JP5720105B2 - Permeable reaction wall and groundwater purification structure - Google Patents
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- 238000006243 chemical reaction Methods 0.000 title claims description 71
- 239000003673 groundwater Substances 0.000 title claims description 30
- 238000000746 purification Methods 0.000 title claims description 19
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 38
- 239000002689 soil Substances 0.000 claims description 38
- 239000003463 adsorbent Substances 0.000 claims description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 18
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- 239000001095 magnesium carbonate Substances 0.000 claims description 17
- 229910000021 magnesium carbonate Inorganic materials 0.000 claims description 17
- 239000011737 fluorine Substances 0.000 claims description 15
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- 239000008187 granular material Substances 0.000 claims description 12
- 150000001450 anions Chemical class 0.000 claims description 9
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 7
- 239000000920 calcium hydroxide Substances 0.000 claims description 7
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 6
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 5
- 239000011790 ferrous sulphate Substances 0.000 claims description 5
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 5
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 5
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 5
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 5
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 5
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 5
- 229910052785 arsenic Inorganic materials 0.000 claims description 4
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims description 4
- 229960002089 ferrous chloride Drugs 0.000 claims description 4
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 4
- 238000011144 upstream manufacturing Methods 0.000 claims description 4
- PMVSDNDAUGGCCE-TYYBGVCCSA-L Ferrous fumarate Chemical class [Fe+2].[O-]C(=O)\C=C\C([O-])=O PMVSDNDAUGGCCE-TYYBGVCCSA-L 0.000 claims description 3
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 3
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims description 3
- 239000011669 selenium Substances 0.000 claims description 3
- 229910052711 selenium Inorganic materials 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 2
- -1 cyan Chemical compound 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims 1
- 150000003839 salts Chemical class 0.000 claims 1
- 150000002505 iron Chemical class 0.000 description 20
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 14
- 238000001179 sorption measurement Methods 0.000 description 13
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- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
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- 229910052748 manganese Inorganic materials 0.000 description 3
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- 238000002156 mixing Methods 0.000 description 3
- 239000008399 tap water Substances 0.000 description 3
- 235000020679 tap water Nutrition 0.000 description 3
- 229910002707 Al–O–H Inorganic materials 0.000 description 2
- 229910021532 Calcite Inorganic materials 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
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- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
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- 150000004045 organic chlorine compounds Chemical class 0.000 description 2
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- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- CYTYCFOTNPOANT-UHFFFAOYSA-N Perchloroethylene Chemical group ClC(Cl)=C(Cl)Cl CYTYCFOTNPOANT-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
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- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、フッ素などで汚染された地下水を原位置で浄化するための透過性反応壁及び地下水浄化構造に係り、特に火山灰土壌の焼成物からなる吸着材を用いた透過性反応壁及び地下水浄化構造に関する。 The present invention relates to a permeable reaction wall and a groundwater purification structure for purifying groundwater contaminated with fluorine or the like in situ, and in particular, a permeable reaction wall and a groundwater purification using an adsorbent made of a calcined product of volcanic ash soil. Concerning structure.
湖水の富栄養化の原因になるリン酸や水系のヒ素やフッ素を吸着除去するための吸着材として、火山灰土壌に鉄塩を混合して焼成したものが特開平６−３０４４７２、特開平１１−３０９４４８に記載されている。後者には、火山灰土壌に鉄塩と併せて酸又はアルカリを混合して焼成することも記載されている。 As an adsorbent for adsorbing and removing phosphoric acid and water-based arsenic and fluorine that cause eutrophication of lake water, those obtained by mixing iron salt with volcanic ash soil and calcining are disclosed in JP-A-6-304472 and JP-A-11-11. 309448. The latter also describes that volcanic ash soil is mixed with an iron salt and mixed with an acid or alkali and fired.
フッ素などの重金属類や有機塩素化合物などで汚染された地下水を原位置で浄化する方法として、汚染地下水の流れを遮るように構築した透過性反応壁（ＰＲＢ；Permeable Reactive Barrier）が知られている（特開２００７−２６０５２５、特開２００４−２６１７３８、特表平５−５０１５２０）。 Permeable Reactive Barrier (PRB) constructed to block the flow of contaminated groundwater is known as a method for purifying groundwater contaminated with heavy metals such as fluorine and organic chlorine compounds in situ. (Japanese Patent Laid-Open No. 2007-260525, Japanese Patent Laid-Open No. 2004-261738, Japanese Patent Laid-Open No. 5-501520).
