JP2004057954A - Water treatment catalyst and method of treating water - Google Patents
Water treatment catalyst and method of treating water Download PDFInfo
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- JP2004057954A JP2004057954A JP2002220679A JP2002220679A JP2004057954A JP 2004057954 A JP2004057954 A JP 2004057954A JP 2002220679 A JP2002220679 A JP 2002220679A JP 2002220679 A JP2002220679 A JP 2002220679A JP 2004057954 A JP2004057954 A JP 2004057954A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 113
- 239000003054 catalyst Substances 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims description 29
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 claims abstract description 60
- 229910052742 iron Inorganic materials 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims abstract description 5
- 239000010419 fine particle Substances 0.000 claims description 86
- 229910052751 metal Inorganic materials 0.000 claims description 56
- 239000002184 metal Substances 0.000 claims description 56
- 239000003638 chemical reducing agent Substances 0.000 claims description 34
- 239000002245 particle Substances 0.000 claims description 31
- 229910052763 palladium Inorganic materials 0.000 claims description 8
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 229910052737 gold Inorganic materials 0.000 claims description 5
- 229910052707 ruthenium Inorganic materials 0.000 claims description 5
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910052787 antimony Inorganic materials 0.000 claims description 3
- 229910052738 indium Inorganic materials 0.000 claims description 3
- 150000002739 metals Chemical class 0.000 claims description 3
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- 230000002829 reductive effect Effects 0.000 description 11
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 10
- 239000011790 ferrous sulphate Substances 0.000 description 10
- 235000003891 ferrous sulphate Nutrition 0.000 description 10
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 10
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- 239000012299 nitrogen atmosphere Substances 0.000 description 8
- JUBNUQXDQDMSKL-UHFFFAOYSA-N palladium(2+);dinitrate;dihydrate Chemical compound O.O.[Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O JUBNUQXDQDMSKL-UHFFFAOYSA-N 0.000 description 8
- 239000001509 sodium citrate Substances 0.000 description 8
- HRXKRNGNAMMEHJ-UHFFFAOYSA-K trisodium citrate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O HRXKRNGNAMMEHJ-UHFFFAOYSA-K 0.000 description 8
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- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
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- 101000692878 Homo sapiens Regulator of MON1-CCZ1 complex Proteins 0.000 description 4
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- 102100026436 Regulator of MON1-CCZ1 complex Human genes 0.000 description 4
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- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 4
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- 238000000926 separation method Methods 0.000 description 4
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- 238000006243 chemical reaction Methods 0.000 description 3
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- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- AZQWKYJCGOJGHM-UHFFFAOYSA-N 1,4-benzoquinone Chemical compound O=C1C=CC(=O)C=C1 AZQWKYJCGOJGHM-UHFFFAOYSA-N 0.000 description 2
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 2
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- 229910052757 nitrogen Inorganic materials 0.000 description 2
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- 239000002253 acid Substances 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
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- 239000000084 colloidal system Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
