JP2015105920A - Soil decontamination apparatus and soil decontamination method - Google Patents

Soil decontamination apparatus and soil decontamination method Download PDF

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JP2015105920A
JP2015105920A JP2013249386A JP2013249386A JP2015105920A JP 2015105920 A JP2015105920 A JP 2015105920A JP 2013249386 A JP2013249386 A JP 2013249386A JP 2013249386 A JP2013249386 A JP 2013249386A JP 2015105920 A JP2015105920 A JP 2015105920A
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soil
ammonium oxalate
decontamination apparatus
solution
hydrogen ion
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JP6376547B2 (en
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中村　秀樹
Hideki Nakamura
秀樹 中村
紘子 阿部
Hiroko Abe
紘子 阿部
直樹 田嶋
Naoki Tajima
直樹 田嶋
金子　昌章
Masaaki Kaneko
昌章 金子
福島　正
Tadashi Fukushima
正 福島
紘 竹迫
Hiroshi Takesako
紘 竹迫
俊六郎 藤原
Shunrokuro Fujiwara
俊六郎 藤原
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Toshiba Corp
Meiji University
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Meiji University
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Abstract

PROBLEM TO BE SOLVED: To provide a soil decontamination technique capable of easily, efficiently removing radioactive cesium from the soil contaminated with the radioactive cesium.SOLUTION: A soil decontamination apparatus 10 includes: an elution tank 12 for storing therein soil 11 contaminated with cesium; a holding tank 13 for holding an ammonium oxalate solution to be mixed into the soil 11; a pH meter 15 for measuring a hydrogen ion exponent of a mixture 14 of the soil 11 with the ammonium oxalate solution; and a pH adjustment tank 16 (16a, 16b) for loading a pH adjuster into the mixture 14 so that a measured value of the hydrogen ion exponent falls within a range from pH6 to pH9.

Description

本発明は、放射性物質に汚染された土壌の除染技術に関する。   The present invention relates to a decontamination technique for soil contaminated with radioactive substances.

原子力発電所において大規模な事故が発生した場合、大量の放射性核種が飛散し、環境汚染を引き起こすことが懸念される。この環境汚染は、土壌、樹木、建築物、建造物、海洋および湖沼水、などの汚染を引き起こす。
汚染された土壌に含有される放射性核種の大部分は、134Ｃｓ、137Ｃｓ、90Ｓｒであり、特に137Ｃｓは半減期が３０．２年と長く、長期に影響を及ぼすことが想定される。 When a large-scale accident occurs at a nuclear power plant, there is a concern that a large amount of radionuclide will be scattered and cause environmental pollution. This environmental pollution causes contamination of soil, trees, buildings, buildings, oceans and lakes.
The majority of radionuclides contained in contaminated soil are 134 Cs, 137 Cs, and 90 Sr. In particular, 137 Cs has a long half-life of 30.2 years and is expected to affect the long term. .

そのため、放射能に汚染された土壌、建築・建造物、汚泥及び焼却灰等から、セシウムを除去する技術の確立が模索されている。
先行提案された放射能汚染物質の除染技術として、汚染土壌に有機酸を添加してＣｓを液中に溶離した後、吸着剤を用いてＣｓを回収する方法がある（例えば、特許文献１）。 For this reason, establishment of a technique for removing cesium from soil, buildings / buildings, sludge, incinerated ash, etc. contaminated by radioactivity is being sought.
As a previously proposed decontamination technique for radioactive pollutants, there is a method of recovering Cs using an adsorbent after adding organic acid to contaminated soil and eluting Cs into the liquid (for example, Patent Document 1). ).

