JP2015077593A - Goethite photocatalyst and production method thereof - Google Patents
Goethite photocatalyst and production method thereof Download PDFInfo
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- JP2015077593A JP2015077593A JP2014159199A JP2014159199A JP2015077593A JP 2015077593 A JP2015077593 A JP 2015077593A JP 2014159199 A JP2014159199 A JP 2014159199A JP 2014159199 A JP2014159199 A JP 2014159199A JP 2015077593 A JP2015077593 A JP 2015077593A
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- goethite
- photocatalyst
- iron
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- polyethylene glycol
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- 229910052598 goethite Inorganic materials 0.000 title claims abstract description 84
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 title claims abstract description 84
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 73
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 239000002202 Polyethylene glycol Substances 0.000 claims abstract description 39
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 39
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 claims abstract description 35
- 239000002245 particle Substances 0.000 claims abstract description 19
- 230000001590 oxidative effect Effects 0.000 claims abstract description 5
- 229910021506 iron(II) hydroxide Inorganic materials 0.000 claims description 19
- 239000003054 catalyst Substances 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 235000014413 iron hydroxide Nutrition 0.000 abstract description 16
- 230000001699 photocatalysis Effects 0.000 abstract description 12
- 230000001747 exhibiting effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 23
- 239000011259 mixed solution Substances 0.000 description 22
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 18
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 15
- 239000007864 aqueous solution Substances 0.000 description 15
- 238000000034 method Methods 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 230000000694 effects Effects 0.000 description 12
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 12
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 230000005587 bubbling Effects 0.000 description 9
- 239000001569 carbon dioxide Substances 0.000 description 9
- 229910002092 carbon dioxide Inorganic materials 0.000 description 9
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 9
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 239000006185 dispersion Substances 0.000 description 7
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical group CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 6
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 6
- 229910001882 dioxygen Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 238000005119 centrifugation Methods 0.000 description 5
- 238000000635 electron micrograph Methods 0.000 description 5
- 229910052697 platinum Inorganic materials 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 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 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 239000004570 mortar (masonry) Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052763 palladium Inorganic materials 0.000 description 4
- 238000013032 photocatalytic reaction Methods 0.000 description 4
- 238000000634 powder X-ray diffraction Methods 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 238000010298 pulverizing process Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 239000003637 basic solution Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 235000013980 iron oxide Nutrition 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002256 photodeposition Methods 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 239000001632 sodium acetate Substances 0.000 description 2
- 235000017281 sodium acetate Nutrition 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 229910021577 Iron(II) chloride Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- CUPCBVUMRUSXIU-UHFFFAOYSA-N [Fe].OOO Chemical compound [Fe].OOO CUPCBVUMRUSXIU-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- MSNWSDPPULHLDL-UHFFFAOYSA-K ferric hydroxide Chemical compound [OH-].[OH-].[OH-].[Fe+3] MSNWSDPPULHLDL-UHFFFAOYSA-K 0.000 description 1
- MQLVWQSVRZVNIP-UHFFFAOYSA-L ferrous ammonium sulfate hexahydrate Chemical compound [NH4+].[NH4+].O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O MQLVWQSVRZVNIP-UHFFFAOYSA-L 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- UCNNJGDEJXIUCC-UHFFFAOYSA-L hydroxy(oxo)iron;iron Chemical compound [Fe].O[Fe]=O.O[Fe]=O UCNNJGDEJXIUCC-UHFFFAOYSA-L 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- 229910021519 iron(III) oxide-hydroxide Inorganic materials 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- -1 lepidoclocite Chemical compound 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229940031182 nanoparticles iron oxide Drugs 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 229910006540 α-FeOOH Inorganic materials 0.000 description 1
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- Catalysts (AREA)
Abstract
Description
本発明は、光触媒およびその製造方法に係り、特に高活性なゲーサイト光触媒とその製
造方法に関する。
The present invention relates to a photocatalyst and a method for producing the same, and more particularly to a highly active goethite photocatalyst and a method for producing the same.
近年、オキシ水酸化鉄の一種であるゲーサイト（α−ＦｅＯＯＨ）は、非特許文献１に
あるように可視光に応答して光触媒作用を示すことから、太陽光や室内光などに含まれる
可視光を有効に利用できる材料として高活性化が期待されている。このゲーサイトは、非
特許文献２に記載のように、鉄（III）イオン水溶液をアルカリ処理し、得られた水酸化
鉄（III）を１００℃以上の高温高圧条件に保持する水熱合成や、水酸化鉄（II）を酸化
することで得られてきた。しかし、従来法で得られたゲーサイトは未だ光触媒活性が低く
、実用化のためには更なる高活性化が必要である。
In recent years, goethite (α-FeOOH), which is a type of iron oxyhydroxide, exhibits a photocatalytic action in response to visible light as described in Non-Patent Document 1, so that it is visible in sunlight or indoor light. High activation is expected as a material that can effectively use light. As described in Non-Patent Document 2, this goethite is hydrothermally synthesized such that an iron (III) ion aqueous solution is treated with alkali and the obtained iron (III) hydroxide is maintained at a high temperature and high pressure condition of 100 ° C. or higher. It has been obtained by oxidizing iron (II) hydroxide. However, the goethite obtained by the conventional method still has low photocatalytic activity, and further high activation is necessary for practical use.
高活性な光触媒を得るためには、比表面積を増やすことが有効であると考えられている
。これまでに用いられているゲーサイト光触媒の比表面積は、非特許文献１に示すように
２５ｍ２／ｇと小さい。これを解決するため、一般には光触媒の粒子径を小さくすること
で比表面積を増し、光触媒活性の向上を図る。ゲーサイトを含む酸化鉄材料の微粒子を得
るには、非特許文献２で述べられているように、合成中の水溶液にキレート剤としての酢
酸塩や金属イオンを添加する方法が知られている。しかし、これらの方法で得られたゲー
サイトは結晶性が低く、高い比表面積の割には光触媒活性が低いという問題がある。これ
は、結晶性の低下によって増える格子欠陥が、光触媒反応の担い手となるキャリアの再結
合を促進させ、その結果として反応効率が落ちることに起因している。
In order to obtain a highly active photocatalyst, it is considered effective to increase the specific surface area. The specific surface area of the goethite photocatalyst used so far is as small as 25 m 2 / g as shown in Non-Patent Document 1. In order to solve this, in general, the specific surface area is increased by reducing the particle diameter of the photocatalyst to improve the photocatalytic activity. In order to obtain fine particles of iron oxide material containing goethite, as described in Non-Patent Document 2, a method of adding acetate or metal ion as a chelating agent to an aqueous solution during synthesis is known. However, there is a problem that goethite obtained by these methods has low crystallinity and low photocatalytic activity for a high specific surface area. This is due to the fact that the lattice defects that increase due to the decrease in crystallinity promote the recombination of carriers that are responsible for the photocatalytic reaction, resulting in a decrease in reaction efficiency.
