JP2015231610A - Method for processing contaminated water - Google Patents
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Abstract
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本発明は、放射能汚染水等の汚染水の処理方法に関する。 The present invention relates to a method for treating contaminated water such as radioactively contaminated water.
２０１１年３月１１日に発生した東北地方太平洋沖地震により、福島第一原子力発電所が甚大な被害を受けた結果、大量の放射能汚染水が発生し、その処理が大きな課題となっている。この放射能汚染水に含まれる主な放射性核種は、セシウム（１３７Ｃｓ）、ストロンチウム（８５Ｓｒ）及びトリチウムである。 The Fukushima Daiichi Nuclear Power Station suffered enormous damage due to the 2011 off the Pacific coast of Tohoku Earthquake that occurred on March 11, 2011. As a result, a large amount of radioactively contaminated water was generated, and its treatment has become a major issue. . Major radionuclides in the radioactive contaminated water, cesium (137 Cs), strontium (85 Sr) and tritium.
現在、この放射能汚染水の処理は、前処理、中間処理及び吸着処理を含む、いわゆる吸着法によって実施されている。しかし、吸着法による処理システムは設備構成が複雑であり、設備稼働と維持管理に多額な費用を要する。更に、吸着法では、放射能汚染水の処理にゼオライトや活性炭などの吸着材を使用するため、高レベルに汚染された使用後の吸着材の廃棄処理という困難な問題が新たに生じる。 Currently, this radioactively contaminated water is treated by a so-called adsorption method including pretreatment, intermediate treatment and adsorption treatment. However, the treatment system using the adsorption method has a complicated equipment configuration, and requires a large amount of money for operation and maintenance of the equipment. Furthermore, in the adsorption method, an adsorbent such as zeolite or activated carbon is used for the treatment of radioactively contaminated water, so that a difficult problem of disposal of the adsorbent after use contaminated at a high level newly arises.
一方、特許文献１には、セシウム含有廃棄物の処理方法として、アルミノケイ酸塩原料、及びアルカリ活性剤を含む溶液に、セシウム含有廃棄物を添加する工程、及び前記溶液をゲル化させる工程を含む、処理方法が提案されている。すなわち、特許文献１の方法は、ジオポリマーを用いてセシウム含有廃棄物を固化してセシウム含有廃棄物中のＣｓを不溶化させようとするものである。 On the other hand, Patent Document 1 includes, as a method for treating cesium-containing waste, a step of adding cesium-containing waste to a solution containing an aluminosilicate raw material and an alkali activator, and a step of gelling the solution. A processing method has been proposed. That is, the method of Patent Document 1 attempts to insolubilize Cs in cesium-containing waste by solidifying cesium-containing waste using a geopolymer.
しかし、特許文献１の方法は、主としてセシウムが付着した瓦礫を焼却して生じる飛灰、すなわち粉状物を処理するもので、セシウムの固定率が比較的低く、かつ水分を多く取り込めないので、放射能汚染水の処理には適用できない。 However, the method of Patent Document 1 mainly treats fly ash generated by incineration of rubble with cesium attached thereto, that is, a powdery material, and the cesium fixation rate is relatively low and a large amount of moisture cannot be taken in. It cannot be applied to the treatment of radioactively contaminated water.
本発明が解決しようとする課題は、放射能汚染水の処理に適用可能な、従来の吸着法に替わる新たな汚染水の処理方法を提供することにある。 The problem to be solved by the present invention is to provide a new contaminated water treatment method that can be applied to the treatment of radioactively contaminated water, replacing the conventional adsorption method.
上記課題の解決にあたり、本発明者らは、汚染水をジオポリマー化することに着目した。そして、汚染水のジオポリマー化にあたり、製紙スラッジ焼却灰を活性フィラーとすることが適当であることを初めて知見し、本発明を完成するに至った。 In solving the above problems, the present inventors have focused on geopolymerizing contaminated water. And when geopolymerization of contaminated water, it discovered for the first time that it was appropriate to use papermaking sludge incineration ash as an active filler, and came to complete this invention.
すなわち、本発明の汚染水の処理方法は、製紙スラッジ焼却灰と、アルカリ活性剤と、汚染水とを混合して、ジオポリマー固化体とすることを特徴とするものである。 That is, the method for treating contaminated water of the present invention is characterized in that a papermaking sludge incinerated ash, an alkali activator, and contaminated water are mixed to form a solidified geopolymer.
