JP2013075252A - Treatment method removing cesium and heavy metal from wastewater - Google Patents
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本発明は、セシウムと共に重金属類を含有する排水について、セシウムと重金属類とを同時に除去することができる処理方法に関する。 The present invention relates to a treatment method capable of simultaneously removing cesium and heavy metals from wastewater containing heavy metals together with cesium.
セシウムの除去方法として、不溶性フェロシアン化物を吸着剤として用いる方法が従来から知られている。例えば、特開平０４−１１８５９６号公報（特許文献１）には、セシウムを含む硝酸性溶液を不溶性フェロシアン化物に還元剤の存在下で接触させてセシウムを不溶性フェロシアン化物に吸着させる分離方法が記載されている。 As a method for removing cesium, a method using an insoluble ferrocyanide as an adsorbent is conventionally known. For example, JP 04-118596 A (Patent Document 1) discloses a separation method in which a nitrate solution containing cesium is brought into contact with an insoluble ferrocyanide in the presence of a reducing agent to adsorb cesium to the insoluble ferrocyanide. Have been described.
また、特開平０５−２５４８２８号公報（特許文献２）には、酸化-還元型不溶性鉄シアノ錯塩を用い、還元状態の不溶性鉄シアノ錯塩にセシウム含有水を接触させてセシウムを吸着させた後に、該鉄シアノ錯塩を酸化処理してセシウムを脱着させるセシウムの回収方法が記載されている。 JP-A-05-254828 (Patent Document 2) uses an oxidation-reduction type insoluble iron cyano complex salt, adsorbs cesium by bringing cesium-containing water into contact with the reduced state insoluble iron cyano complex salt, A method for recovering cesium is described in which the iron cyano complex is oxidized to desorb cesium.
さらに、特開平０５−３１７６９７号公報（特許文献３）には、不溶性フェロシアン化物を用いてセシウムを吸着分離するときに、チオグリコール酸などの酸化防止剤やヒドラジン誘導体などの還元剤の存在下で行うことが記載されている。 Furthermore, in Japanese Patent Application Laid-Open No. 05-317697 (Patent Document 3), when cesium is adsorbed and separated using an insoluble ferrocyanide, an antioxidant such as thioglycolic acid or a reducing agent such as a hydrazine derivative is present. It is described to do in.
従来の上記処理方法は、何れもセシウム吸着剤として予め製造された不溶性のフェロシアン化物を用いており、繰り返して使用する場合には、セシウム吸着後に脱着処理などの再生処理を行う必要がある。また、不溶性フェロシアン化物は親水性であり微粒子になりやすく、フィルターなどで分離しても微粒子の一部は通過してしまうため、処理水の全シアン濃度が排水基準値（１mg/L）や環境基準（検出されないこと）を満足することができず、後処理が必要になる。さらに、セシウムと共に重金属類を含む排水について、フェロシアン化物では重金属類を除去することができないので、セシウムと重金属類を除去するにはセシウムの除去工程と重金属の除去工程の二段処理が必要になり、操作が煩雑になる。 All of the conventional treatment methods described above use insoluble ferrocyanide prepared in advance as a cesium adsorbent, and when repeatedly used, it is necessary to perform a regeneration treatment such as a desorption treatment after cesium adsorption. Insoluble ferrocyanide is hydrophilic and tends to become fine particles, and some of the fine particles pass even if separated by a filter, so the total cyanide concentration in the treated water is the drainage standard value (1 mg / L) or Environmental standards (not detected) cannot be met and post-processing is required. Furthermore, for wastewater containing cesium and heavy metals, ferrocyanide cannot remove heavy metals, so two-step treatment of cesium removal and heavy metal removal is required to remove cesium and heavy metals. The operation becomes complicated.
