JP4465696B2

JP4465696B2 - Method and apparatus for decomposing organic substances in water

Info

Publication number: JP4465696B2
Application number: JP36255499A
Authority: JP
Inventors: 望育野
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 1999-12-21
Filing date: 1999-12-21
Publication date: 2010-05-19
Anticipated expiration: 2019-12-21
Also published as: JP2001170663A

Description

【０００１】
【発明の属する技術分野】
本発明は、水中の有機物の分解方法及び分解装置に関する。さらに詳しくは、本発明は、半導体製造工程や液晶製造工程などで使用されたリンス排水などの有機物を含有する水の回収再利用に好適に用いることができる水中の有機物の分解方法及び分解装置に関する。
【０００２】
【従来の技術】
半導体製造工程では、シリコン基板などの洗浄のために多量の超純水が使用されており、環境への負荷低減、水資源の有効活用などの観点から、リンス排水の回収再利用が広く行われている。しかし、リンス排水中には、アルコール、界面活性剤などの有機物が含まれているので、リンス排水を再利用するためにはこれらの物質を除去する必要がある。
リンス排水中の有機物を除去する技術として、従来から、オゾンと過酸化水素、オゾンと紫外線、紫外線と過酸化水素、オゾンとアルカリなどを組み合わせ、促進酸化を行う技術が提案されている。これらの技術は、非常に強い酸化力を有するヒドロキシルラジカルを発生させて、この強力な酸化力を用いて有機物を分解するものである。また、これらの方法において使用されるオゾンと過酸化水素は、処理後は分解されて酸素又は水になるだけであり、二次廃棄物を生成しないという利点も有している。
しかし、これらの技術のみでは有機物を完全に分解することは難しく、中間生成物までしか分解することができないために、分解処理の後段に脱イオン設備を設けたり、さらにもう一段の分解処理を行う二段階の分解処理を行うなどの方法がとられている。例えば、特開平１１−９９３９４号公報には、水中の有機物除去方法として、被処理水に過酸化水素及び／又はオゾンを添加して有機物を分解除去する第１工程と、第１工程の処理水にペルオキシド基を含む硫黄化合物を添加して有機物を分解除去する第２工程を行う方法が提案されている。このように処理を多段階に行うことにより、有機物の除去率を高めることはできるが、イニシャルコストの増加、設置スペースの増加を招くという不都合が生ずる。また、二段階の分解処理を行った場合でも後段で副生成物が発生するために、さらにその後段に脱イオン処理設備を設ける必要があり、かつその設備に加わる負荷が大きいという問題がある。
一方、リンス排水に過酸化水素とオゾンを添加し、反応槽に触媒を充填することにより酸化反応を促進し、有機物の分解率を高める方法も見いだされたが、この方法は単に過酸化水素の分解反応を促進するものであり、触媒によってオゾンの分解も促進されるが、有機物の分解に有効なヒドロキシルラジカルは生成しないので、顕著な触媒充填効果は得られない。
【０００３】
【発明が解決しようとする課題】
本発明は、半導体製造工程や液晶製造工程などで使用されたリンス排水などの有機物を含有する水の回収再利用に好適に用いることができる水中の有機物の分解方法及び分解装置を提供することを目的としてなされたものである。
【０００４】
【課題を解決するための手段】
本発明者は、上記の課題を解決すべく鋭意研究を重ねた結果、有機物を含有する被処理水のｐＨを７〜１０に調整して加温したのち、過酸化水素とオゾンを添加して、有機物を酸化分解することにより、一段の処理で水中の有機物を効果的に分解除去し得ることを見いだし、この知見に基づいて本発明を完成するに至った。
すなわち、本発明は、
（１）半導体製造工程又は液晶製造工程で発生したリンス排水をｐＨを７〜１０に調整し、温度を４５〜６０℃に調整して、加温されたｐＨ７〜１０のリンス排水を得て、該排水に排水中の有機体炭素の２〜２０重量倍の過酸化水素と、同じく２〜２０重量倍のオゾンを添加して、反応槽又は反応塔でリンス排水中に含まれる有機物を酸化分解し、有機物が酸化分解されたリンス排水を酸化剤分解触媒を充填した反応槽又は充填塔に通水して、リンス排水中に残存する過酸化水素とオゾンを酸化剤分解触媒により分解除去処理して、半導体製造工程又は液晶製造工程で発生したリンス排水からの処理水を回収し、該処理水を、イオン交換塔を経由することなく直接再利用することを特徴とするリンス排水中の有機物の分解方法、及び、
（２）半導体製造工程又は液晶製造工程で発生したリンス排水のｐＨを７〜１０に調整する手段、リンス排水の温度を４５〜６０℃に調整する手段、加温されたｐＨを７〜１０のリンス排水に排水中の有機体炭素の２〜２０重量倍の過酸化水素と同じく２〜２０重量倍のオゾンを添加する手段、リンス排水中に含まれる有機物を酸化分解する反応槽又は反応塔及び有機物が酸化分解されたリンス排水が通水される過酸化水素とオゾンの酸化剤分解触媒を充填した反応槽又は充填塔並びに該反応槽又は充填塔で処理された半導体製造工程又は液晶製造工程で発生したリンス排水からの回収処理水をイオン交換塔を経由することなく直接再利用する手段を有することを特徴とするリンス排水中の有機物の分解装置、
を提供するものである。
さらに、本発明の好ましい態様として、
（３）被処理水のｐＨを８〜９.５に調整する第１項記載の水中の有機物の分解方法、及び、
（４）過酸化水素を添加したのち、オゾンを添加する第１項記載の水中の有機物の分解方法、
を挙げることができる。
【０００５】
【発明の実施の形態】
本発明の水中の有機物の分解方法は、被処理水のpHを７〜１０に調整する工程、被処理水の温度を３５℃以上に調整する工程、加温された被処理水に過酸化水素とオゾンを添加する工程、被処理水中に含まれる有機物を酸化分解する工程、有機物が酸化分解された被処理水中に残存する過酸化水素とオゾンを分解除去する工程を有する。
本発明の水中の有機物の分解装置は、被処理水のpHを７〜１０に調整する手段、被処理水の温度を３５℃以上に調整する手段、加温された被処理水に過酸化水素とオゾンを添加する手段、被処理水中に含まれる有機物を酸化分解する手段及び有機物が酸化分解された被処理水中に残存する過酸化水素とオゾンを分解する手段を有する。
本発明方法及び本発明装置を適用する被処理水に特に制限はないが、電子材料洗浄工程で発生するリンス排水のように、有機体炭素濃度が１〜１００mg／Ｌである水に特に好適に適用することができる。
【０００６】
本発明においては、被処理水のpHを７〜１０、好ましくは８〜９.５に調整する。pHが７未満であっても、１０を超えても、有機物の分解除去率が低下するおそれがある。被処理水のpHを調整する方法に特に制限はなく、例えば、水酸化ナトリウム、水酸化カリウムなどのアルカリを添加することにより、pHを調整することができる。被処理水のpH調整は、被処理水への過酸化水素とオゾンの添加より前の工程であれば、いずれの段階においても行うことができる。
