filtrant

Filtrant is a term used in filtration science to denote the material that passes through a filter, yielding the filtrate. In many English-language texts, filtrant is synonymous with filtrate, though in other sources filtrant may also refer to the filter medium or to the substance being filtered; usage varies by discipline. The contrasting product is the retentate, the material retained on the filter.

In practice, the composition of the filtrant depends on the filtration method. Gravity filtration typically yields a filtrant that is the liquid phase containing dissolved substances. Vacuum filtration accelerates this flow, often improving clarity and speed. In membrane filtration, the filtrant is called the permeate, the portion that passes the membrane with a certain molecular weight cut-off, while the retained particles form the retentate.

Filtrant terminology is influenced by context and technique. Etymologically, filtrant derives from Latin filtrare, to filter. In modern standard usage, filtrate is the preferred term for the liquid that has passed through the filter, and permeate is used for membrane-based processes. Filtration is widely employed to purify liquids, clarify suspensions, or concentrate solids across laboratory and industrial settings.

See also: filtrate; retentate; permeate; filtration; membrane filtration.