JP3924381B2 - Method for adsorbing and removing arsenic dissolved in water - Google Patents
Method for adsorbing and removing arsenic dissolved in water Download PDFInfo
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- JP3924381B2 JP3924381B2 JP19334798A JP19334798A JP3924381B2 JP 3924381 B2 JP3924381 B2 JP 3924381B2 JP 19334798 A JP19334798 A JP 19334798A JP 19334798 A JP19334798 A JP 19334798A JP 3924381 B2 JP3924381 B2 JP 3924381B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、砒素含有水からそれに含まれる砒素を吸着除去する方法に関するものである。
【０００２】
【従来の技術】
従来、水中から砒素を除去するための方法としては、凝集沈殿法、吸着法、逆浸透法が提案、実施されている。
しかしながら、沈殿法では砒素を含有する含水率の高いスラッジの処理が問題となる。逆浸透法では、膜の強度、寿命、汚染などの問題がある。また、吸着法では従来適当な吸着剤が見つかっていなかった。例えば、アルミナ、活性炭は吸着容量が小さ過ぎるし、また、希土類系は表面積が小さく、粒子が不安定である。希土類金属を多孔質体に担持する方法は有効だが、従来は高価なイオン交換樹脂を担体としていたため、高価であった。
【０００３】
【発明が解決しようとする課題】
本発明は、水中に含まれる砒素を吸着法により除去する方法において、砒素吸着能にすぐれるとともに、低コストの吸着剤を用いる方法を提供することをその課題とする。
【０００４】
【課題を解決するための手段】
本発明者らは、前記課題を解決すべく鋭意研究を重ねた結果、本発明を完成するに至った。
即ち、本発明によれば、砒素を含有する水を吸着剤に接触させて該砒素を該吸着剤に吸着させて水中から除去する方法において、該吸着剤として、表面積１５０ｍ2／ｇ以上、細孔容積０．５５ｃｍ3／ｇ以上、平均細孔径９０〜２００オングストロームを有し、かつ細孔径９０〜２００オングストロームの細孔が全細孔容積の６０％以上を占めるγ−アルミナ担体に希土類金属の酸化物又は水酸化物を５〜６０重量％担持したものを用いることを特徴とする砒素の吸着除去方法が提供される。
【０００５】
【発明の実施の形態】
水中からそれに含まれる砒素を吸着剤を用いて分離する場合、吸着剤の吸着容量を高めるには、吸着剤の表面積を大きくすることが重要である。また、砒素に対する選択性を高め、かつ吸着剤の劣化を抑制するためには、砒素を優先的に吸着するような表面特性を与えることが重要である。したがって、活性や選択性の低下を防止するためには、上記表面積や表面特性の変化が小さいことが重要となる。本発明では、特定のγ−アルミナ担体に特定量の希土類金属を担持した吸着剤を用いることによって、大きな表面積及び好ましい表面特性を長期にわたって維持するものである。
【０００６】
本発明で用いる多孔性γ−アルミナ担体において、その表面積は１５０ｍ2／ｇ以上、好ましくは１８０ｍ2／ｇ以上であり、その上限値は特に制約されないが、通常、３００ｍ2／ｇ程度である。その細孔容積は０．５５ｃｍ3／ｇ以上、好ましくは０．６ｃｍ3／ｇ以上であり、その上限値は特に制約されないが、通常、１．０ｃｍ3／ｇ程度である。その平均細孔径は、９０〜２００Å、好ましくは１００〜２００Åであり、かつその９０〜２００Åの細孔が全細孔容積の６０％以上、好ましくは７０％を占めるものである。