火山灰土壌から製造した吸着材は、無機成分で構成される剤であるため微生物分解を受けることがなく、長期にわたり化学的に安定であるところから、透過性反応壁に好適であると考えられる。 Since the adsorbent produced from volcanic ash soil is an agent composed of inorganic components, it is not susceptible to microbial degradation and is chemically stable over a long period of time, so it is considered suitable for a permeable reaction wall.
ところが、上記吸着材を透過性反応壁に適用しようと試みたところ、水浄化材として使用する際にはｐＨ調整が不要であるとされていた吸着材であるにも拘わらず、透過性反応壁に適用すると、初期の段階で透過反応壁内を通過する地下水のｐＨが低下して処理性能が低くなるという予期しない問題が発生した。さらにはｐＨ低下によりマンガンが溶出するという問題も併発した。 However, when an attempt was made to apply the adsorbent to the permeable reaction wall, the permeable reaction wall was used even though it was an adsorbent that was said to require no pH adjustment when used as a water purification material. As a result, an unexpected problem arises in that the pH of groundwater passing through the permeation reaction wall is lowered in the initial stage and the treatment performance is lowered. Furthermore, the problem of manganese elution due to a decrease in pH occurred.
この理由については、明確ではないが以下によるものと推定される。即ち、通常の水処理においては多量の水、大流量の水の存在下で吸着処理を行っているため、火山灰土壌焼成物から溶出した硫酸イオンや塩化物イオンが大量の水で希釈されることによりｐＨ低下が無視できるレベルである。ところが、一般に地下水は流速が極めて遅く、１ｃｍ／日〜１０ｍ／日程度である。このように地下水の流量が小さいため上記吸着材を適用した透過性反応壁においては硫酸イオンや塩化物イオンの溶出により透過性反応壁内を通過する地下水のｐＨが低下し、特に溶出が多い初期に顕著にｐＨが低下してしまうものと考えられる。 The reason for this is not clear but is presumed to be as follows. That is, in ordinary water treatment, adsorption treatment is performed in the presence of a large amount of water and a large amount of water, so that sulfate ions and chloride ions eluted from the calcined volcanic ash soil are diluted with a large amount of water. Therefore, the pH drop is negligible. However, in general, groundwater has a very slow flow rate of about 1 cm / day to 10 m / day. Since the flow rate of groundwater is small in this way, in the permeable reaction wall to which the above adsorbent is applied, the pH of the groundwater passing through the permeable reaction wall is lowered due to elution of sulfate ions and chloride ions, and in particular, there is a large amount of elution. It is thought that pH will fall remarkably.
本発明は上記問題を解決するものであって、火山灰土壌に鉄塩を混合して焼成した吸着材を透過性反応壁に適用する際に透過性反応壁内を通過する地下水のｐＨ低下による透過性反応壁の性能低下や透過性反応壁から地下水へのマンガン溶出を防止することができる透過性反応壁及び地下水浄化構造を提供することを目的とする。 The present invention solves the above-mentioned problem, and the permeation due to the lowering of the pH of groundwater that passes through the permeable reaction wall when the adsorbent obtained by mixing iron salt with volcanic ash soil and firing is applied to the permeable reaction wall. It is an object of the present invention to provide a permeable reaction wall and a groundwater purification structure that can prevent degradation of the performance of the permeable reaction wall and elution of manganese from the permeable reaction wall to groundwater.