特開２０１３−８８３６２号公報JP 2013-88362 A

この先行技術によれば、溶離液として使用される有機酸は、水素イオン指数がｐＨ０．７〜２と強酸で、毒性および腐食性が高いため、取り扱いが難しく、システムコストも高くなる課題があった。また、溶離工程で高温にする必要があった。
同様に、溶離液に強アルカリ（例えば、水酸化カリウム）を使用する場合も、高温に設定する必要があり、雰囲気に漂うヒューム等の対策が必要となり、取り扱いが困難である課題があった。 According to this prior art, the organic acid used as an eluent is a strong acid having a hydrogen ion index of pH 0.7-2, and is highly toxic and corrosive, which makes it difficult to handle and increases the system cost. It was. In addition, it was necessary to increase the temperature in the elution process.
Similarly, when a strong alkali (for example, potassium hydroxide) is used as the eluent, it is necessary to set the temperature to a high temperature, and countermeasures such as fumes floating in the atmosphere are required, which makes it difficult to handle.

本発明はこのような事情を考慮してなされたもので、放射性セシウムに汚染された土壌から、セシウムを簡易かつ効率的に除去する土壌除染技術を提供することを目的とする。   The present invention has been made in view of such circumstances, and an object of the present invention is to provide a soil decontamination technique for easily and efficiently removing cesium from soil contaminated with radioactive cesium.

本発明の土壌除染装置において、セシウムに汚染された土壌を収容する溶離槽と、前記土壌に混合させるシュウ酸アンモニウム溶液を保持する保持槽と、前記土壌及びシュウ酸アンモニウム溶液の混合系の水素イオン指数を計測し前記水素イオン指数の計測値がｐＨ６〜ｐＨ９の範囲に含まれるように前記混合系のｐＨを調整するｐＨ調整装置と、を備えることを特徴とする。   In the soil decontamination apparatus of the present invention, an elution tank for storing soil contaminated with cesium, a holding tank for holding an ammonium oxalate solution to be mixed with the soil, and a hydrogen in a mixed system of the soil and the ammonium oxalate solution A pH adjusting device that measures the ion index and adjusts the pH of the mixed system so that the measured value of the hydrogen ion index is included in the range of pH 6 to pH 9.

本発明により、放射性セシウムに汚染された土壌から、セシウムを簡易かつ効率的に除去する土壌除染技術が提供される。   According to the present invention, there is provided a soil decontamination technique for easily and efficiently removing cesium from soil contaminated with radioactive cesium.

本発明に係る土壌除染装置の実施形態を示すブロック図。The block diagram which shows embodiment of the soil decontamination apparatus which concerns on this invention. シュウ酸アンモニウム水溶液に対する浸漬時間と汚染土壌のＣｓ溶離率との関係を示すグラフ。The graph which shows the relationship between the immersion time with respect to ammonium oxalate aqueous solution, and the Cs elution rate of contaminated soil. シュウ酸アンモニウム水溶液又はシュウ酸水溶液（比較例）による洗浄処理回数と汚染土壌のＣｓ溶離率との関係を示すグラフ。The graph which shows the relationship between the frequency | count of the washing process by the ammonium oxalate aqueous solution or the oxalic acid aqueous solution (comparative example), and the Cs elution rate of contaminated soil. シュウ酸アンモニウム水溶液と汚染土壌の混合系の水素イオン指数（ｐＨ）とＣｓ溶離率の関係を示すグラフ。The graph which shows the relationship between the hydrogen ion exponent (pH) and Cs elution rate of the mixed system of ammonium oxalate aqueous solution and contaminated soil. シュウ酸アンモニウム水溶液の水素イオン指数（ｐＨ）とアンモニウムイオン濃度及びシュウ酸イオン濃度との関係を示すグラフ。The graph which shows the relationship between the hydrogen ion exponent (pH) of ammonium oxalate aqueous solution, ammonium ion concentration, and oxalate ion concentration. シュウ酸アンモニウム水溶液のモル濃度と汚染土壌のＣｓ溶離率との関係を示すグラフ。The graph which shows the relationship between the molar concentration of ammonium oxalate aqueous solution, and the Cs elution rate of contaminated soil. シュウ酸アンモニウム水溶液の使用を連続した場合とＣｓ回収処理を介在させた場合とにおけるＣｓ溶離率を示すグラフ。The graph which shows the Cs elution rate in the case where use of ammonium oxalate aqueous solution is continued, and the case where Cs collection processing is interposed. シュウ酸水溶液のみで洗浄した場合（比較例）、シュウ酸アンモニウム水溶液のみで洗浄した場合、及びシュウ酸アンモニウム水溶液で洗浄後さらにシュウ酸水溶液で洗浄した場合における汚染土壌のＣｓ溶離率を示すグラフ。The graph which shows the Cs elution rate of the contaminated soil when it wash | cleans only with an oxalic acid aqueous solution, when it wash | cleans only with an oxalic acid aqueous solution after washing | cleaning only with an ammonium oxalate aqueous solution when it wash | cleans only with an oxalic acid aqueous solution.

