surface of the granular clay mineral. It is something that is kept. The reason why the clay mineral is used as a carrier for the concentrated sulfuric acid is that the clay mineral is a constituent component of the soil, so that there is no problem if the clay mineral remains in the soil after being mixed with the soil. Activated carbon, vitreous volcanic ash and the like are porous but do not absorb water, so that concentrated sulfuric acid cannot be impregnated and cannot be used.
[0014]
Granular clay minerals that can be used in the present invention include Kanuma soil, Akadama soil, acid clay, zeolite, bentonite and diatomaceous earth. These may be used alone or in combination of two or more.
[0015]
The particle size of the granular clay mineral is preferably about 1 to 40 mm. If the particle size of the granular clay mineral is less than 1 mm, the particles of the granular clay mineral are too small and the amount absorbed by swelling is small. It cannot spread well on the surface and cannot penetrate into the pores, so that the granular clay mineral and sulfuric acid are mixed into a sticky state. If the particle size of the granular clay mineral exceeds 40 mm, the surface area of the granular clay mineral per unit weight is too small, and the reduction in the amount of concentrated sulfuric acid that can be held by a certain amount of the granular clay mineral cannot be ignored.
[0016]
In the present invention, concentrated sulfuric acid is used as the sulfuric acid penetrating the granular clay mineral. In the present invention, sulfuric acid having a concentration of 60% or more is defined as concentrated sulfuric acid. If the concentration is 60% or more, the used waste sulfuric acid can be used.
[0017]
The purpose of using concentrated sulfuric acid is to make the granular clay mineral hold a large amount of net sulfuric acid, that is, pure substance sulfuric acid. When the concentration of concentrated sulfuric acid is less than 60%, the pure clay to be retained by the granular clay mineral is used. The amount of sulfuric acid in the substance is too small to be efficient. The best concentrated sulfuric acid is fuming sulfuric acid. Since fuming sulfuric acid is not corrosive, concentrated sulfuric acid is added to the granular clay mineral in the container and mixed with stirring. The container can be used and is convenient for handling.
[0018]
In order to increase the net sulfuric acid retention, concentrated sulfuric acid is added as much as possible within a range where the granular clay mineral does not become sticky after stirring and mixing. The amount varies depending on the type of the granular clay mineral, but, for example, about 3 parts by weight of 98% concentrated sulfuric acid per 1 to 3 parts by weight of the granular clay mineral.
[0019]
In the present invention, the surface of the granular clay mineral impregnated with concentrated sulfuric acid is covered with fine powder to prevent the reaction of concentrated sulfuric acid with the quicklime to be mixed later, so as to cut off the contact between the concentrated sulfuric acid and the quicklime. This fine powder may be in the range of weakly acidic to weakly alkaline, which has substantially no reactivity with sulfuric acid and quicklime. Such fine powders include Kanuma soil, Akadama soil, acid clay, zeolite, diatomaceous earth, fly ash, bentonite, sepiolite and volcanic ash. These may be used alone or in combination of two or more.
[0020]
The particle size of the fine powder is preferably about 10 to 75 μm. If the particle size of the fine powder is less than 10 μm, it is not available as a commercial product, and it is necessary to specially process the fine powder, which increases the cost. If the particle size of the fine powder exceeds 75 μm, the particles are too large, and it becomes difficult to cover the surface of the granular clay mineral with the fine powder densely. The amount of the fine powder is appropriately determined depending on the amounts of the granular clay mineral and the concentrated sulfuric acid, but is added in a large amount so as to sufficiently cover the surface of the granular clay mineral impregnated with the concentrated sulfuric acid. For example, under the condition that the granular clay mineral is 1 to 3 parts by weight and the 98% concentrated sulfuric acid is 3 parts by weight, the fine powder is about 1 to 3 parts by weight. To cover the surface of the granular clay mineral with fine powder, fine sulfuric acid is impregnated into the granular clay mineral, and then the fine powder is added and stirred, and the fine powder may be applied to the granular clay mineral.
[0021]
In the present invention, concentrated sulfuric acid is infiltrated, and granulated clay mineral whose surface is covered with fine powder is finally mixed with quicklime to obtain a soil modifying material. This quicklime is added in an amount (equivalent) to substantially neutralize concentrated sulfuric acid. The theoretical neutralization amount of quicklime relative to sulfuric acid is H 2 SO 4 /CaO=98/56≒1.7, which is about 1.7 times the weight of sulfuric acid. However, since the CaO content of a commercially available quicklime is reduced to, for example, about 40% due to incomplete calcination, this is converted and the quicklime is added.
