Study of the Association Behavior Between Bromophenol Blue and Octylphenol Polyoxyethylene Ether (10) in Aqueous Solution and the Solubilization of Bromophenol Blue by Micelles

This paper reports a study of the association between the anionic dye bromophenol blue (BPB) and nonionic surfactant octylphenol polyoxyethylene ether (10) (OP–10) in aqueous solution. Addition of OP–10 causes marked changes in the characteristic absorption peaks of BPB, indicating that interactions exist between BPB and OP–10. We calculated thermodynamic parameters for the interaction by establishing a reasonable physical model of the association. Moreover, an in-depth study of variations in the absorption spectrum shows that the value of absorbance at the maximum absorption peak changes systematically with increasing OP–10 concentration. The critical micelle concentration values determined from measurements of electric conductivity are consistent with the variations in regions of the spectrum. In order to study the dispersion of dye in OP–10 aqueous solution, the water–micelle partition coefficient was determined while the value of Gibbs energy of partition was calculated from the value of the partition coefficient.