Filtering is the mechanical separation of a suspension into its liquid and solid particles with the help of a liquid-permeable filter medium.

The filter medium allows the generally solid-free liquid – the filtrate – to pass through and holds back the solid particles as a filter cake. Both filtrate and filter cake can be recovered as a product.

Frequently, such filtration processes are combined with washing or extraction processes and so are utilised as multi-level processes.

In particular in the field of organics or in chemistry/pharmacy, active ingredients are washed or extracted from their carrier material. The wash fluid is separated as a filtrate, in order for it then to be separated from the filtrate again in the subsequent process.

The parameters of pressure, temperature and/or vacuum can also be utilised in this procedure in order to increase the motivating forces of filtration.

Vacuum is often an important instrument here for the realisation of such processes.