JP5578730B2 - Arsenic treatment method - Google Patents
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- JP5578730B2 JP5578730B2 JP2011032398A JP2011032398A JP5578730B2 JP 5578730 B2 JP5578730 B2 JP 5578730B2 JP 2011032398 A JP2011032398 A JP 2011032398A JP 2011032398 A JP2011032398 A JP 2011032398A JP 5578730 B2 JP5578730 B2 JP 5578730B2
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- iron
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- oxidizing bacteria
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- 229910052785 arsenic Inorganic materials 0.000 title claims description 81
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 title claims description 79
- 238000000034 method Methods 0.000 title claims description 46
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 140
- 229910052742 iron Inorganic materials 0.000 claims description 69
- 241000894006 Bacteria Species 0.000 claims description 49
- 238000007254 oxidation reaction Methods 0.000 claims description 38
- 230000003647 oxidation Effects 0.000 claims description 30
- BMWMWYBEJWFCJI-UHFFFAOYSA-K iron(3+);trioxido(oxo)-$l^{5}-arsane Chemical compound [Fe+3].[O-][As]([O-])([O-])=O BMWMWYBEJWFCJI-UHFFFAOYSA-K 0.000 claims description 15
- 239000002689 soil Substances 0.000 claims description 15
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 10
- 229910052569 sulfide mineral Inorganic materials 0.000 claims description 10
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 claims description 9
- 229910052683 pyrite Inorganic materials 0.000 claims description 9
- 239000011028 pyrite Substances 0.000 claims description 9
- 241000203069 Archaea Species 0.000 claims description 6
- 241000205101 Sulfolobus Species 0.000 claims description 5
- 230000003100 immobilizing effect Effects 0.000 claims description 4
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 4
- 229910052952 pyrrhotite Inorganic materials 0.000 claims description 4
- 241000726121 Acidianus Species 0.000 claims description 3
- 241001134777 Sulfobacillus Species 0.000 claims description 3
- 239000011790 ferrous sulphate Substances 0.000 claims description 3
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 3
- 241000521593 Acidimicrobium Species 0.000 claims 1
- 239000000243 solution Substances 0.000 claims 1
- 230000001590 oxidative effect Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 150000002506 iron compounds Chemical class 0.000 description 4
- -1 iron ions Chemical class 0.000 description 4
- RMBBSOLAGVEUSI-UHFFFAOYSA-H Calcium arsenate Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-][As]([O-])([O-])=O.[O-][As]([O-])([O-])=O RMBBSOLAGVEUSI-UHFFFAOYSA-H 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 229940103357 calcium arsenate Drugs 0.000 description 3
- 239000006228 supernatant Substances 0.000 description 3
- 241000132982 Acidianus brierleyi Species 0.000 description 2
- DJHGAFSJWGLOIV-UHFFFAOYSA-N Arsenic acid Chemical compound O[As](O)(O)=O DJHGAFSJWGLOIV-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 2
- 239000003463 adsorbent Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 241000726120 Acidianus infernus Species 0.000 description 1
- 241000521595 Acidimicrobium ferrooxidans Species 0.000 description 1
- DJHGAFSJWGLOIV-UHFFFAOYSA-K Arsenate3- Chemical compound [O-][As]([O-])([O-])=O DJHGAFSJWGLOIV-UHFFFAOYSA-K 0.000 description 1
- 241000193830 Bacillus <bacterium> Species 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 241000219470 Mirabilis Species 0.000 description 1
- 241001134779 Sulfobacillus thermosulfidooxidans Species 0.000 description 1
- 241000205098 Sulfolobus acidocaldarius Species 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- DGEZNRSVGBDHLK-UHFFFAOYSA-N [1,10]phenanthroline Chemical compound C1=CN=C2C3=NC=CC=C3C=CC2=C1 DGEZNRSVGBDHLK-UHFFFAOYSA-N 0.000 description 1
- CBIFDJDRCNEMQB-UHFFFAOYSA-N [Al].O[As](O)(O)=O Chemical compound [Al].O[As](O)(O)=O CBIFDJDRCNEMQB-UHFFFAOYSA-N 0.000 description 1
- 229940000489 arsenate Drugs 0.000 description 1
- 229940000488 arsenic acid Drugs 0.000 description 1
- 150000001495 arsenic compounds Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- NFMAZVUSKIJEIH-UHFFFAOYSA-N bis(sulfanylidene)iron Chemical compound S=[Fe]=S NFMAZVUSKIJEIH-UHFFFAOYSA-N 0.000 description 1
- 238000004113 cell culture Methods 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 229960002089 ferrous chloride Drugs 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 230000009036 growth inhibition Effects 0.000 description 1
- 229940093920 gynecological arsenic compound Drugs 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- 229910000339 iron disulfide Inorganic materials 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- HEQWEGCSZXMIJQ-UHFFFAOYSA-M potassium;oxoarsinite Chemical compound [K+].[O-][As]=O HEQWEGCSZXMIJQ-UHFFFAOYSA-M 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-O sulfonium Chemical compound [SH3+] RWSOTUBLDIXVET-UHFFFAOYSA-O 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- Micro-Organisms Or Cultivation Processes Thereof (AREA)
- Processing Of Solid Wastes (AREA)
- Removal Of Specific Substances (AREA)
- Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Description
本発明は、溶液又は土壌に含まれる砒素の処理方法に関し、詳細には、溶液又は土壌に含まれる砒素を、鉄酸化菌を利用して安定な形態で固定する砒素の処理方法に関する。 The present invention relates to a method for treating arsenic contained in a solution or soil, and more particularly, to a method for treating arsenic in which arsenic contained in a solution or soil is fixed in a stable form using iron-oxidizing bacteria.
