Abstract: Research on surfactant-dye interaction has important theoretical and practical values. The interaction between a quaternary ammonium Gemini-type surfactant (EB-CDAC) and C. I. Direct Blue 199 with copper phthalocyanine structure was investigated by conductivity testing, ultraviolet spectrophotometry and surface tension measurement. The results indicated that the combination of the dye and the surfactant induced dye λmax red-shifted. The absorbance of the mixed solution decreased when the concentration of EB-CDAC was lower than its CMC and increased when the concentration was higher than its CMC. The dye-surfactant complex formed by electrostatic forces occupied the air-water interface at first. With the increase of the concentration of EB-CDAC, the complexes on the air-water interface were replaced by EB-CDAC molecules gradually.

Key words: Gemini cationic surfactant, C.I.Direct Blue 199, interaction, absorption spectrum, surface tension