JP2004181303A - Treatment method and treating agent for soil contaminated with arsenic or waste contaminated with arsenic - Google Patents
Treatment method and treating agent for soil contaminated with arsenic or waste contaminated with arsenic Download PDFInfo
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- JP2004181303A JP2004181303A JP2002348987A JP2002348987A JP2004181303A JP 2004181303 A JP2004181303 A JP 2004181303A JP 2002348987 A JP2002348987 A JP 2002348987A JP 2002348987 A JP2002348987 A JP 2002348987A JP 2004181303 A JP2004181303 A JP 2004181303A
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- 239000002689 soil Substances 0.000 title claims abstract description 61
- 229910052785 arsenic Inorganic materials 0.000 title claims abstract description 45
- 239000003795 chemical substances by application Substances 0.000 title claims abstract description 44
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 239000002699 waste material Substances 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 26
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- 239000007864 aqueous solution Substances 0.000 claims abstract description 17
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- 229910019142 PO4 Inorganic materials 0.000 claims description 14
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 14
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- 239000003638 chemical reducing agent Substances 0.000 claims description 9
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- DCCWEYXHEXDZQW-BYPYZUCNSA-N (2s)-2-[bis(carboxymethyl)amino]butanedioic acid Chemical compound OC(=O)C[C@@H](C(O)=O)N(CC(O)=O)CC(O)=O DCCWEYXHEXDZQW-BYPYZUCNSA-N 0.000 claims description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical class OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical class [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 claims 1
- 239000000243 solution Substances 0.000 abstract description 3
- 239000000126 substance Substances 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 238000005406 washing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- DJHGAFSJWGLOIV-UHFFFAOYSA-N Arsenic acid Chemical compound O[As](O)(O)=O DJHGAFSJWGLOIV-UHFFFAOYSA-N 0.000 description 4
- 229940000488 arsenic acid Drugs 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- -1 alkali metal salts Chemical class 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000010828 elution Methods 0.000 description 3
