Reaktiiviväreillä värjättyjen puuvillakankaiden värinpoisto alkalisen hydrolyysin ja pelkistävän käsittelyn avulla

Global textile waste generation is approaching 100 million tonnes annually, with most discarded textiles ending up in municipal waste rather than being recycled into new products. This leads to the loss of valuable raw materials and significant environmental impacts. Therefore, textile recycling is essential to reduce the industry’s environmental footprint, and effective colour removal from textile waste is a crucial step to enable both mechanical and chemical recycling processes. Cotton is the most widely used natural textile fibre, often dyed with reactive dyes that form covalent bonds with hydroxyl groups of cellulose. The strength and stability of these bonds make reactive dyes difficult to remove, thus conventional colour stripping methods often rely on harsh, hazardous, and high-energy process conditions that reduce the fabric strength significantly. Therefore, it is important to develop gentler and more sustainable colour stripping practices. The aim of this research was to investigate the stripping of reactive dyes from dark cotton fabrics using alkaline hydrolysis followed by reductive treatment. The objective was to improve colour stripping efficiency while minimising fibre damage, chemical use, and environmental impact. Stripping treatments were optimised through preliminary experiments, and their effects on fabric lightness and quality were evaluated. Two sequential methods, namely one-bath and two-bath treatments, were developed and compared. The results demonstrated that reactive dyes can be efficiently removed while maintaining fabric strength and overall quality. The one-bath stripping process outperformed the two-bath process, producing fabrics with high lightness (L* 74 to 84) and minimal fibre degradation. The results indicate that the efficiency of the reductive treatment is strongly dependent on the pH of the stripping liquor, as the process conditions were otherwise identical in both approaches. Moreover, the one-bath method not only minimised chemical consumption but also reduced freshwater demand by roughly half. Overall, this research showcases the potential of combined alkaline hydrolysis and reductive stripping treatments as an effective approach for removing reactive dyes from cotton fabrics, contributing to the sustainable development of textile recycling practices.