Solubility silicate

When acid is added to any soluble silicate, the following reaction occurs ... 

A soluble silicate—a trioxosilicate— is obtained when silica is fused with sodium carbonate ... 

J. G. Vail, Soluble Silicates, Their Properties and Uses, Reinhold Publishing Corp., New York, 1952. 

Commercial soluble silicates have the general formula... 

J. S. Falcone, Jr., ed.. Soluble Silicates ACS Symposium Series 194, American Chemical Society, Washington, D.C., 1982. 

Corrective Action Application In Massachusetts, a municipal wastewater treatment plant receives a number of wastestreams containing heavy metals from local industries. When tested, the dewatered sludge failed the EP toxicity test. In order to permit landfill disposal of the sludge, solidification processes were examined. A soluble, silicate-based system, developed by Chemfix, was ultimately selected which produced a product whose leachate passed the EP toxicity test (Sullivan, 1984). 

Silica fouling is the accumulation of insoluble silica on anion resins. It is caused by improper regeneration which allows the silicate (ionic form) to hydrolyze to soluble silicic acid which in turn polymerizes to form colloidal silicic acid with the beads. Silica fouling occurs in weak-base anion resins when they are regenerated with silica-laden waste caustic from the strongbase anion resin unless intermediate partial dumping is done. 

Silicon shows a rich variety of chemical properties and it lies at the heart of much modern technology/ Indeed, it ranges from such bulk commodities as concrete, clays and ceramics, through more chemically modified systems such as soluble silicates, glasses and glazes to the recent industries based on silicone polymers and solid-state electronics devices. The refined technology of ultrapure silicon itself is perhaps the most elegant example of the close relation between chemistry and solid-state physics and has led to numerous developments such as the transistor, printed circuits and microelectronics (p. 332). 

SiOj-xHsO. This hydrated oxide docs react with hydroxide ion to form soluble silicate ions ... 

For analytical purposes silicates may be conveniendy divided into the following two classes (a) those ( soluble silicates) which are decomposed by acids, such as hydrochloric acid, to form silicic acid and the salts (e.g. chlorides) of the metals present and (b) those ( insoluble silicates) which are not decomposed by any acid, except hydrofluoric acid. There are also many silicates which are partially decomposed by acids for analytical purposes these will be included in class (b). 

A. Determination of silica in a soluble silicate Discussion. Most of the silicates which come within the classification of soluble silicates are the orthosilicates formed from SiO units in combination with just one or two cations. More highly condensed silicate structures give rise to the insoluble silicates. 

Andersson, K. R., Dent Glasser, L. S. Smith, D. (1982). Polymerization and colloid formation in silicate solutions. In Falcone, J. G. (ed.) Soluble Silicates. ACS Symposium Series No. 194, Chapter 8. Washington, DC American Chemical Society. 

Soluble oil metal-working fluids, 1 22 Soluble oils, 15 240 Soluble silicates, 22 451-452 dissolution of, 22 455-456 history and applications of, 22 452 Soluble starch synthases, 12 492 Soluble titanium glycolate complexes, 25 87 Solute clearances... 

Pozzolanic S/S systems use portland cement and pozzolan materials (e.g., fly ash) to produce a strucmrally stronger waste/concrete composite. The waste is contained in the concrete matrix by microencapsulation (physical entrapment). It is a chemical treatment that uses commercially available soluble silicate solutions and various cementious materials such as cement, lime, poz-zolans, and fly ash. By addition of these reagents and rigorous mixing, the waste is fixed or stabilized. Contaminant mobility is reduced through the binding of contaminants within a solid matrix, which reduces permeability and the amount of surface area available for the release of toxic components. 

Solubility. An important aspect of silica chemistry concerns the silica— water system. The interaction of the various forms of silica with water has geological significance and is applied in steam-power engineering where the volatilization of silica and its deposition on turbine blades may occur (see Power GENERATION), in the production of synthetic quartz crystals by hydrothermal processes (qv), and in the preparation of commercially important soluble silicates, colloidal silica, and silica gel. 

Polymerization. The basic features of silica polymerization and its technical relevance have been summarized (9). A general polymerization scheme is shown in Figure 2. When a solution of Si(OH)4 is formed, eg, by acidification of a solution of a soluble silicate, at a concentration greater than... 

Crystalline Silica. Quartz sand is of course the principal raw material for the production of glass (qv). Cristobalite and 3-quartz are used in glass ceramics (qv), ie, ceramics produced by the controlled crystallization of glass. Silica is a main constituent of ceramics (qv). For example, refractory silica brick containing small amounts of A O is used as roof brick for open-hearth furnaces at temperatures >1600° C (see Refractories). Silica sand or flour (ground quartz) is the raw material for soluble silicates, such as sodium silicate, which is consistently ranked as one of the top 50 U.S. industrial chemicals (98) (see Silicon compounds, synthetic inorganic silicates). 

Vitreous silica does not react significantly with water under ambient conditions. The solution process involves the formation of monosilicic acid, Si(OH)4. Solubility is fairly constant at low pH but increases rapidly when the pH exceeds 9 (84—86). Above a pH of 10.7 silica dissolves mainly as soluble silicates. Solubility also increases with higher temperatures and pressures. At 200—400°C and 1—30 MPa (<10"300 atm), for example, the solubility, S, of Si02 in g/kg H20 can be expressed as follows, where dis the density of the vapor phase and Tis the absolute temperature in Kelvin. 

Tetrabaoio... SiUo,. Dibasic... SiOHo,. Preparation,—1. By treating a solution of a soluble silicate with hydroeliloric acid ... 

By passing a stream of carbonic anhydride through a solution of a soluble silicate —... 

---