本発明においては、被処理水の温度を３５℃以上に調整し、以後の処理を加温された状態で行う。被処理水の温度が３５℃未満であると、有機物が十分に分解除去されないおそれがある。被処理水の温度を高めると、有機物の分解除去率は向上するが、４５℃あたりで除去率が平衡に近づくので、被処理水の温度は４５〜６０℃に調整することが好ましい。６０℃以上に加温するためには、熱エネルギーコストが嵩むおそれがある。
本発明において、被処理水の温度調整方法に特に制限はないが、被処理水と処理水の間で熱交換したのち、被処理水を所定の温度まで加温することが、熱エネルギーの節減の上から好ましい。本発明において、被処理水のpHの７〜１０への調整と、被処理水の温度の３５℃以上への調整の順序に制限はなく、被処理水のpH調整を行ったのちに温度調整することができ、被処理水を温度調整したのちにpH調整することもでき、あるいは、被処理水を温度調整しつつpH調整することもできる。
【０００７】
本発明において、被処理水の温度調整と、過酸化水素とオゾンの添加の順序に特に制限はなく、例えば、被処理水を温度調整したのち、過酸化水素とオゾンを添加することができ、被処理水に過酸化水素とオゾンを添加したのち、温度調整することもでき、被処理水を温度調整しつつ、過酸化水素とオゾンを添加することもでき、あるいは、被処理水に過酸化水素を添加し、温度調整したのち、オゾンを添加することもできる。これらの中で、被処理水を温度調整したのち、過酸化水素とオゾンを添加する方法は、熱交換器配管の腐食を防止することができ、オゾンの自己分解による損失を防いで、過酸化水素とオゾンの添加直後より有機物の分解が開始されるので、好適に用いることができる。
本発明において、被処理水への過酸化水素とオゾンの添加順序に特に制限はなく、過酸化水素を添加したのちオゾンを添加することができ、オゾンを添加したのち過酸化水素を添加することもでき、あるいは、過酸化水素とオゾンを同時に添加することもできる。しかし、オゾンは自己分解しやすい物質であり、有機物の分解に効率よくオゾンを利用するためには、オゾンを最後に添加することが好ましい。
【０００８】
本発明方法において、被処理水への過酸化水素の添加量に特に制限はないが、被処理水中の有機体炭素に対して、２〜２０重量倍であることが好ましく、５〜１０重量倍であることがより好ましい。過酸化水素の添加量が有機体炭素の２重量倍未満であると、有機物が十分に分解除去されないおそれがある。過酸化水素の添加量は、通常は有機体炭素の２０重量倍以下で十分であり、有機体炭素の２０重量倍を超える過酸化水素の添加は、後段の過酸化水素除去工程の負荷が増大するとともに、設備の腐食を招くおそれがある。
本発明方法において、被処理水へのオゾンの添加量に特に制限はないが、被処理水中の有機体炭素に対して、２〜２０重量倍であることが好ましく、５〜１０重量倍であることがより好ましい。オゾンの添加量が有機体炭素の２重量倍未満であると、有機体物が十分に分解除去されないおそれがある。オゾンの添加量は、通常は有機体炭素の２０重量倍以下で十分であり、有機体炭素の２０重量倍を超えるオゾンの添加は、いたずらに自己分解するオゾンの量が増えるとともに、後段のオゾン除去工程の負荷が増大するおそれがある。
本発明において、被処理水にオゾンを添加する方法に特に制限はなく、例えば、二国機械工業(株)製の１５ＵＰＤ０２Ｓようなポンプを用いて給水ポンプ吸い込み口にオゾンを添加することができ、エジェクターを設置してオゾンを添加することもでき、あるいは、溶解槽又は反応槽の下部にオゾンを直接散気することもできる。被処理水に添加したオゾンは、必ずしも物理的に完全に溶解した状態である必要はなく、微細な気泡となって被処理水中に分散した状態であってもよい。
【０００９】
本発明において、過酸化水素とオゾンが添加された被処理水中に含まれる有機物を分解する方式に特に制限はなく、例えば、反応装置において回分式に分解処理することができ、あるいは、連続式に処理することもできる。反応装置の形態に特に制限はなく、例えば、被処理水が均一に混合される反応槽とすることができ、あるいは、被処理水が連続的に通水される反応塔とすることもできる。
本発明においては、被処理水中に含まれる有機物を酸化分解したのちに、被処理水中に残存する過酸化水素とオゾンを分解する。温度調整された被処理水に過酸化水素とオゾンを添加して処理することにより、被処理水中の有機物の大部分が酸化分解されるが、有機物を酸化分解したのちの水中には、余剰の過酸化水素とオゾンが残存する。有機物の酸化分解後に、残存する過酸化水素とオゾンを分解除去することにより、回収水の水質を高めることができる。過酸化水素とオゾンの分解方法に特に制限はなく、例えば、活性炭又は白金、ルテニウムなどの酸化剤分解触媒を充填した反応槽や充填塔などに通水することにより、残存する過酸化水素とオゾンを分解除去することができる。
【００１０】
図１は、本発明装置の一態様の工程系統図である。熱回収用熱交換器１において、被処理水と処理水の間で熱交換が行われ、処理水から熱エネルギーが回収されて被処理水が予熱される。次いで、加温用熱交換器２において、被処理水が所定の温度まで加温される。加温された被処理水にアルカリが添加されて所定のpHに調整され、次いで、過酸化水素が添加され、さらに、オゾン溶解槽３において、オゾンが添加される。オゾン溶解槽の余剰ガスは、加温用熱交換器とオゾン溶解槽の間に設けられたエジェクター４へ返送され、再溶解される。オゾン溶解槽の余剰ガスを給水ラインに戻すことにより、排オゾンガス処理の負担を軽減することができる。過酸化水素とオゾンが添加された被処理水は、ポンプ５により反応槽６へ送られ、水中に含まれる有機物が酸化分解される。有機物が酸化分解された水は、ポンプ７により酸化剤分解塔８に送られ、水中に残存する過酸化水素とオゾンが分解されて処理水となる。処理水は、熱回収用熱交換器１を経由して熱エネルギーを放出し、冷却されたのち再利用される。反応槽６から排出されるガスは、排オゾンガス分解塔９でオゾンを分解除去したのち、大気中に放出される。
本発明方法及び装置によれば、多段処理をすることなく、単一の反応槽による一段処理で被処理水中の有機物を効率的に分解除去することができる。また、反応槽を通過した水をさらに酸化剤分解塔に通水し、残存する過酸化水素とオゾンを分解することにより良質の処理水を得ることができる。さらに、pH調整及び加温の効果により、オゾンと過酸化水素が効率的に有機物の分解反応に使用されるために、酸化剤のコストと、酸化剤の分解処理コストを低減することができる。
【００１１】
【実施例】
以下に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらの実施例によりなんら限定されるものではない。
図２は、実施例及び比較例において用いた装置の説明図である。反応槽１０に被処理水を仕込み、温度調整とアルカリ添加によるｐＨ調整とを行う。次いで、所定時間被処理水を撹拌しつつ有機物を酸化分解する。有機物が酸化分解された被処理水は、ポンプ１１により酸化剤分解塔１２に送り、水中に残存する過酸化水素とオゾンを分解し、処理水を得る。
