JP2005270773A - Cleaning reactant of water containing pollutant and cleaning treatment method of polluted aquifer using the same - Google Patents
Cleaning reactant of water containing pollutant and cleaning treatment method of polluted aquifer using the same Download PDFInfo
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- JP2005270773A JP2005270773A JP2004086717A JP2004086717A JP2005270773A JP 2005270773 A JP2005270773 A JP 2005270773A JP 2004086717 A JP2004086717 A JP 2004086717A JP 2004086717 A JP2004086717 A JP 2004086717A JP 2005270773 A JP2005270773 A JP 2005270773A
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- 229910052793 cadmium Inorganic materials 0.000 claims description 6
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims description 6
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims description 6
- 229910052753 mercury Inorganic materials 0.000 claims description 6
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- 239000003638 chemical reducing agent Substances 0.000 description 17
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- 229910001567 cementite Inorganic materials 0.000 description 4
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 4
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- 229910052757 nitrogen Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
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- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- DJHGAFSJWGLOIV-UHFFFAOYSA-K Arsenate3- Chemical group [O-][As]([O-])([O-])=O DJHGAFSJWGLOIV-UHFFFAOYSA-K 0.000 description 1
- 241001465754 Metazoa Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 1
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- 238000011835 investigation Methods 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- BMWMWYBEJWFCJI-UHFFFAOYSA-K iron(3+);trioxido(oxo)-$l^{5}-arsane Chemical compound [Fe+3].[O-][As]([O-])([O-])=O BMWMWYBEJWFCJI-UHFFFAOYSA-K 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
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- CEOCDNVZRAIOQZ-UHFFFAOYSA-N pentachlorobenzene Chemical compound ClC1=CC(Cl)=C(Cl)C(Cl)=C1Cl CEOCDNVZRAIOQZ-UHFFFAOYSA-N 0.000 description 1
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- PTLRDCMBXHILCL-UHFFFAOYSA-M sodium arsenite Chemical compound [Na+].[O-][As]=O PTLRDCMBXHILCL-UHFFFAOYSA-M 0.000 description 1
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- Processing Of Solid Wastes (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
Description
本発明は、汚染物質を含有する水の浄化反応剤及びこの浄化反応剤を用いた汚染帯水層の浄化処理方法に係り、特に重金属の汚染物質を含有する水の浄化反応剤及びこの浄化反応剤を用いた汚染帯水層の浄化処理方法に関する。 The present invention relates to a water purification reaction agent containing a pollutant and a purification treatment method for a contaminated aquifer using this purification reaction agent, and in particular, a water purification reaction agent containing a heavy metal pollutant and this purification reaction. The present invention relates to a method for purifying a contaminated aquifer using an agent.
汚染物質であるヒ素、カドミウム、シアン、鉛、6価クロム、水銀、セレンなどの重金属は、大量摂取によって生物に悪影響を及ぼし、特に動物においては直接飲料水摂取または汚染された穀物、家畜などの摂取によって神経障害などを引き起こす原因となる。従って、これら重金属は、国においても、土壌・地下水汚染に係る調査・対策指針に定める重金属とされている(平成11年環境庁指針)。 Pollutants such as arsenic, cadmium, cyanide, lead, hexavalent chromium, mercury, selenium and other heavy metals adversely affect living organisms, especially in animals such as drinking water directly or contaminated grains, livestock, etc. Ingestion can cause neuropathy. Therefore, these heavy metals are also considered as heavy metals in the national guidelines for investigation and countermeasures related to soil and groundwater contamination (1999 Environmental Agency Guidelines).
これら重金属は、メッキ塗装業、半導体製造業、化学工業、電池製造業などで広く製造原料として使用されており、不適切な管理や予期せぬ流出事故などによってこれらの重金属を含む物質が工場や管理倉庫などから流失し、土壌を汚染させると共に、その周辺の地下水も汚染させる場合がある。また、これら工場周辺のみならず、古くは鉱山周辺、近年ではごみの最終処分場所や不法投棄場所周辺など、これら重金属が高濃度になりやすい場所からのこれら重金属の流失も懸念されるようになってきている。 These heavy metals are widely used as manufacturing raw materials in the plating painting industry, the semiconductor manufacturing industry, the chemical industry, the battery manufacturing industry, etc. It may be washed away from a management warehouse and contaminate the soil as well as the surrounding groundwater. In addition, not only in the vicinity of these factories, but also in the old mine area, in recent years the final disposal site for waste and illegal dumping areas, etc., these heavy metals are likely to be washed away from places where the concentration of heavy metals tends to be high. It is coming.
周辺環境に甚大な影響を及ぼすこれら重金属による地下水の汚染の機構は、以下に大別される。通常、陰イオンで存在している6価クロム、ヒ素、シアン、セレンは、比較的土壌に吸収されにくいが、かえって雨水などに混ざって帯水層まで到達し、地下水が汚染されることが多い。また、鉛、カドミウム、水銀なども、汚染土壌周辺の帯水層地下水面が高い場合や、工場などの地下配管の損傷による漏洩により帯水層を汚染する場合がある。 The mechanisms of groundwater contamination by these heavy metals that have a profound effect on the surrounding environment can be broadly classified as follows. Normally, hexavalent chromium, arsenic, cyanide, and selenium that are present in anions are relatively difficult to be absorbed by the soil, but they are often mixed with rainwater to reach the aquifer and often contaminate groundwater. . Lead, cadmium, mercury, and the like may also contaminate the aquifer when the aquifer groundwater surface around the contaminated soil is high or due to leakage due to damage to underground piping in factories and the like.
このため、地下水がこれら重金属などの汚染物質に汚染された場合または汚染のおそれがある場合には、汚染物質を何らかの手段によって速やかに浄化できる方法が必要となり、汚染物質除去処理施設を用いる方法が一般的である。 For this reason, when groundwater is contaminated by these heavy metals or other contaminants, or there is a risk of contamination, a method that can quickly purify the contaminants by some means is required, and a method using a contaminant removal treatment facility is required. It is common.
