Adsorption of perfluorooctane sulfonate on carbonized poly-melamine-formaldehyde sponge

In this study, we developed a simple carbonized poly-melamine-formaldehyde sponge (CMF) acting as an adsorbent for adsorbing perfluorooctane sulfonate (PFOS) from the waste poly-melamine-formaldehyde (MF) sponge. The PFOS removal by the developed adsorbent was comprehensively investigated using batch adsorption, including kinetics, isotherm, ionic strength and ionic type and pH edge. PFOS adsorption kinetics followed a pseudo-second-order kinetic model, and reached equilibrium within 3 min. The adsorption isotherm was well described by the Freundlich model, as well as by the Langmuir model at a low initial concentration. The adsorption capacity gradually decreased with the increase of pH, and it was up to 216.4 μg/g even at pH 12.1. However, the adsorption capacity increased with the increase in ionic strength. Furthermore, the co-existing ions and small organic acids also promoted the PFOS adsorption on CMF sponge to different extents. Both the hydrophobic interaction and electrostatic attraction played an important role on adsorption, as well as chemical interaction and hydrogen bonding from spectroscopic results.