なお、実施例及び比較例において、有機体炭素（ＴＯＣ）濃度は、ＪＩＳＫ０５５１にしたがって測定した。また、過酸化水素（Ｈ₂Ｏ₂）濃度は、ＤＭＰ法（ネオクロプロインの還元による吸光度測定）により、オゾン（Ｏ₃）濃度は、吸光度（波長２５４ｎｍ）により測定した。ただし、曝気してオゾンを脱離させた液を対照試料として測定した。
比較例１
超純水にイソプロピルアルコール５.０mg／Ｌを添加して、有機体炭素（ＴＯＣ）３.０mgＣ／Ｌを含有する水を調製し、試験用の被処理水とした。被処理水のｐＨは７.０、水温は２５℃であった。
この被処理水２Ｌを反応槽に入れ、過酸化水素水を過酸化水素の濃度が３０mg／Ｌになるように添加し、次いで電解式オゾン発生器［笹倉(株)、オゾンマスターＯＭ−２］で発生させたオゾンを濃度が３０mg／Ｌになるように添加した。被処理水の温度２５℃を保ったまま、反応槽の中で３０分撹拌し、イソプロピルアルコールの酸化分解処理を行った。酸化分解処理後の水のＴＯＣ濃度は２.４mgＣ／Ｌであり、ＴＯＣ除去率は２０.０％であった。また、残存過酸化水素濃度は５.５mg／Ｌであり、残存オゾン濃度は２mg／Ｌであった。この水を、白金メッキした線径０.４ｍｍのステンレス鋼網０.４Ｌを充填した触媒反応塔に、空間速度５ｈ^-1で通水した。触媒反応塔から流出した処理水中には、過酸化水素、オゾンともに検出されなかった。
参考例
比較例１と同じ被処理水を用い、処理温度を変えて、イソプロピルアルコールの分解を行った。
被処理水２Ｌを反応槽に入れ、３５℃に加温し、過酸化水素水を過酸化水素の濃度が３０mg／Ｌになるように添加し、次いで電解式オゾン発生器［笹倉(株)、オゾンマスターＯＭ−２］で発生させたオゾンを濃度が３０mg／Ｌになるように添加した。被処理水の温度３５℃を維持したまま、反応槽の中で３０分撹拌し、イソプロピルアルコールの酸化分解処理を行った。酸化分解処理後の水のＴＯＣ濃度は１.２mgＣ／Ｌであり、ＴＯＣ除去率は６０.０％であった。また、残存過酸化水素濃度は３.１mg／Ｌであり、残存オゾン濃度は１.２mg／Ｌであった。この水を、白金メッキした線径０.４ｍｍのステンレス鋼網０.４Ｌを充填した触媒反応塔に、温度３５℃を維持して、空間速度５ｈ^-1で通水した。触媒反応塔から流出した処理水中には、過酸化水素、オゾンともに検出されなかった。
実施例１
参考例と同一の条件で被処理水の温度を４５℃、５５℃、６５℃及び９０℃として、同じ操作を繰り返した。被処理水の温度４５℃のとき、酸化分解処理後の水のＴＯＣ濃度は０.３mgＣ／Ｌであり、ＴＯＣ除去率は９０.０％であった。また、残存過酸化水素濃度は１.２mg／Ｌであり、残存オゾン濃度は０.８mg／Ｌであった。触媒反応塔通水後の処理水中には、過酸化水素、オゾンともに検出されなかった。
被処理水の温度５５℃のとき、酸化分解処理後の水のＴＯＣ濃度は０.０６mgＣ／Ｌであり、ＴＯＣ除去率は９８.０％であった。また、残存過酸化水素濃度は０.４mg／Ｌであり、残存オゾン濃度は０.３mg／Ｌであった。触媒反応塔通水後の処理水中には、過酸化水素、オゾンともに検出されなかった。
被処理水の温度６５℃のとき、酸化分解処理後の水のＴＯＣ濃度は０.００６mgＣ／Ｌであり、ＴＯＣ除去率は９９.８％であった。また、残存過酸化水素濃度は０.２mg／Ｌであり、残存オゾン濃度は０.０８mg／Ｌであった。触媒反応塔通水後の処理水中には、過酸化水素、オゾンともに検出されなかった。
被処理水の温度９０℃のとき、酸化分解処理後の水にはＴＯＣは検出されず、ＴＯＣ除去率は１００％であった。また、残存過酸化水素濃度は０.０２mg／Ｌであり、残存オゾン濃度は０.０１mg／Ｌであった。触媒反応塔通水後の処理水中には、過酸化水素、オゾンともに検出されなかった。
比較例１、参考例及び実施例１の結果を、第１表に示す。
【００１２】
【表１】

【００１３】
第１表に見られるように、被処理水の温度を３５℃に調整し、過酸化水素とオゾンを添加して酸化分解することにより、水中の有機物の６０％が除去され、被処理水の温度を５５℃に調整すると、除去率は９８％に達する。また、有機物の酸化分解後に水中に残存する過酸化水素とオゾンは、白金触媒を充填した触媒反応塔へ通水することにより、完全に分解除去される。
一般的に、水温が高くなるとヘンリー定数が大きくなるために、ガスの溶解度は減少する。この場合も例外ではなく、反応系の温度が高くなるとオゾンの溶解度が減少するために、溶存オゾン不足による酸化反応の停滞が心配される。しかし、第１表より明らかなように、加温効果は、有機体炭素除去率の向上に貢献するという結果が得られている。これは、加温により、過酸化水素とオゾンの分解が効率よく促進され、有機物分解に必要なヒドロキシルラジカルの発生が促進されることとイソプロピルアルコール分解過程の活性化エネルギーが低下することによるものと考えられる。また、温度を高めるほど有機体炭素除去率は向上するが、４５℃あたりで除去率が平衡に近づくことから、被処理水の温度は４５〜６０℃であることが好ましいと考えられる。６０℃以上に加温するためには、加温コストが高くなる。
実施例２
超純水にイソプロピルアルコール５.０mg／Ｌを添加して、有機体炭素（ＴＯＣ）３.０mgＣ／Ｌを含有する水を調製し、試験用の被処理水とした。
被処理水２Ｌを反応槽に入れ、pHを７.３、温度を６０℃に調整したのち、過酸化水素水を過酸化水素の濃度が３０mg／Ｌになるように添加し、次いで電解式オゾン発生器［笹倉(株)、オゾンマスターＯＭ−２］で発生させたオゾンを濃度が３０mg／Ｌになるように添加した。被処理水の温度６０℃を保ったまま、反応槽の中で３０分撹拌し、イソプロピルアルコールの酸化分解処理を行った。酸化分解処理後の水にはＴＯＣは検出されず、ＴＯＣ除去率は１００％であった。また、残存過酸化水素濃度は０.２mg／Ｌであり、残存オゾン濃度は０.０８mg／Ｌであった。この水を、白金メッキした線径０.４mmのステンレス鋼網０.４Ｌを充填した触媒反応塔に、空間速度５ｈ^-1で通水した。触媒反応塔から流出した処理水中には、過酸化水素、オゾンともに検出されなかった。
さらに、被処理水のpHを９.０に調整して、同じ操作を繰り返した。酸化分解処理後の水にはＴＯＣは検出されず、ＴＯＣ除去率は１００％であった。また、残存過酸化水素濃度は０.０２mg／Ｌであり、残存オゾン濃度は０.０３mg／Ｌであった。この水を、白金メッキした線径０.４mmのステンレス鋼網０.４Ｌを充填した触媒反応塔に、空間速度５ｈ^-1で通水した。触媒反応塔から流出した処理水中には、過酸化水素、オゾンともに検出されなかった。
比較例２
実施例２と同じ被処理水を用い、pHを２.３、３.２及び１１.８、温度を６０℃に調整し、実施例２と同様にしてイソプロピルアルコールの分解を行い、酸化分解処理後の水のＴＯＣ濃度、残存過酸化水素濃度、残存オゾン濃度と、触媒反応塔から流出した処理水中の過酸化水素濃度、オゾン濃度を測定した。
被処理水のpHを２.３に調整したとき、酸化分解処理後の水のＴＯＣ濃度は０.６５mgＣ／Ｌであり、ＴＯＣ除去率は７８.３％であった。
被処理水のpHを３.２に調整したとき、酸化分解処理後の水のＴＯＣ濃度は０.１８mgＣ／Ｌであり、ＴＯＣ除去率は９４.０％であった。
