Bleaching of indigo-dyed denim fabric by electrochemical formation of hypohalogenites in situ

The use of hypochlorite, formed in situ by anodic oxidation of sodium chloride solution, for bleaching indigo-dyed denim has been studied at room temperature and at 50 °C. A direct relationship between the charge flow applied and the bleaching effect was observed. This enables consistent oxidative bleaching to be achieved by controlling the electrochemical process. The use of mixed anolytes containing small concentrations of bromide ions enhanced the bleaching effect considerably, even after lowering the temperature to room temperature. The molar concentration of bromide ions required was much lower than that of chloride in the anolyte.