溶液又は土壌に含まれる砒素を処理する手段として、砒酸塩を形成させて安定化する方法が広く知られている。溶液中の砒素を安定した形態で固定する方法としては、特許文献１に開示されているように砒酸鉄として沈殿析出させる方法や、特許文献２に開示されているような鉄の複合塩等の吸着剤に砒素を吸着させる方法がある。 As means for treating arsenic contained in a solution or soil, a method of stabilizing by forming arsenate is widely known. As a method of fixing arsenic in a solution in a stable form, a method of precipitation as iron arsenate as disclosed in Patent Document 1, a complex salt of iron as disclosed in Patent Document 2, etc. There is a method of adsorbing arsenic on the adsorbent.
また、土壌中の砒素を安定した形態で固定する方法としては、特許文献３に開示されているような砒酸鉄として固定化する方法がある。これらは、いずれの方法も鉄化合物として安定化している。その他、安定性が良く、溶出性の低い砒素の化合物としては、例えば、砒酸カルシウム、砒酸アルミニウム等がある。砒酸カルシウムとして安定化させる方法については、特許文献４，５に開示されている。 Moreover, as a method for fixing arsenic in soil in a stable form, there is a method for fixing it as iron arsenate as disclosed in Patent Document 3. Any of these methods is stabilized as an iron compound. Other examples of arsenic compounds with good stability and low elution are calcium arsenate and aluminum arsenate. Patent Documents 4 and 5 disclose methods for stabilizing calcium arsenate.
しかしながら、特許文献１，３に開示されている方法は、コストパフォーマンスが低く、経済的な処理方法とはいえない。また、特許文献２に開示されている方法は、吸着剤の合成という煩雑な作業を必要とし、やはり経済的ではない。さらに、特許文献４，５に開示されている方法は、熱処理が必要であるためエネルギー消費が多く、また、長期安定性や形成の容易さを考慮すると、砒酸カルシウムよりも砒酸鉄による安定化が好ましい。 However, the methods disclosed in Patent Documents 1 and 3 have low cost performance and cannot be said to be economical. Moreover, the method disclosed in Patent Document 2 requires a complicated operation of synthesizing the adsorbent, and is also not economical. Furthermore, the methods disclosed in Patent Documents 4 and 5 consume much energy because heat treatment is necessary, and in view of long-term stability and ease of formation, stabilization with iron arsenate is more effective than calcium arsenate. preferable.
そして、上記特許文献１〜５に開示されているいずれの方法も、五価砒素については容易に安定化できるものの、三価砒素の除去には薬剤の添加による酸化を必要とするか、或いは除去自体が困難であった。 Although any of the methods disclosed in Patent Documents 1 to 5 can be easily stabilized for pentavalent arsenic, the removal of trivalent arsenic requires oxidation by addition of a chemical agent or is removed. It was difficult.
本発明は、上記事情に鑑みてなされたものであって、その目的とするところは、溶液又は土壌に含まれる砒素を、効率的に且つ経済的に、再溶出し難い安定な形態で固定することができる、砒素の処理方法を提供することである。 The present invention has been made in view of the above circumstances, and an object thereof is to fix arsenic contained in a solution or soil efficiently and economically in a stable form that is difficult to re-elute. It is possible to provide a method for treating arsenic.