- CIOXZGOUEYHNBF-UHFFFAOYSA-N (carboxymethoxy)succinic acid Chemical compound OC(=O)COC(C(O)=O)CC(O)=O CIOXZGOUEYHNBF-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- JYXGIOKAKDAARW-UHFFFAOYSA-N N-(2-hydroxyethyl)iminodiacetic acid Chemical compound OCCN(CC(O)=O)CC(O)=O JYXGIOKAKDAARW-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- OWTFKEBRIAXSMO-UHFFFAOYSA-N arsenite(3-) Chemical compound [O-][As]([O-])[O-] OWTFKEBRIAXSMO-UHFFFAOYSA-N 0.000 description 2
- GCPXMJHSNVMWNM-UHFFFAOYSA-N arsenous acid Chemical compound O[As](O)O GCPXMJHSNVMWNM-UHFFFAOYSA-N 0.000 description 2
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- XYBHHDIIOKAINY-UHFFFAOYSA-N 2-(1,2-dicarboxyethylamino)-3-hydroxybutanedioic acid Chemical compound OC(=O)C(O)C(C(O)=O)NC(C(O)=O)CC(O)=O XYBHHDIIOKAINY-UHFFFAOYSA-N 0.000 description 1
- CIEZZGWIJBXOTE-UHFFFAOYSA-N 2-[bis(carboxymethyl)amino]propanoic acid Chemical compound OC(=O)C(C)N(CC(O)=O)CC(O)=O CIEZZGWIJBXOTE-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
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- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 1
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- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 description 1
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- Processing Of Solid Wastes (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、ヒ素汚染土壌またはヒ素汚染廃棄物の処理方法および処理薬剤に関するものであり、詳しくは、処理対象物に損傷を与えることなくヒ素を良好に分離除去することができ、取り扱い性に優れ、かつコスト的にも有利であるヒ素汚染土壌またはヒ素汚染廃棄物の処理方法および処理薬剤に関するものである。
【０００２】
【従来の技術】
ヒ素は有機物のように分解できないためヒ素汚染土壌またはヒ素汚染廃棄物に対してはこれまで、封じ込め、飛散防止、セメントによる固定・不溶化、最終処分場への埋め立て処分といった対策がとられてきた。しかしこれらの方法では、ヒ素は土壌中または廃棄物中に残留したままであるため、雨水や地下水の浸透などによってヒ素が溶出して、再び環境汚染を引き起こすことが心配されている。このような問題を解決するために、ヒ素で汚染された土壌を強アルカリ性の水酸化ナトリウム水溶液で洗浄する方法（例えば、非特許文献１参照）、リン酸で洗浄する方法（重金属類除去方法）（例えば、特許文献１参照）、リン酸塩により洗浄する方法（ヒ素汚染土壌浄化剤およびこのものを用いたヒ素汚染土壌の浄化方法）（例えば、特許文献２参照）などが提案されている。
【０００３】
【非特許文献１】
Ｉ．Ａ．Ｌｅｇｉｅｃ， “ＤｕＰｏｎｔ Ｓｏｉｌ Ｗａｓｈｉｎｇ Ｔｅｃｈｎｏｌｏｇｙ Ｐｒｏｇｒａｍ ａｎｄ
Ｔｒｅｔｍｅｎｔ ｏｆ Ａ ｒｓｅｎｉｃ Ｃｏｎｔａｍｉｎａｔｅｄ Ｓｏｉｌｓ”， Ｅｎｉｖｒｏｎｍｅｎｔａｌ
Ｐｒｏｇｒｅｓｓ， １６（１）， ２９−３４（１９９７）
【特許文献１】
特許第３２４５１３８号公報
【特許文献２】
特開２００１−２２５０５２号公報
【０００４】
【発明が解決しようとする課題】
しかしながら、前記非特許文献１に開示された技術は、強アルカリで洗浄するため土壌に著しく損傷を与える上、強アルカリ溶液の保管およびその取り扱いに細心の注意が必要である。
また前記特許文献１および２に開示された技術は、１０質量％を超えてリン酸またはリン酸塩の高濃度溶液を使用するため、コストが高くなるという問題点がある。
したがって本発明の目的は、処理対象物に損傷を与えることなくヒ素を良好に分離除去することができ、取り扱い性に優れ、かつコスト的にも有利であるヒ素汚染土壌またはヒ素汚染廃棄物の処理方法および処理薬剤を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者らは鋭意研究を重ねた結果、前記の目的を達成することができた。
