Hydrothermal transformation behavior and degradation pathway analysis of waste surgical masks in supercritical water

The massive use of surgical masks around the world has exacerbated plastic pollution. Efficient treatment of these surgical masks is urgently needed. Supercritical water degradation has been considered as a promising method for treating surgical masks. In this study, analysis of the products revealed that the production rate of H2 and olefins from surgical masks with nose clips treated by supercritical water were significantly higher than that without nose clips. Therefore, it was concluded that Fe in the nose clip could catalyze the dehydrogenation of alkanes and inhibit the aromatization of cycloalkanes and alkenes compounds in the supercritical water treatment process of waste surgical masks. However, the ethylene vinyl acetate (EVA) hot melt adhesive in the surgical masks degraded at a low temperature, producing ketone compounds that negatively impacted the quality of liquid oil. This study could provide a basic understanding and effective guidance for surgical masks degradation in supercritical water.