Dyeing of Cotton Fabric With Reactive Dyes Using Ozonated, Spent Dyebath Water

A dyebath reuse study using reactive dyes was completed. Dyeingswere done with blue, red and yellow dyes and a dye mixure containing equal amounts ofeach of the three dyes. The spent dyebath water from these four dyeings was mixed,filtered and ozonated. The four shades were dyed again in baths containing 90 % ozonated water and 10 % fresh tap water. Only 10 % of the amount of salt used in the originaldyeings in recycled water was required for the dyeings since the salt in the 90%. recycled water was still present. The experiment was repeated through five reuse cycles.Color reproducibility of dyeings done in the recycled water was excellent, closely matching the color attained using fresh tap water as the dyeing medium. The PH of the spentdyebath water decreased uPOn ozonation. Although the PH decrease was about the samein each new cyCle, the amounts of caustic soda needed to adjust back to the original dyebath PH value increased with each cycle. This shows that ozonation of spent dyebathwater produces substances which tend to buffer the solution.Keywrods: Dyebath Reuse; Effluent; Ozonation; Spectrophotometer; Wastewater