JP2004016935A

JP2004016935A - Electrochemical treatment method and electrochemical treatment apparatus

Info

Publication number: JP2004016935A
Application number: JP2002176230A
Authority: JP
Inventors: Hiroshi Nomura; 野村　洋; Shinichi Matsumoto; 松本　真一; Morio Ito; 伊藤　守男; Hajime Okura; 大倉　一; Noriyuki Oyatsu; 大谷津　紀之; Michio Egashira; 江頭　道夫
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 2002-06-17
Filing date: 2002-06-17
Publication date: 2004-01-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical treatment method which can be easily and inexpensively implemented at an arbitrary place such as a site. <P>SOLUTION: The method includes a step of forming an enclosure frame 1 having imperviousness, a step of arranging an anode 13 and a cathode 12 so as to face each other in the enclosure frame 1, a step of carrying a material 16 to be treated into the space between the anode 13 and the cathode 12 in the enclosure frame 1, a step of injecting infiltration water 17 into the enclosure frame 1, a step of electrochemically treating the material 16 to be treated by making an electric current flow between the anode 13 and the cathode 12, and a step of breaking down at least part of sidewalls 2 of the enclosure frame 1 after electrochemically treating the material 16 to be treated and carrying the treated material for treatment out of the enclosure frame 1. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は，電気泳動・電気浸透などの作用により例えば土壌中の重金属類などを処理する電気化学的処理方法ならびに電気化学的処理装置に係り、特に現地などの任意な所で容易にかつ安価に実施することができる電気化学的処理方法ならびに電気化学的処理装置に関する。
【０００２】
【従来の技術】
重金属類などの有害成分を含む土壌浄化方法には、
▲１▼．土壌から重金属類を電気化学的に処理する方法、
▲２▼．水や薬剤で土壌を洗浄する方法、
▲３▼．酸化剤や還元剤で無害なものに分解する方法、
▲４▼．土壌を加熱して脱離・揮発する方法、
▲５▼．土壌を溶融炉でスラグ化する方法、
▲６▼．土壌を高電圧でガラス固化する方法、
▲７▼．土壌をセメントで固化する方法、
▲８▼．薬剤で難溶性物質に固定化する方法、
▲９▼．土壌をシートパイルで遮蔽して閉じ込める方法、
などがある。前記▲２▼の土壌洗浄法は砂質には向いているが、粘土質には不向きである。前記▲３▼の酸化，還元法は具体的には６価クロムやシアンなどにのみ適用可能であり、適用範囲が狭い。前記▲４▼の熱脱離法、▲５▼の溶融固化法、▲６▼のガラス固化は必要エネルギーが大でランニングコストが高い。前記▲７▼のセメント固化法や▲８▼の不溶化法は封じ込めするだけで有害成分を除去するものではない。前記▲９▼の遮蔽法も単に遮蔽するだけで有害成分を除去するものではない。
【０００３】
これに対して前記▲１▼の電気化学的処理法は、土壌が粘土質でも有害成分の分離・除去が可能であり、処理の適用範囲が広く、熱脱離法、溶融固化法、ガラス固化法などに比べると必要エネルギーが小でランニングコストが低いなどの特長を有している。
【０００４】
汚染された土壌から重金属類を電気化学的に回収する従来の方法は主に、陽極と陰極を内側に設置した大型で常設の処理槽を製作し、汚染された土壌を例えばトラックなどで現地から処理槽の所まで搬送して、ベルトコンベアなどで処理槽内に投入し、陽極と陰極の間に直流を流して電気化学的に処理していた。そして浄化された土壌は、処理槽から取り出してまたトラックなどで元の位置に戻される。
【０００５】
【発明が解決しようとする課題】
従来の常設処理槽を利用する方法は、汚染土壌の搬送時にそれが脱落、飛散、拡散して２次公害を招く恐れがあり、また土壌の往復の搬送に経費と時間がかかり、さらに大型の処理槽を設置するスペースも必要であり、処理槽も高価なものとなる。さらにまた一旦現地から搬出された汚染土壌は廃棄物と見做され、再利用が難しいなどの法的な問題点も有している。
【０００６】
そのため汚染された土壌を有する原位置（現地）において、土壌中に陽極と陰極を対向するように挿入・埋設し、両電極間に電圧を印加して重金属イオンを土壌から回収する原位置方式が検討されている。しかしながら直流を通電することにより陰極近傍がアルカリ性となり、鉛やカドミウムなどの重金属イオンが水酸化物となって沈澱して、重金属の回収が困難となる。
【０００７】
これを解消するため塩酸や酢酸などの酸を加えて土壌を酸性化する方法が採られるが、酸を加えることにより地下水などに重金属イオンが流出して、２次公害を招く恐れがある。また、土壌中に酸を加えても一様には浸透せずｐＨ値にばらつきを生じ、そのために土壌中に不溶化物質が残り、重金属の回収率、すなわち土壌浄化率が低い。
【０００８】
さらに、印加した電気エネルギーは、水の電気分解反応、および土壌の電気抵抗に起因するジュール熱の発生に使われてしまい、電気泳動への寄与分が低下するため、無駄が多いなどの問題点もある。
【０００９】
本発明の目的は、前述した従来技術の欠点を解消し、現地などの任意な所で容易にかつ安価に実施することができる電気化学的処理方法ならびに電気化学的処理装置を提供することにある。
【００１０】
【課題を解決するための手段】
前記目的を達成するため、本発明の第１の手段は、遮水を有する囲い枠を形成する工程と、その囲い枠内に陽極と陰極を対向するように配置する工程と、その囲い枠内の陽極と陰極の間に被処理物を搬入する工程と、その囲い枠内に水あるいは酸水溶液などの浸透水を注入する工程と、前記陽極と陰極の間に電流を流して前記被処理物を電気化学的に処理する工程と、前記被処理物を電気化学的に処理した後に前記囲い枠の側壁の少なくとも一部を取り壊して処理済みの処理物を囲い枠から搬出する工程とを含むことを特徴とするものである。
【００１１】
本発明の第２の手段は前記第１の手段において、前記囲い枠が、パイプと取外し可能な締め付け金具とを組み合わせて構成したフレームと、そのフレームの内側に取り付けられた板材と、その板材の内側に張られた遮水シートからなることを特徴とするものである。
【００１２】
本発明の第３の手段は前記第１の手段において、前記遮水シートの継ぎ目部分ならびに折り目部分が接着あるいは融着されて液密にシールされていることを特徴とするものである。
【００１３】
本発明の第４の手段は前記第１の手段において、前記陽極が透水フィルターを有する陽極槽内に、前記陰極が透水フィルターを有する陰極槽内にそれぞれ挿入され、その陽極槽と陰極槽が前記囲い枠に対して挿抜可能に配置されていることを特徴とするものである。
【００１４】
本発明の第５の手段は前記第１の手段において、前記陽極を挿入する陽極槽が透水フィルターを有し、前記陰極を挿入する陰極槽が透水フィルターを有して、前記陽極槽ならびに陰極槽の少なくともいづれか一方の電極槽に前記浸透水を注入して、電極槽を通してその浸透水を前記被処理物の層に浸透させることを特徴とするものである。
【００１５】
本発明の第６の手段は前記第１の手段において、前記電気化学的処理工程中に、雨水の侵入を防止する覆いが前記囲い枠の上側に設けられることを特徴とするものである。
【００１６】
本発明の第７の手段は前記第１の手段において、前記被処理物中に含まれている夾雑物を除去してから被処理物を前記囲い枠内に搬入することを特徴とするものである。
【００１７】
本発明の第８の手段は前記第１の手段において、前記被処理物が重金属類を含む土壌であることを特徴とするものである。
【００１８】
本発明の第９の手段は前記第８の手段において、前記土壌と酸を混合して前記囲い枠内に搬入することを特徴とするものである。
【００１９】
本発明の第１０の手段は前記第８の手段において、前記陽極が透水フィルターを有する陽極槽内に、前記陰極が透水フィルターを有する陰極槽内にそれぞれ挿入され、前記浸透水が陽極槽内、陰極槽内ならびに被処理物の隙間に充満されて、陰極槽内に引き寄せられた重金属イオンを浸透水とともに陰極槽から取り出し、陽極槽内の水位が陰極槽内の水位よりも高くなるように水位制御されていることを特徴とするものである。
【００２０】
本発明の第１１の手段は前記第８の手段において、前記土壌を含む処理すべきエリア内を少なくとも区画１、区画２、区画３の３つに区分けして、前記区画１と区画２の２区画分を掘削し、区画１から出た掘削土壌と区画２から出た掘削土壌を分けて山積し、掘削により形成された穴の区画２の所に前記囲い枠と、電極を含む処理槽を仮設し、前記一方の掘削土壌をその処理槽に搬入して浄化処理を行ない、処理が完了したら処理槽の区画１と隣接している側の側壁を区画１側に倒して、処理済土壌を区画１側に移動し、次に区間３を掘削してその掘削土壌を別の所に山積みし、その区間３に形成された穴に処理槽を仮設し、一方の掘削土壌を処理槽に搬入して浄化処理を行ない、処理が完了したら処理槽の区画２と隣接している側の側壁を区画２側に倒して、処理済土壌を区画２側に移すことを特徴とするものである。
【００２１】
本発明の第１２の手段は前記第１の手段において、前記電極の面と直交する方向に配置されている囲い枠の側壁を取り壊すことを特徴とするものである。
【００２２】
本発明の第１３の手段は前記第１の手段において、前記囲い枠から搬出する処理済の処理物が多量の水を含んでおり、その水とともに処理物を流出することを特徴とするものである。
【００２３】
本発明の第１４の手段は前記第１の手段において、前記囲い枠の内側寸法が処理物搬出用の建設機械が囲い枠内に進入可能な寸法になっていることを特徴とするものである。
【００２４】
本発明の第１５の手段は前記第１の手段において、前記電流の波形が矩形波、正弦波、パルス波、鋸波または三角波であって、その印加電流の電圧が正側と負側で時間とともに推移して、電圧の正の期間の電圧積分値が電圧の負の期間の電圧積分値よりも大きいことを特徴とするものである。
【００２５】
本発明の第１６の手段は、パイプと取外し可能な締め付け金具とを組み合わせて構成した枠型のフレームと、そのフレームの内側に取り付けられた板材と、その板材の内側に張られた遮水シートを有する囲い枠と、透水フィルターを備えて前記囲い枠内に挿抜可能に配置された陽極槽ならびに陰極槽と、その陽極槽ならびに陰極槽にそれぞれ挿入された陽極ならびに陰極と、その陽極と陰極に接続された電源装置とを備え、前記陽極槽と陰極槽の間に被処理物が搬入され、前記陽極槽内、陰極槽内ならびに被処理物の隙間に浸透水を充満させて被処理物を電気化学的に処理することを特徴とするものである。
【００２６】
本発明の第１７の手段は前記第１６の手段において、前記遮水シートの継ぎ目部分ならびに折り目部分が接着あるいは融着により液密にシールされていることを特徴とするものである。
【００２７】
本発明の第１８の手段は前記第１６の手段において、前記囲い枠の内側底面には地面が露出しており、その地面の上を前記遮水シートで直接覆っていることを特徴とするものである。
【００２８】
本発明の第１９の手段は前記第１６の手段において、前記囲い枠の上側に雨水の侵入を防止する覆いが設けられることを特徴とするものである。
【００２９】
本発明の第２０の手段は前記第１６の手段において、前記被処理物が重金属類を含む土壌であることを特徴とするものである。
【００３０】
本発明の第２１の手段は前記第１６の手段において、前記電源装置の電流波形が矩形波、正弦波、パルス波、鋸波または三角波であって、その印加電流の電圧が正側と負側で時間とともに推移して、電圧の正の期間の電圧積分値が電圧の負の期間の電圧積分値よりも大きいことを特徴とするものである。
【００３１】
【発明の実施形態】
次に本発明の実施形態を図とともに説明する。図１は、実施形態に係る電気化学的処理方法を説明するためのフローチャートである。
【００３２】
例えば再開発土地などの土地に対してまず例えばカドミウムや鉛などの重金属類の含有量ならびに土壌のｐＨ値測定の土壌検査を行ない、その検査結果に基づいて汚染されて電気化学的に処理する必要のある土壌領域を特定する。重金属類は土壌に吸着され易く、その重金属類を吸着した汚染土壌は地表からせいぜい２〜３ｍ程度の深さであり、その汚染土壌を確実に含む面積と深さを有する領域が処理すべき土壌領域として特定される。
次にその土壌領域をバックホーなどの建設機械で掘り起こし、土壌の塊を粉砕する（Ｓ１）。掘削した土壌中に岩石、コンクリート塊、合成樹脂シート、板などの夾雑物があれば、電気化学的処理に障害を及ぼすためそれら夾雑物は振動ふるいなどで分別・除去される（Ｓ２）。
【００３３】
このように夾雑物を除去した土壌に酸を添加し（Ｓ３）、土壌全体を均一に酸性化するために混練する（Ｓ４）。この前処理により、土壌全体がムラなく酸性化され、重金属イオンが溶出されて、処理速度の向上が図れる。酸としては塩酸、硫酸、硝酸などの無機酸、あるいはギ酸、蓚酸、ベンゼンスルホン酸などの有機酸などが用いられる。
【００３４】
本実施形態では土壌を前もって酸性化するため、土壌と酸を土壌処理槽に搬入する前に混練している。しかしこれは必ずしも必要ではなく、例えば混練する代わりに土壌処理槽に土壌と酸性水を交互に入れる方式、土壌を入れる前に土壌処理槽に酸性水を入れておく方式、または、土壌処理槽に土壌を搬入した後に電極槽（後述）から酸性水を注入する方式などがある。
【００３５】
現地あるいは現地のすぐ近くで、足場部材やコンパネなどの建築設備部材を用いて処理槽のフレームを製作し、フレームの内側に遮水シートを張って仮設の土壌処理槽を製作する（Ｓ５）。この工程は、前もってあるいはＳ１〜Ｓ４などと並行して実施することもできる。
【００３６】
次に前記酸性化した土壌を土壌処理槽に入れ（Ｓ６）、各電極槽（図２の符号２、３参照）から土壌とほぼ同濃度の酸性水を入れて土壌中に浸透せしめ、図２に示すように各電極槽内の酸性水の水面が土壌の上面とほぼ同じになるまで酸性水（浸透水）を注入する（Ｓ７）。後述のように各電極槽２、３は透水フィルタ１４を備えているため、酸性水を電極槽２、３から注入して土壌に浸透すれば、浸透速度が速く、かつ土壌全体に均等に浸透する。
【００３７】
その後通電し（Ｓ８）、土壌浄化を開始する（Ｓ９）。浄化は、電気泳動及び電気浸透により陰極側に引き寄せられた重金属イオン（陽イオン）を陰極槽２（図２参照）から揚水し（Ｓ１０）、揚水した汚水をアルカリ凝集などで処理して重金属として回収する（Ｓ１１）。この処理によって浄化された処理水（Ｓ１２）はユーティリティー費削減のため浸透水として陽極槽３（図２参照）に供給し（Ｓ１３）、陰極槽２には無機酸または有機酸を添加する（Ｓ１４）。なお、Ｓ１１で回収されたケーキ状の重金属類は産業廃棄物として所定の処理がなされる（Ｓ１５）。
【００３８】
前述のステップを繰り返して土壌浄化を行ない、浄化が終了した時点で、土壌を搬出するために土壌処理槽の１面あるいは必要に応じて２面以上取り崩し（Ｓ１６）、取り崩した部分から土壌を搬出し（Ｓ１７）、掘削した元の位置に埋め戻して（Ｓ１８）一連の処理を終了する。
【００３９】
図１のフローチャートは処理の概念を示したものであり、必ずしもこのフローの通りに連続的に処理する必要はない。例えば、土壌処理槽の製作は土壌の掘削や分別をしながら並行に実施することができ、浄化のサブフローについても各プロセスは並行して行なえる。
【００４０】
図２は、この電気化学的処理方法に用いる簡易電気化学的処理装置の概略構成図である。この簡易電気化学的処理装置は、処理槽１、陰極槽２、陽極槽３、汚水槽４、凝集槽５、沈澱槽６、揚水ポンプ７、給水タンク８、ｐＨ計９、酸供給装置１０、電源装置１１、陰極１２、陽極１３、透水フィルタ１４などから構成されている。
【００４１】
図中の１５は汚染土壌と酸を混練する混練機（ミキサー）、１６は処理すべき汚染土壌などの被処理物、１７は処理槽１内に満たされる水あるいは酸水溶液からなる浸透水、１８は凝集剤である。
【００４２】
処理槽１は浸透水１７を注入する陰極槽２と陽極槽３と、被処理物１６を投入する投入エリアを有し、陰極槽２と投入エリアならびに陽極槽３と投入エリアは透水フィルタ１４で仕切られている。前処理として汚染土壌と酸を混練機１５で均一に混合して、酸性土壌（ｐＨ値が約２）とした後、前記投入エリアに投入する。
【００４３】
図に示すように投入エリアの両側に陰極槽２と陽極槽３があり、それぞれに陰極１２と陽極１３が設置され、両電極１２，１３に電源装置１１が接続されて、所定の電圧を印加する。このとき被処理物１６である土壌の全体に均一に電圧がかかるように、電極１２，１３として板状電極が用いられる。
【００４４】
電圧をかけることにより、被処理物１６（土壌）中の汚染物質である鉛などの重金属類は、イオン化して電気泳動および電気浸透の作用により、陽極側から陰極側に移動する。しかし、通電を継続すると陽極側は水素イオンで酸性領域となり、陰極側は水酸イオンでアルカリ性領域となる。アルカリ性領域では、移動して来た重金属イオンが水酸化物となって沈澱し、不溶化してしまう。そのため酸供給装置１０から陰極槽２に酸性溶液を供給し、重金属が水酸化物とならない値にｐＨコントロールする。
【００４５】
ｐＨコントロールは、陰極槽２から汚水槽４に移行した重金属イオンを含む浸透水１７のｐＨ値をｐＨ計９で測定し、そのｐＨ値に対応して酸供給装置１０から酸性溶液を陰極槽２に添加する。陰極槽２側に目標ｐＨ値は、汚染対象などで若干異なるが、鉛の場合は約２にコントロールされる。
【００４６】
陰極槽２側の浸透水１７の水位は、陽極槽３側の浸透水１７の水位と同じか、若干低く設定し、電気泳動及び電気浸透により引き寄せられた量の汚水が隣の汚水槽４にオーバーフローして自然流下する。また、陽極槽３側の浸透水１７の水位を陰極槽２側の浸透水１７の水位よりも若干高くして高低差をつければ、浸透水の移動速度を上げて、結果的には処理速度が速くなる。この水位制御は、陽極槽３側への浸透水１７の供給量と、陰極槽２側からの浸透水１７の取り出し量の調整によって行なわれる。
【００４７】
凝集槽６も汚水槽４に隣接させ、汚水槽４に溜まった汚水を凝集槽６にオーバーフローして自然流下する。このように自然流下する構成を採ることにより、装置の省力化、小型化ならびに設備費の削減を図ることができる。凝集槽６に十分汚水が溜まった時点で、キレートなどの凝集剤１８を入れ、沈澱槽６に移し，汚泥１９を分離し、上澄水はポンプ７により給水タンク８に戻してｐＨ調整された後に再利用する。
【００４８】
