The samples were centrifuged, and the obtained supernatants
were filtered through a 0.45 lm filter. Major and trace elements
were determined in the solutions using a Perkin Elmer Model
OPTIMA 3200RL ICP-OES. The detection limits of the inductively
coupled plasma optical emission spectrometer are shown in the
Supplementary material.
The metal sorbed concentrations were calculated from the
quantification of the metal concentration in the initial solution
(Ci) and after equilibrium (Ceq) using the following equation: