JP2011178602A - Method for generating crystalline iron arsenate from arsenic-containing solution - Google Patents
Method for generating crystalline iron arsenate from arsenic-containing solution Download PDFInfo
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- 229910052785 arsenic Inorganic materials 0.000 title claims abstract description 124
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 title claims abstract description 124
- BMWMWYBEJWFCJI-UHFFFAOYSA-K iron(3+);trioxido(oxo)-$l^{5}-arsane Chemical compound [Fe+3].[O-][As]([O-])([O-])=O BMWMWYBEJWFCJI-UHFFFAOYSA-K 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 279
- 229910052742 iron Inorganic materials 0.000 claims abstract description 139
- 239000007800 oxidant agent Substances 0.000 claims abstract description 28
- 239000000243 solution Substances 0.000 claims description 105
- 238000006243 chemical reaction Methods 0.000 claims description 81
- 238000004519 manufacturing process Methods 0.000 claims description 35
- 239000007789 gas Substances 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 11
- 239000001301 oxygen Substances 0.000 claims description 11
- 229910052760 oxygen Inorganic materials 0.000 claims description 11
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 7
- 229910001882 dioxygen Inorganic materials 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 5
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 3
- 239000003570 air Substances 0.000 claims description 3
- 238000010790 dilution Methods 0.000 claims description 3
- 239000012895 dilution Substances 0.000 claims description 3
- PPNXXZIBFHTHDM-UHFFFAOYSA-N aluminium phosphide Chemical compound P#[Al] PPNXXZIBFHTHDM-UHFFFAOYSA-N 0.000 claims description 2
- 239000002245 particle Substances 0.000 abstract description 35
- UYZMAFWCKGTUMA-UHFFFAOYSA-K iron(3+);trioxido(oxo)-$l^{5}-arsane;dihydrate Chemical compound O.O.[Fe+3].[O-][As]([O-])([O-])=O UYZMAFWCKGTUMA-UHFFFAOYSA-K 0.000 description 47
- 239000011259 mixed solution Substances 0.000 description 26
- 239000000047 product Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 239000013078 crystal Substances 0.000 description 11
- -1 iron ion Chemical class 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 238000005755 formation reaction Methods 0.000 description 10
- 239000007788 liquid Substances 0.000 description 9
- 238000005259 measurement Methods 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 239000003929 acidic solution Substances 0.000 description 7
- 239000003002 pH adjusting agent Substances 0.000 description 7
- 230000002378 acidificating effect Effects 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 238000007664 blowing Methods 0.000 description 6
- 239000003153 chemical reaction reagent Substances 0.000 description 6
- 239000000706 filtrate Substances 0.000 description 6
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 6
- 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 description 5
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 239000011790 ferrous sulphate Substances 0.000 description 4
- 235000003891 ferrous sulphate Nutrition 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- DJHGAFSJWGLOIV-UHFFFAOYSA-N Arsenic acid Chemical compound O[As](O)(O)=O DJHGAFSJWGLOIV-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229940000488 arsenic acid Drugs 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 229940079593 drug Drugs 0.000 description 3
- 239000003814 drug Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 150000002505 iron Chemical class 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 1
- DJHGAFSJWGLOIV-UHFFFAOYSA-K Arsenate3- Chemical compound [O-][As]([O-])([O-])=O DJHGAFSJWGLOIV-UHFFFAOYSA-K 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229940000489 arsenate Drugs 0.000 description 1
- 150000001495 arsenic compounds Chemical class 0.000 description 1
- 238000003556 assay Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 229960002089 ferrous chloride Drugs 0.000 description 1
- 150000004688 heptahydrates Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- 229910000358 iron sulfate Inorganic materials 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 1
- VXWSFRMTBJZULV-UHFFFAOYSA-H iron(3+) sulfate hydrate Chemical compound O.[Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O VXWSFRMTBJZULV-UHFFFAOYSA-H 0.000 description 1
- 238000002386 leaching Methods 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
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 150000003388 sodium compounds Chemical class 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G28/00—Compounds of arsenic
- C01G28/02—Arsenates; Arsenites
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Iron (AREA)
Abstract
Description
溶液中に存在するヒ素（本発明において「Ａｓ」の意味である。）を、安定なヒ素化合物として当該溶液から分離回収する技術であり、特には、溶液中に存在するヒ素を、安定なヒ素化合物である結晶性ヒ酸鉄（例えば、スコロダイト結晶）として当該溶液から分離回収する方法に関する。 It is a technique for separating and recovering arsenic present in a solution (meaning “As” in the present invention) from the solution as a stable arsenic compound, and in particular, arsenic present in a solution is stable arsenic. The present invention relates to a method for separating and recovering from a solution as crystalline iron arsenate (for example, scorodite crystal) which is a compound.
３価鉄（本発明において「Ｆｅ３＋」の意味である。）と、５価ヒ素（本発明において「Ａｓ５＋」の意味である。）とを、反応させて結晶性ヒ酸鉄を生成させる場合、従来の技術では反応速度を向上させる為、溶液のｐＨ値を、１を超えた条件下において行っていた。その結果、得られるヒ酸鉄は非常に微細なものとなり、さらに、非晶質のヒ酸鉄も含み易くなることが、ハンドリング上の課題である。 Trivalent iron (meaning “Fe 3+ ” in the present invention) and pentavalent arsenic (meaning “As 5+ ” in the present invention) are reacted to produce crystalline iron arsenate. In this case, in the conventional technique, the pH value of the solution was set under a condition exceeding 1 in order to improve the reaction rate. As a result, the obtained iron arsenate becomes very fine, and further, it is easy to contain amorphous iron arsenate.
ここで、溶液中に存在するヒ素をスコロダイトとして当該溶液から分離回収する方法に関して、特許文献１、２が提案されている。
特許文献１の提案は、５価ヒ素と３価鉄とを含有する酸性水溶液からヒ酸鉄を製造する方法であって、当該酸性水溶液中に含まれる５価ヒ素に対する３価鉄のモル比を０．９以上、１．１以下に調節した後に、スコロダイトの生成を行う方法である。
特許文献２の提案は、５価ヒ素と３価鉄とを含有する酸性水溶液からスコロダイトを製造する方法であって、当該酸性水溶液中のナトリウム濃度が、０ｇ／Ｌを超え、４ｇ／Ｌ以下となるように、塩基性ナトリウム化合物を当該酸性水溶液に添加し、スコロダイトの生成を行う方法である。
Here, Patent Documents 1 and 2 have been proposed regarding a method for separating and recovering arsenic present in a solution from the solution as scorodite.
The proposal of Patent Document 1 is a method for producing iron arsenate from an acidic aqueous solution containing pentavalent arsenic and trivalent iron, wherein the molar ratio of trivalent iron to pentavalent arsenic contained in the acidic aqueous solution is determined. This is a method of generating scorodite after adjusting to 0.9 or more and 1.1 or less.
The proposal of Patent Document 2 is a method for producing scorodite from an acidic aqueous solution containing pentavalent arsenic and trivalent iron, wherein the sodium concentration in the acidic aqueous solution exceeds 0 g / L and is 4 g / L or less. Thus, a basic sodium compound is added to the acidic aqueous solution to generate scorodite.
本発明者らは特許文献１、２に記載された結晶性ヒ酸鉄（スコロダイト）の生成方法を検討した。
特許文献１に記載の提案は、５価ヒ素と３価鉄とを含有する酸性水溶液へ、多量の種結晶（実施例では、５０ｇ／Ｌ）を添加し、高温での熱処理（実施例では、９５℃、２４時間）を行うことでスコロダイトの生成を行うものである。つまり、スコロダイト生成の際は、常に種結晶の添加を必要とするものである。
The present inventors examined the production method of crystalline iron arsenate (scorodite) described in Patent Documents 1 and 2.
In the proposal described in Patent Document 1, a large amount of seed crystals (50 g / L in the example) are added to an acidic aqueous solution containing pentavalent arsenic and trivalent iron, and heat treatment at a high temperature (in the example, (95 ° C., 24 hours) to generate scorodite. In other words, it is always necessary to add seed crystals when producing scorodite.
