Reuse of water from real reactive monochromic and trichromic wastewater for new cotton dyes after efficient treatment using H₂O₂ catalyzed by UV light

The textile industry widely uses reactive dyes to obtain cotton fabrics having good resistance to color removal despite frequent washing. This level of dye usage generates substantial volumes of wastewater containing significant quantities of residual dye requiring treatment before discharges from commercial dyeing operations to public waterways. As part of a study aimed at recycling/reusing rather than discharging reactive dye wastewater, well-known dyes Reactive Yellow 176, Reactive Red 241, and Reactive Blue 221 were used in dyeing cotton fabric, and the generated wastewater samples were decolorized with H2O2 catalyzed by UV light. The efficiency of UV/H2O2 decolorization for trichromic wastewater was determined by UV-Vis monitoring at 550 nm, wherein it was found that more than 91% of color removal in trichromic wastewater occurred at pH 4. The reuse of wastewater was investigated by a total of three sequential cycles of wastewater treatments. The quality of cotton dyed with reused wastewater was assessed through color measurements using CIELAB, fastness to light, and wash fastness testing. Results showed that MCT/VS-based reactive dye wastewater arising from UV/ H2O2 treatment could be used for two subsequent dyeing cycles without compromising the quality of the color of the dyed cotton fabrics. The proposed treatment can also save water and salt, enhancing the economy of the dyeing process.