Efficient color management in closed-loop recycling of cotton fabrics by using fiber modification and salt-free dyeing strategy

Abstract

Color management and efficient decolorization of waste textiles have become a central focus, driving the need for transformative approaches in cotton textile recycling. There is an urgent need to develop a waste cotton textile closed-loop recycling strategy that is integrated with a new dyeing method to achieve efficient color management. By the method of fiber modification, salt-free dyeing and effective decolorization were simultaneously achieved in this study. The results show that the salt-free dyed cotton fabrics exhibited a significantly improved decolorization rate compared with the conventionally dyed fabrics, with a decolorization rate higher than 95% when using non-reactive dyes and a salt-alkali method, while maintaining mechanical properties comparable to the control cotton fabric. It was revealed that covalent bonding plays a critical role in decolorization efficiency, whereas the decolorization of salt-free dyed fabrics primarily resulted from the disruption of ionic bonds between the dyes and cationized fibers. The recycling feasibility of salt-free dyed cotton fabrics was also confirmed by evaluating the re-dyeing performance of decolorized fabrics by dyes with different colors, and the performance of multiple dyeing-decolorization cycles showed good stability, laid a solid foundation for the closed-loop recycling of cotton fabrics. Notably, compared with the conventional dyeing method, this work not only improves the recycling efficiency of waste cotton fabrics, but also reduces 28.4% in chemical consumption, 67.1% in dyeing costs, and 83.3% in waste disposal per cumulative ton of fabric production, providing an economical and promising new strategy for the industrial application of textile recycling and color management methods for waste textiles.