【０００７】
本発明で用いる吸着剤は、前記γ−アルミナに希土類金属を担持させることによって得ることができる。γ−アルミナに対する希土類金属の担持は、従来公知の各種の方法により行うことができるが、一般的には、含浸法により実施される。この含浸法によれば、あらかじめ希土類金属を含有する溶液を作り、この溶液中にγ−アルミナを含浸してγ−アルミナ中に希土類金属を含浸させ、次いで乾燥し、焼成することによって、所望吸着剤を得ることができる。
前記希土類金属を溶解させるための溶剤としては、水、有機溶剤／水との混合物、及び有機溶剤が用いられるが、好ましくは水が用いられる。溶剤に溶解させる希土類金属は、その溶剤に溶解する形態であればよく、一般的には、ハロゲン化物、硝酸塩、硫酸塩、カルボン酸塩等であることができる。
溶液中の希土類金属の濃度は、金属換算量で、１〜３０重量％、好ましくは２〜２０重量％である。希土類金属を含浸させたγ−アルミナの乾燥温度は、５０〜２５０℃、好ましくは１００〜２００℃であり、その乾燥物の焼成温度は２００〜７００℃、好ましくは２００〜５００℃である。
【０００８】
本発明で用いる吸着剤において、その希土類金属の含有量は、金属換算量で、全吸着剤中、５〜６０重量％、好ましくは５〜３０重量％である。また、希土類金属は、通常、吸着剤中、酸化物及び／又は水酸化物の形態であり、例えば含水酸化物、塩基性塩で存在していてもよい。
希土類金属としては、セリウム、ランタン、プラセオジム、ネオジム等が挙げられるが、本発明の場合、特に、（ｉ）セリウム及び／又はランタン、あるいは（ii）セリウム及び／又はランタンを含有する希土類金属混合物が好ましい。本発明で用いる吸着剤において、その平均細孔径が９０Åより小さいと、砒素化合物分子の細孔内拡散が律速になり、全吸着剤表面積を有効に利用することができない。一方、その平均細孔径が２００Åより大きいと、表面積が大きくとれなくなる。上記条件を満足するγ−アルミナ担体は、アルミニウム塩の中和により生成した水酸化アルミニウムのスラリーを濾過洗浄し、これを脱水乾燥した後、４００〜８００℃で１〜６時間程度焼成することにより得ることができる。
【０００９】
本発明で用いる吸着剤において、希土類金属は酸化物又は水酸化物として存在し、アルミナ表面にアルミナとの複合体を形成し、好ましい表面特性を与える役割を果たすと思われる。その含有量が５重量％より低いとγ−アルミナ担体表面をアルミナと希土類金属との複合体が均一に覆うことができないため十分な効果が得られず、一方、その含有量が６０重量％を越えるとアルミナとの複合体の表面特性が変化するとともに表面積自体の減少が著しいものとなる。γ−アルミナ担体上に希土類金属酸化物を担持させるには、希土類金属のハロゲン化物・硝酸塩などの水溶液を担体に含浸させた後、乾燥して焼成する方法等がある。また、希土類金属水酸化物をγ−アルミナ担体上に担持させるには、希土類金属のハロゲン化物・硝酸塩の水溶液を担体に含浸させた後、熱アンモニア水中に漬けてから水洗し、乾燥し、焼成する方法等がある。
【００１０】
本発明により水中に溶存する砒素を除去するには、前記吸着剤に対して、砒素を溶存する水を接触すればよい。この場合の接触方法としては、吸着剤を充填した充填塔に砒素含有水を流通させる方法や、砒素含有水に吸着剤を投入し、撹拌する方法等があり、特に制約されない。処理対象となる水中の砒素濃度は、Ａｓとして、通常、０．０１〜５０ｍｇ／Ｌ、特に、０．０１〜１０ｍｇ／Ｌである。
【００１１】
【実施例】
次に本発明を実施例によりさらに詳細に説明する。
【００１２】
実施例１