[0022]
In addition, if the soil to be treated is acidic, quicklime is consumed, and if it is alkaline, sulfuric acid may be consumed.In the present invention, it is prohibited to increase or decrease the amount of quicklime added depending on the pH of the soil to be treated. Not something.
[0023]
The particle size of quicklime is preferably about 0.1 to 5 mm. If the particle size of quicklime is less than 1 mm, it cannot be homogeneously mixed with the processed granular clay mineral, and if it exceeds 5 mm, it takes time to react with moisture and the soil can be kept at a high temperature. And the rate of water evaporation and contaminant removal is not improved. This quicklime may be added to the sulfuric acid-containing granular clay mineral whose surface is covered with fine powder, and then stirred and mixed.
[0024]
Since the soil modifying material of the present invention contains equivalent amounts of sulfuric acid and quicklime, the soil can be treated from weakly acidic to weakly alkaline with a pH of about 5-8. In the conventional soil modification method using lime, the soil is generally treated in a strongly alkaline state, and then a neutralization treatment is required. However, the soil modification material of the present invention requires such post-treatment. No problem.
[0025]
In order to produce the soil modifying material of the present invention, a granular clay mineral is put in a stirring vessel, concentrated sulfuric acid is added thereto, and the mixture is stirred and mixed. When the heat generation due to the hydration of the concentrated sulfuric acid is completed, fine powder is added and mixed. Finally, quicklime may be added and mixed with stirring. As a result, it is a neutral soil modification that is free-flowing and soil-like, containing particulate matter, which is a mixture of granular clay mineral grains impregnated with concentrated sulfuric acid, fine powder applied on the surface of the granular clay mineral, and grains of quicklime. Wood is obtained.
[0026]
One of the features of the soil modifying material of the present invention is that it is easy to produce in this way and can be produced at low cost because no special expensive material is used.
[0027]
As the stirring vessel and the stirring means, a concrete mixer can be simply used. Since concentrated sulfuric acid is added, the inner surface of the drum of the mixer is used after being subjected to acid resistance coating. However, when fuming sulfuric acid is used, acid resistance treatment is not required.
[0028]
The modifying agent of the present invention can be added to soil as it is, and can be treated.However, when drying a highly hydrated sludge such as activated sludge or dredged sludge, the modifying agent can be saved and the treatment efficiency of the modifying agent can be reduced. In order to improve the sludge, it is preferable that these raw sludges are dewatered by natural drainage by filtration, squeezing or sedimentation into dewatered sludge and then treated with a modifier.
[0029]
Further, the present invention does not prevent the addition of other additives to the modifying agent for the treatment of the soil with the modifying agent. For example, when the contaminated soil emits an odor, an oxidizing agent such as sodium percarbonate may be mixed in the modifier to decompose the odor component of the soil and suppress the generation of the odor. . Further, when the contaminated soil contains a high concentration of harmful heavy metals, the harmful heavy metals of the soil may be chelated by adding a chelating agent to the modifier, and the harmful heavy metals may be made insoluble by insolubilizing the harmful heavy metals. .
[0030]
To explain the outline of an example of the treatment method using the modifier of the present invention, for dewatered sludge of activated sludge or dredged sludge, bring a stirring container such as a concrete mixer onto the dewatered sludge pile, and in the stirring container What is necessary is just to mix and agitate the sludge and the modifying agent for the treatment. As a result, the sludge can be easily and quickly dried by the heat generated by the reaction of quicklime, and the sludge can be reformed to a neutral and smooth soil (moisture of about 40% or less) which is convenient for handling.
[0031]
Regarding the contaminated soil, a soil modifying agent is sprayed on the contaminated part of the soil at the site of the contaminated soil, and the contaminated soil is stirred and mixed from the ground with a backhoe, a stabilizer, a deep mixing mixer, or the like. A caterpillar-type self-propelled soil improvement machine equipped with a release mechanism and a chemical mixing tank is commercially available, and can be used to scrape contaminated soil and lay modified soil on the ground.) . As a result, the contaminated soil is dried by the heat generated by the reaction of quick lime, and the soil is reformed into neutral and smooth soil.At the same time, the contaminants in the soil are wrapped in gypsum by the reaction between sulfuric acid and quick lime, and the contaminants are insolubilized. Can be promoted and made harmless.
[0032]
【Example】
An embodiment of the present invention will be described.
