Grain coat

This special form of granular iron hydroxide consists of sand grains coated with iron hydroxides. This material has very good mechanical properties and a high content of the active phase iron hydroxide (RFA 56 % Fe203). 

Fungicides have caused a number of human health disasters. In the late 1950s, approximately 4000 people in Turkey were poisoned by hexachlorobenzene that had been applied to seed grain to protect against soil fungus. Adults and particularly children developed diseases of the skin and bone. In Iraq, a similar incident occurred when people consumed grain coated with a mercury compound. 

CA 60, 10472(1964) [Trilaminar expl was prepd by coating granular AN at 115° with 2-5% Nitron aphtha lene (mp 90°). Then the temp was reduced to 80°, and the grains coated with 2—20% TNT (mp 74°). Finally the mass was placed in a rotary drum with wood balls (maintained at 50°) and, while agitating, the grains were coated with 2—10% mixture of Al, activated charcoal (or powd coal) ]... 

This is relevant for calculating extinction of dust grains coated by an ice mantle, e.g. for dust in molecular clouds or in the cool (T < 150 K) parts of accretion disks. 

Zachara, J.M. et al., Oxidation and adsorption of Co(II)EDTA2- complexes in subsurface materials with iron and manganese oxide grain coatings, Geochim. Cosmochim. Acta, 59, 4449, 1995. 

Aase N. E., BjprkumP. A., and Nadeau P. H. (1996) The effect of grain-coating microquartz on preservation of reservoir quality. Am. Assoc. Petrol. Geologists 80, 1654-1673. 

Preliminary experiments on such a strategy of coupled separation and photodegradation were carried out on a simplified experimental device schematically represented in Figure 25.15a. It consists of two tanks separated by a 1.8 pm pore size alumina microfiltration symmetric membrane with grains coated with an anatase layer. The feed tank contained methylene blue (MB) and the reception tank was initially filled with pure water. Under continuous UV irradiation, MB is completely destroyed as it arrives in the reception tank (Figure 25.15b). The quantity of destroyed MB per surface area unit is equal to 1.0 X 10 mol.s. m . 

Cracker ball. Each of these is spherical and about 10 mm in diameter. When it is thrown on the ground or other hard surfaces it explodes. The construction is shown in Fig.136. A quantity of sand grains coated with... 

Ehrenberg, S.N. 1993 Preservation of anomalously high porosity in deeply buried sandstones by grain-coating chlorite examples from the Norwegian continental shelf. Am. Assoc. Pet. Geol. Bull., 77 1260-1286. 

Calcareous soil Very weakly cemented or uncemented soil with small carbonate accumulations as grain coatings, patches of powdery carbonate including needle-fibre calcite, carbonate-filled fractures and small nodules... 

A CA approach described zinc adsorption on aquifer sand material from Cape Cod by assuming that the aluminum and iron phases present in the quartz grain coatings have a surface area and site density similar to those of poorly crystalline materials (Davis et al., 1998). A similar approach provided only a semiquantitative prediction of uranium adsorption on an alluvial aquifer sediment from Naturita, Colorado, depending on the assumptions made about the relative amounts of surface area of quartz, ferrihydrite, and goethite (Davis et al., 2004). In both of these studies, the surface complexation model considered... 

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