A Study on Mesoporous Silica Recovery from Geothermal Brine

Abstract

The produced brine from production wells tends to deposit siliceous scale at the surface facilities such as brine transportation lines, because of high silica concentration in the brine. Then, research and development to extract supersaturated silica as a starting substance of a kind of zeolite groups was undertaken. Unlike a commonly used zeolite, mesoporous silica has large pore size between 12-100A, so it can be used as carrier materials introducing new functional characteristics. In a newly developed process, the brine with a temperature of 91 Åã C and a SiO2 concentration of 850 ppm(w/w) is flowed into moving bed packed with É¡-alumina after adding cationic surfactant of 10ppm so that the silicasurfactant compound is grown efficiently with occurrence of polymerization. The treated brine is stored at a holding tank and filtered to recover the white silica precipitate. An alkaline reagent is added into the silica powder (SiO2;65.4w%,Al2O3; 24.5w%, specific surface area; 23 m2/g) as raw material, and normal cationic surfactant and HCl are added with constant stirring for three hours at room temperature. A precipitate is filtered and it is calcined at 450ÅãC for one hour to remove cationic surfactant. The calcined precipitate was identified as a mesoporous silica by X-ray diffraction analysis (XRD). The final silica product has a 861 m2/g of specific surface area that is a relatively higher value than about 500-600 m2/g of other zeolite crystals.

We considered that the benefits of this process are to adopt an efficient separation systems and to eliminate minor chemical disturbance in the brine.