JP2004105882A - Soil cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil cleaning method capable of uniformly and easily pouring a soil cleaning agent comprising an iron fine particle slurry to the contaminated soil contaminated with a contaminant such as an organic halogen compound and hexavalent chromium. <P>SOLUTION: The soil cleaning method comprises pouring a water base slurry containing the iron fine particle to the contaminated soil. The soil cleaning method is characterized in that a raw liquid of the water base slurry containing the iron fine particle is mixed/diluted with water and just after the mixing, the mixture liquid is poured to the contaminated soil; and that a pouring pipe having a mixing part at an upper part is inserted to the contaminated soil, the raw liquid of the water base slurry containing the iron fine particle and water are fed to the mixing part, these are mixed/diluted in the mixing part and just after the mixing, the mixture liquid is poured to the contaminated soil. <P>COPYRIGHT: (C)2004,JPO

Description

【００４１】
前記細粒鉄粉の組成例は下記の通り。
【００４２】

【００４３】
上記略語の意味；
ＳＳ：浮遊物質、湿粉：水分を含んだ状態の鉄粉。
【００４４】
前記細粒鉄粉の成分の範囲は下記の通り。
【００４５】

上記表３の数値の単位は全て質量％である。
【００４６】
本発明では、シックナーで濃縮する前の製鋼ダストスラリー、或いはシックナーで濃縮化され、最終的にフィルタープレスにより微粒子のみに選別されて、細粒鉄粉に対して、ハイドロタルサイトが添加され、一般に、混合することにより精製処理しても良い。
【００４７】
前記のゲーサイト経由の還元鉄粉は、前記のように粒度分布の狭い、そのため水との親和性の低い鉄微粒子である。例えば、平均粒径の０．２μｍ程度のゲーサイト（ＦｅＯＯＨ）を経由して得られ、同じ粒径のアトマイズ鉄粉に比べて、例えばトリクロロエチレンの分解速度が１０倍程度速く、好適な鉄微粒子である。この還元鉄粉は、原液の鉄微粒子濃度を３０質量％程度以下にすることが可能であり、１０質量％程度の濃度も、コロイダルシリカ及び／又は親水性樹脂を併用することにより得ることができる。しかしながら、このような還元鉄粉のスラリーも、汚染土壌に注入する際の濃度、例えば１％程度にすると、上記添加剤を用いても鉄粉の分離を防止する困難である。従って、本発明の方法を用いることにより、容易に、均一な注入が可能となる。還元鉄粉は、戸田工業（株）で製造、販売されており、入手することができる。このような鉄微粒子の平均粒径が一般に０．１〜３μｍであることが好ましい。さらに、鉄微粒子の８０質量％の粒径が０．１〜１．０μｍの範囲、特に０．１〜０．３μｍの範囲にあることが好ましい。
【００４８】
本発明で使用される鉄微粒子スラリー（即ち、土壌浄化剤）の原液は、さらに鉄以外の金属でも、還元作用を有する金属であるＭｎ、Ｍｇ、Ｚｎ、Ａｌ、Ｔｉ等を併用することができる。これらの金属も。その平均粒径はできるだけ小さいことが好ましい。
【００４９】
微粒子の鉄粉は、表面積が大きく表面に酸化（不働態化）され易いため、本発明ではこれを防止するため親水性バインダー及び／又は金属ハロゲン化物を併用することが好ましい。
【００５０】
金属ハロゲン化物は、ＮａＣｌ、ＫＣｌ、ＭｇＣｌ_２、ＣａＣｌ_２等を挙げることができ、特にＮａＣｌが好ましい。金属ハロゲン化物は、鉄の水酸化物、酸化物を金属鉄に還元する働きがある。その使用量は、固形分に対して０．５〜２００質量％が一般的で、０．５〜５０質量％が好ましい。
【００５１】
上記親水性樹脂は、鉄微粒子の表面を覆い、有機ハロゲン化物を還元作用を示すまでに酸化されないように保護する機能を有する。またこのような親水性樹脂は分散製の向上にも寄与することができる。このような親水性樹脂の例としては、スクロース等の二糖類、スクロース誘導体（例、スクロース高級脂肪酸エステル）、グルコース等の単糖類、アルギン酸；プルラン、ＰＶＡ（ポリビニルアルコール）、ＣＭＣ（カルボキシルメチルセルロース）、ポリアクリルアミド、グアガム、メチルセルロース、ヒドロキシエチルセルロース等の水溶性樹脂を挙げることができる。プルラン（水溶液にした際の粘度が低く特に好ましい）、ヒドロキシエチルセルロース、スクロース、グルコース、ＰＶＡが好ましい。分散製の向上に効果的な樹脂としてはポリアクリル酸ナトリウム、ポリアクリルアミド、ＰＶＡ等を挙げることができる。親水性樹脂として生分解性ポリマーを用いると二次的な環境汚染に対して特に有効である。その使用量は、固形分に対して０．０１〜２００質量％が一般的で、０．０１〜１００質量％が好ましい。
【００５２】
上記土壌浄化剤は、更に鉄微粒子の分散安定性を確保するためにシリカ微粒子を含むことできる。上記シリカ微粒子は、粉体状シリカまたはコロイダルシリカであり、一次粒径が１〜２００ｎｍ（ｍμ）の範囲、さらに好ましくは１０〜５０ｎｍの範囲である。シリカ微粒子の形状は球状、中空状、多孔質状、棒状、板状、繊維状、もしくは不定形状であり、好ましくは球状である。シリカ微粒子の比表面積は０．１〜３０００ｍ_２／ｇであり、好ましくは１０〜１５００ｍ_２／ｇである。これらのシリカ微粒子の使用形態は乾燥状態の粉末、もしくは水に分散した状態で用いることができ、コロイダルシリカとして知られている微粒子状のシリカ微粒子の分散液を直接用いることができる。コロイダルシリカとしては、その水素イオン濃度はｐＨ値として２〜１０の範囲であり、好ましくはｐＨ３〜７の酸性コロイダルシリカが用いられる。シリカ微粒子の市販品としては、例えば、コロイダルシリカとしては日産化学工業（株）製のメタノールシリカゾル、ＩＰＡ−ＳＴ、ＭＥＫ−ＳＴ、ＮＢＡ−ＳＴ、ＸＢＡ−ＳＴ、ＤＭＡＣ−ＳＴおよびＳＴ−ＵＰ、ＳＴ−ＯＵＰ、ＳＴ−２０、ＳＴ−４０、ＳＴ−Ｃ、ＳＴ−Ｎ、ＳＴ−Ｏ、ＳＴ−５０、ＳＴ−ＯＬ等を挙げることができる。また粉体状シリカとしては、日本アエロジル（株）製のアエロジル１３０、アエロジル３００、アエロジル３８０、アエロジルＴＴ６００及びアエロジルＯＸ５０、旭硝子（株）製のシルデックスＨ３１、Ｈ３２、Ｈ５１、Ｈ５２、Ｈ１２１、Ｈ１２２、日本シリカ工業（株）製のＥ２２０Ａ、Ｅ２２０、　富士シリシア化学（株）製のサイリシア４７０、日本板硝子（株）製のＳＧフレ−ク等を挙げることができる。
【００５３】
本発明で使用される土壌浄化剤（一般に原液）は、一般に、上記精製した製鋼ダストスラリーに、所望により酸化防止剤、金属ハロゲン化物又は親水性樹脂、又は金属ハロゲン化物及び親水性樹脂とを加えて、懸濁、あるいは分散させて得られるものである。更に適宜水を加えて所望の濃度にすることができる。また必要により分散時に界面活性剤を使用することもできる。上記親水性バインダーの代わりに生分解性ポリマー（例、生分解性ポリカプロラクトン）を用いると二次的な環境汚染に対して特に有効である。
【００５４】
上記土壌浄化剤は、さらに還元剤として金属硫酸塩（特に硫酸第一鉄）を含有することが好ましい。これは空気中の酸素と反応するため、金属鉄微粒子の表面の酸化を防ぐことができる。