汚染物質除去処理施設を用いる方法としては、揚水井戸を掘り、地下水を揚水して汚染物質除去処理施設で汚染物質を除去する浄化処理を行って、川などに放流する方法や、汚染土壌を掘削して汚染物質除去処理施設に搬送して加熱・焼却や微生物などで汚染物質を除去する浄化処理を行ってもとの掘削地に埋設または最終処分場に密閉埋設する方法がある。後者の方法は、集約的に浄化を行うことができるが、汚染土壌すべての掘削、掘削土壌の搬送や処理後の埋設が必要となる。 Methods for using the pollutant removal treatment facility include digging a pumping well, pumping up groundwater, removing the pollutant at the pollutant removal treatment facility, and discharging it to a river, or excavating contaminated soil. Then, there is a method of burying it in the original excavation site or sealingly burying it in the final disposal site even if it is transported to the pollutant removal treatment facility and subjected to purification treatment that removes the pollutant by heating and incineration or microorganisms. The latter method can intensively purify, but requires excavation of all contaminated soil, transportation of excavated soil and embedding after treatment.
また、汚染物質除去処理施設を用いない方法としては、例えば、帯水層中の地下水に金属鉄を存在させて低酸素濃度下で有機ハロゲン化合物を脱ハロゲン反応させ、汚染された地下水を浄化させる方法や、例えば、特許文献1に示すように、汚染された地下水が流れる帯水層の流路に、帯水層の下の不透水層まで至る溝を掘削して金属鉄を埋没させて汚染物質を除去する透過反応壁を形成し、地下水が透過反応壁を透過する際に浄化させる方法などが挙げられる。 In addition, as a method that does not use the pollutant removal treatment facility, for example, metallic iron is present in the groundwater in the aquifer and the organic halogen compound is dehalogenated under a low oxygen concentration to purify the contaminated groundwater. Method, for example, as shown in Patent Document 1, the channel of the aquifer where the contaminated groundwater flows is excavated into a channel that reaches the impermeable layer below the aquifer to bury metal iron and contaminate it. Examples include a method of forming a permeation reaction wall for removing substances and purifying the groundwater when it passes through the permeation reaction wall.
また、例えば非特許文献1及び非特許文献2に示すように、汚染物質の分解速度を向上させる透過反応壁の金属鉄を金属還元体として用い、地下水中の重金属を還元して除去する方法なども挙げられている。
しかしながら、汚染物質除去処理施設を用いる方法では、重金属排水処理施設や高熱分解処理施設などの設備コスト及び浄化完了までの長期間の維持管理コストや、掘削、搬送する場合には掘削・搬送コストや掘削・搬送中に汚染土壌を飛散させないための2次汚染防止コストが高くなり、総コストが高くなるという問題がある。 However, in the method using the pollutant removal treatment facility, equipment costs such as heavy metal wastewater treatment facilities and high thermal decomposition treatment facilities, long-term maintenance and management costs until completion of purification, and excavation / transportation costs when excavating and transporting, There is a problem that the secondary pollution prevention cost for preventing the contaminated soil from being scattered during excavation and transportation becomes high, and the total cost becomes high.
また、汚染物質除去処理施設を用いない方法では、金属還元体を埋設した透過反応壁を用いて汚染された地下水を浄化する場合には、埋設金属の処理能力に限界があるため一定期間ごとの埋設した金属還元体の交換をする、または、浄化処理能力が低いため多量の金属還元体の埋設をする必要があるという問題がある。 In addition, in the method that does not use the pollutant removal treatment facility, when purifying contaminated groundwater using a permeation reaction wall with a metal reductant buried, there is a limit to the treatment capacity of the buried metal, so that the There is a problem that it is necessary to replace a buried metal reductant or to bury a large amount of metal reductant because of its low purification capacity.
本発明は、前記した点に鑑みてなされたものであり、汚染地下水を浄化する場合に、総コストを軽減し、長期間、安全性が高く、安定的に除去性能および透過性がよく汚染物質の除去を行うことができる汚染物質を含有する水の浄化反応剤及びこの浄化反応剤を用いた汚染帯水層の浄化処理方法を提供することを目的とする。 The present invention has been made in view of the above points. When purifying contaminated groundwater, the total cost is reduced, the safety is high for a long period of time, the removal performance and permeability are stable and the pollutant is good. It is an object of the present invention to provide a purification agent for water containing a pollutant capable of removing water and a method for purifying a contaminated aquifer using this purification reagent.
以上の課題を解決するため、請求項1に記載の発明は、炭素を0.06重量%から5重量%含有し、平均粒径0.1mm以上かつ比表面積0.5m2/g以上である鉄粉からなることを特徴とする。 In order to solve the above problems, the invention described in claim 1 contains 0.06 wt% to 5 wt% of carbon, has an average particle size of 0.1 mm or more and a specific surface area of 0.5 m 2 / g or more. It consists of iron powder.
この請求項1に記載の発明によれば、前記炭素を0.06重量%以上から5重量%含有する鉄粉からなる浄化反応剤であることにより、鉄表面でセメンタイトFe3−Cを生成しやすく、これによりカソード表面が増加し、鉄の酸化反応を増進し、前記鉄粉と前記汚染物質との反応を良好にすることができる。さらに前記平均粒径0.1mm以上かつ比表面積0.5m2/g以上の鉄粉からなる浄化反応剤であることにより、前記汚染水の透過速度を遅くすることなく、汚染水に含有される重金属などの汚染物質と接する比表面積を大きくすることができる。 According to the first aspect of the present invention, cementite Fe 3 -C is produced on the iron surface by being a purification reaction agent comprising iron powder containing 0.06 wt% to 5 wt% of the carbon. This facilitates the increase in the surface of the cathode, enhances the iron oxidation reaction, and improves the reaction between the iron powder and the contaminants. Furthermore, it is contained in the contaminated water without slowing the permeation rate of the contaminated water by being a purification reagent comprising iron powder having an average particle size of 0.1 mm or more and a specific surface area of 0.5 m 2 / g or more. The specific surface area in contact with contaminants such as heavy metals can be increased.