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- QUQFTIVBFKLPCL-UHFFFAOYSA-L copper;2-amino-3-[(2-amino-2-carboxylatoethyl)disulfanyl]propanoate Chemical compound [Cu+2].[O-]C(=O)C(N)CSSCC(N)C([O-])=O QUQFTIVBFKLPCL-UHFFFAOYSA-L 0.000 description 1
- SXTLQDJHRPXDSB-UHFFFAOYSA-N copper;dinitrate;trihydrate Chemical compound O.O.O.[Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O SXTLQDJHRPXDSB-UHFFFAOYSA-N 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
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- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
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- 238000005868 electrolysis reaction Methods 0.000 description 1
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- 150000002431 hydrogen Chemical class 0.000 description 1
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- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 229910017464 nitrogen compound Inorganic materials 0.000 description 1
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 1
- YJVFFLUZDVXJQI-UHFFFAOYSA-L palladium(ii) acetate Chemical compound [Pd+2].CC([O-])=O.CC([O-])=O YJVFFLUZDVXJQI-UHFFFAOYSA-L 0.000 description 1
- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 1
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- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、原水中に含まれる硝酸性窒素を分解除去するための水処理用触媒、および該水処理用触媒を用いる硝酸性窒素含有水の処理方法に関する。
【０００２】
【発明の技術的背景】
従来より、人体等に重大な影響を及ぼす物質として知られる水中に含まれる硝酸性窒素を分解除去する試みがなされている。硝酸性窒素の除去技術としては、吸着法、イオン交換法、逆浸透膜法、電気透析法、および生物学的脱窒法等が実用化されているものの、いずれの方法も飲料水等の大量処理および分解除去効率の点において十分な処理方法として完成されたものとはなっていない。
特開２００１−８６６号公報には、金属パラジウムと銅−パラジウム合金との混合物からなる水処理用触媒が開示されている。当該水処理用触媒による処理方法は大量処理の点では優れているものの、分解除去効率において必ずしも満足の行く処理方法ではなかった。
【０００３】
【発明の目的】
本発明は、大量処理に優れ、分解除去効率の高い硝酸性窒素含有水のための水処理用触媒、並びに、該触媒を用いた硝酸性窒素を含む水の処理方法を提供することを目的としている。
【０００４】
【発明の概要】
本発明に係る硝酸性窒素含有水処理用触媒は、Ａｕ、Ａｇ、Ｐｔ、Ｐｄ、Ｒｈ、Ｃｕ、Ｆｅ、Ｎｉ、Ｃｏ、Ｓｎ、Ｉｎ、Ｔｉ、Ａｌ、Ｔａ、Ｓｂ、Ｒｕから選ばれる１種または２種以上の金属からなる金属微粒子であって、平均粒子径が１〜２００ｎｍの範囲にあることを特徴とするものである。
前記金属微粒子はＣｕを含むものであることが好ましい。また、前記金属微粒子はＦｅを含み、Ｆｅの少なくとも一部が酸化物および／または水酸化物であることが好ましい。
本発明に係る硝酸性窒素含有水処理方法は、下記の工程（ａ）〜（ｃ）からなることを特徴とするものである。
（ａ）前記した水処理用触媒と硝酸性窒素含有水とを、還元剤の存在下で接触させる工程
（ｂ）前記接触済の硝酸性窒素含有水から水処理用触媒を分離する工程
（ｃ）必要に応じて前記分離した水処理用触媒を再生し、工程（ａ）に戻す工程本発明の硝酸性窒素含有水処理方法は、前記工程（ａ）〜（ｃ）を繰り返すことが好ましい。また、前記工程（ａ）〜（ｃ）を連続的に行うことが好ましい。
【０００５】
【発明の具体的説明】
先ず、本発明に係る水処理用触媒について説明する。
本発明の触媒微粒子にはＡｕ、Ａｇ、Ｐｔ、Ｐｄ、Ｒｈ、Ｃｕ、Ｆｅ、Ｎｉ、Ｃｏ、Ｓｎ、Ｉｎ、Ｔｉ、Ａｌ、Ｔａ、Ｓｂ、Ｒｕから選ばれる１種または２種以上の金属または合金からなる金属微粒子が用いられる。なかでもＣｕを主成分として含み、ＣｕとＰｄおよび／またはＰｔからなる合金微粒子は、還元剤である水素の吸着能が高く、常温で硝酸性窒素をＮ２ とＨ２ Ｏに選択的に還元分解する。好ましい２成分以上の組み合わせとしては、Ｐｄ−Ｃｕ、Ｐｄ−Ａｕ、Ｐｄ−Ｗ、Ｐｄ−Ｖ、Ｐｄ−Ｍｏ、Ｐｄ−Ｆｅ、Ｐｄ−Ｃｕ／Ｐｄ、Ｐｄ−Ｃｕ−Ｒｕ、Ｐｄ−Ｃｕ−Ｆｅ、Ｐｄ−Ｃｕ−Ａｕ、Ｐｔ−Ｃｕ、Ｐｔ−Ａｕ、Ｐｔ−Ｗ、Ｐｔ−Ｖ、Ｐｔ−Ｍｏ、Ｐｔ−Ｆｅ、Ｐｔ−Ｐｄ−Ｃｕ、Ｐｔ−Ｃｕ−Ｒｕ、Ｐｔ−Ｃｕ−Ｆｅ、Ｐｔ−Ｃｕ−Ａｕ等が挙げられる。
【０００６】
前記金属微粒子はＦｅを含み、Ｆｅの少なくとも一部が酸化物および／または水酸化物となっていることが好ましく、Ｆｅとして０． １〜３． ０重量％、特に０． ２〜２重量％の範囲で含まれていることが好ましい。金属微粒子中のＦｅの含有量が３． ０重量％を越えると硝酸性窒素の還元分解活性が低下し、Ｆｅの含有量が０． １重量％未満の場合は、Ｆｅの酸化物および／または水酸化物も少なく、分散安定性を向上させる効果が不充分となることがある。ここで、Ｆｅの酸化物および／または水酸化物の存在により金属微粒子の分散安定性が向上する理由は必ずしも明らかではないが、通常の金属酸化物あるいは金属水酸化物の微粒子が安定なコロイドとして得られるのと同様の理由によるものと推測される。
なお、前記において、合金とは２種以上の金属成分が均一に混合している必要はなく、単に混合物である場合も含んで意味している。また、結晶性であっても非晶質であってもよい。
このような金属微粒子は、硝酸性窒素を還元して分解する活性が高く、且つ活性劣化が小さく、また再生によって容易に活性が復元し、長期にわたって活性を維持することができる。
【０００７】
金属微粒子の平均粒子径は１〜２００ｎｍであり、特に２〜１００ｎｍの範囲にあることが好ましい。金属微粒子の平均粒子径が１ｎｍ未満の場合は、分散安定性が不充分となったり、反応後に金属微粒子を処理水（以下、清浄水と言うことがある。）から分離することが困難となることがあり、触媒が散逸し易い。金属微粒子の平均粒子径が２００ｎｍを越えると、金属微粒子の表面積が低下し、還元剤の吸着量が低下して、硝酸性窒素の還元分解活性が低下する。また、金属微粒子が処理水中で沈降して長期連続運転が困難となることがあり、停止してメインテナンスが必要となる。
【０００８】
このような金属微粒子の製造方法は、前記した平均粒子径範囲の金属微粒子が得られれば特に制限はなく、従来公知の方法を採用することができる。以下、本発明に用いることのできる金属微粒子の製造方法について例示的に説明する。
第１の方法として、所定濃度の１種または２種以上の金属塩水溶液に、水素化硼素ナトリウム（ＮａＢＨ４ ）、次亜リン酸ソーダ、ヒドラジン、硫酸第１鉄等の還元剤を加えことによって金属微粒子を析出させる方法が挙げられる。具体的には、硝酸パラジウムと硝酸銅と、必要に応じて硫酸第２鉄との混合水溶液に、クエン酸水溶液と、還元剤として硫酸第１鉄を溶解した溶液を添加してＰｄ−Ｃｕ合金微粒子分散液を調製することができる。クエン酸は有機安定化剤の１つであり、金属微粒子に配位して金属微粒子の分散安定性を高める。次いで、必要に応じて約１００〜３００℃の温度範囲でオートクレーブ処理してもよい。