特許文献２に記載の提案は、スコロダイトの生成時間に２４時間という非常に長時間を要するものであった。この点は、特許文献１に記載の提案も、スコロダイトの生成時間に２４時間という非常に長時間を要するものであった。
さらに、結晶粒の大きなヒ酸鉄の生成については、特許文献１、２を初めとする従来技術に係るいずれの方法にも記載がない。
The proposal described in Patent Document 2 requires a very long time of 24 hours for the generation time of scorodite. In this respect, the proposal described in Patent Document 1 also requires a very long time of 24 hours for the generation time of scorodite.
Furthermore, the production of iron arsenate having large crystal grains is not described in any of the conventional methods including Patent Documents 1 and 2.
本発明は、上述の状況もとでなされたものであり、その解決しようとする課題は、ヒ素を含む溶液から、大きな粒子径を有する結晶性ヒ酸鉄粒子を容易且つ短時間で生成可能とする、結晶性ヒ酸鉄を得る方法を提供することである。 The present invention has been made under the above circumstances, and the problem to be solved is that crystalline iron arsenate particles having a large particle diameter can be easily and quickly produced from a solution containing arsenic. And providing a method for obtaining crystalline iron arsenate.
上述の課題を解決する為、本発明者らは鋭意研究を行ない、以下の知見を得た。
ヒ素と３価鉄とを含有する酸性溶液から結晶性ヒ酸鉄を生成する場合には、当該酸性溶液のｐＨ値を１よりも高く、好ましくは１．５前後とすることで、その生成反応速度が向上し、ヒ素の処理効率は上がる。しかし、当該生成するヒ酸鉄粒子は非常に微細なものになり易い。
一方、当該酸性溶液のｐＨ値が１以下の場合、種結晶が存在しないと、結晶性ヒ酸鉄は殆ど生成しない。さらに、当該ｐＨ値が１以下の酸性溶液へ酸化剤として、例えば、酸素や空気を吹き込んでも結晶性ヒ酸鉄は殆ど生成しない。
In order to solve the above-mentioned problems, the present inventors have conducted intensive research and obtained the following knowledge.
When producing crystalline iron arsenate from an acidic solution containing arsenic and trivalent iron, the pH of the acidic solution is higher than 1, preferably about 1.5, so that the production reaction Speed increases and arsenic processing efficiency increases. However, the iron arsenate particles produced tend to be very fine.
On the other hand, when the pH value of the acidic solution is 1 or less, crystalline iron arsenate is hardly produced unless seed crystals are present. Furthermore, even when oxygen or air is blown into the acidic solution having a pH value of 1 or less as an oxidizing agent, for example, crystalline iron arsenate is hardly generated.
本発明者らは、上述したようにｐＨ値１を境界として、いずれの領域においてもヒ素を含む溶液から、大きな粒子径を有する結晶性ヒ酸鉄粒子を容易且つ短時間で生成することが困難な状況を解決すべく、研究を行った。
そして、当該ヒ素を含む酸性溶液において、３価鉄と２価鉄（本発明において「Ｆｅ２＋」の意味である。）とを存在させ、ｐＨ値を１．０以下とした後、さらに酸化剤を添加することで、当該溶液から、大きな粒子径を有する結晶性ヒ酸鉄粒子を容易且つ短時間で生成出来るという、画期的な知見を得て本発明を完成したものである。
As described above, the present inventors have difficulty in easily producing crystalline iron arsenate particles having a large particle diameter in a short time from a solution containing arsenic in any region with a pH value of 1 as a boundary. Research was conducted to solve this situation.
Then, in the acidic solution containing arsenic, trivalent iron and divalent iron (meaning “Fe 2+ ” in the present invention) are present and the pH value is adjusted to 1.0 or less, and then an oxidizing agent. The present invention has been completed by obtaining the epoch-making knowledge that crystalline iron arsenate particles having a large particle diameter can be easily and quickly produced from the solution by adding.
すなわち、本発明に係る第１の発明は、
５価ヒ素と３価鉄とを含有する溶液へ２価鉄を添加し、前記溶液のｐＨ値を１．０以下とし、酸化剤を添加して、結晶性ヒ酸鉄を生成する方法であって、
前記ヒ素を含有する溶液中における、５価ヒ素のモル数をＡモル、３価鉄のモル数をＢモル、２価鉄のモル数をＣモルとするとき、Ｂ／Ａ＜１．０およびＣ＞０およびＢ＞０とする、ことを特徴とするヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法である。
That is, the first invention according to the present invention is:
In this method, divalent iron is added to a solution containing pentavalent arsenic and trivalent iron, the pH value of the solution is adjusted to 1.0 or less, and an oxidizing agent is added to produce crystalline iron arsenate. And
In the arsenic-containing solution, when the mole number of pentavalent arsenic is A mole, the mole number of trivalent iron is B mole, and the mole number of divalent iron is C mole, B / A <1.0 and A method for producing crystalline iron arsenate from a solution containing arsenic, characterized in that C> 0 and B> 0.
第２の発明は、
さらに、（Ｂ＋Ｃ）≧Ａである、ことを特徴とする第１の発明に記載のヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法である。
The second invention is
Furthermore, (B + C) ≧ A is the method for producing crystalline iron arsenate from a solution containing arsenic according to the first aspect of the invention.
第３の発明は、
上記酸化剤が、酸素ガス、空気、酸素を含むガス、空気希釈ガス、過酸化水素水から選択されるいずれか１種以上である、ことを特徴とする第１または第２の発明に記載のヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法である。
The third invention is
The oxidizing agent is at least one selected from oxygen gas, air, oxygen-containing gas, air dilution gas, and hydrogen peroxide solution, according to the first or second invention, A method for producing crystalline iron arsenate from a solution containing arsenic.
第４の発明は、
前記結晶性ヒ酸鉄の生成反応において、溶液中のヒ素濃度が、反応開始時点におけるヒ素濃度の３０％以下となる時期以降に、前記溶液のｐＨ値を、１を超え、２以下とする、ことを特徴とする第１から第３のいずれかの発明に記載のヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法である。
The fourth invention is:
In the production reaction of crystalline iron arsenate, the pH value of the solution is more than 1 and 2 or less after the time when the arsenic concentration in the solution becomes 30% or less of the arsenic concentration at the start of the reaction. A method for producing crystalline iron arsenate from a solution containing arsenic according to any one of the first to third inventions.
第５の発明は、
ヒ素を含有する溶液から結晶性ヒ酸鉄を生成させた後の反応後液を、２価鉄源として再度使用する、ことを特徴とする第１から第４のいずれかの発明に記載のヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法である。
The fifth invention is:
The arsenic according to any one of the first to fourth inventions, wherein the post-reaction solution after producing crystalline iron arsenate from a solution containing arsenic is reused as a divalent iron source Is a method for producing crystalline iron arsenate from a solution containing
本発明に係るヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法によれば、結晶粒径の大きい結晶性ヒ酸鉄粒子を短時間で生成させることが可能となった。 According to the method for producing crystalline iron arsenate from a solution containing arsenic according to the present invention, crystalline iron arsenate particles having a large crystal grain size can be produced in a short time.
本発明は、ヒ素を含有する溶液に３価鉄と２価鉄とを共に存在させ、当該溶液のｐＨ値が１以下の下で、当該３価鉄を、２価鉄に優先してヒ素と反応させ、結晶性ヒ酸鉄を生成させるものである。尚、結晶性ヒ酸鉄には、スコロダイト（ＦｅＡｓＯ４・２Ｈ２Ｏ）を始めとして、ｋａｎｋｉｔ（ＦｅＡｓＯ４・１．５Ｈ２Ｏ），ｚｙｋａｉｔｅ（Ｆｅ４（ＡｓＯ４）３（ＳＯ４）（ＯＨ）・１５Ｈ２Ｏ）、ｂｕｋｏｖｓｋｙｉｔｅ（Ｆｅ４（ＡｓＯ４）３（ＳＯ４）（ＯＨ）・７Ｈ２Ｏ）、ｓａｒｍｉｅｎｔｅ（Ｆｅ４（ＡｓＯ４）３（ＳＯ４）（ＯＨ）・７Ｈ２Ｏ）等がある。 In the present invention, both trivalent iron and divalent iron are present in a solution containing arsenic, and the trivalent iron is prioritized over divalent iron under a pH value of 1 or less. It reacts to produce crystalline iron arsenate. In addition, crystalline iron arsenate includes scorodite (FeAsO 4 .2H 2 O), kankit (FeAsO 4 .1.5H 2 O), zykaite (Fe 4 (AsO 4 ) 3 (SO 4 ) (OH 4 ) ) · 15H 2 O), bukovskyite (Fe 4 (AsO 4 ) 3 (SO 4 ) (OH) · 7H 2 O), saliente (Fe 4 (AsO 4 ) 3 (SO 4 ) (OH) · 7H 2 O) Etc.
