JP2016190221A - Selenate reduction catalyst, production method of selenate reduction catalyst and reduction method of selenate solution - Google Patents

Selenate reduction catalyst, production method of selenate reduction catalyst and reduction method of selenate solution Download PDF

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JP2016190221A
JP2016190221A JP2015072855A JP2015072855A JP2016190221A JP 2016190221 A JP2016190221 A JP 2016190221A JP 2015072855 A JP2015072855 A JP 2015072855A JP 2015072855 A JP2015072855 A JP 2015072855A JP 2016190221 A JP2016190221 A JP 2016190221A
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selenate
reduction catalyst
selenium
reduction
solution
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岸田 昌浩
Masahiro Kishida
昌浩 岸田
竹中 壮
Takeshi Takenaka
竹中  壮
松根 英樹
Hideki Matsune
英樹 松根
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Sumitomo Metal Mining Co Ltd
Kyushu University NUC
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Sumitomo Metal Mining Co Ltd
Kyushu University NUC
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Abstract

PROBLEM TO BE SOLVED: To enable selenium in waste water to be precipitated and efficiently separated by providing technique allowing for quick reduction of selenium present in a hexavalent form.SOLUTION: A selenate reduction catalyst related to the present invention has a carrier containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or compound oxide thereof, and one or more kind of metal particle selected from rhodium, platinum, palladium, iridium, ruthenium and a mixture thereof is carried on the carrier. It is preferable that amount of the carried metal particle is 0.5 mass% or more based on dry mass of the carrier and degree of dispersion of the metal by a CO pulse adsorption method is 20% or more. By adding sulfuric acid to a selenate solution containing hexavalent selenic acid so that sulfuric acid concentration becomes 0.005 mol/l or more and further adding the selenate reduction catalyst related to the present invention and selenate reducer, hexavalent selenium contained in the selenate solution can be precipitated and efficiently separated.SELECTED DRAWING: Figure 1

Description

本発明は、セレン酸還元触媒、セレン酸還元触媒の製造方法及びセレン酸溶液の還元方法に関する。   The present invention relates to a selenate reduction catalyst, a method for producing a selenate reduction catalyst, and a method for reducing a selenate solution.

セレンは、光電池や複写機の感光体として用いられる有価な元素であり、銅等の鉱石に微量含まれている。銅を製錬する一般的な方法として用いられる銅鉱石を炉に投入して高温で熔解するプロセスでは、セレンは、揮発して排ガスに含まれ、その後、排ガス処理工程においてセレン酸として溶液中に濃縮される。こうした排ガス処理工程で得られる溶液中に存在するセレン酸は、二酸化硫黄(SO)等のガスと接触させ還元させて単体のセレン(元素状セレン)として回収できる。 Selenium is a valuable element used as a photoreceptor for photovoltaic cells and copying machines, and is contained in trace amounts in ores such as copper. In a process in which copper ore used as a general method for smelting copper is put into a furnace and melted at a high temperature, selenium volatilizes and is contained in exhaust gas, and then in the solution as selenic acid in the exhaust gas treatment process. Concentrated. The selenic acid present in the solution obtained in such an exhaust gas treatment step can be recovered by bringing it into contact with a gas such as sulfur dioxide (SO 2 ) and reducing it to obtain simple selenium (elemental selenium).

一方で、セレンは有毒な元素でもあり、排水中のセレンがそのまま海域等に放流されないように、排水から分離する処理が必要である。   On the other hand, selenium is also a toxic element and needs to be separated from the wastewater so that the selenium in the wastewater is not released into the sea as it is.

例えば、特許文献1には、石炭ガス化工程において発生するガス洗浄排水等の石炭ガス化排水中に含まれる浮遊物質(SS)、フッ素、シアン、セレン、アンモニア等を効率よく除去して、放流可能な或いは再利用可能な良好な水質の処理水を得る方法が提案されている。この方法は、下記(1)〜(4)の工程を含み、(1)を(2)よりも先に行う石炭ガス化排水の処理方法である。
(1)凝集沈殿によりフッ素を除去するフッ素除去工程
(2)湿式酸化または熱加水分解によりシアンを分解するシアン分解工程
(3)金属還元体によりセレン酸イオンを還元処理するセレン処理工程
(4)アンモニア等を除去するアンモニア等の除去工程
For example, in Patent Document 1, suspended solids (SS), fluorine, cyanide, selenium, ammonia, etc. contained in coal gasification wastewater such as gas washing wastewater generated in the coal gasification process are efficiently removed and discharged. There has been proposed a method for obtaining treated water having good water quality that is possible or reusable. This method includes the following steps (1) to (4), and is a method for treating coal gasification wastewater in which (1) is performed before (2).
(1) Fluorine removal step for removing fluorine by coagulation precipitation (2) Cyanide decomposition step for decomposing cyanide by wet oxidation or thermal hydrolysis (3) Selenium treatment step for reducing selenate ions by metal reductant (4) Ammonia removal process to remove ammonia, etc.

また、溶液ないし排水中のセレンは4価と6価の形態で存在することが知られている。このような溶液からセレンを効率よく回収するために、6価の形態で存在するセレン酸(VI)を4価の形態のセレン酸(IV)又は元素状セレンに還元し、分離することが一般的に行われている。   In addition, it is known that selenium in solution or waste water exists in tetravalent and hexavalent forms. In order to efficiently recover selenium from such a solution, selenic acid (VI) existing in a hexavalent form is generally reduced to a tetravalent form of selenic acid (IV) or elemental selenium and separated. Has been done.