金属塩としては、硝酸パラジウム、塩化パラジウム、酢酸パラジウム、テトラアンミンパラジウム、塩化白金、硝酸銀、硝酸銅、硝酸ニッケル、硫酸第２鉄、酢酸ルテニウム等、前記した金属の塩で水に可溶な塩を用いることができる。なお、金属微粒子の粒子径はＴＥＭにより測定することができる。
【０００９】
第２の方法として、金属塩水溶液に超音波を照射することによって金属微粒子を析出させる方法が挙げられる。この場合も必要に応じて有機安定化剤を用いることができる。上記のようにして得られる金属微粒子分散液は、濃度が金属として通常１〜２０重量％の範囲にあり、必要に応じて濃縮したり、希釈して用いることができる。
【００１０】
続いて、本発明に係る硝酸性窒素を含む水の処理方法について、工程（ａ）から順に説明する。図１は本発明に係る水処理方法を示すフロー図の１例である。
工程（ａ）
本発明の水処理方法に用いられる処理設備の方式には格別の制限はなく、工程（ａ）では、完全混合槽型、流通型、多段型、バッチ型等、固定床以外の種々の方式が採用可能である。
本発明が対象とする硝酸性窒素を含む水（以下、原水と言うこともある。）中の硝酸性窒素化合物の濃度は、Ｎとして５０〜１０，０００ｐｐｍ、特に、１００〜５０００ｐｐｍの範囲にある。濃度がＮとして５０ｐｐｍ未満の場合は、還元分解処理することは可能であるが経済性が問題となることがある。他方、濃度がＮとして１０，０００ｐｐｍを越えると、還元剤によっては必要量を共存させることができないために硝酸性窒素の還元分解が不充分となることがあり、また処理時間を長くするか、触媒微粒子濃度を高める必要があり、触媒微粒子濃度を高めた場合は触媒の分散安定性が低下して、凝集した場合は濾過分離が困難となって連続運転ができなくなったり、水中硝酸性窒素との接触効率が低下して還元分解活性が低下する等の問題がある。
【００１１】
水処理用触媒は原水と混合して投入しても良いし、別に触媒微粒子の分散液を調製しておき、後述する工程（ｂ）の分離触媒と、あるいは工程（ｃ）の必要に応じて再生した触媒と混合して投入しても良い。
投入される原水中の硝酸性窒素Ｎの量をＷＮ とし、水処理用触媒量（分離触媒および／または補充用触媒も含む。）をＷＭ で表した場合、原水と触媒の投入量比（ＷＮ ／ＷＭ ）は１〜５００、さらには２０〜１００の範囲とすることが好ましい。前記比ＷＮ ／ＷＭ が１未満の場合は、触媒の使用量が多過ぎて経済性が悪く、前記比ＷＮ ／ＷＭ が５００を越えると、処理温度が常温以下の場合に還元分解速度が不充分となり、硝酸性窒素を所望の濃度以下に低減することが困難となる。
【００１２】
触媒とともに供給される還元剤としては、水素、ヒドラジン、水素化硼素ナトリウム、次亜リン酸ナトリウム、キノン、ヒドロキノン等を挙げることができるが、特に水素は電気分解等により容易に製造することができ、水中に残存しても問題となることはなく、必要に応じて回収することができるので好適である。
還元剤は、後述する必要に応じて再生する工程で供給する場合は必ずしも工程（ａ）で供給する必要はなく、工程（ａ）において硝酸性窒素の分解に必要な還元剤が存在していればよい。
【００１３】
水処理用触媒、還元剤および原水の投入は、夫々、連続的でも、断続的でもよい。触媒と原水との接触時間（滞留時間）は、処理を必要とする原水の量、原水中の硝酸性窒素の濃度、要求される処理水（清浄水）中のＮ濃度レベル、処理温度、触媒中の金属微粒子の量、粒子径、処理水のｐＨや不純物等によっても異なるが、概ね２０時間以下、通常１０分間〜５時間の範囲にあることが好ましい。また、還元剤の投入量は、下記化学反応式（１）に示されるように、硝酸性窒素に対する量論量以上であればよいが、本発明の処理方法では、還元剤のモル数（ＭＲ ）と硝酸性窒素のモル数（ＭＮ ）の比（ＭＲ ／ＭＮ ）が３〜２０、特に４〜１０の範囲にあることが好ましい。
２ＮＯ３ ＋６Ｈ２ →Ｎ２ ＋６Ｈ２ Ｏ・・・（１）
前記モル比が３未満の場合は還元分解が不充分となり、得られる処理水中の硝酸性窒素濃度が高く、所期の目的を達成できないことがあり、モル比が２０を越えると、ＮＨ３ の生成が増加したり還元剤の利用率が低下して、経済性が悪くなる。
なお、工程（ａ）では、必要に応じて、酸またはアルカリを添加してｐＨを調整することができる。
【００１４】
工程（ｂ）
本工程は主として触媒の分離工程であり、分離装置としては限外濾過膜、セラミックフィルター等を用いることができる。特に流通式セラミックフィルターは口径を触媒粒子径に応じて選択することができるので効率的に分離することができ、またフィルターの圧密化などによる口径の変化がなく、耐久性に優れているので好ましい。しかしながら、本発明では必ずしもこのような分離装置を用いる必要はなく、工程（ａ）の後、貯槽に貯え、沈降させるか、必要に応じて凝集させて分離回収することもできる。
【００１５】
本工程では、触媒微粒子と処理水を抜き出しながら、触媒微粒子分散液の濃度が固形分として５〜５０重量％の範囲となるように、触媒微粒子を分離・濃縮する。濃度が５重量％未満の場合は、後述する再生時の還元剤の利用効率が低下したり、再循環される清浄水が多くなるので経済性が低下する。また、濃度が５０重量％を越える濃縮は困難であると共に、触媒微粒子の凝集により連続処理（運転）が困難となることがある。
濃縮された触媒微粒子分散液は、工程（ａ）に戻すか、または次の工程（ｃ）に供給される。
処理水中のＮ濃度（硝酸性窒素および副生することのあるアンモニア性窒素の合計）は１００ｐｐｍ以下、好ましくは１０ｐｐｍ以下、特に１ｐｐｍ以下となる。
【００１６】
工程（ｃ）
本工程は任意工程であり、使用済触媒を再生機（再生塔）に供給し、還元剤と接触させて再生し、この再生触媒を工程（ａ）に戻すものである。
還元剤としては、工程（ａ）で挙げたものが使用可能であり、工程（ｂ）からの触媒微粒子分散液に直接、還元剤を溶解させるか、または還元剤を溶解した水を前記分散液に混合する。この際、必要に応じて加圧して還元剤の溶解量を調節することができる。還元剤の混合量は、還元剤モル数／触媒金属モル数が０． １〜１０、特に０． ２〜２の範囲とすることが好ましい。
【００１７】
上記工程（ａ）〜工程（ｃ）によって硝酸性窒素を含む水を処理することができるが、本発明方法では、前記工程（ａ）〜（ｃ）を順次工程毎に行ってもよく、これを繰り返し行うこともできるが、前記工程（ａ）〜（ｃ）を連続的に行うことが好ましい。
なお、下記化学反応式（２）に示されるように、硝酸性窒素を含む水の処理によって発生することのあるＮＨ３ ガスは、必要に応じてアンモニアストリッピング等、従来公知の方法によって処理することができる。
２ＮＯ３ ＋９Ｈ２ →２ＮＨ３ ＋６Ｈ２ Ｏ・・・（２）
【００１８】
【発明の効果】
本発明に係る水処理用触媒は粒子径が小さく、硝酸性窒素の還元分解活性が高い。また、当該触媒は原水中で安定に高分散して容易に沈降することがない。
本発明に係る前記水処理用触媒を用いる水処理方法は、硝酸性窒素含有水の処理方法として好適である。
【００１９】
【実施例１】
触媒微粒子（ ＭＣ１ ）の調製
純水１００ｇに、硝酸パラジウム２水塩９． ６ｇおよび硝酸銅３水塩１． ６ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２３７． ４ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液水溶液９５． ６ｇを加え、窒素雰囲気下で２０時間攪拌して触媒微粒子の分散液を得た。
得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度１０重量％の触媒微粒子（ＭＣ１）の分散液（Ａ液）とした。分散液のｐＨは６であった。触媒微粒子（ＭＣ１） の組成を表１に示す。触媒微粒子（ＭＣ１） の平均粒子径は４ｎｍであった。
【００２０】
硝酸性窒素含有水の処理
水素を溶存させた還元剤水溶液（Ｂ液）を調製した。
ロートを垂直に立て、上方から触媒微粒子（ＭＣ１ ）の分散液（Ａ液）と、還元剤水溶液（Ｂ液）と、硝酸性Ｎ濃度が５００ｐｐｍの原水とを、前記ＷＮ ／ＷＭ が２０となり、前記モル比ＭＲ ／ＭＮ が３となるように同時に、連続的に供給した。ロートの管状部の滞留時間は１時間となるように調整した。
ロート下部から流出した処理水は、触媒微粒子と清浄水とに分離し、清浄水中のＮ濃度を測定し、結果を表２に示した。
次に、分離した触媒を容器に充填し、水素加圧下で２時間放置した後、再び触媒微粒子（Ｃ１）の水分散液（固形分濃度１０重量％）を調製し、還元剤を供給しなかった以外は前記と同様に処理したところ、前記処理水と同じＮ濃度の清浄水が得られた。
【００２１】
【実施例２】
触媒微粒子（ ＭＣ２ ）の調製