以下、本発明の実施形態を添付図面に基づいて説明する。
図１に示すように実施形態に係る土壌除染装置１０は、セシウムに汚染された土壌１１を収容する溶離槽１２と、土壌１１に混合させるシュウ酸アンモニウム溶液を保持する保持槽１３と、ｐＨ調整装置とを備え、このｐＨ調整装置として、土壌及びシュウ酸アンモニウム溶液の混合系１４の水素イオン指数を計測するｐＨメータ１５と、この水素イオン指数の計測値がｐＨ６〜ｐＨ９の範囲に含まれるように混合系１４にｐＨ調整剤を投入するｐＨ調整槽１６（１６ａ，１６ｂ）と、を備えている。 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the soil decontamination apparatus 10 according to the embodiment includes an elution tank 12 that contains soil 11 contaminated with cesium, a holding tank 13 that holds an ammonium oxalate solution to be mixed with the soil 11, and a pH. A pH meter 15 for measuring the hydrogen ion index of the mixed system 14 of soil and ammonium oxalate solution, and the measured value of the hydrogen ion index is included in the range of pH 6 to pH 9. Thus, a pH adjusting tank 16 (16a, 16b) for supplying a pH adjusting agent to the mixing system 14 is provided.

さらに土壌除染装置１０は、混合系１４からシュウ酸アンモニウム溶液を回収し含まれているセシウムを吸着する吸着塔１７と、温度保持装置として混合系１４の温度を６０℃以上に保持するヒータ１８とをさらに備えている。この温度保持装置は特にヒータに限定することなく温度を６０℃以上に保持するために、加温または冷却させる機能を有している。   Further, the soil decontamination apparatus 10 collects an ammonium oxalate solution from the mixing system 14 and adsorbs the contained cesium, and a heater 18 that maintains the temperature of the mixing system 14 at 60 ° C. or more as a temperature holding device. And further. This temperature holding device is not limited to a heater, and has a function of heating or cooling in order to keep the temperature at 60 ° C. or higher.

土壌１１は、陸地の表面を覆っている生物活動の影響を受けた物質層を指し、落葉や枯枝等を含む場合もある。
溶離槽１２に収容される土壌１１は、原子力事故により飛散した放射性核種（セシウム等）を吸着した表土を削り取ったものが挙げられる。 The soil 11 refers to a material layer affected by biological activities covering the surface of land, and may include defoliation, dead branches, and the like.
Examples of the soil 11 accommodated in the elution tank 12 include those obtained by scraping off the top soil that has adsorbed radionuclides (such as cesium) scattered by a nuclear accident.

シュウ酸アンモニウムの水に対する溶解度（飽和溶液の濃度）は、常温（２０℃）で０．３ｍｏｌ／Ｌ、６０℃で１ｍｏｌ／Ｌ、９５℃で２ｍｏｌ／Ｌを示す。
そして、シュウ酸アンモニウムの水溶液の水素イオン係数は、ｐＨ６．０〜ｐＨ７．０の値を示す。 The solubility of ammonium oxalate in water (saturated solution concentration) is 0.3 mol / L at room temperature (20 ° C.), 1 mol / L at 60 ° C., and 2 mol / L at 95 ° C.
And the hydrogen ion coefficient of the aqueous solution of ammonium oxalate shows the value of pH 6.0-pH 7.0.