本発明者らは、上記課題を解決するために鋭意研究を重ねたところ、鉄酸化菌による鉄の酸化反応を利用して、三価砒素を五価砒素に酸化し、該五価砒素を安定な結晶性砒酸鉄として固定化することで、上記課題が解決できることを見出し、本発明を完成するに至った。 The inventors of the present invention have made extensive studies in order to solve the above-mentioned problems. As a result, the trivalent arsenic is oxidized to pentavalent arsenic by utilizing iron oxidation reaction by iron-oxidizing bacteria, and the pentavalent arsenic is stabilized. The present inventors have found that the above-mentioned problems can be solved by fixing as crystalline iron arsenate, and have completed the present invention.
具体的には、以下のようなものを提供する。 Specifically, the following are provided.
（１）溶液又は土壌に含まれる砒素の処理方法であって、鉄酸化菌により鉄を酸化させる鉄酸化工程と、上記鉄酸化工程で生成する三価鉄により、上記溶液又は土壌に含まれる三価砒素を五価砒素に酸化させる砒素酸化工程と、上記五価砒素を結晶性砒酸鉄として固定化する砒素固定化工程と、を有することを特徴とする砒素の処理方法。 (1) A method for treating arsenic contained in a solution or soil, comprising an iron oxidation step in which iron is oxidized by iron-oxidizing bacteria and trivalent iron produced in the iron oxidation step. An arsenic treatment method comprising: an arsenic oxidation step of oxidizing valent arsenic to pentavalent arsenic; and an arsenic immobilization step of immobilizing the pentavalent arsenic as crystalline iron arsenate.
（２）上記鉄酸化菌は、好熱性の古細菌である（１）に記載の砒素の処理方法。 (2) The arsenic treatment method according to (1), wherein the iron-oxidizing bacterium is a thermophilic archaea.
（３）上記鉄酸化工程では、ｐＨ０〜２．２の条件下で鉄酸化菌により鉄を酸化させる（１）又は（２）に記載の砒素の処理方法。 (3) The arsenic treatment method according to (1) or (2), wherein in the iron oxidation step, iron is oxidized by iron-oxidizing bacteria under a pH of 0 to 2.2.
（４）上記鉄酸化工程では、鉄酸化菌に対して菌数の保持が可能な量の二価鉄を供給する（１）〜（３）いずれかに記載の砒素の処理方法。 (4) The arsenic treatment method according to any one of (1) to (3), wherein in the iron oxidation step, an amount of divalent iron capable of maintaining the number of bacteria is supplied to the iron-oxidizing bacteria.
（５）上記二価鉄の供給源は、硫化鉄鉱物である（４）に記載の砒素の処理方法。 (5) The arsenic treatment method according to (4), wherein the source of divalent iron is iron sulfide mineral.
（６）上記硫化鉄鉱物は、黄鉄鉱及び／又は磁硫鉄鉱である（５）に記載の砒素の処理方法。 (6) The arsenic treatment method according to (5), wherein the iron sulfide mineral is pyrite and / or pyrrhotite.
本発明によれば、溶液又は土壌に含まれる砒素を、効率的に且つ経済的に、再溶出し難い安定な形態で固定することができる。 According to the present invention, arsenic contained in a solution or soil can be efficiently and economically fixed in a stable form that is difficult to re-elute.
以下、本発明の具体的な実施形態について詳細に説明するが、本発明は以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. Can do.