請求項2の記載の発明は、請求項1に記載の汚染物質を含有する水の浄化反応剤において、前記汚染物質は、ヒ素、カドミウム、鉛、シアン、6価クロム、水銀、アルキル水銀、セレンのいずれか1種または複数の重金属を含有するものであることを特徴とする。 The invention described in claim 2 is the water purification reagent containing the pollutant according to claim 1, wherein the pollutant is arsenic, cadmium, lead, cyan, hexavalent chromium, mercury, alkyl mercury, selenium. Any one or more of heavy metals are contained.
この請求項2に記載の発明によれば、前記汚染水は、ヒ素、カドミウム、鉛などの前記重金属の前記汚染物質を含有するものであることにより、前記浄化反応剤の鉄粉とヒ素、鉛などの前記重金属とは良好に化学反応をすることができる。 According to the second aspect of the present invention, the contaminated water contains the contaminants of the heavy metal such as arsenic, cadmium, and lead, so that the iron powder, arsenic, and lead of the purification reagent are contained. The above-mentioned heavy metals such as can be chemically reacted well.
請求項3に記載の発明は、汚染帯水層の処理方法において、前記汚染物質を含有する帯水層に請求項1または請求項2に記載の前記浄化反応剤を埋設することにより前記汚染物質を除去することを特徴とする。 According to a third aspect of the present invention, in the method for treating a contaminated aquifer, the pollutant is obtained by embedding the purification reaction agent according to the first or second aspect in the aquifer containing the contaminant. It is characterized by removing.
この請求項3に記載の発明によれば、前記浄化反応剤を埋設することにより、前記汚染物質を含有する帯水層を浄化することができる。 According to this invention of Claim 3, the aquifer containing the said pollutant can be purified by embedding the said purification reaction agent.
請求項4に記載の発明は、前記汚染帯水層の処理方法において、前記汚染物質を含有する帯水層を流れる地下水の下流部分に請求項1または請求項2に記載の前記浄化反応剤を埋設して透過反応壁を形成し、地下水を前記透過反応壁に透過させることにより前記汚染物質を除去することを特徴とする。 Invention of Claim 4 WHEREIN: In the processing method of the said contaminated aquifer, the said purification reaction agent of Claim 1 or Claim 2 is put in the downstream part of the groundwater which flows through the aquifer containing the said pollutant. It is buried to form a permeation reaction wall, and the contaminant is removed by allowing groundwater to permeate the permeation reaction wall.
この請求項4に記載の発明によれば、前記汚染物質を含有する帯水層を流れる地下水の下流部分に前記浄化反応剤を埋没して前記透過反応壁を形成して汚染地下水を透過させることにより、汚染物質を除去することができる。 According to the fourth aspect of the present invention, the contaminated groundwater is permeated by forming the permeation reaction wall by burying the purification reaction agent in a downstream portion of the groundwater flowing through the aquifer containing the contaminant. Thus, contaminants can be removed.
請求項1に記載の発明によれば、炭素を含有する鉄粉である金属還元体と汚染物質との反応を良好にすることができるので、汚染物質の除去性能を高めることができるという効果を奏する。また、平均粒径0.1mm以上かつ比表面積を0.5m2/g以上の鉄粉であることにより、汚染水の透過速度の維持及び汚染水に含まれる汚染物質と接する比表面積の確保ができるので、汚染水の汚染物質の除去速度を維持し、かつ汚染物質と鉄粉との反応がしやすくなるという効果を奏する。 According to the invention described in claim 1, since the reaction between the metal reductant, which is iron powder containing carbon, and the pollutant can be improved, the effect of improving the pollutant removal performance can be obtained. Play. In addition, by using iron powder having an average particle size of 0.1 mm or more and a specific surface area of 0.5 m 2 / g or more, it is possible to maintain the permeation rate of the contaminated water and to secure the specific surface area in contact with the contaminant contained in the contaminated water. As a result, it is possible to maintain the removal rate of the pollutant in the polluted water and to facilitate the reaction between the pollutant and the iron powder.
請求項2に記載の発明によれば、浄化反応剤の鉄粉とヒ素、鉛などの汚染物質とは良好に反応をすることができるので、重金属を含有する汚染水を良好に浄化することができる。 According to the second aspect of the present invention, the iron powder as the purification reagent and the pollutants such as arsenic and lead can react well, so that the contaminated water containing heavy metals can be purified well. it can.
請求項3に記載の発明によれば、汚染物質を含有する帯水層に汚染地下水を浄化する浄化反応剤を埋設することにより浄化できるので、浄化処理施設を建設せず、総コストを軽減し、長期間、安全性が高く、安定的に除去性能および透過性がよく汚染物質の除去を行うことができるとともに予防的に浄化処理剤を埋設することもできるという効果を奏する。 According to the invention described in claim 3, since purification can be achieved by embedding a purification reagent that purifies contaminated groundwater in an aquifer containing a pollutant, the total cost can be reduced without constructing a purification treatment facility. The long-term safety is high, the removal performance and permeability are stable, the contaminants can be removed, and the purification treatment agent can be buried in a preventive manner.