汚泥１９は図示していないが脱水機で脱水し重金属類を含むケーキを得て、このケーキを産業廃棄物として所定の処分を行なう。このように凝集、沈澱、脱水の工程を経ることにより、重金属類を高濃度に含有したケーキを得ることができ、その後のケーキの処分が簡便である。前述のようにして土壌内の重金属類が電気化学的に回収され、土壌浄化が行なわれる。
【００４９】
図３は処理槽の斜視図、図４は処理槽の断面図、図５はその処理槽に用いる壁板の正面図である。この処理槽は、堅牢で運搬が容易で、簡単に入手できる安価な建設部材から構成される。まず、処理槽１を設置する場所の地面２０を均して平らにし、後述の遮水シートを地面２０（図４参照）上に直接敷置して、被処理物１６である土壌を投入・堆積しても破けないようにする。
【００５０】
次に平らになった地面２０の周囲四辺に、足場を作る際に用いるパイプ２１と、パイプ２１をＸ方向とＹ方向に繋ぐ取外し可能な締め付け金具２２を用いて四角の枠型のフレーム２３を構成する。このフレーム２３の内側に、ベニヤ板やコンパネなどからなる壁板２４を取り付けて、内側に空間部を有する枠を形成する。図５に示すように、壁板２４の一面には角棒などからなる補強部材２５が複数本取付けられ、図３に示すように補強部材２５が外側を向くようにして壁板２４をフレーム２３の内側に設置する。
【００５１】
図３において符号２６は、フレーム２３の各角部に連結された補強用パイプである。本実施形態では壁板２４をフレーム２３の側面だけに設置したが、必要に応じてフレーム２３の内側底面にも壁板２４を敷設することもできる。この場合、地面２０を均して平らにする作業は必ずしも必要ではない。
【００５２】
壁板２４の設置の次に図４に示すように、壁板２４の内側下部に木材などからなる断面形状がほぼ三角形のコーナ部材２７が配置され、その後に図４に示すように、壁板２４の内側から地面２０に沿って比較的厚手（シート厚約２ｍｍ〜３ｍｍ）の遮水シート２８を張り、漏水がないようにする。遮水シート２８は施工現場において処理槽１の大きさに合わせてカッティングし、折り目部分や継ぎ目部分は漏水を生じないように接着剤あるいは融着で液密にシールする。遮水シート２８の上端部２８ａは、折り返されて壁板２４の外側に接着あるいは融着で固定されている。
【００５３】
遮水シート２８を張るとき、壁板２４の下側角部では遮水シート２８が直角に曲がらず斜めになることがある。そしてその上に被処理物（土壌）１６が投入されて、遮水シート２８が部分的に延びて破れる恐れがあるから、これを防止するために壁板２４の内側下部に断面形状がほぼ三角形のコーナ部材２７が配置されている。
【００５４】
遮水シート２８には、例えばポリエチレンテレフタレート、ポリアミド、ポリプロピレン、ゴムなどの廃棄物最終処分場で常用されている合成樹脂シートあるいはゴムシートが用いられる。
【００５５】
処理槽１の寸法は、建設部材の標準寸法に合わせて横幅、奥行きとも０．９ｍ単位で増加させる。図示していないが処理槽１の内側に陰極槽２と陽極槽３を挿抜可能に挿入する（図２参照）。
【００５６】
被処理物１６（土壌）の処理槽１への搬入は、バックホーなどの建設機械で堀り起こした土壌を一旦山積みし、振動ふるいで大きい石などの夾雑物を分別した後にベルトコンベアやショベルカーなどで処理槽１の上から搬入する。
【００５７】
土壌処理槽１内に電極槽（陰極槽２、陽極槽３）を多数設置した場合、搬入した土壌の圧力により電極槽が移動したり、変形する可能性がある。それを避けるために、電極槽を処理槽１に固定すると同時に、土壌搬入時の工夫が必要である。一般的に土壌などを搬入する場合、バックホーなどの建設機械で直接搬入するか、山積みの土壌をコンベアで搬入する方法が採られるが、いずれの方式にしても複数に分割された処理槽１に搬入量をほぼ等分に分配し、偏って無理な圧力が掛からないようにすることが必要である。
【００５８】
図６は、ベルトコンベアを用いた土壌の搬入状態を示している斜視図である。図中の５２は電極槽底部固定用垂木、５３は電極槽上部固定用サポート、５４はベルトコンベアである。
【００５９】
図に示すように処理槽１はその長手方向に沿って電極槽（陰極槽２、陽極槽３）により多数に分割されており、処理槽１の各空間に土壌をほぼ等分に分配するように前記ベルトコンベア５４は矢印で示すように処理槽１の長手方向に沿って移動可能になっている。
【００６０】
必要に応じて処理槽１の上方に、雨避けのために屋根などの覆いを設けることができる。この覆いは、農業用のビニールハウスや簡易テントを用いてもよい。またフレーム２３に用いたパイプを利用して覆いの骨格を構成することもできる。さらに陰極槽２と陽極槽３の上端開口部に蓋などの覆いをして、雨水の侵入を防止することもできる。処理槽１内に雨水が入るとｐＨ値が変化するため、雨水の侵入は避けた方がよい。
【００６１】
処理後の被処理物１６（土壌）の処理槽１からの搬出は、小型の処理槽１であれば、クレーンなどを用いて処理槽１をひっくり返して被処理物１６（土壌）を処理槽１からの搬出することも可能であるが、大型になると被処理物１６（土壌）を処理槽１から掘り出すしかない。
【００６２】
従来の常設処理槽は何回も繰り返して使用する関係上、槽に耐酸性をもたせるため内面にゴムや樹脂のコーティングを施している。そのため処理槽から機械的に掘り出す際に前記コート層が傷ついたり剥がれたりすることがあり、処理槽のメンテナンスが煩雑であるとともに、処理槽の耐用寿命が短い。
【００６３】
その点本発明の実施形態に係る処理槽１は仮設槽であり、基本的に槽の構成部材である壁板２４や遮水シート２８などは半消耗品（再利用も可能だが、痛んだら破棄する）で、繰り返して使用するのではなく１回の処理であるから、従来の常設処理槽のように槽内面にコート層を設ける必要はなく、遮水シート２８で十分である。
【００６４】
搬出時には処理槽１の１面（掘削した場所に近い方の１面）の締め付け金具２２とパイプ２１を外し、図４に示すよう壁板２４を外側に倒す。被処理物１６（土壌）は多量の水を含んでいるから自然に流れ出し、それをバックホーやブルトーザーなどの建設機械を使って取り除き、掘削した所に埋め戻す（図１のＳ１７参照）。処理槽１の内側の寸法を建設機械が槽内に進入できる寸法にしておけば、被処理物１６（土壌）の搬出が効率的に行なわれる。
【００６５】
なお、処理槽１からの陰極槽２と陽極槽３の取り出しは、被処理物１６（土壌）をある程度搬出して、陰極槽２と陽極槽３が被処理物１６（土壌）の中から容易に抜き出せる状態になってから取り出せばよい。本実施形態では処理槽１の１面を取り壊したが、必要に応じて処理槽１の２面以上を取り壊すことも可能である。
【００６６】
図７は、陰極槽２と陽極槽３の配置と被処理物１６（土壌）の搬出方向との関係を示す図である。本実施形態の場合、処理槽１の長手方向に沿って陰極槽２と陽極槽３が対向するように配置されているから、それらが配置されていない面、すなわち陰極槽２ならびに陽極槽３と直交する面を壊して、矢印Ａ方向または矢印Ｂ方向に被処理物１６（土壌）を搬出すれば、陰極槽２ならびに陽極槽３が邪魔にならず搬出することができる。換言すれば、被処理物１６（土壌）の搬出方向を考慮して陰極槽２と陽極槽３の配置位置を決めるとよい。
【００６７】
図８は、電極槽（陰極槽２，陽極槽３）を示す斜視図である。透水フィルタ１４は暗渠構築用透水フィルタ、合成樹脂などの非金属製の網を重ね合わせた重合体、非金属製のフィルタなどからなり、浸透水１７の通過は自由であるが、被処理物１６（土壌）が電極槽（陰極槽２，陽極槽３）内に侵入するのを阻止している。透水フィルタ１４はポリアミド樹脂などの合成樹脂の糸２９などを用いて槽本体板３０の両面に取り付けらている。槽本体板３０は、例えば木や塩化ビニールなどの耐酸性で土圧に耐える機械的強度を有する素材で構成されている。
【００６８】
本実施形態では、槽本体板３０の両面に透水フィルタ１４を取り付けたが、槽本体板３０の被処理物１６と対向する側には透水フィルタ１４を取り付け、槽本体板３０の処理槽１と対向する側はプレートを取り付けることも可能である。
【００６９】
槽内には板状電極（陰極１２，陽極１３）が所定枚数挿入され、各電極（陰極１２，陽極１３）は互いにケーブル３１で電気的に接続されている。また槽内には櫛歯状をした配管３２の先端側が挿入されている。電極槽が陰極槽２の場合は配管３２は酸供給配管であり、電極槽が陽極槽３の場合は配管３２は揚水配管である。
【００７０】
図８に示すように、槽本体板３０の両面に透水フィルタ１４を取り付けて、あるいは槽本体板３０を間にして片面に透水フィルタ１４を取り付け、他方の片面にプレートを取り付けたサンドイッチ構造の電極槽を構成し、槽内の透水フィルタ１４，１４の隙間、あるいは透水フィルタ１４とプレートの隙間に板状電極（陰極１２，陽極１３）と配管３２の先端側が交互に挿入されて薄型構造になっている。
【００７１】
図２ならびに図７では陰極槽２と陽極槽３を１対設けた例を示しているが、装置を大型化して１回の処理量を多くする場合、あるいは処理時間を短縮する場合、概ね０．５ｍ〜２ｍ間隔で電極槽を３個以上設けることもできる。
【００７２】
図９と図１０は、その電極槽の配置例を示す処理槽の概略平面図である。図９の例は、処理槽１の長手方向に沿って複数に分割し、陰極槽２と陽極槽３が複数対交互に配置されている。図１０の例は、処理槽１の長手方向の両側に陽極槽３が配置され、処理槽１の中央部に陰極槽２が配置されている。このように処理槽１の中央部に陰極槽２を配置した場合、陽イオンである重金属イオンは処理槽１の中央部に集められる。
【００７３】
図９の配置例では、処理槽１の側面のうち陰極槽２ならびに陽極槽３と直交する側面が壊され、矢印Ｃ方向または矢印Ｄ方向に被処理物１６（土壌）を搬出する。図１０の配置例では、処理槽１の側面のうち陰極槽２ならびに陽極槽３と直交する側面が壊され、矢印Ｅ方向または矢印Ｆ方向に被処理物１６（土壌）を搬出する。このようにすれば、陰極槽２ならびに陽極槽３が邪魔にならず被処理物１６（土壌）の搬出ができる。
【００７４】
これらの例では長方形の処理槽１の場合について説明したが、正方形の処理槽１の場合も前述と同様の電極槽の配置ならびに被処理物１６（土壌）の搬出が可能である。
【００７５】
処理する土壌の量が多くなると、処理槽１の寸法を大きくする必要がある。土壌に印加する電圧は、電位勾配（単位長さ当たりの電位差）をそのようなスケールアップに対して同等に保てないと、予測した効果を得ることができない。従って、電極間の間隔（電極槽の間隔）を長くすると、それだけ大きな直流電圧を与える必要がある。商用電圧（１００Ｖ，２００Ｖ）を超える大きな直流電圧を作るにはコストがかかる。また、安全上では過大な直流電圧は好ましくなく、高くても１００Ｖ程度が適切な電圧である。適切な電位勾配としては、多くの実験例で１Ｖ／ｃｍであることが判明している。単純には電位勾配は高いほど電気泳動力は大きくなるが、水の電気分解も激しくなり、発熱によるロスも増加し、そのために土壌の浄化効率が低下する。以上のことから、適切な電極間隔は１ｍ程度を基本とし、設置場所の状況、処理槽１の寸法により０．５ｍ〜２ｍの範囲で調整することが好ましい。
【００７６】
処理槽１が大きい場合、図９，図１０に示した電極槽の配置例のように、処理槽１の中に何列かの電極槽を設置することが必要である。電極槽は処理槽１の両端を除き、土壌と土壌に挟まれ、土壌から受ける圧力に耐えなければならない。また、土壌の隙間水（浸透水１７）を電極槽内に導くため、透水フィルタ１４で仕切る必要がある。さらに電極槽内で浸透水１７のｐＨ調整を行なうため、極力自由な空間があるとよい。そこで本実施形態では図８に示すような構造の電極槽を使用している。図１１は、電極槽の変形例を示す斜視図である。この変形例では図８に示す槽本体板３０の代わりに非導電性で耐酸性に優れ、土圧に耐える機械的強度を有する例えば木材や塩化ビニールなどから構成された箱型の電極槽フレーム５５を作り、その両面に透水フィルタ１４を取り付けている。このように電極槽フレーム５５を用いることにより、電極槽内に十分な空間を形成することができ、浸透水１７の保有量が十分でｐＨ調整も容易である。
【００７７】
電極槽は図９，図１０のように被処理物（土壌）１６を挟み込む形で設置するが、土壌搬入の際に予め処理槽１に固定しておき、土壌を搬入の際に電極槽が移動しないように工夫する必要である。電極槽が移動すると、適切な電極槽の間隔が保てなくなり、土壌の浄化率が低下する。図１２は、電極槽の固定構造を示す斜視図である。この例では各電極槽（陰極槽２，陽極槽３）の底部を電極槽底部固定用垂木５２で固定し、電極槽（陰極槽２，陽極槽３）の上部を処理槽１を構成するパイプ２１に連結されたパイプ状の電極槽上部固定用サポート５３で固定している。前記垂木５２は電極槽と同様に、非導電性で耐酸性に優れ、ある程度の機械的強度を有する木材で構成されている。
【００７８】
電極槽内のｐＨが均一になるように、図１３に示す空気ヘッダー３３により空気を電極槽下部に送り、空気Ａをバブリングさせ、電極槽内の浸透水を攪拌し、ｐＨの均一化を図っている。空気ヘッダー３３は同図に示すように、ヘッダー母管３４と、ヘッダー母管３４に所定の間隔（２００ｍｍ〜５００ｍｍ程度）をおいて取り付けられたコック３５と、各コック３５に取り付けられたチューブ３６と、各チューブ３６の先端部に取り付けられたノズル３７から構成され、各チューブ３６は電極槽の底部近くまで延びている。ヘッダー母管３４は空気ポンプ（図示せず）に接続されており、前記コック３５は空気が均等に流れるように空気圧を調整するためのものである。コック３５、チューブ３６ならびにノズル３７は、耐酸性に優れたポリテトラフルオロエチレンなどのフッ素樹脂で構成されている。
【００７９】
電極槽内の浸透水の攪拌手段として図１３のような空気ヘッダー３３の他に、図１４に示すように攪拌スクリュー５６を用いたり、図１５に示すように水流ポンプ５７を用いたりすることもできる。これらの図において符号５８モータ、５９はホース、６０はノズルである。
【００８０】
これらの図は攪拌スクリュー５６や水流ポンプ５７を用いて電極槽内の浸透水を再循環する例を示しているが、図２に示しているように揚水ポンプ７を用いて電極槽に供給する浸透水１７や酸供給装置１０を用いて電極槽に供給する酸の噴射力を利用して、電極槽内の浸透水を攪拌することも考えられる。
【００８１】
図１６は、土壌処理法の展開を説明するための図である。展開手順をステップ毎に説明する。
（ステップ１）
処理すべき汚染エリアの区画分けをする。本例の場合、区画１から区画４までの４区間に分けられ、各区画の広さはほぼ同じにする。これら汚染エリアは事前の土壌検査で把握される。
【００８２】
（ステップ２）
区画１と区画２の２区画分掘削し、掘削して出た土壌は石などの夾雑物を除く分別前処理を行ない、次の区画付近に山積みする。例えば区画１の掘削土壌３８ａは区画２付近に、区画２の掘削土壌３８ｂは区画３付近に、それぞれ別々に山積みする。
【００８３】
（ステップ３）
掘削により形成された穴３９の区画２の所に処理槽１を仮設し、前記掘削土壌３８ａを処理槽１に搬入して浄化処理する。
【００８４】
（ステップ４）
処理槽１の区画１と隣接している側の壁板２４を区画１側に倒し、処理済土壌４０を区画１側にバックホーなどで移す。次に区間３を掘削し、その掘削土壌３８ｃは分別前処理後に区画４付近に山積みする。区間３に形成された穴に処理槽１を仮設し、前記掘削土壌３８ｂを処理槽１に搬入して浄化処理を行ない、処理が完了したら、処理槽１の区画２と隣接している側の壁板２４を取り崩し、処理済土壌４０を区画２側に移す。このようにして区間１，区間２，区間３，区間４の汚染土壌を順次浄化処理して、また元の位置に戻すことができる。
【００８５】
この展開方法を採用すれば、地面に処理槽を建設する場合に比べて、処理槽に搬入した土壌の土圧は、掘削して形成した穴の壁面で受けることができるため、強度的に有利である。また処理槽を掘削部分に建設するため、処理槽を設置するスペースが少なくて済み、さらに土壌を移動させる距離が短くできる。さらにまた掘削を除き、土壌の移動が下方向（処理槽への土壌の搬入）または横方向（処理済土壌の移動）であるため、土壌の移動が容易である。
【００８６】
本実施形態では、土壌が強アルカリ性であった場合を想定して、混練時ならびに陰極近傍に酸を加えて酸性化している。これにより土壌中に水酸化物として不溶化している重金属類は溶解して、水分とともに陰極１２側に移動して回収される。また、陽極側に酸を加えて（図２参照）処理すべき土壌の全体を酸性化することも可能である。土壌が酸性ならば酸の添加は不要である。
【００８７】
通電により陰極１２側に移動した重金属類イオンを溶液の状態で汚水槽４に移行する。処理槽１から取り出した汚染液の質量とほぼ等しい質量の水分（水あるいは酸水溶液）を陽極槽３に浸透水１７として補給する。
【００８８】
この重金属類イオンの回収を継続していると、陰極１２の表面に固形物が付着し、それが電気抵抗となり回収効率が下がるから、付着した固形物を陰極１２から物理的に落とす必要があり、そのために図１３に示した空気ヘッダー３３により気泡状の空気Ａを陰極１２の表面に噴射している。従って空気ヘッダー３３はｐＨの均一化と固形物の付着防止の２つの機能を有している。
【００８９】
なお、浄化後の土壌は酸性になっているため、例えば石灰などのアルカリ性物質を土壌に適量添加して攪拌、混合することにより、土壌のｐＨ値を６〜７程度に調整する。
【００９０】
処理済の処理物を処理槽１から搬出する際に処理槽１の一部を取り壊すため、前記壁板２４の一部ならびに遮水シート２８は再利用不可能であるが、電極槽２，３、電極１２，１３、パイプ２１、締め付け金具２２などは再利用が可能である。
【００９１】
電気化学的処理の基準となる電源波形は任意であり、図１７（ａ）〜（ｇ）に示すように正弦波、パルス波、矩形波、鋸波、三角波等のいずれも使用できる。同図に示す斜線部が印加する電圧値である。また、一定あるいは不定期間をもって、直流と正弦波、パルス波、矩形波、鋸波または三角波等を交互に与える方法もある。
【００９２】
図１８と図１９は、図１７に示すような波形が得られる電源装置の具体例を示す回路図である。図中の４１は周波数が５０Ｈｚあるいは６０Ｈｚの交流電源、４２はトランス、４３はコンバータ、４４は増幅器、４５は信号発生器、４６は波形、周波数、デューティ比、バイアス調整機能付きのインバータである。図１８に示す電源装置は安価であり、図１９に示す電源装置は８０％以上の電源効率を有している。なお本例では周波数が５０Ｈｚあるいは６０Ｈｚの交流電源４１を用いているが、モータジェネレータ方式あるいはインバータ方式で最適な周波数に調整することができる。
【００９３】
図２０は別の電源波形を示す図、図２１と図２２はその波形が得られる電源装置の回路図である。図中の４７は整流器、４８は抵抗器で、正弦波の正側と負側の電圧を適宜変えている。
【００９４】
図２３はさらに別の電源波形を示す図、図２４はその波形が得られる電源装置の回路図である。図中の４９はＳＣＲ制御回路である。図２３に示すように負側の大部分をカットし、正と負のサイクルの電圧積分値の差（正−負）が正値となるように制御した波形を図２４に示す電源装置で生成する。
【００９５】
図２５と図２６はさらに別の電源波形を示す図、図２７と図２８はそれら波形が得られる電源装置の回路図で、図２７の電源装置で図２５に示す波形が、図２８の電源装置で図２６に示す波形が得られる。図中の４９ａは第１のＳＣＲ制御回路、４９ｂは第２のＳＣＲ制御回路、５０はＧＴＯ制御回路である。図２５と図２６に示すように、一定周期で交流をＯＮ−ＯＦＦして負側の大部分と正側の一部をカットしている。ＯＦＦの期間分だけ電流が流れないため、一定の省力化が図れる。
【００９６】
図２５と図２６に示すように負側から正側に切り変わった初期の部分を一部カットして正側の立ち上がりが急峻になった急峻部５１を設けるか、あるいは図１７の（ａ），（ｂ），（ｅ），（ｆ），（ｇ）のように急峻部５１を有する矩形波や三角波を用いれば、回収効率が高くなる。
【００９７】
これら正弦波、パルス波、矩形波、鋸波または三角波等は、正側と負側のサイクルの電圧積分値が（正＞負）となるように制御する。すなわち、時刻ｔにおいて電圧Ｖ（ｔ）で示され、電圧Ｖ（　ｔ）が正値である期間をｔ１、負値である期間をｔ２とした場合、電圧の絶対値｜Ｖ（ｔ）｜に関して、次の式（１）の関係を持つようにすればよい。
【００９８】
【数１】

