JP2004000963A

JP2004000963A - Treatment method of boron-containing drainage, and medicament used for the same

Info

Publication number: JP2004000963A
Application number: JP2003124485A
Authority: JP
Inventors: Kenji Tatsumi; 辰巳　憲司; Shinji Wada; 和田　愼二; Yasuhiro Yugawa; 湯川　恭啓
Original assignee: Mitsubishi Corp; National Institute of Advanced Industrial Science and Technology AIST
Current assignee: Mitsubishi Corp; National Institute of Advanced Industrial Science and Technology AIST
Priority date: 2002-04-26
Filing date: 2003-04-28
Publication date: 2004-01-08
Anticipated expiration: 2023-04-28
Also published as: JP4086297B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently removing dissolved boron from water to be treated and a boron removing agent used for the same. <P>SOLUTION: The dissolved boron is settled and separated as a hardly soluble substance by allowing a polyvalent anionic substance and rare earth element ions to exist in the dissolved boron-containing water to be treated, then adjusting its pH to 9 to 13. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、被処理水中に含まれる溶存ホウ素の除去方法および除去剤ならびに発生スラッジ量を低減するための方法に関するものである。
【０００２】
【従来の技術】
ホウ素の排水基準は、海域以外に排出する場合、１０ｐｐｍと定められている（平成１３年７月１日に施行され、業種ごとに３年間の暫定基準が定められている）。従来、ホウ素含有水の処理方法としては、イオン交換樹脂により吸着させる方法や、硫酸アルミニウム及び水酸化カルシウムにより不溶性沈殿物とする方法等が知られているが、いずれも効率的な方法とはいえず、また、多量のスラッジを生成するという問題があった。
近年では、工業排水などによる環境汚染の問題の解決が重要視されていることから、ホウ素の有効な除去方法に対する要求も高い。
凝集沈殿法と陰イオン交換樹脂又はホウ素選択性イオン交換樹脂を組み合わせた方法が提案されている（特許文献１参照）が、凝集沈殿法の除去効率が悪いため後段の吸着樹脂に負荷が掛かり、そのためコストが掛かりすぎる問題と、吸着樹脂の再生液の処理の問題があり、実用には供されていない。さらに、低濃度のホウ素含有排水を希土類元素の含水酸化物を用いて処理する方法も提案されている（特許文献２参照）が、固体を用いるため処理性が悪く、処理に時間が掛かる等の問題があり実用には供されていない。
一方、ホウ素含有排水をホウ素選択吸着イオン交換樹脂等に一旦吸着させ、その濃縮された脱離液に、希土類元素イオン及び／又はＩＶＢ族元素イオンを放出する化合物を添加することにより、ホウ素を除去できることを見出した（特許文献３参照）。しかし、希土類元素イオン及び／又はＩＶＢ族元素イオンを放出する化合物を添加する方法は、低濃度のホウ素含有排水の処理には有効ではなく、一旦濃縮しなければならない。このため、新たに吸着装置を必要とし、さらに煩雑な吸着及び脱離の操作を必要とする。また、一般に希土類元素とホウ素が反応して生成するフロックは嵩高く、沈降性が良くない。
また、ホウ素含有排水を濃縮した後に、ランタン化合物からなるホウ素固定剤を添加して不溶性沈殿物を生成し、ホウ素を除去できることを見出した（特許文献４参照）。しかし、この方法も特許文献３と同様に、一旦濃縮しなければならないし、一般にランタンイオンとホウ素が反応して生成するフロックは嵩高く、沈降性が良くない。
【０００３】
【特許文献１】
特開昭５７−１８０４９３号公報
【特許文献２】
特公平３−２２２３８号公報
【特許文献３】
特開平１１−２３５５９５号公報
【特許文献４】
特開２０００−２６３０６４号公報
【０００４】
【発明が解決しようとする課題】
本発明は、被処理水中から溶存ホウ素を効率よく除去する方法を提供することを目的とする。また、それに用いるホウ素の除去剤を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明者らは、前記課題を解決すべく鋭意研究を重ねた結果、被処理水中に多価陰イオン性物質と希土類元素イオンを存在させた状態でｐＨを９〜１３に調整することにより、被処理水中に溶存するホウ素を難溶性物質として沈殿分離させることができることを見い出し、この知見に基づき本発明を完成するに至った。
すなわち、本発明は、
（１）溶存ホウ素を含有する被処理水中に、多価陰イオン性物質と希土類元素イオンを存在させｐＨを９〜１３において、該溶存ホウ素を難溶性物質として沈殿分離させることを特徴とするホウ素含有排水の処理方法、
（２）該多価陰イオンが硫酸イオンで、多価陰イオン性物質が水中で溶解して硫酸イオンを放出する硫酸化合物である（１）項記載の該溶存ホウ素を難溶性物質として沈殿分離させることを特徴とするホウ素含有排水の処理方法、
（３）該多価陰イオンが炭酸イオンで、多価陰イオン性物質が水中で溶解して炭酸イオンを放出する炭酸化合物である（１）項記載の該溶存ホウ素を難溶性物質として沈殿分離させることを特徴とするホウ素含有排水の処理方法、
（４）該多価陰イオンが陰イオン性高分子化合物である（１）項記載の該溶存ホウ素を難溶性物質として沈殿分離させることを特徴とするホウ素含有排水の処理方法、
（５）該陰イオン性高分子化合物が陰イオン性高分子凝集剤である（４）項に記載のホウ素含有排水の処理方法、
（６）無害性多価金属イオンを存在させる（１）〜（５）項記載のいずれか１項に記載の方法、
（７）該無害性多価金属イオンが、カルシウムイオン、マグネシウムイオン、鉄イオン又はアルミニウムイオンの少なくとも１種であることを特徴とする（６）項に記載のホウ素含有排水の処理方法、
（８）該希土類元素イオンが、希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液として被処理水中に添加されることを特徴とする（１）〜（７）項のいずれか１項に記載のホウ素含有排水の処理方法、
（９）該溶存ホウ素を難溶性物質として沈殿分離させた後、処理によって発生したスラッジを原被処理水に返送することを特徴とする（１）〜（８）項のいずれか１項に記載のホウ素含有排水の処理方法、
（１０）（１）〜（９）項のいずれか１項に記載の方法に使用される薬剤であって、希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液からなる群から選択される少なくとも一種からなることを特徴とする薬剤、
（１１）（１）〜（９）項のいずれか１項に記載の方法に使用される薬剤であって、供給される希土類元素イオンおよび硫酸イオンが薬剤として構成されるものであり、その薬剤が、（ｉ）希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液からなる群から選択される少なくとも一種と（ｉｉ）硫酸、硫酸塩水溶液又はそれらの混合物、との混合物からなることを特徴とする薬剤、
（１２）（１）〜（９）項のいずれか１項に記載の方法に使用される薬剤であって、供給される希土類元素イオンおよび鉄イオンが薬剤として構成されるものであり、その薬剤が、（ｉ）希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液からなる群から選択される少なくとも一種と（ｉｉ）塩化第二鉄溶液、ポリ鉄水溶液又はそれらの混合物、との混合物からなることを特徴とする薬剤、および
（１３）（１）〜（９）項のいずれか１項に記載の方法に使用される薬剤であって、供給される希土類元素イオンおよびアルミニウムイオンが薬剤として構成されるものであり、その薬剤が、（ｉ）希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液からなる群から選択される少なくとも一種と（ｉｉ）硫酸アルミニウム溶液、ポリ塩化アルミニウム溶液又はそれらの混合物、との混合物からなることを特徴とする薬剤
を提供するものである。
【０００６】
【発明の実施の形態】
以下、本発明について詳細に説明する。
本発明では、希土類元素イオンを被処理水中に存在させる。この希土類元素イオンがホウ素除去剤（以下、単に除去剤ともいう）としての役割を果たす。被処理水への添加する際の希土類元素イオンは本発明の目的を達成できればいかなる状態であってもよいが希土類元素含有溶液として添加するのが好ましく、希土類元素の酸化物、水酸化物、炭酸塩、リン酸塩、酢酸塩又はハロゲン化物の水溶液、塩酸溶液又は硫酸溶液として被処理水へ添加するのが好ましい。その濃度は特に限定されるものではないが、操作性を考慮すると、例えば希土類元素酸化物の塩酸溶液の場合は、塩酸溶液中の希土類元素を酸化物として好ましくは１０〜４０質量％、より好ましくは２０〜３５質量％である。
【０００７】
希土類元素イオンの中でもランタンイオン、セリウムイオンの使用が好ましくランタンイオンの使用がより好ましい。
また、本発明において除去剤として用いる希土類元素含有溶液は、希土類元素の混合物の溶液もしくは、希土類元素の単独又は混合液の形態で用いることができる。ランタンとセリウム及びイッテルビウムの溶液の使用が好ましく、ランタンとセリウムとの溶液がより好ましい。好ましい具体例としては、ランタンとセリウムとイッテルビウムの塩酸溶液（濃度は酸化物として３２．５質量％、その中の組成は、ランタン９５質量％、セリウム４．９質量％、イッテルビウム０．１質量％）である。
【０００８】
本発明の特徴の一つは、除去剤への希土類元素イオンの供給源として、高度に精製分離された高価な希土類化合物を用いることは必要ではないことである。すなわち、本発明で使用される除去剤（以下、除去剤［Ｉ］ともいう）は、精製された希土類元素で調製する必要はない。例えば、希土類元素を含有している鉱石から、礫、及び鉛等の重金属や放射性元素を除いたものを塩酸溶解させた後に粗精製したものを使用することができる。このときの塩酸濃度は、０．１〜１２規定が好ましく、より好ましくは５〜１２規定、さらに好ましくは８〜１２規定であり、希土類元素イオンの濃度は特に限定されるものではないが、操作性を考慮すると、酸化物として好ましくは１０〜６０質量％、より好ましくは２０〜６０質量％、さらに好ましくは３０〜５０質量％である。溶解時間は、完全に溶解すればよく、特に限定されないが、０．５時間から２時間程度で十分である。
【０００９】
本発明において、希土類元素イオンの添加量は、被処理水中のホウ素の濃度にもよるが、ホウ素１モル当たり、好ましくは０．０５〜５０モル、より好ましくは０．１〜３０モル、さらに好ましくは０．５〜２０モルである。
【００１０】
本発明では、多価陰イオン性物質を併用する。多価陰イオン性物質を添加することによって、沈降性、脱水性のよい沈殿を生成し、沈殿を固液分離しやすくなる。多価陰イオン性物質としては、硫酸塩、炭酸塩、陰イオン性高分子凝集剤等が好ましく、これらを単独で用いても良いし、併せて用いても良い。硫酸塩としては、例えば硫酸ナトリウム、硫酸第一鉄、硫酸第二鉄等が挙げられる。炭酸塩としては炭酸ナトリウム、炭酸カリウム等が挙げられる。陰イオン性高分子凝集剤としては、例えばカルボキシメチルセルロースナトリウム、アルギン酸ナトリウム、ポリアクリル酸、アクリルアミドとアクリル酸との共重合体及び／その塩等のアニオン性有機系凝集剤が挙げられる。被処理水への添加量は、例えば硫酸塩や炭酸塩では、好ましくは０．０１〜１００ｍＭ、より好ましくは０．０５〜５０ｍＭ、さらに好ましくは０．１〜１０ｍＭである。高分子凝集剤では、好ましくは０．０１〜２０ｐｐｍ、より好ましくは０．０５〜２０ｐｐｍ、さらに好ましくは０．１〜１０ｐｐｍである。
【００１１】
本発明では用いられる多価陰イオンとしては、硫酸イオンが特に好ましい。硫酸イオンを併用する場合、前述のように硫酸塩を添加してもよいが、あらかじめ希土類元素イオンと硫酸イオンを含む処理剤として調製しておき、その処理剤をホウ素を含む被処理水に添加してもよい。処理剤を調製する方法としては、希土類元素の水溶液、塩酸溶液、硫酸溶液などと硫酸塩化合物を混合するなど、いずれの方法でも良いが、入手が容易な希土類の塩酸溶液と硫酸を混合して調製するのがより簡便である。好ましい具体例としては、ランタンとセリウムとイッテルビウムの塩酸溶液（特に具体例を挙げると濃度は酸化物として３２．５質量％、その中の組成は、ランタン９５質量％、セリウム４．９質量％、イッテルビウム０．１質量％）と硫酸（１８Ｍ）の容積比９０：１の混合溶液である。
