where qt (mg/g) and qe (mg/g) are the amount of 2+ absorbed on the
adsorbent at time t and at equilibrium, respectively; k1 (min1) and
k2 (g/mg min) are the rate constants of the pseudo-first-order and
pseudo-second-order model, respectively. The fitting of the two
models to the copper adsorption kinetic data are shown in
Figs. S1 and 3c and d. The model parameters obtained by curvefitting
kinetic data are listed in Table 1.