JP4450677B2 - Treatment method for nitrate-containing water - Google Patents
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- JP4450677B2 JP4450677B2 JP2004176435A JP2004176435A JP4450677B2 JP 4450677 B2 JP4450677 B2 JP 4450677B2 JP 2004176435 A JP2004176435 A JP 2004176435A JP 2004176435 A JP2004176435 A JP 2004176435A JP 4450677 B2 JP4450677 B2 JP 4450677B2
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本発明は、硝酸性窒素含有水の処理方法に関し、さらに詳しくは、硝酸性窒素含有水を還元剤の存在下に触媒と接触させて硝酸性窒素を還元分解する硝酸性窒素含有水の処理方法に関する。 The present invention relates to a method for treating nitrate nitrogen-containing water, and more specifically, a method for treating nitrate nitrogen-containing water by reductively decomposing nitrate nitrogen by bringing nitrate nitrogen-containing water into contact with a catalyst in the presence of a reducing agent. About.
従来、排水等の中に含まれる硝酸性窒素を除去する処理方法としては、微生物による生物学的処理方法、吸着法、イオン交換法、逆浸透膜法、電気透析法などの物理化学的処理方法および水素などの還元剤の存在下に硝酸性窒素を触媒と接触させて還元分解する化学的処理方法などが知られている。特に、硝酸性窒素を還元剤の存在下に触媒と接触させて還元分解する化学的処理方法は低濃度の硝酸性窒素を含む飲料水の原水や高濃度の硝酸性窒素を含む工業排水など、大量の硝酸性窒素含有水から硝酸性窒素を除去するのに適しており、種々の処理方法が提案されている。 Conventional treatment methods for removing nitrate nitrogen contained in wastewater, etc. include biological treatment methods using microorganisms, adsorption methods, ion exchange methods, reverse osmosis membrane methods, electrodialysis methods, and other physicochemical treatment methods. Also known is a chemical treatment method in which nitrate nitrogen is brought into contact with a catalyst in the presence of a reducing agent such as hydrogen to perform reductive decomposition. In particular, chemical treatment methods in which nitrate nitrogen is brought into contact with a catalyst in the presence of a reducing agent for reductive decomposition include raw water for drinking water containing low concentrations of nitrate nitrogen and industrial wastewater containing high concentrations of nitrate nitrogen, etc. It is suitable for removing nitrate nitrogen from a large amount of nitrate nitrogen-containing water, and various treatment methods have been proposed.
例えば、本出願人の出願にかかる特許文献１には、無機酸化物担体および／またはカーボン担体に、Ｐｔ、Ａｕ、Ａｇ、Ｐｄ、Ｒｕ、Ｃｕ、Ｎｉ、Ｗ、Ｖ、Ｍｏ、Ｆｅから選ばれる１種または２種以上の金属微粒子および／または合金微粒子が担持されてなる、平均粒子径が５ｎｍ〜２０μｍの範囲にある硝酸性窒素含有水処理用触媒が記載されており、更に、硝酸性窒素含有水処理方法として、
（ａ）前述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
からなる硝酸性窒素含有水処理方法が開示されている。
For example, in
(A) a step of bringing the water treatment catalyst and nitrate nitrogen-containing water into contact with each other in the presence of a reducing agent (b) a step of separating the water treatment catalyst from the contacted nitrate nitrogen-containing water (c) ) A nitrate nitrogen-containing water treatment method comprising a step of regenerating the separated water treatment catalyst as necessary and returning to the step (a) is disclosed.
特許文献２には、原水中の硝酸性窒素および亜硝酸性窒素を、触媒を用いて水素で還元分解するにあたり、金属パラジウムと、元素比がＣｕ≧Ｐｄである銅−パラジウム合金との混合物を触媒とする水処理方法が記載されている。
特許文献３には、硝酸性窒素とアンモニア性窒素を含む排水中の硝酸性窒素を、水中で水素を発生する金属と接触させることにより、亜硝酸性窒素または窒素ガスまで還元し、溶出した金属を軟化処理によって除去した後、生成した亜硝酸性窒素およびアンモニア性窒素を触媒存在下で反応させ、窒素に転換する硝酸性窒素およびアンモニア性窒素を含む排水の処理方法が記載されている。
Patent Document 2 discloses a mixture of metallic palladium and a copper-palladium alloy having an element ratio of Cu ≧ Pd in reducing and decomposing nitrate nitrogen and nitrite nitrogen in raw water with hydrogen using a catalyst. A water treatment method using a catalyst is described.
In Patent Document 3, nitrate nitrogen in wastewater containing nitrate nitrogen and ammonia nitrogen is reduced to nitrite nitrogen or nitrogen gas by contacting with metal that generates hydrogen in water, and the eluted metal A method for treating waste water containing nitrate nitrogen and ammonia nitrogen, in which nitrite nitrogen and ammonia nitrogen are reacted in the presence of a catalyst after being removed by softening treatment and converted to nitrogen is described.
しかしながら、従来の硝酸性窒素含有水の処理方法では、硝酸性窒素を還元分解する反応速度が遅く、硝酸性窒素含有水を処理するのに長時間を要するという問題があった。また、硝酸性窒素の還元分解反応でアンモニアの生成量が多いという問題があった。
本発明の目的は、低濃度の硝酸性窒素を含む飲料水の原水や、高濃度の硝酸性窒素を含む工業排水など大量の硝酸性窒素含有水から硝酸性窒素を除去する硝酸性窒素含有水の処理方法において、硝酸性窒素を還元分解する反応速度が速く、硝酸性窒素含有水を短時間で処理することができる硝酸性窒素含有水の処理方法を提供することにある。
また、本発明の他の目的は、硝酸性窒素含有水の処理方法において、硝酸性窒素の還元分解反応でアンモニアの生成量が少ない硝酸性窒素含有水の処理方法を提供することにある。
An object of the present invention is to remove nitrate nitrogen from a large amount of nitrate nitrogen-containing water such as raw water of drinking water containing low-concentration nitrate nitrogen or industrial wastewater containing high-concentration nitrate nitrogen. It is an object of the present invention to provide a method for treating nitrate nitrogen-containing water that has a high reaction rate for reducing and decomposing nitrate nitrogen and that can treat nitrate nitrogen-containing water in a short time.
Another object of the present invention is to provide a method for treating nitrate nitrogen-containing water that produces a small amount of ammonia in the reductive decomposition reaction of nitrate nitrogen in the method for treating nitrate nitrogen-containing water.
本発明の第１は、硝酸性窒素含有水を還元剤の存在下に触媒と接触させて硝酸性窒素を還元分解するに際して、硝酸性窒素含有水中に可溶性硫酸塩および／または硫酸水素塩を共存させることを特徴とする硝酸性窒素含有水の処理方法に関する。
本発明の第２は、前記可溶性硫酸塩が硫酸ナトリウムであることを特徴とする請求項１記載の硝酸性窒素含有水の処理方法に関する。
本発明の第３は、前記可溶性硫酸水素塩が硫酸水素ナトリウムであることを特徴とする請求項１記載の硝酸性窒素含有水の処理方法に関する。
本発明の第４は、前記可溶性硫酸塩および／または硫酸水素塩が硝酸性窒素含有水中に０．５〜１０００ｍｏｌ／ｍ3の範囲で存在することを特徴とする請求項１〜３記載の硝酸性窒素含有水の処理方法に関する。
本発明の第５は、前記可溶性硫酸塩および／または硫酸水素塩が共存する硝酸性窒素含有水は、ｐＨ４〜１０の範囲にあることを特徴とする請求項１〜４記載の硝酸性窒素含有水の処理方法に関する。
本発明の第６は、前記硝酸性窒素含有水中の硝酸性窒素の濃度が、Ｎとして５〜１００００ｐｐｍの範囲であることを特徴とする請求項１〜５記載の硝酸性窒素含有水の処理方法に関する。
本発明の第７は、前記触媒がパラジウムを含有する触媒であることを特徴とする請求項１〜６記載の硝酸性窒素含有水の処理方法に関する。
According to the first aspect of the present invention, when nitrate nitrogen-containing water is brought into contact with a catalyst in the presence of a reducing agent to reduce and decompose nitrate nitrogen, soluble nitrate and / or hydrogen sulfate coexist in nitrate nitrogen-containing water. The present invention relates to a method for treating nitrate nitrogen-containing water.
The second of the present invention relates to the method for treating nitrate nitrogen-containing water according to
A third aspect of the present invention relates to the method for treating nitrate nitrogen-containing water according to
A fourth aspect of the present invention is that the soluble sulfate and / or hydrogen sulfate is present in nitrate nitrogen-containing water in a range of 0.5 to 1000 mol / m 3. The present invention relates to a method for treating water containing nitrogen.
The fifth aspect of the present invention is the nitrate nitrogen-containing water according to any one of
The sixth of the present invention is the method for treating nitrate nitrogen-containing water according to
A seventh aspect of the present invention relates to the method for treating nitrate nitrogen-containing water according to
本発明の硝酸性窒素含有水の処理方法では、通常の硝酸性窒素含有水を還元剤の存在下に触媒と接触させて硝酸性窒素を還元分解して無害化する化学的処理方法において、硝酸性窒素含有水中に可溶性硫酸塩および／または硫酸水素塩を共存させるだけで従来の処理方法に比較して速い反応速度で硝酸性窒素を還元分解することができ、かつアンモニアの副生も抑えることができる。従って、本発明の処理方法は、従来の硝酸性窒素含有水の処理方法に適用して処理速度を大幅に改善することができるので工業的に有用である。 In the method for treating nitrate-nitrogen-containing water of the present invention, in a chemical treatment method in which ordinary nitrate-nitrogen-containing water is brought into contact with a catalyst in the presence of a reducing agent, nitrate nitrogen is reduced and detoxified to render it harmless. Nitrogen-containing nitrogen can be reduced and decomposed at a higher reaction rate than conventional treatment methods by reducing the presence of soluble sulfates and / or hydrogen sulfate, and ammonia by-product can also be suppressed. Can do. Therefore, the treatment method of the present invention is industrially useful because it can be applied to the conventional treatment method of nitrate nitrogen-containing water to greatly improve the treatment speed.
本発明の硝酸性窒素含有水の処理方法は、処理する硝酸性窒素含有水中に可溶性硫酸塩および／または硫酸水素塩を添加して、硝酸性窒素と硫酸塩および／または硫酸水素塩が溶けて共存している処理水を還元剤の存在下に触媒と接触させて硝酸性窒素を還元分解する方法である。従って、本発明の処理方法では、従来の硝酸性窒素含有水を還元剤の存在下に触媒と接触させて硝酸性窒素を還元分解する硝酸性窒素含有水の処理方法及びその処理装置が採用可能である。 In the method for treating nitrate nitrogen-containing water of the present invention, soluble nitrate and / or hydrogen sulfate is added to the nitrate nitrogen-containing water to be treated, so that nitrate nitrogen and sulfate and / or hydrogen sulfate are dissolved. In this method, nitrate water is reductively decomposed by contacting coexisting treated water with a catalyst in the presence of a reducing agent. Therefore, in the treatment method of the present invention, it is possible to adopt a treatment method and treatment apparatus for nitrate nitrogen-containing water in which nitrate nitrogen-containing water is brought into contact with a catalyst in the presence of a reducing agent to reduce and decompose nitrate nitrogen. It is.
本発明において可溶性硫酸塩および／または硫酸水素塩とは、２０℃において１００ｇの飽和水溶液中に溶存する硫酸塩および／または硫酸水素塩の質量が１．０ｇ以上の硫酸塩および／または硫酸水素塩をいう。
前記可溶性硫酸塩としては、硫酸ナトリウム、硫酸カリウム、硫酸リチウム、硫酸アルミニウム、硫酸アンモニウムアルミニウム、硫酸ナトリウムアルミニウム、硫酸アンモニウム、硫酸セシウム、硫酸アンモニウム第一鉄、硫酸銅、硫酸ニッケル、硫酸亜鉛、硫酸ジメチルなどが例示され、前記硫酸水素塩としては、硫酸水素ナトリウム、硫酸水素カリウム、硫酸水素セシウム、硫酸水素メチルなどが例示される。特に、硫酸ナトリウムおよび硫酸水素ナトリウムは排水中に含まれていても、排水のｐＨを５．８〜８．６に調整するだけで、これらの化合物を除去するための２次処理を必要とすることなく放水できるので好ましい。
In the present invention, the soluble sulfate and / or hydrogen sulfate is a sulfate and / or hydrogen sulfate having a mass of 1.0 g or more of sulfate and / or hydrogen sulfate dissolved in 100 g of a saturated aqueous solution at 20 ° C. Say.
Examples of the soluble sulfate include sodium sulfate, potassium sulfate, lithium sulfate, aluminum sulfate, ammonium aluminum sulfate, sodium aluminum sulfate, ammonium sulfate, cesium sulfate, ferrous ammonium sulfate, copper sulfate, nickel sulfate, zinc sulfate, and dimethyl sulfate. Examples of the hydrogen sulfate include sodium hydrogen sulfate, potassium hydrogen sulfate, cesium hydrogen sulfate, and methyl hydrogen sulfate. In particular, even if sodium sulfate and sodium hydrogen sulfate are contained in the waste water, a secondary treatment for removing these compounds is necessary only by adjusting the pH of the waste water to 5.8 to 8.6. It is preferable because it can be discharged without any trouble.
本発明の方法では、硝酸性窒素含有水中に前記可溶性硫酸塩および／または硫酸水素塩が０．５〜１０００ｍｏｌ／ｍ3の範囲で溶解して存在することが好ましい。該可溶性硫酸塩および／または硫酸水素塩が硝酸性窒素含有水中に存在する量が０．５ｍｏｌ／ｍ3未満の場合には、本発明の所望の効果が得られないことがあり、また、該量が１０００ｍｏｌ／ｍ3を超えると、１０００ｍｏｌ／ｍ3の場合と効果に大差がないので経済的でない。該可溶性硫酸塩および／または硫酸水素塩の硝酸性窒素含有水中に溶解して存在する量は、さらに好ましくは１〜８００ｍｏｌ／ｍ3の範囲である。 In the method of the present invention, it is preferable that the nitrate nitrogen containing water soluble sulfate and / or hydrogen sulfate salt is present in solution in the range of 0.5~1000mol / m 3. When the amount of the soluble sulfate and / or hydrogen sulfate present in the nitrate nitrogen-containing water is less than 0.5 mol / m 3 , the desired effect of the present invention may not be obtained. when the amount is more than 1000 mol / m 3, not economical because there is no great difference when the effect of the 1000 mol / m 3. The amount of the soluble sulfate and / or hydrogen sulfate dissolved in the nitrate nitrogen-containing water is more preferably in the range of 1 to 800 mol / m 3 .
一般に、硝酸性窒素含有水の処理方法では、処理水に酸またはアルカリを添加してｐＨ調整することが行われているが、本発明の方法でも、硝酸性窒素含有水に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。
本発明の方法では、前記可溶性硫酸塩および／または硫酸水素塩が溶解して共存する硝酸性窒素含有水は、ｐＨ４〜１０の範囲にあることが好ましい。該硝酸性窒素含有水のｐＨが４未満の場合には、触媒を構成する金属成分の溶出などにより触媒活性が低下することがあり、また、該ｐＨが１０を超えると、硝酸性窒素の還元反応速度が低下することがあり、さらにアンモニアの生成量が増加する傾向にある。該可溶性硫酸塩および／または硫酸水素塩が溶解して共存する硝酸性窒素含有水のｐＨは、さらに好ましくは５〜９の範囲である。
本発明の方法では、硝酸性窒素の還元分解反応の進行と共に硝酸性窒素含有水のｐＨが高くなるので、硫酸、塩酸、炭酸ガスなどの酸を用いて前記可溶性硫酸塩および／または硫酸水素塩が溶解して共存する硝酸性窒素含有水のｐＨを所定の範囲に調節することができる。特に、硫酸は前記可溶性硫酸塩および／または硫酸水素塩の共存効果を加速するので好適である。
In general, in the method for treating nitrate nitrogen-containing water, acid or alkali is added to the treated water to adjust the pH, but in the method of the present invention, acid or alkali is added to nitrate nitrogen-containing water. Thus, the pH can be adjusted.
In the method of the present invention, the nitrate nitrogen-containing water in which the soluble sulfate and / or hydrogen sulfate is dissolved and coexists is preferably in the range of pH 4-10. When the pH of the nitrate nitrogen-containing water is less than 4, the catalytic activity may decrease due to elution of metal components constituting the catalyst. When the pH exceeds 10, the nitrate nitrogen is reduced. The reaction rate may decrease, and the amount of ammonia produced tends to increase. The pH of the nitrate nitrogen-containing water in which the soluble sulfate and / or hydrogen sulfate is dissolved and coexist is more preferably in the range of 5-9.
In the method of the present invention, the pH of nitrate-containing water increases with the progress of the reductive decomposition reaction of nitrate nitrogen. Therefore, the soluble sulfate and / or hydrogen sulfate using an acid such as sulfuric acid, hydrochloric acid, carbon dioxide, etc. It is possible to adjust the pH of nitrate-containing water coexisting by dissolving in a predetermined range. In particular, sulfuric acid is preferable because it accelerates the coexistence effect of the soluble sulfate and / or hydrogen sulfate.
