JP4568893B2 - Purification method of contaminated soil - Google Patents
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- JP4568893B2 JP4568893B2 JP2001050932A JP2001050932A JP4568893B2 JP 4568893 B2 JP4568893 B2 JP 4568893B2 JP 2001050932 A JP2001050932 A JP 2001050932A JP 2001050932 A JP2001050932 A JP 2001050932A JP 4568893 B2 JP4568893 B2 JP 4568893B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Description
【０００１】
【発明の属する技術分野】
本発明は鉛等の重金属と、有機ハロゲン化合物、揮発性有機化合物および油脂のうちの少なくとも一種のカーボン質有機汚染物とによって複合汚染された土壌からこれらの重金属とカーボン質有機汚染物を除去、回収により分離して汚染土壌を浄化する方法と装置に関する。
【０００２】
【従来の技術】
近年、新たな化学物質による環境汚染の懸念や、急増する廃棄物の処理問題に関連して、産業界における汚染物質の除去、公害防止活動が活発化している。そしてまた、都市部における工場跡地のように過去に蓄積された重金属類の他有機ハロゲン化合物、揮発性有機化合物、油脂等のカーボン質有機汚染物を含む土壌の複合汚染の問題がクローズアップされている。重金属については、環境庁の規定する「土壌環境基準」に従って重金属等有害物質を除去して土壌環境を修復する有効な対策が求められている。なお、重金属汚染土壌における汚染重金属としては、一般に鉛、カドミウム、砒素、クロム、水銀、セレン等が含まれている。
【０００３】
重金属に汚染された土壌環境を修復する手段としては、化学処理手段やセメント固化手段等による重金属不溶化処理方法があり、化学処理手段としては、汚染土壌に水と共に２価鉄塩又はアルミニウム塩を添加し混合撹拌することにより、土壌中の重金属をスピネル型の複酸化物とする方法も提案されている（特開平９−８５２２４、特開平９−８５２２５）。
【０００４】
一方、汚染重金属の回収を意図した土壌浄化法としては、例えば、重金属汚染土壌を水で解いた後、分級し、粒度別に比重選別処理、電気泳動処理等重金属を濃縮して排出する処理方法が提案されている（特開平１０−２９６２３０）。この方法では、特に、重金属含有量の多い細粒土壌部分について土壌中に電極を配置して直流電圧を印加し、重金属イオンを泳動させて電極付近の土壌に重金属を濃縮させて回収する電気泳動法による汚染土壌の浄化方法を特徴としている。
【０００５】
【発明が解決しようとする課題】
しかしながら、前者におけるスピネル型複酸化物とする重金属固定方法は、複数の重金属を同時に且つ短時間で完全に固定化して無害化する上では有用な手段であるが、汚染土壌中の重金属の再利用のための経済的な回収手段が求められる場合においては対応できない。
また、後者の電気泳動法による重金属回収手段を主体とする重金属汚染土壌の浄化方法は、重金属イオンに限られた除去方法であって、陰極部において粒子化する重金属のみを対象とするものであり、効率のよい汚染土壌の浄化手段としては未だ十分でなかった。
さらに、前記重金属汚染土壌に対して前記したような有機ハロゲン化合物、揮発性有機化合物、油脂等が絡む複合汚染については、汚染土壌中の重金属が、有機物、無機物と化合、または同伴して存在する複雑な形態であり、一般的な鉱石と違いその成分も均質なものは得らないことから特に見るべき対策はなく、汚染土壌中の重金属およびカーボン質有機汚染物等を粒子形態として効率的に除去できる土壌浄化技術が望まれていた。
【０００６】
以上の状況に鑑み、本発明は、汚染土壌からカーボン質有機汚染物を分離すると共に、金属精錬に対応可能な程度に重金属を濃縮させた土壌粒子を効率よく回収でき、元土の汚染土壌を再利用可能な程度に清浄化できる経済性に優れた汚染土壌の浄化法および装置の提供を目的とする。
【０００７】
【課題を解決するための手段】
本発明者等は、上記の目的を達成するため、鋭意研究の結果、汚染土壌における有機ハロゲン化合物、揮発性有機化合物、油脂さらには微生物等カーボン質有機汚染物が重金属の分離回収の障害になることを見出し、先ずこのカーボン質有機汚染物を高率で除去し、そのカーボン質有機汚染物分離後の重金属含有土壌を対象に重金属分離回収処理を行うことにより、汚染土壌からのカーボン質有機汚染物の分離と重金属の分離回収が効果的に行うことができ、また、このカーボン質有機汚染物の分離工程、重金属の分離回収処理工程には浮選手段を適用し、連続的に、また必要に応じて複数段階の浮選処理を繰り返すことにより、効率的に重金属濃縮精鉱が回収できると共に覆土材等再利用に供し得る清浄化土壌が得られることを見出した。
【０００８】
すなわち、本発明は、第１に、重金属およびカーボン質有機汚染物を含有する汚染土壌のスラリー中に気泡を導入して該カーボン質有機汚染物を該気泡に同伴させるための捕収剤を該スラリーに添加し、該スラリー中から該カーボン質有機汚染物を高率で同伴した気泡を浮上分離させる脱カーボン浮選を行った後に、該重金属の分離回収処理を行うことを特徴とする汚染土壌の浄化法であり、第２に、 前記カーボン質有機汚染物が有機ハロゲン化合物、揮発性有機化合物および油脂のうちの少なくとも一種である、第１記載の汚染土壌の浄化法であり、第３に、前記重金属の前記分離回収処理の工程が、前記脱カーボン浮選工程後のスラリー中に気泡を導入するとともに、該スラリーに硫化剤と捕収剤とを添加し、該重金属を浮上気泡に同伴させて分離回収し、該重金属溶出値が低減された清浄化土壌を得る工程である、第１または２に記載の汚染土壌の浄化法であり、第４に、前記重金属の前記分離回収処理を複数段階にわたって連続的に行う、第１〜３のいずれかに記載の汚染土壌の浄化法であり、第５に、前記スラリー中の汚染土壌は破砕、分級されて、５００μｍ以下の粒径を有するものである、第１〜４のいずれかに記載の汚染土壌の浄化法であり、第6に、前記脱カーボン浮選および前記重金属の前記分離回収処理を行うにあたり、前記スラリーをｐＨ２〜１２に調整する、第１〜５のいずれかに記載の汚染土壌の浄化法であり、第7に、前記重金属の前記分離回収処理を行うことにより前記清浄化土壌中の鉛溶出値が０．