本発明は、溶液又は土壌に含まれる砒素の処理方法であり、鉄酸化菌により鉄を酸化させる鉄酸化工程と、上記鉄酸化工程で生成する三価鉄により、上記溶液又は土壌に含まれる三価砒素を五価砒素に酸化させる砒素酸化工程と、上記五価砒素を結晶性砒酸鉄として固定化する砒素固定化工程と、を有することを特徴とする。本発明の方法では、砒素に汚染された水又は土壌を無害化するために、溶液又は土壌に含まれる砒素を、再溶出し難い安定な結晶性の砒酸鉄（ＦｅＡｓＯ４）の形態で固定化する。このように、砒素を砒酸鉄の形態とすることは、長期安定性に優れるという観点から望ましいが、溶液又は土壌における砒素の存在形態が三価砒素の場合、五価砒素に酸化しなければ、安定な砒酸鉄を形成することはできない。本発明では、この三価砒素から五価砒素へ酸化するに際し、鉄酸化菌による鉄の酸化反応を利用することで、効率的且つ経済的な砒素の安定化を実現した点に意義がある。本発明によれば、鉄酸化菌の特性を利用することで、従来、三価砒素の酸化に必要であった高価な薬剤や、三価砒素の除去に必要であった煩雑な作業が不要となる。 The present invention is a method for treating arsenic contained in a solution or soil, and includes an iron oxidation step in which iron is oxidized by iron-oxidizing bacteria, and trivalent iron produced in the iron oxidation step. It has an arsenic oxidation process for oxidizing valent arsenic to pentavalent arsenic and an arsenic immobilization process for immobilizing the pentavalent arsenic as crystalline iron arsenate. In the method of the present invention, arsenic contained in a solution or soil is immobilized in the form of stable crystalline iron arsenate (FeAsO 4 ) that is difficult to re-elute in order to detoxify water or soil contaminated with arsenic. To do. Thus, arsenic in the form of iron arsenate is desirable from the viewpoint of excellent long-term stability, but when the arsenic presence form in solution or soil is trivalent arsenic, it must be oxidized to pentavalent arsenic, Stable iron arsenate cannot be formed. The present invention is significant in that efficient and economical stabilization of arsenic is realized by utilizing an iron oxidation reaction by iron-oxidizing bacteria when oxidizing from trivalent arsenic to pentavalent arsenic. According to the present invention, the use of the characteristics of iron-oxidizing bacteria eliminates the need for expensive chemicals conventionally required for oxidation of trivalent arsenic and the complicated work required for removal of trivalent arsenic. Become.
［鉄酸化工程］
鉄酸化工程は、鉄酸化菌により鉄を酸化させる工程である。鉄酸化菌は、二価鉄イオンを三価鉄イオンに酸化し、その際に発生するエネルギーを利用して増殖する。本発明では、この鉄酸化菌の特性を利用し、従来、その除去が困難であった砒素汚染水や砒素汚染土壌中の三価砒素を酸化し、安定化しやすい五価砒素とした。鉄酸化菌による鉄の酸化反応は、下記式（１）のように進行する。
４Ｆｅ２＋＋Ｏ２＋４Ｈ＋＝４Ｆｅ３＋＋２Ｈ２Ｏ ・・・（１）
[Iron oxidation process]
The iron oxidation step is a step of oxidizing iron by iron oxidizing bacteria. Iron-oxidizing bacteria oxidize divalent iron ions to trivalent iron ions and grow using the energy generated at that time. In the present invention, the characteristics of this iron-oxidizing bacterium are used to oxidize trivalent arsenic in arsenic-contaminated water and arsenic-contaminated soil, which has been difficult to remove in the past, to form pentavalent arsenic that is easy to stabilize. The iron oxidation reaction by iron-oxidizing bacteria proceeds as shown in the following formula (1).