特公平６−７２００５号公報中の実施例１に記載されるようにして、γ−アルミナ担体を製造した。この方法のあらましを述べると、熱希硫酸中に激しく撹拌しながら瞬時にアルミン酸ソーダ水溶液を加えることにより水酸化アルミニウムスラリーの懸濁液（ｐＨ１０）を得、これを種子水酸化アルミニウムとして、撹拌を続けながら熱希硫酸とアルミン酸ソーダ水溶液を交互に一定時間おいて加える操作を繰り返し、濾過洗浄してケーキを得、これを押し出し成形して乾燥した後、５００℃で３時間焼成するという方法である。こうして得られたγ−アルミナの性状は典型的には次の通りである。
【表１】
平均細孔径 １１９ Å
細孔容積 ０．７１３ ｃｍ3／ｇ
表面積 ２４０ ｍ2／ｇ
全細孔容積に占める９０〜２００Åの細孔の割合 ８８ ％
上記γ−アルミナ担体１００ｇを取り、これにＣｅＯ2／Ａｌ2Ｏ3の重量比が約５０／１００になるよう、３０ｗｔ％濃度のＣｅ(ＮＯ3)3水溶液を含浸させ、水分除去後、４００℃で焼成し吸着剤を調製した。
この吸着剤１ｇを、５０〜２００ｍｇ／Ｌの砒素水溶液０．１リットルに加え、１時間撹拌した後、液中の砒素濃度を測定した。この場合、砒素水溶液中に含まれる砒素の形態は、三酸化砒素であった。
その結果得られた砒素の吸着量を表３に示す。
【００１３】
実施例２
実施例１において、Ｃｅ(ＮＯ3)3の代わりにＬａ(ＮＯ3)3を用いた以外は同様にして、Ｌａ2Ｏ3／Ａｌ2Ｏ3の重量比が約５０／１００となるようＬａ2Ｏ3を含有する吸着剤を得た。
次に、この吸着剤を用いて、実施例１と同様にして砒素の吸着試験を行った。その結果を表３に示す。
【００１４】
実施例３
実施例１と同じγ−アルミナ担体を用い、これにＣｅ(ＯＨ)3／ＡｌＯ3の重量比が約５５／１００になるよう３０ｗｔ％濃度のＣｅ(ＮＯ3)3水溶液を含浸させ、乾燥した。この吸着剤１リットルをほぼ同量の１０ｗｔ％熱アンモニア水に９５℃で１時間漬け、熱アンモニア水を交換して同じ操作を２回繰り返した後水洗して乾燥し、Ｃｅ（ＯＨ）3を含有する吸着剤を得た。
次に、この吸着剤を用いて、実施例１と同様にして砒素の吸着試験を行った。その結果を表３に示す。
【００１５】
比較例１
上記γ−アルミナ担体に代えて市販のアルミナ担体（水沢化学製）を用いた以外、実施例１と同様にして吸着剤の調製及び吸着試験を行った。この場合、使用したアルミナ担体の性状は次の通りである。
【表２】
平均細孔径 １１１ Å
細孔容積 ０．６１５ ｃｍ3／ｇ
表面積 ２２０ ｍ2／ｇ
全細孔容積に占める９０〜２００Åの細孔の割合 ４９ ％
この吸着剤に対する砒素の吸着量を実施例１と同様にして測定した。その結果を表３に示す。
【００１６】
【表３】
なお、本発明で用いる吸着剤に関わる表面積の測定は、カルロエルバ社製自動気体吸脱着装置「Ｓｏｒｐｔｏｍａｔｉｃ １８００」を用いた窒素吸着により、ＢＥＴ法に従い行った。また、細孔容積及び平均細孔径は、カルロエルバ社製細孔分布測定装置「Ｍｅｒｃｕｒｙ ｐｒｅｓｓｕｒｅ ｐｏｒｏｓｉｍｅｔｅｒ ｍｏｄｅｌ ７０」を用いて、いわゆる水銀圧入法で求めた。
【００１８】
【発明の効果】
本発明によれば、水中に溶存する砒素を効率よくかつ低コストで除去することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for adsorbing and removing arsenic contained in arsenic-containing water.
[0002]
[Prior art]
Conventionally, coagulation precipitation, adsorption, and reverse osmosis have been proposed and implemented as methods for removing arsenic from water.