正側と負側のサイクルの積分値は、ピーク電圧値や、パルス幅、或いはパルス数を制御することにより制御できる。ただし、正側と負側のサイクルの積分値を制御すればよいので、他の実現可能な方法を使っても構わない。
【００９９】
また印加電流の電圧が一定電圧（＋Ｖ１：正値）と、一定電圧（−Ｖ２：負値）間で推移し、正値（＋Ｖ１）である期間（ｔ１）と負値（−Ｖ２）である期間（ｔ２）との間に、（Ｖ１×ｔ１）　＞　（Ｖ２×ｔ２）の関係が成立するように調整されている。
【０１００】
さらに印加電流の電圧が，±Ｖ１（Ｖ１：正値）間で推移し、かつ、＋Ｖ１である期間（ｔ１）と−Ｖ１である期間（ｔ２）との間に、ｔ１≧ｔ２の関係が成立するように調整されている。
【０１０１】
直流電源を用いた従来の方式では、処理土壌中の重金属類は、重金属イオンとして電気泳動及び電気浸透の作用により処理土壌に浸透させた溶液とともに、通常、陰極側に移動する。
【０１０２】
しかし、本実施形態で用いた電源では、一部負方向の電圧が含まれており、ある周波数でもって正負の両方向に電圧が切り替わる、すなわち電極の極性が切り替わるため、電極近傍では、水の電気分解反応が進行する前に極性が切り替わる。このとき、陽極側では水の電気分解に起因する水素イオンの発生が抑えられて、強酸性化は起こらず、電極の溶損が抑えられる。
【０１０３】
従来の方法では、陽極の溶損、陰極部でのアルカリ化という問題点を有している。本発明者らは、前述のように印加する電流を、単純な定電圧の直流電源または交流電源を半波整流した直流の代わりに、印加電流を任意周波数に制御し、正負両範囲を含めた正弦波、パルス波、矩形波、鋸波、三角波などとし、正側の期間の電圧（電流）の積分値と負側の期間の電圧（電流）の積分値の差（正−負）が正値となるように制御することで解決した。
【０１０４】
土壌中のマトリックスが一種の分子ふるい作用を持っているかのように振舞うため、通常電気泳動の速度は非常に遅く、一定の除去率に到達するためには膨大な時間を要する。
【０１０５】
前述の半波整流電源などを用いる方法においても、電圧の変化は０Ｖ〜一定電圧であり、電極近傍で水（または電極液）の電気分解反応が進行してしまい、陽極部での強酸性化による電極の溶損、陰極部でのアルカリ化による重金属類の不溶化・沈殿という問題点が生じる。
【０１０６】
また、水（または酸性水溶液）の電気分解反応が進行すると、印加した電気エネルギーが無駄に消費されるばかりでなく、陰極近傍の土壌がアルカリ化し、このアルカリ成分および不溶化重金属が電気抵抗となり、陰極近傍で特に電位差が大きくなる。このため、さらに土壌の電気抵抗が増え、ジュール熱の発生を増加させる要因となる。
【０１０７】
図２９は、この直流電流を流した場合の弊害を示す模式図である。同図に示すように電気的中和を保つために、電極面（帯電面）の近傍にこれを中和する対イオンの強い吸着層（電気二重層）が形成される。一方、溶液相では、電極から遠ざかるにつれて正負の電荷が中和していくような拡散的な分布を示す。そして電流を流し続けると陰極側はアルカリ化、陽極側は酸性化し、電極と溶液間で電子の授受が起きて水の電気分解が進行する。
【０１０８】
本発明では、電圧波形が正、負に渡る正弦波、パルス波、矩形波、鋸波または三角波を用いることで、ある周波数でもって電極の極性が切り替わるため、電極近傍では、水の電気分解反応が進行する前に極性が切り替わることになる。このとき、陽極部では水の電気分解に起因する水素イオンの発生が抑えられて、強酸性化は起こらず、電極の溶損が抑えられる。従って、高価な貴金属を用いる必要がなく、コストを削減できる。
【０１０９】
一方、陰極部では、水の電気分解に起因する水酸化物イオンの発生が抑えられて、強アルカリ化は起こらない。従って、土壌を適正なｐＨ値にコントロールするために添加する酸濃度を従来法よりも低くする、または酸の添加を不要とすることが可能となり、コストを削減できる。さらに、陰極近傍の土壌内で重金属類が不溶化・沈殿するという問題が生じないため、効率的に重金属類の除去が可能となる。
【０１１０】
さらにまた、陰極付近の土壌が強アルカリ化しないことから、陰極近傍の土壌で電気抵抗が増える要因が無くなるため、特に陰極近傍での電位差を増加させることがなく、ジュール熱の発生を抑える効果が得られる。
【０１１１】
本発明による、正、負に渡る正弦波、パルス波、矩形波、鋸波、三角波を用いると、印加した電気エネルギーは、水の電気分解反応に使われることはなく、また、土壌の電気抵抗に起因するジュール熱の発生等に使われる割合が非常に少ない。電気エネルギーの大部分は重金属類の電気泳動に使用されるため、無駄が非常に少なく、効率よく重金属類を電気泳動できる。
【０１１２】
また、比較的低い電圧値にした場合でも、従来方法より重金属類の電気泳動効果を効率的に高めることができ、さらにジュール熱による電極液の蒸発、重金属類の系外への飛散を抑えることができる。逆に、電圧値を高くしても、ジュール熱の発生は従来方法よりも抑えられるため、問題なく重金属類の除去効率を高めることができる。
【０１１３】
交流電源を用いたり、正と負が対称なパルス波形を用いたりした場合は、同様に電極の溶損は起きないが、電気泳動効果による重金属イオンの移動が起こらないため、土壌中の重金属類を除去するには、浸透した溶液（酸、酸水溶液または水）を順次置換させるしかなく、作業効率の面で望ましくはない。
【０１１４】
電気泳動を推進させるためには、印加電流の正の期間に流れる電流の積分値が、負の期間に流れる電流の積分値と比べて大きくなるように制御し、一方向に重金属イオンを移動させるようにする。当然、正の期間の電流の積分値と負の期間の積分値の差（正−負）が大きいほど、電気泳動速度は速くなる。電極部での水の電気分解反応の抑制効果、および周囲への電波障害の影響を考慮すると、周波数１Ｈｚから１００ｋＨｚ程度の間、好ましくは５０Ｈｚから１０００Ｈｚの間で使用される。
【０１１５】
図３０は、本実施形態の陰極近傍での状態を模式的に示す図である。同図に示すようにある周波数でもって正負の両方向に電圧（極性）が切り替わることにより、電気二重層の形成と崩壊が繰り返して起こり、そのために水の電気分解が生じないで、陰極側のアルカリ化、陽極側の酸性化が抑制され、結果的には陰極側では重金属類の不溶化・沈殿が抑制され、陽極側では電極の溶損が抑制されるという効果を有している。
【０１１６】
図３１は、本発明法および従来法で汚染土壌の浄化を行なった場合の、陽極の重量の経時変化を比較して示す図である。この図で明らかなように従来法（破線）では陽極の溶損（重量変化）が激しいが、本発明法（実線）では陽極の重量はほとんど変化せず、陽極の耐用寿命が長い。従って、陽極に高価な貴金属を用いる必要がなく、例えば鉄系の電極が使用可能となりコストを削減できる。
【０１１７】
一方、陰極部では、水の電気分解に起因する水酸化物イオンの発生が抑えられ、強アルカリ化は起こらない。従って、土壌を適正なｐＨにコントロールするために添加する酸濃度を従来法よりも低くすることが可能となり、陰極近傍の土壌内で重金属類が不溶化・沈殿するという問題は生じなかった。
【０１１８】
図３２は陽極近くの土壌、陰極近くの土壌、ならびにその間の土壌の電位を測定した電位特性図で、横軸に土壌の位置、縦軸に電位を示している。実線のａ）は本発明法、破線のｂ）とｃ）は従来法の特性曲線である。この図から明らかなように、本発明法ａ）では両電極間の電位の勾配はほぼ等しいが、本発明ａ）と同じ電圧Ｅ１を両電極間にかけても従来法ｂ）では、陰極近傍で急激な電位差があり、陽極から中央部近傍までの土壌での電位勾配（角度θｂ）が小さい。電気泳動効果は電位勾配が大きいほど大きくなることから、従来法ｂ）では陽極から中央部近傍までの電気泳動効果は小さくなると考えられる。
【０１１９】
また陰極近傍の急な電位勾配は、陰極近傍での電気抵抗の増加に起因するものであり、陰極近傍でのジュール熱の発生原因となる。陰極近傍の電気抵抗の増加の原因は、陰極液の電気分解に基づく強アルカリ化、陰極近傍での重金属類の不溶化である。従ってこの領域では、重金属類は不溶化していると考えられ、電位勾配が大きくなっていても、電気泳動効果は非常に小さい。
【０１２０】
従来法ｂ）よりも電気泳動効果を上げるためには、さらに両電極間の電圧を上げる必要がある。従来法ｃ）に電圧をＥ２まで上げたときの状態を示す。この時の電位勾配（角度θｃ）が、本発明での電位勾配（θａ）とほぼ同等である。
【０１２１】
この場合さらに陰極液の電気分解が促進し、強アルカリ化領域が拡大てし、陰極での電気抵抗が増大し、電位勾配が増加していることがわかる。従って、ジュール熱発生量が増え、電気エネルギーの無駄使いとなる。
【０１２２】
本発明法ａ）では、土壌中の電位勾配（θａ）は土壌全域でほぼ一定に保たれており、電気泳動効果は従来法ｂ）と比べて高いこと分かる。このように本発明では、印加した電気エネルギーは、水の電気分解、土壌のジュール熱発生等に使われることはなく、その大部分が重金属類の電気泳動に使用されるため、無駄が非常に少なく、効率よく重金属類を電気泳動できる。
【０１２３】
前記実施形態では汚水からキレートにより重金属類を処理したが、イオン交換樹脂や活性炭などの吸着材を使用する方法、凝集沈澱添加剤、アルカリ化による水酸化物沈澱などの方法も可能である。
【０１２４】
前記実施形態では陰極槽と汚水槽との間、汚水槽と凝集槽との間の液の移動をオーバーフローによって行なったが、ポンプを用いて液の移動を行なうこともできる。
【０１２５】
前記実施形態では土壌から鉛やカドミウムなどの重金属類を回収する場合を説明したが、本発明は陽イオン化した希土類元素や陰イオン化したアルミ酸などの金属成分を回収することも可能である。
【０１２６】
本発明の電気化学的処理方法は、土壌の浄化だけでなく、例えば燃焼装置から排出される燃焼灰、ばいじん、汚泥、河川や沼などに溜まった泥、その被処理物質を含む粉体、粉末、コロイド溶液、溶液などから被処理物質を処理するときにも適用可能である。
【０１２７】
【発明の効果】
本発明の第１の手段は、電気化学的に処理した後に囲い枠の側壁の少なくとも一部を取り壊して処理済みの処理物を囲い枠から搬出する構成になっているから、現地などの任意な所で容易に実施することができ、従来のように被処理物の搬送に伴う２次公害の心配がなく、運搬費と運搬時間の節減ができる。
【０１２８】
本発明の第２の手段は囲い枠が、パイプと金具と板材と遮水シートから構成されており、これらは通常の建設部材であり、運搬が容易で、現地などにおいても簡単に入手でき安価である。
【０１２９】
本発明の第３の手段は、遮水シートの継ぎ目部分ならびに折り目部分が接着あるいは融着により液密にシールされているから、被処理物に酸などの化学物質を添加しても、それが囲い枠の外側に流出することがなく、従って２次公害の心配がない。
【０１３０】
本発明の第４の手段は、陽極槽と陰極槽が囲い枠に対して挿抜可能に配置されているから、囲い枠を取り壊して処理物を搬出する際に陽極槽と陰極槽を囲い枠から取り出すことができ、再利用が可能となる。
【０１３１】
本発明の第５の手段は、透水フィルタを有する電極槽に浸透水を注入し、その電極槽を通して浸透水を被処理物層に浸透させるから、被処理物層への浸透速度が速く、全体にほぼ均一に浸透する。
【０１３２】
本発明の第６の手段は雨水の侵入を防止する覆いが囲い枠の上側に設けられているから、囲い枠内のｐＨ値などの処理条件が雨水の侵入で変化することがなくなり、安定した電気化学的処理が可能である。
【０１３３】
本発明の第７の手段は、被処理物中に含まれている夾雑物を除去してから処理するため、夾雑物による電気化学的処理の阻害が解消される。
【０１３４】
本発明の第８の手段は被処理物が重金属類を含む土壌であり、土壌中の重金属類を２次公害の恐れがなく簡便に除去することができる。
【０１３５】
本発明の第９の手段は土壌と酸を混合して処理するため、重金属類の除去率が高い。
【０１３６】
本発明の第１０の手段は、陽極槽内の水位が陰極槽内の水位よりも高くなるように水位制御されているから、陽極側から陰極側への浸透水の移動が速く、処理時間の短縮が図れる。
【０１３７】
本発明の第１１の手段は前述のような構成になっており、処理槽を設置する特別のスペースを設ける必要がなく、効率よく連続的に処理できる。
【０１３８】
本発明の第１２の手段は、電極の面と直交する方向に配置されている囲い枠の側壁を取り壊すことにより、電極が邪魔になることなく、処理槽から処理物を搬出できる。
【０１３９】
本発明の第１３の手段は、多量の水とともに処理物を流出することにより、処理槽からの処理物の搬出が簡便である。
【０１４０】
本発明の第１４の手段は、囲い枠の内側寸法が処理物搬出用の建設機械が囲い枠内に進入可能な寸法になっているから、建設機械が囲い枠の内側に入り込んで作業することができ、搬出作業が効率的に行なわれる。
【０１４１】
本発明の第１５の手段は前述のような構成になっており、従来法のように電極近傍で水の電気分解が進行し、陽極部での強酸性化による電極の溶損、陰極部での強アルカリ化による重金属などの被処理物の不溶化・沈澱という問題、ならびに印加した電気エネルギーが、水の電気分解、および被処理物の電気抵抗に起因するジュール熱の発生に使われて、無駄が多いなどの問題点が解消される。
【０１４２】
本発明の第１６の手段は、パイプと取外し可能な締め付け金具とで構成した枠型のフレームと、そのフレームの内側に取り付けられた板材と、その板材の内側に張られた遮水シートで囲い枠が構成されているから、被処理物の処理後に囲い枠を容易に取り壊して、処理済みの処理物を囲い枠から搬出するができ、現地などの任意な所に容易に囲い枠を設置することができ、従来のように被処理物の搬送に伴う２次公害の心配がなく、運搬費と運搬時間の節減ができる。
【０１４３】
本発明の第１７の手段は、前記遮水シートの継ぎ目部分ならびに折り目部分が液密にシールされているから、被処理物に酸などの化学物質を添加しても、それが囲い枠の外側に流出することがなく、従って２次公害の心配がない。
【０１４４】
本発明の第１８の手段は、囲い枠の内側底面には地面が露出しており、その地面の上を遮水シートで直接覆うから、囲い枠の内側底面への板材の敷設が不要となり、コストの低減が図れる。
【０１４５】
本発明の第１９の手段は囲い枠の上側に雨水の侵入を防止する覆いが設けられるから、囲い枠内でのｐＨ値などの処理条件が雨水の侵入で変化することがなくなり、安定した電気化学的処理が可能である。
【０１４６】
本発明の第２０の手段は、被処理物が重金属類を含む土壌であり、土壌中の重金属類を２次公害の恐れがなく簡便に除去することができる。
【０１４７】
本発明の第２１の手段は前述のような構成になっており、従来法のように電極近傍で水の電気分解が進行し、陽極部での強酸性化による電極の溶損、陰極部での強アルカリ化による重金属などの被処理物の不溶化・沈澱という問題、ならびに印加した電気エネルギーが、水の電気分解、および被処理物の電気抵抗に起因するジュール熱の発生に使われて、無駄が多いなどの問題点が解消される。
【図面の簡単な説明】
【図１】本発明の実施形態に係る電気化学的処理方法を説明するためのフローチャートである。
【図２】この電気化学的処理方法に用いる簡易電気化学的処理装置の概略構成図である。
【図３】その処理装置に用いる処理槽の斜視図である。
【図４】その処理槽の断面図である。
【図５】その処理槽に用いる壁板の正面図である。
【図６】コンベアで土壌を処理槽に搬入する状態を示す斜視図である。
【図７】陰極槽と陽極槽の配置と被処理物の搬出方向との関係を示す図である。
【図８】電極槽の斜視図である。
【図９】他の変形例における陰極槽と陽極槽の配置と被処理物の搬出方向との関係を示す図である。
【図１０】さらに他の変形例における陰極槽と陽極槽の配置と被処理物の搬出方向との関係を示す図である。
【図１１】電極槽の変形例を示す斜視図である。
【図１２】電極槽の固定構造を示す斜視図である。
【図１３】空気ヘッダーの正面図である。
【図１４】電極槽の変形例を示す斜視図である。
【図１５】電極槽の固定構造を示す斜視図である。
【図１６】土壌処理法の展開を説明するための図である。
【図１７】本発明の実施形態に係る電源波形図である。
【図１８】本発明の実施形態に係る電源装置の回路図である。
【図１９】本発明の実施形態に係る電源装置の回路図である。
【図２０】本発明の実施形態に係る電源波形図である。
【図２１】本発明の実施形態に係る電源装置の回路図である。
【図２２】本発明の実施形態に係る電源装置の回路図である。
【図２３】本発明の実施形態に係る電源波形図である。
【図２４】本発明の実施形態に係る電源装置の回路図である。
【図２５】本発明の実施形態に係る電源波形図である。
【図２６】本発明の実施形態に係る電源波形図である。
【図２７】本発明の実施形態に係る電源装置の回路図である。
【図２８】本発明の実施形態に係る電源装置の回路図である。
【図２９】従来の直流電流を流した場合の弊害を示す模式図である。
【図３０】本実施形態の効果を示す模式図である。
【図３１】本発明法と従来法で汚染土壌の浄化を行なった際の陽極重量の変化を示す図である。
【図３２】陽極近くの土壌、陰極近くの土壌、ならびにその間の土壌の電位を測定した電位特性図である。
【符号の説明】
１：処理槽、２：陰極槽、３：陽極槽、４：汚水槽、５：凝集槽、６：沈澱槽、７：揚水ポンプ、８：給水タンク、９：ｐＨ計、１０：酸供給装置、１１：電源装置、１２：陰極、１３：陽極、１４：透水フィルタ、１５：混練機、１６：被処理物、１７：浸透水、１８：凝集剤、１９：汚泥、２０：地面、２１：パイプ、２２：締め付け金具、２３：フレーム、２４：壁板、２５：補強部材、２６：補強用パイプ、２７：コーナ部材、２８：遮水シート、２９：糸、３０：槽本体板、３１：ケーブル、３２：配管、３３：空気ヘッダー、３４：ヘッダー母管、３５：コック、３６：チューブ、３７：ノズル、３８：掘削土壌、３９：穴、４０：処理済土壌、４１：交流電源、４２：トランス、４３：コンバータ、４４：増幅器、４５：信号発生器、４６：インバータ、４７：整流器、４８：抵抗器、４９：ＳＣＲ制御回路、５０：ＧＯＴ制御回路、５１：急峻部、５２：電極槽底部固定用垂木、５３：電極槽上部固定用サポート、５４：ベルトコンベア、５５：電極槽フレーム、５６：拡散スクリュ、５７：水流ポンプ、５８：モータ、５９：ホース、６０：ノズル、Ａ：空気[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrochemical treatment method and an electrochemical treatment device for treating, for example, heavy metals and the like in soil by the action of electrophoresis and electroosmosis, and particularly easily and inexpensively at any place such as a site. The present invention relates to an electrochemical processing method and an electrochemical processing apparatus that can be implemented.
[0002]
[Prior art]
Soil purification methods that include harmful components such as heavy metals include:
▲ 1 ▼. A method of electrochemically treating heavy metals from soil,
▲ 2 ▼. How to wash the soil with water or chemicals,
(3). Decomposition into harmless by oxidizing agent or reducing agent,
▲ 4 ▼. Method of desorption and volatilization by heating the soil,
▲ 5 ▼. How to slag the soil in a melting furnace,
▲ 6 ▼. How to vitrify the soil at high voltage,
▲ 7 ▼. How to solidify the soil with cement,
▲ 8 ▼. A method of immobilizing a poorly soluble substance with a drug,
▲ 9 ▼. A method of shielding and confining the soil with a sheet pile,
and so on. The soil washing method of (2) is suitable for sandy materials, but is not suitable for clayey materials. The oxidation and reduction methods (3) are specifically applicable only to hexavalent chromium, cyanide, and the like, and have a narrow application range. The thermal desorption method of (4), the melt-solidification method of (5), and the vitrification of (6) require a large amount of energy and a high running cost. The cement solidification method of (7) and the insolubilization method of (8) do not remove harmful components only by sealing. The shielding method of (9) does not remove harmful components simply by shielding.
[0003]
On the other hand, the electrochemical treatment method (1) can separate and remove harmful components even if the soil is clayey, has a wide application range, and has a thermal desorption method, a melt solidification method, and a vitrification method. It has features such as lower required energy and lower running cost compared to the law.
[0004]
The conventional method of electrochemically recovering heavy metals from contaminated soil mainly consists of manufacturing a large, permanent treatment tank with an anode and a cathode installed inside, and removing the contaminated soil from the site using a truck, for example. They were transported to the processing tank, charged into the processing tank by a belt conveyor or the like, and electrochemically processed by passing a direct current between the anode and the cathode. The purified soil is taken out of the treatment tank and returned to its original position by a truck or the like.
[0005]
[Problems to be solved by the invention]
The conventional method using a permanent treatment tank may cause secondary pollution by dropping, scattering, and spreading when contaminated soil is transported. A space for installing the processing tank is also required, and the processing tank becomes expensive. Furthermore, contaminated soil once removed from the site is regarded as waste, and has a legal problem that it is difficult to reuse.
[0006]
For this reason, an in-situ method in which an anode and a cathode are inserted and buried in the soil at the in-situ site with contaminated soil, and a voltage is applied between both electrodes to recover heavy metal ions from the soil. Is being considered. However, when a direct current is applied, the vicinity of the cathode becomes alkaline, and heavy metal ions such as lead and cadmium precipitate as hydroxides, making it difficult to recover heavy metals.