被処理水のpHを１１.８に調整したとき、酸化分解処理後の水のＴＯＣ濃度は０.８２mgＣ／Ｌであり、ＴＯＣ除去率は７２.７％であった。
比較例３
実施例２と同じ被処理水を用い、pHを２.３、３.２、７.３、９.０及び１１.８、温度を２５℃に調整して、実施例２と同様にしてイソプロピルアルコールの分解を行い、酸化分解処理後の水のＴＯＣ濃度、残存過酸化水素濃度、残存オゾン濃度と、触媒反応塔から流出した処理水中の過酸化水素濃度、オゾン濃度を測定した。
被処理水のpHを２.３に調整したとき、酸化分解処理後の水のＴＯＣ濃度は２.７mgＣ／Ｌであり、ＴＯＣ除去率は１０.０％であった。
被処理水のpHを３.２に調整したとき、酸化分解処理後の水のＴＯＣ濃度は２.５３mgＣ／Ｌであり、ＴＯＣ除去率は１５.７％であった。
被処理水のpHを７.３に調整したとき、酸化分解処理後の水のＴＯＣ濃度は２.３３mgＣ／Ｌであり、ＴＯＣ除去率は２２.３％であった。
被処理水のpHを９.０に調整したとき、酸化分解処理後の水のＴＯＣ濃度は２.２５mgＣ／Ｌであり、ＴＯＣ除去率は２５.０％であった。
被処理水のpHを１１.８に調整したとき、酸化分解処理後の水のＴＯＣ濃度は２.３７mgＣ／Ｌであり、ＴＯＣ除去率は２１.０％であった。
実施例２及び比較例２〜３の結果を、第２表に示す。
【００１４】
【表２】

【００１５】
第２表に見られるように、被処理水のpHを７.３又は９.０に調整し、温度を６０℃に調整したとき、過酸化水素とオゾンを添加して酸化分解することにより、水中のイソプロピルアルコールは完全に分解除去される。これに対して、pHが低すぎる場合も、高すぎる場合も、有機体炭素の除去率は低下する。また、被処理水の温度が２５℃である場合は、有機体炭素の除去率は最高２５％にまでしか達しない。また、有機物の酸化分解後に水中に残存する過酸化水素とオゾンは、白金触媒を充填した触媒反応塔へ通水することにより、完全に分解除去される。
この結果から、すべてのpH領域において、加温により有機体炭素の除去が促進されることが分かる。これは、加温によるオゾンと過酸化水素の分解反応が促進され、有機物の分解に必要なヒドロキシルラジカルの生成が促進されることとイソプロピルアルコールの分解過程の活性化エネルギーが低下することによるものと考えられる。また、被処理水のpHをアルカリ側に傾けることによって有機体炭素の除去率は向上するが、pH１１以上の領域においては有機体炭素除去率は低下する。この除去率の低下は、ヒドロキシルラジカルの強力なスカベンジャーである炭酸イオンの影響が高pH領域において強くなるためと考えられる。以上の結果から、有機物の分解反応を促進させ、かつヒドロキシルラジカルへのスカベンジャー効果を最低限に抑えるpH領域は７〜１０であり、好ましくは８〜９.５であることが分かる。
【００１６】
【発明の効果】
本発明方法及び装置によれば、有機物を含有する被処理水のpHを７〜１０に調整し、３５℃以上に加温して、過酸化水素とオゾンを添加することにより、有機物を分解して有機体炭素を除去し、後段にイオン交換塔を設置するなどの多段処理を行うことなく、電子材料洗浄工程のリンス排水などを回収して再利用することができる。また、過酸化水素とオゾンが有機物の分解に消費されるために、後段の過酸化水素とオゾンの分解処理コストの負担を軽減し、処理コストを低減することができる。
【図面の簡単な説明】
【図１】図１は、本発明装置の一態様の工程系統図である。
【図２】図２は、実施例において用いた装置の説明図である。
【符号の説明】
１熱回収用熱交換器
２加温用熱交換器
３オゾン溶解槽
４エジェクター
５ポンプ
６反応槽
７ポンプ
８酸化剤分解塔
９排オゾンガス分解塔
１０反応槽
１１ポンプ
１２酸化剤分解塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for decomposing organic substances in water. More specifically, the present invention relates to a decomposition method and a decomposition apparatus for organic substances in water that can be suitably used for recovery and reuse of water containing organic substances such as rinse wastewater used in semiconductor manufacturing processes, liquid crystal manufacturing processes, and the like. .
[0002]
[Prior art]
In the semiconductor manufacturing process, a large amount of ultrapure water is used to clean silicon substrates, etc., and rinse wastewater is widely recovered and reused from the viewpoint of reducing environmental impact and effective use of water resources. ing. However, since the rinse waste water contains organic substances such as alcohol and surfactant, it is necessary to remove these substances in order to reuse the rinse waste water.
As a technique for removing organic substances in the rinsing waste water, a technique for promoting oxidation by combining ozone and hydrogen peroxide, ozone and ultraviolet light, ultraviolet light and hydrogen peroxide, ozone and alkali has been proposed. These techniques generate hydroxyl radicals having very strong oxidizing power, and decompose organic substances using this strong oxidizing power. Further, ozone and hydrogen peroxide used in these methods are only decomposed into oxygen or water after the treatment, and have an advantage of not generating secondary waste.