０１ mg/L以下に低減される、第３〜６のいずれかに記載の汚染土壌の浄化法であり、第８に、前記清浄化土壌についてさらに、含有される前記重金属の不溶化処理を行う、第３〜７のいずれかに記載の汚染土壌の浄化法であり、第９に、第１〜８のいずれかに記載の汚染土壌の浄化法において用いられる装置であって、気泡発生手段、撹拌機、スクレーパー、水流桶を備えた浮選機と添加剤の添加手段とを有することを特徴とする汚染土壌の浄化装置である。
【０００９】
【発明の実施の形態】
浮選手段を適用した図１および図２のフローシートによって本発明を説明する。
汚染土壌は、前記のように、鉛、砒素、カドミウム、クロム、水銀、セレン等重金属の他に、一般に有機ハロゲン化合物、揮発性有機化合物、油脂さらには微生物等カーボン質有機汚染物をも含んでいる。
図１に示したように、この処理に供する汚染土壌を元土として洗浄装置、破砕機、分級機を経由して土壌粒子を粒径５００μｍ以下、好ましくは１５０μｍ以下とし（破砕・分級工程）、水を加えて３〜４０％パルプ濃度の汚染土壌スラリーとする。
【００１０】
すなわち、汚染土壌は、処理負担の軽減を図るため前処理工程としてスクラバー等による水洗浄手段により予め可溶性成分を除去する。洗浄した汚染土壌は浮選処理のため破砕して分級する。破砕は例えば粗破砕と細破砕の２段で行い、分級についても２段階に構成し、それぞれの分級粗粒を破砕機に返戻し、気泡に同伴させるのに適した５００μｍ以下、好ましくは１５０μｍ以下の微粉体とする。粗破砕機にはクラッシャー、細破砕機にはロッドミル及び／又はボールミルを利用する。破砕機として細破砕機のみとし各分級装置からの循環粗粒を処理するようにしてもよい。分級装置には通常のサイクロンが利用できる。なお、破砕と分級は処理汚染土壌に水を加えて湿式処理とすることもできる。
【００１１】
この微粉体の汚染土壌を水と共に撹拌機付きのコンディショナーに供給してスラリー化し、条件剤、捕収剤、起泡剤等の添加剤を添加して浮選条件を整え浮選機に供給して空気を導入することにより、カーボン粗選浮鉱と脱カーボン粗選沈鉱とに分離する（脱カーボン浮選工程）。
すなわち、汚染土壌におけるカーボン質有機汚染物を粒子状態に保ち気泡によく同伴させるために条件剤として硫酸、塩酸、水酸化ナトリウム、水酸化カルシウム、炭酸化カルシウム等を使用してｐＨを２〜１２に条件付けし、また、常温〜７０℃の浮選に最適の温度に保持する。
捕収剤としては、ザンセートに代表される官能基に硫黄を有するもの、またはジチオ燐酸系、カルバミン酸系のもの、例えばジアルキルジチオカルバミン酸塩、ジアルキルジチオ燐酸塩等が好ましい。起泡剤としては一般にパイン油を用いる。 なお、この脱カーボン浮選工程においては、含有されている重金属は酸化物あるいはメタル等の状態にあって捕収剤に対して不活性な状態にあるが、前記カーボン質有機汚染物との分離を図るため、特に硫化剤を添加する硫化処理は行わない。
【００１２】
このように調整した汚染土壌スラリーを浮選機に連続的に供給し、浮選機の型式に従い自動吸引方式又は外部供給方式によって空気を導入することにより、浮上気泡に同伴されたカーボン質有機汚染物を含む土壌粒子からなるカーボン粗選浮鉱を、カーボン質有機汚染物が低減され鉛等重金属を含む土壌粒子からなる脱カーボン粗選沈鉱から分離させることができる。
【００１３】
得られた前記カーボン粗選浮鉱は分離槽に導入して沈降処理により脱カーボン固層をカーボン浮層即ちカーボン質有機汚染物を多量に含む土壌粒子を同伴する浮上気泡と分離する（カーボン浮鉱分離工程）。
カーボン浮層については、カーボン質有機汚染物を多量に含むので、焼却等別途処理に供し、重金属を含む脱カーボン固層は、前記脱カーボン粗選沈鉱に合体させる。
この脱カーボン浮選処理によって得られた脱カーボン粗選沈鉱はカーボン質有機汚染物質が低減され、以後の浮選処理において、カーボン質有機汚染物に影響されることなく効率的に鉛等重金属の分離回収が行えるものである。
【００１４】
次に、前記脱カーボン固層と前記脱カーボン粗選沈鉱を併せたスラリー状の脱カーボン粗選鉱は、図２のように、コンディショナーに供給し、ｐＨを２〜１２に保持しながら、硫化剤を添加する。すなわち、土壌中の重金属類はメタルや酸化物が多いため、硫化鉱物浮選が適用できるように硫化処理する。硫化剤としては硫化ソーダまたは水硫化ソーダが使用でき、その添加量は脱カーボン粗選鉱スラリー中の土壌量に対して０．１〜５ｋｇ／ｔである。添加量が０．１ｋｇ／ｔ未満では硫化効果が小さく、また５ｋｇ／ｔ以上では添加効果が飽和する。さらに、ザンセート剤等捕収剤と起泡剤を添加した後、浮選機において空気を導入して重金属粗選浮選を行う（重金属粗選工程）。
【００１５】
この重金属粗選浮選により精鉱として重金属粗選浮鉱を得ると共に尾鉱として重金属粗選沈鉱を得る。
重金属粗選沈鉱はさらに、分離槽において気泡からなる浮層から固層を沈降分離させる。脱水処理した固層は重金属低減土壌であり、清浄化土壌として元土採集場所の埋戻し材あるいは別途覆土材等として利用できる。
【００１６】
重金属粗選工程からの重金属粗選浮鉱スラリーは、コンディショナーに供し、硫化剤と捕収剤と起泡剤を添加した後、ｐＨ２〜１２に保持しながら、浮選機に供給して重金属精選浮選を行う（重金属精選工程）。この重金属精選浮選により、精鉱として重金属精選浮鉱（一次）および尾鉱として重金属精選沈鉱（一次）を得る。気泡発生手段、例えば、空気導入口より導入された空気を回転インペラなどの手段により気泡を形成し、浮遊した鉱物をスクレーパーで液面から掻き取りる装置を使用する。気泡量、気泡の大きさ、液の撹拌状況は土壌の状態により随時設定を行い、場合により複数の繰り返し、例えば多段処理を行えばより重金属精選浮選が安定する。
