CO₂-mediated catalytic pyrolysis of cigarette filters over Co/SiO₂

Improper disposal of cigarette butts (CBs) has posed a hazardous risk due to inevitable releases of toxic chemicals and microplastics into our ecosystem. As a precautious measure, this study carried out to develop an eco-friendly disposal platform for CBs. As such, cigarette filter (CF) and E-cigarette filter (ECF) were thermally degraded (pyrolyzed) using greenhouse gas (CO₂) as a co-feedstock. Before pyrolysis studies, a hazardous potential of CF and ECF was qualitatively and quantitatively assessed. From the pyrolysis tests, it was observed that toxic chemicals in CF and ECF were thermally degraded/transformed into the non-toxic pyrogenic products. The enhanced thermolyses of CF and ECF were further realized in the presence of CO₂. Catalytic pyrolyses over Co/SiO₂ were also done to further promote their thermal decomposition. The enhanced mechanistic functionality of CO₂ imparted by the catalytic capability of Co/SiO₂ directly led to additional syngas formation (up to 50 %). The beneficial features were originated from the homogeneous reactions of CO₂ and volatile toxic chemicals stemming from CF and ECF over Co catalyst. Thus, all findings in this work highlighted that the CO₂-supported catalytic pyrolysis could be a reliable/practical disposal platform for CBs.