Silicates chlorination

If the standard free energy change associated with the metal silicate chlorination reaction is given by AG , then... 

Environment Near the end of a dead leg. Dispersant, tolyltriazole, silicate 15-25 ppm residual, bromine/chlorine, 1 hr/day... 

Paints are complex formulations of polymeric binders with additives including anti-corrosion pigments, colors, plasticizers, ultraviolet absorbers, flame-retardant chemicals, etc. Almost all binders are organic materials such as resins based on epoxy, polyurethanes, alkyds, esters, chlorinated rubber and acrylics. The common inorganic binder is the silicate used in inorganic zinc silicate primer for steel. Specific formulations are available for application to aluminum and for galvanized steel substrates. 

An extension of the reduction-chlorination technique described so far, wherein reduction and chlorination occur simultaneously, is a process in which the oxide is first reduced and then chlorinated. This technique is particularly useful for chlorinating minerals which contain silica. The chlorination of silica (Si02) by chlorine, in the presence of carbon, occurs above about 1200 °C. However, the silica present in the silicate minerals readily undergoes chlorination at 800 °C. This reaction is undesirable because large amounts of chlorine are wasted to remove silica as silicon tetrachloride. Silica is, therefore, removed by other methods, as described below, before chlorination. Zircon, a typical silicate mineral, is heated with carbon in an electric furnace to form crude zirconium carbide or carbonitride. During this treatment, the silicon in the mineral escapes as the volatile oxide, silicon monoxide. This vapor, on contact with air, oxidizes to silica, which collects as a fine powder in the furnace off-gas handling system ... 

The metal chlorides normally used as chlorinating agents are the low-cost reagents sodium chloride and calcium chloride. Silicates, carbonates and sulfates can be chloridized... 

If AG has a value which is more negative than that of AG, then AG° becomes more negative than the standard free energy change for the metal oxide chlorination reaction (AG ). An oxide which is difficult to chlorinate in the free state may, therefore, be chlorinated more easily when compounded into a silicate. 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

Multimedia filters, which consist of a top layer of coarse and low density anthracite, layers of silica, and then dense finest medium vitreous silicate, remove about 98% of particulates >20 tm. These filters are regularly back-washed to avoid buildup of particulates. Finer filters (S-lO tm) are used to remove suspended matter and colloidal materials. To prevent scaling due to water hardness, sodium ions generated from brine are exchanged with calcium and magnesium ions in the water. Activated carbon or metabisulfite is used to remove chlorine. 

Natural isotope variations in chlorine isotope ratios might be expected due to both the mass difference between Cl and Cl as well as to variations in coordination of chlorine in the vapor, aqueous and solid phases. Schauble et al. (2003) calculated equilibrium fractionation factors for some geochemically important species. They showed that the magnitude of fractionations systematically varies with the oxidation state of Cl, but also depends on the oxidation state of elements to which Cl is bound with greater fractionations for 2+ cations than for 1+ cations. Silicates are predicted to be enriched compared to coexisting brines and organic molecules are enriched to dissolved Cl. ... 

Polyisoprene (rubber), chlorinated polyethylene Wood, complex silicates (cement or ceramic tile), carpet (nylon, polyester, polyolefin)... 

Wastes with water content greater than 85% increase the energy costs of the process. Some problems have been noted with phase separations in the final waste form. The technology cannot treat gases or iodine. Mercury is difficult to incorporate. There are concentration limits for some elements in a silicate glass final waste form. Phosphate glass final waste forms can incorporate greater concentrations of some metal oxides, chlorine salts, and mercury in some cases. 

By heating a mixture of carbon and silicic anhydride in a stream of chlorine —... 

---