【００５５】
上記土壌浄化剤は、さらに無機炭酸塩又は炭酸塩系鉱物を含有していることが好ましい。これらの例としては、炭酸カルシウム、沈降性炭酸カルシウム、炭酸マグネシウム、珊瑚化石石灰岩、石灰岩、ドロマイトを挙げることができ、特に沈降性炭酸カルシウムが好ましい。本発明の土壌浄化剤は微粒子の鉄を使用しているため、土壌内の土壌粒子の間隙に注入することが可能である。しかしながら、微粒子にすることにより地下水等に溶出する可能性も高くなることから、本発明では上記炭酸塩を用いて、溶出した鉄イオンを固定し、これを防止することが好ましい。
【００５６】
本発明で使用される土壌浄化剤は、一般に、前述のように、上記鉄微粒子（通常スラリーとして）、及び所望により親水性樹脂、金属ハロゲン化物又は金属ハロゲン化物を添加して、懸濁、あるいは分散させて得られるものである。その際分散に用いる水としては、鉄の酸化を極力抑制する観点から、還元性電解水（ｐＨ＝７〜１２が好ましい）を用いることが好ましい。分散剤として、ナフタレンスルホン酸系等の界面活性剤を使用しても良い。分散剤の使用量は、固形分に対して０．０１〜１０質量％が一般的で、０．１〜５質量％が好ましい。また前述の酸化防止剤を前記範囲内にてさらに使用しても良い。
【００５７】
本発明の土壌浄化方法は、前記のように土壌浄化剤を混合後、即座に注入するものであるが、他の点では従来の方法を適用することができる。
【００５８】
上記方法は、例えば下記のように行うことができる。
【００５９】
有機ハロゲン化物で汚染されたの表面にボーリングにより土壌浄化剤を供給するための注入管を設ける。注入管は必要により間隔を隔てて複数設けることができる。土壌浄化剤を供給用注入管に注入する。これにより、汚染土壌内に鉄微粒子等が浸透し、有機ハロゲン化物と徐々に接触し、有機ハロゲン化物を分解除去する。注入管で注入する前に、注入管から地下水を排出し、その後土壌浄化剤を注入しても良い。注入液が土壌表面からあふれ出ないように土壌表面に不透水性シート（例、ベントナイトシート）で覆っても良い。あるいは土壌内にシートを埋め込んでも良い。
【００６０】
上記浄化方法を例えば下記のように行っても良い。即ち、図４に示すように、汚染土壌の周囲を、地下の不透水性地盤５１に至る不通気層５２で遮断し、その内側の土壌中に注入管４９、必要により通気性柱状部４２及び水平通気層４４を設置し、これらの上に不通気性のシー４ト６で覆い、その周縁部を不通気層の外側で糊材を混入させた埋め戻し土砂からなる不通気４層７によって遮断することができる。上記水平通気層４４内には、通気性材４３を透過しない大きさの孔の多数からなる多孔管である吸気管４５が埋設されている。本発明では注入管４９を前記図１で示したものを使用するようにする。
【００６１】
そして、浄化処理は、例えば、注水管を通して排水し、注入管から本発明の洗浄剤を注入し、必要により減圧して、洗浄剤の拡散と、鉄による還元作用により発生する物質を除去することができる。
【００６２】
上記の方法のように、有機ハロゲン化物で汚染された土壌の表面を、不通気性のシートで覆うこと（一般に、シートの覆いは浄化剤注入後に設置される）が好ましく、必要により通気性柱状部（上記発生物質の除去に有用）を設けることができる。
【００６３】
有機ハロゲン化物以外の汚染物質で汚染された土壌も、上記と同様に行うことができる。また、汚染された土壌（特に６価クロムで汚染された土壌）を、土壌掘削法により掘削土壌を反応槽等に投入して本発明の土壌浄化剤で処理することもでき、そして、処理したクロム化合物等を除去することも有利な場合がある。土壌に注入する注入量は、一般に土壌１ｍ_３当たり鉄微粒子１〜４００ｋｇであり、１０〜２００ｋｇが好ましい。
【００６４】
【実施例】
［実施例１］
＜鉄微粒子スラリーの原液の作製　＞
（配合）
ゲーサイト経由の還元鉄粉　　　　　　　　　　　　　３０質量％
（平均粒径：０．２μｍ、鉄微粒子の８０質量％の粒径が
０．１〜０．３μｍの範囲、戸田工業（株）製）
ポリアクリル酸ナトリウム　　　　　　　　　　　　　　０．０５質量％
（商品名ＳＮシックナー　６３０；サンノプコ（株）製）
コロイダルシリカ　　　　　　　　　　　　　　　　　　０．０１質量％
（商品名　Ｎｉｐｓｉｌ　Ｅ−２００Ａ；日本シリカ工業株）製）
水道水　　　　　　　　　　　　　　　　　　　　　　　６９．９４質量％
上記配合したものを水中攪拌機で混合し、鉄微粒子スラリーの原液を得た。
【００６５】
＜浄化試験＞
次いで、上記で得られた鉄微粒子スラリーの原液を連続的にビーズミル（分散用装置）に導入し、分散後ＨＣｌを後述するｐＨメータでｐＨ４になるように添加し、ラインミキサで混合し、混合後ｐＨメータでｐＨを測定し（これにより前記ＨＣｌの添加量の調節を行う）、その後ＮａＯＨを後述するｐＨメータでｐＨ７になるように添加し、このように調整された鉄微粒子スラリーの原液を、図１に示す注入管の上部のパイプ３ａに供給し、もう一方のパイプ３ｂには４質量％の硝酸第１鉄及びアスコルビン酸０．０２質量％を含む水（前記原液の５倍量で）を供給し、トリクロロエチレンで汚染された土壌に連続的に注入した。
【００６６】
汚染土壌は、地面から深さ３０ｃｍの砕石の層があり、そこから深さ２ｍまでがシルトの層、さらに３０ｍまでが粘土の層である土壌で、分散液の注入のため地面の上に床スラブを敷いた。床スラブには左右に３ｍおきに５個ずつ、合計２５個の孔（直径１０ｃｍ）をあけ、そこから分散液の注入を行った。各孔への注入には、図１（ａ）に示す様な混合部と、パイプラインが付属した短い注入管を用いた（各孔に注入管を設置した）。注入量は４ｍ_３／時間で、４８時間行った。
途中で４回１０分間停止させた。
【００６７】
この結果、土壌中の５カ所（ランダムに設定）のトリクロロエチレンの濃度が、注入１ヶ月後に下記のように変化した。
【００６８】
シルト層（注入前→１ヶ月後（単位：ｐｐｍ））：
１）１．８５→０．０００５未満、２）０．０１→０．０００５未満、
３）３．２２→０．０００５未満、４）１．９７→０．０００５未満、
５）０．０８→０．０００５未満。
【００６９】
粘土層（注入前→１ヶ月後（単位：ｐｐｍ））：
１）５．０６→０．０００５未満、２）１．０３→０．０００５未満、
３）３．０８→０．０００５未満、４）１．５３→０．０００５未満、
５）２．９３→０．０００５未満。
【００７０】
また、上記土壌中の５カ所のうち注入口から最も遠い位置が水平距離５ｍ、深さ２ｍで、この位置でも浄化剤が有効に作用していたことから、本発明の浄化方法は土壌に対して良好な浸透性を示すことが分かる。
【００７１】
さらに、４８時間の注入及び途中の４回の停止中に、パイプライン等の閉塞が発生せず、連続して注入作業を行うことができた。
【００７２】
［比較例１］
実施例１における原液と水と混合した混合液を作製し、これを直接、図１（ａ）に示す様な混合部を持たない注入管に導入して、（但し、注入部の短いもの）注入を行った。注入量は４ｍ_３／時間で、４８時間行った。途中１０分間停させたところパイプラインが閉塞し作業を中止せざるを得なかった。
【００７３】
【発明の効果】
本発明の土壌浄化方法により、有機ハロゲン化物、６価クロム等の汚染物質により汚染された土壌に鉄微粒子スラリーからなる土壌浄化剤を、汚染土壌に均一に且つ容易に注入することが可能にするものである。即ち、従来の鉄微粒子スラリーを土壌に注入する方法では、スラリーを移動作業中、或いは注入作業の停止中に供給パイプ内が閉塞する場合があり、連続的な作業が困難であった。また鉄微粒子の均一な分散状態の保持が難しく、均一な鉄微粒子の注入にも問題があった。本発明の方法はこれらの問題を解決し、連続的な作業を容易にし、且つ鉄微粒子の均一注入を可能にたものである。
【図面の簡単な説明】
【図１】（ａ）は、本発明の浄化方法に使用される混合器の１例を示す断面図である。
（ｂ）は、本発明の注入管を用いた浄化方法を説明するための概略図の一例である。
【図２】本発明の浄化方法に使用することができる混合器の例を示す概略図である。
【図３】製鋼ダストスラリーの精製方法の実施形態の例を示すフローチャートである。
【図４】本発明において利用することができる浄化方法の実施形態の例を示す断面図である。
【符号の説明】
１　混合領域
２、３　切り換えバルブ
４ａ　原液を導入する管
４ｂ　水を導入する管
５ａ　通過した液を排出する管
