JP3748649B2 - Treatment of cacodylic acid or cacodylate-containing effluent - Google Patents
Treatment of cacodylic acid or cacodylate-containing effluent Download PDFInfo
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- JP3748649B2 JP3748649B2 JP35637596A JP35637596A JP3748649B2 JP 3748649 B2 JP3748649 B2 JP 3748649B2 JP 35637596 A JP35637596 A JP 35637596A JP 35637596 A JP35637596 A JP 35637596A JP 3748649 B2 JP3748649 B2 JP 3748649B2
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- cacodylate
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- arsenic
- caco
- effluent
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- Separation Of Suspended Particles By Flocculating Agents (AREA)
- Removal Of Specific Substances (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明はカコジル酸のような有機砒素化合物を含有する排液から砒素を効率よく除去する処理法に関する。
【０００２】
【従来の技術】
有害な廃棄物の一つとして有機砒素化合物があり，これらを含有する排液は排水規制を受ける。とくに，平成５年１２月施行の水質汚濁防止法によって砒素の排水規制が強化されたので，排液中の砒素の除去を徹底する必要がある。
【０００３】
しかし，有機砒素化合物含有排液から砒素を除去する技術は必ずしも確立されていない。とくにカコジル酸〔（ＣＨ3)2ＡｓＯ (ＯＨ) 〕またはその塩類を含有した排液から砒素を除去することは困難である。カコジル酸は，例えば組織培養などしたものを電子顕微鏡試料とするための緩衝液と使用されたり，皮膚科領域においては治療薬として使用されることもあるので，大学，各種の試験研究機関，病院等からは分離が困難なカコジル酸含有排液が発生することがある。またカコジル酸は除草剤として使用されることもある。
【０００４】
従来より，砒素等を含有する排液の一般的な処理法として，フエライト法（例えば特開昭４９−１２７４６９号公報，特公昭４９−３４９１８号公報），フェントン法（例えば水質汚濁研究第１２巻第１１号，７３６−７４０，１９８９），鉄粉法（例えば特公昭６０−１７５９５号）などが知られている。
【０００５】
【発明が解決しようとする課題】
前記の従来の処理法では有機砒素化合物，とりわけカコジル酸を含有する排液から砒素を効率よく除去することができない。したがって本発明は，難分解性有機砒素化合物特にカコジル酸またはその塩を含有する排液から砒素を効率よく分離除去する技術の開発を課題としたものである。
【０００６】
【課題を解決するための手段】
本発明は、鉄イオンが共存するｐＨ５以下に調整したカコジル酸またはカコジル酸塩含有排液にＮａＣｌＯを添加したあと、ＣａＣＯ3を過剰に添加して撹拌しＣａＣＯ3の不溶解物を液中に懸濁させて砒素分が吸着されたフロックを形成し、次いで固液分離することからなるカコジル酸またはカコジル酸塩含有排液の処理法を提供する。
【０００７】
【発明の実施の形態】
本発明が処理対象とする排液は有機砒素化合物代表的にはジメチルアルシン酸（カコジル酸）を含有した排液である。前述のように研究機関等でのカコジル酸含有排液の発生が多くなっているので，その処理が急務化している。以下に，カコジル酸またはカコジル酸塩類（これらを総称してカコジル酸（塩）と略記する）を例として本発明の実施の形態を説明する。
【０００８】
先ず，本発明においては，カコジル酸（塩）含有排液のｐＨを測定し，該液のｐＨが５を越えていれば，塩酸等の酸を添加してｐＨを５以下，好ましくは４前後，例えば３〜４.５に調整し，ＮａＣｌＯを添加する。そのさい，排液中に鉄イオンが共存していない場合には２価または３価の鉄塩を添加して液中に鉄イオンを共存させる。鉄塩の添加量は，液中砒素濃度の当量以上となるように，好ましくは少なくとも砒素の２０倍当量以上，例えば砒素の２０〜３０倍当量となるようにするのがよい。ＮａＣｌＯの添加量は酸化還元電位が１０００ｍＶ以上，好ましくは１２００ｍＶ以上となるようなものとするのが望ましい。
【０００９】
