Control of pore size distribution of silica gel through sol-gel process using inorganic salts and surfactants as additives

For control of the pore size distribution of silica gel, the gel was prepared using the sol-gel process modified by adding several kinds of inorganic salts and surfactants. The addition of any inorganic salt decreased the gel surface area and depressed the formation of mesopores. The surface area and the volume occupied by mesopores changed with the valency of the cation of the salt used. When surfactants were employed as additives, the surface area and the pore size distribution were greatly dependent on the kind of head group of the surfactant: non-ionic surfactant addition monotonously increased the surface area owing to the formation of larger mesopores; anionic surfactant addition significantly decreased the surface area because of the decrease in the volume of mesopores; cationic surfactants caused the surface area to decrease with small additions as anionic surfactants did, while further addition raised the surface area. The rise in the surface area was due to a marked formation of smaller mesopores. These results are discussed on the basis of the interfacial properties of the additives.