JP4008977B2 - Chitosan derivative, production method thereof and metal ion adsorbent - Google Patents

Description

【０００７】
（式中、Ｒ¹ ，Ｒ² ，Ｒ³ は、同一もしくは異なって炭素数１〜３の直鎖状アルキレン基を表わす）
また、上記キトサン誘導体を製造するための本発明の方法は、
▲１▼キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方を、下記一般式［２］で示されるアシル基で置換し、より具体的には
【０００８】
【化４】

【０００９】
（式中、Ｒ¹ ，Ｒ² ，Ｒ³ は、同一もしくは異なって炭素数１〜３の直鎖状アルキレン基を表わす）
▲２▼キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子に、下記一般式［３］で示されるアミノトリカルボン酸の１無水物を反応させる、
【００１０】
【化５】

【００１１】
（式中、Ｒ¹ ，Ｒ² ，Ｒ³ は、同一もしくは異なって炭素数１〜３の直鎖状アルキレン基を表わす）
ところに要旨がある。
【００１２】
また本発明に係る第二のキトサン誘導体は、下記一般式［４］で示される化学修飾アミノ糖構造を分子中に有するものであるところに特徴があり、また該キトサン誘導体を製造するための本発明の方法は
【００１３】
【化６】

【００１４】
（式中、Ｒは水素または低級アルキル基を表わす）
▲３▼キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方を、下記一般式［５］で示されるアルキレンホスホン酸基で置換し、より具体的には
【００１５】
【化７】

【００１６】
（式中、Ｒは水素または低級アルキル基を表わす）
▲４▼キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方に、Ｒ−ＣＨＯ（Ｒは水素または低級アルキル基を表わす）で示されるアルデヒドと亜燐酸を逐次もしくは同時に反応させる
ところにその特徴を有している。
また本発明に係る金属イオン吸着剤は、上記一般式［１］または［４］で示されるキトサン誘導体を有効成分として含有するところに特徴を有している。
【００１７】
【発明の実施の形態】
キトサンは、下記化学式［６］で示されるアミノ糖構造を有する高分子化合物であって、
【００１８】
【化８】

【００１９】
様々の分子量物の混合物であり、該キトサンから本発明方法によって誘導されるキトサン誘導体も、分子量や固有粘度などを特定することはできないが、その製法から予測される化学構造とＮＭＲやＩＲスペクトル等を照合すると、分子中に前記化学式［１］または［４］で示される化学修飾されたアミノ糖構造を有する高分子化合物であることを確認することができる。
【００２０】
アミノ基に修飾される上記アシル基における前記Ｒ¹ ，Ｒ² ，Ｒ³ で示される直鎖状アルキレン基の中でも最も一般的なのは、Ｒ¹ ，Ｒ² およびＲ³ がいずれもメチレンであり、また上記アルキレンホスホン酸基におけるＲで示される水素または低級アルキル基の中で特に好ましいのは水素である。
【００２１】
上記の様なキトサン誘導体は、上記キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方を、前記一般式［２］で示されるアシル基で置換する方法、より具体的には、キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子に、前記一般式［３］で示されるアミノトリカルボン酸の１無水物を反応させる方法、および、キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方を、前記一般式［５］で示されるアルキレンホスホン酸基で置換する方法、より具体的には、キトサン分子中の２位の炭素原子に結合したアミノ基の水素原子の一方に、Ｒ−ＣＨＯ（Ｒは水素または低級アルキル基を表わす）で示されるアルデヒドと亜燐酸を逐次もしくは同時に反応させる方法によって得ることができ、その代表的な方法を例示すると下記式Ａ，Ｂの通りである。
【００２２】
【化９】

