Oxidations using clays

Siilfuric acid from iron pyrites Paint pigments roasting of metallic oxides Refractory clays calcination of refractory clay to reduce shrinkage Foundry sand removal of carbon from used foundry sand Fullers earth calcination of fuller s-earth material... 

Pick-up of stray current (a.c. or d.c.) (Section 10.5). Decreased use of d.c. in many areas has led to less possibilities of pick-up of direct current from utilities, mines, etc. The importance of grounded a.c. systems has been discounted, but Waters has shown that alternating currents can accelerate corrosion. Furthermore the rectifying effects of oxide films, clay minerals and other soil factors are not understood. 

Ceramics and minerals present many common problems, but ceramics warrant special treatment because elements of low atomic number predominate in them and they consequently offer x-ray emission spectrog-raphy of the light elements an excellent opportunity to prove its usefulness. Scott,8 in making this clear, emphasized the absorption and enhancement effects to be expected, and pointed out the need for careful sample preparation. By use of a General Electric XRD-5 spectrograph and associated equipment, he set up working curves for alumina, silica, potash, lime, phosphate, titania, and iron oxide in clays, refractories, and other ceramic materials. 

Environmental Fate. It is not known if 3,3 -dichlorobenzidine, like benzidine, is oxidized by clay minerals or if cations in water ean have the same oxidizing effect. 3,3 -Dichlorobenzidine does not appear to biodegrade easily, but the few studies in this area did not state the type(s) or concentrations of mieroorganisms used in eaeh study. More systematic studies with other organisms may prove useful. A reeent study (Nyman et al. 1997) provides evidence that in the span of a year up to 80% of 3,3 -dichloro-benzidine can degrade to benzidine in anaerobic mixtures of sediment/water. Further research to identify the pathways and produets of deeomposition of 3,3 -dichlorobenzidine in various soils is needed. The toxieologieal profile for benzidine eontains information on the environmental fate of that compound (ATSDR 1995). 

Dispersant Activity Tests were conducted utilizing iron oxide and clay suspensions in order to establish the efficacy of the copolymers as dispersants for suspended particulate matter. Kaolin clay was used for the clay dispersion study. According to the procedure, separate 0.1% iron oxides and 0.1% clay suspensions in... 

A number of clays are layered silicate-like materials. Most clays contain finely divided quartz, micas, and feldspars. Iron oxide-rich clays are employed to make pottery and terracotta articles. Clays containing iron oxide and sand are used to make bricks and tiles. Clays rich in calcium and magnesium carbonate are known as marls and are used in the cement industry (Section 12.2). 

Summarizing, the efficiency of the oxidant use can substantially be improved with a hydrophobic LDH. There seems to be an optimum surface polarity, which in the present set of catalysts is most closely approached by the pTos-exchanged material. Similar effects of surface polarity on catalytic performance have been observed for cationic clays [16]. 

Besides using the EPR to evaluate the binding capacity of NOM for metal ions, it is also possible to use the latter as spin probe (Senesi, 1990a). Analyses of spectroscopic data comprise studying the adsorptive properties, surface interactions, and structural chemistry of soil, synthetic metal oxides, hydrous oxides, and clay minerals (McBride et al., 1984 Coyne and Banin, 1986 Senesi et al., 1991a Spagnuolo et al., 2004). 

Many cation-exchanged clays are suitable for the production of metal-oxide-pillared clays. The hydrolysis of the cation helps the pillaring step, so, at first, the aluminum ion was applied as a pillaring agent. Later, other elements were also used, for example, zirconia chromium iron transition metal elements and some lantanoids, organometallic complexes, surfactants, and polymers. 

The acidity of pillared clays has been characterized by both microcalorimetric measurements of the adsorphon of aromatic molecules and pyridine and the catalytic ethylbenzene test reaction [111]. The aromatic probe molecules used were a reactant and a product of the catalytic reaction ethylbenzene and m-diethylben-zene, respectively. In this way, only the strongest of the accessible acid sites were htrated. The heats of adsorphon of these molecules indicate that a zirconium oxide pillared clay had stronger acidity than an aluminum oxide pillared clay, whereas the pyridine results were equal for both samples. 

Many studies that have investigated the effects of different geochemical properties on adsorption of As species have used controlled laboratory experiments to evaluate adsorption of As by pure mineral phases such as Fe, Al, and Mn oxides, and clay minerals. Since these mineral phases are often components of aquifer solids, the data from such experiments can be used to help interpret the behavior of As in groundwater. Such an approach has commonly been used to assess As adsorption by soils and lacustrine sediments (Belzile and Tessier, 1990 Bowell, 1994 Fordham and Norrish, 1979 Jacobs et al., 1970). 

The discovery of NS-W was a fluke. In the early days of wire fabrication (1910-1925), it was realized that the source of the tungsten oxide used for metal powder fabrication played an important role in determining the wire quality [6.7]. Tungsten filaments, originating fix>m material which was treated in clay crucibles, preferably those manufactured by the Battersea Company near London, were shown to be much more stable in shape at incandescent temperatures. Subsequent chemical analysis indicated that a... 

A method based on a shift in pH induced by addition of BaCl2 was used in [663]. Certainly, such a method does not produce a pristine PZC. A boehmite layer on aluminum was studied in [3018] by means of the streaming potential, which is not a suitable method for such a system. In [125], an intersection point of charging curves is reported for composites containing Fe and Al oxides and clay minerals. Intersection of two charging curves is generally not recommended as a method to determine the PZC, especially for clay minerals, which usually do not show a CIP of charging curves (see Chapter 2). The results reported in [933] refer to very basic pH, without adequate COj protection. The powder used in [3019] reacts with the solution. 

The titanium oxide used for the present experiment was first grade experimental TiO 2. The Korean kaolin used was a clay primarily consisting of kaolin ore, having the chemical formula SiO 2 -A1 2 0 s. 

Eventually, the average masses N(t) and 5(0 depend on the mass value affected to each aggregate constituent. For monosized latex particles the mass 1 is attributed to single particles. When, as for oxides and clays, the original colloid is polydisperse in mass and size, the mass 1 is attributed either to particles of diameter d, of the smallest constituent (as for aluminum oxide) or to particles characterized by the average diameter dn given by the counter (as for the kaolinite clay). This choice only affects the absolute values of 5(f) or N(t) but does not modify the exponents of the power laws used to express fragmentation and breakup rates. 

Copper nitrate on montmorillonite (Claycop) has been used with acetic anhydride to nitrate chlorobenzene in 100% yield, giving 13 85 orthdpara isomers.249 When an iron oxide pillared clay was used, 94% para-isomer was obtained.250 Claycop and its iron analogue have been used to oxidize a pyrazoline to a pyrazole (6.47) in 64-97% yields.251... 

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