ＣａＣＯ3 の添加にさいしては，粉状のＣａＣＯ3 を過剰に添加する。過剰に添加するとは，ＣａＣＯ3 の不溶解分が液中に懸濁浮遊するに十分な過飽和量を添加するという意味である。この過剰のＣａＣＯ3 の添加により，液中には砒素分が吸着されたフロックが形成する。そのさい，ＣａＣＯ3 を添加しながら，または添加後に液を攪拌するのが望ましい。このフロックはそのままでは濾別が困難なときには，通常の高分子凝集剤例えば商品名アコーフロックＮ−１００（三井サイアナミッド株式会社製）などを添加して，フロックを濾別しやすい沈澱に変えてから固液分離（例えば濾別）する。この固液分離によって，沈澱側に砒素が移行し液中の砒素濃度が低減する。
【００１０】
本発明に従う排液の処理は，ＮａＣｌＯ添加による酸化とＣａＣＯ3 の中和剤の組合せに特徴がある。ＮａＣｌＯに代わる酸化剤例えば過酸化水素等を使用してもそれほど効果はない。ｐＨ４前後の当該排液にＮａＣｌＯを添加すると有機砒素化合物の分子機構が変化し，その結果，過剰に存在するＣａＣＯ3 に吸着しやすくなるのではないかと考えられる。そのさいＣａＣＯ3 はＣａ2+とＣＯ3 2- のイオンに解離していると効果はなく，ＣａＣＯ3 の不溶解物が存在していることが肝要である。
【００１１】
なお，ＣａＣＯ3 添加前の液中に適量の鉄イオンが共存していると，ＮａＣｌＯ添加によって有機性砒素が無機化されることがその要因ではないかと考えられるが，ＣａＣＯ3 添加時において砒素がヒ酸鉄として共沈する現象も同時に起きる。したがって，鉄塩の併用添加は本発明法を極めて有利にする。
【００１２】
カコジル酸（塩）含有排液を対象として本発明を実施し，固液分離したあとの液中になお排水基準を越える砒素が含有されている場合には，この処理済液を対象として再び本発明法を実施すれば，さらに砒素濃度が低減した液が得られる。したがって，処理対象液中のカコジル酸（塩）濃度が高い場合や特殊な排液では本発明法を数回繰り返すことで十分に砒素を除去することができる。
【００１３】
【実施例】
〔実施例１〕
カコジル酸〔（ＣＨ3)2ＡｓＯ (ＯＨ) 〕の試薬を水に溶解することにより，Ａｓとして２０ｍｇ／Ｌ（リットル）含有するカコジル酸水溶液を作り，これを供試液とした。この供試液に塩酸を添加してｐＨを４前後に調整後，ＦｅＣｌ3 をＦｅ3+濃度が３００ｐｐｍとなるように添加した。次に，ＮａＣｌＯを，Ｅｈ（酸化還元電位）が１２００ｍＶ以上となるように添加してから，ＣａＣＯ3 の粉体を，不溶解物が生ずるに十分な量添加して攪拌した。液のｐＨは５〜７の範囲であった。懸濁物を商品名アコーフロックＮ−１００（三井サイアナミッド株式会社製）の高分子凝集剤を用いて濾過性のよいものにしてから濾別した。得られた濾液を分析したところ，Ａｓ濃度は５ｍｇ／Ｌであった。
【００１４】
このＡｓ濃度５ｍｇ／Ｌの液を供試液として，前記と全く同じ操作を繰り返したところ，Ａｓ濃度が０.３ｍｇ／Ｌの液となった。
再び，このＡｓ濃度０.３ｍｇ／Ｌの液を供試液として，前記と同じ操作を繰り返したところ，Ａｓ濃度が０.１ｍｇ／Ｌ以下の液となった。
【００１５】
〔実施例２〕
医療施設の病理研究で使用された緩衝液の排液を供試液とした。この排液を分析したところ，Ａｓ濃度として１３ｍｇ／Ｌのカコジル酸を含有していた。
この排液を塩酸でｐＨ４.０に調整し，ＦｅＣｌ3 をＦｅ3+濃度が３００ｐｐｍとなるように添加した。次に，ＮａＣｌＯを，Ｅｈ（酸化還元電位）が１２００ｍＶ以上となるように添加してから，ＣａＣＯ3 の粉体を過剰に添加してその不溶解物を浮遊させた状態で攪拌した。液のｐＨは５〜７の範囲であった。次いでフロック分を実施例１と同じ高分子凝集剤を用いて濾過性のよいものにしてから濾別した。得られた濾液を分析したところ，Ａｓ濃度は１.１５ｍｇ／Ｌであった。
【００１６】
この液を対象として前記の同じ処理を繰り返したところ，Ａｓ濃度が０.３３ｍｇ／Ｌの液となった。この液を対象として再び同じ処理を繰り返したところ，Ａｓ濃度が０.１ｍｇ／Ｌ以下となり，排水規制を満足する液となった。
【００１７】
〔比較例〕
実施例２と同じ排液を塩酸でｐＨ３.０に調整し，鉄粉を１２ｇ／Ｌ添加して３０分間攪拌後，ＮａＯＨでｐＨを９.５にして，さらに攪拌を続行した。得られた懸濁液に実施例１と同じ高分子凝集剤を添加して固液分離したところ，濾液中のＡｓ濃度は１２.１ｍｇ／Ｌであり，処理前の排液のＡｓ濃度１３ｍｇ／Ｌと比べて殆んど変化はなかった。
【００１８】
【発明の効果】
以上説明したように，本発明によれば，従来その除去が困難であった有機砒素化合物例えばカコジル酸（塩）を高い除去効率で除去することができる。しかもその除去操作は，入手し易くて安価な試薬による簡易なものであるから経済的に行うことができる。したがって環境の水質改善におおいに貢献できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment method for efficiently removing arsenic from an effluent containing an organic arsenic compound such as cacodylic acid.