4Fe 2+ + O 2 + 4H + = 4Fe 3+ + 2H 2 O (1)
鉄酸化菌は、鉄鉱山の採鉱場やそこで発生した廃水、鉄分を多く含む地下水や湖沼の深層水等、自然界に広く分布している。本発明で用いられる鉄酸化菌は、特に限定されるものではないが、好ましくは好熱性の古細菌である。好熱性の古細菌は、常温菌に比べて鉄酸化速度が格段に速いからである。好熱性の古細菌である鉄酸化菌としては、例えば、Ａｃｉｄｉａｎｕｓ ｂｒｉｅｒｌｅｙｉ、Ａｃｉｄｉａｎｕｓ ｉｎｆｅｒｎｕｓ等のＡｃｉｄｉａｎｕｓ（アシディアヌス）属、Ｓｕｌｆｏｂａｃｉｌｌｕｓ ｔｈｅｒｍｏｓｕｌｆｉｄｏｏｘｉｄａｎｓ、Ｓｕｌｆｏｂａｃｉｌｌｕｓ ａｃｉｄｏｐｈｉｌｌｕｓ等のＳｕｌｆｏｂａｃｉｌｌｕｓ（スルフォバチルス）属、Ａｃｉｄｉｍｉｃｒｏｂｉｕｍ ｆｅｒｒｏｏｘｉｄａｎｓ等のＡｃｉｄｉｍｉｃｒｏｂｉｕｍ（アシジミクロビウム）属、Ｓｕｌｆｏｌｏｂｕｓ ａｃｉｄｏｃａｌｄａｒｉｕｓ、Ｓｕｌｆｏｌｏｂｕｓ ｓｏｌｆａｔａｒｉｃｕｓ、Ｓｕｌｆｏｌｏｂｕｓ ｍｉｒａｂｉｌｉｓ等のＳｕｌｆｏｌｏｂｕｓ（スルフォロブス）属、Ｄｅｓｕｌｆｏｌｏｂｕｓ ａｍｂｉｖａｌｅｎｓ等のＤｅｓｕｌｆｏｌｏｂｕｓ（デスルフォロブス）属等が挙げられる。これらの鉄酸化菌は、公的な菌保存機関から入手可能である。 Iron-oxidizing bacteria are widely distributed in nature, such as mines in iron mines, wastewater generated there, groundwater containing a lot of iron, and deep water in lakes. The iron-oxidizing bacterium used in the present invention is not particularly limited, but is preferably a thermophilic archaea. This is because thermophilic archaea have a much faster iron oxidation rate than room temperature bacteria. The iron-oxidizing bacteria are archaebacteria thermophilic, for example, Acidianus brierleyi, Acidianus infernus etc. Acidianus (Ashidianusu) genus, Sulfobacillus thermosulfidooxidans, Sulfobacillus (sulfonium Bacillus) such Sulfobacillus acidophillus genus, such Acidimicrobium ferrooxidans Acidimicrobium (Assisi Microbium), Sulfolobus acidocaldarius, Sulfolobus solfalicus, Sulfolobus mirabilis, etc., Sulfolobus, Sulfolobus ambus Desulfolobus (Desuruforobusu) species such as valens and the like. These iron-oxidizing bacteria can be obtained from public bacteria storage organizations.
鉄酸化菌による鉄の酸化反応を効率良く進行させるためには、使用する鉄酸化菌が良好に生育する至適生育ｐＨに環境設定することが好ましい。鉄酸化菌の多くは好酸性であり、強酸性領域で良好に生育する。また、鉄酸化菌は、細胞内外のｐＨ勾配を利用してエネルギーを獲得しているため、基質である二価鉄イオンが溶存しやすい強酸性領域に環境設定することは、鉄酸化菌を良好に生育させ、鉄の酸化反応を効率良く進行させることができるので好ましい。具体的には、ｐＨ０〜２．２の条件下で鉄酸化菌により鉄を酸化させることが好ましい。なお、温度環境は、使用する鉄酸化菌が良好に生育する至適生育温度に設定することが好ましい。 In order to efficiently advance the iron oxidation reaction by the iron-oxidizing bacteria, it is preferable to set the environment to an optimum growth pH at which the iron-oxidizing bacteria to be used grow well. Many iron-oxidizing bacteria are acidophilic and grow well in strongly acidic regions. In addition, since iron-oxidizing bacteria acquire energy using a pH gradient inside and outside the cell, setting the environment in a strongly acidic region where divalent iron ions as substrates are easily dissolved is good for iron-oxidizing bacteria. It is preferable that the iron oxidation reaction can proceed efficiently. Specifically, it is preferable to oxidize iron with iron-oxidizing bacteria under the condition of pH 0 to 2.2. The temperature environment is preferably set to an optimum growth temperature at which the iron-oxidizing bacteria used grows well.