具体的には、本発明は、ヒ素Ａモルと、３価鉄Ｂモルと、２価鉄Ｃモルとを含むｐＨ値が１以下の溶液において、ヒ素に対する３価鉄のモル比であるＢ／Ａ＜１．０（即ち、Ａ＞Ｂ）の状態として酸化剤を加え、結晶性ヒ酸鉄粒子を生成させるものである。この結晶性ヒ酸鉄生成反応において、鉄は３価鉄Ｂモルと２価鉄Ｃモルとの混在であって、Ａ＞Ｂであり、且つ、Ａ≦（Ｂ＋Ｃ）である。ヒ素量よりも鉄量の方が上回るためヒ素の殆どが反応されつくし、結果として反応後液中におけるヒ素の残存が少なくなる。この結果、後工程である水処理におけるヒ素負荷が軽減される。尤も、３価鉄と２価鉄の殆どを結晶性ヒ酸鉄としたい場合にはＡ＞（Ｂ＋Ｃ）であっても良い。このとき、ヒ素は５価ヒ素であることが好ましい。ヒ酸鉄は、３価鉄と５価ヒ素との化合物である為である。
ここで、３価鉄Ｂモルと２価鉄Ｃモルとのモル比は、結晶性ヒ酸鉄の生成目標量、状況に応じて設定すればよいが、モル比（Ｂ／Ｃの値）を０．１〜２の範囲に設定することが、結晶性ヒ酸鉄の生産性の観点から好ましい。当該モル比は、反応前、反応中において変化させても良い。
Specifically, the present invention relates to B /, which is a molar ratio of trivalent iron to arsenic in a solution having a pH value of 1 or less containing arsenic A mole, trivalent iron B mole, and divalent iron C mole. An oxidizing agent is added as A <1.0 (that is, A> B) to produce crystalline iron arsenate particles. In this crystalline iron arsenate production reaction, iron is a mixture of B moles of trivalent iron and C moles of divalent iron, A> B, and A ≦ (B + C). Since the amount of iron exceeds the amount of arsenic, most of the arsenic is completely reacted, and as a result, arsenic remains in the post-reaction solution. As a result, the arsenic load in the water treatment which is a subsequent process is reduced. However, if it is desired that most of trivalent iron and divalent iron be crystalline iron arsenate, A> (B + C) may be satisfied. At this time, the arsenic is preferably pentavalent arsenic. This is because iron arsenate is a compound of trivalent iron and pentavalent arsenic.
Here, the molar ratio of the trivalent iron B mole and the divalent iron C mole may be set according to the target amount of crystalline iron arsenate production and the situation, but the molar ratio (value of B / C) is Setting in the range of 0.1 to 2 is preferable from the viewpoint of productivity of crystalline iron arsenate. The molar ratio may be changed before and during the reaction.
本発明者らは、３価鉄と５価ヒ素とによる結晶性ヒ酸鉄生成反応において、溶液のｐＨ値を１以下とし、上述したようにＢ／Ａ＜１とし、且つ２価鉄Ｃモルを共存させ、さらに酸化剤を加える構成により、３価鉄と５価ヒ素との結晶化反応が、２価鉄と５価ヒ素との結晶化反応に比較して優先的、且つ迅速に進み、大きな粒径を有する結晶性ヒ酸鉄粒子が短時間で生成されることを知見したものである。
以下、本発明が適用されるヒ素含有物、３価鉄源、２価鉄源、３価および２価鉄源の添加方法、酸化剤、溶液のｐＨ値制御、ｐＨ調整剤、反応容器の順で詳細に説明する。
In the crystalline iron arsenate production reaction using trivalent iron and pentavalent arsenic, the present inventors set the pH value of the solution to 1 or less, B / A <1 as described above, and divalent iron C mol. In addition, the crystallization reaction of trivalent iron and pentavalent arsenic proceeds preferentially and quickly compared to the crystallization reaction of divalent iron and pentavalent arsenic, by adding an oxidizing agent. It has been found that crystalline iron arsenate particles having a large particle size are produced in a short time.
Hereinafter, arsenic-containing material to which the present invention is applied, trivalent iron source, divalent iron source, trivalent and divalent iron source addition method, oxidizing agent, solution pH value control, pH adjuster, reaction vessel Will be described in detail.
（本発明が適用されるヒ素含有物）
本発明が適用されるヒ素含有物としては、ヒ酸塩、ヒ酸がある。具体的には、製錬工程から発生する排水、煙灰、殿物である。製錬工程において発生する、これらのヒ素含有物を安全に処理する為、浸出等を行い、ヒ素溶液としたものが本発明の対象溶液となる。尤も、この他、ヒ素を含む廃棄物や、土壌、河川等で天然に含有されるヒ素の浄化に伴って発生するヒ素溶液へ、本発明を適用することも可能である。但し、いずれの場合でも溶液中のヒ素は、予め５価ヒ素に酸化しておくことが好ましい。
(Arsenic-containing material to which the present invention is applied)
Arsenic-containing substances to which the present invention is applied include arsenate and arsenic acid. Specifically, waste water, smoke ash, and shrine generated from the smelting process. In order to safely treat these arsenic-containing materials generated in the smelting process, leaching or the like is performed to obtain an arsenic solution, which is the target solution of the present invention. However, the present invention can also be applied to waste containing arsenic, and arsenic solutions generated with the purification of arsenic naturally contained in soil, rivers, and the like. However, in any case, arsenic in the solution is preferably oxidized beforehand to pentavalent arsenic.
ここで本発明者らは、ｐＨ値が１以下の酸性溶液中に、ヒ素と３価鉄と２価鉄（本発明において「Ｆｅ２＋」の意味である。）とを共存させ、且つ、所定反応条件下で、当該酸性溶液中へ酸化剤として酸素や空気を吹き込むことで、結晶性ヒ酸鉄生成反応が迅速に進み、且つ、粒子径の大きな結晶性ヒ酸鉄粒子が生成することを知見した。
本発明者らは上述した所定反応条件として、溶液中に存在するヒ素１モルに対して、１モル未満（０．１〜１．０モル）の３価鉄と、２価鉄とを共に存在させ、当該溶液へ酸化剤の添加（空気、酸素の吹き込み、等）を行なうという反応条件に想到した。そして、当該所定反応条件下では、粒子径の大きな結晶性ヒ酸鉄粒子の生成反応が迅速に進む現象を知見したものである。
Here, the present inventors coexisted arsenic, trivalent iron, and divalent iron (meaning “Fe 2+ ” in the present invention) in an acidic solution having a pH value of 1 or less, and a predetermined value. By blowing oxygen or air as an oxidant into the acidic solution under the reaction conditions, the crystalline iron arsenate production reaction proceeds rapidly and crystalline iron arsenate particles having a large particle size are produced. I found out.
As the above-mentioned predetermined reaction conditions, the present inventors present both less than 1 mol (0.1 to 1.0 mol) of trivalent iron and divalent iron with respect to 1 mol of arsenic present in the solution. The reaction conditions of adding an oxidizing agent (air, oxygen blowing, etc.) to the solution were conceived. Under the predetermined reaction conditions, the inventors have found a phenomenon in which the formation reaction of crystalline iron arsenate particles having a large particle diameter proceeds rapidly.
さらに、当該溶液中にヒ素と３価鉄と２価鉄とが共に存在した場合、結晶性ヒ酸鉄生成反応の進行開始に伴い、３価鉄イオン濃度は、２価鉄イオン濃度と比べ圧倒的に早く低下
してしまうが、２価鉄イオン濃度は、それ程大きな減少変化がないことが知見された。しかし、当該３価鉄イオンおよび２価鉄イオンの濃度の動向にも拘らず、２価鉄の量が多いことで結晶性ヒ酸鉄生成反応の進行が促進されることも判明した。
Furthermore, when arsenic, trivalent iron, and divalent iron exist together in the solution, the trivalent iron ion concentration is overwhelming with the divalent iron ion concentration as the crystalline iron arsenate formation reaction starts. However, it was found that the divalent iron ion concentration did not change so much. However, it has also been found that the progress of the crystalline iron arsenate formation reaction is promoted by increasing the amount of divalent iron in spite of the trend of the concentration of trivalent iron ions and divalent iron ions.
