Acid treated mesoporous carbon foams, with surface areas (SBET)
as high as 2207 m2 g-1, were synthesised by the carbonisation of fructose over
ZnCl2 templates and tested as adsorbents of Pb(II) ions from aqueous solutions.
Whilst the oxidising acid treatment disrupted the morphology of the foams, it
also led to a proliferation of oxide moieties on the surface of the material which
acted as binding sites for Pb(II) ions. Characterisation of the oxidised
surfaces by IR spectroscopy and measurement of the zero point charge (pHpzc)
showed that the number of acidic surface sites increased with increasing acid
concentration and temperature. The oxidised carbon foams were tested for their
efficiency at removing Pb(II) ions from aqueous solutions, using batch
adsorption techniques. The concentration dependence of Pb(II) ion uptake by the
mesoporous carbon adsorbents could be fitted to Langmuir, Freundlich and
Dubinin–Kaganer–Radushkevich (DKR) isotherms, from which the maximum adsorption
capacity (Qm) and the energy of adsorption (Ea) was derived. Ea values obtained
for the mesoporous carbon adsorbents were associated with weak adsorption
(<8 kJ mol-1), ion exchange adsorption (8–16 kJ mol-1) and chelation (>16
kJ mol-1) depending on the surface oxidation conditions used.