純水１００ｇに、硝酸パラジウム２水塩７． ４ｇおよび硝酸銅３水塩４． ９ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２６５． ０ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液水溶液１２９． ０ｇを加え、窒素雰囲気下で２０時間攪拌して触媒微粒子の分散液を得た。得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度１０重量％の触媒微粒子（ＭＣ２） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ２） の平均粒子径は４ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ２ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２２】
【実施例３】
触媒微粒子（ ＭＣ３ ）の調製
純水１００ｇに、硝酸パラジウム２水和塩７． ４ｇおよび硝酸銅３水塩４． ９ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２６５． ０ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液２５８． ０ｇを加え、窒素雰囲気下で２０時間攪拌して金属微粒子の分散液を得た。得られた分散液は、遠心分離機により分離回収し、濃度１ 重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度が１０重量％の触媒微粒子（ＭＣ３） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ３）の平均粒子径は３０ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ３ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２３】
【実施例４】
触媒微粒子（ ＭＣ４ ）の調製
純水１００ｇに、硝酸パラジウム２水和塩７． ４ｇおよび硝酸銅３水塩４． ９ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液１３２． ５ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液２５８． ０ｇを加え、窒素雰囲気下で２０時間攪拌して金属微粒子の分散液を得た。得られた分散液は、遠心分離機により分離回収し、濃度１ 重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度が１０重量％の触媒微粒子（ＭＣ４） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ４）は凝集体粒子であり、１次粒子径は３０ｎｍ、凝集粒子（２次粒子）の平均粒子径は１２０ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ４ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２４】
【実施例５】
硝酸性窒素含有水の処理
実施例２において、ＷＮ ／ＷＭ が５０となるように同時に、連続的に供給した以外は実施例１と同様に硝酸性窒素含有水の処理を行った。
【００２５】
【実施例６】
触媒微粒子（ ＭＣ５ ）の調製
純水１００ｇに、硝酸パラジウム２水塩５． ３ｇおよび硝酸銅３水塩８． １ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２９８． ２ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液水溶液１２０． １ｇを加え、窒素雰囲気下で２０時間攪拌して触媒微粒子の分散液を得た。得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度１０重量％の触媒微粒子（ＭＣ５） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ５） の平均粒子径は５ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ５ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２６】
【実施例７】
触媒微粒子（ ＭＣ６ ）の調製
純水１００ｇに、硝酸パラジウム２水塩１０． ７ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２２０． ９ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液水溶液８９． ０ｇを加え、窒素雰囲気下で２０時間攪拌して触媒微粒子の分散液を得た。得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度１０重量％の触媒微粒子（ＭＣ６） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ６） の平均粒子径は４ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ６ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２７】
【実施例８】
触媒微粒子（ ＭＣ７ ）の調製
純水１００ｇに、硝酸パラジウム２水和塩７． ４ｇ、硝酸銅３水和塩４． ８ｇおよび硫酸第二鉄０． １４ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２６５． ０ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液１０６． ８ｇを加え、窒素雰囲気下で２０時間攪拌して金属微粒子の分散液を得た。得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度１０重量％の触媒微粒子（ＭＣ７） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ７） の平均粒子径は４ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ７ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２８】
【実施例９】
触媒微粒子（ ＭＣ８ ）の調製
純水１００ｇに、硝酸パラジウム２水和塩７． ４ｇ、硝酸銀２． ０ｇおよび硫酸第二鉄ｎ水和物０． １４ｇを溶解した金属塩水溶液に、安定化剤として濃度３０重量％のクエン酸３ナトリウム水溶液２１５． ３ｇと還元剤として濃度２５重量％の硫酸第１鉄水溶液８６． ７ｇを加え、窒素雰囲気下で２０時間攪拌して金属微粒子の分散液を得た。得られた分散液は、遠心分離器により分離回収し、濃度１重量％の塩酸水溶液で洗浄した後、純水に分散させ、金属換算で濃度３重量％の触媒微粒子（ＭＣ８） の分散液（Ａ液）とした。分散液のｐＨは６であった。また触媒微粒子（ＭＣ８） の平均粒子径は５ｎｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＭＣ８ ）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００２９】
【比較例１】
触媒微粒子（ ＲＭＣ１ ）の調製
純水１００ｇに、金属換算で濃度が１０重量％となり、合金微粒子を構成する銅とパラジウムの重量比が３／７となるように硝酸銅および硝酸パラジウムを加え、これに、カーボン担体粒子（平均粒子径５０μｍ）４０ｇを加えて１時間撹拌した。次いで、凍結乾燥した後、Ｈ２ −Ｎ２ 混合ガス雰囲気下、２５０℃で２時間加熱処理して触媒微粒子（ＲＭＣ１）を調製した。触媒微粒子（ＲＭＣ１）の平均粒子径は５３μｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＲＭＣ１）の水分散液を用いた以外は実施例１と同様にして硝酸性窒素含有水の処理を行った。
【００３０】
【比較例２】
触媒微粒子（ ＲＭＣ２ ）の調製
比較例１において、カーボン担体粒子の代わりにシリカ・アルミナ粒子（触媒化成工業（株）製：ＨＡ、平均粒子径７０μｍ）４０ｇを用いた以外は同様にして触媒微粒子（ＲＭＣ２）を調製した。触媒微粒子（ＲＭＣ２）の平均粒子径は７２μｍであった。
硝酸性窒素含有水の処理
触媒微粒子（ＲＭＣ２）の水分散液を用いた以外は比較例１と同様にして硝酸性窒素含有水の処理を行った。
【００３１】
【表１】
【表２】
【図面の簡単な説明】
【図１】本発明に係る水処理方法を示すフロー図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a water treatment catalyst for decomposing and removing nitrate nitrogen contained in raw water, and a method for treating nitrate nitrogen-containing water using the water treatment catalyst.