（３価鉄源）
３価鉄源としては、３価鉄塩がある。具体的には、硫酸第２鉄、塩化第２鉄、硝酸第２鉄等、酸化鉄、水酸化鉄等が挙げられる。ここで、設備への腐食性の観点、汎用的な薬剤としての入手が容易性の観点から、硫酸第２鉄が好ましい。
当該硫酸第２鉄は、温水に溶解し３価鉄イオンの溶液として添加することが好ましいが、液量を抑える観点から、直接、粉状で被処理溶液へ添加しても良い。
(Trivalent iron source)
A trivalent iron source is a trivalent iron salt. Specifically, ferric sulfate, ferric chloride, ferric nitrate, etc., iron oxide, iron hydroxide, etc. are mentioned. Here, ferric sulfate is preferable from the viewpoint of corrosiveness to equipment and easy availability as a general-purpose drug.
The ferric sulfate is preferably dissolved in warm water and added as a solution of trivalent iron ions. However, from the viewpoint of suppressing the amount of liquid, it may be added directly to the solution to be treated in powder form.
（２価鉄源）
２価鉄源としては、２価鉄塩がある。具体的には、硫酸第１鉄、塩化第１鉄、硝酸第１鉄等、酸化鉄、水酸化鉄等が挙げられる。ここで、設備への腐食性の観点、汎用的な薬剤としての入手容易性の観点から、硫酸第１鉄が好ましい。
当該硫酸第１鉄は、温水に溶解し２価鉄イオンの溶液として添加しても良いが、液量を抑える観点から、粉状のまま、直接、対象溶液へ添加することが好ましい。
(Divalent iron source)
As a divalent iron source, there is a divalent iron salt. Specifically, ferrous sulfate, ferrous chloride, ferrous nitrate, etc., iron oxide, iron hydroxide and the like can be mentioned. Here, ferrous sulfate is preferable from the viewpoint of corrosiveness to equipment and easy availability as a general-purpose drug.
The ferrous sulfate may be dissolved in warm water and added as a solution of divalent iron ions. However, it is preferable to add the ferrous sulfate directly to the target solution in a powder form from the viewpoint of suppressing the amount of liquid.
（３価および２価鉄源の添加方法）
上記、３価および２価鉄源の被処理溶液への添加は、全量一括添加も良いし、結晶性ヒ酸鉄生成反応の進行に伴って、複数回に分けて分割添加することも出来る。尤も、全量一括添加によれば、操作が簡便化し、作業コストの低減を行うことが出来る。
また、被処理溶液から結晶性ヒ酸鉄が生成した後に得られる反応後液中には、３価鉄および５価ヒ素が殆ど含有されておらず、一方、２価鉄は残留している。そこで、当該反応後液は、再度２価鉄源として使用可能である。当該構成により、薬剤コストの低減を図ることが出来るので好ましい。
(Method of adding trivalent and divalent iron sources)
The trivalent and divalent iron sources can be added to the solution to be treated at once, or they can be added in a plurality of divided portions as the crystalline iron arsenate formation reaction proceeds. However, according to the total addition all at once, the operation can be simplified and the working cost can be reduced.
Further, the trivalent iron and pentavalent arsenic are scarcely contained in the post-reaction solution obtained after the crystalline iron arsenate is produced from the solution to be treated, while the divalent iron remains. Therefore, the post-reaction solution can be used again as a divalent iron source. This configuration is preferable because the drug cost can be reduced.
（酸化剤）
酸化剤は、酸素ガス、空気、酸素を含むガス、空気希釈ガス、オゾン、過酸化水素水等、から選択される１種以上を用いることが出来る。これらのガスの分圧をもちいて濃度調整しても良い。
尚、酸素を含むガスとは、酸素含有組成が２１％（空気含有酸素量）より多く１００％より少ないガスを示し、空気希釈ガスとは、例えば窒素ガス等の不活性ガスを空気に混合し、酸素含有組成が０％より多く２１％（空気含有酸素量）より少ないガスを示す。
添加方法は、ガス体ならば被処理溶液へ吹き込めば良いし、液体ならば当該溶液へ投入すれば良い。
(Oxidant)
As the oxidant, one or more selected from oxygen gas, air, oxygen-containing gas, air dilution gas, ozone, hydrogen peroxide solution, and the like can be used. The concentration may be adjusted using the partial pressure of these gases.
The oxygen-containing gas means a gas having an oxygen-containing composition of more than 21% (air-containing oxygen amount) and less than 100%, and the air-diluting gas is an inert gas such as nitrogen gas mixed with air. A gas having an oxygen-containing composition of more than 0% and less than 21% (air-containing oxygen content).
As for the addition method, if it is a gas body, it may be blown into the solution to be treated.
（溶液のｐＨ値制御）
本発明に係る結晶性ヒ酸鉄生成反応は水素イオンを発生する反応である。この為、当該結晶性ヒ酸鉄生成反応の進行と共に、被処理溶液のｐＨ値は低下する。ここで、溶液のｐＨ値低下を成行きに任せ、当該結晶性ヒ酸鉄生成反応進行時のｐＨ値が０．７０から０.
７９まで低下すれば、反応速度が著しく低下し、且つ反応後液に残留するヒ素濃度が高くなるという知見を得た。
一方、本発明者らは、当該結晶性ヒ酸鉄生成反応において、３価鉄を用い粒径の大きな結晶性ヒ酸鉄を生成させるためには、溶液のｐＨ値が１以下の領域が好ましいという知見を得ている。
(Control of pH value of solution)
The crystalline iron arsenate production reaction according to the present invention is a reaction that generates hydrogen ions. For this reason, as the crystalline iron arsenate production reaction proceeds, the pH value of the solution to be treated decreases. Here, the pH value of the solution was allowed to decrease, and the pH value during the crystalline iron arsenate formation reaction proceeded from 0.70 to 0.00.
It has been found that if it is reduced to 79, the reaction rate is remarkably reduced and the concentration of arsenic remaining in the post-reaction solution increases.
On the other hand, in order to produce crystalline iron arsenate having a large particle size using trivalent iron in the crystalline iron arsenate production reaction, the inventors preferably have a solution having a pH value of 1 or less. I have obtained the knowledge.
以上の知見より、本発明者らは、当該結晶性ヒ酸鉄生成反応の進行中は、発生する水素イオンを中和し、且つ反応終了時のｐＨ値を所定範囲内に収めるのが良いと考えた。
具体的には、例えば、溶液のｐＨ値が０．８以下となる際は、ｐＨ値を０．８以上に保
持し、ｐＨ１迄上昇させることが出来る。
そして、被処理溶液中のヒ素濃度が、反応開始時点におけるヒ素濃度の３０％以下となる反応後期では、結晶性ヒ酸鉄生成反応が緩慢になる。そこで、当該反応後期においては、ｐＨ値を１〜２前後迄上昇させて、結晶性ヒ酸鉄生成反応を促進する構成を採ることも好ましい。当該反応後期においては、既に生成した結晶性ヒ酸鉄は安定しており、ｐＨ値上昇による結晶性ヒ酸鉄の再溶解は起こらないので問題はない。
Based on the above findings, the present inventors should neutralize the generated hydrogen ions and keep the pH value at the end of the reaction within a predetermined range during the progress of the crystalline iron arsenate production reaction. Thought.
Specifically, for example, when the pH value of the solution is 0.8 or less, the pH value can be maintained at 0.8 or more and raised to pH 1.
Then, the crystalline iron arsenate production reaction becomes slow at the late stage of the reaction when the arsenic concentration in the solution to be treated is 30% or less of the arsenic concentration at the start of the reaction. Therefore, in the latter stage of the reaction, it is also preferable to increase the pH value to about 1 to 2 to promote the crystalline iron arsenate production reaction. In the latter stage of the reaction, the crystalline iron arsenate already produced is stable, and there is no problem because the crystalline iron arsenate does not re-dissolve due to an increase in pH value.