請求項4に記載の発明によれば、汚染物質を含有する帯水層を流れる地下水の下流部分に浄化反応剤を埋設して透過反応壁を形成し、これに汚染物質を透過させるので、より効率よく、コストを軽減し、長期間、安全性が高く、安定的に除去性能および透過性がよく汚染物質の除去を行うことができるとともに予防的に浄化処理剤を埋設することもできるという効果を奏する。 According to the fourth aspect of the present invention, the purification reaction agent is embedded in the downstream portion of the groundwater flowing through the aquifer containing the pollutant to form the permeation reaction wall, and the pollutant is permeated therethrough. Effectively reducing costs, providing high safety for a long period of time, providing stable removal performance and permeability with good removal of pollutants as well as preventive embedding of purification agents Play.
以下、本発明に係る汚染物質を含有する水の浄化反応剤の実施形態について説明する。ただし、以下の実施形態に限定されない。 Hereinafter, an embodiment of a purification agent for water containing a pollutant according to the present invention will be described. However, it is not limited to the following embodiment.
本実施形態における汚染物質を含有する水の浄化反応剤は、炭素を0.06重量%から5重量%含有し、平均粒径0.1mm以上かつ比表面積0.5m2/g以上である鉄粉からなる。 In the present embodiment, the purification agent for water containing contaminants contains 0.06 wt% to 5 wt% of carbon, has an average particle size of 0.1 mm or more and a specific surface area of 0.5 m 2 / g or more. Made of powder.
浄化反応剤に用いられる鉄粉は、重金属イオンを還元して自身の表面に析出させる働きをする金属であって、酸化されてコロイド状の不溶性水酸化物を形成して重金属などの汚染物質と共沈殿するものである。鉄粉でなくとも金属還元体であれば、この作用を有するが、鉄粉は、反応性が高く、安全性が高く、価格が安く、取り扱いが容易であるので、好ましい。 Iron powder used as a purification reagent is a metal that acts to reduce heavy metal ions and deposit them on its surface. It is oxidized to form colloidal insoluble hydroxides and pollutants such as heavy metals. Coprecipitates. If it is not an iron powder but a metal reductant, it has this action, but iron powder is preferable because it has high reactivity, high safety, low price, and easy handling.
浄化反応剤は、炭素を0.06重量%以上含有する鉄粉である。炭素を含有する鉄粉であることにより、鉄粉表面でセメンタイトFe3Cを生成しやすく、これによりカソード表面が増加し、鉄の酸化反応を促進することとなる。従って、鉄粉中の炭素を含有する割合が増加したときには、鉄粉の比表面積が大きいと、より反応速度が向上し、重金属などの除去性能を高めることができる。炭素を0.06重量%より少なく含有する鉄粉では、鉄の溶出速度が遅くなって重金属などの除去性能が低下するために、多量の鉄粉を必要し、高コストとなるためである。より鉄の抽出速度を向上させて重金属などの除去性能を向上させるため、炭素を0.3重量%以上含有する鉄粉であることが好ましい。 The purification reaction agent is iron powder containing 0.06% by weight or more of carbon. By being an iron powder containing carbon, it is easy to produce cementite Fe 3 C on the surface of the iron powder, thereby increasing the cathode surface and promoting the oxidation reaction of iron. Therefore, when the proportion of carbon in the iron powder increases, the reaction rate is further improved and the removal performance of heavy metals and the like can be enhanced if the specific surface area of the iron powder is large. This is because an iron powder containing less than 0.06% by weight of carbon slows the elution rate of iron and lowers the removal performance of heavy metals and the like, so a large amount of iron powder is required and the cost is increased. In order to improve the iron extraction rate and improve the removal performance of heavy metals and the like, iron powder containing 0.3% by weight or more of carbon is preferable.
浄化反応剤に用いられる鉄粉の平均粒径は、平均粒径0.1mm以上である。平均粒径0.1mm以下の鉄粉では、透過反応壁の透過性が低下し、汚染地下水が透過反応壁内を通過しにくくなり、汚染物質の除去性能が低下するためである。透過反応壁の汚染地下水の透過性をより良好にするため、平均粒径0.25mm以上が好ましい。最も良好にするため、平均粒径0.5mm以上が好ましい。 The average particle diameter of the iron powder used for the purification reaction agent is an average particle diameter of 0.1 mm or more. This is because, with iron powder having an average particle size of 0.1 mm or less, the permeability of the permeation reaction wall is reduced, and contaminated groundwater is less likely to pass through the permeation reaction wall, thereby reducing the contaminant removal performance. In order to improve the permeability of the contaminated groundwater of the permeation reaction wall, the average particle diameter is preferably 0.25 mm or more. In order to make it the best, an average particle diameter of 0.5 mm or more is preferable.
浄化反応剤に用いられる鉄粉の比表面積は、比表面積0.5m2/g以上である。鉄粉の比表面積が小さいと、重金属などの汚染物質への接する比表面積が小さくなって除去性能が低下するために、多量の鉄粉を必要とし、高コストとなるためである。より比表面積を大きくして重金属などの除去性能を高めるため、比表面積1m2/g以上が好ましい。確実に良好に反応させるため比表面積5.0m2/g以上が好ましい。 The specific surface area of the iron powder used for the purification reagent is 0.5 m 2 / g or more. This is because if the specific surface area of the iron powder is small, the specific surface area in contact with contaminants such as heavy metals becomes small and the removal performance is lowered, so that a large amount of iron powder is required and the cost becomes high. In order to increase the specific surface area and improve the removal performance of heavy metals and the like, the specific surface area is preferably 1 m 2 / g or more. A specific surface area of 5.0 m 2 / g or more is preferable in order to ensure good reaction.
従って、浄化反応剤の鉄粉は、上述の炭素を含有し、平均粒径かつ比表面積を満たす微粉末状、切片状、あるいはスティールウール状が好ましい。また、金属加工処理過程によって発生する汚染されていない金属粉や金属片でも良い。 Therefore, the iron powder of the purification reaction agent preferably has a fine powder shape, a slice shape, or a steel wool shape containing the above-described carbon and satisfying the average particle size and specific surface area. Moreover, the metal powder and metal piece which are not contaminated and which generate | occur | produce by a metal processing process may be sufficient.