本発明によれば、放射能汚染水等の汚染水をジオポリマー固化体とすることで、汚染水に含まれる放射性核種等の汚染物質をジオポリマー固化体内に固定して閉じ込めることができる。すなわち本発明によれば、汚染水そのものをジオポリマー化して処理することができる。 According to the present invention, by using contaminated water such as radioactively contaminated water as a geopolymer solidified body, contaminants such as radionuclides contained in the contaminated water can be fixed and confined in the geopolymer solidified body. That is, according to the present invention, the contaminated water itself can be treated by being geopolymerized.
また、本発明によれば、製紙スラッジ焼却灰と、アルカリ活性剤と、汚染水とを混合するという簡単な工程で汚染水の処理を行うことができるので、従来の吸着法に比べ簡単な設備構成で汚染水の処理を行うことができ、また吸着材の廃棄処理という問題も発生しない。したがって、従来の吸着法に比べ、低コストで効率の高い汚染水の処理を実現できる。 In addition, according to the present invention, the contaminated water can be treated by a simple process of mixing the paper sludge incineration ash, the alkali activator, and the contaminated water, so that the equipment is simpler than the conventional adsorption method. Contaminated water can be treated with the configuration, and the problem of adsorbent disposal does not occur. Therefore, compared to the conventional adsorption method, it is possible to realize highly efficient treatment of contaminated water at a low cost.
本発明の汚染水の処理方法は、基本的にはジオポリマー技術を応用したものである。ジオポリマー技術自体は公知であり、可溶性のケイ素及びアルミニウムを含む活性フィラーと、これを活性化させるアルカリ活性剤を含むアルカリ溶液とを混合し縮重合反応させることで、ジオポリマー固化体を得る技術である。 The method for treating contaminated water according to the present invention is basically an application of geopolymer technology. The geopolymer technology itself is known, and a technology for obtaining a solidified geopolymer by mixing an active filler containing soluble silicon and aluminum and an alkali solution containing an alkali activator for activating the filler and subjecting it to a polycondensation reaction. It is.
従来、活性フィラーとしては、メタカオリンを筆頭に、フライアッシュ、高炉スラグ、下水汚泥溶融スラグ等が知られているが、本発明では製紙スラッジ焼却灰を活性フィラーとして用いる。製紙スラッジ焼却灰とは、パルプ製造工程、紙製造工程、古紙処理工程等から発生する製紙スラッジ（ペーパースラッジ）を焼却処理した際に発生する焼却灰であり、従来、製紙スラッジ焼却灰をジオポリマーの活性フィラーとして用いることは知られていなかった。 Conventionally, fly ash, blast furnace slag, sewage sludge molten slag, etc. are known as active fillers with metakaolin at the top, but in the present invention, paper sludge incinerated ash is used as the active filler. Papermaking sludge incineration ash is incineration ash generated when incineration of papermaking sludge (paper sludge) generated from pulp manufacturing process, paper manufacturing process, waste paper processing process, etc., and conventionally papermaking sludge incineration ash is geopolymer It has not been known to be used as an active filler.
詳細は後述するが、本発明者らが製紙スラッジ焼却灰（以下「ＰＳ灰」という。）の性状を調査したところ、ＰＳ灰はＳｉＯ２とＡｌ２Ｏ３を含み、ジオポリマーの活性フィラーとして利用可能であることがわかった。更に、ＰＳ灰は巣状多孔構造を有し、吸水性が高いため、ＰＳ灰を活性フィラーとしてジオポリマー固化体を作製するには、従来一般的な活性フィラーを用いる場合に比べ多量の液体が必要であることもわかった。すなわち、従来一般的な活性フィラーを用いた場合の液固比（アルカリ溶液の質量／活性フィラーの質量）は高々０．５程度であるところ、ＰＳ灰を活性フィラーとした場合、液固比は１．０〜１．２程度が適正であることがわかった。 Although details will be described later, the present inventors have investigated the properties of paper sludge incineration ash (hereinafter referred to as “PS ash”). As a result, PS ash contains SiO 2 and Al 2 O 3 and serves as an active filler for geopolymers. It turns out that it is available. Furthermore, since PS ash has a nest-like porous structure and high water absorption, a larger amount of liquid is required to produce a solidified geopolymer using PS ash as an active filler than when using a conventional active filler. I also found it necessary. That is, the liquid-solid ratio (mass of alkali solution / mass of active filler) when using a conventional active filler is about 0.5 at most. However, when PS ash is used as the active filler, the liquid-solid ratio is It was found that about 1.0 to 1.2 was appropriate.
