Sorption of perfluorooctane sulfonate and perfluorooctanoate on polyacrylonitrile fiber-derived activated carbon fibers: in comparison with activated carbon

Abstract

Polyacrylonitrile fiber (PANF)-derived activated carbon fibers (PACFs) were successfully prepared using a one step carbonation–activation, and were used for the sorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA). High specific surface areas (SSAs) of 1782 m² g⁻¹ and micro/mesoporous structures of the PACFs were obtained by optimizing the preparation conditions of the PANF-based pre-oxidized fibers (PANOFs)/KOH ratio of 1 : 2 and an activation temperature of 800 °C. The as-prepared PACFs exhibited flexibility and endless forms, and sorption capacities of 1.52 mmol g⁻¹ for PFOS and 0.73 mmol g⁻¹ for PFOA, much higher than the commercially available coal-based powder activated carbon (PAC) and granular activated carbon (GAC), which was also indicated by the site energy distributions. The sorption system followed a pseudo-second-order kinetic model and a Freundlich isotherm model. The intra-particle diffusion and Boy’s film-diffusion models were also used to verify that intra-particle diffusion is the main rate-controlling step. It was assumed that the multilayer sorption most probably occurs through electrostatic attraction and hydrophobic interaction, and some micelles and hemi-micelles form on the ACF surfaces. The PACFs show good reusability over five sorption–desorption cycle studies.