The morphology of the spherical silica and the particle size
were examined by TEM. RH-Silica consists of uniform and
aggregate spherical particles with a diameter range
between 15 and 91 nm. In basic condition, silica particles
aggregate to form negatively charged colloidal gel. These
colloidal particles induce strong electrostatic repulsive
energy to avoid gelation and agglomeration [21]. It can be
seen that the nanoparticles are basically amorphous as
shown in the XRD (Fig. 3).