Alumina hydrous

We applied a nonlinear least squares method to determined the four constants Ki, Kj, Ni, and Nj in Eq. (3). The eonstants that gave the best fit with the experimental data are listed in Fig. 3. The solid line in Fig. 3 represents the theoretical curve calculated from Eq. using the constants. Figure 4 shows a comparison of the proton-binding capacity of HA with that of some inorganic adsorbents such as silica gel (Silikagel H and Aerosol 200), hydrous titanium oxide (HTiO), y-alumina, hydrous throium oxide (HThO), and magnetite. It is evident that the number of... 

Figure 1 shows the decomposition sequence for several hydrous precursors and indicates approximate temperatures at which the activated forms occur (1). As activation temperature is increased, the crystal stmctures become more ordered as can be seen by the x-ray diffraction patterns of Figure 2 (2). The similarity of these patterns combined with subtie effects of precursor crystal size, trace impurities, and details of sample preparation have led to some confusion in the Hterature (3). The crystal stmctures of the activated aluminas have, however, been well-documented by x-ray diffraction (4) and by nmr techniques (5).

Two pigment production routes ate in commercial use. In the sulfate process, the ore is dissolved in sulfuric acid, the solution is hydrolyzed to precipitate a microcrystalline titanium dioxide, which in turn is grown by a process of calcination at temperatures of ca 900—1000°C. In the chloride process, titanium tetrachloride, formed by chlorinating the ore, is purified by distillation and is then oxidized at ca 1400—1600°C to form crystals of the required size. In both cases, the taw products are finished by coating with a layer of hydrous oxides, typically a mixture of siUca, alumina, etc. 

Purification actually starts with the precipitation of the hydrous oxides of iron, alumina, siUca, and tin which carry along arsenic, antimony, and, to some extent, germanium. Lead and silver sulfates coprecipitate but lead is reintroduced into the electrolyte by anode corrosion, as is aluminum from the cathodes and copper by bus-bar corrosion. 

Clays used in foundries include hydrous alumina silicates, known as bentonites. Their properties provide cohesion and plasticity in the green state and also high strength when dried. There are three clays that are commonly used in foundries western bentonite [sodium bentonite, burnout point 1290°C (2350°F)], southern bentonite [calcium bentonite, burnout point 1065°C (1950°F)], and fire clay [kaolinite, burnout point 1425°C (2600°F)]. 

Hydrotreating catalysis, molybdenum compounds in, 17 37-38 Hydro trioxides, 18 435-436 Hydrotrioxides, formation of, 17 784. See also Hydrogen trioxide Hydrotropes, cosmetic surfactants, 7 834t Hydrous aluminas, decomposition sequence, 2 392... 

Zutib, V., and J. Tomaic (1988), "On the Formation of Organic Coatings on Marine Particles Interactions of Organic Matter at Hydrous Alumina/Seawater Interfaces", Mar. Chem. 23,51-67. 

Tomaic, J., and V. Zuti6 (1988), "Humic Material Polydispersity in Adsorption at Hydrous Alumina Seawater Interface", J. Colloid and Interface Sci. 126, 482-492. 

Zutic, V., and W. Stumm (1984), "Effect of Organic Acids and Fluoride on the Dissolution Kinetics of Hydrous Alumina. A Model Study Using the Rotation Disc Electrode", Geochim. Cosmochim. Acta 48, 1493-1503. 

A number of reagents containing oxide components are used in zeolite manufacture [19]. Silica is provided by addihon of sodium or other alkali silicate solutions, precipitated, colloidal, or fumed silica, or tetraalkylorthosihcate (alkyl = methyl, ethyl) and certain mineral silicates such as clays and kaolin. Alumina is provided as sodium aluminate, aluminum sulfate soluhon, hydrous aluminum oxides such as pseudo boehmite, aluminum nitrate, or aluminum alkoxides. Additional alkali is added as hydroxide or as halide salts, while organic amines and/or... 

With hydrous zinc oxide there is a slight adsorption of yellow alizarinic acid and purple sodium alizarate. A variation in the degree of acidity with stannic oxide and zinc oxide will give all variations of color between yellow and purple, while the presence of alumina introduces a red. This accounts for the fact of alizarin being what is called a polygenetic color, because the color varies with the nature of the mordant. Other examples of this class are said to be cochineal and logwood but we have not yet studied these dyes. 

Adsorption of mercury. All chemicals used were Merck or Baker analytical quality reagents, unless stated otherwise. From the commercially available adsorbents the following were used silica gel 60 A porosity, 0.063-0.200 mm particle size (Merck) charcoal 0.3-0.5 mm particle size, gas-chromatographic quality (Merck) alumina R Woelm hydrous zirconium oxide HZ0-1, 100-200 mesh, (Bio-Rad). Except for zirconium phosphate, which was prepared according to Amphlett ( ), all other sorbents were prepared by coating (precipitation) on acid-purified silica gel, as described in (1 ). The Si0 -NH was prepared according to Leyden et al (11). L... 