例えば、特許文献2には、排水のセレン濃度が高い場合に、排水からセレンを回収して有効利用を可能とするために、セレンの排水からの回収コストの低減を図る方法が示されている。具体的には、セレン含有排水からのセレン回収方法で、4価のセレンと6価のセレンが含まれている排水において、酸性で溶かした鉄イオンを中和して水酸化鉄のスラッジとして沈殿させ、この際に鉄とともに4価セレンも沈殿させる。この際に6価セレンは沈殿しない。6価セレンを沈殿させるために鉄を用いて6価セレンを4価セレンに還元すると多くの鉄スラッジが発生する。6価セレンを還元する前に4価セレンだけを鉄により沈殿させることで、鉄スラッジ中のセレン濃度を高くし、回収コストの低減を図るものである。   For example, Patent Document 2 discloses a method for reducing the cost of recovering selenium from wastewater in order to recover selenium from wastewater and enable effective use when the concentration of selenium in the wastewater is high. . Specifically, in a method for recovering selenium from selenium-containing wastewater, wastewater containing tetravalent selenium and hexavalent selenium is neutralized with acid-dissolved iron ions and precipitated as iron hydroxide sludge. At this time, tetravalent selenium is also precipitated together with iron. At this time, hexavalent selenium does not precipitate. When iron is used to precipitate hexavalent selenium and hexavalent selenium is reduced to tetravalent selenium, a lot of iron sludge is generated. By precipitating only tetravalent selenium with iron before reducing hexavalent selenium, the concentration of selenium in the iron sludge is increased, and the recovery cost is reduced.

特開2010−221151号公報JP 2010-221151 A 特開2014−156380号公報JP 2014-156380 A

しかしながら、6価から4価への還元反応の進行は遅く、大量の鉄メタルと接触させることが必要だった。また、この還元反応を進めるには、高温及び高い酸濃度の下で時間をかけることが必要であり、多くのエネルギーと手間が必要である。   However, the progress of the reduction reaction from hexavalent to tetravalent was slow, requiring contact with a large amount of iron metal. Moreover, in order to advance this reduction reaction, it is necessary to spend time under high temperature and high acid concentration, and much energy and labor are required.

鉄の溶出を適正に維持するには酸濃度を低く抑える必要があるが、大量の鉄メタルを用いるため、高い酸濃度の溶液に対して適用し難いという課題があった。   In order to properly maintain the elution of iron, it is necessary to keep the acid concentration low. However, since a large amount of iron metal is used, there is a problem that it is difficult to apply to a solution having a high acid concentration.

遅い還元反応の進行を促進し、時間を短縮するには、触媒を用いることが考えられる。しかしながら、6価のセレンを4価の形態に迅速に還元できるのに適した触媒はなく、排水を効率よく処理する方法は見当たらなかった。   In order to promote the progress of the slow reduction reaction and shorten the time, it is conceivable to use a catalyst. However, there is no catalyst suitable for rapidly reducing hexavalent selenium to the tetravalent form, and no method for efficiently treating waste water has been found.

本発明は、6価の形態で存在するセレンを迅速に還元できる触媒を提供し、この触媒を用いることで排水中のセレンを沈殿させて効率よく分離しようとするものである。   The present invention provides a catalyst capable of rapidly reducing selenium present in a hexavalent form, and by using this catalyst, selenium in waste water is precipitated and is intended to be separated efficiently.

本発明者らは、上記課題を解決すべく鋭意研究を重ねた結果、担体及び担持物質をいずれも特定の材料にすることで、上記の課題を解決できることを見出し、本発明を完成するに至った。   As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by making both the carrier and the support material specific materials, and the present invention has been completed. It was.

具体的に、本発明では、以下のようなものを提供する。   Specifically, the present invention provides the following.

(1)本発明は、二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物を含む担体に、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属の粒子が担持されているセレン酸還元触媒である。   (1) The present invention provides a carrier containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof selected from rhodium, platinum, palladium, iridium, ruthenium and a mixture thereof. This is a selenate reduction catalyst carrying the above metal particles.

(2)また、本発明は、前記金属の粒子の担持量が前記担体の乾燥質量に対して0.1質量%以上である、(1)に記載のセレン還元触媒である。   (2) Moreover, this invention is a selenium reduction catalyst as described in (1) whose load of the said metal particle is 0.1 mass% or more with respect to the dry mass of the said support | carrier.

(3)また、本発明は、COパルス吸着法による前記金属の分散度が5%以上である、(1)又は(2)に記載のセレン還元触媒である。   (3) Moreover, this invention is a selenium reduction catalyst as described in (1) or (2) whose dispersibility of the said metal by a CO pulse adsorption method is 5% or more.

(4)また、本発明は、二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物を含む担体に、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属を含有する金属含有溶液を含浸させる、セレン還元触媒の製造方法である。   (4) Further, the present invention is selected from rhodium, platinum, palladium, iridium, ruthenium and a mixture thereof as a support containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof. A method for producing a selenium reduction catalyst, wherein a metal-containing solution containing one or more metals is impregnated.