本発明が対象とする硝酸性窒素含有水中の硝酸性窒素の濃度は、従来の硝酸性窒素含有水の処理方法で処理される濃度範囲で処理可能である。本発明の方法では、特に、硝酸性窒素含有水中の硝酸性窒素の濃度はＮ（窒素）として５〜１００００ｐｐｍの範囲にあることが好ましい。該濃度がＮとして５ｐｐｍ未満の場合は、排水規制の対象外で、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、該濃度がＮとして１００００ｐｐｍ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、処理に長時間を要し処理効率が悪くなることがある。前記硝酸性窒素含有水中の硝酸性窒素の濃度は、さらに好ましくはＮとして５０〜５０００ｐｐｍの範囲である。 The concentration of nitrate nitrogen in the nitrate nitrogen-containing water targeted by the present invention can be treated within a concentration range that is treated by a conventional method for treating nitrate nitrogen-containing water. In the method of the present invention, in particular, the concentration of nitrate nitrogen in the nitrate nitrogen-containing water is preferably in the range of 5 to 10,000 ppm as N (nitrogen). When the concentration is less than 5 ppm as N, it is possible to carry out reductive decomposition treatment outside the scope of wastewater regulation, but there are cases where economic efficiency becomes a problem. On the other hand, if the concentration exceeds 10,000 ppm as N, the reductive decomposition of nitrate nitrogen may be insufficient due to the inability to coexist with the required amount depending on the reducing agent, and the treatment takes a long time. Processing efficiency may deteriorate. The concentration of nitrate nitrogen in the nitrate nitrogen-containing water is more preferably in the range of 50 to 5000 ppm as N.
また、本発明の方法では、従来の硝酸性窒素含有水の処理方法で使用される公知の触媒が使用可能である。この様な触媒としては、例えば、本出願人の出願にかかる特開２００４−５７９５４号公報に記載の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の範囲にある硝酸性窒素含有水処理用触媒や、無機酸化物担体および／またはカーボン担体にＰｔ、Ａｕ、Ａｇ、Ｐｄ、Ｒｕ、Ｃｕ、Ｎｉ、Ｗ、Ｖ、Ｍｏ、Ｆｅから選ばれる１種または２種以上の金属成分を担持した硝酸性窒素含有水処理用触媒などが例示される。 Moreover, in the method of this invention, the well-known catalyst used with the processing method of the conventional nitrate nitrogen containing water can be used. Examples of such a catalyst include Au, Ag, Pt, Pd, Rh, Cu, Fe, Ni, Co, Sn, In, Ti, and the like described in JP 2004-57954 A filed by the present applicant. A metal fine particle composed of one or more metals selected from Al, Ta, Sb, and Ru, a nitrate nitrogen-containing water treatment catalyst having an average particle diameter in the range of 1 to 200 nm, and an inorganic oxide Nitrate nitrogen-containing water treatment in which one or more metal components selected from Pt, Au, Ag, Pd, Ru, Cu, Ni, W, V, Mo, Fe are supported on a carrier and / or carbon carrier Examples include catalysts.
特に、パラジウムあるいはパラジウムと白金、金、銀、銅、鉄、バナジウム、モリブデン、タングステンなどの金属成分をアルミナ、シリカ、シリカ−アルミナ、活性炭、チタニア、シリカ−チタニア、ジルコニア、ゼオライトなどの担体に担持させたパラジウム含有触媒は、常温で硝酸性窒素を効果的に還元分解することができるので好適である。
なお、該触媒の形状については、制限されるものではなく、粒状、ペレット状、ハニカム状など種々の形状のものが採用可能である。
In particular, palladium or palladium and platinum, gold, silver, copper, iron, vanadium, molybdenum, tungsten and other metal components are supported on a carrier such as alumina, silica, silica-alumina, activated carbon, titania, silica-titania, zirconia, and zeolite. The palladium-containing catalyst thus made is preferable because nitrate nitrogen can be effectively reduced and decomposed at room temperature.
The shape of the catalyst is not limited, and various shapes such as a granular shape, a pellet shape, and a honeycomb shape can be adopted.
本発明の方法で用いる還元剤には特に制限はなく、水素ガス、ヒドラジン、ヒドロキシルアミン、水素化硼素ナトリウム、次亜リン酸ナトリウム、キノン、ヒドロキノンなど、通常、硝酸性窒素含有水の処理方法で使用される還元性を有する物質が使用可能である。特に水素ガスは電気分解等により容易に製造することができ、必要に応じて回収することができるので好適である。 There is no particular limitation on the reducing agent used in the method of the present invention, and hydrogen gas, hydrazine, hydroxylamine, sodium borohydride, sodium hypophosphite, quinone, hydroquinone, etc. The reducing substance used can be used. In particular, hydrogen gas is suitable because it can be easily produced by electrolysis or the like and can be recovered as necessary.
また、本発明の硝酸性窒素含有水の処理方法では、通常の硝酸性窒素含有水の処理方法および処理条件が採用可能で、処理設備の方式にも格別の制限はなく従来の完全混合槽型、流通型、多段型、バッチ型、固定床型などの種々の方式が採用可能である。
以下に実施例を示して本発明をさらに具体的に説明するが、本発明はこれにより何ら限定されるものではない。
Further, in the method for treating nitrate nitrogen-containing water of the present invention, the usual method for treating nitrate nitrogen-containing water and treatment conditions can be adopted, and there is no particular limitation on the method of treatment equipment, and the conventional complete mixing tank type Various systems such as a distribution type, a multistage type, a batch type, and a fixed bed type can be adopted.
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto.
窒素（Ｎ）として４００ｐｐｍの硝酸性窒素を含有することになる硝酸ナトリウム水溶液５００ｍｌに硫酸ナトリウム(関東化学(株)製：試薬特級)1.0ｇを添加して溶解し、濃度14.1ｍｏｌ／ｍ3（０．２ｗｔ％に相当）の硫酸ナトリウムが共存するｐＨ８の水溶液とした。該水溶液に、炭素担体に金属として10ｗｔ％Pd及び3.3ｗｔ％Cuを担持させた粉末状触媒を、乾燥重量で1.5g加えて分散させた。該水溶液（温度２５℃）を640rpmの回転速度で攪拌しながらH2ガスを底部より流速20ml/minでバブリングさせると共に、該水溶液のｐＨが５〜６の範囲（目標ｐＨ５．８）に維持されるように1ｗｔ%硫酸水溶液で調整しながら硝酸性窒素の還元分解反応を、反応開始から１５分間毎に該水溶液を５ｍｌサンプリングしながら５時間行った。
サンプリングした水溶液中の硝酸性窒素、亜硝酸性窒素、アンモニア性窒素の濃度を分析装置ＡＡＳ‐III（ブラン・ルーベ（株）製：ＮＯ3,ＮＯ2,ＮＨ3の窒素（Ｎ）測定装置）を用いて分析を行った結果、水溶液中の硝酸性窒素は反応開始から150分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はＮとして6.5 ppmであった。これは硝酸性窒素の1.6％がＮＨ3へ転換したことになる。
水溶液中の硝酸性窒素が無くなるまでの還元分解に要する時間、その時の生成アンモニア量および硝酸性窒素のアンモニアへの転換率を表１および図１に示す。
To 500 ml of an aqueous sodium nitrate solution containing 400 ppm of nitrate nitrogen as nitrogen (N), 1.0 g of sodium sulfate (manufactured by Kanto Chemical Co., Inc .: reagent grade) is added and dissolved to a concentration of 14.1 mol / m 3 ( PH 8 aqueous solution in which sodium sulfate (equivalent to 0.2 wt%) coexists. In the aqueous solution, 1.5 g of a dry catalyst in which 10 wt% Pd and 3.3 wt% Cu as metals were supported on a carbon support was added and dispersed. Aqueous solution with bubbling in than a flow rate of 20 ml / min bottom of H 2 gas with stirring (temperature 25 ° C.) at a rotational speed of 640rpm, pH of the aqueous solution is maintained in the range of 5-6 (target pH 5.8) In this way, the reductive decomposition reaction of nitrate nitrogen was performed for 5 hours while sampling 5 ml of the aqueous solution every 15 minutes from the start of the reaction while adjusting with 1 wt% sulfuric acid aqueous solution.