本発明は、高い結晶性と大きな比表面積を有することによって高い光触媒活性を示すゲ
ーサイト光触媒と、この光触媒の製造法を提供することを目的とする。
An object of this invention is to provide the goethite photocatalyst which shows high photocatalytic activity by having high crystallinity and a large specific surface area, and the manufacturing method of this photocatalyst.
上記目的を達成するために、本発明の第１の態様は、ゲーサイトからなり、長軸長さが
１００ｎｍ以上、長軸長さと短軸長さの比が４〜１０の範囲の針状の形状をなし、比表面
積が１００ｍ２／ｇ以上であるゲーサイト光触媒であることを要旨とする。
In order to achieve the above object, the first aspect of the present invention is a needle-like shape comprising a goethite, having a major axis length of 100 nm or more and a ratio of the major axis length to the minor axis length of 4 to 10. The gist is a goethite photocatalyst having a shape and a specific surface area of 100 m 2 / g or more.
本発明の第２の態様は、水酸化鉄（II）を、ポリエチレングリコール水溶液中で酸化す
る工程を含む、第１の態様で述べた形状のゲーサイト光触媒の製造方法であることを要旨
とする。
The gist of the second aspect of the present invention is a method for producing a goethite photocatalyst having the shape described in the first aspect, which comprises a step of oxidizing iron (II) hydroxide in a polyethylene glycol aqueous solution. .
本発明によれば、高い結晶性と大きな比表面積を有することで高い光触媒活性を示すゲ
ーサイト光触媒と、この光触媒の製造法を提供することができる。
ADVANTAGE OF THE INVENTION According to this invention, the goethite photocatalyst which shows high photocatalytic activity by having high crystallinity and a large specific surface area, and the manufacturing method of this photocatalyst can be provided.
次に、図面を参照して本発明の実施の形態を説明する。以下に示す実施の形態は、本発
明の技術的思想を具体化するための装置や方法を例示するものであって、本発明の技術的
思想は、構成する材料、形状、構造などを下記のものに特定するものではない。特に、以
下におけるゲーサイト光触媒とその製造方法は、一例であり、特許請求の範囲に記載した
趣旨の範囲内であれば、この変形例を含めて、これ以外の種々の製造方法により、実現可
能であることは勿論である。このように、本発明の技術的思想は、特許請求の範囲に記載
された技術的範囲内において、種々の変更を加えることができる。
Next, embodiments of the present invention will be described with reference to the drawings. The embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention includes the following materials, shapes, structures, etc. It is not something specific. In particular, the following goethite photocatalyst and its manufacturing method are examples, and can be realized by various other manufacturing methods including this modification as long as it is within the scope of the claims. Of course. Thus, the technical idea of the present invention can be variously modified within the technical scope described in the claims.
本発明の実施の形態に係るゲーサイト光触媒は、ゲーサイトからなる針状（または棒状
）の粒子であって、長軸長さが１００ｎｍ以上、長軸長さと短軸長さの比が４〜１０の範
囲の針状（または棒状）の形状をなし、比表面積が１００ｍ２／ｇ以上のゲーサイトから
なる粒子である。ここで「比表面積」は、ゲーサイト光触媒の表面積と質量との比で定義
される量であり、本発明においては、ＢＥＴ法により測定した比表面積の値を用いている
。長軸長さは、長くなりすぎると比表面積の低下に繋がるため、１００〜１０００ｎｍの
範囲にあることが望ましい。例えば、長軸長さと短軸長さの比が１５〜２０の場合では、
長軸長さが１２００ｎｍ程度になると、比表面積が５０ｍ２／ｇ程度に低下するので好ま
しくない。より好ましくは、１００〜３００ｎｍの範囲であり、最も良いのは１００〜２
００ｎｍの範囲である。長軸長さの標準偏差は±５０ｎｍ以内であることが望ましい。短
軸長さについて特に制限はないが、１０〜８０ｎｍの範囲にあることが望ましい。比表面
積は、大きくなりすぎる場合は結晶性が低下し、かえって光触媒活性が低下することにな
るため、１００〜２００ｍ２／ｇの範囲にあることが望ましい。さらに好ましくは、１０
０〜１５０ｍ２／ｇの範囲であり、最も好ましいのは１００〜１３０ｍ２／ｇの範囲であ
る。
The goethite photocatalyst according to the embodiment of the present invention is needle-like (or rod-like) particles made of goethite, the major axis length is 100 nm or more, and the ratio of the major axis length to the minor axis length is 4 to 4. It is a particle made of goethite having a needle-like (or rod-like) shape in the range of 10 and a specific surface area of 100 m 2 / g or more. Here, the “specific surface area” is an amount defined by the ratio between the surface area and the mass of the goethite photocatalyst. In the present invention, the value of the specific surface area measured by the BET method is used. If the long axis length is too long, the specific surface area is reduced, and therefore, the long axis length is desirably in the range of 100 to 1000 nm. For example, when the ratio of the major axis length to the minor axis length is 15 to 20,
A major axis length of about 1200 nm is not preferable because the specific surface area is reduced to about 50 m 2 / g. More preferably, it is in the range of 100 to 300 nm, the best being 100 to 2
The range is 00 nm. The standard deviation of the major axis length is desirably within ± 50 nm. Although there is no restriction | limiting in particular about short axis length, It is desirable to exist in the range of 10-80 nm. When the specific surface area becomes too large, the crystallinity is lowered and the photocatalytic activity is lowered. Therefore, the specific surface area is desirably in the range of 100 to 200 m 2 / g. More preferably, 10
The range is 0 to 150 m 2 / g, and the most preferable range is 100 to 130 m 2 / g.
