JP4010976B2 - Iron-based flocculant - Google Patents
Iron-based flocculant Download PDFInfo
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- JP4010976B2 JP4010976B2 JP2003104471A JP2003104471A JP4010976B2 JP 4010976 B2 JP4010976 B2 JP 4010976B2 JP 2003104471 A JP2003104471 A JP 2003104471A JP 2003104471 A JP2003104471 A JP 2003104471A JP 4010976 B2 JP4010976 B2 JP 4010976B2
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- Prior art keywords
- iron
- flocculant
- polyferric chloride
- chloride
- based flocculant
- Prior art date
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims description 277
- 229910052742 iron Inorganic materials 0.000 title claims description 139
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 108
- 239000007788 liquid Substances 0.000 claims description 38
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 27
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 26
- 229910052782 aluminium Inorganic materials 0.000 claims description 26
- 230000002378 acidificating effect Effects 0.000 claims description 25
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 21
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 19
- -1 silicic acid compound Chemical class 0.000 claims description 18
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 17
- 229940085991 phosphate ion Drugs 0.000 claims description 16
- 230000002776 aggregation Effects 0.000 claims description 12
- 238000004220 aggregation Methods 0.000 claims description 11
- 238000006116 polymerization reaction Methods 0.000 claims description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims description 10
- 238000000108 ultra-filtration Methods 0.000 claims description 9
- 239000012528 membrane Substances 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 description 24
- 239000008394 flocculating agent Substances 0.000 description 21
- 241000894007 species Species 0.000 description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 18
- 239000000126 substance Substances 0.000 description 18
- 238000012360 testing method Methods 0.000 description 13
- 230000000694 effects Effects 0.000 description 10
- 238000000034 method Methods 0.000 description 8
- 239000005416 organic matter Substances 0.000 description 8
- 239000000701 coagulant Substances 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 6
- 230000004931 aggregating effect Effects 0.000 description 5
- 238000010828 elution Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000015271 coagulation Effects 0.000 description 4
- 238000005345 coagulation Methods 0.000 description 4
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000006228 supernatant Substances 0.000 description 4
- 239000008399 tap water Substances 0.000 description 4
- 235000020679 tap water Nutrition 0.000 description 4
- 238000010998 test method Methods 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 239000012670 alkaline solution Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 3
- 239000012085 test solution Substances 0.000 description 3
- 241000894006 Bacteria Species 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-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
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 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 2
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 238000010979 pH adjustment Methods 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 150000004760 silicates Chemical class 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 239000005995 Aluminium silicate Substances 0.000 description 1
- 208000024827 Alzheimer disease Diseases 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 235000012211 aluminium silicate Nutrition 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 231100000315 carcinogenic Toxicity 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- 239000008235 industrial water Substances 0.000 description 1
