In this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV-Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl-trimethyl-ammonium bromide (CTAB) as cationic, tert-octylphenol ethoxylates (N=9.5, 7.5 and 40) and alcohol ethoxylate as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in the membrane technology.

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