尚、所定ｐＨ値でのｐＨ値保持制御幅は、結晶性ヒ酸鉄の粒子成長の観点からは狭い程好ましい。例えば、所定ｐＨ値を１．０として保持する場合のｐＨ値制御幅は、ｐＨ値が０．９より低下せず１．０を超さない範囲よりも狭い範囲で制御することが好ましい。
当該ｐＨ値の制御幅を実現するには、後述するｐＨ調整剤を水に添加して、高スラリー濃度の液状としてから被処理溶液へ添加することで、当該溶液への濡れを確保し、当該溶液中への拡散を容易せしめる方法等が有効である。
In addition, the pH value holding control width at a predetermined pH value is preferably as narrow as possible from the viewpoint of particle growth of crystalline iron arsenate. For example, it is preferable that the pH value control range when the predetermined pH value is held as 1.0 is controlled in a narrower range than the range where the pH value does not fall below 0.9 and does not exceed 1.0.
In order to realize the control range of the pH value, a pH adjusting agent to be described later is added to water, and added to the solution to be treated after forming a liquid with a high slurry concentration, thereby ensuring wetting of the solution. A method of facilitating diffusion into the solution is effective.
（ｐＨ調整剤）
ｐＨ調整剤には、アルカリ土類金属系のアルカリ、例えば、Ｍｇ（ＯＨ）２、Ｃａ（ＯＨ）２、ＭｇＯ、ＣａＯ、等が好ましく、アルカリ金属系のアルカリ、例えば、ＮａＯＨ、ＫＯＨ、等でも良い。これらの単種または複数の混合でも良い。
(PH adjuster)
The pH adjuster is preferably an alkaline earth metal alkali such as Mg (OH) 2, Ca (OH) 2, MgO, CaO, or the like, or an alkali metal alkali such as NaOH or KOH. good. These single species or a mixture of a plurality of species may be used.
（反応容器）
当該結晶性ヒ酸鉄の生成反応に用いる容器は開放型で良い。当該生成反応は大気圧下でおこなう為、容器には特別な耐圧性は不要である。
(Reaction vessel)
The container used for the production reaction of the crystalline iron arsenate may be an open type. Since the production reaction takes place under atmospheric pressure, the container does not require special pressure resistance.
（まとめ）
以上説明した、本発明に係る対象溶液からの結晶性ヒ酸鉄生成方法によれば、結晶粒径の大きいヒ酸鉄粒子を短時間で生成させることが可能となった。さらに、得られた結晶性ヒ酸鉄粒子は、ヒ素の溶出値が低いものであった。この結果、生成した結晶性ヒ酸鉄は、濾過性、ハンドリング性とも優れていた。
一方、結晶性ヒ酸鉄粒子の径を大きく出来たことは、粒子径の調整幅を拡大出来たことである。当該調整幅の拡大手法は、結晶性ヒ酸鉄粒子の様々な用途、保管方法、等に応用可能であり、結晶性ヒ酸鉄粒子の保管、利用範囲が拡大される可能性は高い。
(Summary)
According to the method for producing crystalline iron arsenate from the target solution according to the present invention described above, iron arsenate particles having a large crystal grain size can be produced in a short time. Furthermore, the obtained crystalline iron arsenate particles had low arsenic elution values. As a result, the produced crystalline iron arsenate was excellent in both filterability and handling properties.
On the other hand, the fact that the diameter of the crystalline iron arsenate particles can be increased is that the adjustment range of the particle diameter can be expanded. The method for expanding the adjustment range can be applied to various uses and storage methods of the crystalline iron arsenate particles, and there is a high possibility that the storage and use range of the crystalline iron arsenate particles will be expanded.
以下、実施例を参照しながら本発明に関し詳細に説明する。
（実施例１）
１）試験ユニットおよび試験規模
試験容器としては１Ｌビーカーを使用した。当該試験容器に設置する撹拌装置は、４枚邪魔板付き、２段タービン羽根、回転数６００ｒｐｍを使用した。
このとき、１バッチ当たりにおけるヒ素、鉄混合溶液の処理量は総量で６５０ｍＬとした。なお、いずれの実施例も大気圧（常圧）下である。
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
1) Test unit and test scale A 1 L beaker was used as a test container. The stirrer installed in the test vessel was equipped with four baffle plates, a two-stage turbine blade, and a rotation speed of 600 rpm.
At this time, the total amount of arsenic and iron mixed solution processed per batch was 650 mL. All examples are under atmospheric pressure (normal pressure).
２）３価鉄溶液の調製
試薬硫酸鉄（III）水和物（鉄品位として２１.６％）１，８１５ｇを量り取り、これを５Ｌビーカーに投入し、純水を加えて液量を１，９００ｍＬとした。そして、当該溶液を８０℃に加温し、攪拌して硫酸鉄（III）溶液を得た。
当該硫酸鉄（III）溶液を室温まで放冷し、さらに、当該溶液の液量が２,０００ｍＬになるように純水を補加し、実施例１および、後述する他実施例に係る３価鉄溶液を得た。
当該３価鉄溶液に対する分析の結果、鉄濃度は１９６ｇ／Ｌであることが判明した。
2) Preparation of trivalent iron solution
Reagent iron (III) sulfate hydrate (21.6% as iron grade) 1,815 g was weighed out, put into a 5 L beaker, and pure water was added to make the liquid volume 1,900 mL. Then, the solution was heated to 80 ° C. and stirred to obtain an iron (III) sulfate solution.
The iron (III) sulfate solution is allowed to cool to room temperature, and further, pure water is supplemented so that the liquid volume of the solution becomes 2,000 mL. Example 1 and trivalents according to other examples described later An iron solution was obtained.
Analysis of the trivalent iron solution revealed that the iron concentration was 196 g / L.
３）ヒ素、鉄混合溶液の調製
５価ヒ素として試薬６０％砒酸溶液を準備した。
３価鉄として、上述した２）の３価鉄溶液を準備した。
２価鉄として試薬硫酸鉄（II）７水和物を準備した。
ここで、５価ヒ素が２５ｇ／Ｌであって、３価鉄が５価ヒ素総モル量にたいして０．７５倍当量（０．７５倍モル）、２価鉄が５価ヒ素総モル量にたいして０．５倍当量（０．５倍モル）のヒ素と鉄との混合溶液を製造した。
具体的には、試薬６０％砒酸溶液３２．５ｍＬと、試薬硫酸鉄（II）７水和物３０．１ｇと、上述した２）の３価鉄溶液４６．５ｍＬとを混合し、さらに、水を加えて全量を６５０ｍＬにした。
こうして得られたヒ素と鉄との混合溶液は、ヒ素濃度２５．１ｇ／Ｌ、３価鉄濃度１４．１ｇ／Ｌ、２価鉄濃度９．４ｇ／Ｌであった。
3) Preparation of Arsenic and Iron Mixed Solution A reagent 60% arsenic acid solution was prepared as pentavalent arsenic.
The trivalent iron solution of 2) described above was prepared as the trivalent iron.
The reagent iron sulfate (II) heptahydrate was prepared as divalent iron.
Here, pentavalent arsenic is 25 g / L, trivalent iron is 0.75 times equivalent to the total molar amount of pentavalent arsenic (0.75 times mol), and divalent iron is 0 to the total molar amount of pentavalent arsenic. A mixed solution of arsenic and iron having a 5-fold equivalent (0.5-fold mole) was produced.
Specifically, 32.5 mL of a reagent 60% arsenic acid solution, 30.1 g of reagent iron (II) sulfate heptahydrate, and 46.5 mL of the trivalent iron solution of 2) described above were mixed, To a total volume of 650 mL.
The mixed solution of arsenic and iron thus obtained had an arsenic concentration of 25.1 g / L, a trivalent iron concentration of 14.1 g / L, and a divalent iron concentration of 9.4 g / L.
４）ｐＨ調整剤
本実施例においては、ｐＨ調整剤としてキシダ化学株式会社製試薬、水酸化マグネシウムＭｇ（ＯＨ）２（ａｓｓａｙ ｍｉｎ９５％）を準備した。
4) pH adjuster In this example, a reagent manufactured by Kishida Chemical Co., Ltd., magnesium hydroxide Mg (OH) 2 (assay min 95%) was prepared as a pH adjuster.
５）酸化剤
本実施例においては、反応開始から溶液中にヒ酸鉄の核が発生するまでの段階では、酸化剤として空気を用い、これ以降、結晶性ヒ酸鉄の粒子が成長する段階では、酸化剤として酸素ガスを用いた。
5) Oxidizing agent In this example, air is used as the oxidizing agent in the stage from the start of the reaction until iron arsenate nuclei are generated in the solution, and thereafter, the crystalline iron arsenate particles grow. Then, oxygen gas was used as the oxidizing agent.
