Abstract：
The widespread use of surgical masks made of polyolefin and face shields made of polyester during pandemics contributes significantly to plastic pollution. An eco-friendly approach to process plastic waste is using supercritical water, but the reaction of mixed polyolefin and polyester in this solvent is not well understood, which hinders practical applications. This study aimed to investigate the reaction of waste surgical masks (SM) and face shields (FS) mixed in supercritical water. Results showed that the optimal treatment conditions were 400 °C and 60 min, achieving a liquid oil yield of 823.03 mg·g-1 with 25 wt% FS. The interaction between polypropylene (PP), polyethylene terephthalate (PET), and iron (Fe) in SM and FS mainly determined the production of liquid oil products such as olefins and benzoic acid. The methyl-branched structure of PP enhanced PET hydrolysis, resulting in higher production of terephthalic acid (TPA). The degradation of PP was facilitated by the acidic environment created by TPA and benzoic acid in the reaction. Moreover, the hydrolysis of PET produced carboxylic acid, which coordinated with Fe3+ to form Fe-H that catalyzed the polymerization of small olefins, contributing to higher selectivity for C9 olefins. Therefore, this study provides valuable insights into the degradation mechanism of mixed PPE waste in supercritical water and guidance for industrial treatment.
摘要：
在大流行期间，由聚烯烃制成的外科口罩和由聚酯制成的面罩的广泛使用极大地导致了塑料污染。处理塑料废物的一种环保方法是使用超临界水，但是混合聚烯烃和聚酯在这种溶剂中的反应还没有很好的理解，这阻碍了实际应用。本研究旨在研究混合在超临界水中的废弃外科口罩（SM）和面罩（FS）的反应。结果表明，最佳处理条件为400℃和60min，以25wt％的FS获得823.03mg·g-1的液体油产率。聚丙烯（PP）之间的相互作用，聚对苯二甲酸乙二醇酯(PET),SM和FS中的铁（Fe）主要决定了烯烃和苯甲酸等液体油产品的生产。PP的甲基支化结构增强了PET的水解，导致更高的对苯二甲酸(TPA)产量。反应中TPA和苯甲酸产生的酸性环境促进了PP的降解。此外，PET水解产生的羧酸，与Fe3配位形成Fe-H，催化小烯烃的聚合，有助于提高C9烯烃的选择性。因此,该研究为超临界水中混合PPE废物的降解机理提供了有价值的见解，并为工业处理提供了指导。
