DEGRADATION OF AN AZO-DYE BY SODIUM-HYPOCHLORITE IN AQUEOUS SURFACTANT SOLUTIONS

The degradation behaviour of sodium ylphenylazo)-2-hydroxy-3,6-naphtha lenedisulphonate (o-TR) by sodium hypochlorite solution in the presenc e of three kinds of surfactants, viz. dodecytrimethylammonium bromide (DTAB), sodium dodecylsulphate (SDS), and sodium 2-(dodecylmethylamino )-ethane-1-sulphonate (SDAS) was investigated by means of visible abso rption spectrum measurements. The degradation rate of o-TR was markedl y dependent on the head groups of the surfactants. DTAB containing a q uaternary ammonium head group significantly enhanced the degradation r ate. SDS containing a sulphate head group enhanced the rate below the critical micelle concentration (CMC), whereas if did not change above CMC. SDAS containing a tertiary amino and suphonate group immediately degraded the dye existing outside of the micelle formed by SDAS, while the dye solubilized into the micelle remained without degradation. (C ) 1998 Elsevier Science Ltd.