Pore size control of silica gels in basic water conditions using sol-gel processing

Pore size of silica gels can be affected by the molar ratio between TMOS and water and by pH solution due to hydrolysis reaction. The molar ratio of TMOS: Methanol: Water was 1:7.5: 22.5. For hydrolysis reaction, basic water of pH 8.5, pH 10.2, and pH 11.2 were used. After making gels with these solutions, the pore sizes of gels turned out to be 37 Å, 43 Å, and 49 Å, respectively. The pore size was increased with higher pH. However, gels made by the same method above were washed 3 times during 36 hours with various pHs of water; pH 1, pH 5, pH 10.5, and pH 12.5. The pore size of washed gels were increased with increase in pH value. Significantly, with pH 12.5, the pore of washed gels were enlarged about 2.2 times compared with unwashed gels. Thus, this washing technique can be used for controlling pore size of silica gels