However, with these technologies alone, it is difficult to completely decompose organic substances and only intermediate products can be decomposed. Therefore, a deionization facility is provided after the decomposition process, or one more decomposition process is performed. Methods such as performing a two-stage decomposition process are taken. For example, JP-A-11-99394 discloses, as a method for removing organic matter in water, a first step of decomposing and removing organic matter by adding hydrogen peroxide and / or ozone to water to be treated, and treated water in the first step. There has been proposed a method of performing a second step of decomposing and removing organic substances by adding a sulfur compound containing a peroxide group. By performing the treatment in multiple stages as described above, the organic matter removal rate can be increased, but there is a disadvantage that the initial cost is increased and the installation space is increased. In addition, even when the two-stage decomposition treatment is performed, by-products are generated in the subsequent stage. Therefore, it is necessary to further provide a deionization treatment facility in the subsequent stage, and there is a problem that the load applied to the facility is large.
On the other hand, a method has been found in which hydrogen peroxide and ozone are added to the rinse waste water and the reaction tank is filled with a catalyst to accelerate the oxidation reaction and increase the decomposition rate of organic matter. Although it promotes the decomposition reaction and the decomposition of ozone is promoted by the catalyst, hydroxyl radicals effective for the decomposition of organic substances are not generated, so that a remarkable catalyst packing effect cannot be obtained.
[0003]
[Problems to be solved by the invention]
The present invention provides a method and apparatus for decomposing organic substances in water that can be suitably used for recovering and reusing water containing organic substances such as rinse wastewater used in semiconductor manufacturing processes and liquid crystal manufacturing processes. It was made as a purpose.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor adjusted the pH of water to be treated containing organic matter to 7 to 10 and then added hydrogen peroxide and ozone. The inventors have found that the organic matter in water can be effectively decomposed and removed by one-step treatment by oxidizing and decomposing the organic matter, and the present invention has been completed based on this finding.
That is, the present invention
(1) Adjust the pH of the rinse drain generated in the semiconductor manufacturing process or the liquid crystal manufacturing process to 7 to 10, adjust the temperature to 45 to 60 ° C., and obtain a heated rinse drain of pH 7 to 10 , 2-20 times by weight of hydrogen peroxide in organic carbon in the waste water in drainage, also with the addition of 2 to 20 times by weight of ozone, oxidative decomposition of the organic matter contained in the rinsing waste water in a reaction vessel or reaction column Then, the rinse waste water in which organic substances are oxidatively decomposed is passed through a reaction tank or packed tower filled with an oxidant decomposition catalyst, and hydrogen peroxide and ozone remaining in the rinse waste water are decomposed and removed by the oxidant decomposition catalyst. Te, the treated water from the rinsing waste water generated in the semiconductor manufacturing process or liquid crystal manufacturing process is collected and the treated water, the organic matter in the rinsing waste water, characterized in that the direct reuse without passing through the ion exchange column Decomposition method, and
(2) a semiconductor manufacturing process or means for adjusting the pH of the rinse wastewater generated in the liquid crystal manufacturing process 7-10, means for adjusting the temperature of the rinse wastewater 45 to 60 ° C., warmed pH of 7-10 Means for adding 2 to 20 times as much ozone as hydrogen peroxide of 2 to 20 times the organic carbon in the waste water to the rinse waste water, a reaction tank or a reaction tower for oxidatively decomposing organic substances contained in the rinse waste water, and In a reaction tank or packed tower filled with hydrogen peroxide and ozone oxidizing agent decomposition catalyst through which rinsing waste water in which organic matter is oxidatively decomposed is passed , and in a semiconductor manufacturing process or liquid crystal manufacturing process processed in the reaction tank or packed tower An apparatus for decomposing organic matter in rinse wastewater, characterized in that it has means for directly reusing the recovered treated water from the generated rinse wastewater without going through an ion exchange tower ;
Is to provide.
Furthermore, as a preferred embodiment of the present invention,
(3) The method for decomposing organic substances in water according to item 1, wherein the pH of the water to be treated is adjusted to 8 to 9.5, and
(4) The method for decomposing organic substances in water according to item 1, wherein ozone is added after hydrogen peroxide is added,
Can be mentioned.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The method for decomposing organic matter in water according to the present invention includes a step of adjusting the pH of the water to be treated to 7 to 10, a step of adjusting the temperature of the water to be treated to 35 ° C. or higher, hydrogen peroxide in the heated water to be treated. And a step of adding ozone, a step of oxidizing and decomposing organic substances contained in the water to be treated, and a step of decomposing and removing hydrogen peroxide and ozone remaining in the water to be treated in which the organic substances are oxidized and decomposed.
The apparatus for decomposing organic matter in water according to the present invention comprises means for adjusting the pH of the water to be treated to 7 to 10, means for adjusting the temperature of the water to be treated to 35 ° C. or higher, hydrogen peroxide on the heated water to be treated. And means for adding ozone, means for oxidizing and decomposing organic substances contained in the water to be treated, and means for decomposing hydrogen peroxide and ozone remaining in the water to be treated in which organic substances are oxidized and decomposed.
There is no particular limitation on the water to be treated to which the method of the present invention and the apparatus of the present invention are applied, but particularly suitable for water having an organic carbon concentration of 1 to 100 mg / L, such as rinse wastewater generated in the electronic material cleaning step. Can be applied.
[0006]
In the present invention, the pH of the water to be treated is adjusted to 7 to 10, preferably 8 to 9.5. Even if the pH is less than 7 or more than 10, the decomposition and removal rate of organic substances may be reduced. There is no restriction | limiting in particular in the method of adjusting the pH of to-be-processed water, For example, pH can be adjusted by adding alkalis, such as sodium hydroxide and potassium hydroxide. The pH of the water to be treated can be adjusted at any stage as long as it is a step prior to the addition of hydrogen peroxide and ozone to the water to be treated.
In this invention, the temperature of to-be-processed water is adjusted to 35 degreeC or more, and the subsequent process is performed in the heated state. If the temperature of the water to be treated is less than 35 ° C., the organic matter may not be sufficiently decomposed and removed. Increasing the temperature of the water to be treated improves the decomposition and removal rate of organic matter, but the removal rate approaches equilibrium around 45 ° C, so the temperature of the water to be treated is preferably adjusted to 45 to 60 ° C. In order to heat to 60 degreeC or more, there exists a possibility that a heat energy cost may increase.
In the present invention, there is no particular limitation on the temperature adjustment method of the water to be treated. However, after heat exchange between the water to be treated and the treated water, heating the water to be treated to a predetermined temperature can reduce thermal energy. Preferred from above. In the present invention, there is no limitation on the order of adjusting the pH of the water to be treated to 7 to 10 and adjusting the temperature of the water to be treated to 35 ° C. or higher, and the temperature is adjusted after adjusting the pH of the water to be treated. The pH can be adjusted after adjusting the temperature of the water to be treated, or the pH can be adjusted while adjusting the temperature of the water to be treated.