保持槽１３は、収容された土壌１１に対し、所定の液固比となるようポンプ３１により、保持するシュウ酸アンモニウム溶液を溶離槽１２に投入する。
溶離槽１２で形成された混合系１４のｐＨメータ１５による計測値（水素イオン指数）は、混合した土壌１１の種類に依存する。 The holding tank 13 puts the ammonium oxalate solution to be held into the elution tank 12 by the pump 31 so as to have a predetermined liquid-solid ratio with respect to the stored soil 11.
The measured value (hydrogen ion index) of the mixed system 14 formed in the elution tank 12 by the pH meter 15 depends on the kind of the mixed soil 11.

ｐＨ調整槽１６は、混合系１４の水素イオン指数をアルカリ側にシフトさせるアンモニア溶液がｐＨ調整剤として保持される第１調整槽１６ａと、混合系１４の水素イオン指数を酸性側にシフトさせるシュウ酸溶液がｐＨ調整剤として保持される第２調整槽１６ｂと、から構成されている。
ｐＨメータ１５で計測される水素イオン指数が、酸性を示す場合には、第１調整槽１６ａからアンモニア溶液をポンプ３２により溶離槽１２に送り、アルカリ性を示す場合には、第２調整槽１６ｂからシュウ酸溶液をポンプ３３により溶離槽１２に送る。
そして、混合系１４の水素イオン指数の計測値がｐＨ６〜ｐＨ９の範囲に含まれるように調整する。なお、ｐＨ調整剤の種類は、特に限定されないが、好ましくはアンモニア溶液とシュウ酸溶液である。 The pH adjusting tank 16 includes a first adjusting tank 16a in which an ammonia solution that shifts the hydrogen ion exponent of the mixed system 14 to the alkali side is held as a pH adjuster, and a shuff that shifts the hydrogen ion exponent of the mixed system 14 to the acidic side. And a second adjustment tank 16b in which the acid solution is held as a pH adjuster.
When the hydrogen ion index measured by the pH meter 15 indicates acidity, the ammonia solution is sent from the first adjustment tank 16a to the elution tank 12 by the pump 32, and when it indicates alkalinity, from the second adjustment tank 16b. The oxalic acid solution is sent to the elution tank 12 by the pump 33.
And it adjusts so that the measured value of the hydrogen ion index | exponent of the mixed system 14 may be contained in the range of pH6-pH9. The type of pH adjuster is not particularly limited, but is preferably an ammonia solution and an oxalic acid solution.

吸着塔１７は、ポンプ３４及びフィルタ４１の機能により混合系１４から分離した液相成分（シュウ酸アンモニウム溶液）を導入する。
この吸着塔１７には、フェロシアン化物、ケイチタン酸、ゼオライトのいずれか一つまたはいずれかの混合物からなるセシウム吸着材が充填されている。
そして、吸着塔１７を通過してセシウムが除去された液相成分（シュウ酸アンモニウム溶液）は、三方弁４２の設定により、その液相成分が予め定められた所定値によって溶離槽１２の内部に戻されたり、外部に排出されたりする。 The adsorption tower 17 introduces the liquid phase component (ammonium oxalate solution) separated from the mixing system 14 by the functions of the pump 34 and the filter 41.
The adsorption tower 17 is filled with a cesium adsorbent made of any one or a mixture of ferrocyanide, silicotitanate, and zeolite.
Then, the liquid phase component (ammonium oxalate solution) from which cesium has been removed after passing through the adsorption tower 17 is set in the elution tank 12 according to a predetermined value determined in advance by setting the three-way valve 42. Returned or discharged to the outside.