また、本発明のゲーサイト光触媒には、上述の構成に加えて、ゲーサイトの表面に金属
触媒が担持されたものであってもよい。金属触媒は、ゲーサイト光触媒表面で起こる酸化
還元反応の助触媒として働き、その結果として光触媒活性をより一層高めることができる
。金属触媒としては、例えば白金（Pt）、パラジウム（Pd）、ルテニウム（Ru）、金（Au
）、銀（Ag）、イリジウム（Ir）、ニッケル（Ni）触媒などがあげられる。この中でも特
に白金またはパラジウム触媒が好ましい。金属触媒の担持量は、ゲーサイト光触媒に対し
て０．２〜５質量％程度であるのが好ましい。５質量％以上になると、かえって活性を落
とす場合がある。
In addition to the above-described configuration, the goethite photocatalyst of the present invention may have a metal catalyst supported on the surface of the goethite. The metal catalyst acts as a promoter for the oxidation-reduction reaction that occurs on the surface of the goethite photocatalyst, and as a result, the photocatalytic activity can be further enhanced. Examples of metal catalysts include platinum (Pt), palladium (Pd), ruthenium (Ru), and gold (Au
), Silver (Ag), iridium (Ir), nickel (Ni) catalyst and the like. Of these, platinum or palladium catalysts are particularly preferred. The supported amount of the metal catalyst is preferably about 0.2 to 5% by mass with respect to the goethite photocatalyst. If it is 5% by mass or more, the activity may be reduced.
前述の本発明の実施の形態に係るゲーサイト光触媒は、水酸化鉄（II）をポリエチレン
グリコール溶液中で酸化することで製造することができる。
The goethite photocatalyst according to the above-described embodiment of the present invention can be produced by oxidizing iron (II) hydroxide in a polyethylene glycol solution.
具体的には、まず図１に示すように、鉄（II）塩１１とポリエチレングリコール１２を
溶媒１３Ｌに溶解させ、鉄（II）／ポリエチレングリコール混合溶液１４Ｌを得る。鉄（
II）塩１１とポリエチレングリコール１２を溶媒１３Ｌに加える順序は問わないが、完全
に溶解させることが必要である。溶媒１３Ｌとしては、通常は水を用いればよいが、後の
工程や生成物に支障がないかぎり、適宜アルコール、塩化物、硫酸塩など、水に対して混
和性や溶解性のある成分が含まれていても差し支えない。鉄（II）塩１１としては、硫酸
鉄（II）、硫酸アンモニウム鉄（II）、硝酸鉄（II）、塩化鉄（II）といった水溶性の鉄
（II）塩を用いればよい。鉄（II）塩１１の濃度は、続く工程における添加物の混合や撹
拌、生成物の組成に支障がないかぎり、自由に設定してよい。ポリエチレングリコール１
２の重合度に特に制限は無いが１００以上であることが好ましく、さらに好ましくは６０
００以上である。ポリエチレングリコール１２の添加量は、鉄（II）／ポリエチレングリ
コール混合溶液１４Ｌにおいて０．５〜１５質量％となるようにするのが適当であり、さ
らに好ましくは、０．５〜５質量％の範囲である。
Specifically, first, as shown in FIG. 1, an iron (II) salt 11 and polyethylene glycol 12 are dissolved in a solvent 13L to obtain an iron (II) / polyethylene glycol mixed solution 14L. iron(
II) The order in which the salt 11 and the polyethylene glycol 12 are added to the solvent 13L is not limited, but it is necessary to completely dissolve them. As the solvent 13L, water is usually used. However, as long as there is no hindrance to the subsequent process or product, components that are miscible or soluble in water such as alcohol, chloride, sulfate, etc. are included as appropriate. It can be done. As the iron (II) salt 11, a water-soluble iron (II) salt such as iron (II) sulfate, iron (II) ammonium sulfate, iron (II) nitrate, or iron (II) chloride may be used. The concentration of the iron (II) salt 11 may be freely set as long as it does not hinder the mixing and stirring of additives and the composition of the product in the subsequent steps. Polyethylene glycol 1
The degree of polymerization of 2 is not particularly limited but is preferably 100 or more, more preferably 60
00 or more. The addition amount of polyethylene glycol 12 is suitably 0.5 to 15% by mass in the iron (II) / polyethylene glycol mixed solution 14L, and more preferably in the range of 0.5 to 5% by mass. It is.
これに続く工程では、図２で示すように、鉄（II）／ポリエチレングリコール混合溶液
２１Ｌに塩基性溶液２２Ｌを混合し、鉄（II）イオン２３を水酸化鉄（II）２４に加水分
解して水酸化鉄（II）／ポリエチレングリコール混合溶液２５Ｌを得る。塩基性溶液２２
Ｌとしては、水酸化ナトリウム、水酸化カリウム、アンモニアなどの塩基を含む水溶液を
適宜用いればよい。また、この塩基は、溶液としてではなく固体または気体のものを、直
接、鉄（II）／ポリエチレングリコール混合溶液２１Ｌに加えて溶解させ、これによって
水酸化鉄（II）／ポリエチレングリコール混合溶液２５Ｌを得ても差し支えない。いずれ
の方法によっても、その添加量は、水酸化鉄（II）／ポリエチレングリコール混合溶液２
５ＬのｐＨが８以上になるように調整すればよい。これよりｐＨが低い条件では、次の工
程において、レピドクロサイトなど、ゲーサイト以外の鉄酸化物が生成しやすくなる。尚
、一般に鉄（II）イオンや水酸化鉄（II）は、酸素により酸化されやすいため、これら一
連の操作は、不活性ガス雰囲気中で行うことが望ましい。不活性ガスとしてはＡｒ、Ｎ２
、Ｈｅなどを用いればよい。
In the subsequent step, as shown in FIG. 2, the basic solution 22L is mixed with the iron (II) / polyethylene glycol mixed solution 21L to hydrolyze the iron (II) ions 23 into iron hydroxide (II) 24. As a result, 25 L of iron hydroxide (II) / polyethylene glycol mixed solution is obtained. Basic solution 22
As L, an aqueous solution containing a base such as sodium hydroxide, potassium hydroxide, or ammonia may be used as appropriate. In addition, this base is not a solution but a solid or a gas is directly added to and dissolved in the iron (II) / polyethylene glycol mixed solution 21L, whereby 25 L of iron hydroxide (II) / polyethylene glycol mixed solution is dissolved. You can get it. In any of the methods, the amount added is iron (II) hydroxide / polyethylene glycol mixed solution 2
What is necessary is just to adjust so that pH of 5L may be 8 or more. Under conditions where the pH is lower than this, iron oxides other than goethite, such as lepidoclocite, are easily generated in the next step. In general, iron (II) ions and iron (II) hydroxide are easily oxidized by oxygen. Therefore, these series of operations are desirably performed in an inert gas atmosphere. As inert gas, Ar, N 2
, He or the like may be used.
