Filter Aid
also known as precoat · diatomaceous earth · body feed
Filter aids such as diatomaceous earth or perlite are applied either as a thin precoat layer on the filter medium or as body feed dosed into the slurry. Their rigid, irregular particles hold the collected solids apart and prevent the cake from compacting, keeping the channels through which liquid flows open. They are essential for gelatinous or compressible solids that would otherwise blind the medium immediately.
Why it matters in practice
Body feed is often what makes the difference between a filtration step that works and one that requires daily cloth replacement. The trade-off is that the aid itself reports to the cake, increasing cake mass and reducing the grade of any solids that are the product.
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Reference entry GL-FILTER-AID. Definitions on this page describe engineering practice in hydrometallurgical process design; they are not a substitute for test work on your own material.