汚染物質は、四塩化炭素、トリクロロエチレン、PCBなどの有機ハロゲン化合物またはヒ素、カドミウム、鉛、シアン、6価クロム、水銀、アルキル水銀、セレンのいずれか1種または複数の重金属を含有するものである。重金属は、下記の反応式に示すように、標準電極電位の差から鉄粉の鉄イオンを生成しやすく、水溶性鉄イオンと反応または共沈殿しやすいので、好ましい。さらに、下記の反応式に示すように、陰イオンで存在しやすい重金属、例えば、6価クロム、ヒ素、シアン、セレンなどは、鉄イオンとの反応が良好なので、好ましい。 The pollutant contains an organic halogen compound such as carbon tetrachloride, trichlorethylene, PCB, or one or more heavy metals selected from arsenic, cadmium, lead, cyan, hexavalent chromium, mercury, alkylmercury, and selenium. . As shown in the following reaction formula, heavy metals are preferable because they easily generate iron ions of iron powder from the difference in standard electrode potential, and easily react or coprecipitate with water-soluble iron ions. Furthermore, as shown in the following reaction formula, heavy metals that are likely to be present as anions, such as hexavalent chromium, arsenic, cyan, selenium, etc., are preferable because they react well with iron ions.
以下に作用について説明する。
汚染物質を含有している水が、浄化反応剤である炭素を含有する金属還元体と反応して不溶性の汚染物質−金属還元体となり、汚染物質を除去する。
特に、金属還元体が鉄の場合、陰イオンとして水に溶解している重金属は、鉄イオンと反応して鉄粉−重金属の不溶性物を形成する。または、コロイドを形成している鉄イオンに、そのまま取り込まれて共沈殿して、不溶性物を形成する。
The operation will be described below.
The water containing the pollutant reacts with the metal reductant containing carbon which is the purification reaction agent to become an insoluble pollutant-metal reductant, and removes the pollutant.
In particular, when the metal reductant is iron, a heavy metal dissolved in water as an anion reacts with the iron ion to form an insoluble matter of iron powder-heavy metal. Or it is taken in and co-precipitated in the iron ion which has formed the colloid, and forms an insoluble matter.
下記の反応式に従って、金属還元体(鉄粉)による重金属など、特にヒ素の除去機構について説明する。
下記の反応式に従って、鉄粉は、水の溶存酸素と反応し、または、イオン化して水溶性の重金属M(2価、3価)の標準電極電位の差からFe2+、Fe3+を生成し、水に溶解しやすくなる。また、水溶性重金属は、電子を渡して鉄粉表面に析出し、除去される。(aq:水溶性、s:不溶性)
2Fe(s)+O2(aq)+2H2O → Fe2+(aq)+4OH-
Fe(s)+M2+(aq) → Fe2++M(s)
4Fe2+(aq)+O2(aq)+4H+ → 4Fe3+(aq)+2H2O
Fe(s)+M3+(aq) → Fe3++M(s)
In accordance with the following reaction formula, a mechanism for removing arsenic such as heavy metal by a metal reductant (iron powder) will be described.
According to the following reaction formula, iron powder reacts with dissolved oxygen in water or is ionized to convert Fe 2+ and Fe 3+ from the difference in standard electrode potential of water-soluble heavy metal M (divalent and trivalent). Produces and dissolves easily in water. Further, the water-soluble heavy metal is transferred to the surface of the iron powder by passing electrons and removed. (Aq: water-soluble, s: insoluble)
2Fe (s) + O 2 (aq) + 2H 2 O → Fe 2+ (aq) + 4OH −
Fe (s) + M 2+ (aq) → Fe 2+ + M (s)
4Fe 2+ (aq) + O 2 (aq) + 4H + → 4Fe 3+ (aq) + 2H 2 O
Fe (s) + M 3+ (aq) → Fe 3+ + M (s)
下記の反応式に示すように、このFe3+と水中の重金属Mの酸化物イオンと反応し、鉄粉−重金属酸化物を形成し、不溶性となる。また、水溶性重金属Mは、コロイド状に水酸化鉄(2価または3価)が形成された場合には、そのまま取り込まれて共沈殿して不溶性となる。不溶性物になることによって、重金属Mは、水から除去される。(n,m,pは自然数)
Fe3+(aq)+nMOm 3-(aq) → Fe(MOm)n(s)
Fe3+(aq)+Mp+(aq)+(p+3)OH-
→ M(OH)p,Fe(OH)3(s)
As shown in the following reaction formula, this Fe 3+ reacts with oxide ions of heavy metal M in water to form iron powder-heavy metal oxide, which becomes insoluble. The water-soluble heavy metal M is taken in as it is and co-precipitated and becomes insoluble when iron hydroxide (divalent or trivalent) is formed in a colloidal form. By becoming insoluble, the heavy metal M is removed from the water. (N, m and p are natural numbers)
Fe 3+ (aq) + nMO m 3− (aq) → Fe (MO m ) n (s)
Fe 3+ (aq) + M p + (aq) + (p + 3) OH −
→ M (OH) p , Fe (OH) 3 (s)
特に、水中でヒ酸イオンとなっているヒ素は、以下の反応式に従って、不溶性となる。
Fe3+(aq)+AsO3 3-(aq)→FeAsO3(s)
Fe3+(aq)+AsO4 3-(aq)→FeAsO4(s)
In particular, arsenic that is an arsenate ion in water becomes insoluble according to the following reaction formula.