重金属精選浮鉱は重金属硫化物を濃縮的に含む土壌粒子からなり、さらに分離槽において沈降分離処理することにより気泡からなる浮層と重金属含有固層を得、脱水処理したこの固層は重金属含有精鉱として精錬用リサイクル原料に利用できる。
一方、重金属精選沈鉱については、まだ比較的多くの重金属硫化物を含むので好ましくは前記重金属粗選工程のコンディショナーに返戻して重金属回収率の向上に役立てる。
【００１７】
以上の方法によれば、例えば６００〜５００００ｍｇ／ｋｇの鉛を含む鉛汚染土壌から鉛を除去回収し、鉛含有量低減率５０％以上の鉛含有量低減土壌（清浄化土壌）を元土の６０％以上得ることができる。また、鉛回収産物（重金属含有精鉱）の鉛含有量は５％以上とすることができる。他の汚染重金属も鉛と同時回収することができる。
【００１８】
重金属含有量に関し、必要があれば、前記重金属精選浮鉱（一次）を対象として、さらに重金属精選浮選処理を繰り返すことができる。すなわち、前記重金属精選浮鉱のスラリーを二次コンディショナーに供して適宜硫化剤、捕収剤および起泡剤を添加し、二次浮選機において重金属をさらに濃縮させた重金属精選浮鉱（二次）と重金属精選沈鉱（二次）とに分離回収することができる。重金属精選沈鉱（二次）は前工程のコンディショナーに繰り返す。
【００１９】
このように、本方法によれば、重金属の含有状況に応じて、容易に二次さらに三次等多段階の重金属精選分離処理を継続し、重金属を回収すると共に重金属、有機ハロゲン化合物、揮発性有機化合物、油脂等を含まない清浄化土壌を得ることができるものである。なお、重金属粗選沈鉱について、残存重金属のスピネル型化等の不溶化処理を行うことにより、土壌浄化をさらに進めることもできる。
【００２０】
【実施例】
〔実施例１〕 図３のフローシートに従って汚染土壌を処理した。
元土として鉛含有量が４７５１ｍｇ／ｋｇの汚染土壌５００ｇを破砕・分級して１５０μｍ以下の土壌粒子とした分級土壌を用いた。
この分級土壌のスラリーを浮選機に投入し、捕収剤としてアミルザンセートカリウムを２００ｇ／ｔと起泡剤としてパイン油剤による「日香＃１２５」（日本香料株式会社商品名）１０ｇ／ｔを添加して撹拌して条件付けを行い、脱カーボン浮選処理を行った。浮選機としては京大式浮遊選鉱機（１８００ｃｃ、１２５００ｒｐｍ）を用いた（以下の浮選機においても同様）。
この脱カーボン浮選処理でカーボン粗選浮鉱と脱カーボン粗選沈鉱を得た。さらに、カーボン粗選浮鉱スラリーの分離槽における２分間の沈降分離でカーボン浮層と脱カーボン固層が得られた。
【００２１】
この脱カーボン固層を前記脱カーボン粗選沈鉱に加えて脱カーボン粗選鉱とし、Ｐｂ粗選浮選処理にかけた。この処理に際し、硫化剤としてＮａＳＨ１０００ｇ／ｔを添加し、捕収剤としてアミルザンセートカリウム２００ｇ／ｔを３回にわたり添加した。また起泡剤として「日香＃１２５」を１０ｇ／ｔ添加し、ｐＨを６．０に保持した。
このＰｂ粗選処理により、Ｐｂ粗選浮鉱とＰｂ粗選沈鉱を得、Ｐｂ粗選浮鉱については、さらに浮選機に供して捕収剤と起泡剤を添加し、Ｐｂ精選浮選を行い、Ｐｂ精選浮鉱とＰｂ精選沈鉱を得た。
【００２２】
得られた各産物について、土壌分布率とＰｂ含有量とＰｂ分布率を図３に示した。Ｐｂ粗選沈鉱としてＰｂの含有量が元土の３７．７％まで低減した清浄化土壌が回収された。また、図３中に示したカーボン浮層とＰｂ粗選沈鉱と合体した場合の数値からもわかるように、元土のＰｂの５０％を超える量のＰｂが元土のほぼ１４％の量の土壌に濃縮されて回収されたことになる。
本試験に用いた元土の鉛溶出値と清浄化土壌の鉛溶出値を表１に示した。元土の鉛溶出値は環境基準値を超過していたが、本処理を施すことにより得られたカーボン浮層とＰｂ粗選沈鉱の合体物では鉛溶出値が環境基準値以下となった。
【００２３】
【表１】
〔実施例２〕 ２３０８０ｍｇ／ｋｇのＰｂを含む元土の鉛汚染土壌５００ｇを破砕・分級処理により、１５０μｍ以下の土壌粒子にした後、水を加えてスラリーの濃度を１５％に調節し、分級土壌スラリーとした。
この分級土壌スラリーを、図４のフローシートに従い、浮選機（京大式浮遊選鉱機、以下同様）に供し、ザンセート捕収剤２００ｇ／ｔ、起泡剤「日香＃１２５」５０ｇ／ｔを添加し条件付けを行った後、１０分間空気を導入して浮選を行うことにより、カーボン粗選浮鉱と脱カーボン粗選沈鉱とに分離した（脱カーボン浮選工程）。
【００２５】
得られたカーボン粗選浮鉱は、分離槽における沈降分離処理によりカーボン質有機汚染物を濃縮的に含むカーボン浮層と脱カーボン固層とに分離し、脱カーボン固層は前記脱カーボン粗選沈鉱に合体させて脱カーボン粗選鉱とした。
脱カーボン粗選鉱スラリーは、浮選機に供し、１０００ｇ／ｔからなる水硫化ナトリウムからなる活性剤、２００ｇ／ｔのアミルザンセートカリウムからなる捕収剤と５０ｇ／ｔの起泡剤「日香＃１２５」を添加し、ｐＨを６．０に保持し、１０分間空気を導入し、Ｐｂ粗選浮選を行い、Ｐｂ粗選浮鉱とＰｂ粗選沈鉱とに分離した（Ｐｂ粗選工程）。
次いで、浮選分離後のＰｂ粗選浮鉱スラリーを浮選機に供し、捕収剤としてアミルザンセートカリウムを１００ｇ／ｔ、起泡剤として「日香＃１２５」を１０ｇ／ｔ、それぞれ添加して５分間撹拌し、１０分間空気を導入して浮選処理を行った（Ｐｂ精選工程）。
【００２６】
この結果、汚染土壌中のＰｂは、Ｐｂ精選浮鉱およびＰｂ精選沈鉱に濃縮して分離回収された。Ｐｂ精選浮鉱はＰｂを濃縮的に含む土壌粒子からなる。また、Ｐｂ精選沈鉱はなおＰｂを多く含むので、実操業においては、Ｐｂ粗選工程の浮選機に繰り返すものである。
回収された産物について、分級土壌に対する土壌分布率とＰｂ分布率およびＰｂ含有量を図４に示した。
元土の１９．８％のＰｂを含む清浄化土壌がＰｂ粗選沈鉱として得られた。また、精錬原料に適したＰｂ精選浮鉱として元土のＰｂの３２．９％を占める２６０２３０ｍｇ/ｋｇのＰｂ含有量のものが得られた。また、回収可能な産物として合計で元土の６５．８％のＰｂを含むＰｂ精選浮鉱およびＰｂ精選沈鉱が得られた。