【００２３】
即ち上記式Ａの反応は、キトサンにおける２位の炭素原子に結合したアミノ基の水素原子に、前記一般式［３］で示されるアミノトリカルボン酸の１無水物を反応させることによって行なわれるが、アミノトリカルボン酸として特に好ましいのは、Ｒ¹ ，Ｒ² ，Ｒ³ がいずれもメチレン基である無水ニトリロトリ酢酸である。
【００２４】
この反応は、たとえば酢酸とメタノールの混合水溶液などを溶剤として使用し、１０〜５０℃で１〜２４時間程度反応させることによって容易に進行する。このとき、アミノトリカルボン酸１無水物、たとえば無水ニトリロトリ酢酸（ＮＴＡ無水物）は、キトサンのアミノ基における１つの水素原子に対してほぼ理論量反応するので、キトサンに対するアミノトリカルボン酸１無水物の使用量を変えることにより、必要に応じた任意の修飾量を得ることができる。
【００２５】
この反応によって得られるキトサン誘導体は、例えば上記の反応によりゲル状物として生成するので、これを濾取しアルカリ水溶液等で洗浄して未反応のＮＴＡ無水物を除去し、更に塩酸水溶液等を用いた酸処理および水洗を繰り返してから乾燥すると、遊離カルボン酸を有する目的物を白色粉末として得ることができる。
【００２６】
上記で得られるキトサン誘導体において、キトサンのアミノ基に修飾されるアシル基の導入量は特に制限されないが、例えば金属イオン吸着剤などとして実用化するときに、化学修飾により導入されるカルボキシル基の効果、例えば金属イオン捕捉効果等を有効に発揮させるには、キトサンを構成するアミノ糖の１００単位当たり１〜１００モル、より一般的には１０〜５０モルのアシル基を導入することが望ましい。これらアシル基の導入量は、たとえばカルボキシル基の量を中和滴定することによって容易に確認することができる。
【００２７】
また上記式Ｂで示される反応は、キトサンにおける２位の炭素原子に結合したアミノ基の水素原子に、ホルムアルデヒド等の低級アルキルアルデヒドと亜燐酸を逐次もしくは同時に反応させることによって行なわれるが、アルデヒドとして特に好ましいのはホルムアルデヒドである。
【００２８】
この反応は、たとえば塩酸等の酸性水溶液中、８０〜１００℃で１〜１０時間程度反応させることによって容易に進行する。即ちホルムアルデヒドと亜燐酸を使用したときの反応では、まずキトサンのアミノ基にアルデヒドが付加してアミノメチロール基となり、これに亜燐酸が反応することによってメチレンホスホン酸基が導入される。従ってこの反応を行なうに当たっては、先ずキトサンにホルムアルデヒドを反応させることによってアミノメチロール基を導入し、引き続いてこれに亜燐酸を反応させる逐次反応を採用することも可能であるが、反応系にキトサンと共にホルムアルデヒドと亜燐酸を同時に共存させてこの反応を進めることも可能である。
【００２９】
このとき、アルキレンホスホン酸基は、キトサンのアミノ基における１つの水素原子に対してほぼ理論量反応するので、キトサンに対するアルデヒトと亜燐酸の使用量を変えることにより、必要に応じた任意の修飾量を得ることができる。
【００３０】
上記で得られるキトサン誘導体においても、キトサンのアミノ基に修飾されるアルキルホスホン酸基の導入量も特に制限されないが、例えば金属イオン吸着剤などとして実用化するときに、化学修飾により導入されるホスホン酸基の効果、例えば金属イオン捕捉効果等を有効に発揮させるには、キトサンを構成するアミノ糖の１００単位当たり１〜１００モル、より一般的には１０〜５０モルのアルキレンホスホン酸基を導入することが望ましい。これらアルキレンホスホン酸基の導入量は、たとえばホスホン酸基の量を中和滴定することによって容易に確認することができる。
【００３１】
この反応の場合も、キトサン誘導体はゲル状物として生成するので、これを濾取しアルカリ水溶液等で洗浄して未反応のアルデヒドや亜燐酸を除去し、更に塩酸水溶液等を用いた酸処理および水洗を繰り返してから乾燥すると、遊離のアルキレンホスホン酸基を有する目的物を白色粉末として得ることができる。
【００３２】
上記方法によって得られるキトサン誘導体は、母体がキトサンであるから環境に優しい生分解性を有しており、また導入されたアシル基またはアルキレンホスホン酸基によって優れた金属捕捉作用を発揮し、更にこれらの基の導入量によっては、一部のアミノ基がそのまま残されるので、分子中に該アミノ基とカルボキシル基またはホスホン酸基を共有する両性高分子としての特性を与えることも可能であり、こうした特性を有効に活用すれば、金属イオン吸着剤や凝集剤などとして有効に利用できる他、化粧品用途、生理・薬理活性を利用した医薬・医療用途などに広く活用することができる。中でも、化学修飾によって導入されたカルボキシル基やホスホン酸基は、各種重金属イオンに対して広いｐＨ域で優れた選択吸着性を発揮するので、工場廃水などの重金属捕捉剤として活用し、公害防止用途に極めて有効に活用することができる。
【００３３】
【実施例】
次に実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも可能であり、それらは全て本発明の技術的範囲に包含される。
【００３４】
実施例１