- 229910000358 iron sulfate Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 229920000137 polyphosphoric acid Polymers 0.000 description 1
- 229940005657 pyrophosphoric acid Drugs 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
- UNXRWKVEANCORM-UHFFFAOYSA-N triphosphoric acid Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(O)=O UNXRWKVEANCORM-UHFFFAOYSA-N 0.000 description 1
Images
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- Separation Of Suspended Particles By Flocculating Agents (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、酸性領域でも使用可能な鉄系凝集剤に関する。
【０００２】
【従来の技術】
従来、河川水、湖沼水、地下水等の原水から水道水及び工業用水を生成する浄化プロセスは、原水中の土砂、粘土等の懸濁性物質を凝集剤で凝集させ、凝集物を沈殿後、急速濾過操作により、除去し、その処理水に残存する細菌類を塩素によって滅菌するという、凝集、沈殿、急速濾過及び塩素滅菌の４つのプロセスよりなっている。
【０００３】
この浄化プロセスにおいて使用される凝集剤としては、従来ポリ塩化アルミニウム（ＰＡＣ）や硫酸アルミニウム（硫酸バンド）等のアルミニウム系凝集剤が広く使用されてきた。しかしながら、ＰＡＣや硫酸バンド等のアルミニウム系凝集剤は、人体への悪影響が懸念され、現在、ＷＨＯによるアルミニウム規制強化への動きや、アルツハイマー病のアルミニウム原因説等が社会問題となっている。
【０００４】
また、近年、水道水源の汚濁が進み、水道水源に下水、産業廃水、下水処理水が混入し、汚濁が進み、各種の溶解性有機物が増加し、この溶解性有機物が塩素滅菌の過程で塩素と結合し、発癌性のあるトリハロメタン等の有害物質を生成するという問題が生じている。そのため、塩素処理過程の前に溶解性有機物を極力除去することが強く求められるようになっている。
【０００５】
従って、有機物の除去性能がアルミニウム系凝集剤に比べ優れ、かつ安全性の高い凝集剤として、塩化第二鉄、ポリ硫酸第二鉄等の鉄系凝集剤が注目され、更に、鉄系凝集剤として塩化第二鉄、ポリ塩化第二鉄、硫酸第二鉄、及びポリ硫酸第二鉄を使用した水中の汚濁物質及び溶解性有機物を凝集させる方法も提案されている（例えば、特許文献１参照）。
【０００６】
【特許文献１】
特開２００２−５９１７３号公報
【０００７】
【発明が解決しようとする課題】
しかしながら、塩化第二鉄は通常使用する中性付近のｐＨ領域で示す優れた濁度除去性能を、有機物の除去に有利な酸性領域で維持することができない。また、腐食作用があるため、使用に注意が必要となる欠点があった。
また、ポリ硫酸第二鉄はアルミニウム系凝集剤よりも金属含有量が高く、低添加量で使用でき、腐食の問題も少なく、有機物の除去性能もアルミニウム系凝集剤に較べ良好である等の利点があるが、有機物の除去に有利な酸性領域で優れた濁度除去性能の発揮という点では不十分という問題があった。
【０００８】
また、特許文献１の発明では、鉄系凝集剤として、塩化第二鉄、ポリ塩化第二鉄、硫酸第二鉄、又はポリ硫酸第二鉄を用い、ｐＨが４から６の領域で凝集操作を行っているが、従来の凝集剤をそのまま使用しているため、個々の凝集剤の凝集性能の向上に寄与している訳ではない。
本発明はかかる事情に鑑みてなされたもので、有機物の除去に有利な酸性領域においても、通常の水処理で使用される中性領域での濁度除去性能を維持することができ、優れた凝集性能を有する鉄系凝集剤を提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記目的に沿う本発明に係る鉄系凝集剤は、ポリ塩化第二鉄を含有し、限外濾過膜による平均分画分子量が５００以上であるポリ塩化第二鉄分子中の鉄が、全鉄の２０重量％以上であって、酸性領域においても良好な濁度除去性能を維持する。
これは、種種の分画分子量の混在したポリ塩化第二鉄を鉄系凝集剤としてそのまま使用するのではなく、ある特定範囲の分画分子量を有するポリマー状の鉄種を一定割合以上含有するポリ塩化第二鉄（ＰＦＣ）溶液が有機物の除去に有利なｐＨ４〜６の酸性領域においても良好な濁度除去性能を維持し、有機物、濁度の両方の除去に有効に作用することを見いだし本発明に至ったものである。
酸性領域においても良好な濁度除去性能を維持することによって、凝集沈殿処理と同時に有機物の除去をすることができる。
【００１０】
ここで、限外濾過膜による平均分画分子量が５００以上とは、平均分画分子量が５００の限外濾過膜を通過しないポリ塩化第二鉄分子をいう。限外濾過膜による平均分画分子量が５００以上であるポリ塩化第二鉄分子の鉄は、全鉄の２０重量％以上がよく、更に、この割合が大きくなるにしたがって、酸性領域における濁度除去性能は高くなる傾向を示し、２０重量％未満であると酸性領域における凝集が起こりにくい。
【００１１】
鉄系凝集剤の全鉄の２０重量％以上含有されるポリ塩化第二鉄の平均分画分子量は、５００以上がよく、好ましくは１００００以上がよい。但し、平均分画分子量が大き過ぎて、ポリ塩化第二鉄がコロイド状になっている場合には、濁度除去性能が低下するので、コロイド状にならない範囲で、平均分画分子量が５００以上のポリ塩化第二鉄分子とする。
また、ポリ塩化第二鉄の平均分画分子量が５００より小さい場合には、酸性領域において凝集が起こりにくい。
【００１２】
本発明に係る鉄系凝集剤において、リン酸イオン種が１又は２以上含有され、平均分画分子量５００以上のポリ塩化第二鉄を長期に渡って安定化するのが好ましい。
ポリ塩化第二鉄溶液中の鉄イオン（Ｆｅ3+）は、水酸基（ＯＨ基）ないしは酸素基（Ｏ基）とを介在する形で結合し、ポリマー状構造を有していると考えられ、ポリ塩化第二鉄中の鉄ポリマーはあまり安定ではない。液状のポリ塩化第二鉄にリン酸イオン種を添加して含有させることによって、鉄ポリマーの安定性が増すと考えられる。
これによって、鉄系凝集剤を長期に渡って使用することができ、経済的である。また、リン酸イオン種によって、鉄系凝集剤のポリマー化度が適正に調整され、平均分画分子量が５００以上の鉄系凝集剤中の鉄分子を増加させることができる。
【００１３】
ここで、リン酸イオン種としては、液状の鉄系凝集剤中でリン酸イオンを放出するものであれば、いずれも使用可能であるが、例えば、オルトリン酸や、ポリリン酸（例えば、ピロリン酸、トリポリリン酸）等のリン酸塩を用いることができる。なお、リン酸イオン種を適量、例えば、ポリ塩化第二鉄凝集剤中の鉄のモル濃度を１としたときのリン（Ｐ）のモル比が０又は０を超えて０．３以下になるように含有したときに、鉄系凝集剤の長期安定性がよくなる。
ここで、液状の鉄系凝集剤とは、固体状のポリ塩化第二鉄を水又は、酸性、アルカリ性水溶液で液状にしたもの、及び、液状のポリ塩化第二鉄を水又は溶液で希釈したものを含む。
【００１４】
本発明に係る鉄系凝集剤において、硫酸イオン種が１又は２以上含有され、平均分画分子量５００以上のポリ塩化第二鉄のポリマー化度を適正に調整するのが好ましい。
これによって、鉄系凝集剤のポリマー化度が適正に調整され、平均分画分子量が５００以上の鉄系凝集剤中の鉄分子を増加させることができる。
【００１５】
また、硫酸イオン種としては、液状の鉄系凝集剤中で硫酸イオンを放出するものであれば、いずれも使用可能であるが、例えば硫酸鉄等の硫酸塩を用いることができる。なお、硫酸イオン種を適量、例えば、ポリ塩化第二鉄凝集剤中の鉄のモル濃度を１としたときの硫黄（Ｓ）のモル比が０又は０を超えて１．０以下で含有したときに、鉄系凝集剤のポリマー化度は、適正に調整される。
【００１６】
本発明に係る鉄系凝集剤において、ケイ酸化合物が含有され、凝集性能を向上させることもできる。
これによって、鉄系凝集剤としてのポリ塩化第二鉄の添加量を少なくすることができ、経済的である。
ここで、ケイ酸化合物としては、重合ケイ酸、シリカ等を用いることができる。ケイ酸化合物は、架橋作用により、被処理液中の汚濁物質を凝集させることができる。なお、ケイ酸化合物中のケイ酸を適量、例えばポリ塩化第二鉄中の鉄のモル濃度を１としたときのケイ素（Ｓｉ）のモル比が０又は０を超えて２．０以下で含有したときに、鉄系凝集剤の凝集性能が向上する。
【００１７】
本発明に係る鉄系凝集剤において、アルミニウム化合物が含有され、ポリ塩化第二鉄の鉄の一部をアルミニウムに代替させることによって、鉄の含有割合を調整するのが好ましい。
これによって、ポリ塩化第二鉄の鉄の一部をアルミニウムに代替させることによって、鉄の含有割合を調整することができる。水の浄化プロセスにおいて、処理水中へ鉄が溶出すると処理水が黄色になり、健康には害はないが水道水として不適当となる恐れがあるが、ポリ塩化第二鉄の鉄の一部をアルミニウムに代替させることによって、鉄の含有割合を抑制することにより、処理水への鉄の溶出量を抑制することができる。
