3.2. Sorption study
3.2.1. Sorption kinetics
The results of sorption studies, carried out as a function of contact
time, for Cd2+ and Zn2+were presented in Fig. 4. It suggested
that the removal of Cd2+ and Zn2+ by the MNHAP adsorbents took
place in two distinct steps: a relatively quick phase (first 2 h), followed
by a slow increase until the equilibrium was reached. The
necessary time to reach the equilibrium was about 24 h. Though
there was a slight increase of adsorption quantity after 24 h, it
did not bring any remarkable effect, so a contact time of 24 h was
chosen for further experiments.