Effect of terbium(III) chloride on the micellization properties of sodium decyl- and dodecyl-sulfate solutions

Abstract

The effect of TbCl 3 on the aggregation processes of the anionic surfactants sodium decyl sulfate (SDeS) and sodium dodecyl sulfate (SDS) has been investigated. Electrical conductivity data, combined with Tb(III) luminescence measurements suggest that the formation of micelles involving TbCl 3 and SDS occurs at concentrations below the critical micelle concentration (cmc) of the pure surfactants; the formation of these mixed aggregates was also monitored by light scattering, which indicates that the addition of TbCl 3 to surfactant concentration at values below the pure surfactant cmc results in a much greater light scattering than that found with pure sodium alkylsulfate surfactant micelles. This phenomenon is dependent upon the alkyl chain length of the surfactant. With Tb(III)/DS − , complexes are formed with a cation/anion binding ratio varying from 3 to 6, which depends upon the initial concentration of Tb(III). This suggests that the majority of the cation hydration water molecules can be exchanged by the anionic surfactant. When the carbon chain length decreases, interactions between surfactant and Tb(III) also decrease, alterations in conductivity and fluorescence data are not so significant and, consequently, no binding ratio can be detected even if existing. The surfactant micellization is dependent on the presence of electrolyte in solution with apparent cmc being lower than the corresponding cmc value of pure SDS.

Aggregation and micellization of sodium dodecyl sulfate in the presence of Ce(III) at different temperatures: A conductometric study

“…These values (0.49-0.59 mM, at 298.15 K) occur in the same concentration interval of those found to other lanthanide trivalent cations [18,19,26]. With the exception of lowest Ce(III) concentration systems, it is possible to observe that cac 1 decreases as cerium(III) concentration increases and as temperature decreases.…”

“…Comparing these results with those found for the Eu(III) and Tb(III)/SDS systems [18,19], it is possible to observe that in the present case the stoichiometry of aggregate formation (a) only changes slightly with Ce(III) concentration (between 6 and 4, compared with 4 < β(Eu/SDS) < 20 and 3 < β(Tb/SDS) < 6), and (b) does not change with temperature. Two different aspects of the nature of the three lanthanide ions may be considered to explain these differences: Ce(III) has a lower charge density than the other trivalent lanthanide ions [27], and, secondly, hydrolysis is less significant with CeCl 3 aqueous solutions than with the other trivalent lanthanides [28].…”

“…Further, the fluorescent properties of these trivalent cations can be significantly changed in the presence of both cationic and anionic surfactants [16,17]. Recently [18,19] we have shown that the fluorescence intensity of a number of trivalent rare-earth ions (in particular, europium and terbium) is enhanced in the presence of sub-micellar concentrations of anionic surfactants. This can be justified by an exchange of hydrated water molecules of the cations by the surfactant.…”

The interaction of long chain sodium carboxylates and sodium dodecylsulfate with lead(II) ions in aqueous solutions

“…2). It should be noted that such behavior has also been observed for solutions of trivalent metal ions with sodium dodecylsulfate [55,56]. As with the other carboxylates, at higher molar ratios, the electrical conductance of octanoate-lead(II) solutions increases upon increasing sodium octanoate concentration, since above the mic, sodium octanoate is in excess and the neutral lead(II) complexes do not contribute significantly to the overall ionic conductivity.…”

Molecular Thermodynamics of Micellization: Micelle Size Distributions and Geometry Transitions

“…In general, we are in good qualitative agreement with the trends observed by experiments. (Khan and Shah, 2008;Neves et al, 2007;Evans, 1956;Zhao et al, 2012, Velázquez andLopezDías, 2007). (a) Sodium nc-alkyl sulfate, (b) nc-alkyl pyridinium bromide, (c) nc-alkyl trimethylammonium bromide, (d) nc-alkyl(dimethyl)phosphine.…”