JP2004154645A - Stabilization treatment method for heavy metals - Google Patents
Stabilization treatment method for heavy metals Download PDFInfo
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- JP2004154645A JP2004154645A JP2002321207A JP2002321207A JP2004154645A JP 2004154645 A JP2004154645 A JP 2004154645A JP 2002321207 A JP2002321207 A JP 2002321207A JP 2002321207 A JP2002321207 A JP 2002321207A JP 2004154645 A JP2004154645 A JP 2004154645A
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、重金属類を溶出するおそれがある重金属類含有汚染土壌または汚泥中の重金属類を安定化して、地表や地中、地下水などの周囲環境に汚染を拡散させないための重金属類安定化処理方法に関する。
【０００２】
【従来の技術】
土壌は元来水質を浄化する機能および地下水を涵養する機能を有しているが、近年の急速な工業化に伴い、土壌自体が有害物質に汚染され、水質の浄化機能や地下水の涵養機能を有しないばかりか周辺環境へ汚染を拡大させている事例も多く、社会的な問題として、その対策法が多く報告されている。
【０００３】
重金属を溶出する汚染土壌の処理方法として、従来より広く一般的に行われているのがセメント固化法、薬剤による不溶化法である。
【０００４】
セメント固化法は、セメント鉱物の水和生成物に重金属を取り込み、固化安定化させる方法であり、一般的にはポルトランドセメントなどと汚染土壌を混合、混錬して、土壌の付着水によるセメント鉱物の水和反応により土壌を凝結させて重金属類の溶出を抑制するものである。しかし、セメント鉱物の水和反応時に生成される水酸化カルシウム（Ｃａ（ＯＨ）２）により、土壌中のｐＨは１２以上に上昇するため、重金属の中でも鉛等の両性元素は溶解度を増大させ、周辺環境への汚染を拡大させる問題を抱えている。
【０００５】
上記したｐＨ上昇の問題点を解決すべく、特許文献１にはｐＨが１１以下の低アルカリ性セメントによる重金属溶出抑制材を用いることが提案されており、それにより両性元素である鉛等を安定化することができる。
【０００６】
しかし、この方法は、セメントを混合するために土壌が固形化し、土壌として再生することは困難である。また、セメントは混合放置すると凝結してしまうため作業中断毎に設備を洗浄する必要があるなど作業性も悪い。さらに、セメントは高価であり浄化必要土壌量が多量の場合は膨大な処理費用が必要となる。
【０００７】
薬剤による不溶化法は、重金属捕集剤等の薬剤を添加混合することで可溶性重金属を化学反応または吸着などにより難溶性物質に変えて不溶化する方法であるが、この方法は対象とする重金属の種類により薬剤を選定する必要があり、複数の重金属類を溶出する土壌に対しては、複数の薬剤が必要になるうえ、薬剤同士による化学反応による影響などを考慮する必要がある。
【０００８】
また、薬剤による不溶化法は、短期的に重金属を不溶化できたとしても、その不溶化効果の持続性は酸性雨等の外的環境の変化によっては大きく損なわれる可能性があるため、長期的には十分な処理方法とはいえない。
【０００９】
一方、特許文献２には、鉄鋼スラグを利用した重金属含有廃棄物用処理剤および重金属含有廃棄物の安定化処理法も提案されているが、この技術ではスラグを粉砕する必要がある上、水や分散剤を加えて混合する必要がある。スラグは製鉄過程で副生する２次産物であるため安価ではあるが粉砕するためにはエネルギー、粉砕専用設備が必要となりコストがかかる。また、水や分散剤を加えて混合するため混合用の設備が必要となる上、広範囲に汚染された土壌においては長期にわたる工期期間が必要となる。
【００１０】
また、特許文献３には、高炉スラグ、転炉スラグ等のアルカリ資材を用いて土壌の酸性化防止および土壌ｐＨ安定化方法が提案されているが、ｐＨを調整して水酸化物として不溶化する方法であるため、水酸化物を生成しない砒素や水酸化物の溶解度が十分低くない重金属に対して不溶化は困難である。また、最大粒径３０ｍｍのアルカリ資材を用いているが、粒径が１０ｍｍを越えるとアルカリ成分の溶出が極めて緩慢になり、目的のｐＨに調整するのに大量のアルカリ資材が必要となり経済的ではない。
【００１１】
【特許文献１】
特開平１０−２５８２６３号公報（特許請求の範囲等）
【特許文献２】
特開平９−１９４３５号公報（特許請求の範囲等）
【特許文献３】
特開２０００−２８２０３４号公報（特許請求の範囲等）
【００１２】
【発明が解決しようとする課題】
以上のように、従来の技術では、重金属類含有汚染土壌に対して重金属類安定化処理する有効な技術が未だ得られていないのが現状である。重金属類含有汚泥に対しても同様である。
【００１３】
本発明はかかる事情に鑑みてなされたものであって、重金属類を溶出する重金属類含有汚染土壌または汚泥に対して簡単でかつ安価に、さらには、広範囲または大量の汚染土壌または汚泥に対して短期間で安定化処理することができ、しかもその効果を長期に亘って持続させることができる重金属類安定化処理方法を提供することを目的とする。
【００１４】
【課題を解決するための手段】
本発明者等は課題を解決出来る処理法について研究を重ねてきた結果、重金属類を溶出する重金属含有汚染土壌または汚泥に対し、鉄鋼スラグを散布あるいは混合することにより、鉄鋼スラグへの吸着固定化、鉄鋼スラグの含有成分による化学反応により難溶性物質に変えて長期にわたり安定化させることを見出し、本発明に至った。
【００１５】
本発明は、自然起因、人為起因に関わらず重金属類を含有し、その重金属類の一部を溶出するおそれのあるいわゆる汚染土壌または汚泥において長期間にわたり重金属類を不溶化することにより、重金属類の流出による周辺土壌、地下水への二次的汚染拡大を防止する方法を提供するものである。
【００１６】
第１発明は、重金属類を溶出するおそれのある重金属類含有汚染土壌または汚泥に対し、鉄鋼スラグを散布することにより、前記汚染土壌または汚泥中の重金属類を安定化することを特徴とする重金属類安定化処理方法を提供するものである。
【００１７】
