DETERMINATION OF PHYSICO-CHEMICAL PARAMETERS OF SURFACTANTS IN THE PRESENCE OF UREA AT DIFFERENT TEMPERATURES

Surface physico-chemical and thermodynamic parameters of some aqueous surfactant solutions were studied using conductance, surface tension and dye spectroscopic techniques. From conductivity and absorbance measurements, critical micelle concentration(CMC),counter-ion association constant(α), surface excess concentration (?max), surface pressure at CMC (?cmc) and thermodynamic parameters of micellization (?Go mic, ?Ho mic, ?S o mic) were determined and compared with the literature values for anionic (sodium dodecyi sulphate), cationic (Hexadecyl trimethyl ammonium bromide) and non-ionic (tween 20) surfactant solutions. Effect of mixing co-solute (Urea) on physicochemical parameters of surfactant systems at 298K, 308K and 318K has been investigated. The addition of co-solute caused an increase in CMC as well as in degree of counter ion dissociation (β) of surfactant solutions whereas the thermodynamic analysis shows that, although the micellization is endothermic (for nonionic surfactant) and less favorable in mixed solvent compared to pure water, yet the process is spontaneous and mainly controlled by entropy gain.