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

Abstract

Aggregation properties of sodium dodecyl sulfate (SDS) in the presence of cerium(III) chloride, at various temperatures (298.15-323.15 K) have been measured by the electrical conductance technique. The experimental data on aqueous solutions as a function of SDS concentration show the presence of two inflexion points indicating the presence of two distinct interaction mechanisms: the first, occurring at SDS concentrations below the critical micelle concentration of the pure surfactant, which can be explained by the formation of aggregates between dodecyl sulfate (DS − ) and Ce(III), while the second one, at SDS concentrations around the critical micelle concentration (cmc) of the pure surfactant which is due to the SDS micellization. The aggregation between DS − and Ce(III) was confirmed by static light scattering. The binding ratio of DS − /Ce(III) changes from 6 to 4, shows a slight dependence on the Ce(III) concentration and is independent of the temperature. The thermodynamic micellization parameters, Gibbs energy, enthalpy and entropy of micellization were calculated on the basis of the experimental data for the aggregation concentration, and the degree of counterion dissociation of the micelles. The SDS micellization is energetically favoured by increasing either the concentration of CeCl 3 or the temperature. Such behaviour is clearly dominated by a decrease of the micellization (exothermic) enthalpy. The entropy of micellization approaches zero as the cerium(III) chloride concentration and temperature increase.

New insights on the interaction between hydroxypropylmethyl cellulose and sodium dodecyl sulfate

“…1(a)), the SDS electrical conductance shows two different linear regimes as a function of surfactant concentration, corresponding to the behavior below and above the critical micelle concentration cmc). From these data, and by using the intersection of the data regression lines method (Ribeiro, Lobo, et al, 2004), the cmc and the degree of counterion dissociation (˛), have been calculated yielding 8.34 (±0.09) mM and 0.331 (±0.002), respectively, in close agreement with the values reported in literature (Goddard & Benson, 1957;Valente et al, 2008).…”

On the flocculation and re-dissolution of trivalent lanthanide metal ions by sodium dodecyl sulfate in aqueous solutions

“…These concentrations are fairly similar to those obtained by electrical conductivity measurements for the same systems (10 (±0.1) and 10.5 (±0.1) mM, respectively [29]), and are justified by the initial formation of mixed lanthanide/sodium dodecyl sulfate aggregates, followed by that of SDS micelles. However, these values are greater than the critical micelle concentration of pure SDS in aqueous solution (8.38 mM) [32]. Although this may imply that such a process is thermodynamically unfavorable, more detailed examination of the data suggests an alternative explanation.…”

“…The addition of SDS to an aqueous lanthanide solution (La 3+ and Gd 3+ , generically referred as M 3+ ) initially leads to phase separation, followed by re-dissolution of the precipitate upon increasing the SDS concentration [32]. The characterization of these mixed M 3+ /SDS systems has been carried out by measuring the solution metal ion concentration in the flocculation and re-dissolution regions using a variety of techniques, such as: inductively coupled plasma-atomic emission spectroscopy (ICP-AES), 139 La NMR, Gd 3+ luminescence, in addition to X-ray diffraction of the precipitated phase.…”

Interactions between cationic surfactants and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin tetrasodium salt as seen by electric conductometry and spectroscopic techniques

“…psc values have been calculated by using the intersection of two straight line equations [29]; on the other hand, the apparent critical micelle concentration, cmc*, and the respective degree of dissociation of counter ions () in the micelle have been calculated by fitting the raw data of specific conductance as a function of surfactant concentration to a nonlinear function obtained by direct integration of a Boltzman-type sigmoidal function [30]. The critical micelle concentration of C n TAB in the presence of porphyrin were calculated as cmc=cmc*−psc [31].…”