本試験に用いた元土の鉛溶出値と清浄化土壌の鉛溶出値を表２に示した。元土の鉛溶出値は環境基準値を超過していたが、本処理を施すことにより得られたカーボン浮層と鉛粗選沈鉱では鉛溶出値が環境基準値以下となった。
【００２７】
【表２】
〔実施例３〕 ８７７ｍｇ／ｋｇのＰｂと５．３％の油分を含む、鉛と油の複合汚染土壌５００ｇを破砕・分級処理により、１５０μｍ以下の土壌粒子にした後、水を加えてスラリーの濃度を１５％に調節し、分級土壌スラリーとした。
この分級土壌スラリーを、図５のフローシートに従い、浮選機（京大式浮遊選鉱機、以下同様）に供し、起泡剤「日香＃１２５」５０ｇ／ｔを添加し条件付けを行った後、１０分間空気を導入して浮選を行うことにより、カーボン粗選浮鉱と脱カーボン粗選沈鉱とに分離した（脱カーボン浮選工程）。
【００２９】
得られたカーボン粗選浮鉱は、分離槽における沈降分離処理によりカーボン質有機汚染物を濃縮的に含むカーボン浮層と脱カーボン固層とに分離し、脱カーボン固層は前記脱カーボン粗選沈鉱に合体させて脱カーボン粗選鉱とした。
脱カーボン粗選鉱スラリーは、浮選機に供し、５００ｇ／ｔの硫化ナトリウムからなる活性剤と２００ｇ／ｔのアミルザンセートカリウムからなる捕収剤と５０ｇ／ｔの起泡剤「日香＃１２５」を添加し、ｐＨを６．０に保持し、１０分間空気を導入し、Ｐｂ粗選浮選を行い、Ｐｂ粗選浮鉱とＰｂ粗選沈鉱とに分離した（Ｐｂ粗選工程）。
次いで、浮選分離後のＰｂ粗選浮鉱スラリーを浮選機に供し、捕収剤としてアミルザンセートカリウムを１００ｇ／ｔ、起泡剤として「日香＃１２５」を１０ｇ／ｔ、それぞれ添加して５分間撹拌し、１０分間空気を導入して浮選処理を行った（Ｐｂ精選工程）。
【００３０】
この結果、汚染土壌中のＰｂは、Ｐｂ精選浮鉱およびＰｂ精選沈鉱に濃縮除去回収された。Ｐｂ精選浮鉱はＰｂを濃縮的に含む土壌粒子からなる。また、Ｐｂ精選沈鉱はなおＰｂを多く含むので、実操業においては、Ｐｂ粗選工程の浮選機に繰り返すものである。
回収された産物について、分級土壌に対する土壌分布率、Ｐｂ分布率、Ｐｂ含有量、油分含有量、油分分布率を図５に示した。
元土の１０．０％のＰｂおよび２５．９％の油分を含む清浄化土壌がＰｂ粗選沈鉱として得られた。また、精錬原料に適したＰｂ精選浮鉱として元土のＰｂの３０．９％を占める８４６４０ｍｇ／ｋｇのＰｂ含有量のものが得られた。また、回収可能な産物として合計で元土の６９．４％のＰｂを含むＰｂ精選浮鉱およびＰｂ精選沈鉱が得られた。
本試験に用いた元土の鉛溶出値と清浄化土壌の鉛溶出値を表３に示した。元土の鉛溶出値は環境基準値を超過していたが、本処理を施すことにより得られたカーボン浮層と鉛粗選沈鉱では鉛溶出値が環境基準値以下となった。
【００３１】
【表３】
〔比較例１〕 図６に示したように、Ｐｂ含有量が１１８６７ｍｇ／ｋｇの鉛汚染土壌を脱カーボン浮選を行うことなく、Ｐｂ粗選浮選およびＰｂ精選浮選を行った。このＰｂ粗選処理およびＰｂ精選処理は同一の京大式浮選機を用い、実施例２と同様条件で行った。すなわち、Ｐｂ粗選処理において、浮選処理時に活性剤として硫化ナトリウム、捕収剤としてアミルザンセートカリウム２００ｇ／ｔと、起泡剤「日香＃１２５」を５０ｇ／ｔを添加した。この処理により、Ｐｂ粗選浮鉱とＰｂ粗選沈鉱を得た。Ｐｂ粗選浮鉱はさらに浮選機に供してＰｂ精選処理を行い、捕収剤と起泡剤に前記と同一のものを使用し同一量で添加してＰｂ精選浮鉱とＰｂ精選沈鉱を得た。
【００３３】
得られた産物のＰｂ含有量とＰｂ分布率を図６に示した。
Ｐｂ精選浮鉱のＰｂ含有量は実施例２の場合に比べても低く、そのＰｂ分布率も２６．８％に止まった。また、Ｐｂ精選浮鉱についてさらに同様の浮選処理を繰り返したが、浮鉱の鉛品位は向上しなかった。すなわち、Ｐｂを濃縮できなかった。
【００３４】
【発明の効果】
上記の通り、重金属およびカーボン質有機汚染物を含有する汚染土壌から予めカーボン質有機汚染物を浮選手段により除去した後浮選手段等による重金属分離回収処理を行う本発明の土壌浄化法によれば、カーボン質有機汚染物除去処理と重金属分離回収処理が容易に効率的に行うことができ、覆土材等に用い得る清浄化土壌を得ることができる。また、本発明によれば、土壌スラリーに適宜重金属捕収剤、硫化剤、起泡剤を添加して撹拌する比較的単純な浮選操作を連続的に行い、また、必要に応じて複数段階の連続処理を行うことにより、効率的に従って経済的にカーボン質有機汚染物分離と、重金属分離回収、さらに土壌からの重金属溶出値が低減された清浄化土壌の回収という、汚染土壌の浄化が行えるという効果を有する。また、前記土壌スラリーをｐＨ２〜１２および常温〜７０℃に保持する本発明によれば、カーボン質有機汚染物および重金属の分離回収が容易になるという効果が得られる。
【図面の簡単な説明】
【図１】本発明の汚染土壌の浄化法における脱カーボン浮選工程を示すフロー図である。
【図２】本発明の汚染土壌の浄化法における脱カーボン粗選鉱の重金属分離回収工程を示すフロー図である。
【図３】本発明の浄化法の実施例１を示すフロー図である。
【図４】本発明の浄化法の実施例２を示すフロー図である。
【図５】本発明の浄化法の実施例３を示すフロー図である。
【図６】比較例１の浄化法を示すフロー図である。[0001]
BACKGROUND OF THE INVENTION
The present invention removes these heavy metals and carbonaceous organic contaminants from soil that is complex-contaminated by heavy metals such as lead and at least one carbonaceous organic contaminant of organic halogen compounds, volatile organic compounds and oils and fats, The present invention relates to a method and an apparatus for separating and purifying contaminated soil by recovery.
