Effective Dye Removal from Post-Consumer Cotton Textiles and Its Influence on the Quality of the Textiles

A major obstacle to textile recycling is the presence of dyes, which limits the reuse of fibers in high-value applications. Despite previous studies on, cotton decolorization, the systematic development of an optimal formulation that preserves fabric integrity remains lacking. This study addresses this gap by investigating a decolorization method for mixed-dyed cotton textiles that enables successful redyeing while preserving fabric quality. Reactive and vat-dyed cotton fabrics were treated with sequential reductive and oxidative processes, in a full factorial design. The impact of input parameters on tensile strength was evaluated through statistical analysis using analysis of variance at a significance level of α = 0.05. The developed recipe was subsequently validated on post-consumer cotton textiles. Stripping efficiency was assessed using K/S values, and fabric quality was evaluated through tensile strength, pilling, and fuzzing appearance. Temperature showed the strongest influence on dye removal. Fabric strength was significantly affected by temperature and oxidizing agent, and by interactions of temperature with reducing agent and oxidation time. The optimized process achieved 98–99.5% color removal and retained 95% of the fabric’s tenacity. A stripping efficiency of >90% for post-consumer cotton validates the method’s applicability in real-world circular systems.