Name: ion exchange resins and charged molecules
Uploaded: 2024-04-04T10:51:25.000Z
Duration: 1 min 17 s
Channel: JoVE

Der Ionenaustausch trennt geladene Moleküle von einer Lösung, indem er sie reversibel mit mobilen oder "aktiven" Ionen austauscht, die mit der entgegengesetzt geladenen stationären Phase assoziiert sind.
Die stationäre Phase ist in der Regel ein poröser, aber unlöslicher Feststoff, wie z. B. vernetzte organische Polymere mit hohen Molekulargewichten, die eine große Anzahl von Monomeren aufweisen, die ionische funktionelle Gruppen tragen.
Anionische Polymere mit aktiven Kationen sind Kationenaustauscher, während kationische Polymere mit aktiven Anionen Anionenaustauscher sind.
Die kationischen und anionischen Austauscher werden anhand ihrer funktionellen Gruppen weiter als schwach und stark klassifiziert.
Die an die Ionenaustauscher gebundenen mobilen Ionen wandern in die Lösung und werden durch die ähnlich geladenen Ionen aus der Lösung ersetzt, bis das Gleichgewicht erreicht ist.
Wendet man das Massenwirkungsgesetz auf das Ionenaustauschgleichgewicht an, so drückt man den Selektivitätskoeffizienten für die Reaktion aus.
Erschöpfte kationische und anionische Austauscher werden regeneriert, indem sie mit einem Überschuss an sauren bzw. basischen Lösungen gewaschen werden.

ionenaustausch

Ion Exchange

Die Ionenaustauschchromatographie trennt geladene Moleküle aus einer Lösung, indem sie sie reversibel gegen mobile oder „aktive“ Ionen austauscht, die mit der entgegengesetzt geladenen stationären Phase verbunden sind. Mit dieser Methode können Ionen getrennt, Wasser enthärtet und entionisiert sowie Lösungen gereinigt werden. Die Polymere, aus denen die Ionenaustauschsäule besteht, sind hochmolekulare und chemisch stabile Polymere, die porös und im Wesentlichen unlöslich vernetzt sind. Sie sind außerdem entweder mit sauren oder basischen Gruppen funktionalisiert. Bei der Funktionalisierung mit sauren Gruppen werden die Säulen oder das Harz als Kationenaustauscher bezeichnet und enthalten negativ geladene Polymere mit positiven Gegenionen. Diese ermöglichen den Austausch von Kationen aus der mobilen Phase. Bei der Funktionalisierung mit basischen Gruppen werden die Säulen oder das Harz als Anionenaustauscher bezeichnet, die positiv geladene Polymere mit negativen Gegenionen enthalten und Anionen mit der Lösung austauschen.

Beim Ionenaustausch gelangen die mit den Festphasenpolymeren verbundenen Gegenionen in die Lösung, während an ihrer Stelle Ionen aus der Lösung mit dem Polymer interagieren. Beachten Sie, dass die Fähigkeit zum Ionenaustausch zunimmt, wenn das Ausmaß der Vernetzung steigt und die Anzahl der Ionenaustauschgruppen im Polymer zunimmt. Dieser Austausch ist reversibel und dauert, bis das Gleichgewicht hergestellt ist.

Saure Kationenaustauscher können entweder mit starken Säuren wie Sulfonsäure (−SO3H), wie sie in Polystyrolsulfonsäure vorkommen, oder schwachen Säuren wie Carbonsäure (−COOH), wie sie in Poly(methylmethylacryl)säure vorkommen, funktionalisiert werden. Ebenso werden Anionenaustauscher entweder als stark oder als schwach klassifiziert. Starke Anionenaustauscher enthalten oft quaternäre Ammoniumgruppen (−CH2N(CH3)3+), wie etwa die im quartären Ammoniumchlorid von Polystyrol, und schwache Anionenaustauscher sind oft mit substituierten Aminen (−NH3+) funktionalisiert, wie etwa die im tertiären Aminhydroxid von Polystyrol .

Ionenaustausch

Der Ionenaustausch trennt geladene Moleküle von einer Lösung, indem er sie reversibel mit mobilen oder "aktiven" Ionen austauscht, die mit dem ...

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ion exchange resins and charged molecules

Ion exchange chromatography separates charged molecules from a solution by swapping them with mobile, or active, ions on a stationary phase. It is used to separate ions, soften and deionize water, and purify solutions. The method depends on a solid column made of high-molecular-weight, chemically stable polymers that are crosslinked to make them porous and essentially insoluble.

These polymers are functionalized with either acidic or basic groups. When acidic groups are present, the resin is a cation exchanger. It has a negatively charged polymer with positive counterions, so it can exchange cations from the mobile phase.

When basic groups are present, the resin is an anion exchanger. It has a positively charged polymer with negative counterions, so it can exchange anions from the solution. During ion exchange, the counterions on the solid polymer move into the solution, and ions from the solution take their place.

The exchange is reversible and continues until equilibrium is reached. The ability to exchange ions increases when the polymer has more crosslinking and more ion-exchange groups. Cation exchangers can be strong or weak. Strong cation exchangers often use sulfonic acid groups, such as in polystyrene sulfonic acid, while weak cation exchangers often use carboxylic acid groups, such as in poly(methyl methylacrylic) acid.

Anion exchangers are also classified as strong or weak. Strong anion exchangers often contain quaternary ammonium groups, such as in polystyrene quaternary ammonium chloride. Weak anion exchangers are often functionalized with substituted amines, such as in polystyrene tertiary amine hydroxide.

Ion Exchange Resins and Charged Molecules

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ion exchange

Ion exchange chromatography separates charged molecules from a solution by swapping them with mobile, or active, ions on a stationary phase. It is used to separate ions, soften and deionize water, and purify solutions. The method depends on a solid column made of high-molecular-weight, chemically stable polymers that are crosslinked to make them porous and essentially insoluble. These polymers are functionalized with either acidic or basic groups. When acidic groups are present, the resin is a...

key terms and concepts

Learn how ion exchange chromatography uses cation and anion exchangers to separate charged molecules, purify solutions, and soften water.

Ion Exchange Resins and Charged Molecules | JoVE K12

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Ion Exchange Resins and Charged Molecules

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