Toward a Minimal Waste, One-Pot, Supercritical Carbon Dioxide-Based Route for Closed-Loop Recycling of Poly(ethylene terephthalate)

Abstract Plastic waste is an ever-growing problem in the modern world. Our reliance on plastic has led to the production of significant volumes, for which disposal is often challenging. This compounds many of the pollution and health concerns, such as release of plastic waste into rivers and oceans, and the associated issues surrounding microplastics. Closed loop recycling pathways do prolong the lifespan of plastic, but typically, large volumes of waste solvent are generated during such recycling processes. Here, supercritical carbon dioxide is exploited as a reaction medium for the depolymerization of poly(ethylene terephthalate) in a new process that uses a substantially less organic solvent than competing methods and does not generate large volumes of wastewater. Two post-depolymerization purification methods were developed, each delivering highly pure monomers that can be repolymerized to PET. The significant reduction in waste that this new method achieves is quantified and, compared with previous literature, through an adaptation of the E-factor.