５ｂ　原液タンクに戻すための管
１０　混合器
１１　グラウト
１２　パッカー
１３　ゴム
１４　穴
１５　注入管
１６　汚染土壌
１７　注入部
４２　通気性柱状部
４３　通気性材
４４　水平通気層
４５　吸気管
４６　不通気性のシート
４９　注入管
５１　地下の不透水性地盤
５２　不通気層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soil purification method for removing contaminants from soil contaminated with an organic halide, hexavalent chromium, and the like using a soil purification agent of a slurry of iron fine particles.
[0002]
[Prior art]
Organic halides such as trichloroethylene have been used in large quantities for industrial cleaning such as removal of oils from machinery. From the viewpoint of environmental pollution, the use of such organic halides has recently been regulated. However, a large amount of organic halides has already been used, and as a result, soil pollution or water pollution has been progressing. That is, organic halides such as trichlorethylene are stable and hard to be decomposed by microorganisms, and organic halides dumped in the natural environment not only contaminate soil, but also eventually contaminate rivers and groundwater, which is It can be a source of water, which is a problem. It is known that such pollution of the natural environment is also caused by hexavalent chromium left on the site of a factory such as a plating factory.
[0003]
As a method for purifying soil contaminated with volatile organic compounds such as the above-mentioned organic halides, a soil gas suction method, a groundwater pumping method, a soil excavation method and the like are known. The soil gas suction method forcibly sucks the target substance present in the unsaturated zone.A suction well is installed in the ground by boring, the pressure in the suction well is reduced by a vacuum pump, and the vaporized organic Compounds are collected in a suction well, guided underground, and treated by a method such as adsorption of organic compounds in soil gas to activated carbon.
In the case where the contamination by the organic compound reaches the aquifer, a method of installing a submersible pump in the suction well and pumping and treating the soil gas at the same time is adopted.
[0004]
The underground pumping method is a method in which a pumping well is installed in soil, and contaminated groundwater is pumped and treated. Further, the soil excavation method is a method in which contaminated soil is excavated, and the excavated soil is subjected to wind drying and heat treatment to remove and recover organic compounds.
[0005]
However, these methods are not a method of directly purifying soil, but a method of purifying contaminated water collected by the above-mentioned soil gas suction method, groundwater pumping method, or contaminated water such as rivers and groundwater. The amount is extremely large, and the processing often takes a long time. Another drawback is that the processing steps are often complicated. Therefore, there is a need for a method for directly and simply purifying soil, which is a pollution source.
[0006]
As described above, the conventional method of purifying soil contaminated with organic halides involves collecting contaminated water from contaminated soil and purifying it, or collecting and purifying the soil itself and purifying the contaminated soil itself. Is not a direct and simple way to purify.
[0007]
WO-01 / 08825 discloses that iron particles are finely divided to increase the surface area of iron to increase the treatment capacity of contaminants. In addition to atomization, spherical particles are formed into soil. Discloses a soil purification agent comprising a slurry of spherical iron fine particles having a particle size of less than 10 μm, which allows rapid penetration of iron.
