Silicates aluminosilicates

Site-binding constants have been determined for only a limited range of simple oxides with only one type of surface site. Multiple-surface site minerals occurring in the deep-well environment such as silicates, aluminosilicates, and complex oxides (such as manganese oxide) will require much more complex TLMs. 

Anhydrite, CaSC>4 Barite (trace), BaSC>4 Cubanite (trace), CuFe2S3 Wurtzite (trace), ZnS Covellite (trace), CuS Marcasite (trace), FeS2 Unidentified silicates, aluminosilicates (traces)... 

One of the major problems associated with beneficiation of PGM from sulphide-dominated deposits is the presence of hydrophobic gangues, such as talc, chlorites, carbonates and aluminosilicates. The concentrates produced in most of the Morensky Reef operations (South Africa) varies from 80 to 150 g/t of combined PGM, where most of the contaminants are silicates, aluminosilicates and talc (i.e. up to 60%). The major hydrophobic gangue depressants used are carboxymethyl cellulose (CMC) and different modifications of guar gums. 

In contrast to the partial pressure, temperature rise does not generally contribute to the increase of the solubility. According to the principle of the smallest constraint (Le Chatelier), only endothermic dissolutions, i.e. reactions, which need additional heat, are favored (e.g. dissolution of silicates, aluminosilicates, oxides, etc.). Yet the dissolution of carbonates and sulfates is an exothermic reaction. Therefore the solubility of carbonates and sulfates is less favorable with increasing temperature. 

There has been recent interest in a somewhat different aspect of adsorption and reaction on metal oxides photocatalysis. The interest stems partially from that role that some transition-metal oxides can play in photochemical reactions in the atmosphere. Atmospheric aerosol particles can act as substrates to catalyze heterogeneous photochemical reactions in the troposphere. Most tropospheric aerosols are silicates, aluminosilicates and salts whose bandgaps are larger than the cutoff of solar radiation in the troposphere (about 4.3 eV) they are thus unable to participate directly in photoexcited reactions. However, transition-metal oxides that have much smaller bandgaps also occur as aerosols — the most prevalent ones are the oxides of iron and manganese — and these materials may thus undergo charge-transfer excitations (discussed above) in the pres-... 

A new family of silicate/aluminosilicate mesoporous molecular sieves designated as M41S and kanemite were introduced a few years ago (39-43), and NMR investigations have been done to characterize those materials. 

Both the rigid ion and shell potential models have been used in energy minimization studies of dense and microporous silica and molecular sieves. Kramer and coworkers reported parameters of the rigid ion potential model for silicates, aluminosilicates, and aluminophosphates. The model also includes parameters for extra-framework cations such as Na and Cl . Both the rigid ion and shell models were used by Catlow and coworkers in modeling silicate and zeolite structures. ... 

Kramer and co-workers used ab initio calculations of H4TO4 (T = Si, Al, P) clusters to derive parameters for the rigid ion potential model. The potential energy surface of the clusters was scanned along two modes of distortion, and the resulting potential curves were fitted using Eq. [15]. The set of parameters was refined by the use of experimental data on a-quartz. This procedure resulted in a parameterization that well reproduced both structure and elastic moduli of silicates, aluminosilicates, and aluminophosphates. Subsequently, this approach was extended to protonated forms of zeolites. ... 

Supports other than AI2O3 for Co-Mo catalysts have included Si02, MgO i60 i6i Xi02-Zr02, Mg aluminate, Mg silicate,aluminosilicate, Na montmoriUonite, and carbon (see below). 

Porous materials discussed at the International Conference on Materials for Advanced Technologies 2005 included clay minerals, silicates, aluminosilicates, organosilicas, metals, silicon, metal oxides, carbons and carbon nanotubes, polymers and coordination polymers, or metal-organic frameworks (MOFs), metal and metal oxide nanoparticles, thin films, membranes, and monoliths (Zhao, 2006). 

Decompaction Due to Solution of Binding Compounds of Sandstones (Carbonates, Silicates, Aluminosilicates)... 

Silicon Solid-state Chemistry. Following the pattern set in the previous volume, this aspect of silicon chemistry will be subdivided into four sections in which the literature published on silicon dioxide, silicates, aluminosilicates, and zeolites is described separately. In all four sections, emphasis will be laid on the inorganic chemistry of these materials, and papers describing solely their... 