[0007]
In order to solve this, a method of adding acid such as hydrochloric acid or acetic acid to acidify the soil is adopted. However, the addition of the acid may cause heavy metal ions to flow into groundwater or the like, which may cause secondary pollution. Further, even if an acid is added to the soil, the acid does not penetrate uniformly and the pH value varies, so that the insolubilized substance remains in the soil, and the recovery rate of heavy metals, that is, the soil purification rate is low.
[0008]
Furthermore, the applied electric energy is used for the electrolysis reaction of water and the generation of Joule heat due to the electric resistance of the soil, and the contribution to electrophoresis is reduced. There is also.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electrochemical processing method and an electrochemical processing apparatus which can solve the above-mentioned disadvantages of the prior art and can be easily and inexpensively implemented at any place such as a site. .
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first means of the present invention comprises a step of forming an enclosure having a water barrier, a step of disposing an anode and a cathode in the enclosure so as to face each other, Carrying in the object to be treated between the anode and the cathode, injecting impregnated water such as water or an acid aqueous solution into the surrounding frame, and flowing an electric current between the anode and the cathode to cause the object to be treated. Electrochemically treating the object to be treated and, after electrochemically treating the object to be treated, removing at least a part of the side wall of the enclosure and carrying out the treated object from the enclosure. It is characterized by the following.
[0011]
According to a second aspect of the present invention, in the first aspect, the enclosing frame includes a frame formed by combining a pipe and a detachable fastener, a plate attached to the inside of the frame, It is characterized by comprising a water-impervious sheet stretched inside.
[0012]
A third means of the present invention is characterized in that, in the first means, the seam portion and the fold portion of the impermeable sheet are adhered or fused to be liquid-tightly sealed.
[0013]
According to a fourth aspect of the present invention, in the first aspect, the anode is inserted into an anode tank having a water-permeable filter, and the cathode is inserted into a cathode tank having a water-permeable filter. It is characterized by being arranged so as to be able to be inserted into and removed from the surrounding frame.
[0014]
According to a fifth aspect of the present invention, in the first aspect, the anode tank for inserting the anode has a water permeable filter, and the cathode tank for inserting the cathode has a water permeable filter. The infiltration water is injected into at least one of the electrode tanks, and the permeation water is caused to permeate into the layer of the object through the electrode tank.
[0015]
According to a sixth aspect of the present invention, in the first aspect, a cover for preventing rainwater from entering during the electrochemical treatment step is provided above the enclosure.
[0016]
According to a seventh aspect of the present invention, in the first aspect, the contaminant contained in the object is removed, and then the object is carried into the enclosure. is there.
[0017]
According to an eighth aspect of the present invention, in the first aspect, the object to be treated is soil containing heavy metals.
[0018]
According to a ninth aspect of the present invention, in the eighth aspect, the soil and the acid are mixed and carried into the enclosure.
[0019]
In a tenth aspect of the present invention, in the eighth aspect, the anode is inserted into an anode tank having a water permeable filter, and the cathode is inserted into a cathode tank having a water permeable filter. The heavy metal ions that are filled in the cathode tank and the gap between the objects to be treated and drawn into the cathode tank are taken out of the cathode tank together with the infiltration water, and the water level is set so that the water level in the anode tank is higher than the water level in the cathode tank. It is characterized by being controlled.
[0020]
According to an eleventh aspect of the present invention, in the eighth aspect, the inside of the area to be treated including the soil is divided into at least three of a section 1, a section 2, and a section 3, and the section 1 and the section 2 are divided into two sections. The section is excavated, the excavated soil coming out of section 1 and the excavated soil coming out of section 2 are separately piled and piled up, and a processing tank containing an electrode and an electrode is placed at section 2 of a hole formed by excavation. Temporarily, the one excavated soil is carried into the treatment tank to perform purification treatment, and when the treatment is completed, the side wall of the treatment tank adjacent to the section 1 is moved down to the section 1 side to remove the treated soil. After moving to the section 1, the section 3 is excavated, the excavated soil is piled up in another place, a processing tank is temporarily installed in the hole formed in the section 3, and one excavated soil is carried into the processing tank. And after the treatment is completed, the side wall adjacent to the section 2 of the treatment tank is removed. Tilt the image 2 side, and is characterized in that transferring the processed soil compartment 2 side.
[0021]
According to a twelfth aspect of the present invention, in the first aspect, the side wall of the surrounding frame disposed in a direction orthogonal to the surface of the electrode is demolished.
[0022]
According to a thirteenth aspect of the present invention, in the first aspect, the processed material carried out of the enclosure includes a large amount of water, and the processed material flows out together with the water. is there.
[0023]
According to a fourteenth aspect of the present invention, in the first aspect, the inside dimension of the enclosure is such that a construction machine for carrying out a processing object can enter the enclosure. .
[0024]
According to a fifteenth aspect of the present invention, in the first aspect, the waveform of the current is a rectangular wave, a sine wave, a pulse wave, a sawtooth wave or a triangular wave, and the voltage of the applied current is time-dependent on the positive side and the negative side. And the voltage integrated value during the positive period of the voltage is larger than the voltage integrated value during the negative period of the voltage.
[0025]
A sixteenth aspect of the present invention is a frame type frame formed by combining a pipe and a detachable fastening, a plate material attached to the inside of the frame, and a waterproof sheet stretched inside the plate material. And an anode tank and a cathode tank which are provided with a water-permeable filter and can be inserted into and removed from the enclosure, and an anode and a cathode respectively inserted into the anode tank and the cathode tank; and the anode and the cathode. A connected power supply device is provided, and an object to be processed is carried in between the anode tank and the cathode tank. It is characterized by electrochemical treatment.
[0026]
According to a seventeenth aspect of the present invention, in the sixteenth aspect, a seam portion and a fold portion of the impermeable sheet are liquid-tightly sealed by bonding or fusion.
[0027]
According to an eighteenth aspect of the present invention, in the sixteenth aspect, the ground is exposed on the inner bottom surface of the enclosure, and the ground is directly covered with the water-blocking sheet. It is.
[0028]
According to a nineteenth aspect of the present invention, in the sixteenth aspect, a cover for preventing rainwater from entering is provided above the enclosure.
[0029]
According to a twentieth aspect of the present invention, in the sixteenth aspect, the object is soil containing heavy metals.
[0030]
According to a twenty-first aspect of the present invention, in the sixteenth aspect, the current waveform of the power supply device is a rectangular wave, a sine wave, a pulse wave, a sawtooth wave or a triangular wave, and the voltage of the applied current is positive and negative. , And the voltage integrated value during the positive period of the voltage is larger than the voltage integrated value during the negative period of the voltage.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining an electrochemical treatment method according to the embodiment.
[0032]
For example, land such as redeveloped land must first be subjected to a soil inspection to measure the content of heavy metals such as cadmium and lead and the pH value of the soil, and based on the inspection results, it must be contaminated and electrochemically treated. Identify soiled areas. Heavy metals are easily adsorbed to the soil, and the contaminated soil adsorbed by the heavy metals is at most about 2 to 3 m deep from the surface of the earth, and the area having the area and depth that definitely includes the contaminated soil is the soil to be treated. Specified as an area.
Next, the soil area is dug up by a construction machine such as a backhoe to crush the soil mass (S1). If there are foreign substances such as rocks, concrete lumps, synthetic resin sheets and plates in the excavated soil, they impede the electrochemical treatment and are separated and removed by a vibration sieve or the like (S2).
[0033]
An acid is added to the soil from which contaminants have been removed (S3), and the soil is kneaded to uniformly acidify the soil (S4). By this pretreatment, the entire soil is acidified evenly, heavy metal ions are eluted, and the treatment speed can be improved. As the acid, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, or an organic acid such as formic acid, oxalic acid or benzenesulfonic acid is used.
[0034]
In the present embodiment, in order to acidify the soil in advance, the soil and the acid are kneaded before being carried into the soil treatment tank. However, this is not always necessary, for example, a method in which soil and acid water are alternately put in a soil treatment tank instead of kneading, a method in which acid water is put in a soil treatment tank before putting soil, or a method in which a soil treatment tank is used. There is a method of injecting acidic water from an electrode tank (described later) after carrying in the soil.
[0035]
At the site or in the immediate vicinity of the site, a frame of the treatment tank is manufactured using building equipment such as a scaffold member and a control panel, and a water-impervious sheet is provided inside the frame to manufacture a temporary soil treatment tank (S5). This step can be performed in advance or in parallel with S1 to S4.
[0036]
Next, the acidified soil is put into a soil treatment tank (S6), and acidic water having almost the same concentration as that of the soil is put into each of the electrode tanks (see

