Upcycling of waste polyethylene terephthalate plastic bottles into porous carbon for CF₄ adsorption

Thermo-chemical processes for converting plastic wastes into useful materials are considered promising technologies to mitigate the environmental pollution caused by plastic wastes. In this study, polyethylene terephthalate (PET) plastic wastes were used to develop cost-effective and value-added porous carbons; the developed porous carbons were subsequently tested for capturing CF₄, a greenhouse gas with a high global-warming potential. The activation temperature was varied from 600 °C to 1000 °C and the mass ratio of KOH/carbon ranged from 1 to 3 in the preparation process and their effects on the textural properties and CF₄-capture performance of the PET plastic waste-derived porous carbons were investigated. The CF₄-adsorption uptake was dictated by the specific surface area and pore volume of narrow micropores less than 0.9 nm in diameter. PET-K(2)700, which was developed by KOH activation at 700 °C and KOH/carbon mass ratio of 2, showed the highest CF₄-adsorption uptake of 2.43 mmol g⁻¹ at 25 °C and 1 atm. Also, the CF₄-adsorption data were fitted well with the Langmuir isotherm model and pseudo second-order kinetic model. The PET plastic waste-derived porous carbons exhibited a high CF₄ uptake, good CF₄/N₂ selectivity at relatively low CF₄ pressures, easy regeneration, rapid adsorption/desorption kinetics, and excellent recyclability, which are promising for practical CF₄-capture applications. Waste polyethylene terephthalate (PET) bottles could be used as a carbon precursor to prepare novel microporous carbons for CF₄ capture.