本発明は、従来の処理方法における上記問題を解決したものであり、予め製造された不溶性フェロシアン化物を用いるのではなく、可溶性シアン化合物を用い、これを還元性鉄化合物（硫酸第一鉄など）と共に排水に添加して、セシウムに対して吸着性のある難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱（グリーンラストと鉄フェライトの混合物）を生成させ、この還元性鉄化合物沈澱に排水中のセシウムを重金属類と共に吸着させることによって、セシウムと重金属類を同時に除去できる処理方法を提供する。なお、セシウムに対して吸着性のある難溶性シアノ鉄酸塩を略して単に難溶性シアノ鉄酸塩と云う。 The present invention solves the above-mentioned problems in the conventional treatment method, and does not use a previously produced insoluble ferrocyanide, but uses a soluble cyanide compound, which is used as a reducing iron compound (such as ferrous sulfate). ) Together with wastewater to form a reductive iron compound precipitate (a mixture of green last and iron ferrite) containing a sparingly soluble cyanoferrate that is adsorbable to cesium, and the reductive iron compound precipitate is drained. Provided is a treatment method capable of simultaneously removing cesium and heavy metals by adsorbing cesium therein together with heavy metals. In addition, the hardly soluble cyanoferrate having an adsorptivity to cesium is abbreviated and simply referred to as a hardly soluble cyanoferrate.
本発明は以下の構成からなる処理方法である。
〔１〕排水に還元性鉄化合物を添加して還元性鉄化合物からなる沈澱を生成させ、該沈澱に排水中の重金属類を吸着させ、重金属類を吸着した濃縮汚泥を固液分離して重金属類を排水から除去する処理方法において、重金属類と共にセシウムを含む排水に還元性鉄化合物と可溶性シアン化合物を添加してセシウムに対して吸着性のある難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱を生成させ、該沈澱に排水中のセシウムと重金属類を吸着させ、セシウムと重金属類を吸着した濃縮汚泥を固液分離して排水からセシウムと重金属類を除去することを特徴とする処理方法。
〔２〕セシウムに対して吸着性のある難溶性シアノ鉄酸塩が難溶性ヘキサシアノ鉄酸塩であり、該難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱がグリーンラストと鉄フェライトの混合物である上記[１]に記載する処理方法。
〔３〕上記[１]または上記[２]に記載する処理方法において、セシウムと重金属類を吸着した濃縮汚泥を固液分離し、分離した汚泥の一部または全部を反応工程に戻して再使用することによって、難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱の生成を促す処理方法。
The present invention is a processing method having the following configuration.
[1] A reductive iron compound is added to the waste water to form a precipitate made of the reducible iron compound, the heavy metal in the waste water is adsorbed to the precipitate, and the concentrated sludge that has adsorbed the heavy metal is separated into solid and liquid to separate the heavy metal Reductive compound containing a sparingly soluble cyanoferrate adsorbable to cesium by adding a reductive iron compound and a soluble cyanide compound to a wastewater containing cesium together with heavy metals A treatment method characterized by forming a precipitate, adsorbing cesium and heavy metals in the waste water to the precipitate, separating the concentrated sludge adsorbing the cesium and heavy metals by solid-liquid separation, and removing the cesium and heavy metals from the waste water .
[2] The sparingly soluble cyanoferrate adsorbing to cesium is a sparingly soluble hexacyanoferrate, and the reducing iron compound precipitate containing the sparingly soluble cyanoferrate is a mixture of green last and iron ferrite. A processing method according to [1] above.
[3] In the treatment method described in [1] or [2] above, the concentrated sludge adsorbing cesium and heavy metals is solid-liquid separated, and part or all of the separated sludge is returned to the reaction step and reused. A treatment method that promotes the formation of a reducible iron compound precipitate containing a hardly soluble cyanoferrate.
