Pyrolysis dynamics of two medical plastic wastes: Drivers, behaviors, evolved gases, reaction mechanisms, and pathways

The public has started to increasingly scrutinize the proper disposal and treatment of rapidly growing medical wastes, in particular, given the COVID-19 pandemic, raised awareness, and the advances in the health sector. This research aimed to characterize pyrolysis drivers, behaviors, products, reaction mechanisms, and pathways via TG-FTIR and Py-GC/MS analyses as a function of the two medical plastic wastes of syringes (SY) and medical bottles (MB), conversion degree, degradation stage, and the four heating rates (5,10, 20, and 40 degrees C/min). SY and MB pyrolysis ranged from 394.4 to 501 and from 417.9 to 517 degrees C, respectively. The average activation energy was 246.5 and 268.51 kJ/mol for the SY and MB devolatilization, respectively. MB appeared to exhibit a better pyrolysis performance with a higher degradation rate and less residues. The most suitable reaction mechanisms belonged to a geometrical contraction model (R-2) for the SY pyrolysis and to a nucleation growth model (A(1.2)) for the MB pyrolysis. The main evolved gases were C-4-C-24 alkenes and dienes for SY and C-6-C-41 alkanes and C-8 -C-41 alkenes for MB. The pyrolysis dynamics and reaction pathways of the medical plastic wastes have important implications for waste stream reduction, pollution control, and reactor optimization.

Automated summary

This study characterized the pyrolysis process of medical plastic wastes through TG-FTIR and Py-GC/MS analyses, finding that medical bottles showed better pyrolysis performance with lower residue content.