これにより、雨水などにより鉄鋼スラグから重金属類の不溶化に有効な成分が溶出し、汚染土壌または汚泥中に浸透する過程における化学反応により含有する重金属類が不溶化される。この第１発明は、土壌表面あるいは表層部に鉄鋼スラグを散布するだけでよく、特別な設備を必要とせず、広範囲に及ぶ汚染土壌においても短期間かつ低コストでの施工が可能である。
【００１８】
第２発明は、重金属類を溶出するおそれのある重金属類含有汚染土壌または汚泥に対し、鉄鋼スラグを混合することにより、前記汚染土壌または汚泥中の重金属類を安定化することを特徴とする重金属類安定化処理方法を提供するものである。
【００１９】
これにより、土壌間隙水により鉄鋼スラグから重金属類の不溶化に有効な成分が溶出することに伴う化学反応によって溶出重金属類の不溶化が生じ、さらには、鉄鋼スラグ自体への汚染土壌からの溶出重金属類の吸着、固定化によって重金属類が不溶化される。この第２発明は、化学反応による不溶化のみならずスラグ自体への吸着、固定化も寄与するため、高汚染土壌の不溶化に効果的である。また、混合することにより鉄鋼スラグが処理土壌中に均一に拡散するため即効的不溶化効果が得られる。
【００２０】
【発明の実施の形態】
以下に本発明の実施の形態について説明する。
本発明の第１の実施形態においては重金属類を溶出するおそれがある重金属類含有汚染土壌または汚泥に鉄鋼スラグを散布することにより汚染土壌または汚泥中の重金属類を不溶化して安定化させ、重金属類の溶出を抑制する。
【００２１】
この場合に、鉄鋼スラグは、土壌等を掘削せずにその表面に散布すれば十分である。すなわち、鉄鋼スラグを汚染土壌または汚泥の表面または表層に散布することにより、雨水等により鉄鋼スラグから溶出した重金属類の不溶化に有効な成分が、汚染土壌または汚泥中に浸透する過程における化学反応により含有する重金属類を不溶化する。
【００２２】
散布の方法は特に限定するものではないが、例えば、空気による圧送散布、ロータリーによる切り出し散布、粉末の場合は水と混錬してスラリー状としポンプで散布する方法などが挙げられる。
【００２３】
本発明の第２の実施形態においては、重金属類を溶出するおそれのある重金属類含有汚染土壌または汚泥に対し、鉄鋼スラグを混合することにより、前記汚染土壌または汚泥中の重金属類を不溶化して安定化させ、重金属類の溶出を抑制する。
【００２４】
この場合に、重金属類含有汚染土壌または汚泥を掘削した後に、鉄鋼スラグが混合されることが好ましい。これにより、上述のような鉄鋼スラグから重金属類の不溶化に有効な成分が溶出することに伴う化学反応によって溶出重金属類の不溶化のみならず、鉄鋼スラグ自体への汚染土壌からの溶出重金属類の吸着、固定化によっても重金属類が不溶化されるので、重金属類の安定化に対する寄与が高い。
【００２５】
混合の方法は特に限定するものではないが、例えば、パドルミキサー、パン型ミキサー、振動スクリーン、インパクトクラッシャー、自走式土質改良機、バケットによる混合方法などが挙げられる。
【００２６】
上記第１および第２の実施形態において鉄鋼スラグは、製鉄所内の製銑、製鋼工程で発生する高炉スラグ、製鋼スラグ、電気炉製鋼過程で発生する電気炉スラグを指し、高炉スラグは高炉水砕スラグ、高炉徐冷スラグ、製鋼スラグは転炉スラグ、転炉精錬前に予め脱珪、脱硫、脱リン等を行う際に発生する脱珪スラグ、脱硫スラグ、脱リンスラグ、転炉精錬後の２次精錬工程で発生する２次精錬スラグを意味し、これらのスラグの少なくとも１種を適用することができる。
【００２７】
このような鉄鋼スラグの粒度については、土壌としての特性上１０ｍｍ以下が好ましい。鉄鋼スラグは、土壌の使用目的に応じ、そのまま使用してもよいし、さらに破砕、粉砕した細粒や粉状の鉄鋼スラグを用いても構わない。特に特定の粒径の単一の鉄鋼スラグを用いる必要はなく、製鉄過程で発生した鉄鋼スラグの最終処理形態または中間処理形態など、粒状および粉状のものを混合したスラグであっても一向に構わない。不溶化効果を短時間で得るためには粉状の鉄鋼スラグが効果的であり、一方、長期間の効果を持続するためには粒状の鉄鋼スラグが効果的である。これらの利点を相乗的に得るためには粉状スラグおよび粒状スラグを適切な割合で混合して粒度範囲に幅をもたせた鉄鋼スラグが好ましい。
【００２８】
粉状の鉄鋼スラグを得るために鉄鋼スラグを必ずしも粉砕する必要はなく、大半が粉状である脱硫スラグ等であればそのまま粉状鉄鋼スラグとして使用することができる。
【００２９】
以下に重金属類宇の安定化メカニズムについて詳細に説明する。
鉄鋼スラグによる重金属不溶化は、以下の（ａ）〜（ｈ）によるものと考えられる。
【００３０】
（ａ） スラグ自体への吸着効果
（ｂ） 以下の（１）式で示されるスラグから溶出するカルシウム起因のｐＨ上昇による溶出性重金属の難溶性水酸化物形成
（ｃ） 以下の（２）〜（５）式で示される脱硫スラグや高炉徐冷スラグなどに多く含有する硫化カルシウムやその多硫化塩からの硫黄イオンの溶出に起因する溶出重金属類と硫黄イオンの化学反応による難溶性硫化重金属塩の生成
（ｄ） 以下の（６）式で示される脱リンスラグに多く含有するヒドロキシアパタイト、リン酸カルシウムやリン酸塩と溶出重金属類の化学反応により生成する難溶性重金属置換アパタイトの生成
（ｅ） 以下の（７）式で示される鉄鋼スラグから溶出するカルシウムイオンとの反応による難溶性カルシウム塩の生成
（ｆ） 以下の（８）〜（１０）式で示される鉄鋼スラグからの溶出カルシウムイオンや二次精錬スラグに多く含有するカルシウムアルミネート、カルシウムアルミネートフェライトからのアルミニウムの溶出、脱硫スラグや高炉徐冷スラグなどから溶出した硫化物イオンの酸化により生成する硫酸イオンの水和反応時に生成するエトリンガイドやモノサルフェートへの溶出重金属の固定化
（ｇ） 以下の（１１）式で示される鉄鋼スラグから溶出するカルシウムイオンとシリケートイオン、高炉徐冷スラグなどから溶出した硫化物イオンの酸化により生成する硫酸イオンの反応によるＣａＯ−ＳｉＯ２−Ｈ２Ｏ−ＳＯ４系化合物生成時の溶出重金属類の取り込み、
（ｈ） 以下の（１２）式で示される二次精錬スラグに多く含有するカルシウムアルミネートの水和反応時での溶出重金属の固定化
などと考えられる。
【００３１】
【化１】
カドミウムの不溶化の場合、土壌間隙水中に溶出した重金属イオンは、上述の（１）、（３）、（５）式の反応によりスラグから溶出するカルシウム起因によるｐＨの上昇による難溶性水酸化物の形成や、高炉徐冷スラグまたは脱硫スラグから溶出する硫化物イオンとの反応による難溶性の硫化物金属塩を形成し固定化される。鉄鋼スラグを散布または混合した土壌は長期間にわたりカルシウムイオンや硫化物イオンを溶出して土壌中に供給するため、土壌はアルカリ性を維持し、持続的硫化物イオンの供給によって生成した難溶性物は安定を保ち長期間に亘ってカドミウムを固定化する。
【００３３】
