Interfacial and Micellar Properties
of Anionic Azo DyeSurfactant Binary Systems¹

Halide Akbas and Melike Aydemir

Department of Chemistry, Faculty of Sciences and Letters, Trakya University, 22030 Turkey

Received July 2, 2007

Abstract—The association of an anionic dye C.I. Reactive Orange 16 (RO16) and different types of surfac-
tants, i.e., anionic surfactant sodium dodecylsulfate, nonionic surfactants poly(oxyethylene) ethers (C_mPOE₁₀,
m = 12, 16, and 18; C₁₂POE_n, n = 4, 10, and 23), was investigated using tensiometry in a certain micellar con-
centration range. RO16 was shown to aggregate in water when its concentration is above the threshold value.
The surface tension lowering and critical micellar concentration (CMC) values were interpreted on the same
grounds as those for surfactants mixtures. The tensiometric measurements of dye–surfactant systems are carried
out as a function of the molar concentration of solution at 25°C. Using Rubingh’s regular solution theory, the
values of interaction parameters were found to be negative for all studied binary mixtures. These negative values
indicate that there is an attractive interaction of the surfactants in mixed micelles and reflect synergistic behavior
of a mixture. In all studied systems, deviations from ideal behavior were observed depending on the type of
surfactant. Interaction parameters calculated using regular solution theory are changed from –2.62 to –12.43.
The smallest deviation from ideal behavior is obtained for the RO16C₁₂POE₄ mixed system; i.e., in the case
when nonionic surfactant has the shortest alkyl chain and the smallest number of ethylene oxide units.

DOI: 10.1134/S1061933X08050025

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