本発明（請求項１）の透過性反応壁は、アニオン汚染地下水の流れを遮るように帯水層に壁状に設けた透過性反応壁において、硫酸第一鉄、硫酸第二鉄、塩化第一鉄及び塩化第二鉄よりなる群から選ばれた少なくとも１種の鉄塩を火山灰土壌に添加して焼成した火山灰土壌焼成物からなる吸着材と、炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体との混合物を含有し、炭酸カルシウム及び／又は炭酸マグネシウムが１〜５０ｗｔ％存在することを特徴とするものである。 The permeable reaction wall of the present invention (Claim 1) is a permeable reaction wall provided in a wall shape in an aquifer so as to block the flow of anion-contaminated groundwater. Ferrous sulfate, ferric sulfate, chloride chloride An adsorbent comprising a calcined product of volcanic ash soil obtained by adding at least one iron salt selected from the group consisting of ferrous iron and ferric chloride to the volcanic ash soil and calcining, and a granular material containing calcium carbonate and / or magnesium carbonate containing a mixture of calcium carbonate and / or magnesium carbonate and is characterized in that there 1 to 50 wt%.
請求項２の透過性反応壁は、請求項１において、前記吸着材は、火山灰土壌にさらに水酸化カルシウムを添加して焼成したものであることを特徴とするものである。 A permeable reaction wall according to a second aspect is characterized in that, in the first aspect, the adsorbent is obtained by further adding calcium hydroxide to a volcanic ash soil and baking it.
請求項３の透過性反応壁は、請求項１又は２において、前記アニオンはフッ素、ヒ素、シアン、六価クロム及びセレンよりなる群から選ばれた少なくとも１種又はそれを含む化合物のアニオンであることを特徴とするものである。
The permeable reaction wall according to claim 3 is the anion of at least one selected from the group consisting of fluorine, arsenic, cyan, hexavalent chromium and selenium or a compound containing the same in
本発明（請求項４）の地下水浄化構造は、アニオン汚染地下水の流れを遮るように帯水層に壁状に設けられ、硫酸第一鉄、硫酸第二鉄、塩化第一鉄及び塩化第二鉄よりなる群から選ばれた少なくとも１種の鉄塩を火山灰土壌に添加して焼成した火山灰土壌焼成物からなる吸着材と、炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体との混合物を含有する第１の透過性反応壁と、該第１の透過性反応壁の上流側に設けられた、鉄粉を含有する第２の透過性反応壁とを備えてなるものである。 The groundwater purification structure of the present invention (Claim 4) is provided in the aquifer in a wall shape so as to block the flow of anion-contaminated groundwater, and ferrous sulfate, ferric sulfate, ferrous chloride and ferric chloride. Contains a mixture of an adsorbent composed of a calcined volcanic ash soil obtained by adding at least one iron salt selected from the group consisting of iron to volcanic ash soil and calcined, and a granular material containing calcium carbonate and / or magnesium carbonate A first permeable reaction wall and a second permeable reaction wall containing iron powder provided on the upstream side of the first permeable reaction wall are provided.
請求項５の地下水浄化構造は、請求項４において、該第２の透過性反応壁は、さらに粒状の透水材を含有することを特徴とするものである。
The groundwater purification structure according to claim 5 is characterized in that, in
本発明の透過性反応壁（第１の透過性反応壁）は、炭酸カルシウム及び／又は炭酸マグネシウムの粒状体を含有しているので、硫酸イオンや塩化物イオンなどが地下水中に溶出しても、透過性反応壁内を通過する地下水のｐＨが中性域に維持される。このため、透過性反応壁の性能低下や透過性反応壁からのマンガンの溶出が防止される。 Since the permeable reaction wall (first permeable reaction wall) of the present invention contains granules of calcium carbonate and / or magnesium carbonate, even if sulfate ions or chloride ions are eluted into the groundwater. The pH of groundwater passing through the permeable reaction wall is maintained in a neutral range. For this reason, the performance fall of a permeable reaction wall and the elution of manganese from a permeable reaction wall are prevented.
炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体を含有した本発明の透過性反応壁は、少なくとも処理開始初期において透過性反応壁内を通過する地下水をｐＨ７〜９程度に維持することができるため、ｐＨ７〜９で安定して吸着されるアニオンであるフッ素、ヒ素、シアン、六価クロム、セレンを効率よく除去することができる。 Since the permeable reaction wall of the present invention containing granules containing calcium carbonate and / or magnesium carbonate can maintain the groundwater passing through the permeable reaction wall at least at the initial stage of the treatment at a pH of about 7 to 9, Fluorine, arsenic, cyanide, hexavalent chromium and selenium, which are anions that are stably adsorbed at pH 7 to 9, can be efficiently removed.