Fe 3+ (aq) + AsO 3 3− (aq) → FeAsO 3 (s)
Fe 3+ (aq) + AsO 4 3− (aq) → FeAsO 4 (s)
上記の反応に際して、炭素を含有する鉄粉は、鉄表面でセメンタイトFe3−Cが生成されやすく、よりカソード表面が増加し、鉄粉の酸化反応が増進する。また、平均粒径が大きい鉄粉は、滞ることなく鉄粉と溶存酸素及び重金属との反応が順次進み、比表面積が大きい鉄粉は、重金属との接する表面積が大きく、重金属との反応が増進する。 In the case of the above reaction, in the iron powder containing carbon, cementite Fe 3 —C is easily generated on the iron surface, the cathode surface is further increased, and the oxidation reaction of the iron powder is promoted. In addition, iron powder with a large average particle size undergoes a reaction between iron powder, dissolved oxygen, and heavy metal sequentially without any delay, and iron powder with a large specific surface area has a large surface area in contact with heavy metal and promotes a reaction with heavy metal. To do.
以上のことより、浄化反応剤の鉄粉によって、汚染物質を含有する水から汚染物質を取り除くことができる。 As described above, the contaminants can be removed from the water containing the contaminants by the iron powder of the purification reagent.
次に、前述の浄化反応剤を用いた汚染帯水層の浄化処理方法の実施形態について説明する。
上記の指針に示された重金属などの汚染物質、特にヒ素に汚染されたまたは汚染されるおそれのある土壌の地下水の流向、流速、汚染濃度を把握する。把握した結果より、透過反応壁の溝は、汚染された地下水が流れ込む帯水層を流れる地下水の下流部分に、地下水が流れる方向と垂直に帯水層の下の不透水層まで至るまで掘削して厚さ300cmに形成される。この形成された溝には、炭素を0.06重量%以上含有し、平均粒径0.1mm以上かつ比表面積0.5mm2/g以上の鉄粉からなる前記浄化反応剤を埋没させて、透過反応壁が形成される。
Next, an embodiment of a purification method for a contaminated aquifer using the above-described purification reagent will be described.
Identify the groundwater flow direction, flow velocity, and contamination concentration in soils contaminated with or likely to be contaminated with heavy metals and other pollutants as indicated in the above guidelines. Based on the results, the perforation reaction channel groove was drilled in the downstream part of the groundwater flowing through the aquifer where contaminated groundwater flows up to the impermeable layer below the aquifer perpendicular to the direction in which the groundwater flows. To a thickness of 300 cm. In this formed groove, 0.06% by weight or more of carbon is contained, the purification reaction agent made of iron powder having an average particle size of 0.1 mm or more and a specific surface area of 0.5 mm 2 / g or more is buried, A permeation reaction wall is formed.
透過反応壁に用いる浄化反応剤の原材料には、金属還元体の鉄粉の他に、より透水性を高めるために石やレキなどを混入させても良い。また透過反応壁の溝の厚さは、金属還元体の除去性能と汚染地下水の濃度によるが、30cmから300cmである。金属還元体のコスト面や埋設場所の確保などから、50cmから200cmが好ましい。 The raw material of the purification reaction agent used for the permeation reaction wall may be mixed with stones, rakes, and the like in order to increase water permeability in addition to the iron powder of the metal reductant. The thickness of the groove of the permeation reaction wall is 30 cm to 300 cm depending on the metal reductant removal performance and the concentration of contaminated groundwater. In view of the cost of the metal reductant and securing of the burial location, 50 to 200 cm is preferable.
透過反応壁を形成する時に、礫土からなる緩い地盤構造である場合には、drill&jet工法を用いても良い。この工法は、まず透過反応壁を形成する位置に適度な間隔をおいて帯水層の下の不透水層まで至る試掘工を掘削する。次に各試掘孔に底まで届くパイプを挿入し、浄化反応剤を加圧下、パイプを通して試掘孔から地盤中の礫土や他の材料の間に注入し、パイプを除去することで透過反応壁とする。試掘孔の間隔、鉄の量、注入圧は透過反応壁が途切れず、十分な厚さを保つように決定する。 When the permeation reaction wall is formed, the drill & jet method may be used in the case of a loose ground structure made of gravel. In this method, a test digging is first excavated to reach the impermeable layer below the aquifer at an appropriate interval at the position where the permeation reaction wall is formed. Next, pipes that reach the bottom are inserted into each borehole, and the purifying reaction agent is injected between the gravel soil and other materials in the ground from the borehole through the pipe under pressure while removing the pipe. To do. The distance between the boreholes, the amount of iron, and the injection pressure are determined so that the permeation reaction wall is not interrupted and a sufficient thickness is maintained.
本発明の作用は、汚染物質によって汚染された土壌から溶け出したイオン化物などが地下水に流入して汚染された地下水が、前記浄化反応剤を埋設した透過反応壁を透過する。上記の反応式に従って、前記浄化反応剤に含まれる炭素及び地下水中の溶存酸素によってイオン化された金属還元体(鉄イオン:2価、3価)となり、透過反応壁を汚染地下水が透過することによって、このイオン化された金属還元体と汚染物質のイオン化物とが結合して不溶性の汚染物質−金属還元体(鉄)を形成し、地下水から汚染物質などは取り除かれる。特に、汚染物質である重金属のヒ素と金属還元体である鉄の場合には、地下水中でヒ酸イオンとなって、鉄イオンと反応してヒ酸鉄が形成される。 According to the operation of the present invention, ionized substances or the like dissolved from the soil contaminated with the contaminants flow into the groundwater, and the contaminated groundwater passes through the permeation reaction wall in which the purification reaction agent is embedded. According to the above reaction formula, carbon is contained in the purification reagent and a metal reductant (iron ion: divalent, trivalent) ionized by dissolved oxygen in the groundwater, and the contaminated groundwater permeates through the permeation reaction wall. The ionized metal reductant and the ionized contaminant are combined to form an insoluble contaminant-metal reductant (iron), and the contaminant is removed from the groundwater. In particular, in the case of heavy metal arsenic, which is a contaminant, and iron, which is a metal reductant, arsenate ions are formed in groundwater and react with iron ions to form iron arsenate.