本発明の処理方法は、可溶性シアン化合物と還元性鉄化合物を排水に添加して沈澱を生成させる。この沈澱は難溶性シアノ鉄酸塩を含み、グリーンラストと鉄フェライトの混合物からなる還元性鉄化合物沈澱であり、このグリーンラストは第一鉄と第二鉄の水酸化物からなる層状化合物であり、層間にアニオンを取り込む構造を有しているので、排水中のクロム、セレン、ヒ素、アンチモンなどのオキシアニオン系の重金属類はこの層間に取り込まれた状態で沈澱する。さらに、鉄の一部が陽イオン系の重金属類と置換することにより、カドミウム、鉛、銅、亜鉛、鉄、ニッケル、マンガン、コバルトなどの重金属類が取り込まれる。 In the treatment method of the present invention, a soluble cyanide compound and a reducing iron compound are added to waste water to form a precipitate. This precipitate contains a sparingly soluble cyanoferrate and is a reducing iron compound precipitate consisting of a mixture of green last and iron ferrite. This green last is a layered compound consisting of hydroxides of ferrous iron and ferric iron. Since it has a structure for taking in an anion between layers, oxyanion heavy metals such as chromium, selenium, arsenic and antimony in the waste water are precipitated in the state taken up between the layers. Furthermore, heavy metals such as cadmium, lead, copper, zinc, iron, nickel, manganese, and cobalt are taken in by replacing a part of iron with cationic heavy metals.
本発明の処理方法は、さらに可溶性シアン化合物を添加するので、上記還元性鉄化合物沈澱は難溶性シアノ鉄酸塩を含み、この難溶性シアノ鉄酸塩によってセシウム吸着能を有する還元性鉄化合物沈澱が形成される。排水中で上記還元性鉄化合物沈澱が生成されると、排水中のセシウムは重金属類と共にこの還元性鉄化合物沈澱に取り込まれて沈澱する。このように本発明の処理方法は排水中のセシウムと重金属類を同時に沈澱化して除去することができるので、セシウムの除去工程と重金属の除去工程の二段処理を行う必要がない。 In the treatment method of the present invention, since a soluble cyanide compound is further added, the reducible iron compound precipitate contains a hardly soluble cyanoferrate, and the reducible iron compound precipitated having a cesium adsorption ability by the hardly soluble cyanoferrate. Is formed. When the reducible iron compound precipitate is generated in the wastewater, cesium in the wastewater is taken into the reducible iron compound precipitate together with heavy metals. As described above, the treatment method of the present invention can simultaneously precipitate and remove cesium and heavy metals in the waste water, so that it is not necessary to perform a two-stage treatment of the cesium removal step and the heavy metal removal step.
また、本発明の処理方法は、セシウムと重金属類を吸着した濃縮汚泥を固液分離し、分離した濃縮汚泥の一部または全部を反応工程に戻して再使用することによって、難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱の生成を促すことができ、セシウムの脱着処理せずに汚泥を再利用して処理効果を高めることができる。また、濃縮汚泥の一部または全部を沈殿生成工程にもどすことにより、沈降速度を増加させることができ、短時間に固液分離することができる。さらに、固液分離後の処理水中の浮遊粒子（ＳＳ）はほとんどなく、シアン化合物は還元性鉄化合物沈澱中のグリーンラストによって吸着可能であるため、溶解性および不溶性のシアン化合物の濃度を検出限界未満まで低減することができる。 In addition, the treatment method of the present invention separates the concentrated sludge adsorbing cesium and heavy metals into a solid and liquid, and returns a part or all of the separated concentrated sludge to the reaction step and reuses it, thereby making the hardly soluble cyanoferric acid Formation of reductive iron compound precipitates containing salts can be promoted, and the treatment effect can be enhanced by reusing sludge without cesium desorption treatment. Moreover, by returning a part or all of the concentrated sludge to the precipitation generation step, the sedimentation rate can be increased, and solid-liquid separation can be performed in a short time. In addition, there are almost no suspended particles (SS) in the treated water after solid-liquid separation, and cyanide can be adsorbed by the green last in the reductive iron compound precipitation, so the concentration of soluble and insoluble cyanide can be detected. It can be reduced to less than.