However, in the precipitation method, treatment of sludge containing arsenic and having a high water content becomes a problem. The reverse osmosis method has problems such as membrane strength, lifetime, and contamination. Also, no suitable adsorbent has been found in the adsorption method. For example, the adsorption capacity of alumina and activated carbon is too small, and the rare earth system has a small surface area and the particles are unstable. Although a method of supporting a rare earth metal on a porous body is effective, it has been expensive since conventionally an expensive ion exchange resin was used as a carrier.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for removing arsenic contained in water by an adsorption method and using a low-cost adsorbent as well as excellent arsenic adsorption ability.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, according to the present invention, in the method of removing water from arsenic by adsorbing water containing arsenic to the adsorbent and adsorbing the arsenic from the water, the adsorbent has a surface area of 150 m 2 / g or more. A rare earth metal is contained in a γ-alumina support having a pore volume of 0.55 cm 3 / g or more, an average pore diameter of 90 to 200 angstroms, and pores having a pore diameter of 90 to 200 angstroms occupying 60% or more of the total pore volume. Provided is a method for adsorbing and removing arsenic, characterized by using an oxide or hydroxide carrying 5 to 60% by weight.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
When separating arsenic contained in water using an adsorbent, it is important to increase the surface area of the adsorbent in order to increase the adsorption capacity of the adsorbent. In addition, in order to enhance selectivity to arsenic and suppress deterioration of the adsorbent, it is important to provide surface characteristics that preferentially adsorb arsenic. Therefore, in order to prevent a decrease in activity and selectivity, it is important that the change in the surface area and surface characteristics is small. In the present invention, a large surface area and preferable surface characteristics are maintained over a long period of time by using an adsorbent in which a specific amount of rare earth metal is supported on a specific γ-alumina support.
[0006]
The surface area of the porous γ-alumina carrier used in the present invention is 150 m 2 / g or more, preferably 180 m 2 / g or more, and the upper limit is not particularly limited, but is usually about 300 m 2 / g. Its pore volume of 0.55 cm 3 / g or more, preferably 0.6 cm 3 / g or more, its upper limit is not particularly limited, it is usually, 1.0 cm 3 / g approximately. The average pore diameter is 90 to 200 Å, preferably 100 to 200 Å, and the 90 to 200 細孔 pores occupy 60% or more, preferably 70% of the total pore volume.
[0007]
The adsorbent used in the present invention can be obtained by supporting a rare earth metal on the γ-alumina. The rare earth metal can be supported on the γ-alumina by various conventionally known methods, but is generally carried out by an impregnation method. According to this impregnation method, a solution containing a rare earth metal is prepared in advance, γ-alumina is impregnated in this solution, γ-alumina is impregnated with the rare earth metal, and then dried and fired to obtain the desired adsorption. An agent can be obtained.
As the solvent for dissolving the rare earth metal, water, an organic solvent / water mixture, and an organic solvent are used, and water is preferably used. The rare earth metal to be dissolved in the solvent may be in the form of being dissolved in the solvent, and can generally be a halide, nitrate, sulfate, carboxylate or the like.
The concentration of the rare earth metal in the solution is 1 to 30% by weight, preferably 2 to 20% by weight, in terms of metal. The drying temperature of γ-alumina impregnated with the rare earth metal is 50 to 250 ° C., preferably 100 to 200 ° C., and the firing temperature of the dried product is 200 to 700 ° C., preferably 200 to 500 ° C.
[0008]
In the adsorbent used in the present invention, the rare earth metal content is 5 to 60% by weight, preferably 5 to 30% by weight in the total adsorbent in terms of metal. The rare earth metal is usually in the form of an oxide and / or hydroxide in the adsorbent, and may be present, for example, as a hydrous oxide or a basic salt.
Examples of the rare earth metal include cerium, lanthanum, praseodymium, neodymium and the like. In the present invention, in particular, (i) cerium and / or lanthanum, or (ii) a rare earth metal mixture containing cerium and / or lanthanum. preferable. In the adsorbent used in the present invention, if the average pore diameter is smaller than 90 mm, the diffusion of arsenic compound molecules in the pores becomes rate-determined, and the entire adsorbent surface area cannot be used effectively. On the other hand, if the average pore diameter is larger than 200 mm, the surface area cannot be increased. The γ-alumina carrier satisfying the above conditions is obtained by filtering and washing a slurry of aluminum hydroxide produced by neutralization of an aluminum salt, dehydrating and drying the slurry, and then firing it at 400 to 800 ° C. for about 1 to 6 hours. Obtainable.
