In my diploma thesis, the effects of the structures of anionic dyes and cationic surfactant on the
formation of anionic dye-cationic surfactant complexes in binary and ternary mixtures was
studied by potentiometric and spectrophotometric methods at 25 °C. The anionic dyes C.I. Acid
Red 14 (AR14) and C.I. Acid Red 18 (AR18), the cationic surfactant
dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB),
and the nonionic surfactant Triton X-100 (TX100) were used in the study. The equilibrium
constants of formation of anionic dye-cationic surfactant complexes in the presence and absence
of TX100 non-ionic surfactant micelles as well as the equilibrium constants of formation of
cationic surfactant-micelle non-ionic surfactant complexes were calculated using an appropriate
theoretical model. The effect of the addition of a cationic surfactant, a non-ionic surfactant or
their mixture to the anionic dye solution was also spectrophotometrically evaluated. The results
showed that the formation of anionic dye-cationic surfactant complexes is influenced by the
structure of the dye, the hydrocarbon chain elongation of the cationic surfactant as well as by
the addition of non-ionic surfactant, concentrations higher than c.m.c. In a ternary system where
the anionic dye-cationic surfactant, cationic surfactant-non-ionic surfactant micelle and anionic
dye-non-ionic surfactant micelle interactions occur simultaneously, the equilibrium constant
for the formation of the anionic dye-cationic surfactant complex is lower than in binary
mixtures. It was found that the interactions between the cationic surfactant and the micelle of
the non-ionic surfactant as well as the interactions between the anionic dye and the micelle of
the non-ionic surfactant counterbalance the interactions between the anionic dye and the
cationic surfactant in ternary mixtures. The latter was demonstrated potentiometrically and
spectrophotometrically with the two methods used in the research.
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