【００１２】
多価陰イオン性物質の添加の順序は制限がない。多価陰イオン性物質を添加しておいて、その後に希土類元素イオンを存在させてｐＨ調整を行うのが好ましいが希土類元素イオンを存在させてｐＨ調整をした後に多価陰イオン性物質を添加してもよい。少なくとも溶存ホウ素を難溶性物質とするときにｐＨ９〜１３であればよい。
【００１３】
本発明では、除去剤の添加後、沈殿が生じるようにｐＨを調整して排水中に溶存するホウ素を除去する。そのｐＨは、一般的には９〜１３の範囲、好ましくは９〜１２の範囲、より好ましくは１０〜１２の範囲である。
【００１４】
被処理水のｐＨをアルカリ性領域や酸性領域に調節する場合、ｐＨ調節剤が用いられるが、このようなｐＨ調節剤としては、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸カリウム、水酸化カルシウム等のアルカリ性物質、もしくは塩酸、硫酸、硝酸、硫酸アルミニウム等の酸性物質が用いられる。
【００１５】
本発明では、無害性多価金属イオンを被処理水中に存在させることが好ましい。無害性多価金属イオンとは、一般に排水処理で凝集に使用される多価金属イオンであり、カルシウムイオン、マグネシウムイオン、鉄イオン、アルミニウムイオンなどが挙げられる。
多価金属イオンを被処理水中に存在させるには、多価金属化合物を添加する。それらには、カルシウム化合物、マグネシウム化合物、鉄化合物、アルミニウム化合物等が包含される。それらの具体例としては、例えば、塩化カルシウム、水酸化カルシウム、炭酸カルシウム、塩化マグネシウム、塩化第二鉄、硫酸第二鉄、塩化アルミニウム、ポリ塩化アルミニウム、硫酸アルミニウム等が挙げられる。
【００１６】
本発明において、無害性多価金属イオンの添加量は、被処理水中のホウ素の濃度にもよるが、ホウ素１モル当たり、好ましくは０．０１〜１０モル、より好ましくは０．０５〜２モル、さらに好ましくは０．１〜１モルである。
【００１７】
さらに本発明においては、凝集剤を併用することが好ましい。この場合の凝集剤は、希土類元素イオン及び多価陰イオン性物質の添加後分散しているホウ素化合物のフロックを凝集させるのに用いられ、ホウ素化合物の沈殿分離をより容易にすることができる。具体例としては、塩化第１鉄、塩化第２鉄、硫酸第１鉄、硫酸第２鉄、ポリ硫酸第一鉄、ポリ硫酸第二鉄等の無機系凝集剤の他、ポリアクリルアミドのカチオン化変性物、ポリアクリル酸ジメチルアミノエチルエステル、ポリメタクリル酸ジメチルアミノエチルエステル、ポリエチレンイミン、キトサン等のカチオン性有機系凝集剤、ポリアクリルアミド等のノニオン性有機系凝集剤、ポリアクリル酸、アクリルアミドとアクリル酸との共重合体及び／その塩等のアニオン性有機系凝集剤等が挙げられる。
【００１８】
一連の工程終了後、被処理水を固液分離処理する。この固液分離は常法により行なうことができ、例として、濾過分離、遠心分離、沈降分離等が挙げられるが、通常は重力による沈降分離で十分固液分離可能である。
【００１９】
発生したスラッジは再び原被処理水に返送することが好ましい。スラッジが返送された被処理水について更に上記一連の処理を行うことにより、スラッジ中に含有している希土類元素イオンを効率的に利用することができる。また、返送されたスラッジがさらに成長して、沈降しやすくかつ脱水しやすいスラッジとなり、これによって溶存ホウ素を更に低濃度まで除去することが可能となる。返送する汚泥量は、原水１容量に対して、好ましくは１〜１５質量％、より好ましくは４〜１０質量％、さらに好ましくは６〜８質量％である。また、返送する汚泥の比重は、好ましくは１．００〜１．３０、より好ましくは１．００〜１．２０、さらに好ましくは１．００〜１．１０の範囲である。
【００２０】
【実施例】
次に本発明を実施例に基づきさらに詳細に説明する。
【００２１】
参考例１
希土類元素化合物の粗精製品を１２Ｎの塩酸溶液に溶解して調製した溶液（希土類元素の濃度は酸化物として３２．５質量％、組成はランタン９５質量％、セリウム４．９質量％、イッテルビウム０．１質量％）を除去剤［Ｉ］とした。
【００２２】
参考例２
参考例１で得られた除去剤（Ｉ）と硫酸（１８Ｍ）を容積比９０：１で混合し除去剤［ＩＩ］を得た。
【００２３】
参考例３
除去剤〔Ｉ〕と塩化第二鉄水溶液（工業用、３７．５％）を容量比８：１で混合し撹拌した。これを除去剤〔ＩＩＩ〕とした。
【００２４】
参考例４
除去剤〔Ｉ〕と硫酸アルミニウム水溶液（硫酸バンド、６０％）を容量比８：１で混合し撹拌した。これを除去剤〔ＩＶ〕とした。
【００２５】
実施例１
ホウ素濃度２．３５ｐｐｍ（０．２１８ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）をランタン濃度２．６４ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．２ｍＭとなるように添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、０．６２ｐｐｍであった。
【００２６】
実施例２
ホウ素濃度１０ｐｐｍ（０．９２６ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）をランタン濃度３．２ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．３ｍＭとなるように添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、１．７５ｐｐｍであった。
【００２７】
比較例１
実施例１、２で、硫酸ナトリウム溶液を添加しない以外は実施例１、２と同様にして処理したところと、いずれの場合も沈殿の生成はほとんど認められなかった。
【００２８】
実施例３
ホウ素濃度５０ｐｐｍ（４．６３ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）をランタン濃度８ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．８ｍＭとなるように添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、４．７ｐｐｍであった。
【００２９】
実施例４
ホウ素濃度５０ｐｐｍ（４．６３ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５％）をランタン濃度８ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、アニオン性高分子凝集剤ＡＰ５１７Ｃ（商品名、ダイヤニトリクス社製）を０．５ｐｐｍとなるように添加したところ、溶液のｐＨ１１で白濁したが、重力沈降では完全に固液分離するのは困難であった。ろ過して固液分離し、処理水中のホウ素濃度を測定したところ、７．９ｐｐｍであった。
【００３０】
比校例２
実施例３、４で、硫酸ナトリウム溶液やアニオン性高分子凝集剤を添加しない以外は実施例３、４と同様にして処理したところと、いずれの場合も僅かに白濁しただけであった。
【００３１】
実施例５
ホウ素濃度２０ｐｐｍ（１．８５ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）を１．６ｍｌ／リットル添加し（ランタン濃度３．２ｍＭとなる）、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．３ｍＭとなるように添加し、アニオン性高分子凝集剤ＡＰ５１７Ｃを３ｐｐｍ添加したところ、溶液のｐＨ１１で沈降性の良い巨大なフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、３．７ｐｐｍであった。
【００３２】
実施例６
実施例３において、硫酸ナトリウム水溶液の代わりに炭酸ナトリウム水溶液を炭酸根として０．３ｍＭとなるように添加した以外は実施例３と同様に行ったところ、溶液のｐＨ１１で沈殿の生成は認められ、固液分離後の、処理水中のホウ素濃度は、４．５ｐｐｍで、炭酸ナトリウムも有効であることが分かった。
【００３３】
実施例７
ホウ素濃度１０ｐｐｍ（０．９２６ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）をランタン濃度３．２ｍＭとなるよう添加し、塩化カルシウム水溶液（２．７Ｍ）を０．５ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．３ｍＭとなるように添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、１．４５ｐｐｍであった。
【００３４】
実施例８
ホウ素濃度１００ｐｐｍ（９．２６ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）をランタン濃度１３．９ｍＭとなるよう添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．８ｍＭとなるように添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、５．６ｐｐｍであった。
【００３５】
比較例３
実施例８において、ｐＨ調整をｐＨ９とした以外は実施例８と同様に行ったところ、処理水中のホウ素濃度は、３７．１ｐｐｍであった。
【００３６】
実施例９
ホウ素濃度２０ｐｐｍ（１．８５ｍＭ）のモデル排水（ｐＨ５．５）に、前記参考例１で調製した除去剤を１．６ｍｌ／リットル添加し、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間攪拌した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．３ｍＭとなるように添加し、アニオン性高分子凝集剤ＡＰ５１７Ｃを０．３ｐｐｍ添加したところ、溶液のｐＨ１１で非常に沈降性の良い巨大なフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、３．９ｐｐｍであった。
【００３７】
実施例１０
ホウ素濃度２０ｐｐｍ（１．８５ｍＭ）のモデル排水（ｐＨ５．５）に、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）を１．６ｍｌ／リットル添加し（ランタン濃度３．２ｍＭとなる）、塩化第二鉄溶液（工業用、濃度３７．５％）を０．２ｍｌ／リットル添加し（鉄濃度０．４６ｍＭとなる）、１０分間攪拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間撹件した。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．３ｍＭとなるように添加し、アニオン性高分子凝集剤ＡＰ５１７Ｃを０．３ｐｐｍ添加になるように添加したところ、溶液のｐＨ１１で非常に沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離し、処理水中のホウ素濃度を測定したところ、２．１ｐｐｍであった。
【００３８】
実施例１１
ホウ素濃度１２．３ｐｐｍ、ｐＨ６．９の実排水は、従来の方法ではホウ素を除去することができなかった。この排水を塩酸でｐＨ３に調整し、塩化ランタン水溶液（Ｌａ_２Ｏ_３として３２．５質量％）３ｍｌ／リットル添加し、水酸化ナトリウム水溶液でｐＨ１０とした。この溶液に、硫酸ナトリウム水溶液を硫酸根として０．２ｍＭとなるように添加し、アニオン性高分子凝集剤ＡＰ１２０Ｃを３ｐｐｍ添加したところ、溶液のｐＨ１０で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、１．６ｐｐｍであった。
生成した汚泥を原水に返送して、上記と同様に処理（塩化ランタン溶液の添加量１ｍｌ／リットル）したところ、処理水中のホウ素濃度は、２回目の処埋では１．５ｐｐｍ、３回目１．３ｐｐｍ、４回目１．９ｐｐｍとなり、汚泥返送により塩化ランタン水溶液の添加量をさらに減らすことができた。
【００３９】
実施例１２
ホウ素濃度１００ｐｐｍ（９．２６ｍＭ）のモデル排水（ｐＨ５．５）に、除去剤［ＩＩ］をランタン濃度１３．９ｍＭとなるよう添加し、１０分間撹拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間撹拌したところ、沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、４．９ｐｐｍであった。
【００４０】
実施例１３
ホウ素濃度５０ｐｐｍ（４．６３ｍＭ）のモデル排水（ｐＨ５．５）に、除去剤〔ＩＩＩ〕を４．５ｍｌ／リットル添加し（ランタン濃度８ｍＭ、鉄濃度１．２ｍＭとなる）、１０分間撹拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、１０分間撹拌し、硫酸ナトリウム水溶液を硫酸根として０．６ｍＭとなるよう添加したところ、溶液のｐＨ１１で沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、７．９ｐｐｍであった。
【００４１】
