2012 Volume 64 Issue 4 Pages 651-657
Framework substitution of silica into high-valence phosphorus ion was carried out to bring forth an anion-exchangeable property on an inorganic solid surface. Phosphorus was mostly incorporated on silica network as a phosphate ion by a conventional hydrothermal synthesis method as zeolites or mesoporous silica, even though various pH, reactive phosphorus sources, and a wide variety of surfactant were applied for the syntheses. At last, we could find a thermal method called “solvent-free dehydrocondensation” using normal silica and phosphate sources, where phosphorus was wholly incorporated inside silicate network having four Si-O-P bonds around phosphorus. However, the phosphosilicate species was found weak against water treatment even at 50 °C, and the Si-O-P bond was hydrolyzed to leach phosphate. Unique properties were also developed by the phosphosilicate species obtained in this study, which adsorbed/ion-exchanged fluoride ion and oxidized nitrite ion into nitrate ion at room temperature.