２容量％の酢酸水溶液３００ｍｌに５ｇのキトサンを溶解し、これにメタノールを加えて６００ｍｌとする。この溶液に、１６．１ｇの無水ニトリロトリ酢酸（ＮＴＡ無水物）を溶解させた２００ｍｌのメタノール溶液を加え、更にメタノールを追加して１，０００ｍｌの溶液とした後、攪拌しつつ２０℃で２０時間反応させる。反応終了後、生成したゲル状物を濾取し、０．５モル／ｌの水酸化ナトリウム水溶液５００ｍｌで洗浄して未反応のＮＴＡ無水物を溶解除去する。
【００３５】
その後５００ｍｌの蒸留水にゲル状物を分散させ、塩酸を用いてｐＨ２に調整した後、蒸留水で洗浄液が中性になるまで洗浄・濾過を繰り返す。次いで２０℃で真空乾燥すると、白色粉末状の目的物（ＮＴＡ修飾キトサン誘導体）６．１ｇが得られる。このキトサン誘導体のカルボキシル基量を中和滴定によって測定したところ、原料キトサン中の全アミノ基に対するＮＴＡの置換量は３５モル％であることが確認された。
【００３６】
上記で得たＮＴＡ修飾キトサン誘導体０．０３ｇを、Ｃｕ、ＺｎおよびＮｉイオンをそれぞれ約１ミリモル／ｌ濃度で含む希硫酸水溶液５０ｍｌに添加し、２０℃で２０時間処理し、各金属イオンの吸着量とｐＨの関係を調べたところ、図１に示す結果を得た。図１からも明らかである様に、本発明のＮＴＡ修飾キトサンは、ｐＨ１程度の低いｐＨ域からでも高い金属イオン吸着能を示し、廃水等からの金属イオン除去用として有効に活用できることが分かる。
【００３７】
実施例２
キトサン１０ｇ、亜燐酸１２．２ｇ、３６％塩酸６．３ｇ、蒸留水６００ｍｌを混合して１００℃に加熱し、攪拌しつつこれに３４％ホルムアルデヒド水溶液２６．４ｇを３０分かけて滴下する。滴下終了後、更に１００℃で３時間攪拌することによって反応を完結させる。その後、２０℃に冷却してから苛性ソーダ水溶液を用いてｐＨ３に調整すると、ゲル状物が析出してくるので、これを濾取し、蒸留水：エタノール＝１：１（容量比）の混合液を用いて、洗浄液が中性となるまで洗浄、濾過を繰り返す。次いで２０℃で真空乾燥すると、白色粉末状の目的物１１．１ｇが得られる。
【００３８】
得られたキトサン誘導体のホスホン酸基量を中和滴定によって測定したところ、原料キトサン中の全アミノ基に対するメチレンホスホン酸基の置換量は４８モル％であることが確認された。
【００３９】
上記で得たメチレンホスホン酸修飾キトサン０．０３ｇを、Ｃｕ、ＺｎおよびＮｉイオンをそれぞれ約１ミリモル／ｌ濃度で含む希硫酸水溶液５０ｍｌに添加し、２０℃で２０時間処理し、各金属イオンの吸着量とｐＨの関係を調べたところ、図２に示す結果を得た。図２からも明らかである様に、本発明によって得られるキトサン誘導体は、ｐＨ２程度の低いｐＨ域からでも高い金属イオン吸着能を示し、廃水等からの金属イオン除去用として有効に活用できることが分かる。
【００４０】
比較例１
上記実施例１，２における後段の金属イオン吸着実験において、化学修飾を行なっていないキトサンをそのまま使用した以外は上記と同様にして、金属イオン吸着能を調べた。結果は図３に示す通りであり、図１，２と比較すれば明らかである様に、実施例１，２のキトサン誘導体に比べると低ｐＨ域での金属イオン吸着能に欠けるものであることが分かる。
【００４１】
比較例２
吸着剤として市販のスチレン−イミノジ酢酸系キレート剤を使用し、前記と同様にして金属イオンの吸着量とｐＨの関係を調べた。結果は図４に示す通りであり、銅イオンについては低ｐＨ域でも高い吸着能を示すが、ニッケルと亜鉛については、ｐＨを３〜４以上に高めなければ満足のいく吸着能を得ることができない。
【００４２】
【発明の効果】
本発明は以上の様に構成されており、生分解性で環境汚染を招くことのない新規なキトサン誘導体を提供することができ、このキトサン誘導体は化学修飾により導入されたアミノカルボン酸基やアルキレンホスホン酸基の特性を利用して金属イオン吸着剤として有効に活用できる他、化粧品、生理・薬理活性を利用した医薬・医療分野などへも幅広く活用することができ、特に金属イオン吸着剤として使用すると、低ｐＨ域においても優れた重金属イオン吸着能を示し、有害イオン除去用として極めて有効に活用することができる。
【図面の簡単な説明】
【図１】実施例１で得たキトサン誘導体の金属イオン吸着能を示すグラフである。
【図２】実施例２で得たキトサン誘導体の金属イオン吸着能を示すグラフである。
【図３】比較例１で用いた未修飾キトサンの金属イオン吸着能を示すグラフである。
【図４】比較例（市販のキレート剤）の金属イオン吸着能を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel chitosan derivative and a production method thereof, and an adsorbent having excellent heavy metal ion scavenging properties containing the chitosan derivative as an active ingredient.
[0002]
[Prior art]
