JP2004066129A - Method of restoring soil polluted with heavy metal - Google Patents
Method of restoring soil polluted with heavy metal Download PDFInfo
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- JP2004066129A JP2004066129A JP2002230202A JP2002230202A JP2004066129A JP 2004066129 A JP2004066129 A JP 2004066129A JP 2002230202 A JP2002230202 A JP 2002230202A JP 2002230202 A JP2002230202 A JP 2002230202A JP 2004066129 A JP2004066129 A JP 2004066129A
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Landscapes
- Processing Of Solid Wastes (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、重金属で汚染された土壌（重金属汚染土壌）の修復方法に関するものである。
【０００２】
【従来の技術】
工場・事業所跡地等で土壌汚染の判明件数が年々増加している（平成１２年度土壌汚染調査・対策事例及び対応状況に関する調査結果の概要、平成１４年２月環境省環境管理局水環境部）。こうした土壌汚染原因物質として、重金属類が半分以上を占めている。
重金属で汚染された土壌については、これまでは（１）掘削除去、封じ込め、飛散防止、セメントによる固型化・不溶化、最終処分場への埋立処分及び（２）強酸による溶出といった対策がとられてきた。しかし、（１）の方法では、重金属はその全量がそのまま土壌中に残留するため、長期間にわたってその対策効果が持続するものではない。風雨や地下水の浸透などによって土壌中の重金属が溶出して、二次環境汚染を引き起こすリスクが存在する。また、（２）の方法については、汚染物質以外の土壌成分も抽出されて、後処理としての排水処理の困難さをもたらすと共に、土壌の損傷が大きいために土壌の再利用が困難になることが問題となっていた。
【０００３】
【発明が解決しようとする課題】
本発明は、土壌中の重金属を高効率で抽出除去することにより、環境リスクを大幅に低減するとともに、土壌を殆ど損傷せず、その再利用を可能にする重金属汚染土壌の修復方法を提供することをその課題とする。
【０００４】
【課題を解決するための手段】
本発明者らは、前記課題を解決すべく鋭意研究を重ねた結果、本発明を実施するに至った。
即ち、本発明によれば、以下に示す重金属汚染土壌の修復方法が提供される。（１）重金属汚染土壌を、該重金属に対して錯体形成能を有するキレート剤を含む水溶液を用いて洗浄処理する方法であって、該重金属と該キレート剤との反応により形成される重金属錯体が水溶性を示すｐＨ領域において、該水溶液のｐＨを、少なくとも１回変動させることを特徴とする重金属汚染土壌の修復方法。
（２）該洗浄処理中における該水溶液のｐＨが少なくとも１回は、１〜６の範囲に調節され、該洗浄処理の終了時における該水溶液のｐＨが４〜８の範囲にあることを特徴とする前記（１）に記載の重金属汚染土壌の修復方法。
（３）該洗浄処理を、超音波照射下において行うことを特徴とする前記（１）又は（２）に記載の重金属汚染土壌の修復方法。
（４）該重金属が、カドミウム、銅、鉛及び亜鉛の中から選ばれる少なくとも１種であることを特徴とする前記（１）〜（３）のいずれかに記載の重金属汚染土壌の修復方法。
【０００５】
【発明の実施の形態】
本発明の重金属汚染土壌の修復方法は、該土壌を、該重金属に対して錯体形成能を有するキレート剤を含む水溶液からなる洗浄液と接触させる洗浄工程を含む。
【０００６】
キレート剤としては、従来公知の各種のものを用いることができる。このようなものには、例えば、ポリアミノカルボン酸系キレート剤の他、ポリカルボン酸系キレート剤、アミン系キレート剤等が包含される。
