Silica can clog pores of adsorption media. Can cause undesirable scale formation in boilers, cooling towers. Why treat? Silica precipitation and colloidal silica can foul reverse osmosis (RO) membranes under some conditions.These can usually be removed by coagulation and settling or filtering. In its colloidal form it consists of very fine particles in suspension. The silica content of water ranges from a few parts per million in surface supplies to well over 100 ppm in certain well waters. A colloid diffuses very slowly or not at all through a membrane, and has little, if any, effect upon the freezing point, boiling point, or vapor pressure of the solution. Colloidal particles are thought to have a charge which causes the particles to repel each other, and prevent their agglomeration into larger particles. The weight of the individual particle is so low that a true colloid will not settle out, even after standing for an indefinite period. Silica often exists in water in colloidal form.Ĭolloids are extremely small solid particles suspended in a solution such as water. However, if cations such as calcium, magnesium or iron are present in high-enough concentrations at these higher pH levels, they will combine with the silicate anions and precipitate out as insoluble silicate salts. When pH exceeds 8.0: Silicic acid turns into silicate anions and silica’s solubility increases. At low pH, silica can condense to form uncharged particles of colloidal silica, some as small as 0.02 micron. Below pH 9.0: If silicic acid’s solubility is exceeded, silica and silicates will precipitate out of solution. Dissolved silica is in the form of hydrated, dissolved silicic acid, or Si(OH)4. Only slightly soluble, but counted as part of TDS.In water, the term silica can include all reactive (dissolved) and inert (nonreactive, undissolved or colloidal) forms of SiO2. Occupational disease silicosis is contracted by breathing air containing silica dust, which lodges in and irritates the lungs.Inert and harmless in water passes through the body without effect has no nutritional value.Salts of silica (silicates) are used as pipe corrosion inhibitors and to sequester soluble iron and manganese in water. Pure sand is a chemically stable, low-cost water filtration media. Constituent element silicon is used in many products, from metal alloys to lubricants to semiconductors.
Found in nature as glassy sand or quartz, and in rocks/minerals.
Silica, or silicon dioxide (SiO2), is the most abundant mineral in the Earth’s crust.
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