６）結晶性ヒ酸鉄生成反応
本実施例、および、実施例２〜４、比較例１、２では、結晶性ヒ酸鉄としてスコロダイト結晶を生成させた。そこで、以下の説明においては、「結晶性ヒ酸鉄」に代えて「スコロダイト」と表記した。
上述したヒ素と鉄との混合溶液を９５℃へ加温する。このとき、９５℃到達時点で混合溶液のｐＨ値が１を超えないようにする為、加温中に混合溶液へ硫酸を添加した。そして、当該混合溶液の液温が９５℃到達時点で、混合溶液のｐＨ値が１となるように、添加する硫酸量を調整した。
6) Crystalline iron arsenate production reaction In this example, Examples 2 to 4, and Comparative Examples 1 and 2, scorodite crystals were produced as crystalline iron arsenate. Therefore, in the following description, “scorodite” is used instead of “crystalline iron arsenate”.
The above-mentioned mixed solution of arsenic and iron is heated to 95 ° C. At this time, in order to prevent the pH value of the mixed solution from exceeding 1 when reaching 95 ° C., sulfuric acid was added to the mixed solution during heating. Then, the amount of sulfuric acid to be added was adjusted so that the pH value of the mixed solution became 1 when the liquid temperature of the mixed solution reached 95 ° C.
混合溶液の液温が９５℃、ｐＨ１であることを確認し、酸化剤の添加を開始してスコロダイト生成反応を開始した。
酸化剤の添加は、反応開始から溶液中にスコロダイトの核が発生するまでの３０分間は、空気を１Ｌ／ｍｉｎで吹き込み、その後、スコロダイトの粒子が成長する段階では酸素ガスに替え、１Ｌ／ｍｉｎで反応終了まで２１０分間、吹き込みを継続した（結局、スコロダイト生成反応時間は、全体で４時間となった。）。混合溶液のｐＨ値は、開始当初は１．０であったが、ｐＨ調整剤としてＭｇ（ＯＨ）２を粉末のまま添加し、溶液のｐＨ値を０．９３〜０．９９間にて制御した。次いで、反応開始から１２０分間後に溶液のｐＨ値を１．５迄上昇させ、ｐＨ値を１．４６〜１．５４間にて制御した。反応終了後は生成物を濾過し、反応後液と生成残さ（スコロダイト）とを得た。なお、本実施例において濾過は極めてスムーズに進行し、１０秒とかからない数秒で完了した。
After confirming that the temperature of the mixed solution was 95 ° C. and pH 1, addition of an oxidizing agent was started to start a scorodite production reaction.
Addition of the oxidizing agent is performed by blowing air at 1 L / min for 30 minutes from the start of the reaction until nuclei of scorodite are generated in the solution. After that, when the scorodite particles grow, the oxygen gas is changed to 1 L / min. Then, blowing was continued for 210 minutes until the end of the reaction (eventually, the scorodite production reaction time was 4 hours). The pH value of the mixed solution was 1.0 at the beginning, but Mg (OH) 2 was added as a pH adjuster as a powder, and the pH value of the solution was controlled between 0.93 and 0.99. did. Subsequently, 120 minutes after the start of the reaction, the pH value of the solution was increased to 1.5, and the pH value was controlled between 1.46 and 1.54. After completion of the reaction, the product was filtered to obtain a post-reaction solution and a product residue (scorodite). In this example, the filtration proceeded very smoothly and was completed in a few seconds, not 10 seconds.
７）生成したスコロダイトの評価
得られた反応終了時点での濾過物を純水洗浄した後、Ｘ線回折測定を行い、スコロダイト生成状況を評価した。得られたスコロダイトの粒子径測定結果を表４に示す。
Ｘ線回折結果より、反応終了時点での濾過物には、スコロダイト（ＦｅＡｓＯ４・２Ｈ２Ｏ）の結晶を示すシャープなピークが広い回折角の範囲で確認され、スコロダイト結晶であると同定した。
7) Evaluation of generated scorodite After the obtained filtered product was washed with pure water, X-ray diffraction measurement was performed to evaluate the state of scorodite generation. Table 4 shows the particle size measurement results of the obtained scorodite.
From the X-ray diffraction result, a sharp peak indicating a scorodite (FeAsO 4 .2H 2 O) crystal was confirmed in a wide diffraction angle range in the filtrate at the end of the reaction, and the scorodite crystal was identified.
（実施例２）
上述した実施例１の「３）ヒ素、鉄混合溶液の調製」において、５価ヒ素を２５ｇ／Ｌ
、３価鉄を５価ヒ素総モル量にたいして０．７５倍当量（０．７５倍モル）、２価鉄を５価ヒ素総モル量にたいして０．７５倍当量（０．７５倍モル）の、ヒ素と鉄との混合溶液とし、反応初期における空気吹き込み時間を６０分間とした以外は、実施例１と同様にして、実施例２に係る生成物を得た。
当該生成物を濾過し、溶液と生成残さ（スコロダイト）とを得た。なお、本実施例においても濾過は極めてスムーズに進行し、１０秒とかからない数秒で完了した。
得られた反応終了時点での濾過物を純水洗浄した後、得られたスコロダイトの粒子径測定結果を表４示す。
(Example 2)
In “3) Preparation of Arsenic and Iron Mixed Solution” in Example 1 described above, pentavalent arsenic was added at 25 g / L.
0.75 times equivalent (0.75 times mole) trivalent iron to pentavalent arsenic total mole amount, 0.75 times equivalent (0.75 times mole) divalent iron to pentavalent arsenic total mole amount, A product according to Example 2 was obtained in the same manner as in Example 1 except that a mixed solution of arsenic and iron was used and the air blowing time in the initial reaction was 60 minutes.
The product was filtered to obtain a solution and a product residue (scorodite). In this example as well, the filtration proceeded very smoothly and was completed in a few seconds, not 10 seconds.
Table 4 shows the particle size measurement results of the obtained scorodite after the filtrate at the end of the reaction was washed with pure water.
また、本実施例においては、反応開始時、反応開始６０分間後、反応開始１２０分間後、反応開始２４０分間後における、被処理溶液中の５価ヒ素濃度、３価鉄濃度、２価鉄濃度を測定した。当該測定結果を表１に記載する。 In this example, the pentavalent arsenic concentration, trivalent iron concentration, divalent iron concentration in the solution to be treated at the start of the reaction, 60 minutes after the start of the reaction, 120 minutes after the start of the reaction, and 240 minutes after the start of the reaction. Was measured. The measurement results are shown in Table 1.
表１の結果より、被処理溶液のｐＨ値が１以下であるところの、反応開始１２０分間後までに、３価鉄の殆ど全量がスコロダイト生成反応に消費され、一方、２価鉄の消費量は少量であることが確認された。当該結果より、被処理溶液のｐＨ値が１以下の下で、５価ヒ素と３価鉄とが、短時間で、且つ２価鉄に優先してスコロダイトを生成する反応を行っていることが確認出来た。 From the results shown in Table 1, almost all of the trivalent iron was consumed in the scorodite formation reaction until 120 minutes after the start of the reaction where the pH value of the solution to be treated was 1 or less, while the consumption of divalent iron. Was confirmed to be small. From the results, it is found that pentavalent arsenic and trivalent iron are performing a reaction that produces scorodite in a short time and in preference to divalent iron under a pH value of 1 or less. I was able to confirm.
反応開始２４０分間後における、被処理溶液中の５価ヒ素濃度、３価鉄濃度、２価鉄濃度を見ると、５価ヒ素濃度および３価鉄濃度は非常に低いが、２価鉄濃度は高い。従って、反応後液である当該反応開始２４０分間後における被処理溶液は、２価鉄源として再度の利用が可能であることが判明した。 Looking at the pentavalent arsenic concentration, trivalent iron concentration, and divalent iron concentration in the solution to be treated 240 minutes after the start of the reaction, the pentavalent arsenic concentration and trivalent iron concentration are very low, but the divalent iron concentration is high. Accordingly, it was found that the solution to be treated, which is a post-reaction solution 240 minutes after the start of the reaction, can be reused as a divalent iron source.
