FTIR analysis was used to identify the type of functional groups
on the adsorbent surface (Supplementary information, Fig. S1).
Similar features were seen for unmodified hybrid materials as
was reported earlier [16], i.e., peaks at 1090–1060 cm1 related
to Si–O–Si and Si–O–C valent vibrations and at 3400 cm1 related
to symmetrical valent vibration of free NH2 and OH groups. However,
after EDTA functionalization bands attributed to the asymmetric
and symmetric stretching in carbonyl groups of
carboxylates were observed at 1387 and 1560 cm1 and stretching
vibrations in carboxyl carbonyl groups at 1734 cm1 [15]. Furthermore,
the intensity of these EDTA-related peaks increased as the
chitosan content increased, indicating an increasing surface coverage
of EDTA groups.