Spontaneous distillation of silica-bearing solution in closed system with rough walls

Abstract

The 300°C experiments were conducted in hermetic platinum ampoules with aqueous solution saturated by SiO2 with respect to quartz. The solute SiO2 concentration did not change with time in ampoules with the smooth walls, however in the ampoules with the induced roughness on their walls it decreased exponentially with time and amorphous silica precipitated on the ampoule walls contacted with the water vapor. The experimental results were explained by the distillation initiated through preferential water evaporation in the thin layer (<100 nm) at the meniscus edge and strengthened by the surface wall roughness because of the evaporation surface area increase at the wall wetting in the impregnation regime. This process was accompanied by the progressive disturbance of the equilibrium distribution of the dissolved silica between liquid water and vapor. The similar mechanism might exist in the systems of the different composition. It may initiate the continuous renewal of the water dissolving ability, which can lead at natural conditions to the migration of the voids partially filled by the solution.