(5)また、本発明は、6価のセレン酸を含有するセレン酸溶液に硫酸を硫酸濃度が0.005mol/l以上になるように加え、(1)から(3)のいずれかに記載のセレン還元触媒及び還元剤をさらに加える、セレン酸溶液の還元方法である。   (5) Moreover, this invention adds a sulfuric acid to the selenic acid solution containing hexavalent selenic acid so that a sulfuric acid concentration may be 0.005 mol / l or more, and it is described in any one of (1) to (3) This is a method for reducing a selenic acid solution in which a selenium reduction catalyst and a reducing agent are further added.

本発明によると、6価で存在するセレン酸を効率よく還元できる。また、排水に含まれるセレンの処理について、効率化を図ることができる。   According to the present invention, selenic acid existing in hexavalence can be efficiently reduced. In addition, the efficiency of the treatment of selenium contained in the waste water can be improved.

セレン還元触媒の担体に担持される白金の担持量と白金の分散度及び白金1質量%あたりの還元率との関係を示す。The relationship between the amount of platinum supported on the carrier of the selenium reduction catalyst, the degree of dispersion of platinum, and the reduction rate per 1% by mass of platinum is shown. セレン還元触媒の担体に担持される白金の分散度と白金1質量%あたりの還元率との関係を示すShows the relationship between the degree of dispersion of platinum supported on the carrier of the selenium reduction catalyst and the reduction rate per 1% by mass of platinum.

以下、本発明の具体的な実施形態について詳細に説明するが、本発明は以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。   Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. Can do.

<セレン酸還元触媒>
本発明のセレン酸還元触媒は、二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物を含む担体を有し、この担体には、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属粒子が担持されている。
<Selenate reduction catalyst>
The selenate reduction catalyst of the present invention has a support containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof, which includes rhodium, platinum, palladium, iridium, ruthenium and One or more kinds of metal particles selected from these mixtures are supported.

〔担体〕
一般に、セレンを含有する溶液や排水は、酸性であることが多い。そのため、担体は、酸性領域での溶解を抑えられる材料であることを要する。この観点から、担体は、二酸化チタン(TiO)、二酸化ジルコニウム(ZrO)、三酸化二アルミニウム(アルミナ,Al)、二酸化ケイ素(シリカ,SiO)、酸化マグネシウム(MgO)、アルカリ土類金属の酸化物又はこれらの複合酸化物(例えば、SiO−Al(シリカアルミナ)、ZrO−MgO等)であることを要する。
[Carrier]
In general, solutions and waste water containing selenium are often acidic. Therefore, the carrier is required to be a material that can suppress dissolution in the acidic region. From this viewpoint, the carrier is titanium dioxide (TiO 2 ), zirconium dioxide (ZrO 2 ), dialuminum trioxide (alumina, Al 2 O 3 ), silicon dioxide (silica, SiO 2 ), magnesium oxide (MgO), alkali It is necessary to be an oxide of an earth metal or a composite oxide thereof (for example, SiO 2 —Al 2 O 3 (silica alumina), ZrO 2 —MgO, etc.).

また、担体は、担持された金属粒子が脱落することを防止できる材料であることを要する。この観点から、担体は、二酸化チタン(TiO)、二酸化ジルコニウム(ZrO)、三酸化二アルミニウム(アルミナ,Al)、二酸化ケイ素(シリカ,SiO)、三酸化二ホウ素(B)又はこれらの複合酸化物(SiO−Al(シリカアルミナ)、SiO−ZrO等)、珪藻土、ゼオライト、リン酸塩等であることを要する。 Further, the carrier is required to be a material that can prevent the supported metal particles from falling off. From this viewpoint, the carrier is titanium dioxide (TiO 2 ), zirconium dioxide (ZrO 2 ), dialuminum trioxide (alumina, Al 2 O 3 ), silicon dioxide (silica, SiO 2 ), diboron trioxide (B 2). O 3 ) or a composite oxide thereof (SiO 2 —Al 2 O 3 (silica alumina), SiO 2 —ZrO 2, etc.), diatomaceous earth, zeolite, phosphate, or the like.

酸性への耐性、金属粒子の脱落防止の両方を考慮すると、担体は、二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物(例えば、SiO−Al(シリカアルミナ)、SiO−ZrO等)を含むことを要する。 In consideration of both acid resistance and prevention of falling off of metal particles, the support is made of titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof (for example, SiO 2 -Al 2 O 3 (silica Alumina), SiO 2 —ZrO 2, etc.).

〔担持物質〕
担体には、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属の粒子が担持されている。一般的に、材料の還元を促す触媒として、ロジウム、白金、パラジウム、イリジウム、ルテニウム等が知られている。触媒活性は、ロジウムが最も高く、白金が次に高く、パラジウム、イリジウム及びルテニウムが次に高い。これらの金属であれば、触媒としての効果を十分に発揮するが、触媒活性及びコストの両方を考慮すると、担持物質として白金を用いることが好ましい。
[Supported material]
The support carries one or more kinds of metal particles selected from rhodium, platinum, palladium, iridium, ruthenium, and mixtures thereof. In general, rhodium, platinum, palladium, iridium, ruthenium, and the like are known as catalysts for promoting reduction of materials. The catalytic activity is highest for rhodium, next highest for platinum, and second highest for palladium, iridium and ruthenium. If these metals are used, the effect as a catalyst is sufficiently exhibited. However, in consideration of both catalyst activity and cost, it is preferable to use platinum as a support material.