以上のことのより、汚染物質で汚染された土壌によって汚染された地下水は、前記浄化剤を用いた透過反応壁を透過させることによって、汚染物質が取り除かれ、汚染地下水は浄化される。特に、重金属のヒ素などに汚染された土壌から流出などして汚染されていた地下水は浄化されて、国の指針以下の重金属などを含まない安全な地下水となる。 From the above, the groundwater contaminated by the soil contaminated with the contaminant is removed through the permeation reaction wall using the purification agent, and the contaminated groundwater is purified. In particular, groundwater contaminated by spilling from soil contaminated with heavy metal arsenic is purified and becomes safe groundwater that does not contain heavy metals below the national guidelines.
本発明を実施例により、更に詳細に説明する。 The present invention will be described in more detail with reference to examples.
[実施例1]
濃度10mg/Lの模擬ヒ素汚染地下水80mLを容量160mLのバイアル瓶に入れ、鉄粉1(比表面積5.6m2/g、炭素含有率0.29重量%)0.5g添加し、容器上部の空気を窒素置換後、密閉し、3日間振とうした。振とう後、孔径0.45μmのフィルタでろ過を行い、溶液中に残存するヒ素濃度を測定した。
ヒ素除去率(%)は、(実施前の初期濃度−実施後の残存濃度/実施前の初期濃度)×100とした。
[Example 1]
80 mL of simulated arsenic-contaminated groundwater with a concentration of 10 mg / L is placed in a 160 mL vial, and 0.5 g of iron powder 1 (specific surface area 5.6 m 2 / g, carbon content 0.29 wt%) is added. The air was replaced with nitrogen, sealed, and shaken for 3 days. After shaking, filtration was performed with a filter having a pore diameter of 0.45 μm, and the concentration of arsenic remaining in the solution was measured.
The arsenic removal rate (%) was defined as (initial concentration before execution−residual concentration after execution / initial concentration before execution) × 100.
本実験の模擬ヒ素汚染地下水は、水道水を活性炭で処理した水を用いて亜ヒ酸ナトリウム水溶液(キシダ化学製)を濃度10mg/Lに希釈調製し、鉄粉1添加後、容器上部の空気を窒素置換したものである。測定法は、水素化物発生ICP発光分析法(リガク製ICP発光分析装置)で行った。 The simulated arsenic-contaminated groundwater in this experiment was prepared by diluting a sodium arsenite aqueous solution (manufactured by Kishida Chemical Co., Ltd.) to a concentration of 10 mg / L using water obtained by treating tap water with activated carbon. Is substituted with nitrogen. The measurement method was the hydride generation ICP emission analysis method (Rigaku ICP emission analysis apparatus).
[実施例2]
鉄粉2(比表面積1.5m2/g、炭素含有率0.29重量%)を実施例1と同様の方法でヒ素除去率を求めた。
[Example 2]
The arsenic removal rate of iron powder 2 (specific surface area 1.5 m 2 / g, carbon content 0.29 wt%) was determined in the same manner as in Example 1.
[実施例3]
鉄粉3(比表面積4.7m2/g、炭素含有率0.06重量%)を実施例1と同様の方法でヒ素除去率を求めた。
[Example 3]
The arsenic removal rate of the iron powder 3 (specific surface area 4.7 m 2 / g, carbon content 0.06 wt%) was determined in the same manner as in Example 1.
[実施例4]
鉄粉4(比表面積0.1m2/g、炭素含有率1重量%)を実施例1と同様の方法でヒ素除去率を求めた。
[Example 4]
The arsenic removal rate of iron powder 4 (specific surface area 0.1 m 2 / g, carbon content 1 wt%) was determined in the same manner as in Example 1.
実施例1から実施例4の結果を表1に示す。
表1より、実施例1及び実施例2より炭素含有率は同じであるものの、比表面積が増加したことによって、ヒ素除去率が17%増加した。また、実施例3より、炭素を0.06%含有した鉄粉は、ヒ素を20%除去できた。さらに、実施例1及び実施例3より、鉄粉の比表面積はほぼ同じであるものの、鉄粉中の炭素を含有する割合が0.23重量%増加すると、ヒ素除去率が62%増加した。また、実施例2及び実施例3より、鉄粉の比表面積が小さくとも、鉄粉中の炭素を含有する割合が増加すると、ヒ素除去率は35%増加した。また、実施例4より炭素を1重量%含有した鉄粉は、ヒ素を22%除去できた。 From Table 1, the carbon content was the same as in Example 1 and Example 2, but the arsenic removal rate increased by 17% due to the increase in specific surface area. Moreover, from Example 3, the iron powder containing 0.06% of carbon was able to remove 20% of arsenic. Furthermore, from Example 1 and Example 3, although the specific surface area of the iron powder was substantially the same, the arsenic removal rate increased by 62% when the proportion of carbon contained in the iron powder increased by 0.23% by weight. Moreover, even if the specific surface area of iron powder was small from Example 2 and Example 3, when the ratio containing the carbon in iron powder increased, the arsenic removal rate increased by 35%. Further, from Example 4, the iron powder containing 1% by weight of carbon was able to remove 22% of arsenic.
以上のことより、鉄粉は比表面積が増加するにつれてヒ素除去率も増加することが明らかにされ、ヒ素除去率を50%以上にする場合には、鉄粉の比表面積を0.5mm2/g以上にするのが好ましいと考えた。 From the above, it has been clarified that the iron powder increases the arsenic removal rate as the specific surface area increases. When the arsenic removal rate is 50% or more, the specific surface area of the iron powder is 0.5 mm 2 / It was considered preferable to be g or more.