【０００７】
前記ポリアミノカルボン酸系キレート剤としては、例えば、エチレンジアミン四酢酸、イミノ二酢酸、ニトリロ三酢酸、ヒドロキシエチルイミノ二酢酸、１，２−ジアミノシクロヘキサン−Ｎ，Ｎ，Ｎ′，Ｎ′−四酢酸、エチレンジエチルトリアミン−Ｎ，Ｎ，Ｎ′，Ｎ′′，Ｎ′′−五酢酸、ヒドロキシエチルエチレンジアミン三酢酸、ジヒドロキシエチルグリシン、酸性アミノ酸、それらの水溶性塩（ナトリウム塩等）等が挙げられる。
【０００８】
ポリカルボン酸系キレート剤としては、例えば、クエン酸、リンゴ酸、酒石酸、それらの水溶性塩等が挙げられる。
アミン系キレート剤としては、例えば、エチレンジアミン等が挙げられる。
【０００９】
洗浄液（水溶液）中のキレート剤の濃度は、土壌の汚染度にもよるが、一般的には、０．５〜３０％（ｗ／ｖ）、好ましくは１〜１０％（ｗ／ｖ）である。
【００１０】
洗浄液の使用割合は、土壌中に含まれる重金属を錯形成するのに必要な化学量論的量以上であればよい。一般的には、土壌中の重金属１当量当り、洗浄液中のキレート剤が１〜１０００、好ましくは１０〜５００当量となるような割合である。
洗浄液と汚染土壌との接触時間（洗浄処理時間）は、特に制約されないが、１２〜２４時間程度で充分である。
【００１１】
本発明により土壌と洗浄液とを接触させる場合、超音波照射を併用するのが好ましい。この場合、超音波の周波数は１０〜６００ＫＨｚ、好ましくは１０〜２００ＫＨｚである。その超音波処理時間は、１０〜６０分間、好ましくは２０〜４０分間程度である。
【００１２】
本発明の方法は、前記のようにして重金属汚染土壌を洗浄液を用いて洗浄処理するのに際し、該重金属と該キレート剤との反応により形成される重金属錯体が水溶性を示すｐＨ領域において、該洗浄液（水溶液）のｐＨを、少なくとも１回変動させる。この洗浄処理において、洗浄処理開始時の洗浄液のｐＨは重金属錯体が水溶性を示すｐＨ領域においていずれでも構わないが、好ましくは１〜６、さらに好ましくは１〜４の範囲に調節するのがよい。一方、洗浄処理終了時の洗浄液のｐＨは、４〜８、好ましくは６〜８の範囲になるようにするのがよい。
【００１３】
本発明においては、前記のように、洗浄処理中に、洗浄液のｐＨを少なくとも１回変動させるが、このｐＨ変動回数は複数回、例えば、２〜３回であることができる。この場合のｐＨの変動は、ｐＨを酸性又はアルカリ側に変動させるｐＨ調節剤を用いて行うことができる。このようなｐＨ調節剤としては、酸性物質又はアルカリ性物質が用いられる。このようなものとしては、例えば酸性物質としては、塩酸、硫酸、硝酸等が、アルカリ性物質としては、例えば、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸水素ナトリウム、水酸化カルシウム等が挙げられる。
【００１４】
洗浄処理中での洗浄液のｐＨ変動は、例えば、洗浄処理開始時の洗浄液のｐＨを１〜２の範囲に調節し、処理途中（中間部）の洗浄液のｐＨをｐＨ調節剤を用いて４〜５の範囲に調節し、処理後半での洗浄液のｐＨを６〜８の範囲になるよう行うことができる。また、処理開始時の洗浄液のｐＨを３〜５の範囲に調節し、処理途中又は処理後半時の洗浄液のｐＨを６〜８の範囲になるように行うことができる。また、洗浄処理開始時の洗浄液のｐＨを２〜３の範囲に調節し、処理途中（中間部）の洗浄液のｐＨをｐＨ調節剤を用いて１〜２の範囲に調節し、処理後半での洗浄液のｐＨを６〜８の範囲になるよう行うことができる。
【００１５】
洗浄液の温度は、通常、常温であるが、必要に応じて加温（例えば４０〜５０℃）に加温することもできる。
【００１６】
本発明で用いる被処理物質は、重金属汚染土壌であるが、この場合の重金属は、有害性重金属であり、このようなものには、例えば、カドミウム、銅、鉛、亜鉛等が包含される。その土壌中の濃度は、乾燥物基準で、通常、１０〜１００００ｍｇ／ｋｇであり、特に５００〜３０００ｍｇ／ｋｇ程度である。
【００１７】
前記土壌の洗浄処理後には、土壌と洗浄液とを分離する。この場合の分離方法としては、従来公知の固液分離法、例えば、濾過分離法、遠心分離法、沈降分離法等が用いられる。また、このようにして分離された土壌は、必要に応じ、水洗し、乾燥することができる。