[0008]
[Patent Document 1]
[Patent Document 1] WO-01 / 08825
[Problems to be solved by the invention]
The soil purifying agent of the iron fine particle slurry described in the above WO-01 / 08825 has a large particle size and is far superior in permeability to soil as compared with the conventional amorphous fine particle slurry. By reducing these contaminants directly and efficiently from soil contaminated with contaminants such as chloride and hexavalent chromium, they can be detoxified or removed after detoxification. However, when the iron fine particle slurry is injected into the contaminated soil, since the iron fine particle content (concentration) is a slurry having a low content of about several% due to its effectiveness and economy, the iron fine particles are easily separated. There is a tendency.
[0010]
According to the study of the present inventors, among iron fine particles, compared to iron powder having a wide particle size distribution such as atomized iron powder such as steelmaking dust, goethite (FeOOH) and the like are obtained from a compound obtained by recrystallization of a raw material. The reduced iron powder obtained by reduction via the iron oxide of Example 1 has a very narrow particle size distribution (the narrower the particle size distribution, the lower the affinity for water). , Settles very easily and separates easily from water. For example, it has been found that if the injection pump is stopped for a few minutes during the injection operation, the pipe or hose for supplying the slurry is blocked, and the operation cannot be continued. The atomized iron powder also has the same tendency, and when the pump is stopped during the injection operation, the pipe or the hose is likely to be clogged.
[0011]
It is an object of the present invention to provide a soil purification method capable of uniformly and easily injecting a soil purification agent comprising a slurry of iron fine particles into soil contaminated with a contaminant such as an organic halide or hexavalent chromium. To provide
[Means for Solving the Problems]
In order to solve the above problem, as a result of intensive studies by the present inventor, by mixing the undiluted solution of iron fine particle slurry and water immediately before injecting into the contaminated soil, any type of iron powder can be used. It was found that the injection work could be performed smoothly.
Therefore, the present invention is a soil purification method comprising injecting an aqueous slurry containing iron fine particles into contaminated soil, wherein a stock solution of the aqueous slurry containing iron fine particles is mixed with water, and immediately after the mixing, The soil purification method (1) is characterized by injecting the mixed solution into contaminated soil. The term “immediately after mixing” in the present invention means that the interval between mixing and injection is generally within 10 seconds, preferably within 5 seconds, particularly within 1 second.
[0013]
In the above-mentioned soil purification method (1), the iron fine particle content (also referred to as a concentration) of the stock solution of the aqueous slurry containing iron fine particles is preferably 10 to 50% by mass, particularly preferably 20 to 40% by mass. It is set from dispersion stability and economy. The amount of water mixed with the stock solution of the aqueous slurry containing iron fine particles is preferably 1 to 50 times the stock solution.
The content of iron fine particles in the mixture is preferably 0.5 to 10% by mass, particularly preferably 1 to 8% by mass. Appropriate for purification effect and economy.
[0014]
Further, the iron fine particles are preferably steelmaking dust, reduced iron powder via goethite, or a mixture thereof. The average particle size of the iron fine particles is generally less than 10 μm, preferably 0.1 to 6 μm, and particularly preferably 0.1 to 3 μm. The particle size of 80% by mass of the iron fine particles is preferably in the range of 0.1 to 0.3 μm. Such fine iron particles having a narrow particle size distribution are suitable for the method of the present invention because they are easily separated.
[0015]
The stock solution preferably contains a hydrophilic resin and / or silica fine particles.
Dispersion stability is improved. Water can also contain hydrophilic resin and / or silica microparticles. It is preferable that the hydrophilic resin is at least one selected from polyacrylate, polyacrylamide and polyvinyl alcohol. It is preferred that the contaminant in the contaminated soil is an organic halide and / or hexavalent chromium, especially an organic halide.
[0016]
Further, the present invention inserts an injection pipe having a mixing section on the upper part of the contaminated soil, supplies an undiluted solution of an aqueous slurry containing iron fine particles and water to the mixing section, and mixes these in the mixing section. Mixing, and immediately after the mixing, injecting the mixed solution into contaminated soil is a soil purification method (2).
[0017]
In the above soil purification method (2), it is preferable that the mixing section is composed of a static mixer without a driving section. Effective mixing in a compact form with low energy is possible. Preferably, the static mixer without a drive is a pipe or a static mixer filled with gravel, such as river gravel. Further, also in the soil purification method (2), the preferred embodiment in the soil purification method (1) can be applied.
[0018]
In the soil purification method (1), the undiluted solution is mixed with water and injected into soil.
The mixing area, the pipe for introducing the undiluted solution fed from the undiluted solution tank and the pipe for introducing water to the upper part, and the pipe for discharging the passed liquid to the lower part, and the upper part of the upper part, where water is not introduced in the upper part, the passing liquid is If left as is, it is a mixer having a pipe for returning it to the stock solution tank, a pipe for introducing water is connected to a pipe for introducing stock solution via a switching valve, and a pipe for returning stock solution discharges the passing solution. Connected to the stock solution tank via a switching valve, and when water is not introduced, the stock solution that has passed through the mixing area is returned to the stock solution tank, and when water is introduced, the stock solution is used. Using a mixer whose switching valve can be set to discharge a mixture of water for injection, injection into the soil by introducing water through the switching valve and discharging the resulting mixture. Do Door is preferable.
[0019]
Also in the soil purification method (2), it is preferable to use the mixer in the mixing section.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
In the soil purification method (1) of the present invention, when injecting an aqueous slurry containing iron fine particles into contaminated soil, the slurry is easily injected while preventing separation of the iron fine particles. This is a method in which a highly concentrated stock solution is not mixed with water in advance, but is performed immediately before soil injection.
[0021]
For example, as shown in FIG. 1A, the purified liquid can be injected into the soil using a mixer. The mixer 10 includes a mixing area 1, a pipe 4a for introducing the undiluted solution fed from the undiluted solution tank and a pipe 4b for introducing the water, a pipe 5a for discharging the liquid passed therethrough, and a water at the top. Is not introduced, the pipe 5b is used for returning the undiluted solution to the undiluted solution tank when the undiluted solution remains as it is. The pipe 4b for introducing water is connected to the pipe 4a for introducing the undiluted solution via the switching valve 3, and the pipe 5b for returning the undiluted solution to the undiluted solution tank or the like is connected to the undiluted solution tank via the switching valve 2 from the pipe 5a for discharging the passing liquid. Connected to return to. When the water is not introduced, the mixer is switched so that the stock solution that has passed through the mixing area is returned to the stock solution tank, and when water is introduced, the stock solution and the mixed solution of water are discharged for injection. Valve can be set. Using such a mixer, the injection into the soil can be performed by introducing water (dilution water) by the switching valve 3 and discharging the obtained mixed liquid (soil purification liquid). That is, when the undiluted solution and water are supplied from the pipes 4a and 4b, they are immediately mixed in the mixing area 1 immediately below the pipe and injected into the contaminated soil.