さらに、実施例1から実施例4までより、炭素を含有する鉄粉は、鉄粉中の鉄粉表面でセメンタイトを生成しやすく、カソード表面増加し、鉄粉の酸化反応を増進させ、ヒ素除去率が飛躍的に増加することを明らかにした。また、実施例3より炭素を0.06重量%含有する鉄粉であることは少なくとも必要であると考え、実施例4よりヒ素を100%除去するには、炭素を5重量%含有する鉄粉であれば可能と考えた。従って、炭素を0.06重量%から5重量%含有する鉄粉が好ましいと考えた。 Furthermore, from Example 1 to Example 4, the iron powder containing carbon easily generates cementite on the iron powder surface in the iron powder, increases the cathode surface, promotes the oxidation reaction of the iron powder, and removes arsenic. It has been clarified that the rate will increase dramatically. Further, it is considered necessary at least that the iron powder contains 0.06% by weight of carbon from Example 3, and in order to remove 100% of arsenic from Example 4, the iron powder containing 5% by weight of carbon. I thought it would be possible. Therefore, an iron powder containing 0.06 wt% to 5 wt% of carbon was considered preferable.
また、浄化反応剤として重金属に対応する鉄粉の量は、実施例1より、炭素0.3重量%を含有し、比表面積5.6m2/gの鉄粉であるとき、除去率80%以上の場合には、処理する重金属1mgに対して鉄粉0.49g以上が好ましく、除去率100%の場合には、処理する重金属1mgに対して鉄粉0.61g以上が好ましいと考えた。 Further, the amount of iron powder corresponding to heavy metal as a purification reaction agent is 0.3% by weight of carbon from Example 1, and when the iron powder has a specific surface area of 5.6 m 2 / g, the removal rate is 80%. In the above case, 0.49 g or more of iron powder was preferable with respect to 1 mg of heavy metal to be processed, and when the removal rate was 100%, it was considered that 0.61 g or more of iron powder was preferable with respect to 1 mg of heavy metal to be processed.
[実施例5]
鉄粉5(平均粒径0.52mm)の透水係数を定水位法で測定した。測定器は土壌透過性測定器DIK4,000(大紀理化工業社製)を用いた。
[Example 5]
The water permeability coefficient of iron powder 5 (average particle size 0.52 mm) was measured by a constant water level method. The measuring instrument used was a soil permeability measuring instrument DIK4,000 (manufactured by Daiki Rika Kogyo Co., Ltd.).
[実施例6]
鉄粉6(平均粒径0.45mm)の透水係数を実施例5と同様の定水位法で測定した。
[Example 6]
The water permeability coefficient of iron powder 6 (average particle size 0.45 mm) was measured by the same water level method as in Example 5.
[実施例7]
鉄粉7(平均粒径0.09mm)の透水係数を実施例5と同様の定水位法で測定した。
[Example 7]
The water permeability coefficient of iron powder 7 (average particle size 0.09 mm) was measured by the same water level method as in Example 5.
[実施例8]
鉄粉8(平均粒径0.04mm)の透水係数を実施例5と同様の定水位法で測定した。
[Example 8]
The water permeability coefficient of iron powder 8 (average particle size 0.04 mm) was measured by the same water level method as in Example 5.
実施例5から実施例8の結果を表2に示す。
表2より、実施例5から実施例8より、平均粒径を増加させることによって、透水係数も増加している。一般に帯水層の透水係数は0.1m/dayから102m/dayであるため、透過反応壁の透水係数が0.1m/day以下では地下水が透過しがたいため、汚染物質の除去性能は低下し、処理速度が低下する。従って、平均粒径が0.09mm以下では、0.1m/day以下となり、除去性能が大幅に低下してしまうことが明らかにされた。 From Table 2, from Example 5 to Example 8, the permeability coefficient is also increased by increasing the average particle diameter. In general, the permeability coefficient of the aquifer is from 0.1 m / day to 10 2 m / day, and the permeability of the permeation reaction wall is less than 0.1 m / day, so it is difficult for groundwater to pass through. Decreases, and the processing speed decreases. Therefore, when the average particle size is 0.09 mm or less, it becomes 0.1 m / day or less, and it has been clarified that the removal performance is greatly deteriorated.
以上のことより、炭素を0.06重量%から5重量%含有し、平均粒径0.1mm以上かつ比表面積0.5m2/g以上の鉄粉であることによって、ヒ素除去性能が高く、透過性も高いことを明らかにした。 From the above, 0.06 wt% to 5 wt% of carbon, an iron powder having an average particle size of 0.1 mm or more and a specific surface area of 0.5 m 2 / g or more, high arsenic removal performance, It was revealed that the permeability is high.
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Cited By (4)
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JP2008155105A (en) * | 2006-12-22 | 2008-07-10 | Sumitomo Metal Mining Co Ltd | Removal method of arsenic from arsenic-containing aqueous solution |
JP2009235204A (en) * | 2008-03-26 | 2009-10-15 | Dowa Eco-System Co Ltd | Organohalogen compound decomposing agent, its production process and purification process using the decomposing agent |
CN103121032A (en) * | 2013-03-19 | 2013-05-29 | 中国科学院城市环境研究所 | Method for rapidly removing and recycling hexavalent chromium from chromium-contaminated soil |
JP2014168744A (en) * | 2013-03-04 | 2014-09-18 | Dowa Eco-System Co Ltd | Method for purifying selenium-containing matter |
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JP2008155105A (en) * | 2006-12-22 | 2008-07-10 | Sumitomo Metal Mining Co Ltd | Removal method of arsenic from arsenic-containing aqueous solution |
JP2009235204A (en) * | 2008-03-26 | 2009-10-15 | Dowa Eco-System Co Ltd | Organohalogen compound decomposing agent, its production process and purification process using the decomposing agent |
JP2014168744A (en) * | 2013-03-04 | 2014-09-18 | Dowa Eco-System Co Ltd | Method for purifying selenium-containing matter |
CN103121032A (en) * | 2013-03-19 | 2013-05-29 | 中国科学院城市环境研究所 | Method for rapidly removing and recycling hexavalent chromium from chromium-contaminated soil |
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