As with other hydrous metal oxides, such as alumina and zirconia, tin oxide is an amphoteric ion exchanger that exhibits cation exchange properties at basic pH. Hydrous tin oxide, however, appears to be particularly favored by virtue of its high Sr(ll) distribution coefficient (Kd Sr-bound/Sr-free) and high separation factor, Kd[Sr(ll)/Rb(l)], over a broad pH range (Table II Figure 1). 

Experimental phase equilibria studies by Campbell and Fyfe (1965) Thompson (1971)and Liou (1971a) indicate an approximate 180°C. lower stability for albite in the presence of quartz and analcite from 12 to 2000 atmospheres pressure. A calculated stability for analcite at 3Kb is about 120°C. (Campbell and Fyfe, 1965), conditions equivalent to rock pressures at 7.5Km depth. However, if water pressure is lower than total, litho-static pressure, the termal stability of a very hydrous, low-density mineral such as analcite can be significantly lowered (Greenwood, 1961). The experimental transformation of alkali zeolites to analcite at 100°C. and 2-3 atmospheres pressures was demonstrated by Boles (1971). The alumina content of the alkali zeolites used in this latter study was found to influence that of the analcite produced, and this independently of the amount of crystalline quartz added to the initial materials. 

In Figure 10 the experimental ZPCs of hydrous silica-alumina coprecipitates (64) are compared with those of dried and ignited silica-alumina catalysts (49), some of the previously discussed aluminosilicate minerals, and the composition dependence derived from Equation 18 assuming ... 

Hanning [4], Miller and Ishida [5], and McKenzie and Koenig [6] favored transmission measurements using FT-IR for monitoring silanized mica quantitatively. Berger and Desmond [3] demonstrated the ability of FT-IR diffuse reflectance measurements to quantitate various silanized substrates including mercapto silane on hydrous clay and epoxy silane on alumina trihydrate. Later Vagberg el at. 

Rajan, S. S. S. (1978). Sulfate adsorbed on hydrous alumina, ligands displaced, changes in surface charge. Soil Sci. Soc. Am. J. 42, 39-44. 

Sorption on oxides and hydrous oxides has been extensively studied both experimentally and theoretically. In order to define an ideal oxide or hydrous oxide exchanger, we will rely on experiments with well-defined sorbents such as chromatographic alumina (1-4). Briefly, the adsorption characteristics of oxides and hydrous oxides are (1) At high pH, they act as cation exchangers but with less sensitivity to the total salt concentration than clay minerals. This behavior is illustrated in Figure 2, where sorption of strontium on alumina is shown. 

Hohl, H. and Stumm, W. (1976) Interaction of lead(2+) with hydrous y-alumina.J. Coll. Interface Sci., 55, 281-288. 

Several other processes for producing alumina based on ores other than bauxite have been announced. One process uses alunite, a hydrous sulfate of aluminum and potassium. It is claimed to be capable of producing 99% pure alumina from alunite containing only 10 to 15% alumina, compared with bauxite that assays 50% alumina. The alunite is crushed, dehydroxy-lated by heating to 750°C, ground, and treated with aqueous ammonia. Filtration removes the alumina hydrate, and potassium and aluminum sulfates are recovered from the filtrate (to be used as fertilizer constituents). The alumina hydrate is treated with sulfur dioxide gas, and the resulting aluminum sulfate is converted to alumina by heating in a kiln. 

Property Calcium carbonate Kaolin Talc Mica Glass microballoons Hydrous alumina Silica Wood flour... 

By October 1949, I started experimenting with crystallization at 100 C, reasoning that the higher water content zeolites with larger pore volumes and, presumably, larger pore sizes, would be more likely to crystallize at temperatures lower than 200 -300 C. In nature the anhydrous aluminosilicates were formed at relatively high temperatures, and the hydrous ones were believed to have been formed later as the earth s surface cooled. Not surprisingly, when we first tried low temperature synthesis with relatively insoluble silica and alumina in mildly alkaline solutions, there was no reaction in reasonable time periods. 

Zeolites — are any of various natural or synthesized hydrous framework silicates, consisting of interlocked tetrahedrons of SiC>4 and AIO4, with a ratio (Si + Al)/0 equal to 0.5. Z. were firstly discovered and named in 1756, by the Swedish mineralogist Axel Fredrick Cronst-edt, in case of stilbite. Other natural z., as, e.g., analcime, heulandite, natrolite, and stilbite, are often formed near volcanic activity centers, have been formed from rocks by interaction with alkaline groundwaters. Synthetic z., produced since the 1930s, can be made by a slow crystallization process of a silica-alumina gel in the presence... 

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