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Interactions of Some Large Organic Cations with Bentonite in Dilute Aqueous Systems

Published online by Cambridge University Press:  01 July 2024

Deoraj R. Narine*
Affiliation:
Trace Analysis Research Centre, Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada
Robert D. Guy
Affiliation:
Trace Analysis Research Centre, Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada
*
1Present address: School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405
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Abstract

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Adsorption studies indicate that paraquat, diquat, and thionine are bound on bentonite by amounts greater than the measured cation-exchange capacity (CEC) of the clay. Methylene blue, new methylene blue, and malachite green are bound by amounts equal to the CEC. The unipositive organocations form aggregates on the clay surface. Aggregation increases with ionic strength and increases the apparent adsorption capacity by 25%. The aggregates are removed by washing with distilled water. Desorption studies show that the dyes are irreversibly bound, whereas the dipositive organocations are reversibly bound. Ionic strength variation reduces adsorption by 15 and 36% in the monovalent and divalent organocation-clay systems, respectively. In the clay-divalent organocation systems adsorption is greater on Na-saturated clay than on K-saturated clay. Adsorption is unchanged over the pH range 4.5–8.5 and decreases steadily below pH 4.0. Changes in adsorption due to changes in temperature are small. The study indicates that ionic strength is the most important variable in clay-organocation interactions.

Резюме

Резюме

Исследования по адсорбции показывают, что паракват, дикват, и тионин связаны в бентоните в количествах больших, чем измеренная катионообменная способность (КОС) глины. Голубой метилен, новый голубой метилен, и зелёный малахит связаны в количествах, соответствующих KОС. Униположительные органокатионы образуют агрегаты на поверхности глины. Агрегация увеличивается с увеличением ионной силы и приводит к увеличению видимой адсорбционной способности до 25%. Агрегаты удаляются при промывке дистиллированной водой. Исследования по десорбции показывают, что красители связаны необратимо, тогда как двухположительные органокатионы связаны обратимо. Изменение ионной силы уменьшает адсорбцию в одновалентных и двухвалентных системах органокатион-глина на 15 и 36% соответственно. В системах глина-двухвалентный органокатион адсорбция значительнее на глине насыщенной натрием, чем на глине насыщенной калием. Адсорбция не изменяется в диапазоне рН 4,5-8,5, и уменьшается равномерно, если рН меньше 4,0. Изменения в адсорбции вследствие изменений температуры малы. Исследования показывают, что ионная сила является наиболее важным фактором в глино-органокатионных взаимодействиях. [Е.С.]

Resümee

Resümee

Die Adsorptionsuntersuchungen deuten darauf hin, daß Paraquat, Diquat, und Thionin an Bentonite in größeren Mengen gebunden sind als die gemessene Kationenaustauschkapazität (CEC) der Tone erlaubt. Methylenblau, Neu-Methylenblau, und Malachitgrün sind in Mengen gebunden, die denen des CEC entsprechen. Die einwertigen organischen Kationen bilden auf der Tonoberfläche Aggregate. Die Aggregatbildung nimmt mit der Ionenstärke zu und vergrößert die scheinbare Adsorptionskapazität um 25%. Die Aggregate werden durch Waschen mit destilliertem Wasser entfernt. Desorptionsuntersuchungen zeigen, daß die Farben irreversibel gebunden sind, während die zweiwertigen organischen Kationen reversibel gebunden sind. Die Variation der Ionenstärke reduzierte die Adsorption um 15 bzw. um 36% in den einwertigen bzw. zweiwertigen organischen Kationen-Ton Systemen. In den Systemen Ton-awei-wertige organische Kationen ist die Adsorption an Na-gesäittigten Ton größer als an K-gesättigten. Die Adsorption bleibt im pH-Bereich von 4,5 bis 8,5 unveräindert und nimmt unter pH 4,0 regelmäßig ab. Änderungen in der Adsorption, die auf Temperaturäinderungen zuräckzufähren sind, sind klein. Die Untersuchnng deutet darauf hin, daß die Ionenstärke die wichtigste Variable bei der Wechselwirkung Ton-organisches Kation ist. [U.W.]

Résumé

Résumé

Des études d'adsorption indiquent que le paraquat, diquat, et la thionine sont lié à la bentonite en quantités plus grandes que la capacité d’échange de cations (CEC) mesurée de l'argile. Le bleu de méthylène, le nouveau bleu de méthylètne, et le vert de malachite sont liés en quantités égales à la CEC. Les organocations unipositifs forment des aggrégats sur la surface de l'argile. L'aggrégation croît proportionnellement â la force ionique et accroît la capacité d'adsorption apparente de 25%. Les aggrégats sont retirés par un lavage à l'eau distillée. Des études de désorption montrent que les teintures sont liées irréversiblement, tandis que les organocations dispositifs le sont réversiblement. La variation de force ionique réduit l'adsorption de 15 et 36% dans les systèmes argile-organocations monovalents et divalents, respectivement. Dans les systémes argile-organocations divalents, l'adsorption est plus grande sur l'argile saturtée de Na que sur l'argile saturtée de K. L'adsorption demeure inchangée sur l’étendue de pH 4,5-8,5 et décroît de manière constante sous un pH de 4,0. Les changements d'adsorption dûs à des changements de température soit petits. L’étude indique que la force ionique est la variable la plus importante dans les interactions argile-organocations. [D.J.]

Type
Research Article
Copyright
Copyright © 1981, The Clay Minerals Society

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