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 1175m²g^-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 11.1mgg^-1, compared to 7.6mgg^-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 4.8×10²gmg^-1min^-1.