[0022]
Of course, the purification liquid is injected into the soil without using such a mixer. A pipe for supplying the undiluted solution and a pipe for supplying water are installed up to the contaminated soil, and the two pipes are provided at or near the contaminated soil. It is also possible to mix the undiluted solution released from the water with water and then immediately inject it into the soil.
[0023]
Soil purification can also be performed using an injection pipe in which the mixer (mixing section) is incorporated in FIG. A method of injecting into the contaminated soil 16 through a hole provided in a side wall of the injection pipe through an injection pipe, which is known as, for example, a soletanche double pipe injection method.
[0024]
A hole is drilled in the contaminated soil 16, the periphery of the hole is solidified with a sleeve material to form a grout 11, and an injection pipe 15 is set therein. The above-mentioned mixer 10 is installed in the mixing part near the center of the injection pipe, and an injection part 17 in which the side surface is made of rubber 13 and several holes 14 are formed is formed below the mixer. Is provided. When water (dilution water) is introduced by the switching valve 3 and the obtained mixed liquid (soil purification liquid) is discharged, the pressure increases in the region sealed by the packer due to the pressure, and the mixed liquid flows into the soil from the hole. Injected. At this time, the grout is destroyed by the pressure of the mixture discharged from the hole, and the mixture is injected into the soil. As an example of the dimensions of the above structure, the diameter of the hole is generally about 100 mm, the diameter of the injection pipe is about 50 mm, and the injection part is generally provided every about 33 mm.
[0025]
Therefore, mixing and injection are performed instantaneously, so that no matter how low the concentration of the mixed diluent is, no matter how small the particle size distribution is and the fine iron particles are easily separated, the fine iron particles are separated. There is no. For this reason, even if the iron fine particle aqueous slurry is injected, or if the injection is stopped and then re-injected after a long period of time, there is no clogging in the middle of a pipe, an injection pipe or the like. Even without using the above-mentioned circulating mixer, the stock solution has a high concentration of iron fine particles and a good dispersibility, and does not easily separate iron fine particles, so that it does not become clogged in the middle of pipes, injection pipes and the like. Further, since the diluted mixed solution is injected into the soil in a state where the iron fine particles are well dispersed, the iron fine particles uniformly and deeply penetrate into the soil. Therefore, the purification effect is also efficient.
[0026]
By injecting this mixture (soil purifying agent), the pollutants can be detoxified from the contaminated soil by reduction or the like, or removed after detoxification, and the soil can be purified.
[0027]
As a device or a mixer used in the mixing section, a static mixer without a driving section is preferable, and specifically, a pipe or a static mixer filled with gravel such as river gravel is preferable. FIGS. 2A and 2B are schematic diagrams of examples of the structure.
[0028]
FIG. 2A is a schematic diagram of a static mixer, in which a plurality of right elements 21 and left elements 22 are provided continuously. Each element has a rectangular plate twisted by 180 degrees, and has right and left elements depending on the direction of twist. By the combination of these elements, a dividing action, a conversion action, and a reversing action occur according to the inflow of the stock solution and water, and the mixing of the stock solution with water can be performed immediately.
[0029]
FIG. 2 (b) shows a simple stationary of a gravel-filled pipe in which river gravel (generally spherical with a diameter of about 20 mm) 25 is innumerably filled in an area defined by a net 24 and an eye panel 26 in the pipe 23. A mold mixer is shown. A flange 27 is formed on the outside of the pipe provided with the net 24 and the mesh plate 26. The batting board 26 has packings fitted above and below countless holes (eg, 1-5 mm in diameter) in the board. In this mixer, when the undiluted solution and water flow from the top, they are instantaneously mixed by passing through a very small gap between the gravel. This mixer is preferable in terms of mixing efficiency and economy.
[0030]
Organic pollutants, hexavalent chromium, and cyanide can be mentioned as the contamination source to be purified according to the present invention, and organic halides and hexavalent chromium are suitable, and organic halides are particularly suitable. Examples of organic halides include 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-dichloroethane. Trichloroethane, 1,1,2,2-tetrachloroethane, dichlorodifluoroethane and the like can be mentioned. It is considered that these organic halides lose halogens and become corresponding hydrocarbons by the dehalogenating action (reducing action) of iron, and are removed from soil. As an organic halide, it is particularly effective for an organic chloride (organic chlorine-substituted compound). Hexavalent chromium can be efficiently reduced to trivalent chromium by an effective iron reducing action over a long period of time, and then can be removed from the soil if necessary. Furthermore, cyanide (cyan ion) forms a complex with iron ion and is detoxified.
[0031]
In the method of the present invention, the iron fine particles contained in the aqueous slurry used as the soil remediation agent are generally extremely fine particles, and therefore quickly penetrate into the soil when directly applied to contaminated soil. The iron fine particles are preferably steelmaking dust, reduced iron powder via goethite, or a mixture thereof. The average particle size of such iron fine particles is generally less than 10 μm, preferably 0.1 to 6 μm, and particularly preferably 0.1 to 3 μm. Further, the particle diameter of 80% by mass of the iron fine particles is preferably in the range of 0.1 to 0.3 μm. Such fine iron particles having a narrow particle size distribution are characteristics found in the above-described reduced iron powder, and are easily separated, so that the method of the present invention can be effectively used.
[0032]
By using such ultrafine iron powder, the cleaning power can be greatly improved.
In particular, when applied to contaminated soil, the iron fine particles having a spherical shape penetrate into the soil very quickly and exhibit a purifying action.
[0033]
The iron fine particle content (concentration) of the stock solution of the aqueous slurry containing iron fine particles used in the present invention is preferably 10 to 50% by mass, particularly preferably 20 to 40% by mass. It is set from dispersion stability and economy. It is preferable that the amount of water mixed with the stock solution of the aqueous slurry containing iron fine particles is 1 to 50 times, particularly 2 to 20 times the stock solution. This depends on the concentration of the stock solution. The concentration of iron fine particles in the diluting liquid is preferably 0.5 to 10% by mass, particularly preferably 1 to 8% by mass. It is set appropriately from the purification effect and economy.
[0034]
The stock solution preferably contains a hydrophilic resin and / or silica fine particles.
This improves the dispersion stability. Water can also contain hydrophilic resin and / or silica microparticles. It is preferable that the hydrophilic resin is at least one selected from polyacrylate, polyacrylamide and polyvinyl alcohol.
Further, the stock solution preferably contains an antioxidant. This can keep the iron from being oxidized. 90% by mass or more of the solid content is metallic iron and iron-containing compounds. Metallic iron accounts for 30% by mass or more of the solid content.
[0035]
The iron fine particles suitably used in the present invention are steelmaking dust and reduced iron powder via goethite as described above.
[0036]
The method for producing the steelmaking dust slurry before the purification will be described with reference to FIG.
[0037]
In an oxygen blowing furnace for steelmaking, pig iron or the like containing impurities such as C, Si, P, and F is charged, and oxygen is rapidly blown from above while being stirred. In this state, a reaction occurs between the impurity-containing pig iron and oxygen, and C, Si, P, etc. turn into oxides to form slag with fluorite calcium, and at this time, some fluorine compounds are taken into the pig iron (this Such a reaction may occur in a blast furnace during pig iron production.) During this time, the exhaust gas containing fine iron powder generated by blowing oxygen is collected by wet dust collection through a gas recovery hood. In wet dust collection, gases such as CO are sent to a gas recovery tank. The steelmaking dust obtained by collecting the exhaust gas is in the form of an aqueous slurry, this slurry is subjected to coarse fractionation (at 60 μm), the coarse one is recovered as coarse iron powder, and the fine one is concentrated with a thickener. Then, only fine particles are finally sorted out by a filter press to obtain fine-grain iron powder (that is, iron fine-particle slurry).
[0038]
The iron fine particles obtained in this way also contain iron oxides in various oxidation stages, but such iron oxides are considered to exhibit a reducing action that leads to a purifying action, since dust captured in a gaseous combustion state is in a reduced state. Can be Therefore, even if metallic iron does not account for 30% by mass or more, the above-mentioned iron fine particles can often exhibit a high reducing action.
[0039]
Examples of the particle size of 97 mass% Fe in the coarse iron powder are as follows.
[0040]

[0041]
The composition examples of the fine iron powder are as follows.
[0042]

[0043]
Meaning of the above abbreviations;
SS: suspended solids, wet powder: iron powder containing water.
[0044]
The ranges of the components of the fine iron powder are as follows.
[0045]

The units of the numerical values in Table 3 above are all mass%.
[0046]
In the present invention, the steelmaking dust slurry before being concentrated with a thickener, or concentrated with a thickener, and finally separated into fine particles only by a filter press, and hydrotalcite is added to fine-grained iron powder. , May be purified by mixing.
[0047]
The reduced iron powder passing through the goethite is iron fine particles having a narrow particle size distribution as described above, and thus having low affinity for water. For example, it is obtained via goethite (FeOOH) having an average particle size of about 0.2 μm, and has a decomposition rate of trichlorethylene, for example, about 10 times faster than atomized iron powder having the same particle size. is there. In the reduced iron powder, the concentration of iron fine particles in the stock solution can be reduced to about 30% by mass or less, and the concentration of about 10% by mass can be obtained by using colloidal silica and / or a hydrophilic resin together. . However, if the concentration of such a reduced iron powder slurry is set to a concentration at the time of injecting it into contaminated soil, for example, about 1%, it is difficult to prevent the separation of the iron powder even by using the above-mentioned additive. Therefore, uniform injection can be easily performed by using the method of the present invention. Reduced iron powder is manufactured and sold by Toda Kogyo Co., Ltd. and can be obtained. Generally, it is preferable that the average particle diameter of such iron fine particles is 0.1 to 3 μm. Further, the particle diameter of 80% by mass of the iron fine particles is preferably in the range of 0.1 to 1.0 μm, particularly preferably in the range of 0.1 to 0.3 μm.
[0048]
In the stock solution of the iron fine particle slurry (that is, the soil purification agent) used in the present invention, metals other than iron, such as Mn, Mg, Zn, Al, and Ti, which have a reducing action, can be used in combination. . These metals too. The average particle size is preferably as small as possible.
[0049]
Since fine iron powder has a large surface area and is easily oxidized (passivated) on the surface, in the present invention, it is preferable to use a hydrophilic binder and / or a metal halide in combination to prevent this.
[0050]
Examples of the metal halide include NaCl, KCl, MgCl ₂ , and CaCl ₂ , and NaCl is particularly preferable. Metal halides have the function of reducing iron hydroxides and oxides to metallic iron. The amount used is generally 0.5 to 200% by mass relative to the solid content, and preferably 0.5 to 50% by mass.
[0051]
The hydrophilic resin has a function of covering the surface of the iron fine particles and protecting the organic halide from being oxidized before exhibiting a reducing action. Such a hydrophilic resin can also contribute to the improvement of the dispersion. Examples of such a hydrophilic resin include disaccharides such as sucrose, sucrose derivatives (eg, higher fatty acid esters of sucrose), monosaccharides such as glucose, alginic acid; pullulan, PVA (polyvinyl alcohol), CMC (carboxymethylcellulose), Water-soluble resins such as polyacrylamide, guar gum, methylcellulose and hydroxyethylcellulose can be mentioned. Pullulan (having a particularly low viscosity in aqueous solution), hydroxyethylcellulose, sucrose, glucose and PVA are preferred. Examples of resins effective for improving dispersion are sodium polyacrylate, polyacrylamide, and PVA. The use of a biodegradable polymer as the hydrophilic resin is particularly effective against secondary environmental pollution. The use amount is generally 0.01 to 200% by mass relative to the solid content, and preferably 0.01 to 100% by mass.
[0052]
The soil purifying agent may further contain silica fine particles in order to secure the dispersion stability of the iron fine particles. The silica fine particles are powdery silica or colloidal silica, and have a primary particle size in the range of 1 to 200 nm (mμ), more preferably in the range of 10 to 50 nm. The shape of the silica fine particles is spherical, hollow, porous, rod-like, plate-like, fibrous, or irregular, and is preferably spherical. The specific surface area of the silica fine particles is from 0.1 to 3000 m ₂ / g, preferably from 10 to 1500 m ₂ / g. These silica fine particles can be used in the form of dry powder or dispersed in water, and a dispersion of fine silica particles known as colloidal silica can be used directly. As the colloidal silica, the hydrogen ion concentration is in the range of 2 to 10 as a pH value, and acidic colloidal silica having a pH of 3 to 7 is preferably used. Examples of commercially available silica fine particles include colloidal silica such as methanol silica sol manufactured by Nissan Chemical Industries, Ltd., IPA-ST, MEK-ST, NBA-ST, XBA-ST, DMAC-ST and ST-UP, ST. -OUP, ST-20, ST-40, ST-C, ST-N, ST-O, ST-50, ST-OL, and the like. Examples of the powdery silica include Aerosil 130, Aerosil 300, Aerosil 380, Aerosil TT600 and Aerosil OX50 manufactured by Nippon Aerosil Co., Ltd., and Sildex H31, H32, H51, H52, H121, H122, manufactured by Asahi Glass Co., Ltd. Examples include E220A and E220 manufactured by Nippon Silica Kogyo Co., Ltd., Sylysia 470 manufactured by Fuji Silysia Chemical Ltd., and SG flake manufactured by Nippon Sheet Glass Co., Ltd.
