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R. F. Bakeeva, R. A. Karimullin, R. F. Kurabasheva, T. S. Gorbunova, O. E. Vakhitova, V. F. Sopin

Author affiliations
Department of Analytical Chemistry, Kazan National Research Technological University,
68 K. Marx St., Kazan, 420015, Russia
E-mail: bakeeva@kstu.ru

Abstract
The process of micelle formation in a mixture of nonionic surfactant (cetyl ether of polyoxyethylene (10), Brij56) and anionic surfactant (sodium dodecyl sulfate, SDS) in the presence of NaCl electrolyte in dimethyl sulfoxide – water binary solvent by the tensiometric method was studied. The influence of content of dimethyl sulfoxide, NaCl, Brij 56 and SDS was studied. A multifactorial experiment was performed to optimize the selecting process of a system based on the mixture of surfactants in the binary solvent with the lowest values of the critical micelle concentration (CMC). For this, the methodology for determining the response surfaces and the three-level Box – Behnken plans were applied. Using the "Statistica 10" software package, the most significant factors were identified, the interaction effects between them were evaluated, the response surfaces were constructed and the optimal conditions for obtaining mixed systems with minimal CMC values were determined. The minimum value of CMC in the SDS + Brij 56 + NaCl + DMSO + H₂O system was achieved under the following composition: α_Brij56 = 0,680; C_NaCl = 0,140 mol/l; ω_DMSO = 0,024 (2,4 %). The minimum CMC of this mixture equals to 3,137·10^–5 mol/l. The experimental data are consistent with the calculated values of CMC (3,05 ± 0.091)·10^–5 mol/l.

Keywords: micelles, surface tension, tensiometry, ionic and nonionic surfactants, dimethyl sulfoxide, sodium dodecyl sulfate, Brij 56, Box – Behnken plans