AbstractReaction kinetics of Reactive Blue C.I. 19 (RB 19) dye and sodium hypochlorite (NaOCl) were investigated. Decline of RB 19 was monitored continuously by an ultraviolet (UV)-Vis spectrophotometer to avoid sampling errors. The purpose of this study is to develop a kinetic model for reactor and process design to establish hypochlorite oxidation as a viable alternative to advanced oxidation processes for textile effluent decolorization. Results were in agreement with 0.5-order reaction kinetics with respect to the RB 19 concentration. The lumped rate constant of the pseudo-0.5-order reaction is proportional to the NaOCl concentration. The Arrhenius activation energy obtained from the slope of the best-fit line is 76.6?kJ/mol, with a corresponding preexponential factor of 1.388?×?1010. The reaction rate is strongly affected by the pH of the solution. During the oxidation decomposition process, color was rapidly removed by the NaOCl but chemical oxygen demand (COD) resisted the treatment. A molar ratio of more than 44 is essential for OCl-to completely decompose the dye molecules thus removing COD from the solution. A system of liquid chromatography mass spectrometry (LC/MS) was used to determine the intermediates in the initial steps of the decomposition process.