請求項２のように、火山灰土壌に対し鉄塩と炭酸カルシウム及び／又は炭酸マグネシウムに併せてさらに水酸化カルシウムを混合して焼成した吸着材は、アニオン吸着効果に優れる。 As described in claim 2, an adsorbent obtained by mixing and baking calcium hydroxide in addition to iron salt and calcium carbonate and / or magnesium carbonate to volcanic ash soil is excellent in anion adsorption effect.
ところで、透過性反応壁として鉄粉を含有するものが従来より用いられており、上記本発明の透過性反応壁（第１の透過性反応壁）とこの鉄粉含有透過性反応壁（第２の透過性反応壁）とを併用してもよい。この場合、第１の透過性反応壁からは炭酸塩が溶出するので、炭酸塩が鉄粉に作用しないようにするために、第２の透過性反応壁を第１の透過性反応壁の地下水流れ方向の上流側に設ける。 By the way, what contains iron powder as a permeable reaction wall is used conventionally, The permeable reaction wall (1st permeable reaction wall) of this invention and this iron powder containing permeable reaction wall (2nd) Or a permeable reaction wall). In this case, since carbonate elutes from the first permeable reaction wall, in order to prevent the carbonate from acting on the iron powder, the second permeable reaction wall is used as groundwater of the first permeable reaction wall. Provided upstream in the flow direction.
以下に図面を参照して本発明の実施の形態に係る透過性反応壁による地下水浄化構造を詳細に説明する。第１図は、本発明の透過性反応壁の断面図である。 Hereinafter, a groundwater purification structure using a permeable reaction wall according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a permeable reaction wall of the present invention.
第１図の通り、地表１から所定深さに不透水層３あるいは難透水層が存在し、その上側に帯水層２が存在する。４は地下水位である。地下水の流れＷ１、Ｗ２を横断するように透過性反応壁５を設けると共に、この透過性反応壁５の両端に連なるようにして遮水壁（図示略）を設け、上流側からの地下水が確実に透過性反応壁５を通過するようにする。
As shown in FIG. 1, an impermeable layer 3 or a hardly permeable layer is present at a predetermined depth from the
透過性反応壁５の施工手順の一例は以下の通りである。ボウリングして浄化材を含む充填材で埋め戻すことにより柱状の第１の浄化体を作成し、次いでこの柱状の第１の浄化体と部分的に重なるようにボウリングして同様に浄化材を含む充填材で埋め戻すことにより柱状の第２の浄化体を作成する、という作業を繰り返して柱状の浄化体を並列して作成することによって壁状の浄化体よりなる透過性反応壁を作成する。必要に応じ、この透過性反応壁５の両端に隣接するようにＨ型鋼と鉄矢板等を打ち込んで遮水壁を構築する。 An example of the construction procedure of the permeable reaction wall 5 is as follows. A columnar first purification body is created by bowling and backfilling with a filler containing a purification material, and then bowling so as to partially overlap the columnar first purification body and similarly including the purification material A permeable reaction wall made of a wall-shaped purification body is created by repeating the operation of creating a columnar second purification body by backfilling with a filler to create a columnar purification body in parallel. If necessary, a water-impervious wall is constructed by driving in H-shaped steel and steel sheet piles so as to be adjacent to both ends of the permeable reaction wall 5.
＜透過性反応壁５の材料＞
透過性反応壁５は、火山灰土壌焼成物からなるアニオン吸着材と、炭酸カルシウム及び／又は炭酸マグネシウム含有粒状体とを含む。
<Material of permeable reaction wall 5>
The permeable reaction wall 5 includes an anion adsorbent composed of a calcined product of volcanic ash soil, and calcium carbonate and / or magnesium carbonate-containing granules.
アニオン吸着材としては火山灰土壌に鉄塩と必要に応じ水酸化カルシウムを添加し、混合し、好ましくは造粒して焼成したものが用いられる。 As an anion adsorbent, iron salt and calcium hydroxide as necessary are added to volcanic ash soil, mixed, preferably granulated and fired.
