How does diatomaceous earth improve filtration of difficult slurries?

Diatomaceous earth improves the filtration of difficult slurries by acting as a filter aid. When a slurry contains solids that are extremely compressible, gelatinous, or slimy, these materials often tend to "blind" or clog the filter medium, significantly slowing the process.1

By adding porous, easily filtered solids like diatomaceous earth to the slurry, the material helps maintain permeability and prevents the filter from becoming blocked. In cases involving particularly slimy precipitates, a technique known as "precoating" is used. A layer of diatomaceous earth, typically one to two inches thick, is deposited onto the filter surface before the slurry is introduced. As the filter operates, the system continuously removes thin, successive layers of the precoat along with the trapped solids, ensuring that a fresh, non-blinded surface is always available for filtration.1

This material is highly effective because it is a light, porous sedimentary rock composed of the microscopic, siliceous shells of diatoms.2