[0053]
The soil purification agent (generally, undiluted solution) used in the present invention generally comprises an antioxidant, a metal halide or a hydrophilic resin, or a metal halide and a hydrophilic resin, if desired, added to the purified steelmaking dust slurry. And obtained by suspending or dispersing. Further, water can be appropriately added to obtain a desired concentration. If necessary, a surfactant can be used at the time of dispersion. Use of a biodegradable polymer (eg, biodegradable polycaprolactone) instead of the hydrophilic binder is particularly effective against secondary environmental pollution.
[0054]
It is preferable that the soil purification agent further contains a metal sulfate (particularly, ferrous sulfate) as a reducing agent. Since this reacts with oxygen in the air, oxidation of the surface of the metal iron fine particles can be prevented.
[0055]
It is preferable that the soil purification agent further contains an inorganic carbonate or a carbonate mineral. Examples thereof include calcium carbonate, precipitated calcium carbonate, magnesium carbonate, coral fossil limestone, limestone, and dolomite, and particularly preferred is precipitated calcium carbonate. Since the soil purifying agent of the present invention uses fine-particle iron, it can be injected into the gap between the soil particles in the soil. However, the fine particles increase the possibility of elution into groundwater or the like. Therefore, in the present invention, it is preferable to fix the eluted iron ions using the above-mentioned carbonate and prevent this.
[0056]
As described above, the soil purifying agent used in the present invention generally contains the iron fine particles (usually as a slurry) and, if desired, a hydrophilic resin, a metal halide or a metal halide, and suspends or It is obtained by dispersing. In this case, it is preferable to use reducing electrolyzed water (preferably having a pH of 7 to 12) as water used for dispersion from the viewpoint of minimizing iron oxidation. As the dispersant, a surfactant such as naphthalenesulfonic acid may be used. The amount of the dispersant used is generally 0.01 to 10% by mass relative to the solid content, and preferably 0.1 to 5% by mass. Further, the above-mentioned antioxidant may be further used within the above range.
[0057]
The soil purification method of the present invention is such that the soil purification agent is immediately injected after mixing as described above, but in other respects, a conventional method can be applied.
[0058]
The above method can be performed, for example, as follows.
[0059]
An injection pipe is provided for supplying soil cleanser by boring to surfaces contaminated with organic halides. A plurality of injection tubes can be provided at intervals as needed. Inject the soil cleanser into the supply inlet tube. As a result, iron fine particles and the like penetrate into the contaminated soil, gradually come into contact with the organic halide, and decompose and remove the organic halide. Before injecting with an injection pipe, groundwater may be drained from an injection pipe, and then a soil purifying agent may be injected. The soil surface may be covered with a water-impermeable sheet (eg, bentonite sheet) so that the injection liquid does not overflow from the soil surface. Alternatively, a sheet may be embedded in the soil.
[0060]
The above purification method may be performed, for example, as follows. That is, as shown in FIG. 4, the surrounding of the contaminated soil is blocked by an impermeable layer 52 reaching the underground impermeable ground 51, and the injection pipe 49, if necessary, the air-permeable columnar portion 42 and A horizontal air-permeable layer 44 is provided, covered with an air-impermeable sheet 4 on the horizontal air-permeable layers 44, and the periphery thereof is surrounded by an impermeable 4-layer 7 made of backfilled earth and sand mixed with a glue material outside the air-impermeable layer. Can be shut off. In the horizontal ventilation layer 44, an intake pipe 45, which is a perforated pipe composed of many holes having a size that does not allow the gas permeable material 43 to pass through, is embedded. In the present invention, the injection tube 49 shown in FIG. 1 is used.
[0061]
In the purification treatment, for example, drainage is performed through a water injection pipe, the cleaning agent of the present invention is injected from an injection pipe, and if necessary, pressure is reduced to remove a substance generated by diffusion of the cleaning agent and reduction action by iron. Can be.
[0062]
As in the above method, it is preferable to cover the surface of the soil contaminated with the organic halide with an impermeable sheet (generally, the sheet cover is installed after the cleaning agent is injected). (Useful for the removal of the generated substances) can be provided.
[0063]
Soil contaminated with contaminants other than organic halides can be performed in the same manner as described above. Further, contaminated soil (particularly soil contaminated with hexavalent chromium) can be treated with the soil purification agent of the present invention by excavating soil into a reaction tank or the like by a soil excavation method and treating it. It may be advantageous to remove chromium compounds and the like. Injection volume to be injected into the soil, generally a soil 1 m ₃ per iron particles 1～400Kg, 10 to 200 is preferable.
[0064]
【Example】
[Example 1]
<Preparation of stock solution of iron fine particle slurry>
(Combination)
30% by mass of reduced iron powder via goesite
(Average particle size: 0.2 μm, particle size of 80% by mass of iron fine particles in the range of 0.1 to 0.3 μm, manufactured by Toda Kogyo Co., Ltd.)
Sodium polyacrylate 0.05% by mass
(Product name SN Thickener 630; manufactured by San Nopco Co., Ltd.)
Colloidal silica 0.01% by mass
(Product name: Nipsil E-200A; manufactured by Nippon Silica Industry Co., Ltd.)
Tap water 69.94% by mass
The above compound was mixed with an underwater stirrer to obtain a stock solution of iron fine particle slurry.
[0065]
<Purification test>
Next, the stock solution of the iron fine particle slurry obtained above is continuously introduced into a bead mill (a dispersing device), and after dispersion, HCl is added so as to have a pH of 4 with a pH meter described later, and mixed with a line mixer. Thereafter, the pH was measured with a pH meter (the amount of HCl added was adjusted thereby), and then NaOH was added so as to have a pH of 7 with a pH meter to be described later. And water containing 4% by mass of ferrous nitrate and 0.02% by mass of ascorbic acid (5 times the amount of the undiluted solution) is supplied to the upper pipe 3a of the injection pipe shown in FIG. ) Was continuously injected into soil contaminated with trichlorethylene.
[0066]
Contaminated soil is a layer of crushed stone at a depth of 30 cm from the ground, a layer of silt up to a depth of 2 m, and a layer of clay up to a depth of 30 m. I laid a slab. A total of 25 holes (diameter: 10 cm) were made in the floor slab, five on the left and right every 3 m, from which the dispersion was injected. For injection into each hole, a short injection pipe with a mixing section and a pipeline as shown in FIG. 1A was used (an injection pipe was installed in each hole). The injection rate was 4 m ₃ / hour and was performed for 48 hours.
On the way, it was stopped four times for 10 minutes.
[0067]
As a result, the concentration of trichlorethylene in five places (set at random) in the soil changed as described below one month after the injection.
[0068]
Silt layer (before injection → one month later (unit: ppm)):
1) 1.85 → less than 0.0005, 2) 0.01 → less than 0.0005,
3) 3.22 → less than 0.0005, 4) 1.97 → less than 0.0005,
5) 0.08 → less than 0.0005.