火山灰土壌としては、噴出源より遠く離れた非火山地域をも広く覆い、細粒の火山灰が褐色に風化したいわゆるローム層を母材とするアンドソルが例示される。火山灰土壌はフッ素などのアニオンの吸着・不溶化作用を有する。この吸着・不溶化は、例えば次式のように火山灰粒子表面の反応活性部位で起こる。
Ｒ−Ｆｅ−Ｏ−Ｈ２ ＋＋Ｆ−→Ｒ−Ｆｅ−Ｏ−Ｈ２Ｆ
Ｒ−Ａｌ−Ｏ−Ｈ２ ＋＋Ｆ−→Ｒ−Ａｌ−Ｏ−Ｈ２Ｆ（Ｒ：火山灰を構成する鉱物成分（例えばアルミノシリケート）の基本骨格）
Examples of the volcanic ash soil include Andol, which covers a non-volcanic area far away from the eruption source and uses a so-called loam layer in which fine-grained volcanic ash is browned as a base material. Volcanic ash soil has an adsorption and insolubilization action of anions such as fluorine. This adsorption / insolubilization occurs at the reactive site on the surface of the volcanic ash particles, for example, as in the following equation.
R—Fe—O—H 2 + + F − → R—Fe—O—H 2 F
R—Al—O—H 2 + + F − → R—Al—O—H 2 F (R: basic skeleton of mineral components (for example, aluminosilicate) constituting volcanic ash)
鉄塩としては、硫酸第一鉄、硫酸第二鉄、塩化第一鉄、塩化第二鉄の１種又は２種以上を用いる。 As the iron salt, one or more of ferrous sulfate, ferric sulfate, ferrous chloride, and ferric chloride are used.
火山灰土壌に混合する鉄塩の添加量は、火山灰土壌１００重量部に対し好ましくは５〜４０重量部、より好ましくは１０〜３０重量部である。また、鉄塩と共にさらに水酸化カルシウムを添加する場合、水酸化カルシウムの添加量は火山灰土壌１００重量部に対し１〜１０重量部であることが好ましい。 The addition amount of the iron salt mixed with the volcanic ash soil is preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the volcanic ash soil. Moreover, when adding calcium hydroxide with an iron salt, it is preferable that the addition amount of calcium hydroxide is 1-10 weight part with respect to 100 weight part of volcanic ash soil.
火山灰土壌と鉄塩さらに水酸化カルシウムを混合するには、まず乾式で混合してから水を添加して造粒し、これを乾燥してから焼成するのが好ましい。造粒方法としては、ブリケットマシン、転動造粒法など各種手法を用いることができる。焼成条件は３００〜７００℃特に４００〜６００℃で５〜６０分間程度とするのが好ましい。このようにして得られる粒子の粒径は、透水性を考慮して０．０１〜５ｍｍ特に０．１〜３ｍｍ程度が好ましい。 In order to mix the volcanic ash soil, the iron salt and the calcium hydroxide, it is preferable to first mix them in a dry manner, add water to granulate them, dry them, and fire them. As a granulation method, various methods such as a briquette machine and a rolling granulation method can be used. The firing conditions are preferably 300 to 700 ° C., particularly 400 to 600 ° C., for about 5 to 60 minutes. The particle size of the particles thus obtained is preferably about 0.01 to 5 mm, particularly about 0.1 to 3 mm in consideration of water permeability.
この吸着材は、透過性反応壁中において１０〜１００ｗｔ％特に２０〜１００ｗｔ％程度存在することが好ましい。 This adsorbent is preferably present in the permeable reaction wall in an amount of about 10 to 100 wt%, particularly about 20 to 100 wt%.
この透過性反応壁には、さらに炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体を含有させる。炭酸カルシウムとしては石灰石、寒水石などの炭酸カルシウム系鉱物を用いるのが好ましい。炭酸マグネシウムとしては苦灰石、菱苦土石などを用いることができる。 The permeable reaction wall further contains a granular body containing calcium carbonate and / or magnesium carbonate. As calcium carbonate, it is preferable to use calcium carbonate minerals such as limestone and cold water stone. As the magnesium carbonate, dolomite, rhodolite, etc. can be used.
この粒状体は、炭酸カルシウム及び／又は炭酸マグネシウムの鉱物の破砕物のみからなってもよく、これらの破砕物や粉砕物に必要に応じ砂などを添加して造粒したものであってもよいが、前者の方が低コストである。 This granular material may consist of crushed materials of calcium carbonate and / or magnesium carbonate, or may be granulated by adding sand or the like to these crushed materials or pulverized materials as necessary. However, the former is cheaper.
炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体は、透過性反応壁中において炭酸カルシウム及び／又は炭酸マグネシウムが１〜５０ｗｔ％特に１〜２０ｗｔ％存在するのが好ましい。 The granule containing calcium carbonate and / or magnesium carbonate preferably contains 1 to 50 wt%, particularly 1 to 20 wt% of calcium carbonate and / or magnesium carbonate in the permeable reaction wall.
透過性反応壁は、上記の吸着材と、この炭酸カルシウム及び／又は炭酸マグネシウム含有粒状体のみからなってもよく、さらに他の材料、例えば透過性反応壁の透水性を高めるために砂利などの粒状体を含んでもよい。 The permeable reaction wall may consist of the above adsorbent and the calcium carbonate and / or magnesium carbonate-containing granule alone, and other materials such as gravel to increase the water permeability of the permeable reaction wall. Granules may be included.
本発明では、この透過性反応壁のみを地中に設けてもよく、さらに他の浄化材により構成される透過性反応壁を並設してもよい。このような並設される透過性反応壁として鉄粉含有透過性反応壁（第２の透過性反応壁）が挙げられる。 In the present invention, only this permeable reaction wall may be provided in the ground, or a permeable reaction wall composed of another purification material may be provided in parallel. Examples of such permeable reaction walls arranged side by side include an iron powder-containing permeable reaction wall (second permeable reaction wall).
鉄粉としては、炭素を０．２９重量％〜５重量％含有し、平均粒径０．１ｍｍ以上（例えば０．１〜５ｍｍ）かつ比表面積１ｍ２／ｇ以上（例えば０．５〜５ｍ２／ｇ）である鉄粉を用いるのが好ましい。この鉄粉は、トリクロロエチレン（ＴＣＥ）、テトラクロロエチレンなどの有機塩素化合物を分解する機能を有する。鉄粉によるＴＣＥの分解反応は次式で示される。
３Ｆｅ＋Ｃ２ＨＣｌ３＋３Ｈ２Ｏ→Ｃ２Ｈ４＋３Ｆｅ３＋＋３Ｃｌ−＋３ＯＨ−
The iron powder contains 0.29 wt% to 5 wt% of carbon, has an average particle size of 0.1 mm or more (for example, 0.1 to 5 mm), and a specific surface area of 1 m 2 / g or more (for example, 0.5 to 5 m 2 ). / G) is preferably used. This iron powder has a function of decomposing organochlorine compounds such as trichlorethylene (TCE) and tetrachloroethylene. The decomposition reaction of TCE by iron powder is shown by the following formula.
3Fe + C 2 HCl 3 + 3H 2 O → C 2 H 4 + 3Fe 3+ + 3Cl − + 3OH −
この鉄粉含有透過性反応壁としては、鉄粉や、必要に応じ活性炭、酸化マグネシウム、水酸化マグネシウムなどの浄化成分を混合したものが用いられる。鉄粉は透過性反応壁中において１０〜１００ｗｔ％特に２０〜１００ｗｔ％程度存在することが好ましい。鉄粉を含有した第２の透過性反応壁は、前述の通り、第１の透過性反応壁の地下水流れ方向の上流側に設けられる。 As this iron powder containing permeable reaction wall, what mixed iron powder and purification components, such as activated carbon, magnesium oxide, and magnesium hydroxide as needed, is used. The iron powder is preferably present in the permeable reaction wall in an amount of about 10 to 100 wt%, particularly about 20 to 100 wt%. As described above, the second permeable reaction wall containing iron powder is provided on the upstream side of the first permeable reaction wall in the groundwater flow direction.
本発明のように火山灰土壌に鉄塩を添加して焼成した吸着材と共に炭酸カルシウム及び／又は炭酸マグネシウムをさらに併用した場合の効果を示す実験例を次に示す。 The experiment example which shows the effect at the time of further using together calcium carbonate and / or magnesium carbonate with the adsorbent which added iron salt to the volcanic ash soil like this invention and baked is shown next.