reference numerals

2 and 3 in FIG. 2) and allowed to penetrate into the soil. As shown in (5), acidic water (permeated water) is injected until the surface of the acidic water in each electrode tank becomes almost the same as the upper surface of the soil (S7). As will be described later, since each of the

electrode tanks

2 and 3 is provided with the water permeable filter 14, if the acidic water is injected from the

electrode tanks

2 and 3 and penetrates into the soil, the permeation speed is high, and the permeation rate is uniform throughout the soil. I do.
[0037]
Thereafter, electricity is supplied (S8), and soil purification is started (S9). In the purification, heavy metal ions (cations) attracted to the cathode side by electrophoresis and electroosmosis are pumped from the cathode tank 2 (see FIG. 2) (S10), and the pumped sewage is treated by alkali coagulation or the like to become heavy metal. Collect (S11). The treated water (S12) purified by this treatment is supplied as permeation water to the anode tank 3 (see FIG. 2) to reduce utility costs (S13), and an inorganic acid or an organic acid is added to the cathode tank 2 (S14). ). The cake-like heavy metals recovered in S11 are subjected to predetermined treatment as industrial waste (S15).
[0038]
The above steps are repeated to purify the soil, and when the purification is completed, one or more of the soil treatment tanks are demolished in order to carry out the soil (S16), and the soil is carried out from the reclaimed portion. Then (S17), it is buried back to the original excavated position (S18), and a series of processing ends.
[0039]
The flowchart of FIG. 1 shows the concept of the processing, and it is not always necessary to perform the processing continuously according to this flow. For example, the production of the soil treatment tank can be performed in parallel while excavating and sorting the soil, and each process can be performed in parallel for the purification subflow.
[0040]
FIG. 2 is a schematic configuration diagram of a simple electrochemical processing apparatus used in this electrochemical processing method. This simple electrochemical treatment apparatus comprises a treatment tank 1, a cathode tank 2, an anode tank 3, a sewage tank 4, a flocculation tank 5, a sedimentation tank 6, a pump 7, a water supply tank 8, a pH meter 9, an acid supply device 10, It comprises a power supply device 11, a cathode 12, an anode 13, a water-permeable filter 14, and the like.
[0041]
In the figure, reference numeral 15 denotes a kneader (mixer) for kneading contaminated soil and acid, 16 denotes an object to be treated such as contaminated soil to be treated, 17 denotes water filled in the treatment tank 1 or permeated water composed of an acid aqueous solution, 18 Is a flocculant.
[0042]
The treatment tank 1 has a cathode tank 2 for injecting permeated water 17, an anode tank 3, and an input area for charging the object 16 to be treated. The cathode tank 2 and the input area, and the anode tank 3 and the input area are filtered by a water-permeable filter 14. It is partitioned. As a pretreatment, the contaminated soil and the acid are uniformly mixed by the kneading machine 15 to obtain an acidic soil (having a pH value of about 2), and then, is charged into the charging area.
[0043]
As shown in the figure, a cathode cell 2 and an anode cell 3 are provided on both sides of the input area, and a cathode 12 and an anode 13 are provided respectively. A power supply 11 is connected to both

electrodes

12 and 13 to apply a predetermined voltage. I do. At this time, plate-like electrodes are used as the