[0009]
In the adsorbent used in the present invention, the rare earth metal is present as an oxide or a hydroxide, and it seems to form a complex with alumina on the surface of the alumina and give a preferable surface property. If the content is lower than 5% by weight, the composite of alumina and rare earth metal cannot be uniformly covered on the surface of the γ-alumina carrier, so that a sufficient effect cannot be obtained. On the other hand, the surface properties of the composite with alumina change and the surface area itself decreases significantly. In order to support the rare earth metal oxide on the γ-alumina support, there is a method in which the support is impregnated with an aqueous solution of a rare earth metal halide or nitrate, and then dried and fired. In order to support the rare earth metal hydroxide on the γ-alumina carrier, the carrier is impregnated with a rare earth metal halide / nitrate aqueous solution, then immersed in hot ammonia water, washed with water, dried and fired. There are ways to do this.
[0010]
In order to remove arsenic dissolved in water according to the present invention, the adsorbent may be brought into contact with water in which arsenic is dissolved. As a contact method in this case, there are a method of circulating arsenic-containing water through a packed tower packed with an adsorbent, a method of adding an adsorbent to the arsenic-containing water, and agitation, and the like. The arsenic concentration in the water to be treated is usually 0.01 to 50 mg / L, particularly 0.01 to 10 mg / L as As.
[0011]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0012]
Example 1
A γ-alumina support was produced as described in Example 1 of JP-B-6-72005. An outline of this method is as follows. A sodium aluminate aqueous solution is instantaneously added to hot dilute sulfuric acid while stirring vigorously to obtain an aluminum hydroxide slurry suspension (pH 10), which is used as seed aluminum hydroxide and stirred. The process of repeatedly adding hot dilute sulfuric acid and sodium aluminate aqueous solution for a certain time while continuing the process, filtering and washing to obtain a cake, extruding and drying this, followed by baking at 500 ° C. for 3 hours It is. The properties of γ-alumina thus obtained are typically as follows.
[Table 1]
Average pore size 119 Å
Pore volume 0.713 cm 3 / g
Surface area 240 m 2 / g
Percentage of 90-200cm pores in total pore volume 88%
100 g of the above-mentioned γ-alumina support was taken and impregnated with a 30 wt% Ce (NO 3 ) 3 aqueous solution so that the weight ratio of CeO 2 / Al 2 O 3 was about 50/100. The adsorbent was prepared by baking at 0 ° C.
1 g of this adsorbent was added to 0.1 liter of 50 to 200 mg / L arsenic aqueous solution and stirred for 1 hour, and then the arsenic concentration in the liquid was measured. In this case, the form of arsenic contained in the arsenic aqueous solution was arsenic trioxide.
Table 3 shows the arsenic adsorption obtained as a result.
[0013]
Example 2
In Example 1, La (NO 3 ) 3 was used in place of Ce (NO 3 ) 3 , and the La 2 O 3 / Al 2 O 3 weight ratio was about 50/100 in the same manner. An adsorbent containing 2 O 3 was obtained.
Next, using this adsorbent, an arsenic adsorption test was conducted in the same manner as in Example 1. The results are shown in Table 3.
[0014]
Example 3
The same γ-alumina support as in Example 1 was used, impregnated with a 30 wt% Ce (NO 3 ) 3 aqueous solution so that the weight ratio of Ce (OH) 3 / AlO 3 was about 55/100, and dried. . 1 liter of this adsorbent is soaked in approximately the same amount of 10wt% hot ammonia water at 95 ° C for 1 hour, the hot ammonia water is exchanged, the same operation is repeated twice, washed with water and dried, and Ce (OH) 3 is added. The containing adsorbent was obtained.
Next, using this adsorbent, an arsenic adsorption test was conducted in the same manner as in Example 1. The results are shown in Table 3.
[0015]
Comparative Example 1
An adsorbent was prepared and an adsorption test was conducted in the same manner as in Example 1 except that a commercially available alumina carrier (manufactured by Mizusawa Chemical) was used instead of the γ-alumina carrier. In this case, the properties of the alumina support used are as follows.
[Table 2]
Average pore diameter 111 Å
Pore volume 0.615 cm 3 / g
Surface area 220 m 2 / g
Ratio of 90-200cm pores in total pore volume 49%
The amount of arsenic adsorbed on this adsorbent was measured in the same manner as in Example 1. The results are shown in Table 3.
[0016]
[Table 3]
The surface area of the adsorbent used in the present invention was measured according to the BET method by nitrogen adsorption using an automatic gas adsorption / desorption device “Sorptomatic 1800” manufactured by Carlo Elba. The pore volume and average pore diameter were determined by a so-called mercury intrusion method using a pore distribution measuring device “Mercury pressure porosimeter model 70” manufactured by Carlo Elba.
[0018]
【The invention's effect】
According to the present invention, arsenic dissolved in water can be removed efficiently and at low cost.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19334798A JP3924381B2 (en) | 1998-07-08 | 1998-07-08 | Method for adsorbing and removing arsenic dissolved in water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19334798A JP3924381B2 (en) | 1998-07-08 | 1998-07-08 | Method for adsorbing and removing arsenic dissolved in water |
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| Publication Number | Publication Date |
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| JP2000024647A JP2000024647A (en) | 2000-01-25 |
| JP3924381B2 true JP3924381B2 (en) | 2007-06-06 |
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| JP19334798A Expired - Fee Related JP3924381B2 (en) | 1998-07-08 | 1998-07-08 | Method for adsorbing and removing arsenic dissolved in water |
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Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002153864A (en) * | 2000-11-21 | 2002-05-28 | Chiyoda Corp | Method for adsorbing and removing fluorine and/or boron dissolved in water |
| US6863825B2 (en) | 2003-01-29 | 2005-03-08 | Union Oil Company Of California | Process for removing arsenic from aqueous streams |
| WO2004078374A1 (en) * | 2003-03-03 | 2004-09-16 | Nippon Sheet Glass Company, Limited | Soil conditioner |
| US8066874B2 (en) | 2006-12-28 | 2011-11-29 | Molycorp Minerals, Llc | Apparatus for treating a flow of an aqueous solution containing arsenic |
| US8349764B2 (en) | 2007-10-31 | 2013-01-08 | Molycorp Minerals, Llc | Composition for treating a fluid |
| US8252087B2 (en) | 2007-10-31 | 2012-08-28 | Molycorp Minerals, Llc | Process and apparatus for treating a gas containing a contaminant |
| JP4920007B2 (en) * | 2008-05-16 | 2012-04-18 | 地方独立行政法人 東京都立産業技術研究センター | Method for producing glass foam, glass foam and method for regenerating glass foam |
| WO2011052008A1 (en) * | 2009-10-29 | 2011-05-05 | 株式会社Ｎｈｖコーポレーション | Adsorbent, method for producing same, and use of same |
| JP5950326B2 (en) * | 2011-11-01 | 2016-07-13 | 国立研究開発法人物質・材料研究機構 | Mesoporous alumina carrying arsenic ion-adsorbing compound, arsenic ion recovery method using the same, and arsenic-free aqueous solution production method |
| JP5757610B2 (en) * | 2011-01-14 | 2015-07-29 | 国立研究開発法人物質・材料研究機構 | Arsenic (As) ion adsorption element, As ion concentration detection method in water using the same, and As removal method from water |
| CN103338857B (en) * | 2011-01-14 | 2016-10-19 | 独立行政法人物质材料研究机构 | The nanostructure having loaded arsenic ion adsorptivity compound and the method carrying out arsenic ion recovery with it |
| US9233863B2 (en) | 2011-04-13 | 2016-01-12 | Molycorp Minerals, Llc | Rare earth removal of hydrated and hydroxyl species |
| US9975787B2 (en) | 2014-03-07 | 2018-05-22 | Secure Natural Resources Llc | Removal of arsenic from aqueous streams with cerium (IV) oxide compositions |
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1998
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| JP2000024647A (en) | 2000-01-25 |
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