鉛の不溶化の場合、土壌間隙水中に溶出した重金属イオンは、上記（１）、（３）、（５）、（６）式の反応によりスラグから溶出するカルシウム起因によるｐＨの上昇による難溶性水酸化物の形成や、高炉徐冷スラグまたは脱硫スラグから溶出する硫化物イオンとの反応による難溶性の硫化物金属塩の形成、さらに脱リンスラグ中のヒドロキシアパタイトとの反応により生成する鉛ヒドロキシモルファイトとして固定化される。
【００３４】
水銀の不溶化の場合、土壌間隙水中に溶出した重金属イオンは、上記（２）〜（４）式の反応により高炉徐冷スラグまたは脱硫スラグから溶出する硫化物イオンによる難溶性の硫化物金属塩の形成により固定化される。
【００３５】
六価クロムの不溶化の場合、土壌間隙水中から溶出した六価のクロムイオンは、高炉徐冷スラグ、脱硫スラグから溶出する硫化物が酸化する過程、即ち、還元性雰囲気中で六価のクロムが三価に還元される。還元した三価のクロムイオンは前述（１）式、スラグから溶出するカルシウム起因によるｐＨの上昇による難溶性の水酸化物を速やかに形成して安定化する。
【００３６】
ひ素の不溶化において、土壌間隙水中に溶出した砒素イオンは、上記（７）式に示される鉄鋼スラグから溶出するカルシウムイオンとの反応によりアルカリ性環境中では難溶性であるひ酸カルシウムを形成し不溶化する。鉄鋼スラグを散布または混合した土壌は長期間にわたりカルシウムイオンを溶出して土壌中に供給するため土壌はアルカリ性を維持することで生成したひ酸カルシウムは安定を保ちひ素を固定化する。
【００３７】
フッ素の不溶化の場合、上記（８）〜（１０）式に示される、スラグから溶出するＣａ２＋イオン、二次精錬スラグなどに含まれるカルシウムアルミネート、カルシウムアルミネートフェライトから溶出するアルミニウムイオン、脱硫スラグや高炉徐冷スラグから溶出する硫酸イオンと反応することにより、エトリンガイド及びモノサルフェートを生成し、この反応過程で一部の硫酸基が溶出したフッ素イオンと置換され、エトリンガイド及びモノサルフェート中にフッ素が固定化される反応と、上記（１１）式に示されるスラグから溶出するカルシウムイオン（Ｃａ２＋イオン）およびシリケートイオン（ｐＨ値が１０以上でＨＳｉＯ３ −イオン、１２以上でＳｉＯ３ ２−）、脱硫スラグや高炉徐冷スラグから溶出する硫酸イオン（ＳＯ４ ２−イオン）と反応することにより、Ｃａ１０（ＳｉＯ４）３（ＳＯ４）３（ＯＨ）２やＣａ５［（Ｓｉ，Ｓ）Ｏ４］３（ＯＨ）等のＣａＯ−ＳｉＯ２−Ｈ２Ｏ−ＳＯ４系化合物を生成し、この生成反応の過程で溶出フッ素イオン（Ｆ−イオン）が水酸基（ＯＨ−イオン）サイトに組み込まれて固定化、さらに、（１２）式で示される二次精錬スラグなどに多く含有するカルシウムアルミネートの水和過程において溶出フッ素イオンが水酸基サイトに取り込まれて固定化する。
【００３８】
以上の効果により、各種スラグは可溶性重金属を安定化させ、さらにスラグはカルシウムイオンや硫化物イオン、溶出硫化物イオンの酸化により生成する硫酸イオン、アルミニウムイオン、シリケートイオンなどを持続的に溶出するため、長期にわたって重金属を安定化することが可能である。
【００３９】
使用する鉄鋼スラグの散布、混合量は、溶出する重金属の量により調整するが、鉛等の両性元素を含む場合、スラグの散布、混合量が多すぎると高アルカリとなりすぎ、重金属の溶解度を増大させる恐れがあるため、土壌ｐＨを１３以下になるように調整する必要がある。また、酸性度などで土壌ｐＨが７未満になると、鉛等の水酸化物の溶解度が増大し、安定化が不十分となるため、土壌のｐＨを７以上にする必要がある。
【００４０】
汚染土壌または汚泥に含有される重金属類が鉛である場合には、鉄鋼スラグが加えられた汚染土壌または汚泥のｐＨが１２以下であることが好ましい。汚染土壌または汚泥に含有される重金属類がひ素である場合には、鉄鋼スラグが加えられた汚染土壌または汚泥のｐＨが９以上であることが好ましい。
【００４１】
本発明による処理方法では、可溶性重金属を含む土壌の表面に鉄鋼スラグを散布するだけ、または、土壌を掘削し、土壌とスラグが接触するように攪拌混合し、埋め戻す操作のみで可溶性重金属を安定化でき、さらには、安価なスラグを用いるので、処理コストを低くすることができる。
【００４２】
本発明に基づいて、可溶性重金属を含む土壌に対し鉄鋼スラグを散布または混合することにより、環境庁告示第４６号に定められた溶出試験方法により試験を行った場合に、環境基準値に適合することが確認された。
【００４３】
さらに、本発明においては複数の可溶性重金属を含む土壌と鉄鋼スラグを混合して長期的な溶出挙動を調査したところ、鉄鋼スラグを混合した土壌は長期にわたって溶出が起こらないことが確認された。
【００４４】
【実施例】
以下、本発明の実施例について説明する。なお、本発明は以下の実施例に限定されるものではない。
【００４５】
（実施例１）
工場跡地から採取した重金属類含有汚染土壌Ａ、Ｂについて、環境庁告示第４６号で規定された溶出試験を行った。溶出試験結果と溶出基準値を表１に示す。表１より、土壌Ａについては砒素、鉛、総水銀の溶出量が基準値を超えており、土壌Ｂについては砒素、鉛、六価クロムの溶出量が基準値を超えている弱アルカリ性土壌であることがわかる。
【００４６】
【表１】
前記重金属類含有汚染土壌Ａ、Ｂの１００質量部に対して、粒度を０．０７５ｍｍ以下に粉砕した高炉徐冷スラグ、脱珪スラグ、脱硫スラグ、脱リンスラグ、２次精錬スラグを５質量部混合した。
【００４８】
得られた処理品について、環境庁告示第４６号で規定された溶出試験を行った。重金属類含有汚染土壌Ａの処理品の溶出試験結果を表２に、重金属類含有汚染土壌Ｂの処理品の溶出試験結果を表３に示す。表２、３から、いずれの重金属類含有汚染土壌に対しても処理品は未処理に比べて溶出量が低減していることが確認された。また、脱珪スラグ、脱硫スラグについては環境庁の定める溶出基準値を満足する結果が得られた。
【００４９】
【表２】
【表３】
（実施例２）
前記重金属類含有汚染土壌Ａの１００質量部に対し、粉砕して粒度を０．０７５ｍｍ以下にした脱硫スラグをそれぞれ２、５、１０質量部混合した。得られた処理品について、環境庁告示第４６号で規定された溶出試験を行った。重金属類含有汚染土壌Ａの処理品の溶出試験結果を表４に示す。表４から、ひ素、総水銀はそれぞれの混合量で溶出量を低減させたのに対し、鉛は１０質量部の混合の場合において溶出量が増大する結果が得られた。この原因は、スラグの混合量が多すぎたためにｐＨが１２以上の強アルカリとなり、両性元素である鉛の溶解度が増大したことによるものと考えられる。この結果より、鉛のような両性元素を含む重金属類汚染土壌の場合はｐＨを１２以下とすることが望ましいことがわかる。
【００５２】
【表４】
（実施例３）
前記重金属類含有汚染土壌Ａの１００質量部に対し、粉砕して粒度をそれぞれ０．０７５ｍｍ以下、０．５ｍｍ以下、５ｍｍ以下にした脱珪スラグを５および１０質量部混合した。