Analytical device AAS-III (Blan Roube Co., Ltd .: NO 3 , NO 2 , NH 3 nitrogen (N) measuring device) concentration of nitrate nitrogen, nitrite nitrogen and ammonia nitrogen in the sampled aqueous solution As a result, the nitrate nitrogen in the aqueous solution disappeared by reductive decomposition within 150 minutes from the start of the reaction, and the concentration of by-product ammonia nitrogen was 6.5 ppm as N. This means that 1.6% of nitrate nitrogen was converted to NH 3 .
Table 1 and FIG. 1 show the time required for reductive decomposition until the nitrate nitrogen in the aqueous solution disappears, the amount of ammonia produced at that time, and the conversion rate of nitrate nitrogen to ammonia.
実施例１において、硫酸ナトリウムの添加量を変えて表１に示す濃度の硫酸ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。 In Example 1, a reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the amount of sodium sulfate added was changed to an aqueous solution in which sodium sulfate having the concentration shown in Table 1 coexists. The reaction results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムの添加量を変えて表１に示す濃度の硫酸ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。 In Example 1, a reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the amount of sodium sulfate added was changed to an aqueous solution in which sodium sulfate having the concentration shown in Table 1 coexists. The reaction results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムの添加量を変えて表１に示す濃度の硫酸ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。 In Example 1, a reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the amount of sodium sulfate added was changed to an aqueous solution in which sodium sulfate having the concentration shown in Table 1 coexists. The reaction results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムの添加量を変えて表１に示す濃度の硫酸ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。 In Example 1, a reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the amount of sodium sulfate added was changed to an aqueous solution in which sodium sulfate having the concentration shown in Table 1 coexists. The reaction results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムの添加量を変えて表１に示す濃度の硫酸ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。 In Example 1, a reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the amount of sodium sulfate added was changed to an aqueous solution in which sodium sulfate having the concentration shown in Table 1 coexists. The reaction results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムを添加しなかったこと以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。反応結果を表１および図１に示す。
その結果、水溶液中の硝酸性窒素は反応開始から１９５分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はNとして１８．１ ppmであった。これは硝酸性窒素の４．５％がNH3へ転換したことになる。結果を表１および図１に示す。
In Example 1, nitrate nitrogen was subjected to a reductive decomposition reaction in the same manner as in Example 1 except that sodium sulfate was not added. The reaction results are shown in Table 1 and FIG.
As a result, nitrate nitrogen in the aqueous solution disappeared by reductive decomposition within 195 minutes from the start of the reaction, and the concentration of by-product ammonia nitrogen was 18.1 ppm as N. This means that 4.5% of nitrate nitrogen has been converted to NH 3 . The results are shown in Table 1 and FIG.
実施例１において、硫酸ナトリウムの代わりに硫酸水素ナトリウム(関東化学(株)製：特級)1.0ｇを添加して溶解し、濃度１６．７ｍｏｌ／ｍ3（０．２ｗｔ％に相当）の硫酸水素ナトリウムが共存する水溶液とした以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。
その結果、水溶液中の硝酸性窒素は反応開始から１６５分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はNとして７．０ ppmであった。これは硝酸性窒素の１．７％がNH3へ転換したことになる。結果を表１に示す。
In Example 1, 1.0 g of sodium hydrogen sulfate (manufactured by Kanto Chemical Co., Ltd .: special grade) was added and dissolved in place of sodium sulfate, and hydrogen sulfate having a concentration of 16.7 mol / m 3 (corresponding to 0.2 wt%) was dissolved. A reductive decomposition reaction of nitrate nitrogen was performed in the same manner as in Example 1 except that the aqueous solution coexists with sodium.
As a result, nitrate nitrogen in the aqueous solution disappeared by reductive decomposition in 165 minutes from the start of the reaction, and the concentration of by-produced ammoniacal nitrogen was 7.0 ppm as N. This means that 1.7% of nitrate nitrogen has been converted to NH 3 . The results are shown in Table 1.
実施例１において、分解還元反応時の硝酸性窒素と硫酸ナトリウムが共存する水溶液のｐＨ調整を、1ｗｔ%硫酸水溶液の代わりに１ｗｔ％塩酸水溶液を用いて調整したこと以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。
その結果、水溶液中の硝酸性窒素は反応開始から１６５分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はNとして１４．０ppmであった。これは硝酸性窒素の３．５％がNH3へ転換したことになる。結果を表１に示す。
In Example 1, the pH adjustment of the aqueous solution in which nitrate nitrogen and sodium sulfate coexist during the decomposition and reduction reaction was adjusted using a 1 wt% hydrochloric acid aqueous solution instead of the 1 wt% sulfuric acid aqueous solution. Then, reductive decomposition reaction of nitrate nitrogen was performed.
As a result, nitrate nitrogen in the aqueous solution disappeared by reductive decomposition in 165 minutes from the start of the reaction, and the concentration of by-product ammonia nitrogen was 14.0 ppm as N. This means that 3.5% of the nitrate nitrogen has been converted to NH 3 . The results are shown in Table 1.
実施例１において、硫酸ナトリウムを添加しなかったことと、分解還元反応時の硝酸性窒素含有水溶液のｐＨ調整を1ｗｔ%硫酸水溶液の代わりに１ｗｔ％塩酸水溶液を用いて調整したこと以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。
その結果、水溶液中の硝酸性窒素は反応開始から２１０分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はNとして３８．７ppmであった。これは硝酸性窒素の９．７％がNH3へ転換したことになる。結果を表１に示す。
In Example 1, except that sodium sulfate was not added and the pH adjustment of the aqueous solution containing nitrate nitrogen during the decomposition and reduction reaction was adjusted using a 1 wt% hydrochloric acid aqueous solution instead of the 1 wt% sulfuric acid aqueous solution. In the same manner as in Example 1, reductive decomposition reaction of nitrate nitrogen was performed.
As a result, nitrate nitrogen in the aqueous solution disappeared by reductive decomposition within 210 minutes from the start of the reaction, and the concentration of by-product ammonia nitrogen was 38.7 ppm as N. This means that 9.7% of nitrate nitrogen was converted to NH 3 . The results are shown in Table 1.
実施例１において、硫酸ナトリウムの代わりに塩化ナトリウム(関東化学(株)：特級)１．０ｇを添加して溶解し、濃度５４．８ｍｏｌ／ｍ3（０．２ｗｔ％に相当）の塩化ナトリウムが共存する水溶液としたことと、該水溶液のｐＨ調整に1ｗｔ%硫酸水溶液の代わりに１ｗｔ％塩酸水溶液を用いたこと以外は、実施例１と同様にして硝酸性窒素の還元分解反応を行った。
その結果、水溶液中の硝酸性窒素は反応開始から２５５分間で還元分解して無くなり、その時副成したアンモニア性窒素の濃度はNとして９８．７ppmであった。これは硝酸性窒素の２４．７％がNH3へ転換したことになる。結果を表１に示す。
In Example 1, 1.0 g of sodium chloride (Kanto Chemical Co., Ltd .: special grade) was added and dissolved instead of sodium sulfate, and sodium chloride with a concentration of 54.8 mol / m 3 (corresponding to 0.2 wt%) was dissolved. A reductive decomposition reaction of nitrate nitrogen was carried out in the same manner as in Example 1 except that a coexisting aqueous solution was used and that a 1 wt% hydrochloric acid aqueous solution was used instead of a 1 wt% sulfuric acid aqueous solution for pH adjustment of the aqueous solution.
As a result, nitrate nitrogen in the aqueous solution disappeared by reduction and decomposition in 255 minutes from the start of the reaction, and the concentration of by-produced ammoniacal nitrogen was 98.7 ppm as N. This means that 24.7% of the nitrate nitrogen has been converted to NH 3 . The results are shown in Table 1.
実施例１において、硫酸ナトリウムの代わりに亜硫酸ナトリウム(関東化学(株)：特級)１．０ｇを添加して溶解し、濃度１６．１ｍｏｌ／ｍ3（０．２ｗｔ％に相当）の亜硫酸ナトリウムが共存する水溶液としたこと以外は、実施例１と同様にして硝酸性窒素の還元分解反応を３００分間行ったが、水溶液中の硝酸性窒素の濃度は減少しておらず、還元分解は進まなかった。 In Example 1, instead of sodium sulfate, 1.0 g of sodium sulfite (Kanto Chemical Co., Ltd .: special grade) was added and dissolved, and sodium sulfite having a concentration of 16.1 mol / m 3 (corresponding to 0.2 wt%) was dissolved. Except for the coexisting aqueous solution, the reductive decomposition reaction of nitrate nitrogen was performed for 300 minutes in the same manner as in Example 1. However, the concentration of nitrate nitrogen in the aqueous solution did not decrease, and the reductive decomposition did not proceed. It was.
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