Study on the interaction of anionic dye-nonionic surfactants in a mixture of anionic and nonionic surfactants by absorption spectroscopy

The interaction between an anionic dye C.I. Reactive Orange 16 (RO16) and different surfactants, i.e., the anionic surfactant sodium dodecylsulfate (SDS) and nonionic surfactants polyoxyethylene ethers (CmPOEn; m = 12, 16 and 18, n = 4, 10 and 23) has been researched spectrophotometrically in a certain micellar concentration range. Light absorbances in the visible spectral range are measured as a function of mole fraction of surfactant at four different temperatures and at 24 h over the periodic time intervals. For this reason, a typical system occurred at 1.0 × 10−2 mol/l for surfactants and at 1.0 × 10−4 mol/l for dye concentrations. It is evident from the experimental measurements that while nonionic surfactants form a complex with the anionic dye RO16 in aqueous solution in studied concentration range, anionic surfactant does not. The formation of CmPOEn-RO16 complex in the SDS solutions of different mole fractions in its micellar concentration range has been determined and compared to those obtained in the dye-surfactant binary mixtures. Spectrophotometric measurements indicated that the value of absorbance of SDS-RO16 is greater than that of nonionic surfactant-RO16 in the binary systems. This state explains that the ionic and hydrophobic interactions between SDS-RO16 are less than that of nonionic surfactant-RO16 interactions. The addition of SDS to the mixture of CmPOEn-RO16 causes an increase in the value of absorbance. This increase is due to changed hydrophobic-hydrophilic balance of the studied mixtures. Furthermore, we observed that the alkyl chain length and the number of polyoxyethylene in nonionic surfactants do not have an enormous effect on the values of absorbance.