本発明者らは、ＰＳ灰を活性フィラーとした場合、液固比を高くする必要があることに着目し、汚染水を溶媒とするアルカリ溶液を大量に混合することにより汚染水をジオポリマー化して処理するという発想を得、本発明に想到したものである。言い換えれば、本発明は、ＰＳ灰の吸水特性と、ジオポリマー固化体の金属イオン、放射性核種等の汚染物質を固定できるという特性を活かして、汚染水の安価・簡便な処理方法を提供するものである。 The present inventors pay attention to the need to increase the liquid-solid ratio when PS ash is used as the active filler, and geopolymerize the contaminated water by mixing a large amount of an alkaline solution using the contaminated water as a solvent. The idea of processing is obtained, and the present invention has been conceived. In other words, the present invention provides an inexpensive and simple treatment method for contaminated water by taking advantage of the water absorption characteristics of PS ash and the ability to fix pollutants such as metal ions and radionuclides in solidified geopolymers. It is.
このように本発明は、ＰＳ灰を活性フィラーとして用いることを特徴の一つとするが、ＰＳ灰を活性フィラーとすることによる吸水特性を消失させない範囲で、他の活性フィラーを併用することは可能である。また、放射性核種等の汚染物質を吸着できる吸着改質剤をＰＳ灰と併用しても良い。前記吸着改質剤としては、例えばゼオライト、酸化チタン、ベントナイト等を併用することが好ましい。この併用によって、ＰＳ灰ジオポリマー固化体の放射性核種等の吸着性を更に改善できる。 As described above, the present invention is characterized in that PS ash is used as an active filler. However, other active fillers can be used in combination as long as the water absorption characteristics of PS ash as an active filler are not lost. It is. In addition, an adsorption modifier that can adsorb contaminants such as radionuclides may be used in combination with PS ash. As the adsorption modifier, for example, zeolite, titanium oxide, bentonite and the like are preferably used in combination. By this combined use, the adsorptivity of the radionuclide of the PS ash geopolymer solidified body can be further improved.
一方、アルカリ溶液中のアルカリ活性剤は、活性フィラーから溶出したケイ素成分、及び金属成分（主としてアルミニウム）の重合を促進させる成分である。アルカリ活性剤としては、水酸化カリウム、水酸化ナトリウム、ケイ酸ナトリウム又はケイ酸カリウムが挙げられ、中でも、より安価なケイ酸ナトリウム及び水酸化ナトリウムを用いることが好ましい。典型的には、汚染水を溶媒として粉末乃至粒状のケイ酸ナトリウム及び苛性ソーダを所定の割合で混合してアルカリ溶液とする。 On the other hand, the alkali activator in the alkaline solution is a component that accelerates the polymerization of the silicon component eluted from the active filler and the metal component (mainly aluminum). Examples of the alkali activator include potassium hydroxide, sodium hydroxide, sodium silicate or potassium silicate, and among them, it is preferable to use cheaper sodium silicate and sodium hydroxide. Typically, powdered or granular sodium silicate and caustic soda are mixed at a predetermined ratio using contaminated water as a solvent to form an alkaline solution.
そして、本発明では上述のとおり、ＰＳ灰と、アルカリ活性剤と、汚染水とを混合して、ジオポリマー固化体とすることで、当該汚染水を処理する。このとき、液固比は１．０〜１．２程度とすることが好ましい。 And in this invention, as mentioned above, the said contaminated water is processed by mixing PS ash, an alkali activator, and contaminated water, and making it a geopolymer solidified body. At this time, the liquid-solid ratio is preferably about 1.0 to 1.2.
本発明が主に処理対象とする汚染水は、放射性核種を含む放射能汚染水、典型的には福島第一原子力発電所で発生しているセシウム（１３７Ｃｓ、１３４Ｃｓ）及びストロンチウム（９０Ｓｒ）等を含む放射能汚染水であるが、一般の原子力廃棄物処理で排出される低レベル汚染水の処理にも適用できる。ただし、本発明の適用範囲は放射能汚染水には限定されない。ジオポリマー固化体は、放射性核種のほかに重金属イオン等の汚染物質を固定できるという特性を有しているので、メッキ廃液や鉱山廃液等の重金属イオンを含む汚染水の処理にも適用可能である。また、水以外の汚染灰等の固化処理にも適用できる。 Contaminated water to be treated mainly by the present invention is radioactive contaminated water containing radionuclides, typically cesium ( 137 Cs, 134 Cs) and strontium ( 90 Sr) generated at the Fukushima Daiichi Nuclear Power Station. ), Etc., but can also be applied to the treatment of low-level contaminated water discharged in general nuclear waste treatment. However, the application range of the present invention is not limited to radioactively contaminated water. The geopolymer solidified material has the property that it can fix pollutants such as heavy metal ions in addition to radionuclides, so it can be applied to the treatment of contaminated water containing heavy metal ions such as plating waste liquid and mine waste liquid. . It can also be applied to solidification treatment of contaminated ash other than water.