図２のグラフは、シュウ酸アンモニウム水溶液に対する浸漬時間と汚染土壌のＣｓ溶離率との関係を示している。
溶離液であるシュウ酸アンモニウム水溶液を、●は濃度０．３ｍｏｌ／Ｌ、温度９５℃、液固比６００ｍｌ／ｇに設定し、◇は濃度０．３ｍｏｌ／Ｌ、室温、液固比６００ｍｌ／ｇに設定し、×は濃度０．３ｍｏｌ／Ｌ、温度９５℃、液固比５０ｍｌ／ｇに設定した結果を示している。
なお、溶離率は次式で定義される。
溶離率[％]＝（１−溶離後の土壌の放射能[Ｂｑ]÷土壌の放射能[Ｂｑ]）×１００ The graph of FIG. 2 shows the relationship between the immersion time for the ammonium oxalate aqueous solution and the Cs elution rate of the contaminated soil.
The ammonium oxalate aqueous solution that is the eluent is set to a concentration of 0.3 mol / L, a temperature of 95 ° C., and a liquid-solid ratio of 600 ml / g, and ◇ is a concentration of 0.3 mol / L, room temperature, a liquid-solid ratio of 600 ml / g. X indicates the result of setting the concentration to 0.3 mol / L, the temperature to 95 ° C., and the liquid-solid ratio to 50 ml / g.
The elution rate is defined by the following equation.
Elution rate [%] = (1−Radioactivity of soil after elution [Bq] ÷ Radioactivity of soil [Bq]) × 100

この図２の結果より、シュウ酸アンモニウム水溶液による溶離率の到達上限値は、液固比に対する依存度及び温度に対する依存度は大きく、高温の場合には、浸漬時間に対する依存度が比較的小さいことが判る。
また、シュウ酸アンモニウム水溶液による溶離速度は、温度に対する依存度が大きい（高温である程、高速で溶離する）ことが判る。混合系の温度としては、溶離率の到達上限値及び溶解速度並びに浸漬時間及び温度管理コストの観点から、６０℃以上が好ましく、さらに９５℃以上が特に好ましい。 From the results shown in FIG. 2, the upper limit of the elution rate with the ammonium oxalate aqueous solution is highly dependent on the liquid-solid ratio and highly dependent on the temperature, and is relatively small on the immersion time at high temperatures. I understand.
It can also be seen that the elution rate with the aqueous ammonium oxalate solution is highly dependent on temperature (the higher the temperature, the higher the elution rate). The temperature of the mixing system is preferably 60 ° C. or higher, and more preferably 95 ° C. or higher, from the viewpoints of the upper limit of the elution rate, the dissolution rate, the immersion time, and the temperature management cost.

図３のグラフは、シュウ酸アンモニウム水溶液又はシュウ酸水溶液による洗浄処理回数と汚染土壌のＣｓ溶離率との関係を示している。
濃度０．５ｍｏｌ／Ｌ、液固比５０ｍｌ／ｇ、温度９５℃、一回当り１時間処理を共通条件に設定し、○は溶離液としてシュウ酸アンモニウム水溶液、■は溶離液としてシュウ酸水溶液（比較例）を使用した結果を示している。
なお、一回の処理毎に、新しい溶離液に交換している。 The graph of FIG. 3 shows the relationship between the number of washing treatments with an ammonium oxalate aqueous solution or an oxalic acid aqueous solution and the Cs elution rate of contaminated soil.
A concentration of 0.5 mol / L, a liquid-solid ratio of 50 ml / g, a temperature of 95 ° C., and a treatment for 1 hour per time are set as common conditions, ○ is an ammonium oxalate aqueous solution as an eluent, ■ is an oxalic acid aqueous solution ( The result of using the comparative example) is shown.
In addition, it replaces | exchanges for a new eluent for every process.

この図３の結果より、液固比が小さい場合であっても、シュウ酸アンモニウム水溶液の場合は、処理回数を増加させることにより溶離率が向上することが判る。
一方、シュウ酸水溶液（比較例）の場合は、溶離率が低く、処理回数を増加させても溶離率の向上が望めないことが判る。 From the results of FIG. 3, it can be seen that the elution rate is improved by increasing the number of treatments in the case of an aqueous ammonium oxalate solution even when the liquid-solid ratio is small.
On the other hand, in the case of an oxalic acid aqueous solution (comparative example), the elution rate is low, and it can be seen that the elution rate cannot be improved even if the number of treatments is increased.