すなわち本発明の処理方法は、少なくともキレート剤が溶解した水溶液からなる処理薬剤をヒ素汚染土壌またはヒ素汚染廃棄物に接触させる接触工程と、前記接触工程後、前記土壌または廃棄物から前記処理薬剤を回収する回収工程とを有することを特徴としている。
この構成によれば、処理薬剤にキレート剤が含まれているため、処理薬剤をヒ素汚染土壌またはヒ素汚染廃棄物に接触させると、ヒ素汚染土壌またはヒ素汚染廃棄物に含まれるヒ素が溶出され易くなり、ヒ素が処理薬剤に溶解される。次いで、このような処理薬剤を回収することで、ヒ素が処理薬剤と共に回収され、ヒ素汚染土壌またはヒ素汚染廃棄物からヒ素が良好に分離除去される。
また強アルカリ等を使用する必要がないため、処理対象物に損傷を与えることがなく、取り扱い性に優れる。さらに、高価な薬剤を多量に使用する必要がないため、コスト的にも有利である。
また本発明は、少なくともキレート剤が溶解した水溶液からなることを特徴とするヒ素汚染土壌またはヒ素汚染廃棄物用処理薬剤を提供するものであり、この構成によれば前記処理方法と同様の効果が得られる。
【０００６】
【発明の実施の形態】
まず、本発明の処理薬剤について説明する。
本発明の処理薬剤は、前記のように少なくともキレート剤が溶解した水溶液からなることを特徴としている。キレート剤は、金属イオン封鎖剤とも呼ばれ、金属との間で水溶性の金属配位化合物を形成する機能を有するものである。このようなキレート剤としては、例えば分子内にカルボキシル基および／またはアミノ基を有し、鉄やアルミニウムなどの金属と安定な水溶性キレートを生成するものを挙げることができ、さらに具体的には、エチレンジアミン四酢酸（ＥＤＴＡ）、Ｌ−アスパラギン酸−Ｎ，Ｎ−二酢酸（ＡＳＤＡ）、グルタミン酸二酢酸（ＧＬＤＡ）、ヒドロキシエチルイミノ二酢酸（ＨＥＩＤＡ）、カルボキシメチルオキシコハク酸（ＣＭＯＳ）、３−ヒドロキシ−２、２’−イミノジコハク酸（ＨＩＤＳ）、ニトリロ三酢酸、ジエチレントリアミン五酢酸、ヒドロキシエチレンジアミン三酢酸、ヒドロキシエチレンジホスホン酸、メチルグリシン二酢酸などが挙げられ、中でもエチレンジアミン四酢酸（ＥＤＴＡ）、Ｌ−アスパラギン酸−Ｎ，Ｎ−二酢酸（ＡＳＤＡ）が好ましい。
また本発明によれば、キレート剤が水溶液中０．０１〜３質量％の範囲で溶解されていると、ヒ素の抽出効率が高まり好ましい。この抽出効率は、キレート剤が水溶液中０．０３〜０．３質量％の範囲で溶解されていることによりさらに高まる。
【０００７】
また本発明の処理薬剤は、リン酸またはリン酸塩をさらに含むことができる。リン酸塩としては、例えばリン酸のナトリウム塩、カリウム塩などのアルカリ金属塩が挙げられる。
リン酸またはリン酸塩は、例えば土壌からのヒ素の溶出を促進させる効果を提供するものである。この効果は、リン酸またはリン酸塩の使用割合が水溶液中０．１〜１０質量％の範囲であるときに一層高まる。前述のように従来技術ではリン酸またはリン酸塩を１０質量％を超えて使用していたが、本発明の一実施形態によれば、キレート剤と併用することにより、リン酸またはリン酸塩の使用割合を前記のように非常に少なくしても、該効果を享受することができる。
【０００８】
また本発明の処理薬剤は還元剤をさらに含むことができる。還元剤は、前記のリン酸またはリン酸塩と併用してもしなくてもよい。還元剤は、例えば亜硫酸塩、亜硫酸水素塩、次亜硫酸塩などが挙げられ、例えば土壌からのヒ素の溶出を促進させる効果を提供するものである。この効果は、還元剤の使用割合が水溶液中０．５〜１０質量％の範囲であるときに一層高まる。
【０００９】
次に本発明の処理方法について説明する。
本発明の処理方法は、前記の処理薬剤をヒ素汚染土壌またはヒ素汚染廃棄物に接触させる接触工程と、接触工程後、前記土壌または廃棄物から処理薬剤を回収する回収工程とを有している。
具体的なヒ素汚染土壌の処理方法は、次に示す２つの方法を例示することができる。
１）先ず土壌中のヒ素汚染された部分を特定し、この部分を矢板等の遮水壁で囲う。次に、遮水壁で囲われた領域に、注入井戸（処理薬剤注入用の縦穴）と揚水井戸（処理薬剤回収用の縦穴）を掘孔する。続いて、注入井戸から本発明の処理薬剤を注入し、汚染土壌と処理薬剤を接触させる。処理薬剤注入後あるいは処理薬剤を注入しながら揚水井戸から揚水し、注入した処理薬剤を回収する。この場合の接触時間は通常数ヶ月程度である。
２）土壌中のヒ素汚染された部分を特定し、掘削して汚染土壌を分離する。こ汚染土壌と本発明の処理薬剤とを洗浄槽に入れ攪拌する。その後、固液分離を行い、清浄土壌と水溶液に分離する。この場合の接触時間は通常数時間〜１ヵ月程度である。
ここで、汚染土壌に対する本発明の処理薬剤の使用割合は、土壌に含まれるヒ素量、土質などを勘案して予備実験から簡単に決定することができるが、例えば乾燥土壌１ｋｇに対し、本発明の処理薬剤を１〜２０ｌの割合で使用することができる。
なお、いずれの場合も接触終了は、被処理対象物の一部をサンプリングし、その中のヒ素濃度が所定以下の値となった時とする。
なお、ヒ素汚染廃棄物についても前記１）、２）と同様の方法で処理がなされる。
また、本発明の処理薬剤は、前記の各種成分の他、必要に応じてその他の各種添加剤を含有することができることは言うまでもない。
【００１０】
【作用】
土壌中のヒ素は主にヒ酸、亜ヒ酸の形で存在し、特に鉄、アルミニウム、マンガンの酸化物あるいは水和酸化物と複雑な化合物を形成して存在していると考えられている。
本発明の処理薬剤がキレート剤を含むことにより、ヒ酸、亜ヒ酸が結合している鉄、マンガンがキレートされ、キレート化合物と共に、フリーとなったヒ酸イオン、亜ヒ酸イオンが溶出し、本発明の処理薬剤に溶解される。
次に、このようにヒ酸イオンや亜ヒ酸イオンが溶解された処理薬剤を回収することで、ヒ素が分離除去される。
