Selective Textile Recycling with Deep Eutectic Solvents: A Mechanistic Framework

Textile waste is no longer dominated by simple single-polymer materials. Most post-consumer textiles contain combinations of natural and synthetic fibres, elastane, dyes, coatings, finishes, and other additives, which makes selective recycling considerably more difficult. Deep eutectic solvents (DES) offer a promising route for addressing this complexity because their composition and physicochemical properties can be widely tuned. However, the outcome of DES treatment is often discussed mainly in terms of solvent composition or solvent-polymer affinity, although these factors alone cannot explain why similar DES formulations may lead to different responses in different polymeric or textile systems. In this review, DES-assisted textile recycling is examined from a mechanistic polymer-science perspective. The discussion focuses on how polymer morphology, transport accessibility, supramolecular organization, chemical reactivity, and processing conditions jointly determine whether a material undergoes swelling, molecular dissolution, structural destabilization, or chemical degradation. Particular attention is paid to the distinction between these processes, since changes in sample mass, fibre appearance, or crystallinity do not by themselves prove either true polymer dissolution or chain scission. Evidence from cellulose-based fibres, polyesters, polyamides, polyurethanes, elastane-containing materials, and multicomponent textile systems is used to show how different material outcomes may arise from apparently related DES-polymer interactions. The reviewed studies indicate that selectivity in DES-assisted textile recycling should not be treated as a fixed property of the solvent or of the polymer alone. It is more appropriately understood as the result of a coupled and time-dependent interaction between the DES medium, polymer morphology, textile architecture, and processing conditions. The mechanistic framework proposed here provides a basis for comparing reported DES-based recycling strategies, identifying the experimental evidence needed to support mechanistic claims, and guiding the rational selection of DES composition, process conditions, and recovery pathways for complex textile waste.