Sustainable Cotton Dyeing Using Vat Dye Derived from Eucalyptus Bark Waste

Waste valorization is a crucial step toward sustainability. The present study aims to valorize the eucalyptus waste generated during wood processing as a natural source of vat dye for cotton. Sodium sulfite was used as a reducing agent to reduce the coloring component present in eucalyptus bark under alkaline conditions, using sodium hydroxide. The prepared dye was characterized by using Fourier transform infrared spectroscopy, phytochemical analysis, and high-resolution liquid chromatography mass spectroscopy (HR-LCMS). The HR-LCMS results indicated the decarboxylation of flavonoids and the autocondensation of tannins under alkaline conditions. The brown color of the dye achieved was due to the presence of 3,8-dihydroxy-1-methyl anthraquinone-2-carboxylic acid. The fabrics were dyed using the pad-dry technique at pH 13, which exhibited excellent washing, rubbing, and light fastness, suggesting a good alum-dye complex and no photodegradation. Overall, this novel approach demonstrates a promising application of eucalyptus waste and addresses sustainability in the textile sector by providing economical, environmentally friendly alternatives to toxic synthetic dyes.