また、リン酸またはリン酸塩は、ヒ酸と同様な形態で土壌又は汚染廃棄物に吸着すると考えられている。そのため、土壌中のヒ酸を溶出し易くする効果がある。さらにリン酸またはリン酸塩をキレート剤と併用することにより、それぞれの薬剤の使用量を減少させることもできる。
また、還元剤を用いると、鉄やマンガンが還元され土壌とこれらの金属の結合が弱くなるため、土壌中のヒ素を溶出し易くする効果がある。
【００１１】
【実施例】
以下、本発明を実施例および比較例によりさらに説明するが、本発明はこれらの例に限定されるものではない。
実施例１〜５および比較例１〜３
化学工場の敷地から採取したヒ素汚染土壌を風乾し、２ｍｍ以下にふるい分けした。この土壌試料５ｇと下記表１に示すような各種水溶液５０ｍｌとを、１００ｍｌ容のフタ付きポリ容器に入れ、２００ｒｐｍの条件で２４時間振盪した。振盪液を遠心分離し、上澄み液を０．４５μｍのフィルターでろ過した後、ろ液のヒ素濃度を水素化物発生原子吸光法にて測定した。結果を表１に併せて示す。なお水をコントロールとし、水のヒ素の溶出量を１倍としたときの相対値も記載した。
【００１２】
【表１】
表１から明らかなように本発明の処理薬剤を用いた実施例によれば、キレート剤を含まない比較例の処理薬剤に比べ、約４倍から８倍超の割合でヒ素を除去することができる。
【００１４】
実施例６〜７
化学工場の敷地から採取したヒ素汚染土壌を風乾し、５ｍｍ以下にふるい分けした。この土壌試料５０ｇをアクリル製カラム（内径３０ｍｍφ、長さ１００ｍｍ）に充填し、下記表２に示す各水溶液を５０ｍｌ／ｄａｙの条件で上向流で合計８００ｍｌ通水した。カラム出口から採水してヒ素濃度を水素化物発生原子吸引光法にて測定した。結果を併せて表２に示す。なお表２の結果は、ヒ素の除去率（溶出量／含有量）を示している。
【００１５】
【表２】
表２から明らかなように本発明の処理薬剤を用いた実施例によれば、キレート剤を含まない比較例の処理薬剤に比べ、約１．５倍から３倍超の割合でヒ素を除去することができる。
【００１７】
【発明の効果】
以上の説明で明らかなように本発明によれば、処理対象物に損傷を与えることなくヒ素を良好に分離除去することができ、取り扱い性に優れ、かつコスト的にも有利であるヒ素汚染土壌またはヒ素汚染廃棄物の処理方法および処理薬剤が提供され、ヒ素による環境汚染を防止し、地球環境保全を図る上で極めて有意義である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and a chemical for treating arsenic-contaminated soil or arsenic-contaminated waste. More specifically, the present invention can satisfactorily separate and remove arsenic without damaging the object to be treated, and is excellent in handleability. The present invention also relates to a method and a chemical for treating arsenic-contaminated soil or arsenic-contaminated waste, which are advantageous in terms of cost.
[0002]
[Prior art]
Since arsenic cannot be decomposed like organic matter, measures have been taken for arsenic-contaminated soil or arsenic-contaminated waste, such as containment, shatter prevention, cement fixation / insolubilization, and landfill disposal at final disposal sites. However, in these methods, since arsenic remains in soil or waste, there is a concern that arsenic is eluted due to infiltration of rainwater or groundwater and causes environmental pollution again. In order to solve such a problem, a method of washing soil contaminated with arsenic with a strongly alkaline sodium hydroxide aqueous solution (for example, see Non-Patent Document 1) and a method of washing with phosphoric acid (a method of removing heavy metals) (For example, see Patent Document 1), a method of washing with a phosphate (an arsenic-contaminated soil purifying agent and a method for purifying arsenic-contaminated soil using the same) (for example, see Patent Document 2).
