Inorganic aluminosilicates

Aluminosilicate Inorganic Compounds, Minerals, and Mineral Glasses Connections Forged by Quantum Chemistry and NMR Spectroscopy... 

J. Brus, L. Kobera, M. Urbanova, D. Kolousek, J. Kotek, Insights into the structural transformations of aluminosilicate inorganic polymers a comprehensive solid-state NMR study. J. Phys. Chem. C 116 (2012) 14627-14637. 

K.J.D. MacKenzie and M.J. Bolton, Electrical and Mechanical Properties of Aluminosilicate Inorganic Polymer Composites with Carbon Nanotubes. J. Mat. Sci., (Submitted). 

The slow reaction process is likely due to multiple factors including (I) hindered reaction kinetics and diffusivity within the viscous gel, (2) inadequate or sluggish dissolution of precursor powder, and (3) a limited potential of iron to form a potassium-based aluminosilicate inorganic polymer. Hematite is not expected to be very soluble in concentrated alkali hydroxide solution, although it dissolution is dependent on the alkali used such that solubility is highest in NaOH, followed by KOH and LiOH. It is expected that as maghemite, magnetite and hematite dissolve, Fe and Fe ions would be released and would then be free to interact with the silica gel. Iron is versatile and can exist in multiple oxidation and coordination states in the final material. In zeolite systems, the more dilute conditions favors the diffusion of iron and other species, and a more thermodynamically stable state can be reached. The use of water-soluble iron sources such as iron nitrate and potassium ferrate in hydrothermal conditions have been shown to be an effective way to produce iron zeolites in which iron is located in tetrahedral coordination. ... 

Dental silicate cement was also variously known in the past as a translucent, porcelain or vitreous cement. The present name is to some extent a misnomer, probably attached to the cement in the mistaken belief that it was a silicate cement, whereas we now know that it is a phosphate-bonded cement. It is formed by mixing an aluminosilicate glass with an aqueous solution of orthophosphoric acid. After preparation the cement paste sets within a few minutes in the mouth. It is, perhaps, the strongest of the purely inorganic cements when prepared by conventional methods, with a compressive strength that can reach 300 MPa after 24 hours (Wilson et al, 1972). 

In 1968 Wilson published an account of his early search for alternatives to orthophosphoric acid as a cement-former with aluminosilicate glasses. Aluminosilicate glasses of the type used in dental silicate cements were used in the study and were reacted with concentrated solutions of various organic and inorganic adds. Wilson (1968) made certain general observations on the nature of cement formation which apply to all cements based on aluminosilicate glasses. 

Taking this one step further, perhaps even an inorganic gene may have been provided by clay mineral sources. Earliest clay samples are of a mineral called montmorillonite that consists of sheets of aluminosilicates in which Fe2+, Fe3+ and Mg2+ are substituted for some of the Al3+, and Al3+ is substituted for Si4+. The oxygen content of the layers does not change and the alternative valencies allow the production of positive and negatively charged layers. Dramatically, Paecht-Horowitz and co-workers showed that the amino acid adenylate could be polymerised with up to 50 units on the montmorillonite surface in aqueous solution. Similar condensation reactions for carbohydrates on hydrotalcite surfaces have... 

Sealosafe A family of processes for encapsulating inorganic and organic wastes in a cementitious material suitable for landfill. The product, known as Stablex, is made from a cement and an aluminosilicate and may incorporate pulverized fly ash. Developed by C. Chappell in the United Kingdom in the 1970s and now operated in a number of countries. Offered by the Stablex Corporation, Radnor, PA. The environmental acceptability of the product has since been criticized. 

As a function of their structural properties, clays interact differently with organic and inorganic contaminants. Two major groups of clay minerals are selected for discussion here (a) kaolinite, with a 1 1 layered structured aluminosilicate and a surface area ranging from 6 to 39 m g" (Schofield and Samson 1954) and (b) smectites with a 2 1 silicate layer and a total surface area of about 800m g" (Borchardt 1989). 

The surface modification of an inorganic support with organophosphorus coupling agents (OPCA) is an extremely versatile route to hybrid materials. This route has been applied to a variety of supports, including metal oxides, metals, aluminosilicates, silica, metal hydroxides, and carbonates. 

Zeolites are aluminosilicate crystallines consisting of pores of molecular dimensions, interconnected by small windows(5-8A diameter). Strict regularity of the pore structure enables higher slectivities to be achieved in both catalysis and sorption processes. The intrazeolite circumstances alike a "solid-solvent" accomodate the selected reactant molecules and promote some inorganic and organic synthetic reactions, similarly in solution. 

Two alternative explanations have been suggested which are both quite speculative. First, portions of mineral surfaces of intermediate polarity (e.g., siloxane regions, -Si-O-Si-) may permit some exchange of polar water and nonpolar organic sorbates (Hundal et al., 2001). Such surfaces occur in minerals like the faces of aluminosilicates. However, amorphous solids like silica (-Si-OH) and alumina (-A1-OH) have very hydrophilic exteriors when these inorganic materials are suspended in water. Yet these amorphous materials still clearly show sorption of apolar substances (e.g., Mills and Biggar, 1969a Schwarzenbach and Westall, 1981 Estes et al., 1988 Szecsody and Bales, 1989 Farrell et al., 1999). 

The feldspars are aluminosilicates in which up to half the Si44 ions have been replaced by Al3+ ions. They are the most abundant silicate materials on Earth and are a major component of granite, a compressed mixture of mica, quartz, and feldspar (Fig. 14.45). When some of the cations between the crystal layers are washed away as these rocks weather, the structure crumbles to clay, one of the main inorganic components of soil. A typical feldspar has the formula KAlSi3Og. Its weathering by carbon dioxide and water can be described by the equation... 

Most metals occur in nature as minerals, the crystalline, inorganic constituents of the rocks that make up the earth s crust. Silicates and aluminosilicates (Section 19.7) are the most abundant minerals, but they are difficult to concentrate and reduce and are therefore generally unimportant as commercial sources of metals. More important are oxides and sulfides, such as hematite (Fe203), rutile (Ti02), and cinnabar (HgS) (Figure 21.1), which yield iron, titanium, and... 

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