Assessing pyrolysis performance and product evolution of various medical wastes based on model-free and TG-FTIR-MS methods

The COVID-19 pandemic has caused a substantial rise in the amount of medical waste, posing additional hurdles in waste management. Disposing of this waste properly is essential to curb transmission of the diseases. The pyrolysis reaction kinetics, synergistic interactions, and pyrolysis gas release behavior of typical constituents of medical waste (MW): syringe (SY), medical gloves (MG), cotton swab sticks (CS), and their blends were examined by utilizing advanced analytical techniques including TG, TG-FTIR, TG-MS, and kinetic models (Friedman, KAS). The experiments were conducted using a wide range of heating rates, namely 10, 20, 30, and 40 °C⋅min−1. The pyrolysis reactions were mainly endothermic, with main stages ranging from 352.0–480.0 °C, from 381.0–511.0 °C, from 200.0–404.5 °C, 336.6–509.9 °C, 375.4–477.6 °C, 384.0–500.9 °C, for SY, MG, CS, SY5MG5, SY7CS3, and MG7CS3, respectively. According to the KAS method, the average activation energies for the mono-pyrolysis of SY, MG, and CS were determined as 240.8, 226.1, and 147.5 kJ⋅mol−1 respectively. Interestingly, during the pyrolysis of blends such as SY5MG5, SY7CS3, and MG7CS3, the activation energies decreased to 177.2, 159.9, and 149.1 kJ⋅mol−1 respectively. Notably, the experimental activation energy values (Eexp) obtained during the co-pyrolysis were significantly lower than the calculated values (Ecal), revealing an apparent synergistic effect during the pyrolysis of various MW blends. The pyrolysis process of MW blends resulted in the release of significant volatile components, including CH4, CO, C3H6, CO2, C2H5OH, C4H8, C5H8, C6H6, C6H14, C7H8, and C8H10. The specific composition of these volatile components varied depending on the types of waste present in the blends.