図４のグラフは、シュウ酸アンモニウム水溶液と汚染土壌の混合系の水素イオン指数（ｐＨ）とＣｓ溶離率の関係を示している。濃度０．５ｍｏｌ／Ｌ、液固比５０ｍｌ／ｇ、温度９５℃が共通条件として設定されている。
この結果より、溶離率向上の観点から、混合系は、水素イオン指数がｐＨ６〜ｐＨ９の範囲に設定されるべきで、特にｐＨ８±０．５の範囲に設定されることが好ましいことが判る。 The graph of FIG. 4 shows the relationship between the hydrogen ion index (pH) and the Cs elution rate of a mixed system of an ammonium oxalate aqueous solution and contaminated soil. A concentration of 0.5 mol / L, a liquid-solid ratio of 50 ml / g, and a temperature of 95 ° C. are set as common conditions.
From this result, it can be seen that, from the viewpoint of improving the elution rate, the mixed system should have a hydrogen ion index in the range of pH 6 to pH 9, particularly preferably in the range of pH 8 ± 0.5.

図５のグラフは、シュウ酸アンモニウム水溶液の水素イオン指数（ｐＨ）とアンモニウムイオン濃度及びシュウ酸イオン濃度との関係を示している。
この図５のグラフは、化学反応データベース（phreeC interactive 2.18.5570）に基づき、水溶液中のシュウ酸アンモニウムの化学平衡状態を計算した結果である。
この図５のグラフから、水素イオン指数がｐＨ６〜ｐＨ９の範囲において、アンモニウムイオン（ＮＨ4 +）とシュウ酸イオン（Ｃ2Ｏ4）2-が互いに高濃度で共存することが確認される。この図５の確認結果と、図４の計測結果との関連が示唆される。 The graph of FIG. 5 shows the relationship between the hydrogen ion index (pH) of the ammonium oxalate aqueous solution, the ammonium ion concentration, and the oxalate ion concentration.
The graph of FIG. 5 is a result of calculating the chemical equilibrium state of ammonium oxalate in an aqueous solution based on the chemical reaction database (phreeC interactive 2.18.5570).
From the graph of FIG. 5, it is confirmed that ammonium ion (NH 4 + ) and oxalate ion (C 2 O 4 ) 2− coexist at a high concentration in the range of pH 6 to pH 9. The relationship between the confirmation result of FIG. 5 and the measurement result of FIG. 4 is suggested.

図６のグラフは、シュウ酸アンモニウム水溶液のモル濃度と汚染土壌のＣｓ溶離率との関係を示している。液固比５０ｍｌ／ｇ、温度９５℃が共通条件として設定されている。
この図６の結果より、シュウ酸アンモニウム水溶液は、濃度０．５ｍｏｌ／Ｌで溶離率がほぼ平衡に達するといえる。混合系のシュウ酸アンモニウム水溶液の濃度としては、０．３ｍｏｌ／Ｌ以上が好ましく、０．５ｍｏｌ／Ｌ以上が特に好ましい。 The graph in FIG. 6 shows the relationship between the molar concentration of the ammonium oxalate aqueous solution and the Cs elution rate of the contaminated soil. A liquid-solid ratio of 50 ml / g and a temperature of 95 ° C. are set as common conditions.
From the result of FIG. 6, it can be said that the elution rate of the aqueous solution of ammonium oxalate reaches almost equilibrium at a concentration of 0.5 mol / L. The concentration of the mixed aqueous ammonium oxalate solution is preferably 0.3 mol / L or more, particularly preferably 0.5 mol / L or more.

