Solving two environmental issues simultaneously: Waste polyethylene terephthalate plastic bottle-derived microporous carbons for capturing CO₂

The treatment of plastic waste is a global issue, and the demand for technologies to reuse or upgrade plastic waste is increasing. In this study, waste polyethylene terephthalate (PET) plastic bottles were used to prepare cost-effective porous carbons, and the prepared carbon materials were tested for capturing CO₂. PET plastic bottles were carbonized and activated using KOH or NaOH to develop porous carbons, and their CO₂ adsorption behaviors were investigated from both equilibrium and kinetic perspectives. Varying the activation temperature had a significant effect on the textural properties of the prepared carbons. PET-KOH-973, which was prepared by activation with KOH at 973 K, exhibited the highest CO₂ uptake of 4.42 mol kg⁻¹ at 298 K and 101.3 kPa among the tested samples. The experimental adsorption data were well fitted to the Langmuir isotherm and pseudo second-order kinetic models, and the CO₂ adsorption on the PET-derived porous carbons was mainly related to the pore volumes of the narrow pores under 0.8 nm in diameter. Grand canonical Monte Carlo simulation and density functional theory calculation were also performed to understand adsorption mechanism and selectivity, and the theoretical calculation agreed well with experimental data. The PET-derived porous carbons exhibited not only high CO₂ uptake, but also good selectivity of CO₂ over N₂ and CO, simple regeneration, excellent cyclic stability, and fast CO₂ adsorption and desorption kinetics.