【００１８】
【実施例】
以下、本発明を実施例によりさらに詳細に説明する。
【００１９】
参考例１（モデル汚染土壌の調製）
茨城県つくば市において採集した黄褐色森林土を１週間風乾したのち、標準ふるいで粒径２ｍｍ以下の土壌をふるい分けた。その適当量を塩化ビニル製容器にとり、各々２５ｍＭのカドミウム、銅、鉛、亜鉛混合水溶液を加え、ｐＨ４．０に調整し、随時しんとうさせながら３ヶ月間処理して汚染させた。水相をろ別し、得られたろ過残渣を数回水洗した後風乾して、モデル重金属汚染土壌Ａを調製した。モデル汚染土壌中の重金属含有量は米国ＥＰＡ Ｍｅｔｈｏｄ ３０５０Ｂに従って求め、その含有量はカドミウム９８２ｍｇ／ｋｇ、銅５，８５４ｍｇ／ｋｇ、鉛１７，０６１ｍｇ／ｋｇ、亜鉛９６１ｍｇ／ｋｇであった。
【００２０】
参考例２（土壌の洗浄方法）
３５ｍガラス遠沈管に汚染土壌Ａ１ｇと洗浄剤２０ｍＬをいれ、２０℃に保持した恒温槽中でしんとう器にて横方向（振幅１０ｃｍ）に所定時間しんとうした。この時、洗浄剤のｐＨは３Ｍ ＮａＯＨ又は１Ｍ ＨＣｌを用いて調節した。次に、ろ紙５種Ｂにて土壌をろ別し、さらにろ液を孔径０．４５μｍのメンブランフィルターでろ過した。得られたろ液について、重金属濃度をＩＣＰ発光分析法により測定した。
【００２１】
参考例３（超音波を用いる土壌の洗浄方法）
超音波発生装置はオートチェーサー型を用いた。３０ｍＬビーカーに汚染土壌１ｇと洗浄剤２０ｍＬを加え、プローブ先端を液面下２．５ｍｍに調節固定した後、超音波を照射した。この時、洗浄剤のｐＨは３Ｍ ＮａＯＨ又は１Ｍ ＨＣｌを用いて調節した。なお、超音波照射は室温にて実施した。超音波照射した処理液は、ろ紙５種Ｂにて土壌をろ別し、さらにろ液を孔径０．４５μｍのメンブランフィルターでろ過した。得られたろ液について、重金属濃度をＩＣＰ発光分析法により測定した。
【００２２】
実施例１
参考例１で調製したモデル汚染土壌Ａ１ｇに、参考例２に従って、０．０５ＭＥＤＴＡ（エチレンジアミン四酢酸）水溶液（ｐＨ３．５）２０ｍＬを洗浄剤として加え、２２時間洗浄した。次にｐＨを６．５に調節して、２時間洗浄した。重金属除去率は、未処理土壌中の重金属含有量に対する水相の重金属溶出量の割合で示した。得られた結果を表１に示す。いずれの重金属も洗浄剤のｐＨを３．５から６．５に調節することによって、ｐＨ３．５のみで洗浄した場合（比較例１）と同等の除去率を維持しながら、ｐＨ６．５のみで洗浄した場合（比較例２）よりも高い除去率を示した。これらの結果から、洗浄剤のｐＨを調節することにより、高い除去率を維持しつつ、土壌の中和処理も完了することができることを認めた。
【００２３】
【表１】
実施例２
参考例１で調製したモデル汚染土壌Ａ１ｇに、参考例２に従って、０．１Ｍ クエン酸水溶液（ｐＨ２．０）２０ｍＬを洗浄剤として加え、６時間洗浄した。次に、ｐＨを５．３に調節して１６時間洗浄した。さらに、ｐＨを６．５に調節して、２時間洗浄した。重金属除去率は、未処理土壌中の重金属含有量に対する水相の重金属溶出量の割合で示した。得られた結果を表２に示す。カドミウム、銅、鉛の除去率は、洗浄剤のｐＨを２から６．５へ調節することで、ｐＨ２．０（比較例３）、ｐＨ５．３（比較例４）、ｐＨ６．５（比較例５）各々のみで洗浄した場合のいずれよりも高い値を示した。特に鉛に関しては、顕著に除去率の上昇がみられ、銅についても除去率は大きく上昇した。しかしながら、亜鉛に関しては、処理ｐＨ５．３、ｐＨ６．５のみの場合と比べて除去率は高かったものの、処理ｐＨ２．０の場合に比べると除去率は低かった。これらの結果から、洗浄剤のｐＨを調節することにより、重金属除去率を向上させうることが確認された。また同時に土壌の中和処理も完了した。
【００２５】
【表２】
実施例３
