The separation of some contaminating materials like organic dyes with foam fraction method is important and it is depended to the intramolecular interactions for acceptable removal efficiency. In this work, the interaction between anionic surfactant, sodium dodecyl sulfate (SDS), with methyl violet, (MV) as a cationic dye was studied by UV–vis absorption spectroscopy, surface tension measurement, and foam analysis. An obvious change is occurred in the UV–vis absorption spectra and surface tensions of the mixed SDS/MV solutions by increasing the SDS concentration. Surface tension measurements show that MV solution is not a surface active agent and does not reduce surface tension. Surface tension measurements of the mixed SDS/MV indicate that the equilibrium surface tension remarkably depletes by increasing the concentration of MV with a constant concentration of SDS (1 mM). Based on the Job’s continuous change method, it was determined that the stoichiometric ratio is 1:1 in the MV/SDS formed ion pair. The foam analyses have been shown that the increase of MV concentration leads to a depletion in foam stability and capacity.