２箇所の製紙工場からＰＳ灰のサンプル（それぞれ「ＯＴｏ灰」及び「ＯＴｓ灰」という。）を採取して、その化学組成、密度、ブレーン比表面積及び材料構造の特徴を評価した。 Samples of PS ash (referred to as “OTo ash” and “OTs ash”, respectively) from two paper mills were collected and evaluated for their chemical composition, density, brane specific surface area and material structure characteristics.
次に、ＰＳ灰とアルカリ活性剤と汚染水の三者を混合することを想定してジオポリマー固化体（以下「ＰＳ灰ジオポリマー」という。）を作製した。型枠寸法は２×２×８ｃｍの３個取である。各例におけるＰＳ灰ジオポリマーの配合を表１に示す。 Next, a geopolymer solidified body (hereinafter referred to as “PS ash geopolymer”) was prepared on the assumption that the PS ash, the alkali activator, and the contaminated water were mixed. The mold size is 3 × 2 × 2 × 8 cm. Table 1 shows the composition of the PS ash geopolymer in each example.
アルカリ溶液としては、０号液及び１号液の２種類を用いた。０号液とは、１号水ガラス水溶液（比重１．２７、濃度Ｎａ２Ｏ・２ＳｉＯ２として２４％）と苛性ソーダ水溶液（比重１．３３、濃度３２％、モル濃度１０Ｍ）を３：１の体積比で混合したものである。１号液とは、上記１号水ガラス水溶液のみからなるものである。なお、これらのアルカリ溶液の溶媒は、実際には汚染水とする。 As the alkaline solution, two kinds of solution No. 0 and No. 1 were used. No. 0 solution is No. 1 water glass aqueous solution (specific gravity 1.27, concentration Na 2 O · 24SiO 2 as 24%) and caustic soda aqueous solution (specific gravity 1.33, concentration 32%, molar concentration 10M) 3: 1. It is a mixture by volume ratio. The No. 1 liquid consists only of the No. 1 water glass aqueous solution. Note that the solvent of these alkaline solutions is actually contaminated water.
ジオポリマー固化体（ＰＳ灰ジオポリマー）の放射性核種固定率を試験するために、非放射性のストロンチウム（Ｓｒ）とセシウム（Ｃｓ）の硝酸塩粉末をＰＳ灰１００質量部に対してそれぞれ外割で１質量部混合し、表１に示した液固比で上記の０号液及び１号液をそれぞれ加え、十分混練した後に型枠に流し込んだ。このやり方に従えば、液固比が１より大きくなるにつれて、対汚染水の模擬核種濃度は少しずつ低下するが、実汚染水の再現には優に十分過ぎる量であり、模擬核種固定率の計算を単純に行うことができる利点がある。この添加量を原子換算すると、Ｓｒ＝０．４１４０％、Ｃｓ＝０．６８１９％に相当する。（注：福島第一原発の事故で想定される汚染水の最高放射線量は１０９Ｂｑのオーダーである。本実施例では１０１２Ｂｑオーダーに相当する模擬核種を混合した。） In order to test the radionuclide fixation rate of the geopolymer solidified body (PS ash geopolymer), non-radioactive strontium (Sr) and cesium (Cs) nitrate powders were each divided by 1 per 100 parts by mass of PS ash. After mixing by mass, the above-mentioned No. 0 solution and No. 1 solution were respectively added at the liquid-solid ratio shown in Table 1, sufficiently kneaded, and then poured into a mold. According to this method, as the liquid-solid ratio becomes larger than 1, the concentration of simulated nuclide against contaminated water gradually decreases, but it is an amount that is much more than sufficient for reproduction of actual contaminated water. There is an advantage that the calculation can be performed simply. When this addition amount is converted into atoms, it corresponds to Sr = 0.4140% and Cs = 0.6819%. (Note: The highest radiation dose of contaminated water assumed in the accident at the Fukushima Daiichi nuclear power plant is on the order of 10 9 Bq. In this example, simulated nuclides corresponding to the order of 10 12 Bq were mixed.)
本実施例では、ＯＴｏ灰を用いた例では、Ｓｒ、Ｃｓを単独で添加し、ＯＴｓ灰を用いた例では、Ｓｒ及びＣｓを同時に添加した。 In this example, Sr and Cs were added alone in the example using OTo ash, and Sr and Cs were added simultaneously in the example using OTs ash.