参考例１で調製したモデル汚染土壌Ａ１ｇに、参考例３に従って、０．１Ｍ クエン酸水溶液（ｐＨ２．０）２０ｍＬを洗浄剤として加え、２０分間超音波を照射した。次に、ｐＨを５．３に調整して、８分間超音波を照射した。さらに、ｐＨを６．５に調整し２分間超音波を照射した。除去率は、未処理土壌中の重金属含有量に対する水相の重金属溶出量の割合で示した。得られた結果を表３に示す。カドミウム、銅、鉛の除去率は、ｐＨ２．０（比較例６）、ｐＨ５．３（比較例７）、ｐＨ６．５（比較例８）各々のみで処理した場合のいずれよりも高い値を示した。特に鉛に関しては、顕著に除去率の上昇がみられ、銅についても除去率は上昇した。しかしながら、亜鉛に関しては、ｐＨ５．３、ｐＨ６．５のみの場合と比べて除去率は上昇したものの、ｐＨ２．０の場合に比べると除去率は低かった。また除去率は、ｐＨを調節して２４時間洗浄した場合（実施例２の表２を参考）に比べ、短時間処理にも関らず上昇した。これらの結果から、洗浄剤のｐＨを調節することにより、除去率を向上させうることが確認された。また、同時に土壌の中和処理も完了した。また、超音波照射により、処理時間を大幅に短縮しつつ、除去効果を促進することが確認された。
【００２７】
【表３】
【発明の効果】
本発明によれば、重金属で汚染された土壌から重金属を高効率で抽出除去することができ、これによって該土壌を損傷することなく修復することができる。本発明により修復された土壌は、植物栽培用土壌や埋立用土壌等として利用することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for repairing soil contaminated with heavy metals (heavy metal contaminated soil).
[0002]
[Prior art]
The number of cases where soil contamination has been identified has been increasing year by year on the sites of factories and business sites (Summary of the 2000 survey results on soil contamination surveys, countermeasures, and response status, February 2002, Ministry of the Environment, Environment Management Bureau, Water Environment Department) ). Heavy metals account for more than half of these soil pollutants.
For soils contaminated with heavy metals, measures such as (1) excavation removal, containment, scattering prevention, solidification and insolubilization with cement, landfill disposal at final disposal sites, and (2) elution with strong acid have been taken so far. Have been. However, in the method (1), since the entire amount of heavy metal remains in the soil as it is, the countermeasure effect is not sustained for a long time. There is a risk that heavy metals in the soil will elute out due to wind and rain and infiltration of groundwater, causing secondary environmental pollution. In the method (2), soil components other than contaminants are also extracted, which causes difficulty in wastewater treatment as a post-treatment, and also makes it difficult to reuse soil due to large damage to the soil. Was a problem.
