Effect of Surface Chemistry and Physical Properties of Carbon Nanotubes on the Adsorption of Polycyclic Aromatic Hydrocarbons in Aqueous Solutions

Abstract

Adsorption behavior of seven different carbon nanotubes (CNTs) towards polycyclic aromatic hydrocarbons (PAHs) was studied in moderately hard reconstituted water (MHRW) with and without dissolved natural organic matter (NOM). At one concentration, adsorption of phenanthrene towards these CNTs was determined using negligible depletion solid phase micro extraction (nd-SPME) followed by GC-MS analysis. The single walled carbon nanotubes (SWCNTs) showed much higher adsorption than all other CNTs. Functionalized multi-walled CNTs showed lower adsorption potential than their non-functionalized (MWCNTs) analogue. The adsorption potential of CNTs is affected by the type and extent of functionalization. Presence of NOM reduced phenanthrene adsorption towards the CNTs from 26-88 % of what was observed in MHRW. NOM decreases the adsorption potential of CNTs according to the type and extent of functionalization. The results suggest that increased diameter of MWCNTs might have supporting effect for the adsorption potential of CNTs for phenanthrene. The study could not find a clear correlation between the adsorption potential of the CNTs and one of the single parameter like specific surface area (SSA), outer diameter (OD), total pore volume (VT) and length of the CNTs. The CNTs characterization results in this study seem to differ from manufacturer?s specifications for these CNTs.