[0002]
[Technical Background of the Invention]
Conventionally, attempts have been made to decompose and remove nitrate nitrogen contained in water, which is known as a substance that has a significant effect on the human body and the like. Adsorption, ion exchange, reverse osmosis, electrodialysis, biological denitrification, and other techniques have been put into practical use as nitrate nitrogen removal techniques, but all of these methods treat large quantities of drinking water and the like. In addition, it has not been completed as a sufficient treatment method in terms of decomposition and removal efficiency.
JP-A-2001-866 discloses a water treatment catalyst comprising a mixture of metal palladium and a copper-palladium alloy. Although the treatment method using the water treatment catalyst is excellent in terms of large-scale treatment, it is not always a satisfactory treatment method in terms of decomposition and removal efficiency.
[0003]
[Object of the invention]
An object of the present invention is to provide a water treatment catalyst for nitrate nitrogen-containing water that is excellent in large-scale treatment and has high decomposition removal efficiency, and a method for treating nitrate-nitrogen-containing water using the catalyst. I have.
[0004]
Summary of the Invention
The catalyst for treating nitrate nitrogen-containing water according to the present invention is one kind selected from Au, Ag, Pt, Pd, Rh, Cu, Fe, Ni, Co, Sn, In, Ti, Al, Ta, Sb, and Ru. Or, it is a metal fine particle composed of two or more kinds of metals, and has an average particle diameter in a range of 1 to 200 nm.
It is preferable that the metal fine particles contain Cu. Preferably, the metal fine particles contain Fe, and at least a part of Fe is an oxide and / or a hydroxide.
The method for treating nitrate nitrogen-containing water according to the present invention comprises the following steps (a) to (c).
(A) contacting the water treatment catalyst with nitrate nitrogen-containing water in the presence of a reducing agent; (b) separating the water treatment catalyst from the contacted nitrate nitrogen-containing water (c) ) Regenerating the separated water treatment catalyst as needed and returning to step (a) In the method for treating nitrate nitrogen-containing water of the present invention, it is preferable to repeat the above steps (a) to (c). Preferably, the steps (a) to (c) are continuously performed.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
First, the water treatment catalyst according to the present invention will be described.
The catalyst fine particles of the present invention include one or more metals selected from Au, Ag, Pt, Pd, Rh, Cu, Fe, Ni, Co, Sn, In, Ti, Al, Ta, Sb, and Ru, or Fine metal particles made of an alloy are used. Among them, alloy fine particles containing Cu as a main component and composed of Cu, Pd and / or Pt have a high ability to adsorb hydrogen as a reducing agent and selectively reduce nitrate nitrogen to N 2 and H 2 O at room temperature. Decompose. Preferred combinations of two or more components include Pd-Cu, Pd-Au, Pd-W, Pd-V, Pd-Mo, Pd-Fe, Pd-Cu / Pd, Pd-Cu-Ru, Pd-Cu-Fe. , Pd-Cu-Au, Pt-Cu, Pt-Au, Pt-W, Pt-V, Pt-Mo, Pt-Fe, Pt-Pd-Cu, Pt-Cu-Ru, Pt-Cu-Fe, Pt —Cu—Au and the like.
[0006]
Preferably, the metal fine particles contain Fe, and at least a part of Fe is an oxide and / or a hydroxide. 1-3. 0% by weight, in particular 0. Preferably, it is contained in the range of 2 to 2% by weight. 2. The content of Fe in the metal fine particles is 3. If the content exceeds 0% by weight, the activity of reducing and decomposing nitrate nitrogen is reduced, and the Fe content is reduced to 0.1%. When the amount is less than 1% by weight, the amount of Fe oxides and / or hydroxides is small, and the effect of improving the dispersion stability may be insufficient. Here, the reason why the dispersion stability of metal fine particles is improved by the presence of Fe oxides and / or hydroxides is not necessarily clear, but ordinary metal oxide or metal hydroxide fine particles are used as stable colloids. It is presumed to be for the same reason as obtained.
In the above description, the term “alloy” does not require that two or more metal components are uniformly mixed, but includes a case where the alloy is simply a mixture. Further, it may be crystalline or amorphous.
Such metal fine particles have a high activity of reducing and decomposing nitrate nitrogen and have a small activity deterioration, and the activity is easily restored by regeneration, and the activity can be maintained for a long time.
