Effects of pH and Operational Conditions on Silica Removal from Geothermal Brine by Seeding Method Using Silica Gel

Abstract

For the seeding method by using silica gel, the effects of pH and operational conditions on the silica removal performance are experimentally investigated. The silica removal ratio is estimated by the quasi-stable concentration of silica measured under various conditions.
The initial pH was changed in the range of 5-9. When the initial silica concentration is 0.5 kg-SiO₂·m^-3, the silica removal ratio increases with increasing initial pH. The silica removal ratio has a maximum and a minimum when the initial silica concentration is 0.7 kg-SiO₂·m^-3, and has a minimum when the initial silica concentration is 0.9 kg-SiO₂·m^-3. When the initial pH is the same, the silica removal ratio increases with increasing temperature and with decreasing initial silica concentration. While the silica removal ratio is not affected by the pre-seeding time in the case of lower initial silica concentrations, it increases with decreasing pre-seeding time in the case of higher initial silica concentrations. The seeding method is considered to be applicable to treat the present geothermal brine.