Chitosan is an amino sugar obtained by deacetylation of chitin, which is a natural polymer isolated from salmon and shrimp shells, and has various uses as a biodegradable polymer material that does not cause environmental pollution. Typical applications include water treatment agents (flocculating agents, etc.), separation agents, cosmetics, and pharmaceutical / medical fields using pharmacological / physiological activity that utilize the properties of polycations. . In addition, various researches are underway to further improve performance while taking advantage of the above characteristics of chitosan.
[0003]
On the other hand, industrial wastewater and the like may contain various harmful metal ions, and from the viewpoint of preventing environmental pollution, it is necessary to sufficiently remove these harmful metal ions by wastewater treatment. Many of these toxic metal ions can be effectively used as heavy metals and the like, and if they can be separated and recovered and effectively used as secondary resources, they are two birds with one stone. As a metal ion adsorbent applied to such applications, there is a movement to use the above chitosan. For example, use development as an adsorbent for harmful metal ions such as mercury, copper, and cadmium is being promoted.
[0004]
[Problems to be solved by the invention]
Under the circumstances as described above, the present inventors have made use of the excellent characteristics of chitosan, particularly the biodegradability that is friendly to the environment, and are aiming to further improve the performance as a metal ion adsorbent. We have planned the development of chitosan derivatives and have been conducting research with the aim of developing their use. Accordingly, an object of the present invention is to develop a new chitosan derivative using chitosan, which is a biodegradable polymer that does not cause environmental pollution, as a raw material, and to establish a production method thereof. It is intended to provide a performance metal ion adsorbent.
[0005]
[Means for Solving the Problems]
The gist of the first chitosan derivative of the present invention that has solved the above problems is that it has a chemically modified amino sugar structure represented by the following general formula [1] in the molecule.
[0006]
[Chemical 3]