次に、図３に示すように、水酸化鉄（II）／ポリエチレングリコール混合溶液３１Ｌに
分子状酸素３２を添加する。これにより分子状酸素３２が水酸化鉄（II）／ポリエチレン
グリコール混合溶液３１Ｌに含まれる水酸化鉄（II）３３を酸化し、溶液中にゲーサイト
の結晶粒子が析出する。すなわち、本発明のゲーサイト光触媒３４が得られる。ここで、
分子状酸素３２を加える方法に特に制限はないが、水酸化鉄（II）／ポリエチレングリコ
ール混合溶液３１Ｌを大気環境などの酸素含有雰囲気下に曝露する、水酸化鉄（II）／ポ
リエチレングリコール混合溶液３１Ｌに酸素ガスを吹き込む、溶存酸素を含む溶液を水酸
化鉄（II）／ポリエチレングリコール混合溶液３１Ｌに添加するといった方法があげられ
る。分子状酸素３２を添加する際には、水酸化鉄（II）／ポリエチレングリコール混合溶
液３１Ｌの温度を５〜８０℃の範囲に設定しておくことが望ましい。さらに好ましくは５
〜６０℃の範囲である。これより高い温度条件、例えば８０℃を超える温度条件では、マ
グネタイトが生成しやすく、ゲーサイトを得にくくなる。逆に５℃より低い温度では、酸
化速度が遅くなるのみならず、得られるゲーサイトの結晶性が著しく低いため光触媒が低
下する。ゲーサイト光触媒３４を得た後は、遠心分離やろ過により洗浄分離、乾燥してゲ
ーサイト光触媒３４の粉末を得ることができるが、用途によっては必ずしも乾燥する必要
はない。
Next, as shown in FIG. 3, molecular oxygen 32 is added to the iron hydroxide (II) / polyethylene glycol mixed solution 31L. As a result, molecular oxygen 32 oxidizes iron (II) hydroxide 33 contained in 31 L of iron hydroxide (II) / polyethylene glycol mixed solution, and crystal grains of goethite are precipitated in the solution. That is, the goethite photocatalyst 34 of the present invention is obtained. here,
The method of adding molecular oxygen 32 is not particularly limited, but iron (II) hydroxide / polyethylene glycol mixed solution in which iron hydroxide (II) / polyethylene glycol mixed solution 31L is exposed to an oxygen-containing atmosphere such as the atmospheric environment. For example, oxygen gas is blown into 31 L, and a solution containing dissolved oxygen is added to 31 L of iron (II) hydroxide / polyethylene glycol mixed solution. When the molecular oxygen 32 is added, it is desirable to set the temperature of the iron hydroxide (II) / polyethylene glycol mixed solution 31L in the range of 5 to 80 ° C. More preferably 5
It is the range of -60 degreeC. If the temperature is higher than this, for example, if the temperature exceeds 80 ° C., magnetite is easily generated, and it is difficult to obtain goethite. On the other hand, at a temperature lower than 5 ° C., not only the oxidation rate is slowed but also the photocatalyst is lowered because the crystallinity of the obtained goethite is extremely low. After obtaining the goethite photocatalyst 34, it is possible to obtain a powder of the goethite photocatalyst 34 by washing, separating and drying by centrifugation or filtration, but it is not always necessary to dry depending on the application.
ゲーサイト光触媒にさらに金属触媒を担持する場合は、上記のようにしてゲーサイト光
触媒を得た後、公知の方法、例えば光電着法、混練法、真空蒸着法、スパッタリング法な
どを用いて金属触媒を担持させることができる。この中でも、光電着法によるものが好ま
しい。
In the case of further supporting a metal catalyst on the goethite photocatalyst, after obtaining the goethite photocatalyst as described above, the metal catalyst can be obtained by using a known method such as a photo-deposition method, a kneading method, a vacuum deposition method, a sputtering method, etc. Can be supported. Among these, the one based on the photo-deposition method is preferable.
こうして得られた本発明の実施の形態に係るゲーサイト光触媒は、光照射下で有機物を
分解して水素やメタンといった化学燃料を発生する反応や、有機物を水と二酸化炭素に酸
化分解する反応に使用することができる。また、ゲーサイト光触媒は可視光に応答するた
め、太陽光だけではなく、蛍光灯やＬＥＤなどの可視光を多く含む光源を利用することも
できる。使用にあたっては、粉末状のまま用いてもよいし、シリカやアルミナなどの無機
物に担持したり、壁などに塗布して用いてもよい。
The goethite photocatalyst according to the embodiment of the present invention thus obtained is used for reactions that decompose organic substances under light irradiation to generate chemical fuels such as hydrogen and methane, and reactions that oxidize and decompose organic substances into water and carbon dioxide. Can be used. In addition, since the goethite photocatalyst responds to visible light, it is possible to use not only sunlight but also a light source containing a lot of visible light such as a fluorescent lamp or LED. In use, the powder may be used as it is, or may be supported on an inorganic material such as silica or alumina, or may be applied to a wall or the like.
以下、実施例によって本発明をより詳細に説明するが、本発明はかかる実施例に限定さ
れるものではない。
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this Example.
＜光触媒の調製＞
実施例１ ゲーサイト光触媒の調製
２００ｍｌの純水を、Ａｒガス（純度９９．９９９％以上）でバブリングして溶存酸素
を除去し、これに硫酸鉄（II）・７水和物２．０ｇを加えて硫酸鉄（II）水溶液を得た。
この水溶液に、ポリエチレングリコール（重合度２０，０００）を０．５質量％となるよ
うに１．０ｇ加えて溶解させ、硫酸鉄（II）／ポリエチレングリコール混合溶液を得た。
次に、この混合溶液を撹拌しながら１０ｍｏｌ／ｌ水酸化ナトリウム水溶液を２０ｍｌ加
え、水酸化鉄（II）／ポリエチレングリコール混合溶液を得た。ここで、水酸化鉄（II）
／ポリエチレングリコール混合溶液へのＡｒガスのバブリングを停止し、空気によるバブ
リングを開始した。バブリングを継続したまま１８時間撹拌を続け、水酸化鉄（II）を十
分に酸化した。得られた褐色の析出物を、遠心分離によって純水洗浄して分離し、８０℃
で乾燥した。その後、乳鉢で粉砕して実施例１のゲーサイト光触媒を得た。
<Preparation of photocatalyst>
Example 1 Preparation of Goethite Photocatalyst 200 ml of pure water was bubbled with Ar gas (purity 99.999% or more) to remove dissolved oxygen, and 2.0 g of iron (II) sulfate heptahydrate was added thereto. In addition, an aqueous iron (II) sulfate solution was obtained.
To this aqueous solution, 1.0 g of polyethylene glycol (polymerization degree 20,000) was added and dissolved so as to be 0.5% by mass to obtain an iron (II) sulfate / polyethylene glycol mixed solution.
