Synthesis, characterization and sorption studies of nitrogen–doped carbon nanotubes

Nitrogen doped carbon nanotubes were synthesized using cobalt and silver co-catalyst on magnesium oxide support. Their morphological features were studied using Raman spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction spectroscopy. Equilibrium and thermodynamic batch sorption experiments were carried using concentration, time and temperature effects respectively. The morphological images showed amorphous multiwall nanotubes with crystalline regions that are attributable to the doping of carbon nanotube with nitrogen. The sorption studies indicated a rapid uptake of Cr³⁺ by the nitrogen doped carbon nanotubes which was mainly diffusion controlled. The thermodynamic study suggests relatively low temperature (low energy) favoured sorption which is exothermic with a physic-sorption mechanism.