Alumina silicate filters

Furthermore, perlite has been reported to be a suitable support for titanium dioxide nanomaterials [516-520]. Basically an amorphous alumina silicate (see Table 13), Perlite is an industrial mineral and a commercial product, useful for its light weight after processing. Due to its low density and relatively low price, many commercial applications for perlite have been developed including construction and manufacturing fields, horticultural aggregates, filter aid and fillers [519]. 

NaY zeolite is produced by digesting a mixture of silica, alumina, and caustic for several hours at a prescribed temperature until crystallization occurs (Figure 3-8). Typical sources of silica and alumina are sodium silicate and sodium aluminate. Crystallization of Y-zeolite typically takes 10 hours at about 210°F (100°C). Production of a quality zeolite requires proper control of temperature, time, and pH of the crystallization solution. NaY zeolite is separated after filtering and water-washing of the crystalline solution. 

In the process to produce alumina (Fig. 1), bauxite is crushed and wet ground to 100-mesh, dissolved under pressure and heated in digesters with concentrated spent caustic soda solution from a previous cycle and sufficient lime and soda ash. Sodium aluminate is formed, and the dissolved silica is precipitated as sodium aluminum silicate. The undissolved residue (red mud) is separated from the alumina solution by filtration and washing and sent to recovery. Thickeners and Kelly or drum filters are used. The filtered solution of sodium aluminate is hydrolyzed to precipitate aluminum hydroxide by cooling. The precipitate is filtered from the liquor, washed, and heated to 980°C in a rotary kiln to calcine the aluminum hydroxide. 

Alumina-pillared silicates were prepared by ion-exchanging the interlayer hexylam-monium ions with an excess of 0.086M-[Al13O4(OH)24(H2O)12]7+ liquid solution with stirring at 50 °C for 1 d, and then filtered, washed, and heated at 300 °C. After the XRD characterization, the measured free interlayer spaces are listed in Table 4.8. 

This alkali can only be obtained from either of the above minerals, which are silicates. One part of the mineral in fine powder is mixed with two of fluor-spar, and the mixture heated with sulphuric acid, until the whole of the silica is dissipated. There then remains a mixture of sulphates of alumina, lime, and lithia, and, in the case of lepidolite or spodumene, potash. By boiling with carbonate of ammonia in excess, the alumina and lime are precipitated, and the filtered liquid is evaporated to dryness, and ignited to expel the sulphate of ammonia. The residue is sulphate of lithra, or sulphates of lithia and potash. In the latter case, by the cautious addition of chloride of barium, the sulphuric acid is separated as sulphate of baryta, and the lithia and potash converted into chlorides. These being dried, are digested in absolute alcohol, which dissolves the chloride of lithium. The lithia is now free from other bases to obtain it in the separate state, the chloride is converted into sulphate, by being boiled with oil of vitriol, and the solution of the sulphate decomposed by the exact equivalent of barytic water, by which the sulphuric acid is precipitated, while the free lithia is dissolved, and the solution, if evaporated, leaves hydrate of lithia, LO, HO. 

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