The
filtrate and washing were allowed to cool to room
temperature. Concentrated sulfuric acid was added
to the obtained solution until pH 7.0 and incubated
for 48 hours to promote silica gel formation. The
silica gel produced was separated from soluble salt
solution by vacuum filtration and washed with
de-ionized water. Then silica gel was dried at 150o
C
for 48 hours and ground into powder. The obtained
silica gel was white rough powder.