（実施例３）
上述した実施例１の「３）ヒ素、鉄混合溶液の調製」において、５価ヒ素を２５ｇ／Ｌ、３価鉄を５価ヒ素総モル量にたいして０．９倍当量（０．９倍モル）、２価鉄を５価ヒ素総モル量にたいして０．５倍当量（０．５倍モル）とした以外は、実施例１と同様にして、実施例３に係る生成物を得た。
当該生成物を濾過し、溶液と生成残さ（スコロダイト）とを得た。なお、本実施例においても濾過は極めてスムーズに進行し、１０秒とかからない数秒で完了した。
得られた反応終了時点での濾過物を純水洗浄した後、得られたスコロダイトの粒子径測定結果を表４に示す。
(Example 3)
In “3) Preparation of Arsenic and Iron Mixed Solution” in Example 1 described above, pentavalent arsenic is 25 g / L, and trivalent iron is 0.9 times equivalent (0.9 times mole) to the total molar amount of pentavalent arsenic. The product according to Example 3 was obtained in the same manner as in Example 1 except that divalent iron was changed to 0.5 times equivalent (0.5 times mol) with respect to the total molar amount of pentavalent arsenic.
The product was filtered to obtain a solution and a product residue (scorodite). In this example as well, the filtration proceeded very smoothly and was completed in a few seconds, not 10 seconds.
Table 4 shows the particle size measurement results of the obtained scorodite after the filtrate at the end of the reaction was washed with pure water.
（実施例４）
上述した実施例１の「３）ヒ素、鉄混合溶液の調製」において、５価ヒ素を２５ｇ／Ｌ、３価鉄を５価ヒ素総モル量にたいして０．９倍当量（０．９倍モル）、２価鉄を５価ヒ素総モル量にたいして０．７５倍当量（０．７５倍モル）とした以外は、実施例１と同様
にして、実施例４に係る生成物を得た。
当該生成物を濾過し、溶液と生成残さ（スコロダイト）とを得た。なお、本実施例においても濾過は極めてスムーズに進行し、１０秒とかからない数秒で完了した。
得られた反応終了時点での濾過物を純水洗浄した後、得られたスコロダイトの粒子径測定結果を表４に示す。
Example 4
In “3) Preparation of Arsenic and Iron Mixed Solution” in Example 1 described above, pentavalent arsenic is 25 g / L, and trivalent iron is 0.9 times equivalent (0.9 times mole) to the total molar amount of pentavalent arsenic. A product according to Example 4 was obtained in the same manner as in Example 1 except that divalent iron was changed to 0.75 times equivalent (0.75 times mol) with respect to the total molar amount of pentavalent arsenic.
The product was filtered to obtain a solution and a product residue (scorodite). In this example as well, the filtration proceeded very smoothly and was completed in a few seconds, not 10 seconds.
Table 4 shows the particle size measurement results of the obtained scorodite after the filtrate at the end of the reaction was washed with pure water.
（比較例１）
１）ヒ素、鉄混合溶液の調製
上述した実施例１の「３）ヒ素、鉄混合溶液の調製」において、５価ヒ素を２５ｇ／Ｌとし、３価鉄を５価ヒ素総モル量にたいして１．０倍当量（１．０倍モル）、２価鉄を５価ヒ素総モル量にたいして０．５倍当量（０．５倍モル）とした以外は、実施例１と同様にして比較例１に係る操作を行った。
(Comparative Example 1)
1) Preparation of Arsenic / Iron Mixed Solution In “3) Preparation of Arsenic / Iron Mixed Solution” in Example 1 described above, the pentavalent arsenic was 25 g / L, and the trivalent iron was adjusted to the total molar amount of pentavalent arsenic. Comparative Example 1 was carried out in the same manner as in Example 1 except that 0-fold equivalent (1.0-fold mole) and divalent iron were changed to 0.5-fold equivalent (0.5-fold mole) with respect to the total mole amount of pentavalent arsenic. This operation was performed.
２）スコロダイトの生成反応
調製したヒ素と鉄との混合溶液を９５℃へ加温した。このとき、９５℃到達時点で混合溶液のｐＨ値が１を超えないようにする為、加温中に混合溶液へ硫酸を添加した。そして、当該混合溶液の液温が９５℃到達時点で、混合溶液のｐＨ値が１となるように、添加する硫酸量を調整した。
2) Formation reaction of scorodite The prepared mixed solution of arsenic and iron was heated to 95 ° C. At this time, in order to prevent the pH value of the mixed solution from exceeding 1 when reaching 95 ° C., sulfuric acid was added to the mixed solution during heating. Then, the amount of sulfuric acid to be added was adjusted so that the pH value of the mixed solution became 1 when the liquid temperature of the mixed solution reached 95 ° C.
混合溶液の液温が９５℃、ｐＨ１であることを確認し、酸化剤（酸素ガス）の添加を開始してスコロダイト生成反応開始とした。尚、酸化剤の量、及び、ｐＨの制御は実施例１と同様に行った。しかし、本比較例１においては、反応開始から１２０分間経っても反応生成物による溶液の濁りは僅かであった。
この後、当該溶液にｐＨ調整剤を添加してｐＨ値を１．５まで上昇させた。酸化剤は継続して吹き込み、反応開始から２４０分間後に酸化剤の吹き込みを止めて反応終了とし、本反応に係る生成物を得た。
当該生成物を濾過し、溶液と生成残さ（スコロダイト）とを得た。比較例１に係るスコロダイトの濾過性は、非常に悪いものであった。
After confirming that the liquid temperature of the mixed solution was 95 ° C. and pH 1, addition of an oxidizing agent (oxygen gas) was started to start a scorodite production reaction. The amount of oxidant and pH were controlled in the same manner as in Example 1. However, in Comparative Example 1, the turbidity of the solution due to the reaction product was slight even after 120 minutes from the start of the reaction.
Thereafter, a pH adjuster was added to the solution to raise the pH value to 1.5. The oxidizing agent was continuously blown, and after 240 minutes from the start of the reaction, the blowing of the oxidizing agent was stopped to complete the reaction, and a product according to this reaction was obtained.
The product was filtered to obtain a solution and a product residue (scorodite). The filterability of the scorodite according to Comparative Example 1 was very bad.
３）生成したスコロダイトの評価
得られた反応終了時点での濾過物を純水洗浄した後、得られたスコロダイトの粒子径測定結果を表４に示す。
3) Evaluation of produced scorodite After the obtained filtrate at the end of the reaction was washed with pure water, the particle size measurement result of the obtained scorodite is shown in Table 4.
また、本比較例においては、反応開始時、反応開始６０分間後、反応開始１２０分間後、反応開始２４０分間後における、被処理溶液中の５価ヒ素濃度、３価鉄濃度、２価鉄濃度を測定した。当該測定結果を表２に記載する。 In this comparative example, the pentavalent arsenic concentration, trivalent iron concentration, and divalent iron concentration in the solution to be treated at the start of the reaction, 60 minutes after the start of the reaction, 120 minutes after the start of the reaction, and 240 minutes after the start of the reaction. Was measured. The measurement results are shown in Table 2.
表２の結果より、３価Ｆｅ／５価Ａｓのモル比が１の場合で、溶液のｐＨ値が１以下の
状態では、５価ヒ素はほとんど濃度変化が起きないことが判明した。当該濃度変化が起きないことは、３価鉄、２価鉄も同様であった。つまり、３価鉄ｅ／５価ヒ素のモル比が１以上であって、溶液のｐＨ値が１以下の場合、実施例で説明した様な、迅速なスコロダイト生成反応は進まないことが判明した。
From the results in Table 2, it was found that when the molar ratio of trivalent Fe / 5valent As is 1, and the pH value of the solution is 1 or less, the concentration of pentavalent arsenic hardly changes. The fact that the concentration did not change was the same for trivalent iron and divalent iron. That is, when the molar ratio of trivalent iron e / 5 arsenic was 1 or more and the pH value of the solution was 1 or less, it was found that the rapid scorodite formation reaction did not proceed as described in the examples. .
