Water treatment sodium zeolite

Sodium aluminate, 2 345t, 358-359 analysis, 2 275-276 economic aspects, 2 275 health and safety factors, 2 276 manufacture, 2 274-275 neutralization, 2 424 physical and chemical properties of, 2 273-274 uses of, 2 276-277 in water treatment, 26 111 Sodium aluminosilicate gels, synthetic zeolites prepared from, 16 831t Sodium aluminosilicates, 12 578 Sodium aluminum hydride, 13 621, 623-624... 

Using thallium—sodium zeolites of type X (n = 2.30), we observed an increase of adsorption capacity for water vapor and benzene at 38% replacement of sodium ions by thallium ions, and then its decrease with an increase in the degree of exchange. As thallium ions replace sodium ions in the position Sm (25) we may assume redistribution of cations at dehydration under the conditions of high vacuum and thermal treatment at 350°C, and stronger chemical bonds of thallium atoms in screened positions in comparison with sodium atoms. 

Exchange resins are taking the place of zeolites for certain water treatment. Thus, although a zeolite will replace calcium sulphate in water by sodium sulphate, a mixture of an anionic exchanger with a cationic one wil 1 remove all the dissolved inorganic salts. This demineralisation, as it is termed, is being used increasingly in industry, particularly for boiler-water treatment. 

Sodium silicoaluminate Sodium tetraborate pentahydrate Tetrasodium iminodisuccinate Tetrasodium pyrophosphate . Zeolite synthetic softener, water treatment Calcium hydroxide Calcium oxide ... 

Important inorganic aluminum compounds are aluminum sulfate (e.g., for water treatment), potassium alum (KA1(S04)2-12H20 e.g., for tanning skins, mordants, coagulating agents, styptic pencils, cosmetics, and hardening and setting acceleration in the production of marble cement and alabaster plaster), sodium and barium aluminates (e.g., for water purification, acceleration of concrete solidification, production of synthetic zeolites, in the paper industry, and in the enamel industry), and the Friedel-Crafts catalyst aluminum chloride [4]. 

Zeolites are naturally occurring hydrous aluminum-sodium silicates in porous granule form. They are capable of exchanging their sodium base for calcium or magnesium and of expelling these alkaline earth metals for sodium by treatment with salt. Thus, they are a type of ion-exchange media. (Some zeolites act as molecular sieves by adsorption of water and polar compounds.)... 

A preformed chitosan-silica composite with 60% weight inorganic part [7] is used as the source of silica for the zeolite synthesis. An alkaline solution of sodium aluminate (Na 2.1 M, Al 1 M) was used in three methods of preparation (A) beads of the chitosan-silica composite were stirred overnight in the aluminate solution, extracted and submitted to a hydrothermal treatment at 80 °C during 48h (B) beads of the chitosan-silica composite were immersed in the aluminate solution and the system underwent a hydrothermal treatment at 80 °C for 48h (C) beads of the chitosan-silica composite were stirred overnight in the aluminate solution, extracted, dried at 80 °C and exposed to water vapour at 80°C during 48h. 

Replenishing the sodium 10ns of a zeolite of similar ion-exchange agent by treatment with sodium chloride solution. Molecular sieves are regenerated by heat removal of the water (200°C), followed by treatment with an inert gas. 

The standard zeolite synthesis solution chosen [82,97,98] was characterised by the molar ratios 100 Si02 15 (TPA)20 5.3 Na2O 1420 H2O. The mixture was obtained by mixing sodium hydroxide (Merck, > 99%) and TPA hydroxide in water to which silica (Baker, 99.75%) was added. The silica was dissolved at 100°C in about 300 s after which the solution was cooled down to room temperature in 1.5 h and aged (at 25°C) for an additional 1.5 h. The pH of the solution was > 12.5. To control crystal size and layer thickness, hydrothermal treatments were applied in a stainless steel autoclave under autogenous pressure at temperatures of 40-180°C for 10-200 h with the support on the bottom of the autoclave. 

The sodium ions of Na zeolite Y may be substituted by ammonium ions [110]. The degree of hydration of the NH4Y depends on the thermal treatment water is retained up to 373 K and lost at 473 K. The sodium ions may be replaced partly by ammonium ions and partly by caesium ions. Ammonium ions may also be introduced by treatment of the acidic zeolite with ammonia gas. The caesium ions occupy the supercages and the ammonium ions are restricted to the sodalite cages. 

There are many other methods of preparing active synthetic silica-alumina catalysts. A fair catalyst can be made by impregnating dried silica gel with an aluminum compound which is easily converted to the oxide by calcination, e.g., A1(NC>3)3. A preferred impregnation technique is to soak a sodium-free silica hydrogel in a solution of an aluminum salt and to follow this with an aqueous ammonia treatment to precipitate the hydrous alumina on the silica (Thomas, 16 Ryland and Tamele, 17). It should be noted that silica hydrogel can easily be freed of sodium ions by water washing, since it is not a zeolite. Exceptionally pure silica-alumina composites can also be prepared by the hydrolysis of mixtures of ethyl orthosilicate and aluminum alkoxides (Thomas, 18). 

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