実施例１４
ホウ素濃度５０ｐｐｍ（４．６３ｍＭ）のモデル排水に、除去剤〔ＩＶ〕を４．５ｍｌ／リットル添加し（ランタン濃度８ｍＭ、アルミニウム濃度０．９ｍＭ、硫酸根濃度１．３５ｍＭとなる）、１０分間撹拌した後、水酸化ナトリウム水溶液でｐＨ１１に調整し、撹拌したところ、沈降性の良いフロックが生成し、重力沈降によって完全に固液分離できた。固液分離した処理水中のホウ素濃度を測定したところ、６．２ｐｐｍであった。
【００４２】
【発明の効果】
本発明の方法によれば、被処理水中に含まれる溶存ホウ素を効率よく除去することができる。また、処理により発生したスラッジを原被処理水に返送して再度処理することにより、希土類元素イオンを再利用しかつスラッジ発生量を低減させることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for removing dissolved boron contained in water to be treated, a removing agent, and a method for reducing the amount of generated sludge.
[0002]
[Prior art]
The standard for effluent of boron is set at 10 ppm when discharged to areas other than the sea (effective on July 1, 2001, and provisional standards for three years are set for each type of business). Conventionally, as a treatment method of boron-containing water, a method of adsorbing with an ion-exchange resin, a method of forming an insoluble precipitate with aluminum sulfate and calcium hydroxide, and the like are known, but any method can be said to be an efficient method. In addition, there is a problem that a large amount of sludge is generated.
In recent years, the importance of solving the problem of environmental pollution due to industrial wastewater and the like has been emphasized, and there is a high demand for an effective boron removal method.
A method combining the coagulation sedimentation method with an anion exchange resin or a boron-selective ion exchange resin has been proposed (see Patent Document 1). However, since the removal efficiency of the coagulation sedimentation method is low, a load is imposed on the subsequent adsorption resin, Therefore, there is a problem that the cost is too high and a problem of treating the regenerated liquid of the adsorbing resin, which is not practically used. Furthermore, a method of treating low-concentration boron-containing wastewater using a hydrated oxide of a rare-earth element has been proposed (see Patent Document 2). However, since solids are used, the processability is poor and the treatment takes time. There is a problem and it has not been put to practical use.
On the other hand, the boron-containing wastewater is once adsorbed on a boron selective adsorption ion exchange resin or the like, and boron is removed by adding a compound that releases a rare earth element ion and / or a group IVB element ion to the concentrated desorbed liquid. We found that we can do it (see Patent Document 3). However, the method of adding a compound that releases rare earth element ions and / or group IVB element ions is not effective for treating low-concentration boron-containing wastewater, and must be once concentrated. Therefore, a new adsorption device is required, and more complicated adsorption and desorption operations are required. In general, flocs generated by the reaction of a rare earth element with boron are bulky and have poor sedimentation.
Further, they have found that after concentrating a boron-containing wastewater, a boron fixing agent composed of a lanthanum compound is added to form an insoluble precipitate and boron can be removed (see Patent Document 4). However, this method also has to be concentrated once, similarly to Patent Document 3, and the floc generated by the reaction of lanthanum ion and boron is bulky and has poor sedimentation.
[0003]
[Patent Document 1]
JP-A-57-180493 [Patent Document 2]
Japanese Patent Publication No. 3-22238 [Patent Document 3]
JP-A-11-235595 [Patent Document 4]
JP 2000-263064 A
[Problems to be solved by the invention]
An object of the present invention is to provide a method for efficiently removing dissolved boron from water to be treated. Another object of the present invention is to provide a boron remover used for the same.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by adjusting the pH to 9 to 13 in a state where a polyanionic substance and a rare earth element ion are present in the water to be treated, It has been found that boron dissolved in the water to be treated can be precipitated and separated as a hardly soluble substance, and based on this finding, the present invention has been completed.
That is, the present invention
(1) Boron, characterized in that a polyvalent anionic substance and a rare-earth element ion are present in water to be treated containing dissolved boron, and the dissolved boron is precipitated and separated as a hardly soluble substance at a pH of 9 to 13. Wastewater treatment method,
(2) The polyanion is a sulfate ion, and the polyanionic substance is a sulfate compound that dissolves in water to release a sulfate ion. A method for treating boron-containing wastewater,
(3) The polyvalent anion is a carbonate ion, and the polyvalent anionic substance is a carbonate compound which releases a carbonate ion by dissolving in water to precipitate and separate the dissolved boron as a hardly soluble substance according to the above (1). A method for treating boron-containing wastewater,
(4) The method for treating a boron-containing wastewater according to (1), wherein the polyanion is an anionic polymer compound, wherein the dissolved boron is precipitated and separated as a hardly soluble substance.
(5) The method for treating a boron-containing wastewater according to (4), wherein the anionic polymer compound is an anionic polymer coagulant.
(6) The method according to any one of (1) to (5), wherein a harmless polyvalent metal ion is present,
(7) The method for treating a boron-containing wastewater according to (6), wherein the harmless polyvalent metal ion is at least one of a calcium ion, a magnesium ion, an iron ion, and an aluminum ion.
(8) The rare earth element ion is added to the water to be treated as an aqueous solution, a hydrochloric acid solution or a sulfuric acid solution of an oxide, hydroxide, carbonate, phosphate, acetate or halide of the rare earth element. The method for treating a boron-containing wastewater according to any one of (1) to (7),