図７のグラフは、シュウ酸アンモニウム水溶液の使用を連続した場合とＣｓ回収処理を介在させた場合とにおけるＣｓ溶離率を示している。濃度０．３ｍｏｌ／Ｌ、液固比５０ｍｌ／ｇ、温度９５℃が共通条件として設定されている。
この図７の結果より、図１において土壌１１の除染をバッチ処理する場合、溶離処理後の溶離液（シュウ酸アンモニウム溶液）は、吸着塔１７を通過させることにより、溶離率を低下させることなく繰り返し利用できることが判る。 The graph of FIG. 7 shows the Cs elution rate when the use of the ammonium oxalate aqueous solution is continued and when the Cs recovery process is interposed. A concentration of 0.3 mol / L, a liquid-solid ratio of 50 ml / g, and a temperature of 95 ° C. are set as common conditions.
From the results of FIG. 7, when the decontamination of the soil 11 is batch-treated in FIG. 1, the eluent (ammonium oxalate solution) after the elution treatment is allowed to pass through the adsorption tower 17 to lower the elution rate. It can be seen that it can be used repeatedly.

図８のグラフは、シュウ酸水溶液のみで洗浄した場合（比較例）、シュウ酸アンモニウム水溶液のみで洗浄した場合、及びシュウ酸アンモニウム水溶液で洗浄後さらにシュウ酸水溶液で洗浄した場合における汚染土壌のＣｓ溶離率を示している。
濃度０．５ｍｏｌ／Ｌ（シュウ酸アンモニウム）、０．３ｍｏｌ／Ｌ（シュウ酸）、液固比５０ｍｌ／ｇ、温度９５℃が共通条件として設定されている。
この図８の結果より、シュウ酸アンモニウム溶液による洗浄、シュウ酸溶液による洗浄を組み合わせることにより、高い溶離率が達成されることが判る。 The graph of FIG. 8 shows Cs of contaminated soil when washed with only an oxalic acid aqueous solution (comparative example), washed with only an aqueous ammonium oxalate solution, and washed with an aqueous oxalic acid solution and then washed with an aqueous oxalic acid solution. The elution rate is shown.
Concentrations of 0.5 mol / L (ammonium oxalate), 0.3 mol / L (oxalic acid), a liquid-solid ratio of 50 ml / g, and a temperature of 95 ° C. are set as common conditions.
From the results of FIG. 8, it can be seen that a high elution rate is achieved by combining washing with an ammonium oxalate solution and washing with an oxalic acid solution.

以上述べた少なくともひとつの実施形態の土壌除染装置によれば、溶離液としてシュウ酸アンモニウム溶液を用いＣｓ汚染土壌との混合系をｐＨ６〜ｐＨ９の範囲に設定することにより、Ｃｓの溶離率を向上させることが可能となる。   According to the soil decontamination apparatus of at least one embodiment described above, by using an ammonium oxalate solution as an eluent and setting a mixed system with Cs-contaminated soil in a range of pH 6 to pH 9, the elution rate of Cs is increased. It becomes possible to improve.

本発明のいくつかの実施形態を説明したが、これらの実施形態は、例として提示したものであり、発明の範囲を限定することは意図していない。これら実施形態は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、置き換え、変更、組み合わせを行うことができる。これら実施形態やその変形は、発明の範囲や要旨に含まれると同様に、特許請求の範囲に記載された発明とその均等の範囲に含まれるものである。   Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

１０…土壌除染装置、１１…土壌、１２…溶離槽、１３…シュウ酸アンモニウム溶液の保持槽、１４…混合系、１５…ｐＨメータ、１６…ｐＨ調整槽、１６ａ…第１調整槽、１６ｂ…第２調整槽、１７…吸着塔、１８…ヒータ、３１，３２，３３，３４…ポンプ、４１…フィルタ、４２…三方弁。   DESCRIPTION OF SYMBOLS 10 ... Soil decontamination apparatus, 11 ... Soil, 12 ... Elution tank, 13 ... Holding tank of ammonium oxalate solution, 14 ... Mixing system, 15 ... pH meter, 16 ... pH adjustment tank, 16a ... First adjustment tank, 16b 2nd adjustment tank, 17 ... Adsorption tower, 18 ... Heater, 31, 32, 33, 34 ... Pump, 41 ... Filter, 42 ... Three-way valve.