なお、実操業においては、放射性核種で汚染された汚染水を用いるわけであるから、アルカリ溶液として、前もって上記のような０号液及び１号液を調製して用いると反応沈殿を生ずる恐れがある。それを避けるために、０号液及び１号液に使用するアルカリ活性剤は粉末あるいはペレット（粒状体）の形態で所定量加えることが好ましい。また、アルカリ溶液としては、総合的に０号液の組成がより好ましいが、これに限定されるものではない。 In actual operation, since contaminated water contaminated with radionuclides is used, there is a risk that reaction precipitation may occur if the above-mentioned No. 0 and No. 1 solutions are prepared and used as an alkaline solution. is there. In order to avoid this, it is preferable to add a predetermined amount of the alkaline activator used in the No. 0 solution and No. 1 solution in the form of powder or pellets (granular bodies). Moreover, as an alkaline solution, although the composition of No. 0 solution is more preferable comprehensively, it is not limited to this.
作製した曲げ試験体を飽和湿度の大気中に２０℃の室温に保持し、一晩経過してから脱型し、その後、材齢２８日まで養生を続けた。２８日材齢の密度と曲げ強度をそれぞれ測定し、各３本の供試体の平均値を用いて密度と曲げ強度を評価した。 The produced bending test body was kept at a room temperature of 20 ° C. in an atmosphere of saturated humidity, demolded after one night, and then continued to be cured until the age of 28 days. The density and bending strength at the age of 28 days were measured, and the density and bending strength were evaluated using the average values of the three specimens.
また、曲げ試験後の供試体を更に１４日間、常温の大気中に放置し養生した。その後、４ｍｍアンダーに粉砕して１２．５ｇの粉粒体を採取し、酸性雨を想定してｐＨ４．０１の液を使い、液固比が１０の条件で６時間振盪し、ＩＣＰ−ＡＥＳによってストロンチウムとセシウムの溶出量を評価した。 Further, the specimen after the bending test was further left for 14 days to be cured in a normal temperature atmosphere. After that, 12.5 g of powder particles were collected by grinding to under 4 mm, using a liquid with a pH of 4.01 assuming acid rain, shaking for 6 hours under the condition of a liquid-solid ratio of 10, and by ICP-AES The elution amount of strontium and cesium was evaluated.
以下、評価結果を説明する。 Hereinafter, the evaluation results will be described.
（１）ＰＳ灰の物理・化学特性
２箇所の製紙工場で発生したＰＳ灰（ＯＴｏ灰及びＯＴｓ灰）の密度、比表面積及び化学組成を表２に示す。
(1) Physical and chemical characteristics of PS ash Table 2 shows the density, specific surface area, and chemical composition of PS ash (OTo ash and OTs ash) generated at two paper mills.
ＰＳ灰は、密度と粉末度（ブレーン比表面積）がJISII種フライアッシュと同程度であり、主な成分がＳｉＯ２，Ａｌ２Ｏ３及びＣａＯである。すなわち、ＰＳ灰は、ジオポリマー固化体の作製に必須の活性成分ＳｉＯ２，Ａｌ２Ｏ３を有するため、活性フィラーとして使うことができる。ＰＳ灰の主成分を従来一般的に知られている活性フィラーと対比して、ＣａＯ−ＳｉＯ２−Ａｌ２Ｏ３三成分系の三角座標で示すと図１のようになる。 PS ash has the same density and fineness (brane specific surface area) as JIS II type fly ash, and main components are SiO 2 , Al 2 O 3 and CaO. That is, PS ash can be used as an active filler because it has active components SiO 2 and Al 2 O 3 essential for producing a geopolymer solidified body. When the main component of PS ash is compared with the active fillers generally known in the past, the triangular coordinate of the CaO—SiO 2 —Al 2 O 3 ternary system is shown in FIG.
ＰＳ灰を活性フィラーとしてジオポリマー固化体を作製する場合、一般的な活性フィラーを用いるのに比べ、液固比を高くする必要があった（表１参照）。すなわち、ＰＳ灰ジオポリマーを作製するには、従来に比べ多くの液体が必要であった。このメカニズムを解明するために、ＳＥＭ（走査型電子顕微鏡）によってＰＳ灰の構造を観察した。ＰＳ灰のＳＥＭ写真を図２に示す。ＰＳ灰は巣状多孔構造を有する。この巣状多孔構造のためＰＳ灰が高い吸水性を示し、結果として、ＰＳ灰ジオポリマーの作製に多くの液体が必要になると推測される。 When producing a geopolymer solidified body using PS ash as an active filler, it was necessary to increase the liquid-solid ratio compared to using a general active filler (see Table 1). That is, in order to produce PS ash geopolymer, more liquid was required than before. In order to elucidate this mechanism, the structure of PS ash was observed by SEM (scanning electron microscope). An SEM photograph of PS ash is shown in FIG. PS ash has a nest-like porous structure. Due to this nest-like porous structure, PS ash exhibits high water absorption, and as a result, it is assumed that a lot of liquid is required for the production of PS ash geopolymer.
