Silicate, soluble reviews

Both organic and inorganic ligands such as Cl and dissolved organic carbon (fulvie acid and carboxylic acids) decrease metal adsorption. In the arid soils with higher pH, folic acids increase the solubility of metals such as Cu and Zn. The interaction between the transition of heavy metals and silicate surfaces was reviewed by McBride (1991). 

In their study The production of available potash from the natural silicates, A. S. Cushman and G. W. Coggleshall reviewed the methods which have been proposed for extracting water-soluble potash salts from natural silicates. These may be arranged in three groups. There is a dreadful monotony in various patents, for in spite of their great number, very rarely does a novel principle appear which offers any promise of success. 

Sodium tetraphenylborate, Na B(C6H5)4, is an important ionic predpitant for potassium ion. The solubility product of the potassium salt is 2.25 x 10 . Introduced by Raff and Brotz in 1951, this reagent has many analytical uses. A review of the various applications has been given by Cluley, who also described procedures for the separation and determination of potassium in silicates. In add solution at pH 2 or pH 6.5 in the presence of EDTA, the separation is almost specific... 

The trimethylsilylated silicic acids formed in this instance are soluble in conventional organic solvents, and their volatility is sufficiently high for them to be analysed by gas chromatography. Carzo and Hoebbel [411] carried out a comprehensive study of the chromatographic retention of various trimethylsilylated silicic acids on different stationary phases Apiezon L and silicone OV-1 and OV-17. The analysis of metals in the form of volatile complexes continues to attract attention, and have been described for analysing sodium [412], potassium [412], radium [413], caesium [413], barium [414], calcium [414], strontium [415], beryllium [416, 417], magnesium [418], zinc [419, 420], nickel [419], mercury [421], copper [422, 423], silver [424, 425], cadmium [421], indium [426, 427], g ium [428], scandium [217], cobalt [421], thallium [426], hafnium [429, 430], lead [431, 432], titanium [430], vanadium [433], chromium [434-436], manganese [426], iron [437], yttrium [438], platinum [439,440], palladium [439, 441, 442], zirconium [430], molybdenum [443], ruthenium [444], rhodium [445], rare earths [446—449], thorium [221, 450, 451] and uranium [221, 452]. The literature on GC analysis of metal chelates was reviewed by Sokolov [458]. 

Silicates" in two volumes.O) While much has happened since 1952, the book has not yet been replaced as the primary reference for soluble silicate technology and should be reviewed for references and basic information on processes and products I have so briefly mentioned. James Vail was a man of great insight, a poet, author, and above all a humanitarian. 

Vail, J,G, "Soluble Silicates" 1 and ACS Monograph Series 116 Reinhold Publishing Corp, New York, 1951 (Chap. 1, especially p. 4-7, gives a brief historical review),... 

Sodium silicate was the 45th largest volume chemical produced in the United States in 1980, according to the 1981 Chemical and Engineering News Survey ( ). Obviously, the analysis of this material as well as the other major soluble alkali silicate, potassium silicate, is very important commercially. This paper will briefly review the modern analytical instrumental methods that are used to determine the quality of commercial soluble silicates and instrumental... 

The objective of this review is to draw together and briefly discuss the available information on the health, safety and environmental aspects of the soluble silicates. The sources of information for this review include scientific publications, reports of regulatory bodies and government agencies, and the incidental records of a corporation which has manufactured soluble silicates for over 120 years( ). ... 

The benefits derived from the soluble silicates in these processes will be reviewed and are analogous to the benefits derived in the detergency and mining industries where silicates have been successfully utilized for many years. 

Soluble silicates have been widely used in laundry detergents for many years. A comprehensive review of their properties and their utility as detergent ingredients up to 1952 can be found in the last ACS Monograph on soluble silicates ( 1). 

The manufacture of molecular sieve adsorbents has been reviewed by Breck > and more recently by Roberts. The steps in the process are shown schematically in Figure 1.12. A variety of different starting materials may be used. In the hydrogel process the reagents are added in soluble form as sodium silicate and sodium aluminate, whereas in the clay conversion process the alumina is added as a clay mineral, usually metakaolin. Formation of the desired zeolite depends on maintenance of the correct conditions of pH, temperature, and concentration. Seeding may be used to promote crystalliza-... 

Although Si(OH) is nonvolatile at ordinary temperature and polymerizes quickly when heated, nevertheless at elevated temperature and pressure in-water its solubility is greatly increased and it can exist in equilibrium as the vapor phase in the steam, as shown by Kennedy (25). This is of importance in very high pressure boilers in power plants where deposits build up on turbine blades unless all silica is removed from the feedwater. Brady (26) supposes the volatile species is Si(OH)4 o., (HO)3SiOSi(OH)3. Astrand (27) found that volatility increased with decreasing alkalinity in experiments conducted up to 350°C and 300 atm. This, of course, suggests that Si(OH)4 is more volatile than the silicate ion. Wendlandt and Glemser (28) reviewed evidence from earlier workers and calculated the equilibrium constants involved whence the species in the vapor were related to the density of the water vapor ... 

In laboratory studies, silica was adsorbed and precipitated by hydroxides of aluminum, iron, manganese, and magnesium, according to Harder (42). After precipitating 15 ppm Al(OH), from a 3 ppm SiO in solution, the residual silica was 0.8 ppm, whereas with 30 ppm aluminum hydroxide, no measurable silica remained. Willey has given an excellent review of the extensive literature on the interaction of silica and alumina in dilute solutions. The low levels of soluble silica reached (39) depended on the particular solid aluminum silicate phase that was formed or present. She studied the interaction at very low concentrations, generally less than 10 ppm, and found that only I ppm SiO is required to initiate the precipitation of 1 ppm of AljOs from solution, and if more than about I ppm AljO, is in solution the silica concentration becomes exceedingly low. 

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