【００５４】
得られた処理品について、環境庁告示第４６号で規定された溶出試験を行った。処理品の溶出試験結果を表５に示す。表５より、５質量部混合した処理品の粒度に関して、より細かく粉砕した方が溶出量低減効果が認められ、粗めの粒度に調整したものは一部の重金属について溶出量が基準値を上回る結果が得られた。しかし、５質量部混合して溶出量が基準値を上回った粒度域でも混合量を増量することで基準値以下にまで低減することが出来た。
【００５５】
【表５】
（実施例４）
工場跡地から採取した重金属類含有汚染土壌Ｃについて、環境庁告示第４６号で規定された溶出試験を行った。溶出試験結果と溶出基準値を表６に示す。表６より、土壌Ｃについては鉛の溶出量が基準値を超えている酸性土壌であることがわかる。
【００５７】
【表６】
前記重金属類含有汚染土壌Ｃの１００質量部に対して、粒度を０．０７５ｍｍ以下に粉砕した脱硫スラグをそれぞれ０．０５、０．１および１質量部混合し、得られた処理品について、環境庁告示第４６号で規定された溶出試験を行った。重金属類含有汚染土壌Ｃの処理品の溶出試験結果を表７に示す。表７より、０．０５質量部の混合処理品のみがひ素、鉛の溶出量を低減させることができなかった。この結果より、難溶性化作用を得るにはｐＨ７以上が望ましいことがわかる。
【００５９】
【表７】
（実施例５）
工場跡地から採取したフッ素溶出汚染土壌Ｄについて、環境庁告示第４６号で規定された溶出試験を行った。溶出試験結果と溶出基準値を表８に示す。表より、土壌Ｄはフッ素溶出量が基準値を超えている土壌であることがわかる。
【００６１】
【表８】
前記フッ素溶出汚染土壌Ｄの１００重量部に対して、粒度を０．０７５ｍｍ以下に粉砕した二次精錬スラグを１および３質量部混合し、得られた処理品について、環境庁告示第４６号で規定された溶出試験を行った。フッ素含有汚染土壌Ｄの処理品の溶出試験結果を表９に示す。
【００６３】
【表９】
表９より、二次精錬スラグを１質量部添加することで環境基準以下まで下げることができることが確認された。また、添加量を増やすことにより溶出抑制効果が増すことがわかる。
【００６５】
実施例１から実施例５の結果から、重金属類含有汚染土壌から溶出する各種重金属類に対して各種スラグを適正に混合することにより、これらの溶出量を低減することができることが確認された。
【００６６】
なお、実施例１から実施例５では、環境庁告示第４６号で定める溶出試験方法にて評価を行ったが、この溶出試験方法は、試料と溶媒（純水に塩酸を加え、水素イオン濃度指数が５．８以上６．３以下となるようにしたもの）を重量体積比１０％の割合で混合した混合液を振とう機で６時間連続振とうしたものを検液としており、この方法では振とう中に溶出した重金属類が土壌へ再吸着され、６時間後に抽出した検液は未検出となる場合もあり、必ずしも実状況を反映しているとはいえない。そこで、本発明による処理方法が周囲環境に溶出することがないことを以下の実施例６、実施例７で実証する。実施例６では重金属類含有汚染土壌にスラグを混合する処理方法、実施例７では重金属類含有汚染土壌にスラグを散布する処理方法を想定した。
【００６７】
（実施例６）
前記重金属類含有汚染土壌Ａの１００質量部に対し有姿の脱硫スラグを５質量部混合した処理品、および比較として重金属類含有汚染土壌Ａのみを、それぞれ５０φ×１００ｍｍのアクリル容器に詰め、０．６ｋｇ／ｃｍ３の載荷をかけて充填した。充填後、アクリル容器上部、下部にチューブを取り付け、アクリル容器下部のチューブから水を１分間に１ｍｌの速度でアクリル容器内を通水した。通水後、アクリル容器上部のチューブから出てくる水を定期的に採取し、０．４５μｍのメンブランフィルターでろ過したろ液を検液として、ひ素、鉛はＪＩＳ−Ｋ−原子吸光光度法により重金属濃度を測定した。ひ素溶出量の推移図を図１のグラフ、鉛溶出量の推移図を図２、総水銀溶出量の推移図を図３のグラフに示す。
【００６８】
図１、図２、図３より、いずれの重金属についても土壌から重金属が溶出し続ける間、処理品は混合直後から再溶出を起こすことなく溶出量を基準値以下にまで安定化することを確認することができた。
【００６９】
（実施例７）
前記重金属類含有汚染土壌汚染土壌Ａの１００質量部に対し、５質量部に相当する有姿の脱硫スラグを５０φ×１００ｍｍのアクリル容器の容器下部に敷き、その上に重金属類含有汚染土壌汚染土壌Ａを入れて、０．６ｋｇ／ｃｍ３の載荷をかけて充填した。また比較として汚染土壌Ａのみを入れて０．６ｋｇ／ｃｍ３の載荷をかけて充填した。充填後は（実施例６）と同様の手順でおこなった。ひ素溶出量の推移図を図４のグラフ、鉛溶出量の推移図を図５、総水銀溶出量の推移図を図６のグラフに示す。
【００７０】
図４、図５、図６より、いずれの重金属についても土壌から重金属が溶出し続ける間、処理品は散布直後から再溶出を起こすことなく溶出量を基準値以下にまで安定化することを確認することができた。
【００７１】
【発明の効果】
以上説明したように、本発明によれば、重金属類を溶出する重金属類含有汚染土壌または汚泥に対して広範囲または大量の汚染土壌または汚泥に対して短期間で重金属類の溶出を抑え土壌環境基準値を満足させる安定化処理を行うことができ、しかもその効果を長期に亘って持続させることができる。
【００７２】
また、本発明によれば、廉価なスラグを安定化材として用い、特別な設備を必要とせず散布または混合処理のみであるから、極めて簡易で低コストな処理方法を提供することができる。
【図面の簡単な説明】
【図１】脱硫スラグ混合処理品、未処理品のひ素溶出推移図。
【図２】脱硫スラグ混合処理品、未処理品の鉛溶出推移図。
【図３】脱硫スラグ混合処理品、未処理品の水銀溶出推移図。
【図４】脱硫スラグ散布処理品、未処理品の砒素溶出推移図。
【図５】脱硫スラグ散布処理品、未処理品の鉛溶出推移図。
【図６】脱硫スラグ散布処理品、未処理品の水銀溶出推移図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention stabilizes heavy metals in contaminated soil or sludge containing heavy metals that may elute heavy metals, and stabilizes heavy metals in order to prevent the diffusion of contamination to the surrounding environment such as the ground surface, underground, and groundwater. About the method.
