Inorganic Precipitated Silica Gel. Part 2: Fragmentation by Mechanical Energy

Precipitated silica (SiO(2)) is industrially produced by mixing a silicate solution with acid in a semi-batch process. Polycondensation of monomeric silica leads to the formation of particles which aggregate and eventually form a particulate gel. However, this is instantly fragmented by the mechanical energy input caused by the stirrer. Shrinkage and compaction of these fragments lead to the final product aggregates. It is the aim of this study to enable tailoring of the structure and size of these product particles via the process parameters. In the present paper this is achieved by varying the stirrer speed. It can be shown that there is an analogy between the behavior of the gel and that of highly viscous liquids. Unexpectedly, however, the fragment size can not be reversibly controlled by the power input. The influence of the process parameters on the strength of the gel has been described in the first part of this series [1].(1)