[0007]
In the present invention, the temperature adjustment of the water to be treated and the order of addition of hydrogen peroxide and ozone are not particularly limited. For example, after adjusting the temperature of the water to be treated, hydrogen peroxide and ozone can be added, After hydrogen peroxide and ozone are added to the water to be treated, the temperature can be adjusted, and hydrogen peroxide and ozone can be added while adjusting the temperature of the water to be treated. It is also possible to add ozone after adding hydrogen and adjusting the temperature. Among these, after adjusting the temperature of the water to be treated, the method of adding hydrogen peroxide and ozone can prevent corrosion of the heat exchanger piping, prevent loss due to ozone self-decomposition, and overoxidize Since decomposition of the organic substance starts immediately after the addition of hydrogen and ozone, it can be suitably used.
In the present invention, there is no particular limitation on the order of adding hydrogen peroxide and ozone to the water to be treated. After adding hydrogen peroxide, ozone can be added, and after adding ozone, hydrogen peroxide is added. Alternatively, hydrogen peroxide and ozone can be added simultaneously. However, ozone is a substance that is easily self-degraded, and it is preferable to add ozone last in order to efficiently use ozone for decomposing organic substances.
[0008]
In the method of the present invention, the amount of hydrogen peroxide added to the water to be treated is not particularly limited, but is preferably 2 to 20 times by weight with respect to organic carbon in the water to be treated, and 5 to 10 times by weight. It is more preferable that If the amount of hydrogen peroxide added is less than 2 times the weight of organic carbon, the organic matter may not be sufficiently decomposed and removed. The amount of hydrogen peroxide added is usually less than 20 times the weight of organic carbon, and the addition of hydrogen peroxide exceeding 20 weight times of organic carbon increases the load of the subsequent hydrogen peroxide removal process. In addition, the equipment may be corroded.
In the method of the present invention, the amount of ozone added to the water to be treated is not particularly limited, but it is preferably 2 to 20 times by weight and preferably 5 to 10 times by weight with respect to the organic carbon in the water to be treated. It is more preferable. If the amount of ozone added is less than 2 times the weight of organic carbon, the organic matter may not be sufficiently decomposed and removed. The amount of ozone added is usually less than 20 times the weight of organic carbon, and the addition of ozone exceeding 20 times the amount of organic carbon increases the amount of ozone that self-decomposes and increases the amount of ozone in the latter stage. There is a risk of increasing the load of the removal process.
In the present invention, there is no particular limitation on the method of adding ozone to the water to be treated, for example, ozone can be added to the feed water pump suction port using a pump such as 15UPD02S manufactured by Nigoku Machine Industry Co., Ltd. Ejector can be installed to add ozone, or ozone can be directly diffused into the lower part of the dissolution tank or reaction tank. The ozone added to the water to be treated does not necessarily need to be physically completely dissolved, and may be in the form of fine bubbles dispersed in the water to be treated.
[0009]
In the present invention, there is no particular limitation on the method for decomposing organic substances contained in the water to be treated to which hydrogen peroxide and ozone are added. For example, it can be decomposed batchwise in a reaction apparatus, or continuously. It can also be processed. There is no restriction | limiting in particular in the form of a reaction apparatus, For example, it can be set as the reaction tank in which to-be-processed water is mixed uniformly, or it can also be set as the reaction tower in which to-be-processed water is continuously passed.
In the present invention, after oxidizing and decomposing organic substances contained in the water to be treated, hydrogen peroxide and ozone remaining in the water to be treated are decomposed. By adding hydrogen peroxide and ozone to the temperature-treated water to be treated, most of the organic substances in the water to be treated are oxidatively decomposed. Hydrogen peroxide and ozone remain. The quality of recovered water can be improved by decomposing and removing the remaining hydrogen peroxide and ozone after the oxidative decomposition of the organic matter. There is no particular limitation on the method for decomposing hydrogen peroxide and ozone. For example, residual hydrogen peroxide and ozone can be obtained by passing water through a reaction tank or packed tower filled with an oxidant decomposition catalyst such as activated carbon or platinum or ruthenium. Can be decomposed and removed.
[0010]
FIG. 1 is a process flow diagram of one aspect of the apparatus of the present invention. In the heat recovery heat exchanger 1, heat exchange is performed between the treated water and the treated water, and heat energy is collected from the treated water to preheat the treated water. Next, the water to be treated is heated to a predetermined temperature in the heat exchanger 2 for heating. Alkali is added to the heated water to be treated to adjust to a predetermined pH, hydrogen peroxide is then added, and ozone is further added in the ozone dissolution tank 3. The surplus gas in the ozone dissolution tank is returned to the ejector 4 provided between the heat exchanger for heating and the ozone dissolution tank, and is dissolved again. By returning the surplus gas in the ozone dissolution tank to the water supply line, the burden of exhaust ozone gas treatment can be reduced. The water to be treated to which hydrogen peroxide and ozone are added is sent to the reaction tank 6 by the pump 5, and the organic matter contained in the water is oxidatively decomposed. The water in which the organic matter is oxidatively decomposed is sent to the oxidant decomposition tower 8 by the pump 7, and the hydrogen peroxide and ozone remaining in the water are decomposed to become treated water. The treated water is reused after it is cooled by releasing heat energy via the heat recovery heat exchanger 1. The gas discharged from the reaction tank 6 is released into the atmosphere after decomposing and removing ozone in the exhaust ozone gas decomposition tower 9.
According to the method and apparatus of the present invention, organic substances in the water to be treated can be efficiently decomposed and removed by one-stage treatment using a single reaction tank without performing multi-stage treatment. Further, the water that has passed through the reaction tank is further passed through an oxidant decomposition tower, and the remaining hydrogen peroxide and ozone are decomposed to obtain high-quality treated water. Furthermore, due to the effects of pH adjustment and heating, ozone and hydrogen peroxide are efficiently used for the decomposition reaction of organic matter, so that the cost of the oxidant and the cost of the oxidant decomposition treatment can be reduced.
[0011]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
FIG. 2 is an explanatory diagram of an apparatus used in Examples and Comparative Examples. Water to be treated is charged into the reaction tank 10, and temperature adjustment and pH adjustment by alkali addition are performed. Next, the organic matter is oxidatively decomposed while stirring the water to be treated for a predetermined time. The treated water in which the organic matter has been oxidatively decomposed is sent to the oxidant decomposition tower 12 by the pump 11 to decompose hydrogen peroxide and ozone remaining in the water to obtain treated water.
In Examples and Comparative Examples, the organic carbon (TOC) concentration was measured according to JIS K 0551. The hydrogen peroxide (H ₂ O ₂ ) concentration was measured by the DMP method (absorbance measurement by reduction of neocloproin), and the ozone (O ₃ ) concentration was measured by the absorbance (wavelength 254 nm). However, the liquid from which ozone was desorbed by aeration was measured as a control sample.