[0002]
[Prior art]
Soil originally has a function of purifying water quality and a function of recharging groundwater.However, with the rapid industrialization in recent years, the soil itself has been contaminated with harmful substances, and has a function of purifying water quality and a function of recharging groundwater. In many cases, pollution is spreading to the surrounding environment, and many countermeasures have been reported as social problems.
[0003]
As a method of treating contaminated soil that elutes heavy metals, cement solidification methods and chemical insolubilization methods have been widely and more commonly used than ever before.
[0004]
The cement solidification method incorporates heavy metals into the hydration product of cement minerals and stabilizes the solidification.Generally, Portland cement and other contaminated soil are mixed and kneaded, and the cement minerals due to water adhering to the soil are mixed. The hydration reaction causes the soil to condense and suppress the elution of heavy metals. However, calcium hydroxide (Ca (OH)) generated during the hydration reaction of cement minerals2), The pH in the soil rises to 12 or more, and therefore, among heavy metals, amphoteric elements such as lead have the problem of increasing the solubility and contaminating the surrounding environment.
[0005]
In order to solve the problem of the above-mentioned increase in pH,
[0006]
However, in this method, the soil is solidified due to mixing of the cement, and it is difficult to regenerate the soil. In addition, the workability is poor, such as the need to wash the equipment every time the work is interrupted because the cement will set if left mixed. Furthermore, cement is expensive, and when the amount of soil required for purification is large, enormous treatment costs are required.
[0007]
The insolubilization method using a chemical is a method in which a soluble heavy metal is converted into a hardly soluble substance by a chemical reaction or adsorption to make it insoluble by adding and mixing a chemical such as a heavy metal collecting agent. Therefore, it is necessary to select a plurality of agents for soil that elutes a plurality of heavy metals, and it is necessary to consider the influence of chemical reaction between the agents.
[0008]
In addition, in the insolubilization method using chemicals, even if heavy metals can be insolubilized in the short term, the persistence of the insolubilizing effect may be greatly impaired by changes in the external environment such as acid rain, so in the long term, This is not a sufficient treatment method.
[0009]
On the other hand, Patent Document 2 proposes a treating agent for heavy metal-containing waste and a method for stabilizing heavy metal-containing waste using steel slag. However, this technique requires pulverization of slag and water. It is necessary to add and mix a dispersant. Slag is a secondary product produced as a by-product in the iron-making process, but is inexpensive. However, crushing requires energy and equipment dedicated to crushing, and costs are high. In addition, mixing equipment is required for adding and mixing water and a dispersant, and a long period of time is required for soil that is widely contaminated.
[0010]
Patent Literature 3 proposes a method for preventing acidification of soil and stabilizing soil pH using alkaline materials such as blast furnace slag and converter slag, but adjusts pH to insolubilize as hydroxide. Since it is a method, it is difficult to insolubilize arsenic that does not generate hydroxides and heavy metals that do not have sufficiently low solubility of hydroxides. In addition, although an alkali material having a maximum particle size of 30 mm is used, elution of the alkali component becomes extremely slow when the particle size exceeds 10 mm, and a large amount of the alkali material is required to adjust the pH to a target value. Absent.
[0011]
[Patent Document 1]
JP-A-10-258263 (Claims, etc.)
[Patent Document 2]
JP-A-9-19435 (Claims, etc.)
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-282034 (Claims, etc.)
[0012]
[Problems to be solved by the invention]
As described above, in the conventional technology, an effective technology for stabilizing heavy metals containing contaminated soil containing heavy metals has not yet been obtained. The same applies to sludge containing heavy metals.
[0013]
The present invention has been made in view of such circumstances, and is simple and inexpensive for heavy metal-containing contaminated soil or sludge that elutes heavy metals, and also for a wide range or a large amount of contaminated soil or sludge. It is an object of the present invention to provide a method for stabilizing heavy metals which can stabilize in a short period of time and maintain its effect for a long period of time.
[0014]
[Means for Solving the Problems]
The present inventors have conducted research on a treatment method that can solve the problem, and as a result, by spraying or mixing steel slag on heavy metal-containing contaminated soil or sludge that elutes heavy metals, adsorption and immobilization on steel slag The present inventors have found that a chemical reaction by a component contained in iron and steel slag is used to convert the substance into a hardly soluble substance and to stabilize the substance for a long time.
[0015]
The present invention includes heavy metals irrespective of natural or anthropogenic causes, and insolubilizes heavy metals over a long period of time in so-called contaminated soil or sludge that may elute some of the heavy metals, thereby reducing heavy metals. It is intended to provide a method to prevent the spread of secondary pollution to surrounding soil and groundwater due to runoff.
[0016]
The first invention is characterized by stabilizing heavy metals in contaminated soil or sludge by spraying steel slag on the contaminated soil or sludge containing heavy metals that may elute heavy metals. A class stabilization treatment method is provided.
[0017]
As a result, components effective for insolubilizing heavy metals are eluted from the steel slag by rainwater or the like, and the contained heavy metals are insolubilized by a chemical reaction in a process of infiltrating into contaminated soil or sludge. According to the first invention, it is only necessary to spray the steel slag on the soil surface or the surface layer, no special equipment is required, and the construction can be performed in a short period of time and at low cost even in a wide range of contaminated soil.
[0018]
The second invention is characterized by stabilizing heavy metals in the contaminated soil or sludge by mixing steel slag with heavy metal-containing contaminated soil or sludge that may elute heavy metals. A class stabilization treatment method is provided.
[0019]
As a result, the chemical reaction that accompanies the elution of components effective for insolubilizing heavy metals from steel slag due to soil pore water causes insolubilization of the eluting heavy metals, and further, the elution of heavy metals from the contaminated soil into the steel slag itself. Heavy metals are insolubilized by the adsorption and immobilization of the metal. This second invention contributes not only to insolubilization by a chemical reaction but also to adsorption and immobilization to the slag itself, so that it is effective in insolubilizing highly contaminated soil. Further, by mixing, the steel slag is uniformly diffused in the treated soil, so that an immediate insolubilizing effect can be obtained.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
In the first embodiment of the present invention, heavy metals in the contaminated soil or sludge are insolubilized and stabilized by spraying steel slag on the heavy metal-containing contaminated soil or sludge which may elute heavy metals. Suppresses the dissolution of the species.
[0021]
In this case, it is sufficient that the steel slag is sprayed on the surface without excavating the soil or the like. In other words, by spraying steel slag onto the surface or surface of contaminated soil or sludge, a chemical reaction in the process of infiltrating heavy metals eluted from steel slag by rainwater etc. into the contaminated soil or sludge is effective. Insolubilizes the heavy metals contained.
[0022]
The method of spraying is not particularly limited, and examples thereof include pressure spraying by air, cut-out spraying by a rotary, and in the case of powder, a method of kneading with water to form a slurry and spraying by a pump.
[0023]
In the second embodiment of the present invention, heavy metals-containing contaminated soil or sludge that may elute heavy metals is mixed with steel slag to insolubilize heavy metals in the contaminated soil or sludge. Stabilizes and suppresses elution of heavy metals.
