Removal of V(V) ions from aqueous solutions using oxidized multi-walled carbon nanotubes

In this paper, multi-walled carbon nanotubes (MWCNTs) were oxidized and used as an adsorbent for the removal of vanadium (V(V)) ions from aqueous solution. Oxidized MWCNTs were characterized by scanning electron microscope and Brunauer–Emmett–Teller measurements. The effects of various parameters such as solution pH (1.0–8.0), adsorbent dose (0.001–0.08 g), contact time (7.0–150 min), and temperature (25–55 °C) were investigated. The results demonstrated that the maximum percentage of V(V) adsorption was found at pH 5.0 and 90 min contact time with 0.03 g oxidized MWCNTs. Kinetic adsorption data were analyzed using the first-order model and the pseudo-second-order model. The regression results showed that the adsorption kinetics were more accurately represented by the pseudo-second-order model. The equilibrium data in aqueous solutions were fitted to Langmuir, Freundlich, and Tempkin isotherms and the equilibrium adsorption of V(V) was best described by the Freundlich isotherm model.