[0003]
[Non-patent document 1]
I. A. Legiec, “DuPont Soil Washing Technology Program and
"Treatment of Arsenic Contained Soils", Environmental
Progress, 16 (1), 29-34 (1997)
[Patent Document 1]
Japanese Patent No. 3245138 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2001-225052
[Problems to be solved by the invention]
However, the technique disclosed in Non-Patent Document 1 significantly damages soil because it is washed with a strong alkali, and requires careful attention to storage and handling of a strong alkali solution.
In addition, the techniques disclosed in Patent Documents 1 and 2 have a problem that the cost is increased because a high concentration solution of phosphoric acid or phosphate is used in excess of 10% by mass.
Therefore, an object of the present invention is to treat arsenic-contaminated soil or arsenic-contaminated waste, which can satisfactorily separate and remove arsenic without damaging the object to be treated, is excellent in handleability, and is advantageous in cost. It is to provide a method and a treatment agent.
[0005]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have achieved the above object.
That is, the treatment method of the present invention is a contact step of contacting a treatment agent comprising an aqueous solution containing at least a chelating agent with arsenic-contaminated soil or arsenic-contaminated waste, and after the contacting step, the treatment agent is removed from the soil or waste. And a collecting step of collecting.
According to this configuration, since the treatment agent contains the chelating agent, when the treatment agent is brought into contact with arsenic-contaminated soil or arsenic-contaminated waste, arsenic contained in the arsenic-contaminated soil or arsenic-contaminated waste is easily eluted. Arsenic is dissolved in the treatment agent. Next, by collecting such a treatment agent, arsenic is collected together with the treatment agent, and arsenic is satisfactorily separated and removed from arsenic-contaminated soil or arsenic-contaminated waste.
Further, since it is not necessary to use a strong alkali or the like, the object to be treated is not damaged, and the handleability is excellent. Further, since it is not necessary to use a large amount of expensive drugs, it is advantageous in terms of cost.
Further, the present invention provides a treating agent for arsenic-contaminated soil or arsenic-contaminated waste, which is characterized by comprising at least an aqueous solution in which a chelating agent is dissolved. can get.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the treatment agent of the present invention will be described.
The treatment agent of the present invention is characterized by comprising an aqueous solution in which at least a chelating agent is dissolved as described above. The chelating agent is also called a sequestering agent and has a function of forming a water-soluble metal coordination compound with a metal. Examples of such a chelating agent include those having a carboxyl group and / or an amino group in the molecule and generating a stable water-soluble chelate with a metal such as iron or aluminum, and more specifically, , Ethylenediaminetetraacetic acid (EDTA), L-aspartic acid-N, N-diacetic acid (ASDA), glutamic acid diacetate (GLDA), hydroxyethyliminodiacetic acid (HEIDA), carboxymethyloxysuccinic acid (CMOS), 3- Hydroxy-2,2'-iminodisuccinic acid (HIDS), nitrilotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylenediaminetriacetic acid, hydroxyethylenediphosphonic acid, methylglycinediacetic acid, etc., among which ethylenediaminetetraacetic acid (EDTA), L -Aspartic acid-N, N-divinegar Acids (ASDA) are preferred.
According to the present invention, when the chelating agent is dissolved in the aqueous solution in the range of 0.01 to 3% by mass, the arsenic extraction efficiency increases, which is preferable. This extraction efficiency is further enhanced by the fact that the chelating agent is dissolved in the aqueous solution in the range of 0.03 to 0.3% by mass.
[0007]
Further, the treatment agent of the present invention can further contain phosphoric acid or phosphate. Examples of the phosphate include alkali metal salts such as sodium salt and potassium salt of phosphoric acid.
Phosphoric acid or phosphate provides an effect of promoting elution of arsenic from soil, for example. This effect is further enhanced when the proportion of phosphoric acid or phosphate used is in the range of 0.1 to 10% by mass in the aqueous solution. As described above, in the prior art, phosphoric acid or phosphate was used in excess of 10% by mass. However, according to one embodiment of the present invention, phosphoric acid or phosphate is used in combination with a chelating agent. The effect can be enjoyed even if the use ratio of is extremely small as described above.
