Diatomaceous earth, also known as diatomite or kieselgur, is historically the first ore used as filter aid. Originated by deposited and fossilized algae on the bottom of oceans and lake basins during and after the Miocene epoch, from 100.000 to 15.000.000 years ago, diatomite is dig out from deposits where it is present in stratifications with different height and clarity because of the presence of other aggregated chemical elements (calcium, iron, aluminium, etc.). After the extraction, the ore looks like soft and powdery whitish, gray or ivory coloured soil. Diatomite particles, when observed under the microscope, present a wide range of shapes that, in their turn, affect the filtration properties of the finished products (circular, cylindrical, needle-shaped, etc.). The ore is dig out from the deposits and pre-dried: it can be used then as “natural product” in a series of formulas as filler, carrier, etc. In order to produce filter aids instead, the pre-dried ore is then calcined at temperatures higher than 800°C in rotating kilns. The results of the calcination process are the so called “pink products”, a range of very thin products used to achieve fine and very fine filtrations. In order to obtain products with medium-fine, medium and coarse-sized particles, during calcination it is necessary to add a fondant salt facilitating particles sinteration and whitening. They are the so called “white products” or “flux-calcinated products”.
PALUMBO TRADING markets the whole range of diatomite-based filter aids and fillers produced in the United States by Dicalite Minerals Corp..