[0007]
The average particle diameter of the metal fine particles is 1 to 200 nm, and particularly preferably in the range of 2 to 100 nm. When the average particle diameter of the metal fine particles is less than 1 nm, the dispersion stability becomes insufficient or it becomes difficult to separate the metal fine particles from the treated water (hereinafter sometimes referred to as clean water) after the reaction. The catalyst may be easily dissipated. When the average particle diameter of the metal fine particles exceeds 200 nm, the surface area of the metal fine particles decreases, the adsorption amount of the reducing agent decreases, and the reductive decomposition activity of nitrate nitrogen decreases. In addition, the metal fine particles may settle in the treated water, making long-term continuous operation difficult, and stopping and requiring maintenance.
[0008]
The method for producing such metal fine particles is not particularly limited as long as metal fine particles having the above-mentioned average particle diameter range can be obtained, and a conventionally known method can be employed. Hereinafter, a method for producing metal fine particles that can be used in the present invention will be illustratively described.
As a first method, a reducing agent such as sodium borohydride (NaBH 4 ), sodium hypophosphite, hydrazine, ferrous sulfate or the like is added to an aqueous solution of one or more metal salts having a predetermined concentration. A method of depositing metal fine particles can be used. Specifically, an aqueous solution of citric acid and a solution in which ferrous sulfate is dissolved as a reducing agent are added to a mixed aqueous solution of palladium nitrate, copper nitrate, and, if necessary, ferric sulfate, to form a Pd-Cu alloy. A fine particle dispersion can be prepared. Citric acid is one of the organic stabilizers, and coordinates with metal fine particles to enhance the dispersion stability of the metal fine particles. Then, if necessary, the mixture may be autoclaved in a temperature range of about 100 to 300 ° C.
Examples of the metal salt include water-soluble salts such as palladium nitrate, palladium chloride, palladium acetate, tetraammine palladium, platinum chloride, silver nitrate, copper nitrate, nickel nitrate, ferric sulfate, and ruthenium acetate. Can be used. The particle diameter of the metal fine particles can be measured by TEM.
[0009]
As a second method, there is a method of irradiating an aqueous solution of a metal salt with ultrasonic waves to precipitate fine metal particles. Also in this case, an organic stabilizer can be used if necessary. The metal fine particle dispersion obtained as described above has a concentration of usually 1 to 20% by weight as a metal, and can be used after being concentrated or diluted as necessary.
[0010]
Subsequently, the method for treating water containing nitrate nitrogen according to the present invention will be described in order from step (a). FIG. 1 is an example of a flowchart showing a water treatment method according to the present invention.
Step (a )
There are no particular restrictions on the type of treatment equipment used in the water treatment method of the present invention. In step (a), various types other than fixed beds, such as a complete mixing tank type, a flow type, a multi-stage type, and a batch type, are used. Can be adopted.
The concentration of a nitrate nitrogen compound in water containing nitrate nitrogen (hereinafter, also referred to as raw water) targeted by the present invention is in the range of 50 to 10,000 ppm as N, particularly 100 to 5000 ppm. . When the concentration is less than 50 ppm as N, reductive decomposition treatment can be performed, but economy may be a problem. On the other hand, if the concentration exceeds 10,000 ppm as N, the required amount cannot be made to coexist depending on the reducing agent, so that the reductive decomposition of nitrate nitrogen may be insufficient, and the treatment time may be lengthened. It is necessary to increase the concentration of catalyst fine particles.If the concentration of catalyst fine particles is increased, the dispersion stability of the catalyst is reduced.If the catalyst is aggregated, filtration and separation become difficult and continuous operation cannot be performed. However, there are problems such as a reduction in the contacting efficiency of the compound and a reduction in the reductive decomposition activity.
[0011]
The catalyst for water treatment may be mixed with the raw water and added. Alternatively, a dispersion of catalyst fine particles may be separately prepared, and the separated catalyst may be used in the step (b) to be described later or as needed in the step (c). It may be mixed with the regenerated catalyst and charged.
The amount of the inserted are the raw water nitrate nitrogen N and W N, if the water treatment catalytic amount (separated catalyst and / or supplementary catalysts including.) Expressed in W M, the raw water and the input amount ratio of catalyst (W N / W M ) is preferably in the range of 1 to 500, more preferably 20 to 100. When the ratio W N / W M is less than 1, the amount of the catalyst used is too large and the economy is poor. When the ratio W N / W M exceeds 500, reductive decomposition occurs when the processing temperature is lower than normal temperature. The speed becomes insufficient, and it becomes difficult to reduce nitrate nitrogen to a desired concentration or less.
[0012]
Examples of the reducing agent supplied together with the catalyst include hydrogen, hydrazine, sodium borohydride, sodium hypophosphite, quinone, and hydroquinone. Particularly, hydrogen can be easily produced by electrolysis or the like. It is preferable because it does not cause a problem even if it remains in water and can be recovered as needed.
When the reducing agent is supplied in the step of regenerating as needed, which will be described later, it is not always necessary to supply the reducing agent in the step (a). In the step (a), the reducing agent necessary for decomposing nitrate nitrogen is present. Just fine.
[0013]
The input of the water treatment catalyst, the reducing agent and the raw water may be continuous or intermittent. The contact time (residence time) between the catalyst and the raw water depends on the amount of the raw water requiring treatment, the concentration of nitrate nitrogen in the raw water, the required N concentration level in the treated water (clean water), the treatment temperature, and the catalyst. Although it depends on the amount and particle size of the metal fine particles therein, the pH of the treated water, impurities and the like, it is preferably about 20 hours or less, usually in the range of 10 minutes to 5 hours. In addition, as shown in the following chemical reaction formula (1), the input amount of the reducing agent may be not less than the stoichiometric amount with respect to nitrate nitrogen, but in the treatment method of the present invention, the number of moles of the reducing agent (M It is preferable that the ratio (M R / M N ) of the number of moles (M N ) of R 3 ) and nitrate nitrogen be in the range of 3 to 20, particularly 4 to 10.
2NO 3 + 6H 2 → N 2 + 6H 2 O (1)
If the molar ratio is less than 3, reductive decomposition becomes insufficient, the concentration of nitrate nitrogen in the resulting treated water is high, and the intended purpose may not be achieved. If the molar ratio exceeds 20, NH 3 The production is increased and the utilization of the reducing agent is reduced, resulting in poor economy.
In step (a), the pH can be adjusted by adding an acid or an alkali, if necessary.
[0014]
Step (b )
This step is mainly a catalyst separation step, and an ultrafiltration membrane, a ceramic filter, or the like can be used as a separation device. In particular, a flow-type ceramic filter is preferable because the diameter can be selected according to the catalyst particle diameter, so that it can be separated efficiently, and there is no change in the diameter due to compaction of the filter and the durability is excellent, so that it is preferable. . However, in the present invention, it is not always necessary to use such a separation device, and after the step (a), it can be stored in a storage tank and settled, or if necessary, can be separated and collected by aggregation.
[0015]
In this step, while extracting catalyst fine particles and treated water, the catalyst fine particles are separated and concentrated so that the concentration of the catalyst fine particle dispersion is in the range of 5 to 50% by weight as a solid content. When the concentration is less than 5% by weight, the use efficiency of the reducing agent at the time of regeneration, which will be described later, decreases, and the amount of recirculated clean water increases, so that the economic efficiency decreases. Concentration exceeding 50% by weight is difficult, and continuous treatment (operation) may be difficult due to aggregation of catalyst fine particles.
The concentrated catalyst fine particle dispersion is returned to the step (a) or supplied to the next step (c).
The N concentration (total of nitrate nitrogen and ammoniacal nitrogen which may be by-produced) in the treated water is 100 ppm or less, preferably 10 ppm or less, particularly 1 ppm or less.
[0016]
Step (c )
This step is an optional step, in which the used catalyst is supplied to a regenerator (regeneration tower), is brought into contact with a reducing agent to regenerate, and the regenerated catalyst is returned to step (a).
As the reducing agent, those mentioned in the step (a) can be used. The reducing agent is directly dissolved in the catalyst fine particle dispersion from the step (b), or the water in which the reducing agent is dissolved is added to the dispersion. Mix. At this time, if necessary, the dissolution amount of the reducing agent can be adjusted by applying pressure. The mixing amount of the reducing agent is such that the number of moles of the reducing agent / the number of moles of the catalytic metal is 0.1. 1 to 10, especially 0. It is preferred to be in the range of 2 to 2.
[0017]
Although water containing nitrate nitrogen can be treated by the above steps (a) to (c), in the method of the present invention, the steps (a) to (c) may be sequentially performed for each step. Can be repeated, but it is preferable to perform the steps (a) to (c) continuously.
As shown in the following chemical reaction formula (2), NH 3 gas which may be generated by the treatment of water containing nitrate nitrogen is treated by a conventionally known method such as ammonia stripping as necessary. be able to.
2NO 3 + 9H 2 → 2NH 3 + 6H 2 O (2)
[0018]
【The invention's effect】
The catalyst for water treatment according to the present invention has a small particle size and high reductive decomposition activity of nitrate nitrogen. Further, the catalyst is stably highly dispersed in raw water and does not easily settle.
The water treatment method using the water treatment catalyst according to the present invention is suitable as a method for treating nitrate nitrogen-containing water.
[0019]
Embodiment 1
Preparation of catalyst fine particles ( MC1 ) Palladium nitrate dihydrate 9 in 100 g of pure water. 6 g and copper nitrate trihydrate 6 g of a metal salt aqueous solution was dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 4 g of an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent 6 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of catalyst fine particles.
The obtained dispersion is separated and collected by a centrifugal separator, washed with an aqueous hydrochloric acid solution having a concentration of 1% by weight, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC1) having a concentration of 10% by weight in terms of metal (MC1). A liquid). The pH of the dispersion was 6. Table 1 shows the composition of the catalyst fine particles (MC1). The average particle size of the catalyst fine particles (MC1) was 4 nm.
[0020]
Treatment of nitrate nitrogen-containing water An aqueous reducing agent solution (solution B) in which hydrogen was dissolved was prepared.
Making a funnel vertically, dispersion of the catalyst particles (MC1) from above and (A solution), and the reducing agent solution (B solution), the raw water Metropolitan nitrate N concentration of 500 ppm, the W N / W M is 20 And the above-mentioned molar ratios M R / M N were simultaneously and continuously supplied so as to be 3. The residence time of the tubular part of the funnel was adjusted to one hour.
The treated water flowing out from the lower part of the funnel was separated into fine catalyst particles and clean water, and the N concentration in the clean water was measured. The results are shown in Table 2.
Next, the separated catalyst was filled in a container, left for 2 hours under hydrogen pressure, and then an aqueous dispersion (solid content concentration: 10% by weight) of the catalyst fine particles (C1) was prepared again without supplying a reducing agent. Other than the above, the same treatment was performed as described above, and clean water having the same N concentration as the treated water was obtained.
[0021]
Embodiment 2
Preparation of catalyst fine particles ( MC2 ) Palladium nitrate dihydrate in 100 g of pure water. 4 g and copper nitrate trihydrate4. 9 g of an aqueous solution of a metal salt were dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 0 g and an aqueous solution of aqueous ferrous sulfate having a concentration of 25% by weight as a reducing agent After adding 0 g, the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of fine catalyst particles. The obtained dispersion is separated and collected by a centrifugal separator, washed with a 1% by weight aqueous hydrochloric acid solution, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC2) having a metal concentration of 10% by weight (MC2). A liquid). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC2) was 4 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC2) was used.
[0022]
Embodiment 3
Preparation of catalyst fine particles ( MC3 ) Palladium nitrate dihydrate salt in 100 g of pure water. 4 g and copper nitrate trihydrate4. 9 g of an aqueous solution of a metal salt were dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 0 g and an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent. 0 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of metal fine particles. The resulting dispersion is separated and recovered by a centrifuge, washed with a 1% by weight aqueous hydrochloric acid solution, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC3) having a concentration of 10% by weight in terms of metal. (Solution A). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC3) was 30 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC3) was used.