[0024]
In this case, it is preferable that the steel slag is mixed after excavating the heavy metal-containing contaminated soil or sludge. As a result, not only the insolubilization of the eluting heavy metals due to the chemical reaction resulting from the elution of the components effective for insolubilizing the heavy metals from the steel slag as described above, but also the adsorption of the eluting heavy metals from the contaminated soil to the steel slag itself. Since the heavy metals are also insolubilized by the immobilization, the contribution to the stabilization of the heavy metals is high.
[0025]
The mixing method is not particularly limited, and examples thereof include a paddle mixer, a pan-type mixer, a vibrating screen, an impact crusher, a self-propelled soil conditioner, and a mixing method using a bucket.
[0026]
In the above first and second embodiments, the steel slag refers to blast furnace slag generated in a steelmaking process, a steelmaking process, a steelmaking slag, an electric furnace slag generated in an electric furnace steelmaking process, and blast furnace slag refers to blast furnace water granulation. Slag, blast furnace slowly cooled slag, and steelmaking slag are converted from converter slag, desiliconized slag, desulfurized slag, dephosphorized slag, and dephosphorized slag that are generated when desiliconization, desulfurization, dephosphorization, etc. are performed before converter refining. It means secondary refining slag generated in the secondary refining step, and at least one of these slags can be applied.
[0027]
The particle size of such steel slag is preferably 10 mm or less in terms of soil characteristics. The steel slag may be used as it is, or may be crushed or pulverized fine granules or powdered steel slag according to the purpose of use of the soil. In particular, it is not necessary to use a single steel slag having a specific particle size, and a slag that is a mixture of granular and powdery slag, such as a final treatment form or an intermediate treatment form of steel slag generated in the iron making process, may be used. Absent. Powdered steel slag is effective for obtaining the insolubilizing effect in a short time, while granular steel slag is effective for maintaining the effect for a long time. In order to obtain these advantages synergistically, a steel slag in which a powder slag and a granular slag are mixed in an appropriate ratio to have a wide particle size range is preferable.
[0028]
It is not always necessary to pulverize the steel slag in order to obtain the powdered steel slag, and any desulfurized slag or the like that is mostly powdery can be used as it is as the powdered steel slag.
[0029]
Hereinafter, the stabilization mechanism of the heavy metal class will be described in detail.
The heavy metal insolubilization by the steel slag is considered to be due to the following (a) to (h).
[0030]
(A) Adsorption effect on slag itself
(B) Formation of a sparingly soluble hydroxide of a dissolvable heavy metal due to an increase in pH due to calcium eluted from the slag represented by the following formula (1)
(C) Heavy metals and sulfur ions eluted due to the elution of sulfur ions from calcium sulfide and polysulfides thereof, which are contained in large amounts in desulfurized slag and blast furnace slowly cooled slag represented by the following formulas (2) to (5): Of sparingly soluble heavy metal sulphide salts by chemical reaction of water
(D) Formation of poorly soluble heavy metal-substituted apatite generated by a chemical reaction between hydroxyapatite, calcium phosphate or phosphate, and the eluted heavy metals, which is largely contained in the dephosphorization slag represented by the following formula (6):
(E) Formation of sparingly soluble calcium salt by reaction with calcium ions eluted from steel slag represented by the following formula (7)
(F) Elution of calcium ions from steel slag represented by the following formulas (8) to (10), calcium aluminate contained in secondary refining slag, and aluminum from calcium aluminate ferrite, desulfurization slag and blast furnace Immobilization of eluted heavy metals on etrin guide and monosulfate generated during hydration reaction of sulfate ion generated by oxidation of sulfide ion eluted from slowly cooled slag
(G) CaO—SiO by reaction of calcium ions and silicate ions eluted from steel slag represented by the following formula (11) and sulfate ions generated by oxidation of sulfide ions eluted from blast furnace slowly cooled slag, etc.2-H2O-SO4Incorporation of heavy metals eluted during production of system compounds,
(H) Immobilization of heavy metals eluted during hydration of calcium aluminate contained in secondary refining slag represented by the following formula (12):
And so on.
[0031]
Embedded image
In the case of cadmium insolubilization, heavy metal ions eluted into the soil pore water are converted into poorly soluble hydroxides due to the increase in pH caused by calcium eluted from the slag by the above-mentioned reactions (1), (3) and (5). Formation and reaction with sulfide ions eluted from the blast furnace slowly cooled slag or desulfurized slag form a hardly soluble sulfide metal salt to be fixed. Soil sprayed or mixed with steel slag elutes calcium ions and sulfide ions over a long period of time and supplies it to the soil, so the soil maintains alkalinity, and the hardly soluble substances generated by the continuous supply of sulfide ions are Immobilize cadmium over a long period of time while maintaining stability.
[0033]
In the case of lead insolubilization, heavy metal ions eluted into the soil pore water are hardly soluble water due to the increase in pH due to calcium eluted from the slag by the reaction of the above formulas (1), (3), (5) and (6). Formation of oxides, formation of sparingly soluble sulfide metal salts by reaction with sulfide ions eluted from blast furnace slag or desulfurization slag, and lead hydroxymorphite generated by reaction with hydroxyapatite in dephosphorization slag Immobilized as
[0034]
In the case of insolubilization of mercury, heavy metal ions eluted in the soil pore water are converted into hardly soluble sulfide metal salts by sulfide ions eluted from the blast furnace slowly cooled slag or the desulfurized slag by the reaction of the above formulas (2) to (4). Immobilized by formation.
[0035]
In the case of insolubilization of hexavalent chromium, hexavalent chromium ions eluted from soil pore water are converted into sulfides eluted from blast furnace slowly cooled slag and desulfurized slag, that is, hexavalent chromium is reduced in a reducing atmosphere. It is reduced to trivalent. The reduced trivalent chromium ion quickly forms a hardly soluble hydroxide due to an increase in pH due to calcium eluted from the slag, and stabilizes it.
[0036]
In the insolubilization of arsenic, arsenic ions eluted into the pore water of the soil form calcium arsenate, which is hardly soluble in an alkaline environment, by the reaction with calcium ions eluted from the iron and steel slag represented by the above formula (7) and insolubilized. . Soil in which steel slag is sprayed or mixed elutes calcium ions for a long time and is supplied to the soil, so that calcium arsenate generated by maintaining the alkalinity of the soil maintains stability and immobilizes arsenic.
[0037]
In the case of insolubilizing fluorine, Ca eluted from the slag represented by the above formulas (8) to (10)2+Ethrin guide and monosulfate are generated by reacting with ions, calcium aluminate contained in secondary refining slag, aluminum ion eluted from calcium aluminate ferrite, and sulfate ion eluted from desulfurized slag and blast furnace slowly cooled slag In this reaction, a part of the sulfate groups is replaced by the eluted fluoride ions, and the fluorine is fixed in the ettrine guide and monosulfate. The calcium eluted from the slag represented by the above formula (11) Ion (Ca2+Ions and silicate ions (HSiO at pH 10 or more)3 −Ion, 12 or more SiO3 2-), Sulfate ion (SO) eluted from desulfurized slag and blast furnace slowly cooled slag4 2-Ion) to react with Ca10(SiO4)3(SO4)3(OH)2And Ca5[(Si, S) O4]3CaO-SiO such as (OH)2-H2O-SO4-Based compounds, and eluted fluorine ions (F−Ion) is a hydroxyl group (OH−In the hydration process of calcium aluminate, which is largely contained in the secondary refining slag represented by the formula (12), the eluted fluorine ions are incorporated into the hydroxyl sites and fixed.