[0007]
(Wherein R ¹ , R ² and R ³ are the same or different and represent a linear alkylene group having 1 to 3 carbon atoms)
The method of the present invention for producing the chitosan derivative is as follows.
(1) One of the hydrogen atoms of the amino group bonded to the carbon atom at the 2-position in the chitosan molecule is substituted with an acyl group represented by the following general formula [2], and more specifically:
[Formula 4]

[0009]
(Wherein R ¹ , R ² and R ³ are the same or different and represent a linear alkylene group having 1 to 3 carbon atoms)
(2) The aminotricarboxylic acid monoanhydride represented by the following general formula [3] is reacted with the hydrogen atom of the amino group bonded to the carbon atom at the 2-position in the chitosan molecule.
[0010]
[Chemical formula 5]

[0011]
(Wherein R ¹ , R ² and R ³ are the same or different and represent a linear alkylene group having 1 to 3 carbon atoms)
There is a gist.
[0012]
The second chitosan derivative according to the present invention is characterized in that it has a chemically modified amino sugar structure represented by the following general formula [4] in the molecule, and a book for producing the chitosan derivative. The method of the invention is:
[Chemical 6]

[0014]
(Wherein R represents hydrogen or a lower alkyl group)
(3) One of the hydrogen atoms of the amino group bonded to the carbon atom at the 2-position in the chitosan molecule is substituted with an alkylenephosphonic acid group represented by the following general formula [5], more specifically:
[Chemical 7]

[0016]
(Wherein R represents hydrogen or a lower alkyl group)
(4) An aldehyde represented by R—CHO (where R represents hydrogen or a lower alkyl group) and phosphorous acid are reacted sequentially or simultaneously with one of the hydrogen atoms of the amino group bonded to the carbon atom at the 2-position in the chitosan molecule. It has that characteristic.
The metal ion adsorbent according to the present invention is characterized by containing a chitosan derivative represented by the above general formula [1] or [4] as an active ingredient.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Chitosan is a polymer compound having an amino sugar structure represented by the following chemical formula [6],
[0018]
[Chemical 8]

[0019]
It is a mixture of various molecular weights, and the chitosan derivative derived from the chitosan by the method of the present invention cannot specify the molecular weight, intrinsic viscosity, etc., but the chemical structure predicted from the production method, NMR, IR spectrum, etc. Can be confirmed to be a polymer compound having a chemically modified amino sugar structure represented by the chemical formula [1] or [4] in the molecule.
[0020]
The most common among the straight-chain alkylene group represented by in the acyl group to be modified to the amino group R ^1, R ^2, R ^3, both R ^1, R ² and R ³ is methylene, also Of the hydrogen or lower alkyl group represented by R in the alkylenephosphonic acid group, hydrogen is particularly preferred.
[0021]
The chitosan derivative as described above is a method in which one of the hydrogen atoms of the amino group bonded to the carbon atom at the 2-position in the chitosan molecule is substituted with an acyl group represented by the general formula [2], more specifically. Is a method of reacting a monoanhydride of an aminotricarboxylic acid represented by the general formula [3] with a hydrogen atom of an amino group bonded to a carbon atom at the 2-position in the chitosan molecule, and a 2-position in the chitosan molecule. A method in which one of the hydrogen atoms of the amino group bonded to the carbon atom is substituted with an alkylenephosphonic acid group represented by the general formula [5], more specifically, bonded to the carbon atom at the 2-position in the chitosan molecule One of the hydrogen atoms of the amino group can be obtained by a method in which an aldehyde represented by R—CHO (R represents hydrogen or a lower alkyl group) and phosphorous acid are reacted sequentially or simultaneously. To illustrate the table method is as following formulas A, B.
[0022]
[Chemical 9]