（２）ＰＳ灰ジオポリマーの力学性能及び放射性核種の添加の影響
表１に示した各配合のＰＳ灰ジオポリマーの２８日材齢における力学性能、及びストロンチウム（Ｓｒ）とセシウム（Ｃｓ）の添加有無の影響を表３に示す。
(2) Mechanical performance of PS ash geopolymer and effect of addition of radionuclide Mechanical performance at 28 days of age of PS ash geopolymer of each formulation shown in Table 1, and addition of strontium (Sr) and cesium (Cs) Table 3 shows the effect of presence or absence.
アルカリ溶液として１号液を用いた場合、０号液を用いた場合に比べ強度と嵩密度は高いが、可使時間が約３分であった。可使時間が短いと、成型が難しくなる。ただし、ＰＳ灰との混練と成型の作業を機械的に連続して行えるようにすれば、約３分という可使時間は問題とはならない。 When No. 1 solution was used as the alkaline solution, the strength and bulk density were higher than when No. 0 solution was used, but the pot life was about 3 minutes. If the pot life is short, molding becomes difficult. However, if the kneading and molding operations with PS ash can be performed mechanically continuously, the pot life of about 3 minutes is not a problem.
一方、アルカリ溶液として０号液を用いた場合、可使時間は約１５分で、非連続的な作業の場合でも成型は問題なく行える。曲げ強度は１ＭＰａ弱（推定圧縮強度は５ＭＰａ弱）と、１号液を用いた場合に比べ低下しているが、本発明におけるＰＳ灰ジオポリマーの使途は構造用ではなく汚染水の処理用であるから、汚染水を閉じ込めて固化している状態であればよく、高い強度は必要ではない。また、この０号液を用いた場合のＰＳ灰ジオポリマーの強度は、通常の気泡コンクリート（ＡＬＣ）と同程度である。ＰＳ灰ジオポリマーの密度を１．６ｇ／ｃｍ３とした試算によると、ＰＳ灰ジオポリマーのブロックを３００ｍまで積み上げても、自重で最下層のブロックが壊れることはない。 On the other hand, when No. 0 solution is used as the alkaline solution, the pot life is about 15 minutes, and molding can be performed without problems even in discontinuous work. The bending strength is less than 1 MPa (estimated compressive strength is less than 5 MPa), which is lower than the case of using No. 1 solution, but the use of PS ash geopolymer in the present invention is not for structural use but for treatment of contaminated water. Therefore, it is sufficient that the contaminated water is confined and solidified, and high strength is not necessary. Moreover, the strength of the PS ash geopolymer when this No. 0 solution is used is comparable to that of ordinary cellular concrete (ALC). According to a trial calculation that the density of the PS ash geopolymer is 1.6 g / cm 3 , even if the blocks of the PS ash geopolymer are stacked up to 300 m, the lowermost block is not broken by its own weight.
また、ストロンチウム（Ｓｒ）とセシウム（Ｃｓ）の硝酸塩を添加した場合の影響であるが、無添加の場合に比べ、セシウムを添加した場合にやや強度が低下する傾向が認められたが、力学性能を損なう程のものではない。また、実際の汚染水濃度は本模擬実験の濃度より遥かに低いので問題にならない。 Moreover, although it is an effect when the nitrates of strontium (Sr) and cesium (Cs) are added, there is a tendency that the strength is slightly lowered when cesium is added compared to the case where no strontium is added. It is not something that damages. Moreover, since the actual contaminated water concentration is much lower than the concentration of this simulation experiment, there is no problem.
（３）ＰＳ灰ジオポリマーから放射性核種の溶出
ストロンチウムとセシウムの溶出試験結果を表４に示す。
(3) Elution of radionuclide from PS ash geopolymer Table 4 shows the dissolution test results of strontium and cesium.