鉄酸化工程に用いられる鉄源は、０価鉄であっても二価鉄であってもよいが、鉄酸化菌が直接利用できる二価鉄であることが好ましい。鉄源としては、例えば、硫酸第一鉄（ＦｅＳＯ４）、二硫化鉄（ＦｅＳ２）等の二価鉄化合物、黄鉄鉱、磁硫鉄鉱等の二価鉄を含む硫化鉄鉱物等が挙げられ、これらを１種又は２種以上の組み合わせて用いることができる。ただし、二価鉄化合物の１つである塩化第一鉄（ＦｅＣｌ２）については、鉄酸化菌が塩素イオンにより生育阻害を受けやすいため、その使用は好ましいとはいえない。なお、好ましくは少なくとも二価鉄を含む硫化鉄鉱物を鉄源として用い、より好ましくは少なくとも黄鉄鉱及び／又は磁硫鉄鉱を用いる。二価鉄を含む硫化鉄鉱物の存在は、単に二価鉄化合物のみを存在させる以上に、次の砒素固定化工程における三価砒素の五価砒素への酸化を促進させるからである。これは、鉄酸化菌は、その種類によっては鉄だけでなく、硫黄も基質として利用することができ、また、硫化鉄鉱物には砒素を吸着する作用があり、硫化鉄鉱物の表面では、特に活発に酸化反応が進行するからではないかと推測される。さらに、硫化鉄鉱物は、天然に存在し、安価に入手可能である点においても、その使用が好ましい。なお、黄鉄鉱は、水、特に酸性領域の水に対して非常に安定であり、ほとんど溶解しないが、鉄酸化菌による鉄の酸化反応が起こり、三価鉄が生成すると、この三価鉄が黄鉄鉱の酸化剤として作用し、黄鉄鉱の溶解が促進される。 The iron source used in the iron oxidation step may be zero-valent iron or divalent iron, but is preferably divalent iron that can be directly used by iron-oxidizing bacteria. Examples of the iron source include divalent iron compounds such as ferrous sulfate (FeSO 4 ) and iron disulfide (FeS 2 ), and iron sulfide minerals containing divalent iron such as pyrite and pyrrhotite. Can be used alone or in combination of two or more. However, it is not preferable to use ferrous chloride (FeCl 2 ), which is one of divalent iron compounds, because iron-oxidizing bacteria are susceptible to growth inhibition by chloride ions. Preferably, an iron sulfide mineral containing at least divalent iron is used as the iron source, and more preferably at least pyrite and / or pyrrhotite is used. This is because the presence of iron sulfide minerals containing divalent iron promotes the oxidation of trivalent arsenic to pentavalent arsenic in the next arsenic immobilization process, rather than merely the presence of a divalent iron compound. This is because, depending on the type of iron-oxidizing bacteria, not only iron but also sulfur can be used as a substrate, and the iron sulfide mineral has an action of adsorbing arsenic. It is presumed that the oxidation reaction proceeds actively. Furthermore, the use of iron sulfide mineral is also preferable in that it exists in nature and is available at a low cost. Pyrite is very stable in water, especially in the acidic region, and hardly dissolves. However, when iron oxidation occurs by iron-oxidizing bacteria and trivalent iron is produced, this trivalent iron is converted into pyrite. It acts as an oxidant for the pyrite and promotes the dissolution of pyrite.
鉄酸化工程では、鉄酸化菌に対して菌数の保持が可能な量の二価鉄を供給することが好ましい。二価鉄が全て消費されると鉄酸化菌の増殖は停止し、その後死滅する。また、死滅に至らない場合であっても、一旦、鉄酸化菌の増殖が停止すると、鉄酸化能力の回復に時間を要し、効率性が低下するからである。二価鉄は、鉄酸化工程中、連続的に供給してもよいし、あらかじめ飽和量を供給しておいてもよいが、全鉄イオンの濃度が高くなりすぎると、鉄酸化菌の生育が阻害されるため、菌数や酸化反応の状況を確認しながら、必要に応じて添加することが好ましい。 In the iron oxidation step, it is preferable to supply an amount of divalent iron capable of maintaining the number of bacteria with respect to iron-oxidizing bacteria. When all of the divalent iron is consumed, the iron-oxidizing bacteria stop growing and then die. Moreover, even if it does not lead to death, once the growth of iron-oxidizing bacteria is stopped, it takes time to recover the iron-oxidizing ability, and the efficiency decreases. Bivalent iron may be supplied continuously during the iron oxidation process, or a saturated amount may be supplied in advance, but if the concentration of total iron ions becomes too high, the growth of iron-oxidizing bacteria Since it is inhibited, it is preferable to add as needed while confirming the number of bacteria and the state of the oxidation reaction.
［砒素酸化工程］
砒素酸化工程は、上記鉄酸化工程で生成する三価鉄により、砒素汚染水又は砒素汚染土壌に含まれる三価砒素を五価砒素に酸化させる工程である。砒素酸化工程では、例えば、下記式（２）のように、上記鉄酸化工程で生成した上記式（１）の三価鉄により、三価砒素である亜砒酸（Ｈ３ＡｓＯ３）を五価砒素である砒酸（Ｈ３ＡｓＯ４）に酸化させる。
２Ｆｅ３＋＋Ｈ３ＡｓＯ３＋Ｈ２０＝２Ｆｅ２＋＋Ｈ３ＡｓＯ４＋２Ｈ＋ ・・・（２）
[Arsenic oxidation process]
The arsenic oxidation process is a process in which trivalent arsenic contained in arsenic-contaminated water or arsenic-contaminated soil is oxidized to pentavalent arsenic by trivalent iron generated in the iron oxidation process. In the arsenic oxidation step, for example, trivalent arsenic acid (H 3 AsO 3 ) is converted to pentavalent arsenic by the trivalent iron of the formula (1) generated in the iron oxidation step as shown in the following formula (2). To arsenic acid (H 3 AsO 4 ).
