Adsorption of perfluorooctane sulfonate (PFOS) on mesoporous carbon nitride

Abstract

Mesoporous carbon nitride (MCN-1) has been prepared using mesoporous silica SBA-15 as the template via a polymerization reaction between ethylenediamine and carbon tetrachloride. The structural and surface properties of MCN-1 are evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption–desorption analysis, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), element analysis, zeta potential and Boehm titration analysis. Kinetics studies reveal that the adsorption of perfluorooctane sulfonate (PFOS) on MCN-1 follows the pseudo-second-order kinetic model. Additionally, the adsorption fits the Langmuir model better than the Freundlich model. The adsorption amounts of PFOS on MCN-1 monotonically decrease as the pH values of PFOS solution increase. Thermodynamic results indicate that the adsorption process of PFOS by MCN-1 is spontaneous and endothermic in nature. Moreover, the adsorption capacities of MCN-1 calcined at 673, 773 and 873 K are 625.0, 555.5 and 433.7 mg g⁻¹, indicative of a decreased adsorption with calcination temperature. The adsorption of PFOS on MCN-1 is mainly controlled by electrostatic interaction between PFOS and basic groups of MCN-1, and hydrophobic interaction.