The effect of CO 2 at low temperature and pressure on solutions supersaturated with silica in the presence of limestone and dolomite

Abstract

The effect of 1 atm of CO 2 over initially neutral solutions supersaturated with silica, at room temperature, as contrasted with 1 atm of air was determined over a period of 5 months, together with changes brought about by the introduction of calcite and dolomite to these solutions in the form of either chips or finely ground powder. In the absence of CO 2 all solutions quickly reached equilibrium and no silica precipitated. In the presence of CO 2 approximately two-thirds of the silica precipitated as silica gel within the first 2 months; the amount of silica precipitated was not affected by the presence of limestone or dolomite. Silica gel precipitated as a fine powder in the presence of finely ground calcite and dolomite, but as a cloudy gelatinous mass in the presence of coarse chips of dolomite and calcite, and in the absence of either calcite or dolomite. Preferential leaching of calcium from dolomite took place, both in the presence of air and in the presence of CO 2, but was more pronounced in the presence of air. There was no evidence of physical replacement of either limestone or dolomite by precipitated silica.