Next, 20 ml of 10 mol / l sodium hydroxide aqueous solution was added while stirring the mixed solution to obtain an iron (II) hydroxide / polyethylene glycol mixed solution. Where iron hydroxide (II)
/ Bubbling of Ar gas into the polyethylene glycol mixed solution was stopped, and bubbling with air was started. Stirring was continued for 18 hours while continuing bubbling to sufficiently oxidize iron (II) hydroxide. The obtained brown precipitate was separated by washing with pure water by centrifugal separation.
And dried. Then, the goethite photocatalyst of Example 1 was obtained by pulverizing with a mortar.
実施例２
実施例１における硫酸鉄（II）水溶液へのポリエチレングリコール添加量を、２．０質
量％となるよう４．１ｇにし、他は実施例１と同一の条件でゲーサイト光触媒を得て実施
例２とした。
Example 2
The amount of polyethylene glycol added to the iron (II) sulfate aqueous solution in Example 1 was changed to 4.1 g so as to be 2.0% by mass, and a goethite photocatalyst was obtained under the same conditions as in Example 1 except for Example 2. It was.
実施例３
実施例１における硫酸鉄（II）水溶液へのポリエチレングリコール添加量を、４．０質
量％となるよう８．４ｇにし、他は実施例１と同一の条件でゲーサイト光触媒を得て実施
例３とした。
Example 3
A goethite photocatalyst was obtained under the same conditions as in Example 1 except that the amount of polyethylene glycol added to the iron (II) sulfate aqueous solution in Example 1 was 4.0% by mass, and the others were the same as in Example 1. It was.
実施例４
実施例１における硫酸鉄（II）水溶液へのポリエチレングリコール添加量を、１５．０
質量％となるよう３５．６ｇにし、他は実施例１と同一の条件でゲーサイト光触媒を得て
実施例４とした。
Example 4
The amount of polyethylene glycol added to the iron (II) sulfate aqueous solution in Example 1 was 15.0.
A goethite photocatalyst was obtained as Example 4 under the same conditions as in Example 1 except that the amount was 35.6 g so as to be mass%.
実施例５ 金属触媒を担持したゲーサイト光触媒の調製
実施例１で得られたゲーサイト光触媒０．１ｇを、５ｍｍｏｌ／ｌ酢酸ナトリウム水溶
液に分散させ、塩化白金酸を白金担持量がゲーサイト光触媒に対して１質量％になるよう
に加えた。この分散液に、水銀ランプ（照射強度約１８０ｍＷ／ｃｍ２）で５時間光照射
を行い、ゲーサイト光触媒の表面に白金を担持した。その後、遠心分離によって純水で洗
浄して分離し、乾燥して得られた白金担持ゲーサイト光触媒を実施例５とした。
Example 5 Preparation of a goethite photocatalyst carrying a metal catalyst 0.1 g of the goethite photocatalyst obtained in Example 1 was dispersed in a 5 mmol / l sodium acetate aqueous solution, and the amount of platinum chloroplatinic acid supported on the goethite photocatalyst. It added so that it might become 1 mass% with respect to it. This dispersion was irradiated with light for 5 hours with a mercury lamp (irradiation intensity of about 180 mW / cm 2 ), and platinum was supported on the surface of the goethite photocatalyst. Thereafter, the platinum-supported goethite photocatalyst obtained by washing with pure water by centrifugation and separating and drying was designated as Example 5.
実施例６
実施例５における塩化白金酸を塩化金酸にし、その量は金担持量がゲーサイト光触媒に
対して１質量％になるようにし、他は実施例５と同様にして金担持ゲーサイト光触媒を得
て実施例６とした。
Example 6
Chloroplatinic acid in Example 5 was changed to chloroauric acid, and the amount of gold supported was 1% by mass with respect to the goethite photocatalyst. Otherwise, a gold-supported goethite photocatalyst was obtained in the same manner as in Example 5. Example 6 was made.
実施例７
実施例５における塩化白金酸を塩化パラジウムにし、その量はパラジウム担持量がゲー
サイト光触媒に対して１質量％になるようにし、他は実施例５と同様にしてパラジウム担
持ゲーサイト光触媒を得て実施例７とした。
Example 7
The chloroplatinic acid in Example 5 was changed to palladium chloride, and the amount thereof was adjusted so that the amount of supported palladium was 1% by mass with respect to the goethite photocatalyst. Example 7 was adopted.
実施例８
実施例５における塩化白金酸を硝酸銀にし、その量は銀担持量がゲーサイト光触媒に対
して１質量％になるようにし、他は実施例５と同様にして銀担持ゲーサイト光触媒を得て
、実施例８とした。
Example 8
The chloroplatinic acid in Example 5 was changed to silver nitrate, and the amount thereof was adjusted so that the amount of supported silver was 1% by mass with respect to the goethite photocatalyst. Otherwise, a silver-supported goethite photocatalyst was obtained in the same manner as in Example 5. Example 8 was adopted.
比較例１
２００ｍｌの純水に、Ａｒガス（純度９９．９９９％以上）でバブリングしながら硫酸
鉄（II）・７水和物２．０ｇを加えて撹拌し、硫酸鉄（II）水溶液を得た。この水溶液に
１０ｍｏｌ／ｌ水酸化ナトリウム水溶液を２０ｍｌ加え、水酸化鉄（II）分散液を得た。
ここで、水酸化鉄（II）分散液のバブリングに用いていた気体をＡｒから空気に切り替え
、１８時間撹拌を続けて水酸化鉄（II）を酸化した。こうして得られた褐色の析出物を、
遠心分離によって純水洗浄し、８０℃で乾燥した後、乳鉢で粉砕し得られたゲーサイトを
比較例１とした。
Comparative Example 1
To 200 ml of pure water, 2.0 g of iron (II) sulfate heptahydrate was added while bubbling with Ar gas (purity 99.999% or more) and stirred to obtain an aqueous iron (II) sulfate solution. 20 ml of 10 mol / l sodium hydroxide aqueous solution was added to this aqueous solution to obtain an iron (II) hydroxide dispersion.
Here, the gas used for bubbling the iron (II) hydroxide dispersion was switched from Ar to air, and stirring was continued for 18 hours to oxidize the iron (II) hydroxide. The brown precipitate thus obtained is
A goethite obtained by washing with pure water by centrifugation, drying at 80 ° C. and then pulverizing with a mortar was used as Comparative Example 1.
