Chemical recycling of polyester-based textile waste via solvolysis aided by an ionic liquid and supercritical CO₂

The increasing accumulation of synthetic textile waste, especially poly(ethylene terephthalate) (PET)-based fibers, poses a critical environmental challenge. Conventional recycling techniques are often inefficient. Solvolysis with supercritical CO₂ (scCO₂) emerges as a green and efficient alternative, enabling the depolymerization of polyester chains under mild conditions and facilitating the recovery of platform chemicals with minimal solvent waste. In addition, ionic liquids have been proven to reduce the energy requirements of the solvolysis. This approach aligns with circular economy principles and offers a route toward high-purity monomer production for polymer regeneration. The solvolytic depolymerization of PET-based textile waste was carried out in a high-pressure batch reactor using scCO₂ as co-solvent under fixed conditions of 15 minutes of reaction time and CO₂ pressure up to 120 bar. Experimental variables included temperature (183–217 °C), textile-to-ionic liquid ratio ([Tex]:[IL] = 1.7–6.0), and textile-to-solvent ratio ([Tex]:[Sol] = 14.1–33.0). A specific ionic liquid was used as catalytic co-solvent. The influence of these parameters on depolymerization efficiency and product selectivity was assessed. Under optimal conditions, a conversion rate of up to 99% was achieved. Temperature proved to be the most influential parameter, significantly affecting the extent of depolymerization in both solvolysis methodologies. In contrast, the textile-to-ionic liquid ratio showed a moderate effect, and the textile-to-solvent ratio exhibited negligible influence on the conversion, indicating that the process could be optimized with reduced solvent consumption. The low sensitivity of the process to solvent and ionic liquid ratios, combined with the strong influence of temperature, supports the feasibility of a cost-efficient, greener recycling method adaptable to industrial applications.