【００１８】
ここで、アルミニウム化合物としては、ＰＡＣや硫酸バンド等のアルミニウム系凝集剤を用いることができる。
また、鉄系凝集剤中の鉄のモル濃度を１としたときのアルミニウム（Ａｌ）のモル比を適量、例えば０又は０を超えて１．０以下となるように含有したときに、ポリ塩化第二鉄中の鉄の処理水への溶出量が好適に抑制される。
【００１９】
本発明に係る鉄系凝集剤において、前記鉄系凝集剤は、液状であるのが好ましい。
ここで、液状とは、ポリ塩化第二鉄が固体状の場合であっても、水溶液や酸性又はアルカリ性溶液で溶解して液状にしたものも含み、また、もともと液状のものを水溶液や酸性又はアルカリ性溶液で希釈したものも含む。
これによって、被処理液に鉄系凝集剤を混合する際に固体の鉄系凝集剤では、鉄系凝集剤の一部が被処理液に溶解せずに凝集剤の効果が低くなる恐れがあるが、液状の場合には被処理液に全部が混合されて効果が確実である。従って、予め溶解させる必要がなく、使い勝手がよい。
【００２０】
本発明に係る鉄系凝集剤において、前記鉄系凝集剤は、固体状であるのが好ましい。
これによって、輸送コストを削減することができる。
ここで、固体状とは、ポリ塩化第二鉄を製造する際にもともと固体状に製造されたものでもよいし、液状の鉄系凝集剤から水分を蒸発させるなどして、通常の固化方法により固体化させて製造したものでもよい。
【００２１】
【発明の実施の形態】
続いて、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。本発明の一実施の形態に係る鉄系凝集剤について、以下に説明する。まず、ポリマー化度をそれぞれ変化させて作成した複数のポリ塩化第二鉄液を調製し、更に、それぞれのポリ塩化第二鉄液に水を添加して、例えば、鉄のモル濃度が０．２ｍｏｌ／Ｌのポリ塩化第二鉄溶液とする。これらのポリ塩化第二鉄溶液中のポリ塩化第二鉄のポリマー化度を以下の方法により測定した。
ここで、予め含有する鉄モル濃度を０．２ｍｏｌ／Ｌとするのは、０．２ｍｏｌ／Ｌ程度の濃度が限外濾過を適正に行うことができるからである。
【００２２】
次に、このポリ塩化第二鉄溶液を、ポア（孔）サイズ５０ｎｍのフィルターで濾過した後、平均分画分子量５００、１００００、３０００００、及び５０００００の各限外濾過膜を通過するポリ塩化第二鉄溶液を作成する。
そして、上記、平均分画分子量が５００未満、１００００未満、３０００００未満、５０００００未満、及びポアサイズ５０ｎｍ未満の５つに分画されたポリ塩化第二鉄溶液を、高周波プラズマ発光分析装置により分析を行い、それぞれのポリ塩化第二鉄溶液中の鉄原子の濃度を測定する。
【００２３】
ここで、上記の測定結果と、分画する前のポリ塩化第二鉄溶液中の鉄の濃度が０．２ｍｏｌ／Ｌであることから、ポリ塩化第二鉄溶液の平均分画分子量が５００未満、平均分画分子量が５００以上〜１００００未満、平均分画分子量が１００００以上〜３０００００未満、平均分画分子量が３０００００以上〜５０００００未満、平均分画分子量が５０００００以上〜ポアサイズが５０ｎｍ未満、ポアサイズが５０ｎｍ以上の６つの分画中のそれぞれの鉄の全鉄に対する割合は、計算により求められる。
【００２４】
ここで、複数のポリ塩化第二鉄溶液の中から、平均分画分子量５００以上のポリ塩化第二鉄の鉄が全鉄の２０重量％以上の任意の値をとるポリ塩化第二鉄を含有する鉄系凝集剤（以下、ポリ塩化第二鉄凝集剤という）を５つ選択した。平均分画分子量５００以上のポリ塩化第二鉄の鉄が全鉄の２０重量％以上、例えば、２５重量％に調整されているものをポリ塩化第二鉄凝集剤（Ａ）、５０重量％のものをポリ塩化第二鉄凝集剤（Ｂ）、８０重量％のものをポリ塩化第二鉄凝集剤（Ｃ）とした。
【００２５】
また、平均分画分子量５００以上、１００００未満のポリ塩化第二鉄の鉄が全鉄の２０重量％以上のものをポリ塩化第二鉄凝集剤（Ｄ）、平均分画分子量１００００以上、３０００００未満のポリ塩化第二鉄の鉄が全鉄の２０重量％以上のものをポリ塩化第二鉄凝集剤（Ｅ）とした。
更に、比較液としてポリ塩化第二鉄の鉄が全鉄の２０重量％未満つまり、平均分画分子量５００以下のポリ塩化第二鉄中の鉄が全鉄の８０重量％以上のポリ塩化第二鉄溶液（Ｘ）とした。
【００２６】
また、上記ポリ塩化第二鉄凝集剤（Ａ）〜（Ｅ）に、リン酸イオン種として、例えば、リン酸カルシウム、硫酸イオン種として、例えば、硫酸ナトリウム、ケイ酸化合物として、例えば、重合ケイ酸、アルミニウム化合物として、例えば、塩化アルミニウムのそれぞれ適量を添加したリン酸イオン含有ポリ塩化第二鉄凝集剤、硫酸イオン含有ポリ塩化第二鉄凝集剤、ケイ酸化合物含有ポリ塩化第二鉄凝集剤、アルミニウム含有ポリ塩化第二鉄凝集剤を作成した。
【００２７】
上記（Ａ）〜（Ｅ）のポリ塩化第二鉄凝集剤は、黒褐色の液体であるが、経時安定性が悪く、時間の経過と共に、茶色や黄土色となり、コロイド状となるか、固液が分離した状態となる。しかしながら、上記適量のリン酸イオン種を添加して、含有させたリン酸イオン含有ポリ塩化第二鉄凝集剤は、前記したような状態にはならず、黒褐色の液体のままであり、ポリ塩化第二鉄凝集剤の安定化に寄与していることが分かる。
【００２８】
ここで、適量とは、ポリ塩化第二鉄凝集剤がそれぞれの添加によって安定化する量であって、例えばポリ塩化第二鉄凝集剤中の鉄モル濃度を１としたときのリン（Ｐ）のモル比で０又は０を超えて０．３以下のリン酸イオン種を添加して含有させるのが好ましい。なお、リン酸イオン種の添加量が少なすぎる場合には、その効果を発揮することができず、また、添加量が多い場合には、ポリ塩化第二鉄がコロイド状になるのでよくない。
【００２９】
また、ポリ塩化第二鉄凝集剤に硫酸イオン種の適量添加した硫酸イオン含有ポリ塩化第二鉄凝集剤は、平均分画分子量５００以上のポリ塩化第二鉄のポリマー化度を適正に調整することができる。ここで、適量とは、平均分画分子量５００以上のポリ塩化第二鉄のポリマー化度を適正に調整するのに適当な量であって、例えば、ポリ塩化第二鉄凝集剤中の鉄のモル濃度を１としたときの硫黄（Ｓ）のモル比で０又は０を超えて１．０以下の硫酸イオン種を含有量させる。
【００３０】
また、ポリ塩化第二鉄凝集剤にケイ酸化合物の適量を添加したケイ酸化合物含有ポリ塩化第二鉄凝集剤は、ポリ塩化第二鉄凝集剤の凝集性能を更に上昇し得る。ここで、適量とはポリ塩化第二鉄凝集剤の凝集性能を上昇させるのに適当な量であって、例えば、ポリ塩化第二鉄凝集剤中の鉄モル濃度を１としたときのケイ素（Ｓｉ）のモル比で０又は０を超えて２．０以下のケイ酸化合物を添加して含有させるのが好ましい。
【００３１】
あるいは、ポリ塩化第二鉄凝集剤にアルミニウム化合物の適量を添加したアルミニウム含有ポリ塩化第二鉄凝集剤は、ポリ塩化第二鉄の鉄の一部をアルミニウムに代替させることによって、鉄の含有割合を調整し、ポリ塩化第二鉄中の鉄の処理水への溶出量を抑制することができる。ここで、適量とは、ポリ塩化第二鉄中の鉄の処理水への溶出量が好適に抑制されるのに適当な量であって、例えば、ポリ塩化第二鉄中の鉄のモル濃度を１としたときのアルミニウム（Ａｌ）のモル比でそれぞれ０又は０を超えて１．０以下を含有するのが好ましい。
【００３２】
次に、鉄系凝集剤を使用した凝集処理方法について説明する。
被処理液に、硫酸を添加して、被処理液のｐＨを酸性とした後、前記したポリ塩化第二鉄凝集剤を添加して、撹拌し、被処理液中の懸濁物質（汚濁物質）を凝集して、沈殿させる。ここで、被処理液のｐＨは酸性となっているため、懸濁物質と共に有機物も同時に凝集し、沈殿する。
この後、濾過することによって、懸濁物質と有機物を同時に除去することができる。
【００３３】
ここで、鉄系凝集剤としてポリ塩化第二鉄凝集剤の代わりにケイ酸化合物含有ポリ塩化第二鉄凝集剤を使用すると、ポリ塩化第二鉄凝集剤よりも、更に大きな浮遊物（フロック）を形成し、沈殿物の降下時間が短く、濁度除去性能も向上していることがわかる。
あるいは鉄系凝集剤としてリン酸イオン含有ポリ塩化第二鉄凝集剤、硫酸イオン含有ポリ塩化第二鉄凝集剤、アルミニウム含有ポリ塩化第二鉄凝集剤等を使用しても良い。
【００３４】
（実施例１）
次に、図１を参照しながら、本発明の一実施の形態に係る鉄系凝集剤と他の凝集剤との濁度除去性能について、更に具体的に説明する。ここで、図１は本発明の一実施の形態に係る鉄系凝集剤と他の凝集剤との濁度除去性能を比較したグラフである。
濁度除去性能の試験方法は、ポリ塩化第二鉄凝集剤、塩化第二鉄、ポリ塩化アルミニウム、及び硫酸バンドについて行った。ポリ塩化第二鉄凝集剤として平均分画分子量５００以上のポリ塩化第二鉄中の鉄を全鉄の２０重量％含有するものを先に調製し、使用した。
以下に、試験方法を示す。
【００３５】
（１）試験用被処理液として、水１Ｌに、結晶性・不完全結晶性粘土鉱物であるカオリン（ＡＬ2 Ｏ3 ，２ＳｉＯ2 ・２Ｈ2 Ｏ）５０ｍｇ及び炭酸ナトリウム（Ｎａ2 ＣＯ3 ）３０ｍｇを添加したものを用意した。
