Silica extraction from geothermal heat carrier of Mutnovsky GeoPP and utilization of extracted material

Abstract

Silica sols and powders extracted from hydrothermal solutions have been investigated. Hydrothermal heat carrier piped to the surface through production well of Mutnovsky geothermal electrical power station (GeoPP). Liquid phase of heat carrier contain the colloidal silica of about 0.5 g/dm3 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 diameters of 5-100 nm are obtained. The silica powders with the specific surface of 50-500 m2/g, average pore diameter of 2-15 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. Samples of silica sols and powders were characterized by Dynamic Light Scattering, Scanning and Tunneling Electron Microscope, X-Ray Diffraction, BET Surface Area. In particular, it was shown that diameters of SiO2 nanoparticles in sols and nanopowders were in the range of 5-100 nm. The possibility of obtained silica use as a modifying additive for concrete strength increase was substantiated. The test results on concrete compressive strength rise using nanosilica additive extracted from hydrothermal solution are presented. Silica sols and powders were used as additivities for rising concrete compressive strength.