Decolorization properties and mechanism of reactive-dyed cotton fabrics with different structures utilized to prepare cotton pulp

Abstract It is critical to develop the mild decolorization technology to accomplish clean pulping in order to overcome the issues caused by the high consumption of energy and severe degradation of cellulose during the preparation of cotton pulp from waste cotton textiles. Discarded cotton fabrics was treated using a technique named as the sodium hydroxide-sodium dithionite system to remove color. During the procedure, the function of decolorization parameters, the effect of decolorization treatment on the structure and properties of cotton fabrics, and mild decolorization mechanism were investigated according to the different chromogenic systems and active groups of reactive dyes, especially. The findings demonstrate that NaOH can hydrolyzes covalent bonds between dye and cotton fiber and Na2S2O4 destroys chromophores to achieve decolorization. The chemical makeup and crystal structures of cotton cellulose are barely affected throughout the decolorization process. It is worth noting that the strength of the decolored cotton fabric can be retained by more than 90%, thus not affecting the subsequent pulping requirements.