Metal solutions were prepared daily by diluting the stock
solution to the desired concentration. Before the beginning of each
experiment an aliquot of the solution (ca. 10 mL) was collected to
confirm the initial metal concentration (CA,0). The sorption
experiments began when an accurately known amount of sorbent
(m) was added to the solution. Aliquots (ca. 10 mL) were collected
from the system, at increasing times and
filtered through a washed
(HNO3 2% v/v followed by ultra-pure water until neutral pH)
0.45 mm Millipore membrane. The
filtrate was adjusted to
pH < 2 with nitric acid and then analysed for Hg2+ and/or Cd2+
quantification. Each experiment was maintained until the metal
concentration in solution remained constant, corresponding to the
solution-solid equilibration. Mercury quantification were per-
formed by could vapour atomic
fluorescence spectroscopy (CVAFS),
on a
flow-injection cold vapour atomic
fluorescence
spectrometer (hydride/vapour generator PS Analytical Model
10.003, coupled to a PS Analytical Model 10.023 Merlin atomic
fluorescence spectrometer) and using SnCl2 (10% m/v) as reducing
agent. Cadmium quantification was performed by inductively
coupled plasma mass spectrometry (ICP-MS) on a Thermo ICP-MS