以下、本発明を実施形態に基づいて具体的に説明する。
本発明の処理方法は、排水に還元性鉄化合物を添加して還元性鉄化合物からなる沈澱を生成させ、該沈澱に排水中の重金属類を吸着させ、重金属類を吸着した濃縮汚泥を固液分離して重金属類を排水から除去する処理方法において、重金属類と共にセシウムを含む排水に還元性鉄化合物と可溶性シアン化合物を添加して難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱を生成させ、該沈澱に排水中のセシウムと重金属類を吸着させ、セシウムと重金属類を吸着した濃縮汚泥を固液分離して排水からセシウムと重金属類を除去することを特徴とする排水からセシウムと重金属類を除去する処理方法である。本発明の処理方法の概略を図１に示す。
Hereinafter, the present invention will be specifically described based on embodiments.
In the treatment method of the present invention, a reducing iron compound is added to wastewater to form a precipitate made of a reducing iron compound, heavy metals in the wastewater are adsorbed to the precipitate, and the concentrated sludge adsorbing heavy metals is solid-liquid. In a treatment method that separates and removes heavy metals from wastewater, a reductive iron compound and a soluble cyanide compound are added to wastewater containing cesium together with heavy metals to form a reducible iron compound precipitate containing a sparingly soluble cyanoferrate. The cesium and heavy metals in the waste water are adsorbed on the precipitate, and the concentrated sludge adsorbing the cesium and heavy metals is solid-liquid separated to remove the cesium and heavy metals from the waste water. It is the processing method which removes. An outline of the treatment method of the present invention is shown in FIG.
本発明の処理方法は、重金属類と共にセシウムを含む排水からセシウムと重金属類を同時に除去する処理方法である。この排水は自然発生的および人為的に生じた各種の廃水や排水等を含み、例えば、工場排水や下水、海水、河川水、沼や湖池の水、地表の溜り水、河川等の堰止域の水、地下の流水や溜り水、暗渠の水、放射性物質で汚染された地下水、放射性物質で汚染された土壌、瓦礫、建造物、農作物、飛灰、あるいは汚泥などを除染したときに発生する洗浄水などを含めて広く排水と云う。また、重金属類とは、例えば、セレン、カドミウム、六価クロム、鉛、亜鉛、銅、ニッケル、ヒ素、アンチモン、コバルト、マンガン、鉄などの金属元素である。 The treatment method of the present invention is a treatment method for simultaneously removing cesium and heavy metals from wastewater containing cesium together with heavy metals. This wastewater includes various types of wastewater and wastewater that are generated naturally and artificially. For example, industrial wastewater and sewage, seawater, river water, water in swamps and lakes, surface pool water, rivers, etc. When decontaminating area water, underground running water or pool water, underdrain water, groundwater contaminated with radioactive materials, soil contaminated with radioactive materials, rubble, buildings, crops, fly ash, or sludge It is widely referred to as drainage, including the generated wash water. The heavy metals are metal elements such as selenium, cadmium, hexavalent chromium, lead, zinc, copper, nickel, arsenic, antimony, cobalt, manganese, and iron.
本発明の処理方法は、重金属類およびセシウムを含むこれらの排水に、還元性鉄化合物と可溶性シアン化合物を添加して、難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱を生成させる。還元性鉄化合物としては、硫酸第一鉄(ＦｅＳＯ4)、塩化第一鉄(ＦｅＣｌ2)などの第一鉄化合物を用いることができる。可溶性シアン化合物としては、フェロシアン化カリウム〔Ｋ4[Ｆｅ(ＣＮ)6]〕、フェリシアン化カリウム〔Ｋ3[Ｆｅ(ＣＮ)6]〕フェロシアン化ナトリウム〔Ｎａ4[Ｆｅ(ＣＮ)6]〕、フェリシアン化ナトリウム〔Ｎａ3[Ｆｅ(ＣＮ)6]〕、シアン化ナトリウム〔ＮａＣＮ〕、シアン化カリウム〔ＫＣＮ〕などを用いることができる。また、シアン化合物を含む廃メッキ浴なども用いることができる。
還元性鉄化合物および可溶性シアン化合物の添加量は、還元性鉄化合物沈澱が十分に生成する量であればよい。
In the treatment method of the present invention, a reductive iron compound and a soluble cyanide compound are added to these wastewaters containing heavy metals and cesium to form a reducible iron compound precipitate containing a hardly soluble cyanoferrate. As the reducing iron compound, ferrous compounds such as ferrous sulfate (FeSO 4 ) and ferrous chloride (FeCl 2 ) can be used. Soluble cyanide compounds include potassium ferrocyanide [K 4 [Fe (CN) 6 ]], potassium ferricyanide [K 3 [Fe (CN) 6 ]] sodium ferrocyanide [Na 4 [Fe (CN) 6 ]], ferricia Sodium cyanide [Na 3 [Fe (CN) 6 ]], sodium cyanide [NaCN], potassium cyanide [KCN] and the like can be used. A waste plating bath containing a cyanide compound can also be used.
The addition amount of the reducing iron compound and the soluble cyanide compound may be an amount that sufficiently produces a reducing iron compound precipitate.
排水に還元性鉄化合物と共に可溶性シアン化合物を添加することにより、難溶性シアノ鉄酸塩が生成し、この難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱が生成する。難溶性シアノ鉄酸塩は、例えば、難溶性ヘキサシアノ鉄酸塩〔ＭI xＭII (4-x)/2[ＦｅII（ＣＮ）６]（ＭI：１価金属、アンモニウムイオンなど、ＭII：２価金属）〕などであり、ＭIやＭIIの一部が置換することによってセシウムを吸着することができる。 By adding a soluble cyanide compound together with a reducible iron compound to the wastewater, a hardly soluble cyanoferrate is produced, and a reducible iron compound precipitate containing this hardly soluble cyanoferrate is produced. The hardly soluble cyanoferrate is, for example, a hardly soluble hexacyanoferrate [M I x M II (4-x) / 2 [Fe II (CN) 6] (M I : monovalent metal, ammonium ion, M II : divalent metal)], etc., and cesium can be adsorbed by substituting part of M I and M II .
上記排水に還元性鉄化合物を添加し、反応条件を整えると、グリーンラストと鉄フェライトの混合物からなる還元性鉄化合物沈澱を生成させることができる。グリーンラストは次式[１]に示すように、第一鉄と第二鉄の水酸化物からなる層状化合物であり、層間にアニオンを取り込む構造を有しているので、排水中のオキシアニオン系の重金属類（クロム、ヒ素、セレン、アンチモンなど）はこの層間に取り込まれて、汚泥と一緒に沈澱する。
〔ＦｅII (6-x)ＦｅIII x（ＯＨ）12〕x+〔Ａx/n・ｙＨ2Ｏ〕x-……[１]
（０.９＜ｘ＜４.２、Ｆｅ2+/全Ｆｅ＝０.４〜０.８、Ａ：オキシアニオン系重金属類）
When a reducing iron compound is added to the waste water and the reaction conditions are adjusted, a reducing iron compound precipitate composed of a mixture of green last and iron ferrite can be generated. As shown in the following formula [1], the green last is a layered compound composed of ferrous hydroxide and ferric hydroxide, and has a structure for taking in an anion between layers. Heavy metals (chromium, arsenic, selenium, antimony, etc.) are trapped between the layers and settle together with the sludge.
[Fe II (6-x) Fe III x (OH) 12 ] x + [A x / n · yH 2 O] x- ...... [1]
(0.9 <x <4.2, Fe 2+ / total Fe = 0.4 to 0.8, A: oxyanion heavy metals)
さらに、鉄の一部が陽イオン系の重金属類と置換することにより、カドミウム、鉛、銅、亜鉛、鉄、ニッケル、マンガン、コバルトなどの重金属類が取り込まれて、汚泥と一緒に沈澱する。また、グリーンラストはシアン化合物も吸着することができるため、排水中にシアンが残留することがなく、環境汚染の心配がない。 Furthermore, heavy metals such as cadmium, lead, copper, zinc, iron, nickel, manganese, cobalt, etc. are taken in and replaced with sludge by replacing some of the iron with cationic heavy metals. In addition, since the green last can also adsorb cyanide compounds, cyan does not remain in the waste water, and there is no concern about environmental pollution.
鉄フェライトは鉄(III)酸塩であり、マグネタイト（ＦｅIIＦｅIII 3Ｏ4）を主体とするが、一部に重金属類の鉄酸塩を含むものでもよい。排水中の重金属類はグリーンラストに取り込まれ、グリーンラストは重金属類を一部に含んだ状態で鉄フェライト化する。 The iron ferrite is an iron (III) acid salt and is mainly composed of magnetite (Fe II Fe III 3 O 4 ), but may contain a heavy metal iron salt in part. Heavy metals in the wastewater are taken into the green rust, and the green rust is converted to iron ferrite with some heavy metals included.
図１に示すように、還元性鉄化合物および可溶性シアン化合物を添加した排水は反応工程（沈澱生成工程）の反応槽に導入される。反応槽は密閉された非酸化性雰囲気のものが好ましい。ｐＨ８.５〜１１、好ましくはｐＨ９.０〜１０のアルカリ性下で反応させる。液温は１０℃〜３０℃程度で良く、加熱する必要はない。反応時間は３０分〜３時間程度で良い。添加するアルカリ剤としては、特に限定されず、消石灰、生石灰、水酸化ナトリウムなどを用いることができる。 As shown in FIG. 1, the waste water to which the reducing iron compound and the soluble cyanide compound are added is introduced into the reaction tank of the reaction process (precipitation production process). The reaction vessel is preferably a sealed non-oxidizing atmosphere. The reaction is carried out under alkaline pH 8.5 to 11, preferably pH 9.0 to 10. The liquid temperature may be about 10 ° C. to 30 ° C. and does not need to be heated. The reaction time may be about 30 minutes to 3 hours. It does not specifically limit as an alkaline agent to add, Slaked lime, quicklime, sodium hydroxide, etc. can be used.
生成した沈澱が還元力を有するように、該沈澱の２価鉄イオンと全鉄イオンの比〔Fe2+/Fe(T)〕が０.４〜０.８になるようにするのが良く、上記鉄イオン比を０.５５〜０.６５に制御するのが更に好ましい。この比が上記範囲を外れると還元性が不十分になり、また澱物の沈降性が低下するので好ましくない。上記還元性鉄化合物沈澱を生成させることによって、排水中の重金属類が還元され、容易に沈澱（汚泥）に取り込まれる。さらに、還元力を有することにより、セシウムの吸着能力も高めることができる。 The ratio of the divalent iron ions to the total iron ions [Fe 2+ / Fe (T)] of the precipitate should be 0.4 to 0.8 so that the generated precipitate has a reducing power. More preferably, the iron ion ratio is controlled to 0.55 to 0.65. If this ratio is out of the above range, the reducing property becomes insufficient and the sedimentation property of the starch is lowered, which is not preferable. By generating the reducible iron compound precipitate, heavy metals in the wastewater are reduced and easily taken into the precipitate (sludge). Furthermore, the ability to adsorb cesium can be increased by having a reducing power.
排水に還元性鉄化合物と可溶性シアン化合物を添加することによって、上記還元性鉄化合物沈澱は難溶性シアノ鉄酸塩を含み、この難溶性シアノ鉄酸塩によってセシウム吸着能を有する還元性鉄化合物沈澱が生成される。このような沈澱が排水中で生成されることによって、この沈澱に排水中のセシウム（Ｃｓ）が重金属類と共に取り込まれる。また、添加順序は還元性鉄化合物、可溶性シアン化合物のどちらが先でもよく、添加方法も特に限定されない。 By adding a reductive iron compound and a soluble cyanide compound to the waste water, the reductive iron compound precipitate contains a hardly soluble cyanoferrate, and this hardly soluble cyanoferrate has a cesium adsorption ability. Is generated. By generating such a precipitate in the waste water, cesium (Cs) in the waste water is taken into the precipitate together with heavy metals. The order of addition may be either the reducing iron compound or the soluble cyanide, and the addition method is not particularly limited.
反応槽で生成した還元性鉄化合物沈澱を含むスラリーは、セシウムおよび重金属類を取り込んだ状態で、固液分離工程の固液分離槽（シックナーなど）に導入され、固液分離する時間（数時間〜数十時間）静置される。 The slurry containing the reducible iron compound precipitate generated in the reaction tank is introduced into the solid-liquid separation tank (such as thickener) in the solid-liquid separation process with cesium and heavy metals taken in, and the time for solid-liquid separation (several hours) ~ Tens of hours)
本発明の処理方法によれば、固液分離槽内で沈降した汚泥は沈降性・脱水性が良く圧密した汚泥（濃縮汚泥）を得ることができるので、取扱いやすく、また小型の固液分離槽を使用することができる。濃縮汚泥に含まれるセシウムおよび重金属類の濃度が高くなったものは余剰汚泥として系外に取り出し、適切に処分することができる。 According to the treatment method of the present invention, the sludge settled in the solid-liquid separation tank can obtain a compacted sludge (concentrated sludge) with good sedimentation and dewaterability, and is easy to handle and a small solid-liquid separation tank. Can be used. The cesium and heavy metals contained in the concentrated sludge can be taken out of the system as excess sludge and disposed of appropriately.
また、セシウムおよび重金属類の濃度があまり高くない濃縮汚泥は、その一部または全部にアルカリを添加してｐＨ１１〜１３に調整し（アルカリ調整工程）、これを反応工程の密閉反応槽に戻して繰り返し使用し、難溶性シアノ鉄酸塩を含む還元性鉄化合物沈澱の生成を促すことができる。
Concentrated sludge with a very low concentration of cesium and heavy metals is adjusted to
一方、固液分離した液分（処理水）は、セシウムおよび重金属類の大部分が除去されており、重金属類の排水基準（０.０１mg/L以下）を容易に満たすことができる。排水基準を満たすものは系外に放流される。 On the other hand, most of the cesium and heavy metals are removed from the liquid (separated water) that has been subjected to solid-liquid separation, and can easily meet the wastewater standard for heavy metals (0.01 mg / L or less). Those that meet the drainage standards are discharged outside the system.
〔実施例１〕
原水（Ｃｓ濃度５mg/L、Ｃｏ濃度１mg/L、Ｎｉ濃度１mg/L）に、フェロシアン化カリウム４mg/Lを添加し、１５分間撹拌する。次いで、原水にさらに硫酸第一鉄１.５g/L（鉄として３００mg/L）を加えて反応槽に導入した。この反応槽に、直前のバッチ処理で分離した濃縮汚泥全量に５％濃度の消石灰液を加えて１５分間撹拌し、ｐＨ１１〜１３に調整したアルカリ汚泥を添加して、フェロシアン化カリウムおよび硫酸第一鉄を加えた原水と混合した。反応槽にさらに５％濃度の消石灰液を加えて槽内をｐＨ９.５に調整し、１５分間撹拌して沈澱（汚泥）を生成させた。汚泥を含むスラリーを取り分けて一晩放置し、固液分離した。分離した汚泥は次のバッチ処理に使用した。分離した液分のＣｓ濃度、Ｃｏ濃度、およびＮｉ濃度をＩＣＰ発光分析法により測定した。この結果を表１に示した。
[Example 1]
To raw water (Cs concentration 5 mg / L, Co concentration 1 mg / L, Ni concentration 1 mg / L), potassium ferrocyanide 4 mg / L is added and stirred for 15 minutes. Next, 1.5 g / L of ferrous sulfate (300 mg / L as iron) was further added to the raw water and introduced into the reaction vessel. To this reaction tank, 5% concentrated slaked lime solution is added to the total amount of concentrated sludge separated in the immediately preceding batch treatment, and the mixture is stirred for 15 minutes. Then, alkaline sludge adjusted to pH 11-13 is added, and potassium ferrocyanide and ferrous sulfate are added. And mixed with raw water. A 5% strength slaked lime solution was further added to the reaction tank to adjust the inside of the tank to pH 9.5, and the mixture was stirred for 15 minutes to generate a precipitate (sludge). Slurry containing sludge was separated and allowed to stand overnight for solid-liquid separation. The separated sludge was used for the next batch treatment. The Cs concentration, Co concentration, and Ni concentration of the separated liquid were measured by ICP emission spectrometry. The results are shown in Table 1.
〔実施例２〕
フェロシアン化カリウム８mg/Lを使用した以外は実施例１と同様にして原水を処理し、分離した液分のＣｓ濃度、Ｃｏ濃度、およびＮｉ濃度を測定した。この結果を表１に示した。
[Example 2]
Raw water was treated in the same manner as in Example 1 except that potassium ferrocyanide 8 mg / L was used, and the Cs concentration, Co concentration, and Ni concentration of the separated liquid were measured. The results are shown in Table 1.
表１に示すように、実施例１および実施例２の何れにおいても、処理水のＣｏ濃度およびＮｉ濃度は０.０１mg/L未満であり、重金属類が除去されている。また、実施例１の処理水のＣｓ濃度は２.９〜３.６mg/Lであり、原水のＣｓ濃度の約６０％〜約７０％に低下している。さらに、実施例２の処理水のＣｓ濃度は１.５〜１.９mg/Lであり、原水のＣｓ濃度の約３０％〜約４０％に低下しており、重金属と同時にセシウムが除去されている。また、残留ＣＮ濃度も繰り返し回数の増加により低下していくことがわかった。さらに繰り返し回数の増加により、沈降速度が上昇して分離性が向上することがわかった。 As shown in Table 1, in both Example 1 and Example 2, the Co concentration and Ni concentration of treated water were less than 0.01 mg / L, and heavy metals were removed. Moreover, the Cs density | concentration of the treated water of Example 1 is 2.9-3.6 mg / L, and has fallen to about 60%-about 70% of Cs density | concentration of raw | natural water. Furthermore, the Cs concentration of the treated water of Example 2 is 1.5 to 1.9 mg / L, which is reduced to about 30% to about 40% of the Cs concentration of the raw water, and cesium is removed simultaneously with the heavy metal. Yes. In addition, it was found that the residual CN concentration also decreases as the number of repetitions increases. Furthermore, it was found that the segregation rate was increased and the separability was improved by increasing the number of repetitions.
Claims (3)
A reducing iron compound is added to the wastewater to form a precipitate made of the reducing iron compound, the heavy metals in the wastewater are adsorbed to the precipitate, and the concentrated sludge adsorbing the heavy metals is separated into solid and liquid to drain the heavy metals. In the treatment method to remove from the wastewater, a reductive iron compound and a soluble cyanide compound are added to the wastewater containing cesium together with heavy metals to form a reductive iron compound precipitate containing a sparingly soluble cyanoferrate adsorbing to cesium And cesium and heavy metals in the waste water are adsorbed on the precipitate, and the concentrated sludge adsorbing the cesium and heavy metals is solid-liquid separated to remove the cesium and heavy metals from the waste water.
A sparingly soluble cyanoferrate adsorbing to cesium is a sparingly soluble hexacyanoferrate, and the reducing iron compound precipitate containing the sparingly soluble cyanoferrate is a mixture of green last and iron ferrite. The processing method described in 1.
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