[0002]
[Prior art]
Organic arsenic compounds are one of the harmful wastes, and wastewater containing them is subject to drainage regulations. In particular, the arsenic drainage regulations were strengthened by the Water Pollution Control Law, which came into effect in December 1993, so it is necessary to thoroughly remove arsenic in the effluent.
[0003]
However, a technique for removing arsenic from organic arsenic compound-containing effluent has not necessarily been established. In particular, it is difficult to remove arsenic from effluent containing cacodylic acid [(CH 3 ) 2 AsO (OH)] or salts thereof. Cacodylic acid can be used as a buffer solution for making tissue culture samples, for example, tissue culture samples, or as a therapeutic agent in the dermatological field, so universities, various research institutes, hospitals In some cases, a cacodylic acid-containing effluent, which is difficult to separate, may be generated. Cacodylic acid may also be used as a herbicide.
[0004]
Conventionally, as a general method for treating effluent containing arsenic or the like, the ferrite method (for example, JP-A-49-127469, JP-B-49-34918), the Fenton method (for example, Water Pollution Research Vol. 12) No. 11, 736-740, 1989), an iron powder method (for example, Japanese Patent Publication No. 60-17595), and the like are known.
[0005]
[Problems to be solved by the invention]
The conventional treatment method described above cannot efficiently remove arsenic from waste liquid containing an organic arsenic compound, particularly cacodylic acid. Accordingly, an object of the present invention is to develop a technique for efficiently separating and removing arsenic from a effluent containing a hardly decomposable organic arsenic compound, particularly cacodylic acid or a salt thereof.
[0006]
[Means for Solving the Problems]
In the present invention, NaClO is added to cacodylic acid or cacodylate- containing effluent adjusted to pH 5 or less in which iron ions coexist , and then CaCO 3 is added excessively and stirred to dissolve insoluble CaCO 3 in the liquid. There is provided a method for treating cacodylic acid or cacodylate- containing effluent comprising suspending to form flocs adsorbed with arsenic and then solid-liquid separation.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The effluent to be treated by the present invention is an effluent containing an organic arsenic compound, typically dimethylarsinic acid (cacodylic acid). As mentioned above, the generation of cacodylic acid-containing effluent in research institutions is increasing, so the treatment is urgently needed. In the following, embodiments of the present invention will be described using cacodylic acid or cacodylates (collectively abbreviated as cacodylic acid (salt)) as an example.
[0008]
First, in the present invention, the pH of cacodylic acid (salt) -containing effluent is measured, and if the pH of the solution exceeds 5, the pH is reduced to 5 or less, preferably around 4 by adding an acid such as hydrochloric acid. , Adjust to 3 to 4.5, for example, and add NaClO. At that time, when iron ions do not coexist in the effluent, a divalent or trivalent iron salt is added to allow the iron ions to coexist in the liquid. The amount of iron salt added is preferably at least 20 times the equivalent of arsenic, for example, 20 to 30 times the equivalent of arsenic, so that the equivalent amount of the arsenic concentration in the liquid is greater. It is desirable that the amount of NaClO added is such that the oxidation-reduction potential is 1000 mV or more, preferably 1200 mV or more.
[0009]
When adding CaCO 3 , powdery CaCO 3 is added excessively. Adding excessively means adding a supersaturated amount sufficient to cause the insoluble matter of CaCO 3 to be suspended and suspended in the liquid. By adding this excess CaCO 3 , flocs in which arsenic is adsorbed are formed in the liquid. At that time, it is desirable to stir the liquid while adding CaCO 3 or after the addition. If it is difficult to filter the floc as it is, add a conventional polymer flocculant such as Accor flock N-100 (made by Mitsui Cyanamid Co., Ltd.) to change the floc into a precipitate that is easy to filter. Solid-liquid separation (for example, filtration). By this solid-liquid separation, arsenic migrates to the precipitation side and the arsenic concentration in the liquid is reduced.
[0010]
The treatment of waste liquid according to the present invention is characterized by a combination of oxidation by adding NaClO and a neutralizing agent for CaCO 3 . The use of an oxidizing agent instead of NaClO such as hydrogen peroxide is not very effective. When NaClO is added to the effluent at a pH of around 4, the molecular mechanism of the organic arsenic compound changes, and as a result, it may be easy to adsorb to excess CaCO 3 . At that time, CaCO 3 has no effect if it is dissociated into Ca 2+ and CO 3 2− ions, and it is important that CaCO 3 is insoluble.
