Sorptive removal of phenanthrene from water by magnetic carbon nanomaterials

Abstract In the present study, magnetic multi-walled carbon nanotubes (MMWCNTs), magnetic single-walled carbon nanotubes (MSWCNT) and magnetic graphene nanosheets (MGNS) were prepared and the sorptive removal of phenanthrene from water by them was investigated. TEM analysis showed that carbon nanomaterials (CNMs) were coated with iron oxide nanoparticles, which were proved by Fourier transform infrared spectrometer. Magnetism determination also confirmed the formation of strong magnetic nanoparticles with saturation magnetization >31 emu/g. pH slightly affected the removal rate of phenanthrene and the adsorption performed better under weak acid conditions. Pseudo-second-order kinetic model was more suitable to describe the kinetic process, while Polanyi theory-based Dubinin−Astakhov model fitted the isothermal data best. MSWCNT exhibited the highest adsorption capacity, followed by MGNS and MMWCNTs. Adsorption thermodynamic parameters, including Gibbs free energy changes, enthalpy changes and entropy changes, were all negative, suggesting that the adsorption was a spontaneous, exothermic and entropy reduction process. The MCNMs prepared could be easily regenerated and reused, providing a promising alternative for the sorptive removal of phenanthrene from contaminated water.