controlled by the attachment of the metal ions on the surfaces [29].
The equilibrium adsorption quantities of Chitosan-Fe-S-C are
367.6 mg/g (200 mg/L) and 380 mg/g (300 mg/L). Obviously, it
has a better ability to remove Cu2+ under these two concentrations,
as these values are almost twice as large as Chitosan-Fe-S and
Chitosan-S-C. In order to further describe the kinetics of Cu2+
adsorption on three chitosan adsorbents, kinetic data were fitted
with linear forms of pseudo-first-order and pseudo-second-order
models. Their equations are given as Eqs. (2) and (3), respectively: