Pink diatomite

It has been well established that the surfaces of diatomites are covered with silanol (Si-OH) and siloxane (Si-O-Si) groups. Pink diatomite is more adsorptive than white this difference is due to the greater surface area per unit volume rather than to any fundamental surface characteristic. Pink diatomite is slightly acidic (pH 6 to 7), whereas white diatomite is slightly basic (pH 8 to 10). Both types of... 

Gas chromatography (GC) employs a gaseous mobile phase, known as the carrier gas. In gas-liquid chromatography (GLC) the stationary phase is a liquid held on the surface and in the pores of a nominally inert solid support. By far the most commonly used support is diatomaceous silica, in the form of pink crushed firebrick, white diatomite filter aids or proprietary variants. Typical surface areas of 0.5-4 m2/g give an equivalent film thickness of 0.05-1 pm for normal liquid/support loadings of 5-50 per cent by mass. 

The pink or brick diatomite has been crushed, blended and pressed into bricks, which are calcined (burned) at temperatures greater than 900°C. During the process the mineral impurities form complex oxides and/or silicates. 

These are prepared by crushing the diatomaceous earth, pressing it into brick form, and then calcining it above 9(X)°C. The characteristic pink color is probably due to the formation of an iron oxide from complete silicates. In the case of the white diatomite, the absence of pink color is probably due to the reaction of the sodium carbonate with iron oxide to form a colorless complex sodium iron silicate. A number of pink diatomaceous supports are commercially available the more common of these are Anakrom P, Chromosorb P, Diatomite S, and Gas-Chrom R. 

Diatomite Supports. Basically, two types of support are made from diatomite. One is pink and derived from firebrick, and the other is white and derived from filter aid. German diatomite firebrick is known as Sterchmal. Diatomite itself, diatomaceous... 

Calcined diatomite - Also known as straight-calcined, this is diatomite which has been calcined at between 870° and 1100°C in a rotary kiln. This process bums off organic matter, converts some of die opaline silica to ciistobalite, shrinks, hardens, and reduces the fine stmcture of individual particles, and forms agglomerates or clusters of particles duough fusion. The overall effect is to decrease surface area but to increase bulk density and void volume due to the nature of agglomerate packing. Calcination generally turns the white to off-white natural diatomite pink fi om iron oxidation. The ealcined diatomite is carefiiUy milled, sereened, and air classified to various size fi actions, primarily for filtration uses. 

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