Silicon Compounds: Anthropogenic Silicas and Silicates

Abstract

Synthetic akali silicates, M 2 O· m SiO 2 · n H 2 O, where M = Li, Na, and K, are manufactured as liquids or glasses that readily dissolve in water to form alkaline solutions. These silicates contain a complex mixture of polymeric species that vary as a function of modulus, m , of the material, solution concentration, impurities content, and pH value. The polymer chemistry of silicates influences the properties and function of these materials in a variety of applications including detergency, water treatment, mineral beneficiation, bleach stabilization, and as a raw material for the syntheses of silica sols, gels and precipites, zeolites, clays, and other siliceous materials. The speciation and structure of silicates have been studied using a broad variety of analytical methods including Fourier transform infrared, ft–nmr, laser Raman, and X‐ray photoelectron spectroscopic techniques. The current article discusses the properties of the synthetic alkali silicates that determine their function in a variety of commercial applications. Economic, manufacturing, regulatory and environmental aspects of silicate production and usage are reviewed.

The Determination of Sodium Silicate Composition Using ATR FT-IR

“…The commercial aqueous solutions of the sodium silicates are colloidal in nature and contain complex silicate species, Na + ions, and OHions. 1 They are analyzed 2 routinely using a density measurement with a hydrometer and classical titrimetric methods appropriate for a weak base 3 to determine the alkali content. Generally, standardized 0.2 M HCl is used as the titrant to a methyl orange end point, and the result is reported as %Na 2 O with a relative precision 0.1%.…”

“…The commercial aqueous solutions of the sodium silicates are colloidal in nature and contain complex silicate species, Na + ions, and OH − ions . They are analyzed routinely using a density measurement with a hydrometer and classical titrimetric methods appropriate for a weak base to determine the alkali content.…”