比較例２
２００ｍｌの純水に、Ａｒガス（純度９９．９９９％以上）でバブリングしながら硫酸
鉄（II）・７水和物２．０ｇを加えて撹拌し、硫酸鉄（II）水溶液を得た。この水溶液に
炭酸ナトリウムを３．４ｇ加え、水酸化鉄（II）分散液を得た。ここで、水酸化鉄（II）
分散液のバブリングに用いていた気体をＡｒから空気に切り替え、１８時間撹拌を続けて
水酸化鉄（II）を酸化した。得られた褐色の析出物を、遠心分離によって純水洗浄し８０
℃で乾燥した。その後、乳鉢で粉砕し、得られたゲーサイトを比較例２とした。
Comparative Example 2
To 200 ml of pure water, 2.0 g of iron (II) sulfate heptahydrate was added while bubbling with Ar gas (purity 99.999% or more) and stirred to obtain an aqueous iron (II) sulfate solution. To this aqueous solution, 3.4 g of sodium carbonate was added to obtain an iron hydroxide (II) dispersion. Where iron hydroxide (II)
The gas used for bubbling the dispersion was switched from Ar to air, and stirring was continued for 18 hours to oxidize iron (II) hydroxide. The resulting brown precipitate was washed with pure water by centrifugation and 80
Dried at ℃. Then, the goethite obtained by pulverizing with a mortar was used as Comparative Example 2.
比較例３
２００ｍｌの純水に、Ａｒガス（純度９９．９９９％以上）でバブリングしながら硫酸
鉄（II）・７水和物２．０ｇを加えて撹拌し、硫酸鉄（II）水溶液を得た。この水溶液に
酢酸ナトリウム１．１ｇと１０ｍｏｌ／ｌ水酸化ナトリウム水溶液を２０ｍｌ加え、水酸
化鉄（II）分散液を得た。ここで、水酸化鉄（II）分散液のバブリングに用いていた気体
をＡｒから空気に切り替え、１８時間撹拌を続けて水酸化鉄（II）を酸化した。こうして
得られた褐色の析出物を、遠心分離によって純水洗浄し８０℃で乾燥した。その後、乳鉢
で粉砕し、得られたゲーサイトを比較例３とした。
Comparative Example 3
To 200 ml of pure water, 2.0 g of iron (II) sulfate heptahydrate was added while bubbling with Ar gas (purity 99.999% or more) and stirred to obtain an aqueous iron (II) sulfate solution. To this aqueous solution, 1.1 g of sodium acetate and 20 ml of a 10 mol / l aqueous sodium hydroxide solution were added to obtain an iron (II) hydroxide dispersion. Here, the gas used for bubbling the iron (II) hydroxide dispersion was switched from Ar to air, and stirring was continued for 18 hours to oxidize the iron (II) hydroxide. The brown precipitate thus obtained was washed with pure water by centrifugation and dried at 80 ° C. Then, the goethite obtained by pulverizing with a mortar was used as Comparative Example 3.
＜構造評価＞
実施例１〜４及び比較例１〜３のゲーサイト光触媒の構造を、粉末エックス線回折、走
査型電子顕微鏡観察、及び比表面積測定によって評価した。
<Structural evaluation>
The structures of the goethite photocatalysts of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by powder X-ray diffraction, scanning electron microscope observation, and specific surface area measurement.
まず、図４に粉末エックス線回折（島津製作所製、ＸＤ−６１０）による測定結果を示
す。２θ＝１７．８°付近、２１．２°付近、２６．３°付近、３３．２°付近、３４．
７°付近、３６．６°付近、４０．０°付近、４１．２°付近、５３．２°付近、５９．
０°付近のすべてのピークがゲーサイトに由来することが確認できたことから、実施例１
〜４及び比較例１〜３の全がゲーサイトであることがわかる。また、２θ＝２１．２°付
近と３６．６°付近のピークの強度に着目すると、実施例１から４へと少しずつ強くなっ
ていくことから、ポリエチレングリコールの添加が結晶性を低下させることはなく、添加
により結晶性が高まることがわかる。逆に、比較例２と比較例３では、添加物の存在によ
って比較例１よりも特に２θ＝２１．２°付近と３６．６°付近のピーク強度が明らかに
低下し、ブロードになっていることから、結晶性が著しく低下していることがわかる。
First, the measurement result by powder X-ray diffraction (made by Shimadzu Corporation, XD-610) is shown in FIG. 2θ = 17.8 °, 21.2 °, 26.3 °, 33.2 °, 34.
Near 7 °, 36.6 °, 40.0 °, 41.2 °, 53.2 °, 59.
Since it was confirmed that all peaks near 0 ° were derived from goethite, Example 1
It can be seen that all of -4 and Comparative Examples 1 to 3 are goethite. In addition, when attention is focused on the peak intensities near 2θ = 21.2 ° and 36.6 °, it gradually increases from Example 1 to 4, so that the addition of polyethylene glycol decreases the crystallinity. It can be seen that the crystallinity is increased by the addition. On the contrary, in Comparative Example 2 and Comparative Example 3, the peak intensities in the vicinity of 2θ = 21.2 ° and in the vicinity of 36.6 ° are clearly lower and broader than Comparative Example 1 due to the presence of the additive. This shows that the crystallinity is significantly lowered.
次に、実施例１〜４のゲーサイト光触媒の形状を走査型電子顕微鏡（日立ハイテクノロ
ジーズ社製、ＳＵ６６００）によって観察した。その結果を図５〜８に示す。これによる
と、実施例１〜４のいずれにおいても、長軸長さが８０〜２００ｎｍ程度の範囲にあり、
短軸長が２０〜６０ｎｍ程度の範囲にあり、長軸長さと短軸長さの比が４〜１０の範囲に
あることから、針状の粒子が得られていることがわかる。比較例１〜３についても同様に
電子顕微鏡により観察した結果、比較例１では長軸長さが３０〜１５０ｎｍ程度の範囲、
短軸長が１５〜６０ｎｍ程度の範囲にあり、針状粒子が、比較例２と比較例３では、長軸
長さが４０〜１００ｎｍ程度の範囲、短軸長が４０〜６０ｎｍ程度の範囲にあり、微細な
楕円形の粒子が得られていた。ここで、これらの粒子の大きさを比較するため、電子顕微
鏡写真から無作為に１００個の粒子を選び長軸長さを読み取り、平均と標準偏差を求めた
。比較例２と比較例３については、楕円形粒子の長軸長さについて同様に測定した。得ら
れた粒子の平均長軸長さを表１に示した。また、ＢＥＴ法（島津製作所製、Ｆｌｏｗｓｏ
ｒｂII２３００）によって測定した比表面積についても、あわせて表１に示した。尚、実
施例１〜４における粒子の幅（短軸長さ）は１０〜６０ｎｍであった。
Next, the shapes of the goethite photocatalysts of Examples 1 to 4 were observed with a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, SU6600). The results are shown in FIGS. According to this, in any of Examples 1 to 4, the major axis length is in the range of about 80 to 200 nm,
Since the minor axis length is in the range of about 20 to 60 nm and the ratio of the major axis length to the minor axis length is in the range of 4 to 10, it can be seen that acicular particles are obtained. As a result of observing similarly with Comparative Examples 1 to 3 with an electron microscope, in Comparative Example 1, the major axis length is in the range of about 30 to 150 nm,
The short axis length is in the range of about 15 to 60 nm, and the acicular particles are in the range of about 40 to 100 nm in the long axis length and in the range of about 40 to 60 nm in the short axis length in Comparative Example 2 and Comparative Example 3. In other words, fine elliptical particles were obtained. Here, in order to compare the sizes of these particles, 100 particles were randomly selected from the electron micrograph, the major axis length was read, and the average and standard deviation were obtained. In Comparative Example 2 and Comparative Example 3, the major axis length of the elliptical particles was measured in the same manner. Table 1 shows the average major axis length of the obtained particles. The BET method (Shimadzu Corporation, Flowso
The specific surface area measured by rbII2300) is also shown in Table 1. In addition, the width | variety (short-axis length) of the particle | grains in Examples 1-4 was 10-60 nm.