[0023]
That is, the reaction of the above formula A is carried out by reacting the aminotricarboxylic acid monoanhydride represented by the general formula [3] with the hydrogen atom of the amino group bonded to the carbon atom at the 2-position in chitosan. Particularly preferred as the aminotricarboxylic acid is nitrilotriacetic anhydride, in which R ¹ , R ² and R ³ are all methylene groups.
[0024]
This reaction proceeds easily by using, for example, a mixed aqueous solution of acetic acid and methanol as a solvent and reacting at 10 to 50 ° C. for about 1 to 24 hours. At this time, aminotricarboxylic acid monoanhydride, for example, nitrilotriacetic anhydride (NTA anhydride) reacts with a theoretical amount with respect to one hydrogen atom in the amino group of chitosan, so use of aminotricarboxylic acid monoanhydride with respect to chitosan By changing the amount, an arbitrary modification amount can be obtained as required.
[0025]
The chitosan derivative obtained by this reaction is produced, for example, as a gel by the above reaction. This is filtered and washed with an alkaline aqueous solution to remove unreacted NTA anhydride, and further an aqueous hydrochloric acid solution is used. When the acid treatment and washing with water are repeated and then dried, the desired product having a free carboxylic acid can be obtained as a white powder.
[0026]
In the chitosan derivative obtained above, the introduction amount of the acyl group modified to the amino group of chitosan is not particularly limited, but for example, when put into practical use as a metal ion adsorbent, the effect of the carboxyl group introduced by chemical modification For example, in order to effectively exhibit a metal ion scavenging effect or the like, it is desirable to introduce 1 to 100 moles, more generally 10 to 50 moles of acyl groups per 100 units of amino sugar constituting chitosan. The amount of these acyl groups introduced can be easily confirmed, for example, by neutralizing titration of the amount of carboxyl groups.
[0027]
The reaction represented by the above formula B is carried out by reacting a lower alkyl aldehyde such as formaldehyde and phosphorous acid sequentially or simultaneously with the hydrogen atom of the amino group bonded to the carbon atom at the 2-position in chitosan. Particularly preferred is formaldehyde.
[0028]
This reaction proceeds easily by reacting at 80 to 100 ° C. for about 1 to 10 hours in an acidic aqueous solution such as hydrochloric acid. That is, in the reaction when formaldehyde and phosphorous acid are used, an aldehyde is first added to the amino group of chitosan to form an aminomethylol group, and methylenephosphonic acid group is introduced by the reaction of phosphorous acid with this. Therefore, in carrying out this reaction, it is possible to adopt a sequential reaction in which an aminomethylol group is first introduced by reacting chitosan with formaldehyde and subsequently reacted with phosphorous acid. It is also possible to proceed with this reaction by simultaneously coexisting formaldehyde and phosphorous acid.
[0029]
At this time, the alkylene phosphonic acid group reacts with a theoretical amount with respect to one hydrogen atom in the amino group of chitosan. Therefore, by changing the amount of aldehyde and phosphorous acid used for chitosan, any amount of modification can be made as required. Can be obtained.
[0030]
Also in the chitosan derivative obtained above, the amount of alkylphosphonic acid group modified to the amino group of chitosan is not particularly limited, but for example, when it is put into practical use as a metal ion adsorbent, phosphone introduced by chemical modification. In order to effectively exhibit the effect of an acid group, such as a metal ion scavenging effect, 1 to 100 mol, more generally 10 to 50 mol of alkylenephosphonic acid groups are introduced per 100 units of amino sugar constituting chitosan. It is desirable to do. The introduction amount of these alkylenephosphonic acid groups can be easily confirmed by, for example, neutralizing titration of the amount of phosphonic acid groups.
[0031]
