Comparative study of heavy metal ions sorption onto activated carbon, carbon nanotubes, and carbon-encapsulated magnetic nanoparticles

The paper presents the advantages and limitations of heavy metals sorption onto three different carbon materials: activated carbon, carbon nanotubes, and carbon-encapsulated magnetic nanoparticles. Studied carbon sorbents differed with the grain size, crystallinity, and active surface area, which were derived from electron microscopy, Raman spectroscopy, and methylene blue adsorption, respectively. Detailed sorption studies were based on two model metal ions, namely Co(II) and Cu(II), and covered the influence of pH and ionic strength. It has been showed that carbon nanotubes and carbon-encapsulated magnetic nanoparticles have significantly higher sorption efficiency towards both studied metal ions in comparison with activated carbons. It has been shown that the observed differences in metal uptake yields resulted primarily from surface charge densities and overall graphitization degree, whilst the effect of the particle size was the most pronounced in the case of sorption at high ionic strengths.