The solubility of amorphous silica is important to the operation of water-dominated production processes. In areas such as Texas, New Mexico, Arizona, parts of California, southern Europe, the Pacific Rim and Latin America, the water used for industrial applications contains high silica concentrations (50 parts per million [ppm] to 100 ppm, expressed as silicon dioxide [SiO2]). These concentrations result from quartz (crystalline SiO2) dissolution from rock formations into the groundwater. The potential for silica-scale deposition poses serious problems in water with a high dissolved silica content. In fact, silica-scale problems could be termed the Gordian Knot of water treatment," such problems are extremely difficult to resolve. Personnel responsible for power plants, evaporative cooling systems, semiconductor manufacturing and geothermal systems must monitor water silica levels very closely. Silica precipitation/deposition frequently is encountered in evaporative cooling systems, where salt concentrations increase through partial evaporation of the cooling water. Silica solubility in water generally is 150 ppm to 180 ppm, depending on water chemistry and temperature. This imposes severe limits on water users, leading either to operation at very low cycles of concentration and consuming enormous amounts of water, or to use of chemical water treatment techniques that prevent silica-scale formation and deposition.

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• Water Treatment

• Silica Scale

• Chemical Processing

• Article