Preparation And Applications Of High Purity Porous Silica Spheres

Conventionally manufactured silica gels are usually prepared from water glass (alkaline silicate). The process of preparation is as followed, including reaction, gelling, aging, washing, dipping, drying and calcinations. It is clear that water glass contains a high concentration of sodium, iron and aluminum ions. These ions cannot be completely eliminated from the silica gel by subsequent treatment (e.g., in the case of acidic washing) during the manufacturing process. As a result, metal contaminants remain in the silica and on the silica surface. On one hand, these impurities have a chelating effect on certain substances; on the other, they increase the acidity of neighboring silanol groups. Subsequently, this can lead to a low bonded efficiency, catalytic activity and non-specific adsorption. To avoid the occurrence of metals in the silica gel, tetraethoxysilane has been used for preparation of high purity porous silica spheres in this thesis. The formation of high purity porous silica spheres consists of two stages. In the first stage, a viscous liquid polyethoxysiloxane is prepared by partial hydrolysis of tetraethoxysilane, and in the second step the polyethoxysiloxane is emulsified with a mixture of water and ethanol and finally yielded high purity porous silica spheres. In order to attain all these requirements for different particle sizes and pore structure, a series of reaction conditions in the procedure of preparing high purity porous silica spheres have been investigated. The way of controlling particle sizes and pore structure has been set up. Furthermore, the high purity porous silica bonded C15 has been synthesized and their cbromatographic behaviors have been studied. The results of separation for samples were satisfactory.