Selective separation strategies of elastane for recycling of textile blends

The environmental burden of the textile and clothing industry, in terms of resource consumption, chemical usage and waste generation, highlights the priority to enhance fibre recycling rates. An obstacle for the implementation of efficient recycling processes within the sector is the widespread use of fibre blends, which are often adopted to improve textile properties. Elastane is one of the most commonly found fibres in textile blends, used to increase elasticity and comfort of products. The presence of mixed fibres affects recycling process making necessary a preliminary separation step. The aim of this thesis is to investigate two alternative methods for fibre separation in elastane-containing blends, ensuring the recyclability of recovered fractions. The first approach focused on elastane dissolution and recovery from polyamide/elastane and cotton/elastane blends using green solvents. An optimised solvent mixture, consisting of 20% (v/v) dimethyl sulfoxide and 80% (v/v) 2-methyltetrahydrofuran at room temperature, enabled effective recovery for polyamide fractions, whereas further research is required for cotton-elastane blends. The second approach employed enzymatic hydrolysis on cotton-elastane textile blends with the main goal of depolymerising cellulose chains, thereby recovering intact elastane fibres and a cellulose-derived pulp potentially suitable for textile-to-textile recycling. Hydrolysis was carried out with both endo- and exocellulases, testing different conditions, enzymatic concentrations, and reaction times. Results showed efficient separation of the two fractions with a concentration of 25 mL/L for exocellulases and of 5 mL/L for endocellulases, after optimisation, for 1 hour at 50°C, highlighting the necessity of an alkaline pre-treatment. This research explored the feasibility of two sustainable fibre separation strategies on different elastane textile blends, providing insights into the development of recycling processes for mixed fibre textiles, addressing one of the main barriers to a circular economy in the textile sector.