(9) The method according to any one of (1) to (8), wherein after the dissolved boron is precipitated and separated as a hardly soluble substance, sludge generated by the treatment is returned to the raw water to be treated. A method for treating boron-containing wastewater,
(10) A drug used in the method according to any one of (1) to (9), which is an oxide, hydroxide, carbonate, phosphate, acetate or halogen of a rare earth element. Aqueous solution of the compound, a drug characterized by at least one selected from the group consisting of a hydrochloric acid solution or a sulfuric acid solution,
(11) A drug used in the method according to any one of (1) to (9), wherein the rare earth element ion and the sulfate ion to be supplied are constituted as a drug, and the drug is used as the drug. (I) at least one selected from the group consisting of aqueous solutions of rare earth element oxides, hydroxides, carbonates, phosphates, acetates or halides, hydrochloric acid solutions or sulfuric acid solutions, and (ii) sulfuric acid, An aqueous solution of sulfate or a mixture thereof, a drug comprising a mixture thereof,
(12) A drug used in the method according to any one of (1) to (9), wherein the supplied rare earth element ion and iron ion are constituted as a drug, and the drug is used as the drug. And (ii) at least one selected from the group consisting of aqueous solutions, hydrochloric acid solutions and sulfuric acid solutions of oxides, hydroxides, carbonates, phosphates, acetates or halides of rare earth elements, and (ii) chlorides A drug comprising a mixture with a diiron solution, an aqueous solution of polyiron or a mixture thereof, and a drug used in the method according to any one of (13) (1) to (9). Wherein the supplied rare earth element ion and aluminum ion are constituted as a medicine, and the medicine is (i) an oxide, hydroxide, carbonate, phosphate, acetate, or the like of the rare earth element. Aqueous solution of halide At least one and (ii) aluminum sulfate solution is selected from the group consisting of hydrochloric acid solution or sulfuric acid solution, polyaluminum chloride solution or a mixture thereof, to consist of a mixture of is to provide a drug characterized by.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
In the present invention, rare earth element ions are present in the water to be treated. This rare earth element ion plays a role as a boron remover (hereinafter, also simply referred to as a remover). The rare earth element ion when added to the water to be treated may be in any state as long as the object of the present invention can be achieved, but is preferably added as a rare earth element-containing solution, and oxides, hydroxides, and carbonates of the rare earth element are added. It is preferably added to the water to be treated as an aqueous solution of a salt, a phosphate, an acetate or a halide, a hydrochloric acid solution or a sulfuric acid solution. The concentration is not particularly limited, but considering operability, for example, in the case of a hydrochloric acid solution of a rare earth element oxide, the rare earth element in the hydrochloric acid solution is preferably used as an oxide in an amount of preferably 10 to 40% by mass, more preferably Is from 20 to 35% by mass.
[0007]
Of the rare earth element ions, lanthanum ions and cerium ions are preferably used, and lanthanum ions are more preferably used.
In addition, the rare earth element-containing solution used as the removing agent in the present invention can be used in the form of a solution of a mixture of rare earth elements or a single or mixed solution of rare earth elements. The use of a solution of lanthanum and cerium and ytterbium is preferred, and a solution of lanthanum and cerium is more preferred. As a preferred specific example, a hydrochloric acid solution of lanthanum, cerium, and ytterbium (concentration is 32.5% by mass as an oxide, in which the composition is 95% by mass of lanthanum, 4.9% by mass of cerium, 0.1% by mass of ytterbium ).
[0008]
One of the features of the present invention is that it is not necessary to use a highly purified and separated expensive rare earth compound as a source of rare earth element ions to the removing agent. That is, the removing agent used in the present invention (hereinafter, also referred to as removing agent [I]) does not need to be prepared with a purified rare earth element. For example, an ore containing rare earth elements from which heavy metals such as lead and lead and other radioactive elements and radioactive elements have been removed can be used after dissolving in hydrochloric acid and then roughly refined. The concentration of hydrochloric acid at this time is preferably 0.1 to 12 normal, more preferably 5 to 12 normal, and still more preferably 8 to 12 normal. The concentration of rare earth element ions is not particularly limited. In consideration of the properties, the oxide is preferably 10 to 60% by mass, more preferably 20 to 60% by mass, and still more preferably 30 to 50% by mass. The dissolution time is not particularly limited as long as it is completely dissolved, but about 0.5 to 2 hours is sufficient.
[0009]
In the present invention, the amount of the rare earth element ion to be added depends on the concentration of boron in the water to be treated, but is preferably 0.05 to 50 mol, more preferably 0.1 to 30 mol, and still more preferably 1 mol of boron. Is 0.5 to 20 mol.
[0010]
