Modification of hydrous ferric oxide by chitosan to enhance its adsorption performance toward perfluorooctane sulfonate

The aquatic environment is the main sink for perfluorooctane sulfonate (PFOS) accumulation, which is a typical persistent organic pollutant with high toxicity. In this study, a novel modification method was developed to prepare chitosan-modified hydrous ferric oxide (HFO), and then the adsorbent was used to remove PFOS from aqueous solution. The results found that the suitable added amount of chitosan for HFO modification was 8%. The influence of chitosan modification on HFO was characterized using scanning electron microscopy, Brunauer-Emmett-Teller, zeta potential, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. Chitosan modification could introduce functional groups on HFO, change its surface charge, and reduce its surface area. The pseudo-second-order kinetic model and Freundlich model could best describe the adsorption process of PFOS on 8%C-mHFO. The maximum adsorption capacity of PFOS on 8%C-mHFO reached 221.6 mg g(-1). The adsorption capacity gradually decreased with the increase of pH. Furthermore, coexisting anions and organic acids also reduced PFOS adsorption on 8%C-mHFO. Hydrophobic interaction, hydrogen bonding, ion-exchange, and electrostatic attraction may jointly play important roles in PFOS removal. Therefore, chitosan-modified HFO has the potential to remove PFOS from an aquatic environment.