[0003]
[Problems to be solved by the invention]
The present invention provides a method for remediating heavy metal-contaminated soil, which significantly reduces environmental risks by extracting and removing heavy metals in soil with high efficiency, hardly damages the soil, and enables its reuse. That is the subject.
[0004]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have accomplished the present invention.
That is, according to the present invention, there is provided the following method for repairing heavy metal contaminated soil. (1) A method for washing heavy metal-contaminated soil with an aqueous solution containing a chelating agent capable of forming a complex with the heavy metal, wherein the heavy metal complex formed by the reaction between the heavy metal and the chelating agent is A method for repairing a soil contaminated with heavy metals, wherein the pH of the aqueous solution is changed at least once in a pH range showing water solubility.
(2) The pH of the aqueous solution is adjusted to a range of 1 to 6 at least once during the washing process, and the pH of the aqueous solution is 4 to 8 at the end of the washing process. The method for repairing heavy metal contaminated soil according to the above (1).
(3) The method for repairing heavy metal contaminated soil according to (1) or (2), wherein the cleaning treatment is performed under ultrasonic irradiation.
(4) The method for repairing heavy metal-contaminated soil according to any one of (1) to (3), wherein the heavy metal is at least one selected from cadmium, copper, lead, and zinc.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The method for repairing soil contaminated with heavy metals of the present invention includes a washing step of bringing the soil into contact with a washing solution comprising an aqueous solution containing a chelating agent capable of forming a complex with the heavy metal.
[0006]
Various conventionally known chelating agents can be used. Such a substance includes, for example, a polycarboxylic acid-based chelating agent, an amine-based chelating agent, and the like, in addition to a polyaminocarboxylic acid-based chelating agent.
[0007]
Examples of the polyaminocarboxylic acid-based chelating agent include ethylenediaminetetraacetic acid, iminodiacetic acid, nitrilotriacetic acid, hydroxyethyliminodiacetic acid, 1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid, Ethylene diethyltriamine-N, N, N ', N ", N" -pentaacetic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylglycine, acidic amino acids, and water-soluble salts thereof (such as sodium salts).
[0008]
Examples of the polycarboxylic acid-based chelating agent include citric acid, malic acid, tartaric acid, and water-soluble salts thereof.
Examples of the amine chelating agent include ethylenediamine.
[0009]
The concentration of the chelating agent in the washing solution (aqueous solution) is generally 0.5 to 30% (w / v), preferably 1 to 10% (w / v), depending on the degree of soil contamination. is there.
[0010]
The use ratio of the washing solution may be any amount as long as it is equal to or more than the stoichiometric amount necessary to complex heavy metals contained in soil. Generally, the ratio is such that the chelating agent in the washing solution is 1 to 1000, preferably 10 to 500 equivalents per equivalent of heavy metal in the soil.
The contact time (washing treatment time) between the washing liquid and the contaminated soil is not particularly limited, but about 12 to 24 hours is sufficient.
[0011]
When the soil and the washing liquid are brought into contact according to the present invention, it is preferable to use ultrasonic irradiation in combination. In this case, the frequency of the ultrasonic wave is 10 to 600 KHz, preferably 10 to 200 KHz. The ultrasonic treatment time is about 10 to 60 minutes, preferably about 20 to 40 minutes.
[0012]
In the method of the present invention, when the heavy metal-contaminated soil is subjected to the washing treatment using the washing solution as described above, the heavy metal complex formed by the reaction of the heavy metal and the chelating agent exhibits a water solubility in a pH range where the solubility is high. The pH of the washing solution (aqueous solution) is changed at least once. In this washing treatment, the pH of the washing solution at the start of the washing treatment may be any pH range in which the heavy metal complex exhibits water solubility, but is preferably adjusted to a range of 1 to 6, more preferably 1 to 4. . On the other hand, the pH of the cleaning solution at the end of the cleaning process is preferably in the range of 4 to 8, preferably 6 to 8.