[0011]
Note that if an appropriate amount of iron ions in the solution prior to CaCO 3 added coexist, although organic arsenic by NaClO addition be mineralized believed that it is the that factor, arsenic in CaCO 3 during addition The phenomenon of coprecipitation as iron arsenate also occurs at the same time. Therefore, the combined use of iron salts makes the process of the present invention very advantageous.
[0012]
When the present invention is applied to cacodylic acid (salt) -containing waste liquid and arsenic exceeding the drainage standard is still contained in the liquid after solid-liquid separation, the present liquid is again used for this treated liquid. By carrying out the inventive method, a liquid with a further reduced arsenic concentration can be obtained. Therefore, arsenic can be sufficiently removed by repeating the method of the present invention several times when the concentration of cacodylic acid (salt) in the liquid to be treated is high or in a special drainage.
[0013]
【Example】
[Example 1]
A cacodylic acid [(CH 3 ) 2 AsO (OH)] reagent was dissolved in water to prepare a cacodylic acid aqueous solution containing 20 mg / L (liter) of As, and this was used as a test solution. Hydrochloric acid was added to this test solution to adjust the pH to around 4, and then FeCl 3 was added so that the Fe 3+ concentration was 300 ppm. Next, NaClO was added so that Eh (redox potential) would be 1200 mV or more, and then CaCO 3 powder was added in an amount sufficient to produce insoluble matter and stirred. The pH of the liquid was in the range of 5-7. The suspension was filtered with a polymer flocculant having a trade name of Accor Flock N-100 (manufactured by Mitsui Cyanamid Co., Ltd.) and filtered. When the obtained filtrate was analyzed, As concentration was 5 mg / L.
[0014]
When the same operation as described above was repeated using this As concentration solution of 5 mg / L as the test solution, the As concentration became 0.3 mg / L.
Again, when the same operation as described above was repeated using this As concentration solution of 0.3 mg / L as a test solution, the As concentration became a solution of 0.1 mg / L or less.
[0015]
[Example 2]
The buffer solution used in the pathological study of the medical facility was used as the test solution. When this drainage liquid was analyzed, it contained 13 mg / L of cacodylic acid as the As concentration.
The effluent was adjusted to pH 4.0 with hydrochloric acid, and FeCl 3 was added so that the Fe 3+ concentration was 300 ppm. Next, NaClO was added so that Eh (oxidation-reduction potential) was 1200 mV or more, and then CaCO 3 powder was added excessively and stirred in a state where the insoluble matter was suspended. The pH of the liquid was in the range of 5-7. Next, the floc content was made good by using the same polymer flocculant as in Example 1 and then filtered. When the obtained filtrate was analyzed, As concentration was 1.15 mg / L.
[0016]
When the same treatment was repeated for this solution, the solution had an As concentration of 0.33 mg / L. When the same treatment was repeated again for this solution, the As concentration became 0.1 mg / L or less, and the solution satisfied the drainage regulations.
[0017]
[Comparative Example]
The same effluent as in Example 2 was adjusted to pH 3.0 with hydrochloric acid, 12 g / L of iron powder was added and stirred for 30 minutes, then pH was adjusted to 9.5 with NaOH, and stirring was further continued. When the same polymer flocculant as in Example 1 was added to the resulting suspension for solid-liquid separation, the As concentration in the filtrate was 12.1 mg / L, and the As concentration in the effluent before treatment was 13 mg / L. There was little change compared to L.
[0018]
【The invention's effect】
As described above, according to the present invention, an organic arsenic compound such as cacodylic acid (salt), which has been difficult to remove, can be removed with high removal efficiency. Moreover, the removal operation can be carried out economically because it is easy to obtain and simple with inexpensive reagents. Therefore, it can greatly contribute to improving the water quality of the environment.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35637596A JP3748649B2 (en) | 1996-12-26 | 1996-12-26 | Treatment of cacodylic acid or cacodylate-containing effluent |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35637596A JP3748649B2 (en) | 1996-12-26 | 1996-12-26 | Treatment of cacodylic acid or cacodylate-containing effluent |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10180267A JPH10180267A (en) | 1998-07-07 |
| JP3748649B2 true JP3748649B2 (en) | 2006-02-22 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35637596A Expired - Lifetime JP3748649B2 (en) | 1996-12-26 | 1996-12-26 | Treatment of cacodylic acid or cacodylate-containing effluent |
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| Country | Link |
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| JP (1) | JP3748649B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2010075880A (en) * | 2008-09-26 | 2010-04-08 | Nippon Poly-Glu Co Ltd | Method for purification of arsenic-containing water to be treated |
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| Publication number | Publication date |
|---|---|
| JPH10180267A (en) | 1998-07-07 |
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