2Fe 3+ + H 3 AsO 3 + H 2 0 = 2Fe 2+ + H 3 AsO 4 + 2H + (2)
［砒素固定化工程］
砒素固定化工程は、上記砒素酸化工程で生成する五価砒素を再溶出し難い安定な結晶性の砒酸鉄の形態で固定化する工程である。砒素固定化工程では、例えば、下記式（３）のように、上記砒素酸化工程で生成した五価砒素が、結晶性の砒酸鉄の形態で固定化される。
Ｆｅ３＋＋Ｈ３ＡｓＯ４＋２Ｈ２Ｏ＝ＦｅＡｓＯ４・２Ｈ２０＋３Ｈ＋ ・・・（３）
[Arsenic immobilization process]
The arsenic immobilization step is a step of immobilizing pentavalent arsenic produced in the arsenic oxidation step in the form of stable crystalline iron arsenate that is difficult to elute again. In the arsenic immobilization step, for example, pentavalent arsenic generated in the arsenic oxidation step is immobilized in the form of crystalline iron arsenate as shown in the following formula (3).
Fe 3+ + H 3 AsO 4 + 2H 2 O = FeAsO 4 .2H 2 0 + 3H + (3)
砒酸鉄は、非晶状態では安定せず、結晶状態となることで安定し、再溶出し難くなる。なお、砒素を安定な結晶性の砒酸鉄の形態で固定化するためには、例えば、常圧下で鉄酸化菌により二価鉄を三価鉄に酸化させながら砒素と反応させるとよい。 Iron arsenate is not stable in the amorphous state, but is stable when it is in the crystalline state, and it is difficult to re-elute. In order to immobilize arsenic in the form of stable crystalline iron arsenate, for example, it may be reacted with arsenic while oxidizing divalent iron to trivalent iron by an iron-oxidizing bacterium under normal pressure.
以下、実施例により、本発明をさらに詳細に説明するが、本発明はこれらの記載に何ら制限を受けるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.
［実施例１］
表１に示す組成の硫酸第一鉄を除いた９Ｋ培地２００ｍＬに、３５．８１ｍｍｏｌ／Ｌの硫酸鉄（ＦｅＳＯ４）と、０．６５９ｍｍｏｌ／Ｌの亜砒酸カリウム（ＫＡｓＯ２）とを加え、希硫酸でｐＨ１．５に調整した後、黄鉄鉱（純度：９８％）１．０質量％を加えた。これに、好熱性鉄酸化菌であるＡｃｉｄｉａｎｕｓ ｂｒｉｅｒｌｅｙｉ（保存機関：Ｄｅｕｔｓｃｈｅ Ｓａｍｍｌｕｎｇ ｖｏｎ Ｍｉｋｒｏｏｒｇａｎｉｓｍｅｎ ｕｎｄ Ｚｅｌｌｋｕｌｔｕｒｅｎ ＧｍｂＨ Ｇｅｒｍａｎ Ｃｏｌｌｅｃｔｉｏｎ ｏｆ Ｍｉｃｒｏｏｒｇａｎｉｓｍｓ ａｎｄ Ｃｅｌｌ Ｃｕｌｔｕｒｅｓ，保存番号：１６５１）を１．０×１０８ｃｅｌｌ／ｍＬとなるように接種し、７０℃の恒温槽にて回転数１００ｒｐｍの振盪条件で撹拌した。そして、１５日後に、生成した沈殿物と、上澄み液とを固液分離し、上澄み液中のＦｅ（ＩＩ）濃度をオルトフェナントロリン法により定量し、Ａｓ濃度をＩＣＰ−ＡＥＳ法により定量した。また、沈殿物については、構成元素の価数をＸ線光電子分光法（ＸＰＳ法）により分析した。さらに、好熱性鉄酸化菌の菌数を、顕微鏡による直接計数法により測定した。菌数の経時変化を図１に示す。
[Example 1]
35.81 mmol / L iron sulfate (FeSO 4 ) and 0.659 mmol / L potassium arsenite (KAsO 2 ) were added to 200 mL of 9K medium excluding ferrous sulfate having the composition shown in Table 1, and diluted sulfuric acid. After adjusting the pH to 1.5, 1.0% by mass of pyrite (purity: 98%) was added. This, Acidianus brierleyi a thermophilic iron-oxidizing bacteria (storage engine: Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH German Collection of Microorganisms and Cell Cultures, stored ID NO: 1651) so as to have a 1.0 × 10 8 cell / mL The seed was inoculated and stirred in a constant temperature bath at 70 ° C. under shaking conditions at a rotation speed of 100 rpm. After 15 days, the produced precipitate and the supernatant were separated into solid and liquid, the Fe (II) concentration in the supernatant was quantified by the orthophenanthroline method, and the As concentration was quantified by the ICP-AES method. Moreover, about the deposit, the valence of the constituent element was analyzed by X-ray photoelectron spectroscopy (XPS method). Furthermore, the number of thermophilic iron-oxidizing bacteria was measured by a direct counting method using a microscope. The time course of the number of bacteria is shown in FIG.