[0013]
In the present invention, as described above, the pH of the cleaning solution is changed at least once during the cleaning process, and the number of times of the pH change may be a plurality of times, for example, two to three times. In this case, the pH can be changed using a pH adjuster that changes the pH to an acidic or alkaline side. As such a pH adjuster, an acidic substance or an alkaline substance is used. Examples of such substances include acidic substances such as hydrochloric acid, sulfuric acid, and nitric acid, and examples of alkaline substances include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate, and calcium hydroxide. .
[0014]
The pH fluctuation of the cleaning solution during the cleaning process may be adjusted, for example, by adjusting the pH of the cleaning solution at the start of the cleaning process to a range of 1 to 2 and adjusting the pH of the cleaning solution during the process (intermediate portion) to 4 to 4 using a pH regulator. 5, the pH of the washing solution in the latter half of the treatment can be adjusted to a range of 6 to 8. Further, the pH of the cleaning liquid at the start of the treatment can be adjusted to a range of 3 to 5 so that the pH of the cleaning liquid during the treatment or at the latter half of the treatment is in the range of 6 to 8. Further, the pH of the cleaning solution at the start of the cleaning process was adjusted to a range of 2 to 3, and the pH of the cleaning solution in the middle of the process (intermediate portion) was adjusted to a range of 1 to 2 using a pH adjuster. The washing can be performed so that the pH of the washing solution is in the range of 6 to 8.
[0015]
The temperature of the cleaning solution is usually room temperature, but it can be heated (for example, 40 to 50 ° C.) if necessary.
[0016]
The substance to be treated used in the present invention is a soil contaminated with heavy metals. In this case, the heavy metals are toxic heavy metals, and such substances include, for example, cadmium, copper, lead, zinc and the like. The concentration in the soil is usually 10 to 10000 mg / kg, and particularly about 500 to 3000 mg / kg on a dry matter basis.
[0017]
After the soil washing treatment, the soil and the washing liquid are separated. As a separation method in this case, a conventionally known solid-liquid separation method, for example, a filtration separation method, a centrifugal separation method, a sedimentation separation method, or the like is used. The soil thus separated can be washed with water and dried if necessary.
[0018]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
[0019]
Reference Example 1 (Preparation of model contaminated soil)
After the yellow-brown forest soil collected in Tsukuba City, Ibaraki Prefecture was air-dried for one week, soil having a particle size of 2 mm or less was sieved with a standard sieve. An appropriate amount thereof was placed in a container made of vinyl chloride, and a 25 mM aqueous solution of cadmium, copper, lead, and zinc was added thereto, and the pH was adjusted to 4.0. The aqueous phase was separated by filtration, and the obtained filtration residue was washed several times with water and air-dried to prepare a model heavy metal-contaminated soil A. The heavy metal content in the model contaminated soil was determined according to US EPA Method 3050B, and the content was 982 mg / kg of cadmium, 5,854 mg / kg of copper, 17,061 mg / kg of lead, and 961 mg / kg of zinc.
[0020]
Reference Example 2 (Soil cleaning method)
1 g of contaminated soil A and 20 mL of a detergent were placed in a 35-m glass centrifuge tube, and the mixture was shaken in a constant temperature bath maintained at 20 ° C. in a horizontal direction (amplitude: 10 cm) for a predetermined time. At this time, the pH of the detergent was adjusted using 3M NaOH or 1M HCl. Next, the soil was filtered off with filter paper type 5 B, and the filtrate was further filtered with a membrane filter having a pore size of 0.45 μm. About the obtained filtrate, the heavy metal concentration was measured by ICP emission spectrometry.