[0069]
Clay layer (before injection → 1 month later (unit: ppm)):
1) 5.06 → less than 0.0005, 2) 1.03 → less than 0.0005,
3) 3.08 → less than 0.0005, 4) 1.53 → less than 0.0005,
5) 2.93 → less than 0.0005.
[0070]
Further, among the five places in the soil, the farthest position from the injection port was a horizontal distance of 5 m and a depth of 2 m, and the purifying agent was also effective at this position. It shows that it shows good permeability.
[0071]
Further, during the injection for 48 hours and during the four stoppages during the injection, there was no blockage of the pipeline or the like, and the injection operation could be performed continuously.
[0072]
[Comparative Example 1]
A mixed solution prepared by mixing the undiluted solution and water in Example 1 was prepared, and directly introduced into an injection pipe having no mixing section as shown in FIG. 1A (however, the injection section was short). An injection was made. The injection rate was 4 m ₃ / hour and was performed for 48 hours. After stopping for 10 minutes on the way, the pipeline was blocked and the work had to be stopped.
[0073]
【The invention's effect】
ADVANTAGE OF THE INVENTION By the soil purification method of this invention, it becomes possible to inject | pour uniformly and easily the soil purification agent which consists of iron fine particle slurry into contaminated soil by the soil contaminated with contaminants, such as an organic halide and hexavalent chromium. Things. That is, in the conventional method of injecting the iron fine particle slurry into the soil, the inside of the supply pipe may be clogged while the slurry is being moved or the pouring operation is stopped, so that it is difficult to perform the continuous operation. Further, it is difficult to maintain a uniform dispersion state of the iron fine particles, and there is a problem in injecting the uniform iron fine particles. The method of the present invention solves these problems, facilitates continuous operation, and enables uniform injection of iron fine particles.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view showing one example of a mixer used in the purification method of the present invention.
(B) is an example of a schematic diagram for explaining the purification method using the injection tube of the present invention.
FIG. 2 is a schematic view showing an example of a mixer that can be used in the purification method of the present invention.
FIG. 3 is a flowchart illustrating an example of an embodiment of a method for purifying a steelmaking dust slurry.
FIG. 4 is a sectional view showing an example of an embodiment of a purification method that can be used in the present invention.
[Explanation of symbols]
Reference Signs List 1 Mixing area 2, 3 Switching valve 4a Pipe 4b for introducing undiluted liquid 5a Pipe for introducing water 5a Pipe for discharging liquid passed through 5b Pipe for returning to raw liquid tank 10 Mixer 11 Grout 12 Packer 13 Rubber 14 Hole 15 Injection pipe 16 Contaminated soil 17 Injection part 42 Air-permeable columnar part 43 Air-permeable material 44 Horizontal air-permeable layer 45 Intake pipe 46 Impermeable sheet 49 Injection pipe 51 Underground impermeable ground 52 Impermeable layer

Claims (17)

A soil purification method comprising injecting an aqueous slurry containing iron fine particles into contaminated soil, wherein a stock solution of the aqueous slurry containing iron fine particles is mixed with water, and immediately after the mixing, the mixed solution is contaminated. Soil purification method characterized by injecting into soil. Mixing the stock solution with water and injecting it into the soil,
The mixing area, the pipe for introducing the undiluted solution fed from the undiluted solution tank and the pipe for introducing water to the upper part, and the pipe for discharging the passed liquid to the lower part, and the upper part of the upper part, where water is not introduced in the upper part, the passing liquid is the undiluted liquid. If left as is, it is a mixer having a pipe for returning it to the stock solution tank, a pipe for introducing water is connected to a pipe for introducing stock solution via a switching valve, and a pipe for returning stock solution discharges the passing solution. Connected to the stock solution tank via a switching valve, and when water is not introduced, the stock solution that has passed through the mixing area is returned to the stock solution tank, and when water is introduced, the stock solution is used. Using a mixer whose switching valve can be set to discharge a mixture of water for injection, injection into the soil by introducing water through the switching valve and discharging the resulting mixture. Do Soil remediation method according to Motomeko 1. To the contaminated soil, insert an injection tube having a mixing section, supply an undiluted solution of an aqueous slurry containing iron fine particles and water to the mixing section, mix them in the mixing section, and immediately after mixing, A soil purification method comprising injecting the mixture into contaminated soil. As the mixing section,
The mixing area, the pipe for introducing the undiluted solution fed from the undiluted solution tank and the pipe for introducing water to the upper part, and the pipe for discharging the passed liquid to the lower part, and the upper part of the upper part, where water is not introduced in the upper part, the passing liquid is the undiluted liquid. If left as is, it is a mixer having a pipe for returning it to the stock solution tank, a pipe for introducing water is connected to a pipe for introducing stock solution via a switching valve, and a pipe for returning stock solution discharges the passing solution. Connected to the stock solution tank via a switching valve, and when water is not introduced, the stock solution that has passed through the mixing area is returned to the stock solution tank, and when water is introduced, the stock solution is used. Using a mixer whose switching valve can be set to discharge a mixture of water for injection, injection into the soil by introducing water through the switching valve and discharging the resulting mixture. Do Soil remediation method according to Motomeko 3. The soil purification method according to claim 3 or 4, wherein the mixing section is provided above or inside the injection pipe. The soil purification method according to any one of claims 2 to 5, wherein the mixing unit or the mixing region includes a static mixer without a driving unit. The soil purification method according to claim 6, wherein the static mixer without a driving unit is a pipe or a static mixer filled with gravel. The soil purification method according to any one of claims 1 to 7, wherein the content of iron fine particles in the stock solution of the aqueous slurry containing iron fine particles is 10 to 50% by mass. The soil purification method according to any one of claims 1 to 8, wherein the amount of water mixed with the stock solution of the aqueous slurry containing iron fine particles is 1 to 50 times the stock solution. The soil purification method according to any one of claims 1 to 9, wherein the mixed solution has an iron fine particle content of 0.5 to 10% by mass. The soil purification method according to any one of claims 1 to 10, wherein the iron fine particles are steelmaking dust, reduced iron powder via goethite, or a mixture thereof. The soil purification method according to claim 1, wherein the average particle diameter of the iron fine particles is less than 10 μm. The soil purification method according to claim 1, wherein a particle diameter of 80% by mass of the iron fine particles is in a range of 0.1 to 0.3 μm. The soil purification method according to any one of claims 1 to 13, wherein the stock solution contains a hydrophilic resin and / or silica fine particles. The soil purification method according to any one of claims 1 to 14, wherein the water contains a hydrophilic resin and / or silica fine particles. The soil purification method according to claim 14 or 15, wherein the hydrophilic resin is at least one selected from polyacrylate, polyacrylamide, and polyvinyl alcohol. The soil purification method according to any one of claims 1 to 16, wherein the contaminants of the contaminated soil are organic halides and / or hexavalent chromium.

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