Effects of pH and Temperature on Precipitation Rate of Silicic Acid on Silica Gel Seed.

概要

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In order to remove supersaturated silicic acid from geothermal brines, a seeding method using silica gels has been proposed. In this study, the effects of pH and temperature on silica precipitation on the silica gel seeds were experimentally and kinetically examined in model geothermal brines. The apparent activation energy of silica precipitation on the silica gel seeds ΔE [J·mol-1] is presented as a function of the hydroxide ion concentration:ΔE=(5340+275ln[OH-])Rwhere R is gas constant. The apparent rate constant of silica precipitation K [s-1] is presented as a function of the hydroxide ion concentration and the temperature T [K] and further is combined with two important characteristics of the silica gel seeds ; the surface area As and the particle diameter Dp50K=θAsDp50-0.72[OH-]1.06e-ΔE/RT.where θ is constant, 7×10-4 for the silica gel seed. By combining the equation for activation energy with the reaction rate equation for silica precipitation, the removal rate and removal quantity of silicic acid can be calculated.
日本地熱学会の論文