金属(担持物質)の担持量は特に限定されるものでないが、担体の乾燥質量に対して0.1質量%以上であることが好ましく、0.5質量%以上であることがより好ましく、0.8質量%以上であることがさらに好ましい。担持量が少なすぎると、セレン酸を還元する効率に影響を及ぼし得る。   The amount of the metal (support material) supported is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the dry mass of the carrier, More preferably, it is 8 mass% or more. If the loading is too small, the efficiency of reducing selenic acid can be affected.

担持量の上限は特に限定されるものでないが、担持量が多すぎると、担持物質である金属の分散度が十分でなく、担持物質の単位質量あたりの還元効率に影響を及ぼし得る。担持物質が高コストであることを考慮すると、見かけ上の還元効率のみならず、担持物質の単位質量あたりの還元効率についても考慮することが好ましい。この観点から、担持量の上限は、担体の乾燥質量に対して20質量%以下であることが好ましく、15質量%以下であることがより好ましく、10質量%以下であることがさらに好ましい。   The upper limit of the loading amount is not particularly limited, but if the loading amount is too large, the degree of dispersion of the metal that is the loading material is not sufficient, which may affect the reduction efficiency per unit mass of the loading material. Considering the high cost of the support material, it is preferable to consider not only the apparent reduction efficiency but also the reduction efficiency per unit mass of the support material. From this viewpoint, the upper limit of the loading amount is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less with respect to the dry mass of the carrier.

また、本発明に係るセレン酸還元触媒では、一酸化炭素(CO)ガスを一定量流して、触媒表面への吸着量を測定するCOパルス吸着法にしたがって測定した金属(担持物質)の分散度が5%以上であることが好ましく、10%以上であることがより好ましく、20%以上であることがさらに好ましい。分散度は、CO吸着量に相当する金属(担持物質)のモル量の触媒に含まれる金属(担持物質)の総モル量に対する割合、すなわち、(CO吸着量に相当する金属(担持物質)のモル量)/(触媒に含まれる金属(担持物質)の総モル量)×100から求められる。一般に、分散度は、担持量と相関があり、担持量が少ないほど分散度が大きい。   In the selenate reduction catalyst according to the present invention, the dispersity of the metal (supported material) measured according to the CO pulse adsorption method in which a certain amount of carbon monoxide (CO) gas is flowed and the amount adsorbed on the catalyst surface is measured. Is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more. The degree of dispersion is the ratio of the molar amount of the metal (supporting material) corresponding to the CO adsorption amount to the total molar amount of the metal (supporting material) contained in the catalyst, that is, (the metal (supporting material) corresponding to the CO adsorption amount). Mole amount) / (total amount of metal (support material) contained in catalyst) × 100. In general, the degree of dispersion has a correlation with the loading amount, and the smaller the loading amount, the larger the degree of dispersion.

分散度が低すぎると、金属(担持物質)の単位質量あたりの還元効率に影響を及ぼし得る。金属(担持物質)が高コストであることを考慮すると、見かけ上の還元効率のみならず、金属(担持物質)の単位質量あたりの還元効率についても考慮することが好ましい。   If the degree of dispersion is too low, the reduction efficiency per unit mass of the metal (support material) can be affected. In view of the high cost of the metal (support material), it is preferable to consider not only the apparent reduction efficiency but also the reduction efficiency per unit mass of the metal (support material).

<セレン酸還元触媒の製造方法>
本発明に係るセレン酸還元触媒の製造方法は特に限定されるものでない。例えば、二酸化チタン、二酸化ジルコニウム又はこれらの複合酸化物を含む担体に、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属の溶液を含浸させて乾燥し、焼成する方法のほか、希薄溶液で繰り返し含浸する方法、限界近い高濃度で含浸するincipinent wetness法、噴霧乾燥法等が挙げられる。
<Method for Producing Selenate Reduction Catalyst>
The method for producing the selenate reducing catalyst according to the present invention is not particularly limited. For example, a support containing titanium dioxide, zirconium dioxide or a composite oxide thereof is impregnated with a solution of one or more metals selected from rhodium, platinum, palladium, iridium, ruthenium and mixtures thereof, dried, and fired. In addition to the above method, there are a method of repeatedly impregnating with a dilute solution, an incipient wetness method of impregnating at a high concentration close to the limit, a spray drying method, and the like.

ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属の担持量は、白金溶液の白金濃度や担体の白金溶液への含浸時間によって調整される。この観点から、白金溶液の白金濃度は、0.5g/l以上20g/l以下であることが好ましく、1g/l以上20g/l以下であることがより好ましく、3g/l以上10g/l以下であることがさらに好ましい。   The loading amount of one or more kinds of metals selected from rhodium, platinum, palladium, iridium, ruthenium and mixtures thereof is adjusted by the platinum concentration of the platinum solution and the impregnation time of the support in the platinum solution. From this viewpoint, the platinum concentration of the platinum solution is preferably 0.5 g / l or more and 20 g / l or less, more preferably 1 g / l or more and 20 g / l or less, and 3 g / l or more and 10 g / l or less. More preferably.