Comparative Example 1
Isopropyl alcohol 5.0 mg / L was added to ultrapure water to prepare water containing organic carbon (TOC) 3.0 mg C / L, which was treated water for testing. The pH of the water to be treated was 7.0, and the water temperature was 25 ° C.
2 L of this water to be treated is put into a reaction tank, hydrogen peroxide is added so that the concentration of hydrogen peroxide is 30 mg / L, and then an electrolytic ozone generator [Sakura, Inc., Ozone Master OM-2] Was added so that the concentration was 30 mg / L. While maintaining the temperature of the water to be treated at 25 ° C., the reaction vessel was stirred for 30 minutes to oxidatively decompose isopropyl alcohol. The TOC concentration of water after the oxidative decomposition treatment was 2.4 mg C / L, and the TOC removal rate was 20.0%. The residual hydrogen peroxide concentration was 5.5 mg / L and the residual ozone concentration was 2 mg / L. This water was passed through a catalytic reaction tower filled with 0.4 L of a platinum-plated stainless steel net having a wire diameter of 0.4 mm at a space velocity of 5 h ⁻¹ . Neither hydrogen peroxide nor ozone was detected in the treated water flowing out from the catalytic reaction tower.
Reference Example The same treated water as in Comparative Example 1 was used, and the treatment temperature was changed to decompose isopropyl alcohol.
2L of water to be treated is put into a reaction vessel, heated to 35 ° C., hydrogen peroxide solution is added so that the concentration of hydrogen peroxide becomes 30 mg / L, and then an electrolytic ozone generator [Sakura Co., Ltd., Ozone generated by ozone master OM-2] was added so that the concentration was 30 mg / L. While maintaining the temperature of the water to be treated at 35 ° C., the reaction vessel was stirred for 30 minutes to oxidatively decompose isopropyl alcohol. The TOC concentration of water after the oxidative decomposition treatment was 1.2 mg C / L, and the TOC removal rate was 60.0%. Further, the residual hydrogen peroxide concentration was 3.1 mg / L, and the residual ozone concentration was 1.2 mg / L. This water was passed through a catalytic reaction tower packed with 0.4 L of a platinum-plated stainless steel net having a wire diameter of 0.4 mm at a space velocity of 5 h ^-1 while maintaining a temperature of 35 ° C. Neither hydrogen peroxide nor ozone was detected in the treated water flowing out from the catalytic reaction tower.
Example 1
The same operation was repeated with the temperature of the water to be treated being 45 ° C, 55 ° C, 65 ° C and 90 ° C under the same conditions as in the reference example . When the temperature of to-be-processed water was 45 degreeC, the TOC density | concentration of the water after an oxidative decomposition process was 0.3 mgC / L, and the TOC removal rate was 90.0%. The residual hydrogen peroxide concentration was 1.2 mg / L, and the residual ozone concentration was 0.8 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalytic reaction tower.
When the temperature of to-be-processed water was 55 degreeC, the TOC density | concentration of the water after an oxidative decomposition process was 0.06 mgC / L, and the TOC removal rate was 98.0%. The residual hydrogen peroxide concentration was 0.4 mg / L, and the residual ozone concentration was 0.3 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalytic reaction tower.
When the temperature of the water to be treated was 65 ° C., the TOC concentration of the water after the oxidative decomposition treatment was 0.006 mg C / L, and the TOC removal rate was 99.8%. The residual hydrogen peroxide concentration was 0.2 mg / L, and the residual ozone concentration was 0.08 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalytic reaction tower.
When the temperature of the water to be treated was 90 ° C., TOC was not detected in the water after the oxidative decomposition treatment, and the TOC removal rate was 100%. The residual hydrogen peroxide concentration was 0.02 mg / L, and the residual ozone concentration was 0.01 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalytic reaction tower.
The results of Comparative Example 1 , Reference Example and Example 1 are shown in Table 1.
[0012]
[Table 1]

[0013]
As can be seen in Table 1, by adjusting the temperature of the water to be treated to 35 ° C. and adding hydrogen peroxide and ozone to oxidative decomposition, 60% of the organic matter in the water is removed, and the water to be treated is removed. When the temperature is adjusted to 55 ° C., the removal rate reaches 98%. Further, hydrogen peroxide and ozone remaining in water after the oxidative decomposition of organic matter are completely decomposed and removed by passing water through a catalytic reaction tower packed with a platinum catalyst.
In general, as the water temperature increases, the Henry's constant increases, so the gas solubility decreases. In this case, there is no exception, and the solubility of ozone decreases as the temperature of the reaction system rises, so there is a concern about the stagnation of the oxidation reaction due to the lack of dissolved ozone. However, as is apparent from Table 1, the result that the heating effect contributes to the improvement of the organic carbon removal rate is obtained. This is because heating effectively promotes the decomposition of hydrogen peroxide and ozone, promotes the generation of hydroxyl radicals necessary for organic matter decomposition, and decreases the activation energy of the isopropyl alcohol decomposition process. Conceivable. Further, the organic carbon removal rate is improved as the temperature is increased. However, since the removal rate approaches equilibrium at around 45 ° C, it is considered that the temperature of the water to be treated is preferably 45 to 60 ° C. In order to heat to 60 degreeC or more, a heating cost becomes high.
Example 2
Isopropyl alcohol 5.0 mg / L was added to ultrapure water to prepare water containing organic carbon (TOC) 3.0 mg C / L, which was treated water for testing.
2L of water to be treated is placed in a reaction tank, pH is adjusted to 7.3, temperature is adjusted to 60 ° C, hydrogen peroxide is added so that the concentration of hydrogen peroxide is 30 mg / L, and then electrolytic ozone Ozone generated by a generator [Sakura, Inc., Ozone Master OM-2] was added so that the concentration was 30 mg / L. While maintaining the temperature of the water to be treated at 60 ° C., the reaction vessel was stirred for 30 minutes to oxidatively decompose isopropyl alcohol. TOC was not detected in the water after oxidative decomposition treatment, and the TOC removal rate was 100%. The residual hydrogen peroxide concentration was 0.2 mg / L, and the residual ozone concentration was 0.08 mg / L. This water was passed through a catalytic reaction tower packed with 0.4 L of a platinum-plated stainless steel net having a wire diameter of 0.4 mm at a space velocity of 5 h- ¹ . Neither hydrogen peroxide nor ozone was detected in the treated water flowing out from the catalytic reaction tower.
Furthermore, the same operation was repeated by adjusting the pH of the water to be treated to 9.0. TOC was not detected in the water after oxidative decomposition treatment, and the TOC removal rate was 100%. Further, the residual hydrogen peroxide concentration was 0.02 mg / L, and the residual ozone concentration was 0.03 mg / L. This water was passed through a catalytic reaction tower packed with 0.4 L of a platinum-plated stainless steel net having a wire diameter of 0.4 mm at a space velocity of 5 h- ¹ . Neither hydrogen peroxide nor ozone was detected in the treated water flowing out from the catalytic reaction tower.