[0008]
Further, the treatment agent of the present invention can further contain a reducing agent. The reducing agent may or may not be used in combination with the above-mentioned phosphoric acid or phosphate. Examples of the reducing agent include a sulfite, a bisulfite, a hyposulfite, and the like, which provide an effect of promoting elution of arsenic from soil, for example. This effect is further enhanced when the usage ratio of the reducing agent is in the range of 0.5 to 10% by mass in the aqueous solution.
[0009]
Next, the processing method of the present invention will be described.
The treatment method of the present invention includes a contact step of bringing the treatment agent into contact with the arsenic-contaminated soil or arsenic-contaminated waste, and a collection step of collecting the treatment agent from the soil or the waste after the contact step. .
Specific methods for treating arsenic-contaminated soil include the following two methods.
1) First, an arsenic-contaminated portion in the soil is specified, and this portion is surrounded by a water impervious wall such as a sheet pile. Next, an injection well (a vertical hole for injecting the processing chemical) and a pumping well (a vertical hole for collecting the processing chemical) are dug in the area surrounded by the impermeable wall. Subsequently, the treatment agent of the present invention is injected from the injection well, and the contaminated soil is brought into contact with the treatment agent. After injecting the treatment chemical or while injecting the treatment chemical, the water is pumped from the pumping well and the injected treatment chemical is collected. The contact time in this case is usually about several months.
2) Identify the arsenic-contaminated part of the soil and excavate to separate the contaminated soil. The contaminated soil and the treatment agent of the present invention are put into a washing tank and stirred. Thereafter, solid-liquid separation is performed to separate into clean soil and an aqueous solution. The contact time in this case is usually several hours to one month.
Here, the use ratio of the treatment agent of the present invention to the contaminated soil can be easily determined from preliminary experiments in consideration of the amount of arsenic contained in the soil, the soil quality, and the like. Can be used in a ratio of 1 to 20 l.
In any case, the end of the contact is determined when a part of the object to be processed is sampled and the arsenic concentration in the sample becomes a predetermined value or less.
Arsenic-contaminated waste is also treated in the same manner as in 1) and 2).
Needless to say, the treatment agent of the present invention can contain other various additives as required in addition to the above-mentioned various components.
[0010]
[Action]
Arsenic in soil is thought to exist mainly in the form of arsenic acid and arsenous acid, especially as a complex compound with iron, aluminum and manganese oxides or hydrated oxides. .
Since the treatment agent of the present invention contains a chelating agent, arsenic acid, iron and manganese to which arsenous acid is bound are chelated, and together with the chelate compound, free arsenic ions and arsenite ions are eluted. Dissolved in the treatment agent of the present invention.
Next, arsenic is separated and removed by collecting the treatment agent in which the arsenic ions and arsenite ions are dissolved as described above.
It is also believed that phosphoric acid or phosphate adsorbs to soil or contaminated waste in a form similar to arsenic acid. Therefore, there is an effect that arsenic acid in soil is easily eluted. Further, by using phosphoric acid or phosphate in combination with a chelating agent, the amount of each drug used can be reduced.
In addition, when a reducing agent is used, iron and manganese are reduced and the bond between the soil and these metals is weakened, so that there is an effect that arsenic in the soil is easily eluted.
[0011]
【Example】
Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
Examples 1 to 5 and Comparative Examples 1 to 3
The arsenic-contaminated soil collected from the site of the chemical factory was air-dried and sieved to 2 mm or less. 5 g of this soil sample and 50 ml of various aqueous solutions as shown in Table 1 below were placed in a 100-ml poly-container with a lid, and shaken at 200 rpm for 24 hours. The shaker was centrifuged, and the supernatant was filtered with a 0.45 μm filter, and the arsenic concentration of the filtrate was measured by a hydride generation atomic absorption method. The results are shown in Table 1. The relative value when water was used as a control and the amount of arsenic eluted in water was made 1 time is also described.
[0012]
[Table 1]
As is clear from Table 1, according to the example using the treatment agent of the present invention, arsenic can be removed at a ratio of about 4 to more than 8 times as compared with the treatment agent of the comparative example containing no chelating agent. it can.
