Carbon nanocages as heavy metal ion adsorbents

Heavy metal ion contamination in drinking water poses a major risk to human health, whilst contamination in wastewater streams can cause damage to the wider environment. In this study carbon nanocages, synthesised using a supercritical fluid deposition method, were examined as adsorbents of Pb2+ ions from aqueous solutions. Through careful selection of the catalyst and the carbon deposition temperature and pressure, high yields of nanocages with surface areas up to 1175 m2 g−1 were synthesised. These high surface area materials were subsequently tested for their ability to absorb Pb2+ ions, as a function of pH, from simulated wastewater. The nanocages were found to be effective at removing the Pb2+ ions at levels of 11.1 mg g−1, compared to 7.6 mg g−1 for commercially available activated carbon. The kinetics of metal ion adsorption by the nanocages and activated carbon can be described by a pseudo-second-order kinetics model, with a rate coefficient (k2) of 4.8 × 102 g mg−1 min−1.

► Synthesis of high surface area carbon nanocages (CNCs).
► Optimisation of the CNC production process to generate high surface areas and increase yields.
► CNCs exhibit excellent dispersibility in aqueous solution.
► CNCs permit fast transport of aqueous media through a fix bed system.
► CNCs and AC were tested for the removal of lead ions (Pb2+) from simulated wastewater conditions.