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Issue 28, 2007
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Relation between the hydrophile/hydrophobe ratio of malonamide extractants and the stability of the organic phase: investigation at high extractant concentrations

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Abstract

In the present paper, it is shown that in malonamide extractant/dodecane mixtures, change in the shape of the extractant aggregate may promote phase demixion. This phenomenon is known as the 3rd phase formation in extractant systems. The shape of the aggregates is dictated by the length of the alkyl chains stabilizing the reverse microemulsion by steric repulsion. Small angle scattering experiments are used to investigate the aggregation states of diamide extractant molecules, namely N,N′dimethyl-N,N′dibutyl-tetradecyl malonamide (DMDBTDMA) and N,N′dimethyl-N,N′dibutyl-pentyl malonamide (DMDBPMA), in dodecane. The results are described in a consistent way by the packing parameter concept and by expressing steric repulsion versus Van der Waals inter-aggregate interactions, both curvature dependants. Non-monotonous change in the extractant Critical Micellar Concentration (CMC) as a function of the extractant alkyl chain length is rationalized by comparing Van der Waals attraction between the alkyl chains of both the extractant and the solvent.

Graphical abstract: Relation between the hydrophile/hydrophobe ratio of malonamide extractants and the stability of the organic phase: investigation at high extractant concentrations

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Article information


Submitted
31 Jan 2007
Accepted
20 Apr 2007
First published
18 May 2007

Phys. Chem. Chem. Phys., 2007,9, 3776-3785
Article type
Paper

Relation between the hydrophile/hydrophobe ratio of malonamide extractants and the stability of the organic phase: investigation at high extractant concentrations

P. Bauduin, F. Testard, L. Berthon and Th. Zemb, Phys. Chem. Chem. Phys., 2007, 9, 3776
DOI: 10.1039/B701479A

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