3.1. Characterization of adsorbent
Elemental analysis of the diphenylcarbazide-functionalized
nanoporous and colloidal silicas gave a diphenylcarbazide concentration
of 1.95 and 0.36 mmol g−1, respectively. The low-angle Xray
diffraction pattern of DPC-SBA-15 showed that the nanoporous
structure of silica after functionalization with diphenylcarbazide
remains intact (Fig. 2). The TEM study also confirmed that the nanopore structure of the SBA-15 remained intact after functionalization.
As the image in Fig. 3 shows, the pores of SBA-15 with
approximately 10 nm wide, bright spots, and the walls, dark spots,
clearly are visible. Considering colloidal silica is not a porous material
and has smaller surface area, lower efficiency, less capacity and
preconcentration factor is expected in comparison with SBA-15.
The FT-IR spectra of SBA-15 and diphenylcarbazide functionalized
SBA-15 (KBr pellets) was evaluated. The characteristic
stretching vibration bands of diphenylcarbazide and organosilane
(1652, 1548 and 2945 cm−1, respectively) in the spectrum of the
functionalized material confirmed the presence of diphenylcarbazide
groups on the surface of the nanoporous silica. Furthermore,the Si O Si and Si O H stretching vibration bands of nanoporous
silica appeared at 1038, 809 and 3000–3500 cm−1, respectively.