A Sustainable Approach to Dyed Cotton Fabric Stripping Using Ozone

Sodium hydrosulfite is conventionally used for the color stripping of reactive dyes in the textile industry. However, research has been focused on eco-friendly processes to reduce wastewater generation in recent years. This study is aimed at estimating the color stripping efficacy of ozone according to reactive dyes’ chromophore groups. The dyed cotton-knitted fabric with three reactive dyes that have phthalocyanine (Reactive blue 21), diazo (Reactive black 5) and monoazo (Reactive yellow 84) chromophores was treated with ozone. The effect of the experimental parameters (pH, ozone dose and treatment time) was examined on the dyed fabric samples in terms of lightness and bursting strength properties. The results show that the decolorization efficiency of ozone varies with the type of chromophore group. The maximum color removal was achieved for the Reactive blue 21 dye of the phthalocyanine group at optimum process conditions (pH 3, Ozone dose 7 g/h, exposure time 40 min) followed by the reactive dyes that have dioazo and monoazo chromophore groups, respectively. The bursting strength of the fabric sample decolorized using ozone remained stable throughout the study. Moreover, the ozone-stripping effluent meets the environmental quality standards and can be reused up to at least four cycles without affecting the stripping efficiency. Hence, it can provide a sustainable alternative to reduce water consumption in the textile sector.