Study on the Decontamination of Contaminants in Polyethylene Terephthalate by Supercritical Carbon Dioxide: From the Perspective of Molecular Descriptors

The escalating issue of global plastic pollution necessitates the development of efficient and sustainable recycling technologies, particularly for producing safe, food-contact-grade recycled plastics. Within a circular economy framework, polyethylene terephthalate (PET) holds significant promise due to its excellent recyclability. However, contaminants introduced throughout its lifecycle pose a major challenge, and conventional decontamination methods often involve high energy consumption, thermal degradation risks, or chemical residues. Supercritical carbon dioxide (scCO 2 ) emerges as a promising green alternative, yet a systematic understanding of its efficacy, especially from a molecular structure perspective, is lacking. This study therefore aims to comprehensively evaluate the decontamination performance of scCO 2 on PET contaminated with 44 representative contaminants and, crucially, to elucidate the intrinsic relationship between decontamination efficiency and molecular descriptors of the contaminants. The results demonstrated that scCO 2 achieved high removal efficiency (>95%) for most contaminants within a short treatment time (<30 min). Correlation analyses of decontamination efficiency with the 126 molecular descriptors as well as the five-solute ESABV descriptor system both revealed that contaminants with high sp 3 -hybridized carbon content, flexible aliphatic chains, and uniform electrostatic distributions were readily removed, whereas those with aromatic rings, strong hydrogen-bonding propensity, and rigid conformations exhibited lower efficiency. The introduction of ethanol as a cosolvent enhanced the removal of recalcitrant contaminants. Furthermore, scCO 2 outperformed conventional vacuum decontamination for over 90% of the substances. This work establishes a critical structure-efficiency relationship, providing a theoretical foundation for optimizing scCO 2 -based processes to achieve food-grade recycled PET and advance sustainable plastic recycling.