Filtration

Filtration is the process by which solid materials are removed from a fluid mixture, either a gas or liquid mixture. One of the most familiar kinds of filtration is that which students of chemistry encounter in their early laboratory experiences. In these experiences, suspensions of a solid precipitate in water are passed through filter paper supported in a glass funnel. The filter paper traps solid particles in the mixture, while a clear solution passes through the filter, down the funnel, and into a receiving container.

Filtration is carried out for one of two general purposes: in order to capture the solid material suspended in the fluid or in order to clarify the fluid in which the solid is suspended. The general principle is the same in either case although the specific filtration system employed may differ depending on which of these objectives is intended.

In the world outside of chemistry laboratories, a very great variety of filtration systems are available. These systems can be categorized according to the fluids on which they operate (gaseous or liquid) and the driving force that moves fluids through them (gravity, vacuum, or pressure). They can also be sub-divided depending on the type of material used as a filter.