[0002]
[Prior art]
In recent years, in connection with concerns about environmental pollution caused by new chemical substances and the problem of waste disposal that has been increasing rapidly, the removal of pollutants and pollution prevention activities in the industrial sector have become active. Also, the problem of complex contamination of soil containing carbonaceous organic contaminants such as organic halogen compounds, volatile organic compounds, oils and fats in addition to heavy metals accumulated in the past, such as factory sites in urban areas, has been highlighted. Yes. For heavy metals, effective measures are required to restore the soil environment by removing toxic substances such as heavy metals in accordance with the “Soil Environmental Standards” stipulated by the Environment Agency. In general, the contaminated heavy metals in heavy metal contaminated soil include lead, cadmium, arsenic, chromium, mercury, selenium and the like.
[0003]
As a means to repair soil environment contaminated with heavy metals, there are heavy metal insolubilization treatment methods such as chemical treatment means and cement solidification means. As chemical treatment means, divalent iron salt or aluminum salt is added to contaminated soil together with water In addition, a method has been proposed in which heavy metals in the soil are converted into a spinel double oxide by mixing and stirring (JP-A-9-85224, JP-A-9-85225).
[0004]
On the other hand, as a soil purification method intended for recovery of contaminated heavy metals, for example, there is a processing method for concentrating and discharging heavy metals such as specific gravity sorting processing, electrophoresis processing, etc. according to particle size after classifying and grading heavy metal contaminated soil with water. It has been proposed (Japanese Patent Laid-Open No. 10-296230). In this method, in particular, electrophoresis is performed on a fine-grained soil portion with a high heavy metal content by placing an electrode in the soil, applying a DC voltage, migrating heavy metal ions to concentrate heavy metal in the soil near the electrode, and collecting it. It features a method for remediating contaminated soil by law.
[0005]
[Problems to be solved by the invention]
However, the former heavy metal fixing method using spinel type double oxide is a useful means to completely fix a plurality of heavy metals in a short time and make them harmless, but the reuse of heavy metals in contaminated soil It is not possible to cope with the case where an economical recovery means is required.
The latter method for purifying heavy metal-contaminated soil, mainly consisting of heavy metal recovery means by electrophoresis, is a removal method limited to heavy metal ions, and is intended only for heavy metals that become particles at the cathode. It was not yet sufficient as an efficient means of remediating contaminated soil.
Furthermore, for complex pollution involving organic halogen compounds, volatile organic compounds, oils and fats as described above with respect to the heavy metal-contaminated soil, heavy metals in the contaminated soil exist in combination with or accompanied by organic substances and inorganic substances. Since it is a complex form and its components are not homogeneous unlike ordinary ores, there are no special measures to be taken, and heavy metals and carbonaceous organic pollutants in contaminated soil are efficiently used as particle forms. A soil purification technology that can be removed was desired.
[0006]
In view of the above situation, the present invention can separate carbonaceous organic pollutants from contaminated soil and can efficiently recover soil particles enriched with heavy metals to a degree that can be used for metal refining. An object of the present invention is to provide a method and an apparatus for cleaning contaminated soil, which are highly economical and can be cleaned to a reusable level.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted intensive research, and as a result, organic halogen compounds, volatile organic compounds, oils and fats, and carbonaceous organic contaminants such as microorganisms in contaminated soil become obstacles to the separation and recovery of heavy metals. First, this carbonaceous organic pollutant is removed at a high rate, and the heavy metal-containing soil after separation of the carbonaceous organic pollutant is subjected to heavy metal separation and recovery treatment, so that the carbonaceous organic pollution from the contaminated soil Separation of substances and heavy metal separation and recovery can be carried out effectively. In addition, the flotation means is applied to the separation process of carbonaceous organic contaminants and the separation and collection process of heavy metals, and it is necessary continuously. It was found that by repeating a plurality of stages of flotation according to the above, it is possible to efficiently collect heavy metal concentrate and obtain a purified soil that can be reused as a covering material.
[0008]
That is, the present invention firstly provides a collection agent for introducing bubbles into a slurry of contaminated soil containing heavy metals and carbonaceous organic contaminants to entrain the carbonaceous organic contaminants in the bubbles. A contaminated soil which is added to a slurry and is subjected to decarbonization flotation to float and separate bubbles entrained with the carbonaceous organic pollutant in the slurry at a high rate, followed by separation and recovery of the heavy metal. And second, the carbonaceous organic contaminant is at least one of an organic halogen compound, a volatile organic compound, and fats and oils, and the third method is for purifying contaminated soil. The step of separating and recovering the heavy metal introduces bubbles into the slurry after the decarbonization flotation step, and adds a sulfiding agent and a collection agent to the slurry, and entrains the heavy metal in the floating bubbles. The method for purifying contaminated soil according to the first or second aspect, wherein the heavy metal elution value is reduced and recovered to obtain purified soil with reduced heavy metal elution value. Fourth, the heavy metal separation and recovery process is performed. The method for purifying contaminated soil according to any one of 1 to 3, which is performed continuously over a plurality of stages, and fifth, the contaminated soil in the slurry is crushed and classified to have a particle size of 500 μm or less. The method for purifying contaminated soil according to any one of 1 to 4, wherein the slurry is adjusted to a pH of 2 to 12 in performing the decarbonization flotation and the heavy metal separation and recovery process. It is the purification method of the contaminated soil according to any one of 1 to 5, wherein the lead elution value in the purified soil is 0.01 mg by performing the separation and recovery treatment of the heavy metal. Any of Nos. 3 to 6 reduced to / L or less 8 is the method for purifying contaminated soil according to any one of Nos. 3 to 7, in which the heavy metal contained is further insolubilized in the purified soil. Ninth, an apparatus used in the method for purifying contaminated soil according to any one of 1 to 8, wherein a bubble generating means, a stirrer, a scraper, a flotation machine equipped with water flutes and an additive adding means It is the purification apparatus of the contaminated soil characterized by having.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described with reference to the flow sheets of FIGS. 1 and 2 to which a flotation means is applied.
