The adsorption study of surfactant/dye mixed systems on natural fibres is important because these bioactive systems used in dyeing processes may reach surface waters and have a consistent impact upon health. The contamination of soil and surface water with the strongly active organic compounds (surfactants and dyes) was recognized as an important problem in the last years.

 By UV-VIS spectrophotometry and surface tension measurements the formation of colloidal associates between cationic surfactants and dyes used for dyeing of fibres was put in evidence. A clear difference between the adsorbent system in the case of monomer surfactant and the adsorbent system in the presence of the dye in solution was found by calculating the surface occupied by surfactant molecules on the cotton/water interface. The type of interaction and the organization mode of surfactant-dye complexes on the cotton/water interface were established by treating the original data using classical and recent equations of adsorption isotherms (Fowler-Guggenheim, Langmuir)