[0014]
Examples 6 and 7
The arsenic-contaminated soil collected from the site of the chemical factory was air-dried and sieved to 5 mm or less. 50 g of this soil sample was packed into an acrylic column (inner diameter 30 mmφ, length 100 mm), and a total of 800 ml of each aqueous solution shown in the following Table 2 was passed upward in a 50 ml / day condition. Water was collected from the column outlet, and the arsenic concentration was measured by hydride generation atomic absorption spectroscopy. Table 2 also shows the results. The results in Table 2 show the arsenic removal rate (elution amount / content).
[0015]
[Table 2]
As is apparent from Table 2, according to the example using the treatment agent of the present invention, arsenic is removed at a ratio of about 1.5 to more than 3 times as compared with the treatment agent of the comparative example containing no chelating agent. be able to.
[0017]
【The invention's effect】
As is apparent from the above description, according to the present invention, arsenic-contaminated soil that can satisfactorily separate and remove arsenic without damaging the object to be treated, has excellent handleability, and is advantageous in cost Alternatively, a method and a chemical for treating arsenic-contaminated waste are provided, which are extremely significant in preventing environmental pollution by arsenic and conserving the global environment.
Claims (11)
前記接触工程後、前記土壌または廃棄物から前記処理薬剤を回収する回収工程と、
を有することを特徴とするヒ素汚染土壌またはヒ素汚染廃棄物の処理方法。A contacting step of contacting a treatment agent comprising an aqueous solution in which at least a chelating agent is dissolved with arsenic-contaminated soil or arsenic-contaminated waste;
After the contacting step, a collecting step of collecting the treatment agent from the soil or waste,
A method for treating arsenic-contaminated soil or arsenic-contaminated waste, comprising:
前記処理薬剤が、少なくともキレート剤が溶解した水溶液からなる、
ことを特徴とするヒ素汚染土壌またはヒ素汚染廃棄物用処理薬剤。A treatment agent used to separate arsenic from arsenic-contaminated soil or waste, comprising:
The treatment agent comprises an aqueous solution in which at least a chelating agent is dissolved,
A treatment agent for arsenic-contaminated soil or arsenic-contaminated waste, characterized in that:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002348987A JP2004181303A (en) | 2002-11-29 | 2002-11-29 | Treatment method and treating agent for soil contaminated with arsenic or waste contaminated with arsenic |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002348987A JP2004181303A (en) | 2002-11-29 | 2002-11-29 | Treatment method and treating agent for soil contaminated with arsenic or waste contaminated with arsenic |
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| JP2004181303A true JP2004181303A (en) | 2004-07-02 |
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|---|---|---|---|
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006028201A1 (en) * | 2004-09-10 | 2006-03-16 | Chubu Electric Power Co., Inc. | Method of purifying heavy metal-containing soil |
| JP2011190428A (en) * | 2010-02-17 | 2011-09-29 | Univ Of Tsukuba | Remover composition for heavy metal in soil, and method for removing heavy metal using the same |
| KR101548460B1 (en) * | 2014-05-16 | 2015-08-31 | 전북대학교산학협력단 | Soil washing solution composed of reducing and chelating agents and washing method using the same for remediation of arsenic contaminated soil |
| JP2015206205A (en) * | 2014-04-21 | 2015-11-19 | 株式会社大林組 | Foaming material for foam shield method, and foam shield method |
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2002
- 2002-11-29 JP JP2002348987A patent/JP2004181303A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006028201A1 (en) * | 2004-09-10 | 2006-03-16 | Chubu Electric Power Co., Inc. | Method of purifying heavy metal-containing soil |
| JP2006075777A (en) * | 2004-09-10 | 2006-03-23 | Chubu Electric Power Co Inc | Method for purifying heavy metal-containing soil |
| US7829754B2 (en) | 2004-09-10 | 2010-11-09 | Chubu Electric Power Co., Inc. | Method of cleaning heavy metals-containing soil |
| JP2011190428A (en) * | 2010-02-17 | 2011-09-29 | Univ Of Tsukuba | Remover composition for heavy metal in soil, and method for removing heavy metal using the same |
| JP2015206205A (en) * | 2014-04-21 | 2015-11-19 | 株式会社大林組 | Foaming material for foam shield method, and foam shield method |
| KR101548460B1 (en) * | 2014-05-16 | 2015-08-31 | 전북대학교산학협력단 | Soil washing solution composed of reducing and chelating agents and washing method using the same for remediation of arsenic contaminated soil |
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