（２）上記試験用被処理液を硫酸水溶液、又は水酸化ナトリウム水溶液によってｐＨ調整した。ここで、試験用被処理液のｐＨは、沈殿処理終了後の試験用被処理液の上澄み液のｐＨが実質的に所定のｐＨとなるように予め、調整される。なお、試験用被処理液のｐＨ調整後の濁度は、およそ３５〜３６である。
【００３６】
（３）それぞれの凝集剤を、鉄又はアルミニウムの濃度が、０．２ｍ ｍｏｌ／Ｌとなるように添加した。
（４）試験用被処理液を、撹拌機によって１分間に１２０回転の速さ（１２０ｒｐｍ）で、５分間撹拌した。
（５）更に、４０ｒｐｍで、１０分間撹拌した。
（６）撹拌終了後、２０分間静置し、生成したフロックを降下させ沈殿物を得た。
（７）試験用被処理液の上澄み液のｐＨ、及び濁度を測定した。
【００３７】
図１は、横軸に凝集処理終了後の試験用被処理液のｐＨ、縦軸に凝集処理終了後の試験用被処理液の濁度を示している。図１に示すように、ポリ塩化第二鉄凝集剤（図中、「●」で示す）は、凝集処理終了後の試験用被処理液のｐＨが、４．２〜８．１付近において、良好な濁度除去性能を有することが分かった。ここで、塩化第二鉄凝集剤（図中、「■」で示す）、ポリ塩化アルミニウム凝集剤（図中、「▲」で示す）、及び硫酸バンド凝集剤（図中、「◆」で示す）は、それぞれ中性付近の濁度除去性能は良いが、酸性領域では良好な結果は得られなかった。
【００３８】
（実施例２）
次に、前記ポリ塩化第二鉄凝集剤（Ａ）〜（Ｅ）及び前記ポリ塩化第二鉄溶液（Ｘ）について、実施例１と同じ方法で凝集剤の効果を試験した。平均分画分子量５００以上のポリ塩化第二鉄の鉄を全鉄の２０重量％含有するポリ塩化第二鉄凝集剤（Ａ）〜（Ｅ）については上記実験例と略同じ結果が見られた。特に、ポリ塩化第二鉄の鉄の全鉄に対する割合が大きく成るほど、また、平均分画分子量が大きくなるほど良好な効果を示す傾向が見られた。ポリ塩化第二鉄の鉄が全鉄の２０重量％未満のポリ塩化第二鉄溶液（Ｘ）についてはｐＨ４〜６の酸性領域での効果が小さかった。
【００３９】
（実施例３）
次に、前記実施例１のポリ塩化第二鉄凝集剤と他の凝集剤の酸性領域においての有機物除去性能について説明する。
濁度除去性能の試験方法は、ポリ塩化第二鉄凝集剤、塩化第二鉄、ポリ塩化アルミニウム、及び硫酸バンドについて行った。以下に、試験方法を示す。
なお、試験用被処理液として、全有機炭素が１０ｍｇ／Ｌ含有するものを用いた。ポリ塩化第二鉄凝集剤については実施例１と同様のポリ塩化第二鉄凝集剤として平均分画分子量５００以上のポリ塩化第二鉄中の鉄を全鉄の２０重量％含有するものを予め、調製し、使用した。
【００４０】
（１）全有機炭素が１０ｍｇ／Ｌの標準溶液１Ｌに、硫酸水溶液を添加し、ｐＨ調整を行い、試験用被処理液とする。ここで、試験用被処理液のｐＨは、予め沈殿処理終了後の試験用被処理液の上澄み液のｐＨが約５．５となるように調整する。
（２）次に、それぞれの凝集剤を、鉄又はアルミニウムの濃度が、０．２ｍ ｍｏｌ／Ｌとなるように添加した。
【００４１】
（３）試験用被処理液を、撹拌機によって１２０ｒｐｍで、５分間撹拌した。
（４）更に、４０ｒｐｍで、１０分間撹拌した。
（５）撹拌終了後、２０分間静置し、生成したフロックを降下させ沈殿物を得た。
（６）試験用被処理液の上澄み液のｐＨ、及び全有機物炭素量を全有機炭素分析装置により測定した。
【００４２】
【表１】
表１に示すように、ポリ塩化第二鉄凝集剤は、塩化第二鉄、ポリ塩化アルミニウム、及び硫酸バンドと比較して、優れた有機物の除去性能を有していることが分かる。
【００４４】
（実施例４）
次に、前記ポリ塩化第二鉄凝集剤（Ａ）〜（Ｅ）及び前記ポリ塩化第二鉄溶液（Ｘ）について、実施例３と同じ方法で凝集剤の効果を試験した。平均分画分子量５００以上のポリ塩化第二鉄の鉄を全鉄の２０重量％含有するポリ塩化第二鉄凝集剤（Ａ）〜（Ｅ）については上記実験例と略同じ結果が見られた。特に、ポリ塩化第二鉄の鉄の全鉄に対する割合が大きく成るほど、また、平均分画分子量が大きくなるほど酸性領域における有機物除去機能が良好な効果を示す傾向が見られた。ポリ塩化第二鉄の鉄が全鉄の２０重量％未満のポリ塩化第二鉄溶液（Ｘ）についてはｐＨ４〜６の酸性領域での有機物の除去性能が低かった。
【００４５】
上記実施例１〜実施例４から、平均分画分子量５００以上のポリ塩化第二鉄中の鉄が全鉄の２０重量％以上のポリ塩化第二鉄溶液が、有機物除去に有利な酸性領域についても濁度除去作用を有する事がわかった。更に、限外濾過膜による平均分画分子量が５００以上であるポリ塩化第二鉄分子中の鉄の割合は、全鉄の２０重量％以上がよく、更に、この割合が大きくなるにしたがって、濁度除去性能は高くなる傾向を示すことがわかった。
また、鉄系凝集剤中に含有されるポリ塩化第二鉄の平均分画分子量は、５００以上がよく、好ましくは１００００以上がよいことがわかった。
以上のように、本発明のポリ塩化第二鉄凝集剤は、酸性領域において、優れた濁度除去性能及び有機物除去性能を有することが確認された。
【００４６】
本発明は、前記した実施の形態に限定されるものではなく、本発明の要旨を変更しない範囲での変更は可能であり、例えば、前記した実施の形態や変形例の一部又は全部を組み合わせて本発明の鉄系凝集剤を構成する場合も本発明の権利範囲に含まれる。
例えば、前記実施の形態において、被処理液のｐＨを低く、つまり、酸性側にするために硫酸を用いているが、ポリ塩化第二鉄凝集剤を多く添加してもよい。
【００４７】
また、鉄系凝集剤は、リン酸イオン種、硫酸イオン種、ケイ酸化合物、及びアルミニウム化合物の１又は２以上含有してもよい。
また、酸性領域で凝集処理を行った後、被処理液のｐＨを中性に戻す必要がある場合は、凝集処理時の凝集物が除去された後で、アルカリ性溶液を添加してｐＨ調整を行ってもよい。
【００４８】
【発明の効果】
請求項１〜７記載の鉄系凝集剤においては、ポリ塩化第二鉄を含有し、限外濾過膜による平均分画分子量が５００以上であるポリ塩化第二鉄分子中の鉄が、全鉄の２０重量％以上であって、酸性領域においても良好な濁度除去性能を維持するので、凝集沈殿処理と同時に有機物の除去をすることができる。
【００４９】
特に、請求項２記載の鉄系凝集剤においては、リン酸イオン種が含有され、平均分画分子量５００以上のポリ塩化第二鉄を長期に渡って安定化するので、鉄系凝集剤を長期に渡って使用することができ、経済的である。また、リン酸イオン種によって、鉄系凝集剤のポリマー化度が適正に調整され、平均分画分子量が５００以上の鉄系凝集剤中の鉄分子を増加させることができる。
特に、請求項３記載の鉄系凝集剤においては、硫酸イオン種が含有され、平均分画分子量５００以上のポリ塩化第二鉄のポリマー化度を適正に調整するので、平均分画分子量が５００以上の鉄系凝集剤中の鉄分子を増加させることができる。
【００５０】
請求項４記載の鉄系凝集剤においては、ケイ酸化合物が含有され、凝集性能を向上させるので、鉄系凝集剤の添加量を少なくすることができ、経済的である。
請求項５記載の鉄系凝集剤においては、アルミニウム化合物が含有され、ポリ塩化第二鉄の鉄の一部をアルミニウムに代替させることによって、鉄の含有割合を調整するので、ポリ塩化第二鉄の鉄の含有割合を制御することができる。更に、処理水中への鉄の溶出量を抑制することができる。
【００５１】
請求項６記載の鉄系凝集剤においては、鉄系凝集剤は、液状なので被処理液に混合する際に溶かす必要がなく、使い勝手がよい。
請求項７記載の鉄系凝集剤においては、鉄系凝集剤は、固体状であるので、輸送コストを削減することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る鉄系凝集剤と他の凝集剤との濁度除去性能を比較したグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an iron-based flocculant that can be used even in an acidic region.
[0002]
[Prior art]
Conventionally, the purification process to produce tap water and industrial water from raw water such as river water, lake water, groundwater, etc., aggregates suspended substances such as earth and sand, clay, etc. in the raw water with a flocculant, and precipitates the aggregate. It consists of four processes: agglomeration, precipitation, rapid filtration and chlorine sterilization, in which bacteria removed by rapid filtration operation and bacteria remaining in the treated water are sterilized by chlorine.
[0003]
As flocculants used in this purification process, aluminum flocculants such as polyaluminum chloride (PAC) and aluminum sulfate (sulfuric acid band) have been widely used. However, aluminum-based flocculants such as PAC and sulfuric acid band are concerned about adverse effects on the human body, and currently there are social problems such as the movement to strengthen aluminum regulations by WHO and the cause of aluminum in Alzheimer's disease.
[0004]
In recent years, pollution of tap water sources has progressed, and sewage, industrial wastewater, and sewage treated water have been mixed into tap water sources, pollution has increased, and various soluble organic substances have increased. This causes a problem of generating harmful substances such as carcinogenic trihalomethanes. Therefore, it is strongly demanded to remove soluble organic substances as much as possible before the chlorination process.
[0005]
Therefore, iron-based flocculants such as ferric chloride and polyferric sulfate are attracting attention as flocculants having excellent organic substance removal performance and higher safety than aluminum-based flocculants. A method of aggregating pollutants and soluble organic substances in water using ferric chloride, polyferric chloride, ferric sulfate, and polyferric sulfate is also proposed (for example, see Patent Document 1). ).
[0006]
[Patent Document 1]
JP 2002-59173 A
[0007]
[Problems to be solved by the invention]
However, ferric chloride cannot maintain the excellent turbidity removing performance shown in the pH range near neutrality that is normally used in an acidic region advantageous for removing organic substances. In addition, since it has a corrosive action, there is a drawback that requires careful use.
In addition, polyferric sulfate has higher metal content than aluminum-based flocculants, can be used in low addition amounts, has less problems of corrosion, and has better organic substance removal performance than aluminum-based flocculants. However, there is a problem that it is insufficient in terms of exhibiting excellent turbidity removal performance in an acidic region advantageous for removal of organic substances.
[0008]
Further, in the invention of Patent Document 1, ferric chloride, polyferric chloride, ferric sulfate, or polyferric sulfate is used as the iron-based flocculant, and the coagulation operation is performed in a pH range of 4 to 6. However, since the conventional flocculant is used as it is, it does not contribute to the improvement of the flocculant performance of each flocculant.
The present invention has been made in view of such circumstances, and can maintain turbidity removal performance in a neutral region used in normal water treatment even in an acidic region advantageous for removal of organic matter. An object is to provide an iron-based flocculant having aggregating performance.
[0009]
[Means for Solving the Problems]
The iron-based flocculant according to the present invention that meets the above object contains polyferric chloride, and the iron in the polyferric chloride molecule having an average molecular weight cut off by an ultrafiltration membrane of 500 or more is all iron. The turbidity removal performance is good even in the acidic region.
This is not to use polyferric chloride mixed with various fractional molecular weights as an iron-based flocculant as it is, but to use a polymer containing a certain proportion or more of polymer-like iron species having a fractional molecular weight in a specific range. It has been found that ferric chloride (PFC) solution maintains good turbidity removal performance even in the acidic range of pH 4-6, which is advantageous for organic matter removal, and effectively works for both organic matter and turbidity removal. Invented.
By maintaining good turbidity removal performance even in the acidic region, organic substances can be removed simultaneously with the coagulation precipitation treatment.
[0010]
Here, the average molecular weight cut-off by the ultrafiltration membrane of 500 or more refers to polyferric chloride molecules that do not pass through the ultrafiltration membrane having an average molecular weight cut-off of 500. The iron of poly ferric chloride molecules whose average molecular weight cut by ultrafiltration membrane is 500 or more should be 20% by weight or more of the total iron. Further, as this ratio increases, turbidity removal in the acidic region is achieved. The performance tends to increase, and if it is less than 20% by weight, aggregation in the acidic region hardly occurs.
[0011]
The average molecular weight cut off of ferric chloride contained in the iron-based flocculant in an amount of 20% by weight or more of the total iron is preferably 500 or more, and more preferably 10,000 or more. However, if the average molecular weight cut off is too large and the ferric chloride is colloidal, the turbidity removal performance is reduced. Of poly ferric chloride molecules.
Further, when the average molecular weight cutoff of polyferric chloride is smaller than 500, aggregation is unlikely to occur in the acidic region.
[0012]
In the iron-based flocculant according to the present invention, it is preferable to stabilize polyferric chloride containing one or more phosphate ion species and having an average molecular weight cut-off of 500 or more over a long period of time.
Iron ions (Fe) in polyferric chloride solution 3+ ) Is bonded with a hydroxyl group (OH group) or an oxygen group (O group), and is considered to have a polymer structure, and the iron polymer in polyferric chloride is not very stable. . It is considered that the stability of the iron polymer is increased by adding phosphate ion species to liquid polyferric chloride.
As a result, the iron-based flocculant can be used for a long time, which is economical. Further, the degree of polymerization of the iron-based flocculant is appropriately adjusted by the phosphate ion species, and the iron molecules in the iron-based flocculant having an average fractional molecular weight of 500 or more can be increased.
[0013]
Here, any phosphate ion species may be used as long as it releases phosphate ions in a liquid iron-based flocculant. For example, orthophosphoric acid or polyphosphoric acid (for example, pyrophosphoric acid) , Tripolyphosphoric acid) and the like can be used. In addition, the molar ratio of phosphorus (P) when the molar amount of phosphate ion species is an appropriate amount, for example, when the molar concentration of iron in the polyferric chloride flocculant is 1, becomes 0 or more than 0.3 and 0.3 or less. When contained in such a manner, the long-term stability of the iron-based flocculant is improved.
Here, the liquid iron-based flocculant means that solid polyferric chloride is liquefied with water or an acidic or alkaline aqueous solution, and liquid polyferric chloride is diluted with water or a solution. Including things.
[0014]
In the iron-based flocculant according to the present invention, it is preferable to appropriately adjust the degree of polymerization of ferric chloride containing one or more sulfate ion species and having an average molecular weight cut-off of 500 or more.
As a result, the degree of polymerization of the iron-based flocculant is appropriately adjusted, and the number of iron molecules in the iron-based flocculant having an average fractional molecular weight of 500 or more can be increased.
[0015]
Any sulfate ion species can be used as long as it releases sulfate ions in a liquid iron-based flocculant. For example, sulfates such as iron sulfate can be used. An appropriate amount of sulfate ion species was contained, for example, the molar ratio of sulfur (S) when the molar concentration of iron in the polyferric chloride flocculant was 1 was 0 or more than 0 and 1.0 or less. Sometimes, the degree of polymerization of the iron-based flocculant is adjusted appropriately.
[0016]
In the iron-based flocculant according to the present invention, a silicate compound is contained, and the aggregation performance can be improved.
As a result, the amount of polyferric chloride added as an iron-based flocculant can be reduced, which is economical.
Here, polymerized silicic acid, silica or the like can be used as the silicic acid compound. The silicic acid compound can aggregate the pollutant in the liquid to be treated by the crosslinking action. In addition, the silicic acid in the silicic acid compound is contained in an appropriate amount, for example, the molar ratio of silicon (Si) when the molar concentration of iron in polyferric chloride is 1 is 0 or more than 0 and not more than 2.0. When this is done, the aggregation performance of the iron-based flocculant is improved.
[0017]
In the iron-based flocculant according to the present invention, an aluminum compound is contained, and the iron content is preferably adjusted by substituting a part of iron of polyferric chloride with aluminum.
Thereby, the iron content can be adjusted by substituting a part of iron of polyferric chloride with aluminum. In the water purification process, if iron elutes into the treated water, the treated water turns yellow, which is not harmful to health but may be inappropriate as tap water. By substituting for aluminum, the elution amount of iron into the treated water can be suppressed by suppressing the iron content.
[0018]
Here, as the aluminum compound, an aluminum-based flocculant such as PAC or a sulfuric acid band can be used.
Further, when the molar ratio of aluminum (Al) when the molar concentration of iron in the iron-based flocculant is 1 is contained in an appropriate amount, for example, 0 or more than 0 and 1.0 or less, polychlorination The amount of elution of ferric iron into the treated water is suitably suppressed.
[0019]
In the iron-based flocculant according to the present invention, the iron-based flocculant is preferably liquid.
Here, the liquid state includes a case where polyferric chloride is in a solid state, including a solution obtained by dissolving it in an aqueous solution or an acidic or alkaline solution, Including those diluted with an alkaline solution.
As a result, when the iron-based flocculant is mixed with the liquid to be treated, the solid iron-based flocculant may not dissolve in the liquid to be treated, and the effect of the flocculant may be reduced. However, in the case of a liquid, the effect is certain because it is mixed with the liquid to be treated. Therefore, it is not necessary to dissolve in advance, and it is easy to use.
[0020]
In the iron-based flocculant according to the present invention, the iron-based flocculant is preferably solid.
Thereby, the transportation cost can be reduced.
Here, the solid form may be one that is originally produced in solid form when producing polyferric chloride, or by evaporating moisture from a liquid iron-based flocculant, and by a normal solidification method. It may be produced by solidification.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Subsequently, an embodiment of the present invention will be described to provide an understanding of the present invention. An iron-based flocculant according to an embodiment of the present invention will be described below. First, a plurality of polyferric chloride solutions prepared by changing the degree of polymerization are prepared, and water is added to each polyferric chloride solution. A 2 mol / L polyferric chloride solution is used. The degree of polymerization of polyferric chloride in these ferric chloride solutions was measured by the following method.
Here, the iron molar concentration contained in advance is 0.2 mol / L because a concentration of about 0.2 mol / L can appropriately perform ultrafiltration.
[0022]
Next, this polyferric chloride solution is filtered through a filter having a pore (pore) size of 50 nm, and then passed through each ultrafiltration membrane having an average fractional molecular weight of 500, 10,000, 300,000, and 500,000. Make an iron solution.
The above-described polyferric chloride solution having an average fractional molecular weight of less than 500, less than 10,000, less than 300,000, less than 500,000 and a pore size of less than 50 nm is analyzed by a high frequency plasma emission spectrometer. The concentration of iron atoms in each polyferric chloride solution is measured.