electrodes

12 and 13 so that a voltage is uniformly applied to the whole of the soil which is the object 16 to be treated.
[0044]
When a voltage is applied, heavy metals such as lead, which are pollutants in the object 16 (soil), are ionized and move from the anode side to the cathode side by the action of electrophoresis and electroosmosis. However, when energization is continued, the anode side becomes an acidic region with hydrogen ions, and the cathode side becomes an alkaline region with hydroxyl ions. In the alkaline region, the moved heavy metal ions precipitate as hydroxides and become insoluble. Therefore, an acidic solution is supplied from the acid supply device 10 to the cathode tank 2, and the pH is controlled to a value at which heavy metals do not become hydroxides.
[0045]
The pH control is performed by measuring the pH value of the permeated water 17 containing the heavy metal ions transferred from the cathode tank 2 to the sewage tank 4 with the pH meter 9, and corresponding to the pH value, the acidic solution is supplied from the acid supply device 10 to the cathode tank 2. To be added. The target pH value on the side of the cathode tank 2 is slightly different depending on the contamination target and the like, but is controlled to about 2 in the case of lead.
[0046]
The water level of the permeated water 17 on the cathode tank 2 side is set to be equal to or slightly lower than the water level of the permeated water 17 on the anode tank 3 side, and the amount of sewage drawn by electrophoresis and electroosmosis is transferred to the adjacent sewage tank 4. It overflows and flows down naturally. Also, if the level of the permeated water 17 on the anode tank 3 side is slightly higher than the level of the permeated water 17 on the cathode tank 2 side to give a height difference, the moving speed of the permeated water is increased, and as a result, the processing speed is increased. Is faster. This water level control is performed by adjusting the supply amount of the permeated water 17 to the anode tank 3 side and the removal amount of the permeated water 17 from the cathode tank 2 side.
[0047]
The coagulation tank 6 is also adjacent to the sewage tank 4, and the sewage collected in the sewage tank 4 overflows to the coagulation tank 6 and flows down naturally. By adopting such a configuration in which natural flow occurs, it is possible to save labor and size of the device and reduce equipment costs. When the sewage is sufficiently collected in the coagulation tank 6, a coagulant 18 such as a chelate is put into the coagulation tank 6, transferred to the precipitation tank 6, the sludge 19 is separated, and the supernatant water is returned to the water supply tank 8 by the pump 7 and the pH is adjusted. Reuse.
[0048]
Although not shown, the sludge 19 is dehydrated by a dehydrator to obtain a cake containing heavy metals, and the cake is subjected to predetermined disposal as industrial waste. Through the steps of coagulation, precipitation and dehydration, a cake containing heavy metals in a high concentration can be obtained, and the subsequent disposal of the cake is simple. As described above, heavy metals in the soil are electrochemically recovered, and the soil is purified.
[0049]
3 is a perspective view of the processing tank, FIG. 4 is a sectional view of the processing tank, and FIG. 5 is a front view of a wall plate used for the processing tank. This treatment tank is made of inexpensive construction members that are robust, easy to transport, and readily available. First, the ground 20 at the place where the processing tank 1 is installed is leveled and flattened, and a water-impervious sheet described later is laid directly on the ground 20 (see FIG. 4), and the soil, which is the object 16 to be processed, is introduced. Do not break when deposited.
[0050]
Next, on the four sides around the flattened ground 20, a pipe 21 used for forming a scaffold and a square frame type frame 23 using a detachable fastener 22 for connecting the pipe 21 in the X direction and the Y direction. Constitute. A wall plate 24 made of a plywood, a control panel, or the like is attached inside the frame 23 to form a frame having a space inside. As shown in FIG. 5, a plurality of reinforcing members 25, such as square bars, are attached to one surface of the wall plate 24, and as shown in FIG. Installed inside.
[0051]
In FIG. 3, reference numeral 26 denotes a reinforcing pipe connected to each corner of the frame 23. In the present embodiment, the wall plate 24 is provided only on the side surface of the frame 23. However, the wall plate 24 may be provided on the inner bottom surface of the frame 23 as needed. In this case, the work of leveling the ground 20 is not always necessary.
[0052]
Next to the installation of the wall plate 24, as shown in FIG. 4, a corner member 27 made of wood or the like and having a substantially triangular cross section is arranged at the lower portion inside the wall plate 24. Thereafter, as shown in FIG. A relatively thick (28 mm to 3 mm sheet thickness) impermeable sheet 28 is stretched along the ground 20 from the inside of 24 to prevent water leakage. The water-blocking sheet 28 is cut according to the size of the processing tank 1 at the construction site, and the folds and seams are sealed in a liquid-tight manner with an adhesive or fusion so as not to cause water leakage. The upper end portion 28a of the water-blocking sheet 28 is folded back and fixed to the outside of the wall plate 24 by adhesion or fusion.
[0053]
When the water-impervious sheet 28 is stretched, the water-impervious sheet 28 may be inclined at the lower corner of the wall plate 24 without being bent at a right angle. Then, the object (soil) 16 is put thereon, and the impermeable sheet 28 may be partially extended and torn, so that in order to prevent this, the cross-sectional shape of the inside of the wall plate 24 is substantially triangular. Corner member 27 is disposed.
[0054]
As the water-blocking sheet 28, for example, a synthetic resin sheet or a rubber sheet, such as polyethylene terephthalate, polyamide, polypropylene, and rubber, which is commonly used in a final waste disposal site is used.
[0055]
The dimensions of the processing tank 1 are increased in both width and depth by 0.9 m in accordance with the standard dimensions of the construction member. Although not shown, the cathode tank 2 and the anode tank 3 are removably inserted inside the processing tank 1 (see FIG. 2).
[0056]
The object 16 (soil) is carried into the treatment tank 1 by piled up the soil excavated by a construction machine such as a backhoe, separated by a vibrating sieve, and then separated into contaminants such as large stones. It is carried in from above the processing tank 1 by the above method.
[0057]
When a large number of electrode tanks (cathode tank 2 and anode tank 3) are installed in the soil treatment tank 1, there is a possibility that the electrode tank moves or is deformed due to the pressure of the carried-in soil. In order to avoid this, it is necessary to fix the electrode tank to the processing tank 1 and at the same time, to convey the soil. Generally, when carrying soil or the like, a method of directly carrying in with a construction machine such as a backhoe or carrying in piles of soil with a conveyor is adopted. In either case, the treatment tank 1 is divided into a plurality of divided treatment tanks. It is necessary to distribute the carry-in amount almost equally so as not to apply unreasonable pressure.
[0058]
FIG. 6 is a perspective view illustrating a state in which soil is carried in using a belt conveyor. In the figure, 52 is a rafter for fixing the bottom of the electrode tank, 53 is a support for fixing the upper part of the electrode tank, and 54 is a belt conveyor.
[0059]
As shown in the figure, the treatment tank 1 is divided into a number of parts along the longitudinal direction by electrode tanks (cathode tank 2 and anode tank 3) so that the soil is almost equally distributed to each space of the treatment tank 1. The belt conveyor 54 is movable along the longitudinal direction of the processing tank 1 as shown by an arrow.
[0060]
If necessary, a cover such as a roof can be provided above the processing tank 1 to avoid rain. For this covering, an agricultural greenhouse or a simple tent may be used. Further, the skeleton of the cover can be formed by using the pipe used for the frame 23. Further, a cover such as a lid may be provided on the upper end openings of the cathode tank 2 and the anode tank 3 to prevent rainwater from entering. Since the pH value changes when rainwater enters the treatment tank 1, it is better to avoid rainwater intrusion.
[0061]
If the processing target 16 (soil) is carried out of the processing tank 1 after the processing, if the processing tank 1 is a small processing tank 1, the processing tank 1 is turned over using a crane or the like, and the processing target 16 (soil) is processed. Although it is possible to carry the material 16 out of the treatment tank 1, the object 16 (soil) to be treated must be excavated from the treatment tank 1 when the size of the object becomes large.
[0062]
Since the conventional permanent treatment tank is repeatedly used many times, the inner surface is coated with rubber or resin in order to impart acid resistance to the tank. Therefore, when the coating layer is mechanically dug out of the processing tank, the coating layer may be damaged or peeled off, so that the maintenance of the processing tank is complicated and the service life of the processing tank is short.
[0063]
In this regard, the processing tank 1 according to the embodiment of the present invention is a temporary tank, and the wall members 24 and the water-blocking sheets 28, which are constituent members of the tank, are basically semi-consumables (can be reused, but are discarded if they are damaged). Therefore, since the treatment is performed once instead of being used repeatedly, there is no need to provide a coat layer on the inner surface of the tank as in a conventional permanent treatment tank, and the water-blocking sheet 28 is sufficient.
[0064]
At the time of unloading, the fastener 22 and the pipe 21 on one surface of the processing tank 1 (one surface closer to the excavated place) are removed, and the wall plate 24 is turned outward as shown in FIG. Since the object 16 (soil) contains a large amount of water, it naturally flows out, is removed using a construction machine such as a backhoe or a bulltozer, and is buried in the excavated place (see S17 in FIG. 1). If the inside size of the processing tank 1 is set to a size that allows the construction machine to enter the tank, the object 16 (soil) can be efficiently carried out.
[0065]
It is to be noted that the cathode tank 2 and the anode tank 3 can be taken out of the treatment tank 1 by taking the object 16 (soil) out of the object 16 (soil) easily. It may be taken out after it is ready to be taken out. In this embodiment, one surface of the processing tank 1 is demolished, but it is also possible to demolish two or more surfaces of the processing tank 1 as necessary.
[0066]
FIG. 7 is a diagram showing the relationship between the arrangement of the cathode cell 2 and the anode cell 3 and the carrying-out direction of the object 16 (soil). In the case of this embodiment, since the cathode tank 2 and the anode tank 3 are arranged so as to face each other along the longitudinal direction of the processing tank 1, the surface where they are not arranged, that is, the cathode tank 2 and the anode tank 3, If the surface to be processed 16 (soil) is carried out in the direction of arrow A or the direction of arrow B by breaking the orthogonal plane, the cathode vessel 2 and the anode vessel 3 can be carried out without obstruction. In other words, it is preferable to determine the arrangement positions of the cathode tank 2 and the anode tank 3 in consideration of the direction in which the object 16 (soil) is carried out.
[0067]
FIG. 8 is a perspective view showing the electrode tanks (the cathode tank 2 and the anode tank 3). The permeable filter 14 is made of a permeable filter for constructing a culvert, a polymer in which non-metal nets such as synthetic resin are superposed, a non-metal filter, and the like. (Soil) is prevented from entering the electrode tanks (cathode tank 2 and anode tank 3). The water permeable filter 14 is attached to both sides of the tank body plate 30 using a synthetic resin thread 29 such as a polyamide resin. The tank body plate 30 is made of, for example, a material such as wood or vinyl chloride which has acid resistance and mechanical strength to withstand earth pressure.
[0068]
In the present embodiment, the water permeable filters 14 are attached to both sides of the tank body plate 30, but the water permeable filters 14 are attached to the tank body plate 30 on the side facing the object 16, and the treatment tank 1 of the tank body plate 30 A plate can be attached to the opposite side.
[0069]
A predetermined number of plate-like electrodes (cathode 12, anode 13) are inserted into the tank, and the electrodes (cathode 12, anode 13) are electrically connected to each other by a cable 31. The tip of the comb-shaped pipe 32 is inserted into the tank. When the electrode tank is the cathode tank 2, the pipe 32 is an acid supply pipe, and when the electrode tank is the anode tank 3, the pipe 32 is a pumping pipe.
[0070]
As shown in FIG. 8, an electrode having a sandwich structure in which a water-permeable filter 14 is attached to both sides of a tank body plate 30, or a water-permeable filter 14 is attached to one surface with the tank body plate 30 interposed, and a plate is attached to the other surface. A tank is formed, and a plate-like electrode (cathode 12, anode 13) and a distal end side of a pipe 32 are alternately inserted into a gap between the water-

permeable filters

14 and 14 or a gap between the water-permeable filter 14 and a plate in the tank to form a thin structure. ing.
[0071]
FIGS. 2 and 7 show an example in which the cathode tank 2 and the anode tank 3 are provided as a pair. However, when the apparatus is increased in size to increase the amount of one processing, or when the processing time is shortened, approximately 0% is used. Three or more electrode tanks can be provided at intervals of 0.5 m to 2 m.
[0072]
9 and 10 are schematic plan views of a processing tank showing an example of the arrangement of the electrode tank. In the example of FIG. 9, the processing tank 1 is divided into a plurality of pieces along the longitudinal direction, and a plurality of pairs of cathode tanks 2 and anode tanks 3 are arranged alternately. In the example of FIG. 10, the anode tank 3 is arranged on both sides in the longitudinal direction of the processing tank 1, and the cathode tank 2 is arranged at the center of the processing tank 1. When the cathode tank 2 is arranged at the center of the processing tank 1 as described above, heavy metal ions, which are cations, are collected at the center of the processing tank 1.
[0073]
In the arrangement example of FIG. 9, the side surface of the processing tank 1 that is orthogonal to the cathode tank 2 and the anode tank 3 is broken, and the object 16 (soil) is carried out in the arrow C direction or the arrow D direction. In the arrangement example of FIG. 10, a side surface of the processing tank 1 that is orthogonal to the cathode tank 2 and the anode tank 3 is broken, and the object 16 (soil) is carried out in the direction of arrow E or the direction of arrow F. In this way, the object 16 (soil) can be carried out without the cathode vessel 2 and the anode vessel 3 being in the way.
[0074]
In these examples, the case of the rectangular processing tank 1 has been described. However, in the case of the square processing tank 1 as well, the same arrangement of the electrode tanks as described above and the transfer of the object 16 (soil) can be carried out.
[0075]
When the amount of soil to be treated increases, the size of the treatment tank 1 needs to be increased. The voltage applied to the soil cannot achieve the expected effect unless the potential gradient (potential difference per unit length) is kept equal for such scale-up. Therefore, when the interval between the electrodes (the interval between the electrode tanks) is increased, it is necessary to apply a correspondingly large DC voltage. Producing a large DC voltage exceeding the commercial voltage (100 V, 200 V) is costly. In addition, an excessive DC voltage is not preferable in terms of safety, and an appropriate voltage is about 100 V at the highest. A suitable potential gradient has been found to be 1 V / cm in many experimental examples. Simply, the higher the potential gradient, the higher the electrophoretic force, but the more severe the electrolysis of water, the greater the loss due to heat generation, and the lower the purification efficiency of the soil. From the above, it is preferable that the appropriate electrode interval is basically about 1 m, and is adjusted in the range of 0.5 m to 2 m depending on the installation location and the size of the processing tank 1.
[0076]
When the processing tank 1 is large, it is necessary to install several rows of electrode tanks in the processing tank 1 as in the arrangement examples of the electrode tanks shown in FIGS. The electrode tank, except for both ends of the processing tank 1, is sandwiched between the soil and must withstand the pressure received from the soil. In addition, it is necessary to partition with the water permeable filter 14 in order to guide the interstitial water (permeate 17) of the soil into the electrode tank. Furthermore, in order to adjust the pH of the permeated water 17 in the electrode tank, it is preferable to have a space as free as possible. Therefore, in this embodiment, an electrode tank having a structure as shown in FIG. 8 is used. FIG. 11 is a perspective view showing a modification of the electrode tank. In this modification, a box-shaped electrode tank frame 55 made of, for example, wood or vinyl chloride, which is non-conductive, has excellent acid resistance, and has mechanical strength to withstand earth pressure, is used instead of the tank body plate 30 shown in FIG. And the water-permeable filters 14 are attached to both sides thereof. By using the electrode tank frame 55 in this manner, a sufficient space can be formed in the electrode tank, the amount of the permeated water 17 is sufficient, and the pH adjustment is easy.
[0077]
As shown in FIGS. 9 and 10, the electrode tank is installed so as to sandwich the object (soil) 16, but is fixed to the processing tank 1 in advance when the soil is carried in, and the electrode tank is fixed when the soil is carried in. It is necessary to devise it so that it does not move. When the electrode tank moves, an appropriate distance between the electrode tanks cannot be maintained, and the soil purification rate decreases. FIG. 12 is a perspective view showing a fixing structure of the electrode tank. In this example, the bottom of each electrode tank (cathode tank 2 and anode tank 3) is fixed with an electrode tank bottom fixing rafter 52, and the upper part of the electrode tanks (cathode tank 2 and anode tank 3) is a pipe constituting the processing tank 1. It is fixed by a pipe-shaped electrode tank upper fixing support 53 connected to 21. The rafter 52 is made of wood, which is non-conductive, has excellent acid resistance, and has a certain level of mechanical strength, like the electrode tank.
[0078]
In order to make the pH in the electrode tank uniform, air is sent to the lower part of the electrode tank by the air header 33 shown in FIG. 13, the air A is bubbled, and the permeated water in the electrode tank is stirred to make the pH uniform. ing. As shown in the figure, the air header 33 includes a header mother pipe 34, cocks 35 attached to the header mother pipe 34 at a predetermined interval (about 200 mm to 500 mm), and tubes 36 attached to the cocks 35. And a nozzle 37 attached to the tip of each tube 36, and each tube 36 extends to near the bottom of the electrode tank. The header mother pipe 34 is connected to an air pump (not shown), and the cock 35 is for adjusting air pressure so that air flows evenly. The cock 35, the tube 36, and the nozzle 37 are made of fluorine resin such as polytetrafluoroethylene having excellent acid resistance.
[0079]
In addition to the air header 33 as shown in FIG. 13 as a means for stirring the permeated water in the electrode tank, a stirring screw 56 as shown in FIG. 14 or a water pump 57 as shown in FIG. 15 may be used. it can. In these figures, reference numeral 58 denotes a motor, 59 denotes a hose, and 60 denotes a nozzle.
[0080]
These figures show an example in which the permeated water in the electrode tank is recirculated using the stirring screw 56 or the water flow pump 57, but is supplied to the electrode tank using the water pump 7 as shown in FIG. It is also conceivable to stir the permeated water in the electrode tank using the blasting force of the acid supplied to the electrode tank using the permeated water 17 or the acid supply device 10.
[0081]
FIG. 16 is a diagram for explaining the development of the soil treatment method. The expansion procedure will be described step by step.
(Step 1)
Partition the contaminated area to be treated. In the case of this example, the area is divided into four sections from section 1 to section 4, and each section has substantially the same size. These contaminated areas will be identified by prior soil inspection.
[0082]
(Step 2)
Excavation is performed for two sections, Section 1 and Section 2, and the excavated soil is subjected to pre-sorting treatment for removing impurities such as stones, and piled up near the next section. For example, the excavated soil 38a of the section 1 is piled up near the section 2 and the excavated soil 38b of the section 2 is piled up near the section 3 separately.
[0083]
(Step 3)
The treatment tank 1 is temporarily provided at the section 2 of the hole 39 formed by excavation, and the excavated soil 38a is carried into the treatment tank 1 for purification treatment.
[0084]
(Step 4)
The wall plate 24 on the side of the processing tank 1 adjacent to the section 1 is lowered to the section 1 side, and the treated soil 40 is transferred to the section 1 side by a backhoe or the like. Next, the section 3 is excavated, and the excavated soil 38c is piled up near the section 4 after the pre-sorting treatment. The treatment tank 1 is temporarily installed in the hole formed in the section 3, the excavated soil 38 b is carried into the treatment tank 1, and the purification treatment is performed. When the treatment is completed, the excavated soil 38 b is located on the side of the treatment tank 1 adjacent to the section 2. The wall board 24 is dismantled, and the treated soil 40 is moved to the section 2 side. In this way, the contaminated soil in section 1, section 2, section 3, section 4 can be sequentially purified and returned to the original position.
[0085]
If this deployment method is adopted, the earth pressure of the soil carried into the treatment tank can be received by the wall surface of the hole formed by excavation as compared with the case where the treatment tank is constructed on the ground, which is advantageous in strength. It is. Further, since the treatment tank is constructed in the excavated portion, the space for installing the treatment tank is small, and the distance for moving the soil can be shortened. Furthermore, except for excavation, the movement of the soil is downward (transfer of the soil into the treatment tank) or laterally (movement of the treated soil), so that the movement of the soil is easy.
[0086]
In the present embodiment, assuming that the soil is strongly alkaline, acidification is performed by adding an acid at the time of kneading and near the cathode. As a result, the heavy metals insolubilized as hydroxides in the soil are dissolved and moved to the cathode 12 side together with the water to be collected. It is also possible to add an acid to the anode side (see FIG. 2) to acidify the whole soil to be treated. No acid addition is required if the soil is acidic.
[0087]
The heavy metal ions which have moved to the cathode 12 side by energization are transferred to the sewage tank 4 in a solution state. Water (water or an acid aqueous solution) having a mass substantially equal to the mass of the contaminated liquid taken out of the treatment tank 1 is supplied to the anode tank 3 as permeated water 17.
[0088]
If the collection of heavy metal ions is continued, solids adhere to the surface of the cathode 12, and the solids adhere to the surface of the cathode 12, thereby lowering the collection efficiency. Therefore, it is necessary to physically drop the attached solids from the cathode 12. For this purpose, air A in the form of bubbles is jetted onto the surface of the cathode 12 by the air header 33 shown in FIG. Therefore, the air header 33 has two functions of making pH uniform and preventing solid matter from adhering.
[0089]
Since the soil after purification is acidic, the pH value of the soil is adjusted to about 6 to 7 by adding an appropriate amount of an alkaline substance such as lime to the soil, stirring and mixing.
[0090]
A part of the processing tank 1 is demolished when the processed material is carried out of the processing tank 1, so that a part of the wall plate 24 and the impermeable sheet 28 cannot be reused. The