As described above, contaminated soil generally contains organic halogen compounds, volatile organic compounds, oils and fats, and carbonaceous organic contaminants such as microorganisms in addition to heavy metals such as lead, arsenic, cadmium, chromium, mercury, and selenium. Yes.
As shown in FIG. 1, the soil particles subjected to this treatment are treated as a base soil with a soil particle size of 500 μm or less, preferably 150 μm or less via a cleaning device, a crusher, and a classifier (crushing / classifying step), Add water to make a contaminated soil slurry with 3-40% pulp concentration.
[0010]
That is, in order to reduce the processing burden, the contaminated soil is preliminarily removed of soluble components by a water cleaning means such as a scrubber. The washed contaminated soil is crushed and classified for flotation treatment. Crushing is performed in two stages, for example, coarse crushing and fine crushing, and classification is also configured in two stages. Each classification coarse particle is returned to the crusher and is suitable for being accompanied by bubbles, 500 μm or less, preferably 150 μm or less. Of fine powder. A crusher is used for the rough crusher, and a rod mill and / or a ball mill is used for the fine crusher. Only the fine crusher may be used as the crusher, and the circulating coarse particles from each classifier may be processed. A normal cyclone can be used for the classification device. In addition, crushing and classification can also be wet-treated by adding water to the treated contaminated soil.
[0011]
This fine powder-contaminated soil is supplied to a conditioner with a stirrer together with water to form a slurry, and additives such as a conditioner, a collection agent, and a foaming agent are added to adjust the flotation conditions and supply to the flotation machine. In this way, air is introduced to separate the carbon rough fractionation flotation and the decarbonization coarse fractionation ore (decarbonization flotation step).
In other words, sulfuric acid, hydrochloric acid, sodium hydroxide, calcium hydroxide, calcium carbonate or the like is used as a condition agent in order to keep carbonaceous organic contaminants in the contaminated soil in a particulate state and entrained in the air bubbles, and the pH is adjusted to 2-12. In addition, the temperature is kept at an optimum temperature for flotation at room temperature to 70 ° C.
As the collector, those having sulfur in the functional group typified by xanthate, or those having a dithiophosphoric acid or carbamic acid such as dialkyldithiocarbamate or dialkyldithiophosphate are preferable. Pine oil is generally used as a foaming agent. In this decarbonization flotation step, the contained heavy metal is in an oxide or metal state and inactive to the collection agent, but is separated from the carbonaceous organic contaminants. Therefore, the sulfiding treatment in which a sulfiding agent is added is not performed.
[0012]
Contaminated soil slurry thus adjusted is continuously supplied to the flotation machine, and air is introduced by an automatic suction system or an external supply system according to the type of the flotation machine, thereby causing carbon organic contamination accompanied by the floating bubbles. The rough carbon float ore made of soil particles containing matter can be separated from the decarbonized coarse ore deposit made of soil particles containing heavy metals such as lead with reduced carbonaceous organic contaminants.
[0013]
The obtained coarse carbon flotation ore is introduced into a separation tank, and the decarbonized solid layer is separated from the carbon floating layer, that is, the floating bubbles accompanied with soil particles containing a large amount of carbonaceous organic contaminants by the sedimentation process (carbon floating layer). Ore separation step).
Since the carbon floating layer contains a large amount of carbonaceous organic contaminants, the carbon floating layer is subjected to separate treatment such as incineration, and the decarbonized solid layer containing heavy metal is combined with the decarbonized coarsely separated ore.
The decarbonized coarsely settled ore obtained by this decarbonization flotation treatment has reduced carbonaceous organic pollutants, and in subsequent flotation treatment, heavy metals such as lead can be efficiently processed without being affected by carbonaceous organic contaminants. Can be separated and recovered.
[0014]
Next, the slurry-like decarbonized mineral combined with the decarbonized solid layer and the decarbonized coarsely settled ore is supplied to a conditioner as shown in FIG. Add agent. That is, since heavy metals in the soil are rich in metals and oxides, they are subjected to sulfurization treatment so that sulfide mineral flotation can be applied. As the sulfiding agent, sodium sulfide or sodium hydrosulfide can be used, and the amount added is 0.1 to 5 kg / t with respect to the amount of soil in the decarbonized coarse beneficiation slurry. When the addition amount is less than 0.1 kg / t, the sulfidation effect is small, and when it is 5 kg / t or more, the addition effect is saturated. Further, after adding a collection agent such as xanthate and a foaming agent, air is introduced in a flotation machine to perform heavy metal rough flotation (heavy metal rough selection step).
[0015]
By this heavy metal rough flotation, heavy metal rough flotation is obtained as concentrate, and heavy metal rough flotation is obtained as tailing.
The heavy metal coarsely separated sedimentation further settles and separates the solid layer from the floating layer composed of bubbles in the separation tank. The dehydrated solid layer is heavy metal-reduced soil, and can be used as a back-up material at the original soil collection site or a separate soil covering material as a purified soil.
[0016]
The heavy metal crude flotation slurry from the heavy metal roughing step is supplied to a conditioner, and after adding a sulfiding agent, a collecting agent and a foaming agent, while maintaining the pH at 2 to 12, it is supplied to a flotation machine and selected for heavy metal. Flotation is performed (heavy metal selection process). By this heavy metal selective flotation, heavy metal selective flotation (primary) is obtained as concentrate and heavy metal selective precipitation (primary) is obtained as tailing. For example, a device is used that forms air bubbles by means of a bubble generating means, for example, air introduced through an air inlet, and scrapes off the suspended mineral from the liquid surface with a scraper. The amount of bubbles, the size of bubbles, and the state of agitation of the liquid are set as needed depending on the state of the soil. In some cases, a plurality of repetitions, for example, multistage treatment, can stabilize the heavy metal selective flotation.