[0021]
Reference Example 3 (Soil cleaning method using ultrasonic waves)
The ultrasonic generator used was an auto chaser type. 1 g of contaminated soil and 20 mL of a detergent were added to a 30 mL beaker, and the probe tip was adjusted and fixed at 2.5 mm below the liquid level, and then irradiated with ultrasonic waves. At this time, the pH of the detergent was adjusted using 3M NaOH or 1M HCl. The ultrasonic irradiation was performed at room temperature. The treated solution subjected to the ultrasonic irradiation was subjected to filtration of soil using a filter paper type 5 B, and the filtrate was further filtered through a membrane filter having a pore size of 0.45 μm. About the obtained filtrate, the heavy metal concentration was measured by ICP emission spectrometry.
[0022]
Example 1
According to Reference Example 2, 20 mL of 0.05 M EDTA (ethylenediaminetetraacetic acid) aqueous solution (pH 3.5) was added as a detergent to 1 g of the model-contaminated soil A prepared in Reference Example 1, and washed for 22 hours. Then the pH was adjusted to 6.5 and washed for 2 hours. The heavy metal removal rate was represented by the ratio of the heavy metal elution amount of the aqueous phase to the heavy metal content in the untreated soil. Table 1 shows the obtained results. By adjusting the pH of the cleaning agent from 3.5 to 6.5 for all heavy metals, the removal rate was maintained at the same level as in the case of cleaning only at pH 3.5 (Comparative Example 1). The removal rate was higher than in the case of washing (Comparative Example 2). From these results, it was recognized that by adjusting the pH of the detergent, the neutralization treatment of the soil could be completed while maintaining a high removal rate.
[0023]
[Table 1]
Example 2
To 1 g of the model-contaminated soil A prepared in Reference Example 1, 20 mL of a 0.1 M aqueous citric acid solution (pH 2.0) was added as a cleaning agent according to Reference Example 2, and washed for 6 hours. Next, the pH was adjusted to 5.3 and washing was performed for 16 hours. Further, the pH was adjusted to 6.5, and washing was performed for 2 hours. The heavy metal removal rate was represented by the ratio of the heavy metal elution amount of the aqueous phase to the heavy metal content in the untreated soil. Table 2 shows the obtained results. The removal rates of cadmium, copper, and lead were adjusted to pH 2.0 (Comparative Example 3), pH 5.3 (Comparative Example 4), and pH 6.5 (Comparative Example) by adjusting the pH of the detergent from 2 to 6.5. 5) The value was higher than any of the cases where only each washes. In particular, the removal rate of lead was markedly increased, and the removal rate of copper was also significantly increased. However, with respect to zinc, although the removal rate was higher than in the case of only treatment pH 5.3 and pH 6.5, the removal rate was lower than in the case of treatment pH 2.0. From these results, it was confirmed that by adjusting the pH of the cleaning agent, the heavy metal removal rate could be improved. At the same time, soil neutralization was completed.
[0025]
[Table 2]
Example 3
To 1 g of the model-contaminated soil A prepared in Reference Example 1, 20 mL of a 0.1 M aqueous citric acid solution (pH 2.0) was added as a detergent according to Reference Example 3, and irradiated with ultrasonic waves for 20 minutes. Next, the pH was adjusted to 5.3, and ultrasonic waves were irradiated for 8 minutes. Further, the pH was adjusted to 6.5 and ultrasonic waves were irradiated for 2 minutes. The removal rate was represented by the ratio of the heavy metal elution amount of the aqueous phase to the heavy metal content in the untreated soil. Table 3 shows the obtained results. The removal rates of cadmium, copper, and lead show higher values than any of the treatments with only pH 2.0 (Comparative Example 6), pH 5.3 (Comparative Example 7), and pH 6.5 (Comparative Example 8). Was. In particular, the removal rate of lead was markedly increased, and the removal rate of copper was also increased. However, with respect to zinc, although the removal rate increased as compared to the case of only pH 5.3 and pH 6.5, the removal rate was lower than that of the case of pH 2.0. In addition, the removal rate increased in spite of the short-time treatment as compared with the case where washing was performed for 24 hours while adjusting the pH (see Table 2 of Example 2). From these results, it was confirmed that the removal rate could be improved by adjusting the pH of the detergent. At the same time, soil neutralization was completed. In addition, it was confirmed that the ultrasonic irradiation accelerated the removal effect while significantly shortening the processing time.