また、金属(担持物質)の分散度は、金属(担持物質)の担持量が好適な範囲内にあるセレン酸還元触媒の分散度を測定してさらに選別すること、担体に金属(担持物質)を担持させる際の撹拌の強弱を調整すること等によって調整される。   The dispersity of the metal (support material) is further determined by measuring the dispersibility of the selenate reduction catalyst in which the supported amount of the metal (support material) is within a suitable range, and the metal (support material) on the support. It is adjusted by adjusting the intensity of agitation at the time of loading.

反応中に金属(担持物質)の成分が溶出するのを防ぐために乾燥及び焼成する場合、乾燥は、白金溶液に含まれる液体成分を蒸発できる態様であれば、特に限定されるものではない。また、焼成についても、担体に及び担持物質を焼成できる態様であれば、特に限定されるものではない。なお、還元剤を用いて金属(担持物質)の前駆体を還元して担体に析出・固定化する触媒調製法では、乾燥・焼成を特に必要としない。   In the case of drying and baking to prevent the metal (supporting substance) component from eluting during the reaction, the drying is not particularly limited as long as the liquid component contained in the platinum solution can be evaporated. Also, the firing is not particularly limited as long as it can be fired on the carrier and the support material. In the catalyst preparation method in which a metal (support material) precursor is reduced using a reducing agent and deposited and immobilized on a support, drying and firing are not particularly required.

<セレン酸溶液の還元方法>
6価のセレン酸を含有するセレン酸溶液は、セレン酸溶液に硫酸を硫酸濃度が0.005mol/l以上になるように加え、上述したセレン酸還元触媒とセレン酸還元剤とをさらに加えることによって還元される。
<Reduction method of selenate solution>
In the selenate solution containing hexavalent selenate, sulfuric acid is added to the selenate solution so that the sulfuric acid concentration is 0.005 mol / l or more, and the above-described selenate reduction catalyst and selenate reducer are further added. Reduced by

セレン酸溶液に加える酸は、硫酸であることが好ましい。塩酸、硝酸等、他の酸であると、塩酸や硝酸では、担持物質としての金属が溶出する可能性があるため、好ましくない。   The acid added to the selenic acid solution is preferably sulfuric acid. Other acids such as hydrochloric acid and nitric acid are not preferable because hydrochloric acid and nitric acid may elute the metal as the support material.

硫酸は、硫酸濃度が0.005mol/l以上になるように加えることを要し、硫酸濃度が0.005mol/l以上になるように加えることが好ましく、0.01mol/l以上になるように加えることがより好ましい。還元反応は、低pH条件ほど進行しやすく、硫酸濃度が低すぎると、セレン酸還元触媒とセレン酸還元剤とを加えても、触媒作用が発現しても反応が進行せず、結果として、6価のセレン酸を好適に還元できない可能性があるため、好ましくない。   Sulfuric acid needs to be added so that the sulfuric acid concentration is 0.005 mol / l or more, and is preferably added so that the sulfuric acid concentration is 0.005 mol / l or more, so that it becomes 0.01 mol / l or more. More preferably, it is added. The reduction reaction proceeds more easily under low pH conditions. If the sulfuric acid concentration is too low, the reaction does not proceed even if the selenate reducing catalyst and the selenate reducing agent are added, or the catalytic action is expressed. Since hexavalent selenic acid may not be reduced suitably, it is not preferable.

硫酸濃度の上限は、セレンの析出状態に影響を及ぼさない程度であれば、特に限定されるものではない。   The upper limit of the sulfuric acid concentration is not particularly limited as long as it does not affect the precipitation state of selenium.

セレン酸還元剤は、6価のセレン酸を還元できる材料であれば特に限定されるものでなく、ヒドラジン、水和ヒドラジンン等が挙げられる。   The selenate reducing agent is not particularly limited as long as it is a material capable of reducing hexavalent selenate, and examples thereof include hydrazine and hydrated hydrazine.

セレン酸還元剤の供給量も特に限定されるものでないが、6価のセレン酸を効率よく還元できるようにすること、及びセレン酸還元剤の残存を防止することの両方を考慮すると、セレン酸還元剤の供給量は、6価のセレン酸のモル量に対し、3倍以上10倍以下であることが好ましい。   The supply amount of the selenate reducing agent is not particularly limited, but considering both the ability to efficiently reduce hexavalent selenate and the prevention of the remaining selenate reducing agent, The supply amount of the reducing agent is preferably 3 to 10 times the molar amount of hexavalent selenic acid.

還元反応が進むと、液中のSe(VI)は還元されてSe元素となって沈降する。そのため、本発明に係るセレン酸還元触媒を用いると、6価の形態で存在するセレンを迅速に還元できるとともに、排水中のセレンを沈殿させて効率よく分離できる。   As the reduction reaction proceeds, Se (VI) in the liquid is reduced to settle as Se elements. Therefore, when the selenate reducing catalyst according to the present invention is used, selenium present in a hexavalent form can be rapidly reduced, and selenium in the waste water can be precipitated and efficiently separated.

以下、実施例により、本発明をさらに詳細に説明するが、本発明はこれらの記載に何ら制限を受けるものではない。   EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.

