Magnesium silicate synthetic

Methenyl-5,6,7,8-tetrahydrofolic acid, chloride hydrochloride dihydrate (20 g) was added in one portion to 100 ml water at 60°C followed by N,N-diethylethanolamine (14.9 g) which adjusted the pH to 6. The mixture was maintained at reflux for 5 hours and the pH kept between 5.7 and 6.2 by addition of N,N-diethylethanolamine. The mixture was cooled, synthetic magnesium silicate (15 g) added and slurried, and filtered through celite and diluted with 40 ml SD3A (95% ethanol with 5% methanol). The filtrate was kept at -5°C for 16 hours, aqueous calcium chloride (4.0 g) was added dropwise to the cold filtrate, and the precipitate filtered, washed with SD3A (100 ml) and with ethyl acetate (100 ml) and dried under reduced pressure. 

TABLE 7.10 Energy-dispersive X-ray (EDX) data for the synthetic magnesium silicate gels... 

Cleanup is performed by column chromatography. Silica/allumina or Florisil (synthetic magnesium silicate salt), deactivated or suitably activated (for instance 130 °C for 12 h ) are the most frequently used stationary phases. Their performances are checked by standard solution in order to find out the best solvent or mixture of solvents and the optimum volume to be used for selectively eluting PCBs and leaving interferents in the column. V-Hexane and dichloromethane are the most widely used solvents. Better precision on cleanup results has been observed when Florisil cartridges are used instead of silica gel ones. In some cases, in order to minimize interference from other non-PCB organic compounds, additional fractionations are performed. 

Major matrix components or other trace organic compoimds, such as polycyclic aromatic hydrocarbons (PAH) and pesticides, are coextracted with PCBs and might cause interference to the instrumental response, thus they should be eliminated by suitable cleanup procedures. The cleanup is generally performed by column chromatography on suitably activated or deactivate silica [24,54,68,97,128,138,146], sulfuric acid impregned silica [131], alumina [9,14,15,90-92,142], or Florisil (synthetic magnesium silicate) [24,44,67,83], and styrene-divinylbenzene resin [121]. Multilayer columns are frequently utilized. The retention of analytes in the column should be checked by standard solutions in order to find both the best solvent or mixture of solvents and the optimum volume to be used to selectively elute PCBs and leave interferents in the column. n-Hexane and dichloromethane are the most widely used solvents to elute the PCBs from the stationary phase. In addition, special treatments are very often used to eliminate specific interfering substances. For instance, activated copper powder with [23] or without mercury [14,49,81,87,151] or tetrabutyl ammonium sulfite [4] is used to remove elemental sulfur and sulfuric acid is used to remove lipids [107]. 

Synthetic magnesium silicate hydrates (M-S-IT) are gel-like solids and show a water loss related to loosely bound water up to 270"C (Nied et al. 2015) similarly as C-S-H, as shown in Figure 5.14. In contrast to C-S-H, a second weight loss between 270 and 700°C is visible, which is related to the dehydroxylation of hydroxyl groups, 2 =OH + H20(g), in the M-S-H. 

For synthesis of biomimetic catalysts four versions of granulated carriers were used neutral and activated A1203, NaX zeolite and synthetic amorphous aluminum-magnesium silicate and aluminum-chromium silicate. 

Magnesium Silicate occurs as a very fine, white powder free from grittiness. It is a synthetic, usually amorphous form of magnesium silicate in which the molar ratio of magnesium oxide (MgO) to silicon dioxide (Si02) is approximately 2 5. It is insoluble in water and in alcohol, but is readily decomposed by mineral acids. The pH of a 1 10 slurry is between 7.0 and 10.8. 

Many other materials, including synthetic aluminas, aluminum carbonates, aluminum silicates, magnesium silicates, various forms of attapulgite and sepiolite (81-83), alumina-pillared acid-activated montmorillonite (84), synthetic mica mont-morillonite, HY-zeolite, zirconium phosphate (85), mica, kaolin, and synthetic hectorite (86), have been evaluated for their ability to purify virgin fats and oils, but none were as good as acid-activated bentonite. 

The crystal structures of synthetic silica-magnesia and Filtrol SR catalyst have not been published. However, it has been reported that silica-magnesia is converted to a crystalline nonporous magnesium silicate when heated to about 1400°F. (354). 

Magnesol [Dallas]. TM for a synthetic, amorphous, adsorptive magnesium silicate. 

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