A review of those silicates containing octahedral SiOg groups has been effected, and a total of 37 references are quoted. A review of the hydro-thermal method for the synthesis of crystals has been compiled by Kuznetsov and Lobachev included in the review is a detailed consideration of the growth of silicates, aluminosilicates, and other related minerals. 

Blast furnace slag (BFS) is a nonmetallic co-product produced in the process. It consists primarily of silicates, aluminosilicates, and calcium-alumina silicates. The molten slag, which absorbs much of the sulfur from the charge, comprises about 20% by mass of iron production. 

Montmorillonite, silicate, aluminosilicate, titanosilicate, calcium phosphate, zirconium phosphate, metal oxides, and heteropolyacids composites with Nation exhibit in general a modest barrier effect to methanol permeation (F, > 0.1), with a couple of exceptions aCloisite lOA composite [62] with 0.013 < F, < 0.065, and a chitosan-functionalized montmorillonite composite [71] with 0.028 < F < 0.050, in both cases for clay contents between 1 and 10 wt%. 

MCM-41 molecular sieves with different chemical composition (silicates, aluminosilicates, titanosilicates) can be prepared by a liquid-crystal templating method with good reproducibility. When an auxiliary organic compound is used in order to enlarge the pore size a tuning of the synthesis procedure is needed. 

As the synthesis of materials with pores considerably varying in their size and differing in their chemical composition (silicates, aluminosilicates, titanosilicate) was aimed at, three procedures were used. Tab.1 and 2 present an overview of samples prepared with procedures used. As concerns the chemical composition of sieves, SiMS, AIMS and TiMS stand for a silicate, aluminosilicate and titanosilicate, respectively. The number after the hyphen corresponds to the serial number of the sample in laboratory records. All aluminosilicate sieves contained 3.1 mol % of AI2O3. The content of Ti in titanosilicates is given in Tab.1 (determined by AAS). 

The MCM-type materials belong to a new family of ordered, mesoporous silicate/aluminosilicate prepared by hydrothermal formation of silica gels in the presence of surfactant templates (Beck et al., 1992). They were discovered only recently, by Beck et al. in 1992, and hold promise for a number of interesting applications. Hence they are included in this chapter. 

The combination of HMDO and trimethylsilyl chloride has been used to sUylate a family of silicate/aluminosilicate mesoporous molecular sieves. ... 

ILs can also be covalently immobilized on inorganic materials of silica, mesoporous silicates, aluminosilicate, and alumina. For that three ways are known (Scheme 10). The first method is the co-condensation of a trialkoxysdylalkyl onium salt and triethoxysilane (Scheme 10-A) [37-39]. The second one is the immobilization by the reaction between surface hydroxyl groups of the solid and the alkoxysilyl group (Scheme 10-B) [40,41]. For the last one (Scheme 10-C), the inorganic materials modified with alkyl halide (usually propylchloride) are used [42-46] on them, corresponding amine, phosphine, or pyridine can be immobilized and quaternized. For the preparation of imidazolium-based immobilized IL, imidazole is fixed on the modified support in the presence of alkali compounds, followed by quaternization with alkyl halides. 

Similarly detailed information on the chemistry of atoms at. surface sites and on the relationships of such sites to surface reactivity may be obtained for oxide, silicate, aluminosilicate and other minerals using XPS in a.s.sociation with EXAFS and adsorption studies. The reviews by Bancroft and Hyland [481. and Brown et al. [16], provide many examples of the types of information obtainable for these surfaces. 

The study of the products of the oxidation reaction of powders or monociystals (SiC) up to temperatures of 1,600°C shows that the silica layer is amorphous and then crystallizes gradually into cristobalite finm 1,100°C onwards. For sintered materials that contain impurities or sintering additives, the nature of the formed products is much more complex (silicates, aluminosilicates, etc.). However, for all these materials, the oxidation reaction results in a volume expansioa The coefficient of expansion, which represents the ratio of the molar volume of silica or silicates on the molar volume of SiC (or Si3N4>, is higher than one. The reaction product is covering and protective. 

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