Molecular investigation of pyrolysis and thermal gasification pathways in polyethylene microplastics degradation

Polyethylene (PE) microplastics are a persistent environmental threat due to their widespread presence and potential for long-range transport. This study uses reactive molecular dynamics (ReaxFF) simulations to explore the atomic-level thermal degradation mechanisms of PE microplastics through pyrolysis and thermal gasification (TG). A key finding of the research is the comparison of activation energies for pyrolysis and TG. Results show that pyrolysis begins with chain scission, producing volatile compounds, while TG generates hydrogen, carbon monoxide, water, and small hydrocarbons. Oxygen plays a key role in controlling gas fractions during TG. The activation energy for pyrolysis is 315 kJ/mol, higher than TG, which ranges from 197 to 262 kJ/mol depending on oxygen content, indicating TG is a more efficient degradation pathway. These findings offer molecular insights into PE microplastic degradation, aiding the development of targeted remediation strategies and advancing research on microplastic waste treatment. • Reactive molecular dynamics explored pyrolysis and thermal gasification of PE microplastics at the atomic level. • Early pyrolysis stages show chain scission and volatile formation, key for remediation strategies. • Oxygen levels in thermal gasification control gas fraction, offering pathway optimization potential. • Thermal gasification has lower activation energy than pyrolysis, enhancing its efficiency for PE degradation.