Closing the Loop: Greener and Efficient Hydrolytic Depolymerization for the Recycling of Polyesters Using Biobased Eutectic Solvents

The imperative for achieving circularity in the realm of postconsumer polymers predominantly hinges upon the adoption of efficient recycling methodologies with a greener footprint. As such, this study introduces an innovative and eco-friendly depolymerization process for recycling highly consumed poly(ethylene terephthalate) (PET) and innovative bioderived poly(ethylene 2,5-furandicarboxylate) (PEF) which is easily extrapolated to other polyesters. This study demonstrates the pivotal role of eutectic solvents based on biobased phenols with safe design to efficiently mediate the hydrolytic depolymerization, under alkaline conditions, of these recalcitrant polymers into terephthalic acid (TPA) or 2,5-furandicarboxylic acid (FDCA). Additionally, optimization through a design of experiments approach yields TPA and FDCA with over 90% and 80% recovery, respectively, under mild conditions of temperature, below 150 °C, and not exceeding 5 h of reaction time. Structural characterization analyses confirm the chemical nature and the high purity of the recovered products, while eutectic solvent reuse assessments underscore its potential for multiple cycles with minimal loss of catalytic activity, reducing process waste. A proof-of-concept for monomer repolymerization demonstrates feasibility. Green metrics align with the fine chemicals industry, indicating promising market potential for this low-energy eutectic solvent-based approach to enhance circularity in polyester waste management.