Comparative Example 2
Using the same water to be treated as in Example 2, adjusting the pH to 2.3, 3.2 and 11.8, adjusting the temperature to 60 ° C., the isopropyl alcohol was decomposed in the same manner as in Example 2, and the oxidative decomposition treatment was performed. The water TOC concentration, residual hydrogen peroxide concentration, residual ozone concentration, and the hydrogen peroxide concentration and ozone concentration in the treated water flowing out from the catalytic reaction tower were measured.
When the pH of the water to be treated was adjusted to 2.3, the TOC concentration of the water after the oxidative decomposition treatment was 0.65 mg C / L, and the TOC removal rate was 78.3%.
When the pH of the water to be treated was adjusted to 3.2, the TOC concentration of the water after the oxidative decomposition treatment was 0.18 mg C / L, and the TOC removal rate was 94.0%.
When the pH of the water to be treated was adjusted to 11.8, the TOC concentration of the water after the oxidative decomposition treatment was 0.82 mg C / L, and the TOC removal rate was 72.7%.
Comparative Example 3
Using the same treated water as in Example 2, adjusting the pH to 2.3, 3.2, 7.3, 9.0 and 11.8, and the temperature to 25 ° C., the same as in Example 2, the isopropyl The alcohol was decomposed, and the TOC concentration, residual hydrogen peroxide concentration, residual ozone concentration of water after the oxidative decomposition treatment, and the hydrogen peroxide concentration and ozone concentration in the treated water flowing out from the catalytic reaction tower were measured.
When the pH of the water to be treated was adjusted to 2.3, the TOC concentration of the water after the oxidative decomposition treatment was 2.7 mgC / L, and the TOC removal rate was 10.0%.
When the pH of the water to be treated was adjusted to 3.2, the TOC concentration of the water after the oxidative decomposition treatment was 2.53 mg C / L, and the TOC removal rate was 15.7%.
When the pH of the water to be treated was adjusted to 7.3, the TOC concentration of the water after the oxidative decomposition treatment was 2.33 mg C / L, and the TOC removal rate was 22.3%.
When the pH of the water to be treated was adjusted to 9.0, the TOC concentration of the water after the oxidative decomposition treatment was 2.25 mg C / L, and the TOC removal rate was 25.0%.
When the pH of the water to be treated was adjusted to 11.8, the TOC concentration of the water after the oxidative decomposition treatment was 2.37 mg C / L, and the TOC removal rate was 21.0%.
The results of Example 2 and Comparative Examples 2-3 are shown in Table 2.
[0014]
[Table 2]

[0015]
As can be seen in Table 2, when the pH of the water to be treated is adjusted to 7.3 or 9.0 and the temperature is adjusted to 60 ° C., by adding hydrogen peroxide and ozone to oxidative decomposition, Isopropyl alcohol in water is completely decomposed and removed. On the other hand, when the pH is too low or too high, the organic carbon removal rate decreases. Moreover, when the temperature of to-be-processed water is 25 degreeC, the removal rate of organic carbon reaches only a maximum of 25%. Further, hydrogen peroxide and ozone remaining in water after the oxidative decomposition of organic matter are completely decomposed and removed by passing water through a catalytic reaction tower packed with a platinum catalyst.
From this result, it is understood that the removal of organic carbon is promoted by heating in all pH ranges. This is because the decomposition reaction of ozone and hydrogen peroxide by heating is accelerated, the generation of hydroxyl radicals necessary for the decomposition of organic matter is promoted, and the activation energy of the decomposition process of isopropyl alcohol is reduced. Conceivable. Further, the removal rate of organic carbon is improved by inclining the pH of the water to be treated to the alkali side, but the removal rate of organic carbon is lowered in the region of pH 11 or higher. This decrease in the removal rate is thought to be because the influence of carbonate ions, which are strong scavengers of hydroxyl radicals, becomes stronger in the high pH region. From the above results, it can be seen that the pH range that promotes the decomposition reaction of organic substances and minimizes the scavenger effect on the hydroxyl radical is 7 to 10, preferably 8 to 9.5.
[0016]
【The invention's effect】
According to the method and apparatus of the present invention, the pH of water to be treated containing organic matter is adjusted to 7 to 10, heated to 35 ° C. or higher, and hydrogen peroxide and ozone are added to decompose the organic matter. Thus, it is possible to collect and reuse the rinse waste water in the electronic material cleaning step without performing multi-stage treatment such as removing organic carbon and installing an ion exchange tower in the subsequent stage. Further, since hydrogen peroxide and ozone are consumed for the decomposition of the organic matter, the burden of the decomposition treatment cost of the subsequent hydrogen peroxide and ozone can be reduced, and the treatment cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a process flow diagram of one embodiment of the apparatus of the present invention.
FIG. 2 is an explanatory diagram of an apparatus used in the example.
[Explanation of symbols]
1 Heat recovery heat exchanger 2 Heating heat exchanger 3 Ozone dissolution tank 4 Ejector 5 Pump 6 Reaction tank 7 Pump 8 Oxidant decomposition tower 9 Waste ozone gas decomposition tower 10 Reaction tank 11 Pump 12 Oxidizer decomposition tower

Claims

The semiconductor manufacturing process or pH of the rinsing waste water generated in the liquid crystal manufacturing process is adjusted to 7-10, and the temperature adjusted to 45 to 60 ° C., to obtain a rinsing waste water pH7~10 which is heated, the drainage 2-20 times by weight of hydrogen peroxide in organic carbon in the waste water, also with the addition of 2 to 20 times by weight of ozone, oxidative decomposition of the organic matter contained in the rinsing waste water in a reaction vessel or reaction column, organic Rinse wastewater that has been oxidatively decomposed is passed through a reaction tank or packed tower filled with an oxidizer decomposition catalyst, and hydrogen peroxide and ozone remaining in the rinse wastewater are decomposed and removed by the oxidizer decomposition catalyst , and the semiconductor A method for decomposing organic matter in rinsing waste water, wherein treated water from a rinsing waste water generated in a manufacturing process or a liquid crystal manufacturing process is collected, and the treated water is directly reused without going through an ion exchange tower .

Means for adjusting the pH of the rinse water generated in the semiconductor manufacturing process or the liquid crystal manufacturing process to 7 to 10, means for adjusting the temperature of the rinse water to 45 to 60 ° C., and the heated pH to the rinse water of 7 to 10 Means for adding 2 to 20 times by weight of ozone as well as 2 to 20 times by weight of hydrogen peroxide of organic carbon in the waste water, reaction tank or reaction tower for oxidizing and decomposing organic substances contained in the rinse waste water, and the organic matter is oxidized Reactor or packed tower filled with hydrogen peroxide and ozone oxidizing agent decomposition catalyst through which decomposed rinse wastewater is passed , and rinse generated in the semiconductor manufacturing process or liquid crystal manufacturing process processed in the reaction tank or packed tower An apparatus for decomposing organic matter in rinsing waste water, comprising means for directly recycling treated water from waste water without passing through an ion exchange tower .