In the present invention, a polyvalent anionic substance is used in combination. By adding a polyvalent anionic substance, a precipitate having good sedimentation and dehydration properties is generated, and the precipitate is easily separated into solid and liquid. As the polyvalent anionic substance, a sulfate, a carbonate, an anionic polymer flocculant and the like are preferable, and these may be used alone or in combination. Examples of the sulfate include sodium sulfate, ferrous sulfate, and ferric sulfate. Examples of the carbonate include sodium carbonate and potassium carbonate. Examples of the anionic polymer coagulant include anionic organic coagulants such as sodium carboxymethylcellulose, sodium alginate, polyacrylic acid, a copolymer of acrylamide and acrylic acid, and / or a salt thereof. The amount added to the water to be treated is, for example, preferably 0.01 to 100 mM, more preferably 0.05 to 50 mM, and still more preferably 0.1 to 10 mM for sulfate or carbonate. In the case of the polymer flocculant, it is preferably 0.01 to 20 ppm, more preferably 0.05 to 20 ppm, and still more preferably 0.1 to 10 ppm.
[0011]
As the polyvalent anion used in the present invention, a sulfate ion is particularly preferred. When sulfate ions are used in combination, a sulfate may be added as described above.However, a treatment agent containing rare earth element ions and sulfate ions is prepared in advance, and the treatment agent is added to the water to be treated containing boron. May be. As a method for preparing the treating agent, any method such as mixing an aqueous solution of a rare earth element, a hydrochloric acid solution, a sulfuric acid solution and a sulfate compound may be used, but mixing a readily available rare earth hydrochloric acid solution and sulfuric acid. It is more convenient to prepare. As a preferred specific example, a hydrochloric acid solution of lanthanum, cerium, and ytterbium (in particular, the concentration is 32.5% by mass as an oxide, and the composition therein is 95% by mass of lanthanum, 4.9% by mass of cerium, It is a mixed solution of 90% by volume of ytterbium (0.1% by mass) and sulfuric acid (18M).
[0012]
The order of addition of the polyvalent anionic substance is not limited. It is preferable to adjust the pH by adding a rare earth element ion after adding the polyvalent anionic substance, but after adding the rare earth element ion and adjusting the pH, the polyvalent anionic substance is added. May be. It is sufficient that the pH is at least 9 to 13 when at least dissolved boron is used as the hardly soluble substance.
[0013]
In the present invention, after the removal agent is added, the pH is adjusted so that precipitation occurs, and boron dissolved in the wastewater is removed. The pH is generally in the range 9-13, preferably in the range 9-12, more preferably in the range 10-12.
[0014]
When the pH of the water to be treated is adjusted to an alkaline region or an acidic region, a pH adjuster is used. Examples of such a pH adjuster include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and calcium hydroxide. Or an acidic substance such as hydrochloric acid, sulfuric acid, nitric acid, and aluminum sulfate.
[0015]
In the present invention, it is preferable that harmless polyvalent metal ions be present in the water to be treated. Harmless polyvalent metal ions are polyvalent metal ions generally used for coagulation in wastewater treatment, and include calcium ions, magnesium ions, iron ions, aluminum ions and the like.
To make polyvalent metal ions exist in the water to be treated, a polyvalent metal compound is added. They include calcium compounds, magnesium compounds, iron compounds, aluminum compounds and the like. Specific examples thereof include, for example, calcium chloride, calcium hydroxide, calcium carbonate, magnesium chloride, ferric chloride, ferric sulfate, aluminum chloride, polyaluminum chloride, and aluminum sulfate.
[0016]
In the present invention, the addition amount of the harmless polyvalent metal ion depends on the concentration of boron in the water to be treated, but is preferably 0.01 to 10 mol, more preferably 0.05 to 2 mol, per mol of boron. And more preferably 0.1 to 1 mol.
[0017]
Further, in the present invention, it is preferable to use a coagulant in combination. The coagulant in this case is used to coagulate the floc of the boron compound dispersed after the addition of the rare earth element ion and the polyvalent anionic substance, and can facilitate the precipitation and separation of the boron compound. Specific examples include inorganic coagulants such as ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous polysulfate, and ferric polysulfate, as well as cationization of polyacrylamide. Modified products, dimethylaminoethyl ester of polyacrylic acid, dimethylaminoethyl ester of polymethacrylic acid, cationic organic coagulants such as polyethyleneimine and chitosan, nonionic organic coagulants such as polyacrylamide, polyacrylic acid, acrylamide and acrylic Anionic organic coagulants such as copolymers with acids and / or their salts are mentioned.
[0018]
After a series of steps, the water to be treated is subjected to solid-liquid separation. This solid-liquid separation can be performed by a conventional method, and examples thereof include filtration separation, centrifugation, sedimentation separation, and the like. Usually, solid-liquid separation can be sufficiently performed by sedimentation separation by gravity.
[0019]
It is preferable that the sludge generated is returned to the raw water to be treated again. By performing the above series of treatments on the water to be treated to which the sludge has been returned, the rare earth element ions contained in the sludge can be efficiently used. In addition, the returned sludge further grows and becomes a sludge which is easy to settle and is easily dewatered, whereby the dissolved boron can be removed to a lower concentration. The amount of sludge to be returned is preferably 1 to 15% by mass, more preferably 4 to 10% by mass, and still more preferably 6 to 8% by mass with respect to 1 volume of raw water. The specific gravity of the sludge to be returned is preferably in the range of 1.00 to 1.30, more preferably 1.00 to 1.20, and even more preferably 1.00 to 1.10.
[0020]
【Example】
Next, the present invention will be described in more detail based on examples.
[0021]
Reference Example 1
A solution prepared by dissolving a crude product of a rare earth element compound in a 12N hydrochloric acid solution (the concentration of the rare earth element is 32.5% by mass as an oxide, the composition is 95% by mass of lanthanum, 4.9% by mass of cerium, 0% of ytterbium) .1% by mass) was defined as a removing agent [I].
[0022]
Reference Example 2
The remover (I) obtained in Reference Example 1 and sulfuric acid (18M) were mixed at a volume ratio of 90: 1 to obtain a remover [II].
[0023]
Reference Example 3
The remover [I] and an aqueous ferric chloride solution (for industrial use, 37.5%) were mixed at a volume ratio of 8: 1 and stirred. This was used as a remover [III].
[0024]
Reference example 4
The remover [I] and an aqueous solution of aluminum sulfate (sulfuric acid band, 60%) were mixed at a volume ratio of 8: 1 and stirred. This was used as a remover [IV].
[0025]
Example 1
An aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 2.35 ppm (0.218 mM) so as to have a lanthanum concentration of 2.64 mM, and stirred for 10 minutes. After that, the pH was adjusted to 11 with an aqueous sodium hydroxide solution, and the mixture was stirred for 10 minutes. When an aqueous solution of sodium sulfate was added to this solution to a concentration of 0.2 mM as a sulfate group, a floc having good sedimentation was formed at pH 11 of the solution, and solid-liquid separation was completed by gravity sedimentation. When the boron concentration in the treated water subjected to solid-liquid separation was measured, it was 0.62 ppm.
[0026]
Example 2
An aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 10 ppm (0.926 mM) so that the lanthanum concentration became 3.2 mM, and the mixture was stirred for 10 minutes. The pH was adjusted to 11 with an aqueous sodium hydroxide solution, and the mixture was stirred for 10 minutes. When an aqueous solution of sodium sulfate was added to this solution to a concentration of 0.3 mM as a sulfate group, a floc having good sedimentation was formed at pH 11 of the solution, and solid-liquid separation was completely performed by gravity sedimentation. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 1.75 ppm.
[0027]
Comparative Example 1
In Examples 1 and 2, treatment was carried out in the same manner as in Examples 1 and 2, except that the sodium sulfate solution was not added. In each case, almost no precipitation was observed.
[0028]
Example 3
An aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 50 ppm (4.63 mM) so as to have a lanthanum concentration of 8 mM, and stirred for 10 minutes. The pH was adjusted to 11 with an aqueous sodium oxide solution, and the mixture was stirred for 10 minutes. When an aqueous solution of sodium sulfate was added to the solution so as to have a concentration of 0.8 mM as a sulfate group, flocs having good sedimentation were formed at pH 11 of the solution, and solid-liquid separation was completed by gravity sedimentation. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 4.7 ppm.
[0029]
Example 4
An aqueous lanthanum chloride solution (32.5% as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 50 ppm (4.63 mM) so as to have a lanthanum concentration of 8 mM. The pH was adjusted to 11 with an aqueous sodium solution, and the mixture was stirred for 10 minutes. To this solution was added an anionic polymer coagulant AP517C (trade name, manufactured by Dyanitrix) so as to have a concentration of 0.5 ppm. The solution became cloudy at pH 11 of the solution, but completely separated by gravity sedimentation. It was difficult. After filtration and solid-liquid separation, the boron concentration in the treated water was measured to be 7.9 ppm.
[0030]
Comparative example 2
In Examples 3 and 4, the treatment was performed in the same manner as in Examples 3 and 4 except that the sodium sulfate solution and the anionic polymer flocculant were not added. In each case, the film was slightly clouded.
[0031]
Example 5
1.6 ml / liter of an aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to model wastewater (pH 5.5) having a boron concentration of 20 ppm (1.85 mM) (to give a lanthanum concentration of 3.2 mM). After stirring for 10 minutes, the mixture was adjusted to pH 11 with an aqueous sodium hydroxide solution and stirred for 10 minutes. To this solution, an aqueous sodium sulfate solution was added so as to have a concentration of 0.3 mM as a sulfate group, and 3 ppm of an anionic polymer flocculant AP517C was added. Solid-liquid separation was completed by sedimentation. The measured boron concentration in the treated water after solid-liquid separation was 3.7 ppm.
[0032]
Example 6
Example 3 was repeated in the same manner as in Example 3 except that an aqueous solution of sodium carbonate was added instead of the aqueous solution of sodium sulfate so as to have a concentration of 0.3 mM as a carbonate group. Precipitation was observed at pH 11 of the solution. The boron concentration in the treated water after solid-liquid separation was 4.5 ppm, and it was found that sodium carbonate was also effective.
[0033]
Example 7
An aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 10 ppm (0.926 mM) so as to have a lanthanum concentration of 3.2 mM. (0.7M) was added to a concentration of 0.5 mM, and the mixture was stirred for 10 minutes, adjusted to pH 11 with an aqueous sodium hydroxide solution, and stirred for 10 minutes. When an aqueous solution of sodium sulfate was added to this solution to a concentration of 0.3 mM as a sulfate group, a floc having good sedimentation was formed at pH 11 of the solution, and solid-liquid separation was completely performed by gravity sedimentation. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 1.45 ppm.
