We are interested in membranes that can be used on a large scale to provide clean air and safe water, and to enable the things we need to be produced more sustainably.

Membranes for industrial processes come in various forms, including flat-sheets and hollow-fibres.

A feed mixture, which may be liquid or gaseous, is applied to one side of the membrane. The permeate (which passes through the membrane) has a different composition to the retentate (which does not pass through the membrane).

There are many different membrane processes that may be employed,

depending on the size and nature

of the molecules or particles to be separated.

There are various ways of generating a driving force for permeation:

Pressure difference.

Concentration difference.

Electric potential gradient.

Temperature gradient.

In the simplest case, a membrane may be a homogenous thin film of a polymer or other material.

Often a very thin separation layer (<1 mm) is needed to achieve sufficient permeation through the membrane for industrial application, so the separation layer needs a support for it to be mechanically robust.

Integrally-skinned asymmetric membranes have a thin surface layer and a highly porous sub-layer, all formed of the same material.

They may be fabricated by a process of phase inversion (polymer precipitation). A polymer solution is formed into a flat sheet or hollow fibre, then immersed in a non-solvent (typically water).

Thin-film composite membranes have a thin separation layer on a highly porous support made of another material.

Membranes are housed in modules. An industrial plant may have very many modules.

Flat-sheet membranes are often housed in spiral wound modules.

A hollow-fibre module may contain thousands of fibres.

Hollow-fibres give a higher effective membrane area than a flat-sheet within a given module volume.