(2017) Journal of Cleaner Production_Utilizing CO₂ to suppress the generation of harmful chemicals from thermal degradation of polyvinyl chloride

Lee T., Lee J., Ok Y.S., Oh J.-I., Lee S.-R., Rinklebe J., Kwon E.E.

(Elsevier Ltd) Journal of Cleaner Production ISSN: 9596526 Vol.162 Issue. Article No. DOI: 10.1016/j.jclepro.2017.06.181

This study put a great emphasis on the role of carbon dioxide (CO₂) in thermal decomposition of polyvinyl chloride (PVC). To do this, systematic experimental works were carried out to explore the influence of CO2 on pyrolysis of PVC by comparing with that in N₂. First of all, a series of thermo-gravimetric analysis (TGA) of PVC in N₂ and CO₂ was performed to characterize the thermal deconstruction of PVC in N₂ and CO₂, which confirmed that any physical aspect (i.e., onset and end temperature of depolymerization of PVC) attributed by CO₂ was nearly negligible as compared to the case in N₂. This phenomenon was also fully evidenced by differential thermogram (DTG) and differential scanning calorimeter (DSC) because both DTG and DSC curves in N₂ and CO₂ were identical. However, the concentration profiles of CO evolved from the thermal degradation of PVC in N₂ and CO₂ was significantly different: the enhanced generation of CO occurred in the presence of CO₂. This observation suggested that the genuine role of CO₂ is to consume carbon source (i.e., acting as a carbon scavenger) for pyrolysis of PVC. It also provided a favorable condition for suppressing the formation of harmful chemical compounds such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). Therefore, the mass portion of the oil in pyrolytic products produced from pyrolysis of PVC in CO₂ was lower than that in N₂. These particular thermal degradation behaviors may be explained by the genuine role of CO₂: the enhanced thermal cracking of volatile organic carbons (VOCs) evolved from the pyrolysis of PVC. The findings of this study strongly suggest that CO₂ can be effectively applied to thermal disposal of recalcitrant wastes since employing CO₂ in thermal treatment provides a means for in-situ mitigation and/or reduction of harmful chemical species. © 2017 Elsevier Ltd

This work was supported by a grant from National Research Foundation of Korea (NRF-2017R1D1A1B03028176).