［実験例Ｎｏ．１〜３］
＜実験条件＞
脱塩素水道水にフッ化ナトリウムを添加して、フッ素濃度を１０ｍｇ／Ｌとした溶液に、表１に示す種々の吸着材を１０ｇ／Ｌの濃度で添加して、Ｎｏ．３，５，６については、併用材として寒水石（炭酸カルシウムを含む鉱石）を添加して２４時間振盪後に濾過し、フッ素濃度の変化を測定した。試験結果を表１に示す。なお、以下の実験例Ｎｏ．２〜７において、鉄塩含有火山灰土壌焼成物としてクレアテラ社製の吸着材「ピーキャッチ（登録商標）」（酸化鉄（Ｆｅ２Ｏ３）として約２０ｗｔ％含有。平均粒径０．８ｍｍ）を用いた。
[Experiment No. 1-3]
<Experimental conditions>
To a solution in which sodium fluoride was added to dechlorinated tap water to a fluorine concentration of 10 mg / L, various adsorbents shown in Table 1 were added at a concentration of 10 g / L. For 3, 5, and 6, cold water stone (ore containing calcium carbonate) was added as a combined material, and the mixture was filtered after shaking for 24 hours, and the change in fluorine concentration was measured. The test results are shown in Table 1. The following experimental examples No. 2-7, as an iron salt-containing volcanic ash soil calcined product, an adsorption material “Peacat (registered trademark)” manufactured by Createrra (containing about 20 wt% as iron oxide (Fe 2 O 3 ), average particle size 0.8 mm) Using.
Ｎｏ．１の未焼成火山灰土壌による吸着材では、処理水ｐＨの低下は起こらないものの十分なフッ素の吸着能力を得られなかった。 No. With the adsorbent of 1 unfired volcanic ash soil, the pH of the treated water did not decrease, but sufficient fluorine adsorption capacity could not be obtained.
Ｎｏ．２のように鉄塩含有火山灰土壌焼成物による吸着材を単独で用いると、フッ素を地下水基準に適合可能な吸着能力が得られたが、吸着材に含まれる酸性成分の影響により処理水のｐＨが２４時間以内に低下してしまった。 No. As shown in Fig. 2, when an adsorbent made of iron salt-containing volcanic ash soil burned material was used alone, it was possible to obtain an adsorption capacity capable of conforming to the groundwater standard for fluorine, but the pH of the treated water was influenced by the influence of acidic components contained in the adsorbent. Fell within 24 hours.
Ｎｏ．３のように鉄塩含有火山灰土壌焼成物からなる吸着材に対し寒水石を火山灰土壌焼成物の１０ｗｔ％添加した場合は、処理水のｐＨを低下させることなく十分な吸着能力を得ることができた。 No. When 10 wt% of calcite is added to the adsorbent composed of the iron salt-containing volcanic ash soil burned material as shown in Fig. 3, sufficient adsorption capacity can be obtained without lowering the pH of the treated water. It was.
［実験Ｎｏ．４，５（吸着等温線による効果確認）］
＜実験条件＞
脱塩素水道水にフッ化ナトリウムを添加してフッ素濃度５０mg/Lにした水溶液を調製し、鉄塩含有火山灰土壌焼成物による吸着材単独の場合（Ｎｏ．４）、および、鉄塩含有火山灰土壌焼成物からなる吸着材に寒水石を火山灰土壌焼成物の１０ｗｔ％添加した場合（Ｎｏ．５）について吸着等温線による評価をおこなった。結果を第２図に示す。
[Experiment No. 4, 5 (confirmation of effect by adsorption isotherm)]
<Experimental conditions>
An aqueous solution prepared by adding sodium fluoride to dechlorinated tap water to a fluorine concentration of 50 mg / L, and using an adsorbent alone with a fired iron salt-containing volcanic ash soil (No. 4), and an iron salt-containing volcanic ash soil Evaluation was performed by adsorption isotherm when 10 wt% of calcite was added to the adsorbent made of the fired product (No. 5). The results are shown in FIG.