その結果、上澄み液中の全Ｆｅ濃度は３７．２８ｍｍｏｌ／Ｌ（Ｆｅ（ＩＩ）濃度：９．２０ｍｍｏｌ／Ｌ）であり、Ａｓ濃度は０．３６６ｍｍｏｌ／Ｌであった。また、沈殿物の砒素の価数は、五価であった。さらに、試験期間中は、好熱性鉄酸化菌の菌数が保持されていた（図１）。これらの結果から、好熱性鉄酸化菌の鉄酸化反応により二価鉄が三価鉄に酸化され、該三価鉄により液中の三価砒素が五価砒素に酸化されることで、該五価砒素が結晶性の砒酸鉄となり、沈殿したものと考えられる。 As a result, the total Fe concentration in the supernatant was 37.28 mmol / L (Fe (II) concentration: 9.20 mmol / L), and the As concentration was 0.366 mmol / L. The arsenic valence of the precipitate was pentavalent. Furthermore, during the test period, the number of thermophilic iron-oxidizing bacteria was retained (FIG. 1). From these results, divalent iron is oxidized to trivalent iron by the iron oxidation reaction of the thermophilic iron-oxidizing bacteria, and trivalent arsenic in the liquid is oxidized to pentavalent arsenic by the trivalent iron. It is considered that the valent arsenic became crystalline iron arsenate and precipitated.
［比較例１］
好熱性鉄酸化菌を接種しなかった以外は、全て同様の方法にて試験を行った。その結果、１５日後のＡｓ濃度及び全Ｆｅ濃度は、初期値と比べて変化が見られなかった。
[Comparative Example 1]
All tests were carried out in the same manner except that no thermophilic iron-oxidizing bacteria were inoculated. As a result, the As concentration and the total Fe concentration after 15 days did not change compared to the initial values.
Claims (6)
Ａｃｉｄｉａｎｕｓ属、Ｓｕｌｆｏｂａｃｉｌｌｕｓ属、Ａｃｉｄｉｍｉｃｒｏｂｉｕｍ属、Ｓｕｌｆｏｌｏｂｕｓ属及びＤｅｓｕｌｆｏｌｏｂｕｓ属から選択される１種以上の好熱性の古細菌を含む鉄酸化菌により、硫化鉄鉱物を含む二価鉄を三価鉄に酸化させる鉄酸化工程と、
前記鉄酸化工程で生成する三価鉄により、前記溶液又は土壌に含まれる三価砒素を五価砒素に酸化させる砒素酸化工程と、
前記五価砒素を結晶性砒酸鉄として固定化する砒素固定化工程と、を有することを特徴とする砒素の処理方法。 A method for treating arsenic contained in a solution or soil,
Iron that oxidizes divalent iron containing iron sulfide minerals to trivalent iron by one or more thermophilic archaebacteria selected from the genera Acidianus, Sulfobacillus, Acidimicrobium, Sulfolobus, and Desulfobus An oxidation process;
An arsenic oxidation step in which trivalent arsenic contained in the solution or soil is oxidized to pentavalent arsenic by trivalent iron produced in the iron oxidation step;
And an arsenic immobilization step of immobilizing the pentavalent arsenic as crystalline iron arsenate.
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