ストロンチウム（Ｓｒ）の固定率は、Ｓｒの単独添加、Ｓｒ，Ｃｓの同時添加を問わず、アルカリ溶液として０号液を用いた場合に、ＯＴｏ灰、ＯＴｓ灰双方とも９９．９９％以上と高く、良好な結果であった。一方、アルカリ溶液として１号液を用いた場合、ストロンチウムの固定率は、ＯＴｏ灰は９９．４６％で、ＯＴＳ灰は９６．７６％であった。 The fixing rate of strontium (Sr) is as high as 99.99% or more for both OTo ash and OTs ash when No. 0 solution is used as an alkaline solution regardless of whether Sr is added alone or Sr and Cs are added simultaneously. It was a good result. On the other hand, when the No. 1 solution was used as the alkaline solution, the fixing rate of strontium was 99.46% for OTo ash and 96.76% for OTS ash.
セシウム（Ｃｓ）の固定率は、Ｃｓの単独添加、Ｓｒ，Ｃｓの同時添加を問わず、０号液と１号液共に９５％前後で、ストロンチウムの固定率に比べて低かった。しかし、固定率が９５％であっても、天水や地下水に浸さなければ溶出しないので安全は維持される。 The fixing rate of cesium (Cs) was about 95% for both No. 0 solution and No. 1 solution regardless of whether Cs was added alone or Sr and Cs were added simultaneously, and was lower than the fixing rate of strontium. However, even if the fixation rate is 95%, safety is maintained because it does not elute unless it is immersed in rainwater or groundwater.
以上の結果をまとめると、以下のとおりである。
１）ＰＳ灰を活性フィラーとしてジオポリマーを製造できる。
２）ＰＳ灰は多孔質構造を有し、水分吸着量が多い。また、ジオポリマーは金属イオンを固定する特徴がある。このため、ＰＳ灰と汚染水を溶媒とするアルカリ溶液でジオポリマー固化体を作製することよって放射能汚染水を処理できる。
３）苛性ソーダを使わない低廉な１号液を用いた場合、ＰＳ灰ジオポリマーの可使時間がかなり短くなることから、ＰＳ灰ジオポリマー化のアルカリ溶液としては苛性ソーダを使う０号液が好適である。
４）一般に、ＰＳ灰ジオポリマーの強度は、ストロンチウムの添加によって低下しないが、セシウムの添加では強度がやや低下する場合がある。しかし、強度を損なうほどではなく問題ではない。
５）ＰＳ灰ジオポリマーにおけるストロンチウムとセシウムの固定率は、それぞれ９９％以上と９５％以上を達成することができる。１号液に比べ、０号液を用いたＰＳ灰ジオポリマーのストロンチウム固定率は高く、ストロンチウムはほとんど溶出しない（固定率は９９．９９％以上）。また、同じアルカリ溶液を使う場合、固定率の測定結果は、セシウムよりストロンチウムの方が高い。仮にセシウムは若干溶出して環境基準をクリアできなければ、後述する措置（非常用ミニ処理システムの稼動）を講じることによって、ＰＳ灰ジオポリマー化で放射能汚染水を問題なく処理することができる。
The above results are summarized as follows.
1) A geopolymer can be produced using PS ash as an active filler.
2) PS ash has a porous structure and a large amount of moisture adsorption. In addition, the geopolymer is characterized by fixing metal ions. For this reason, radioactive contamination water can be processed by producing a geopolymer solidified body with the alkaline solution which uses PS ash and contamination water as a solvent.
3) When the inexpensive No. 1 solution that does not use caustic soda is used, the usable time of the PS ash geopolymer is considerably shortened. Therefore, the No. 0 solution using caustic soda is suitable as the alkaline solution for PS ash geopolymerization. is there.
4) Generally, the strength of PS ash geopolymer is not reduced by the addition of strontium, but the strength may be slightly reduced by the addition of cesium. However, this is not a problem as it does not impair the strength.
5) The fixing ratio of strontium and cesium in the PS ash geopolymer can achieve 99% or more and 95% or more, respectively. Compared with No. 1, the strontium fixation rate of PS ash geopolymer using No. 0 solution is high, and strontium is hardly eluted (fixation rate is 99.99% or more). When the same alkaline solution is used, the measurement result of the fixation rate is higher for strontium than for cesium. If cesium elutes slightly and the environmental standards cannot be cleared, the radioactive contamination water can be treated without problems by PS ash geopolymerization by taking the measures described below (operation of the emergency mini-treatment system). .
図３は、本発明を適用した放射能汚染水の処理フローの一例を示す。これは、福島第一原子力発電所で発生している放射能汚染水の処理を想定したものである。 FIG. 3 shows an example of a treatment flow of radioactively contaminated water to which the present invention is applied. This assumes the treatment of radioactively contaminated water generated at the Fukushima Daiichi Nuclear Power Station.
