Research on the Use of Silica Extracted from the Hydrothermal Solutions

Abstract

Using of silica sols and powders extracted from hydrothermal solutions for building materials and rubber have been investigated. Hydrothermal solutions contain the colloidal silica forming as a result of polycondensation of the molecules of orthosilicic acid. Via ultrafiltration membrane concentration of hydrothermal solutions, silica sols with SiO2 contents up to 940 g/dm3 (62.2 wt %) and particle radii of 29--135 nm are obtained. The silica powders with the specific surface of 110--400 m2/g, average pore diameter of 3--10 nm, and pore volume of 0.2--0.3 cm3/g are obtained via cryochemical vacuum-sublimation drying of sols with the use of liquid nitrogen. The particle size in the powders is in the range from 10 to 100 nm. We used silica sols and powders as additivities for rising concrete and bricks strength, and for forming rubber materials.