<セレン酸還元触媒の調製>
〔実施例1〕
Ptを0.05g含有するジニトロアンミン白金(IV)水溶液10mlに、TiO(製品名:P25,日本エアロジル社製)10gを添加し、スターラーで撹拌しながら75℃に維持して2時間かけて水分を蒸発させた。その後、さらに80℃の温度で真空乾燥し、次いで大気中で500℃に維持しながら2時間かけて焼成することで、実施例1に係るセレン酸還元触媒を得た。このセレン酸還元触媒の白金品位を分析したところ、白金の担持量は、担体の乾燥質量に対して10質量%であった。
<Preparation of selenate reduction catalyst>
[Example 1]
10 g of TiO 2 (product name: P25, manufactured by Nippon Aerosil Co., Ltd.) is added to 10 ml of a dinitroammineplatinum (IV) aqueous solution containing 0.05 g of Pt, and maintained at 75 ° C. with stirring with a stirrer over 2 hours. Water was evaporated. Then, the selenate reduction catalyst which concerns on Example 1 was obtained by vacuum-drying further at the temperature of 80 degreeC, and then baking for 2 hours, maintaining at 500 degreeC in air | atmosphere. When the platinum quality of this selenate reducing catalyst was analyzed, the amount of platinum supported was 10% by mass relative to the dry mass of the carrier.

〔実施例2〕
TiOをZrO(製品名:JRC-ZRO-3,触媒学会製)にしたこと以外は、実施例1と同じ手法により、実施例2に係るセレン酸還元触媒を得た。白金の担持量は、担体の乾燥質量に対して10質量%であった。
[Example 2]
A selenate reduction catalyst according to Example 2 was obtained by the same method as Example 1 except that TiO 2 was changed to ZrO 2 (product name: JRC-ZRO-3, manufactured by the Japan Society for Catalysis). The amount of platinum supported was 10% by mass relative to the dry mass of the carrier.

〔実施例3〕
白金の担持量が担体の乾燥質量に対して0.8質量%であること以外は、実施例1と同じ手法により、実施例3に係るセレン酸還元触媒を得た。
Example 3
A selenate reduction catalyst according to Example 3 was obtained in the same manner as in Example 1 except that the supported amount of platinum was 0.8% by mass with respect to the dry mass of the carrier.

〔実施例4〕
白金の担持量が担体の乾燥質量に対して5質量%であること以外は、実施例1と同じ手法により、実施例4に係るセレン酸還元触媒を得た。
Example 4
A selenate reduction catalyst according to Example 4 was obtained in the same manner as in Example 1 except that the amount of platinum supported was 5% by mass with respect to the dry mass of the carrier.

〔実施例5〕
白金の担持量が担体の乾燥質量に対して20質量%であること以外は、実施例1と同じ手法により、実施例5に係るセレン酸還元触媒を得た。
Example 5
A selenate reduction catalyst according to Example 5 was obtained in the same manner as in Example 1 except that the amount of platinum supported was 20% by mass with respect to the dry mass of the support.

〔比較例〕
実施例1と同じTiOを、ジニトロアンミン白金(IV)水溶液に接触させることなく80℃の温度で真空乾燥し、次いで大気中で500℃に維持しながら2時間かけて焼成することで、比較例に係るセレン酸還元触媒を得た。
[Comparative Example]
The same TiO 2 as in Example 1 was vacuum-dried at a temperature of 80 ° C. without being brought into contact with a dinitroammineplatinum (IV) aqueous solution, and then calcined for 2 hours while maintaining at 500 ° C. in the atmosphere. The selenate reduction catalyst according to the example was obtained.

<評価> セレン酸溶液の還元
〔評価1:セレン酸還元触媒の比較〕
実施例1及び2並びに比較例に係るセレン酸還元触媒に、硫酸濃度がそれぞれ0.01M/l、0.1M/lの水溶液200mlを添加し、さらにNaSeOを0.1mM/l添加して、窒素バブリングしながら80℃に加温し、80℃になった時点でその温度を維持して30分間撹拌しながら保持した。30分経過後、液中のSe濃度をICP分析装置で測定したところ、0.7mM/lだった。
<Evaluation> Reduction of selenate solution [Evaluation 1: Comparison of selenate reduction catalyst]
200 ml of an aqueous solution having a sulfuric acid concentration of 0.01 M / l and 0.1 M / l was added to each of the selenate reduction catalysts according to Examples 1 and 2 and the comparative example, and further Na 2 SeO 4 was added at 0.1 mM / l. Then, the mixture was heated to 80 ° C. while bubbling with nitrogen, and when the temperature reached 80 ° C., the temperature was maintained and held for 30 minutes with stirring. After 30 minutes, the Se concentration in the liquid was measured with an ICP analyzer and found to be 0.7 mM / l.

このときの液に含まれるSeのモル濃度を100%とし、撹拌後のセレン酸溶液に対し、Seのモル量の10倍当量に相当する抱水ヒドラジン(ヒドラジン一水和物)を加えた。そして、抱水ヒドラジンを加えてから2時間経過した後の液をサンプリングし、そのSe濃度を測定した。   The molar concentration of Se contained in the liquid at this time was 100%, and hydrazine hydrate (hydrazine monohydrate) corresponding to 10 times the molar amount of Se was added to the selenic acid solution after stirring. And after adding 2 hours after adding hydrazine hydrate, the liquid was sampled and the Se concentration was measured.

還元反応が進むと、液中のSe(VI)は還元されてSe元素となって沈降する。そのため、抱水ヒドラジンを加える前のSe濃度から抱水ヒドラジンを加えてから2時間経過した後のSe濃度を差し引くことで、還元されたSeの量を計算できる。   As the reduction reaction proceeds, Se (VI) in the liquid is reduced to settle as Se elements. Therefore, the amount of reduced Se can be calculated by subtracting the Se concentration after 2 hours from the addition of hydrazine hydrate from the Se concentration before adding hydrazine hydrate.

そこで、((抱水ヒドラジンを加える前のSe濃度)−(抱水ヒドラジンを加えてから2時間経過した後のSe濃度))/(抱水ヒドラジンを加える前のSe濃度)×100を6価のセレン酸の還元率とした。結果を表1に示す。

Figure 2016190221
Therefore, ((Se concentration before adding hydrazine hydrate) − (Se concentration after 2 hours from adding hydrazine hydrate)) / (Se concentration before adding hydrazine hydrate) × 100 The reduction rate of selenic acid. The results are shown in Table 1.
Figure 2016190221

実施例に係るセレン酸還元触媒を用いると、6価のセレン酸を2時間という短時間で34%という極めて高い効率で還元できる。   When the selenate reduction catalyst according to the example is used, hexavalent selenate can be reduced with an extremely high efficiency of 34% in a short time of 2 hours.

一方、比較例に係るセレン酸還元触媒を用いると、始液の硫酸濃度が好適な範囲内にあっても、6価のセレン酸をほとんど還元できない。   On the other hand, when the selenate reducing catalyst according to the comparative example is used, hexavalent selenate can hardly be reduced even if the sulfuric acid concentration in the starting solution is within a suitable range.

〔評価2:始液の硫酸濃度の比較〕
実施例1に係るセレン酸還元触媒について、硫酸濃度がそれぞれ0.001M/l、0.01M/l、0.1M/l、0.5M/lの4種類の水溶液を添加したこと以外は、〔評価1:セレン酸還元触媒の比較〕と同じ手法によって6価のセレン酸の還元率を求めた。結果を表2に示す。

Figure 2016190221
[Evaluation 2: Comparison of sulfuric acid concentration in the starting solution]
For the selenate reduction catalyst according to Example 1, except that four types of aqueous solutions having sulfuric acid concentrations of 0.001 M / l, 0.01 M / l, 0.1 M / l, and 0.5 M / l were added, [Evaluation 1: Comparison of selenate reduction catalyst] The reduction rate of hexavalent selenate was determined by the same method. The results are shown in Table 2.
Figure 2016190221

実施例に係るセレン酸還元触媒を用いると、始液の硫酸濃度が0.01mol/l以上0.5mol/l以下の範囲にある場合、6価のセレン酸を2時間という短時間で20%以上の割合で還元できる。中でも、始液の硫酸濃度が0.01mol/l以上0.1mol/l以下であると、6価のセレン酸をより効率よく還元でき、始液の硫酸濃度が0.01mol/l程度であると、さらに効率よく還元できる。   When the selenate reducing catalyst according to the example is used, when the sulfuric acid concentration in the starting solution is in the range of 0.01 mol / l or more and 0.5 mol / l or less, hexavalent selenate is reduced to 20% in a short time of 2 hours. It can reduce at the above ratio. In particular, when the sulfuric acid concentration in the starting solution is 0.01 mol / l or more and 0.1 mol / l or less, hexavalent selenic acid can be more efficiently reduced, and the sulfuric acid concentration in the starting solution is about 0.01 mol / l. And can be reduced more efficiently.

一方、始液の硫酸濃度が低すぎると、実施例に係るセレン酸還元触媒を用いたとしても、6価のセレン酸を還元できない。本反応は、低pH条件ほど進行しやすく、0.001mol/lと低すぎる硫酸濃度では、触媒作用が発現しても反応が進行しなかったためであると考えられる。   On the other hand, if the sulfuric acid concentration in the starting solution is too low, hexavalent selenate cannot be reduced even if the selenate reduction catalyst according to the example is used. This reaction is more likely to proceed as the pH is lower, and it is considered that the reaction did not proceed even when the catalytic action was exhibited at a sulfuric acid concentration as low as 0.001 mol / l.

〔評価3:白金粒子の担持量の比較〕
セレン酸還元触媒を実施例1及び3〜5の4種類としたこと以外は、〔評価1:セレン酸還元触媒の比較〕と同じ手法によって6価のセレン酸の還元率を求めた。また、白金粒子1質量%あたりの還元率も求めた。結果を表3に示す。

Figure 2016190221
[Evaluation 3: Comparison of platinum particle loading]
The reduction rate of hexavalent selenate was determined by the same method as [Evaluation 1: Comparison of selenate reduction catalyst] except that the selenate reduction catalyst was changed to the four types of Examples 1 and 3-5. The reduction rate per 1% by mass of platinum particles was also determined. The results are shown in Table 3.
Figure 2016190221

白金粒子の担持量は、担体の乾燥質量に対して0.8質量%以上であれば足り、担持量が0.8質量%以上であれば6価のセレン酸を効率よく還元できるといえる。白金粒子の担持量が多いほど、見かけ上の還元率は高くなる。しかしながら、表3から、担持量が多すぎると、白金粒子の単位質量あたりの還元効率に影響を及ぼし得ることが分かる。白金粒子が高コストであることを考慮すると、見かけ上の還元効率のみならず、白金粒子の単位質量あたりの還元効率についても考慮することが好ましい。この観点から、担持量の上限は、担体の乾燥質量に対して20質量%以下であることが好ましく、15質量%以下であることがより好ましく、10質量%以下であることがさらに好ましい。   It is sufficient that the supported amount of platinum particles is 0.8% by mass or more with respect to the dry mass of the carrier, and it can be said that hexavalent selenic acid can be efficiently reduced if the supported amount is 0.8% by mass or more. The greater the amount of platinum particles supported, the higher the apparent reduction rate. However, it can be seen from Table 3 that if the loading amount is too large, the reduction efficiency per unit mass of the platinum particles can be affected. In view of the high cost of the platinum particles, it is preferable to consider not only the apparent reduction efficiency but also the reduction efficiency per unit mass of the platinum particles. From this viewpoint, the upper limit of the loading amount is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less with respect to the dry mass of the carrier.

担持量が多すぎることの影響を考察するため、実施例1及び3〜5に係るセレン酸還元触媒の分散度を、公知手法であるCOパルス吸着法にしたがって測定した。担持量と分散度及び白金粒子1質量%あたりの還元率の関係を表4及び図1に示す。また、分散度と白金粒子1質量%あたりの還元率との関係を図2に示す。

Figure 2016190221
In order to consider the influence of too much loading, the dispersity of the selenate reduction catalyst according to Examples 1 and 3 to 5 was measured according to a CO pulse adsorption method which is a known method. Table 4 and FIG. 1 show the relationship between the supported amount, the degree of dispersion, and the reduction rate per 1% by mass of platinum particles. FIG. 2 shows the relationship between the degree of dispersion and the reduction rate per 1% by mass of the platinum particles.
Figure 2016190221

表4、図1及び図2から、白金粒子の単位質量あたりの還元効率は、白金の分散度と相関を有するといえる。分散度が低すぎると、白金粒子の単位質量あたりの還元効率に影響を及ぼし得る。白金粒子が高コストであることを考慮すると、見かけ上の還元効率のみならず、白金粒子の単位質量あたりの還元効率についても考慮することが好ましい。   From Table 4 and FIGS. 1 and 2, it can be said that the reduction efficiency per unit mass of the platinum particles has a correlation with the degree of dispersion of platinum. If the degree of dispersion is too low, the reduction efficiency per unit mass of the platinum particles can be affected. In view of the high cost of the platinum particles, it is preferable to consider not only the apparent reduction efficiency but also the reduction efficiency per unit mass of the platinum particles.

Claims (5)

二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物を含む担体に、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属の粒子が担持されているセレン酸還元触媒。   One or more kinds of metal particles selected from rhodium, platinum, palladium, iridium, ruthenium and a mixture thereof are supported on a support containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof. Selenate reduction catalyst. 前記金属の粒子の担持量は、前記担体の乾燥質量に対して0.1質量%以上である、請求項1に記載のセレン酸還元触媒。   2. The selenate reduction catalyst according to claim 1, wherein the supported amount of the metal particles is 0.1% by mass or more based on the dry mass of the carrier. COパルス吸着法による前記金属の分散度が5%以上である、請求項1又は2に記載のセレン酸還元触媒。   The selenate reduction catalyst according to claim 1 or 2, wherein a degree of dispersion of the metal by a CO pulse adsorption method is 5% or more. 二酸化チタン、二酸化ジルコニウム、三酸化二アルミニウム、二酸化ケイ素又はこれらの複合酸化物を含む担体に、ロジウム、白金、パラジウム、イリジウム、ルテニウム及びこれらの混合物から選択される1種類以上の金属を含有する金属含有溶液を含浸させる、セレン酸還元触媒の製造方法。   A metal containing one or more kinds of metals selected from rhodium, platinum, palladium, iridium, ruthenium, and mixtures thereof on a carrier containing titanium dioxide, zirconium dioxide, dialuminum trioxide, silicon dioxide or a composite oxide thereof. A method for producing a selenate-reducing catalyst, wherein the containing solution is impregnated. 6価のセレン酸を含有するセレン酸溶液に硫酸を硫酸濃度が0.005mol/l以上になるように加え、請求項1から3のいずれかに記載のセレン酸還元触媒とセレン酸還元剤とをさらに加える、セレン酸溶液の還元方法。   A sulfuric acid is added to a selenic acid solution containing hexavalent selenic acid so that the sulfuric acid concentration becomes 0.005 mol / l or more, and the selenate reducing catalyst and the selenate reducing agent according to claim 1, A method for reducing a selenic acid solution.
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CN115624971A (en) * 2022-09-30 2023-01-20 浙江工业大学 Amino resin supported palladium nano catalytic material, preparation method and method for removing selenate in water by reduction

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CN114790555A (en) * 2021-01-25 2022-07-26 南开大学 Preparation method and application of selenium-doped porous carbon-based nitrogen reduction electrocatalyst
CN115624971A (en) * 2022-09-30 2023-01-20 浙江工业大学 Amino resin supported palladium nano catalytic material, preparation method and method for removing selenate in water by reduction

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