[0023]
Embodiment 4
Preparation of catalyst fine particles ( MC4 ) Palladium nitrate dihydrate salt in 100 g of pure water. 4 g and copper nitrate trihydrate4. 9 g of an aqueous solution of a metal salt dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer 132. 5 g and an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent. 0 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of metal fine particles. The resulting dispersion is separated and collected by a centrifuge, washed with a 1% by weight aqueous hydrochloric acid solution, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC4) having a concentration of 10% by weight in terms of metal. (Solution A). The pH of the dispersion was 6. The catalyst fine particles (MC4) were aggregate particles, the primary particle diameter was 30 nm, and the average particle diameter of the aggregate particles (secondary particles) was 120 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC4) was used.
[0024]
Embodiment 5
In the processing <br/> Example 2 of nitrate nitrogen containing water, W N / W M simultaneously so that 50, the same processing of nitrate nitrogen-containing water than those continuously fed to Example 1 went.
[0025]
Embodiment 6
Preparation of catalyst fine particles ( MC5 ) Palladium nitrate dihydrate 5 in 100 g of pure water. 3 g and copper nitrate trihydrate8. 1 g of an aqueous solution of a metal salt was dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 2 g and an aqueous solution of aqueous ferrous sulfate having a concentration of 25% by weight as a reducing agent 1 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of catalyst fine particles. The obtained dispersion is separated and collected by a centrifugal separator, washed with an aqueous hydrochloric acid solution having a concentration of 1% by weight, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC5) having a metal concentration of 10% by weight (MC5). A liquid). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC5) was 5 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC5) was used.
[0026]
Embodiment 7
Preparation of catalyst fine particles ( MC6 ) Palladium nitrate dihydrate 10% in 100 g of pure water. 7 g of an aqueous solution of a metal salt was dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 9 g and an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent After adding 0 g, the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of fine catalyst particles. The obtained dispersion is separated and recovered by a centrifugal separator, washed with a 1% by weight aqueous hydrochloric acid solution, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC6) having a concentration of 10% by weight in terms of metal (MC6). A liquid). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC6) was 4 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC6) was used.
[0027]
Embodiment 8
Preparation of catalyst fine particles ( MC7 ) Palladium nitrate dihydrate salt in 100 g of pure water. 4 g, copper nitrate trihydrate4. 8 g and ferric sulfate 0. 14 g of an aqueous solution of a metal salt was dissolved in a 30% by weight aqueous solution of trisodium citrate 265. 0 g and an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent. 8 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of metal fine particles. The obtained dispersion is separated and recovered by a centrifugal separator, washed with an aqueous hydrochloric acid solution having a concentration of 1% by weight, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC7) having a metal concentration of 10% by weight (MC7). A liquid). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC7) was 4 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was performed in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC7) was used.
[0028]
Embodiment 9
Preparation of catalyst fine particles ( MC8 ) Palladium nitrate dihydrate salt in 100 g of pure water. 4 g, silver nitrate 0 g and ferric sulfate n-hydrate. 14 g of an aqueous solution of a metal salt was dissolved in a 30% by weight aqueous solution of trisodium citrate as a stabilizer. 3 g and an aqueous solution of ferrous sulfate having a concentration of 25% by weight as a reducing agent 7 g was added, and the mixture was stirred under a nitrogen atmosphere for 20 hours to obtain a dispersion of metal fine particles. The resulting dispersion is separated and collected by a centrifugal separator, washed with a 1% by weight aqueous hydrochloric acid solution, and then dispersed in pure water to obtain a dispersion of catalyst fine particles (MC8) having a concentration of 3% by weight in terms of metal (MC8). A liquid). The pH of the dispersion was 6. The average particle size of the catalyst fine particles (MC8) was 5 nm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (MC8) was used.
[0029]
[Comparative Example 1]
Preparation of catalyst fine particles ( RMC1 ) Copper nitrate and palladium nitrate were added to 100 g of pure water so that the concentration became 10% by weight in terms of metal and the weight ratio of copper to palladium constituting the alloy fine particles became 3/7. Was added thereto, and 40 g of carbon carrier particles (average particle diameter: 50 μm) were added thereto, followed by stirring for 1 hour. Next, after freeze-drying, a catalyst fine particle (RMC1) was prepared by performing a heat treatment at 250 ° C. for 2 hours in an H 2 —N 2 mixed gas atmosphere. The average particle size of the catalyst fine particles (RMC1) was 53 μm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was carried out in the same manner as in Example 1 except that an aqueous dispersion of catalyst fine particles (RMC1) was used.
[0030]
[Comparative Example 2]
Preparation of catalyst fine particles ( RMC2 ) The same procedure as in Comparative Example 1 was carried out except that 40 g of silica / alumina particles (manufactured by Catalyst Chemical Industry Co., Ltd .: HA, average particle diameter 70 μm) were used instead of the carbon carrier particles. To prepare catalyst fine particles (RMC2). The average particle size of the catalyst fine particles (RMC2) was 72 μm.
Treatment of nitrate-nitrogen-containing water Treatment of nitrate-nitrogen-containing water was performed in the same manner as in Comparative Example 1, except that an aqueous dispersion of catalyst fine particles (RMC2) was used.
[0031]
[Table 1]
[Table 2]
[Brief description of the drawings]
FIG. 1 is a flowchart showing a water treatment method according to the present invention.
Claims (6)
（ａ）請求項１〜３のいずれか記載の水処理用触媒と硝酸性窒素含有水とを、還元剤の存在下で接触させる工程
（ｂ）前記接触済の硝酸性窒素含有水から水処理用触媒を分離する工程
（ｃ）必要に応じて前記分離した水処理用触媒を再生し、工程（ａ）に戻す工程A method for treating nitrate nitrogen-containing water, comprising the following steps (a) to (c).
(A) contacting the water treatment catalyst according to any one of claims 1 to 3 with nitrate nitrogen-containing water in the presence of a reducing agent; and (b) treating the contacted nitrate nitrogen-containing water with water. (C) regenerating the separated water treatment catalyst if necessary and returning to step (a)
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| JP2002220679A JP4111768B2 (en) | 2002-07-30 | 2002-07-30 | Water treatment catalyst and water treatment method |
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| JP2002220679A JP4111768B2 (en) | 2002-07-30 | 2002-07-30 | Water treatment catalyst and water treatment method |
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| JP2002220679A Expired - Lifetime JP4111768B2 (en) | 2002-07-30 | 2002-07-30 | Water treatment catalyst and water treatment method |
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