Influence of surfactants on homogeneous and heterogeneous oxidation of azo dyes

A kinetic and spectroscopic investigation has been made of the oxidation of an azo dye (III), chemically bound to cotton by hypochlorite. It is shown that the physical state of bound dye; e.g., pK(A) tautomeric form, and its oxidation profile with pH are similar to those of dye in solution, suggesting that the mechanism in homogeneous and heterogeneous oxidation is similar. Oxidation rates of an azo dye (II) by hypochlorite were unaffected by the presence of anionic or nonionic surfactant either in micellar or submicellar regions, indicating that specific dye-surfactant interactions are absent. Specific interactions were observed with cationic surfactants in submicellar regions. In micellar regions the dye becomes incorporated into the surface of micelles and is rendered inert to reaction with hypochlorite.