[0033]
Example 1
125 kg of Kanuma soil having a particle size of 3 to 5 mm as a granular clay mineral is put into a drum of a concrete mixer (the inner surface of which is acid-resistant coated), and 125 kg of 98% H 2 SO 4 is added thereto, and the mixture is stirred and mixed for 20 minutes, and heat generation is completed. When the temperature reached about 60 ° C., 50 kg of fly ash having a particle size of 10 to 50 μm was added and mixed with stirring. Finally, 200 kg of quick lime (CaO content of about 40%) having a particle size of 0.1 to 2 mm was added. The mixture was stirred and mixed to produce 500 kg of the soil modifying material A of the present invention.
[0034]
The weight ratio of each material of the soil modifying material A is granular clay mineral: sulfuric acid: fine powder: quicklime = 5: 5: 2: 8.
[0035]
Soil having different contents of oil (carbon tetrachloride extracted substance) as shown in Table 1 was used as raw soil, and this was put into a drum of another concrete mixer. And mixed by stirring to modify the original soil to obtain a modified soil. Table 1 shows the oil content and the reduction of the oil content of the modified soil. JIS K0102 was used for the analysis of the oil component (carbon tetrachloride extracted substance).
[0036]
[Table 1]
Example 2
A soil modifying material B was produced in the same manner as the modifying material A, except that the granular clay mineral and the fine powder were changed to acid clay. Similarly, the modifying material B was added to the original soil (one type), mixed with stirring, and the original soil was modified to obtain a modified soil. Table 1 also shows the oil content of the modified soil and the amount of oil content reduction.
[0038]
The weight ratio of each material of the soil modifying material B is granular clay mineral: sulfuric acid: fine powder: quicklime = 5: 5: 2: 8.
[0039]
As shown in Table 1, all of the soil modifying materials of the present invention were able to remove oil (carbon tetrachloride extracted substance) with high efficiency.
[0040]
Example 3
Using the soil modifying material A used in Example 1, the amount of the soil modifying material A added to the original soil was varied to remove the oil (normal hexane extractable material) and the moisture from the original soil. Raw soil and modified soil No. Table 2 shows the oil content and the water content of 1, 2, 3, and 4.
[0041]
The modified soil No. No. 1 shows 100 kg of modifier A in 1000 kg of raw soil, and No. 1 No. 2 is 200 kg, No. 3 added 250 kg. The n-hexane extract was measured by the JIS K0102 gravimetric method (quantification limit: 250 mg / kg), and the water content (loss on drying) was measured by a 105 ° C heating gravimetric method (1988, Ring Water Pipe No. 127, II-3).
[0042]
[Table 2]
As shown in Table 2, according to the soil modifying material of the present invention, the oil content (n-hexane extracted substance) and the water content (moisture content) contained in the original soil could be greatly reduced.
[0044]
【The invention's effect】
As is clear from the above description, the soil modifying material of the present invention impregnates concentrated sulfuric acid into porous and water-absorbing granular clay minerals, covers the surface with fine powder, and is further covered with the fine powder. Since the clay mineral is mixed with the quick lime powder in a substantially neutralized amount with respect to the concentrated sulfuric acid, it is possible to stabilize the dryness of the soil and insolubilize harmful substances and make it harmless simply by mixing and stirring with highly hydrous soil such as sludge or contaminated soil. It is easy to manufacture and inexpensive.
Claims (3)
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| JP2002370497A JP3592319B2 (en) | 2002-12-20 | 2002-12-20 | Soil modifier |
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| JP2005324146A (en) * | 2004-05-14 | 2005-11-24 | Mitsubishi Materials Corp | Waste acid treatment method |
| JP5009498B2 (en) * | 2004-11-25 | 2012-08-22 | 中野産業株式会社 | Environmental purification material and manufacturing method thereof |
| KR100740006B1 (en) | 2006-03-13 | 2007-07-16 | 조옥현 | Disinfectnat for soil using sludge of purification plant |
| JP5487544B2 (en) * | 2008-02-05 | 2014-05-07 | 吉澤石灰工業株式会社 | Soil improvement material and soil improvement method |
| CN101792671B (en) * | 2010-03-16 | 2011-12-21 | 江汉大学 | Soil curing agent containing sulfonating animal and vegetable oil and preparation method thereof |
| CN110999585A (en) * | 2019-12-02 | 2020-04-14 | 江苏凯帝农业科技发展有限公司 | Soil improvement method for large-scale fruit planting |
| CN112875832B (en) * | 2021-03-17 | 2022-08-23 | 辽宁工程技术大学 | Preparation method of alkaline slow-release material |
| CN116034664A (en) * | 2022-12-13 | 2023-05-02 | 中国恩菲工程技术有限公司 | Ecological restoration structure for extremely-acidified mine abandoned land soil and construction method |
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