次に、溶液のｐＨ値を１．５へ上昇させた１２０分間後においては、ヒ素と３価鉄の濃度が激減し、２価鉄の濃度はほとんど変化しないことが判明した。すなわち、比較例１で得られたスコロダイトは、溶液のｐＨ値が１．５の下で、５価ヒ素と３価鉄との反応により生成したものであること、および、生成したスコロダイトの粒子径は３.３μｍと非常
に微細なものであることが判明した。尚、本反応例において、酸化剤に空気を用いた場合においても同様の結果が得られた。
Next, after 120 minutes when the pH value of the solution was raised to 1.5, it was found that the concentrations of arsenic and trivalent iron were drastically reduced, and the concentration of divalent iron was hardly changed. That is, the scorodite obtained in Comparative Example 1 was produced by the reaction of pentavalent arsenic and trivalent iron under a solution pH value of 1.5, and the particle size of the produced scorodite Was found to be as fine as 3.3 μm. In this reaction example, the same result was obtained when air was used as the oxidizing agent.
（比較例２）
１）ヒ素、鉄混合溶液の調製
上述した実施例１の「３）ヒ素、鉄混合溶液の調製」において、５価ヒ素を２５ｇ／Ｌとし、３価鉄を５価ヒ素総モル量にたいして１．０倍当量（１．０倍モル）、２価鉄を５価ヒ素総モル量にたいして１．５倍当量（１．５倍モル）とした以外は、実施例１と同様にして比較例２に係る操作を行った。
(Comparative Example 2)
1) Preparation of Arsenic / Iron Mixed Solution In “3) Preparation of Arsenic / Iron Mixed Solution” in Example 1 described above, the pentavalent arsenic was 25 g / L, and the trivalent iron was adjusted to the total molar amount of pentavalent arsenic. Comparative Example 2 was carried out in the same manner as in Example 1 except that 0-fold equivalent (1.0-fold mole) and divalent iron were changed to 1.5-fold equivalent (1.5-fold mole) with respect to the total mole amount of pentavalent arsenic. This operation was performed.
２）スコロダイトの生成反応
混合溶液の液温が９５℃、ｐＨ１．０であることを確認し、酸化剤の添加を開始し反応開始とした。
酸化剤（酸素ガス）の添加は、反応開始から２４０分後まで継続した（ｐＨが１以下で全反応時間は４時間とした。）。圧力は、大気圧下において特段の制御なく行った。
反応終了後は生成物を濾過し、溶液と生成残さ（スコロダイト）とを得た。残さはかなりの少量であった。
2) Formation reaction of scorodite After confirming that the liquid temperature of the mixed solution was 95 ° C. and pH 1.0, the addition of an oxidizing agent was started and the reaction was started.
The addition of the oxidizing agent (oxygen gas) was continued for 240 minutes after the start of the reaction (pH was 1 or less and the total reaction time was 4 hours). The pressure was performed under atmospheric pressure without special control.
After completion of the reaction, the product was filtered to obtain a solution and a product residue (scorodite). The residue was quite small.
また、本比較例においては、反応開始時、 反応開始９０分間後、反応開始１８０分間
後、 反応開始２４０分間後における、被処理溶液中の５価ヒ素濃度、３価鉄濃度、２価
鉄濃度を測定した。当該測定結果を表３に記載する。
In this comparative example, the pentavalent arsenic concentration, trivalent iron concentration, divalent iron concentration in the solution to be treated at the start of the reaction, 90 minutes after the start of the reaction, 180 minutes after the start of the reaction, and 240 minutes after the start of the reaction. Was measured. The measurement results are shown in Table 3.
表３の結果より、３価Ｆｅ／５価Ａｓのモル比が１で、溶液のｐＨ値が１以下であり、さらに２価鉄のモル比を１．５まで上昇させた状態でも、５価ヒ素の濃度低下は緩慢であることが判明した。一方、２価鉄の、３価鉄への酸化反応が認められるものの、３価鉄の殆どはスコロダイト生成反応に寄与せず、３価鉄濃度の上昇が認められた。
このことより、３価鉄／５価ヒ素のモル比が１以上であると、溶液のｐＨ値を１以下とし、２価鉄量を増量し、酸化剤を投入しても、迅速なスコロダイト生成反応は起こらないことが判明した。
From the results of Table 3, even when the molar ratio of trivalent Fe / 5valent As is 1, the pH value of the solution is 1 or less, and the molar ratio of divalent iron is increased to 1.5, pentavalent The decrease in arsenic concentration was found to be slow. On the other hand, although an oxidation reaction of divalent iron to trivalent iron was observed, most of the trivalent iron did not contribute to the scorodite formation reaction, and an increase in the trivalent iron concentration was observed.
From this, when the molar ratio of trivalent iron / 5 arsenic is 1 or more, the pH value of the solution is 1 or less, the amount of divalent iron is increased, and rapid scorodite generation is possible even when an oxidizing agent is added. It was found that no reaction occurred.
３）生成したスコロダイトの評価
得られた反応終了時点での濾過物を純水洗浄した後、得られたスコロダイトの粒子径測定結果を表４に示す。
3) Evaluation of produced scorodite After the obtained filtrate at the end of the reaction was washed with pure water, the particle size measurement result of the obtained scorodite is shown in Table 4.
表４に示す結果より、５価ヒ素と３価鉄と２価鉄とを含有しｐＨ値が１．０以下であるヒ素を含有する溶液において、５価ヒ素のモル数をＡモル、３価鉄のモル数をＢモル、２価鉄のモル数をＣモルとするとき、Ｂ／Ａ＜１．０およびＣ＞０およびＢ＞０とし酸化剤とを添加することで、短時間に粗大な粒径を有するスコロダイトが得られることが判明した。そして、ヒ素を含有する溶液において、２価鉄の量が多い程、結晶粒径の大きなものが短時間で得られることが判明した。 From the results shown in Table 4, in a solution containing arsenic containing pentavalent arsenic, trivalent iron, and divalent iron and having a pH value of 1.0 or less, the number of moles of pentavalent arsenic is A mole, trivalent. When the number of moles of iron is B mole and the number of moles of divalent iron is C mole, it is coarse in a short time by adding B / A <1.0 and C> 0 and B> 0 and an oxidizing agent. It has been found that scorodite having an appropriate particle size can be obtained. It has been found that in a solution containing arsenic, the larger the amount of divalent iron, the larger the crystal grain size can be obtained in a shorter time.
Claims (5)
前記ヒ素を含有する溶液中における、５価ヒ素のモル数をＡモル、３価鉄のモル数をＢモル、２価鉄のモル数をＣモルとするとき、Ｂ／Ａ＜１．０およびＣ＞０およびＢ＞０とする、ことを特徴とするヒ素を含有する溶液からの結晶性ヒ酸鉄の生成方法。 In this method, divalent iron is added to a solution containing pentavalent arsenic and trivalent iron, the pH value of the solution is adjusted to 1.0 or less, and an oxidizing agent is added to produce crystalline iron arsenate. And
In the arsenic-containing solution, when the mole number of pentavalent arsenic is A mole, the mole number of trivalent iron is B mole, and the mole number of divalent iron is C mole, B / A <1.0 and A method for producing crystalline iron arsenate from a solution containing arsenic, characterized in that C> 0 and B> 0.
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| JP2008126104A (en) * | 2006-11-17 | 2008-06-05 | Dowa Metals & Mining Co Ltd | Method of treating arsenic-containing liquid |
| JP2008540824A (en) * | 2005-05-03 | 2008-11-20 | オウトテック オサケイティオ ユルキネン | Method for recovering valuable metals and arsenic from solution |
| JP2009018291A (en) * | 2007-07-13 | 2009-01-29 | Dowa Metals & Mining Co Ltd | Method for treating arsenic, where seed crystals are added |
| JP2009079237A (en) * | 2007-09-25 | 2009-04-16 | Nikko Kinzoku Kk | Process for producing scorodite, and process for recycling post-scorodite-synthesis solution |
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| WO2008038401A1 (en) * | 2006-09-27 | 2008-04-03 | Dowa Metals & Mining Co., Ltd. | Process for producing iron arsenide compound with good crystallinity |
| JP2008126104A (en) * | 2006-11-17 | 2008-06-05 | Dowa Metals & Mining Co Ltd | Method of treating arsenic-containing liquid |
| JP2009018291A (en) * | 2007-07-13 | 2009-01-29 | Dowa Metals & Mining Co Ltd | Method for treating arsenic, where seed crystals are added |
| JP2009079237A (en) * | 2007-09-25 | 2009-04-16 | Nikko Kinzoku Kk | Process for producing scorodite, and process for recycling post-scorodite-synthesis solution |
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