[0027]
[Table 3]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, heavy metal can be extracted and removed from the soil contaminated with heavy metal with high efficiency, and thereby the soil can be repaired without being damaged. The soil repaired by the present invention can be used as plant cultivation soil, landfill soil, and the like.
Claims (4)
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| JP2002230202A JP2004066129A (en) | 2002-08-07 | 2002-08-07 | Method of restoring soil polluted with heavy metal |
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| JP2002230202A JP2004066129A (en) | 2002-08-07 | 2002-08-07 | Method of restoring soil polluted with heavy metal |
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| JP2009039601A (en) * | 2007-08-06 | 2009-02-26 | Katsuyoshi Kondo | Method for removing heavy metal element in biomass and method for decontaminating heavy metal-contaminated soil |
| CN102580989A (en) * | 2012-03-01 | 2012-07-18 | 四川农业大学 | Application of polyacrylamide in amaranthus hypochondriacus for restoring soil polluted by heavy metal cadmium |
| JP2016064354A (en) * | 2014-09-24 | 2016-04-28 | 国立大学法人金沢大学 | Contaminated soil treating method |
| CN108971215A (en) * | 2018-06-11 | 2018-12-11 | 华东理工大学 | The heavy-metal contaminated soil restorative procedure filtered based on ultrasound |
| CN111630970A (en) * | 2020-06-03 | 2020-09-08 | 中节能大地环境修复有限公司 | Restoration process of salinized soil and application thereof |
| CN115055510A (en) * | 2022-06-14 | 2022-09-16 | 西北大学 | Remediation method and application of heavy metal contaminated soil |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2009039601A (en) * | 2007-08-06 | 2009-02-26 | Katsuyoshi Kondo | Method for removing heavy metal element in biomass and method for decontaminating heavy metal-contaminated soil |
| CN102580989A (en) * | 2012-03-01 | 2012-07-18 | 四川农业大学 | Application of polyacrylamide in amaranthus hypochondriacus for restoring soil polluted by heavy metal cadmium |
| JP2016064354A (en) * | 2014-09-24 | 2016-04-28 | 国立大学法人金沢大学 | Contaminated soil treating method |
| CN108971215A (en) * | 2018-06-11 | 2018-12-11 | 华东理工大学 | The heavy-metal contaminated soil restorative procedure filtered based on ultrasound |
| CN108971215B (en) * | 2018-06-11 | 2020-07-24 | 华东理工大学 | Heavy metal contaminated soil remediation method based on ultrasonic suction filtration |
| CN111630970A (en) * | 2020-06-03 | 2020-09-08 | 中节能大地环境修复有限公司 | Restoration process of salinized soil and application thereof |
| CN115055510A (en) * | 2022-06-14 | 2022-09-16 | 西北大学 | Remediation method and application of heavy metal contaminated soil |
| CN115055510B (en) * | 2022-06-14 | 2023-09-22 | 西北大学 | Restoration method and application of heavy metal contaminated soil |
| CN116282577A (en) * | 2023-03-25 | 2023-06-23 | 西安建筑科技大学 | Method for repairing copper-containing wastewater by biomineralization based on pH value regulation and control |
| CN116282577B (en) * | 2023-03-25 | 2024-05-28 | 西安建筑科技大学 | Method for repairing copper-containing wastewater by biomineralization based on pH value regulation and control |
| CN116855254A (en) * | 2023-07-03 | 2023-10-10 | 江苏莘野生物科技有限公司 | Long-acting controllable acid soil conditioner and preparation method thereof |
| CN116855254B (en) * | 2023-07-03 | 2024-06-07 | 江苏莘野生物科技有限公司 | Long-acting controllable acid soil conditioner and preparation method thereof |
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