Heavy metal selective floatation is composed of soil particles containing heavy metal sulfides in a concentrated manner, and further, a floating layer consisting of bubbles and a heavy metal-containing solid layer are obtained by sedimentation treatment in a separation tank, and this dehydrated solid layer contains heavy metals. It can be used as a refining material for refining as a concentrate.
On the other hand, since the heavy metal selective sedimentation still contains a relatively large amount of heavy metal sulfide, it is preferably returned to the conditioner of the heavy metal roughing step to improve the heavy metal recovery rate.
[0017]
According to the above method, for example, lead is removed and recovered from lead-contaminated soil containing 600 to 50000 mg / kg of lead, and the lead content reduced soil (cleaned soil) having a lead content reduction rate of 50% or more is used as the original soil. 60% or more can be obtained. Moreover, the lead content of the lead recovery product (heavy metal-containing concentrate) can be 5% or more. Other contaminated heavy metals can be recovered simultaneously with lead.
[0018]
Regarding the heavy metal content, if necessary, the heavy metal selective flotation process can be repeated for the heavy metal selective flotation (primary). That is, the heavy metal refined flotation slurry is subjected to a secondary conditioner, and a sulfiding agent, a collecting agent and a foaming agent are added as appropriate. ) And heavy metal selective sedimentation (secondary). Heavy metal selective sedimentation (secondary) is repeated in the previous conditioner.
[0019]
As described above, according to the present method, depending on the heavy metal content, the secondary and tertiary multi-stage heavy metal selective separation process can be easily continued to recover the heavy metal and to recover the heavy metal, organic halogen compound, volatile organic compound. It is possible to obtain a purified soil that does not contain compounds, fats and oils, and the like. In addition, soil purification can also be further advanced by performing insolubilization processing, such as spinel type | molding of a residual heavy metal, about a heavy metal coarsely settled ore.
[0020]
【Example】
Example 1 Contaminated soil was treated according to the flow sheet of FIG.
As the original soil, classified soil was obtained by crushing and classifying 500 g of contaminated soil having a lead content of 4751 mg / kg to obtain soil particles of 150 μm or less.
This classified soil slurry is put into a flotation machine, and 200 g / t of amyl xanthate potassium as a collecting agent and “Nika # 125” (trade name of Nippon Fragrance Co., Ltd.) with pine oil as a foaming agent are 10 g / t. Was added and stirred for conditioning, and decarbonized flotation treatment was performed. As a flotation machine, a Kyoto University type flotation machine (1800 cc, 12500 rpm) was used (the same applies to the following flotation machines).
By this decarbonized flotation treatment, carbon rough flotation and decarbonized rough precipitation were obtained. Further, a carbon floating layer and a decarbonized solid layer were obtained by settling and separation for 2 minutes in a separation tank of the coarse carbon ore flotation slurry.
[0021]
This decarbonized solid layer was added to the decarbonized coarsely settled ore to obtain decarbonized coarsely ore-treated, and subjected to a Pb coarsely selected flotation process. In this treatment, 1000 g / t of NaSH was added as a sulfiding agent, and 200 g / t of amyl xanthate potassium was added as a collecting agent three times. Further, 10 g / t of “Nika # 125” was added as a foaming agent, and the pH was maintained at 6.0.
By this Pb rough fractionation process, Pb coarse fractionation ore and Pb coarse fractionation ore are obtained, and about Pb coarse fractionation ore, it is further used for a flotation machine, a collection agent and a foaming agent are added, and Pb refinement | purification floatation is carried out. A selection was made to obtain Pb refined floatation and Pb refined sedimentation.
[0022]
About each obtained product, the soil distribution rate, Pb content, and Pb distribution rate were shown in FIG. As Pb coarsely settled ore, cleaned soil with a Pb content reduced to 37.7% of the original soil was recovered. In addition, as can be seen from the numerical values when the carbon floating layer and Pb coarsely settled ore shown in FIG. 3 are combined, the amount of Pb exceeding 50% of the Pb of the main soil is the amount of about 14% of the main soil. It is concentrated and recovered in the soil.
Table 1 shows the lead elution values of the main soil and the purified soil used in this test. The lead elution value of the main soil exceeded the environmental standard value, but the lead elution value was below the environmental standard value in the coalesced carbon floating layer and Pb rough sedimentation obtained by applying this treatment. .
[0023]
[Table 1]
[Example 2] After pulverizing and classifying 500 g of lead-contaminated soil containing 23080 mg / kg of Pb into soil particles of 150 μm or less, water is added to adjust the concentration of the slurry to 15%. A soil slurry was obtained.
This classified soil slurry is subjected to a flotation machine (Kyoto University Flotation Mineralizer, the same applies hereinafter) according to the flow sheet of FIG. 4, and the xanthate collector 200 g / t, the foaming agent “Nika # 125” 50 g / t After adding and conditioning, by carrying out flotation by introducing air for 10 minutes, it separated into the carbon rough fractionation flotation and the decarbonization rough fractionation (decarbonization flotation process).
[0025]
The obtained rough carbonized ore is separated into a carbon floating layer and a decarbonized solid layer that contain carbonaceous organic contaminants in a concentrated manner by a sedimentation separation process in a separation tank. It was combined with the sedimentation to obtain a decarbonized crude beneficiation.
The decarbonized crude beneficiation slurry was subjected to a flotation machine, an activator consisting of 1000 g / t sodium hydrosulfide, a collector consisting of 200 g / t amyl xanthate potassium and a 50 g / t foaming agent “Nika” # 125 "was added, the pH was maintained at 6.0, air was introduced for 10 minutes, Pb coarse flotation was performed, and Pb coarse flotation and Pb coarse flotation were separated (Pb coarse fractionation). Process).
Next, the Pb coarsely separated flotation slurry after flotation separation is supplied to a flotation machine, and 100 g / t of amyl xanthate potassium is added as a collecting agent, and 10 g / t of “Nichika # 125” is added as a foaming agent. Then, the mixture was stirred for 5 minutes, and air was introduced for 10 minutes to perform a flotation process (Pb selection process).
[0026]
As a result, Pb in the contaminated soil was concentrated and separated and recovered in the Pb refined floatation and the Pb refined sedimentation. Pb refined flotation consists of soil particles containing Pb in an enriched manner. Further, since the Pb finely settled ore still contains a large amount of Pb, in the actual operation, it is repeated to the flotation machine in the Pb rough selection process.
FIG. 4 shows the soil distribution ratio, the Pb distribution ratio, and the Pb content of the collected products with respect to the classified soil.
