Dried silicate solutions

Hydrated water-soluble silicates are also known as hydrous polysUicates or dried silicate solutions. The most common soluble silicates are sodium silicates [19]. 

Silica gel. Silica gel is a porous amorphous form of silica (Si02) and is manufactured by acid treatment of sodium silicate solution and then dried. The silica gel surface has an affinity for water and organic material. It is primarily used to dehydrate gases and liquids. 

By achieving random dispersion of the Kaolin in the sodium silicate solution prior to formation of the silica-alumina gel, it was possible to disperse the clay crystals. They condensed somewhat perpendicular to each other and were bound together by silica-alumina gel. I therefore speculated that spray drying, during which the gel system contracts, might create a dual structure. An analogy would be a house built of cards (Kaolin), cemented together with silica-alumina gel. 

Synthesis of MCM-41 with Additives. The hydrothermal crystallization procedure as described earlier [10] was modified by adding additional salts like tetraalkylammonium (TAA+) bromide or alkali bromides to the synthesis gel [11]. Sodium silicate solution ( 14% NaOH, 27% Si02) was used as the silicon source. Cetyltrimethylammonium (CTA) bromide was used as the surfactant (Cl6). Other surfactants like octadecylltrimethylammonium (ODA) bromide (C,8), myristyltrimethylammonium (MTA) bromide (C,4) were also used to get MCM-41 structures with different pore diameter. Different tetralkylammonium or alkali halide salts were dissolved in little water and added to the gel before addition of the silica source. The final gel mixture was stirred for 2 h at room temperature and then transferred into polypropylene bottles and statically heated at 100°C for 4 days under autogeneous pressure. The final solid material obtained was washed with plenty of water, dried and calcined (heating rate l°C/min) at 560°C for 6 h. 

Basic silicate solutions were prepared by using silicic acid (ex Baker, dried at 350 °C) and a solution of the organic bases [25 wt % tetramethylammonium hydroxide (TMAOH), 40 wt % tetra-ethylammonium hydroxide (TEAOH), 20 wt % tetrapropylammonium hydroxide (TPAOH) ex Fluka] and, optionally, dimethyl sulfoxide (DMSO). A solution of hexamethonium hydroxide [ (MejNCgH NM ) (OH) 2] was prepared from the bromide salt (ex Sigma) and A O. 

The dry sodium aluminate was first dissolved in 1.7 times its weight of water and then all 50% caustic requirements were added. The sodium silicate solution was diluted with any water requirement not used to dissolve the dry sodium aluminate. Both solutions were heated to the desired reaction temperature, and then the hot sodium aluminate solution was quickly added to the hot sodium silicate solution (less than 30 seconds) with agitation. The mixture was then agitated until the resulting gel broke down to a homogenous, creamy slurry. 

The silicate anion structures of C-S-H(I) preparations appear to be affected by how long the material remains in contact with its mother liquor and by how strongly it is subsequently dried. Experiments using the molybdate method showed that the anions in precipitates made from CaCl, and sodium silicate solutions at 0 "C were mainly those present in the silicate solution, and thus monomeric if the latter is sufficiently dilute (S45). By allowing such products to stand in contact with their mother liquors at O C. and drying at — 10°C, preparations with Ca/Si ratios of 1.2-1.5 were obtained that contained only dimeric silicate anions. 

Set aside the latex-rubber ball to dry. While it is drying, begin to make a ball from the ethanol and sodium silicate solutions. 

Unlike X type molecular sieve, the Si/Al ratio of Y type molecular sieve normally falls in the range 1.5-3. The laboratory synthetic method introduced here was developed by D.M. Ginter, A.T. Bell, and C.J. Radke (Ref. [125]). Deionized water, sodium aluminate (Na/Al=1.27, 6.1% H20), sodium hydroxide pellets, and sodium silicate solution (28.7% Si02, 8.9% Na20) were used to prepare the reaction gel with a composition of 4.62 Na20 A1203 10 Si02 180 H20. The detailed procedure for the preparation of 32 g of dry product is described below ... 

The characteristics of soluble silicates relevant to various uses include the pH behavior of solutions, the rate of water loss from films, and dried film strength. The pH values of silicate solutions are a function of composition and concentration. These solutions are alkaline, being composed of a salt of a strong base and a weak acid. The solutions exhibit up to twice the buffering action of other alkaline chemicals, eg, phosphate. An approximately linear empirical relationship exists between the modulus of sodium silicate and the maximum solution pH for ratios of 2.0 to 4.0. 

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