Diatomaceous Earth Filtration

Diatomaceous Earth Filter Aids

To see why diatomaceous earth is a great filtration media and filter aid, you’d have to view it under a microscope. Diatoms have a wide variety of shapes and a honeycomb-like structure. The pores with

in and between the cell walls are so small, they trap bacteria, clay particles, some viruses, and other suspended solids from liquids, leaving liquids cleaner and with drastically reduced solids and contaminant levels.

The packing of the small diatoms is irregular and creates a complex matrix with a very high porosity. This allows the filter media to both remove very small particles and extend the flow rate of the material being filtered. The high solids holding capacity of diatomaceous earth allows for much longer filter cycles (allowing more solids to be removed) than what would be possible with other filtration methods.

General Filtration Considerations

Filtration is the separation of solids from liquids by forcing the liquid to flow through a porous filter medium and depositing the solids on the medium. A filter aid is a finely divided material which when added to the liquor to be filtered helps control flow and solids removal. The septum, usually screen or cloth, serves principally as a support for the cake. The filter aid is the filtering medium that traps the solids being removed and prevents them from blinding the septum.

Filter aid filtration is mechanical, not chemical in nature. Irregularly shaped particles interlace and overlay in a fashion that leaves voids or open spaces. These voids form billions of microscopically fine interstices between the filter aid particles. The size of these openings is so minute that the unwanted solids are strained from the liquid. The vast number of openings compensates for their small size resulting in fast flowrates and brilliant clarity.

What Makes a Superior Filter Aid?

Dicalite Management Group’s superior mineral filter aids are light in weight, chemically inert, and form high porosity filter cakes to maintain a free flow of the liquid. The structure of the particles must be such that they will not pack too closely. This not only permits high initial liquid flow but also provides pore spaces to trap and contain the filterable solids and leave a high percentage of channels remaining open for flow. Particle size distribution must be tailored to permit precoating on coarse wire and yet give the desired flow rate and clarity. Diatomaceous earth, perlite, and cellulose are widely used materials that meet these criteria.

Time to Take a Closer Look at Your Filter Aid Requirements

• Low density and rigid, irregular particles allow the material to form a porous matrix with up to 85 % void volume, as the particles interlace and overlay on each other.
• This matrix then functions as a superfine microsieve.
• Mineral filter aid filtration (depth filtration) is mechanical sieving, not a chemical treatment.
• In some fluids, filter aids can be slightly adsorptive, but this effect is negligible. Generally, filter powders are not adsorbents like bleaching earth or powdered activated carbon.