The percent removal (h%) of metal ions on the active groups
such as OH and NH2 depends on the molecular structure of the
sorbent compounds, which bind to the metal ions by coordination
bonds. The proposed adsorption of the transition metals by
the chitosan and its derivatives were represented in Fig. 8. In our
results, we found that the percent removal of the different metal
ions on the surfaces of compounds (I) and (II) are lower than
chitosan itself. That can be attributed to the formation of the
intra-molecular hydrogen bonding between the substitution
groups and unit monomer of chitosan, which leads to the
decrease in the free active groups such as OH and NH2 on
the chitosan. That causes a lower in the percent removal of
metal ions. While in chitosan free which reaching by free
active groups, ceasing a higher adsorption capacity than its
derivatives.