[0038]
Due to the above effects, various slags stabilize soluble heavy metals, and slag continuously elutes sulfate ions, aluminum ions, silicate ions, etc. generated by oxidation of calcium ions, sulfide ions, and eluted sulfide ions. It is possible to stabilize heavy metals for a long time.
[0039]
The amount of steel slag to be sprayed and mixed is adjusted by the amount of heavy metal eluted, but when it contains lead and other amphoteric elements, if the amount of slag sprayed and mixed is too large, it becomes too highly alkaline and increases the solubility of heavy metals. Therefore, it is necessary to adjust the soil pH to 13 or less. Further, when the soil pH is less than 7 due to acidity or the like, the solubility of hydroxides such as lead increases and the stabilization becomes insufficient. Therefore, the soil pH needs to be 7 or more.
[0040]
When the heavy metals contained in the contaminated soil or sludge are lead, the pH of the contaminated soil or sludge to which the steel slag is added is preferably 12 or less. When the heavy metals contained in the contaminated soil or the sludge are arsenic, the pH of the contaminated soil or the sludge to which the steel slag is added is preferably 9 or more.
[0041]
In the treatment method according to the present invention, the soluble heavy metal is stabilized only by spraying steel slag on the surface of the soil containing the soluble heavy metal, or by excavating the soil, stirring and mixing so that the soil and the slag come into contact, and backfilling only. In addition, since inexpensive slag is used, the processing cost can be reduced.
[0042]
According to the present invention, when a test is performed according to a dissolution test method defined in the Environment Agency Notification No. 46 by spraying or mixing steel slag on soil containing a soluble heavy metal, it conforms to environmental standard values. It was confirmed that.
[0043]
Furthermore, in the present invention, long-term elution behavior was investigated by mixing a soil containing a plurality of soluble heavy metals with steel slag, and it was confirmed that soil mixed with steel slag did not elute for a long time.
[0044]
【Example】
Hereinafter, examples of the present invention will be described. Note that the present invention is not limited to the following examples.
[0045]
(Example 1)
For the contaminated soils A and B containing heavy metals collected from the site of the factory, the dissolution test specified in Notification No. 46 of the Environment Agency was conducted. Table 1 shows the dissolution test results and the dissolution reference values. From Table 1, it can be seen from Table 1 that in soil A, the amount of arsenic, lead and total mercury eluted exceeds the reference value, and in soil B, the amount of arsenic, lead and hexavalent chromium eluted exceeds the reference value in a weak alkaline soil. You can see that there is.
[0046]
[Table 1]
5 parts by mass of blast furnace slow cooling slag, desiliconized slag, desulfurized slag, dephosphorized slag, and secondary refining slag, each of which has a particle size of 0.075 mm or less, are mixed with 100 parts by mass of the heavy metal-containing contaminated soils A and B. did.
[0048]
The obtained treated product was subjected to a dissolution test specified in the Environment Agency Notification No. 46. Table 2 shows the dissolution test results of the treated product of the heavy metal-containing contaminated soil A, and Table 3 shows the dissolution test results of the treated product of the heavy metal-containing contaminated soil B. From Tables 2 and 3, it was confirmed that the elution amount of the treated product was reduced in any of the heavy metal-containing contaminated soils as compared with the untreated product. In addition, the results obtained for the desiliconized slag and desulfurized slag satisfied the elution standard values set by the Environment Agency.
[0049]
[Table 2]
[Table 3]
(Example 2)
To 100 parts by mass of the heavy metal-containing contaminated soil A, 2, 5, and 10 parts by mass of desulfurized slag whose particle size was reduced to 0.075 mm or less were mixed. The obtained treated product was subjected to a dissolution test specified in the Environment Agency Notification No. 46. Table 4 shows the dissolution test results of the treated products of the contaminated soil A containing heavy metals. Table 4 shows that arsenic and total mercury reduced the elution amount with each mixing amount, whereas lead increased the elution amount with 10 parts by mass of mixing. It is considered that the reason for this is that the mixing amount of slag was too large, the pH became 12 or more, and the solubility of lead, which is an amphoteric element, increased. From this result, it is understood that the pH is desirably 12 or less in the case of soil contaminated with heavy metals containing an amphoteric element such as lead.
[0052]
[Table 4]
(Example 3)
With respect to 100 parts by mass of the heavy metal-containing contaminated soil A, 5 and 10 parts by mass of desiliconized slag whose particle size was reduced to 0.075 mm or less, 0.5 mm or less, and 5 mm or less, respectively, were mixed.
[0054]
The obtained treated product was subjected to a dissolution test specified in the Environment Agency Notification No. 46. Table 5 shows the dissolution test results of the treated products. From Table 5, with regard to the particle size of the treated product mixed with 5 parts by mass, the effect of reducing the elution amount is recognized when the finer pulverization is performed, and the elution amount exceeds the standard value for some heavy metals when the particle size is adjusted to a coarser particle size. The result was obtained. However, even in the particle size range where the amount of elution exceeded the reference value after mixing 5 parts by mass, the mixing amount could be reduced to below the reference value by increasing the mixing amount.
[0055]
[Table 5]
(Example 4)
For the contaminated soil C containing heavy metals collected from the site of the factory, a dissolution test specified in Notification No. 46 of the Environment Agency was conducted. Table 6 shows the dissolution test results and the dissolution reference values. Table 6 shows that soil C is an acidic soil in which the amount of lead eluted exceeds the reference value.
[0057]
[Table 6]
With respect to 100 parts by mass of the heavy metal-containing contaminated soil C, 0.05, 0.1 and 1 part by mass of desulfurized slag pulverized to a particle size of 0.075 mm or less were mixed, and the resulting treated product was subjected to environmental protection. The dissolution test specified in Agency Notification No. 46 was performed. Table 7 shows the dissolution test results of the treated products of the contaminated soil C containing heavy metals. From Table 7, it was found that only 0.05 part by mass of the mixed product could not reduce the elution amount of arsenic and lead. From this result, it can be seen that a pH of 7 or more is desirable for obtaining the insolubilizing effect.
[0059]
[Table 7]
(Example 5)
For the fluorine-eluting contaminated soil D collected from the site of the factory, the elution test specified in the Environment Agency Notification No. 46 was conducted. Table 8 shows the dissolution test results and the dissolution reference values. From the table, it can be seen that soil D is a soil in which the fluorine elution amount exceeds the reference value.
[0061]
[Table 8]
With respect to 100 parts by weight of the fluorine-eluting contaminated soil D, 1 and 3 parts by mass of a secondary smelting slag pulverized to a particle size of 0.075 mm or less was mixed. A prescribed dissolution test was performed. Table 9 shows the dissolution test results of the treated product of the fluorine-containing contaminated soil D.
[0063]
[Table 9]
From Table 9, it was confirmed that adding 1 part by mass of the secondary smelting slag can lower the slag below the environmental standard. In addition, it can be seen that increasing the amount of addition increases the elution suppression effect.
