The X-ray powder diffraction patterns of the calcined MCM-41
and S-MCM are shown in Fig. 2. The characteristic low-angle peaks
of mesoporous silica materials are evident, indicating that the adsorbent
materials possessed a hexagonal mesophase structure with a
clear (100) peak and weaker reflections assigned to (110) and
(200) reflections. On the other hand, the XRD pattern of MCM-41 revealed
only one reflection peak (100), which is characteristic of an
hexagonal mesoporous structure of spherical particles. The absence
of (110) and (200) reflection peaks for S-MCM indicated that it has
a different pore structure from that of MCM-41, due to the smaller
size of periodic mesoporous areas. It was also observed that the intensity
of the (100) reflection was less than for S-MCM when compared
to that of MCM-41. Besides, the (100) reflection peak of S-MCM
shifted to a higher value reflection angle, which revealed the decrease
in the periodic distance between pores (Hung et al., 2009).