＜結果考察＞
Ｎｏ．５のように鉄塩含有火山灰土壌焼成物からなる吸着材に寒水石を併用することにより、Ｎｏ．４の鉄塩含有火山灰土壌焼成物からなる吸着材単独よりも高い吸着能力を得ることができた。これは寒水石を併用することで吸着に適したｐＨに維持できたからであると考えられる。
<Consideration of results>
No. As shown in No. 5, by using cold water stone together with the adsorbent made of the burned material of iron salt-containing volcanic ash soil, Adsorption capacity higher than that of the adsorbent alone consisting of 4 iron salt-containing volcanic ash soil calcined products could be obtained. This is considered to be because the pH suitable for adsorption could be maintained by using cryogenic stone together.
［実験Ｎｏ．６，７（カラム通水試験）］
＜実験条件＞
充填カラムを用いた比較を実施した。鉄塩含有火山灰土壌焼成物からなる吸着材と寒水石との併用系（Ｎｏ．６）を充填材として充填した充填カラムと、鉄塩含有火山灰土壌焼成物からなる吸着材単独（Ｎｏ．７）を充填材として充填した充填カラムを用いた評価は、実際の使用条件を想定した評価方法である。内径３０ｍｍ、充填長３００ｍｍのアクリル製カラムに、１８０ｃｍ３の充填材を充填した。また、Ｎｏ．６では、火山灰土壌焼成物の１０ｗｔ％の寒水石を混合して充填材とした。
[Experiment No. 6, 7 (column water flow test)]
<Experimental conditions>
A comparison using a packed column was performed. A packed column packed with a combined system (No. 6) of an adsorbent made of iron salt-containing volcanic ash soil and a frozen stone (No. 6), and an adsorbent alone made of iron salt-containing volcanic ash soil and burned (No. 7) Evaluation using a packed column packed with as a filler is an evaluation method assuming actual use conditions. An acrylic column having an inner diameter of 30 mm and a packing length of 300 mm was packed with 180 cm 3 of packing material. No. In No. 6, 10 wt% of cold water stones of the calcined volcanic ash soil were mixed to obtain a filler.
フッ素濃度５０ｍｇ／Ｌの脱塩素水道水を調製し、カラムに０．０５ｍＬ／ｍｉｎで通水した。充填カラム出口のフッ素濃度およびｐＨを測定した。その結果を第３図及び第４図に示す。 Dechlorinated tap water having a fluorine concentration of 50 mg / L was prepared and passed through the column at 0.05 mL / min. The fluorine concentration and pH at the outlet of the packed column were measured. The results are shown in FIG. 3 and FIG.
＜結果考察＞
第３図のように鉄塩含有火山灰土壌焼成物からなる吸着材を寒水石と併用する（Ｎｏ．６）ことによりフッ素の吸着能力が向上した。また、第４図に示す様に、寒水石を併用する（Ｎｏ．６）ことにより充填層出口でのｐＨを中性付近に維持することができた。
<Consideration of results>
As shown in Fig. 3, the adsorption capacity of fluorine was improved by using an adsorbent made of a fired iron salt-containing volcanic ash soil in combination with cryogenic stone (No. 6). Moreover, as shown in FIG. 4, the pH at the packed bed outlet could be maintained in the vicinity of neutrality by using cold water stone together (No. 6).
２ 帯水層
３ 不透水層
５ 透過性反応壁
2 Aquifer 3 Impermeable layer 5 Permeable reaction wall
Claims (5)
硫酸第一鉄、硫酸第二鉄、塩化第一鉄及び塩化第二鉄よりなる群から選ばれた少なくとも１種の鉄塩を火山灰土壌に添加して焼成した火山灰土壌焼成物からなる吸着材と、炭酸カルシウム及び／又は炭酸マグネシウムを含む粒状体との混合物を含有し、
炭酸カルシウム及び／又は炭酸マグネシウムが１〜５０ｗｔ％存在することを特徴とする透過性反応壁。 In the permeable reaction wall provided in the aquifer wall shape so as to block the flow of anion-contaminated groundwater,
An adsorbent comprising a calcined volcanic ash soil obtained by adding at least one iron salt selected from the group consisting of ferrous sulfate, ferric sulfate, ferrous chloride and ferric chloride to the volcanic ash soil and calcining it; , Containing a mixture with granules containing calcium carbonate and / or magnesium carbonate,
A permeable reaction wall characterized in that 1 to 50 wt% of calcium carbonate and / or magnesium carbonate is present.
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