表１の結果から、比較例１〜３では、粒子の平均長軸長さが短くなると比表面積が増し
ていることがわかる。前述の粉末エックス線回折の結果も考慮すると、これらは結晶性を
低下させることによって高い比表面積を得ているといえる。一方、実施例１〜４において
は、低濃度のポリエチレングリコール添加では比表面積が高いが、高濃度になるにつれて
比表面積が低下した。粒子の平均長軸長さは、ポリエチレングリコール濃度の上昇と共に
一旦は伸びるが、さらに高濃度では短くなることがわかる。
From the results in Table 1, it can be seen that in Comparative Examples 1 to 3, the specific surface area increases as the average major axis length of the particles decreases. Considering the result of the above-mentioned powder X-ray diffraction, it can be said that these have obtained a high specific surface area by reducing crystallinity. On the other hand, in Examples 1 to 4, the specific surface area was high when polyethylene glycol was added at a low concentration, but the specific surface area was decreased as the concentration was increased. It can be seen that the average major axis length of the particles once increases as the polyethylene glycol concentration increases, but becomes shorter at higher concentrations.
以上のように、ポリエチレングリコールの添加は、ゲーサイト粒子の結晶性とサイズを
維持したまま比表面積を上下させる効果を持つ。これは、比較例２および３に示したよう
な、粒子サイズと結晶性を同時に低下させて比表面積を向上させるような従来の添加剤と
は異なる効果である。
As described above, the addition of polyethylene glycol has the effect of raising and lowering the specific surface area while maintaining the crystallinity and size of goethite particles. This is an effect different from that of the conventional additive as shown in Comparative Examples 2 and 3 in which the specific surface area is improved by simultaneously reducing the particle size and crystallinity.
＜光触媒反応活性の評価＞
次に、実施例１〜８及び比較例１〜３のゲーサイト光触媒の活性を、アセトアルデヒド
の光触媒的酸化分解によって生じる二酸化炭素の生成速度によって比較した。
<Evaluation of photocatalytic reaction activity>
Next, the activities of the goethite photocatalysts of Examples 1 to 8 and Comparative Examples 1 to 3 were compared by the production rate of carbon dioxide generated by photocatalytic oxidative decomposition of acetaldehyde.
まず、光触媒反応容器としてガラス製の密閉容器（容積２０ｍｌ）を用い、これに１０
ｍｇのゲーサイト光触媒と５０ｍｍｏｌ／ｌアセトアルデヒド水溶液１０ｍｌを加え、大
気条件のままガラス容器を密閉した。このまま暗所にて１時間撹拌し、十分にゲーサイト
光触媒を分散させた。次に、水銀ランプ（照射強度約１００ｍＷ／ｃｍ２）で光を照射し
た。この条件では、アセトアルデヒドが水と二酸化炭素に分解する反応が起こる（ＣＨ３
ＣＨＯ＋５／２Ｏ２→２ＣＯ２＋２Ｈ２Ｏ）。光照射を５時間続けた後、容器内のガスを
採取してガスクロマトグラフを用いて二酸化炭素生成量を測定し、その結果から二酸化炭
素生成速度を求めた。こうして得られた二酸化炭素生成速度を表２に示した。
First, a glass sealed container (volume 20 ml) was used as the photocatalytic reaction container, and 10
mg of goethite photocatalyst and 10 ml of 50 mmol / l acetaldehyde aqueous solution were added, and the glass container was sealed under atmospheric conditions. The mixture was stirred in the dark for 1 hour to fully disperse the goethite photocatalyst. Next, light was irradiated with a mercury lamp (irradiation intensity of about 100 mW / cm 2 ). Under this condition, a reaction occurs in which acetaldehyde is decomposed into water and carbon dioxide (CH 3
CHO + 5 / 2O 2 → 2CO 2 + 2H 2 O). After the light irradiation was continued for 5 hours, the gas in the container was collected, the amount of carbon dioxide produced was measured using a gas chromatograph, and the carbon dioxide production rate was determined from the result. The carbon dioxide production rate thus obtained is shown in Table 2.