Claims (7)

セシウムに汚染された土壌を収容する溶離槽と、
前記土壌に混合させるシュウ酸アンモニウム溶液を保持する保持槽と、
前記土壌及びシュウ酸アンモニウム溶液の混合系の水素イオン指数を計測し前記水素イオン指数の計測値がｐＨ６〜ｐＨ９の範囲に含まれるように前記混合系のｐＨを調整するｐＨ調整装置と、を備えることを特徴とする土壌除染装置。 An elution tank containing soil contaminated with cesium;
A holding tank for holding an ammonium oxalate solution to be mixed with the soil;
A pH adjusting device that measures the hydrogen ion index of the mixed system of the soil and the ammonium oxalate solution and adjusts the pH of the mixed system so that the measured value of the hydrogen ion index is included in the range of pH 6 to pH 9; A soil decontamination apparatus characterized by that. 請求項１に記載の土壌除染装置において、
前記ｐＨ調整装置は、
前記混合系の水素イオン指数をアルカリ側にシフトさせるアンモニア溶液が前記ｐＨ調整剤として保持される第１調整槽と、
前記混合系の水素イオン指数を酸性側にシフトさせるシュウ酸溶液が前記ｐＨ調整剤として保持される第２調整槽と、を有することを特徴とする土壌除染装置。 The soil decontamination apparatus according to claim 1,
The pH adjuster is
A first adjustment tank in which an ammonia solution for shifting the hydrogen ion index of the mixed system to the alkali side is held as the pH adjuster;
A soil decontamination apparatus comprising: a second adjustment tank in which an oxalic acid solution for shifting the hydrogen ion index of the mixed system to the acidic side is held as the pH adjuster. 請求項１又は請求項２に記載に記載の土壌除染装置において、
前記混合系の温度を６０℃以上に保持する温度保持装置を有することを特徴とする土壌除染装置。 In the soil decontamination apparatus according to claim 1 or 2,
A soil decontamination apparatus comprising a temperature holding device for holding the temperature of the mixed system at 60 ° C or higher. 請求項１から請求項３のいずれか１項に記載に記載の土壌除染装置において、
前記混合系の前記シュウ酸アンモニウム溶液の濃度が０．３ｍｏｌ／Ｌ以上に設定されていることを特徴とする土壌除染装置。 In the soil decontamination apparatus according to any one of claims 1 to 3,
The soil decontamination apparatus, wherein the concentration of the ammonium oxalate solution in the mixed system is set to 0.3 mol / L or more. 請求項２から請求項４のいずれか１項に記載の土壌除染装置において、
前記土壌に対し、前記シュウ酸アンモニウム溶液による洗浄、前記シュウ酸溶液による洗浄を組み合わせて実施することを特徴とする土壌除染装置。 In the soil decontamination apparatus according to any one of claims 2 to 4,
A soil decontamination apparatus, wherein the soil is washed with the ammonium oxalate solution and washed with the oxalic acid solution. 請求項１から請求項５のいずれか１項に記載の土壌除染装置において、
前記混合系から前記シュウ酸アンモニウム溶液を回収し含まれているセシウムを吸着する吸着塔をさらに備えることを特徴とする土壌除染装置。 In the soil decontamination apparatus according to any one of claims 1 to 5,
A soil decontamination apparatus, further comprising an adsorption tower that collects the ammonium oxalate solution from the mixed system and adsorbs cesium contained therein. セシウムに汚染された土壌を収容するステップと、
前記土壌に混合させるシュウ酸アンモニウム溶液を保持するステップと、
前記土壌及びシュウ酸アンモニウム溶液の混合系の水素イオン指数を計測するステップと、
前記水素イオン指数の計測値がｐＨ６〜ｐＨ９の範囲に含まれるように前記混合系にｐＨ調整剤を投入するステップと、を含むことを特徴とする土壌除染方法。 Containing soil contaminated with cesium;
Holding an ammonium oxalate solution to be mixed with the soil;
Measuring a hydrogen ion index of the mixed system of the soil and ammonium oxalate solution;
And a step of introducing a pH adjusting agent into the mixed system so that the measured value of the hydrogen ion index is included in a range of pH 6 to pH 9.
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