Eco-friendly bleaching of indigo dyed garment by advanced oxidation processes

Bleaching technology by ozone dissolved in water offers alternative measures to prevent pollution in the textile industry for sustainable development at organizational and economic levels. In this paper, jeans fabric was treated with ozone injected in water combined with ultrasound and H₂O₂. Effectiveness of Fenton process regarding dye degradation was also tested with confirmation of hydroxyl radicals detected by fluorescence and electron paramagnetic resonance (EPR) spectroscopy. Results showed that individual ozone was more effective regarding the bleaching of the jeans samples than the hydroxyl radicals especially when coupled with ultrasound. The mechanical action of ultrasonic cavitations enhanced the diffusion of ozone through the fabric which increased the degradation of the indigo dye. The fading degree of samples treated with ultrasound and 100 g/Nm³ of ozone for 60 min in acidic condition reached 64.49 which gave a full bleach appearance. Scanning electron microscopy (SEM), ultimate tensile strength and fastness tests were performed in order to evaluate the effect of such treatment on the cotton fabric. The said tests proved that moderated concentrations of ozone caused no damage to the cotton fiber and results were very close to those obtained with ordinary bleaching processes.