小中大
Ceramic membrane definition
Description:
The Membralox® ceramic membrane is an asymmetric membrane composed of a porous support and a filtering layer.
The support is the most porous part of the membrane. It is produced by sintering high purity alumina particles, which creates a highly permeable yet very strong macroporous structure.
The active layer is composed of ceramic particles (alumina, zircona or titania depending of the type of layer) with a perfectly defined size to create a filtering layer with a well defined pore size. It lines the inside surface of the filtration channels and is in direct contact with the fluid to be treated.
Of minute thickness, this active layer is usually bedded on an intermediate layer by high temperature sintering to produce an exceptionally robust structure. It lends the asymmetric membrane its selectivity and separation efficiency.
The liquid being filtered flows within each of the channels according to the principles of crossflow filtration and the filtrate passes through the active layer and then through the porous support between the channels before reaching the outside lateral surface, as shown in Figure 2.
As the Membralox® support material is exceptionally permeable, the pressure drop caused by the filtrate passing through the support can generally be considered negligible compared to the pressure drop of the filtrate passing through the active layer.
The liquid being filtered flows within each of the channels according to the principles of crossflow filtration and the filtrate passes through the active layer and then through the porous support between the channels before reaching the outside lateral surface, as shown in Figure 2.
As the Membralox® support material is exceptionally permeable, the pressure drop caused by the filtrate passing through the support can generally be considered negligible compared to the pressure drop of the filtrate passing through the active layer.
In the Membralox® line of ceramic membrane products, the high purity ceramic material of the support and the microfiltration active layer is alumina (> 99.97%). Active layers in the ultrafiltration pore size range are made of zirconia or titania respectively. All these materials are extremely resistant to a wide range of pH values, temperatures, pressures and chemicals. Nevertheless, some chemicals, e.g. phosphoric or hydrofluoric acids could react with ceramic membranes. In case of doubt, please contact our Scientific and Laboratory Services.
Special modifications obtained by coating each of the ceramic particles of the membrane structure can be offered. These modifications change the surface characteristics of the membrane, and may improve performance in specific applications. For example, the B modification provides increased resistance to phosphoric acid. Table 1 summarises the Membralox® range of ceramic membrane pore sizes.
Note: in the early 1980s , Membralox® ultrafiltration membranes with active layer made of gamma alumina were also available, but since this form of alumina has limited chemical resistance and lower permeability, it is now only available for some specific applications.