表２に示すように、比較例１〜３の従来法によるゲーサイト光触媒と比較し、本発明の
実施の形態に係るゲーサイト光触媒は二酸化炭素生成速度が高く、光触媒活性が高いとい
える。特に、実施例１〜３のポリエチレングリコール添加量が０．５〜４．０質量％の範
囲で活性が高く、実施例２では従来の倍以上の活性を示した。表１に示した構造評価結果
も含めると、針状粒子の長軸長さが１００ｎｍ以上であり、比表面積が１００ｍ２／ｇ以
上であるゲーサイト光触媒が特に高い活性を有していることがわかる。言い換えれば、針
状粒子の長軸長さが１００ｎｍ以上であり、長軸長さに対する比表面積の比（比表面積／
長さ）が、０．８〜１．１の範囲にあるものが高活性である。ここで、単位表面積あたり
の活性（二酸化炭素生成速度／（比表面積×光触媒使用量））を算出すると、比較例１で
は０．１０μｍｏｌ／（ｈ・ｍ２）程度であるが、実施例２では０．１５μｍｏｌ／（ｈ
・ｍ２）と大きく上昇していることがわかる。つまり、本発明の実施の形態に係るゲーサ
イト光触媒の活性が高い理由は、大きな比表面積だけではなく、高い結晶性と大きな比表
面積の相乗効果として単位面積当たりの活性が上昇するためであるといえる。さらに、実
施例５〜８の結果から、ゲーサイト光触媒に金属触媒を担持することでより光触媒活性が
向上することがわかる。この中でも、特に白金（実施例５）とパラジウム（実施例７）の
効果が高かった。尚、実施例１〜３及び実施例５〜８においては、二酸化炭素の生成と同
時に、水素とメタンの生成も確認された。
As shown in Table 2, it can be said that the goethite photocatalyst according to the embodiment of the present invention has a higher carbon dioxide production rate and higher photocatalytic activity than the goethite photocatalyst according to the conventional method of Comparative Examples 1 to 3. In particular, the activity was high when the amount of polyethylene glycol added in Examples 1 to 3 was in the range of 0.5 to 4.0% by mass. In Example 2, the activity was more than double that of the conventional one. Including the structure evaluation results shown in Table 1, the goethite photocatalyst having a long axis length of the acicular particles of 100 nm or more and a specific surface area of 100 m 2 / g or more has particularly high activity. Recognize. In other words, the long axis length of the acicular particles is 100 nm or more, and the ratio of the specific surface area to the long axis length (specific surface area /
Those having a length in the range of 0.8 to 1.1 are highly active. Here, when the activity per unit surface area (carbon dioxide production rate / (specific surface area × photocatalyst use amount)) is calculated, it is about 0.10 μmol / (h · m 2 ) in Comparative Example 1, but in Example 2, 0.15 μmol / (h
・ It can be seen that m 2 ) has increased significantly. That is, the reason why the activity of the goethite photocatalyst according to the embodiment of the present invention is high is that not only the large specific surface area but also the activity per unit area increases as a synergistic effect of high crystallinity and large specific surface area. I can say that. Furthermore, it can be seen from the results of Examples 5 to 8 that the photocatalytic activity is further improved by supporting a metal catalyst on the goethite photocatalyst. Among these, the effects of platinum (Example 5) and palladium (Example 7) were particularly high. In Examples 1 to 3 and Examples 5 to 8, the generation of hydrogen and methane was confirmed simultaneously with the generation of carbon dioxide.
上記のように、本発明の実施の形態について記載したが、この開示の一部をなす論述及
び図面は本発明を限定するものであると理解すべきではない。この開示から当業者には様
々な代替実施の形態、実施例及び運用技術が明らかとなろう。したがって、本発明はここ
では記載していない様々な実施の形態等を含むことは勿論である。したがって、本発明の
技術的範囲は上記の説明から妥当な特許請求の範囲に係る発明特定事項によってのみ定め
られるものである。
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. Therefore, it is needless to say that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.
本発明のゲーサイト光触媒とその製造方法によれば、有機汚染物質の酸化分解除去を効
果的に行うことができる光触媒材料が得られるので光触媒材料を用いる種々の技術分野に
利用可能である。特に、有機物からの化学燃料生成にも活性を有するため、自然光エネル
ギーを利用した化学燃料製造の技術分野にも応用することができる。したがって、本発明
のゲーサイト光触媒とその製造方法は、環境関連産業、エネルギー産業、その他広範な産
業分野において利用することができる。
According to the goethite photocatalyst and the method for producing the same of the present invention, a photocatalyst material capable of effectively oxidatively decomposing and removing organic pollutants can be obtained. Therefore, the photocatalyst material can be used in various technical fields using the photocatalyst material. In particular, since it is active in producing chemical fuel from organic matter, it can be applied to the technical field of chemical fuel production using natural light energy. Therefore, the goethite photocatalyst and the production method thereof of the present invention can be used in environment-related industries, energy industries, and other various industrial fields.
１１…鉄（II）塩
１２…ポリエチレングリコール
１３Ｌ…溶媒
１４Ｌ、２１Ｌ…鉄（II）／ポリエチレングリコール混合溶液
２２Ｌ…塩基性溶液
２３…鉄（II）イオン
２４、３３…水酸化鉄（II）
２５Ｌ、３１Ｌ…水酸化鉄（II）／ポリエチレングリコール混合溶液
３２…分子状酸素
３４…ゲーサイト光触媒
DESCRIPTION OF SYMBOLS 11 ... Iron (II) salt 12 ... Polyethylene glycol 13L ... Solvent 14L, 21L ... Iron (II) / polyethylene glycol mixed solution 22L ... Basic solution 23 ... Iron (II) ion 24, 33 ... Iron hydroxide (II)
25L, 31L ... iron hydroxide (II) / polyethylene glycol mixed solution 32 ... molecular oxygen 34 ... goethite photocatalyst
Claims (3)
し、
比表面積が１００ｍ２／ｇ以上のゲーサイトからなることを特徴とするゲーサイト光触媒
。 The long axis length is 100 nm or more, and the ratio of the long axis length to the short axis length is in the range of 4 to 10, forming a needle shape,
A goethite photocatalyst comprising a goethite having a specific surface area of 100 m 2 / g or more.
ーサイト光触媒。 The goethite photocatalyst according to claim 1, wherein a metal catalyst is supported on the surface of the goethite.
長軸長さが１００ｎｍ以上、長軸長さと短軸長さの比が４〜１０の範囲の針状の形状のゲ
ーサイト粒子を形成することを特徴とするゲーサイト光触媒の製造方法。
Oxidizing iron (II) hydroxide in a solution containing polyethylene glycol,
A method for producing a goethite photocatalyst comprising forming acicular goethite particles having a major axis length of 100 nm or more and a ratio of major axis length to minor axis length in the range of 4 to 10.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105498820A (en) * | 2015-12-14 | 2016-04-20 | 浙江大学 | Preparing method for high visible-light electron transfer Au/g-C3N4 supported photocatalytic material |
| CN105536843A (en) * | 2015-12-14 | 2016-05-04 | 浙江大学 | Preparation method of highly visible light electron transfer g-C3N4/ Au/TiO2 Z type photocatalyst |
-
2014
- 2014-08-05 JP JP2014159199A patent/JP2015077593A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105498820A (en) * | 2015-12-14 | 2016-04-20 | 浙江大学 | Preparing method for high visible-light electron transfer Au/g-C3N4 supported photocatalytic material |
| CN105536843A (en) * | 2015-12-14 | 2016-05-04 | 浙江大学 | Preparation method of highly visible light electron transfer g-C3N4/ Au/TiO2 Z type photocatalyst |
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