[0023]
Here, since the measurement result and the concentration of iron in the polyferric chloride solution before fractionation are 0.2 mol / L, the average fractional molecular weight of the polyferric chloride solution is less than 500. The average fractional molecular weight is from 500 to less than 10,000, the average fractional molecular weight is from 10,000 to less than 300,000, the average fractional molecular weight is from 300,000 to less than 500,000, the average fractional molecular weight is from 500,000 to less than 50 nm, and the pore size is less than 50 nm. The ratio of each iron to the total iron in the above six fractions can be obtained by calculation.
[0024]
Here, from a plurality of polyferric chloride solutions, polyferric chloride iron having an average molecular weight cut off of 500 or more contains polyferric chloride having an arbitrary value of 20% by weight or more of the total iron. Five iron-based flocculants to be used (hereinafter referred to as polyferric chloride flocculants) were selected. Poly ferric chloride with an average molecular weight cut off of 500 or more is adjusted to 20% by weight or more of total iron, for example, 25% by weight of polyferric chloride flocculant (A), 50% by weight One was polyferric chloride flocculant (B), and 80% by weight polyferric chloride flocculant (C).
[0025]
In addition, polyferric chloride iron having an average fractional molecular weight of 500 or more and less than 10,000 is 20% by weight or more of the total iron, ferric chloride flocculant (D), average fractional molecular weight of 10,000 or more and less than 300,000 A polyferric chloride flocculant (E) having a polyferric chloride iron content of 20% by weight or more of the total iron was used.
Further, as a comparative solution, polyferric chloride iron is less than 20% by weight of the total iron, that is, polyferric chloride in which the iron in the polyferric chloride having an average fractional molecular weight of 500 or less is 80% by weight or more of the total iron. An iron solution (X) was obtained.
[0026]
Further, in the polyferric chloride flocculants (A) to (E), as phosphate ion species, for example, calcium phosphate, sulfate ion species, for example, sodium sulfate, silicate compounds, for example, polymerized silicic acid, Examples of aluminum compounds include phosphate ion-containing polyferric chloride flocculants, sulfate ion-containing polyferric chloride flocculants, silicic acid compound-containing polyferric chloride flocculants, and aluminum, to which appropriate amounts of aluminum chloride are added. A containing polyferric chloride flocculant was prepared.
[0027]
The polyferric chloride flocculants (A) to (E) above are black-brown liquids, but they are poorly stable over time, become brown or ocher over time, become colloidal, or are solid-liquid Will be separated. However, the phosphate ion-containing polyferric chloride flocculant added by adding the appropriate amount of phosphate ion species is not in the state described above, and remains a black-brown liquid. It can be seen that it contributes to the stabilization of the ferric coagulant.
[0028]
Here, the appropriate amount is the amount that the polyferric chloride flocculant is stabilized by each addition. For example, phosphorus (P) when the molar concentration of iron in the polyferric chloride flocculant is 1 It is preferable that a phosphate ion species of 0 or more than 0 and not more than 0.3 is added and contained. In addition, when there are too few addition amounts of phosphate ion seed | species, the effect cannot be exhibited, and when there are many addition amounts, poly ferric chloride becomes colloidal and is not good.
[0029]
In addition, a sulfate ion-containing polyferric chloride flocculant in which an appropriate amount of sulfate ion species is added to the polyferric chloride flocculant appropriately adjusts the degree of polymerization of polyferric chloride having an average molecular weight cut-off of 500 or more. be able to. Here, the appropriate amount is an amount appropriate for appropriately adjusting the degree of polymerization of polyferric chloride having an average molecular weight cut-off of 500 or more, for example, the amount of iron in the polyferric chloride flocculant. When the molar concentration is 1, the molar ratio of sulfur (S) is 0 or more than 0 and 1.0 or less sulfate ion species is contained.
[0030]
Moreover, the silicate compound-containing polyferric chloride flocculant obtained by adding an appropriate amount of the silicate compound to the polyferric chloride flocculant can further increase the flocculation performance of the polyferric chloride flocculant. Here, the appropriate amount is an amount appropriate for increasing the coagulation performance of the polyferric chloride flocculant. For example, when the molar concentration of iron in the polyferric chloride flocculant is 1, It is preferable to add and contain a silicic acid compound having a molar ratio of Si) of 0 or more than 0 and not more than 2.0.
[0031]
Alternatively, an aluminum-containing polyferric chloride coagulant in which an appropriate amount of an aluminum compound is added to a polyferric chloride coagulant is obtained by substituting a part of iron of polyferric chloride with aluminum, thereby providing an iron content ratio. The amount of elution of iron in polyferric chloride into treated water can be suppressed. Here, the appropriate amount is an appropriate amount for suitably suppressing the elution amount of iron in polyferric chloride into the treated water, for example, the molar concentration of iron in polyferric chloride. It is preferable that the molar ratio of aluminum (Al) is 1 or more than 0 and 1.0 or less.
[0032]
Next, an aggregating method using an iron-based aggregating agent will be described.
After adding sulfuric acid to the liquid to be treated to make the pH of the liquid to be treated acidic, the above-mentioned polyferric chloride flocculant is added and stirred, and suspended substances (contaminated substances) in the liquid to be treated ) Is agglomerated and precipitated. Here, since the pH of the liquid to be treated is acidic, the organic matter is simultaneously aggregated and precipitated together with the suspended substance.
Thereafter, the suspended matter and the organic matter can be removed simultaneously by filtering.
[0033]
Here, when a ferric chloride coagulant containing a silicate compound is used instead of polyferric chloride coagulant as an iron-based coagulant, a floating substance (floc) larger than polyferric chloride coagulant is used. It can be seen that the precipitation time is short and the turbidity removal performance is improved.
Alternatively, a phosphate ion-containing polyferric chloride flocculant, a sulfate ion-containing polyferric chloride flocculant, an aluminum-containing polyferric chloride flocculant, and the like may be used as the iron-based flocculant.
[0034]
Example 1
Next, the turbidity removal performance of the iron-based flocculant and other flocculants according to one embodiment of the present invention will be described more specifically with reference to FIG. Here, FIG. 1 is a graph comparing the turbidity removal performance of an iron-based flocculant and another flocculant according to an embodiment of the present invention.
The test method of turbidity removal performance was performed on polyferric chloride flocculant, ferric chloride, polyaluminum chloride, and sulfate band. A polyferric chloride flocculant containing 20% by weight of iron in polyferric chloride having an average molecular weight cut-off of 500 or more was first prepared and used.
The test method is shown below.
[0035]
(1) As a liquid to be treated for testing, kaolin (AL 2 O Three , 2SiO 2 ・ 2H 2 O) 50 mg and sodium carbonate (Na 2 CO Three ) Prepared with 30 mg added.
(2) The pH of the test liquid to be treated was adjusted with an aqueous sulfuric acid solution or an aqueous sodium hydroxide solution. Here, the pH of the test liquid is adjusted in advance so that the pH of the supernatant of the test liquid after the precipitation process is substantially a predetermined pH. In addition, the turbidity after pH adjustment of the to-be-processed liquid for a test is about 35-36.
[0036]
(3) Each flocculant was added so that the concentration of iron or aluminum was 0.2 mmol / L.
(4) The test liquid was stirred for 5 minutes with a stirrer at a speed of 120 revolutions per minute (120 rpm).
(5) Further, the mixture was stirred at 40 rpm for 10 minutes.
(6) After completion of stirring, the mixture was allowed to stand for 20 minutes, and the generated floc was lowered to obtain a precipitate.
(7) The pH and turbidity of the supernatant of the test solution were measured.
[0037]
FIG. 1 shows the pH of the test liquid after completion of the aggregation treatment on the horizontal axis, and the turbidity of the test liquid after completion of the aggregation treatment on the vertical axis. As shown in FIG. 1, the polyferric chloride flocculant (indicated by “●” in the figure) is such that the pH of the test liquid after completion of the aggregation treatment is around 4.2 to 8.1. It was found to have good turbidity removal performance. Here, ferric chloride flocculant (indicated by “■” in the figure), polyaluminum chloride flocculant (indicated by “▲” in the figure), and sulfuric acid band flocculant (indicated by “♦” in the figure) ) Had good turbidity removal performance near neutrality, but no good results were obtained in the acidic region.
[0038]
(Example 2)
Next, the effect of the flocculant was tested on the polyferric chloride flocculants (A) to (E) and the polyferric chloride solution (X) in the same manner as in Example 1. About the polyferric chloride flocculants (A) to (E) containing 20% by weight of iron of polyferric chloride having an average molecular weight cut-off of 500 or more, substantially the same results as in the above experimental examples were observed. . In particular, there was a tendency that the better the ratio of polyferric chloride to the total iron of iron and the higher the average molecular weight, the better the effect. For polyferric chloride solution (X) in which the ferric chloride iron is less than 20% by weight of the total iron, the effect in the acidic region of pH 4-6 was small.
[0039]
(Example 3)
Next, the organic substance removal performance in the acidic region of the ferric chloride flocculant of Example 1 and other flocculants will be described.
The test method of turbidity removal performance was performed on polyferric chloride flocculant, ferric chloride, polyaluminum chloride, and sulfate band. The test method is shown below.
In addition, as a to-be-processed liquid for a test, what contained 10 mg / L of total organic carbon was used. As for the polyferric chloride flocculant, a polyferric chloride flocculant similar to that used in Example 1 containing in
[0040]
(1) A sulfuric acid aqueous solution is added to 1 L of a standard solution having a total organic carbon content of 10 mg / L, pH adjustment is performed, and a test solution is obtained. Here, the pH of the test liquid is adjusted in advance so that the pH of the supernatant of the test liquid after the precipitation process is about 5.5.
(2) Next, each aggregating agent was added so that the concentration of iron or aluminum was 0.2 mmol / L.
[0041]
(3) The test liquid was stirred with a stirrer at 120 rpm for 5 minutes.
(4) Further, the mixture was stirred at 40 rpm for 10 minutes.
(5) After completion of stirring, the mixture was allowed to stand for 20 minutes, and the generated floc was lowered to obtain a precipitate.
(6) The pH of the supernatant of the test solution and the total organic carbon content were measured by a total organic carbon analyzer.
[0042]
[Table 1]
As shown in Table 1, it can be seen that the polyferric chloride flocculant has an excellent organic substance removal performance as compared with ferric chloride, polyaluminum chloride, and sulfuric acid band.
[0044]
(Example 4)
Next, the effect of the flocculant was tested on the polyferric chloride flocculants (A) to (E) and the polyferric chloride solution (X) in the same manner as in Example 3. About the polyferric chloride flocculants (A) to (E) containing 20% by weight of iron of polyferric chloride having an average molecular weight cut-off of 500 or more, substantially the same results as in the above experimental examples were observed. . In particular, as the ratio of ferric chloride to total iron in the iron increased, and the average fractional molecular weight increased, the organic substance removing function in the acidic region tended to show a better effect. For the polyferric chloride solution (X) in which the ferric chloride iron was less than 20% by weight of the total iron, the organic substance removal performance in the acidic region of pH 4-6 was low.
[0045]
From Examples 1 to 4 above, the ferric chloride solution in which the iron in the ferric chloride having an average molecular weight cut-off of 500 or more is 20% by weight or more of the total iron is an acidic region advantageous for organic matter removal. Was also found to have a turbidity removing action. Furthermore, the ratio of iron in the polyferric chloride molecule having an average molecular weight cut-off by an ultrafiltration membrane of 500 or more is preferably 20% by weight or more of the total iron, and as the ratio increases, the turbidity increases. It was found that the degree removal performance tends to be high.
Further, it was found that the average fractional molecular weight of polyferric chloride contained in the iron-based flocculant is 500 or more, preferably 10,000 or more.
As described above, it was confirmed that the polyferric chloride flocculant of the present invention has excellent turbidity removal performance and organic matter removal performance in the acidic region.
[0046]
The present invention is not limited to the above-described embodiment, and can be changed without changing the gist of the present invention. For example, a part or all of the above-described embodiment and modification examples are combined. Thus, the case where the iron-based flocculant of the present invention is constituted is also included in the scope of the present invention.
For example, in the above embodiment, sulfuric acid is used to lower the pH of the liquid to be treated, that is, to make it acidic.
[0047]
Moreover, the iron-based flocculant may contain one or more of phosphate ion species, sulfate ion species, silicate compounds, and aluminum compounds.
In addition, if it is necessary to return the pH of the liquid to be treated to neutral after the aggregation treatment in the acidic region, the pH is adjusted by adding an alkaline solution after the aggregate during the aggregation treatment is removed. You may go.
[0048]
【The invention's effect】
In the iron-based flocculant according to claims 1 to 7, the iron in the polyferric chloride molecule containing polyferric chloride and having an average fractional molecular weight of 500 or more by the ultrafiltration membrane is all iron. Since the turbidity removal performance is good even in the acidic region, the organic matter can be removed simultaneously with the coagulation precipitation treatment.
[0049]
In particular, the iron-based flocculant according to claim 2 contains phosphate ion species and stabilizes polyferric chloride having an average fractional molecular weight of 500 or more over a long period of time. Can be used over and economical. Further, the degree of polymerization of the iron-based flocculant is appropriately adjusted by the phosphate ion species, and the iron molecules in the iron-based flocculant having an average fractional molecular weight of 500 or more can be increased.
In particular, in the iron-based flocculant according to
[0050]
In the iron-based flocculant according to
In the iron-based flocculant according to
[0051]
In the iron-based flocculant according to
In the iron-based flocculant according to the seventh aspect, since the iron-based flocculant is in a solid state, the transportation cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a graph comparing the turbidity removal performance of an iron-based flocculant and another flocculant according to an embodiment of the present invention.
Claims (7)
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| JP2003104471A JP4010976B2 (en) | 2003-04-08 | 2003-04-08 | Iron-based flocculant |
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| JP2003104471A JP4010976B2 (en) | 2003-04-08 | 2003-04-08 | Iron-based flocculant |
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| JP4010976B2 true JP4010976B2 (en) | 2007-11-21 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108002504A (en) * | 2017-10-30 | 2018-05-08 | 郑州大学 | A kind of preparation method of boron poly aluminium iron silicate-chitin composite flocculant |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108002504A (en) * | 2017-10-30 | 2018-05-08 | 郑州大学 | A kind of preparation method of boron poly aluminium iron silicate-chitin composite flocculant |
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