electrodes

12, 13, the pipe 21, the clamp 22 and the like can be reused.
[0091]
The power supply waveform as a reference for the electrochemical treatment is arbitrary, and any of a sine wave, a pulse wave, a rectangular wave, a sawtooth wave, a triangular wave and the like can be used as shown in FIGS. The shaded portions shown in the figure are applied voltage values. There is also a method in which a DC and a sine wave, a pulse wave, a rectangular wave, a sawtooth wave, a triangular wave, or the like are alternately applied with a fixed or indefinite period.
[0092]
18 and 19 are circuit diagrams showing specific examples of the power supply device that can obtain the waveform shown in FIG. In the figure, 41 is an AC power supply having a frequency of 50 Hz or 60 Hz, 42 is a transformer, 43 is a converter, 44 is an amplifier, 45 is a signal generator, and 46 is an inverter with a waveform, frequency, duty ratio, and bias adjustment function. The power supply shown in FIG. 18 is inexpensive, and the power supply shown in FIG. 19 has a power supply efficiency of 80% or more. In this example, the AC power supply 41 having a frequency of 50 Hz or 60 Hz is used, but the frequency can be adjusted to an optimum frequency by a motor generator method or an inverter method.
[0093]
FIG. 20 is a diagram showing another power supply waveform, and FIGS. 21 and 22 are circuit diagrams of a power supply device capable of obtaining the waveform. In the figure, 47 is a rectifier and 48 is a resistor, which appropriately changes the positive and negative voltages of the sine wave.
[0094]
FIG. 23 is a diagram showing still another power supply waveform, and FIG. 24 is a circuit diagram of a power supply device capable of obtaining the waveform. Reference numeral 49 in the figure is an SCR control circuit. As shown in FIG. 23, most of the negative side is cut off, and a waveform controlled so that the difference (positive-negative) between the voltage integral values of the positive and negative cycles becomes a positive value is generated by the power supply device shown in FIG. I do.
[0095]
FIGS. 25 and 26 are diagrams showing still another power supply waveform. FIGS. 27 and 28 are circuit diagrams of a power supply device from which these waveforms can be obtained. In the power supply device of FIG. 27, the waveform shown in FIG. The apparatus produces the waveform shown in FIG. In the figure, 49a is a first SCR control circuit, 49b is a second SCR control circuit, and 50 is a GTO control circuit. As shown in FIG. 25 and FIG. 26, the alternating current is turned on and off at a constant cycle to cut most of the negative side and part of the positive side. Since current does not flow for the OFF period, a certain power saving can be achieved.
[0096]
As shown in FIG. 25 and FIG. 26, the initial portion where the negative side is switched to the positive side is partially cut to provide a steep portion 51 in which the positive side rises steeply, or FIG. , (B), (e), (f), and (g), the use of a rectangular wave or a triangular wave having a steep portion 51 increases the collection efficiency.
[0097]
These sine waves, pulse waves, rectangular waves, sawtooth waves, triangular waves, and the like are controlled such that the voltage integration values of the positive and negative cycles become (positive> negative). In other words, when the voltage V (t) is indicated by the voltage V (t) at time t, and the period during which the voltage V (t) is positive is t1 and the period during which the voltage V (t) is negative is t2, the absolute value of the voltage | V (t) | , The following equation (1).
[0098]
(Equation 1)

