Influence of CO2 on silica in solution

Ghansityam D. Sharma
1970 Geochemical Journal  
Laboratory experiments show that H4SiO4 (monomeric silica) up to 80ppm in seawater is stable under all C02 pressures from 0 to 17.2 X 103 kg/m2. CaC03i AIC13 6H20, MgC12i and standard clays, when added individually, did not remove silica from solutions containing silica from 50 to 80ppm under these C02 pressures. Addition of CaC03 and AlC13.6H20 together, however, removed silica from solution in inverse pro portion to the C02 pressure. C02 serves to inhibit the removal of silica from solution
more » ... ntaining CaC03 and aluminum chloride. The CaC03 functions as a buffer to maintain the acid to neutral pH. The final reaction appears to follow: 2H4SiO4 + A13++ 2CaCO3 + H2O T AlSi205(OH) • 4H20 + 2Ca2+ + HC03 + C02 . In an open system, where C02 can escape to the atmosphere, the removal of silica from solution is controlled by the available A1C13.6H20 and CaC03. Electron microscopy and infrared analyses confirm that the principal precipitates were clayey sediments and trace amounts of sepiolite. This suggests an intimate interrelationship between the geo chemical cycles of carbon dioxide, calcium carbonate, aluminum, and silica in nature.
doi:10.2343/geochemj.3.213 fatcat:g6chqnvcurcixgpwp4d7n3cqfy