A cleaned soil containing 19.8% Pb of the original soil was obtained as Pb coarsely settled ore. Moreover, the thing of Pb content of 260230 mg / kg which occupies 32.9% of Pb of a native earth as a Pb refined floatation suitable for a refining raw material was obtained. Further, as a recoverable product, a Pb refined floatation and a Pb refined sedimentation containing 65.8% of Pb in the main soil in total were obtained.
Table 2 shows the lead elution values of the main soil and the purified soil used in this test. The lead elution value of the main soil exceeded the environmental standard value, but the lead elution value was below the environmental standard value in the carbon floating layer and lead roughing ore obtained by this treatment.
[0027]
[Table 2]
[Example 3] After pulverizing and classifying 500 g of lead-oil mixed contaminated soil containing 877 mg / kg of Pb and 5.3% oil, the soil particles were reduced to 150 µm or less, and then water was added to the slurry. The concentration was adjusted to 15% to obtain a classified soil slurry.
After subjecting this classified soil slurry to a flotation machine (Kyoto University Flotation Mineralizer, the same applies hereinafter) according to the flow sheet of FIG. 5 and adding 50 g / t of the foaming agent “Nika # 125” By carrying out flotation by introducing air for 10 minutes, the carbon was separated into rough carbonized ore and decarbonized roughened ore (decarbonized flotation step).
[0029]
The obtained rough carbonized ore is separated into a carbon floating layer and a decarbonized solid layer that contain carbonaceous organic contaminants in a concentrated manner by a sedimentation separation process in a separation tank. It was combined with the sedimentation to obtain a decarbonized crude beneficiation.
The decarbonized coarse beneficiation slurry was subjected to a flotation machine, and an activator composed of 500 g / t sodium sulfide, a collection agent composed of 200 g / t amyl xanthate potassium, and a 50 g / t foaming agent “Nika # 125 Was added, the pH was maintained at 6.0, air was introduced for 10 minutes, and Pb coarse flotation was performed to separate Pb coarse flotation and Pb coarse flotation (Pb coarse fractionation step). .
Next, the Pb coarsely separated flotation slurry after flotation separation is supplied to a flotation machine, and 100 g / t of amyl xanthate potassium is added as a collecting agent, and 10 g / t of “Nichika # 125” is added as a foaming agent. Then, the mixture was stirred for 5 minutes, and air was introduced for 10 minutes to perform a flotation process (Pb selection process).
[0030]
As a result, Pb in the contaminated soil was concentrated, removed, and recovered in the Pb refined floatation and the Pb refined sedimentation. Pb refined flotation consists of soil particles containing Pb in an enriched manner. Further, since the Pb finely settled ore still contains a large amount of Pb, in the actual operation, it is repeated to the flotation machine in the Pb rough selection process.
About the collect | recovered product, the soil distribution rate with respect to a classification | category soil, Pb distribution rate, Pb content, oil content content, and oil content distribution rate were shown in FIG.
A cleaned soil containing 10.0% Pb and 25.9% oil content of the original soil was obtained as Pb coarsely settled ore. Moreover, the thing of 84640 mg / kg of Pb content which occupies 30.9% of Pb of a native earth as a Pb refined floatation suitable for a refining raw material was obtained. In addition, as a recoverable product, a Pb refined floatation and a Pb refined sediment containing 69.4% Pb of the original soil in total were obtained.
Table 3 shows the lead elution values of the main soil and the purified soil used in this test. The lead elution value of the main soil exceeded the environmental standard value, but the lead elution value was below the environmental standard value in the carbon floating layer and lead roughing ore obtained by this treatment.
[0031]
[Table 3]
[Comparative Example 1] As shown in FIG. 6, Pb coarse flotation and Pb fine flotation were performed on lead-contaminated soil having a Pb content of 11867 mg / kg without decarbonizing flotation. The Pb coarse selection process and the Pb fine selection process were performed under the same conditions as in Example 2 using the same Kyoto University flotation machine. That is, in the Pb rough selection process, sodium sulfide as an activator, 200 g / t of amyl xanthate potassium as a collection agent, and 50 g / t of a foaming agent “Nika # 125” were added during the flotation process. By this treatment, Pb rough fractionated ore and Pb coarse fractionated ore were obtained. Pb rough fractionation ore is further supplied to a flotation machine and subjected to Pb refinement treatment, and the same amount as above is used for the collection agent and foaming agent, and added in the same amount to obtain Pb refinement floater and Pb refinement sedimentation. Got.
[0033]
The Pb content and Pb distribution rate of the obtained product are shown in FIG.
The Pb content of the finely divided Pb floated was lower than that in Example 2, and the Pb distribution rate was only 26.8%. Moreover, although the same flotation process was further repeated about the Pb refined flotation, the lead quality of the flotation did not improve. That is, Pb could not be concentrated.
[0034]
【The invention's effect】
As described above, according to the soil purification method of the present invention, in which the carbonaceous organic contaminants are previously removed from the contaminated soil containing heavy metals and carbonaceous organic contaminants by the flotation means, and then the heavy metal separation and recovery process is performed by the flotation means. For example, the carbonaceous organic contaminant removal process and the heavy metal separation and recovery process can be performed easily and efficiently, and a purified soil that can be used as a soil covering material or the like can be obtained. Further, according to the present invention, a relatively simple flotation operation in which a heavy metal collector, a sulfurizing agent, and a foaming agent are added to the soil slurry as appropriate and stirred is continuously performed, and a plurality of steps are performed as necessary. By conducting continuous treatment, it is possible to purify contaminated soil by separating carbonaceous organic pollutants efficiently and economically, separating and recovering heavy metals, and recovering purified soil with reduced heavy metal elution from the soil. It has the effect. In addition, according to the present invention in which the soil slurry is maintained at pH 2 to 12 and normal temperature to 70 ° C., the effect of facilitating separation and recovery of carbonaceous organic contaminants and heavy metals can be obtained.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a decarbonization flotation step in a method for purifying contaminated soil according to the present invention.
FIG. 2 is a flowchart showing a heavy metal separation and recovery step of decarbonized rough beneficiation in the method for purifying contaminated soil of the present invention.
FIG. 3 is a flowchart showing Example 1 of the purification method of the present invention.
FIG. 4 is a flowchart showing Example 2 of the purification method of the present invention.
FIG. 5 is a flowchart showing Example 3 of the purification method of the present invention.
6 is a flowchart showing a purification method of Comparative Example 1. FIG.
Claims (6)
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| KR20150018563A (en) * | 2012-05-11 | 2015-02-23 | 꼼미사리아 아 레네르지 아토미끄 에뜨 옥스 에너지스 앨터네이티브즈 | Method for the radioactive decontamination of soil by dispersed air flotation foam and said foam |
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