The integral values of the positive and negative cycles can be controlled by controlling the peak voltage value, the pulse width, or the number of pulses. However, since it is only necessary to control the integral value of the positive side cycle and the negative side cycle, another feasible method may be used.
[0099]
Further, the voltage of the applied current changes between a constant voltage (+ V1: positive value) and a constant voltage (-V2: negative value), and is a period (t1) of a positive value (+ V1) and a negative value (-V2). It is adjusted so that the relationship of (V1 × t1)> (V2 × t2) is established between the period (t2).
[0100]
Further, the voltage of the applied current changes between ± V1 (V1: positive value), and a relationship of t1 ≧ t2 is established between a period (t1) of + V1 and a period (t2) of −V1. Has been adjusted to be.
[0101]
In the conventional method using a DC power supply, heavy metals in the treated soil usually move to the cathode side together with a solution that has been permeated into the treated soil by the action of electrophoresis and electroosmosis as heavy metal ions.
[0102]
However, in the power supply used in the present embodiment, a voltage in the negative direction is partially included, and the voltage switches in both the positive and negative directions at a certain frequency, that is, the polarity of the electrode switches. The polarity switches before the decomposition reaction proceeds. At this time, on the anode side, generation of hydrogen ions due to electrolysis of water is suppressed, strong acidification does not occur, and erosion of the electrode is suppressed.
[0103]
The conventional method has problems of erosion of the anode and alkalinization at the cathode. The present inventors controlled the applied current to an arbitrary frequency instead of applying a simple constant-voltage DC power supply or a DC power obtained by half-wave rectifying an AC power supply as described above, and included both positive and negative ranges. Sine wave, pulse wave, rectangular wave, sawtooth wave, triangular wave, etc., and the difference (positive-negative) between the integral value of the voltage (current) in the positive period and the integral value of the voltage (current) in the negative period is positive. The problem was solved by controlling it to be a value.
[0104]
Since the matrix in the soil behaves as if it has a kind of molecular sieving action, the speed of electrophoresis is usually very slow, and it takes an enormous amount of time to reach a certain removal rate.
[0105]
In the method using a half-wave rectification power supply or the like described above, the change in voltage is 0 V to a constant voltage, and the electrolysis reaction of water (or the electrode solution) proceeds near the electrode, resulting in strong acidification at the anode. Thus, there is a problem that the electrode is melted and the heavy metal is insolubilized and precipitated by alkalizing at the cathode.
[0106]
In addition, when the electrolysis reaction of water (or an acidic aqueous solution) proceeds, the applied electric energy is not only wastefully consumed, but also the soil near the cathode is alkalized, and the alkali component and the insolubilized heavy metal become electric resistance, and In the vicinity, the potential difference becomes particularly large. For this reason, the electric resistance of the soil further increases, which is a factor of increasing the generation of Joule heat.
[0107]
FIG. 29 is a schematic diagram showing the adverse effect when this DC current is passed. As shown in the figure, in order to maintain the electrical neutralization, a strong adsorption layer (electric double layer) of a counter ion for neutralizing the electrode surface (charged surface) is formed near the electrode surface (charged surface). On the other hand, the solution phase exhibits a diffuse distribution in which positive and negative charges are neutralized as the distance from the electrode increases. Then, when current is continued to flow, the cathode side is alkalized and the anode side is acidified, electrons are exchanged between the electrode and the solution, and the electrolysis of water proceeds.
[0108]
In the present invention, the polarity of the electrode is switched at a certain frequency by using a sine wave, a pulse wave, a rectangular wave, a sawtooth wave, or a triangular wave whose voltage waveform ranges from positive to negative. The polarity will be switched before the operation proceeds. At this time, the generation of hydrogen ions due to the electrolysis of water is suppressed at the anode portion, strong acidification does not occur, and erosion of the electrode is suppressed. Therefore, there is no need to use expensive precious metals, and costs can be reduced.
[0109]
On the other hand, in the cathode portion, generation of hydroxide ions caused by electrolysis of water is suppressed, and strong alkalinization does not occur. Therefore, it is possible to reduce the acid concentration added to control the soil to an appropriate pH value as compared with the conventional method, or to eliminate the need for adding an acid, thereby reducing costs. Further, since the problem of insolubilization and precipitation of heavy metals in the soil near the cathode does not occur, heavy metals can be efficiently removed.
[0110]
Furthermore, since the soil near the cathode does not become strongly alkalized, there is no longer a factor that increases the electrical resistance in the soil near the cathode, so that the effect of suppressing the generation of Joule heat does not increase, especially without increasing the potential difference near the cathode. can get.
[0111]
When a sine wave, a pulse wave, a rectangular wave, a sawtooth wave, and a triangular wave which extend over positive and negative according to the present invention, the applied electric energy is not used for the electrolysis reaction of water, and the electric resistance of the soil is reduced. Very little is used for the generation of Joule heat due to the heat. Most of the electric energy is used for electrophoresis of heavy metals, so that waste is very small and heavy metals can be electrophoresed efficiently.
[0112]
In addition, even when the voltage value is relatively low, the electrophoretic effect of heavy metals can be increased more efficiently than the conventional method, and the evaporation of the electrode solution due to Joule heat and the scattering of heavy metals outside the system can be suppressed. Can be. Conversely, even if the voltage value is increased, the generation of Joule heat is suppressed as compared with the conventional method, so that the removal efficiency of heavy metals can be increased without any problem.
[0113]
When using an AC power supply or using a pulse waveform that is symmetrical between positive and negative, the electrode does not melt similarly, but the migration of heavy metal ions due to the electrophoresis effect does not occur. The only way to remove is to sequentially replace the permeated solution (acid, aqueous acid solution or water), which is not desirable in terms of working efficiency.
[0114]
In order to promote electrophoresis, control is performed so that the integrated value of the current flowing during the positive period of the applied current is larger than the integrated value of the current flowing during the negative period, and the heavy metal ions are moved in one direction. To do. Naturally, the larger the difference (positive-negative) between the integrated value of the current in the positive period and the integrated value in the negative period, the faster the electrophoresis speed. Taking into account the effect of suppressing the electrolysis reaction of water at the electrode portion and the influence of radio interference on the surroundings, the frequency is used between about 1 Hz and 100 kHz, preferably between 50 Hz and 1000 Hz.
[0115]
FIG. 30 is a diagram schematically illustrating a state near the cathode according to the present embodiment. As shown in the figure, when the voltage (polarity) is switched in both positive and negative directions at a certain frequency, the formation and collapse of the electric double layer occur repeatedly, so that water electrolysis does not occur, and the alkali on the cathode side And the acidification of the anode side is suppressed, and as a result, the insolubilization and precipitation of heavy metals are suppressed on the cathode side, and the erosion of the electrode is suppressed on the anode side.
[0116]
FIG. 31 is a diagram showing a comparison of changes over time in the weight of the anode when the contaminated soil is purified by the method of the present invention and the conventional method. As is clear from this figure, in the conventional method (broken line), erosion (weight change) of the anode is severe, but in the method of the present invention (solid line), the weight of the anode hardly changes, and the service life of the anode is long. Therefore, it is not necessary to use an expensive noble metal for the anode. For example, an iron-based electrode can be used, and the cost can be reduced.
[0117]
On the other hand, in the cathode portion, generation of hydroxide ions due to electrolysis of water is suppressed, and strong alkalinization does not occur. Therefore, the acid concentration added to control the soil to an appropriate pH can be made lower than in the conventional method, and there is no problem that heavy metals are insolubilized and precipitated in the soil near the cathode.
[0118]
FIG. 32 is a potential characteristic diagram obtained by measuring the potentials of the soil near the anode, the soil near the cathode, and the soil therebetween. The horizontal axis indicates the position of the soil, and the vertical axis indicates the potential. Solid line a) is a characteristic curve of the method of the present invention, and broken lines b) and c) are characteristic curves of the conventional method. As is clear from this figure, in the method a) of the present invention, the potential gradient between the two electrodes is almost equal, but when the same voltage E1 as in the present invention a) is applied between the two electrodes, the conventional method b) has a sharp gradient near the cathode. And the potential gradient (angle θb) in the soil from the anode to the vicinity of the center is small. Since the electrophoretic effect increases as the potential gradient increases, it is considered that the electrophoretic effect from the anode to the vicinity of the center decreases in the conventional method b).
[0119]
Further, a steep potential gradient near the cathode is caused by an increase in electric resistance near the cathode, and causes generation of Joule heat near the cathode. The causes of the increase in electric resistance near the cathode are strong alkalinization based on electrolysis of the catholyte and insolubilization of heavy metals near the cathode. Therefore, in this region, heavy metals are considered to be insolubilized, and the electrophoretic effect is very small even if the potential gradient is large.
[0120]
In order to increase the electrophoretic effect as compared with the conventional method b), it is necessary to further increase the voltage between both electrodes. Conventional method c) shows a state when the voltage is increased to E2. The potential gradient (angle θc) at this time is almost equal to the potential gradient (θa) in the present invention.
[0121]
In this case, it can be seen that the electrolysis of the catholyte is further promoted, the strongly alkaline region is expanded, the electric resistance at the cathode is increased, and the potential gradient is increased. Therefore, the amount of Joule heat generated increases, and electric energy is wasted.
[0122]
According to the method a) of the present invention, the potential gradient (θa) in the soil is kept almost constant over the entire area of the soil, indicating that the electrophoretic effect is higher than that of the conventional method b). As described above, in the present invention, the applied electric energy is not used for electrolysis of water, generation of Joule heat of soil, and the like, and most of it is used for electrophoresis of heavy metals. It is possible to electrophorese heavy metals efficiently with little.
[0123]
In the above-described embodiment, heavy metals are treated with chelates from sewage. However, a method using an adsorbent such as an ion exchange resin or activated carbon, a coagulation precipitation additive, a hydroxide precipitation by alkalization, and the like are also possible.
[0124]
In the above embodiment, the liquid is moved between the cathode tank and the sewage tank and between the sewage tank and the flocculation tank by overflow, but the liquid can be moved by using a pump.
[0125]
In the above embodiment, the case where heavy metals such as lead and cadmium are recovered from soil has been described. However, the present invention can also recover metal components such as cationized rare earth elements and anionized aluminum acid.
[0126]
The electrochemical treatment method of the present invention is not limited to purification of soil, for example, combustion ash discharged from a combustion device, soot and dust, sludge, mud accumulated in rivers and swamps, powder containing the substance to be treated, powder It is also applicable when treating a substance to be treated from a colloid solution, a solution, or the like.
[0127]
【The invention's effect】
The first means of the present invention is configured such that at least a part of the side wall of the enclosure is demolished after the electrochemical treatment, and the processed material is carried out from the enclosure. It can be easily carried out at a place, and there is no need to worry about secondary pollution associated with the transfer of the object to be processed as in the related art, thereby reducing transportation costs and transportation time.
[0128]
The second means of the present invention is that the surrounding frame is composed of a pipe, a metal fitting, a plate material, and a waterproof sheet, these are ordinary construction members, easy to transport, easily available on site, and inexpensive. It is.
[0129]
According to the third means of the present invention, the seam portion and the fold portion of the impermeable sheet are sealed in a liquid-tight manner by bonding or fusion. There is no spill outside the enclosure, so there is no risk of secondary pollution.
[0130]
In the fourth means of the present invention, since the anode tank and the cathode tank are arranged so as to be able to be inserted into and removed from the enclosure, the anode tank and the cathode tank are separated from the enclosure when the enclosure is demolished and the processing object is carried out. It can be taken out and reused.
[0131]
The fifth means of the present invention is that the infiltration water is injected into the electrode tank having the water-permeable filter, and the infiltration water penetrates into the object layer through the electrode tank. Penetrates almost uniformly.
[0132]
In the sixth means of the present invention, since a cover for preventing rainwater intrusion is provided on the upper side of the surrounding frame, the processing conditions such as the pH value in the surrounding frame do not change due to rainwater intrusion, and the sixth means is stable. Electrochemical treatment is possible.
[0133]
Since the seventh means of the present invention performs the treatment after removing the impurities contained in the object to be treated, the inhibition of the electrochemical treatment by the impurities is eliminated.
[0134]
The eighth means of the present invention is a soil in which the object to be treated contains heavy metals, and the heavy metals in the soil can be easily removed without fear of secondary pollution.
[0135]
The ninth means of the present invention mixes soil and acid for treatment, so that the removal rate of heavy metals is high.
[0136]
According to the tenth means of the present invention, the water level is controlled so that the water level in the anode tank is higher than the water level in the cathode tank. Therefore, the movement of the permeated water from the anode side to the cathode side is fast, and the processing time is reduced. It can be shortened.
[0137]
The eleventh means of the present invention is configured as described above, and does not require a special space for installing a processing tank, and can efficiently and continuously process.
[0138]
According to the twelfth aspect of the present invention, the processed material can be carried out of the processing tank without breaking the electrode by breaking the side wall of the surrounding frame arranged in a direction perpendicular to the surface of the electrode.
[0139]
According to the thirteenth aspect of the present invention, it is easy to carry out the processed material from the processing tank by flowing the processed material together with a large amount of water.
[0140]
According to a fourteenth aspect of the present invention, since the inside dimensions of the enclosure are such that the construction machine for carrying out the processing object can enter the enclosure, the construction machine enters the interior of the enclosure and works. Can be carried out efficiently.
[0141]
The fifteenth means of the present invention has the structure as described above, and the electrolysis of water proceeds in the vicinity of the electrode as in the conventional method, the electrode is eroded by strong acidification at the anode, and the cathode is damaged at the cathode. Problems such as insolubilization / precipitation of heavy metals and other substances due to strong alkalinization, and the applied electric energy is used for electrolysis of water and generation of Joule heat due to the electric resistance of the substances to be processed. Problems such as a large number are eliminated.
[0142]
A sixteenth aspect of the present invention is a frame-shaped frame composed of a pipe and a detachable fastening, a plate mounted on the inside of the frame, and a water-tight sheet stretched inside the plate. Since the frame is configured, the enclosing frame can be easily demolished after processing the object to be processed, and the processed object can be carried out of the enclosing frame, and the enclosing frame can be easily installed at any place such as the site. As a result, there is no need to worry about secondary pollution associated with the transfer of the object to be processed as in the related art, and the transportation cost and transportation time can be reduced.
[0143]
According to a seventeenth aspect of the present invention, the seam portion and the fold portion of the water-impervious sheet are sealed in a liquid-tight manner. And no secondary pollution.
[0144]
According to an eighteenth aspect of the present invention, the ground is exposed on the inner bottom surface of the enclosure, and the ground is directly covered with the water-impervious sheet. Therefore, it is unnecessary to lay a plate on the inner bottom of the enclosure, Cost can be reduced.
[0145]
According to the nineteenth aspect of the present invention, since a cover for preventing intrusion of rainwater is provided on the upper side of the enclosing frame, processing conditions such as a pH value in the enclosing frame are not changed by the infiltration of rainwater, and stable electric power is not generated. Chemical treatment is possible.
[0146]
According to a twentieth aspect of the present invention, the object to be treated is soil containing heavy metals, and the heavy metals in the soil can be easily removed without fear of secondary pollution.
[0147]
The twenty-first means of the present invention is configured as described above, and the electrolysis of water proceeds in the vicinity of the electrode as in the conventional method, the electrode is eroded due to strong acidification at the anode, and the cathode is damaged at the cathode. Problems such as insolubilization / precipitation of heavy metals and other substances due to strong alkalinization, and the applied electric energy is used for electrolysis of water and generation of Joule heat due to the electric resistance of the substances to be processed. Problems such as a large number are eliminated.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining an electrochemical treatment method according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a simple electrochemical processing apparatus used in the electrochemical processing method.
FIG. 3 is a perspective view of a processing tank used in the processing apparatus.
FIG. 4 is a sectional view of the processing tank.
FIG. 5 is a front view of a wall plate used for the processing tank.
FIG. 6 is a perspective view showing a state where soil is carried into a treatment tank by a conveyor.
FIG. 7 is a diagram showing the relationship between the arrangement of a cathode vessel and an anode vessel and the direction in which a workpiece is carried out.
FIG. 8 is a perspective view of an electrode tank.
FIG. 9 is a diagram showing a relationship between the arrangement of a cathode vessel and an anode vessel and a carry-out direction of an object in another modification.
FIG. 10 is a diagram showing the relationship between the arrangement of a cathode vessel and an anode vessel and the carrying-out direction of an object in still another modification.
FIG. 11 is a perspective view showing a modification of the electrode tank.
FIG. 12 is a perspective view showing a fixing structure of the electrode tank.
FIG. 13 is a front view of the air header.
FIG. 14 is a perspective view showing a modification of the electrode tank.
FIG. 15 is a perspective view showing a fixing structure of the electrode tank.
FIG. 16 is a diagram for explaining development of a soil treatment method.
FIG. 17 is a power supply waveform diagram according to the embodiment of the present invention.
FIG. 18 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 19 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 20 is a power supply waveform diagram according to the embodiment of the present invention.
FIG. 21 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 22 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 23 is a power supply waveform diagram according to the embodiment of the present invention.
FIG. 24 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 25 is a power supply waveform diagram according to the embodiment of the present invention.
FIG. 26 is a power supply waveform diagram according to the embodiment of the present invention.
FIG. 27 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 28 is a circuit diagram of a power supply device according to an embodiment of the present invention.
FIG. 29 is a schematic diagram showing the adverse effects when a conventional direct current is applied.
FIG. 30 is a schematic view showing the effect of the present embodiment.
FIG. 31 is a view showing a change in anode weight when contaminated soil is purified by the method of the present invention and the conventional method.
FIG. 32 is a potential characteristic diagram obtained by measuring the potentials of the soil near the anode, the soil near the cathode, and the soil between them.
[Explanation of symbols]
1: Treatment tank, 2: Cathode tank, 3: Anode tank, 4: Sewage tank, 5: Coagulation tank, 6: Precipitation tank, 7: Pumping pump, 8: Water supply tank, 9: pH meter, 10: Acid supply device , 11: Power supply device, 12: Cathode, 13: Anode, 14: Water permeable filter, 15: Kneader, 16: Workpiece, 17: Permeated water, 18: Coagulant, 19: Sludge, 20: Ground, 21: Pipe, 22: fastening fitting, 23: frame, 24: wall plate, 25: reinforcing member, 26: reinforcing pipe, 27: corner member, 28: water-blocking sheet, 29: thread, 30: tank body plate, 31: Cable, 32: Piping, 33: Air header, 34: Header mother pipe, 35: Cock, 36: Tube, 37: Nozzle, 38: Excavated soil, 39: Hole, 40: Treated soil, 41: AC power source, 42 : Transformer, 43: Converter, 44: Amplifier, 45: Signal Liver, 46: inverter, 47: rectifier, 48: resistor, 49: SCR control circuit, 50: GOT control circuit, 51: steep part, 52: rafter for fixing the electrode tank bottom, 53: support for fixing the electrode tank top , 54: Belt conveyor, 55: Electrode tank frame, 56: Diffusion screw, 57: Water flow pump, 58: Motor, 59: Hose, 60: Nozzle, A: Air

Claims

Forming a fence having a water barrier;
Arranging the anode and the cathode in the surrounding frame so as to face each other;
A step of loading an object between the anode and the cathode in the enclosure,
A step of injecting permeated water into the enclosure,
A step of flowing an electric current between the anode and the cathode to electrochemically process the object to be processed,
A step of removing at least a part of a side wall of the enclosure after carrying out the electrochemical treatment of the object, and carrying out the treated object from the enclosure.

2. The electrochemical treatment method according to claim 1, wherein the surrounding frame includes a frame formed by combining a pipe and a detachable fastener, a plate attached to the inside of the frame, and a tension applied to the inside of the plate. An electrochemical treatment method comprising a water-impervious sheet provided.

2. The electrochemical treatment method according to claim 1, wherein a seam portion and a fold portion of the impermeable sheet are adhered or fused to be liquid-tightly sealed.

The electrochemical treatment method according to claim 1, wherein the anode is inserted into an anode tank having a water permeable filter, and the cathode is inserted into a cathode tank having a water permeable filter, and the anode tank and the cathode tank are inserted into the surrounding frame. An electrochemical treatment method characterized by being arranged so as to be insertable into and removable from a substrate.

2. The electrochemical treatment method according to claim 1, wherein the anode tank into which the anode is inserted has a water permeable filter, and the cathode tank into which the cathode is inserted has a water permeable filter, and at least one of the anode tank and the cathode tank is inserted. An electrochemical treatment method, comprising injecting the permeated water into one electrode tank and allowing the permeated water to permeate the layer of the object through the electrode tank.

2. The electrochemical treatment method according to claim 1, wherein a cover for preventing intrusion of rainwater is provided on the upper side of the enclosure during the electrochemical treatment step.

2. The electrochemical processing method according to claim 1, further comprising removing the impurities contained in the object to be processed and then carrying the object into the enclosure. .

2. The electrochemical treatment method according to claim 1, wherein the object to be treated is a soil containing heavy metals.

The electrochemical treatment method according to claim 8, wherein the soil and the acid are mixed and carried into the enclosure.

9. The electrochemical treatment method according to claim 8, wherein the anode is inserted into an anode tank having a water permeable filter, and the cathode is inserted into a cathode tank having a water permeable filter, and the permeated water is inserted into the anode tank and the cathode tank. Filled in the gap between the objects to be treated, the heavy metal ions drawn into the cathode tank are taken out of the cathode tank together with the infiltration water, and the water level is controlled so that the water level in the anode tank is higher than the water level in the cathode tank. An electrochemical treatment method.

The electrochemical treatment method according to claim 8, wherein the inside of the area to be treated including the soil is divided into at least three sections 1, 2, and 3,
Excavating two sections of the section 1 and section 2 and excavating soil coming out of section 1 and excavating soil coming out of section 2 and piled up;
At the place of the section 2 of the hole formed by excavation, the surrounding frame and a treatment tank including an electrode are temporarily provided, and the one excavated soil is carried into the treatment tank to perform a purification treatment.
When the treatment is completed, the side wall of the treatment tank adjacent to the section 1 is tilted to the section 1 side, and the treated soil is moved to the section 1 side,
Next, the section 3 is excavated, the excavated soil is piled up in another place, a treatment tank is temporarily provided in a hole formed in the section 3, and one excavated soil is carried into the treatment tank to perform purification treatment. When the treatment is completed, the side wall of the treatment tank adjacent to the section 2 is tilted to the section 2 side, and the treated soil is transferred to the section 2 side.

2. The electrochemical processing method according to claim 1, wherein a side wall of an enclosure arranged in a direction orthogonal to a surface of the electrode is demolished.

2. The electrochemical processing method according to claim 1, wherein the processed material carried out from the enclosure includes a large amount of water, and the processed material flows out together with the water. .

2. The electrochemical processing method according to claim 1, wherein an inner dimension of the enclosure is such that a construction machine for carrying out a processing object can enter the enclosure.

2. The electrochemical processing method according to claim 1, wherein the waveform of the current is a rectangular wave, a sine wave, a pulse wave, a sawtooth wave or a triangular wave, and the voltage of the applied current changes with time on the positive side and the negative side. Wherein the voltage integral during the positive period of the voltage is greater than the voltage integral during the negative period of the voltage.

A frame-type frame configured by combining a pipe and a removable fastening fitting, a plate material attached to the inside of the frame, and an enclosing frame having a water-impervious sheet stretched inside the plate material,
An anode tank and a cathode tank which are provided with a water-permeable filter and are inserted and removed in the enclosure,
An anode and a cathode respectively inserted into the anode and cathode vessels,
A power supply connected to the anode and the cathode,
An object to be treated is carried in between the anode tank and the cathode tank, and the inside of the anode tank, the inside of the cathode tank and the gap between the objects to be treated are filled with permeated water to electrochemically treat the object to be treated. And an electrochemical processing apparatus.

17. The electrochemical processing apparatus according to claim 16, wherein the seam portion and the fold portion of the impermeable sheet are liquid-tightly sealed by adhesion or fusion.

17. The electrochemical processing apparatus according to claim 16, wherein a ground surface is exposed on an inner bottom surface of the surrounding frame, and the ground surface is directly covered with the water shielding sheet. apparatus.

17. The electrochemical processing apparatus according to claim 16, wherein a cover for preventing rainwater from entering is provided above the enclosure.

17. The electrochemical treatment method according to claim 16, wherein the object to be treated is soil containing heavy metals.

17. The electrochemical processing device according to claim 16, wherein the current waveform of the power supply device is a rectangular wave, a sine wave, a pulse wave, a sawtooth wave or a triangular wave, and the voltage of the applied current is positive and negative with time. The electrochemical processing apparatus, wherein the voltage integral value during a positive period of the voltage is larger than the voltage integral value during a negative period of the voltage.