Modification of hexagonal-type mesoporous silica via intercalation of PVA and its adsorption properties were investigated. The hexagonal-type mesoporous silica was formed from Si (OC2H5) 4 and self-assembly of C16H33N (CH3) 3Br. In order to intercalate PVA, the produced mesoporous silica was dipped into PVA aqueous solution with stirring, followed by firing at 300-800°C in N2 atmosphere for immobilization of PVA. Thickness of PVA layer in intercalated mesoporous silica was evaluated from its composition and thermogravimetry. The thickness of around 0.1 nm was found to decrease with elevating the firing temperature and the carbonization fraction of the layer increased linearly. The adsorption properties were investigated by using O2 and N2 gases at 25°C. The ratio of adsorption volume, O2/N2, decreased apparently depending on firing temperature. Since the decrease of the ratio was in agreement with the amount of PVA that was not carbonized yet, the adsorption ability of O2 was considered to be attributed to organic species.
Calcium ferrite mono-nitrate hydrate (hereafter abbreviated as CFMNH) obtained at 60°C by a reaction between Ca (OH) 2 suspension and Fe (NO3) 3 solution was characterized by XRD, FT-IR, DTA-TG and SEM-EDX. The synthesized CFMNH was the puseudo-hexagonal layer compound with basal spacing of 1.04 nm which is equivalent to half of the lattice constant c. By heating CFMNH below 100°C, this basal spacing was decreased from 1.04 nm at room temperature through 0.86 nm at 60°C to 0.80 nm at 100°C. These CFMNHs were also indexed tentatively as puseudo-hexagonal symmetry. To study change of basal spacing with pH, 1.04 nm CFMNH suspension was stirred for 1 hour at room temperature in various pH solutions adjusted from about 12 to 13 with NaOH. The basal spacing of CFMNH decreased from 1.04 nm to 0.76 nm with increase of pH. The 0.76 nm spacing of CFMNH was finally settled to 0.80 nm by a longer aging process. The three types of CFMNH with different basal spacings were obtained by pH control as well as by thermal dehydration. However, the chemical composition and structure of 0.80 nm CFMNH obtained at room temperature by pH control were different from those of 0.80 nm CFMNH obtained by thermal dehydration in terms of carbonate contents, degree of hydrogen bond and stacking mode of layers.