Also in this reaction, since the chitosan derivative is produced as a gel, it is collected by filtration and washed with an alkaline aqueous solution to remove unreacted aldehyde and phosphorous acid, and further an acid treatment using an aqueous hydrochloric acid solution and the like. By repeatedly washing with water and then drying, the desired product having a free alkylenephosphonic acid group can be obtained as a white powder.
[0032]
The chitosan derivative obtained by the above method has environmentally friendly biodegradability since the parent is chitosan, and exhibits an excellent metal scavenging action by the introduced acyl group or alkylenephosphonic acid group. Depending on the amount of the group introduced, a part of the amino group is left as it is, so that it is possible to give characteristics as an amphoteric polymer sharing the amino group and the carboxyl group or phosphonic acid group in the molecule. If the properties are used effectively, they can be used effectively as metal ion adsorbents, flocculants and the like, and can be widely used in cosmetics, medical and medical applications using physiological and pharmacological activities. Among them, carboxyl groups and phosphonic acid groups introduced by chemical modification exhibit excellent selective adsorption properties over a wide pH range for various heavy metal ions, so they can be used as heavy metal scavengers for factory wastewater and other pollution prevention applications. Can be used very effectively.
[0033]
【Example】
EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples as a matter of course, and appropriate modifications are made within a range that can meet the purpose described above and below. It is also possible to carry out and they are all included in the technical scope of the present invention.
[0034]
Example 1
5 g of chitosan is dissolved in 300 ml of a 2% by volume acetic acid aqueous solution, and methanol is added to make 600 ml. To this solution, 200 ml of methanol solution in which 16.1 g of nitrilotriacetic anhydride (NTA anhydride) was dissolved was added, and methanol was further added to make a 1,000 ml solution, and then stirred at 20 ° C. for 20 hours. React. After completion of the reaction, the formed gel is collected by filtration and washed with 500 ml of 0.5 mol / l sodium hydroxide aqueous solution to dissolve and remove unreacted NTA anhydride.
[0035]
Thereafter, the gel-like material is dispersed in 500 ml of distilled water, adjusted to pH 2 with hydrochloric acid, and then repeatedly washed and filtered with distilled water until the washing solution becomes neutral. Subsequently, when vacuum-dried at 20 ° C., 6.1 g of a white powdery target product (NTA-modified chitosan derivative) is obtained. When the amount of carboxyl groups of this chitosan derivative was measured by neutralization titration, it was confirmed that the substitution amount of NTA with respect to all amino groups in the raw material chitosan was 35 mol%.
[0036]
Adsorption of each metal ion by adding 0.03 g of the NTA-modified chitosan derivative obtained above to 50 ml of dilute sulfuric acid aqueous solution containing Cu, Zn and Ni ions at a concentration of about 1 mmol / l, respectively, and treating at 20 ° C. for 20 hours. When the relationship between the amount and pH was examined, the results shown in FIG. 1 were obtained. As is clear from FIG. 1, it can be seen that the NTA-modified chitosan of the present invention exhibits a high metal ion adsorption ability even from a pH range as low as about pH 1, and can be effectively used for removing metal ions from wastewater or the like.
[0037]
Example 2
10 g of chitosan, 12.2 g of phosphorous acid, 6.3 g of 36% hydrochloric acid and 600 ml of distilled water are mixed and heated to 100 ° C., and 26.4 g of 34% formaldehyde aqueous solution is added dropwise over 30 minutes while stirring. After completion of the dropwise addition, the reaction is completed by further stirring at 100 ° C. for 3 hours. Then, after cooling to 20 ° C. and adjusting the pH to 3 using an aqueous caustic soda solution, a gel-like substance is precipitated. This is collected by filtration and mixed with distilled water: ethanol = 1: 1 (volume ratio). Repeat washing and filtration until the washing solution becomes neutral. Subsequently, when vacuum-dried at 20 ° C., 11.1 g of the white powdery target product is obtained.
[0038]
When the amount of phosphonic acid groups in the obtained chitosan derivative was measured by neutralization titration, it was confirmed that the amount of substitution of methylenephosphonic acid groups with respect to all amino groups in the raw material chitosan was 48 mol%.
[0039]
0.03 g of methylenephosphonic acid-modified chitosan obtained above was added to 50 ml of dilute sulfuric acid aqueous solution containing Cu, Zn and Ni ions at a concentration of about 1 mmol / l, respectively, and treated at 20 ° C. for 20 hours. When the relationship between the adsorption amount and pH was examined, the results shown in FIG. 2 were obtained. As is clear from FIG. 2, the chitosan derivative obtained by the present invention shows a high metal ion adsorption ability even from a low pH range of about pH 2, and it can be seen that it can be effectively used for removing metal ions from waste water or the like. .
[0040]
Comparative Example 1
In the latter-stage metal ion adsorption experiments in Examples 1 and 2, the metal ion adsorption ability was examined in the same manner as above except that chitosan without chemical modification was used as it was. The results are as shown in FIG. 3 and, as is clear from comparison with FIGS. 1 and 2, the metal ion adsorption ability in the low pH region is lacking compared to the chitosan derivatives of Examples 1 and 2. I understand.
[0041]
Comparative Example 2
A commercially available styrene-iminodiacetic acid chelating agent was used as the adsorbent, and the relationship between the adsorption amount of metal ions and pH was examined in the same manner as described above. The results are as shown in FIG. 4, and copper ions show a high adsorption ability even in a low pH range, but nickel and zinc can obtain a satisfactory adsorption ability unless the pH is increased to 3 to 4 or more. Can not.
[0042]
【The invention's effect】
The present invention is configured as described above, and can provide a novel chitosan derivative that is biodegradable and does not cause environmental pollution. This chitosan derivative is an aminocarboxylic acid group or alkylene introduced by chemical modification. It can be used effectively as a metal ion adsorbent by utilizing the properties of phosphonic acid groups, and can also be widely used in cosmetics, medicine and medical fields using physiological and pharmacological activities, especially as a metal ion adsorbent. Then, even in a low pH range, it exhibits excellent heavy metal ion adsorption ability and can be used very effectively for removing harmful ions.
[Brief description of the drawings]
1 is a graph showing the metal ion adsorption ability of the chitosan derivative obtained in Example 1. FIG.
2 is a graph showing the metal ion adsorption ability of the chitosan derivative obtained in Example 2. FIG.
3 is a graph showing the metal ion adsorption ability of unmodified chitosan used in Comparative Example 1. FIG.
FIG. 4 is a graph showing the metal ion adsorption ability of a comparative example (commercially available chelating agent).

Claims (3)

A chitosan derivative having a chemically modified amino sugar structure represented by the following general formula [1] in the molecule.

(Wherein R ¹ , R ² and R ³ are the same or different and represent a linear alkylene group having 1 to 3 carbon atoms) The chitosan derivative according to claim 1, wherein a monoanhydride of an aminotricarboxylic acid represented by the following general formula [3] is reacted with a hydrogen atom of an amino group bonded to a carbon atom at the 2-position in the chitosan molecule. Manufacturing method.

(Wherein R ¹ , R ² and R ³ are the same or different and represent a linear alkylene group having 1 to 3 carbon atoms)   A metal ion adsorbent comprising the chitosan derivative according to claim 1.

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