Effect of high-frequency ultrasonication on degradation of polytetrafluoroethylene (PTFE) microplastics/nanoplastics

Polytetrafluoroethylene (PTFE) particle might present a significant contamination in environment due to its dual classification as a microplastic and a fluorinated compound (a type of PFAS, or per- and polyfluoroalkyl substances), coupled with its extreme stability. Identifying an effective degradation method for PTFE microplastics is thus crucial towards remediation, along with the suitable monitoring approaches. This study is the first to use high-frequency (580 kHz) ultrasonication for the degradation of the PTFE microplastics with diameter of similar to 1000 nm. Dispersion of PTFE microplastics with help of surfactant (SDS, or sodium dodecyl sulfate) followed by ultrasonication for 9 h under optimal conditions resulted in a defluorination percentage of similar to 32 %. Particle size analysis demonstrated the effective diameter shrink of PTFE microplastics by ultrasonication (from similar to 1000 nm to similar to 330 nm that can be categorized as nanoplastics). SEM-EDS provided clear visualization of PTFE microplastics/nanoplastics, while Raman imaging confirmed the fine particles from molecular spectrum window. ImageJ analysis algorithms were utilized to estimate particle sizes as well. Based on these findings, a potential degradation mechanism for PTFE microplastics/nanoplastics was proposed. This study contributes to the understanding of PTFE degradation and may facilitate further research in this field.