Adsorption was examined in a batch mode at initial
pH of 3.5 and the pH was not buffered to mimic potential
industrial practice. The beads were immersed in a
known volume of solutions containing known initial
concentrations of metal ions, and agitated on a reciprocal
shaker at 25 C. Samples were withdrawn from
the solution at indicated time for analysis of metal
concentrations by using atomic absorption spectroscopy
(AA-782, Nippon Jarrell Ash, Tokyo, Japan). For
equilibrium adsorption, samples were withdrawn at 3 h.
The amount of beads was varied with the initial concentrations
of metal ions so that bulk metal concentrations
at equilibrium were within a range of 30–70% of
the initial concentrations. The amounts of metal ions
adsorbed on beads were determined from the measured
bulk concentrations, using the following equation,