[0034]
Example 8
An aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to a model wastewater (pH 5.5) having a boron concentration of 100 ppm (9.26 mM) so that the lanthanum concentration became 13.9 mM, and the mixture was stirred for 10 minutes. The pH was adjusted to 11 with an aqueous sodium hydroxide solution, and the mixture was stirred for 10 minutes. When an aqueous solution of sodium sulfate was added to the solution so as to have a concentration of 0.8 mM as a sulfate group, flocs having good sedimentation were formed at pH 11 of the solution, and solid-liquid separation was completed by gravity sedimentation. The concentration of boron in the treated water subjected to solid-liquid separation was measured and found to be 5.6 ppm.
[0035]
Comparative Example 3
When the same procedure as in Example 8 was carried out except that the pH was adjusted to pH 9 in Example 8, the boron concentration in the treated water was 37.1 ppm.
[0036]
Example 9
1.6 ml / L of the remover prepared in Reference Example 1 was added to model wastewater (pH 5.5) having a boron concentration of 20 ppm (1.85 mM), and the mixture was stirred for 10 minutes and adjusted to pH 11 with an aqueous sodium hydroxide solution. And stirred for 10 minutes. To this solution, an aqueous solution of sodium sulfate was added so as to have a concentration of 0.3 mM as a sulfate group, and 0.3 ppm of an anionic polymer flocculant AP517C was added. A solid-liquid separation was completed by gravity sedimentation. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 3.9 ppm.
[0037]
Example 10
1.6 ml / liter of an aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added to model wastewater (pH 5.5) having a boron concentration of 20 ppm (1.85 mM) (to give a lanthanum concentration of 3.2 mM). 0.2 ml / liter of a ferric chloride solution (industrial, concentration: 37.5%) was added (to give an iron concentration of 0.46 mM), and the mixture was stirred for 10 minutes, and then adjusted to pH 11 with an aqueous sodium hydroxide solution. Stirred for 10 minutes. To this solution, an aqueous sodium sulfate solution was added so as to have a concentration of 0.3 mM as a sulfate group, and an anionic polymer coagulant AP517C was added so as to have a concentration of 0.3 ppm. Good floc was formed, and solid-liquid separation was completed by gravity sedimentation. Solid-liquid separation was performed, and the concentration of boron in the treated water was measured to be 2.1 ppm.
[0038]
Example 11
Actual wastewater having a boron concentration of 12.3 ppm and a pH of 6.9 could not remove boron by the conventional method. The waste water was adjusted to pH 3 with hydrochloric acid, 3 ml / liter of an aqueous lanthanum chloride solution (32.5% by mass as La ₂ O ₃ ) was added, and the pH was adjusted to 10 with an aqueous sodium hydroxide solution. To this solution, an aqueous solution of sodium sulfate was added so as to have a concentration of 0.2 mM as a sulfate group, and 3 ppm of an anionic polymer flocculant AP120C was added. Solid-liquid separation was completed. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 1.6 ppm.
When the generated sludge was returned to the raw water and treated in the same manner as described above (the added amount of the lanthanum chloride solution was 1 ml / liter), the boron concentration in the treated water was 1.5 ppm in the second treatment, and 1. The content was 3 ppm, the fourth time was 1.9 ppm, and the amount of the lanthanum chloride aqueous solution added could be further reduced by returning the sludge.
[0039]
Example 12
The remover [II] was added to the model wastewater (pH 5.5) having a boron concentration of 100 ppm (9.26 mM) so as to have a lanthanum concentration of 13.9 mM, and the mixture was stirred for 10 minutes, and then adjusted to pH 11 with an aqueous sodium hydroxide solution. After stirring for 10 minutes, flocs having good sedimentation were formed, and solid-liquid separation could be completed by gravity sedimentation. The concentration of boron in the treated water after solid-liquid separation was measured and found to be 4.9 ppm.
[0040]
Example 13
To a model wastewater (pH 5.5) with a boron concentration of 50 ppm (4.63 mM), 4.5 ml / liter of a removing agent [III] was added (to a lanthanum concentration of 8 mM and an iron concentration of 1.2 mM), followed by stirring for 10 minutes. Then, the pH was adjusted to 11 with an aqueous sodium hydroxide solution, and the mixture was stirred for 10 minutes. An aqueous solution of sodium sulfate was added so that the concentration became 0.6 mM as a sulfate group. Was separated into solid and liquid. When the boron concentration in the treated water subjected to solid-liquid separation was measured, it was 7.9 ppm.
[0041]
Example 14
To the model wastewater having a boron concentration of 50 ppm (4.63 mM), a remover [IV] was added at 4.5 ml / liter (the concentration of lanthanum was 8 mM, the concentration of aluminum was 0.9 mM, and the concentration of sulfate was 1.35 mM), and the mixture was stirred for 10 minutes. After that, the pH was adjusted to 11 with an aqueous sodium hydroxide solution, and the mixture was stirred. As a result, flocs having good sedimentation were formed, and solid-liquid separation was completed by gravity sedimentation. The concentration of boron in the treated water subjected to solid-liquid separation was measured and found to be 6.2 ppm.
[0042]
【The invention's effect】
According to the method of the present invention, dissolved boron contained in the water to be treated can be efficiently removed. Further, by returning the sludge generated by the treatment to the raw water to be treated and treating it again, it is possible to reuse rare earth element ions and reduce the amount of sludge generated.