[0065]
From the results of Examples 1 to 5, it was confirmed that by appropriately mixing various slags with various heavy metals eluted from the heavy metal-containing contaminated soil, the amount of these elutions can be reduced.
[0066]
In Examples 1 to 5, the evaluation was performed by the dissolution test method specified in the Environment Agency Notification No. 46. This dissolution test method was performed by adding a sample and a solvent (hydrochloric acid to pure water and adding hydrogen ion concentration). The mixture was prepared by mixing a mixture having an index of 5.8 or more and 6.3 or less at a ratio of 10% by weight by volume and continuously shaken with a shaker for 6 hours as a test solution. In such a case, heavy metals eluted during shaking are re-adsorbed to the soil, and the test solution extracted after 6 hours may not be detected, and may not necessarily reflect the actual situation. Therefore, the following Examples 6 and 7 demonstrate that the treatment method according to the present invention does not elute into the surrounding environment. In Example 6, a treatment method in which slag was mixed with heavy metal-containing contaminated soil, and in Example 7, a treatment method in which slag was sprayed on heavy metal-containing contaminated soil, were assumed.
[0067]
(Example 6)
A treated product obtained by mixing 5 parts by mass of a desulfurized slag with respect to 100 parts by mass of the heavy metal-containing contaminated soil A and a heavy metal-containing contaminated soil A alone as a comparison were packed in an acrylic container of 50 mm x 100 mm. 0.6 kg / cm3And loaded. After filling, tubes were attached to the upper and lower portions of the acrylic container, and water was passed through the tubes at the lower portion of the acrylic container at a rate of 1 ml per minute. After passing the water, water coming out of the tube at the top of the acrylic container is periodically collected, and the filtrate filtered with a 0.45 μm membrane filter is used as a test solution, and arsenic and lead are determined by JIS-K-atomic absorption spectrophotometry. Heavy metal concentrations were measured. The transition diagram of the arsenic elution amount is shown in the graph of FIG. 1, the transition diagram of the lead elution amount is shown in FIG. 2, and the transition diagram of the total mercury elution amount is shown in the graph of FIG.
[0068]
From Fig.1, Fig.2 and Fig.3, it is confirmed that the treated product stabilizes the elution amount to below the reference value without causing re-elution immediately after mixing, while the heavy metal continues to elute from the soil for all heavy metals. We were able to.
[0069]
(Example 7)
With respect to 100 parts by mass of the heavy metal-containing contaminated soil contaminated soil A, a tangible desulfurized slag corresponding to 5 parts by mass was laid under the container of an acrylic container of 50 mm x 100 mm, and the heavy metal-containing contaminated soil contaminated soil was placed thereon. 0.6kg / cm3And loaded. For comparison, only 0.6 kg / cm3And loaded. After filling, the same procedure as in (Example 6) was performed. The transition diagram of the arsenic elution amount is shown in the graph of FIG. 4, the transition diagram of the lead elution amount is shown in FIG. 5, and the transition diagram of the total mercury elution amount is shown in the graph of FIG.
[0070]
From Fig. 4, Fig. 5, and Fig. 6, it is confirmed that the treated product stabilizes the amount of elution to below the reference value without causing re-elution immediately after spraying while heavy metal continues to elute from the soil for all heavy metals. We were able to.
[0071]
【The invention's effect】
As described above, according to the present invention, a heavy metal-containing contaminated soil or sludge that elutes heavy metals is widely or a large amount of contaminated soil or sludge, and the elution of heavy metals is suppressed in a short period of time. A stabilization process that satisfies the value can be performed, and the effect can be maintained for a long time.
[0072]
Further, according to the present invention, an inexpensive slag is used as a stabilizing material, and only spraying or mixing is performed without requiring special equipment. Therefore, an extremely simple and low-cost processing method can be provided.
[Brief description of the drawings]
FIG. 1 is an arsenic elution transition diagram of a desulfurized slag mixed treated product and an untreated product.
FIG. 2 is a diagram showing the transition of lead elution of a desulfurized slag mixed treated product and an untreated product.
FIG. 3 is a transition diagram of mercury elution of a desulfurized slag mixed treated product and an untreated product.
FIG. 4 is a transition diagram of arsenic elution of desulfurized slag spray-treated and untreated products.
FIG. 5 is a diagram showing the transition of lead elution from desulfurized slag sprayed and untreated products.
FIG. 6 is a transition diagram of mercury elution of a desulfurized slag spray-treated product and an untreated product.
Claims (9)
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| JP2002321207A JP4130762B2 (en) | 2002-11-05 | 2002-11-05 | Heavy metal stabilization treatment method |
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| JP4130762B2 JP4130762B2 (en) | 2008-08-06 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007113226A (en) * | 2005-10-19 | 2007-05-10 | Nippon Steel & Sumikin Stainless Steel Corp | Soil improving method |
| JP2010517754A (en) * | 2007-02-09 | 2010-05-27 | ソルヴェイ（ソシエテ アノニム） | Methods for treating substances contaminated with heavy metals |
| US20110049057A1 (en) * | 2009-09-02 | 2011-03-03 | Grubb Dennis G | Metal Immobilization Using Slag Fines |
| CN101723566B (en) * | 2008-10-21 | 2012-10-10 | 宝山钢铁股份有限公司 | Method for disposing waterworks sludge |
| KR20190000424A (en) * | 2017-06-22 | 2019-01-03 | 한국화학연구원 | Preparing method of fluoride ion adsorbent using steel slag and adsorb method for fluoride thereof |
| KR101949652B1 (en) * | 2018-09-18 | 2019-02-18 | 서울대학교산학협력단 | Stabilization of arsenic using basic oxygen furnace slag |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109570183A (en) * | 2018-10-12 | 2019-04-05 | 云南省环境科学研究院(中国昆明高原湖泊国际研究中心) | A kind of method of arsenic-containing waste residue solidification and stabilization processing |
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2002
- 2002-11-05 JP JP2002321207A patent/JP4130762B2/en not_active Expired - Lifetime
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007113226A (en) * | 2005-10-19 | 2007-05-10 | Nippon Steel & Sumikin Stainless Steel Corp | Soil improving method |
| JP2010517754A (en) * | 2007-02-09 | 2010-05-27 | ソルヴェイ（ソシエテ アノニム） | Methods for treating substances contaminated with heavy metals |
| CN101723566B (en) * | 2008-10-21 | 2012-10-10 | 宝山钢铁股份有限公司 | Method for disposing waterworks sludge |
| US20110049057A1 (en) * | 2009-09-02 | 2011-03-03 | Grubb Dennis G | Metal Immobilization Using Slag Fines |
| KR20190000424A (en) * | 2017-06-22 | 2019-01-03 | 한국화학연구원 | Preparing method of fluoride ion adsorbent using steel slag and adsorb method for fluoride thereof |
| KR102035563B1 (en) * | 2017-06-22 | 2019-10-25 | 한국화학연구원 | Preparing method of fluoride ion adsorbent using steel slag and adsorb method for fluoride thereof |
| KR101949652B1 (en) * | 2018-09-18 | 2019-02-18 | 서울대학교산학협력단 | Stabilization of arsenic using basic oxygen furnace slag |
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