Sustainable cotton decolorization via reversible swelling of cellulosic fibers with N-methylmorpholine-N-oxide aqueous solutions

The exponential growth of the global economy has propelled textile fiber production, creating a pressing issue of non-degradable waste textiles that has outpaced recycling technologies. This research focuses on addressing the challenges of dye removal from cotton garments to enable their reintegration into the production cycle. A quantitative separation of direct dyes from fibers without compromising their integrity and quality was achieved using aqueous N-methylmorpholine-N-oxide, which is capable of reducing the density of the fibers so that dyes can be extracted without damaging either, with efficiencies over 95 %. Characterization of the fabric by size-exclusion chromatography before and after extraction ensures structural integrity as the degrees of polymerization of the cotton fibers are not significantly reduced. The separated dye is completely isolated from the N-methylmorpholine-N-oxide aqueous solution and recovered with efficiencies that depend on the dye structure.