Synthesis, Polymerization, and Assembly of Nanosilica Particles below the Isoelectric Point

The particle growth of silica below the isoelectric point plays a key role in oil well cements, production of silica gels and production of nanosilica by dissolving silicates. In this article, we study the particle growth of silica below the isoelectric point using olivine, a silicate mineral, and sodium silicate solutions as silica sources in acid, where the particle size, soluble silica concentration, specific surface area and gelling time were measured. The size of the primary particles detected by laser light scattering is 3 nm in the experiments with sodium silicate solutions. These particles grow then by aggregation forming linear chains which in time will start to branch. The particle growth follows a quadratic polynomial function and particles as large as 100 and 500 nm are detected in the final stages of experiments using sodium silica solutions and olivine, respectively. Based on these findings, a comprehensive model describing the silica particle development below the isoelectric point is propo...