The history of membrane technology

Even towards the middle of eighteenth century membrane phenomena were observed and studied, primarily to elucidate the barrier properties and related phenomena rather than to develop membranes for technical and industrial applications.

observations:      osmosis: Nollet 1748

                           electroosmosis: Reuss 1803, Porret 1816

                          dialysis: Graham 1861

 relations:            diffusion: Fick 1855

                           osmotic pressure: Van’t Hoff 1887

                           electrolyte transport: Nernst-Planck 1889

 theoretical          osmotic pressure: Einstein 1905

considerations:    membrane potentials: Henderson 1907

                           membrane equilibrium: Donnan 1911

                          anomalous osmosis: Sollner 1930

                          irreversible thermodynamics: Kedem, Katchalsky 1964

 transport models:   ionic membranes: Teorell 1937, Meyer, Sievers 1936

                          pore model: Schmid 1950, Meares 1956

                          solution-diffusion model: Londale 1965

The first commercial membranes for practical applications were manufactured by Sartorius in Germany after World War I, the know-how necessary to prepare these membranes originating from the early work of Zsigmondy.

A breakthrough as far as industrial membrane applications were concerned was achieved by the development of asymmetric membranes(Loeb and Sourirajan). These membranes consist of a very thin dense toplayer(thickness<0.5μm) supported by a porous sublayer (thickness 50-200μm). The toplayer or skin determines the transport rate  while the porous sublayer only acts as a surport. The permeation rate is inversely proportional to the thickness of the actual barrier layer and thus asymmetric membranes show a much higher permeation rate (water flux) than (homogeneous) symmetric membranes of a comparable thickness.

The work of Henis and Tripodi made industrial gas separation economically feasible. They placed a very thin homogenous layer of a polymer with high gas permeability on top of an asymmetric membrane, ensuring that the pores in toplayer were filled and that a leak-free composite membrane suitable for gas separation was obtained.

Although membranes for membrane distillation (hydrophobic porous membranes) have been in existence for a time, this process has only been applied on a pilot-plant scale recently. This is an example of a membrane process that makes use of existing membranes, developed initially for other purposes (microfiltration).