Claims

In the water to be treated containing dissolved boron, a polyvalent anionic substance and a rare earth element ion are present, and at pH of 9 to 13, the dissolved boron is precipitated and separated as a hardly soluble substance. Processing method.

2. The method according to claim 1, wherein the polyvalent anion is a sulfate ion, and the polyanionic substance is a sulfate compound that dissolves in water to release a sulfate ion. Of wastewater containing boron.

The polyvalent anion is a carbonate ion, and the polyvalent anionic substance is a carbonate compound that dissolves in water to release a carbonate ion. The method according to claim 1, wherein the dissolved boron is precipitated and separated as a hardly soluble substance. Of wastewater containing boron.

The method for treating a boron-containing wastewater according to claim 1, wherein the polyanion is an anionic polymer compound, and the dissolved boron is precipitated and separated as a hardly soluble substance.

The method for treating a boron-containing wastewater according to claim 4, wherein the anionic polymer compound is an anionic polymer flocculant.

The method according to any one of claims 1 to 5, wherein a harmless polyvalent metal ion is present.

The method for treating a boron-containing wastewater according to claim 6, wherein the harmless polyvalent metal ion is at least one of calcium ion, magnesium ion, iron ion and aluminum ion.

The rare earth element ions are added to the water to be treated as an aqueous solution, a hydrochloric acid solution or a sulfuric acid solution of an oxide, hydroxide, carbonate, phosphate, acetate or halide of the rare earth element. Item 8. The method for treating a boron-containing wastewater according to any one of Items 1 to 7.

The treatment of the boron-containing wastewater according to any one of claims 1 to 8, wherein after the dissolved boron is precipitated and separated as a hardly soluble substance, sludge generated by the treatment is returned to the raw water to be treated. Method.

An agent used in the method according to any one of claims 1 to 9, comprising an aqueous solution of a rare earth oxide, hydroxide, carbonate, phosphate, acetate or halide, and a hydrochloric acid solution. Or a drug comprising at least one selected from the group consisting of sulfuric acid solutions.

10. A drug used in the method according to any one of claims 1 to 9, wherein the supplied rare earth element ion and sulfate ion are constituted as a drug, and the drug is (i) a rare earth element. At least one selected from the group consisting of aqueous solutions of elemental oxides, hydroxides, carbonates, phosphates, acetates or halides, hydrochloric acid solutions and sulfuric acid solutions, and (ii) sulfuric acid, sulfate aqueous solutions or And a mixture comprising:

10. A drug used in the method according to any one of claims 1 to 9, wherein the supplied rare earth element ion and iron ion are constituted as a drug, and the drug is (i) a rare earth element. At least one element selected from the group consisting of aqueous solutions of elemental oxides, hydroxides, carbonates, phosphates, acetates or halides, hydrochloric acid solutions and sulfuric acid solutions, and (ii) ferric chloride solution, polyiron A drug comprising a mixture with an aqueous solution or a mixture thereof.

10. A drug used in the method according to any one of claims 1 to 9, wherein the supplied rare earth element ion and aluminum ion are constituted as a drug, and the drug is (i) a rare earth element. At least one selected from the group consisting of aqueous solutions of elemental oxides, hydroxides, carbonates, phosphates, acetates or halides, hydrochloric acid solutions and sulfuric acid solutions, and (ii) aluminum sulfate solutions and polyaluminum chloride solutions Or a mixture thereof, or a mixture thereof.