Preparation of polyaniline-coated polystyrene nanoparticles for the sorption of silver ions

Polyaniline-coated polystyrene (PS/PANI) beads with an average diameter of approximately 310 nm were prepared from styrene and divinylbenzene via emulsion polymerization and subsequent oxidative polymerization of aniline. The sorption capacity of the polymer beads towards silver ions in aqueous solution increased substantially as the pH increased, up to a pH of 7, owing to more free amine and imine groups. The FE-SEM images and XRD data indicated that silver ions were reduced to form silver nanoparticles on the polymer beads. The kinetics of silver ion uptake by PS/PANI particles in a 160 ppm silver nitrate solution could be described by a pseudo-second order model. Even though the sorption isotherm correlated to the Freundlich model much better than the Langmuir model, the Langmuir model-based maximum sorption (320 mg g^{- 1}) was closer to the experimentally obtained value of 330 mg g^{- 1}. This study reveals that PS/PANI beads can be readily prepared in large quantities and employed as one of most efficient sorbents of silver ions in the aqueous phase. The high sorption capacity of the polymer nanoparticles was illustrated not to be affected by common alkali and alkaline earth metal ions in a simulated tap water. The PS/PANI nanoparticles were stable enough not to show any significant loss in sorption efficiency even after fourth cycle of adsorption-desorption.