まず、ＰＳ灰にアルカリ活性剤を加えて混合し、更に汚染水を加え練り混ぜて型枠に流し込み、ジオポリマーブロック（ＰＳ灰ＧＰブロック）を作製する。脱型は一晩経過した段階で可能である。 First, an alkali activator is added to PS ash and mixed, and then contaminated water is added and kneaded and poured into a mold to produce a geopolymer block (PS ash GP block). Demolding is possible after one night.
次に、ＰＳ灰ＧＰブロックを積んで、ダムの形でブロックを放置・管理する。このＰＳ灰ＧＰブロックによるダムは、半地下管理、地上管理あるいは廃船流用の洋上管理のいずれもできる。風雨に曝されないように、ダムの頂上には天蓋（キャップ）を設置する。また、水と水蒸気の進入を阻止するために、ダムの壁面には防水仕上げを施す。ダムの頂上からの水蒸気の放出に伴って、トリチウムは放出するが、現在の環境基準はクリアするから問題とならない。なお、ガスクロマト装置等によりトリチウムを安価かつ容易に回収することもできる。 Next, the PS ash GP block is loaded, and the block is left and managed in the form of a dam. This PS ash GP block dam can be used for semi-underground management, ground management, or offshore management for abandoned ships. A canopy (cap) will be installed at the top of the dam so that it will not be exposed to wind and rain. In order to prevent water and water vapor from entering, the dam walls are waterproofed. With the release of water vapor from the top of the dam, tritium is released, but this is not a problem because the current environmental standards are cleared. In addition, tritium can also be recovered inexpensively and easily with a gas chromatograph or the like.
このようなダムによる管理方法では、当該ダムからの水漏れは想定されないが、何らかの原因でダムが浸水した場合、セシウムが少し溶出する恐れがある。そこで、万全を期すために、ダムの底面において浸出水の非常用ミニ処理システムを設置する。収集した浸出水は線量に応じて従来の吸着法で処理して放流する。 In such a management method using a dam, water leakage from the dam is not expected, but if the dam is inundated for some reason, cesium may elute a little. Therefore, an emergency mini-treatment system for leachate will be installed at the bottom of the dam for completeness. The collected leachate is treated and discharged according to the conventional adsorption method according to the dose.
また、将来、仮にダム壁に亀裂が生じてダム側面から水が漏出した場合に備えて、ダム底面の周囲に粉末バリアーを設けており、これにより放射性核種の拡散を食い止めることができる。 Also, in the future, a powder barrier is provided around the bottom of the dam in case a crack occurs in the dam wall and water leaks from the side of the dam, thereby preventing radionuclide diffusion.
上に述べた方法で液体の汚染水自体をタンク管理するよりは固体で管理した方がはるかに安価かつ安全であるが、汚染水の排出が続く限り、タンク群と同様にダム群も増え続けることに変わりはない。これを打破するために、ＰＳ灰ＧＰブロックがある程度乾いた段階で溶融しスラグ化し、いわゆる浅所埋設管理(Shallow burial)を行うのが好ましい。この方法は原発の低レベル廃棄物の処理方法（下記参考文献）と同様である。 It is much cheaper and safer to manage liquid contaminated water as a solid rather than managing it as a tank as described above, but as long as the contaminated water continues to discharge, the number of dams will continue to increase as well as the tanks. That is no different. In order to overcome this, it is preferable to perform so-called shallow burial management by melting the PS ash GP block into a slag when it is somewhat dry. This method is the same as the method for treating low-level waste at the nuclear power plant (reference document below).
参考文献
N. G. Vasil’eva, N. N. Anshits, O. M. Sharonova, M. V. Burdin, and A. G. Anshits：Immobilization of cesium and strontium radionuclides in framework aluminosilicates with the use of porous glass-ceramic materials based on coal fly ash cenospheres. Glass Physics and Chemistry, Vol.31, No. 5, pp. 637-647, 2005.
References
NG Vasil'eva, NN Anshits, OM Sharonova, MV Burdin, and AG Anshits: Immobilization of cesium and strontium radionuclides in framework aluminosilicates with the use of porous glass-ceramic materials based on coal fly ash cenospheres.Glass Physics and Chemistry, Vol. 31, No. 5, pp. 637-647, 2005.
すなわち、本発明の汚染水の処理方法は、製紙スラッジ焼却灰と、アルカリ活性剤と、汚染水とを液固比が１．０以上となるように混合して、ジオポリマー固化体とすることを特徴とするものである。 That is, in the method for treating contaminated water of the present invention, the papermaking sludge incineration ash, the alkali activator, and the contaminated water are mixed so that the liquid-solid ratio is 1.0 or more to obtain a geopolymer solidified body. It is characterized by.
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