Adsorption behavior of phenanthrene on CTAB-modified polystyrene microspheres

Abstract

Adsorption behavior of phenanthrene on cetyltrimethyl ammonium bromide (CTAB)-modified polystyrene (PS) microspheres was investigated thoroughly to develop a novel adsorbent material. CTAB-modified PS microspheres were characterized through atomic force microscopy (AFM) and Brunauer–Emmet–Teller analysis. AFM images showed that conical admicelles made of CTAB replaced polyvinylpyrrolidone (PVP) macromolecules on the surface of the PS microspheres. After CTAB modification, the surface area of the PS microspheres increased noticeably from 0.56 to 2.08 m2 g−1, which confirmed that the formation of discrete CTAB admicelles replaced PVP macromolecules coated on the surface of the PS microspheres. Through conductivity measurements, two critical micelle concentrations (CMCs) were obtained. The first was the CMC of CTAB admicelles on the PS microspheres, and the second was the CMC of CTAB micelles in the solution, which further confirmed the formation of the admicelles on PS microspheres. Cation–π electron interaction between CTAB and phenanthrene helped adsolubilize phenanthrene in the admicelles on the CTAB-modified PS microspheres. The equilibrium adsorption capacity of the CTAB-modified PS microspheres for phenanthrene was 11.67 mg g−1, nearly three times that of the untreated PS microspheres. The adsorption kinetic curves of phenanthrene on CTAB-modified PS microspheres followed a pseudo-second-order model. The adsorption process closely fit the Freundlich model, which indicated a multilayer adsorption process, rather than monolayer behavior.